xref: /openbmc/linux/fs/btrfs/extent-tree.c (revision f5ad1c74)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2007 Oracle.  All rights reserved.
4  */
5 
6 #include <linux/sched.h>
7 #include <linux/sched/signal.h>
8 #include <linux/pagemap.h>
9 #include <linux/writeback.h>
10 #include <linux/blkdev.h>
11 #include <linux/sort.h>
12 #include <linux/rcupdate.h>
13 #include <linux/kthread.h>
14 #include <linux/slab.h>
15 #include <linux/ratelimit.h>
16 #include <linux/percpu_counter.h>
17 #include <linux/lockdep.h>
18 #include <linux/crc32c.h>
19 #include "misc.h"
20 #include "tree-log.h"
21 #include "disk-io.h"
22 #include "print-tree.h"
23 #include "volumes.h"
24 #include "raid56.h"
25 #include "locking.h"
26 #include "free-space-cache.h"
27 #include "free-space-tree.h"
28 #include "sysfs.h"
29 #include "qgroup.h"
30 #include "ref-verify.h"
31 #include "space-info.h"
32 #include "block-rsv.h"
33 #include "delalloc-space.h"
34 #include "block-group.h"
35 #include "discard.h"
36 #include "rcu-string.h"
37 
38 #undef SCRAMBLE_DELAYED_REFS
39 
40 
41 static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
42 			       struct btrfs_delayed_ref_node *node, u64 parent,
43 			       u64 root_objectid, u64 owner_objectid,
44 			       u64 owner_offset, int refs_to_drop,
45 			       struct btrfs_delayed_extent_op *extra_op);
46 static void __run_delayed_extent_op(struct btrfs_delayed_extent_op *extent_op,
47 				    struct extent_buffer *leaf,
48 				    struct btrfs_extent_item *ei);
49 static int alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
50 				      u64 parent, u64 root_objectid,
51 				      u64 flags, u64 owner, u64 offset,
52 				      struct btrfs_key *ins, int ref_mod);
53 static int alloc_reserved_tree_block(struct btrfs_trans_handle *trans,
54 				     struct btrfs_delayed_ref_node *node,
55 				     struct btrfs_delayed_extent_op *extent_op);
56 static int find_next_key(struct btrfs_path *path, int level,
57 			 struct btrfs_key *key);
58 
59 static int block_group_bits(struct btrfs_block_group *cache, u64 bits)
60 {
61 	return (cache->flags & bits) == bits;
62 }
63 
64 int btrfs_add_excluded_extent(struct btrfs_fs_info *fs_info,
65 			      u64 start, u64 num_bytes)
66 {
67 	u64 end = start + num_bytes - 1;
68 	set_extent_bits(&fs_info->excluded_extents, start, end,
69 			EXTENT_UPTODATE);
70 	return 0;
71 }
72 
73 void btrfs_free_excluded_extents(struct btrfs_block_group *cache)
74 {
75 	struct btrfs_fs_info *fs_info = cache->fs_info;
76 	u64 start, end;
77 
78 	start = cache->start;
79 	end = start + cache->length - 1;
80 
81 	clear_extent_bits(&fs_info->excluded_extents, start, end,
82 			  EXTENT_UPTODATE);
83 }
84 
85 static u64 generic_ref_to_space_flags(struct btrfs_ref *ref)
86 {
87 	if (ref->type == BTRFS_REF_METADATA) {
88 		if (ref->tree_ref.root == BTRFS_CHUNK_TREE_OBJECTID)
89 			return BTRFS_BLOCK_GROUP_SYSTEM;
90 		else
91 			return BTRFS_BLOCK_GROUP_METADATA;
92 	}
93 	return BTRFS_BLOCK_GROUP_DATA;
94 }
95 
96 static void add_pinned_bytes(struct btrfs_fs_info *fs_info,
97 			     struct btrfs_ref *ref)
98 {
99 	struct btrfs_space_info *space_info;
100 	u64 flags = generic_ref_to_space_flags(ref);
101 
102 	space_info = btrfs_find_space_info(fs_info, flags);
103 	ASSERT(space_info);
104 	percpu_counter_add_batch(&space_info->total_bytes_pinned, ref->len,
105 		    BTRFS_TOTAL_BYTES_PINNED_BATCH);
106 }
107 
108 static void sub_pinned_bytes(struct btrfs_fs_info *fs_info,
109 			     struct btrfs_ref *ref)
110 {
111 	struct btrfs_space_info *space_info;
112 	u64 flags = generic_ref_to_space_flags(ref);
113 
114 	space_info = btrfs_find_space_info(fs_info, flags);
115 	ASSERT(space_info);
116 	percpu_counter_add_batch(&space_info->total_bytes_pinned, -ref->len,
117 		    BTRFS_TOTAL_BYTES_PINNED_BATCH);
118 }
119 
120 /* simple helper to search for an existing data extent at a given offset */
121 int btrfs_lookup_data_extent(struct btrfs_fs_info *fs_info, u64 start, u64 len)
122 {
123 	int ret;
124 	struct btrfs_key key;
125 	struct btrfs_path *path;
126 
127 	path = btrfs_alloc_path();
128 	if (!path)
129 		return -ENOMEM;
130 
131 	key.objectid = start;
132 	key.offset = len;
133 	key.type = BTRFS_EXTENT_ITEM_KEY;
134 	ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
135 	btrfs_free_path(path);
136 	return ret;
137 }
138 
139 /*
140  * helper function to lookup reference count and flags of a tree block.
141  *
142  * the head node for delayed ref is used to store the sum of all the
143  * reference count modifications queued up in the rbtree. the head
144  * node may also store the extent flags to set. This way you can check
145  * to see what the reference count and extent flags would be if all of
146  * the delayed refs are not processed.
147  */
148 int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
149 			     struct btrfs_fs_info *fs_info, u64 bytenr,
150 			     u64 offset, int metadata, u64 *refs, u64 *flags)
151 {
152 	struct btrfs_delayed_ref_head *head;
153 	struct btrfs_delayed_ref_root *delayed_refs;
154 	struct btrfs_path *path;
155 	struct btrfs_extent_item *ei;
156 	struct extent_buffer *leaf;
157 	struct btrfs_key key;
158 	u32 item_size;
159 	u64 num_refs;
160 	u64 extent_flags;
161 	int ret;
162 
163 	/*
164 	 * If we don't have skinny metadata, don't bother doing anything
165 	 * different
166 	 */
167 	if (metadata && !btrfs_fs_incompat(fs_info, SKINNY_METADATA)) {
168 		offset = fs_info->nodesize;
169 		metadata = 0;
170 	}
171 
172 	path = btrfs_alloc_path();
173 	if (!path)
174 		return -ENOMEM;
175 
176 	if (!trans) {
177 		path->skip_locking = 1;
178 		path->search_commit_root = 1;
179 	}
180 
181 search_again:
182 	key.objectid = bytenr;
183 	key.offset = offset;
184 	if (metadata)
185 		key.type = BTRFS_METADATA_ITEM_KEY;
186 	else
187 		key.type = BTRFS_EXTENT_ITEM_KEY;
188 
189 	ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
190 	if (ret < 0)
191 		goto out_free;
192 
193 	if (ret > 0 && metadata && key.type == BTRFS_METADATA_ITEM_KEY) {
194 		if (path->slots[0]) {
195 			path->slots[0]--;
196 			btrfs_item_key_to_cpu(path->nodes[0], &key,
197 					      path->slots[0]);
198 			if (key.objectid == bytenr &&
199 			    key.type == BTRFS_EXTENT_ITEM_KEY &&
200 			    key.offset == fs_info->nodesize)
201 				ret = 0;
202 		}
203 	}
204 
205 	if (ret == 0) {
206 		leaf = path->nodes[0];
207 		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
208 		if (item_size >= sizeof(*ei)) {
209 			ei = btrfs_item_ptr(leaf, path->slots[0],
210 					    struct btrfs_extent_item);
211 			num_refs = btrfs_extent_refs(leaf, ei);
212 			extent_flags = btrfs_extent_flags(leaf, ei);
213 		} else {
214 			ret = -EINVAL;
215 			btrfs_print_v0_err(fs_info);
216 			if (trans)
217 				btrfs_abort_transaction(trans, ret);
218 			else
219 				btrfs_handle_fs_error(fs_info, ret, NULL);
220 
221 			goto out_free;
222 		}
223 
224 		BUG_ON(num_refs == 0);
225 	} else {
226 		num_refs = 0;
227 		extent_flags = 0;
228 		ret = 0;
229 	}
230 
231 	if (!trans)
232 		goto out;
233 
234 	delayed_refs = &trans->transaction->delayed_refs;
235 	spin_lock(&delayed_refs->lock);
236 	head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
237 	if (head) {
238 		if (!mutex_trylock(&head->mutex)) {
239 			refcount_inc(&head->refs);
240 			spin_unlock(&delayed_refs->lock);
241 
242 			btrfs_release_path(path);
243 
244 			/*
245 			 * Mutex was contended, block until it's released and try
246 			 * again
247 			 */
248 			mutex_lock(&head->mutex);
249 			mutex_unlock(&head->mutex);
250 			btrfs_put_delayed_ref_head(head);
251 			goto search_again;
252 		}
253 		spin_lock(&head->lock);
254 		if (head->extent_op && head->extent_op->update_flags)
255 			extent_flags |= head->extent_op->flags_to_set;
256 		else
257 			BUG_ON(num_refs == 0);
258 
259 		num_refs += head->ref_mod;
260 		spin_unlock(&head->lock);
261 		mutex_unlock(&head->mutex);
262 	}
263 	spin_unlock(&delayed_refs->lock);
264 out:
265 	WARN_ON(num_refs == 0);
266 	if (refs)
267 		*refs = num_refs;
268 	if (flags)
269 		*flags = extent_flags;
270 out_free:
271 	btrfs_free_path(path);
272 	return ret;
273 }
274 
275 /*
276  * Back reference rules.  Back refs have three main goals:
277  *
278  * 1) differentiate between all holders of references to an extent so that
279  *    when a reference is dropped we can make sure it was a valid reference
280  *    before freeing the extent.
281  *
282  * 2) Provide enough information to quickly find the holders of an extent
283  *    if we notice a given block is corrupted or bad.
284  *
285  * 3) Make it easy to migrate blocks for FS shrinking or storage pool
286  *    maintenance.  This is actually the same as #2, but with a slightly
287  *    different use case.
288  *
289  * There are two kinds of back refs. The implicit back refs is optimized
290  * for pointers in non-shared tree blocks. For a given pointer in a block,
291  * back refs of this kind provide information about the block's owner tree
292  * and the pointer's key. These information allow us to find the block by
293  * b-tree searching. The full back refs is for pointers in tree blocks not
294  * referenced by their owner trees. The location of tree block is recorded
295  * in the back refs. Actually the full back refs is generic, and can be
296  * used in all cases the implicit back refs is used. The major shortcoming
297  * of the full back refs is its overhead. Every time a tree block gets
298  * COWed, we have to update back refs entry for all pointers in it.
299  *
300  * For a newly allocated tree block, we use implicit back refs for
301  * pointers in it. This means most tree related operations only involve
302  * implicit back refs. For a tree block created in old transaction, the
303  * only way to drop a reference to it is COW it. So we can detect the
304  * event that tree block loses its owner tree's reference and do the
305  * back refs conversion.
306  *
307  * When a tree block is COWed through a tree, there are four cases:
308  *
309  * The reference count of the block is one and the tree is the block's
310  * owner tree. Nothing to do in this case.
311  *
312  * The reference count of the block is one and the tree is not the
313  * block's owner tree. In this case, full back refs is used for pointers
314  * in the block. Remove these full back refs, add implicit back refs for
315  * every pointers in the new block.
316  *
317  * The reference count of the block is greater than one and the tree is
318  * the block's owner tree. In this case, implicit back refs is used for
319  * pointers in the block. Add full back refs for every pointers in the
320  * block, increase lower level extents' reference counts. The original
321  * implicit back refs are entailed to the new block.
322  *
323  * The reference count of the block is greater than one and the tree is
324  * not the block's owner tree. Add implicit back refs for every pointer in
325  * the new block, increase lower level extents' reference count.
326  *
327  * Back Reference Key composing:
328  *
329  * The key objectid corresponds to the first byte in the extent,
330  * The key type is used to differentiate between types of back refs.
331  * There are different meanings of the key offset for different types
332  * of back refs.
333  *
334  * File extents can be referenced by:
335  *
336  * - multiple snapshots, subvolumes, or different generations in one subvol
337  * - different files inside a single subvolume
338  * - different offsets inside a file (bookend extents in file.c)
339  *
340  * The extent ref structure for the implicit back refs has fields for:
341  *
342  * - Objectid of the subvolume root
343  * - objectid of the file holding the reference
344  * - original offset in the file
345  * - how many bookend extents
346  *
347  * The key offset for the implicit back refs is hash of the first
348  * three fields.
349  *
350  * The extent ref structure for the full back refs has field for:
351  *
352  * - number of pointers in the tree leaf
353  *
354  * The key offset for the implicit back refs is the first byte of
355  * the tree leaf
356  *
357  * When a file extent is allocated, The implicit back refs is used.
358  * the fields are filled in:
359  *
360  *     (root_key.objectid, inode objectid, offset in file, 1)
361  *
362  * When a file extent is removed file truncation, we find the
363  * corresponding implicit back refs and check the following fields:
364  *
365  *     (btrfs_header_owner(leaf), inode objectid, offset in file)
366  *
367  * Btree extents can be referenced by:
368  *
369  * - Different subvolumes
370  *
371  * Both the implicit back refs and the full back refs for tree blocks
372  * only consist of key. The key offset for the implicit back refs is
373  * objectid of block's owner tree. The key offset for the full back refs
374  * is the first byte of parent block.
375  *
376  * When implicit back refs is used, information about the lowest key and
377  * level of the tree block are required. These information are stored in
378  * tree block info structure.
379  */
380 
381 /*
382  * is_data == BTRFS_REF_TYPE_BLOCK, tree block type is required,
383  * is_data == BTRFS_REF_TYPE_DATA, data type is requiried,
384  * is_data == BTRFS_REF_TYPE_ANY, either type is OK.
385  */
386 int btrfs_get_extent_inline_ref_type(const struct extent_buffer *eb,
387 				     struct btrfs_extent_inline_ref *iref,
388 				     enum btrfs_inline_ref_type is_data)
389 {
390 	int type = btrfs_extent_inline_ref_type(eb, iref);
391 	u64 offset = btrfs_extent_inline_ref_offset(eb, iref);
392 
393 	if (type == BTRFS_TREE_BLOCK_REF_KEY ||
394 	    type == BTRFS_SHARED_BLOCK_REF_KEY ||
395 	    type == BTRFS_SHARED_DATA_REF_KEY ||
396 	    type == BTRFS_EXTENT_DATA_REF_KEY) {
397 		if (is_data == BTRFS_REF_TYPE_BLOCK) {
398 			if (type == BTRFS_TREE_BLOCK_REF_KEY)
399 				return type;
400 			if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
401 				ASSERT(eb->fs_info);
402 				/*
403 				 * Every shared one has parent tree block,
404 				 * which must be aligned to sector size.
405 				 */
406 				if (offset &&
407 				    IS_ALIGNED(offset, eb->fs_info->sectorsize))
408 					return type;
409 			}
410 		} else if (is_data == BTRFS_REF_TYPE_DATA) {
411 			if (type == BTRFS_EXTENT_DATA_REF_KEY)
412 				return type;
413 			if (type == BTRFS_SHARED_DATA_REF_KEY) {
414 				ASSERT(eb->fs_info);
415 				/*
416 				 * Every shared one has parent tree block,
417 				 * which must be aligned to sector size.
418 				 */
419 				if (offset &&
420 				    IS_ALIGNED(offset, eb->fs_info->sectorsize))
421 					return type;
422 			}
423 		} else {
424 			ASSERT(is_data == BTRFS_REF_TYPE_ANY);
425 			return type;
426 		}
427 	}
428 
429 	btrfs_print_leaf((struct extent_buffer *)eb);
430 	btrfs_err(eb->fs_info,
431 		  "eb %llu iref 0x%lx invalid extent inline ref type %d",
432 		  eb->start, (unsigned long)iref, type);
433 	WARN_ON(1);
434 
435 	return BTRFS_REF_TYPE_INVALID;
436 }
437 
438 u64 hash_extent_data_ref(u64 root_objectid, u64 owner, u64 offset)
439 {
440 	u32 high_crc = ~(u32)0;
441 	u32 low_crc = ~(u32)0;
442 	__le64 lenum;
443 
444 	lenum = cpu_to_le64(root_objectid);
445 	high_crc = btrfs_crc32c(high_crc, &lenum, sizeof(lenum));
446 	lenum = cpu_to_le64(owner);
447 	low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
448 	lenum = cpu_to_le64(offset);
449 	low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
450 
451 	return ((u64)high_crc << 31) ^ (u64)low_crc;
452 }
453 
454 static u64 hash_extent_data_ref_item(struct extent_buffer *leaf,
455 				     struct btrfs_extent_data_ref *ref)
456 {
457 	return hash_extent_data_ref(btrfs_extent_data_ref_root(leaf, ref),
458 				    btrfs_extent_data_ref_objectid(leaf, ref),
459 				    btrfs_extent_data_ref_offset(leaf, ref));
460 }
461 
462 static int match_extent_data_ref(struct extent_buffer *leaf,
463 				 struct btrfs_extent_data_ref *ref,
464 				 u64 root_objectid, u64 owner, u64 offset)
465 {
466 	if (btrfs_extent_data_ref_root(leaf, ref) != root_objectid ||
467 	    btrfs_extent_data_ref_objectid(leaf, ref) != owner ||
468 	    btrfs_extent_data_ref_offset(leaf, ref) != offset)
469 		return 0;
470 	return 1;
471 }
472 
473 static noinline int lookup_extent_data_ref(struct btrfs_trans_handle *trans,
474 					   struct btrfs_path *path,
475 					   u64 bytenr, u64 parent,
476 					   u64 root_objectid,
477 					   u64 owner, u64 offset)
478 {
479 	struct btrfs_root *root = trans->fs_info->extent_root;
480 	struct btrfs_key key;
481 	struct btrfs_extent_data_ref *ref;
482 	struct extent_buffer *leaf;
483 	u32 nritems;
484 	int ret;
485 	int recow;
486 	int err = -ENOENT;
487 
488 	key.objectid = bytenr;
489 	if (parent) {
490 		key.type = BTRFS_SHARED_DATA_REF_KEY;
491 		key.offset = parent;
492 	} else {
493 		key.type = BTRFS_EXTENT_DATA_REF_KEY;
494 		key.offset = hash_extent_data_ref(root_objectid,
495 						  owner, offset);
496 	}
497 again:
498 	recow = 0;
499 	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
500 	if (ret < 0) {
501 		err = ret;
502 		goto fail;
503 	}
504 
505 	if (parent) {
506 		if (!ret)
507 			return 0;
508 		goto fail;
509 	}
510 
511 	leaf = path->nodes[0];
512 	nritems = btrfs_header_nritems(leaf);
513 	while (1) {
514 		if (path->slots[0] >= nritems) {
515 			ret = btrfs_next_leaf(root, path);
516 			if (ret < 0)
517 				err = ret;
518 			if (ret)
519 				goto fail;
520 
521 			leaf = path->nodes[0];
522 			nritems = btrfs_header_nritems(leaf);
523 			recow = 1;
524 		}
525 
526 		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
527 		if (key.objectid != bytenr ||
528 		    key.type != BTRFS_EXTENT_DATA_REF_KEY)
529 			goto fail;
530 
531 		ref = btrfs_item_ptr(leaf, path->slots[0],
532 				     struct btrfs_extent_data_ref);
533 
534 		if (match_extent_data_ref(leaf, ref, root_objectid,
535 					  owner, offset)) {
536 			if (recow) {
537 				btrfs_release_path(path);
538 				goto again;
539 			}
540 			err = 0;
541 			break;
542 		}
543 		path->slots[0]++;
544 	}
545 fail:
546 	return err;
547 }
548 
549 static noinline int insert_extent_data_ref(struct btrfs_trans_handle *trans,
550 					   struct btrfs_path *path,
551 					   u64 bytenr, u64 parent,
552 					   u64 root_objectid, u64 owner,
553 					   u64 offset, int refs_to_add)
554 {
555 	struct btrfs_root *root = trans->fs_info->extent_root;
556 	struct btrfs_key key;
557 	struct extent_buffer *leaf;
558 	u32 size;
559 	u32 num_refs;
560 	int ret;
561 
562 	key.objectid = bytenr;
563 	if (parent) {
564 		key.type = BTRFS_SHARED_DATA_REF_KEY;
565 		key.offset = parent;
566 		size = sizeof(struct btrfs_shared_data_ref);
567 	} else {
568 		key.type = BTRFS_EXTENT_DATA_REF_KEY;
569 		key.offset = hash_extent_data_ref(root_objectid,
570 						  owner, offset);
571 		size = sizeof(struct btrfs_extent_data_ref);
572 	}
573 
574 	ret = btrfs_insert_empty_item(trans, root, path, &key, size);
575 	if (ret && ret != -EEXIST)
576 		goto fail;
577 
578 	leaf = path->nodes[0];
579 	if (parent) {
580 		struct btrfs_shared_data_ref *ref;
581 		ref = btrfs_item_ptr(leaf, path->slots[0],
582 				     struct btrfs_shared_data_ref);
583 		if (ret == 0) {
584 			btrfs_set_shared_data_ref_count(leaf, ref, refs_to_add);
585 		} else {
586 			num_refs = btrfs_shared_data_ref_count(leaf, ref);
587 			num_refs += refs_to_add;
588 			btrfs_set_shared_data_ref_count(leaf, ref, num_refs);
589 		}
590 	} else {
591 		struct btrfs_extent_data_ref *ref;
592 		while (ret == -EEXIST) {
593 			ref = btrfs_item_ptr(leaf, path->slots[0],
594 					     struct btrfs_extent_data_ref);
595 			if (match_extent_data_ref(leaf, ref, root_objectid,
596 						  owner, offset))
597 				break;
598 			btrfs_release_path(path);
599 			key.offset++;
600 			ret = btrfs_insert_empty_item(trans, root, path, &key,
601 						      size);
602 			if (ret && ret != -EEXIST)
603 				goto fail;
604 
605 			leaf = path->nodes[0];
606 		}
607 		ref = btrfs_item_ptr(leaf, path->slots[0],
608 				     struct btrfs_extent_data_ref);
609 		if (ret == 0) {
610 			btrfs_set_extent_data_ref_root(leaf, ref,
611 						       root_objectid);
612 			btrfs_set_extent_data_ref_objectid(leaf, ref, owner);
613 			btrfs_set_extent_data_ref_offset(leaf, ref, offset);
614 			btrfs_set_extent_data_ref_count(leaf, ref, refs_to_add);
615 		} else {
616 			num_refs = btrfs_extent_data_ref_count(leaf, ref);
617 			num_refs += refs_to_add;
618 			btrfs_set_extent_data_ref_count(leaf, ref, num_refs);
619 		}
620 	}
621 	btrfs_mark_buffer_dirty(leaf);
622 	ret = 0;
623 fail:
624 	btrfs_release_path(path);
625 	return ret;
626 }
627 
628 static noinline int remove_extent_data_ref(struct btrfs_trans_handle *trans,
629 					   struct btrfs_path *path,
630 					   int refs_to_drop, int *last_ref)
631 {
632 	struct btrfs_key key;
633 	struct btrfs_extent_data_ref *ref1 = NULL;
634 	struct btrfs_shared_data_ref *ref2 = NULL;
635 	struct extent_buffer *leaf;
636 	u32 num_refs = 0;
637 	int ret = 0;
638 
639 	leaf = path->nodes[0];
640 	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
641 
642 	if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
643 		ref1 = btrfs_item_ptr(leaf, path->slots[0],
644 				      struct btrfs_extent_data_ref);
645 		num_refs = btrfs_extent_data_ref_count(leaf, ref1);
646 	} else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
647 		ref2 = btrfs_item_ptr(leaf, path->slots[0],
648 				      struct btrfs_shared_data_ref);
649 		num_refs = btrfs_shared_data_ref_count(leaf, ref2);
650 	} else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
651 		btrfs_print_v0_err(trans->fs_info);
652 		btrfs_abort_transaction(trans, -EINVAL);
653 		return -EINVAL;
654 	} else {
655 		BUG();
656 	}
657 
658 	BUG_ON(num_refs < refs_to_drop);
659 	num_refs -= refs_to_drop;
660 
661 	if (num_refs == 0) {
662 		ret = btrfs_del_item(trans, trans->fs_info->extent_root, path);
663 		*last_ref = 1;
664 	} else {
665 		if (key.type == BTRFS_EXTENT_DATA_REF_KEY)
666 			btrfs_set_extent_data_ref_count(leaf, ref1, num_refs);
667 		else if (key.type == BTRFS_SHARED_DATA_REF_KEY)
668 			btrfs_set_shared_data_ref_count(leaf, ref2, num_refs);
669 		btrfs_mark_buffer_dirty(leaf);
670 	}
671 	return ret;
672 }
673 
674 static noinline u32 extent_data_ref_count(struct btrfs_path *path,
675 					  struct btrfs_extent_inline_ref *iref)
676 {
677 	struct btrfs_key key;
678 	struct extent_buffer *leaf;
679 	struct btrfs_extent_data_ref *ref1;
680 	struct btrfs_shared_data_ref *ref2;
681 	u32 num_refs = 0;
682 	int type;
683 
684 	leaf = path->nodes[0];
685 	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
686 
687 	BUG_ON(key.type == BTRFS_EXTENT_REF_V0_KEY);
688 	if (iref) {
689 		/*
690 		 * If type is invalid, we should have bailed out earlier than
691 		 * this call.
692 		 */
693 		type = btrfs_get_extent_inline_ref_type(leaf, iref, BTRFS_REF_TYPE_DATA);
694 		ASSERT(type != BTRFS_REF_TYPE_INVALID);
695 		if (type == BTRFS_EXTENT_DATA_REF_KEY) {
696 			ref1 = (struct btrfs_extent_data_ref *)(&iref->offset);
697 			num_refs = btrfs_extent_data_ref_count(leaf, ref1);
698 		} else {
699 			ref2 = (struct btrfs_shared_data_ref *)(iref + 1);
700 			num_refs = btrfs_shared_data_ref_count(leaf, ref2);
701 		}
702 	} else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
703 		ref1 = btrfs_item_ptr(leaf, path->slots[0],
704 				      struct btrfs_extent_data_ref);
705 		num_refs = btrfs_extent_data_ref_count(leaf, ref1);
706 	} else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
707 		ref2 = btrfs_item_ptr(leaf, path->slots[0],
708 				      struct btrfs_shared_data_ref);
709 		num_refs = btrfs_shared_data_ref_count(leaf, ref2);
710 	} else {
711 		WARN_ON(1);
712 	}
713 	return num_refs;
714 }
715 
716 static noinline int lookup_tree_block_ref(struct btrfs_trans_handle *trans,
717 					  struct btrfs_path *path,
718 					  u64 bytenr, u64 parent,
719 					  u64 root_objectid)
720 {
721 	struct btrfs_root *root = trans->fs_info->extent_root;
722 	struct btrfs_key key;
723 	int ret;
724 
725 	key.objectid = bytenr;
726 	if (parent) {
727 		key.type = BTRFS_SHARED_BLOCK_REF_KEY;
728 		key.offset = parent;
729 	} else {
730 		key.type = BTRFS_TREE_BLOCK_REF_KEY;
731 		key.offset = root_objectid;
732 	}
733 
734 	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
735 	if (ret > 0)
736 		ret = -ENOENT;
737 	return ret;
738 }
739 
740 static noinline int insert_tree_block_ref(struct btrfs_trans_handle *trans,
741 					  struct btrfs_path *path,
742 					  u64 bytenr, u64 parent,
743 					  u64 root_objectid)
744 {
745 	struct btrfs_key key;
746 	int ret;
747 
748 	key.objectid = bytenr;
749 	if (parent) {
750 		key.type = BTRFS_SHARED_BLOCK_REF_KEY;
751 		key.offset = parent;
752 	} else {
753 		key.type = BTRFS_TREE_BLOCK_REF_KEY;
754 		key.offset = root_objectid;
755 	}
756 
757 	ret = btrfs_insert_empty_item(trans, trans->fs_info->extent_root,
758 				      path, &key, 0);
759 	btrfs_release_path(path);
760 	return ret;
761 }
762 
763 static inline int extent_ref_type(u64 parent, u64 owner)
764 {
765 	int type;
766 	if (owner < BTRFS_FIRST_FREE_OBJECTID) {
767 		if (parent > 0)
768 			type = BTRFS_SHARED_BLOCK_REF_KEY;
769 		else
770 			type = BTRFS_TREE_BLOCK_REF_KEY;
771 	} else {
772 		if (parent > 0)
773 			type = BTRFS_SHARED_DATA_REF_KEY;
774 		else
775 			type = BTRFS_EXTENT_DATA_REF_KEY;
776 	}
777 	return type;
778 }
779 
780 static int find_next_key(struct btrfs_path *path, int level,
781 			 struct btrfs_key *key)
782 
783 {
784 	for (; level < BTRFS_MAX_LEVEL; level++) {
785 		if (!path->nodes[level])
786 			break;
787 		if (path->slots[level] + 1 >=
788 		    btrfs_header_nritems(path->nodes[level]))
789 			continue;
790 		if (level == 0)
791 			btrfs_item_key_to_cpu(path->nodes[level], key,
792 					      path->slots[level] + 1);
793 		else
794 			btrfs_node_key_to_cpu(path->nodes[level], key,
795 					      path->slots[level] + 1);
796 		return 0;
797 	}
798 	return 1;
799 }
800 
801 /*
802  * look for inline back ref. if back ref is found, *ref_ret is set
803  * to the address of inline back ref, and 0 is returned.
