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1 /*
2  * fs/fs-writeback.c
3  *
4  * Copyright (C) 2002, Linus Torvalds.
5  *
6  * Contains all the functions related to writing back and waiting
7  * upon dirty inodes against superblocks, and writing back dirty
8  * pages against inodes.  ie: data writeback.  Writeout of the
9  * inode itself is not handled here.
10  *
11  * 10Apr2002    Andrew Morton
12  *              Split out of fs/inode.c
13  *              Additions for address_space-based writeback
14  */
15
16 #include <linux/kernel.h>
17 #include <linux/export.h>
18 #include <linux/spinlock.h>
19 #include <linux/slab.h>
20 #include <linux/sched.h>
21 #include <linux/fs.h>
22 #include <linux/mm.h>
23 #include <linux/pagemap.h>
24 #include <linux/kthread.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/tracepoint.h>
29 #include <linux/device.h>
30 #include "internal.h"
31
32 /*
33  * 4MB minimal write chunk size
34  */
35 #define MIN_WRITEBACK_PAGES     (4096UL >> (PAGE_CACHE_SHIFT - 10))
36
37 /*
38  * Passed into wb_writeback(), essentially a subset of writeback_control
39  */
40 struct wb_writeback_work {
41         long nr_pages;
42         struct super_block *sb;
43         unsigned long *older_than_this;
44         enum writeback_sync_modes sync_mode;
45         unsigned int tagged_writepages:1;
46         unsigned int for_kupdate:1;
47         unsigned int range_cyclic:1;
48         unsigned int for_background:1;
49         unsigned int for_sync:1;        /* sync(2) WB_SYNC_ALL writeback */
50         enum wb_reason reason;          /* why was writeback initiated? */
51
52         struct list_head list;          /* pending work list */
53         struct completion *done;        /* set if the caller waits */
54 };
55
56 /**
57  * writeback_in_progress - determine whether there is writeback in progress
58  * @bdi: the device's backing_dev_info structure.
59  *
60  * Determine whether there is writeback waiting to be handled against a
61  * backing device.
62  */
63 int writeback_in_progress(struct backing_dev_info *bdi)
64 {
65         return test_bit(BDI_writeback_running, &bdi->state);
66 }
67 EXPORT_SYMBOL(writeback_in_progress);
68
69 struct backing_dev_info *inode_to_bdi(struct inode *inode)
70 {
71         struct super_block *sb;
72
73         if (!inode)
74                 return &noop_backing_dev_info;
75
76         sb = inode->i_sb;
77 #ifdef CONFIG_BLOCK
78         if (sb_is_blkdev_sb(sb))
79                 return blk_get_backing_dev_info(I_BDEV(inode));
80 #endif
81         return sb->s_bdi;
82 }
83 EXPORT_SYMBOL_GPL(inode_to_bdi);
84
85 static inline struct inode *wb_inode(struct list_head *head)
86 {
87         return list_entry(head, struct inode, i_wb_list);
88 }
89
90 /*
91  * Include the creation of the trace points after defining the
92  * wb_writeback_work structure and inline functions so that the definition
93  * remains local to this file.
94  */
95 #define CREATE_TRACE_POINTS
96 #include <trace/events/writeback.h>
97
98 EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
99
100 static void bdi_wakeup_thread(struct backing_dev_info *bdi)
101 {
102         spin_lock_bh(&bdi->wb_lock);
103         if (test_bit(BDI_registered, &bdi->state))
104                 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
105         spin_unlock_bh(&bdi->wb_lock);
106 }
107
108 static void bdi_queue_work(struct backing_dev_info *bdi,
109                            struct wb_writeback_work *work)
110 {
111         trace_writeback_queue(bdi, work);
112
113         spin_lock_bh(&bdi->wb_lock);
114         if (!test_bit(BDI_registered, &bdi->state)) {
115                 if (work->done)
116                         complete(work->done);
117                 goto out_unlock;
118         }
119         list_add_tail(&work->list, &bdi->work_list);
120         mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
121 out_unlock:
122         spin_unlock_bh(&bdi->wb_lock);
123 }
124
125 static void
126 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
127                       bool range_cyclic, enum wb_reason reason)
128 {
129         struct wb_writeback_work *work;
130
131         /*
132          * This is WB_SYNC_NONE writeback, so if allocation fails just
133          * wakeup the thread for old dirty data writeback
134          */
135         work = kzalloc(sizeof(*work), GFP_ATOMIC);
136         if (!work) {
137                 trace_writeback_nowork(bdi);
138                 bdi_wakeup_thread(bdi);
139                 return;
140         }
141
142         work->sync_mode = WB_SYNC_NONE;
143         work->nr_pages  = nr_pages;
144         work->range_cyclic = range_cyclic;
145         work->reason    = reason;
146
147         bdi_queue_work(bdi, work);
148 }
149
150 /**
151  * bdi_start_writeback - start writeback
152  * @bdi: the backing device to write from
153  * @nr_pages: the number of pages to write
154  * @reason: reason why some writeback work was initiated
155  *
156  * Description:
157  *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
158  *   started when this function returns, we make no guarantees on
159  *   completion. Caller need not hold sb s_umount semaphore.
