xref: /openbmc/linux/fs/btrfs/extent_io.c (revision 9c1f8594)
1 #include <linux/bitops.h>
2 #include <linux/slab.h>
3 #include <linux/bio.h>
4 #include <linux/mm.h>
5 #include <linux/pagemap.h>
6 #include <linux/page-flags.h>
7 #include <linux/module.h>
8 #include <linux/spinlock.h>
9 #include <linux/blkdev.h>
10 #include <linux/swap.h>
11 #include <linux/writeback.h>
12 #include <linux/pagevec.h>
13 #include <linux/prefetch.h>
14 #include <linux/cleancache.h>
15 #include "extent_io.h"
16 #include "extent_map.h"
17 #include "compat.h"
18 #include "ctree.h"
19 #include "btrfs_inode.h"
20 
21 static struct kmem_cache *extent_state_cache;
22 static struct kmem_cache *extent_buffer_cache;
23 
24 static LIST_HEAD(buffers);
25 static LIST_HEAD(states);
26 
27 #define LEAK_DEBUG 0
28 #if LEAK_DEBUG
29 static DEFINE_SPINLOCK(leak_lock);
30 #endif
31 
32 #define BUFFER_LRU_MAX 64
33 
34 struct tree_entry {
35 	u64 start;
36 	u64 end;
37 	struct rb_node rb_node;
38 };
39 
40 struct extent_page_data {
41 	struct bio *bio;
42 	struct extent_io_tree *tree;
43 	get_extent_t *get_extent;
44 
45 	/* tells writepage not to lock the state bits for this range
46 	 * it still does the unlocking
47 	 */
48 	unsigned int extent_locked:1;
49 
50 	/* tells the submit_bio code to use a WRITE_SYNC */
51 	unsigned int sync_io:1;
52 };
53 
54 int __init extent_io_init(void)
55 {
56 	extent_state_cache = kmem_cache_create("extent_state",
57 			sizeof(struct extent_state), 0,
58 			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
59 	if (!extent_state_cache)
60 		return -ENOMEM;
61 
62 	extent_buffer_cache = kmem_cache_create("extent_buffers",
63 			sizeof(struct extent_buffer), 0,
64 			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
65 	if (!extent_buffer_cache)
66 		goto free_state_cache;
67 	return 0;
68 
69 free_state_cache:
70 	kmem_cache_destroy(extent_state_cache);
71 	return -ENOMEM;
72 }
73 
74 void extent_io_exit(void)
75 {
76 	struct extent_state *state;
77 	struct extent_buffer *eb;
78 
79 	while (!list_empty(&states)) {
80 		state = list_entry(states.next, struct extent_state, leak_list);
81 		printk(KERN_ERR "btrfs state leak: start %llu end %llu "
82 		       "state %lu in tree %p refs %d\n",
83 		       (unsigned long long)state->start,
84 		       (unsigned long long)state->end,
85 		       state->state, state->tree, atomic_read(&state->refs));
86 		list_del(&state->leak_list);
87 		kmem_cache_free(extent_state_cache, state);
88 
89 	}
90 
91 	while (!list_empty(&buffers)) {
92 		eb = list_entry(buffers.next, struct extent_buffer, leak_list);
93 		printk(KERN_ERR "btrfs buffer leak start %llu len %lu "
94 		       "refs %d\n", (unsigned long long)eb->start,
95 		       eb->len, atomic_read(&eb->refs));
96 		list_del(&eb->leak_list);
97 		kmem_cache_free(extent_buffer_cache, eb);
98 	}
99 	if (extent_state_cache)
100 		kmem_cache_destroy(extent_state_cache);
101 	if (extent_buffer_cache)
102 		kmem_cache_destroy(extent_buffer_cache);
103 }
104 
105 void extent_io_tree_init(struct extent_io_tree *tree,
106 			 struct address_space *mapping)
107 {
108 	tree->state = RB_ROOT;
109 	INIT_RADIX_TREE(&tree->buffer, GFP_ATOMIC);
110 	tree->ops = NULL;
111 	tree->dirty_bytes = 0;
112 	spin_lock_init(&tree->lock);
113 	spin_lock_init(&tree->buffer_lock);
114 	tree->mapping = mapping;
115 }
116 
117 static struct extent_state *alloc_extent_state(gfp_t mask)
118 {
119 	struct extent_state *state;
120 #if LEAK_DEBUG
121 	unsigned long flags;
122 #endif
123 
124 	state = kmem_cache_alloc(extent_state_cache, mask);
125 	if (!state)
126 		return state;
127 	state->state = 0;
128 	state->private = 0;
129 	state->tree = NULL;
130 #if LEAK_DEBUG
131 	spin_lock_irqsave(&leak_lock, flags);
132 	list_add(&state->leak_list, &states);
133 	spin_unlock_irqrestore(&leak_lock, flags);
134 #endif
135 	atomic_set(&state->refs, 1);
136 	init_waitqueue_head(&state->wq);
137 	return state;
138 }
139 
140 void free_extent_state(struct extent_state *state)
141 {
142 	if (!state)
143 		return;
144 	if (atomic_dec_and_test(&state->refs)) {
145 #if LEAK_DEBUG
146 		unsigned long flags;
147 #endif
148 		WARN_ON(state->tree);
149 #if LEAK_DEBUG
150 		spin_lock_irqsave(&leak_lock, flags);
151 		list_del(&state->leak_list);
152 		spin_unlock_irqrestore(&leak_lock, flags);
153 #endif
154 		kmem_cache_free(extent_state_cache, state);
155 	}
156 }
157 
158 static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
159 				   struct rb_node *node)
160 {
161 	struct rb_node **p = &root->rb_node;
162 	struct rb_node *parent = NULL;
163 	struct tree_entry *entry;
164 
165 	while (*p) {
166 		parent = *p;
167 		entry = rb_entry(parent, struct tree_entry, rb_node);
168 
169 		if (offset < entry->start)
170 			p = &(*p)->rb_left;
171 		else if (offset > entry->end)
172 			p = &(*p)->rb_right;
173 		else
174 			return parent;
175 	}
176 
177 	entry = rb_entry(node, struct tree_entry, rb_node);
178 	rb_link_node(node, parent, p);
179 	rb_insert_color(node, root);
180 	return NULL;
181 }
182 
183 static struct rb_node *__etree_search(struct extent_io_tree *tree, u64 offset,
184 				     struct rb_node **prev_ret,
185 				     struct rb_node **next_ret)
186 {
187 	struct rb_root *root = &tree->state;
188 	struct rb_node *n = root->rb_node;
189 	struct rb_node *prev = NULL;
190 	struct rb_node *orig_prev = NULL;
191 	struct tree_entry *entry;
192 	struct tree_entry *prev_entry = NULL;
193 
194 	while (n) {
195 		entry = rb_entry(n, struct tree_entry, rb_node);
196 		prev = n;
197 		prev_entry = entry;
198 
199 		if (offset < entry->start)
200 			n = n->rb_left;
201 		else if (offset > entry->end)
202 			n = n->rb_right;
203 		else
204 			return n;
205 	}
206 
207 	if (prev_ret) {
208 		orig_prev = prev;
209 		while (prev && offset > prev_entry->end) {
210 			prev = rb_next(prev);
211 			prev_entry = rb_entry(prev, struct tree_entry, rb_node);
212 		}
213 		*prev_ret = prev;
214 		prev = orig_prev;
215 	}
216 
217 	if (next_ret) {
218 		prev_entry = rb_entry(prev, struct tree_entry, rb_node);
219 		while (prev && offset < prev_entry->start) {
220 			prev = rb_prev(prev);
221 			prev_entry = rb_entry(prev, struct tree_entry, rb_node);
222 		}
223 		*next_ret = prev;
224 	}
225 	return NULL;
226 }
227 
228 static inline struct rb_node *tree_search(struct extent_io_tree *tree,
229 					  u64 offset)
230 {
231 	struct rb_node *prev = NULL;
232 	struct rb_node *ret;
233 
234 	ret = __etree_search(tree, offset, &prev, NULL);
235 	if (!ret)
236 		return prev;
237 	return ret;
238 }
239 
240 static void merge_cb(struct extent_io_tree *tree, struct extent_state *new,
241 		     struct extent_state *other)
242 {
243 	if (tree->ops && tree->ops->merge_extent_hook)
244 		tree->ops->merge_extent_hook(tree->mapping->host, new,
245 					     other);
246 }
247 
248 /*
249  * utility function to look for merge candidates inside a given range.
250  * Any extents with matching state are merged together into a single
251  * extent in the tree.  Extents with EXTENT_IO in their state field
252  * are not merged because the end_io handlers need to be able to do
253  * operations on them without sleeping (or doing allocations/splits).
254  *
255  * This should be called with the tree lock held.
256  */
257 static void merge_state(struct extent_io_tree *tree,
258 		        struct extent_state *state)
259 {
260 	struct extent_state *other;
261 	struct rb_node *other_node;
262 
263 	if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY))
264 		return;
265 
266 	other_node = rb_prev(&state->rb_node);
267 	if (other_node) {
268 		other = rb_entry(other_node, struct extent_state, rb_node);
269 		if (other->end == state->start - 1 &&
270 		    other->state == state->state) {
271 			merge_cb(tree, state, other);
272 			state->start = other->start;
273 			other->tree = NULL;
274 			rb_erase(&other->rb_node, &tree->state);
275 			free_extent_state(other);
276 		}
277 	}
278 	other_node = rb_next(&state->rb_node);
279 	if (other_node) {
280 		other = rb_entry(other_node, struct extent_state, rb_node);
281 		if (other->start == state->end + 1 &&
282 		    other->state == state->state) {
283 			merge_cb(tree, state, other);
284 			state->end = other->end;
285 			other->tree = NULL;
286 			rb_erase(&other->rb_node, &tree->state);
287 			free_extent_state(other);
288 		}
289 	}
290 }
291 
292 static void set_state_cb(struct extent_io_tree *tree,
293 			 struct extent_state *state, int *bits)
294 {
295 	if (tree->ops && tree->ops->set_bit_hook)
296 		tree->ops->set_bit_hook(tree->mapping->host, state, bits);
297 }
298 
299 static void clear_state_cb(struct extent_io_tree *tree,
300 			   struct extent_state *state, int *bits)
301 {
302 	if (tree->ops && tree->ops->clear_bit_hook)
303 		tree->ops->clear_bit_hook(tree->mapping->host, state, bits);
304 }
305 
306 static void set_state_bits(struct extent_io_tree *tree,
307 			   struct extent_state *state, int *bits);
308 
309 /*
310  * insert an extent_state struct into the tree.  'bits' are set on the
311  * struct before it is inserted.
312  *
313  * This may return -EEXIST if the extent is already there, in which case the
314  * state struct is freed.
315  *
316  * The tree lock is not taken internally.  This is a utility function and
317  * probably isn't what you want to call (see set/clear_extent_bit).
318  */
319 static int insert_state(struct extent_io_tree *tree,
320 			struct extent_state *state, u64 start, u64 end,
321 			int *bits)
322 {
323 	struct rb_node *node;
324 
325 	if (end < start) {
326 		printk(KERN_ERR "btrfs end < start %llu %llu\n",
327 		       (unsigned long long)end,
328 		       (unsigned long long)start);
329 		WARN_ON(1);
330 	}
331 	state->start = start;
332 	state->end = end;
333 
334 	set_state_bits(tree, state, bits);
335 
336 	node = tree_insert(&tree->state, end, &state->rb_node);
337 	if (node) {
338 		struct extent_state *found;
339 		found = rb_entry(node, struct extent_state, rb_node);
340 		printk(KERN_ERR "btrfs found node %llu %llu on insert of "
341 		       "%llu %llu\n", (unsigned long long)found->start,
342 		       (unsigned long long)found->end,
343 		       (unsigned long long)start, (unsigned long long)end);
344 		return -EEXIST;
345 	}
346 	state->tree = tree;
347 	merge_state(tree, state);
348 	return 0;
349 }
350 
351 static void split_cb(struct extent_io_tree *tree, struct extent_state *orig,
352 		     u64 split)
353 {
354 	if (tree->ops && tree->ops->split_extent_hook)
355 		tree->ops->split_extent_hook(tree->mapping->host, orig, split);
356 }
357 
358 /*
359  * split a given extent state struct in two, inserting the preallocated
360  * struct 'prealloc' as the newly created second half.  'split' indicates an
361  * offset inside 'orig' where it should be split.
362  *
363  * Before calling,
364  * the tree has 'orig' at [orig->start, orig->end].  After calling, there
365  * are two extent state structs in the tree:
366  * prealloc: [orig->start, split - 1]
367  * orig: [ split, orig->end ]
368  *
369  * The tree locks are not taken by this function. They need to be held
370  * by the caller.
371  */
372 static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
373 		       struct extent_state *prealloc, u64 split)
374 {
375 	struct rb_node *node;
376 
377 	split_cb(tree, orig, split);
378 
379 	prealloc->start = orig->start;
380 	prealloc->end = split - 1;
381 	prealloc->state = orig->state;
382 	orig->start = split;
383 
384 	node = tree_insert(&tree->state, prealloc->end, &prealloc->rb_node);
385 	if (node) {
386 		free_extent_state(prealloc);
387 		return -EEXIST;
388 	}
389 	prealloc->tree = tree;
390 	return 0;
391 }
392 
393 /*
394  * utility function to clear some bits in an extent state struct.
395  * it will optionally wake up any one waiting on this state (wake == 1), or
396  * forcibly remove the state from the tree (delete == 1).
397  *
398  * If no bits are set on the state struct after clearing things, the
399  * struct is freed and removed from the tree
400  */
401 static int clear_state_bit(struct extent_io_tree *tree,
402 			    struct extent_state *state,
403 			    int *bits, int wake)
404 {
405 	int bits_to_clear = *bits & ~EXTENT_CTLBITS;
406 	int ret = state->state & bits_to_clear;
407 
408 	if ((bits_to_clear & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) {
409 		u64 range = state->end - state->start + 1;
410 		WARN_ON(range > tree->dirty_bytes);
411 		tree->dirty_bytes -= range;
412 	}
413 	clear_state_cb(tree, state, bits);
414 	state->state &= ~bits_to_clear;
415 	if (wake)
416 		wake_up(&state->wq);
417 	if (state->state == 0) {
418 		if (state->tree) {
419 			rb_erase(&state->rb_node, &tree->state);
420 			state->tree = NULL;
421 			free_extent_state(state);
422 		} else {
423 			WARN_ON(1);
424 		}
425 	} else {
426 		merge_state(tree, state);
427 	}
428 	return ret;
429 }
430 
431 static struct extent_state *
432 alloc_extent_state_atomic(struct extent_state *prealloc)
433 {
434 	if (!prealloc)
435 		prealloc = alloc_extent_state(GFP_ATOMIC);
436 
437 	return prealloc;
438 }
439 
440 /*
441  * clear some bits on a range in the tree.  This may require splitting
442  * or inserting elements in the tree, so the gfp mask is used to
443  * indicate which allocations or sleeping are allowed.
444  *
445  * pass 'wake' == 1 to kick any sleepers, and 'delete' == 1 to remove
446  * the given range from the tree regardless of state (ie for truncate).
447  *
448  * the range [start, end] is inclusive.
449  *
450  * This takes the tree lock, and returns < 0 on error, > 0 if any of the
451  * bits were already set, or zero if none of the bits were already set.
452  */
453 int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
454 		     int bits, int wake, int delete,
455 		     struct extent_state **cached_state,
456 		     gfp_t mask)
457 {
458 	struct extent_state *state;
459 	struct extent_state *cached;
460 	struct extent_state *prealloc = NULL;
461 	struct rb_node *next_node;
462 	struct rb_node *node;
463 	u64 last_end;
464 	int err;
465 	int set = 0;
466 	int clear = 0;
467 
468 	if (delete)
469 		bits |= ~EXTENT_CTLBITS;
470 	bits |= EXTENT_FIRST_DELALLOC;
471 
472 	if (bits & (EXTENT_IOBITS | EXTENT_BOUNDARY))
473 		clear = 1;
474 again:
475 	if (!prealloc && (mask & __GFP_WAIT)) {
476 		prealloc = alloc_extent_state(mask);
477 		if (!prealloc)
478 			return -ENOMEM;
479 	}
480 
481 	spin_lock(&tree->lock);
482 	if (cached_state) {
483 		cached = *cached_state;
484 
485 		if (clear) {
486 			*cached_state = NULL;
487 			cached_state = NULL;
488 		}
489 
490 		if (cached && cached->tree && cached->start <= start &&
491 		    cached->end > start) {
492 			if (clear)
493 				atomic_dec(&cached->refs);
494 			state = cached;
495 			goto hit_next;
496 		}
497 		if (clear)
498 			free_extent_state(cached);
499 	}
500 	/*
501 	 * this search will find the extents that end after
502 	 * our range starts
503 	 */
504 	node = tree_search(tree, start);
505 	if (!node)
506 		goto out;
507 	state = rb_entry(node, struct extent_state, rb_node);
508 hit_next:
509 	if (state->start > end)
510 		goto out;
511 	WARN_ON(state->end < start);
512 	last_end = state->end;
513 
514 	/*
515 	 *     | ---- desired range ---- |
516 	 *  | state | or
517 	 *  | ------------- state -------------- |
518 	 *
519 	 * We need to split the extent we found, and may flip
520 	 * bits on second half.
521 	 *
522 	 * If the extent we found extends past our range, we
523 	 * just split and search again.  It'll get split again
524 	 * the next time though.
525 	 *
526 	 * If the extent we found is inside our range, we clear
527 	 * the desired bit on it.
528 	 */
529 
530 	if (state->start < start) {
531 		prealloc = alloc_extent_state_atomic(prealloc);
532 		BUG_ON(!prealloc);
533 		err = split_state(tree, state, prealloc, start);
534 		BUG_ON(err == -EEXIST);
535 		prealloc = NULL;
536 		if (err)
537 			goto out;
538 		if (state->end <= end) {
539 			set |= clear_state_bit(tree, state, &bits, wake);
540 			if (last_end == (u64)-1)
541 				goto out;
542 			start = last_end + 1;
543 		}
544 		goto search_again;
545 	}
546 	/*
547 	 * | ---- desired range ---- |
548 	 *                        | state |
549 	 * We need to split the extent, and clear the bit
550 	 * on the first half
551 	 */
552 	if (state->start <= end && state->end > end) {
553 		prealloc = alloc_extent_state_atomic(prealloc);
554 		BUG_ON(!prealloc);
555 		err = split_state(tree, state, prealloc, end + 1);
556 		BUG_ON(err == -EEXIST);
557 		if (wake)
558 			wake_up(&state->wq);
559 
560 		set |= clear_state_bit(tree, prealloc, &bits, wake);
561 
562 		prealloc = NULL;
563 		goto out;
564 	}
565 
566 	if (state->end < end && prealloc && !need_resched())
567 		next_node = rb_next(&state->rb_node);
568 	else
569 		next_node = NULL;
570 
571 	set |= clear_state_bit(tree, state, &bits, wake);
572 	if (last_end == (u64)-1)
573 		goto out;
574 	start = last_end + 1;
575 	if (start <= end && next_node) {
576 		state = rb_entry(next_node, struct extent_state,
577 				 rb_node);
578 		if (state->start == start)
579 			goto hit_next;
580 	}
581 	goto search_again;
582 
583 out:
584 	spin_unlock(&tree->lock);
585 	if (prealloc)
586 		free_extent_state(prealloc);
587 
588 	return set;
589 
590 search_again:
591 	if (start > end)
592 		goto out;
593 	spin_unlock(&tree->lock);
594 	if (mask & __GFP_WAIT)
595 		cond_resched();
596 	goto again;
597 }
598 
599 static int wait_on_state(struct extent_io_tree *tree,
600 			 struct extent_state *state)
601 		__releases(tree->lock)
602 		__acquires(tree->lock)
603 {
604 	DEFINE_WAIT(wait);
605 	prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);
606 	spin_unlock(&tree->lock);
607 	schedule();
608 	spin_lock(&tree->lock);
609 	finish_wait(&state->wq, &wait);
610 	return 0;
611 }
612 
613 /*
614  * waits for one or more bits to clear on a range in the state tree.
615  * The range [start, end] is inclusive.
616  * The tree lock is taken by this function
617  */
618 int wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, int bits)
619 {
620 	struct extent_state *state;
621 	struct rb_node *node;
622 
623 	spin_lock(&tree->lock);
624 again:
625 	while (1) {
626 		/*
627 		 * this search will find all the extents that end after
628 		 * our range starts
629 		 */
630 		node = tree_search(tree, start);
631 		if (!node)
632 			break;
633 
634 		state = rb_entry(node, struct extent_state, rb_node);
635 
636 		if (state->start > end)
637 			goto out;
638 
639 		if (state->state & bits) {
640 			start = state->start;
641 			atomic_inc(&state->refs);
642 			wait_on_state(tree, state);
643 			free_extent_state(state);
644 			goto again;
645 		}
646 		start = state->end + 1;
647 
648 		if (start > end)
649 			break;
650 
651 		cond_resched_lock(&tree->lock);
652 	}
653 out:
654 	spin_unlock(&tree->lock);
655 	return 0;
656 }
657 
658 static void set_state_bits(struct extent_io_tree *tree,
659 			   struct extent_state *state,
660 			   int *bits)
661 {
662 	int bits_to_set = *bits & ~EXTENT_CTLBITS;
663 
664 	set_state_cb(tree, state, bits);
665 	if ((bits_to_set & EXTENT_DIRTY) && !(state->state & EXTENT_DIRTY)) {
666 		u64 range = state->end - state->start + 1;
667 		tree->dirty_bytes += range;
668 	}
669 	state->state |= bits_to_set;
670 }
671 
672 static void cache_state(struct extent_state *state,
673 			struct extent_state **cached_ptr)
674 {
675 	if (cached_ptr && !(*cached_ptr)) {
676 		if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY)) {
677 			*cached_ptr = state;
678 			atomic_inc(&state->refs);
679 		}
680 	}
681 }
682 
683 static void uncache_state(struct extent_state **cached_ptr)
684 {
685 	if (cached_ptr && (*cached_ptr)) {
686 		struct extent_state *state = *cached_ptr;
687 		*cached_ptr = NULL;
688 		free_extent_state(state);
689 	}
690 }
691 
692 /*
693  * set some bits on a range in the tree.  This may require allocations or
694  * sleeping, so the gfp mask is used to indicate what is allowed.
695  *
696  * If any of the exclusive bits are set, this will fail with -EEXIST if some
697  * part of the range already has the desired bits set.  The start of the
698  * existing range is returned in failed_start in this case.
699  *
700  * [start, end] is inclusive This takes the tree lock.
701  */
702 
703 int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
704 		   int bits, int exclusive_bits, u64 *failed_start,
705 		   struct extent_state **cached_state, gfp_t mask)
706 {
707 	struct extent_state *state;
708 	struct extent_state *prealloc = NULL;
709 	struct rb_node *node;
710 	int err = 0;
711 	u64 last_start;
712 	u64 last_end;
713 
714 	bits |= EXTENT_FIRST_DELALLOC;
715 again:
716 	if (!prealloc && (mask & __GFP_WAIT)) {
717 		prealloc = alloc_extent_state(mask);
718 		BUG_ON(!prealloc);
719 	}
720 
721 	spin_lock(&tree->lock);
722 	if (cached_state && *cached_state) {
723 		state = *cached_state;
724 		if (state->start <= start && state->end > start &&
725 		    state->tree) {
726 			node = &state->rb_node;
727 			goto hit_next;
728 		}
729 	}
730 	/*
731 	 * this search will find all the extents that end after
732 	 * our range starts.
733 	 */
734 	node = tree_search(tree, start);
735 	if (!node) {
736 		prealloc = alloc_extent_state_atomic(prealloc);
737 		BUG_ON(!prealloc);
738 		err = insert_state(tree, prealloc, start, end, &bits);
739 		prealloc = NULL;
740 		BUG_ON(err == -EEXIST);
741 		goto out;
742 	}
743 	state = rb_entry(node, struct extent_state, rb_node);
744 hit_next:
745 	last_start = state->start;
746 	last_end = state->end;
747 
748 	/*
749 	 * | ---- desired range ---- |
750 	 * | state |
751 	 *
752 	 * Just lock what we found and keep going
753 	 */
754 	if (state->start == start && state->end <= end) {
755 		struct rb_node *next_node;
756 		if (state->state & exclusive_bits) {
757 			*failed_start = state->start;
758 			err = -EEXIST;
759 			goto out;
760 		}
761 
762 		set_state_bits(tree, state, &bits);
763 
764 		cache_state(state, cached_state);
765 		merge_state(tree, state);
766 		if (last_end == (u64)-1)
767 			goto out;
768 
769 		start = last_end + 1;
770 		next_node = rb_next(&state->rb_node);
771 		if (next_node && start < end && prealloc && !need_resched()) {
772 			state = rb_entry(next_node, struct extent_state,
773 					 rb_node);
774 			if (state->start == start)
775 				goto hit_next;
776 		}
777 		goto search_again;
778 	}
779 
780 	/*
781 	 *     | ---- desired range ---- |
782 	 * | state |
783 	 *   or
784 	 * | ------------- state -------------- |
785 	 *
786 	 * We need to split the extent we found, and may flip bits on
787 	 * second half.
788 	 *
789 	 * If the extent we found extends past our
790 	 * range, we just split and search again.  It'll get split
791 	 * again the next time though.
792 	 *
793 	 * If the extent we found is inside our range, we set the
794 	 * desired bit on it.
795 	 */
796 	if (state->start < start) {
797 		if (state->state & exclusive_bits) {
798 			*failed_start = start;
799 			err = -EEXIST;
800 			goto out;
801 		}
802 
803 		prealloc = alloc_extent_state_atomic(prealloc);
804 		BUG_ON(!prealloc);
805 		err = split_state(tree, state, prealloc, start);
806 		BUG_ON(err == -EEXIST);
807 		prealloc = NULL;
808 		if (err)
809 			goto out;
810 		if (state->end <= end) {
811 			set_state_bits(tree, state, &bits);
812 			cache_state(state, cached_state);
813 			merge_state(tree, state);
814 			if (last_end == (u64)-1)
815 				goto out;
816 			start = last_end + 1;
817 		}
818 		goto search_again;
819 	}
820 	/*
821 	 * | ---- desired range ---- |
822 	 *     | state | or               | state |
823 	 *
824 	 * There's a hole, we need to insert something in it and
825 	 * ignore the extent we found.
826 	 */
827 	if (state->start > start) {
828 		u64 this_end;
829 		if (end < last_start)
830 			this_end = end;
831 		else
832 			this_end = last_start - 1;
833 
834 		prealloc = alloc_extent_state_atomic(prealloc);
835 		BUG_ON(!prealloc);
836 
837 		/*
838 		 * Avoid to free 'prealloc' if it can be merged with
839 		 * the later extent.
840 		 */
841 		err = insert_state(tree, prealloc, start, this_end,
842 				   &bits);
843 		BUG_ON(err == -EEXIST);
844 		if (err) {
845 			free_extent_state(prealloc);
846 			prealloc = NULL;
847 			goto out;
848 		}
849 		cache_state(prealloc, cached_state);
850 		prealloc = NULL;
851 		start = this_end + 1;
852 		goto search_again;
853 	}
854 	/*
855 	 * | ---- desired range ---- |
856 	 *                        | state |
857 	 * We need to split the extent, and set the bit
858 	 * on the first half
859 	 */
860 	if (state->start <= end && state->end > end) {
861 		if (state->state & exclusive_bits) {
862 			*failed_start = start;
863 			err = -EEXIST;
864 			goto out;
865 		}
866 
867 		prealloc = alloc_extent_state_atomic(prealloc);
868 		BUG_ON(!prealloc);
869 		err = split_state(tree, state, prealloc, end + 1);
870 		BUG_ON(err == -EEXIST);
871 
872 		set_state_bits(tree, prealloc, &bits);
873 		cache_state(prealloc, cached_state);
874 		merge_state(tree, prealloc);
875 		prealloc = NULL;
876 		goto out;
877 	}
878 
879 	goto search_again;
880 
881 out:
882 	spin_unlock(&tree->lock);
883 	if (prealloc)
884 		free_extent_state(prealloc);
885 
886 	return err;
887 
888 search_again:
889 	if (start > end)
890 		goto out;
891 	spin_unlock(&tree->lock);
892 	if (mask & __GFP_WAIT)
893 		cond_resched();
894 	goto again;
895 }
896 
897 /* wrappers around set/clear extent bit */
898 int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
899 		     gfp_t mask)
900 {
901 	return set_extent_bit(tree, start, end, EXTENT_DIRTY, 0, NULL,
902 			      NULL, mask);
903 }
904 
905 int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
906 		    int bits, gfp_t mask)
907 {
908 	return set_extent_bit(tree, start, end, bits, 0, NULL,
909 			      NULL, mask);
910 }
911 
912 int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
913 		      int bits, gfp_t mask)
914 {
915 	return clear_extent_bit(tree, start, end, bits, 0, 0, NULL, mask);
916 }
917 
918 int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
919 			struct extent_state **cached_state, gfp_t mask)
920 {
921 	return set_extent_bit(tree, start, end,
922 			      EXTENT_DELALLOC | EXTENT_DIRTY | EXTENT_UPTODATE,
923 			      0, NULL, cached_state, mask);
924 }
925 
926 int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
927 		       gfp_t mask)
928 {
929 	return clear_extent_bit(tree, start, end,
930 				EXTENT_DIRTY | EXTENT_DELALLOC |
931 				EXTENT_DO_ACCOUNTING, 0, 0, NULL, mask);
932 }
933 
934 int set_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
935 		     gfp_t mask)
936 {
937 	return set_extent_bit(tree, start, end, EXTENT_NEW, 0, NULL,
938 			      NULL, mask);
939 }
940 
941 int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
942 			struct extent_state **cached_state, gfp_t mask)
943 {
944 	return set_extent_bit(tree, start, end, EXTENT_UPTODATE, 0,
945 			      NULL, cached_state, mask);
946 }
947 
948 static int clear_extent_uptodate(struct extent_io_tree *tree, u64 start,
949 				 u64 end, struct extent_state **cached_state,
950 				 gfp_t mask)
951 {
952 	return clear_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, 0,
953 				cached_state, mask);
954 }
955 
956 /*
957  * either insert or lock state struct between start and end use mask to tell
958  * us if waiting is desired.
959  */
960 int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
961 		     int bits, struct extent_state **cached_state, gfp_t mask)
962 {
963 	int err;
964 	u64 failed_start;
965 	while (1) {
966 		err = set_extent_bit(tree, start, end, EXTENT_LOCKED | bits,
967 				     EXTENT_LOCKED, &failed_start,
968 				     cached_state, mask);
969 		if (err == -EEXIST && (mask & __GFP_WAIT)) {
970 			wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED);
971 			start = failed_start;
972 		} else {
973 			break;
974 		}
975 		WARN_ON(start > end);
976 	}
977 	return err;
978 }
979 
980 int lock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask)
981 {
982 	return lock_extent_bits(tree, start, end, 0, NULL, mask);
983 }
984 
985 int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end,
986 		    gfp_t mask)
987 {
988 	int err;
989 	u64 failed_start;
990 
991 	err = set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
992 			     &failed_start, NULL, mask);
993 	if (err == -EEXIST) {
994 		if (failed_start > start)
995 			clear_extent_bit(tree, start, failed_start - 1,
996 					 EXTENT_LOCKED, 1, 0, NULL, mask);
997 		return 0;
998 	}
999 	return 1;
1000 }
1001 
1002 int unlock_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
1003 			 struct extent_state **cached, gfp_t mask)
1004 {
1005 	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, cached,
1006 				mask);
1007 }
1008 
1009 int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask)
1010 {
1011 	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, NULL,
1012 				mask);
1013 }
1014 
1015 /*
1016  * helper function to set both pages and extents in the tree writeback
1017  */
1018 static int set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
1019 {
1020 	unsigned long index = start >> PAGE_CACHE_SHIFT;
1021 	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
1022 	struct page *page;
1023 
1024 	while (index <= end_index) {
1025 		page = find_get_page(tree->mapping, index);
1026 		BUG_ON(!page);
1027 		set_page_writeback(page);
1028 		page_cache_release(page);
1029 		index++;
1030 	}
1031 	return 0;
1032 }
1033 
1034 /* find the first state struct with 'bits' set after 'start', and
1035  * return it.  tree->lock must be held.  NULL will returned if
1036  * nothing was found after 'start'
1037  */
1038 struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
1039 						 u64 start, int bits)
1040 {
1041 	struct rb_node *node;
1042 	struct extent_state *state;
1043 
1044 	/*
1045 	 * this search will find all the extents that end after
1046 	 * our range starts.
1047 	 */
1048 	node = tree_search(tree, start);
1049 	if (!node)
1050 		goto out;
1051 
1052 	while (1) {
1053 		state = rb_entry(node, struct extent_state, rb_node);
1054 		if (state->end >= start && (state->state & bits))
1055 			return state;
1056 
1057 		node = rb_next(node);
1058 		if (!node)
1059 			break;
1060 	}
1061 out:
1062 	return NULL;
1063 }
1064 
1065 /*
1066  * find the first offset in the io tree with 'bits' set. zero is
1067  * returned if we find something, and *start_ret and *end_ret are
1068  * set to reflect the state struct that was found.
1069  *
1070  * If nothing was found, 1 is returned, < 0 on error
1071  */
1072 int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
1073 			  u64 *start_ret, u64 *end_ret, int bits)
1074 {
1075 	struct extent_state *state;
1076 	int ret = 1;
1077 
1078 	spin_lock(&tree->lock);
1079 	state = find_first_extent_bit_state(tree, start, bits);
1080 	if (state) {
1081 		*start_ret = state->start;
1082 		*end_ret = state->end;
1083 		ret = 0;
1084 	}
1085 	spin_unlock(&tree->lock);
1086 	return ret;
1087 }
1088 
1089 /*
1090  * find a contiguous range of bytes in the file marked as delalloc, not
1091  * more than 'max_bytes'.  start and end are used to return the range,
1092  *
1093  * 1 is returned if we find something, 0 if nothing was in the tree
1094  */
1095 static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
1096 					u64 *start, u64 *end, u64 max_bytes,
1097 					struct extent_state **cached_state)
1098 {
1099 	struct rb_node *node;
1100 	struct extent_state *state;
1101 	u64 cur_start = *start;
1102 	u64 found = 0;
1103 	u64 total_bytes = 0;
1104 
1105 	spin_lock(&tree->lock);
1106 
1107 	/*
1108 	 * this search will find all the extents that end after
1109 	 * our range starts.
1110 	 */
1111 	node = tree_search(tree, cur_start);
1112 	if (!node) {
1113 		if (!found)
1114 			*end = (u64)-1;
1115 		goto out;
1116 	}
1117 
1118 	while (1) {
1119 		state = rb_entry(node, struct extent_state, rb_node);
1120 		if (found && (state->start != cur_start ||
1121 			      (state->state & EXTENT_BOUNDARY))) {
1122 			goto out;
1123 		}
1124 		if (!(state->state & EXTENT_DELALLOC)) {
1125 			if (!found)
1126 				*end = state->end;
1127 			goto out;
1128 		}
1129 		if (!found) {
1130 			*start = state->start;
1131 			*cached_state = state;
1132 			atomic_inc(&state->refs);
1133 		}
1134 		found++;
1135 		*end = state->end;
1136 		cur_start = state->end + 1;
1137 		node = rb_next(node);
1138 		if (!node)
1139 			break;
1140 		total_bytes += state->end - state->start + 1;
1141 		if (total_bytes >= max_bytes)
1142 			break;
1143 	}
1144 out:
1145 	spin_unlock(&tree->lock);
1146 	return found;
1147 }
1148 
1149 static noinline int __unlock_for_delalloc(struct inode *inode,
1150 					  struct page *locked_page,
1151 					  u64 start, u64 end)
1152 {
1153 	int ret;
1154 	struct page *pages[16];
1155 	unsigned long index = start >> PAGE_CACHE_SHIFT;
1156 	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
1157 	unsigned long nr_pages = end_index - index + 1;
1158 	int i;
1159 
1160 	if (index == locked_page->index && end_index == index)
1161 		return 0;
1162 
1163 	while (nr_pages > 0) {
1164 		ret = find_get_pages_contig(inode->i_mapping, index,
1165 				     min_t(unsigned long, nr_pages,
1166 				     ARRAY_SIZE(pages)), pages);
1167 		for (i = 0; i < ret; i++) {
1168 			if (pages[i] != locked_page)
1169 				unlock_page(pages[i]);
1170 			page_cache_release(pages[i]);
1171 		}
1172 		nr_pages -= ret;
1173 		index += ret;
1174 		cond_resched();
1175 	}
1176 	return 0;
1177 }
1178 
1179 static noinline int lock_delalloc_pages(struct inode *inode,
1180 					struct page *locked_page,
1181 					u64 delalloc_start,
1182 					u64 delalloc_end)
1183 {
1184 	unsigned long index = delalloc_start >> PAGE_CACHE_SHIFT;
1185 	unsigned long start_index = index;
1186 	unsigned long end_index = delalloc_end >> PAGE_CACHE_SHIFT;
1187 	unsigned long pages_locked = 0;
1188 	struct page *pages[16];
1189 	unsigned long nrpages;
1190 	int ret;
1191 	int i;
1192 
1193 	/* the caller is responsible for locking the start index */
1194 	if (index == locked_page->index && index == end_index)
1195 		return 0;
1196 
1197 	/* skip the page at the start index */
1198 	nrpages = end_index - index + 1;
1199 	while (nrpages > 0) {
1200 		ret = find_get_pages_contig(inode->i_mapping, index,
1201 				     min_t(unsigned long,
1202 				     nrpages, ARRAY_SIZE(pages)), pages);
1203 		if (ret == 0) {
1204 			ret = -EAGAIN;
1205 			goto done;
1206 		}
1207 		/* now we have an array of pages, lock them all */
1208 		for (i = 0; i < ret; i++) {
1209 			/*
1210 			 * the caller is taking responsibility for
1211 			 * locked_page
1212 			 */
1213 			if (pages[i] != locked_page) {
1214 				lock_page(pages[i]);
1215 				if (!PageDirty(pages[i]) ||
1216 				    pages[i]->mapping != inode->i_mapping) {
1217 					ret = -EAGAIN;
1218 					unlock_page(pages[i]);
1219 					page_cache_release(pages[i]);
1220 					goto done;
1221 				}
1222 			}
1223 			page_cache_release(pages[i]);
1224 			pages_locked++;
1225 		}
1226 		nrpages -= ret;
1227 		index += ret;
1228 		cond_resched();
1229 	}
1230 	ret = 0;
1231 done:
1232 	if (ret && pages_locked) {
1233 		__unlock_for_delalloc(inode, locked_page,
1234 			      delalloc_start,
1235 			      ((u64)(start_index + pages_locked - 1)) <<
1236 			      PAGE_CACHE_SHIFT);
1237 	}
1238 	return ret;
1239 }
1240 
1241 /*
1242  * find a contiguous range of bytes in the file marked as delalloc, not
1243  * more than 'max_bytes'.  start and end are used to return the range,
1244  *
1245  * 1 is returned if we find something, 0 if nothing was in the tree
1246  */
1247 static noinline u64 find_lock_delalloc_range(struct inode *inode,
1248 					     struct extent_io_tree *tree,
1249 					     struct page *locked_page,
1250 					     u64 *start, u64 *end,
1251 					     u64 max_bytes)
1252 {
1253 	u64 delalloc_start;
1254 	u64 delalloc_end;
1255 	u64 found;
1256 	struct extent_state *cached_state = NULL;
1257 	int ret;
1258 	int loops = 0;
1259 
1260 again:
1261 	/* step one, find a bunch of delalloc bytes starting at start */
1262 	delalloc_start = *start;
1263 	delalloc_end = 0;
1264 	found = find_delalloc_range(tree, &delalloc_start, &delalloc_end,
1265 				    max_bytes, &cached_state);
1266 	if (!found || delalloc_end <= *start) {
1267 		*start = delalloc_start;
1268 		*end = delalloc_end;
1269 		free_extent_state(cached_state);
1270 		return found;
1271 	}
1272 
1273 	/*
1274 	 * start comes from the offset of locked_page.  We have to lock
1275 	 * pages in order, so we can't process delalloc bytes before
1276 	 * locked_page
1277 	 */
1278 	if (delalloc_start < *start)
1279 		delalloc_start = *start;
1280 
1281 	/*
1282 	 * make sure to limit the number of pages we try to lock down
1283 	 * if we're looping.
1284 	 */
1285 	if (delalloc_end + 1 - delalloc_start > max_bytes && loops)
1286 		delalloc_end = delalloc_start + PAGE_CACHE_SIZE - 1;
1287 
1288 	/* step two, lock all the pages after the page that has start */
1289 	ret = lock_delalloc_pages(inode, locked_page,
1290 				  delalloc_start, delalloc_end);
1291 	if (ret == -EAGAIN) {
1292 		/* some of the pages are gone, lets avoid looping by
1293 		 * shortening the size of the delalloc range we're searching
1294 		 */
1295 		free_extent_state(cached_state);
1296 		if (!loops) {
1297 			unsigned long offset = (*start) & (PAGE_CACHE_SIZE - 1);
1298 			max_bytes = PAGE_CACHE_SIZE - offset;
1299 			loops = 1;
1300 			goto again;
1301 		} else {
1302 			found = 0;
1303 			goto out_failed;
1304 		}
1305 	}
1306 	BUG_ON(ret);
1307 
1308 	/* step three, lock the state bits for the whole range */
1309 	lock_extent_bits(tree, delalloc_start, delalloc_end,
1310 			 0, &cached_state, GFP_NOFS);
1311 
1312 	/* then test to make sure it is all still delalloc */
1313 	ret = test_range_bit(tree, delalloc_start, delalloc_end,
1314 			     EXTENT_DELALLOC, 1, cached_state);
1315 	if (!ret) {
1316 		unlock_extent_cached(tree, delalloc_start, delalloc_end,
1317 				     &cached_state, GFP_NOFS);
1318 		__unlock_for_delalloc(inode, locked_page,
1319 			      delalloc_start, delalloc_end);
1320 		cond_resched();
1321 		goto again;
1322 	}
1323 	free_extent_state(cached_state);
1324 	*start = delalloc_start;
1325 	*end = delalloc_end;
1326 out_failed:
1327 	return found;
1328 }
1329 
1330 int extent_clear_unlock_delalloc(struct inode *inode,
1331 				struct extent_io_tree *tree,
1332 				u64 start, u64 end, struct page *locked_page,
1333 				unsigned long op)
1334 {
1335 	int ret;
1336 	struct page *pages[16];
1337 	unsigned long index = start >> PAGE_CACHE_SHIFT;
1338 	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
1339 	unsigned long nr_pages = end_index - index + 1;
1340 	int i;
1341 	int clear_bits = 0;
1342 
1343 	if (op & EXTENT_CLEAR_UNLOCK)
1344 		clear_bits |= EXTENT_LOCKED;
1345 	if (op & EXTENT_CLEAR_DIRTY)
1346 		clear_bits |= EXTENT_DIRTY;
1347 
1348 	if (op & EXTENT_CLEAR_DELALLOC)
1349 		clear_bits |= EXTENT_DELALLOC;
1350 
1351 	clear_extent_bit(tree, start, end, clear_bits, 1, 0, NULL, GFP_NOFS);
1352 	if (!(op & (EXTENT_CLEAR_UNLOCK_PAGE | EXTENT_CLEAR_DIRTY |
1353 		    EXTENT_SET_WRITEBACK | EXTENT_END_WRITEBACK |
1354 		    EXTENT_SET_PRIVATE2)))
1355 		return 0;
1356 
1357 	while (nr_pages > 0) {
1358 		ret = find_get_pages_contig(inode->i_mapping, index,
1359 				     min_t(unsigned long,
1360 				     nr_pages, ARRAY_SIZE(pages)), pages);
1361 		for (i = 0; i < ret; i++) {
1362 
1363 			if (op & EXTENT_SET_PRIVATE2)
1364 				SetPagePrivate2(pages[i]);
1365 
1366 			if (pages[i] == locked_page) {
1367 				page_cache_release(pages[i]);
1368 				continue;
1369 			}
1370 			if (op & EXTENT_CLEAR_DIRTY)
1371 				clear_page_dirty_for_io(pages[i]);
1372 			if (op & EXTENT_SET_WRITEBACK)
1373 				set_page_writeback(pages[i]);
1374 			if (op & EXTENT_END_WRITEBACK)
1375 				end_page_writeback(pages[i]);
1376 			if (op & EXTENT_CLEAR_UNLOCK_PAGE)
1377 				unlock_page(pages[i]);
1378 			page_cache_release(pages[i]);
1379 		}
1380 		nr_pages -= ret;
1381 		index += ret;
1382 		cond_resched();
1383 	}
1384 	return 0;
1385 }
1386 
1387 /*
1388  * count the number of bytes in the tree that have a given bit(s)
1389  * set.  This can be fairly slow, except for EXTENT_DIRTY which is
1390  * cached.  The total number found is returned.
1391  */
1392 u64 count_range_bits(struct extent_io_tree *tree,
1393 		     u64 *start, u64 search_end, u64 max_bytes,
1394 		     unsigned long bits, int contig)
1395 {
1396 	struct rb_node *node;
1397 	struct extent_state *state;
1398 	u64 cur_start = *start;
1399 	u64 total_bytes = 0;
1400 	u64 last = 0;
1401 	int found = 0;
1402 
1403 	if (search_end <= cur_start) {
1404 		WARN_ON(1);
1405 		return 0;
1406 	}
1407 
1408 	spin_lock(&tree->lock);
1409 	if (cur_start == 0 && bits == EXTENT_DIRTY) {
1410 		total_bytes = tree->dirty_bytes;
1411 		goto out;
1412 	}
1413 	/*
1414 	 * this search will find all the extents that end after
1415 	 * our range starts.
1416 	 */
1417 	node = tree_search(tree, cur_start);
1418 	if (!node)
1419 		goto out;
1420 
1421 	while (1) {
1422 		state = rb_entry(node, struct extent_state, rb_node);
1423 		if (state->start > search_end)
1424 			break;
1425 		if (contig && found && state->start > last + 1)
1426 			break;
1427 		if (state->end >= cur_start && (state->state & bits) == bits) {
1428 			total_bytes += min(search_end, state->end) + 1 -
1429 				       max(cur_start, state->start);
1430 			if (total_bytes >= max_bytes)
1431 				break;
1432 			if (!found) {
1433 				*start = max(cur_start, state->start);
1434 				found = 1;
1435 			}
1436 			last = state->end;
1437 		} else if (contig && found) {
1438 			break;
1439 		}
1440 		node = rb_next(node);
1441 		if (!node)
1442 			break;
1443 	}
1444 out:
1445 	spin_unlock(&tree->lock);
1446 	return total_bytes;
1447 }
1448 
1449 /*
1450  * set the private field for a given byte offset in the tree.  If there isn't
1451  * an extent_state there already, this does nothing.
1452  */
1453 int set_state_private(struct extent_io_tree *tree, u64 start, u64 private)
1454 {
1455 	struct rb_node *node;
1456 	struct extent_state *state;
1457 	int ret = 0;
1458 
1459 	spin_lock(&tree->lock);
1460 	/*
1461 	 * this search will find all the extents that end after
1462 	 * our range starts.
1463 	 */
1464 	node = tree_search(tree, start);
1465 	if (!node) {
1466 		ret = -ENOENT;
1467 		goto out;
1468 	}
1469 	state = rb_entry(node, struct extent_state, rb_node);
1470 	if (state->start != start) {
1471 		ret = -ENOENT;
1472 		goto out;
1473 	}
1474 	state->private = private;
1475 out:
1476 	spin_unlock(&tree->lock);
1477 	return ret;
1478 }
1479 
1480 int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private)
1481 {
1482 	struct rb_node *node;
1483 	struct extent_state *state;
1484 	int ret = 0;
1485 
1486 	spin_lock(&tree->lock);
1487 	/*
1488 	 * this search will find all the extents that end after
1489 	 * our range starts.
1490 	 */
1491 	node = tree_search(tree, start);
1492 	if (!node) {
1493 		ret = -ENOENT;
1494 		goto out;
1495 	}
1496 	state = rb_entry(node, struct extent_state, rb_node);
1497 	if (state->start != start) {
1498 		ret = -ENOENT;
1499 		goto out;
1500 	}
1501 	*private = state->private;
1502 out:
1503 	spin_unlock(&tree->lock);
1504 	return ret;
1505 }
1506 
1507 /*
1508  * searches a range in the state tree for a given mask.
1509  * If 'filled' == 1, this returns 1 only if every extent in the tree
1510  * has the bits set.  Otherwise, 1 is returned if any bit in the
1511  * range is found set.
1512  */
1513 int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
1514 		   int bits, int filled, struct extent_state *cached)
1515 {
1516 	struct extent_state *state = NULL;
1517 	struct rb_node *node;
1518 	int bitset = 0;
1519 
1520 	spin_lock(&tree->lock);
1521 	if (cached && cached->tree && cached->start <= start &&
1522 	    cached->end > start)
1523 		node = &cached->rb_node;
1524 	else
1525 		node = tree_search(tree, start);
1526 	while (node && start <= end) {
1527 		state = rb_entry(node, struct extent_state, rb_node);
1528 
1529 		if (filled && state->start > start) {
1530 			bitset = 0;
1531 			break;
1532 		}
1533 
1534 		if (state->start > end)
1535 			break;
1536 
1537 		if (state->state & bits) {
1538 			bitset = 1;
1539 			if (!filled)
1540 				break;
1541 		} else if (filled) {
1542 			bitset = 0;
1543 			break;
1544 		}
1545 
1546 		if (state->end == (u64)-1)
1547 			break;
1548 
1549 		start = state->end + 1;
1550 		if (start > end)
1551 			break;
1552 		node = rb_next(node);
1553 		if (!node) {
1554 			if (filled)
1555 				bitset = 0;
1556 			break;
1557 		}
1558 	}
1559 	spin_unlock(&tree->lock);
1560 	return bitset;
1561 }
1562 
1563 /*
1564  * helper function to set a given page up to date if all the
1565  * extents in the tree for that page are up to date
1566  */
1567 static int check_page_uptodate(struct extent_io_tree *tree,
1568 			       struct page *page)
1569 {
1570 	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
1571 	u64 end = start + PAGE_CACHE_SIZE - 1;
1572 	if (test_range_bit(tree, start, end, EXTENT_UPTODATE, 1, NULL))
1573 		SetPageUptodate(page);
1574 	return 0;
1575 }
1576 
1577 /*
1578  * helper function to unlock a page if all the extents in the tree
1579  * for that page are unlocked
1580  */
1581 static int check_page_locked(struct extent_io_tree *tree,
1582 			     struct page *page)
1583 {
1584 	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
1585 	u64 end = start + PAGE_CACHE_SIZE - 1;
1586 	if (!test_range_bit(tree, start, end, EXTENT_LOCKED, 0, NULL))
1587 		unlock_page(page);
1588 	return 0;
1589 }
1590 
1591 /*
1592  * helper function to end page writeback if all the extents
1593  * in the tree for that page are done with writeback
1594  */
1595 static int check_page_writeback(struct extent_io_tree *tree,
1596 			     struct page *page)
1597 {
1598 	end_page_writeback(page);
1599 	return 0;
1600 }
1601 
1602 /* lots and lots of room for performance fixes in the end_bio funcs */
1603 
1604 /*
1605  * after a writepage IO is done, we need to:
1606  * clear the uptodate bits on error
1607  * clear the writeback bits in the extent tree for this IO
1608  * end_page_writeback if the page has no more pending IO
1609  *
1610  * Scheduling is not allowed, so the extent state tree is expected
1611  * to have one and only one object corresponding to this IO.
1612  */
1613 static void end_bio_extent_writepage(struct bio *bio, int err)
1614 {
1615 	int uptodate = err == 0;
1616 	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
1617 	struct extent_io_tree *tree;
1618 	u64 start;
1619 	u64 end;
1620 	int whole_page;
1621 	int ret;
1622 
1623 	do {
1624 		struct page *page = bvec->bv_page;
1625 		tree = &BTRFS_I(page->mapping->host)->io_tree;
1626 
1627 		start = ((u64)page->index << PAGE_CACHE_SHIFT) +
1628 			 bvec->bv_offset;
1629 		end = start + bvec->bv_len - 1;
1630 
1631 		if (bvec->bv_offset == 0 && bvec->bv_len == PAGE_CACHE_SIZE)
1632 			whole_page = 1;
1633 		else
1634 			whole_page = 0;
1635 
1636 		if (--bvec >= bio->bi_io_vec)
1637 			prefetchw(&bvec->bv_page->flags);
1638 		if (tree->ops && tree->ops->writepage_end_io_hook) {
1639 			ret = tree->ops->writepage_end_io_hook(page, start,
1640 						       end, NULL, uptodate);
1641 			if (ret)
1642 				uptodate = 0;
1643 		}
1644 
1645 		if (!uptodate && tree->ops &&
1646 		    tree->ops->writepage_io_failed_hook) {
1647 			ret = tree->ops->writepage_io_failed_hook(bio, page,
1648 							 start, end, NULL);
1649 			if (ret == 0) {
1650 				uptodate = (err == 0);
1651 				continue;
1652 			}
1653 		}
1654 
1655 		if (!uptodate) {
1656 			clear_extent_uptodate(tree, start, end, NULL, GFP_NOFS);
1657 			ClearPageUptodate(page);
1658 			SetPageError(page);
1659 		}
1660 
1661 		if (whole_page)
1662 			end_page_writeback(page);
1663 		else
1664 			check_page_writeback(tree, page);
1665 	} while (bvec >= bio->bi_io_vec);
1666 
1667 	bio_put(bio);
1668 }
1669 
1670 /*
1671  * after a readpage IO is done, we need to:
1672  * clear the uptodate bits on error
1673  * set the uptodate bits if things worked
1674  * set the page up to date if all extents in the tree are uptodate
1675  * clear the lock bit in the extent tree
1676  * unlock the page if there are no other extents locked for it
1677  *
1678  * Scheduling is not allowed, so the extent state tree is expected
1679  * to have one and only one object corresponding to this IO.
1680  */
1681 static void end_bio_extent_readpage(struct bio *bio, int err)
1682 {
1683 	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
1684 	struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1;
1685 	struct bio_vec *bvec = bio->bi_io_vec;
1686 	struct extent_io_tree *tree;
1687 	u64 start;
1688 	u64 end;
1689 	int whole_page;
1690 	int ret;
1691 
1692 	if (err)
1693 		uptodate = 0;
1694 
1695 	do {
1696 		struct page *page = bvec->bv_page;
1697 		struct extent_state *cached = NULL;
1698 		struct extent_state *state;
1699 
1700 		tree = &BTRFS_I(page->mapping->host)->io_tree;
1701 
1702 		start = ((u64)page->index << PAGE_CACHE_SHIFT) +
1703 			bvec->bv_offset;
1704 		end = start + bvec->bv_len - 1;
1705 
1706 		if (bvec->bv_offset == 0 && bvec->bv_len == PAGE_CACHE_SIZE)
1707 			whole_page = 1;
1708 		else
1709 			whole_page = 0;
1710 
1711 		if (++bvec <= bvec_end)
1712 			prefetchw(&bvec->bv_page->flags);
1713 
1714 		spin_lock(&tree->lock);
1715 		state = find_first_extent_bit_state(tree, start, EXTENT_LOCKED);
1716 		if (state && state->start == start) {
1717 			/*
1718 			 * take a reference on the state, unlock will drop
1719 			 * the ref
1720 			 */
1721 			cache_state(state, &cached);
1722 		}
1723 		spin_unlock(&tree->lock);
1724 
1725 		if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) {
1726 			ret = tree->ops->readpage_end_io_hook(page, start, end,
1727 							      state);
1728 			if (ret)
1729 				uptodate = 0;
1730 		}
1731 		if (!uptodate && tree->ops &&
1732 		    tree->ops->readpage_io_failed_hook) {
1733 			ret = tree->ops->readpage_io_failed_hook(bio, page,
1734 							 start, end, NULL);
1735 			if (ret == 0) {
1736 				uptodate =
1737 					test_bit(BIO_UPTODATE, &bio->bi_flags);
1738 				if (err)
1739 					uptodate = 0;
1740 				uncache_state(&cached);
1741 				continue;
1742 			}
1743 		}
1744 
1745 		if (uptodate) {
1746 			set_extent_uptodate(tree, start, end, &cached,
1747 					    GFP_ATOMIC);
1748 		}
1749 		unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
1750 
1751 		if (whole_page) {
1752 			if (uptodate) {
1753 				SetPageUptodate(page);
1754 			} else {
1755 				ClearPageUptodate(page);
1756 				SetPageError(page);
1757 			}
1758 			unlock_page(page);
1759 		} else {
1760 			if (uptodate) {
1761 				check_page_uptodate(tree, page);
1762 			} else {
1763 				ClearPageUptodate(page);
1764 				SetPageError(page);
1765 			}
1766 			check_page_locked(tree, page);
1767 		}
1768 	} while (bvec <= bvec_end);
1769 
1770 	bio_put(bio);
1771 }
1772 
1773 struct bio *
1774 btrfs_bio_alloc(struct block_device *bdev, u64 first_sector, int nr_vecs,
1775 		gfp_t gfp_flags)
1776 {
1777 	struct bio *bio;
1778 
1779 	bio = bio_alloc(gfp_flags, nr_vecs);
1780 
1781 	if (bio == NULL && (current->flags & PF_MEMALLOC)) {
1782 		while (!bio && (nr_vecs /= 2))
1783 			bio = bio_alloc(gfp_flags, nr_vecs);
1784 	}
1785 
1786 	if (bio) {
1787 		bio->bi_size = 0;
1788 		bio->bi_bdev = bdev;
1789 		bio->bi_sector = first_sector;
1790 	}
1791 	return bio;
1792 }
1793 
1794 static int submit_one_bio(int rw, struct bio *bio, int mirror_num,
1795 			  unsigned long bio_flags)
1796 {
1797 	int ret = 0;
1798 	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
1799 	struct page *page = bvec->bv_page;
1800 	struct extent_io_tree *tree = bio->bi_private;
1801 	u64 start;
1802 
1803 	start = ((u64)page->index << PAGE_CACHE_SHIFT) + bvec->bv_offset;
1804 
1805 	bio->bi_private = NULL;
1806 
1807 	bio_get(bio);
1808 
1809 	if (tree->ops && tree->ops->submit_bio_hook)
1810 		ret = tree->ops->submit_bio_hook(page->mapping->host, rw, bio,
1811 					   mirror_num, bio_flags, start);
1812 	else
1813 		submit_bio(rw, bio);
1814 	if (bio_flagged(bio, BIO_EOPNOTSUPP))
1815 		ret = -EOPNOTSUPP;
1816 	bio_put(bio);
1817 	return ret;
1818 }
1819 
1820 static int submit_extent_page(int rw, struct extent_io_tree *tree,
1821 			      struct page *page, sector_t sector,
1822 			      size_t size, unsigned long offset,
1823 			      struct block_device *bdev,
1824 			      struct bio **bio_ret,
1825 			      unsigned long max_pages,
1826 			      bio_end_io_t end_io_func,
1827 			      int mirror_num,
1828 			      unsigned long prev_bio_flags,
1829 			      unsigned long bio_flags)
1830 {
1831 	int ret = 0;
1832 	struct bio *bio;
1833 	int nr;
1834 	int contig = 0;
1835 	int this_compressed = bio_flags & EXTENT_BIO_COMPRESSED;
1836 	int old_compressed = prev_bio_flags & EXTENT_BIO_COMPRESSED;
1837 	size_t page_size = min_t(size_t, size, PAGE_CACHE_SIZE);
1838 
1839 	if (bio_ret && *bio_ret) {
1840 		bio = *bio_ret;
1841 		if (old_compressed)
1842 			contig = bio->bi_sector == sector;
1843 		else
1844 			contig = bio->bi_sector + (bio->bi_size >> 9) ==
1845 				sector;
1846 
1847 		if (prev_bio_flags != bio_flags || !contig ||
1848 		    (tree->ops && tree->ops->merge_bio_hook &&
1849 		     tree->ops->merge_bio_hook(page, offset, page_size, bio,
1850 					       bio_flags)) ||
1851 		    bio_add_page(bio, page, page_size, offset) < page_size) {
1852 			ret = submit_one_bio(rw, bio, mirror_num,
1853 					     prev_bio_flags);
1854 			bio = NULL;
1855 		} else {
1856 			return 0;
1857 		}
1858 	}
1859 	if (this_compressed)
1860 		nr = BIO_MAX_PAGES;
1861 	else
1862 		nr = bio_get_nr_vecs(bdev);
1863 
1864 	bio = btrfs_bio_alloc(bdev, sector, nr, GFP_NOFS | __GFP_HIGH);
1865 	if (!bio)
1866 		return -ENOMEM;
1867 
1868 	bio_add_page(bio, page, page_size, offset);
1869 	bio->bi_end_io = end_io_func;
1870 	bio->bi_private = tree;
1871 
1872 	if (bio_ret)
1873 		*bio_ret = bio;
1874 	else
1875 		ret = submit_one_bio(rw, bio, mirror_num, bio_flags);
1876 
1877 	return ret;
1878 }
1879 
1880 void set_page_extent_mapped(struct page *page)
1881 {
1882 	if (!PagePrivate(page)) {
1883 		SetPagePrivate(page);
1884 		page_cache_get(page);
1885 		set_page_private(page, EXTENT_PAGE_PRIVATE);
1886 	}
1887 }
1888 
1889 static void set_page_extent_head(struct page *page, unsigned long len)
1890 {
1891 	WARN_ON(!PagePrivate(page));
1892 	set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2);
1893 }
1894 
1895 /*
1896  * basic readpage implementation.  Locked extent state structs are inserted
1897  * into the tree that are removed when the IO is done (by the end_io
1898  * handlers)
1899  */
1900 static int __extent_read_full_page(struct extent_io_tree *tree,
1901 				   struct page *page,
1902 				   get_extent_t *get_extent,
1903 				   struct bio **bio, int mirror_num,
1904 				   unsigned long *bio_flags)
1905 {
1906 	struct inode *inode = page->mapping->host;
1907 	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
1908 	u64 page_end = start + PAGE_CACHE_SIZE - 1;
1909 	u64 end;
1910 	u64 cur = start;
1911 	u64 extent_offset;
1912 	u64 last_byte = i_size_read(inode);
1913 	u64 block_start;
1914 	u64 cur_end;
1915 	sector_t sector;
1916 	struct extent_map *em;
1917 	struct block_device *bdev;
1918 	struct btrfs_ordered_extent *ordered;
1919 	int ret;
1920 	int nr = 0;
1921 	size_t pg_offset = 0;
1922 	size_t iosize;
1923 	size_t disk_io_size;
1924 	size_t blocksize = inode->i_sb->s_blocksize;
1925 	unsigned long this_bio_flag = 0;
1926 
1927 	set_page_extent_mapped(page);
1928 
1929 	if (!PageUptodate(page)) {
1930 		if (cleancache_get_page(page) == 0) {
1931 			BUG_ON(blocksize != PAGE_SIZE);
1932 			goto out;
1933 		}
1934 	}
1935 
1936 	end = page_end;
1937 	while (1) {
1938 		lock_extent(tree, start, end, GFP_NOFS);
1939 		ordered = btrfs_lookup_ordered_extent(inode, start);
1940 		if (!ordered)
1941 			break;
1942 		unlock_extent(tree, start, end, GFP_NOFS);
1943 		btrfs_start_ordered_extent(inode, ordered, 1);
1944 		btrfs_put_ordered_extent(ordered);
1945 	}
1946 
1947 	if (page->index == last_byte >> PAGE_CACHE_SHIFT) {
1948 		char *userpage;
1949 		size_t zero_offset = last_byte & (PAGE_CACHE_SIZE - 1);
1950 
1951 		if (zero_offset) {
1952 			iosize = PAGE_CACHE_SIZE - zero_offset;
1953 			userpage = kmap_atomic(page, KM_USER0);
1954 			memset(userpage + zero_offset, 0, iosize);
1955 			flush_dcache_page(page);
1956 			kunmap_atomic(userpage, KM_USER0);
1957 		}
1958 	}
1959 	while (cur <= end) {
1960 		if (cur >= last_byte) {
1961 			char *userpage;
1962 			struct extent_state *cached = NULL;
1963 
1964 			iosize = PAGE_CACHE_SIZE - pg_offset;
1965 			userpage = kmap_atomic(page, KM_USER0);
1966 			memset(userpage + pg_offset, 0, iosize);
1967 			flush_dcache_page(page);
1968 			kunmap_atomic(userpage, KM_USER0);
1969 			set_extent_uptodate(tree, cur, cur + iosize - 1,
1970 					    &cached, GFP_NOFS);
1971 			unlock_extent_cached(tree, cur, cur + iosize - 1,
1972 					     &cached, GFP_NOFS);
1973 			break;
1974 		}
1975 		em = get_extent(inode, page, pg_offset, cur,
1976 				end - cur + 1, 0);
1977 		if (IS_ERR_OR_NULL(em)) {
1978 			SetPageError(page);
1979 			unlock_extent(tree, cur, end, GFP_NOFS);
1980 			break;
1981 		}
1982 		extent_offset = cur - em->start;
1983 		BUG_ON(extent_map_end(em) <= cur);
1984 		BUG_ON(end < cur);
1985 
1986 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
1987 			this_bio_flag = EXTENT_BIO_COMPRESSED;
1988 			extent_set_compress_type(&this_bio_flag,
1989 						 em->compress_type);
1990 		}
1991 
1992 		iosize = min(extent_map_end(em) - cur, end - cur + 1);
1993 		cur_end = min(extent_map_end(em) - 1, end);
1994 		iosize = (iosize + blocksize - 1) & ~((u64)blocksize - 1);
1995 		if (this_bio_flag & EXTENT_BIO_COMPRESSED) {
1996 			disk_io_size = em->block_len;
1997 			sector = em->block_start >> 9;
1998 		} else {
1999 			sector = (em->block_start + extent_offset) >> 9;
2000 			disk_io_size = iosize;
2001 		}
2002 		bdev = em->bdev;
2003 		block_start = em->block_start;
2004 		if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
2005 			block_start = EXTENT_MAP_HOLE;
2006 		free_extent_map(em);
2007 		em = NULL;
2008 
2009 		/* we've found a hole, just zero and go on */
2010 		if (block_start == EXTENT_MAP_HOLE) {
2011 			char *userpage;
2012 			struct extent_state *cached = NULL;
2013 
2014 			userpage = kmap_atomic(page, KM_USER0);
2015 			memset(userpage + pg_offset, 0, iosize);
2016 			flush_dcache_page(page);
2017 			kunmap_atomic(userpage, KM_USER0);
2018 
2019 			set_extent_uptodate(tree, cur, cur + iosize - 1,
2020 					    &cached, GFP_NOFS);
2021 			unlock_extent_cached(tree, cur, cur + iosize - 1,
2022 			                     &cached, GFP_NOFS);
2023 			cur = cur + iosize;
2024 			pg_offset += iosize;
2025 			continue;
2026 		}
2027 		/* the get_extent function already copied into the page */
2028 		if (test_range_bit(tree, cur, cur_end,
2029 				   EXTENT_UPTODATE, 1, NULL)) {
2030 			check_page_uptodate(tree, page);
2031 			unlock_extent(tree, cur, cur + iosize - 1, GFP_NOFS);
2032 			cur = cur + iosize;
2033 			pg_offset += iosize;
2034 			continue;
2035 		}
2036 		/* we have an inline extent but it didn't get marked up
2037 		 * to date.  Error out
2038 		 */
2039 		if (block_start == EXTENT_MAP_INLINE) {
2040 			SetPageError(page);
2041 			unlock_extent(tree, cur, cur + iosize - 1, GFP_NOFS);
2042 			cur = cur + iosize;
2043 			pg_offset += iosize;
2044 			continue;
2045 		}
2046 
2047 		ret = 0;
2048 		if (tree->ops && tree->ops->readpage_io_hook) {
2049 			ret = tree->ops->readpage_io_hook(page, cur,
2050 							  cur + iosize - 1);
2051 		}
2052 		if (!ret) {
2053 			unsigned long pnr = (last_byte >> PAGE_CACHE_SHIFT) + 1;
2054 			pnr -= page->index;
2055 			ret = submit_extent_page(READ, tree, page,
2056 					 sector, disk_io_size, pg_offset,
2057 					 bdev, bio, pnr,
2058 					 end_bio_extent_readpage, mirror_num,
2059 					 *bio_flags,
2060 					 this_bio_flag);
2061 			nr++;
2062 			*bio_flags = this_bio_flag;
2063 		}
2064 		if (ret)
2065 			SetPageError(page);
2066 		cur = cur + iosize;
2067 		pg_offset += iosize;
2068 	}
2069 out:
2070 	if (!nr) {
2071 		if (!PageError(page))
2072 			SetPageUptodate(page);
2073 		unlock_page(page);
2074 	}
2075 	return 0;
2076 }
2077 
2078 int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
2079 			    get_extent_t *get_extent)
2080 {
2081 	struct bio *bio = NULL;
2082 	unsigned long bio_flags = 0;
2083 	int ret;
2084 
2085 	ret = __extent_read_full_page(tree, page, get_extent, &bio, 0,
2086 				      &bio_flags);
2087 	if (bio)
2088 		ret = submit_one_bio(READ, bio, 0, bio_flags);
2089 	return ret;
2090 }
2091 
2092 static noinline void update_nr_written(struct page *page,
2093 				      struct writeback_control *wbc,
2094 				      unsigned long nr_written)
2095 {
2096 	wbc->nr_to_write -= nr_written;
2097 	if (wbc->range_cyclic || (wbc->nr_to_write > 0 &&
2098 	    wbc->range_start == 0 && wbc->range_end == LLONG_MAX))
2099 		page->mapping->writeback_index = page->index + nr_written;
2100 }
2101 
2102 /*
2103  * the writepage semantics are similar to regular writepage.  extent
2104  * records are inserted to lock ranges in the tree, and as dirty areas
2105  * are found, they are marked writeback.  Then the lock bits are removed
2106  * and the end_io handler clears the writeback ranges
2107  */
2108 static int __extent_writepage(struct page *page, struct writeback_control *wbc,
2109 			      void *data)
2110 {
2111 	struct inode *inode = page->mapping->host;
2112 	struct extent_page_data *epd = data;
2113 	struct extent_io_tree *tree = epd->tree;
2114 	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
2115 	u64 delalloc_start;
2116 	u64 page_end = start + PAGE_CACHE_SIZE - 1;
2117 	u64 end;
2118 	u64 cur = start;
2119 	u64 extent_offset;
2120 	u64 last_byte = i_size_read(inode);
2121 	u64 block_start;
2122 	u64 iosize;
2123 	sector_t sector;
2124 	struct extent_state *cached_state = NULL;
2125 	struct extent_map *em;
2126 	struct block_device *bdev;
2127 	int ret;
2128 	int nr = 0;
2129 	size_t pg_offset = 0;
2130 	size_t blocksize;
2131 	loff_t i_size = i_size_read(inode);
2132 	unsigned long end_index = i_size >> PAGE_CACHE_SHIFT;
2133 	u64 nr_delalloc;
2134 	u64 delalloc_end;
2135 	int page_started;
2136 	int compressed;
2137 	int write_flags;
2138 	unsigned long nr_written = 0;
2139 
2140 	if (wbc->sync_mode == WB_SYNC_ALL)
2141 		write_flags = WRITE_SYNC;
2142 	else
2143 		write_flags = WRITE;
2144 
2145 	trace___extent_writepage(page, inode, wbc);
2146 
2147 	WARN_ON(!PageLocked(page));
2148 	pg_offset = i_size & (PAGE_CACHE_SIZE - 1);
2149 	if (page->index > end_index ||
2150 	   (page->index == end_index && !pg_offset)) {
2151 		page->mapping->a_ops->invalidatepage(page, 0);
2152 		unlock_page(page);
2153 		return 0;
2154 	}
2155 
2156 	if (page->index == end_index) {
2157 		char *userpage;
2158 
2159 		userpage = kmap_atomic(page, KM_USER0);
2160 		memset(userpage + pg_offset, 0,
2161 		       PAGE_CACHE_SIZE - pg_offset);
2162 		kunmap_atomic(userpage, KM_USER0);
2163 		flush_dcache_page(page);
2164 	}
2165 	pg_offset = 0;
2166 
2167 	set_page_extent_mapped(page);
2168 
2169 	delalloc_start = start;
2170 	delalloc_end = 0;
2171 	page_started = 0;
2172 	if (!epd->extent_locked) {
2173 		u64 delalloc_to_write = 0;
2174 		/*
2175 		 * make sure the wbc mapping index is at least updated
2176 		 * to this page.
2177 		 */
2178 		update_nr_written(page, wbc, 0);
2179 
2180 		while (delalloc_end < page_end) {
2181 			nr_delalloc = find_lock_delalloc_range(inode, tree,
2182 						       page,
2183 						       &delalloc_start,
2184 						       &delalloc_end,
2185 						       128 * 1024 * 1024);
2186 			if (nr_delalloc == 0) {
2187 				delalloc_start = delalloc_end + 1;
2188 				continue;
2189 			}
2190 			tree->ops->fill_delalloc(inode, page, delalloc_start,
2191 						 delalloc_end, &page_started,
2192 						 &nr_written);
2193 			/*
2194 			 * delalloc_end is already one less than the total
2195 			 * length, so we don't subtract one from
2196 			 * PAGE_CACHE_SIZE
2197 			 */
2198 			delalloc_to_write += (delalloc_end - delalloc_start +
2199 					      PAGE_CACHE_SIZE) >>
2200 					      PAGE_CACHE_SHIFT;
2201 			delalloc_start = delalloc_end + 1;
2202 		}
2203 		if (wbc->nr_to_write < delalloc_to_write) {
2204 			int thresh = 8192;
2205 
2206 			if (delalloc_to_write < thresh * 2)
2207 				thresh = delalloc_to_write;
2208 			wbc->nr_to_write = min_t(u64, delalloc_to_write,
2209 						 thresh);
2210 		}
2211 
2212 		/* did the fill delalloc function already unlock and start
2213 		 * the IO?
2214 		 */
2215 		if (page_started) {
2216 			ret = 0;
2217 			/*
2218 			 * we've unlocked the page, so we can't update
2219 			 * the mapping's writeback index, just update
2220 			 * nr_to_write.
2221 			 */
2222 			wbc->nr_to_write -= nr_written;
2223 			goto done_unlocked;
2224 		}
2225 	}
2226 	if (tree->ops && tree->ops->writepage_start_hook) {
2227 		ret = tree->ops->writepage_start_hook(page, start,
2228 						      page_end);
2229 		if (ret == -EAGAIN) {
2230 			redirty_page_for_writepage(wbc, page);
2231 			update_nr_written(page, wbc, nr_written);
2232 			unlock_page(page);
2233 			ret = 0;
2234 			goto done_unlocked;
2235 		}
2236 	}
2237 
2238 	/*
2239 	 * we don't want to touch the inode after unlocking the page,
2240 	 * so we update the mapping writeback index now
2241 	 */
2242 	update_nr_written(page, wbc, nr_written + 1);
2243 
2244 	end = page_end;
2245 	if (last_byte <= start) {
2246 		if (tree->ops && tree->ops->writepage_end_io_hook)
2247 			tree->ops->writepage_end_io_hook(page, start,
2248 							 page_end, NULL, 1);
2249 		goto done;
2250 	}
2251 
2252 	blocksize = inode->i_sb->s_blocksize;
2253 
2254 	while (cur <= end) {
2255 		if (cur >= last_byte) {
2256 			if (tree->ops && tree->ops->writepage_end_io_hook)
2257 				tree->ops->writepage_end_io_hook(page, cur,
2258 							 page_end, NULL, 1);
2259 			break;
2260 		}
2261 		em = epd->get_extent(inode, page, pg_offset, cur,
2262 				     end - cur + 1, 1);
2263 		if (IS_ERR_OR_NULL(em)) {
2264 			SetPageError(page);
2265 			break;
2266 		}
2267 
2268 		extent_offset = cur - em->start;
2269 		BUG_ON(extent_map_end(em) <= cur);
2270 		BUG_ON(end < cur);
2271 		iosize = min(extent_map_end(em) - cur, end - cur + 1);
2272 		iosize = (iosize + blocksize - 1) & ~((u64)blocksize - 1);
2273 		sector = (em->block_start + extent_offset) >> 9;
2274 		bdev = em->bdev;
2275 		block_start = em->block_start;
2276 		compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
2277 		free_extent_map(em);
2278 		em = NULL;
2279 
2280 		/*
2281 		 * compressed and inline extents are written through other
2282 		 * paths in the FS
2283 		 */
2284 		if (compressed || block_start == EXTENT_MAP_HOLE ||
2285 		    block_start == EXTENT_MAP_INLINE) {
2286 			/*
2287 			 * end_io notification does not happen here for
2288 			 * compressed extents
2289 			 */
2290 			if (!compressed && tree->ops &&
2291 			    tree->ops->writepage_end_io_hook)
2292 				tree->ops->writepage_end_io_hook(page, cur,
2293 							 cur + iosize - 1,
2294 							 NULL, 1);
2295 			else if (compressed) {
2296 				/* we don't want to end_page_writeback on
2297 				 * a compressed extent.  this happens
2298 				 * elsewhere
2299 				 */
2300 				nr++;
2301 			}
2302 
2303 			cur += iosize;
2304 			pg_offset += iosize;
2305 			continue;
2306 		}
2307 		/* leave this out until we have a page_mkwrite call */
2308 		if (0 && !test_range_bit(tree, cur, cur + iosize - 1,
2309 				   EXTENT_DIRTY, 0, NULL)) {
2310 			cur = cur + iosize;
2311 			pg_offset += iosize;
2312 			continue;
2313 		}
2314 
2315 		if (tree->ops && tree->ops->writepage_io_hook) {
2316 			ret = tree->ops->writepage_io_hook(page, cur,
2317 						cur + iosize - 1);
2318 		} else {
2319 			ret = 0;
2320 		}
2321 		if (ret) {
2322 			SetPageError(page);
2323 		} else {
2324 			unsigned long max_nr = end_index + 1;
2325 
2326 			set_range_writeback(tree, cur, cur + iosize - 1);
2327 			if (!PageWriteback(page)) {
2328 				printk(KERN_ERR "btrfs warning page %lu not "
2329 				       "writeback, cur %llu end %llu\n",
2330 				       page->index, (unsigned long long)cur,
2331 				       (unsigned long long)end);
2332 			}
2333 
2334 			ret = submit_extent_page(write_flags, tree, page,
2335 						 sector, iosize, pg_offset,
2336 						 bdev, &epd->bio, max_nr,
2337 						 end_bio_extent_writepage,
2338 						 0, 0, 0);
2339 			if (ret)
2340 				SetPageError(page);
2341 		}
2342 		cur = cur + iosize;
2343 		pg_offset += iosize;
2344 		nr++;
2345 	}
2346 done:
2347 	if (nr == 0) {
2348 		/* make sure the mapping tag for page dirty gets cleared */
2349 		set_page_writeback(page);
2350 		end_page_writeback(page);
2351 	}
2352 	unlock_page(page);
2353 
2354 done_unlocked:
2355 
2356 	/* drop our reference on any cached states */
2357 	free_extent_state(cached_state);
2358 	return 0;
2359 }
2360 
2361 /**
2362  * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
2363  * @mapping: address space structure to write
2364  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
2365  * @writepage: function called for each page
2366  * @data: data passed to writepage function
2367  *
2368  * If a page is already under I/O, write_cache_pages() skips it, even
2369  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
2370  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
2371  * and msync() need to guarantee that all the data which was dirty at the time
2372  * the call was made get new I/O started against them.  If wbc->sync_mode is
2373  * WB_SYNC_ALL then we were called for data integrity and we must wait for
2374  * existing IO to complete.
2375  */
2376 static int extent_write_cache_pages(struct extent_io_tree *tree,
2377 			     struct address_space *mapping,
2378 			     struct writeback_control *wbc,
2379 			     writepage_t writepage, void *data,
2380 			     void (*flush_fn)(void *))
2381 {
2382 	int ret = 0;
2383 	int done = 0;
2384 	int nr_to_write_done = 0;
2385 	struct pagevec pvec;
2386 	int nr_pages;
2387 	pgoff_t index;
2388 	pgoff_t end;		/* Inclusive */
2389 	int scanned = 0;
2390 	int tag;
2391 
2392 	pagevec_init(&pvec, 0);
2393 	if (wbc->range_cyclic) {
2394 		index = mapping->writeback_index; /* Start from prev offset */
2395 		end = -1;
2396 	} else {
2397 		index = wbc->range_start >> PAGE_CACHE_SHIFT;
2398 		end = wbc->range_end >> PAGE_CACHE_SHIFT;
2399 		scanned = 1;
2400 	}
2401 	if (wbc->sync_mode == WB_SYNC_ALL)
2402 		tag = PAGECACHE_TAG_TOWRITE;
2403 	else
2404 		tag = PAGECACHE_TAG_DIRTY;
2405 retry:
2406 	if (wbc->sync_mode == WB_SYNC_ALL)
2407 		tag_pages_for_writeback(mapping, index, end);
2408 	while (!done && !nr_to_write_done && (index <= end) &&
2409 	       (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
2410 			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
2411 		unsigned i;
2412 
2413 		scanned = 1;
2414 		for (i = 0; i < nr_pages; i++) {
2415 			struct page *page = pvec.pages[i];
2416 
2417 			/*
2418 			 * At this point we hold neither mapping->tree_lock nor
2419 			 * lock on the page itself: the page may be truncated or
2420 			 * invalidated (changing page->mapping to NULL), or even
2421 			 * swizzled back from swapper_space to tmpfs file
2422 			 * mapping
2423 			 */
2424 			if (tree->ops && tree->ops->write_cache_pages_lock_hook)
2425 				tree->ops->write_cache_pages_lock_hook(page);
2426 			else
2427 				lock_page(page);
2428 
2429 			if (unlikely(page->mapping != mapping)) {
2430 				unlock_page(page);
2431 				continue;
2432 			}
2433 
2434 			if (!wbc->range_cyclic && page->index > end) {
2435 				done = 1;
2436 				unlock_page(page);
2437 				continue;
2438 			}
2439 
2440 			if (wbc->sync_mode != WB_SYNC_NONE) {
2441 				if (PageWriteback(page))
2442 					flush_fn(data);
2443 				wait_on_page_writeback(page);
2444 			}
2445 
2446 			if (PageWriteback(page) ||
2447 			    !clear_page_dirty_for_io(page)) {
2448 				unlock_page(page);
2449 				continue;
2450 			}
2451 
2452 			ret = (*writepage)(page, wbc, data);
2453 
2454 			if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
2455 				unlock_page(page);
2456 				ret = 0;
2457 			}
2458 			if (ret)
2459 				done = 1;
2460 
2461 			/*
2462 			 * the filesystem may choose to bump up nr_to_write.
2463 			 * We have to make sure to honor the new nr_to_write
2464 			 * at any time
2465 			 */
2466 			nr_to_write_done = wbc->nr_to_write <= 0;
2467 		}
2468 		pagevec_release(&pvec);
2469 		cond_resched();
2470 	}
2471 	if (!scanned && !done) {
2472 		/*
2473 		 * We hit the last page and there is more work to be done: wrap
2474 		 * back to the start of the file
2475 		 */
2476 		scanned = 1;
2477 		index = 0;
2478 		goto retry;
2479 	}
2480 	return ret;
2481 }
2482 
2483 static void flush_epd_write_bio(struct extent_page_data *epd)
2484 {
2485 	if (epd->bio) {
2486 		if (epd->sync_io)
2487 			submit_one_bio(WRITE_SYNC, epd->bio, 0, 0);
2488 		else
2489 			submit_one_bio(WRITE, epd->bio, 0, 0);
2490 		epd->bio = NULL;
2491 	}
2492 }
2493 
2494 static noinline void flush_write_bio(void *data)
2495 {
2496 	struct extent_page_data *epd = data;
2497 	flush_epd_write_bio(epd);
2498 }
2499 
2500 int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
2501 			  get_extent_t *get_extent,
2502 			  struct writeback_control *wbc)
2503 {
2504 	int ret;
2505 	struct extent_page_data epd = {
2506 		.bio = NULL,
2507 		.tree = tree,
2508 		.get_extent = get_extent,
2509 		.extent_locked = 0,
2510 		.sync_io = wbc->sync_mode == WB_SYNC_ALL,
2511 	};
2512 
2513 	ret = __extent_writepage(page, wbc, &epd);
2514 
2515 	flush_epd_write_bio(&epd);
2516 	return ret;
2517 }
2518 
2519 int extent_write_locked_range(struct extent_io_tree *tree, struct inode *inode,
2520 			      u64 start, u64 end, get_extent_t *get_extent,
2521 			      int mode)
2522 {
2523 	int ret = 0;
2524 	struct address_space *mapping = inode->i_mapping;
2525 	struct page *page;
2526 	unsigned long nr_pages = (end - start + PAGE_CACHE_SIZE) >>
2527 		PAGE_CACHE_SHIFT;
2528 
2529 	struct extent_page_data epd = {
2530 		.bio = NULL,
2531 		.tree = tree,
2532 		.get_extent = get_extent,
2533 		.extent_locked = 1,
2534 		.sync_io = mode == WB_SYNC_ALL,
2535 	};
2536 	struct writeback_control wbc_writepages = {
2537 		.sync_mode	= mode,
2538 		.nr_to_write	= nr_pages * 2,
2539 		.range_start	= start,
2540 		.range_end	= end + 1,
2541 	};
2542 
2543 	while (start <= end) {
2544 		page = find_get_page(mapping, start >> PAGE_CACHE_SHIFT);
2545 		if (clear_page_dirty_for_io(page))
2546 			ret = __extent_writepage(page, &wbc_writepages, &epd);
2547 		else {
2548 			if (tree->ops && tree->ops->writepage_end_io_hook)
2549 				tree->ops->writepage_end_io_hook(page, start,
2550 						 start + PAGE_CACHE_SIZE - 1,
2551 						 NULL, 1);
2552 			unlock_page(page);
2553 		}
2554 		page_cache_release(page);
2555 		start += PAGE_CACHE_SIZE;
2556 	}
2557 
2558 	flush_epd_write_bio(&epd);
2559 	return ret;
2560 }
2561 
2562 int extent_writepages(struct extent_io_tree *tree,
2563 		      struct address_space *mapping,
2564 		      get_extent_t *get_extent,
2565 		      struct writeback_control *wbc)
2566 {
2567 	int ret = 0;
2568 	struct extent_page_data epd = {
2569 		.bio = NULL,
2570 		.tree = tree,
2571 		.get_extent = get_extent,
2572 		.extent_locked = 0,
2573 		.sync_io = wbc->sync_mode == WB_SYNC_ALL,
2574 	};
2575 
2576 	ret = extent_write_cache_pages(tree, mapping, wbc,
2577 				       __extent_writepage, &epd,
2578 				       flush_write_bio);
2579 	flush_epd_write_bio(&epd);
2580 	return ret;
2581 }
2582 
2583 int extent_readpages(struct extent_io_tree *tree,
2584 		     struct address_space *mapping,
2585 		     struct list_head *pages, unsigned nr_pages,
2586 		     get_extent_t get_extent)
2587 {
2588 	struct bio *bio = NULL;
2589 	unsigned page_idx;
2590 	unsigned long bio_flags = 0;
2591 
2592 	for (page_idx = 0; page_idx < nr_pages; page_idx++) {
2593 		struct page *page = list_entry(pages->prev, struct page, lru);
2594 
2595 		prefetchw(&page->flags);
2596 		list_del(&page->lru);
2597 		if (!add_to_page_cache_lru(page, mapping,
2598 					page->index, GFP_NOFS)) {
2599 			__extent_read_full_page(tree, page, get_extent,
2600 						&bio, 0, &bio_flags);
2601 		}
2602 		page_cache_release(page);
2603 	}
2604 	BUG_ON(!list_empty(pages));
2605 	if (bio)
2606 		submit_one_bio(READ, bio, 0, bio_flags);
2607 	return 0;
2608 }
2609 
2610 /*
2611  * basic invalidatepage code, this waits on any locked or writeback
2612  * ranges corresponding to the page, and then deletes any extent state
2613  * records from the tree
2614  */
2615 int extent_invalidatepage(struct extent_io_tree *tree,
2616 			  struct page *page, unsigned long offset)
2617 {
2618 	struct extent_state *cached_state = NULL;
2619 	u64 start = ((u64)page->index << PAGE_CACHE_SHIFT);
2620 	u64 end = start + PAGE_CACHE_SIZE - 1;
2621 	size_t blocksize = page->mapping->host->i_sb->s_blocksize;
2622 
2623 	start += (offset + blocksize - 1) & ~(blocksize - 1);
2624 	if (start > end)
2625 		return 0;
2626 
2627 	lock_extent_bits(tree, start, end, 0, &cached_state, GFP_NOFS);
2628 	wait_on_page_writeback(page);
2629 	clear_extent_bit(tree, start, end,
2630 			 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
2631 			 EXTENT_DO_ACCOUNTING,
2632 			 1, 1, &cached_state, GFP_NOFS);
2633 	return 0;
2634 }
2635 
2636 /*
2637  * a helper for releasepage, this tests for areas of the page that
2638  * are locked or under IO and drops the related state bits if it is safe
2639  * to drop the page.
2640  */
2641 int try_release_extent_state(struct extent_map_tree *map,
2642 			     struct extent_io_tree *tree, struct page *page,
2643 			     gfp_t mask)
2644 {
2645 	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
2646 	u64 end = start + PAGE_CACHE_SIZE - 1;
2647 	int ret = 1;
2648 
2649 	if (test_range_bit(tree, start, end,
2650 			   EXTENT_IOBITS, 0, NULL))
2651 		ret = 0;
2652 	else {
2653 		if ((mask & GFP_NOFS) == GFP_NOFS)
2654 			mask = GFP_NOFS;
2655 		/*
2656 		 * at this point we can safely clear everything except the
2657 		 * locked bit and the nodatasum bit
2658 		 */
2659 		ret = clear_extent_bit(tree, start, end,
2660 				 ~(EXTENT_LOCKED | EXTENT_NODATASUM),
2661 				 0, 0, NULL, mask);
2662 
2663 		/* if clear_extent_bit failed for enomem reasons,
2664 		 * we can't allow the release to continue.
2665 		 */
2666 		if (ret < 0)
2667 			ret = 0;
2668 		else
2669 			ret = 1;
2670 	}
2671 	return ret;
2672 }
2673 
2674 /*
2675  * a helper for releasepage.  As long as there are no locked extents
2676  * in the range corresponding to the page, both state records and extent
2677  * map records are removed
2678  */
2679 int try_release_extent_mapping(struct extent_map_tree *map,
2680 			       struct extent_io_tree *tree, struct page *page,
2681 			       gfp_t mask)
2682 {
2683 	struct extent_map *em;
2684 	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
2685 	u64 end = start + PAGE_CACHE_SIZE - 1;
2686 
2687 	if ((mask & __GFP_WAIT) &&
2688 	    page->mapping->host->i_size > 16 * 1024 * 1024) {
2689 		u64 len;
2690 		while (start <= end) {
2691 			len = end - start + 1;
2692 			write_lock(&map->lock);
2693 			em = lookup_extent_mapping(map, start, len);
2694 			if (IS_ERR_OR_NULL(em)) {
2695 				write_unlock(&map->lock);
2696 				break;
2697 			}
2698 			if (test_bit(EXTENT_FLAG_PINNED, &em->flags) ||
2699 			    em->start != start) {
2700 				write_unlock(&map->lock);
2701 				free_extent_map(em);
2702 				break;
2703 			}
2704 			if (!test_range_bit(tree, em->start,
2705 					    extent_map_end(em) - 1,
2706 					    EXTENT_LOCKED | EXTENT_WRITEBACK,
2707 					    0, NULL)) {
2708 				remove_extent_mapping(map, em);
2709 				/* once for the rb tree */
2710 				free_extent_map(em);
2711 			}
2712 			start = extent_map_end(em);
2713 			write_unlock(&map->lock);
2714 
2715 			/* once for us */
2716 			free_extent_map(em);
2717 		}
2718 	}
2719 	return try_release_extent_state(map, tree, page, mask);
2720 }
2721 
2722 /*
2723  * helper function for fiemap, which doesn't want to see any holes.
2724  * This maps until we find something past 'last'
2725  */
2726 static struct extent_map *get_extent_skip_holes(struct inode *inode,
2727 						u64 offset,
2728 						u64 last,
2729 						get_extent_t *get_extent)
2730 {
2731 	u64 sectorsize = BTRFS_I(inode)->root->sectorsize;
2732 	struct extent_map *em;
2733 	u64 len;
2734 
2735 	if (offset >= last)
2736 		return NULL;
2737 
2738 	while(1) {
2739 		len = last - offset;
2740 		if (len == 0)
2741 			break;
2742 		len = (len + sectorsize - 1) & ~(sectorsize - 1);
2743 		em = get_extent(inode, NULL, 0, offset, len, 0);
2744 		if (IS_ERR_OR_NULL(em))
2745 			return em;
2746 
2747 		/* if this isn't a hole return it */
2748 		if (!test_bit(EXTENT_FLAG_VACANCY, &em->flags) &&
2749 		    em->block_start != EXTENT_MAP_HOLE) {
2750 			return em;
2751 		}
2752 
2753 		/* this is a hole, advance to the next extent */
2754 		offset = extent_map_end(em);
2755 		free_extent_map(em);
2756 		if (offset >= last)
2757 			break;
2758 	}
2759 	return NULL;
2760 }
2761 
2762 int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
2763 		__u64 start, __u64 len, get_extent_t *get_extent)
2764 {
2765 	int ret = 0;
2766 	u64 off = start;
2767 	u64 max = start + len;
2768 	u32 flags = 0;
2769 	u32 found_type;
2770 	u64 last;
2771 	u64 last_for_get_extent = 0;
2772 	u64 disko = 0;
2773 	u64 isize = i_size_read(inode);
2774 	struct btrfs_key found_key;
2775 	struct extent_map *em = NULL;
2776 	struct extent_state *cached_state = NULL;
2777 	struct btrfs_path *path;
2778 	struct btrfs_file_extent_item *item;
2779 	int end = 0;
2780 	u64 em_start = 0;
2781 	u64 em_len = 0;
2782 	u64 em_end = 0;
2783 	unsigned long emflags;
2784 
2785 	if (len == 0)
2786 		return -EINVAL;
2787 
2788 	path = btrfs_alloc_path();
2789 	if (!path)
2790 		return -ENOMEM;
2791 	path->leave_spinning = 1;
2792 
2793 	/*
2794 	 * lookup the last file extent.  We're not using i_size here
2795 	 * because there might be preallocation past i_size
2796 	 */
2797 	ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root,
2798 				       path, btrfs_ino(inode), -1, 0);
2799 	if (ret < 0) {
2800 		btrfs_free_path(path);
2801 		return ret;
2802 	}
2803 	WARN_ON(!ret);
2804 	path->slots[0]--;
2805 	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
2806 			      struct btrfs_file_extent_item);
2807 	btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
2808 	found_type = btrfs_key_type(&found_key);
2809 
2810 	/* No extents, but there might be delalloc bits */
2811 	if (found_key.objectid != btrfs_ino(inode) ||
2812 	    found_type != BTRFS_EXTENT_DATA_KEY) {
2813 		/* have to trust i_size as the end */
2814 		last = (u64)-1;
2815 		last_for_get_extent = isize;
2816 	} else {
2817 		/*
2818 		 * remember the start of the last extent.  There are a
2819 		 * bunch of different factors that go into the length of the
2820 		 * extent, so its much less complex to remember where it started
2821 		 */
2822 		last = found_key.offset;
2823 		last_for_get_extent = last + 1;
2824 	}
2825 	btrfs_free_path(path);
2826 
2827 	/*
2828 	 * we might have some extents allocated but more delalloc past those
2829 	 * extents.  so, we trust isize unless the start of the last extent is
2830 	 * beyond isize
2831 	 */
2832 	if (last < isize) {
2833 		last = (u64)-1;
2834 		last_for_get_extent = isize;
2835 	}
2836 
2837 	lock_extent_bits(&BTRFS_I(inode)->io_tree, start, start + len, 0,
2838 			 &cached_state, GFP_NOFS);
2839 
2840 	em = get_extent_skip_holes(inode, off, last_for_get_extent,
2841 				   get_extent);
2842 	if (!em)
2843 		goto out;
2844 	if (IS_ERR(em)) {
2845 		ret = PTR_ERR(em);
2846 		goto out;
2847 	}
2848 
2849 	while (!end) {
2850 		u64 offset_in_extent;
2851 
2852 		/* break if the extent we found is outside the range */
2853 		if (em->start >= max || extent_map_end(em) < off)
2854 			break;
2855 
2856 		/*
2857 		 * get_extent may return an extent that starts before our
2858 		 * requested range.  We have to make sure the ranges
2859 		 * we return to fiemap always move forward and don't
2860 		 * overlap, so adjust the offsets here
2861 		 */
2862 		em_start = max(em->start, off);
2863 
2864 		/*
2865 		 * record the offset from the start of the extent
2866 		 * for adjusting the disk offset below
2867 		 */
2868 		offset_in_extent = em_start - em->start;
2869 		em_end = extent_map_end(em);
2870 		em_len = em_end - em_start;
2871 		emflags = em->flags;
2872 		disko = 0;
2873 		flags = 0;
2874 
2875 		/*
2876 		 * bump off for our next call to get_extent
2877 		 */
2878 		off = extent_map_end(em);
2879 		if (off >= max)
2880 			end = 1;
2881 
2882 		if (em->block_start == EXTENT_MAP_LAST_BYTE) {
2883 			end = 1;
2884 			flags |= FIEMAP_EXTENT_LAST;
2885 		} else if (em->block_start == EXTENT_MAP_INLINE) {
2886 			flags |= (FIEMAP_EXTENT_DATA_INLINE |
2887 				  FIEMAP_EXTENT_NOT_ALIGNED);
2888 		} else if (em->block_start == EXTENT_MAP_DELALLOC) {
2889 			flags |= (FIEMAP_EXTENT_DELALLOC |
2890 				  FIEMAP_EXTENT_UNKNOWN);
2891 		} else {
2892 			disko = em->block_start + offset_in_extent;
2893 		}
2894 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
2895 			flags |= FIEMAP_EXTENT_ENCODED;
2896 
2897 		free_extent_map(em);
2898 		em = NULL;
2899 		if ((em_start >= last) || em_len == (u64)-1 ||
2900 		   (last == (u64)-1 && isize <= em_end)) {
2901 			flags |= FIEMAP_EXTENT_LAST;
2902 			end = 1;
2903 		}
2904 
2905 		/* now scan forward to see if this is really the last extent. */
2906 		em = get_extent_skip_holes(inode, off, last_for_get_extent,
2907 					   get_extent);
2908 		if (IS_ERR(em)) {
2909 			ret = PTR_ERR(em);
2910 			goto out;
2911 		}
2912 		if (!em) {
2913 			flags |= FIEMAP_EXTENT_LAST;
2914 			end = 1;
2915 		}
2916 		ret = fiemap_fill_next_extent(fieinfo, em_start, disko,
2917 					      em_len, flags);
2918 		if (ret)
2919 			goto out_free;
2920 	}
2921 out_free:
2922 	free_extent_map(em);
2923 out:
2924 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len,
2925 			     &cached_state, GFP_NOFS);
2926 	return ret;
2927 }
2928 
2929 static inline struct page *extent_buffer_page(struct extent_buffer *eb,
2930 					      unsigned long i)
2931 {
2932 	struct page *p;
2933 	struct address_space *mapping;
2934 
2935 	if (i == 0)
2936 		return eb->first_page;
2937 	i += eb->start >> PAGE_CACHE_SHIFT;
2938 	mapping = eb->first_page->mapping;
2939 	if (!mapping)
2940 		return NULL;
2941 
2942 	/*
2943 	 * extent_buffer_page is only called after pinning the page
2944 	 * by increasing the reference count.  So we know the page must
2945 	 * be in the radix tree.
2946 	 */
2947 	rcu_read_lock();
2948 	p = radix_tree_lookup(&mapping->page_tree, i);
2949 	rcu_read_unlock();
2950 
2951 	return p;
2952 }
2953 
2954 static inline unsigned long num_extent_pages(u64 start, u64 len)
2955 {
2956 	return ((start + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) -
2957 		(start >> PAGE_CACHE_SHIFT);
2958 }
2959 
2960 static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
2961 						   u64 start,
2962 						   unsigned long len,
2963 						   gfp_t mask)
2964 {
2965 	struct extent_buffer *eb = NULL;
2966 #if LEAK_DEBUG
2967 	unsigned long flags;
2968 #endif
2969 
2970 	eb = kmem_cache_zalloc(extent_buffer_cache, mask);
2971 	if (eb == NULL)
2972 		return NULL;
2973 	eb->start = start;
2974 	eb->len = len;
2975 	rwlock_init(&eb->lock);
2976 	atomic_set(&eb->write_locks, 0);
2977 	atomic_set(&eb->read_locks, 0);
2978 	atomic_set(&eb->blocking_readers, 0);
2979 	atomic_set(&eb->blocking_writers, 0);
2980 	atomic_set(&eb->spinning_readers, 0);
2981 	atomic_set(&eb->spinning_writers, 0);
2982 	init_waitqueue_head(&eb->write_lock_wq);
2983 	init_waitqueue_head(&eb->read_lock_wq);
2984 
2985 #if LEAK_DEBUG
2986 	spin_lock_irqsave(&leak_lock, flags);
2987 	list_add(&eb->leak_list, &buffers);
2988 	spin_unlock_irqrestore(&leak_lock, flags);
2989 #endif
2990 	atomic_set(&eb->refs, 1);
2991 
2992 	return eb;
2993 }
2994 
2995 static void __free_extent_buffer(struct extent_buffer *eb)
2996 {
2997 #if LEAK_DEBUG
2998 	unsigned long flags;
2999 	spin_lock_irqsave(&leak_lock, flags);
3000 	list_del(&eb->leak_list);
3001 	spin_unlock_irqrestore(&leak_lock, flags);
3002 #endif
3003 	kmem_cache_free(extent_buffer_cache, eb);
3004 }
3005 
3006 /*
3007  * Helper for releasing extent buffer page.
3008  */
3009 static void btrfs_release_extent_buffer_page(struct extent_buffer *eb,
3010 						unsigned long start_idx)
3011 {
3012 	unsigned long index;
3013 	struct page *page;
3014 
3015 	if (!eb->first_page)
3016 		return;
3017 
3018 	index = num_extent_pages(eb->start, eb->len);
3019 	if (start_idx >= index)
3020 		return;
3021 
3022 	do {
3023 		index--;
3024 		page = extent_buffer_page(eb, index);
3025 		if (page)
3026 			page_cache_release(page);
3027 	} while (index != start_idx);
3028 }
3029 
3030 /*
3031  * Helper for releasing the extent buffer.
3032  */
3033 static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
3034 {
3035 	btrfs_release_extent_buffer_page(eb, 0);
3036 	__free_extent_buffer(eb);
3037 }
3038 
3039 struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
3040 					  u64 start, unsigned long len,
3041 					  struct page *page0)
3042 {
3043 	unsigned long num_pages = num_extent_pages(start, len);
3044 	unsigned long i;
3045 	unsigned long index = start >> PAGE_CACHE_SHIFT;
3046 	struct extent_buffer *eb;
3047 	struct extent_buffer *exists = NULL;
3048 	struct page *p;
3049 	struct address_space *mapping = tree->mapping;
3050 	int uptodate = 1;
3051 	int ret;
3052 
3053 	rcu_read_lock();
3054 	eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
3055 	if (eb && atomic_inc_not_zero(&eb->refs)) {
3056 		rcu_read_unlock();
3057 		mark_page_accessed(eb->first_page);
3058 		return eb;
3059 	}
3060 	rcu_read_unlock();
3061 
3062 	eb = __alloc_extent_buffer(tree, start, len, GFP_NOFS);
3063 	if (!eb)
3064 		return NULL;
3065 
3066 	if (page0) {
3067 		eb->first_page = page0;
3068 		i = 1;
3069 		index++;
3070 		page_cache_get(page0);
3071 		mark_page_accessed(page0);
3072 		set_page_extent_mapped(page0);
3073 		set_page_extent_head(page0, len);
3074 		uptodate = PageUptodate(page0);
3075 	} else {
3076 		i = 0;
3077 	}
3078 	for (; i < num_pages; i++, index++) {
3079 		p = find_or_create_page(mapping, index, GFP_NOFS);
3080 		if (!p) {
3081 			WARN_ON(1);
3082 			goto free_eb;
3083 		}
3084 		set_page_extent_mapped(p);
3085 		mark_page_accessed(p);
3086 		if (i == 0) {
3087 			eb->first_page = p;
3088 			set_page_extent_head(p, len);
3089 		} else {
3090 			set_page_private(p, EXTENT_PAGE_PRIVATE);
3091 		}
3092 		if (!PageUptodate(p))
3093 			uptodate = 0;
3094 
3095 		/*
3096 		 * see below about how we avoid a nasty race with release page
3097 		 * and why we unlock later
3098 		 */
3099 		if (i != 0)
3100 			unlock_page(p);
3101 	}
3102 	if (uptodate)
3103 		set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
3104 
3105 	ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
3106 	if (ret)
3107 		goto free_eb;
3108 
3109 	spin_lock(&tree->buffer_lock);
3110 	ret = radix_tree_insert(&tree->buffer, start >> PAGE_CACHE_SHIFT, eb);
3111 	if (ret == -EEXIST) {
3112 		exists = radix_tree_lookup(&tree->buffer,
3113 						start >> PAGE_CACHE_SHIFT);
3114 		/* add one reference for the caller */
3115 		atomic_inc(&exists->refs);
3116 		spin_unlock(&tree->buffer_lock);
3117 		radix_tree_preload_end();
3118 		goto free_eb;
3119 	}
3120 	/* add one reference for the tree */
3121 	atomic_inc(&eb->refs);
3122 	spin_unlock(&tree->buffer_lock);
3123 	radix_tree_preload_end();
3124 
3125 	/*
3126 	 * there is a race where release page may have
3127 	 * tried to find this extent buffer in the radix
3128 	 * but failed.  It will tell the VM it is safe to
3129 	 * reclaim the, and it will clear the page private bit.
3130 	 * We must make sure to set the page private bit properly
3131 	 * after the extent buffer is in the radix tree so
3132 	 * it doesn't get lost
3133 	 */
3134 	set_page_extent_mapped(eb->first_page);
3135 	set_page_extent_head(eb->first_page, eb->len);
3136 	if (!page0)
3137 		unlock_page(eb->first_page);
3138 	return eb;
3139 
3140 free_eb:
3141 	if (eb->first_page && !page0)
3142 		unlock_page(eb->first_page);
3143 
3144 	if (!atomic_dec_and_test(&eb->refs))
3145 		return exists;
3146 	btrfs_release_extent_buffer(eb);
3147 	return exists;
3148 }
3149 
3150 struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
3151 					 u64 start, unsigned long len)
3152 {
3153 	struct extent_buffer *eb;
3154 
3155 	rcu_read_lock();
3156 	eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
3157 	if (eb && atomic_inc_not_zero(&eb->refs)) {
3158 		rcu_read_unlock();
3159 		mark_page_accessed(eb->first_page);
3160 		return eb;
3161 	}
3162 	rcu_read_unlock();
3163 
3164 	return NULL;
3165 }
3166 
3167 void free_extent_buffer(struct extent_buffer *eb)
3168 {
3169 	if (!eb)
3170 		return;
3171 
3172 	if (!atomic_dec_and_test(&eb->refs))
3173 		return;
3174 
3175 	WARN_ON(1);
3176 }
3177 
3178 int clear_extent_buffer_dirty(struct extent_io_tree *tree,
3179 			      struct extent_buffer *eb)
3180 {
3181 	unsigned long i;
3182 	unsigned long num_pages;
3183 	struct page *page;
3184 
3185 	num_pages = num_extent_pages(eb->start, eb->len);
3186 
3187 	for (i = 0; i < num_pages; i++) {
3188 		page = extent_buffer_page(eb, i);
3189 		if (!PageDirty(page))
3190 			continue;
3191 
3192 		lock_page(page);
3193 		WARN_ON(!PagePrivate(page));
3194 
3195 		set_page_extent_mapped(page);
3196 		if (i == 0)
3197 			set_page_extent_head(page, eb->len);
3198 
3199 		clear_page_dirty_for_io(page);
3200 		spin_lock_irq(&page->mapping->tree_lock);
3201 		if (!PageDirty(page)) {
3202 			radix_tree_tag_clear(&page->mapping->page_tree,
3203 						page_index(page),
3204 						PAGECACHE_TAG_DIRTY);
3205 		}
3206 		spin_unlock_irq(&page->mapping->tree_lock);
3207 		unlock_page(page);
3208 	}
3209 	return 0;
3210 }
3211 
3212 int set_extent_buffer_dirty(struct extent_io_tree *tree,
3213 			     struct extent_buffer *eb)
3214 {
3215 	unsigned long i;
3216 	unsigned long num_pages;
3217 	int was_dirty = 0;
3218 
3219 	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
3220 	num_pages = num_extent_pages(eb->start, eb->len);
3221 	for (i = 0; i < num_pages; i++)
3222 		__set_page_dirty_nobuffers(extent_buffer_page(eb, i));
3223 	return was_dirty;
3224 }
3225 
3226 static int __eb_straddles_pages(u64 start, u64 len)
3227 {
3228 	if (len < PAGE_CACHE_SIZE)
3229 		return 1;
3230 	if (start & (PAGE_CACHE_SIZE - 1))
3231 		return 1;
3232 	if ((start + len) & (PAGE_CACHE_SIZE - 1))
3233 		return 1;
3234 	return 0;
3235 }
3236 
3237 static int eb_straddles_pages(struct extent_buffer *eb)
3238 {
3239 	return __eb_straddles_pages(eb->start, eb->len);
3240 }
3241 
3242 int clear_extent_buffer_uptodate(struct extent_io_tree *tree,
3243 				struct extent_buffer *eb,
3244 				struct extent_state **cached_state)
3245 {
3246 	unsigned long i;
3247 	struct page *page;
3248 	unsigned long num_pages;
3249 
3250 	num_pages = num_extent_pages(eb->start, eb->len);
3251 	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
3252 
3253 	if (eb_straddles_pages(eb)) {
3254 		clear_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
3255 				      cached_state, GFP_NOFS);
3256 	}
3257 	for (i = 0; i < num_pages; i++) {
3258 		page = extent_buffer_page(eb, i);
3259 		if (page)
3260 			ClearPageUptodate(page);
3261 	}
3262 	return 0;
3263 }
3264 
3265 int set_extent_buffer_uptodate(struct extent_io_tree *tree,
3266 				struct extent_buffer *eb)
3267 {
3268 	unsigned long i;
3269 	struct page *page;
3270 	unsigned long num_pages;
3271 
3272 	num_pages = num_extent_pages(eb->start, eb->len);
3273 
3274 	if (eb_straddles_pages(eb)) {
3275 		set_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
3276 				    NULL, GFP_NOFS);
3277 	}
3278 	for (i = 0; i < num_pages; i++) {
3279 		page = extent_buffer_page(eb, i);
3280 		if ((i == 0 && (eb->start & (PAGE_CACHE_SIZE - 1))) ||
3281 		    ((i == num_pages - 1) &&
3282 		     ((eb->start + eb->len) & (PAGE_CACHE_SIZE - 1)))) {
3283 			check_page_uptodate(tree, page);
3284 			continue;
3285 		}
3286 		SetPageUptodate(page);
3287 	}
3288 	return 0;
3289 }
3290 
3291 int extent_range_uptodate(struct extent_io_tree *tree,
3292 			  u64 start, u64 end)
3293 {
3294 	struct page *page;
3295 	int ret;
3296 	int pg_uptodate = 1;
3297 	int uptodate;
3298 	unsigned long index;
3299 
3300 	if (__eb_straddles_pages(start, end - start + 1)) {
3301 		ret = test_range_bit(tree, start, end,
3302 				     EXTENT_UPTODATE, 1, NULL);
3303 		if (ret)
3304 			return 1;
3305 	}
3306 	while (start <= end) {
3307 		index = start >> PAGE_CACHE_SHIFT;
3308 		page = find_get_page(tree->mapping, index);
3309 		uptodate = PageUptodate(page);
3310 		page_cache_release(page);
3311 		if (!uptodate) {
3312 			pg_uptodate = 0;
3313 			break;
3314 		}
3315 		start += PAGE_CACHE_SIZE;
3316 	}
3317 	return pg_uptodate;
3318 }
3319 
3320 int extent_buffer_uptodate(struct extent_io_tree *tree,
3321 			   struct extent_buffer *eb,
3322 			   struct extent_state *cached_state)
3323 {
3324 	int ret = 0;
3325 	unsigned long num_pages;
3326 	unsigned long i;
3327 	struct page *page;
3328 	int pg_uptodate = 1;
3329 
3330 	if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
3331 		return 1;
3332 
3333 	if (eb_straddles_pages(eb)) {
3334 		ret = test_range_bit(tree, eb->start, eb->start + eb->len - 1,
3335 				   EXTENT_UPTODATE, 1, cached_state);
3336 		if (ret)
3337 			return ret;
3338 	}
3339 
3340 	num_pages = num_extent_pages(eb->start, eb->len);
3341 	for (i = 0; i < num_pages; i++) {
3342 		page = extent_buffer_page(eb, i);
3343 		if (!PageUptodate(page)) {
3344 			pg_uptodate = 0;
3345 			break;
3346 		}
3347 	}
3348 	return pg_uptodate;
3349 }
3350 
3351 int read_extent_buffer_pages(struct extent_io_tree *tree,
3352 			     struct extent_buffer *eb,
3353 			     u64 start, int wait,
3354 			     get_extent_t *get_extent, int mirror_num)
3355 {
3356 	unsigned long i;
3357 	unsigned long start_i;
3358 	struct page *page;
3359 	int err;
3360 	int ret = 0;
3361 	int locked_pages = 0;
3362 	int all_uptodate = 1;
3363 	int inc_all_pages = 0;
3364 	unsigned long num_pages;
3365 	struct bio *bio = NULL;
3366 	unsigned long bio_flags = 0;
3367 
3368 	if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
3369 		return 0;
3370 
3371 	if (eb_straddles_pages(eb)) {
3372 		if (test_range_bit(tree, eb->start, eb->start + eb->len - 1,
3373 				   EXTENT_UPTODATE, 1, NULL)) {
3374 			return 0;
3375 		}
3376 	}
3377 
3378 	if (start) {
3379 		WARN_ON(start < eb->start);
3380 		start_i = (start >> PAGE_CACHE_SHIFT) -
3381 			(eb->start >> PAGE_CACHE_SHIFT);
3382 	} else {
3383 		start_i = 0;
3384 	}
3385 
3386 	num_pages = num_extent_pages(eb->start, eb->len);
3387 	for (i = start_i; i < num_pages; i++) {
3388 		page = extent_buffer_page(eb, i);
3389 		if (!wait) {
3390 			if (!trylock_page(page))
3391 				goto unlock_exit;
3392 		} else {
3393 			lock_page(page);
3394 		}
3395 		locked_pages++;
3396 		if (!PageUptodate(page))
3397 			all_uptodate = 0;
3398 	}
3399 	if (all_uptodate) {
3400 		if (start_i == 0)
3401 			set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
3402 		goto unlock_exit;
3403 	}
3404 
3405 	for (i = start_i; i < num_pages; i++) {
3406 		page = extent_buffer_page(eb, i);
3407 
3408 		WARN_ON(!PagePrivate(page));
3409 
3410 		set_page_extent_mapped(page);
3411 		if (i == 0)
3412 			set_page_extent_head(page, eb->len);
3413 
3414 		if (inc_all_pages)
3415 			page_cache_get(page);
3416 		if (!PageUptodate(page)) {
3417 			if (start_i == 0)
3418 				inc_all_pages = 1;
3419 			ClearPageError(page);
3420 			err = __extent_read_full_page(tree, page,
3421 						      get_extent, &bio,
3422 						      mirror_num, &bio_flags);
3423 			if (err)
3424 				ret = err;
3425 		} else {
3426 			unlock_page(page);
3427 		}
3428 	}
3429 
3430 	if (bio)
3431 		submit_one_bio(READ, bio, mirror_num, bio_flags);
3432 
3433 	if (ret || !wait)
3434 		return ret;
3435 
3436 	for (i = start_i; i < num_pages; i++) {
3437 		page = extent_buffer_page(eb, i);
3438 		wait_on_page_locked(page);
3439 		if (!PageUptodate(page))
3440 			ret = -EIO;
3441 	}
3442 
3443 	if (!ret)
3444 		set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
3445 	return ret;
3446 
3447 unlock_exit:
3448 	i = start_i;
3449 	while (locked_pages > 0) {
3450 		page = extent_buffer_page(eb, i);
3451 		i++;
3452 		unlock_page(page);
3453 		locked_pages--;
3454 	}
3455 	return ret;
3456 }
3457 
3458 void read_extent_buffer(struct extent_buffer *eb, void *dstv,
3459 			unsigned long start,
3460 			unsigned long len)
3461 {
3462 	size_t cur;
3463 	size_t offset;
3464 	struct page *page;
3465 	char *kaddr;
3466 	char *dst = (char *)dstv;
3467 	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
3468 	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
3469 
3470 	WARN_ON(start > eb->len);
3471 	WARN_ON(start + len > eb->start + eb->len);
3472 
3473 	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
3474 
3475 	while (len > 0) {
3476 		page = extent_buffer_page(eb, i);
3477 
3478 		cur = min(len, (PAGE_CACHE_SIZE - offset));
3479 		kaddr = page_address(page);
3480 		memcpy(dst, kaddr + offset, cur);
3481 
3482 		dst += cur;
3483 		len -= cur;
3484 		offset = 0;
3485 		i++;
3486 	}
3487 }
3488 
3489 int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
3490 			       unsigned long min_len, char **map,
3491 			       unsigned long *map_start,
3492 			       unsigned long *map_len)
3493 {
3494 	size_t offset = start & (PAGE_CACHE_SIZE - 1);
3495 	char *kaddr;
3496 	struct page *p;
3497 	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
3498 	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
3499 	unsigned long end_i = (start_offset + start + min_len - 1) >>
3500 		PAGE_CACHE_SHIFT;
3501 
3502 	if (i != end_i)
3503 		return -EINVAL;
3504 
3505 	if (i == 0) {
3506 		offset = start_offset;
3507 		*map_start = 0;
3508 	} else {
3509 		offset = 0;
3510 		*map_start = ((u64)i << PAGE_CACHE_SHIFT) - start_offset;
3511 	}
3512 
3513 	if (start + min_len > eb->len) {
3514 		printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
3515 		       "wanted %lu %lu\n", (unsigned long long)eb->start,
3516 		       eb->len, start, min_len);
3517 		WARN_ON(1);
3518 		return -EINVAL;
3519 	}
3520 
3521 	p = extent_buffer_page(eb, i);
3522 	kaddr = page_address(p);
3523 	*map = kaddr + offset;
3524 	*map_len = PAGE_CACHE_SIZE - offset;
3525 	return 0;
3526 }
3527 
3528 int memcmp_extent_buffer(struct extent_buffer *eb, const void *ptrv,
3529 			  unsigned long start,
3530 			  unsigned long len)
3531 {
3532 	size_t cur;
3533 	size_t offset;
3534 	struct page *page;
3535 	char *kaddr;
3536 	char *ptr = (char *)ptrv;
3537 	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
3538 	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
3539 	int ret = 0;
3540 
3541 	WARN_ON(start > eb->len);
3542 	WARN_ON(start + len > eb->start + eb->len);
3543 
3544 	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
3545 
3546 	while (len > 0) {
3547 		page = extent_buffer_page(eb, i);
3548 
3549 		cur = min(len, (PAGE_CACHE_SIZE - offset));
3550 
3551 		kaddr = page_address(page);
3552 		ret = memcmp(ptr, kaddr + offset, cur);
3553 		if (ret)
3554 			break;
3555 
3556 		ptr += cur;
3557 		len -= cur;
3558 		offset = 0;
3559 		i++;
3560 	}
3561 	return ret;
3562 }
3563 
3564 void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
3565 			 unsigned long start, unsigned long len)
3566 {
3567 	size_t cur;
3568 	size_t offset;
3569 	struct page *page;
3570 	char *kaddr;
3571 	char *src = (char *)srcv;
3572 	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
3573 	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
3574 
3575 	WARN_ON(start > eb->len);
3576 	WARN_ON(start + len > eb->start + eb->len);
3577 
3578 	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
3579 
3580 	while (len > 0) {
3581 		page = extent_buffer_page(eb, i);
3582 		WARN_ON(!PageUptodate(page));
3583 
3584 		cur = min(len, PAGE_CACHE_SIZE - offset);
3585 		kaddr = page_address(page);
3586 		memcpy(kaddr + offset, src, cur);
3587 
3588 		src += cur;
3589 		len -= cur;
3590 		offset = 0;
3591 		i++;
3592 	}
3593 }
3594 
3595 void memset_extent_buffer(struct extent_buffer *eb, char c,
3596 			  unsigned long start, unsigned long len)
3597 {
3598 	size_t cur;
3599 	size_t offset;
3600 	struct page *page;
3601 	char *kaddr;
3602 	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
3603 	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
3604 
3605 	WARN_ON(start > eb->len);
3606 	WARN_ON(start + len > eb->start + eb->len);
3607 
3608 	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
3609 
3610 	while (len > 0) {
3611 		page = extent_buffer_page(eb, i);
3612 		WARN_ON(!PageUptodate(page));
3613 
3614 		cur = min(len, PAGE_CACHE_SIZE - offset);
3615 		kaddr = page_address(page);
3616 		memset(kaddr + offset, c, cur);
3617 
3618 		len -= cur;
3619 		offset = 0;
3620 		i++;
3621 	}
3622 }
3623 
3624 void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
3625 			unsigned long dst_offset, unsigned long src_offset,
3626 			unsigned long len)
3627 {
3628 	u64 dst_len = dst->len;
3629 	size_t cur;
3630 	size_t offset;
3631 	struct page *page;
3632 	char *kaddr;
3633 	size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
3634 	unsigned long i = (start_offset + dst_offset) >> PAGE_CACHE_SHIFT;
3635 
3636 	WARN_ON(src->len != dst_len);
3637 
3638 	offset = (start_offset + dst_offset) &
3639 		((unsigned long)PAGE_CACHE_SIZE - 1);
3640 
3641 	while (len > 0) {
3642 		page = extent_buffer_page(dst, i);
3643 		WARN_ON(!PageUptodate(page));
3644 
3645 		cur = min(len, (unsigned long)(PAGE_CACHE_SIZE - offset));
3646 
3647 		kaddr = page_address(page);
3648 		read_extent_buffer(src, kaddr + offset, src_offset, cur);
3649 
3650 		src_offset += cur;
3651 		len -= cur;
3652 		offset = 0;
3653 		i++;
3654 	}
3655 }
3656 
3657 static void move_pages(struct page *dst_page, struct page *src_page,
3658 		       unsigned long dst_off, unsigned long src_off,
3659 		       unsigned long len)
3660 {
3661 	char *dst_kaddr = page_address(dst_page);
3662 	if (dst_page == src_page) {
3663 		memmove(dst_kaddr + dst_off, dst_kaddr + src_off, len);
3664 	} else {
3665 		char *src_kaddr = page_address(src_page);
3666 		char *p = dst_kaddr + dst_off + len;
3667 		char *s = src_kaddr + src_off + len;
3668 
3669 		while (len--)
3670 			*--p = *--s;
3671 	}
3672 }
3673 
3674 static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len)
3675 {
3676 	unsigned long distance = (src > dst) ? src - dst : dst - src;
3677 	return distance < len;
3678 }
3679 
3680 static void copy_pages(struct page *dst_page, struct page *src_page,
3681 		       unsigned long dst_off, unsigned long src_off,
3682 		       unsigned long len)
3683 {
3684 	char *dst_kaddr = page_address(dst_page);
3685 	char *src_kaddr;
3686 
3687 	if (dst_page != src_page) {
3688 		src_kaddr = page_address(src_page);
3689 	} else {
3690 		src_kaddr = dst_kaddr;
3691 		BUG_ON(areas_overlap(src_off, dst_off, len));
3692 	}
3693 
3694 	memcpy(dst_kaddr + dst_off, src_kaddr + src_off, len);
3695 }
3696 
3697 void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
3698 			   unsigned long src_offset, unsigned long len)
3699 {
3700 	size_t cur;
3701 	size_t dst_off_in_page;
3702 	size_t src_off_in_page;
3703 	size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
3704 	unsigned long dst_i;
3705 	unsigned long src_i;
3706 
3707 	if (src_offset + len > dst->len) {
3708 		printk(KERN_ERR "btrfs memmove bogus src_offset %lu move "
3709 		       "len %lu dst len %lu\n", src_offset, len, dst->len);
3710 		BUG_ON(1);
3711 	}
3712 	if (dst_offset + len > dst->len) {
3713 		printk(KERN_ERR "btrfs memmove bogus dst_offset %lu move "
3714 		       "len %lu dst len %lu\n", dst_offset, len, dst->len);
3715 		BUG_ON(1);
3716 	}
3717 
3718 	while (len > 0) {
3719 		dst_off_in_page = (start_offset + dst_offset) &
3720 			((unsigned long)PAGE_CACHE_SIZE - 1);
3721 		src_off_in_page = (start_offset + src_offset) &
3722 			((unsigned long)PAGE_CACHE_SIZE - 1);
3723 
3724 		dst_i = (start_offset + dst_offset) >> PAGE_CACHE_SHIFT;
3725 		src_i = (start_offset + src_offset) >> PAGE_CACHE_SHIFT;
3726 
3727 		cur = min(len, (unsigned long)(PAGE_CACHE_SIZE -
3728 					       src_off_in_page));
3729 		cur = min_t(unsigned long, cur,
3730 			(unsigned long)(PAGE_CACHE_SIZE - dst_off_in_page));
3731 
3732 		copy_pages(extent_buffer_page(dst, dst_i),
3733 			   extent_buffer_page(dst, src_i),
3734 			   dst_off_in_page, src_off_in_page, cur);
3735 
3736 		src_offset += cur;
3737 		dst_offset += cur;
3738 		len -= cur;
3739 	}
3740 }
3741 
3742 void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
3743 			   unsigned long src_offset, unsigned long len)
3744 {
3745 	size_t cur;
3746 	size_t dst_off_in_page;
3747 	size_t src_off_in_page;
3748 	unsigned long dst_end = dst_offset + len - 1;
3749 	unsigned long src_end = src_offset + len - 1;
3750 	size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
3751 	unsigned long dst_i;
3752 	unsigned long src_i;
3753 
3754 	if (src_offset + len > dst->len) {
3755 		printk(KERN_ERR "btrfs memmove bogus src_offset %lu move "
3756 		       "len %lu len %lu\n", src_offset, len, dst->len);
3757 		BUG_ON(1);
3758 	}
3759 	if (dst_offset + len > dst->len) {
3760 		printk(KERN_ERR "btrfs memmove bogus dst_offset %lu move "
3761 		       "len %lu len %lu\n", dst_offset, len, dst->len);
3762 		BUG_ON(1);
3763 	}
3764 	if (!areas_overlap(src_offset, dst_offset, len)) {
3765 		memcpy_extent_buffer(dst, dst_offset, src_offset, len);
3766 		return;
3767 	}
3768 	while (len > 0) {
3769 		dst_i = (start_offset + dst_end) >> PAGE_CACHE_SHIFT;
3770 		src_i = (start_offset + src_end) >> PAGE_CACHE_SHIFT;
3771 
3772 		dst_off_in_page = (start_offset + dst_end) &
3773 			((unsigned long)PAGE_CACHE_SIZE - 1);
3774 		src_off_in_page = (start_offset + src_end) &
3775 			((unsigned long)PAGE_CACHE_SIZE - 1);
3776 
3777 		cur = min_t(unsigned long, len, src_off_in_page + 1);
3778 		cur = min(cur, dst_off_in_page + 1);
3779 		move_pages(extent_buffer_page(dst, dst_i),
3780 			   extent_buffer_page(dst, src_i),
3781 			   dst_off_in_page - cur + 1,
3782 			   src_off_in_page - cur + 1, cur);
3783 
3784 		dst_end -= cur;
3785 		src_end -= cur;
3786 		len -= cur;
3787 	}
3788 }
3789 
3790 static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
3791 {
3792 	struct extent_buffer *eb =
3793 			container_of(head, struct extent_buffer, rcu_head);
3794 
3795 	btrfs_release_extent_buffer(eb);
3796 }
3797 
3798 int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
3799 {
3800 	u64 start = page_offset(page);
3801 	struct extent_buffer *eb;
3802 	int ret = 1;
3803 
3804 	spin_lock(&tree->buffer_lock);
3805 	eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
3806 	if (!eb) {
3807 		spin_unlock(&tree->buffer_lock);
3808 		return ret;
3809 	}
3810 
3811 	if (test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
3812 		ret = 0;
3813 		goto out;
3814 	}
3815 
3816 	/*
3817 	 * set @eb->refs to 0 if it is already 1, and then release the @eb.
3818 	 * Or go back.
3819 	 */
3820 	if (atomic_cmpxchg(&eb->refs, 1, 0) != 1) {
3821 		ret = 0;
3822 		goto out;
3823 	}
3824 
3825 	radix_tree_delete(&tree->buffer, start >> PAGE_CACHE_SHIFT);
3826 out:
3827 	spin_unlock(&tree->buffer_lock);
3828 
3829 	/* at this point we can safely release the extent buffer */
3830 	if (atomic_read(&eb->refs) == 0)
3831 		call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
3832 	return ret;
3833 }
3834