804  *
805  * if back ref isn't found, *ref_ret is set to the address where it
806  * should be inserted, and -ENOENT is returned.
807  *
808  * if insert is true and there are too many inline back refs, the path
809  * points to the extent item, and -EAGAIN is returned.
810  *
811  * NOTE: inline back refs are ordered in the same way that back ref
812  *	 items in the tree are ordered.
813  */
814 static noinline_for_stack
815 int lookup_inline_extent_backref(struct btrfs_trans_handle *trans,
816 				 struct btrfs_path *path,
817 				 struct btrfs_extent_inline_ref **ref_ret,
818 				 u64 bytenr, u64 num_bytes,
819 				 u64 parent, u64 root_objectid,
820 				 u64 owner, u64 offset, int insert)
821 {
822 	struct btrfs_fs_info *fs_info = trans->fs_info;
823 	struct btrfs_root *root = fs_info->extent_root;
824 	struct btrfs_key key;
825 	struct extent_buffer *leaf;
826 	struct btrfs_extent_item *ei;
827 	struct btrfs_extent_inline_ref *iref;
828 	u64 flags;
829 	u64 item_size;
830 	unsigned long ptr;
831 	unsigned long end;
832 	int extra_size;
833 	int type;
834 	int want;
835 	int ret;
836 	int err = 0;
837 	bool skinny_metadata = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
838 	int needed;
839 
840 	key.objectid = bytenr;
841 	key.type = BTRFS_EXTENT_ITEM_KEY;
842 	key.offset = num_bytes;
843 
844 	want = extent_ref_type(parent, owner);
845 	if (insert) {
846 		extra_size = btrfs_extent_inline_ref_size(want);
847 		path->keep_locks = 1;
848 	} else
849 		extra_size = -1;
850 
851 	/*
852 	 * Owner is our level, so we can just add one to get the level for the
853 	 * block we are interested in.
854 	 */
855 	if (skinny_metadata && owner < BTRFS_FIRST_FREE_OBJECTID) {
856 		key.type = BTRFS_METADATA_ITEM_KEY;
857 		key.offset = owner;
858 	}
859 
860 again:
861 	ret = btrfs_search_slot(trans, root, &key, path, extra_size, 1);
862 	if (ret < 0) {
863 		err = ret;
864 		goto out;
865 	}
866 
867 	/*
868 	 * We may be a newly converted file system which still has the old fat
869 	 * extent entries for metadata, so try and see if we have one of those.
870 	 */
871 	if (ret > 0 && skinny_metadata) {
872 		skinny_metadata = false;
873 		if (path->slots[0]) {
874 			path->slots[0]--;
875 			btrfs_item_key_to_cpu(path->nodes[0], &key,
876 					      path->slots[0]);
877 			if (key.objectid == bytenr &&
878 			    key.type == BTRFS_EXTENT_ITEM_KEY &&
879 			    key.offset == num_bytes)
880 				ret = 0;
881 		}
882 		if (ret) {
883 			key.objectid = bytenr;
884 			key.type = BTRFS_EXTENT_ITEM_KEY;
885 			key.offset = num_bytes;
886 			btrfs_release_path(path);
887 			goto again;
888 		}
889 	}
890 
891 	if (ret && !insert) {
892 		err = -ENOENT;
893 		goto out;
894 	} else if (WARN_ON(ret)) {
895 		err = -EIO;
896 		goto out;
897 	}
898 
899 	leaf = path->nodes[0];
900 	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
901 	if (unlikely(item_size < sizeof(*ei))) {
902 		err = -EINVAL;
903 		btrfs_print_v0_err(fs_info);
904 		btrfs_abort_transaction(trans, err);
905 		goto out;
906 	}
907 
908 	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
909 	flags = btrfs_extent_flags(leaf, ei);
910 
911 	ptr = (unsigned long)(ei + 1);
912 	end = (unsigned long)ei + item_size;
913 
914 	if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK && !skinny_metadata) {
915 		ptr += sizeof(struct btrfs_tree_block_info);
916 		BUG_ON(ptr > end);
917 	}
918 
919 	if (owner >= BTRFS_FIRST_FREE_OBJECTID)
920 		needed = BTRFS_REF_TYPE_DATA;
921 	else
922 		needed = BTRFS_REF_TYPE_BLOCK;
923 
924 	err = -ENOENT;
925 	while (1) {
926 		if (ptr >= end) {
927 			WARN_ON(ptr > end);
928 			break;
929 		}
930 		iref = (struct btrfs_extent_inline_ref *)ptr;
931 		type = btrfs_get_extent_inline_ref_type(leaf, iref, needed);
932 		if (type == BTRFS_REF_TYPE_INVALID) {
933 			err = -EUCLEAN;
934 			goto out;
935 		}
936 
937 		if (want < type)
938 			break;
939 		if (want > type) {
940 			ptr += btrfs_extent_inline_ref_size(type);
941 			continue;
942 		}
943 
944 		if (type == BTRFS_EXTENT_DATA_REF_KEY) {
945 			struct btrfs_extent_data_ref *dref;
946 			dref = (struct btrfs_extent_data_ref *)(&iref->offset);
947 			if (match_extent_data_ref(leaf, dref, root_objectid,
948 						  owner, offset)) {
949 				err = 0;
950 				break;
951 			}
952 			if (hash_extent_data_ref_item(leaf, dref) <
953 			    hash_extent_data_ref(root_objectid, owner, offset))
954 				break;
955 		} else {
956 			u64 ref_offset;
957 			ref_offset = btrfs_extent_inline_ref_offset(leaf, iref);
958 			if (parent > 0) {
959 				if (parent == ref_offset) {
960 					err = 0;
961 					break;
962 				}
963 				if (ref_offset < parent)
964 					break;
965 			} else {
966 				if (root_objectid == ref_offset) {
967 					err = 0;
968 					break;
969 				}
970 				if (ref_offset < root_objectid)
971 					break;
972 			}
973 		}
974 		ptr += btrfs_extent_inline_ref_size(type);
975 	}
976 	if (err == -ENOENT && insert) {
977 		if (item_size + extra_size >=
978 		    BTRFS_MAX_EXTENT_ITEM_SIZE(root)) {
979 			err = -EAGAIN;
980 			goto out;
981 		}
982 		/*
983 		 * To add new inline back ref, we have to make sure
984 		 * there is no corresponding back ref item.
985 		 * For simplicity, we just do not add new inline back
986 		 * ref if there is any kind of item for this block
987 		 */
988 		if (find_next_key(path, 0, &key) == 0 &&
989 		    key.objectid == bytenr &&
990 		    key.type < BTRFS_BLOCK_GROUP_ITEM_KEY) {
991 			err = -EAGAIN;
992 			goto out;
993 		}
994 	}
995 	*ref_ret = (struct btrfs_extent_inline_ref *)ptr;
996 out:
997 	if (insert) {
998 		path->keep_locks = 0;
999 		btrfs_unlock_up_safe(path, 1);
1000 	}
1001 	return err;
1002 }
1003 
1004 /*
1005  * helper to add new inline back ref
1006  */
1007 static noinline_for_stack
1008 void setup_inline_extent_backref(struct btrfs_fs_info *fs_info,
1009 				 struct btrfs_path *path,
1010 				 struct btrfs_extent_inline_ref *iref,
1011 				 u64 parent, u64 root_objectid,
1012 				 u64 owner, u64 offset, int refs_to_add,
1013 				 struct btrfs_delayed_extent_op *extent_op)
1014 {
1015 	struct extent_buffer *leaf;
1016 	struct btrfs_extent_item *ei;
1017 	unsigned long ptr;
1018 	unsigned long end;
1019 	unsigned long item_offset;
1020 	u64 refs;
1021 	int size;
1022 	int type;
1023 
1024 	leaf = path->nodes[0];
1025 	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
1026 	item_offset = (unsigned long)iref - (unsigned long)ei;
1027 
1028 	type = extent_ref_type(parent, owner);
1029 	size = btrfs_extent_inline_ref_size(type);
1030 
1031 	btrfs_extend_item(path, size);
1032 
1033 	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
1034 	refs = btrfs_extent_refs(leaf, ei);
1035 	refs += refs_to_add;
1036 	btrfs_set_extent_refs(leaf, ei, refs);
1037 	if (extent_op)
1038 		__run_delayed_extent_op(extent_op, leaf, ei);
1039 
1040 	ptr = (unsigned long)ei + item_offset;
1041 	end = (unsigned long)ei + btrfs_item_size_nr(leaf, path->slots[0]);
1042 	if (ptr < end - size)
1043 		memmove_extent_buffer(leaf, ptr + size, ptr,
1044 				      end - size - ptr);
1045 
1046 	iref = (struct btrfs_extent_inline_ref *)ptr;
1047 	btrfs_set_extent_inline_ref_type(leaf, iref, type);
1048 	if (type == BTRFS_EXTENT_DATA_REF_KEY) {
1049 		struct btrfs_extent_data_ref *dref;
1050 		dref = (struct btrfs_extent_data_ref *)(&iref->offset);
1051 		btrfs_set_extent_data_ref_root(leaf, dref, root_objectid);
1052 		btrfs_set_extent_data_ref_objectid(leaf, dref, owner);
1053 		btrfs_set_extent_data_ref_offset(leaf, dref, offset);
1054 		btrfs_set_extent_data_ref_count(leaf, dref, refs_to_add);
1055 	} else if (type == BTRFS_SHARED_DATA_REF_KEY) {
1056 		struct btrfs_shared_data_ref *sref;
1057 		sref = (struct btrfs_shared_data_ref *)(iref + 1);
1058 		btrfs_set_shared_data_ref_count(leaf, sref, refs_to_add);
1059 		btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
1060 	} else if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
1061 		btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
1062 	} else {
1063 		btrfs_set_extent_inline_ref_offset(leaf, iref, root_objectid);
1064 	}
1065 	btrfs_mark_buffer_dirty(leaf);
1066 }
1067 
1068 static int lookup_extent_backref(struct btrfs_trans_handle *trans,
1069 				 struct btrfs_path *path,
1070 				 struct btrfs_extent_inline_ref **ref_ret,
1071 				 u64 bytenr, u64 num_bytes, u64 parent,
1072 				 u64 root_objectid, u64 owner, u64 offset)
1073 {
1074 	int ret;
1075 
1076 	ret = lookup_inline_extent_backref(trans, path, ref_ret, bytenr,
1077 					   num_bytes, parent, root_objectid,
1078 					   owner, offset, 0);
1079 	if (ret != -ENOENT)
1080 		return ret;
1081 
1082 	btrfs_release_path(path);
1083 	*ref_ret = NULL;
1084 
1085 	if (owner < BTRFS_FIRST_FREE_OBJECTID) {
1086 		ret = lookup_tree_block_ref(trans, path, bytenr, parent,
1087 					    root_objectid);
1088 	} else {
1089 		ret = lookup_extent_data_ref(trans, path, bytenr, parent,
1090 					     root_objectid, owner, offset);
1091 	}
1092 	return ret;
1093 }
1094 
1095 /*
1096  * helper to update/remove inline back ref
1097  */
1098 static noinline_for_stack
1099 void update_inline_extent_backref(struct btrfs_path *path,
1100 				  struct btrfs_extent_inline_ref *iref,
1101 				  int refs_to_mod,
1102 				  struct btrfs_delayed_extent_op *extent_op,
1103 				  int *last_ref)
1104 {
1105 	struct extent_buffer *leaf = path->nodes[0];
1106 	struct btrfs_extent_item *ei;
1107 	struct btrfs_extent_data_ref *dref = NULL;
1108 	struct btrfs_shared_data_ref *sref = NULL;
1109 	unsigned long ptr;
1110 	unsigned long end;
1111 	u32 item_size;
1112 	int size;
1113 	int type;
1114 	u64 refs;
1115 
1116 	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
1117 	refs = btrfs_extent_refs(leaf, ei);
1118 	WARN_ON(refs_to_mod < 0 && refs + refs_to_mod <= 0);
1119 	refs += refs_to_mod;
1120 	btrfs_set_extent_refs(leaf, ei, refs);
1121 	if (extent_op)
1122 		__run_delayed_extent_op(extent_op, leaf, ei);
1123 
1124 	/*
1125 	 * If type is invalid, we should have bailed out after
1126 	 * lookup_inline_extent_backref().
1127 	 */
1128 	type = btrfs_get_extent_inline_ref_type(leaf, iref, BTRFS_REF_TYPE_ANY);
1129 	ASSERT(type != BTRFS_REF_TYPE_INVALID);
1130 
1131 	if (type == BTRFS_EXTENT_DATA_REF_KEY) {
1132 		dref = (struct btrfs_extent_data_ref *)(&iref->offset);
1133 		refs = btrfs_extent_data_ref_count(leaf, dref);
1134 	} else if (type == BTRFS_SHARED_DATA_REF_KEY) {
1135 		sref = (struct btrfs_shared_data_ref *)(iref + 1);
1136 		refs = btrfs_shared_data_ref_count(leaf, sref);
1137 	} else {
1138 		refs = 1;
1139 		BUG_ON(refs_to_mod != -1);
1140 	}
1141 
1142 	BUG_ON(refs_to_mod < 0 && refs < -refs_to_mod);
1143 	refs += refs_to_mod;
1144 
1145 	if (refs > 0) {
1146 		if (type == BTRFS_EXTENT_DATA_REF_KEY)
1147 			btrfs_set_extent_data_ref_count(leaf, dref, refs);
1148 		else
1149 			btrfs_set_shared_data_ref_count(leaf, sref, refs);
1150 	} else {
1151 		*last_ref = 1;
1152 		size =  btrfs_extent_inline_ref_size(type);
1153 		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
1154 		ptr = (unsigned long)iref;
1155 		end = (unsigned long)ei + item_size;
1156 		if (ptr + size < end)
1157 			memmove_extent_buffer(leaf, ptr, ptr + size,
1158 					      end - ptr - size);
1159 		item_size -= size;
1160 		btrfs_truncate_item(path, item_size, 1);
1161 	}
1162 	btrfs_mark_buffer_dirty(leaf);
1163 }
1164 
1165 static noinline_for_stack
1166 int insert_inline_extent_backref(struct btrfs_trans_handle *trans,
1167 				 struct btrfs_path *path,
1168 				 u64 bytenr, u64 num_bytes, u64 parent,
1169 				 u64 root_objectid, u64 owner,
1170 				 u64 offset, int refs_to_add,
1171 				 struct btrfs_delayed_extent_op *extent_op)
1172 {
1173 	struct btrfs_extent_inline_ref *iref;
1174 	int ret;
1175 
1176 	ret = lookup_inline_extent_backref(trans, path, &iref, bytenr,
1177 					   num_bytes, parent, root_objectid,
1178 					   owner, offset, 1);
1179 	if (ret == 0) {
1180 		/*
1181 		 * We're adding refs to a tree block we already own, this
1182 		 * should not happen at all.
1183 		 */
1184 		if (owner < BTRFS_FIRST_FREE_OBJECTID) {
1185 			btrfs_crit(trans->fs_info,
1186 "adding refs to an existing tree ref, bytenr %llu num_bytes %llu root_objectid %llu",
1187 				   bytenr, num_bytes, root_objectid);
1188 			if (IS_ENABLED(CONFIG_BTRFS_DEBUG)) {
1189 				WARN_ON(1);
1190 				btrfs_crit(trans->fs_info,
1191 			"path->slots[0]=%d path->nodes[0]:", path->slots[0]);
1192 				btrfs_print_leaf(path->nodes[0]);
1193 			}
1194 			return -EUCLEAN;
1195 		}
1196 		update_inline_extent_backref(path, iref, refs_to_add,
1197 					     extent_op, NULL);
1198 	} else if (ret == -ENOENT) {
1199 		setup_inline_extent_backref(trans->fs_info, path, iref, parent,
1200 					    root_objectid, owner, offset,
1201 					    refs_to_add, extent_op);
1202 		ret = 0;
1203 	}
1204 	return ret;
1205 }
1206 
1207 static int remove_extent_backref(struct btrfs_trans_handle *trans,
1208 				 struct btrfs_path *path,
1209 				 struct btrfs_extent_inline_ref *iref,
1210 				 int refs_to_drop, int is_data, int *last_ref)
1211 {
1212 	int ret = 0;
1213 
1214 	BUG_ON(!is_data && refs_to_drop != 1);
1215 	if (iref) {
1216 		update_inline_extent_backref(path, iref, -refs_to_drop, NULL,
1217 					     last_ref);
1218 	} else if (is_data) {
1219 		ret = remove_extent_data_ref(trans, path, refs_to_drop,
1220 					     last_ref);
1221 	} else {
1222 		*last_ref = 1;
1223 		ret = btrfs_del_item(trans, trans->fs_info->extent_root, path);
1224 	}
1225 	return ret;
1226 }
1227 
1228 static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
1229 			       u64 *discarded_bytes)
1230 {
1231 	int j, ret = 0;
1232 	u64 bytes_left, end;
1233 	u64 aligned_start = ALIGN(start, 1 << 9);
1234 
1235 	if (WARN_ON(start != aligned_start)) {
1236 		len -= aligned_start - start;
1237 		len = round_down(len, 1 << 9);
1238 		start = aligned_start;
1239 	}
1240 
1241 	*discarded_bytes = 0;
1242 
1243 	if (!len)
1244 		return 0;
1245 
1246 	end = start + len;
1247 	bytes_left = len;
1248 
1249 	/* Skip any superblocks on this device. */
1250 	for (j = 0; j < BTRFS_SUPER_MIRROR_MAX; j++) {
1251 		u64 sb_start = btrfs_sb_offset(j);
1252 		u64 sb_end = sb_start + BTRFS_SUPER_INFO_SIZE;
1253 		u64 size = sb_start - start;
1254 
1255 		if (!in_range(sb_start, start, bytes_left) &&
1256 		    !in_range(sb_end, start, bytes_left) &&
1257 		    !in_range(start, sb_start, BTRFS_SUPER_INFO_SIZE))
1258 			continue;
1259 
1260 		/*
1261 		 * Superblock spans beginning of range.  Adjust start and
1262 		 * try again.
1263 		 */
1264 		if (sb_start <= start) {
1265 			start += sb_end - start;
1266 			if (start > end) {
1267 				bytes_left = 0;
1268 				break;
1269 			}
1270 			bytes_left = end - start;
1271 			continue;
1272 		}
1273 
1274 		if (size) {
1275 			ret = blkdev_issue_discard(bdev, start >> 9, size >> 9,
1276 						   GFP_NOFS, 0);
1277 			if (!ret)
1278 				*discarded_bytes += size;
1279 			else if (ret != -EOPNOTSUPP)
1280 				return ret;
1281 		}
1282 
1283 		start = sb_end;
1284 		if (start > end) {
1285 			bytes_left = 0;
1286 			break;
1287 		}
1288 		bytes_left = end - start;
1289 	}
1290 
1291 	if (bytes_left) {
1292 		ret = blkdev_issue_discard(bdev, start >> 9, bytes_left >> 9,
1293 					   GFP_NOFS, 0);
1294 		if (!ret)
1295 			*discarded_bytes += bytes_left;
1296 	}
1297 	return ret;
1298 }
1299 
1300 int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
1301 			 u64 num_bytes, u64 *actual_bytes)
1302 {
1303 	int ret = 0;
1304 	u64 discarded_bytes = 0;
1305 	u64 end = bytenr + num_bytes;
1306 	u64 cur = bytenr;
1307 	struct btrfs_bio *bbio = NULL;
1308 
1309 
1310 	/*
1311 	 * Avoid races with device replace and make sure our bbio has devices
1312 	 * associated to its stripes that don't go away while we are discarding.
1313 	 */
1314 	btrfs_bio_counter_inc_blocked(fs_info);
1315 	while (cur < end) {
1316 		struct btrfs_bio_stripe *stripe;
1317 		int i;
1318 
1319 		num_bytes = end - cur;
1320 		/* Tell the block device(s) that the sectors can be discarded */
1321 		ret = btrfs_map_block(fs_info, BTRFS_MAP_DISCARD, cur,
1322 				      &num_bytes, &bbio, 0);
1323 		/*
1324 		 * Error can be -ENOMEM, -ENOENT (no such chunk mapping) or
1325 		 * -EOPNOTSUPP. For any such error, @num_bytes is not updated,
1326 		 * thus we can't continue anyway.
1327 		 */
1328 		if (ret < 0)
1329 			goto out;
1330 
1331 		stripe = bbio->stripes;
1332 		for (i = 0; i < bbio->num_stripes; i++, stripe++) {
1333 			u64 bytes;
1334 			struct request_queue *req_q;
1335 
1336 			if (!stripe->dev->bdev) {
1337 				ASSERT(btrfs_test_opt(fs_info, DEGRADED));
1338 				continue;
1339 			}
1340 			req_q = bdev_get_queue(stripe->dev->bdev);
1341 			if (!blk_queue_discard(req_q))
1342 				continue;
1343 
1344 			ret = btrfs_issue_discard(stripe->dev->bdev,
1345 						  stripe->physical,
1346 						  stripe->length,
1347 						  &bytes);
1348 			if (!ret) {
1349 				discarded_bytes += bytes;
1350 			} else if (ret != -EOPNOTSUPP) {
1351 				/*
1352 				 * Logic errors or -ENOMEM, or -EIO, but
1353 				 * unlikely to happen.
1354 				 *
1355 				 * And since there are two loops, explicitly
1356 				 * go to out to avoid confusion.
1357 				 */
1358 				btrfs_put_bbio(bbio);
1359 				goto out;
1360 			}
1361 
1362 			/*
1363 			 * Just in case we get back EOPNOTSUPP for some reason,
1364 			 * just ignore the return value so we don't screw up
1365 			 * people calling discard_extent.
1366 			 */
1367 			ret = 0;
1368 		}
1369 		btrfs_put_bbio(bbio);
1370 		cur += num_bytes;
1371 	}
1372 out:
1373 	btrfs_bio_counter_dec(fs_info);
1374 
1375 	if (actual_bytes)
1376 		*actual_bytes = discarded_bytes;
1377 
1378 
1379 	if (ret == -EOPNOTSUPP)
1380 		ret = 0;
1381 	return ret;
1382 }
1383 
1384 /* Can return -ENOMEM */
1385 int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
1386 			 struct btrfs_ref *generic_ref)
1387 {
1388 	struct btrfs_fs_info *fs_info = trans->fs_info;
1389 	int old_ref_mod, new_ref_mod;
1390 	int ret;
1391 
1392 	ASSERT(generic_ref->type != BTRFS_REF_NOT_SET &&
1393 	       generic_ref->action);
1394 	BUG_ON(generic_ref->type == BTRFS_REF_METADATA &&
1395 	       generic_ref->tree_ref.root == BTRFS_TREE_LOG_OBJECTID);
1396 
1397 	if (generic_ref->type == BTRFS_REF_METADATA)
1398 		ret = btrfs_add_delayed_tree_ref(trans, generic_ref,
1399 				NULL, &old_ref_mod, &new_ref_mod);
1400 	else
1401 		ret = btrfs_add_delayed_data_ref(trans, generic_ref, 0,
1402 						 &old_ref_mod, &new_ref_mod);
1403 
1404 	btrfs_ref_tree_mod(fs_info, generic_ref);
1405 
1406 	if (ret == 0 && old_ref_mod < 0 && new_ref_mod >= 0)
1407 		sub_pinned_bytes(fs_info, generic_ref);
1408 
1409 	return ret;
1410 }
1411 
1412 /*
1413  * __btrfs_inc_extent_ref - insert backreference for a given extent
1414  *
1415  * The counterpart is in __btrfs_free_extent(), with examples and more details
1416  * how it works.
1417  *
1418  * @trans:	    Handle of transaction
1419  *
1420  * @node:	    The delayed ref node used to get the bytenr/length for
1421  *		    extent whose references are incremented.
1422  *
1423  * @parent:	    If this is a shared extent (BTRFS_SHARED_DATA_REF_KEY/
1424  *		    BTRFS_SHARED_BLOCK_REF_KEY) then it holds the logical
1425  *		    bytenr of the parent block. Since new extents are always
1426  *		    created with indirect references, this will only be the case
1427  *		    when relocating a shared extent. In that case, root_objectid
1428  *		    will be BTRFS_TREE_RELOC_OBJECTID. Otheriwse, parent must
1429  *		    be 0
1430  *
1431  * @root_objectid:  The id of the root where this modification has originated,
1432  *		    this can be either one of the well-known metadata trees or
1433  *		    the subvolume id which references this extent.
1434  *
1435  * @owner:	    For data extents it is the inode number of the owning file.
1436  *		    For metadata extents this parameter holds the level in the
1437  *		    tree of the extent.
1438  *
1439  * @offset:	    For metadata extents the offset is ignored and is currently
1440  *		    always passed as 0. For data extents it is the fileoffset
1441  *		    this extent belongs to.
1442  *
1443  * @refs_to_add     Number of references to add
1444  *
1445  * @extent_op       Pointer to a structure, holding information necessary when
1446  *                  updating a tree block's flags
1447  *
1448  */
1449 static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
1450 				  struct btrfs_delayed_ref_node *node,
1451 				  u64 parent, u64 root_objectid,
1452 				  u64 owner, u64 offset, int refs_to_add,
1453 				  struct btrfs_delayed_extent_op *extent_op)
1454 {
1455 	struct btrfs_path *path;
1456 	struct extent_buffer *leaf;
1457 	struct btrfs_extent_item *item;
1458 	struct btrfs_key key;
1459 	u64 bytenr = node->bytenr;
1460 	u64 num_bytes = node->num_bytes;
1461 	u64 refs;
1462 	int ret;
1463 
1464 	path = btrfs_alloc_path();
1465 	if (!path)
1466 		return -ENOMEM;
1467 
1468 	path->leave_spinning = 1;
1469 	/* this will setup the path even if it fails to insert the back ref */
1470 	ret = insert_inline_extent_backref(trans, path, bytenr, num_bytes,
1471 					   parent, root_objectid, owner,
1472 					   offset, refs_to_add, extent_op);
1473 	if ((ret < 0 && ret != -EAGAIN) || !ret)
1474 		goto out;
1475 
1476 	/*
1477 	 * Ok we had -EAGAIN which means we didn't have space to insert and
1478 	 * inline extent ref, so just update the reference count and add a
1479 	 * normal backref.
1480 	 */
1481 	leaf = path->nodes[0];
1482 	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
1483 	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
1484 	refs = btrfs_extent_refs(leaf, item);
1485 	btrfs_set_extent_refs(leaf, item, refs + refs_to_add);
1486 	if (extent_op)
1487 		__run_delayed_extent_op(extent_op, leaf, item);
1488 
1489 	btrfs_mark_buffer_dirty(leaf);
1490 	btrfs_release_path(path);
1491 
1492 	path->leave_spinning = 1;
1493 	/* now insert the actual backref */
1494 	if (owner < BTRFS_FIRST_FREE_OBJECTID) {
1495 		BUG_ON(refs_to_add != 1);
1496 		ret = insert_tree_block_ref(trans, path, bytenr, parent,
1497 					    root_objectid);
1498 	} else {
1499 		ret = insert_extent_data_ref(trans, path, bytenr, parent,
1500 					     root_objectid, owner, offset,
1501 					     refs_to_add);
1502 	}
1503 	if (ret)
1504 		btrfs_abort_transaction(trans, ret);
1505 out:
1506 	btrfs_free_path(path);
1507 	return ret;
1508 }
1509 
1510 static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
1511 				struct btrfs_delayed_ref_node *node,
1512 				struct btrfs_delayed_extent_op *extent_op,
1513 				int insert_reserved)
1514 {
1515 	int ret = 0;
1516 	struct btrfs_delayed_data_ref *ref;
1517 	struct btrfs_key ins;
1518 	u64 parent = 0;
1519 	u64 ref_root = 0;
1520 	u64 flags = 0;
1521 
1522 	ins.objectid = node->bytenr;
1523 	ins.offset = node->num_bytes;
1524 	ins.type = BTRFS_EXTENT_ITEM_KEY;
1525 
1526 	ref = btrfs_delayed_node_to_data_ref(node);
1527 	trace_run_delayed_data_ref(trans->fs_info, node, ref, node->action);
1528 
1529 	if (node->type == BTRFS_SHARED_DATA_REF_KEY)
1530 		parent = ref->parent;
1531 	ref_root = ref->root;
1532 
1533 	if (node->action == BTRFS_ADD_DELAYED_REF && insert_reserved) {
1534 		if (extent_op)
1535 			flags |= extent_op->flags_to_set;
1536 		ret = alloc_reserved_file_extent(trans, parent, ref_root,
1537 						 flags, ref->objectid,
1538 						 ref->offset, &ins,
1539 						 node->ref_mod);
1540 	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
1541 		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
1542 					     ref->objectid, ref->offset,
1543 					     node->ref_mod, extent_op);
1544 	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
1545 		ret = __btrfs_free_extent(trans, node, parent,
1546 					  ref_root, ref->objectid,
1547 					  ref->offset, node->ref_mod,
1548 					  extent_op);
1549 	} else {
1550 		BUG();
1551 	}
1552 	return ret;
1553 }
1554 
1555 static void __run_delayed_extent_op(struct btrfs_delayed_extent_op *extent_op,
1556 				    struct extent_buffer *leaf,
1557 				    struct btrfs_extent_item *ei)
1558 {
1559 	u64 flags = btrfs_extent_flags(leaf, ei);
1560 	if (extent_op->update_flags) {
1561 		flags |= extent_op->flags_to_set;
1562 		btrfs_set_extent_flags(leaf, ei, flags);
1563 	}
1564 
1565 	if (extent_op->update_key) {
1566 		struct btrfs_tree_block_info *bi;
1567 		BUG_ON(!(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK));
1568 		bi = (struct btrfs_tree_block_info *)(ei + 1);
1569 		btrfs_set_tree_block_key(leaf, bi, &extent_op->key);
1570 	}
1571 }
1572 
1573 static int run_delayed_extent_op(struct btrfs_trans_handle *trans,
1574 				 struct btrfs_delayed_ref_head *head,
1575 				 struct btrfs_delayed_extent_op *extent_op)
1576 {
1577 	struct btrfs_fs_info *fs_info = trans->fs_info;
1578 	struct btrfs_key key;
1579 	struct btrfs_path *path;
1580 	struct btrfs_extent_item *ei;
1581 	struct extent_buffer *leaf;
1582 	u32 item_size;
1583 	int ret;
1584 	int err = 0;
1585 	int metadata = !extent_op->is_data;
1586 
1587 	if (TRANS_ABORTED(trans))
1588 		return 0;
1589 
1590 	if (metadata && !btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1591 		metadata = 0;
1592 
1593 	path = btrfs_alloc_path();
1594 	if (!path)
1595 		return -ENOMEM;
1596 
1597 	key.objectid = head->bytenr;
1598 
1599 	if (metadata) {
1600 		key.type = BTRFS_METADATA_ITEM_KEY;
1601 		key.offset = extent_op->level;
1602 	} else {
1603 		key.type = BTRFS_EXTENT_ITEM_KEY;
1604 		key.offset = head->num_bytes;
1605 	}
1606 
1607 again:
1608 	path->leave_spinning = 1;
1609 	ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 1);
1610 	if (ret < 0) {
1611 		err = ret;
1612 		goto out;
1613 	}
1614 	if (ret > 0) {
1615 		if (metadata) {
1616 			if (path->slots[0] > 0) {
1617 				path->slots[0]--;
1618 				btrfs_item_key_to_cpu(path->nodes[0], &key,
1619 						      path->slots[0]);
1620 				if (key.objectid == head->bytenr &&
1621 				    key.type == BTRFS_EXTENT_ITEM_KEY &&
1622 				    key.offset == head->num_bytes)
1623 					ret = 0;
1624 			}
1625 			if (ret > 0) {
1626 				btrfs_release_path(path);
1627 				metadata = 0;
1628 
1629 				key.objectid = head->bytenr;
1630 				key.offset = head->num_bytes;
1631 				key.type = BTRFS_EXTENT_ITEM_KEY;
1632 				goto again;
1633 			}
1634 		} else {
1635 			err = -EIO;
1636 			goto out;
1637 		}
1638 	}
1639 
1640 	leaf = path->nodes[0];
1641 	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
1642 
1643 	if (unlikely(item_size < sizeof(*ei))) {
1644 		err = -EINVAL;
1645 		btrfs_print_v0_err(fs_info);
1646 		btrfs_abort_transaction(trans, err);
1647 		goto out;
1648 	}
1649 
1650 	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
1651 	__run_delayed_extent_op(extent_op, leaf, ei);
1652 
1653 	btrfs_mark_buffer_dirty(leaf);
1654 out:
1655 	btrfs_free_path(path);
1656 	return err;
1657 }
1658 
1659 static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
1660 				struct btrfs_delayed_ref_node *node,
1661 				struct btrfs_delayed_extent_op *extent_op,
1662 				int insert_reserved)
1663 {
1664 	int ret = 0;
1665 	struct btrfs_delayed_tree_ref *ref;
1666 	u64 parent = 0;
1667 	u64 ref_root = 0;
1668 
1669 	ref = btrfs_delayed_node_to_tree_ref(node);
1670 	trace_run_delayed_tree_ref(trans->fs_info, node, ref, node->action);
1671 
1672 	if (node->type == BTRFS_SHARED_BLOCK_REF_KEY)
1673 		parent = ref->parent;
1674 	ref_root = ref->root;
1675 
1676 	if (node->ref_mod != 1) {
1677 		btrfs_err(trans->fs_info,
1678 	"btree block(%llu) has %d references rather than 1: action %d ref_root %llu parent %llu",
1679 			  node->bytenr, node->ref_mod, node->action, ref_root,
1680 			  parent);
1681 		return -EIO;
1682 	}
1683 	if (node->action == BTRFS_ADD_DELAYED_REF && insert_reserved) {
1684 		BUG_ON(!extent_op || !extent_op->update_flags);
1685 		ret = alloc_reserved_tree_block(trans, node, extent_op);
1686 	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
1687 		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
1688 					     ref->level, 0, 1, extent_op);
1689 	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
1690 		ret = __btrfs_free_extent(trans, node, parent, ref_root,
1691 					  ref->level, 0, 1, extent_op);
1692 	} else {
1693 		BUG();
1694 	}
1695 	return ret;
1696 }
1697 
1698 /* helper function to actually process a single delayed ref entry */
1699 static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
1700 			       struct btrfs_delayed_ref_node *node,
1701 			       struct btrfs_delayed_extent_op *extent_op,
1702 			       int insert_reserved)
1703 {
1704 	int ret = 0;
1705 
1706 	if (TRANS_ABORTED(trans)) {
1707 		if (insert_reserved)
1708 			btrfs_pin_extent(trans, node->bytenr, node->num_bytes, 1);
1709 		return 0;
1710 	}
1711 
1712 	if (node->type == BTRFS_TREE_BLOCK_REF_KEY ||
1713 	    node->type == BTRFS_SHARED_BLOCK_REF_KEY)
1714 		ret = run_delayed_tree_ref(trans, node, extent_op,
1715 					   insert_reserved);
1716 	else if (node->type == BTRFS_EXTENT_DATA_REF_KEY ||
1717 		 node->type == BTRFS_SHARED_DATA_REF_KEY)
1718 		ret = run_delayed_data_ref(trans, node, extent_op,
1719 					   insert_reserved);
1720 	else
1721 		BUG();
1722 	if (ret && insert_reserved)
1723 		btrfs_pin_extent(trans, node->bytenr, node->num_bytes, 1);
1724 	return ret;
1725 }
1726 
1727 static inline struct btrfs_delayed_ref_node *
1728 select_delayed_ref(struct btrfs_delayed_ref_head *head)
1729 {
1730 	struct btrfs_delayed_ref_node *ref;
1731 
1732 	if (RB_EMPTY_ROOT(&head->ref_tree.rb_root))
1733 		return NULL;
1734 
1735 	/*
1736 	 * Select a delayed ref of type BTRFS_ADD_DELAYED_REF first.
1737 	 * This is to prevent a ref count from going down to zero, which deletes
1738 	 * the extent item from the extent tree, when there still are references
1739 	 * to add, which would fail because they would not find the extent item.
1740 	 */
1741 	if (!list_empty(&head->ref_add_list))
1742 		return list_first_entry(&head->ref_add_list,
1743 				struct btrfs_delayed_ref_node, add_list);
1744 
1745 	ref = rb_entry(rb_first_cached(&head->ref_tree),
1746 		       struct btrfs_delayed_ref_node, ref_node);
1747 	ASSERT(list_empty(&ref->add_list));
1748 	return ref;
1749 }
1750 
1751 static void unselect_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
1752 				      struct btrfs_delayed_ref_head *head)
1753 {
1754 	spin_lock(&delayed_refs->lock);
1755 	head->processing = 0;
1756 	delayed_refs->num_heads_ready++;
1757 	spin_unlock(&delayed_refs->lock);
1758 	btrfs_delayed_ref_unlock(head);
1759 }
1760 
1761 static struct btrfs_delayed_extent_op *cleanup_extent_op(
1762 				struct btrfs_delayed_ref_head *head)
1763 {
1764 	struct btrfs_delayed_extent_op *extent_op = head->extent_op;
1765 
1766 	if (!extent_op)
1767 		return NULL;
1768 
1769 	if (head->must_insert_reserved) {
1770 		head->extent_op = NULL;
1771 		btrfs_free_delayed_extent_op(extent_op);
1772 		return NULL;
1773 	}
1774 	return extent_op;
1775 }
1776 
1777 static int run_and_cleanup_extent_op(struct btrfs_trans_handle *trans,
1778 				     struct btrfs_delayed_ref_head *head)
1779 {
1780 	struct btrfs_delayed_extent_op *extent_op;
1781 	int ret;
1782 
1783 	extent_op = cleanup_extent_op(head);
1784 	if (!extent_op)
1785 		return 0;
1786 	head->extent_op = NULL;
1787 	spin_unlock(&head->lock);
1788 	ret = run_delayed_extent_op(trans, head, extent_op);
1789 	btrfs_free_delayed_extent_op(extent_op);
1790 	return ret ? ret : 1;
1791 }
1792 
1793 void btrfs_cleanup_ref_head_accounting(struct btrfs_fs_info *fs_info,
1794 				  struct btrfs_delayed_ref_root *delayed_refs,
1795 				  struct btrfs_delayed_ref_head *head)
1796 {
1797 	int nr_items = 1;	/* Dropping this ref head update. */
1798 
1799 	if (head->total_ref_mod < 0) {
1800 		struct btrfs_space_info *space_info;
1801 		u64 flags;
1802 
1803 		if (head->is_data)
1804 			flags = BTRFS_BLOCK_GROUP_DATA;
1805 		else if (head->is_system)
1806 			flags = BTRFS_BLOCK_GROUP_SYSTEM;
1807 		else
1808 			flags = BTRFS_BLOCK_GROUP_METADATA;
1809 		space_info = btrfs_find_space_info(fs_info, flags);
1810 		ASSERT(space_info);
1811 		percpu_counter_add_batch(&space_info->total_bytes_pinned,
1812 				   -head->num_bytes,
1813 				   BTRFS_TOTAL_BYTES_PINNED_BATCH);
1814 
1815 		/*
1816 		 * We had csum deletions accounted for in our delayed refs rsv,
1817 		 * we need to drop the csum leaves for this update from our
1818 		 * delayed_refs_rsv.
1819 		 */
1820 		if (head->is_data) {
1821 			spin_lock(&delayed_refs->lock);
1822 			delayed_refs->pending_csums -= head->num_bytes;
1823 			spin_unlock(&delayed_refs->lock);
1824 			nr_items += btrfs_csum_bytes_to_leaves(fs_info,
1825 				head->num_bytes);
1826 		}
1827 	}
1828 
1829 	btrfs_delayed_refs_rsv_release(fs_info, nr_items);
1830 }
1831 
1832 static int cleanup_ref_head(struct btrfs_trans_handle *trans,
1833 			    struct btrfs_delayed_ref_head *head)
1834 {
1835 
1836 	struct btrfs_fs_info *fs_info = trans->fs_info;
1837 	struct btrfs_delayed_ref_root *delayed_refs;
1838 	int ret;
1839 
1840 	delayed_refs = &trans->transaction->delayed_refs;
1841 
1842 	ret = run_and_cleanup_extent_op(trans, head);
1843 	if (ret < 0) {
1844 		unselect_delayed_ref_head(delayed_refs, head);
1845 		btrfs_debug(fs_info, "run_delayed_extent_op returned %d", ret);
1846 		return ret;
1847 	} else if (ret) {
1848 		return ret;
1849 	}
1850 
1851 	/*
1852 	 * Need to drop our head ref lock and re-acquire the delayed ref lock
1853 	 * and then re-check to make sure nobody got added.
1854 	 */
1855 	spin_unlock(&head->lock);
1856 	spin_lock(&delayed_refs->lock);
1857 	spin_lock(&head->lock);
1858 	if (!RB_EMPTY_ROOT(&head->ref_tree.rb_root) || head->extent_op) {
1859 		spin_unlock(&head->lock);
1860 		spin_unlock(&delayed_refs->lock);
1861 		return 1;
1862 	}
1863 	btrfs_delete_ref_head(delayed_refs, head);
1864 	spin_unlock(&head->lock);
1865 	spin_unlock(&delayed_refs->lock);
1866 
1867 	if (head->must_insert_reserved) {
1868 		btrfs_pin_extent(trans, head->bytenr, head->num_bytes, 1);
1869 		if (head->is_data) {
1870 			ret = btrfs_del_csums(trans, fs_info->csum_root,
1871 					      head->bytenr, head->num_bytes);
1872 		}
1873 	}
1874 
1875 	btrfs_cleanup_ref_head_accounting(fs_info, delayed_refs, head);
1876 
1877 	trace_run_delayed_ref_head(fs_info, head, 0);
1878 	btrfs_delayed_ref_unlock(head);
1879 	btrfs_put_delayed_ref_head(head);
1880 	return 0;
1881 }
1882 
1883 static struct btrfs_delayed_ref_head *btrfs_obtain_ref_head(
1884 					struct btrfs_trans_handle *trans)
1885 {
1886 	struct btrfs_delayed_ref_root *delayed_refs =
1887 		&trans->transaction->delayed_refs;
1888 	struct btrfs_delayed_ref_head *head = NULL;
1889 	int ret;
1890 
1891 	spin_lock(&delayed_refs->lock);
1892 	head = btrfs_select_ref_head(delayed_refs);
1893 	if (!head) {
1894 		spin_unlock(&delayed_refs->lock);
1895 		return head;
1896 	}
1897 
1898 	/*
1899 	 * Grab the lock that says we are going to process all the refs for
1900 	 * this head
1901 	 */
1902 	ret = btrfs_delayed_ref_lock(delayed_refs, head);
1903 	spin_unlock(&delayed_refs->lock);
1904 
1905 	/*
1906 	 * We may have dropped the spin lock to get the head mutex lock, and
1907 	 * that might have given someone else time to free the head.  If that's
1908 	 * true, it has been removed from our list and we can move on.
1909 	 */
1910 	if (ret == -EAGAIN)
1911 		head = ERR_PTR(-EAGAIN);
1912 
1913 	return head;
1914 }
1915 
1916 static int btrfs_run_delayed_refs_for_head(struct btrfs_trans_handle *trans,
1917 				    struct btrfs_delayed_ref_head *locked_ref,
1918 				    unsigned long *run_refs)
1919 {
1920 	struct btrfs_fs_info *fs_info = trans->fs_info;
1921 	struct btrfs_delayed_ref_root *delayed_refs;
1922 	struct btrfs_delayed_extent_op *extent_op;
1923 	struct btrfs_delayed_ref_node *ref;
1924 	int must_insert_reserved = 0;
1925 	int ret;
1926 
1927 	delayed_refs = &trans->transaction->delayed_refs;
1928 
1929 	lockdep_assert_held(&locked_ref->mutex);
1930 	lockdep_assert_held(&locked_ref->lock);
1931 
1932 	while ((ref = select_delayed_ref(locked_ref))) {
1933 		if (ref->seq &&
1934 		    btrfs_check_delayed_seq(fs_info, ref->seq)) {
1935 			spin_unlock(&locked_ref->lock);
1936 			unselect_delayed_ref_head(delayed_refs, locked_ref);
1937 			return -EAGAIN;
1938 		}
1939 
1940 		(*run_refs)++;
1941 		ref->in_tree = 0;
1942 		rb_erase_cached(&ref->ref_node, &locked_ref->ref_tree);
1943 		RB_CLEAR_NODE(&ref->ref_node);
1944 		if (!list_empty(&ref->add_list))
1945 			list_del(&ref->add_list);
1946 		/*
1947 		 * When we play the delayed ref, also correct the ref_mod on
1948 		 * head
1949 		 */
1950 		switch (ref->action) {
1951 		case BTRFS_ADD_DELAYED_REF:
1952 		case BTRFS_ADD_DELAYED_EXTENT:
1953 			locked_ref->ref_mod -= ref->ref_mod;
1954 			break;
1955 		case BTRFS_DROP_DELAYED_REF:
1956 			locked_ref->ref_mod += ref->ref_mod;
1957 			break;
1958 		default:
1959 			WARN_ON(1);
1960 		}
1961 		atomic_dec(&delayed_refs->num_entries);
1962 
1963 		/*
1964 		 * Record the must_insert_reserved flag before we drop the
1965 		 * spin lock.
1966 		 */
1967 		must_insert_reserved = locked_ref->must_insert_reserved;
1968 		locked_ref->must_insert_reserved = 0;
1969 
1970 		extent_op = locked_ref->extent_op;
1971 		locked_ref->extent_op = NULL;
1972 		spin_unlock(&locked_ref->lock);
1973 
1974 		ret = run_one_delayed_ref(trans, ref, extent_op,
1975 					  must_insert_reserved);
1976 
1977 		btrfs_free_delayed_extent_op(extent_op);
1978 		if (ret) {
1979 			unselect_delayed_ref_head(delayed_refs, locked_ref);
1980 			btrfs_put_delayed_ref(ref);
1981 			btrfs_debug(fs_info, "run_one_delayed_ref returned %d",
1982 				    ret);
1983 			return ret;
1984 		}
1985 
1986 		btrfs_put_delayed_ref(ref);
1987 		cond_resched();
1988 
1989 		spin_lock(&locked_ref->lock);
1990 		btrfs_merge_delayed_refs(trans, delayed_refs, locked_ref);
1991 	}
1992 
1993 	return 0;
1994 }
1995 
1996 /*
1997  * Returns 0 on success or if called with an already aborted transaction.
1998  * Returns -ENOMEM or -EIO on failure and will abort the transaction.
1999  */
2000 static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
2001 					     unsigned long nr)
2002 {
2003 	struct btrfs_fs_info *fs_info = trans->fs_info;
2004 	struct btrfs_delayed_ref_root *delayed_refs;
2005 	struct btrfs_delayed_ref_head *locked_ref = NULL;
2006 	ktime_t start = ktime_get();
2007 	int ret;
2008 	unsigned long count = 0;
2009 	unsigned long actual_count = 0;
2010 
2011 	delayed_refs = &trans->transaction->delayed_refs;
2012 	do {
2013 		if (!locked_ref) {
2014 			locked_ref = btrfs_obtain_ref_head(trans);
2015 			if (IS_ERR_OR_NULL(locked_ref)) {
2016 				if (PTR_ERR(locked_ref) == -EAGAIN) {
2017 					continue;
2018 				} else {
2019 					break;
2020 				}
2021 			}
2022 			count++;
2023 		}
2024 		/*
2025 		 * We need to try and merge add/drops of the same ref since we
2026 		 * can run into issues with relocate dropping the implicit ref
2027 		 * and then it being added back again before the drop can
2028 		 * finish.  If we merged anything we need to re-loop so we can
2029 		 * get a good ref.
2030 		 * Or we can get node references of the same type that weren't
2031 		 * merged when created due to bumps in the tree mod seq, and
2032 		 * we need to merge them to prevent adding an inline extent
2033 		 * backref before dropping it (triggering a BUG_ON at
2034 		 * insert_inline_extent_backref()).
2035 		 */
2036 		spin_lock(&locked_ref->lock);
2037 		btrfs_merge_delayed_refs(trans, delayed_refs, locked_ref);
2038 
2039 		ret = btrfs_run_delayed_refs_for_head(trans, locked_ref,
2040 						      &actual_count);
2041 		if (ret < 0 && ret != -EAGAIN) {
2042 			/*
2043 			 * Error, btrfs_run_delayed_refs_for_head already
2044 			 * unlocked everything so just bail out
2045 			 */
2046 			return ret;
2047 		} else if (!ret) {
2048 			/*
2049 			 * Success, perform the usual cleanup of a processed
2050 			 * head
2051 			 */
2052 			ret = cleanup_ref_head(trans, locked_ref);
2053 			if (ret > 0 ) {
2054 				/* We dropped our lock, we need to loop. */
2055 				ret = 0;
2056 				continue;
2057 			} else if (ret) {
2058 				return ret;
2059 			}
2060 		}
2061 
2062 		/*
2063 		 * Either success case or btrfs_run_delayed_refs_for_head
2064 		 * returned -EAGAIN, meaning we need to select another head
2065 		 */
2066 
2067 		locked_ref = NULL;
2068 		cond_resched();
2069 	} while ((nr != -1 && count < nr) || locked_ref);
2070 
2071 	/*
2072 	 * We don't want to include ref heads since we can have empty ref heads
2073 	 * and those will drastically skew our runtime down since we just do
2074 	 * accounting, no actual extent tree updates.
2075 	 */
2076 	if (actual_count > 0) {
2077 		u64 runtime = ktime_to_ns(ktime_sub(ktime_get(), start));
2078 		u64 avg;
2079 
2080 		/*
2081 		 * We weigh the current average higher than our current runtime
2082 		 * to avoid large swings in the average.
2083 		 */
2084 		spin_lock(&delayed_refs->lock);
2085 		avg = fs_info->avg_delayed_ref_runtime * 3 + runtime;
2086 		fs_info->avg_delayed_ref_runtime = avg >> 2;	/* div by 4 */
2087 		spin_unlock(&delayed_refs->lock);
2088 	}
2089 	return 0;
2090 }
2091 
2092 #ifdef SCRAMBLE_DELAYED_REFS
2093 /*
2094  * Normally delayed refs get processed in ascending bytenr order. This
2095  * correlates in most cases to the order added. To expose dependencies on this
2096  * order, we start to process the tree in the middle instead of the beginning
2097  */
2098 static u64 find_middle(struct rb_root *root)
2099 {
2100 	struct rb_node *n = root->rb_node;
2101 	struct btrfs_delayed_ref_node *entry;
2102 	int alt = 1;
2103 	u64 middle;
2104 	u64 first = 0, last = 0;
2105 
2106 	n = rb_first(root);
2107 	if (n) {
2108 		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
2109 		first = entry->bytenr;
2110 	}
2111 	n = rb_last(root);
2112 	if (n) {
2113 		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
2114 		last = entry->bytenr;
2115 	}
2116 	n = root->rb_node;
2117 
2118 	while (n) {
2119 		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
2120 		WARN_ON(!entry->in_tree);
2121 
2122 		middle = entry->bytenr;
2123 
2124 		if (alt)
2125 			n = n->rb_left;
2126 		else
2127 			n = n->rb_right;
2128 
2129 		alt = 1 - alt;
2130 	}
2131 	return middle;
2132 }
2133 #endif
2134 
2135 /*
2136  * Takes the number of bytes to be csumm'ed and figures out how many leaves it
2137  * would require to store the csums for that many bytes.
2138  */
2139 u64 btrfs_csum_bytes_to_leaves(struct btrfs_fs_info *fs_info, u64 csum_bytes)
2140 {
2141 	u64 csum_size;
2142 	u64 num_csums_per_leaf;
2143 	u64 num_csums;
2144 
2145 	csum_size = BTRFS_MAX_ITEM_SIZE(fs_info);
2146 	num_csums_per_leaf = div64_u64(csum_size,
2147 			(u64)btrfs_super_csum_size(fs_info->super_copy));
2148 	num_csums = div64_u64(csum_bytes, fs_info->sectorsize);
2149 	num_csums += num_csums_per_leaf - 1;
2150 	num_csums = div64_u64(num_csums, num_csums_per_leaf);
2151 	return num_csums;
2152 }
2153 
2154 /*
2155  * this starts processing the delayed reference count updates and
2156  * extent insertions we have queued up so far.  count can be
2157  * 0, which means to process everything in the tree at the start
2158  * of the run (but not newly added entries), or it can be some target
2159  * number you'd like to process.
2160  *
2161  * Returns 0 on success or if called with an aborted transaction
2162  * Returns <0 on error and aborts the transaction
2163  */
2164 int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
2165 			   unsigned long count)
2166 {
2167 	struct btrfs_fs_info *fs_info = trans->fs_info;
2168 	struct rb_node *node;
2169 	struct btrfs_delayed_ref_root *delayed_refs;
2170 	struct btrfs_delayed_ref_head *head;
2171 	int ret;
2172 	int run_all = count == (unsigned long)-1;
2173 
2174 	/* We'll clean this up in btrfs_cleanup_transaction */
2175 	if (TRANS_ABORTED(trans))
2176 		return 0;
2177 
2178 	if (test_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags))
2179 		return 0;
2180 
2181 	delayed_refs = &trans->transaction->delayed_refs;
2182 	if (count == 0)
2183 		count = atomic_read(&delayed_refs->num_entries) * 2;
2184 
2185 again:
2186 #ifdef SCRAMBLE_DELAYED_REFS
2187 	delayed_refs->run_delayed_start = find_middle(&delayed_refs->root);
2188 #endif
2189 	ret = __btrfs_run_delayed_refs(trans, count);
2190 	if (ret < 0) {
2191 		btrfs_abort_transaction(trans, ret);
2192 		return ret;
2193 	}
2194 
2195 	if (run_all) {
2196 		btrfs_create_pending_block_groups(trans);
2197 
2198 		spin_lock(&delayed_refs->lock);
2199 		node = rb_first_cached(&delayed_refs->href_root);
2200 		if (!node) {
2201 			spin_unlock(&delayed_refs->lock);
2202 			goto out;
2203 		}
2204 		head = rb_entry(node, struct btrfs_delayed_ref_head,
2205 				href_node);
2206 		refcount_inc(&head->refs);
2207 		spin_unlock(&delayed_refs->lock);
2208 
2209 		/* Mutex was contended, block until it's released and retry. */
2210 		mutex_lock(&head->mutex);
2211 		mutex_unlock(&head->mutex);
2212 
2213 		btrfs_put_delayed_ref_head(head);
2214 		cond_resched();
2215 		goto again;
2216 	}
2217 out:
2218 	return 0;
2219 }
2220 
2221 int btrfs_set_disk_extent_flags(struct btrfs_trans_handle *trans,
2222 				struct extent_buffer *eb, u64 flags,
2223 				int level, int is_data)
2224 {
2225 	struct btrfs_delayed_extent_op *extent_op;
2226 	int ret;
2227 
2228 	extent_op = btrfs_alloc_delayed_extent_op();
2229 	if (!extent_op)
2230 		return -ENOMEM;
2231 
2232 	extent_op->flags_to_set = flags;
2233 	extent_op->update_flags = true;
2234 	extent_op->update_key = false;
2235 	extent_op->is_data = is_data ? true : false;
2236 	extent_op->level = level;
2237 
2238 	ret = btrfs_add_delayed_extent_op(trans, eb->start, eb->len, extent_op);
2239 	if (ret)
2240 		btrfs_free_delayed_extent_op(extent_op);
2241 	return ret;
2242 }
2243 
2244 static noinline int check_delayed_ref(struct btrfs_root *root,
2245 				      struct btrfs_path *path,
2246 				      u64 objectid, u64 offset, u64 bytenr)
2247 {
2248 	struct btrfs_delayed_ref_head *head;
2249 	struct btrfs_delayed_ref_node *ref;
2250 	struct btrfs_delayed_data_ref *data_ref;
2251 	struct btrfs_delayed_ref_root *delayed_refs;
2252 	struct btrfs_transaction *cur_trans;
2253 	struct rb_node *node;
2254 	int ret = 0;
2255 
2256 	spin_lock(&root->fs_info->trans_lock);
2257 	cur_trans = root->fs_info->running_transaction;
2258 	if (cur_trans)
2259 		refcount_inc(&cur_trans->use_count);
2260 	spin_unlock(&root->fs_info->trans_lock);
2261 	if (!cur_trans)
2262 		return 0;
2263 
2264 	delayed_refs = &cur_trans->delayed_refs;
2265 	spin_lock(&delayed_refs->lock);
2266 	head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
2267 	if (!head) {
2268 		spin_unlock(&delayed_refs->lock);
2269 		btrfs_put_transaction(cur_trans);
2270 		return 0;
2271 	}
2272 
2273 	if (!mutex_trylock(&head->mutex)) {
2274 		refcount_inc(&head->refs);
2275 		spin_unlock(&delayed_refs->lock);
2276 
2277 		btrfs_release_path(path);
2278 
2279 		/*
2280 		 * Mutex was contended, block until it's released and let
2281 		 * caller try again
2282 		 */
2283 		mutex_lock(&head->mutex);
2284 		mutex_unlock(&head->mutex);
2285 		btrfs_put_delayed_ref_head(head);
2286 		btrfs_put_transaction(cur_trans);
2287 		return -EAGAIN;
2288 	}
2289 	spin_unlock(&delayed_refs->lock);
2290 
2291 	spin_lock(&head->lock);
2292 	/*
2293 	 * XXX: We should replace this with a proper search function in the
2294 	 * future.
2295 	 */
2296 	for (node = rb_first_cached(&head->ref_tree); node;
2297 	     node = rb_next(node)) {
2298 		ref = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
2299 		/* If it's a shared ref we know a cross reference exists */
2300 		if (ref->type != BTRFS_EXTENT_DATA_REF_KEY) {
2301 			ret = 1;
2302 			break;
2303 		}
2304 
2305 		data_ref = btrfs_delayed_node_to_data_ref(ref);
2306 
2307 		/*
2308 		 * If our ref doesn't match the one we're currently looking at
2309 		 * then we have a cross reference.
2310 		 */
2311 		if (data_ref->root != root->root_key.objectid ||
2312 		    data_ref->objectid != objectid ||
2313 		    data_ref->offset != offset) {
2314 			ret = 1;
2315 			break;
2316 		}
2317 	}
2318 	spin_unlock(&head->lock);
2319 	mutex_unlock(&head->mutex);
2320 	btrfs_put_transaction(cur_trans);
2321 	return ret;
2322 }
2323 
2324 static noinline int check_committed_ref(struct btrfs_root *root,
2325 					struct btrfs_path *path,
2326 					u64 objectid, u64 offset, u64 bytenr,
2327 					bool strict)
2328 {
2329 	struct btrfs_fs_info *fs_info = root->fs_info;
2330 	struct btrfs_root *extent_root = fs_info->extent_root;
2331 	struct extent_buffer *leaf;
2332 	struct btrfs_extent_data_ref *ref;
2333 	struct btrfs_extent_inline_ref *iref;
2334 	struct btrfs_extent_item *ei;
2335 	struct btrfs_key key;
2336 	u32 item_size;
2337 	int type;
2338 	int ret;
2339 
2340 	key.objectid = bytenr;
2341 	key.offset = (u64)-1;
2342 	key.type = BTRFS_EXTENT_ITEM_KEY;
2343 
2344 	ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
2345 	if (ret < 0)
2346 		goto out;
2347 	BUG_ON(ret == 0); /* Corruption */
2348 
2349 	ret = -ENOENT;
2350 	if (path->slots[0] == 0)
2351 		goto out;
2352 
2353 	path->slots[0]--;
2354 	leaf = path->nodes[0];
2355 	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
2356 
2357 	if (key.objectid != bytenr || key.type != BTRFS_EXTENT_ITEM_KEY)
2358 		goto out;
2359 
2360 	ret = 1;
2361 	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
2362 	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
2363 
2364 	/* If extent item has more than 1 inline ref then it's shared */
2365 	if (item_size != sizeof(*ei) +
2366 	    btrfs_extent_inline_ref_size(BTRFS_EXTENT_DATA_REF_KEY))
2367 		goto out;
2368 
2369 	/*
2370 	 * If extent created before last snapshot => it's shared unless the
2371 	 * snapshot has been deleted. Use the heuristic if strict is false.
2372 	 */
2373 	if (!strict &&
2374 	    (btrfs_extent_generation(leaf, ei) <=
2375 	     btrfs_root_last_snapshot(&root->root_item)))
2376 		goto out;
2377 
2378 	iref = (struct btrfs_extent_inline_ref *)(ei + 1);
2379 
2380 	/* If this extent has SHARED_DATA_REF then it's shared */
2381 	type = btrfs_get_extent_inline_ref_type(leaf, iref, BTRFS_REF_TYPE_DATA);
2382 	if (type != BTRFS_EXTENT_DATA_REF_KEY)
2383 		goto out;
2384 
2385 	ref = (struct btrfs_extent_data_ref *)(&iref->offset);
2386 	if (btrfs_extent_refs(leaf, ei) !=
2387 	    btrfs_extent_data_ref_count(leaf, ref) ||
2388 	    btrfs_extent_data_ref_root(leaf, ref) !=
2389 	    root->root_key.objectid ||
2390 	    btrfs_extent_data_ref_objectid(leaf, ref) != objectid ||
2391 	    btrfs_extent_data_ref_offset(leaf, ref) != offset)
2392 		goto out;
2393 
2394 	ret = 0;
2395 out:
2396 	return ret;
2397 }
2398 
2399 int btrfs_cross_ref_exist(struct btrfs_root *root, u64 objectid, u64 offset,
2400 			  u64 bytenr, bool strict)
2401 {
2402 	struct btrfs_path *path;
2403 	int ret;
2404 
2405 	path = btrfs_alloc_path();
2406 	if (!path)
2407 		return -ENOMEM;
2408 
2409 	do {
2410 		ret = check_committed_ref(root, path, objectid,
2411 					  offset, bytenr, strict);
2412 		if (ret && ret != -ENOENT)
2413 			goto out;
2414 
2415 		ret = check_delayed_ref(root, path, objectid, offset, bytenr);
2416 	} while (ret == -EAGAIN);
2417 
2418 out:
2419 	btrfs_free_path(path);
2420 	if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
2421 		WARN_ON(ret > 0);
2422 	return ret;
2423 }
2424 
2425 static int __btrfs_mod_ref(struct btrfs_trans_handle *trans,
2426 			   struct btrfs_root *root,
2427 			   struct extent_buffer *buf,
2428 			   int full_backref, int inc)
2429 {
2430 	struct btrfs_fs_info *fs_info = root->fs_info;
2431 	u64 bytenr;
2432 	u64 num_bytes;
2433 	u64 parent;
2434 	u64 ref_root;
2435 	u32 nritems;
2436 	struct btrfs_key key;
2437 	struct btrfs_file_extent_item *fi;
2438 	struct btrfs_ref generic_ref = { 0 };
2439 	bool for_reloc = btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC);
2440 	int i;
2441 	int action;
2442 	int level;
2443 	int ret = 0;
2444 
2445 	if (btrfs_is_testing(fs_info))
2446 		return 0;
2447 
2448 	ref_root = btrfs_header_owner(buf);
2449 	nritems = btrfs_header_nritems(buf);
2450 	level = btrfs_header_level(buf);
2451 
2452 	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state) && level == 0)
2453 		return 0;
2454 
2455 	if (full_backref)
2456 		parent = buf->start;
2457 	else
2458 		parent = 0;
2459 	if (inc)
2460 		action = BTRFS_ADD_DELAYED_REF;
2461 	else
2462 		action = BTRFS_DROP_DELAYED_REF;
2463 
2464 	for (i = 0; i < nritems; i++) {
2465 		if (level == 0) {
2466 			btrfs_item_key_to_cpu(buf, &key, i);
2467 			if (key.type != BTRFS_EXTENT_DATA_KEY)
2468 				continue;
2469 			fi = btrfs_item_ptr(buf, i,
2470 					    struct btrfs_file_extent_item);
2471 			if (btrfs_file_extent_type(buf, fi) ==
2472 			    BTRFS_FILE_EXTENT_INLINE)
2473 				continue;
2474 			bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
2475 			if (bytenr == 0)
2476 				continue;
2477 
2478 			num_bytes = btrfs_file_extent_disk_num_bytes(buf, fi);
2479 			key.offset -= btrfs_file_extent_offset(buf, fi);
2480 			btrfs_init_generic_ref(&generic_ref, action, bytenr,
2481 					       num_bytes, parent);
2482 			generic_ref.real_root = root->root_key.objectid;
2483 			btrfs_init_data_ref(&generic_ref, ref_root, key.objectid,
2484 					    key.offset);
2485 			generic_ref.skip_qgroup = for_reloc;
2486 			if (inc)
2487 				ret = btrfs_inc_extent_ref(trans, &generic_ref);
2488 			else
2489 				ret = btrfs_free_extent(trans, &generic_ref);
2490 			if (ret)
2491 				goto fail;
2492 		} else {
2493 			bytenr = btrfs_node_blockptr(buf, i);
2494 			num_bytes = fs_info->nodesize;
2495 			btrfs_init_generic_ref(&generic_ref, action, bytenr,
2496 					       num_bytes, parent);
2497 			generic_ref.real_root = root->root_key.objectid;
2498 			btrfs_init_tree_ref(&generic_ref, level - 1, ref_root);
2499 			generic_ref.skip_qgroup = for_reloc;
2500 			if (inc)
2501 				ret = btrfs_inc_extent_ref(trans, &generic_ref);
2502 			else
2503 				ret = btrfs_free_extent(trans, &generic_ref);
2504 			if (ret)
2505 				goto fail;
2506 		}
2507 	}
2508 	return 0;
2509 fail:
2510 	return ret;
2511 }
2512 
2513 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
2514 		  struct extent_buffer *buf, int full_backref)
2515 {
2516 	return __btrfs_mod_ref(trans, root, buf, full_backref, 1);
2517 }
2518 
2519 int btrfs_dec_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
2520 		  struct extent_buffer *buf, int full_backref)
2521 {
2522 	return __btrfs_mod_ref(trans, root, buf, full_backref, 0);
2523 }
2524 
2525 int btrfs_extent_readonly(struct btrfs_fs_info *fs_info, u64 bytenr)
2526 {
2527 	struct btrfs_block_group *block_group;
2528 	int readonly = 0;
2529 
2530 	block_group = btrfs_lookup_block_group(fs_info, bytenr);
2531 	if (!block_group || block_group->ro)
2532 		readonly = 1;
2533 	if (block_group)
2534 		btrfs_put_block_group(block_group);
2535 	return readonly;
2536 }
2537 
2538 static u64 get_alloc_profile_by_root(struct btrfs_root *root, int data)
2539 {
2540 	struct btrfs_fs_info *fs_info = root->fs_info;
2541 	u64 flags;
2542 	u64 ret;
2543 
2544 	if (data)
2545 		flags = BTRFS_BLOCK_GROUP_DATA;
2546 	else if (root == fs_info->chunk_root)
2547 		flags = BTRFS_BLOCK_GROUP_SYSTEM;
2548 	else
2549 		flags = BTRFS_BLOCK_GROUP_METADATA;
2550 
2551 	ret = btrfs_get_alloc_profile(fs_info, flags);
2552 	return ret;
2553 }
2554 
2555 static u64 first_logical_byte(struct btrfs_fs_info *fs_info, u64 search_start)
2556 {
2557 	struct btrfs_block_group *cache;
2558 	u64 bytenr;
2559 
2560 	spin_lock(&fs_info->block_group_cache_lock);
2561 	bytenr = fs_info->first_logical_byte;
2562 	spin_unlock(&fs_info->block_group_cache_lock);
2563 
2564 	if (bytenr < (u64)-1)
2565 		return bytenr;
2566 
2567 	cache = btrfs_lookup_first_block_group(fs_info, search_start);
2568 	if (!cache)
2569 		return 0;
2570 
2571 	bytenr = cache->start;
2572 	btrfs_put_block_group(cache);
2573 
2574 	return bytenr;
2575 }
2576 
2577 static int pin_down_extent(struct btrfs_trans_handle *trans,
2578 			   struct btrfs_block_group *cache,
2579 			   u64 bytenr, u64 num_bytes, int reserved)
2580 {
2581 	struct btrfs_fs_info *fs_info = cache->fs_info;
2582 
2583 	spin_lock(&cache->space_info->lock);
2584 	spin_lock(&cache->lock);
2585 	cache->pinned += num_bytes;
2586 	btrfs_space_info_update_bytes_pinned(fs_info, cache->space_info,
2587 					     num_bytes);
2588 	if (reserved) {
2589 		cache->reserved -= num_bytes;
2590 		cache->space_info->bytes_reserved -= num_bytes;
2591 	}
2592 	spin_unlock(&cache->lock);
2593 	spin_unlock(&cache->space_info->lock);
2594 
2595 	percpu_counter_add_batch(&cache->space_info->total_bytes_pinned,
2596 		    num_bytes, BTRFS_TOTAL_BYTES_PINNED_BATCH);
2597 	set_extent_dirty(&trans->transaction->pinned_extents, bytenr,
2598 			 bytenr + num_bytes - 1, GFP_NOFS | __GFP_NOFAIL);
2599 	return 0;
2600 }
2601 
2602 int btrfs_pin_extent(struct btrfs_trans_handle *trans,
2603 		     u64 bytenr, u64 num_bytes, int reserved)
2604 {
2605 	struct btrfs_block_group *cache;
2606 
2607 	cache = btrfs_lookup_block_group(trans->fs_info, bytenr);
2608 	BUG_ON(!cache); /* Logic error */
2609 
2610 	pin_down_extent(trans, cache, bytenr, num_bytes, reserved);
2611 
2612 	btrfs_put_block_group(cache);
2613 	return 0;
2614 }
2615 
2616 /*
2617  * this function must be called within transaction
2618  */
2619 int btrfs_pin_extent_for_log_replay(struct btrfs_trans_handle *trans,
2620 				    u64 bytenr, u64 num_bytes)
2621 {
2622 	struct btrfs_block_group *cache;
2623 	int ret;
2624 
2625 	btrfs_add_excluded_extent(trans->fs_info, bytenr, num_bytes);
2626 
2627 	cache = btrfs_lookup_block_group(trans->fs_info, bytenr);
2628 	if (!cache)
2629 		return -EINVAL;
2630 
2631 	/*
2632 	 * pull in the free space cache (if any) so that our pin
2633 	 * removes the free space from the cache.  We have load_only set
2634 	 * to one because the slow code to read in the free extents does check
2635 	 * the pinned extents.
2636 	 */
2637 	btrfs_cache_block_group(cache, 1);
2638 
2639 	pin_down_extent(trans, cache, bytenr, num_bytes, 0);
2640 
2641 	/* remove us from the free space cache (if we're there at all) */
2642 	ret = btrfs_remove_free_space(cache, bytenr, num_bytes);
2643 	btrfs_put_block_group(cache);
2644 	return ret;
2645 }
2646 
2647 static int __exclude_logged_extent(struct btrfs_fs_info *fs_info,
2648 				   u64 start, u64 num_bytes)
2649 {
2650 	int ret;
2651 	struct btrfs_block_group *block_group;
2652 	struct btrfs_caching_control *caching_ctl;
2653 
2654 	block_group = btrfs_lookup_block_group(fs_info, start);
2655 	if (!block_group)
2656 		return -EINVAL;
2657 
2658 	btrfs_cache_block_group(block_group, 0);
2659 	caching_ctl = btrfs_get_caching_control(block_group);
2660 
2661 	if (!caching_ctl) {
2662 		/* Logic error */
2663 		BUG_ON(!btrfs_block_group_done(block_group));
2664 		ret = btrfs_remove_free_space(block_group, start, num_bytes);
2665 	} else {
2666 		mutex_lock(&caching_ctl->mutex);
2667 
2668 		if (start >= caching_ctl->progress) {
2669 			ret = btrfs_add_excluded_extent(fs_info, start,
2670 							num_bytes);
2671 		} else if (start + num_bytes <= caching_ctl->progress) {
2672 			ret = btrfs_remove_free_space(block_group,
2673 						      start, num_bytes);
2674 		} else {
2675 			num_bytes = caching_ctl->progress - start;
2676 			ret = btrfs_remove_free_space(block_group,
2677 						      start, num_bytes);
2678 			if (ret)
2679 				goto out_lock;
2680 
2681 			num_bytes = (start + num_bytes) -
2682 				caching_ctl->progress;
2683 			start = caching_ctl->progress;
2684 			ret = btrfs_add_excluded_extent(fs_info, start,
2685 							num_bytes);
2686 		}
2687 out_lock:
2688 		mutex_unlock(&caching_ctl->mutex);
2689 		btrfs_put_caching_control(caching_ctl);
2690 	}
2691 	btrfs_put_block_group(block_group);
2692 	return ret;
2693 }
2694 
2695 int btrfs_exclude_logged_extents(struct extent_buffer *eb)
2696 {
2697 	struct btrfs_fs_info *fs_info = eb->fs_info;
2698 	struct btrfs_file_extent_item *item;
2699 	struct btrfs_key key;
2700 	int found_type;
2701 	int i;
2702 	int ret = 0;
2703 
2704 	if (!btrfs_fs_incompat(fs_info, MIXED_GROUPS))
2705 		return 0;
2706 
2707 	for (i = 0; i < btrfs_header_nritems(eb); i++) {
2708 		btrfs_item_key_to_cpu(eb, &key, i);
2709 		if (key.type != BTRFS_EXTENT_DATA_KEY)
2710 			continue;
2711 		item = btrfs_item_ptr(eb, i, struct btrfs_file_extent_item);
2712 		found_type = btrfs_file_extent_type(eb, item);
2713 		if (found_type == BTRFS_FILE_EXTENT_INLINE)
2714 			continue;
2715 		if (btrfs_file_extent_disk_bytenr(eb, item) == 0)
2716 			continue;
2717 		key.objectid = btrfs_file_extent_disk_bytenr(eb, item);
2718 		key.offset = btrfs_file_extent_disk_num_bytes(eb, item);
2719 		ret = __exclude_logged_extent(fs_info, key.objectid, key.offset);
2720 		if (ret)
2721 			break;
2722 	}
2723 
2724 	return ret;
2725 }
2726 
2727 static void
2728 btrfs_inc_block_group_reservations(struct btrfs_block_group *bg)
2729 {
2730 	atomic_inc(&bg->reservations);
2731 }
2732 
2733 void btrfs_prepare_extent_commit(struct btrfs_fs_info *fs_info)
2734 {
2735 	struct btrfs_caching_control *next;
2736 	struct btrfs_caching_control *caching_ctl;
2737 	struct btrfs_block_group *cache;
2738 
2739 	down_write(&fs_info->commit_root_sem);
2740 
2741 	list_for_each_entry_safe(caching_ctl, next,
2742 				 &fs_info->caching_block_groups, list) {
2743 		cache = caching_ctl->block_group;
2744 		if (btrfs_block_group_done(cache)) {
2745 			cache->last_byte_to_unpin = (u64)-1;
2746 			list_del_init(&caching_ctl->list);
2747 			btrfs_put_caching_control(caching_ctl);
2748 		} else {
2749 			cache->last_byte_to_unpin = caching_ctl->progress;
2750 		}
2751 	}
2752 
2753 	up_write(&fs_info->commit_root_sem);
2754 
2755 	btrfs_update_global_block_rsv(fs_info);
2756 }
2757 
2758 /*
2759  * Returns the free cluster for the given space info and sets empty_cluster to
2760  * what it should be based on the mount options.
2761  */
2762 static struct btrfs_free_cluster *
2763 fetch_cluster_info(struct btrfs_fs_info *fs_info,
2764 		   struct btrfs_space_info *space_info, u64 *empty_cluster)
2765 {
2766 	struct btrfs_free_cluster *ret = NULL;
2767 
2768 	*empty_cluster = 0;
2769 	if (btrfs_mixed_space_info(space_info))
2770 		return ret;
2771 
2772 	if (space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
2773 		ret = &fs_info->meta_alloc_cluster;
2774 		if (btrfs_test_opt(fs_info, SSD))
2775 			*empty_cluster = SZ_2M;
2776 		else
2777 			*empty_cluster = SZ_64K;
2778 	} else if ((space_info->flags & BTRFS_BLOCK_GROUP_DATA) &&
2779 		   btrfs_test_opt(fs_info, SSD_SPREAD)) {
2780 		*empty_cluster = SZ_2M;
2781 		ret = &fs_info->data_alloc_cluster;
2782 	}
2783 
2784 	return ret;
2785 }
2786 
2787 static int unpin_extent_range(struct btrfs_fs_info *fs_info,
2788 			      u64 start, u64 end,
2789 			      const bool return_free_space)
2790 {
2791 	struct btrfs_block_group *cache = NULL;
2792 	struct btrfs_space_info *space_info;
2793 	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
2794 	struct btrfs_free_cluster *cluster = NULL;
2795 	u64 len;
2796 	u64 total_unpinned = 0;
2797 	u64 empty_cluster = 0;
2798 	bool readonly;
2799 
2800 	while (start <= end) {
2801 		readonly = false;
2802 		if (!cache ||
2803 		    start >= cache->start + cache->length) {
2804 			if (cache)
2805 				btrfs_put_block_group(cache);
2806 			total_unpinned = 0;
2807 			cache = btrfs_lookup_block_group(fs_info, start);
2808 			BUG_ON(!cache); /* Logic error */
2809 
2810 			cluster = fetch_cluster_info(fs_info,
2811 						     cache->space_info,
2812 						     &empty_cluster);
2813 			empty_cluster <<= 1;
2814 		}
2815 
2816 		len = cache->start + cache->length - start;
2817 		len = min(len, end + 1 - start);
2818 
2819 		if (start < cache->last_byte_to_unpin) {
2820 			len = min(len, cache->last_byte_to_unpin - start);
2821 			if (return_free_space)
2822 				btrfs_add_free_space(cache, start, len);
2823 		}
2824 
2825 		start += len;
2826 		total_unpinned += len;
2827 		space_info = cache->space_info;
2828 
2829 		/*
2830 		 * If this space cluster has been marked as fragmented and we've
2831 		 * unpinned enough in this block group to potentially allow a
2832 		 * cluster to be created inside of it go ahead and clear the
2833 		 * fragmented check.
2834 		 */
2835 		if (cluster && cluster->fragmented &&
2836 		    total_unpinned > empty_cluster) {
2837 			spin_lock(&cluster->lock);
2838 			cluster->fragmented = 0;
2839 			spin_unlock(&cluster->lock);
2840 		}
2841 
2842 		spin_lock(&space_info->lock);
2843 		spin_lock(&cache->lock);
2844 		cache->pinned -= len;
2845 		btrfs_space_info_update_bytes_pinned(fs_info, space_info, -len);
2846 		space_info->max_extent_size = 0;
2847 		percpu_counter_add_batch(&space_info->total_bytes_pinned,
2848 			    -len, BTRFS_TOTAL_BYTES_PINNED_BATCH);
2849 		if (cache->ro) {
2850 			space_info->bytes_readonly += len;
2851 			readonly = true;
2852 		}
2853 		spin_unlock(&cache->lock);
2854 		if (!readonly && return_free_space &&
2855 		    global_rsv->space_info == space_info) {
2856 			u64 to_add = len;
2857 
2858 			spin_lock(&global_rsv->lock);
2859 			if (!global_rsv->full) {
2860 				to_add = min(len, global_rsv->size -
2861 					     global_rsv->reserved);
2862 				global_rsv->reserved += to_add;
2863 				btrfs_space_info_update_bytes_may_use(fs_info,
2864 						space_info, to_add);
2865 				if (global_rsv->reserved >= global_rsv->size)
2866 					global_rsv->full = 1;
2867 				len -= to_add;
2868 			}
2869 			spin_unlock(&global_rsv->lock);
2870 		}
2871 		/* Add to any tickets we may have */
2872 		if (!readonly && return_free_space && len)
2873 			btrfs_try_granting_tickets(fs_info, space_info);
2874 		spin_unlock(&space_info->lock);
2875 	}
2876 
2877 	if (cache)
2878 		btrfs_put_block_group(cache);
2879 	return 0;
2880 }
2881 
2882 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
2883 {
2884 	struct btrfs_fs_info *fs_info = trans->fs_info;
2885 	struct btrfs_block_group *block_group, *tmp;
2886 	struct list_head *deleted_bgs;
2887 	struct extent_io_tree *unpin;
2888 	u64 start;
2889 	u64 end;
2890 	int ret;
2891 
2892 	unpin = &trans->transaction->pinned_extents;
2893 
2894 	while (!TRANS_ABORTED(trans)) {
2895 		struct extent_state *cached_state = NULL;
2896 
2897 		mutex_lock(&fs_info->unused_bg_unpin_mutex);
2898 		ret = find_first_extent_bit(unpin, 0, &start, &end,
2899 					    EXTENT_DIRTY, &cached_state);
2900 		if (ret) {
2901 			mutex_unlock(&fs_info->unused_bg_unpin_mutex);
2902 			break;
2903 		}
2904 		if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags))
2905 			clear_extent_bits(&fs_info->excluded_extents, start,
2906 					  end, EXTENT_UPTODATE);
2907 
2908 		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
2909 			ret = btrfs_discard_extent(fs_info, start,
2910 						   end + 1 - start, NULL);
2911 
2912 		clear_extent_dirty(unpin, start, end, &cached_state);
2913 		unpin_extent_range(fs_info, start, end, true);
2914 		mutex_unlock(&fs_info->unused_bg_unpin_mutex);
2915 		free_extent_state(cached_state);
2916 		cond_resched();
2917 	}
2918 
2919 	if (btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
2920 		btrfs_discard_calc_delay(&fs_info->discard_ctl);
2921 		btrfs_discard_schedule_work(&fs_info->discard_ctl, true);
2922 	}
2923 
2924 	/*
2925 	 * Transaction is finished.  We don't need the lock anymore.  We
2926 	 * do need to clean up the block groups in case of a transaction
2927 	 * abort.
2928 	 */
2929 	deleted_bgs = &trans->transaction->deleted_bgs;
2930 	list_for_each_entry_safe(block_group, tmp, deleted_bgs, bg_list) {
2931 		u64 trimmed = 0;
2932 
2933 		ret = -EROFS;
2934 		if (!TRANS_ABORTED(trans))
2935 			ret = btrfs_discard_extent(fs_info,
2936 						   block_group->start,
2937 						   block_group->length,
2938 						   &trimmed);
2939 
2940 		list_del_init(&block_group->bg_list);
2941 		btrfs_unfreeze_block_group(block_group);
2942 		btrfs_put_block_group(block_group);
2943 
2944 		if (ret) {
2945 			const char *errstr = btrfs_decode_error(ret);
2946 			btrfs_warn(fs_info,
2947 			   "discard failed while removing blockgroup: errno=%d %s",
2948 				   ret, errstr);
2949 		}
2950 	}
2951 
2952 	return 0;
2953 }
2954 
2955 /*
2956  * Drop one or more refs of @node.
2957  *
2958  * 1. Locate the extent refs.
2959  *    It's either inline in EXTENT/METADATA_ITEM or in keyed SHARED_* item.
2960  *    Locate it, then reduce the refs number or remove the ref line completely.
2961  *
2962  * 2. Update the refs count in EXTENT/METADATA_ITEM
2963  *
2964  * Inline backref case:
2965  *
2966  * in extent tree we have:
2967  *
2968  * 	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 16201 itemsize 82
2969  *		refs 2 gen 6 flags DATA
2970  *		extent data backref root FS_TREE objectid 258 offset 0 count 1
2971  *		extent data backref root FS_TREE objectid 257 offset 0 count 1
2972  *
2973  * This function gets called with:
2974  *
2975  *    node->bytenr = 13631488
2976  *    node->num_bytes = 1048576
2977  *    root_objectid = FS_TREE
2978  *    owner_objectid = 257
2979  *    owner_offset = 0
2980  *    refs_to_drop = 1
2981  *
2982  * Then we should get some like:
2983  *
2984  * 	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 16201 itemsize 82
2985  *		refs 1 gen 6 flags DATA
2986  *		extent data backref root FS_TREE objectid 258 offset 0 count 1
2987  *
2988  * Keyed backref case:
2989  *
2990  * in extent tree we have:
2991  *
2992  *	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 3971 itemsize 24
2993  *		refs 754 gen 6 flags DATA
2994  *	[...]
2995  *	item 2 key (13631488 EXTENT_DATA_REF <HASH>) itemoff 3915 itemsize 28
2996  *		extent data backref root FS_TREE objectid 866 offset 0 count 1
2997  *
2998  * This function get called with:
2999  *
3000  *    node->bytenr = 13631488
3001  *    node->num_bytes = 1048576
3002  *    root_objectid = FS_TREE
3003  *    owner_objectid = 866
3004  *    owner_offset = 0
3005  *    refs_to_drop = 1
3006  *
3007  * Then we should get some like:
3008  *
3009  *	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 3971 itemsize 24
3010  *		refs 753 gen 6 flags DATA
3011  *
3012  * And that (13631488 EXTENT_DATA_REF <HASH>) gets removed.
3013  */
3014 static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
3015 			       struct btrfs_delayed_ref_node *node, u64 parent,
3016 			       u64 root_objectid, u64 owner_objectid,
3017 			       u64 owner_offset, int refs_to_drop,
3018 			       struct btrfs_delayed_extent_op *extent_op)
3019 {
3020 	struct btrfs_fs_info *info = trans->fs_info;
3021 	struct btrfs_key key;
3022 	struct btrfs_path *path;
3023 	struct btrfs_root *extent_root = info->extent_root;
3024 	struct extent_buffer *leaf;
3025 	struct btrfs_extent_item *ei;
3026 	struct btrfs_extent_inline_ref *iref;
3027 	int ret;
3028 	int is_data;
3029 	int extent_slot = 0;
3030 	int found_extent = 0;
3031 	int num_to_del = 1;
3032 	u32 item_size;
3033 	u64 refs;
3034 	u64 bytenr = node->bytenr;
3035 	u64 num_bytes = node->num_bytes;
3036 	int last_ref = 0;
3037 	bool skinny_metadata = btrfs_fs_incompat(info, SKINNY_METADATA);
3038 
3039 	path = btrfs_alloc_path();
3040 	if (!path)
3041 		return -ENOMEM;
3042 
3043 	path->leave_spinning = 1;
3044 
3045 	is_data = owner_objectid >= BTRFS_FIRST_FREE_OBJECTID;
3046 
3047 	if (!is_data && refs_to_drop != 1) {
3048 		btrfs_crit(info,
3049 "invalid refs_to_drop, dropping more than 1 refs for tree block %llu refs_to_drop %u",
3050 			   node->bytenr, refs_to_drop);
3051 		ret = -EINVAL;
3052 		btrfs_abort_transaction(trans, ret);
3053 		goto out;
3054 	}
3055 
3056 	if (is_data)
3057 		skinny_metadata = false;
3058 
3059 	ret = lookup_extent_backref(trans, path, &iref, bytenr, num_bytes,
3060 				    parent, root_objectid, owner_objectid,
3061 				    owner_offset);
3062 	if (ret == 0) {
3063 		/*
3064 		 * Either the inline backref or the SHARED_DATA_REF/
3065 		 * SHARED_BLOCK_REF is found
3066 		 *
3067 		 * Here is a quick path to locate EXTENT/METADATA_ITEM.
3068 		 * It's possible the EXTENT/METADATA_ITEM is near current slot.
3069 		 */
3070 		extent_slot = path->slots[0];
3071 		while (extent_slot >= 0) {
3072 			btrfs_item_key_to_cpu(path->nodes[0], &key,
3073 					      extent_slot);
3074 			if (key.objectid != bytenr)
3075 				break;
3076 			if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3077 			    key.offset == num_bytes) {
3078 				found_extent = 1;
3079 				break;
3080 			}
3081 			if (key.type == BTRFS_METADATA_ITEM_KEY &&
3082 			    key.offset == owner_objectid) {
3083 				found_extent = 1;
3084 				break;
3085 			}
3086 
3087 			/* Quick path didn't find the EXTEMT/METADATA_ITEM */
3088 			if (path->slots[0] - extent_slot > 5)
3089 				break;
3090 			extent_slot--;
3091 		}
3092 
3093 		if (!found_extent) {
3094 			if (iref) {
3095 				btrfs_crit(info,
3096 "invalid iref, no EXTENT/METADATA_ITEM found but has inline extent ref");
3097 				btrfs_abort_transaction(trans, -EUCLEAN);
3098 				goto err_dump;
3099 			}
3100 			/* Must be SHARED_* item, remove the backref first */
3101 			ret = remove_extent_backref(trans, path, NULL,
3102 						    refs_to_drop,
3103 						    is_data, &last_ref);
3104 			if (ret) {
3105 				btrfs_abort_transaction(trans, ret);
3106 				goto out;
3107 			}
3108 			btrfs_release_path(path);
3109 			path->leave_spinning = 1;
3110 
3111 			/* Slow path to locate EXTENT/METADATA_ITEM */
3112 			key.objectid = bytenr;
3113 			key.type = BTRFS_EXTENT_ITEM_KEY;
3114 			key.offset = num_bytes;
3115 
3116 			if (!is_data && skinny_metadata) {
3117 				key.type = BTRFS_METADATA_ITEM_KEY;
3118 				key.offset = owner_objectid;
3119 			}
3120 
3121 			ret = btrfs_search_slot(trans, extent_root,
3122 						&key, path, -1, 1);
3123 			if (ret > 0 && skinny_metadata && path->slots[0]) {
3124 				/*
3125 				 * Couldn't find our skinny metadata item,
3126 				 * see if we have ye olde extent item.
3127 				 */
3128 				path->slots[0]--;
3129 				btrfs_item_key_to_cpu(path->nodes[0], &key,
3130 						      path->slots[0]);
3131 				if (key.objectid == bytenr &&
3132 				    key.type == BTRFS_EXTENT_ITEM_KEY &&
3133 				    key.offset == num_bytes)
3134 					ret = 0;
3135 			}
3136 
3137 			if (ret > 0 && skinny_metadata) {
3138 				skinny_metadata = false;
3139 				key.objectid = bytenr;
3140 				key.type = BTRFS_EXTENT_ITEM_KEY;
3141 				key.offset = num_bytes;
3142 				btrfs_release_path(path);
3143 				ret = btrfs_search_slot(trans, extent_root,
3144 							&key, path, -1, 1);
3145 			}
3146 
3147 			if (ret) {
3148 				btrfs_err(info,
3149 					  "umm, got %d back from search, was looking for %llu",
3150 					  ret, bytenr);
3151 				if (ret > 0)
3152 					btrfs_print_leaf(path->nodes[0]);
3153 			}
3154 			if (ret < 0) {
3155 				btrfs_abort_transaction(trans, ret);
3156 				goto out;
3157 			}
3158 			extent_slot = path->slots[0];
3159 		}
3160 	} else if (WARN_ON(ret == -ENOENT)) {
3161 		btrfs_print_leaf(path->nodes[0]);
3162 		btrfs_err(info,
3163 			"unable to find ref byte nr %llu parent %llu root %llu  owner %llu offset %llu",
3164 			bytenr, parent, root_objectid, owner_objectid,
3165 			owner_offset);
3166 		btrfs_abort_transaction(trans, ret);
3167 		goto out;
3168 	} else {
3169 		btrfs_abort_transaction(trans, ret);
3170 		goto out;
3171 	}
3172 
3173 	leaf = path->nodes[0];
3174 	item_size = btrfs_item_size_nr(leaf, extent_slot);
3175 	if (unlikely(item_size < sizeof(*ei))) {
3176 		ret = -EINVAL;
3177 		btrfs_print_v0_err(info);
3178 		btrfs_abort_transaction(trans, ret);
3179 		goto out;
3180 	}
3181 	ei = btrfs_item_ptr(leaf, extent_slot,
3182 			    struct btrfs_extent_item);
3183 	if (owner_objectid < BTRFS_FIRST_FREE_OBJECTID &&
3184 	    key.type == BTRFS_EXTENT_ITEM_KEY) {
3185 		struct btrfs_tree_block_info *bi;
3186 		if (item_size < sizeof(*ei) + sizeof(*bi)) {
3187 			btrfs_crit(info,
3188 "invalid extent item size for key (%llu, %u, %llu) owner %llu, has %u expect >= %zu",
3189 				   key.objectid, key.type, key.offset,
3190 				   owner_objectid, item_size,
3191 				   sizeof(*ei) + sizeof(*bi));
3192 			btrfs_abort_transaction(trans, -EUCLEAN);
3193 			goto err_dump;
3194 		}
3195 		bi = (struct btrfs_tree_block_info *)(ei + 1);
3196 		WARN_ON(owner_objectid != btrfs_tree_block_level(leaf, bi));
3197 	}
3198 
3199 	refs = btrfs_extent_refs(leaf, ei);
3200 	if (refs < refs_to_drop) {
3201 		btrfs_crit(info,
3202 		"trying to drop %d refs but we only have %llu for bytenr %llu",
3203 			  refs_to_drop, refs, bytenr);
3204 		btrfs_abort_transaction(trans, -EUCLEAN);
3205 		goto err_dump;
3206 	}
3207 	refs -= refs_to_drop;
3208 
3209 	if (refs > 0) {
3210 		if (extent_op)
3211 			__run_delayed_extent_op(extent_op, leaf, ei);
3212 		/*
3213 		 * In the case of inline back ref, reference count will
3214 		 * be updated by remove_extent_backref
3215 		 */
3216 		if (iref) {
3217 			if (!found_extent) {
3218 				btrfs_crit(info,
3219 "invalid iref, got inlined extent ref but no EXTENT/METADATA_ITEM found");
3220 				btrfs_abort_transaction(trans, -EUCLEAN);
3221 				goto err_dump;
3222 			}
3223 		} else {
3224 			btrfs_set_extent_refs(leaf, ei, refs);
3225 			btrfs_mark_buffer_dirty(leaf);
3226 		}
3227 		if (found_extent) {
3228 			ret = remove_extent_backref(trans, path, iref,
3229 						    refs_to_drop, is_data,
3230 						    &last_ref);
3231 			if (ret) {
3232 				btrfs_abort_transaction(trans, ret);
3233 				goto out;
3234 			}
3235 		}
3236 	} else {
3237 		/* In this branch refs == 1 */
3238 		if (found_extent) {
3239 			if (is_data && refs_to_drop !=
3240 			    extent_data_ref_count(path, iref)) {
3241 				btrfs_crit(info,
3242 		"invalid refs_to_drop, current refs %u refs_to_drop %u",
3243 					   extent_data_ref_count(path, iref),
3244 					   refs_to_drop);
3245 				btrfs_abort_transaction(trans, -EUCLEAN);
3246 				goto err_dump;
3247 			}
3248 			if (iref) {
3249 				if (path->slots[0] != extent_slot) {
3250 					btrfs_crit(info,
3251 "invalid iref, extent item key (%llu %u %llu) doesn't have wanted iref",
3252 						   key.objectid, key.type,
3253 						   key.offset);
3254 					btrfs_abort_transaction(trans, -EUCLEAN);
3255 					goto err_dump;
3256 				}
3257 			} else {
3258 				/*
3259 				 * No inline ref, we must be at SHARED_* item,
3260 				 * And it's single ref, it must be:
3261 				 * |	extent_slot	  ||extent_slot + 1|
3262 				 * [ EXTENT/METADATA_ITEM ][ SHARED_* ITEM ]
3263 				 */
3264 				if (path->slots[0] != extent_slot + 1) {
3265 					btrfs_crit(info,
3266 	"invalid SHARED_* item, previous item is not EXTENT/METADATA_ITEM");
3267 					btrfs_abort_transaction(trans, -EUCLEAN);
3268 					goto err_dump;
3269 				}
3270 				path->slots[0] = extent_slot;
3271 				num_to_del = 2;
3272 			}
3273 		}
3274 
3275 		last_ref = 1;
3276 		ret = btrfs_del_items(trans, extent_root, path, path->slots[0],
3277 				      num_to_del);
3278 		if (ret) {
3279 			btrfs_abort_transaction(trans, ret);
3280 			goto out;
3281 		}
3282 		btrfs_release_path(path);
3283 
3284 		if (is_data) {
3285 			ret = btrfs_del_csums(trans, info->csum_root, bytenr,
3286 					      num_bytes);
3287 			if (ret) {
3288 				btrfs_abort_transaction(trans, ret);
3289 				goto out;
3290 			}
3291 		}
3292 
3293 		ret = add_to_free_space_tree(trans, bytenr, num_bytes);
3294 		if (ret) {
3295 			btrfs_abort_transaction(trans, ret);
3296 			goto out;
3297 		}
3298 
3299 		ret = btrfs_update_block_group(trans, bytenr, num_bytes, 0);
3300 		if (ret) {
3301 			btrfs_abort_transaction(trans, ret);
3302 			goto out;
3303 		}
3304 	}
3305 	btrfs_release_path(path);
3306 
3307 out:
3308 	btrfs_free_path(path);
3309 	return ret;
3310 err_dump:
3311 	/*
3312 	 * Leaf dump can take up a lot of log buffer, so we only do full leaf
3313 	 * dump for debug build.
3314 	 */
3315 	if (IS_ENABLED(CONFIG_BTRFS_DEBUG)) {
3316 		btrfs_crit(info, "path->slots[0]=%d extent_slot=%d",
3317 			   path->slots[0], extent_slot);
3318 		btrfs_print_leaf(path->nodes[0]);
3319 	}
3320 
3321 	btrfs_free_path(path);
3322 	return -EUCLEAN;
3323 }
3324 
3325 /*
3326  * when we free an block, it is possible (and likely) that we free the last
3327  * delayed ref for that extent as well.  This searches the delayed ref tree for
3328  * a given extent, and if there are no other delayed refs to be processed, it
3329  * removes it from the tree.
3330  */
3331 static noinline int check_ref_cleanup(struct btrfs_trans_handle *trans,
3332 				      u64 bytenr)
3333 {
3334 	struct btrfs_delayed_ref_head *head;
3335 	struct btrfs_delayed_ref_root *delayed_refs;
3336 	int ret = 0;
3337 
3338 	delayed_refs = &trans->transaction->delayed_refs;
3339 	spin_lock(&delayed_refs->lock);
3340 	head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
3341 	if (!head)
3342 		goto out_delayed_unlock;
3343 
3344 	spin_lock(&head->lock);
3345 	if (!RB_EMPTY_ROOT(&head->ref_tree.rb_root))
3346 		goto out;
3347 
3348 	if (cleanup_extent_op(head) != NULL)
3349 		goto out;
3350 
3351 	/*
3352 	 * waiting for the lock here would deadlock.  If someone else has it
3353 	 * locked they are already in the process of dropping it anyway
3354 	 */
3355 	if (!mutex_trylock(&head->mutex))
3356 		goto out;
3357 
3358 	btrfs_delete_ref_head(delayed_refs, head);
3359 	head->processing = 0;
3360 
3361 	spin_unlock(&head->lock);
3362 	spin_unlock(&delayed_refs->lock);
3363 
3364 	BUG_ON(head->extent_op);
3365 	if (head->must_insert_reserved)
3366 		ret = 1;
3367 
3368 	btrfs_cleanup_ref_head_accounting(trans->fs_info, delayed_refs, head);
3369 	mutex_unlock(&head->mutex);
3370 	btrfs_put_delayed_ref_head(head);
3371 	return ret;
3372 out:
3373 	spin_unlock(&head->lock);
3374 
3375 out_delayed_unlock:
3376 	spin_unlock(&delayed_refs->lock);
3377 	return 0;
3378 }
3379 
3380 void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
3381 			   struct btrfs_root *root,
3382 			   struct extent_buffer *buf,
3383 			   u64 parent, int last_ref)
3384 {
3385 	struct btrfs_fs_info *fs_info = root->fs_info;
3386 	struct btrfs_ref generic_ref = { 0 };
3387 	int pin = 1;
3388 	int ret;
3389 
3390 	btrfs_init_generic_ref(&generic_ref, BTRFS_DROP_DELAYED_REF,
3391 			       buf->start, buf->len, parent);
3392 	btrfs_init_tree_ref(&generic_ref, btrfs_header_level(buf),
3393 			    root->root_key.objectid);
3394 
3395 	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
3396 		int old_ref_mod, new_ref_mod;
3397 
3398 		btrfs_ref_tree_mod(fs_info, &generic_ref);
3399 		ret = btrfs_add_delayed_tree_ref(trans, &generic_ref, NULL,
3400 						 &old_ref_mod, &new_ref_mod);
3401 		BUG_ON(ret); /* -ENOMEM */
3402 		pin = old_ref_mod >= 0 && new_ref_mod < 0;
3403 	}
3404 
3405 	if (last_ref && btrfs_header_generation(buf) == trans->transid) {
3406 		struct btrfs_block_group *cache;
3407 
3408 		if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
3409 			ret = check_ref_cleanup(trans, buf->start);
3410 			if (!ret)
3411 				goto out;
3412 		}
3413 
3414 		pin = 0;
3415 		cache = btrfs_lookup_block_group(fs_info, buf->start);
3416 
3417 		if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
3418 			pin_down_extent(trans, cache, buf->start, buf->len, 1);
3419 			btrfs_put_block_group(cache);
3420 			goto out;
3421 		}
3422 
3423 		WARN_ON(test_bit(EXTENT_BUFFER_DIRTY, &buf->bflags));
3424 
3425 		btrfs_add_free_space(cache, buf->start, buf->len);
3426 		btrfs_free_reserved_bytes(cache, buf->len, 0);
3427 		btrfs_put_block_group(cache);
3428 		trace_btrfs_reserved_extent_free(fs_info, buf->start, buf->len);
3429 	}
3430 out:
3431 	if (pin)
3432 		add_pinned_bytes(fs_info, &generic_ref);
3433 
3434 	if (last_ref) {
3435 		/*
3436 		 * Deleting the buffer, clear the corrupt flag since it doesn't
3437 		 * matter anymore.
3438 		 */
3439 		clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
3440 	}
3441 }
3442 
3443 /* Can return -ENOMEM */
3444 int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_ref *ref)
3445 {
3446 	struct btrfs_fs_info *fs_info = trans->fs_info;
3447 	int old_ref_mod, new_ref_mod;
3448 	int ret;
3449 
3450 	if (btrfs_is_testing(fs_info))
3451 		return 0;
3452 
3453 	/*
3454 	 * tree log blocks never actually go into the extent allocation
3455 	 * tree, just update pinning info and exit early.
3456 	 */
3457 	if ((ref->type == BTRFS_REF_METADATA &&
3458 	     ref->tree_ref.root == BTRFS_TREE_LOG_OBJECTID) ||
3459 	    (ref->type == BTRFS_REF_DATA &&
3460 	     ref->data_ref.ref_root == BTRFS_TREE_LOG_OBJECTID)) {
3461 		/* unlocks the pinned mutex */
3462 		btrfs_pin_extent(trans, ref->bytenr, ref->len, 1);
3463 		old_ref_mod = new_ref_mod = 0;
3464 		ret = 0;
3465 	} else if (ref->type == BTRFS_REF_METADATA) {
3466 		ret = btrfs_add_delayed_tree_ref(trans, ref, NULL,
3467 						 &old_ref_mod, &new_ref_mod);
3468 	} else {
3469 		ret = btrfs_add_delayed_data_ref(trans, ref, 0,
3470 						 &old_ref_mod, &new_ref_mod);
3471 	}
3472 
3473 	if (!((ref->type == BTRFS_REF_METADATA &&
3474 	       ref->tree_ref.root == BTRFS_TREE_LOG_OBJECTID) ||
3475 	      (ref->type == BTRFS_REF_DATA &&
3476 	       ref->data_ref.ref_root == BTRFS_TREE_LOG_OBJECTID)))
3477 		btrfs_ref_tree_mod(fs_info, ref);
3478 
3479 	if (ret == 0 && old_ref_mod >= 0 && new_ref_mod < 0)
3480 		add_pinned_bytes(fs_info, ref);
3481 
3482 	return ret;
3483 }
3484 
3485 enum btrfs_loop_type {
3486 	LOOP_CACHING_NOWAIT,
3487 	LOOP_CACHING_WAIT,
3488 	LOOP_ALLOC_CHUNK,
3489 	LOOP_NO_EMPTY_SIZE,
3490 };
3491 
3492 static inline void
3493 btrfs_lock_block_group(struct btrfs_block_group *cache,
3494 		       int delalloc)
3495 {
3496 	if (delalloc)
3497 		down_read(&cache->data_rwsem);
3498 }
3499 
3500 static inline void btrfs_grab_block_group(struct btrfs_block_group *cache,
3501 		       int delalloc)
3502 {
3503 	btrfs_get_block_group(cache);
3504 	if (delalloc)
3505 		down_read(&cache->data_rwsem);
3506 }
3507 
3508 static struct btrfs_block_group *btrfs_lock_cluster(
3509 		   struct btrfs_block_group *block_group,
3510 		   struct btrfs_free_cluster *cluster,
3511 		   int delalloc)
3512 	__acquires(&cluster->refill_lock)
3513 {
3514 	struct btrfs_block_group *used_bg = NULL;
3515 
3516 	spin_lock(&cluster->refill_lock);
3517 	while (1) {
3518 		used_bg = cluster->block_group;
3519 		if (!used_bg)
3520 			return NULL;
3521 
3522 		if (used_bg == block_group)
3523 			return used_bg;
3524 
3525 		btrfs_get_block_group(used_bg);
3526 
3527 		if (!delalloc)
3528 			return used_bg;
3529 
3530 		if (down_read_trylock(&used_bg->data_rwsem))
3531 			return used_bg;
3532 
3533 		spin_unlock(&cluster->refill_lock);
3534 
3535 		/* We should only have one-level nested. */
3536 		down_read_nested(&used_bg->data_rwsem, SINGLE_DEPTH_NESTING);
3537 
3538 		spin_lock(&cluster->refill_lock);
3539 		if (used_bg == cluster->block_group)
3540 			return used_bg;
3541 
3542 		up_read(&used_bg->data_rwsem);
3543 		btrfs_put_block_group(used_bg);
3544 	}
3545 }
3546 
3547 static inline void
3548 btrfs_release_block_group(struct btrfs_block_group *cache,
3549 			 int delalloc)
3550 {
3551 	if (delalloc)
3552 		up_read(&cache->data_rwsem);
3553 	btrfs_put_block_group(cache);
3554 }
3555 
3556 enum btrfs_extent_allocation_policy {
3557 	BTRFS_EXTENT_ALLOC_CLUSTERED,
3558 };
3559 
3560 /*
3561  * Structure used internally for find_free_extent() function.  Wraps needed
3562  * parameters.
3563  */
3564 struct find_free_extent_ctl {
3565 	/* Basic allocation info */
3566 	u64 num_bytes;
3567 	u64 empty_size;
3568 	u64 flags;
3569 	int delalloc;
3570 
3571 	/* Where to start the search inside the bg */
3572 	u64 search_start;
3573 
3574 	/* For clustered allocation */
3575 	u64 empty_cluster;
3576 	struct btrfs_free_cluster *last_ptr;
3577 	bool use_cluster;
3578 
3579 	bool have_caching_bg;
3580 	bool orig_have_caching_bg;
3581 
3582 	/* RAID index, converted from flags */
3583 	int index;
3584 
3585 	/*
3586 	 * Current loop number, check find_free_extent_update_loop() for details
3587 	 */
3588 	int loop;
3589 
3590 	/*
3591 	 * Whether we're refilling a cluster, if true we need to re-search
3592 	 * current block group but don't try to refill the cluster again.
3593 	 */
3594 	bool retry_clustered;
3595 
3596 	/*
3597 	 * Whether we're updating free space cache, if true we need to re-search
3598 	 * current block group but don't try updating free space cache again.
3599 	 */
3600 	bool retry_unclustered;
3601 
3602 	/* If current block group is cached */
3603 	int cached;
3604 
3605 	/* Max contiguous hole found */
3606 	u64 max_extent_size;
3607 
3608 	/* Total free space from free space cache, not always contiguous */
3609 	u64 total_free_space;
3610 
3611 	/* Found result */
3612 	u64 found_offset;
3613 
3614 	/* Hint where to start looking for an empty space */
3615 	u64 hint_byte;
3616 
3617 	/* Allocation policy */
3618 	enum btrfs_extent_allocation_policy policy;
3619 };
3620 
3621 
3622 /*
3623  * Helper function for find_free_extent().
3624  *
3625  * Return -ENOENT to inform caller that we need fallback to unclustered mode.
3626  * Return -EAGAIN to inform caller that we need to re-search this block group
3627  * Return >0 to inform caller that we find nothing
3628  * Return 0 means we have found a location and set ffe_ctl->found_offset.
3629  */
3630 static int find_free_extent_clustered(struct btrfs_block_group *bg,
3631 				      struct find_free_extent_ctl *ffe_ctl,
3632 				      struct btrfs_block_group **cluster_bg_ret)
3633 {
3634 	struct btrfs_block_group *cluster_bg;
3635 	struct btrfs_free_cluster *last_ptr = ffe_ctl->last_ptr;
3636 	u64 aligned_cluster;
3637 	u64 offset;
3638 	int ret;
3639 
3640 	cluster_bg = btrfs_lock_cluster(bg, last_ptr, ffe_ctl->delalloc);
3641 	if (!cluster_bg)
3642 		goto refill_cluster;
3643 	if (cluster_bg != bg && (cluster_bg->ro ||
3644 	    !block_group_bits(cluster_bg, ffe_ctl->flags)))
3645 		goto release_cluster;
3646 
3647 	offset = btrfs_alloc_from_cluster(cluster_bg, last_ptr,
3648 			ffe_ctl->num_bytes, cluster_bg->start,
3649 			&ffe_ctl->max_extent_size);
3650 	if (offset) {
3651 		/* We have a block, we're done */
3652 		spin_unlock(&last_ptr->refill_lock);
3653 		trace_btrfs_reserve_extent_cluster(cluster_bg,
3654 				ffe_ctl->search_start, ffe_ctl->num_bytes);
3655 		*cluster_bg_ret = cluster_bg;
3656 		ffe_ctl->found_offset = offset;
3657 		return 0;
3658 	}
3659 	WARN_ON(last_ptr->block_group != cluster_bg);
3660 
3661 release_cluster:
3662 	/*
3663 	 * If we are on LOOP_NO_EMPTY_SIZE, we can't set up a new clusters, so
3664 	 * lets just skip it and let the allocator find whatever block it can
3665 	 * find. If we reach this point, we will have tried the cluster
3666 	 * allocator plenty of times and not have found anything, so we are
3667 	 * likely way too fragmented for the clustering stuff to find anything.
3668 	 *
3669 	 * However, if the cluster is taken from the current block group,
3670 	 * release the cluster first, so that we stand a better chance of
3671 	 * succeeding in the unclustered allocation.
3672 	 */
3673 	if (ffe_ctl->loop >= LOOP_NO_EMPTY_SIZE && cluster_bg != bg) {
3674 		spin_unlock(&last_ptr->refill_lock);
3675 		btrfs_release_block_group(cluster_bg, ffe_ctl->delalloc);
3676 		return -ENOENT;
3677 	}
3678 
3679 	/* This cluster didn't work out, free it and start over */
3680 	btrfs_return_cluster_to_free_space(NULL, last_ptr);
3681 
3682 	if (cluster_bg != bg)
3683 		btrfs_release_block_group(cluster_bg, ffe_ctl->delalloc);
3684 
3685 refill_cluster:
3686 	if (ffe_ctl->loop >= LOOP_NO_EMPTY_SIZE) {
3687 		spin_unlock(&last_ptr->refill_lock);
3688 		return -ENOENT;
3689 	}
3690 
3691 	aligned_cluster = max_t(u64,
3692 			ffe_ctl->empty_cluster + ffe_ctl->empty_size,
3693 			bg->full_stripe_len);
3694 	ret = btrfs_find_space_cluster(bg, last_ptr, ffe_ctl->search_start,
3695 			ffe_ctl->num_bytes, aligned_cluster);
3696 	if (ret == 0) {
3697 		/* Now pull our allocation out of this cluster */
3698 		offset = btrfs_alloc_from_cluster(bg, last_ptr,
3699 				ffe_ctl->num_bytes, ffe_ctl->search_start,
3700 				&ffe_ctl->max_extent_size);
3701 		if (offset) {
3702 			/* We found one, proceed */
3703 			spin_unlock(&last_ptr->refill_lock);
3704 			trace_btrfs_reserve_extent_cluster(bg,
3705 					ffe_ctl->search_start,
3706 					ffe_ctl->num_bytes);
3707 			ffe_ctl->found_offset = offset;
3708 			return 0;
3709 		}
3710 	} else if (!ffe_ctl->cached && ffe_ctl->loop > LOOP_CACHING_NOWAIT &&
3711 		   !ffe_ctl->retry_clustered) {
3712 		spin_unlock(&last_ptr->refill_lock);
3713 
3714 		ffe_ctl->retry_clustered = true;
3715 		btrfs_wait_block_group_cache_progress(bg, ffe_ctl->num_bytes +
3716 				ffe_ctl->empty_cluster + ffe_ctl->empty_size);
3717 		return -EAGAIN;
3718 	}
3719 	/*
3720 	 * At this point we either didn't find a cluster or we weren't able to
3721 	 * allocate a block from our cluster.  Free the cluster we've been
3722 	 * trying to use, and go to the next block group.
3723 	 */
3724 	btrfs_return_cluster_to_free_space(NULL, last_ptr);
3725 	spin_unlock(&last_ptr->refill_lock);
3726 	return 1;
3727 }
3728 
3729 /*
3730  * Return >0 to inform caller that we find nothing
3731  * Return 0 when we found an free extent and set ffe_ctrl->found_offset
3732  * Return -EAGAIN to inform caller that we need to re-search this block group
3733  */
3734 static int find_free_extent_unclustered(struct btrfs_block_group *bg,
3735 					struct find_free_extent_ctl *ffe_ctl)
3736 {
3737 	struct btrfs_free_cluster *last_ptr = ffe_ctl->last_ptr;
3738 	u64 offset;
3739 
3740 	/*
3741 	 * We are doing an unclustered allocation, set the fragmented flag so
3742 	 * we don't bother trying to setup a cluster again until we get more
3743 	 * space.
3744 	 */
3745 	if (unlikely(last_ptr)) {
3746 		spin_lock(&last_ptr->lock);
3747 		last_ptr->fragmented = 1;
3748 		spin_unlock(&last_ptr->lock);
3749 	}
3750 	if (ffe_ctl->cached) {
3751 		struct btrfs_free_space_ctl *free_space_ctl;
3752 
3753 		free_space_ctl = bg->free_space_ctl;
3754 		spin_lock(&free_space_ctl->tree_lock);
3755 		if (free_space_ctl->free_space <
3756 		    ffe_ctl->num_bytes + ffe_ctl->empty_cluster +
3757 		    ffe_ctl->empty_size) {
3758 			ffe_ctl->total_free_space = max_t(u64,
3759 					ffe_ctl->total_free_space,
3760 					free_space_ctl->free_space);
3761 			spin_unlock(&free_space_ctl->tree_lock);
3762 			return 1;
3763 		}
3764 		spin_unlock(&free_space_ctl->tree_lock);
3765 	}
3766 
3767 	offset = btrfs_find_space_for_alloc(bg, ffe_ctl->search_start,
3768 			ffe_ctl->num_bytes, ffe_ctl->empty_size,
3769 			&ffe_ctl->max_extent_size);
3770 
3771 	/*
3772 	 * If we didn't find a chunk, and we haven't failed on this block group
3773 	 * before, and this block group is in the middle of caching and we are
3774 	 * ok with waiting, then go ahead and wait for progress to be made, and
3775 	 * set @retry_unclustered to true.
3776 	 *
3777 	 * If @retry_unclustered is true then we've already waited on this
3778 	 * block group once and should move on to the next block group.
3779 	 */
3780 	if (!offset && !ffe_ctl->retry_unclustered && !ffe_ctl->cached &&
3781 	    ffe_ctl->loop > LOOP_CACHING_NOWAIT) {
3782 		btrfs_wait_block_group_cache_progress(bg, ffe_ctl->num_bytes +
3783 						      ffe_ctl->empty_size);
3784 		ffe_ctl->retry_unclustered = true;
3785 		return -EAGAIN;
3786 	} else if (!offset) {
3787 		return 1;
3788 	}
3789 	ffe_ctl->found_offset = offset;
3790 	return 0;
3791 }
3792 
3793 static int do_allocation_clustered(struct btrfs_block_group *block_group,
3794 				   struct find_free_extent_ctl *ffe_ctl,
3795 				   struct btrfs_block_group **bg_ret)
3796 {
3797 	int ret;
3798 
3799 	/* We want to try and use the cluster allocator, so lets look there */
3800 	if (ffe_ctl->last_ptr && ffe_ctl->use_cluster) {
3801 		ret = find_free_extent_clustered(block_group, ffe_ctl, bg_ret);
3802 		if (ret >= 0 || ret == -EAGAIN)
3803 			return ret;
3804 		/* ret == -ENOENT case falls through */
3805 	}
3806 
3807 	return find_free_extent_unclustered(block_group, ffe_ctl);
3808 }
3809 
3810 static int do_allocation(struct btrfs_block_group *block_group,
3811 			 struct find_free_extent_ctl *ffe_ctl,
3812 			 struct btrfs_block_group **bg_ret)
3813 {
3814 	switch (ffe_ctl->policy) {
3815 	case BTRFS_EXTENT_ALLOC_CLUSTERED:
3816 		return do_allocation_clustered(block_group, ffe_ctl, bg_ret);
3817 	default:
3818 		BUG();
3819 	}
3820 }
3821 
3822 static void release_block_group(struct btrfs_block_group *block_group,
3823 				struct find_free_extent_ctl *ffe_ctl,
3824 				int delalloc)
3825 {
3826 	switch (ffe_ctl->policy) {
3827 	case BTRFS_EXTENT_ALLOC_CLUSTERED:
3828 		ffe_ctl->retry_clustered = false;
3829 		ffe_ctl->retry_unclustered = false;
3830 		break;
3831 	default:
3832 		BUG();
3833 	}
3834 
3835 	BUG_ON(btrfs_bg_flags_to_raid_index(block_group->flags) !=
3836 	       ffe_ctl->index);
3837 	btrfs_release_block_group(block_group, delalloc);
3838 }
3839 
3840 static void found_extent_clustered(struct find_free_extent_ctl *ffe_ctl,
3841 				   struct btrfs_key *ins)
3842 {
3843 	struct btrfs_free_cluster *last_ptr = ffe_ctl->last_ptr;
3844 
3845 	if (!ffe_ctl->use_cluster && last_ptr) {
3846 		spin_lock(&last_ptr->lock);
3847 		last_ptr->window_start = ins->objectid;
3848 		spin_unlock(&last_ptr->lock);
3849 	}
3850 }
3851 
3852 static void found_extent(struct find_free_extent_ctl *ffe_ctl,
3853 			 struct btrfs_key *ins)
3854 {
3855 	switch (ffe_ctl->policy) {
3856 	case BTRFS_EXTENT_ALLOC_CLUSTERED:
3857 		found_extent_clustered(ffe_ctl, ins);
3858 		break;
3859 	default:
3860 		BUG();
3861 	}
3862 }
3863 
3864 static int chunk_allocation_failed(struct find_free_extent_ctl *ffe_ctl)
3865 {
3866 	switch (ffe_ctl->policy) {
3867 	case BTRFS_EXTENT_ALLOC_CLUSTERED:
3868 		/*
3869 		 * If we can't allocate a new chunk we've already looped through
3870 		 * at least once, move on to the NO_EMPTY_SIZE case.
3871 		 */
3872 		ffe_ctl->loop = LOOP_NO_EMPTY_SIZE;
3873 		return 0;
3874 	default:
3875 		BUG();
3876 	}
3877 }
3878 
3879 /*
3880  * Return >0 means caller needs to re-search for free extent
3881  * Return 0 means we have the needed free extent.
3882  * Return <0 means we failed to locate any free extent.
3883  */
3884 static int find_free_extent_update_loop(struct btrfs_fs_info *fs_info,
3885 					struct btrfs_key *ins,
3886 					struct find_free_extent_ctl *ffe_ctl,
3887 					bool full_search)
3888 {
3889 	struct btrfs_root *root = fs_info->extent_root;
3890 	int ret;
3891 
3892 	if ((ffe_ctl->loop == LOOP_CACHING_NOWAIT) &&
3893 	    ffe_ctl->have_caching_bg && !ffe_ctl->orig_have_caching_bg)
3894 		ffe_ctl->orig_have_caching_bg = true;
3895 
3896 	if (!ins->objectid && ffe_ctl->loop >= LOOP_CACHING_WAIT &&
3897 	    ffe_ctl->have_caching_bg)
3898 		return 1;
3899 
3900 	if (!ins->objectid && ++(ffe_ctl->index) < BTRFS_NR_RAID_TYPES)
3901 		return 1;
3902 
3903 	if (ins->objectid) {
3904 		found_extent(ffe_ctl, ins);
3905 		return 0;
3906 	}
3907 
3908 	/*
3909 	 * LOOP_CACHING_NOWAIT, search partially cached block groups, kicking
3910 	 *			caching kthreads as we move along
3911 	 * LOOP_CACHING_WAIT, search everything, and wait if our bg is caching
3912 	 * LOOP_ALLOC_CHUNK, force a chunk allocation and try again
3913 	 * LOOP_NO_EMPTY_SIZE, set empty_size and empty_cluster to 0 and try
3914 	 *		       again
3915 	 */
3916 	if (ffe_ctl->loop < LOOP_NO_EMPTY_SIZE) {
3917 		ffe_ctl->index = 0;
3918 		if (ffe_ctl->loop == LOOP_CACHING_NOWAIT) {
3919 			/*
3920 			 * We want to skip the LOOP_CACHING_WAIT step if we
3921 			 * don't have any uncached bgs and we've already done a
3922 			 * full search through.
3923 			 */
3924 			if (ffe_ctl->orig_have_caching_bg || !full_search)
3925 				ffe_ctl->loop = LOOP_CACHING_WAIT;
3926 			else
3927 				ffe_ctl->loop = LOOP_ALLOC_CHUNK;
3928 		} else {
3929 			ffe_ctl->loop++;
3930 		}
3931 
3932 		if (ffe_ctl->loop == LOOP_ALLOC_CHUNK) {
3933 			struct btrfs_trans_handle *trans;
3934 			int exist = 0;
3935 
3936 			trans = current->journal_info;
3937 			if (trans)
3938 				exist = 1;
3939 			else
3940 				trans = btrfs_join_transaction(root);
3941 
3942 			if (IS_ERR(trans)) {
3943 				ret = PTR_ERR(trans);
3944 				return ret;
3945 			}
3946 
3947 			ret = btrfs_chunk_alloc(trans, ffe_ctl->flags,
3948 						CHUNK_ALLOC_FORCE);
3949 
3950 			/* Do not bail out on ENOSPC since we can do more. */
3951 			if (ret == -ENOSPC)
3952 				ret = chunk_allocation_failed(ffe_ctl);
3953 			else if (ret < 0)
3954 				btrfs_abort_transaction(trans, ret);
3955 			else
3956 				ret = 0;
3957 			if (!exist)
3958 				btrfs_end_transaction(trans);
3959 			if (ret)
3960 				return ret;
3961 		}
3962 
3963 		if (ffe_ctl->loop == LOOP_NO_EMPTY_SIZE) {
3964 			if (ffe_ctl->policy != BTRFS_EXTENT_ALLOC_CLUSTERED)
3965 				return -ENOSPC;
3966 
3967 			/*
3968 			 * Don't loop again if we already have no empty_size and
3969 			 * no empty_cluster.
3970 			 */
3971 			if (ffe_ctl->empty_size == 0 &&
3972 			    ffe_ctl->empty_cluster == 0)
3973 				return -ENOSPC;
3974 			ffe_ctl->empty_size = 0;
3975 			ffe_ctl->empty_cluster = 0;
3976 		}
3977 		return 1;
3978 	}
3979 	return -ENOSPC;
3980 }
3981 
3982 static int prepare_allocation_clustered(struct btrfs_fs_info *fs_info,
3983 					struct find_free_extent_ctl *ffe_ctl,
3984 					struct btrfs_space_info *space_info,
3985 					struct btrfs_key *ins)
3986 {
3987 	/*
3988 	 * If our free space is heavily fragmented we may not be able to make
3989 	 * big contiguous allocations, so instead of doing the expensive search
3990 	 * for free space, simply return ENOSPC with our max_extent_size so we
3991 	 * can go ahead and search for a more manageable chunk.
3992 	 *
3993 	 * If our max_extent_size is large enough for our allocation simply
3994 	 * disable clustering since we will likely not be able to find enough
3995 	 * space to create a cluster and induce latency trying.
3996 	 */
3997 	if (space_info->max_extent_size) {
3998 		spin_lock(&space_info->lock);
3999 		if (space_info->max_extent_size &&
4000 		    ffe_ctl->num_bytes > space_info->max_extent_size) {
4001 			ins->offset = space_info->max_extent_size;
4002 			spin_unlock(&space_info->lock);
4003 			return -ENOSPC;
4004 		} else if (space_info->max_extent_size) {
4005 			ffe_ctl->use_cluster = false;
4006 		}
4007 		spin_unlock(&space_info->lock);
4008 	}
4009 
4010 	ffe_ctl->last_ptr = fetch_cluster_info(fs_info, space_info,
4011 					       &ffe_ctl->empty_cluster);
4012 	if (ffe_ctl->last_ptr) {
4013 		struct btrfs_free_cluster *last_ptr = ffe_ctl->last_ptr;
4014 
4015 		spin_lock(&last_ptr->lock);
4016 		if (last_ptr->block_group)
4017 			ffe_ctl->hint_byte = last_ptr->window_start;
4018 		if (last_ptr->fragmented) {
4019 			/*
4020 			 * We still set window_start so we can keep track of the
4021 			 * last place we found an allocation to try and save
4022 			 * some time.
4023 			 */
4024 			ffe_ctl->hint_byte = last_ptr->window_start;
4025 			ffe_ctl->use_cluster = false;
4026 		}
4027 		spin_unlock(&last_ptr->lock);
4028 	}
4029 
4030 	return 0;
4031 }
4032 
4033 static int prepare_allocation(struct btrfs_fs_info *fs_info,
4034 			      struct find_free_extent_ctl *ffe_ctl,
4035 			      struct btrfs_space_info *space_info,
4036 			      struct btrfs_key *ins)
4037 {
4038 	switch (ffe_ctl->policy) {
4039 	case BTRFS_EXTENT_ALLOC_CLUSTERED:
4040 		return prepare_allocation_clustered(fs_info, ffe_ctl,
4041 						    space_info, ins);
4042 	default:
4043 		BUG();
4044 	}
4045 }
4046 
4047 /*
4048  * walks the btree of allocated extents and find a hole of a given size.
4049  * The key ins is changed to record the hole:
4050  * ins->objectid == start position
4051  * ins->flags = BTRFS_EXTENT_ITEM_KEY
4052  * ins->offset == the size of the hole.
4053  * Any available blocks before search_start are skipped.
4054  *
4055  * If there is no suitable free space, we will record the max size of
4056  * the free space extent currently.
4057  *
4058  * The overall logic and call chain:
4059  *
4060  * find_free_extent()
4061  * |- Iterate through all block groups
4062  * |  |- Get a valid block group
4063  * |  |- Try to do clustered allocation in that block group
4064  * |  |- Try to do unclustered allocation in that block group
4065  * |  |- Check if the result is valid
4066  * |  |  |- If valid, then exit
4067  * |  |- Jump to next block group
4068  * |
4069  * |- Push harder to find free extents
4070  *    |- If not found, re-iterate all block groups
4071  */
4072 static noinline int find_free_extent(struct btrfs_root *root,
4073 				u64 ram_bytes, u64 num_bytes, u64 empty_size,
4074 				u64 hint_byte_orig, struct btrfs_key *ins,
4075 				u64 flags, int delalloc)
4076 {
4077 	struct btrfs_fs_info *fs_info = root->fs_info;
4078 	int ret = 0;
4079 	int cache_block_group_error = 0;
4080 	struct btrfs_block_group *block_group = NULL;
4081 	struct find_free_extent_ctl ffe_ctl = {0};
4082 	struct btrfs_space_info *space_info;
4083 	bool full_search = false;
4084 
4085 	WARN_ON(num_bytes < fs_info->sectorsize);
4086 
4087 	ffe_ctl.num_bytes = num_bytes;
4088 	ffe_ctl.empty_size = empty_size;
4089 	ffe_ctl.flags = flags;
4090 	ffe_ctl.search_start = 0;
4091 	ffe_ctl.delalloc = delalloc;
4092 	ffe_ctl.index = btrfs_bg_flags_to_raid_index(flags);
4093 	ffe_ctl.have_caching_bg = false;
4094 	ffe_ctl.orig_have_caching_bg = false;
4095 	ffe_ctl.found_offset = 0;
4096 	ffe_ctl.hint_byte = hint_byte_orig;
4097 	ffe_ctl.policy = BTRFS_EXTENT_ALLOC_CLUSTERED;
4098 
4099 	/* For clustered allocation */
4100 	ffe_ctl.retry_clustered = false;
4101 	ffe_ctl.retry_unclustered = false;
4102 	ffe_ctl.last_ptr = NULL;
4103 	ffe_ctl.use_cluster = true;
4104 
4105 	ins->type = BTRFS_EXTENT_ITEM_KEY;
4106 	ins->objectid = 0;
4107 	ins->offset = 0;
4108 
4109 	trace_find_free_extent(root, num_bytes, empty_size, flags);
4110 
4111 	space_info = btrfs_find_space_info(fs_info, flags);
4112 	if (!space_info) {
4113 		btrfs_err(fs_info, "No space info for %llu", flags);
4114 		return -ENOSPC;
4115 	}
4116 
4117 	ret = prepare_allocation(fs_info, &ffe_ctl, space_info, ins);
4118 	if (ret < 0)
4119 		return ret;
4120 
4121 	ffe_ctl.search_start = max(ffe_ctl.search_start,
4122 				   first_logical_byte(fs_info, 0));
4123 	ffe_ctl.search_start = max(ffe_ctl.search_start, ffe_ctl.hint_byte);
4124 	if (ffe_ctl.search_start == ffe_ctl.hint_byte) {
4125 		block_group = btrfs_lookup_block_group(fs_info,
4126 						       ffe_ctl.search_start);
4127 		/*
4128 		 * we don't want to use the block group if it doesn't match our
4129 		 * allocation bits, or if its not cached.
4130 		 *
4131 		 * However if we are re-searching with an ideal block group
4132 		 * picked out then we don't care that the block group is cached.
4133 		 */
4134 		if (block_group && block_group_bits(block_group, flags) &&
4135 		    block_group->cached != BTRFS_CACHE_NO) {
4136 			down_read(&space_info->groups_sem);
4137 			if (list_empty(&block_group->list) ||
4138 			    block_group->ro) {
4139 				/*
4140 				 * someone is removing this block group,
4141 				 * we can't jump into the have_block_group
4142 				 * target because our list pointers are not
4143 				 * valid
4144 				 */
4145 				btrfs_put_block_group(block_group);
4146 				up_read(&space_info->groups_sem);
4147 			} else {
4148 				ffe_ctl.index = btrfs_bg_flags_to_raid_index(
4149 						block_group->flags);
4150 				btrfs_lock_block_group(block_group, delalloc);
4151 				goto have_block_group;
4152 			}
4153 		} else if (block_group) {
4154 			btrfs_put_block_group(block_group);
4155 		}
4156 	}
4157 search:
4158 	ffe_ctl.have_caching_bg = false;
4159 	if (ffe_ctl.index == btrfs_bg_flags_to_raid_index(flags) ||
4160 	    ffe_ctl.index == 0)
4161 		full_search = true;
4162 	down_read(&space_info->groups_sem);
4163 	list_for_each_entry(block_group,
4164 			    &space_info->block_groups[ffe_ctl.index], list) {
4165 		struct btrfs_block_group *bg_ret;
4166 
4167 		/* If the block group is read-only, we can skip it entirely. */
4168 		if (unlikely(block_group->ro))
4169 			continue;
4170 
4171 		btrfs_grab_block_group(block_group, delalloc);
4172 		ffe_ctl.search_start = block_group->start;
4173 
4174 		/*
4175 		 * this can happen if we end up cycling through all the
4176 		 * raid types, but we want to make sure we only allocate
4177 		 * for the proper type.
4178 		 */
4179 		if (!block_group_bits(block_group, flags)) {
4180 			u64 extra = BTRFS_BLOCK_GROUP_DUP |
4181 				BTRFS_BLOCK_GROUP_RAID1_MASK |
4182 				BTRFS_BLOCK_GROUP_RAID56_MASK |
4183 				BTRFS_BLOCK_GROUP_RAID10;
4184 
4185 			/*
4186 			 * if they asked for extra copies and this block group
4187 			 * doesn't provide them, bail.  This does allow us to
4188 			 * fill raid0 from raid1.
4189 			 */
4190 			if ((flags & extra) && !(block_group->flags & extra))
4191 				goto loop;
4192 
4193 			/*
4194 			 * This block group has different flags than we want.
4195 			 * It's possible that we have MIXED_GROUP flag but no
4196 			 * block group is mixed.  Just skip such block group.
4197 			 */
4198 			btrfs_release_block_group(block_group, delalloc);
4199 			continue;
4200 		}
4201 
4202 have_block_group:
4203 		ffe_ctl.cached = btrfs_block_group_done(block_group);
4204 		if (unlikely(!ffe_ctl.cached)) {
4205 			ffe_ctl.have_caching_bg = true;
4206 			ret = btrfs_cache_block_group(block_group, 0);
4207 
4208 			/*
4209 			 * If we get ENOMEM here or something else we want to
4210 			 * try other block groups, because it may not be fatal.
4211 			 * However if we can't find anything else we need to
4212 			 * save our return here so that we return the actual
4213 			 * error that caused problems, not ENOSPC.
4214 			 */
4215 			if (ret < 0) {
4216 				if (!cache_block_group_error)
4217 					cache_block_group_error = ret;
4218 				ret = 0;
4219 				goto loop;
4220 			}
4221 			ret = 0;
4222 		}
4223 
4224 		if (unlikely(block_group->cached == BTRFS_CACHE_ERROR))
4225 			goto loop;
4226 
4227 		bg_ret = NULL;
4228 		ret = do_allocation(block_group, &ffe_ctl, &bg_ret);
4229 		if (ret == 0) {
4230 			if (bg_ret && bg_ret != block_group) {
4231 				btrfs_release_block_group(block_group, delalloc);
4232 				block_group = bg_ret;
4233 			}
4234 		} else if (ret == -EAGAIN) {
4235 			goto have_block_group;
4236 		} else if (ret > 0) {
4237 			goto loop;
4238 		}
4239 
4240 		/* Checks */
4241 		ffe_ctl.search_start = round_up(ffe_ctl.found_offset,
4242 					     fs_info->stripesize);
4243 
4244 		/* move on to the next group */
4245 		if (ffe_ctl.search_start + num_bytes >
4246 		    block_group->start + block_group->length) {
4247 			btrfs_add_free_space(block_group, ffe_ctl.found_offset,
4248 					     num_bytes);
4249 			goto loop;
4250 		}
4251 
4252 		if (ffe_ctl.found_offset < ffe_ctl.search_start)
4253 			btrfs_add_free_space(block_group, ffe_ctl.found_offset,
4254 				ffe_ctl.search_start - ffe_ctl.found_offset);
4255 
4256 		ret = btrfs_add_reserved_bytes(block_group, ram_bytes,
4257 				num_bytes, delalloc);
4258 		if (ret == -EAGAIN) {
4259 			btrfs_add_free_space(block_group, ffe_ctl.found_offset,
4260 					     num_bytes);
4261 			goto loop;
4262 		}
4263 		btrfs_inc_block_group_reservations(block_group);
4264 
4265 		/* we are all good, lets return */
4266 		ins->objectid = ffe_ctl.search_start;
4267 		ins->offset = num_bytes;
4268 
4269 		trace_btrfs_reserve_extent(block_group, ffe_ctl.search_start,
4270 					   num_bytes);
4271 		btrfs_release_block_group(block_group, delalloc);
4272 		break;
4273 loop:
4274 		release_block_group(block_group, &ffe_ctl, delalloc);
4275 		cond_resched();
4276 	}
4277 	up_read(&space_info->groups_sem);
4278 
4279 	ret = find_free_extent_update_loop(fs_info, ins, &ffe_ctl, full_search);
4280 	if (ret > 0)
4281 		goto search;
4282 
4283 	if (ret == -ENOSPC && !cache_block_group_error) {
4284 		/*
4285 		 * Use ffe_ctl->total_free_space as fallback if we can't find
4286 		 * any contiguous hole.
4287 		 */
4288 		if (!ffe_ctl.max_extent_size)
4289 			ffe_ctl.max_extent_size = ffe_ctl.total_free_space;
4290 		spin_lock(&space_info->lock);
4291 		space_info->max_extent_size = ffe_ctl.max_extent_size;
4292 		spin_unlock(&space_info->lock);
4293 		ins->offset = ffe_ctl.max_extent_size;
4294 	} else if (ret == -ENOSPC) {
4295 		ret = cache_block_group_error;
4296 	}
4297 	return ret;
4298 }
4299 
4300 /*
4301  * btrfs_reserve_extent - entry point to the extent allocator. Tries to find a
4302  *			  hole that is at least as big as @num_bytes.
4303  *
4304  * @root           -	The root that will contain this extent
4305  *
4306  * @ram_bytes      -	The amount of space in ram that @num_bytes take. This
4307  *			is used for accounting purposes. This value differs
4308  *			from @num_bytes only in the case of compressed extents.
4309  *
4310  * @num_bytes      -	Number of bytes to allocate on-disk.
4311  *
4312  * @min_alloc_size -	Indicates the minimum amount of space that the
4313  *			allocator should try to satisfy. In some cases
4314  *			@num_bytes may be larger than what is required and if
4315  *			the filesystem is fragmented then allocation fails.
4316  *			However, the presence of @min_alloc_size gives a
4317  *			chance to try and satisfy the smaller allocation.
4318  *
4319  * @empty_size     -	A hint that you plan on doing more COW. This is the
4320  *			size in bytes the allocator should try to find free
4321  *			next to the block it returns.  This is just a hint and
4322  *			may be ignored by the allocator.
4323  *
4324  * @hint_byte      -	Hint to the allocator to start searching above the byte
4325  *			address passed. It might be ignored.
4326  *
4327  * @ins            -	This key is modified to record the found hole. It will
4328  *			have the following values:
4329  *			ins->objectid == start position
4330  *			ins->flags = BTRFS_EXTENT_ITEM_KEY
4331  *			ins->offset == the size of the hole.
4332  *
4333  * @is_data        -	Boolean flag indicating whether an extent is
4334  *			allocated for data (true) or metadata (false)
4335  *
4336  * @delalloc       -	Boolean flag indicating whether this allocation is for
4337  *			delalloc or not. If 'true' data_rwsem of block groups
4338  *			is going to be acquired.
4339  *
4340  *
4341  * Returns 0 when an allocation succeeded or < 0 when an error occurred. In
4342  * case -ENOSPC is returned then @ins->offset will contain the size of the
4343  * largest available hole the allocator managed to find.
4344  */
4345 int btrfs_reserve_extent(struct btrfs_root *root, u64 ram_bytes,
4346 			 u64 num_bytes, u64 min_alloc_size,
4347 			 u64 empty_size, u64 hint_byte,
4348 			 struct btrfs_key *ins, int is_data, int delalloc)
4349 {
4350 	struct btrfs_fs_info *fs_info = root->fs_info;
4351 	bool final_tried = num_bytes == min_alloc_size;
4352 	u64 flags;
4353 	int ret;
4354 
4355 	flags = get_alloc_profile_by_root(root, is_data);
4356 again:
4357 	WARN_ON(num_bytes < fs_info->sectorsize);
4358 	ret = find_free_extent(root, ram_bytes, num_bytes, empty_size,
4359 			       hint_byte, ins, flags, delalloc);
4360 	if (!ret && !is_data) {
4361 		btrfs_dec_block_group_reservations(fs_info, ins->objectid);
4362 	} else if (ret == -ENOSPC) {
4363 		if (!final_tried && ins->offset) {
4364 			num_bytes = min(num_bytes >> 1, ins->offset);
4365 			num_bytes = round_down(num_bytes,
4366 					       fs_info->sectorsize);
4367 			num_bytes = max(num_bytes, min_alloc_size);
4368 			ram_bytes = num_bytes;
4369 			if (num_bytes == min_alloc_size)
4370 				final_tried = true;
4371 			goto again;
4372 		} else if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
4373 			struct btrfs_space_info *sinfo;
4374 
4375 			sinfo = btrfs_find_space_info(fs_info, flags);
4376 			btrfs_err(fs_info,
4377 				  "allocation failed flags %llu, wanted %llu",
4378 				  flags, num_bytes);
4379 			if (sinfo)
4380 				btrfs_dump_space_info(fs_info, sinfo,
4381 						      num_bytes, 1);
4382 		}
4383 	}
4384 
4385 	return ret;
4386 }
4387 
4388 int btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
4389 			       u64 start, u64 len, int delalloc)
4390 {
4391 	struct btrfs_block_group *cache;
4392 
4393 	cache = btrfs_lookup_block_group(fs_info, start);
4394 	if (!cache) {
4395 		btrfs_err(fs_info, "Unable to find block group for %llu",
4396 			  start);
4397 		return -ENOSPC;
4398 	}
4399 
4400 	btrfs_add_free_space(cache, start, len);
4401 	btrfs_free_reserved_bytes(cache, len, delalloc);
4402 	trace_btrfs_reserved_extent_free(fs_info, start, len);
4403 
4404 	btrfs_put_block_group(cache);
4405 	return 0;
4406 }
4407 
4408 int btrfs_pin_reserved_extent(struct btrfs_trans_handle *trans, u64 start,
4409 			      u64 len)
4410 {
4411 	struct btrfs_block_group *cache;
4412 	int ret = 0;
4413 
4414 	cache = btrfs_lookup_block_group(trans->fs_info, start);
4415 	if (!cache) {
4416 		btrfs_err(trans->fs_info, "unable to find block group for %llu",
4417 			  start);
4418 		return -ENOSPC;
4419 	}
4420 
4421 	ret = pin_down_extent(trans, cache, start, len, 1);
4422 	btrfs_put_block_group(cache);
4423 	return ret;
4424 }
4425 
4426 static int alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
4427 				      u64 parent, u64 root_objectid,
4428 				      u64 flags, u64 owner, u64 offset,
4429 				      struct btrfs_key *ins, int ref_mod)
4430 {
4431 	struct btrfs_fs_info *fs_info = trans->fs_info;
4432 	int ret;
4433 	struct btrfs_extent_item *extent_item;
4434 	struct btrfs_extent_inline_ref *iref;
4435 	struct btrfs_path *path;
4436 	struct extent_buffer *leaf;
4437 	int type;
4438 	u32 size;
4439 
4440 	if (parent > 0)
4441 		type = BTRFS_SHARED_DATA_REF_KEY;
4442 	else
4443 		type = BTRFS_EXTENT_DATA_REF_KEY;
4444 
4445 	size = sizeof(*extent_item) + btrfs_extent_inline_ref_size(type);
4446 
4447 	path = btrfs_alloc_path();
4448 	if (!path)
4449 		return -ENOMEM;
4450 
4451 	path->leave_spinning = 1;
4452 	ret = btrfs_insert_empty_item(trans, fs_info->extent_root, path,
4453 				      ins, size);
4454 	if (ret) {
4455 		btrfs_free_path(path);
4456 		return ret;
4457 	}
4458 
4459 	leaf = path->nodes[0];
4460 	extent_item = btrfs_item_ptr(leaf, path->slots[0],
4461 				     struct btrfs_extent_item);
4462 	btrfs_set_extent_refs(leaf, extent_item, ref_mod);
4463 	btrfs_set_extent_generation(leaf, extent_item, trans->transid);
4464 	btrfs_set_extent_flags(leaf, extent_item,
4465 			       flags | BTRFS_EXTENT_FLAG_DATA);
4466 
4467 	iref = (struct btrfs_extent_inline_ref *)(extent_item + 1);
4468 	btrfs_set_extent_inline_ref_type(leaf, iref, type);
4469 	if (parent > 0) {
4470 		struct btrfs_shared_data_ref *ref;
4471 		ref = (struct btrfs_shared_data_ref *)(iref + 1);
4472 		btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
4473 		btrfs_set_shared_data_ref_count(leaf, ref, ref_mod);
4474 	} else {
4475 		struct btrfs_extent_data_ref *ref;
4476 		ref = (struct btrfs_extent_data_ref *)(&iref->offset);
4477 		btrfs_set_extent_data_ref_root(leaf, ref, root_objectid);
4478 		btrfs_set_extent_data_ref_objectid(leaf, ref, owner);
4479 		btrfs_set_extent_data_ref_offset(leaf, ref, offset);
4480 		btrfs_set_extent_data_ref_count(leaf, ref, ref_mod);
4481 	}
4482 
4483 	btrfs_mark_buffer_dirty(path->nodes[0]);
4484 	btrfs_free_path(path);
4485 
4486 	ret = remove_from_free_space_tree(trans, ins->objectid, ins->offset);
4487 	if (ret)
4488 		return ret;
4489 
4490 	ret = btrfs_update_block_group(trans, ins->objectid, ins->offset, 1);
4491 	if (ret) { /* -ENOENT, logic error */
4492 		btrfs_err(fs_info, "update block group failed for %llu %llu",
4493 			ins->objectid, ins->offset);
4494 		BUG();
4495 	}
4496 	trace_btrfs_reserved_extent_alloc(fs_info, ins->objectid, ins->offset);
4497 	return ret;
4498 }
4499 
4500 static int alloc_reserved_tree_block(struct btrfs_trans_handle *trans,
4501 				     struct btrfs_delayed_ref_node *node,
4502 				     struct btrfs_delayed_extent_op *extent_op)
4503 {
4504 	struct btrfs_fs_info *fs_info = trans->fs_info;
4505 	int ret;
4506 	struct btrfs_extent_item *extent_item;
4507 	struct btrfs_key extent_key;
4508 	struct btrfs_tree_block_info *block_info;
4509 	struct btrfs_extent_inline_ref *iref;
4510 	struct btrfs_path *path;
4511 	struct extent_buffer *leaf;
4512 	struct btrfs_delayed_tree_ref *ref;
4513 	u32 size = sizeof(*extent_item) + sizeof(*iref);
4514 	u64 num_bytes;
4515 	u64 flags = extent_op->flags_to_set;
4516 	bool skinny_metadata = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
4517 
4518 	ref = btrfs_delayed_node_to_tree_ref(node);
4519 
4520 	extent_key.objectid = node->bytenr;
4521 	if (skinny_metadata) {
4522 		extent_key.offset = ref->level;
4523 		extent_key.type = BTRFS_METADATA_ITEM_KEY;
4524 		num_bytes = fs_info->nodesize;
4525 	} else {
4526 		extent_key.offset = node->num_bytes;
4527 		extent_key.type = BTRFS_EXTENT_ITEM_KEY;
4528 		size += sizeof(*block_info);
4529 		num_bytes = node->num_bytes;
4530 	}
4531 
4532 	path = btrfs_alloc_path();
4533 	if (!path)
4534 		return -ENOMEM;
4535 
4536 	path->leave_spinning = 1;
4537 	ret = btrfs_insert_empty_item(trans, fs_info->extent_root, path,
4538 				      &extent_key, size);
4539 	if (ret) {
4540 		btrfs_free_path(path);
4541 		return ret;
4542 	}
4543 
4544 	leaf = path->nodes[0];
4545 	extent_item = btrfs_item_ptr(leaf, path->slots[0],
4546 				     struct btrfs_extent_item);
4547 	btrfs_set_extent_refs(leaf, extent_item, 1);
4548 	btrfs_set_extent_generation(leaf, extent_item, trans->transid);
4549 	btrfs_set_extent_flags(leaf, extent_item,
4550 			       flags | BTRFS_EXTENT_FLAG_TREE_BLOCK);
4551 
4552 	if (skinny_metadata) {
4553 		iref = (struct btrfs_extent_inline_ref *)(extent_item + 1);
4554 	} else {
4555 		block_info = (struct btrfs_tree_block_info *)(extent_item + 1);
4556 		btrfs_set_tree_block_key(leaf, block_info, &extent_op->key);
4557 		btrfs_set_tree_block_level(leaf, block_info, ref->level);
4558 		iref = (struct btrfs_extent_inline_ref *)(block_info + 1);
4559 	}
4560 
4561 	if (node->type == BTRFS_SHARED_BLOCK_REF_KEY) {
4562 		BUG_ON(!(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF));
4563 		btrfs_set_extent_inline_ref_type(leaf, iref,
4564 						 BTRFS_SHARED_BLOCK_REF_KEY);
4565 		btrfs_set_extent_inline_ref_offset(leaf, iref, ref->parent);
4566 	} else {
4567 		btrfs_set_extent_inline_ref_type(leaf, iref,
4568 						 BTRFS_TREE_BLOCK_REF_KEY);
4569 		btrfs_set_extent_inline_ref_offset(leaf, iref, ref->root);
4570 	}
4571 
4572 	btrfs_mark_buffer_dirty(leaf);
4573 	btrfs_free_path(path);
4574 
4575 	ret = remove_from_free_space_tree(trans, extent_key.objectid,
4576 					  num_bytes);
4577 	if (ret)
4578 		return ret;
4579 
4580 	ret = btrfs_update_block_group(trans, extent_key.objectid,
4581 				       fs_info->nodesize, 1);
4582 	if (ret) { /* -ENOENT, logic error */
4583 		btrfs_err(fs_info, "update block group failed for %llu %llu",
4584 			extent_key.objectid, extent_key.offset);
4585 		BUG();
4586 	}
4587 
4588 	trace_btrfs_reserved_extent_alloc(fs_info, extent_key.objectid,
4589 					  fs_info->nodesize);
4590 	return ret;
4591 }
4592 
4593 int btrfs_alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
4594 				     struct btrfs_root *root, u64 owner,
4595 				     u64 offset, u64 ram_bytes,
4596 				     struct btrfs_key *ins)
4597 {
4598 	struct btrfs_ref generic_ref = { 0 };
4599 	int ret;
4600 
4601 	BUG_ON(root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID);
4602 
4603 	btrfs_init_generic_ref(&generic_ref, BTRFS_ADD_DELAYED_EXTENT,
4604 			       ins->objectid, ins->offset, 0);
4605 	btrfs_init_data_ref(&generic_ref, root->root_key.objectid, owner, offset);
4606 	btrfs_ref_tree_mod(root->fs_info, &generic_ref);
4607 	ret = btrfs_add_delayed_data_ref(trans, &generic_ref,
4608 					 ram_bytes, NULL, NULL);
4609 	return ret;
4610 }
4611 
4612 /*
4613  * this is used by the tree logging recovery code.  It records that
4614  * an extent has been allocated and makes sure to clear the free
4615  * space cache bits as well
4616  */
4617 int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans,
4618 				   u64 root_objectid, u64 owner, u64 offset,
4619 				   struct btrfs_key *ins)
4620 {
4621 	struct btrfs_fs_info *fs_info = trans->fs_info;
4622 	int ret;
4623 	struct btrfs_block_group *block_group;
4624 	struct btrfs_space_info *space_info;
4625 
4626 	/*
4627 	 * Mixed block groups will exclude before processing the log so we only
4628 	 * need to do the exclude dance if this fs isn't mixed.
4629 	 */
4630 	if (!btrfs_fs_incompat(fs_info, MIXED_GROUPS)) {
4631 		ret = __exclude_logged_extent(fs_info, ins->objectid,
4632 					      ins->offset);
4633 		if (ret)
4634 			return ret;
4635 	}
4636 
4637 	block_group = btrfs_lookup_block_group(fs_info, ins->objectid);
4638 	if (!block_group)
4639 		return -EINVAL;
4640 
4641 	space_info = block_group->space_info;
4642 	spin_lock(&space_info->lock);
4643 	spin_lock(&block_group->lock);
4644 	space_info->bytes_reserved += ins->offset;
4645 	block_group->reserved += ins->offset;
4646 	spin_unlock(&block_group->lock);
4647 	spin_unlock(&space_info->lock);
4648 
4649 	ret = alloc_reserved_file_extent(trans, 0, root_objectid, 0, owner,
4650 					 offset, ins, 1);
4651 	if (ret)
4652 		btrfs_pin_extent(trans, ins->objectid, ins->offset, 1);
4653 	btrfs_put_block_group(block_group);
4654 	return ret;
4655 }
4656 
4657 static struct extent_buffer *
4658 btrfs_init_new_buffer(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4659 		      u64 bytenr, int level, u64 owner,
4660 		      enum btrfs_lock_nesting nest)
4661 {
4662 	struct btrfs_fs_info *fs_info = root->fs_info;
4663 	struct extent_buffer *buf;
4664 
4665 	buf = btrfs_find_create_tree_block(fs_info, bytenr);
4666 	if (IS_ERR(buf))
4667 		return buf;
4668 
4669 	/*
4670 	 * Extra safety check in case the extent tree is corrupted and extent
4671 	 * allocator chooses to use a tree block which is already used and
4672 	 * locked.
4673 	 */
4674 	if (buf->lock_owner == current->pid) {
4675 		btrfs_err_rl(fs_info,
4676 "tree block %llu owner %llu already locked by pid=%d, extent tree corruption detected",
4677 			buf->start, btrfs_header_owner(buf), current->pid);
4678 		free_extent_buffer(buf);
4679 		return ERR_PTR(-EUCLEAN);
4680 	}
4681 
4682 	btrfs_set_buffer_lockdep_class(owner, buf, level);
4683 	__btrfs_tree_lock(buf, nest);
4684 	btrfs_clean_tree_block(buf);
4685 	clear_bit(EXTENT_BUFFER_STALE, &buf->bflags);
4686 
4687 	btrfs_set_lock_blocking_write(buf);
4688 	set_extent_buffer_uptodate(buf);
4689 
4690 	memzero_extent_buffer(buf, 0, sizeof(struct btrfs_header));
4691 	btrfs_set_header_level(buf, level);
4692 	btrfs_set_header_bytenr(buf, buf->start);
4693 	btrfs_set_header_generation(buf, trans->transid);
4694 	btrfs_set_header_backref_rev(buf, BTRFS_MIXED_BACKREF_REV);
4695 	btrfs_set_header_owner(buf, owner);
4696 	write_extent_buffer_fsid(buf, fs_info->fs_devices->metadata_uuid);
4697 	write_extent_buffer_chunk_tree_uuid(buf, fs_info->chunk_tree_uuid);
4698 	if (root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID) {
4699 		buf->log_index = root->log_transid % 2;
4700 		/*
4701 		 * we allow two log transactions at a time, use different
4702 		 * EXTENT bit to differentiate dirty pages.
4703 		 */
4704 		if (buf->log_index == 0)
4705 			set_extent_dirty(&root->dirty_log_pages, buf->start,
4706 					buf->start + buf->len - 1, GFP_NOFS);
4707 		else
4708 			set_extent_new(&root->dirty_log_pages, buf->start,
4709 					buf->start + buf->len - 1);
4710 	} else {
4711 		buf->log_index = -1;
4712 		set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
4713 			 buf->start + buf->len - 1, GFP_NOFS);
4714 	}
4715 	trans->dirty = true;
4716 	/* this returns a buffer locked for blocking */
4717 	return buf;
4718 }
4719 
4720 /*
4721  * finds a free extent and does all the dirty work required for allocation
4722  * returns the tree buffer or an ERR_PTR on error.
4723  */
4724 struct extent_buffer *btrfs_alloc_tree_block(struct btrfs_trans_handle *trans,
4725 					     struct btrfs_root *root,
4726 					     u64 parent, u64 root_objectid,
4727 					     const struct btrfs_disk_key *key,
4728 					     int level, u64 hint,
4729 					     u64 empty_size,
4730 					     enum btrfs_lock_nesting nest)
4731 {
4732 	struct btrfs_fs_info *fs_info = root->fs_info;
4733 	struct btrfs_key ins;
4734 	struct btrfs_block_rsv *block_rsv;
4735 	struct extent_buffer *buf;
4736 	struct btrfs_delayed_extent_op *extent_op;
4737 	struct btrfs_ref generic_ref = { 0 };
4738 	u64 flags = 0;
4739 	int ret;
4740 	u32 blocksize = fs_info->nodesize;
4741 	bool skinny_metadata = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
4742 
4743 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
4744 	if (btrfs_is_testing(fs_info)) {
4745 		buf = btrfs_init_new_buffer(trans, root, root->alloc_bytenr,
4746 					    level, root_objectid, nest);
4747 		if (!IS_ERR(buf))
4748 			root->alloc_bytenr += blocksize;
4749 		return buf;
4750 	}
4751 #endif
4752 
4753 	block_rsv = btrfs_use_block_rsv(trans, root, blocksize);
4754 	if (IS_ERR(block_rsv))
4755 		return ERR_CAST(block_rsv);
4756 
4757 	ret = btrfs_reserve_extent(root, blocksize, blocksize, blocksize,
4758 				   empty_size, hint, &ins, 0, 0);
4759 	if (ret)
4760 		goto out_unuse;
4761 
4762 	buf = btrfs_init_new_buffer(trans, root, ins.objectid, level,
4763 				    root_objectid, nest);
4764 	if (IS_ERR(buf)) {
4765 		ret = PTR_ERR(buf);
4766 		goto out_free_reserved;
4767 	}
4768 
4769 	if (root_objectid == BTRFS_TREE_RELOC_OBJECTID) {
4770 		if (parent == 0)
4771 			parent = ins.objectid;
4772 		flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
4773 	} else
4774 		BUG_ON(parent > 0);
4775 
4776 	if (root_objectid != BTRFS_TREE_LOG_OBJECTID) {
4777 		extent_op = btrfs_alloc_delayed_extent_op();
4778 		if (!extent_op) {
4779 			ret = -ENOMEM;
4780 			goto out_free_buf;
4781 		}
4782 		if (key)
4783 			memcpy(&extent_op->key, key, sizeof(extent_op->key));
4784 		else
4785 			memset(&extent_op->key, 0, sizeof(extent_op->key));
4786 		extent_op->flags_to_set = flags;
4787 		extent_op->update_key = skinny_metadata ? false : true;
4788 		extent_op->update_flags = true;
4789 		extent_op->is_data = false;
4790 		extent_op->level = level;
4791 
4792 		btrfs_init_generic_ref(&generic_ref, BTRFS_ADD_DELAYED_EXTENT,
4793 				       ins.objectid, ins.offset, parent);
4794 		generic_ref.real_root = root->root_key.objectid;
4795 		btrfs_init_tree_ref(&generic_ref, level, root_objectid);
4796 		btrfs_ref_tree_mod(fs_info, &generic_ref);
4797 		ret = btrfs_add_delayed_tree_ref(trans, &generic_ref,
4798 						 extent_op, NULL, NULL);
4799 		if (ret)
4800 			goto out_free_delayed;
4801 	}
4802 	return buf;
4803 
4804 out_free_delayed:
4805 	btrfs_free_delayed_extent_op(extent_op);
4806 out_free_buf:
4807 	free_extent_buffer(buf);
4808 out_free_reserved:
4809 	btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 0);
4810 out_unuse:
4811 	btrfs_unuse_block_rsv(fs_info, block_rsv, blocksize);
4812 	return ERR_PTR(ret);
4813 }
4814 
4815 struct walk_control {
4816 	u64 refs[BTRFS_MAX_LEVEL];
4817 	u64 flags[BTRFS_MAX_LEVEL];
4818 	struct btrfs_key update_progress;
4819 	struct btrfs_key drop_progress;
4820 	int drop_level;
4821 	int stage;
4822 	int level;
4823 	int shared_level;
4824 	int update_ref;
4825 	int keep_locks;
4826 	int reada_slot;
4827 	int reada_count;
4828 	int restarted;
4829 };
4830 
4831 #define DROP_REFERENCE	1
4832 #define UPDATE_BACKREF	2
4833 
4834 static noinline void reada_walk_down(struct btrfs_trans_handle *trans,
4835 				     struct btrfs_root *root,
4836 				     struct walk_control *wc,
4837 				     struct btrfs_path *path)
4838 {
4839 	struct btrfs_fs_info *fs_info = root->fs_info;
4840 	u64 bytenr;
4841 	u64 generation;
4842 	u64 refs;
4843 	u64 flags;
4844 	u32 nritems;
4845 	struct btrfs_key key;
4846 	struct extent_buffer *eb;
4847 	int ret;
4848 	int slot;
4849 	int nread = 0;
4850 
4851 	if (path->slots[wc->level] < wc->reada_slot) {
4852 		wc->reada_count = wc->reada_count * 2 / 3;
4853 		wc->reada_count = max(wc->reada_count, 2);
4854 	} else {
4855 		wc->reada_count = wc->reada_count * 3 / 2;
4856 		wc->reada_count = min_t(int, wc->reada_count,
4857 					BTRFS_NODEPTRS_PER_BLOCK(fs_info));
4858 	}
4859 
4860 	eb = path->nodes[wc->level];
4861 	nritems = btrfs_header_nritems(eb);
4862 
4863 	for (slot = path->slots[wc->level]; slot < nritems; slot++) {
4864 		if (nread >= wc->reada_count)
4865 			break;
4866 
4867 		cond_resched();
4868 		bytenr = btrfs_node_blockptr(eb, slot);
4869 		generation = btrfs_node_ptr_generation(eb, slot);
4870 
4871 		if (slot == path->slots[wc->level])
4872 			goto reada;
4873 
4874 		if (wc->stage == UPDATE_BACKREF &&
4875 		    generation <= root->root_key.offset)
4876 			continue;
4877 
4878 		/* We don't lock the tree block, it's OK to be racy here */
4879 		ret = btrfs_lookup_extent_info(trans, fs_info, bytenr,
4880 					       wc->level - 1, 1, &refs,
4881 					       &flags);
4882 		/* We don't care about errors in readahead. */
4883 		if (ret < 0)
4884 			continue;
4885 		BUG_ON(refs == 0);
4886 
4887 		if (wc->stage == DROP_REFERENCE) {
4888 			if (refs == 1)
4889 				goto reada;
4890 
4891 			if (wc->level == 1 &&
4892 			    (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
4893 				continue;
4894 			if (!wc->update_ref ||
4895 			    generation <= root->root_key.offset)
4896 				continue;
4897 			btrfs_node_key_to_cpu(eb, &key, slot);
4898 			ret = btrfs_comp_cpu_keys(&key,
4899 						  &wc->update_progress);
4900 			if (ret < 0)
4901 				continue;
4902 		} else {
4903 			if (wc->level == 1 &&
4904 			    (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
4905 				continue;
4906 		}
4907 reada:
4908 		readahead_tree_block(fs_info, bytenr);
4909 		nread++;
4910 	}
4911 	wc->reada_slot = slot;
4912 }
4913 
4914 /*
4915  * helper to process tree block while walking down the tree.
4916  *
4917  * when wc->stage == UPDATE_BACKREF, this function updates
4918  * back refs for pointers in the block.
4919  *
4920  * NOTE: return value 1 means we should stop walking down.
4921  */
4922 static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
4923 				   struct btrfs_root *root,
4924 				   struct btrfs_path *path,
4925 				   struct walk_control *wc, int lookup_info)
4926 {
4927 	struct btrfs_fs_info *fs_info = root->fs_info;
4928 	int level = wc->level;
4929 	struct extent_buffer *eb = path->nodes[level];
4930 	u64 flag = BTRFS_BLOCK_FLAG_FULL_BACKREF;
4931 	int ret;
4932 
4933 	if (wc->stage == UPDATE_BACKREF &&
4934 	    btrfs_header_owner(eb) != root->root_key.objectid)
4935 		return 1;
4936 
4937 	/*
4938 	 * when reference count of tree block is 1, it won't increase
4939 	 * again. once full backref flag is set, we never clear it.
4940 	 */
4941 	if (lookup_info &&
4942 	    ((wc->stage == DROP_REFERENCE && wc->refs[level] != 1) ||
4943 	     (wc->stage == UPDATE_BACKREF && !(wc->flags[level] & flag)))) {
4944 		BUG_ON(!path->locks[level]);
4945 		ret = btrfs_lookup_extent_info(trans, fs_info,
4946 					       eb->start, level, 1,
4947 					       &wc->refs[level],
4948 					       &wc->flags[level]);
4949 		BUG_ON(ret == -ENOMEM);
4950 		if (ret)
4951 			return ret;
4952 		BUG_ON(wc->refs[level] == 0);
4953 	}
4954 
4955 	if (wc->stage == DROP_REFERENCE) {
4956 		if (wc->refs[level] > 1)
4957 			return 1;
4958 
4959 		if (path->locks[level] && !wc->keep_locks) {
4960 			btrfs_tree_unlock_rw(eb, path->locks[level]);
4961 			path->locks[level] = 0;
4962 		}
4963 		return 0;
4964 	}
4965 
4966 	/* wc->stage == UPDATE_BACKREF */
4967 	if (!(wc->flags[level] & flag)) {
4968 		BUG_ON(!path->locks[level]);
4969 		ret = btrfs_inc_ref(trans, root, eb, 1);
4970 		BUG_ON(ret); /* -ENOMEM */
4971 		ret = btrfs_dec_ref(trans, root, eb, 0);
4972 		BUG_ON(ret); /* -ENOMEM */
4973 		ret = btrfs_set_disk_extent_flags(trans, eb, flag,
4974 						  btrfs_header_level(eb), 0);
4975 		BUG_ON(ret); /* -ENOMEM */
4976 		wc->flags[level] |= flag;
4977 	}
4978 
4979 	/*
4980 	 * the block is shared by multiple trees, so it's not good to
4981 	 * keep the tree lock
4982 	 */
4983 	if (path->locks[level] && level > 0) {
4984 		btrfs_tree_unlock_rw(eb, path->locks[level]);
4985 		path->locks[level] = 0;
4986 	}
4987 	return 0;
4988 }
4989 
4990 /*
4991  * This is used to verify a ref exists for this root to deal with a bug where we
4992  * would have a drop_progress key that hadn't been updated properly.
4993  */
4994 static int check_ref_exists(struct btrfs_trans_handle *trans,
4995 			    struct btrfs_root *root, u64 bytenr, u64 parent,
4996 			    int level)
4997 {
4998 	struct btrfs_path *path;
4999 	struct btrfs_extent_inline_ref *iref;
5000 	int ret;
5001 
5002 	path = btrfs_alloc_path();
5003 	if (!path)
5004 		return -ENOMEM;
5005 
5006 	ret = lookup_extent_backref(trans, path, &iref, bytenr,
5007 				    root->fs_info->nodesize, parent,
5008 				    root->root_key.objectid, level, 0);
5009 	btrfs_free_path(path);
5010 	if (ret == -ENOENT)
5011 		return 0;
5012 	if (ret < 0)
5013 		return ret;
5014 	return 1;
5015 }
5016 
5017 /*
5018  * helper to process tree block pointer.
5019  *
5020  * when wc->stage == DROP_REFERENCE, this function checks
5021  * reference count of the block pointed to. if the block
5022  * is shared and we need update back refs for the subtree
5023  * rooted at the block, this function changes wc->stage to
5024  * UPDATE_BACKREF. if the block is shared and there is no
5025  * need to update back, this function drops the reference
5026  * to the block.
5027  *
5028  * NOTE: return value 1 means we should stop walking down.
5029  */
5030 static noinline int do_walk_down(struct btrfs_trans_handle *trans,
5031 				 struct btrfs_root *root,
5032 				 struct btrfs_path *path,
5033 				 struct walk_control *wc, int *lookup_info)
5034 {
5035 	struct btrfs_fs_info *fs_info = root->fs_info;
5036 	u64 bytenr;
5037 	u64 generation;
5038 	u64 parent;
5039 	struct btrfs_key key;
5040 	struct btrfs_key first_key;
5041 	struct btrfs_ref ref = { 0 };
5042 	struct extent_buffer *next;
5043 	int level = wc->level;
5044 	int reada = 0;
5045 	int ret = 0;
5046 	bool need_account = false;
5047 
5048 	generation = btrfs_node_ptr_generation(path->nodes[level],
5049 					       path->slots[level]);
5050 	/*
5051 	 * if the lower level block was created before the snapshot
5052 	 * was created, we know there is no need to update back refs
5053 	 * for the subtree
5054 	 */
5055 	if (wc->stage == UPDATE_BACKREF &&
5056 	    generation <= root->root_key.offset) {
5057 		*lookup_info = 1;
5058 		return 1;
5059 	}
5060 
5061 	bytenr = btrfs_node_blockptr(path->nodes[level], path->slots[level]);
5062 	btrfs_node_key_to_cpu(path->nodes[level], &first_key,
5063 			      path->slots[level]);
5064 
5065 	next = find_extent_buffer(fs_info, bytenr);
5066 	if (!next) {
5067 		next = btrfs_find_create_tree_block(fs_info, bytenr);
5068 		if (IS_ERR(next))
5069 			return PTR_ERR(next);
5070 
5071 		btrfs_set_buffer_lockdep_class(root->root_key.objectid, next,
5072 					       level - 1);
5073 		reada = 1;
5074 	}
5075 	btrfs_tree_lock(next);
5076 	btrfs_set_lock_blocking_write(next);
5077 
5078 	ret = btrfs_lookup_extent_info(trans, fs_info, bytenr, level - 1, 1,
5079 				       &wc->refs[level - 1],
5080 				       &wc->flags[level - 1]);
5081 	if (ret < 0)
5082 		goto out_unlock;
5083 
5084 	if (unlikely(wc->refs[level - 1] == 0)) {
5085 		btrfs_err(fs_info, "Missing references.");
5086 		ret = -EIO;
5087 		goto out_unlock;
5088 	}
5089 	*lookup_info = 0;
5090 
5091 	if (wc->stage == DROP_REFERENCE) {
5092 		if (wc->refs[level - 1] > 1) {
5093 			need_account = true;
5094 			if (level == 1 &&
5095 			    (wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))
5096 				goto skip;
5097 
5098 			if (!wc->update_ref ||
5099 			    generation <= root->root_key.offset)
5100 				goto skip;
5101 
5102 			btrfs_node_key_to_cpu(path->nodes[level], &key,
5103 					      path->slots[level]);
5104 			ret = btrfs_comp_cpu_keys(&key, &wc->update_progress);
5105 			if (ret < 0)
5106 				goto skip;
5107 
5108 			wc->stage = UPDATE_BACKREF;
5109 			wc->shared_level = level - 1;
5110 		}
5111 	} else {
5112 		if (level == 1 &&
5113 		    (wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))
5114 			goto skip;
5115 	}
5116 
5117 	if (!btrfs_buffer_uptodate(next, generation, 0)) {
5118 		btrfs_tree_unlock(next);
5119 		free_extent_buffer(next);
5120 		next = NULL;
5121 		*lookup_info = 1;
5122 	}
5123 
5124 	if (!next) {
5125 		if (reada && level == 1)
5126 			reada_walk_down(trans, root, wc, path);
5127 		next = read_tree_block(fs_info, bytenr, generation, level - 1,
5128 				       &first_key);
5129 		if (IS_ERR(next)) {
5130 			return PTR_ERR(next);
5131 		} else if (!extent_buffer_uptodate(next)) {
5132 			free_extent_buffer(next);
5133 			return -EIO;
5134 		}
5135 		btrfs_tree_lock(next);
5136 		btrfs_set_lock_blocking_write(next);
5137 	}
5138 
5139 	level--;
5140 	ASSERT(level == btrfs_header_level(next));
5141 	if (level != btrfs_header_level(next)) {
5142 		btrfs_err(root->fs_info, "mismatched level");
5143 		ret = -EIO;
5144 		goto out_unlock;
5145 	}
5146 	path->nodes[level] = next;
5147 	path->slots[level] = 0;
5148 	path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
5149 	wc->level = level;
5150 	if (wc->level == 1)
5151 		wc->reada_slot = 0;
5152 	return 0;
5153 skip:
5154 	wc->refs[level - 1] = 0;
5155 	wc->flags[level - 1] = 0;
5156 	if (wc->stage == DROP_REFERENCE) {
5157 		if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
5158 			parent = path->nodes[level]->start;
5159 		} else {
5160 			ASSERT(root->root_key.objectid ==
5161 			       btrfs_header_owner(path->nodes[level]));
5162 			if (root->root_key.objectid !=
5163 			    btrfs_header_owner(path->nodes[level])) {
5164 				btrfs_err(root->fs_info,
5165 						"mismatched block owner");
5166 				ret = -EIO;
5167 				goto out_unlock;
5168 			}
5169 			parent = 0;
5170 		}
5171 
5172 		/*
5173 		 * If we had a drop_progress we need to verify the refs are set
5174 		 * as expected.  If we find our ref then we know that from here
5175 		 * on out everything should be correct, and we can clear the
5176 		 * ->restarted flag.