160  *
161  */
162 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
163                         enum wb_reason reason)
164 {
165         __bdi_start_writeback(bdi, nr_pages, true, reason);
166 }
167
168 /**
169  * bdi_start_background_writeback - start background writeback
170  * @bdi: the backing device to write from
171  *
172  * Description:
173  *   This makes sure WB_SYNC_NONE background writeback happens. When
174  *   this function returns, it is only guaranteed that for given BDI
175  *   some IO is happening if we are over background dirty threshold.
176  *   Caller need not hold sb s_umount semaphore.
177  */
178 void bdi_start_background_writeback(struct backing_dev_info *bdi)
179 {
180         /*
181          * We just wake up the flusher thread. It will perform background
182          * writeback as soon as there is no other work to do.
183          */
184         trace_writeback_wake_background(bdi);
185         bdi_wakeup_thread(bdi);
186 }
187
188 /*
189  * Remove the inode from the writeback list it is on.
190  */
191 void inode_wb_list_del(struct inode *inode)
192 {
193         struct backing_dev_info *bdi = inode_to_bdi(inode);
194
195         spin_lock(&bdi->wb.list_lock);
196         list_del_init(&inode->i_wb_list);
197         spin_unlock(&bdi->wb.list_lock);
198 }
199
200 /*
201  * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
202  * furthest end of its superblock's dirty-inode list.
203  *
204  * Before stamping the inode's ->dirtied_when, we check to see whether it is
205  * already the most-recently-dirtied inode on the b_dirty list.  If that is
206  * the case then the inode must have been redirtied while it was being written
207  * out and we don't reset its dirtied_when.
208  */
209 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
210 {
211         assert_spin_locked(&wb->list_lock);
212         if (!list_empty(&wb->b_dirty)) {
213                 struct inode *tail;
214
215                 tail = wb_inode(wb->b_dirty.next);
216                 if (time_before(inode->dirtied_when, tail->dirtied_when))
217                         inode->dirtied_when = jiffies;
218         }
219         list_move(&inode->i_wb_list, &wb->b_dirty);
220 }
221
222 /*
223  * requeue inode for re-scanning after bdi->b_io list is exhausted.
224  */
225 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
226 {
227         assert_spin_locked(&wb->list_lock);
228         list_move(&inode->i_wb_list, &wb->b_more_io);
229 }
230
231 static void inode_sync_complete(struct inode *inode)
232 {
233         inode->i_state &= ~I_SYNC;
234         /* If inode is clean an unused, put it into LRU now... */
235         inode_add_lru(inode);
236         /* Waiters must see I_SYNC cleared before being woken up */
237         smp_mb();
238         wake_up_bit(&inode->i_state, __I_SYNC);
239 }
240
241 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
242 {
243         bool ret = time_after(inode->dirtied_when, t);
244 #ifndef CONFIG_64BIT
245         /*
246          * For inodes being constantly redirtied, dirtied_when can get stuck.
247          * It _appears_ to be in the future, but is actually in distant past.
248          * This test is necessary to prevent such wrapped-around relative times
249          * from permanently stopping the whole bdi writeback.
250          */
251         ret = ret && time_before_eq(inode->dirtied_when, jiffies);
252 #endif
253         return ret;
254 }
255
256 #define EXPIRE_DIRTY_ATIME 0x0001
257
258 /*
259  * Move expired (dirtied before work->older_than_this) dirty inodes from
260  * @delaying_queue to @dispatch_queue.
261  */
262 static int move_expired_inodes(struct list_head *delaying_queue,
263                                struct list_head *dispatch_queue,
264                                int flags,
265                                struct wb_writeback_work *work)
266 {
267         unsigned long *older_than_this = NULL;
268         unsigned long expire_time;
269         LIST_HEAD(tmp);
270         struct list_head *pos, *node;
271         struct super_block *sb = NULL;
272         struct inode *inode;
273         int do_sb_sort = 0;
274         int moved = 0;
275
276         if ((flags & EXPIRE_DIRTY_ATIME) == 0)
277                 older_than_this = work->older_than_this;
278         else if ((work->reason == WB_REASON_SYNC) == 0) {
279                 expire_time = jiffies - (HZ * 86400);
280                 older_than_this = &expire_time;
281         }
282         while (!list_empty(delaying_queue)) {
283                 inode = wb_inode(delaying_queue->prev);
284                 if (older_than_this &&
285                     inode_dirtied_after(inode, *older_than_this))
286                         break;
287                 list_move(&inode->i_wb_list, &tmp);
288                 moved++;
289                 if (flags & EXPIRE_DIRTY_ATIME)
290                         set_bit(__I_DIRTY_TIME_EXPIRED, &inode->i_state);
291                 if (sb_is_blkdev_sb(inode->i_sb))
292                         continue;
293                 if (sb && sb != inode->i_sb)
294                         do_sb_sort = 1;
295                 sb = inode->i_sb;
296         }
297
298         /* just one sb in list, splice to dispatch_queue and we're done */
299         if (!do_sb_sort) {
300                 list_splice(&tmp, dispatch_queue);
301                 goto out;
302         }
303
304         /* Move inodes from one superblock together */
305         while (!list_empty(&tmp)) {
306                 sb = wb_inode(tmp.prev)->i_sb;
307                 list_for_each_prev_safe(pos, node, &tmp) {
308                         inode = wb_inode(pos);
309                         if (inode->i_sb == sb)
310                                 list_move(&inode->i_wb_list, dispatch_queue);
311                 }
312         }
313 out:
314         return moved;
315 }
316
317 /*
318  * Queue all expired dirty inodes for io, eldest first.
319  * Before
320  *         newly dirtied     b_dirty    b_io    b_more_io
321  *         =============>    gf         edc     BA
322  * After
323  *         newly dirtied     b_dirty    b_io    b_more_io
324  *         =============>    g          fBAedc
325  *                                           |
326  *                                           +--> dequeue for IO
327  */
328 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
329 {
330         int moved;
331
332         assert_spin_locked(&wb->list_lock);
333         list_splice_init(&wb->b_more_io, &wb->b_io);
334         moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work);
335         moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
336                                      EXPIRE_DIRTY_ATIME, work);
337         trace_writeback_queue_io(wb, work, moved);
338 }
339
340 static int write_inode(struct inode *inode, struct writeback_control *wbc)
341 {
342         int ret;
343
344         if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
345                 trace_writeback_write_inode_start(inode, wbc);
346                 ret = inode->i_sb->s_op->write_inode(inode, wbc);
347                 trace_writeback_write_inode(inode, wbc);
348                 return ret;
349         }
350         return 0;
351 }
352
353 /*
354  * Wait for writeback on an inode to complete. Called with i_lock held.
355  * Caller must make sure inode cannot go away when we drop i_lock.
356  */
357 static void __inode_wait_for_writeback(struct inode *inode)
358         __releases(inode->i_lock)
359         __acquires(inode->i_lock)
360 {
361         DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
362         wait_queue_head_t *wqh;
363
364         wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
365         while (inode->i_state & I_SYNC) {
366                 spin_unlock(&inode->i_lock);
367                 __wait_on_bit(wqh, &wq, bit_wait,
368                               TASK_UNINTERRUPTIBLE);
369                 spin_lock(&inode->i_lock);
370         }
371 }
372
373 /*
374  * Wait for writeback on an inode to complete. Caller must have inode pinned.
375  */
376 void inode_wait_for_writeback(struct inode *inode)
377 {
378         spin_lock(&inode->i_lock);
379         __inode_wait_for_writeback(inode);
380         spin_unlock(&inode->i_lock);
381 }
382
383 /*
384  * Sleep until I_SYNC is cleared. This function must be called with i_lock
385  * held and drops it. It is aimed for callers not holding any inode reference
386  * so once i_lock is dropped, inode can go away.
387  */
388 static void inode_sleep_on_writeback(struct inode *inode)
389         __releases(inode->i_lock)
390 {
391         DEFINE_WAIT(wait);
392         wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
393         int sleep;
394
395         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
396         sleep = inode->i_state & I_SYNC;
397         spin_unlock(&inode->i_lock);
398         if (sleep)
399                 schedule();
400         finish_wait(wqh, &wait);
401 }
402
403 /*
404  * Find proper writeback list for the inode depending on its current state and
405  * possibly also change of its state while we were doing writeback.  Here we
406  * handle things such as livelock prevention or fairness of writeback among
407  * inodes. This function can be called only by flusher thread - noone else
408  * processes all inodes in writeback lists and requeueing inodes behind flusher
409  * thread's back can have unexpected consequences.
410  */
411 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
412                           struct writeback_control *wbc)
413 {
414         if (inode->i_state & I_FREEING)
415                 return;
416
417         /*
418          * Sync livelock prevention. Each inode is tagged and synced in one
419          * shot. If still dirty, it will be redirty_tail()'ed below.  Update
420          * the dirty time to prevent enqueue and sync it again.
421          */
422         if ((inode->i_state & I_DIRTY) &&
423             (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
424                 inode->dirtied_when = jiffies;
425
426         if (wbc->pages_skipped) {
427                 /*
428                  * writeback is not making progress due to locked
429                  * buffers. Skip this inode for now.
430                  */
431                 redirty_tail(inode, wb);
432                 return;
433         }
434
435         if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
436                 /*
437                  * We didn't write back all the pages.  nfs_writepages()
438                  * sometimes bales out without doing anything.
439                  */
440                 if (wbc->nr_to_write <= 0) {
441                         /* Slice used up. Queue for next turn. */
442                         requeue_io(inode, wb);
443                 } else {
444                         /*
445                          * Writeback blocked by something other than
446                          * congestion. