xref: /openbmc/linux/fs/nilfs2/segment.c (revision 80d0624d)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * NILFS segment constructor.
4  *
5  * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
6  *
7  * Written by Ryusuke Konishi.
8  *
9  */
10 
11 #include <linux/pagemap.h>
12 #include <linux/buffer_head.h>
13 #include <linux/writeback.h>
14 #include <linux/bitops.h>
15 #include <linux/bio.h>
16 #include <linux/completion.h>
17 #include <linux/blkdev.h>
18 #include <linux/backing-dev.h>
19 #include <linux/freezer.h>
20 #include <linux/kthread.h>
21 #include <linux/crc32.h>
22 #include <linux/pagevec.h>
23 #include <linux/slab.h>
24 #include <linux/sched/signal.h>
25 
26 #include "nilfs.h"
27 #include "btnode.h"
28 #include "page.h"
29 #include "segment.h"
30 #include "sufile.h"
31 #include "cpfile.h"
32 #include "ifile.h"
33 #include "segbuf.h"
34 
35 
36 /*
37  * Segment constructor
38  */
39 #define SC_N_INODEVEC	16   /* Size of locally allocated inode vector */
40 
41 #define SC_MAX_SEGDELTA 64   /*
42 			      * Upper limit of the number of segments
43 			      * appended in collection retry loop
44 			      */
45 
46 /* Construction mode */
47 enum {
48 	SC_LSEG_SR = 1,	/* Make a logical segment having a super root */
49 	SC_LSEG_DSYNC,	/*
50 			 * Flush data blocks of a given file and make
51 			 * a logical segment without a super root.
52 			 */
53 	SC_FLUSH_FILE,	/*
54 			 * Flush data files, leads to segment writes without
55 			 * creating a checkpoint.
56 			 */
57 	SC_FLUSH_DAT,	/*
58 			 * Flush DAT file.  This also creates segments
59 			 * without a checkpoint.
60 			 */
61 };
62 
63 /* Stage numbers of dirty block collection */
64 enum {
65 	NILFS_ST_INIT = 0,
66 	NILFS_ST_GC,		/* Collecting dirty blocks for GC */
67 	NILFS_ST_FILE,
68 	NILFS_ST_IFILE,
69 	NILFS_ST_CPFILE,
70 	NILFS_ST_SUFILE,
71 	NILFS_ST_DAT,
72 	NILFS_ST_SR,		/* Super root */
73 	NILFS_ST_DSYNC,		/* Data sync blocks */
74 	NILFS_ST_DONE,
75 };
76 
77 #define CREATE_TRACE_POINTS
78 #include <trace/events/nilfs2.h>
79 
80 /*
81  * nilfs_sc_cstage_inc(), nilfs_sc_cstage_set(), nilfs_sc_cstage_get() are
82  * wrapper functions of stage count (nilfs_sc_info->sc_stage.scnt). Users of
83  * the variable must use them because transition of stage count must involve
84  * trace events (trace_nilfs2_collection_stage_transition).
85  *
86  * nilfs_sc_cstage_get() isn't required for the above purpose because it doesn't
87  * produce tracepoint events. It is provided just for making the intention
88  * clear.
89  */
90 static inline void nilfs_sc_cstage_inc(struct nilfs_sc_info *sci)
91 {
92 	sci->sc_stage.scnt++;
93 	trace_nilfs2_collection_stage_transition(sci);
94 }
95 
96 static inline void nilfs_sc_cstage_set(struct nilfs_sc_info *sci, int next_scnt)
97 {
98 	sci->sc_stage.scnt = next_scnt;
99 	trace_nilfs2_collection_stage_transition(sci);
100 }
101 
102 static inline int nilfs_sc_cstage_get(struct nilfs_sc_info *sci)
103 {
104 	return sci->sc_stage.scnt;
105 }
106 
107 /* State flags of collection */
108 #define NILFS_CF_NODE		0x0001	/* Collecting node blocks */
109 #define NILFS_CF_IFILE_STARTED	0x0002	/* IFILE stage has started */
110 #define NILFS_CF_SUFREED	0x0004	/* segment usages has been freed */
111 #define NILFS_CF_HISTORY_MASK	(NILFS_CF_IFILE_STARTED | NILFS_CF_SUFREED)
112 
113 /* Operations depending on the construction mode and file type */
114 struct nilfs_sc_operations {
115 	int (*collect_data)(struct nilfs_sc_info *, struct buffer_head *,
116 			    struct inode *);
117 	int (*collect_node)(struct nilfs_sc_info *, struct buffer_head *,
118 			    struct inode *);
119 	int (*collect_bmap)(struct nilfs_sc_info *, struct buffer_head *,
120 			    struct inode *);
121 	void (*write_data_binfo)(struct nilfs_sc_info *,
122 				 struct nilfs_segsum_pointer *,
123 				 union nilfs_binfo *);
124 	void (*write_node_binfo)(struct nilfs_sc_info *,
125 				 struct nilfs_segsum_pointer *,
126 				 union nilfs_binfo *);
127 };
128 
129 /*
130  * Other definitions
131  */
132 static void nilfs_segctor_start_timer(struct nilfs_sc_info *);
133 static void nilfs_segctor_do_flush(struct nilfs_sc_info *, int);
134 static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *);
135 static void nilfs_dispose_list(struct the_nilfs *, struct list_head *, int);
136 
137 #define nilfs_cnt32_ge(a, b)   \
138 	(typecheck(__u32, a) && typecheck(__u32, b) && \
139 	 ((__s32)((a) - (b)) >= 0))
140 
141 static int nilfs_prepare_segment_lock(struct super_block *sb,
142 				      struct nilfs_transaction_info *ti)
143 {
144 	struct nilfs_transaction_info *cur_ti = current->journal_info;
145 	void *save = NULL;
146 
147 	if (cur_ti) {
148 		if (cur_ti->ti_magic == NILFS_TI_MAGIC)
149 			return ++cur_ti->ti_count;
150 
151 		/*
152 		 * If journal_info field is occupied by other FS,
153 		 * it is saved and will be restored on
154 		 * nilfs_transaction_commit().
155 		 */
156 		nilfs_warn(sb, "journal info from a different FS");
157 		save = current->journal_info;
158 	}
159 	if (!ti) {
160 		ti = kmem_cache_alloc(nilfs_transaction_cachep, GFP_NOFS);
161 		if (!ti)
162 			return -ENOMEM;
163 		ti->ti_flags = NILFS_TI_DYNAMIC_ALLOC;
164 	} else {
165 		ti->ti_flags = 0;
166 	}
167 	ti->ti_count = 0;
168 	ti->ti_save = save;
169 	ti->ti_magic = NILFS_TI_MAGIC;
170 	current->journal_info = ti;
171 	return 0;
172 }
173 
174 /**
175  * nilfs_transaction_begin - start indivisible file operations.
176  * @sb: super block
177  * @ti: nilfs_transaction_info
178  * @vacancy_check: flags for vacancy rate checks
179  *
180  * nilfs_transaction_begin() acquires a reader/writer semaphore, called
181  * the segment semaphore, to make a segment construction and write tasks
182  * exclusive.  The function is used with nilfs_transaction_commit() in pairs.
183  * The region enclosed by these two functions can be nested.  To avoid a
184  * deadlock, the semaphore is only acquired or released in the outermost call.
185  *
186  * This function allocates a nilfs_transaction_info struct to keep context
187  * information on it.  It is initialized and hooked onto the current task in
188  * the outermost call.  If a pre-allocated struct is given to @ti, it is used
189  * instead; otherwise a new struct is assigned from a slab.
190  *
191  * When @vacancy_check flag is set, this function will check the amount of
192  * free space, and will wait for the GC to reclaim disk space if low capacity.
193  *
194  * Return Value: On success, 0 is returned. On error, one of the following
195  * negative error code is returned.
196  *
197  * %-ENOMEM - Insufficient memory available.
198  *
199  * %-ENOSPC - No space left on device
200  */
201 int nilfs_transaction_begin(struct super_block *sb,
202 			    struct nilfs_transaction_info *ti,
203 			    int vacancy_check)
204 {
205 	struct the_nilfs *nilfs;
206 	int ret = nilfs_prepare_segment_lock(sb, ti);
207 	struct nilfs_transaction_info *trace_ti;
208 
209 	if (unlikely(ret < 0))
210 		return ret;
211 	if (ret > 0) {
212 		trace_ti = current->journal_info;
213 
214 		trace_nilfs2_transaction_transition(sb, trace_ti,
215 				    trace_ti->ti_count, trace_ti->ti_flags,
216 				    TRACE_NILFS2_TRANSACTION_BEGIN);
217 		return 0;
218 	}
219 
220 	sb_start_intwrite(sb);
221 
222 	nilfs = sb->s_fs_info;
223 	down_read(&nilfs->ns_segctor_sem);
224 	if (vacancy_check && nilfs_near_disk_full(nilfs)) {
225 		up_read(&nilfs->ns_segctor_sem);
226 		ret = -ENOSPC;
227 		goto failed;
228 	}
229 
230 	trace_ti = current->journal_info;
231 	trace_nilfs2_transaction_transition(sb, trace_ti, trace_ti->ti_count,
232 					    trace_ti->ti_flags,
233 					    TRACE_NILFS2_TRANSACTION_BEGIN);
234 	return 0;
235 
236  failed:
237 	ti = current->journal_info;
238 	current->journal_info = ti->ti_save;
239 	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
240 		kmem_cache_free(nilfs_transaction_cachep, ti);
241 	sb_end_intwrite(sb);
242 	return ret;
243 }
244 
245 /**
246  * nilfs_transaction_commit - commit indivisible file operations.
247  * @sb: super block
248  *
249  * nilfs_transaction_commit() releases the read semaphore which is
250  * acquired by nilfs_transaction_begin(). This is only performed
251  * in outermost call of this function.  If a commit flag is set,
252  * nilfs_transaction_commit() sets a timer to start the segment
253  * constructor.  If a sync flag is set, it starts construction
254  * directly.
255  */
256 int nilfs_transaction_commit(struct super_block *sb)
257 {
258 	struct nilfs_transaction_info *ti = current->journal_info;
259 	struct the_nilfs *nilfs = sb->s_fs_info;
260 	int err = 0;
261 
262 	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
263 	ti->ti_flags |= NILFS_TI_COMMIT;
264 	if (ti->ti_count > 0) {
265 		ti->ti_count--;
266 		trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
267 			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_COMMIT);
268 		return 0;
269 	}
270 	if (nilfs->ns_writer) {
271 		struct nilfs_sc_info *sci = nilfs->ns_writer;
272 
273 		if (ti->ti_flags & NILFS_TI_COMMIT)
274 			nilfs_segctor_start_timer(sci);
275 		if (atomic_read(&nilfs->ns_ndirtyblks) > sci->sc_watermark)
276 			nilfs_segctor_do_flush(sci, 0);
277 	}
278 	up_read(&nilfs->ns_segctor_sem);
279 	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
280 			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_COMMIT);
281 
282 	current->journal_info = ti->ti_save;
283 
284 	if (ti->ti_flags & NILFS_TI_SYNC)
285 		err = nilfs_construct_segment(sb);
286 	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
287 		kmem_cache_free(nilfs_transaction_cachep, ti);
288 	sb_end_intwrite(sb);
289 	return err;
290 }
291 
292 void nilfs_transaction_abort(struct super_block *sb)
293 {
294 	struct nilfs_transaction_info *ti = current->journal_info;
295 	struct the_nilfs *nilfs = sb->s_fs_info;
296 
297 	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
298 	if (ti->ti_count > 0) {
299 		ti->ti_count--;
300 		trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
301 			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_ABORT);
302 		return;
303 	}
304 	up_read(&nilfs->ns_segctor_sem);
305 
306 	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
307 		    ti->ti_flags, TRACE_NILFS2_TRANSACTION_ABORT);
308 
309 	current->journal_info = ti->ti_save;
310 	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
311 		kmem_cache_free(nilfs_transaction_cachep, ti);
312 	sb_end_intwrite(sb);
313 }
314 
315 void nilfs_relax_pressure_in_lock(struct super_block *sb)
316 {
317 	struct the_nilfs *nilfs = sb->s_fs_info;
318 	struct nilfs_sc_info *sci = nilfs->ns_writer;
319 
320 	if (sb_rdonly(sb) || unlikely(!sci) || !sci->sc_flush_request)
321 		return;
322 
323 	set_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
324 	up_read(&nilfs->ns_segctor_sem);
325 
326 	down_write(&nilfs->ns_segctor_sem);
327 	if (sci->sc_flush_request &&
328 	    test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags)) {
329 		struct nilfs_transaction_info *ti = current->journal_info;
330 
331 		ti->ti_flags |= NILFS_TI_WRITER;
332 		nilfs_segctor_do_immediate_flush(sci);
333 		ti->ti_flags &= ~NILFS_TI_WRITER;
334 	}
335 	downgrade_write(&nilfs->ns_segctor_sem);
336 }
337 
338 static void nilfs_transaction_lock(struct super_block *sb,
339 				   struct nilfs_transaction_info *ti,
340 				   int gcflag)
341 {
342 	struct nilfs_transaction_info *cur_ti = current->journal_info;
343 	struct the_nilfs *nilfs = sb->s_fs_info;
344 	struct nilfs_sc_info *sci = nilfs->ns_writer;
345 
346 	WARN_ON(cur_ti);
347 	ti->ti_flags = NILFS_TI_WRITER;
348 	ti->ti_count = 0;
349 	ti->ti_save = cur_ti;
350 	ti->ti_magic = NILFS_TI_MAGIC;
351 	current->journal_info = ti;
352 
353 	for (;;) {
354 		trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
355 			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_TRYLOCK);
356 
357 		down_write(&nilfs->ns_segctor_sem);
358 		if (!test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags))
359 			break;
360 
361 		nilfs_segctor_do_immediate_flush(sci);
362 
363 		up_write(&nilfs->ns_segctor_sem);
364 		cond_resched();
365 	}
366 	if (gcflag)
367 		ti->ti_flags |= NILFS_TI_GC;
368 
369 	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
370 			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_LOCK);
371 }
372 
373 static void nilfs_transaction_unlock(struct super_block *sb)
374 {
375 	struct nilfs_transaction_info *ti = current->journal_info;
376 	struct the_nilfs *nilfs = sb->s_fs_info;
377 
378 	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
379 	BUG_ON(ti->ti_count > 0);
380 
381 	up_write(&nilfs->ns_segctor_sem);
382 	current->journal_info = ti->ti_save;
383 
384 	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
385 			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_UNLOCK);
386 }
387 
388 static void *nilfs_segctor_map_segsum_entry(struct nilfs_sc_info *sci,
389 					    struct nilfs_segsum_pointer *ssp,
390 					    unsigned int bytes)
391 {
392 	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
393 	unsigned int blocksize = sci->sc_super->s_blocksize;
394 	void *p;
395 
396 	if (unlikely(ssp->offset + bytes > blocksize)) {
397 		ssp->offset = 0;
398 		BUG_ON(NILFS_SEGBUF_BH_IS_LAST(ssp->bh,
399 					       &segbuf->sb_segsum_buffers));
400 		ssp->bh = NILFS_SEGBUF_NEXT_BH(ssp->bh);
401 	}
402 	p = ssp->bh->b_data + ssp->offset;
403 	ssp->offset += bytes;
404 	return p;
405 }
406 
407 /**
408  * nilfs_segctor_reset_segment_buffer - reset the current segment buffer
409  * @sci: nilfs_sc_info
410  */
411 static int nilfs_segctor_reset_segment_buffer(struct nilfs_sc_info *sci)
412 {
413 	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
414 	struct buffer_head *sumbh;
415 	unsigned int sumbytes;
416 	unsigned int flags = 0;
417 	int err;
418 
419 	if (nilfs_doing_gc())
420 		flags = NILFS_SS_GC;
421 	err = nilfs_segbuf_reset(segbuf, flags, sci->sc_seg_ctime, sci->sc_cno);
422 	if (unlikely(err))
423 		return err;
424 
425 	sumbh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
426 	sumbytes = segbuf->sb_sum.sumbytes;
427 	sci->sc_finfo_ptr.bh = sumbh;  sci->sc_finfo_ptr.offset = sumbytes;
428 	sci->sc_binfo_ptr.bh = sumbh;  sci->sc_binfo_ptr.offset = sumbytes;
429 	sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
430 	return 0;
431 }
432 
433 /**
434  * nilfs_segctor_zeropad_segsum - zero pad the rest of the segment summary area
435  * @sci: segment constructor object
436  *
437  * nilfs_segctor_zeropad_segsum() zero-fills unallocated space at the end of
438  * the current segment summary block.
439  */
440 static void nilfs_segctor_zeropad_segsum(struct nilfs_sc_info *sci)
441 {
442 	struct nilfs_segsum_pointer *ssp;
443 
444 	ssp = sci->sc_blk_cnt > 0 ? &sci->sc_binfo_ptr : &sci->sc_finfo_ptr;
445 	if (ssp->offset < ssp->bh->b_size)
446 		memset(ssp->bh->b_data + ssp->offset, 0,
447 		       ssp->bh->b_size - ssp->offset);
448 }
449 
450 static int nilfs_segctor_feed_segment(struct nilfs_sc_info *sci)
451 {
452 	sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
453 	if (NILFS_SEGBUF_IS_LAST(sci->sc_curseg, &sci->sc_segbufs))
454 		return -E2BIG; /*
455 				* The current segment is filled up
456 				* (internal code)
457 				*/
458 	nilfs_segctor_zeropad_segsum(sci);
459 	sci->sc_curseg = NILFS_NEXT_SEGBUF(sci->sc_curseg);
460 	return nilfs_segctor_reset_segment_buffer(sci);
461 }
462 
463 static int nilfs_segctor_add_super_root(struct nilfs_sc_info *sci)
464 {
465 	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
466 	int err;
467 
468 	if (segbuf->sb_sum.nblocks >= segbuf->sb_rest_blocks) {
469 		err = nilfs_segctor_feed_segment(sci);
470 		if (err)
471 			return err;
472 		segbuf = sci->sc_curseg;
473 	}
474 	err = nilfs_segbuf_extend_payload(segbuf, &segbuf->sb_super_root);
475 	if (likely(!err))
476 		segbuf->sb_sum.flags |= NILFS_SS_SR;
477 	return err;
478 }
479 
480 /*
481  * Functions for making segment summary and payloads
482  */
483 static int nilfs_segctor_segsum_block_required(
484 	struct nilfs_sc_info *sci, const struct nilfs_segsum_pointer *ssp,
485 	unsigned int binfo_size)
486 {
487 	unsigned int blocksize = sci->sc_super->s_blocksize;
488 	/* Size of finfo and binfo is enough small against blocksize */
489 
490 	return ssp->offset + binfo_size +
491 		(!sci->sc_blk_cnt ? sizeof(struct nilfs_finfo) : 0) >
492 		blocksize;
493 }
494 
495 static void nilfs_segctor_begin_finfo(struct nilfs_sc_info *sci,
496 				      struct inode *inode)
497 {
498 	sci->sc_curseg->sb_sum.nfinfo++;
499 	sci->sc_binfo_ptr = sci->sc_finfo_ptr;
500 	nilfs_segctor_map_segsum_entry(
501 		sci, &sci->sc_binfo_ptr, sizeof(struct nilfs_finfo));
502 
503 	if (NILFS_I(inode)->i_root &&
504 	    !test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
505 		set_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
506 	/* skip finfo */
507 }
508 
509 static void nilfs_segctor_end_finfo(struct nilfs_sc_info *sci,
510 				    struct inode *inode)
511 {
512 	struct nilfs_finfo *finfo;
513 	struct nilfs_inode_info *ii;
514 	struct nilfs_segment_buffer *segbuf;
515 	__u64 cno;
516 
517 	if (sci->sc_blk_cnt == 0)
518 		return;
519 
520 	ii = NILFS_I(inode);
521 
522 	if (test_bit(NILFS_I_GCINODE, &ii->i_state))
523 		cno = ii->i_cno;
524 	else if (NILFS_ROOT_METADATA_FILE(inode->i_ino))
525 		cno = 0;
526 	else
527 		cno = sci->sc_cno;
528 
529 	finfo = nilfs_segctor_map_segsum_entry(sci, &sci->sc_finfo_ptr,
530 						 sizeof(*finfo));
531 	finfo->fi_ino = cpu_to_le64(inode->i_ino);
532 	finfo->fi_nblocks = cpu_to_le32(sci->sc_blk_cnt);
533 	finfo->fi_ndatablk = cpu_to_le32(sci->sc_datablk_cnt);
534 	finfo->fi_cno = cpu_to_le64(cno);
535 
536 	segbuf = sci->sc_curseg;
537 	segbuf->sb_sum.sumbytes = sci->sc_binfo_ptr.offset +
538 		sci->sc_super->s_blocksize * (segbuf->sb_sum.nsumblk - 1);
539 	sci->sc_finfo_ptr = sci->sc_binfo_ptr;
540 	sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
541 }
542 
543 static int nilfs_segctor_add_file_block(struct nilfs_sc_info *sci,
544 					struct buffer_head *bh,
545 					struct inode *inode,
546 					unsigned int binfo_size)
547 {
548 	struct nilfs_segment_buffer *segbuf;
549 	int required, err = 0;
550 
551  retry:
552 	segbuf = sci->sc_curseg;
553 	required = nilfs_segctor_segsum_block_required(
554 		sci, &sci->sc_binfo_ptr, binfo_size);
555 	if (segbuf->sb_sum.nblocks + required + 1 > segbuf->sb_rest_blocks) {
556 		nilfs_segctor_end_finfo(sci, inode);
557 		err = nilfs_segctor_feed_segment(sci);
558 		if (err)
559 			return err;
560 		goto retry;
561 	}
562 	if (unlikely(required)) {
563 		nilfs_segctor_zeropad_segsum(sci);
564 		err = nilfs_segbuf_extend_segsum(segbuf);
565 		if (unlikely(err))
566 			goto failed;
567 	}
568 	if (sci->sc_blk_cnt == 0)
569 		nilfs_segctor_begin_finfo(sci, inode);
570 
571 	nilfs_segctor_map_segsum_entry(sci, &sci->sc_binfo_ptr, binfo_size);
572 	/* Substitution to vblocknr is delayed until update_blocknr() */
573 	nilfs_segbuf_add_file_buffer(segbuf, bh);
574 	sci->sc_blk_cnt++;
575  failed:
576 	return err;
577 }
578 
579 /*
580  * Callback functions that enumerate, mark, and collect dirty blocks
581  */
582 static int nilfs_collect_file_data(struct nilfs_sc_info *sci,
583 				   struct buffer_head *bh, struct inode *inode)
584 {
585 	int err;
586 
587 	err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
588 	if (err < 0)
589 		return err;
590 
591 	err = nilfs_segctor_add_file_block(sci, bh, inode,
592 					   sizeof(struct nilfs_binfo_v));
593 	if (!err)
594 		sci->sc_datablk_cnt++;
595 	return err;
596 }
597 
598 static int nilfs_collect_file_node(struct nilfs_sc_info *sci,
599 				   struct buffer_head *bh,
600 				   struct inode *inode)
601 {
602 	return nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
603 }
604 
605 static int nilfs_collect_file_bmap(struct nilfs_sc_info *sci,
606 				   struct buffer_head *bh,
607 				   struct inode *inode)
608 {
609 	WARN_ON(!buffer_dirty(bh));
610 	return nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
611 }
612 
613 static void nilfs_write_file_data_binfo(struct nilfs_sc_info *sci,
614 					struct nilfs_segsum_pointer *ssp,
615 					union nilfs_binfo *binfo)
616 {
617 	struct nilfs_binfo_v *binfo_v = nilfs_segctor_map_segsum_entry(
618 		sci, ssp, sizeof(*binfo_v));
619 	*binfo_v = binfo->bi_v;
620 }
621 
622 static void nilfs_write_file_node_binfo(struct nilfs_sc_info *sci,
623 					struct nilfs_segsum_pointer *ssp,
624 					union nilfs_binfo *binfo)
625 {
626 	__le64 *vblocknr = nilfs_segctor_map_segsum_entry(
627 		sci, ssp, sizeof(*vblocknr));
628 	*vblocknr = binfo->bi_v.bi_vblocknr;
629 }
630 
631 static const struct nilfs_sc_operations nilfs_sc_file_ops = {
632 	.collect_data = nilfs_collect_file_data,
633 	.collect_node = nilfs_collect_file_node,
634 	.collect_bmap = nilfs_collect_file_bmap,
635 	.write_data_binfo = nilfs_write_file_data_binfo,
636 	.write_node_binfo = nilfs_write_file_node_binfo,
637 };
638 
639 static int nilfs_collect_dat_data(struct nilfs_sc_info *sci,
640 				  struct buffer_head *bh, struct inode *inode)
641 {
642 	int err;
643 
644 	err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
645 	if (err < 0)
646 		return err;
647 
648 	err = nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
649 	if (!err)
650 		sci->sc_datablk_cnt++;
651 	return err;
652 }
653 
654 static int nilfs_collect_dat_bmap(struct nilfs_sc_info *sci,
655 				  struct buffer_head *bh, struct inode *inode)
656 {
657 	WARN_ON(!buffer_dirty(bh));
658 	return nilfs_segctor_add_file_block(sci, bh, inode,
659 					    sizeof(struct nilfs_binfo_dat));
660 }
661 
662 static void nilfs_write_dat_data_binfo(struct nilfs_sc_info *sci,
663 				       struct nilfs_segsum_pointer *ssp,
664 				       union nilfs_binfo *binfo)
665 {
666 	__le64 *blkoff = nilfs_segctor_map_segsum_entry(sci, ssp,
667 							  sizeof(*blkoff));
668 	*blkoff = binfo->bi_dat.bi_blkoff;
669 }
670 
671 static void nilfs_write_dat_node_binfo(struct nilfs_sc_info *sci,
672 				       struct nilfs_segsum_pointer *ssp,
673 				       union nilfs_binfo *binfo)
674 {
675 	struct nilfs_binfo_dat *binfo_dat =
676 		nilfs_segctor_map_segsum_entry(sci, ssp, sizeof(*binfo_dat));
677 	*binfo_dat = binfo->bi_dat;
678 }
679 
680 static const struct nilfs_sc_operations nilfs_sc_dat_ops = {
681 	.collect_data = nilfs_collect_dat_data,
682 	.collect_node = nilfs_collect_file_node,
683 	.collect_bmap = nilfs_collect_dat_bmap,
684 	.write_data_binfo = nilfs_write_dat_data_binfo,
685 	.write_node_binfo = nilfs_write_dat_node_binfo,
686 };
687 
688 static const struct nilfs_sc_operations nilfs_sc_dsync_ops = {
689 	.collect_data = nilfs_collect_file_data,
690 	.collect_node = NULL,
691 	.collect_bmap = NULL,
692 	.write_data_binfo = nilfs_write_file_data_binfo,
693 	.write_node_binfo = NULL,
694 };
695 
696 static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
697 					      struct list_head *listp,
698 					      size_t nlimit,
699 					      loff_t start, loff_t end)
700 {
701 	struct address_space *mapping = inode->i_mapping;
702 	struct folio_batch fbatch;
703 	pgoff_t index = 0, last = ULONG_MAX;
704 	size_t ndirties = 0;
705 	int i;
706 
707 	if (unlikely(start != 0 || end != LLONG_MAX)) {
708 		/*
709 		 * A valid range is given for sync-ing data pages. The
710 		 * range is rounded to per-page; extra dirty buffers
711 		 * may be included if blocksize < pagesize.
712 		 */
713 		index = start >> PAGE_SHIFT;
714 		last = end >> PAGE_SHIFT;
715 	}
716 	folio_batch_init(&fbatch);
717  repeat:
718 	if (unlikely(index > last) ||
719 	      !filemap_get_folios_tag(mapping, &index, last,
720 		      PAGECACHE_TAG_DIRTY, &fbatch))
721 		return ndirties;
722 
723 	for (i = 0; i < folio_batch_count(&fbatch); i++) {
724 		struct buffer_head *bh, *head;
725 		struct folio *folio = fbatch.folios[i];
726 
727 		folio_lock(folio);
728 		if (unlikely(folio->mapping != mapping)) {
729 			/* Exclude folios removed from the address space */
730 			folio_unlock(folio);
731 			continue;
732 		}
733 		head = folio_buffers(folio);
734 		if (!head) {
735 			create_empty_buffers(&folio->page, i_blocksize(inode), 0);
736 			head = folio_buffers(folio);
737 		}
738 		folio_unlock(folio);
739 
740 		bh = head;
741 		do {
742 			if (!buffer_dirty(bh) || buffer_async_write(bh))
743 				continue;
744 			get_bh(bh);
745 			list_add_tail(&bh->b_assoc_buffers, listp);
746 			ndirties++;
747 			if (unlikely(ndirties >= nlimit)) {
748 				folio_batch_release(&fbatch);
749 				cond_resched();
750 				return ndirties;
751 			}
752 		} while (bh = bh->b_this_page, bh != head);
753 	}
754 	folio_batch_release(&fbatch);
755 	cond_resched();
756 	goto repeat;
757 }
758 
759 static void nilfs_lookup_dirty_node_buffers(struct inode *inode,
760 					    struct list_head *listp)
761 {
762 	struct nilfs_inode_info *ii = NILFS_I(inode);
763 	struct inode *btnc_inode = ii->i_assoc_inode;
764 	struct folio_batch fbatch;
765 	struct buffer_head *bh, *head;
766 	unsigned int i;
767 	pgoff_t index = 0;
768 
769 	if (!btnc_inode)
770 		return;
771 	folio_batch_init(&fbatch);
772 
773 	while (filemap_get_folios_tag(btnc_inode->i_mapping, &index,
774 				(pgoff_t)-1, PAGECACHE_TAG_DIRTY, &fbatch)) {
775 		for (i = 0; i < folio_batch_count(&fbatch); i++) {
776 			bh = head = folio_buffers(fbatch.folios[i]);
777 			do {
778 				if (buffer_dirty(bh) &&
779 						!buffer_async_write(bh)) {
780 					get_bh(bh);
781 					list_add_tail(&bh->b_assoc_buffers,
782 						      listp);
783 				}
784 				bh = bh->b_this_page;
785 			} while (bh != head);
786 		}
787 		folio_batch_release(&fbatch);
788 		cond_resched();
789 	}
790 }
791 
792 static void nilfs_dispose_list(struct the_nilfs *nilfs,
793 			       struct list_head *head, int force)
794 {
795 	struct nilfs_inode_info *ii, *n;
796 	struct nilfs_inode_info *ivec[SC_N_INODEVEC], **pii;
797 	unsigned int nv = 0;
798 
799 	while (!list_empty(head)) {
800 		spin_lock(&nilfs->ns_inode_lock);
801 		list_for_each_entry_safe(ii, n, head, i_dirty) {
802 			list_del_init(&ii->i_dirty);
803 			if (force) {
804 				if (unlikely(ii->i_bh)) {
805 					brelse(ii->i_bh);
806 					ii->i_bh = NULL;
807 				}
808 			} else if (test_bit(NILFS_I_DIRTY, &ii->i_state)) {
809 				set_bit(NILFS_I_QUEUED, &ii->i_state);
810 				list_add_tail(&ii->i_dirty,
811 					      &nilfs->ns_dirty_files);
812 				continue;
813 			}
814 			ivec[nv++] = ii;
815 			if (nv == SC_N_INODEVEC)
816 				break;
817 		}
818 		spin_unlock(&nilfs->ns_inode_lock);
819 
820 		for (pii = ivec; nv > 0; pii++, nv--)
821 			iput(&(*pii)->vfs_inode);
822 	}
823 }
824 
825 static void nilfs_iput_work_func(struct work_struct *work)
826 {
827 	struct nilfs_sc_info *sci = container_of(work, struct nilfs_sc_info,
828 						 sc_iput_work);
829 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
830 
831 	nilfs_dispose_list(nilfs, &sci->sc_iput_queue, 0);
832 }
833 
834 static int nilfs_test_metadata_dirty(struct the_nilfs *nilfs,
835 				     struct nilfs_root *root)
836 {
837 	int ret = 0;
838 
839 	if (nilfs_mdt_fetch_dirty(root->ifile))
840 		ret++;
841 	if (nilfs_mdt_fetch_dirty(nilfs->ns_cpfile))
842 		ret++;
843 	if (nilfs_mdt_fetch_dirty(nilfs->ns_sufile))
844 		ret++;
845 	if ((ret || nilfs_doing_gc()) && nilfs_mdt_fetch_dirty(nilfs->ns_dat))
846 		ret++;
847 	return ret;
848 }
849 
850 static int nilfs_segctor_clean(struct nilfs_sc_info *sci)
851 {
852 	return list_empty(&sci->sc_dirty_files) &&
853 		!test_bit(NILFS_SC_DIRTY, &sci->sc_flags) &&
854 		sci->sc_nfreesegs == 0 &&
855 		(!nilfs_doing_gc() || list_empty(&sci->sc_gc_inodes));
856 }
857 
858 static int nilfs_segctor_confirm(struct nilfs_sc_info *sci)
859 {
860 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
861 	int ret = 0;
862 
863 	if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
864 		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
865 
866 	spin_lock(&nilfs->ns_inode_lock);
867 	if (list_empty(&nilfs->ns_dirty_files) && nilfs_segctor_clean(sci))
868 		ret++;
869 
870 	spin_unlock(&nilfs->ns_inode_lock);
871 	return ret;
872 }
873 
874 static void nilfs_segctor_clear_metadata_dirty(struct nilfs_sc_info *sci)
875 {
876 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
877 
878 	nilfs_mdt_clear_dirty(sci->sc_root->ifile);
879 	nilfs_mdt_clear_dirty(nilfs->ns_cpfile);
880 	nilfs_mdt_clear_dirty(nilfs->ns_sufile);
881 	nilfs_mdt_clear_dirty(nilfs->ns_dat);
882 }
883 
884 static int nilfs_segctor_create_checkpoint(struct nilfs_sc_info *sci)
885 {
886 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
887 	struct buffer_head *bh_cp;
888 	struct nilfs_checkpoint *raw_cp;
889 	int err;
890 
891 	/* XXX: this interface will be changed */
892 	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 1,
893 					  &raw_cp, &bh_cp);
894 	if (likely(!err)) {
895 		/*
896 		 * The following code is duplicated with cpfile.  But, it is
897 		 * needed to collect the checkpoint even if it was not newly
898 		 * created.
899 		 */
900 		mark_buffer_dirty(bh_cp);
901 		nilfs_mdt_mark_dirty(nilfs->ns_cpfile);
902 		nilfs_cpfile_put_checkpoint(
903 			nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
904 	} else if (err == -EINVAL || err == -ENOENT) {
905 		nilfs_error(sci->sc_super,
906 			    "checkpoint creation failed due to metadata corruption.");
907 		err = -EIO;
908 	}
909 	return err;
910 }
911 
912 static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
913 {
914 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
915 	struct buffer_head *bh_cp;
916 	struct nilfs_checkpoint *raw_cp;
917 	int err;
918 
919 	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 0,
920 					  &raw_cp, &bh_cp);
921 	if (unlikely(err)) {
922 		if (err == -EINVAL || err == -ENOENT) {
923 			nilfs_error(sci->sc_super,
924 				    "checkpoint finalization failed due to metadata corruption.");
925 			err = -EIO;
926 		}
927 		goto failed_ibh;
928 	}
929 	raw_cp->cp_snapshot_list.ssl_next = 0;
930 	raw_cp->cp_snapshot_list.ssl_prev = 0;
931 	raw_cp->cp_inodes_count =
932 		cpu_to_le64(atomic64_read(&sci->sc_root->inodes_count));
933 	raw_cp->cp_blocks_count =
934 		cpu_to_le64(atomic64_read(&sci->sc_root->blocks_count));
935 	raw_cp->cp_nblk_inc =
936 		cpu_to_le64(sci->sc_nblk_inc + sci->sc_nblk_this_inc);
937 	raw_cp->cp_create = cpu_to_le64(sci->sc_seg_ctime);
938 	raw_cp->cp_cno = cpu_to_le64(nilfs->ns_cno);
939 
940 	if (test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
941 		nilfs_checkpoint_clear_minor(raw_cp);
942 	else
943 		nilfs_checkpoint_set_minor(raw_cp);
944 
945 	nilfs_write_inode_common(sci->sc_root->ifile,
946 				 &raw_cp->cp_ifile_inode, 1);
947 	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
948 	return 0;
949 
950  failed_ibh:
951 	return err;
952 }
953 
954 static void nilfs_fill_in_file_bmap(struct inode *ifile,
955 				    struct nilfs_inode_info *ii)
956 
957 {
958 	struct buffer_head *ibh;
959 	struct nilfs_inode *raw_inode;
960 
961 	if (test_bit(NILFS_I_BMAP, &ii->i_state)) {
962 		ibh = ii->i_bh;
963 		BUG_ON(!ibh);
964 		raw_inode = nilfs_ifile_map_inode(ifile, ii->vfs_inode.i_ino,
965 						  ibh);
966 		nilfs_bmap_write(ii->i_bmap, raw_inode);
967 		nilfs_ifile_unmap_inode(ifile, ii->vfs_inode.i_ino, ibh);
968 	}
969 }
970 
971 static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci)
972 {
973 	struct nilfs_inode_info *ii;
974 
975 	list_for_each_entry(ii, &sci->sc_dirty_files, i_dirty) {
976 		nilfs_fill_in_file_bmap(sci->sc_root->ifile, ii);
977 		set_bit(NILFS_I_COLLECTED, &ii->i_state);
978 	}
979 }
980 
981 static void nilfs_segctor_fill_in_super_root(struct nilfs_sc_info *sci,
982 					     struct the_nilfs *nilfs)
983 {
984 	struct buffer_head *bh_sr;
985 	struct nilfs_super_root *raw_sr;
986 	unsigned int isz, srsz;
987 
988 	bh_sr = NILFS_LAST_SEGBUF(&sci->sc_segbufs)->sb_super_root;
989 
990 	lock_buffer(bh_sr);
991 	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
992 	isz = nilfs->ns_inode_size;
993 	srsz = NILFS_SR_BYTES(isz);
994 
995 	raw_sr->sr_sum = 0;  /* Ensure initialization within this update */
996 	raw_sr->sr_bytes = cpu_to_le16(srsz);
997 	raw_sr->sr_nongc_ctime
998 		= cpu_to_le64(nilfs_doing_gc() ?
999 			      nilfs->ns_nongc_ctime : sci->sc_seg_ctime);
1000 	raw_sr->sr_flags = 0;
1001 
1002 	nilfs_write_inode_common(nilfs->ns_dat, (void *)raw_sr +
1003 				 NILFS_SR_DAT_OFFSET(isz), 1);
1004 	nilfs_write_inode_common(nilfs->ns_cpfile, (void *)raw_sr +
1005 				 NILFS_SR_CPFILE_OFFSET(isz), 1);
1006 	nilfs_write_inode_common(nilfs->ns_sufile, (void *)raw_sr +
1007 				 NILFS_SR_SUFILE_OFFSET(isz), 1);
1008 	memset((void *)raw_sr + srsz, 0, nilfs->ns_blocksize - srsz);
1009 	set_buffer_uptodate(bh_sr);
1010 	unlock_buffer(bh_sr);
1011 }
1012 
1013 static void nilfs_redirty_inodes(struct list_head *head)
1014 {
1015 	struct nilfs_inode_info *ii;
1016 
1017 	list_for_each_entry(ii, head, i_dirty) {
1018 		if (test_bit(NILFS_I_COLLECTED, &ii->i_state))
1019 			clear_bit(NILFS_I_COLLECTED, &ii->i_state);
1020 	}
1021 }
1022 
1023 static void nilfs_drop_collected_inodes(struct list_head *head)
1024 {
1025 	struct nilfs_inode_info *ii;
1026 
1027 	list_for_each_entry(ii, head, i_dirty) {
1028 		if (!test_and_clear_bit(NILFS_I_COLLECTED, &ii->i_state))
1029 			continue;
1030 
1031 		clear_bit(NILFS_I_INODE_SYNC, &ii->i_state);
1032 		set_bit(NILFS_I_UPDATED, &ii->i_state);
1033 	}
1034 }
1035 
1036 static int nilfs_segctor_apply_buffers(struct nilfs_sc_info *sci,
1037 				       struct inode *inode,
1038 				       struct list_head *listp,
1039 				       int (*collect)(struct nilfs_sc_info *,
1040 						      struct buffer_head *,
1041 						      struct inode *))
1042 {
1043 	struct buffer_head *bh, *n;
1044 	int err = 0;
1045 
1046 	if (collect) {
1047 		list_for_each_entry_safe(bh, n, listp, b_assoc_buffers) {
1048 			list_del_init(&bh->b_assoc_buffers);
1049 			err = collect(sci, bh, inode);
1050 			brelse(bh);
1051 			if (unlikely(err))
1052 				goto dispose_buffers;
1053 		}
1054 		return 0;
1055 	}
1056 
1057  dispose_buffers:
1058 	while (!list_empty(listp)) {
1059 		bh = list_first_entry(listp, struct buffer_head,
1060 				      b_assoc_buffers);
1061 		list_del_init(&bh->b_assoc_buffers);
1062 		brelse(bh);
1063 	}
1064 	return err;
1065 }
1066 
1067 static size_t nilfs_segctor_buffer_rest(struct nilfs_sc_info *sci)
1068 {
1069 	/* Remaining number of blocks within segment buffer */
1070 	return sci->sc_segbuf_nblocks -
1071 		(sci->sc_nblk_this_inc + sci->sc_curseg->sb_sum.nblocks);
1072 }
1073 
1074 static int nilfs_segctor_scan_file(struct nilfs_sc_info *sci,
1075 				   struct inode *inode,
1076 				   const struct nilfs_sc_operations *sc_ops)
1077 {
1078 	LIST_HEAD(data_buffers);
1079 	LIST_HEAD(node_buffers);
1080 	int err;
1081 
1082 	if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {
1083 		size_t n, rest = nilfs_segctor_buffer_rest(sci);
1084 
1085 		n = nilfs_lookup_dirty_data_buffers(
1086 			inode, &data_buffers, rest + 1, 0, LLONG_MAX);
1087 		if (n > rest) {
1088 			err = nilfs_segctor_apply_buffers(
1089 				sci, inode, &data_buffers,
1090 				sc_ops->collect_data);
1091 			BUG_ON(!err); /* always receive -E2BIG or true error */
1092 			goto break_or_fail;
1093 		}
1094 	}
1095 	nilfs_lookup_dirty_node_buffers(inode, &node_buffers);
1096 
1097 	if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {
1098 		err = nilfs_segctor_apply_buffers(
1099 			sci, inode, &data_buffers, sc_ops->collect_data);
1100 		if (unlikely(err)) {
1101 			/* dispose node list */
1102 			nilfs_segctor_apply_buffers(
1103 				sci, inode, &node_buffers, NULL);
1104 			goto break_or_fail;
1105 		}
1106 		sci->sc_stage.flags |= NILFS_CF_NODE;
1107 	}
1108 	/* Collect node */
1109 	err = nilfs_segctor_apply_buffers(
1110 		sci, inode, &node_buffers, sc_ops->collect_node);
1111 	if (unlikely(err))
1112 		goto break_or_fail;
1113 
1114 	nilfs_bmap_lookup_dirty_buffers(NILFS_I(inode)->i_bmap, &node_buffers);
1115 	err = nilfs_segctor_apply_buffers(
1116 		sci, inode, &node_buffers, sc_ops->collect_bmap);
1117 	if (unlikely(err))
1118 		goto break_or_fail;
1119 
1120 	nilfs_segctor_end_finfo(sci, inode);
1121 	sci->sc_stage.flags &= ~NILFS_CF_NODE;
1122 
1123  break_or_fail:
1124 	return err;
1125 }
1126 
1127 static int nilfs_segctor_scan_file_dsync(struct nilfs_sc_info *sci,
1128 					 struct inode *inode)
1129 {
1130 	LIST_HEAD(data_buffers);
1131 	size_t n, rest = nilfs_segctor_buffer_rest(sci);
1132 	int err;
1133 
1134 	n = nilfs_lookup_dirty_data_buffers(inode, &data_buffers, rest + 1,
1135 					    sci->sc_dsync_start,
1136 					    sci->sc_dsync_end);
1137 
1138 	err = nilfs_segctor_apply_buffers(sci, inode, &data_buffers,
1139 					  nilfs_collect_file_data);
1140 	if (!err) {
1141 		nilfs_segctor_end_finfo(sci, inode);
1142 		BUG_ON(n > rest);
1143 		/* always receive -E2BIG or true error if n > rest */
1144 	}
1145 	return err;
1146 }
1147 
1148 static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
1149 {
1150 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
1151 	struct list_head *head;
1152 	struct nilfs_inode_info *ii;
1153 	size_t ndone;
1154 	int err = 0;
1155 
1156 	switch (nilfs_sc_cstage_get(sci)) {
1157 	case NILFS_ST_INIT:
1158 		/* Pre-processes */
1159 		sci->sc_stage.flags = 0;
1160 
1161 		if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags)) {
1162 			sci->sc_nblk_inc = 0;
1163 			sci->sc_curseg->sb_sum.flags = NILFS_SS_LOGBGN;
1164 			if (mode == SC_LSEG_DSYNC) {
1165 				nilfs_sc_cstage_set(sci, NILFS_ST_DSYNC);
1166 				goto dsync_mode;
1167 			}
1168 		}
1169 
1170 		sci->sc_stage.dirty_file_ptr = NULL;
1171 		sci->sc_stage.gc_inode_ptr = NULL;
1172 		if (mode == SC_FLUSH_DAT) {
1173 			nilfs_sc_cstage_set(sci, NILFS_ST_DAT);
1174 			goto dat_stage;
1175 		}
1176 		nilfs_sc_cstage_inc(sci);
1177 		fallthrough;
1178 	case NILFS_ST_GC:
1179 		if (nilfs_doing_gc()) {
1180 			head = &sci->sc_gc_inodes;
1181 			ii = list_prepare_entry(sci->sc_stage.gc_inode_ptr,
1182 						head, i_dirty);
1183 			list_for_each_entry_continue(ii, head, i_dirty) {
1184 				err = nilfs_segctor_scan_file(
1185 					sci, &ii->vfs_inode,
1186 					&nilfs_sc_file_ops);
1187 				if (unlikely(err)) {
1188 					sci->sc_stage.gc_inode_ptr = list_entry(
1189 						ii->i_dirty.prev,
1190 						struct nilfs_inode_info,
1191 						i_dirty);
1192 					goto break_or_fail;
1193 				}
1194 				set_bit(NILFS_I_COLLECTED, &ii->i_state);
1195 			}
1196 			sci->sc_stage.gc_inode_ptr = NULL;
1197 		}
1198 		nilfs_sc_cstage_inc(sci);
1199 		fallthrough;
1200 	case NILFS_ST_FILE:
1201 		head = &sci->sc_dirty_files;
1202 		ii = list_prepare_entry(sci->sc_stage.dirty_file_ptr, head,
1203 					i_dirty);
1204 		list_for_each_entry_continue(ii, head, i_dirty) {
1205 			clear_bit(NILFS_I_DIRTY, &ii->i_state);
1206 
1207 			err = nilfs_segctor_scan_file(sci, &ii->vfs_inode,
1208 						      &nilfs_sc_file_ops);
1209 			if (unlikely(err)) {
1210 				sci->sc_stage.dirty_file_ptr =
1211 					list_entry(ii->i_dirty.prev,
1212 						   struct nilfs_inode_info,
1213 						   i_dirty);
1214 				goto break_or_fail;
1215 			}
1216 			/* sci->sc_stage.dirty_file_ptr = NILFS_I(inode); */
1217 			/* XXX: required ? */
1218 		}
1219 		sci->sc_stage.dirty_file_ptr = NULL;
1220 		if (mode == SC_FLUSH_FILE) {
1221 			nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
1222 			return 0;
1223 		}
1224 		nilfs_sc_cstage_inc(sci);
1225 		sci->sc_stage.flags |= NILFS_CF_IFILE_STARTED;
1226 		fallthrough;
1227 	case NILFS_ST_IFILE:
1228 		err = nilfs_segctor_scan_file(sci, sci->sc_root->ifile,
1229 					      &nilfs_sc_file_ops);
1230 		if (unlikely(err))
1231 			break;
1232 		nilfs_sc_cstage_inc(sci);
1233 		/* Creating a checkpoint */
1234 		err = nilfs_segctor_create_checkpoint(sci);
1235 		if (unlikely(err))
1236 			break;
1237 		fallthrough;
1238 	case NILFS_ST_CPFILE:
1239 		err = nilfs_segctor_scan_file(sci, nilfs->ns_cpfile,
1240 					      &nilfs_sc_file_ops);
1241 		if (unlikely(err))
1242 			break;
1243 		nilfs_sc_cstage_inc(sci);
1244 		fallthrough;
1245 	case NILFS_ST_SUFILE:
1246 		err = nilfs_sufile_freev(nilfs->ns_sufile, sci->sc_freesegs,
1247 					 sci->sc_nfreesegs, &ndone);
1248 		if (unlikely(err)) {
1249 			nilfs_sufile_cancel_freev(nilfs->ns_sufile,
1250 						  sci->sc_freesegs, ndone,
1251 						  NULL);
1252 			break;
1253 		}
1254 		sci->sc_stage.flags |= NILFS_CF_SUFREED;
1255 
1256 		err = nilfs_segctor_scan_file(sci, nilfs->ns_sufile,
1257 					      &nilfs_sc_file_ops);
1258 		if (unlikely(err))
1259 			break;
1260 		nilfs_sc_cstage_inc(sci);
1261 		fallthrough;
1262 	case NILFS_ST_DAT:
1263  dat_stage:
1264 		err = nilfs_segctor_scan_file(sci, nilfs->ns_dat,
1265 					      &nilfs_sc_dat_ops);
1266 		if (unlikely(err))
1267 			break;
1268 		if (mode == SC_FLUSH_DAT) {
1269 			nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
1270 			return 0;
1271 		}
1272 		nilfs_sc_cstage_inc(sci);
1273 		fallthrough;
1274 	case NILFS_ST_SR:
1275 		if (mode == SC_LSEG_SR) {
1276 			/* Appending a super root */
1277 			err = nilfs_segctor_add_super_root(sci);
1278 			if (unlikely(err))
1279 				break;
1280 		}
1281 		/* End of a logical segment */
1282 		sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
1283 		nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
1284 		return 0;
1285 	case NILFS_ST_DSYNC:
1286  dsync_mode:
1287 		sci->sc_curseg->sb_sum.flags |= NILFS_SS_SYNDT;
1288 		ii = sci->sc_dsync_inode;
1289 		if (!test_bit(NILFS_I_BUSY, &ii->i_state))
1290 			break;
1291 
1292 		err = nilfs_segctor_scan_file_dsync(sci, &ii->vfs_inode);
1293 		if (unlikely(err))
1294 			break;
1295 		sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
1296 		nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
1297 		return 0;
1298 	case NILFS_ST_DONE:
1299 		return 0;
1300 	default:
1301 		BUG();
1302 	}
1303 
1304  break_or_fail:
1305 	return err;
1306 }
1307 
1308 /**
1309  * nilfs_segctor_begin_construction - setup segment buffer to make a new log
1310  * @sci: nilfs_sc_info
1311  * @nilfs: nilfs object
1312  */
1313 static int nilfs_segctor_begin_construction(struct nilfs_sc_info *sci,
1314 					    struct the_nilfs *nilfs)
1315 {
1316 	struct nilfs_segment_buffer *segbuf, *prev;
1317 	__u64 nextnum;
1318 	int err, alloc = 0;
1319 
1320 	segbuf = nilfs_segbuf_new(sci->sc_super);
1321 	if (unlikely(!segbuf))
1322 		return -ENOMEM;
1323 
1324 	if (list_empty(&sci->sc_write_logs)) {
1325 		nilfs_segbuf_map(segbuf, nilfs->ns_segnum,
1326 				 nilfs->ns_pseg_offset, nilfs);
1327 		if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
1328 			nilfs_shift_to_next_segment(nilfs);
1329 			nilfs_segbuf_map(segbuf, nilfs->ns_segnum, 0, nilfs);
1330 		}
1331 
1332 		segbuf->sb_sum.seg_seq = nilfs->ns_seg_seq;
1333 		nextnum = nilfs->ns_nextnum;
1334 
1335 		if (nilfs->ns_segnum == nilfs->ns_nextnum)
1336 			/* Start from the head of a new full segment */
1337 			alloc++;
1338 	} else {
1339 		/* Continue logs */
1340 		prev = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
1341 		nilfs_segbuf_map_cont(segbuf, prev);
1342 		segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq;
1343 		nextnum = prev->sb_nextnum;
1344 
1345 		if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
1346 			nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
1347 			segbuf->sb_sum.seg_seq++;
1348 			alloc++;
1349 		}
1350 	}
1351 
1352 	err = nilfs_sufile_mark_dirty(nilfs->ns_sufile, segbuf->sb_segnum);
1353 	if (err)
1354 		goto failed;
1355 
1356 	if (alloc) {
1357 		err = nilfs_sufile_alloc(nilfs->ns_sufile, &nextnum);
1358 		if (err)
1359 			goto failed;
1360 	}
1361 	nilfs_segbuf_set_next_segnum(segbuf, nextnum, nilfs);
1362 
1363 	BUG_ON(!list_empty(&sci->sc_segbufs));
1364 	list_add_tail(&segbuf->sb_list, &sci->sc_segbufs);
1365 	sci->sc_segbuf_nblocks = segbuf->sb_rest_blocks;
1366 	return 0;
1367 
1368  failed:
1369 	nilfs_segbuf_free(segbuf);
1370 	return err;
1371 }
1372 
1373 static int nilfs_segctor_extend_segments(struct nilfs_sc_info *sci,
1374 					 struct the_nilfs *nilfs, int nadd)
1375 {
1376 	struct nilfs_segment_buffer *segbuf, *prev;
1377 	struct inode *sufile = nilfs->ns_sufile;
1378 	__u64 nextnextnum;
1379 	LIST_HEAD(list);
1380 	int err, ret, i;
1381 
1382 	prev = NILFS_LAST_SEGBUF(&sci->sc_segbufs);
1383 	/*
1384 	 * Since the segment specified with nextnum might be allocated during
1385 	 * the previous construction, the buffer including its segusage may
1386 	 * not be dirty.  The following call ensures that the buffer is dirty
1387 	 * and will pin the buffer on memory until the sufile is written.
1388 	 */
1389 	err = nilfs_sufile_mark_dirty(sufile, prev->sb_nextnum);
1390 	if (unlikely(err))
1391 		return err;
1392 
1393 	for (i = 0; i < nadd; i++) {
1394 		/* extend segment info */
1395 		err = -ENOMEM;
1396 		segbuf = nilfs_segbuf_new(sci->sc_super);
1397 		if (unlikely(!segbuf))
1398 			goto failed;
1399 
1400 		/* map this buffer to region of segment on-disk */
1401 		nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
1402 		sci->sc_segbuf_nblocks += segbuf->sb_rest_blocks;
1403 
1404 		/* allocate the next next full segment */
1405 		err = nilfs_sufile_alloc(sufile, &nextnextnum);
1406 		if (unlikely(err))
1407 			goto failed_segbuf;
1408 
1409 		segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq + 1;
1410 		nilfs_segbuf_set_next_segnum(segbuf, nextnextnum, nilfs);
1411 
1412 		list_add_tail(&segbuf->sb_list, &list);
1413 		prev = segbuf;
1414 	}
1415 	list_splice_tail(&list, &sci->sc_segbufs);
1416 	return 0;
1417 
1418  failed_segbuf:
1419 	nilfs_segbuf_free(segbuf);
1420  failed:
1421 	list_for_each_entry(segbuf, &list, sb_list) {
1422 		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
1423 		WARN_ON(ret); /* never fails */
1424 	}
1425 	nilfs_destroy_logs(&list);
1426 	return err;
1427 }
1428 
1429 static void nilfs_free_incomplete_logs(struct list_head *logs,
1430 				       struct the_nilfs *nilfs)
1431 {
1432 	struct nilfs_segment_buffer *segbuf, *prev;
1433 	struct inode *sufile = nilfs->ns_sufile;
1434 	int ret;
1435 
1436 	segbuf = NILFS_FIRST_SEGBUF(logs);
1437 	if (nilfs->ns_nextnum != segbuf->sb_nextnum) {
1438 		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
1439 		WARN_ON(ret); /* never fails */
1440 	}
1441 	if (atomic_read(&segbuf->sb_err)) {
1442 		/* Case 1: The first segment failed */
1443 		if (segbuf->sb_pseg_start != segbuf->sb_fseg_start)
1444 			/*
1445 			 * Case 1a:  Partial segment appended into an existing
1446 			 * segment
1447 			 */
1448 			nilfs_terminate_segment(nilfs, segbuf->sb_fseg_start,
1449 						segbuf->sb_fseg_end);
1450 		else /* Case 1b:  New full segment */
1451 			set_nilfs_discontinued(nilfs);
1452 	}
1453 
1454 	prev = segbuf;
1455 	list_for_each_entry_continue(segbuf, logs, sb_list) {
1456 		if (prev->sb_nextnum != segbuf->sb_nextnum) {
1457 			ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
1458 			WARN_ON(ret); /* never fails */
1459 		}
1460 		if (atomic_read(&segbuf->sb_err) &&
1461 		    segbuf->sb_segnum != nilfs->ns_nextnum)
1462 			/* Case 2: extended segment (!= next) failed */
1463 			nilfs_sufile_set_error(sufile, segbuf->sb_segnum);
1464 		prev = segbuf;
1465 	}
1466 }
1467 
1468 static void nilfs_segctor_update_segusage(struct nilfs_sc_info *sci,
1469 					  struct inode *sufile)
1470 {
1471 	struct nilfs_segment_buffer *segbuf;
1472 	unsigned long live_blocks;
1473 	int ret;
1474 
1475 	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
1476 		live_blocks = segbuf->sb_sum.nblocks +
1477 			(segbuf->sb_pseg_start - segbuf->sb_fseg_start);
1478 		ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
1479 						     live_blocks,
1480 						     sci->sc_seg_ctime);
1481 		WARN_ON(ret); /* always succeed because the segusage is dirty */
1482 	}
1483 }
1484 
1485 static void nilfs_cancel_segusage(struct list_head *logs, struct inode *sufile)
1486 {
1487 	struct nilfs_segment_buffer *segbuf;
1488 	int ret;
1489 
1490 	segbuf = NILFS_FIRST_SEGBUF(logs);
1491 	ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
1492 					     segbuf->sb_pseg_start -
1493 					     segbuf->sb_fseg_start, 0);
1494 	WARN_ON(ret); /* always succeed because the segusage is dirty */
1495 
1496 	list_for_each_entry_continue(segbuf, logs, sb_list) {
1497 		ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
1498 						     0, 0);
1499 		WARN_ON(ret); /* always succeed */
1500 	}
1501 }
1502 
1503 static void nilfs_segctor_truncate_segments(struct nilfs_sc_info *sci,
1504 					    struct nilfs_segment_buffer *last,
1505 					    struct inode *sufile)
1506 {
1507 	struct nilfs_segment_buffer *segbuf = last;
1508 	int ret;
1509 
1510 	list_for_each_entry_continue(segbuf, &sci->sc_segbufs, sb_list) {
1511 		sci->sc_segbuf_nblocks -= segbuf->sb_rest_blocks;
1512 		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
1513 		WARN_ON(ret);
1514 	}
1515 	nilfs_truncate_logs(&sci->sc_segbufs, last);
1516 }
1517 
1518 
1519 static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
1520 				 struct the_nilfs *nilfs, int mode)
1521 {
1522 	struct nilfs_cstage prev_stage = sci->sc_stage;
1523 	int err, nadd = 1;
1524 
1525 	/* Collection retry loop */
1526 	for (;;) {
1527 		sci->sc_nblk_this_inc = 0;
1528 		sci->sc_curseg = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
1529 
1530 		err = nilfs_segctor_reset_segment_buffer(sci);
1531 		if (unlikely(err))
1532 			goto failed;
1533 
1534 		err = nilfs_segctor_collect_blocks(sci, mode);
1535 		sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
1536 		if (!err)
1537 			break;
1538 
1539 		if (unlikely(err != -E2BIG))
1540 			goto failed;
1541 
1542 		/* The current segment is filled up */
1543 		if (mode != SC_LSEG_SR ||
1544 		    nilfs_sc_cstage_get(sci) < NILFS_ST_CPFILE)
1545 			break;
1546 
1547 		nilfs_clear_logs(&sci->sc_segbufs);
1548 
1549 		if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
1550 			err = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
1551 							sci->sc_freesegs,
1552 							sci->sc_nfreesegs,
1553 							NULL);
1554 			WARN_ON(err); /* do not happen */
1555 			sci->sc_stage.flags &= ~NILFS_CF_SUFREED;
1556 		}
1557 
1558 		err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
1559 		if (unlikely(err))
1560 			return err;
1561 
1562 		nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
1563 		sci->sc_stage = prev_stage;
1564 	}
1565 	nilfs_segctor_zeropad_segsum(sci);
1566 	nilfs_segctor_truncate_segments(sci, sci->sc_curseg, nilfs->ns_sufile);
1567 	return 0;
1568 
1569  failed:
1570 	return err;
1571 }
1572 
1573 static void nilfs_list_replace_buffer(struct buffer_head *old_bh,
1574 				      struct buffer_head *new_bh)
1575 {
1576 	BUG_ON(!list_empty(&new_bh->b_assoc_buffers));
1577 
1578 	list_replace_init(&old_bh->b_assoc_buffers, &new_bh->b_assoc_buffers);
1579 	/* The caller must release old_bh */
1580 }
1581 
1582 static int
1583 nilfs_segctor_update_payload_blocknr(struct nilfs_sc_info *sci,
1584 				     struct nilfs_segment_buffer *segbuf,
1585 				     int mode)
1586 {
1587 	struct inode *inode = NULL;
1588 	sector_t blocknr;
1589 	unsigned long nfinfo = segbuf->sb_sum.nfinfo;
1590 	unsigned long nblocks = 0, ndatablk = 0;
1591 	const struct nilfs_sc_operations *sc_op = NULL;
1592 	struct nilfs_segsum_pointer ssp;
1593 	struct nilfs_finfo *finfo = NULL;
1594 	union nilfs_binfo binfo;
1595 	struct buffer_head *bh, *bh_org;
1596 	ino_t ino = 0;
1597 	int err = 0;
1598 
1599 	if (!nfinfo)
1600 		goto out;
1601 
1602 	blocknr = segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk;
1603 	ssp.bh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
1604 	ssp.offset = sizeof(struct nilfs_segment_summary);
1605 
1606 	list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
1607 		if (bh == segbuf->sb_super_root)
1608 			break;
1609 		if (!finfo) {
1610 			finfo =	nilfs_segctor_map_segsum_entry(
1611 				sci, &ssp, sizeof(*finfo));
1612 			ino = le64_to_cpu(finfo->fi_ino);
1613 			nblocks = le32_to_cpu(finfo->fi_nblocks);
1614 			ndatablk = le32_to_cpu(finfo->fi_ndatablk);
1615 
1616 			inode = bh->b_folio->mapping->host;
1617 
1618 			if (mode == SC_LSEG_DSYNC)
1619 				sc_op = &nilfs_sc_dsync_ops;
1620 			else if (ino == NILFS_DAT_INO)
1621 				sc_op = &nilfs_sc_dat_ops;
1622 			else /* file blocks */
1623 				sc_op = &nilfs_sc_file_ops;
1624 		}
1625 		bh_org = bh;
1626 		get_bh(bh_org);
1627 		err = nilfs_bmap_assign(NILFS_I(inode)->i_bmap, &bh, blocknr,
1628 					&binfo);
1629 		if (bh != bh_org)
1630 			nilfs_list_replace_buffer(bh_org, bh);
1631 		brelse(bh_org);
1632 		if (unlikely(err))
1633 			goto failed_bmap;
1634 
1635 		if (ndatablk > 0)
1636 			sc_op->write_data_binfo(sci, &ssp, &binfo);
1637 		else
1638 			sc_op->write_node_binfo(sci, &ssp, &binfo);
1639 
1640 		blocknr++;
1641 		if (--nblocks == 0) {
1642 			finfo = NULL;
1643 			if (--nfinfo == 0)
1644 				break;
1645 		} else if (ndatablk > 0)
1646 			ndatablk--;
1647 	}
1648  out:
1649 	return 0;
1650 
1651  failed_bmap:
1652 	return err;
1653 }
1654 
1655 static int nilfs_segctor_assign(struct nilfs_sc_info *sci, int mode)
1656 {
1657 	struct nilfs_segment_buffer *segbuf;
1658 	int err;
1659 
1660 	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
1661 		err = nilfs_segctor_update_payload_blocknr(sci, segbuf, mode);
1662 		if (unlikely(err))
1663 			return err;
1664 		nilfs_segbuf_fill_in_segsum(segbuf);
1665 	}
1666 	return 0;
1667 }
1668 
1669 static void nilfs_begin_page_io(struct page *page)
1670 {
1671 	if (!page || PageWriteback(page))
1672 		/*
1673 		 * For split b-tree node pages, this function may be called
1674 		 * twice.  We ignore the 2nd or later calls by this check.
1675 		 */
1676 		return;
1677 
1678 	lock_page(page);
1679 	clear_page_dirty_for_io(page);
1680 	set_page_writeback(page);
1681 	unlock_page(page);
1682 }
1683 
1684 static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)
1685 {
1686 	struct nilfs_segment_buffer *segbuf;
1687 	struct page *bd_page = NULL, *fs_page = NULL;
1688 
1689 	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
1690 		struct buffer_head *bh;
1691 
1692 		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
1693 				    b_assoc_buffers) {
1694 			if (bh->b_page != bd_page) {
1695 				if (bd_page) {
1696 					lock_page(bd_page);
1697 					wait_on_page_writeback(bd_page);
1698 					clear_page_dirty_for_io(bd_page);
1699 					set_page_writeback(bd_page);
1700 					unlock_page(bd_page);
1701 				}
1702 				bd_page = bh->b_page;
1703 			}
1704 		}
1705 
1706 		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
1707 				    b_assoc_buffers) {
1708 			if (bh == segbuf->sb_super_root) {
1709 				if (bh->b_page != bd_page) {
1710 					lock_page(bd_page);
1711 					wait_on_page_writeback(bd_page);
1712 					clear_page_dirty_for_io(bd_page);
1713 					set_page_writeback(bd_page);
1714 					unlock_page(bd_page);
1715 					bd_page = bh->b_page;
1716 				}
1717 				break;
1718 			}
1719 			set_buffer_async_write(bh);
1720 			if (bh->b_page != fs_page) {
1721 				nilfs_begin_page_io(fs_page);
1722 				fs_page = bh->b_page;
1723 			}
1724 		}
1725 	}
1726 	if (bd_page) {
1727 		lock_page(bd_page);
1728 		wait_on_page_writeback(bd_page);
1729 		clear_page_dirty_for_io(bd_page);
1730 		set_page_writeback(bd_page);
1731 		unlock_page(bd_page);
1732 	}
1733 	nilfs_begin_page_io(fs_page);
1734 }
1735 
1736 static int nilfs_segctor_write(struct nilfs_sc_info *sci,
1737 			       struct the_nilfs *nilfs)
1738 {
1739 	int ret;
1740 
1741 	ret = nilfs_write_logs(&sci->sc_segbufs, nilfs);
1742 	list_splice_tail_init(&sci->sc_segbufs, &sci->sc_write_logs);
1743 	return ret;
1744 }
1745 
1746 static void nilfs_end_page_io(struct page *page, int err)
1747 {
1748 	if (!page)
1749 		return;
1750 
1751 	if (buffer_nilfs_node(page_buffers(page)) && !PageWriteback(page)) {
1752 		/*
1753 		 * For b-tree node pages, this function may be called twice
1754 		 * or more because they might be split in a segment.
1755 		 */
1756 		if (PageDirty(page)) {
1757 			/*
1758 			 * For pages holding split b-tree node buffers, dirty
1759 			 * flag on the buffers may be cleared discretely.
1760 			 * In that case, the page is once redirtied for
1761 			 * remaining buffers, and it must be cancelled if
1762 			 * all the buffers get cleaned later.
1763 			 */
1764 			lock_page(page);
1765 			if (nilfs_page_buffers_clean(page))
1766 				__nilfs_clear_page_dirty(page);
1767 			unlock_page(page);
1768 		}
1769 		return;
1770 	}
1771 
1772 	if (!err) {
1773 		if (!nilfs_page_buffers_clean(page))
1774 			__set_page_dirty_nobuffers(page);
1775 		ClearPageError(page);
1776 	} else {
1777 		__set_page_dirty_nobuffers(page);
1778 		SetPageError(page);
1779 	}
1780 
1781 	end_page_writeback(page);
1782 }
1783 
1784 static void nilfs_abort_logs(struct list_head *logs, int err)
1785 {
1786 	struct nilfs_segment_buffer *segbuf;
1787 	struct page *bd_page = NULL, *fs_page = NULL;
1788 	struct buffer_head *bh;
1789 
1790 	if (list_empty(logs))
1791 		return;
1792 
1793 	list_for_each_entry(segbuf, logs, sb_list) {
1794 		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
1795 				    b_assoc_buffers) {
1796 			clear_buffer_uptodate(bh);
1797 			if (bh->b_page != bd_page) {
1798 				if (bd_page)
1799 					end_page_writeback(bd_page);
1800 				bd_page = bh->b_page;
1801 			}
1802 		}
1803 
1804 		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
1805 				    b_assoc_buffers) {
1806 			if (bh == segbuf->sb_super_root) {
1807 				clear_buffer_uptodate(bh);
1808 				if (bh->b_page != bd_page) {
1809 					end_page_writeback(bd_page);
1810 					bd_page = bh->b_page;
1811 				}
1812 				break;
1813 			}
1814 			clear_buffer_async_write(bh);
1815 			if (bh->b_page != fs_page) {
1816 				nilfs_end_page_io(fs_page, err);
1817 				fs_page = bh->b_page;
1818 			}
1819 		}
1820 	}
1821 	if (bd_page)
1822 		end_page_writeback(bd_page);
1823 
1824 	nilfs_end_page_io(fs_page, err);
1825 }
1826 
1827 static void nilfs_segctor_abort_construction(struct nilfs_sc_info *sci,
1828 					     struct the_nilfs *nilfs, int err)
1829 {
1830 	LIST_HEAD(logs);
1831 	int ret;
1832 
1833 	list_splice_tail_init(&sci->sc_write_logs, &logs);
1834 	ret = nilfs_wait_on_logs(&logs);
1835 	nilfs_abort_logs(&logs, ret ? : err);
1836 
1837 	list_splice_tail_init(&sci->sc_segbufs, &logs);
1838 	nilfs_cancel_segusage(&logs, nilfs->ns_sufile);
1839 	nilfs_free_incomplete_logs(&logs, nilfs);
1840 
1841 	if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
1842 		ret = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
1843 						sci->sc_freesegs,
1844 						sci->sc_nfreesegs,
1845 						NULL);
1846 		WARN_ON(ret); /* do not happen */
1847 	}
1848 
1849 	nilfs_destroy_logs(&logs);
1850 }
1851 
1852 static void nilfs_set_next_segment(struct the_nilfs *nilfs,
1853 				   struct nilfs_segment_buffer *segbuf)
1854 {
1855 	nilfs->ns_segnum = segbuf->sb_segnum;
1856 	nilfs->ns_nextnum = segbuf->sb_nextnum;
1857 	nilfs->ns_pseg_offset = segbuf->sb_pseg_start - segbuf->sb_fseg_start
1858 		+ segbuf->sb_sum.nblocks;
1859 	nilfs->ns_seg_seq = segbuf->sb_sum.seg_seq;
1860 	nilfs->ns_ctime = segbuf->sb_sum.ctime;
1861 }
1862 
1863 static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
1864 {
1865 	struct nilfs_segment_buffer *segbuf;
1866 	struct page *bd_page = NULL, *fs_page = NULL;
1867 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
1868 	int update_sr = false;
1869 
1870 	list_for_each_entry(segbuf, &sci->sc_write_logs, sb_list) {
1871 		struct buffer_head *bh;
1872 
1873 		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
1874 				    b_assoc_buffers) {
1875 			set_buffer_uptodate(bh);
1876 			clear_buffer_dirty(bh);
1877 			if (bh->b_page != bd_page) {
1878 				if (bd_page)
1879 					end_page_writeback(bd_page);
1880 				bd_page = bh->b_page;
1881 			}
1882 		}
1883 		/*
1884 		 * We assume that the buffers which belong to the same page
1885 		 * continue over the buffer list.
1886 		 * Under this assumption, the last BHs of pages is
1887 		 * identifiable by the discontinuity of bh->b_page
1888 		 * (page != fs_page).
1889 		 *
1890 		 * For B-tree node blocks, however, this assumption is not
1891 		 * guaranteed.  The cleanup code of B-tree node pages needs
1892 		 * special care.
1893 		 */
1894 		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
1895 				    b_assoc_buffers) {
1896 			const unsigned long set_bits = BIT(BH_Uptodate);
1897 			const unsigned long clear_bits =
1898 				(BIT(BH_Dirty) | BIT(BH_Async_Write) |
1899 				 BIT(BH_Delay) | BIT(BH_NILFS_Volatile) |
1900 				 BIT(BH_NILFS_Redirected));
1901 
1902 			if (bh == segbuf->sb_super_root) {
1903 				set_buffer_uptodate(bh);
1904 				clear_buffer_dirty(bh);
1905 				if (bh->b_page != bd_page) {
1906 					end_page_writeback(bd_page);
1907 					bd_page = bh->b_page;
1908 				}
1909 				update_sr = true;
1910 				break;
1911 			}
1912 			set_mask_bits(&bh->b_state, clear_bits, set_bits);
1913 			if (bh->b_page != fs_page) {
1914 				nilfs_end_page_io(fs_page, 0);
1915 				fs_page = bh->b_page;
1916 			}
1917 		}
1918 
1919 		if (!nilfs_segbuf_simplex(segbuf)) {
1920 			if (segbuf->sb_sum.flags & NILFS_SS_LOGBGN) {
1921 				set_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
1922 				sci->sc_lseg_stime = jiffies;
1923 			}
1924 			if (segbuf->sb_sum.flags & NILFS_SS_LOGEND)
1925 				clear_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
1926 		}
1927 	}
1928 	/*
1929 	 * Since pages may continue over multiple segment buffers,
1930 	 * end of the last page must be checked outside of the loop.
1931 	 */
1932 	if (bd_page)
1933 		end_page_writeback(bd_page);
1934 
1935 	nilfs_end_page_io(fs_page, 0);
1936 
1937 	nilfs_drop_collected_inodes(&sci->sc_dirty_files);
1938 
1939 	if (nilfs_doing_gc())
1940 		nilfs_drop_collected_inodes(&sci->sc_gc_inodes);
1941 	else
1942 		nilfs->ns_nongc_ctime = sci->sc_seg_ctime;
1943 
1944 	sci->sc_nblk_inc += sci->sc_nblk_this_inc;
1945 
1946 	segbuf = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
1947 	nilfs_set_next_segment(nilfs, segbuf);
1948 
1949 	if (update_sr) {
1950 		nilfs->ns_flushed_device = 0;
1951 		nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
1952 				       segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
1953 
1954 		clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
1955 		clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
1956 		set_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
1957 		nilfs_segctor_clear_metadata_dirty(sci);
1958 	} else
1959 		clear_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
1960 }
1961 
1962 static int nilfs_segctor_wait(struct nilfs_sc_info *sci)
1963 {
1964 	int ret;
1965 
1966 	ret = nilfs_wait_on_logs(&sci->sc_write_logs);
1967 	if (!ret) {
1968 		nilfs_segctor_complete_write(sci);
1969 		nilfs_destroy_logs(&sci->sc_write_logs);
1970 	}
1971 	return ret;
1972 }
1973 
1974 static int nilfs_segctor_collect_dirty_files(struct nilfs_sc_info *sci,
1975 					     struct the_nilfs *nilfs)
1976 {
1977 	struct nilfs_inode_info *ii, *n;
1978 	struct inode *ifile = sci->sc_root->ifile;
1979 
1980 	spin_lock(&nilfs->ns_inode_lock);
1981  retry:
1982 	list_for_each_entry_safe(ii, n, &nilfs->ns_dirty_files, i_dirty) {
1983 		if (!ii->i_bh) {
1984 			struct buffer_head *ibh;
1985 			int err;
1986 
1987 			spin_unlock(&nilfs->ns_inode_lock);
1988 			err = nilfs_ifile_get_inode_block(
1989 				ifile, ii->vfs_inode.i_ino, &ibh);
1990 			if (unlikely(err)) {
1991 				nilfs_warn(sci->sc_super,
1992 					   "log writer: error %d getting inode block (ino=%lu)",
1993 					   err, ii->vfs_inode.i_ino);
1994 				return err;
1995 			}
1996 			spin_lock(&nilfs->ns_inode_lock);
1997 			if (likely(!ii->i_bh))
1998 				ii->i_bh = ibh;
1999 			else
2000 				brelse(ibh);
2001 			goto retry;
2002 		}
2003 
2004 		// Always redirty the buffer to avoid race condition
2005 		mark_buffer_dirty(ii->i_bh);
2006 		nilfs_mdt_mark_dirty(ifile);
2007 
2008 		clear_bit(NILFS_I_QUEUED, &ii->i_state);
2009 		set_bit(NILFS_I_BUSY, &ii->i_state);
2010 		list_move_tail(&ii->i_dirty, &sci->sc_dirty_files);
2011 	}
2012 	spin_unlock(&nilfs->ns_inode_lock);
2013 
2014 	return 0;
2015 }
2016 
2017 static void nilfs_segctor_drop_written_files(struct nilfs_sc_info *sci,
2018 					     struct the_nilfs *nilfs)
2019 {
2020 	struct nilfs_inode_info *ii, *n;
2021 	int during_mount = !(sci->sc_super->s_flags & SB_ACTIVE);
2022 	int defer_iput = false;
2023 
2024 	spin_lock(&nilfs->ns_inode_lock);
2025 	list_for_each_entry_safe(ii, n, &sci->sc_dirty_files, i_dirty) {
2026 		if (!test_and_clear_bit(NILFS_I_UPDATED, &ii->i_state) ||
2027 		    test_bit(NILFS_I_DIRTY, &ii->i_state))
2028 			continue;
2029 
2030 		clear_bit(NILFS_I_BUSY, &ii->i_state);
2031 		brelse(ii->i_bh);
2032 		ii->i_bh = NULL;
2033 		list_del_init(&ii->i_dirty);
2034 		if (!ii->vfs_inode.i_nlink || during_mount) {
2035 			/*
2036 			 * Defer calling iput() to avoid deadlocks if
2037 			 * i_nlink == 0 or mount is not yet finished.
2038 			 */
2039 			list_add_tail(&ii->i_dirty, &sci->sc_iput_queue);
2040 			defer_iput = true;
2041 		} else {
2042 			spin_unlock(&nilfs->ns_inode_lock);
2043 			iput(&ii->vfs_inode);
2044 			spin_lock(&nilfs->ns_inode_lock);
2045 		}
2046 	}
2047 	spin_unlock(&nilfs->ns_inode_lock);
2048 
2049 	if (defer_iput)
2050 		schedule_work(&sci->sc_iput_work);
2051 }
2052 
2053 /*
2054  * Main procedure of segment constructor
2055  */
2056 static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
2057 {
2058 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
2059 	int err;
2060 
2061 	if (sb_rdonly(sci->sc_super))
2062 		return -EROFS;
2063 
2064 	nilfs_sc_cstage_set(sci, NILFS_ST_INIT);
2065 	sci->sc_cno = nilfs->ns_cno;
2066 
2067 	err = nilfs_segctor_collect_dirty_files(sci, nilfs);
2068 	if (unlikely(err))
2069 		goto out;
2070 
2071 	if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
2072 		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
2073 
2074 	if (nilfs_segctor_clean(sci))
2075 		goto out;
2076 
2077 	do {
2078 		sci->sc_stage.flags &= ~NILFS_CF_HISTORY_MASK;
2079 
2080 		err = nilfs_segctor_begin_construction(sci, nilfs);
2081 		if (unlikely(err))
2082 			goto out;
2083 
2084 		/* Update time stamp */
2085 		sci->sc_seg_ctime = ktime_get_real_seconds();
2086 
2087 		err = nilfs_segctor_collect(sci, nilfs, mode);
2088 		if (unlikely(err))
2089 			goto failed;
2090 
2091 		/* Avoid empty segment */
2092 		if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE &&
2093 		    nilfs_segbuf_empty(sci->sc_curseg)) {
2094 			nilfs_segctor_abort_construction(sci, nilfs, 1);
2095 			goto out;
2096 		}
2097 
2098 		err = nilfs_segctor_assign(sci, mode);
2099 		if (unlikely(err))
2100 			goto failed;
2101 
2102 		if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
2103 			nilfs_segctor_fill_in_file_bmap(sci);
2104 
2105 		if (mode == SC_LSEG_SR &&
2106 		    nilfs_sc_cstage_get(sci) >= NILFS_ST_CPFILE) {
2107 			err = nilfs_segctor_fill_in_checkpoint(sci);
2108 			if (unlikely(err))
2109 				goto failed_to_write;
2110 
2111 			nilfs_segctor_fill_in_super_root(sci, nilfs);
2112 		}
2113 		nilfs_segctor_update_segusage(sci, nilfs->ns_sufile);
2114 
2115 		/* Write partial segments */
2116 		nilfs_segctor_prepare_write(sci);
2117 
2118 		nilfs_add_checksums_on_logs(&sci->sc_segbufs,
2119 					    nilfs->ns_crc_seed);
2120 
2121 		err = nilfs_segctor_write(sci, nilfs);
2122 		if (unlikely(err))
2123 			goto failed_to_write;
2124 
2125 		if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE ||
2126 		    nilfs->ns_blocksize_bits != PAGE_SHIFT) {
2127 			/*
2128 			 * At this point, we avoid double buffering
2129 			 * for blocksize < pagesize because page dirty
2130 			 * flag is turned off during write and dirty
2131 			 * buffers are not properly collected for
2132 			 * pages crossing over segments.
2133 			 */
2134 			err = nilfs_segctor_wait(sci);
2135 			if (err)
2136 				goto failed_to_write;
2137 		}
2138 	} while (nilfs_sc_cstage_get(sci) != NILFS_ST_DONE);
2139 
2140  out:
2141 	nilfs_segctor_drop_written_files(sci, nilfs);
2142 	return err;
2143 
2144  failed_to_write:
2145 	if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
2146 		nilfs_redirty_inodes(&sci->sc_dirty_files);
2147 
2148  failed:
2149 	if (nilfs_doing_gc())
2150 		nilfs_redirty_inodes(&sci->sc_gc_inodes);
2151 	nilfs_segctor_abort_construction(sci, nilfs, err);
2152 	goto out;
2153 }
2154 
2155 /**
2156  * nilfs_segctor_start_timer - set timer of background write
2157  * @sci: nilfs_sc_info
2158  *
2159  * If the timer has already been set, it ignores the new request.
2160  * This function MUST be called within a section locking the segment
2161  * semaphore.
2162  */
2163 static void nilfs_segctor_start_timer(struct nilfs_sc_info *sci)
2164 {
2165 	spin_lock(&sci->sc_state_lock);
2166 	if (!(sci->sc_state & NILFS_SEGCTOR_COMMIT)) {
2167 		if (sci->sc_task) {
2168 			sci->sc_timer.expires = jiffies + sci->sc_interval;
2169 			add_timer(&sci->sc_timer);
2170 		}
2171 		sci->sc_state |= NILFS_SEGCTOR_COMMIT;
2172 	}
2173 	spin_unlock(&sci->sc_state_lock);
2174 }
2175 
2176 static void nilfs_segctor_do_flush(struct nilfs_sc_info *sci, int bn)
2177 {
2178 	spin_lock(&sci->sc_state_lock);
2179 	if (!(sci->sc_flush_request & BIT(bn))) {
2180 		unsigned long prev_req = sci->sc_flush_request;
2181 
2182 		sci->sc_flush_request |= BIT(bn);
2183 		if (!prev_req)
2184 			wake_up(&sci->sc_wait_daemon);
2185 	}
2186 	spin_unlock(&sci->sc_state_lock);
2187 }
2188 
2189 /**
2190  * nilfs_flush_segment - trigger a segment construction for resource control
2191  * @sb: super block
2192  * @ino: inode number of the file to be flushed out.
2193  */
2194 void nilfs_flush_segment(struct super_block *sb, ino_t ino)
2195 {
2196 	struct the_nilfs *nilfs = sb->s_fs_info;
2197 	struct nilfs_sc_info *sci = nilfs->ns_writer;
2198 
2199 	if (!sci || nilfs_doing_construction())
2200 		return;
2201 	nilfs_segctor_do_flush(sci, NILFS_MDT_INODE(sb, ino) ? ino : 0);
2202 					/* assign bit 0 to data files */
2203 }
2204 
2205 struct nilfs_segctor_wait_request {
2206 	wait_queue_entry_t	wq;
2207 	__u32		seq;
2208 	int		err;
2209 	atomic_t	done;
2210 };
2211 
2212 static int nilfs_segctor_sync(struct nilfs_sc_info *sci)
2213 {
2214 	struct nilfs_segctor_wait_request wait_req;
2215 	int err = 0;
2216 
2217 	init_wait(&wait_req.wq);
2218 	wait_req.err = 0;
2219 	atomic_set(&wait_req.done, 0);
2220 	init_waitqueue_entry(&wait_req.wq, current);
2221 
2222 	/*
2223 	 * To prevent a race issue where completion notifications from the
2224 	 * log writer thread are missed, increment the request sequence count
2225 	 * "sc_seq_request" and insert a wait queue entry using the current
2226 	 * sequence number into the "sc_wait_request" queue at the same time
2227 	 * within the lock section of "sc_state_lock".
2228 	 */
2229 	spin_lock(&sci->sc_state_lock);
2230 	wait_req.seq = ++sci->sc_seq_request;
2231 	add_wait_queue(&sci->sc_wait_request, &wait_req.wq);
2232 	spin_unlock(&sci->sc_state_lock);
2233 
2234 	wake_up(&sci->sc_wait_daemon);
2235 
2236 	for (;;) {
2237 		set_current_state(TASK_INTERRUPTIBLE);
2238 
2239 		/*
2240 		 * Synchronize only while the log writer thread is alive.
2241 		 * Leave flushing out after the log writer thread exits to
2242 		 * the cleanup work in nilfs_segctor_destroy().
2243 		 */
2244 		if (!sci->sc_task)
2245 			break;
2246 
2247 		if (atomic_read(&wait_req.done)) {
2248 			err = wait_req.err;
2249 			break;
2250 		}
2251 		if (!signal_pending(current)) {
2252 			schedule();
2253 			continue;
2254 		}
2255 		err = -ERESTARTSYS;
2256 		break;
2257 	}
2258 	finish_wait(&sci->sc_wait_request, &wait_req.wq);
2259 	return err;
2260 }
2261 
2262 static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err, bool force)
2263 {
2264 	struct nilfs_segctor_wait_request *wrq, *n;
2265 	unsigned long flags;
2266 
2267 	spin_lock_irqsave(&sci->sc_wait_request.lock, flags);
2268 	list_for_each_entry_safe(wrq, n, &sci->sc_wait_request.head, wq.entry) {
2269 		if (!atomic_read(&wrq->done) &&
2270 		    (force || nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq))) {
2271 			wrq->err = err;
2272 			atomic_set(&wrq->done, 1);
2273 		}
2274 		if (atomic_read(&wrq->done)) {
2275 			wrq->wq.func(&wrq->wq,
2276 				     TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
2277 				     0, NULL);
2278 		}
2279 	}
2280 	spin_unlock_irqrestore(&sci->sc_wait_request.lock, flags);
2281 }
2282 
2283 /**
2284  * nilfs_construct_segment - construct a logical segment
2285  * @sb: super block
2286  *
2287  * Return Value: On success, 0 is returned. On errors, one of the following
2288  * negative error code is returned.
2289  *
2290  * %-EROFS - Read only filesystem.
2291  *
2292  * %-EIO - I/O error
2293  *
2294  * %-ENOSPC - No space left on device (only in a panic state).
2295  *
2296  * %-ERESTARTSYS - Interrupted.
2297  *
2298  * %-ENOMEM - Insufficient memory available.
2299  */
2300 int nilfs_construct_segment(struct super_block *sb)
2301 {
2302 	struct the_nilfs *nilfs = sb->s_fs_info;
2303 	struct nilfs_sc_info *sci = nilfs->ns_writer;
2304 	struct nilfs_transaction_info *ti;
2305 
2306 	if (sb_rdonly(sb) || unlikely(!sci))
2307 		return -EROFS;
2308 
2309 	/* A call inside transactions causes a deadlock. */
2310 	BUG_ON((ti = current->journal_info) && ti->ti_magic == NILFS_TI_MAGIC);
2311 
2312 	return nilfs_segctor_sync(sci);
2313 }
2314 
2315 /**
2316  * nilfs_construct_dsync_segment - construct a data-only logical segment
2317  * @sb: super block
2318  * @inode: inode whose data blocks should be written out
2319  * @start: start byte offset
2320  * @end: end byte offset (inclusive)
2321  *
2322  * Return Value: On success, 0 is returned. On errors, one of the following
2323  * negative error code is returned.
2324  *
2325  * %-EROFS - Read only filesystem.
2326  *
2327  * %-EIO - I/O error
2328  *
2329  * %-ENOSPC - No space left on device (only in a panic state).
2330  *
2331  * %-ERESTARTSYS - Interrupted.
2332  *
2333  * %-ENOMEM - Insufficient memory available.
2334  */
2335 int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
2336 				  loff_t start, loff_t end)
2337 {
2338 	struct the_nilfs *nilfs = sb->s_fs_info;
2339 	struct nilfs_sc_info *sci = nilfs->ns_writer;
2340 	struct nilfs_inode_info *ii;
2341 	struct nilfs_transaction_info ti;
2342 	int err = 0;
2343 
2344 	if (sb_rdonly(sb) || unlikely(!sci))
2345 		return -EROFS;
2346 
2347 	nilfs_transaction_lock(sb, &ti, 0);
2348 
2349 	ii = NILFS_I(inode);
2350 	if (test_bit(NILFS_I_INODE_SYNC, &ii->i_state) ||
2351 	    nilfs_test_opt(nilfs, STRICT_ORDER) ||
2352 	    test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
2353 	    nilfs_discontinued(nilfs)) {
2354 		nilfs_transaction_unlock(sb);
2355 		err = nilfs_segctor_sync(sci);
2356 		return err;
2357 	}
2358 
2359 	spin_lock(&nilfs->ns_inode_lock);
2360 	if (!test_bit(NILFS_I_QUEUED, &ii->i_state) &&
2361 	    !test_bit(NILFS_I_BUSY, &ii->i_state)) {
2362 		spin_unlock(&nilfs->ns_inode_lock);
2363 		nilfs_transaction_unlock(sb);
2364 		return 0;
2365 	}
2366 	spin_unlock(&nilfs->ns_inode_lock);
2367 	sci->sc_dsync_inode = ii;
2368 	sci->sc_dsync_start = start;
2369 	sci->sc_dsync_end = end;
2370 
2371 	err = nilfs_segctor_do_construct(sci, SC_LSEG_DSYNC);
2372 	if (!err)
2373 		nilfs->ns_flushed_device = 0;
2374 
2375 	nilfs_transaction_unlock(sb);
2376 	return err;
2377 }
2378 
2379 #define FLUSH_FILE_BIT	(0x1) /* data file only */
2380 #define FLUSH_DAT_BIT	BIT(NILFS_DAT_INO) /* DAT only */
2381 
2382 /**
2383  * nilfs_segctor_accept - record accepted sequence count of log-write requests
2384  * @sci: segment constructor object
2385  */
2386 static void nilfs_segctor_accept(struct nilfs_sc_info *sci)
2387 {
2388 	bool thread_is_alive;
2389 
2390 	spin_lock(&sci->sc_state_lock);
2391 	sci->sc_seq_accepted = sci->sc_seq_request;
2392 	thread_is_alive = (bool)sci->sc_task;
2393 	spin_unlock(&sci->sc_state_lock);
2394 
2395 	/*
2396 	 * This function does not race with the log writer thread's
2397 	 * termination.  Therefore, deleting sc_timer, which should not be
2398 	 * done after the log writer thread exits, can be done safely outside
2399 	 * the area protected by sc_state_lock.
2400 	 */
2401 	if (thread_is_alive)
2402 		del_timer_sync(&sci->sc_timer);
2403 }
2404 
2405 /**
2406  * nilfs_segctor_notify - notify the result of request to caller threads
2407  * @sci: segment constructor object
2408  * @mode: mode of log forming
2409  * @err: error code to be notified
2410  */
2411 static void nilfs_segctor_notify(struct nilfs_sc_info *sci, int mode, int err)
2412 {
2413 	/* Clear requests (even when the construction failed) */
2414 	spin_lock(&sci->sc_state_lock);
2415 
2416 	if (mode == SC_LSEG_SR) {
2417 		sci->sc_state &= ~NILFS_SEGCTOR_COMMIT;
2418 		sci->sc_seq_done = sci->sc_seq_accepted;
2419 		nilfs_segctor_wakeup(sci, err, false);
2420 		sci->sc_flush_request = 0;
2421 	} else {
2422 		if (mode == SC_FLUSH_FILE)
2423 			sci->sc_flush_request &= ~FLUSH_FILE_BIT;
2424 		else if (mode == SC_FLUSH_DAT)
2425 			sci->sc_flush_request &= ~FLUSH_DAT_BIT;
2426 
2427 		/* re-enable timer if checkpoint creation was not done */
2428 		if ((sci->sc_state & NILFS_SEGCTOR_COMMIT) && sci->sc_task &&
2429 		    time_before(jiffies, sci->sc_timer.expires))
2430 			add_timer(&sci->sc_timer);
2431 	}
2432 	spin_unlock(&sci->sc_state_lock);
2433 }
2434 
2435 /**
2436  * nilfs_segctor_construct - form logs and write them to disk
2437  * @sci: segment constructor object
2438  * @mode: mode of log forming
2439  */
2440 static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
2441 {
2442 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
2443 	struct nilfs_super_block **sbp;
2444 	int err = 0;
2445 
2446 	nilfs_segctor_accept(sci);
2447 
2448 	if (nilfs_discontinued(nilfs))
2449 		mode = SC_LSEG_SR;
2450 	if (!nilfs_segctor_confirm(sci))
2451 		err = nilfs_segctor_do_construct(sci, mode);
2452 
2453 	if (likely(!err)) {
2454 		if (mode != SC_FLUSH_DAT)
2455 			atomic_set(&nilfs->ns_ndirtyblks, 0);
2456 		if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) &&
2457 		    nilfs_discontinued(nilfs)) {
2458 			down_write(&nilfs->ns_sem);
2459 			err = -EIO;
2460 			sbp = nilfs_prepare_super(sci->sc_super,
2461 						  nilfs_sb_will_flip(nilfs));
2462 			if (likely(sbp)) {
2463 				nilfs_set_log_cursor(sbp[0], nilfs);
2464 				err = nilfs_commit_super(sci->sc_super,
2465 							 NILFS_SB_COMMIT);
2466 			}
2467 			up_write(&nilfs->ns_sem);
2468 		}
2469 	}
2470 
2471 	nilfs_segctor_notify(sci, mode, err);
2472 	return err;
2473 }
2474 
2475 static void nilfs_construction_timeout(struct timer_list *t)
2476 {
2477 	struct nilfs_sc_info *sci = from_timer(sci, t, sc_timer);
2478 
2479 	wake_up_process(sci->sc_timer_task);
2480 }
2481 
2482 static void
2483 nilfs_remove_written_gcinodes(struct the_nilfs *nilfs, struct list_head *head)
2484 {
2485 	struct nilfs_inode_info *ii, *n;
2486 
2487 	list_for_each_entry_safe(ii, n, head, i_dirty) {
2488 		if (!test_bit(NILFS_I_UPDATED, &ii->i_state))
2489 			continue;
2490 		list_del_init(&ii->i_dirty);
2491 		truncate_inode_pages(&ii->vfs_inode.i_data, 0);
2492 		nilfs_btnode_cache_clear(ii->i_assoc_inode->i_mapping);
2493 		iput(&ii->vfs_inode);
2494 	}
2495 }
2496 
2497 int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
2498 			 void **kbufs)
2499 {
2500 	struct the_nilfs *nilfs = sb->s_fs_info;
2501 	struct nilfs_sc_info *sci = nilfs->ns_writer;
2502 	struct nilfs_transaction_info ti;
2503 	int err;
2504 
2505 	if (unlikely(!sci))
2506 		return -EROFS;
2507 
2508 	nilfs_transaction_lock(sb, &ti, 1);
2509 
2510 	err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat);
2511 	if (unlikely(err))
2512 		goto out_unlock;
2513 
2514 	err = nilfs_ioctl_prepare_clean_segments(nilfs, argv, kbufs);
2515 	if (unlikely(err)) {
2516 		nilfs_mdt_restore_from_shadow_map(nilfs->ns_dat);
2517 		goto out_unlock;
2518 	}
2519 
2520 	sci->sc_freesegs = kbufs[4];
2521 	sci->sc_nfreesegs = argv[4].v_nmembs;
2522 	list_splice_tail_init(&nilfs->ns_gc_inodes, &sci->sc_gc_inodes);
2523 
2524 	for (;;) {
2525 		err = nilfs_segctor_construct(sci, SC_LSEG_SR);
2526 		nilfs_remove_written_gcinodes(nilfs, &sci->sc_gc_inodes);
2527 
2528 		if (likely(!err))
2529 			break;
2530 
2531 		nilfs_warn(sb, "error %d cleaning segments", err);
2532 		set_current_state(TASK_INTERRUPTIBLE);
2533 		schedule_timeout(sci->sc_interval);
2534 	}
2535 	if (nilfs_test_opt(nilfs, DISCARD)) {
2536 		int ret = nilfs_discard_segments(nilfs, sci->sc_freesegs,
2537 						 sci->sc_nfreesegs);
2538 		if (ret) {
2539 			nilfs_warn(sb,
2540 				   "error %d on discard request, turning discards off for the device",
2541 				   ret);
2542 			nilfs_clear_opt(nilfs, DISCARD);
2543 		}
2544 	}
2545 
2546  out_unlock:
2547 	sci->sc_freesegs = NULL;
2548 	sci->sc_nfreesegs = 0;
2549 	nilfs_mdt_clear_shadow_map(nilfs->ns_dat);
2550 	nilfs_transaction_unlock(sb);
2551 	return err;
2552 }
2553 
2554 static void nilfs_segctor_thread_construct(struct nilfs_sc_info *sci, int mode)
2555 {
2556 	struct nilfs_transaction_info ti;
2557 
2558 	nilfs_transaction_lock(sci->sc_super, &ti, 0);
2559 	nilfs_segctor_construct(sci, mode);
2560 
2561 	/*
2562 	 * Unclosed segment should be retried.  We do this using sc_timer.
2563 	 * Timeout of sc_timer will invoke complete construction which leads
2564 	 * to close the current logical segment.
2565 	 */
2566 	if (test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags))
2567 		nilfs_segctor_start_timer(sci);
2568 
2569 	nilfs_transaction_unlock(sci->sc_super);
2570 }
2571 
2572 static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *sci)
2573 {
2574 	int mode = 0;
2575 
2576 	spin_lock(&sci->sc_state_lock);
2577 	mode = (sci->sc_flush_request & FLUSH_DAT_BIT) ?
2578 		SC_FLUSH_DAT : SC_FLUSH_FILE;
2579 	spin_unlock(&sci->sc_state_lock);
2580 
2581 	if (mode) {
2582 		nilfs_segctor_do_construct(sci, mode);
2583 
2584 		spin_lock(&sci->sc_state_lock);
2585 		sci->sc_flush_request &= (mode == SC_FLUSH_FILE) ?
2586 			~FLUSH_FILE_BIT : ~FLUSH_DAT_BIT;
2587 		spin_unlock(&sci->sc_state_lock);
2588 	}
2589 	clear_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
2590 }
2591 
2592 static int nilfs_segctor_flush_mode(struct nilfs_sc_info *sci)
2593 {
2594 	if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
2595 	    time_before(jiffies, sci->sc_lseg_stime + sci->sc_mjcp_freq)) {
2596 		if (!(sci->sc_flush_request & ~FLUSH_FILE_BIT))
2597 			return SC_FLUSH_FILE;
2598 		else if (!(sci->sc_flush_request & ~FLUSH_DAT_BIT))
2599 			return SC_FLUSH_DAT;
2600 	}
2601 	return SC_LSEG_SR;
2602 }
2603 
2604 /**
2605  * nilfs_segctor_thread - main loop of the segment constructor thread.
2606  * @arg: pointer to a struct nilfs_sc_info.
2607  *
2608  * nilfs_segctor_thread() initializes a timer and serves as a daemon
2609  * to execute segment constructions.
2610  */
2611 static int nilfs_segctor_thread(void *arg)
2612 {
2613 	struct nilfs_sc_info *sci = (struct nilfs_sc_info *)arg;
2614 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
2615 	int timeout = 0;
2616 
2617 	sci->sc_timer_task = current;
2618 	timer_setup(&sci->sc_timer, nilfs_construction_timeout, 0);
2619 
2620 	/* start sync. */
2621 	sci->sc_task = current;
2622 	wake_up(&sci->sc_wait_task); /* for nilfs_segctor_start_thread() */
2623 	nilfs_info(sci->sc_super,
2624 		   "segctord starting. Construction interval = %lu seconds, CP frequency < %lu seconds",
2625 		   sci->sc_interval / HZ, sci->sc_mjcp_freq / HZ);
2626 
2627 	spin_lock(&sci->sc_state_lock);
2628  loop:
2629 	for (;;) {
2630 		int mode;
2631 
2632 		if (sci->sc_state & NILFS_SEGCTOR_QUIT)
2633 			goto end_thread;
2634 
2635 		if (timeout || sci->sc_seq_request != sci->sc_seq_done)
2636 			mode = SC_LSEG_SR;
2637 		else if (sci->sc_flush_request)
2638 			mode = nilfs_segctor_flush_mode(sci);
2639 		else
2640 			break;
2641 
2642 		spin_unlock(&sci->sc_state_lock);
2643 		nilfs_segctor_thread_construct(sci, mode);
2644 		spin_lock(&sci->sc_state_lock);
2645 		timeout = 0;
2646 	}
2647 
2648 
2649 	if (freezing(current)) {
2650 		spin_unlock(&sci->sc_state_lock);
2651 		try_to_freeze();
2652 		spin_lock(&sci->sc_state_lock);
2653 	} else {
2654 		DEFINE_WAIT(wait);
2655 		int should_sleep = 1;
2656 
2657 		prepare_to_wait(&sci->sc_wait_daemon, &wait,
2658 				TASK_INTERRUPTIBLE);
2659 
2660 		if (sci->sc_seq_request != sci->sc_seq_done)
2661 			should_sleep = 0;
2662 		else if (sci->sc_flush_request)
2663 			should_sleep = 0;
2664 		else if (sci->sc_state & NILFS_SEGCTOR_COMMIT)
2665 			should_sleep = time_before(jiffies,
2666 					sci->sc_timer.expires);
2667 
2668 		if (should_sleep) {
2669 			spin_unlock(&sci->sc_state_lock);
2670 			schedule();
2671 			spin_lock(&sci->sc_state_lock);
2672 		}
2673 		finish_wait(&sci->sc_wait_daemon, &wait);
2674 		timeout = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
2675 			   time_after_eq(jiffies, sci->sc_timer.expires));
2676 
2677 		if (nilfs_sb_dirty(nilfs) && nilfs_sb_need_update(nilfs))
2678 			set_nilfs_discontinued(nilfs);
2679 	}
2680 	goto loop;
2681 
2682  end_thread:
2683 	/* end sync. */
2684 	sci->sc_task = NULL;
2685 	timer_shutdown_sync(&sci->sc_timer);
2686 	wake_up(&sci->sc_wait_task); /* for nilfs_segctor_kill_thread() */
2687 	spin_unlock(&sci->sc_state_lock);
2688 	return 0;
2689 }
2690 
2691 static int nilfs_segctor_start_thread(struct nilfs_sc_info *sci)
2692 {
2693 	struct task_struct *t;
2694 
2695 	t = kthread_run(nilfs_segctor_thread, sci, "segctord");
2696 	if (IS_ERR(t)) {
2697 		int err = PTR_ERR(t);
2698 
2699 		nilfs_err(sci->sc_super, "error %d creating segctord thread",
2700 			  err);
2701 		return err;
2702 	}
2703 	wait_event(sci->sc_wait_task, sci->sc_task != NULL);
2704 	return 0;
2705 }
2706 
2707 static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
2708 	__acquires(&sci->sc_state_lock)
2709 	__releases(&sci->sc_state_lock)
2710 {
2711 	sci->sc_state |= NILFS_SEGCTOR_QUIT;
2712 
2713 	while (sci->sc_task) {
2714 		wake_up(&sci->sc_wait_daemon);
2715 		spin_unlock(&sci->sc_state_lock);
2716 		wait_event(sci->sc_wait_task, sci->sc_task == NULL);
2717 		spin_lock(&sci->sc_state_lock);
2718 	}
2719 }
2720 
2721 /*
2722  * Setup & clean-up functions
2723  */
2724 static struct nilfs_sc_info *nilfs_segctor_new(struct super_block *sb,
2725 					       struct nilfs_root *root)
2726 {
2727 	struct the_nilfs *nilfs = sb->s_fs_info;
2728 	struct nilfs_sc_info *sci;
2729 
2730 	sci = kzalloc(sizeof(*sci), GFP_KERNEL);
2731 	if (!sci)
2732 		return NULL;
2733 
2734 	sci->sc_super = sb;
2735 
2736 	nilfs_get_root(root);
2737 	sci->sc_root = root;
2738 
2739 	init_waitqueue_head(&sci->sc_wait_request);
2740 	init_waitqueue_head(&sci->sc_wait_daemon);
2741 	init_waitqueue_head(&sci->sc_wait_task);
2742 	spin_lock_init(&sci->sc_state_lock);
2743 	INIT_LIST_HEAD(&sci->sc_dirty_files);
2744 	INIT_LIST_HEAD(&sci->sc_segbufs);
2745 	INIT_LIST_HEAD(&sci->sc_write_logs);
2746 	INIT_LIST_HEAD(&sci->sc_gc_inodes);
2747 	INIT_LIST_HEAD(&sci->sc_iput_queue);
2748 	INIT_WORK(&sci->sc_iput_work, nilfs_iput_work_func);
2749 
2750 	sci->sc_interval = HZ * NILFS_SC_DEFAULT_TIMEOUT;
2751 	sci->sc_mjcp_freq = HZ * NILFS_SC_DEFAULT_SR_FREQ;
2752 	sci->sc_watermark = NILFS_SC_DEFAULT_WATERMARK;
2753 
2754 	if (nilfs->ns_interval)
2755 		sci->sc_interval = HZ * nilfs->ns_interval;
2756 	if (nilfs->ns_watermark)
2757 		sci->sc_watermark = nilfs->ns_watermark;
2758 	return sci;
2759 }
2760 
2761 static void nilfs_segctor_write_out(struct nilfs_sc_info *sci)
2762 {
2763 	int ret, retrycount = NILFS_SC_CLEANUP_RETRY;
2764 
2765 	/*
2766 	 * The segctord thread was stopped and its timer was removed.
2767 	 * But some tasks remain.
2768 	 */
2769 	do {
2770 		struct nilfs_transaction_info ti;
2771 
2772 		nilfs_transaction_lock(sci->sc_super, &ti, 0);
2773 		ret = nilfs_segctor_construct(sci, SC_LSEG_SR);
2774 		nilfs_transaction_unlock(sci->sc_super);
2775 
2776 		flush_work(&sci->sc_iput_work);
2777 
2778 	} while (ret && ret != -EROFS && retrycount-- > 0);
2779 }
2780 
2781 /**
2782  * nilfs_segctor_destroy - destroy the segment constructor.
2783  * @sci: nilfs_sc_info
2784  *
2785  * nilfs_segctor_destroy() kills the segctord thread and frees
2786  * the nilfs_sc_info struct.
2787  * Caller must hold the segment semaphore.
2788  */
2789 static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
2790 {
2791 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
2792 	int flag;
2793 
2794 	up_write(&nilfs->ns_segctor_sem);
2795 
2796 	spin_lock(&sci->sc_state_lock);
2797 	nilfs_segctor_kill_thread(sci);
2798 	flag = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) || sci->sc_flush_request
2799 		|| sci->sc_seq_request != sci->sc_seq_done);
2800 	spin_unlock(&sci->sc_state_lock);
2801 
2802 	/*
2803 	 * Forcibly wake up tasks waiting in nilfs_segctor_sync(), which can
2804 	 * be called from delayed iput() via nilfs_evict_inode() and can race
2805 	 * with the above log writer thread termination.
2806 	 */
2807 	nilfs_segctor_wakeup(sci, 0, true);
2808 
2809 	if (flush_work(&sci->sc_iput_work))
2810 		flag = true;
2811 
2812 	if (flag || !nilfs_segctor_confirm(sci))
2813 		nilfs_segctor_write_out(sci);
2814 
2815 	if (!list_empty(&sci->sc_dirty_files)) {
2816 		nilfs_warn(sci->sc_super,
2817 			   "disposed unprocessed dirty file(s) when stopping log writer");
2818 		nilfs_dispose_list(nilfs, &sci->sc_dirty_files, 1);
2819 	}
2820 
2821 	if (!list_empty(&sci->sc_iput_queue)) {
2822 		nilfs_warn(sci->sc_super,
2823 			   "disposed unprocessed inode(s) in iput queue when stopping log writer");
2824 		nilfs_dispose_list(nilfs, &sci->sc_iput_queue, 1);
2825 	}
2826 
2827 	WARN_ON(!list_empty(&sci->sc_segbufs));
2828 	WARN_ON(!list_empty(&sci->sc_write_logs));
2829 
2830 	nilfs_put_root(sci->sc_root);
2831 
2832 	down_write(&nilfs->ns_segctor_sem);
2833 
2834 	kfree(sci);
2835 }
2836 
2837 /**
2838  * nilfs_attach_log_writer - attach log writer
2839  * @sb: super block instance
2840  * @root: root object of the current filesystem tree
2841  *
2842  * This allocates a log writer object, initializes it, and starts the
2843  * log writer.
2844  *
2845  * Return Value: On success, 0 is returned. On error, one of the following
2846  * negative error code is returned.
2847  *
2848  * %-ENOMEM - Insufficient memory available.
2849  */
2850 int nilfs_attach_log_writer(struct super_block *sb, struct nilfs_root *root)
2851 {
2852 	struct the_nilfs *nilfs = sb->s_fs_info;
2853 	int err;
2854 
2855 	if (nilfs->ns_writer) {
2856 		/*
2857 		 * This happens if the filesystem is made read-only by
2858 		 * __nilfs_error or nilfs_remount and then remounted
2859 		 * read/write.  In these cases, reuse the existing
2860 		 * writer.
2861 		 */
2862 		return 0;
2863 	}
2864 
2865 	nilfs->ns_writer = nilfs_segctor_new(sb, root);
2866 	if (!nilfs->ns_writer)
2867 		return -ENOMEM;
2868 
2869 	inode_attach_wb(nilfs->ns_bdev->bd_inode, NULL);
2870 
2871 	err = nilfs_segctor_start_thread(nilfs->ns_writer);
2872 	if (unlikely(err))
2873 		nilfs_detach_log_writer(sb);
2874 
2875 	return err;
2876 }
2877 
2878 /**
2879  * nilfs_detach_log_writer - destroy log writer
2880  * @sb: super block instance
2881  *
2882  * This kills log writer daemon, frees the log writer object, and
2883  * destroys list of dirty files.
2884  */
2885 void nilfs_detach_log_writer(struct super_block *sb)
2886 {
2887 	struct the_nilfs *nilfs = sb->s_fs_info;
2888 	LIST_HEAD(garbage_list);
2889 
2890 	down_write(&nilfs->ns_segctor_sem);
2891 	if (nilfs->ns_writer) {
2892 		nilfs_segctor_destroy(nilfs->ns_writer);
2893 		nilfs->ns_writer = NULL;
2894 	}
2895 	set_nilfs_purging(nilfs);
2896 
2897 	/* Force to free the list of dirty files */
2898 	spin_lock(&nilfs->ns_inode_lock);
2899 	if (!list_empty(&nilfs->ns_dirty_files)) {
2900 		list_splice_init(&nilfs->ns_dirty_files, &garbage_list);
2901 		nilfs_warn(sb,
2902 			   "disposed unprocessed dirty file(s) when detaching log writer");
2903 	}
2904 	spin_unlock(&nilfs->ns_inode_lock);
2905 	up_write(&nilfs->ns_segctor_sem);
2906 
2907 	nilfs_dispose_list(nilfs, &garbage_list, 1);
2908 	clear_nilfs_purging(nilfs);
2909 }
2910