5177 		 */
5178 		if (wc->restarted) {
5179 			ret = check_ref_exists(trans, root, bytenr, parent,
5180 					       level - 1);
5181 			if (ret < 0)
5182 				goto out_unlock;
5183 			if (ret == 0)
5184 				goto no_delete;
5185 			ret = 0;
5186 			wc->restarted = 0;
5187 		}
5188 
5189 		/*
5190 		 * Reloc tree doesn't contribute to qgroup numbers, and we have
5191 		 * already accounted them at merge time (replace_path),
5192 		 * thus we could skip expensive subtree trace here.
5193 		 */
5194 		if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
5195 		    need_account) {
5196 			ret = btrfs_qgroup_trace_subtree(trans, next,
5197 							 generation, level - 1);
5198 			if (ret) {
5199 				btrfs_err_rl(fs_info,
5200 					     "Error %d accounting shared subtree. Quota is out of sync, rescan required.",
5201 					     ret);
5202 			}
5203 		}
5204 
5205 		/*
5206 		 * We need to update the next key in our walk control so we can
5207 		 * update the drop_progress key accordingly.  We don't care if
5208 		 * find_next_key doesn't find a key because that means we're at
5209 		 * the end and are going to clean up now.
5210 		 */
5211 		wc->drop_level = level;
5212 		find_next_key(path, level, &wc->drop_progress);
5213 
5214 		btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, bytenr,
5215 				       fs_info->nodesize, parent);
5216 		btrfs_init_tree_ref(&ref, level - 1, root->root_key.objectid);
5217 		ret = btrfs_free_extent(trans, &ref);
5218 		if (ret)
5219 			goto out_unlock;
5220 	}
5221 no_delete:
5222 	*lookup_info = 1;
5223 	ret = 1;
5224 
5225 out_unlock:
5226 	btrfs_tree_unlock(next);
5227 	free_extent_buffer(next);
5228 
5229 	return ret;
5230 }
5231 
5232 /*
5233  * helper to process tree block while walking up the tree.
5234  *
5235  * when wc->stage == DROP_REFERENCE, this function drops
5236  * reference count on the block.
5237  *
5238  * when wc->stage == UPDATE_BACKREF, this function changes
5239  * wc->stage back to DROP_REFERENCE if we changed wc->stage
5240  * to UPDATE_BACKREF previously while processing the block.
5241  *
5242  * NOTE: return value 1 means we should stop walking up.
5243  */
5244 static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
5245 				 struct btrfs_root *root,
5246 				 struct btrfs_path *path,
5247 				 struct walk_control *wc)
5248 {
5249 	struct btrfs_fs_info *fs_info = root->fs_info;
5250 	int ret;
5251 	int level = wc->level;
5252 	struct extent_buffer *eb = path->nodes[level];
5253 	u64 parent = 0;
5254 
5255 	if (wc->stage == UPDATE_BACKREF) {
5256 		BUG_ON(wc->shared_level < level);
5257 		if (level < wc->shared_level)
5258 			goto out;
5259 
5260 		ret = find_next_key(path, level + 1, &wc->update_progress);
5261 		if (ret > 0)
5262 			wc->update_ref = 0;
5263 
5264 		wc->stage = DROP_REFERENCE;
5265 		wc->shared_level = -1;
5266 		path->slots[level] = 0;
5267 
5268 		/*
5269 		 * check reference count again if the block isn't locked.
5270 		 * we should start walking down the tree again if reference
5271 		 * count is one.
5272 		 */
5273 		if (!path->locks[level]) {
5274 			BUG_ON(level == 0);
5275 			btrfs_tree_lock(eb);
5276 			btrfs_set_lock_blocking_write(eb);
5277 			path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
5278 
5279 			ret = btrfs_lookup_extent_info(trans, fs_info,
5280 						       eb->start, level, 1,
5281 						       &wc->refs[level],
5282 						       &wc->flags[level]);
5283 			if (ret < 0) {
5284 				btrfs_tree_unlock_rw(eb, path->locks[level]);
5285 				path->locks[level] = 0;
5286 				return ret;
5287 			}
5288 			BUG_ON(wc->refs[level] == 0);
5289 			if (wc->refs[level] == 1) {
5290 				btrfs_tree_unlock_rw(eb, path->locks[level]);
5291 				path->locks[level] = 0;
5292 				return 1;
5293 			}
5294 		}
5295 	}
5296 
5297 	/* wc->stage == DROP_REFERENCE */
5298 	BUG_ON(wc->refs[level] > 1 && !path->locks[level]);
5299 
5300 	if (wc->refs[level] == 1) {
5301 		if (level == 0) {
5302 			if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF)
5303 				ret = btrfs_dec_ref(trans, root, eb, 1);
5304 			else
5305 				ret = btrfs_dec_ref(trans, root, eb, 0);
5306 			BUG_ON(ret); /* -ENOMEM */
5307 			if (is_fstree(root->root_key.objectid)) {
5308 				ret = btrfs_qgroup_trace_leaf_items(trans, eb);
5309 				if (ret) {
5310 					btrfs_err_rl(fs_info,
5311 	"error %d accounting leaf items, quota is out of sync, rescan required",
5312 					     ret);
5313 				}
5314 			}
5315 		}
5316 		/* make block locked assertion in btrfs_clean_tree_block happy */
5317 		if (!path->locks[level] &&
5318 		    btrfs_header_generation(eb) == trans->transid) {
5319 			btrfs_tree_lock(eb);
5320 			btrfs_set_lock_blocking_write(eb);
5321 			path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
5322 		}
5323 		btrfs_clean_tree_block(eb);
5324 	}
5325 
5326 	if (eb == root->node) {
5327 		if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF)
5328 			parent = eb->start;
5329 		else if (root->root_key.objectid != btrfs_header_owner(eb))
5330 			goto owner_mismatch;
5331 	} else {
5332 		if (wc->flags[level + 1] & BTRFS_BLOCK_FLAG_FULL_BACKREF)
5333 			parent = path->nodes[level + 1]->start;
5334 		else if (root->root_key.objectid !=
5335 			 btrfs_header_owner(path->nodes[level + 1]))
5336 			goto owner_mismatch;
5337 	}
5338 
5339 	btrfs_free_tree_block(trans, root, eb, parent, wc->refs[level] == 1);
5340 out:
5341 	wc->refs[level] = 0;
5342 	wc->flags[level] = 0;
5343 	return 0;
5344 
5345 owner_mismatch:
5346 	btrfs_err_rl(fs_info, "unexpected tree owner, have %llu expect %llu",
5347 		     btrfs_header_owner(eb), root->root_key.objectid);
5348 	return -EUCLEAN;
5349 }
5350 
5351 static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
5352 				   struct btrfs_root *root,
5353 				   struct btrfs_path *path,
5354 				   struct walk_control *wc)
5355 {
5356 	int level = wc->level;
5357 	int lookup_info = 1;
5358 	int ret;
5359 
5360 	while (level >= 0) {
5361 		ret = walk_down_proc(trans, root, path, wc, lookup_info);
5362 		if (ret > 0)
5363 			break;
5364 
5365 		if (level == 0)
5366 			break;
5367 
5368 		if (path->slots[level] >=
5369 		    btrfs_header_nritems(path->nodes[level]))
5370 			break;
5371 
5372 		ret = do_walk_down(trans, root, path, wc, &lookup_info);
5373 		if (ret > 0) {
5374 			path->slots[level]++;
5375 			continue;
5376 		} else if (ret < 0)
5377 			return ret;
5378 		level = wc->level;
5379 	}
5380 	return 0;
5381 }
5382 
5383 static noinline int walk_up_tree(struct btrfs_trans_handle *trans,
5384 				 struct btrfs_root *root,
5385 				 struct btrfs_path *path,
5386 				 struct walk_control *wc, int max_level)
5387 {
5388 	int level = wc->level;
5389 	int ret;
5390 
5391 	path->slots[level] = btrfs_header_nritems(path->nodes[level]);
5392 	while (level < max_level && path->nodes[level]) {
5393 		wc->level = level;
5394 		if (path->slots[level] + 1 <
5395 		    btrfs_header_nritems(path->nodes[level])) {
5396 			path->slots[level]++;
5397 			return 0;
5398 		} else {
5399 			ret = walk_up_proc(trans, root, path, wc);
5400 			if (ret > 0)
5401 				return 0;
5402 			if (ret < 0)
5403 				return ret;
5404 
5405 			if (path->locks[level]) {
5406 				btrfs_tree_unlock_rw(path->nodes[level],
5407 						     path->locks[level]);
5408 				path->locks[level] = 0;
5409 			}
5410 			free_extent_buffer(path->nodes[level]);
5411 			path->nodes[level] = NULL;
5412 			level++;
5413 		}
5414 	}
5415 	return 1;
5416 }
5417 
5418 /*
5419  * drop a subvolume tree.
5420  *
5421  * this function traverses the tree freeing any blocks that only
5422  * referenced by the tree.
5423  *
5424  * when a shared tree block is found. this function decreases its
5425  * reference count by one. if update_ref is true, this function
5426  * also make sure backrefs for the shared block and all lower level
5427  * blocks are properly updated.
5428  *
5429  * If called with for_reloc == 0, may exit early with -EAGAIN
5430  */
5431 int btrfs_drop_snapshot(struct btrfs_root *root, int update_ref, int for_reloc)
5432 {
5433 	struct btrfs_fs_info *fs_info = root->fs_info;
5434 	struct btrfs_path *path;
5435 	struct btrfs_trans_handle *trans;
5436 	struct btrfs_root *tree_root = fs_info->tree_root;
5437 	struct btrfs_root_item *root_item = &root->root_item;
5438 	struct walk_control *wc;
5439 	struct btrfs_key key;
5440 	int err = 0;
5441 	int ret;
5442 	int level;
5443 	bool root_dropped = false;
5444 
5445 	btrfs_debug(fs_info, "Drop subvolume %llu", root->root_key.objectid);
5446 
5447 	path = btrfs_alloc_path();
5448 	if (!path) {
5449 		err = -ENOMEM;
5450 		goto out;
5451 	}
5452 
5453 	wc = kzalloc(sizeof(*wc), GFP_NOFS);
5454 	if (!wc) {
5455 		btrfs_free_path(path);
5456 		err = -ENOMEM;
5457 		goto out;
5458 	}
5459 
5460 	/*
5461 	 * Use join to avoid potential EINTR from transaction start. See
5462 	 * wait_reserve_ticket and the whole reservation callchain.
5463 	 */
5464 	if (for_reloc)
5465 		trans = btrfs_join_transaction(tree_root);
5466 	else
5467 		trans = btrfs_start_transaction(tree_root, 0);
5468 	if (IS_ERR(trans)) {
5469 		err = PTR_ERR(trans);
5470 		goto out_free;
5471 	}
5472 
5473 	err = btrfs_run_delayed_items(trans);
5474 	if (err)
5475 		goto out_end_trans;
5476 
5477 	/*
5478 	 * This will help us catch people modifying the fs tree while we're
5479 	 * dropping it.  It is unsafe to mess with the fs tree while it's being
5480 	 * dropped as we unlock the root node and parent nodes as we walk down
5481 	 * the tree, assuming nothing will change.  If something does change
5482 	 * then we'll have stale information and drop references to blocks we've
5483 	 * already dropped.
5484 	 */
5485 	set_bit(BTRFS_ROOT_DELETING, &root->state);
5486 	if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
5487 		level = btrfs_header_level(root->node);
5488 		path->nodes[level] = btrfs_lock_root_node(root);
5489 		btrfs_set_lock_blocking_write(path->nodes[level]);
5490 		path->slots[level] = 0;
5491 		path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
5492 		memset(&wc->update_progress, 0,
5493 		       sizeof(wc->update_progress));
5494 	} else {
5495 		btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
5496 		memcpy(&wc->update_progress, &key,
5497 		       sizeof(wc->update_progress));
5498 
5499 		level = root_item->drop_level;
5500 		BUG_ON(level == 0);
5501 		path->lowest_level = level;
5502 		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5503 		path->lowest_level = 0;
5504 		if (ret < 0) {
5505 			err = ret;
5506 			goto out_end_trans;
5507 		}
5508 		WARN_ON(ret > 0);
5509 
5510 		/*
5511 		 * unlock our path, this is safe because only this
5512 		 * function is allowed to delete this snapshot
5513 		 */
5514 		btrfs_unlock_up_safe(path, 0);
5515 
5516 		level = btrfs_header_level(root->node);
5517 		while (1) {
5518 			btrfs_tree_lock(path->nodes[level]);
5519 			btrfs_set_lock_blocking_write(path->nodes[level]);
5520 			path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
5521 
5522 			ret = btrfs_lookup_extent_info(trans, fs_info,
5523 						path->nodes[level]->start,
5524 						level, 1, &wc->refs[level],
5525 						&wc->flags[level]);
5526 			if (ret < 0) {
5527 				err = ret;
5528 				goto out_end_trans;
5529 			}
5530 			BUG_ON(wc->refs[level] == 0);
5531 
5532 			if (level == root_item->drop_level)
5533 				break;
5534 
5535 			btrfs_tree_unlock(path->nodes[level]);
5536 			path->locks[level] = 0;
5537 			WARN_ON(wc->refs[level] != 1);
5538 			level--;
5539 		}
5540 	}
5541 
5542 	wc->restarted = test_bit(BTRFS_ROOT_DEAD_TREE, &root->state);
5543 	wc->level = level;
5544 	wc->shared_level = -1;
5545 	wc->stage = DROP_REFERENCE;
5546 	wc->update_ref = update_ref;
5547 	wc->keep_locks = 0;
5548 	wc->reada_count = BTRFS_NODEPTRS_PER_BLOCK(fs_info);
5549 
5550 	while (1) {
5551 
5552 		ret = walk_down_tree(trans, root, path, wc);
5553 		if (ret < 0) {
5554 			err = ret;
5555 			break;
5556 		}
5557 
5558 		ret = walk_up_tree(trans, root, path, wc, BTRFS_MAX_LEVEL);
5559 		if (ret < 0) {
5560 			err = ret;
5561 			break;
5562 		}
5563 
5564 		if (ret > 0) {
5565 			BUG_ON(wc->stage != DROP_REFERENCE);
5566 			break;
5567 		}
5568 
5569 		if (wc->stage == DROP_REFERENCE) {
5570 			wc->drop_level = wc->level;
5571 			btrfs_node_key_to_cpu(path->nodes[wc->drop_level],
5572 					      &wc->drop_progress,
5573 					      path->slots[wc->drop_level]);
5574 		}
5575 		btrfs_cpu_key_to_disk(&root_item->drop_progress,
5576 				      &wc->drop_progress);
5577 		root_item->drop_level = wc->drop_level;
5578 
5579 		BUG_ON(wc->level == 0);
5580 		if (btrfs_should_end_transaction(trans) ||
5581 		    (!for_reloc && btrfs_need_cleaner_sleep(fs_info))) {
5582 			ret = btrfs_update_root(trans, tree_root,
5583 						&root->root_key,
5584 						root_item);
5585 			if (ret) {
5586 				btrfs_abort_transaction(trans, ret);
5587 				err = ret;
5588 				goto out_end_trans;
5589 			}
5590 
5591 			btrfs_end_transaction_throttle(trans);
5592 			if (!for_reloc && btrfs_need_cleaner_sleep(fs_info)) {
5593 				btrfs_debug(fs_info,
5594 					    "drop snapshot early exit");
5595 				err = -EAGAIN;
5596 				goto out_free;
5597 			}
5598 
5599 			trans = btrfs_start_transaction(tree_root, 0);
5600 			if (IS_ERR(trans)) {
5601 				err = PTR_ERR(trans);
5602 				goto out_free;
5603 			}
5604 		}
5605 	}
5606 	btrfs_release_path(path);
5607 	if (err)
5608 		goto out_end_trans;
5609 
5610 	ret = btrfs_del_root(trans, &root->root_key);
5611 	if (ret) {
5612 		btrfs_abort_transaction(trans, ret);
5613 		err = ret;
5614 		goto out_end_trans;
5615 	}
5616 
5617 	if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
5618 		ret = btrfs_find_root(tree_root, &root->root_key, path,
5619 				      NULL, NULL);
5620 		if (ret < 0) {
5621 			btrfs_abort_transaction(trans, ret);
5622 			err = ret;
5623 			goto out_end_trans;
5624 		} else if (ret > 0) {
5625 			/* if we fail to delete the orphan item this time
5626 			 * around, it'll get picked up the next time.
5627 			 *
5628 			 * The most common failure here is just -ENOENT.
5629 			 */
5630 			btrfs_del_orphan_item(trans, tree_root,
5631 					      root->root_key.objectid);
5632 		}
5633 	}
5634 
5635 	/*
5636 	 * This subvolume is going to be completely dropped, and won't be
5637 	 * recorded as dirty roots, thus pertrans meta rsv will not be freed at
5638 	 * commit transaction time.  So free it here manually.
5639 	 */
5640 	btrfs_qgroup_convert_reserved_meta(root, INT_MAX);
5641 	btrfs_qgroup_free_meta_all_pertrans(root);
5642 
5643 	if (test_bit(BTRFS_ROOT_IN_RADIX, &root->state))
5644 		btrfs_add_dropped_root(trans, root);
5645 	else
5646 		btrfs_put_root(root);
5647 	root_dropped = true;
5648 out_end_trans:
5649 	btrfs_end_transaction_throttle(trans);
5650 out_free:
5651 	kfree(wc);
5652 	btrfs_free_path(path);
5653 out:
5654 	/*
5655 	 * So if we need to stop dropping the snapshot for whatever reason we
5656 	 * need to make sure to add it back to the dead root list so that we
5657 	 * keep trying to do the work later.  This also cleans up roots if we
5658 	 * don't have it in the radix (like when we recover after a power fail
5659 	 * or unmount) so we don't leak memory.
5660 	 */
5661 	if (!for_reloc && !root_dropped)
5662 		btrfs_add_dead_root(root);
5663 	return err;
5664 }
5665 
5666 /*
5667  * drop subtree rooted at tree block 'node'.
5668  *
5669  * NOTE: this function will unlock and release tree block 'node'
5670  * only used by relocation code
5671  */
5672 int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
5673 			struct btrfs_root *root,
5674 			struct extent_buffer *node,
5675 			struct extent_buffer *parent)
5676 {
5677 	struct btrfs_fs_info *fs_info = root->fs_info;
5678 	struct btrfs_path *path;
5679 	struct walk_control *wc;
5680 	int level;
5681 	int parent_level;
5682 	int ret = 0;
5683 	int wret;
5684 
5685 	BUG_ON(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
5686 
5687 	path = btrfs_alloc_path();
5688 	if (!path)
5689 		return -ENOMEM;
5690 
5691 	wc = kzalloc(sizeof(*wc), GFP_NOFS);
5692 	if (!wc) {
5693 		btrfs_free_path(path);
5694 		return -ENOMEM;
5695 	}
5696 
5697 	btrfs_assert_tree_locked(parent);
5698 	parent_level = btrfs_header_level(parent);
5699 	atomic_inc(&parent->refs);
5700 	path->nodes[parent_level] = parent;
5701 	path->slots[parent_level] = btrfs_header_nritems(parent);
5702 
5703 	btrfs_assert_tree_locked(node);
5704 	level = btrfs_header_level(node);
5705 	path->nodes[level] = node;
5706 	path->slots[level] = 0;
5707 	path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
5708 
5709 	wc->refs[parent_level] = 1;
5710 	wc->flags[parent_level] = BTRFS_BLOCK_FLAG_FULL_BACKREF;
5711 	wc->level = level;
5712 	wc->shared_level = -1;
5713 	wc->stage = DROP_REFERENCE;
5714 	wc->update_ref = 0;
5715 	wc->keep_locks = 1;
5716 	wc->reada_count = BTRFS_NODEPTRS_PER_BLOCK(fs_info);
5717 
5718 	while (1) {
5719 		wret = walk_down_tree(trans, root, path, wc);
5720 		if (wret < 0) {
5721 			ret = wret;
5722 			break;
5723 		}
5724 
5725 		wret = walk_up_tree(trans, root, path, wc, parent_level);
5726 		if (wret < 0)
5727 			ret = wret;
5728 		if (wret != 0)
5729 			break;
5730 	}
5731 
5732 	kfree(wc);
5733 	btrfs_free_path(path);
5734 	return ret;
5735 }
5736 
5737 /*
5738  * helper to account the unused space of all the readonly block group in the
5739  * space_info. takes mirrors into account.
5740  */
5741 u64 btrfs_account_ro_block_groups_free_space(struct btrfs_space_info *sinfo)
5742 {
5743 	struct btrfs_block_group *block_group;
5744 	u64 free_bytes = 0;
5745 	int factor;
5746 
5747 	/* It's df, we don't care if it's racy */
5748 	if (list_empty(&sinfo->ro_bgs))
5749 		return 0;
5750 
5751 	spin_lock(&sinfo->lock);
5752 	list_for_each_entry(block_group, &sinfo->ro_bgs, ro_list) {
5753 		spin_lock(&block_group->lock);
5754 
5755 		if (!block_group->ro) {
5756 			spin_unlock(&block_group->lock);
5757 			continue;
5758 		}
5759 
5760 		factor = btrfs_bg_type_to_factor(block_group->flags);
5761 		free_bytes += (block_group->length -
5762 			       block_group->used) * factor;
5763 
5764 		spin_unlock(&block_group->lock);
5765 	}
5766 	spin_unlock(&sinfo->lock);
5767 
5768 	return free_bytes;
5769 }
5770 
5771 int btrfs_error_unpin_extent_range(struct btrfs_fs_info *fs_info,
5772 				   u64 start, u64 end)
5773 {
5774 	return unpin_extent_range(fs_info, start, end, false);
5775 }
5776 
5777 /*
5778  * It used to be that old block groups would be left around forever.
5779  * Iterating over them would be enough to trim unused space.  Since we
5780  * now automatically remove them, we also need to iterate over unallocated
5781  * space.
5782  *
5783  * We don't want a transaction for this since the discard may take a
5784  * substantial amount of time.  We don't require that a transaction be
5785  * running, but we do need to take a running transaction into account
5786  * to ensure that we're not discarding chunks that were released or
5787  * allocated in the current transaction.
5788  *
5789  * Holding the chunks lock will prevent other threads from allocating
5790  * or releasing chunks, but it won't prevent a running transaction
5791  * from committing and releasing the memory that the pending chunks
5792  * list head uses.  For that, we need to take a reference to the
5793  * transaction and hold the commit root sem.  We only need to hold
5794  * it while performing the free space search since we have already
5795  * held back allocations.
5796  */
5797 static int btrfs_trim_free_extents(struct btrfs_device *device, u64 *trimmed)
5798 {
5799 	u64 start = SZ_1M, len = 0, end = 0;
5800 	int ret;
5801 
5802 	*trimmed = 0;
5803 
5804 	/* Discard not supported = nothing to do. */
5805 	if (!blk_queue_discard(bdev_get_queue(device->bdev)))
5806 		return 0;
5807 
5808 	/* Not writable = nothing to do. */
5809 	if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
5810 		return 0;
5811 
5812 	/* No free space = nothing to do. */
5813 	if (device->total_bytes <= device->bytes_used)
5814 		return 0;
5815 
5816 	ret = 0;
5817 
5818 	while (1) {
5819 		struct btrfs_fs_info *fs_info = device->fs_info;
5820 		u64 bytes;
5821 
5822 		ret = mutex_lock_interruptible(&fs_info->chunk_mutex);
5823 		if (ret)
5824 			break;
5825 
5826 		find_first_clear_extent_bit(&device->alloc_state, start,
5827 					    &start, &end,
5828 					    CHUNK_TRIMMED | CHUNK_ALLOCATED);
5829 
5830 		/* Check if there are any CHUNK_* bits left */
5831 		if (start > device->total_bytes) {
5832 			WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
5833 			btrfs_warn_in_rcu(fs_info,
5834 "ignoring attempt to trim beyond device size: offset %llu length %llu device %s device size %llu",
5835 					  start, end - start + 1,
5836 					  rcu_str_deref(device->name),
5837 					  device->total_bytes);
5838 			mutex_unlock(&fs_info->chunk_mutex);
5839 			ret = 0;
5840 			break;
5841 		}
5842 
5843 		/* Ensure we skip the reserved area in the first 1M */
5844 		start = max_t(u64, start, SZ_1M);
5845 
5846 		/*
5847 		 * If find_first_clear_extent_bit find a range that spans the
5848 		 * end of the device it will set end to -1, in this case it's up
5849 		 * to the caller to trim the value to the size of the device.
5850 		 */
5851 		end = min(end, device->total_bytes - 1);
5852 
5853 		len = end - start + 1;
5854 
5855 		/* We didn't find any extents */
5856 		if (!len) {
5857 			mutex_unlock(&fs_info->chunk_mutex);
5858 			ret = 0;
5859 			break;
5860 		}
5861 
5862 		ret = btrfs_issue_discard(device->bdev, start, len,
5863 					  &bytes);
5864 		if (!ret)
5865 			set_extent_bits(&device->alloc_state, start,
5866 					start + bytes - 1,
5867 					CHUNK_TRIMMED);
5868 		mutex_unlock(&fs_info->chunk_mutex);
5869 
5870 		if (ret)
5871 			break;
5872 
5873 		start += len;
5874 		*trimmed += bytes;
5875 
5876 		if (fatal_signal_pending(current)) {
5877 			ret = -ERESTARTSYS;
5878 			break;
5879 		}
5880 
5881 		cond_resched();
5882 	}
5883 
5884 	return ret;
5885 }
5886 
5887 /*
5888  * Trim the whole filesystem by:
5889  * 1) trimming the free space in each block group
5890  * 2) trimming the unallocated space on each device
5891  *
5892  * This will also continue trimming even if a block group or device encounters
5893  * an error.  The return value will be the last error, or 0 if nothing bad
5894  * happens.
5895  */
5896 int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
5897 {
5898 	struct btrfs_block_group *cache = NULL;
5899 	struct btrfs_device *device;
5900 	struct list_head *devices;
5901 	u64 group_trimmed;
5902 	u64 range_end = U64_MAX;
5903 	u64 start;
5904 	u64 end;
5905 	u64 trimmed = 0;
5906 	u64 bg_failed = 0;
5907 	u64 dev_failed = 0;
5908 	int bg_ret = 0;
5909 	int dev_ret = 0;
5910 	int ret = 0;
5911 
5912 	/*
5913 	 * Check range overflow if range->len is set.
5914 	 * The default range->len is U64_MAX.
5915 	 */
5916 	if (range->len != U64_MAX &&
5917 	    check_add_overflow(range->start, range->len, &range_end))
5918 		return -EINVAL;
5919 
5920 	cache = btrfs_lookup_first_block_group(fs_info, range->start);
5921 	for (; cache; cache = btrfs_next_block_group(cache)) {
5922 		if (cache->start >= range_end) {
5923 			btrfs_put_block_group(cache);
5924 			break;
5925 		}
5926 
5927 		start = max(range->start, cache->start);
5928 		end = min(range_end, cache->start + cache->length);
5929 
5930 		if (end - start >= range->minlen) {
5931 			if (!btrfs_block_group_done(cache)) {
5932 				ret = btrfs_cache_block_group(cache, 0);
5933 				if (ret) {
5934 					bg_failed++;
5935 					bg_ret = ret;
5936 					continue;
5937 				}
5938 				ret = btrfs_wait_block_group_cache_done(cache);
5939 				if (ret) {
5940 					bg_failed++;
5941 					bg_ret = ret;
5942 					continue;
5943 				}
5944 			}
5945 			ret = btrfs_trim_block_group(cache,
5946 						     &group_trimmed,
5947 						     start,
5948 						     end,
5949 						     range->minlen);
5950 
5951 			trimmed += group_trimmed;
5952 			if (ret) {
5953 				bg_failed++;
5954 				bg_ret = ret;
5955 				continue;
5956 			}
5957 		}
5958 	}
5959 
5960 	if (bg_failed)
5961 		btrfs_warn(fs_info,
5962 			"failed to trim %llu block group(s), last error %d",
5963 			bg_failed, bg_ret);
5964 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
5965 	devices = &fs_info->fs_devices->devices;
5966 	list_for_each_entry(device, devices, dev_list) {
5967 		ret = btrfs_trim_free_extents(device, &group_trimmed);
5968 		if (ret) {
5969 			dev_failed++;
5970 			dev_ret = ret;
5971 			break;
5972 		}
5973 
5974 		trimmed += group_trimmed;
5975 	}
5976 	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
5977 
5978 	if (dev_failed)
5979 		btrfs_warn(fs_info,
5980 			"failed to trim %llu device(s), last error %d",
5981 			dev_failed, dev_ret);
5982 	range->len = trimmed;
5983 	if (bg_ret)
5984 		return bg_ret;
5985 	return dev_ret;
5986 }
5987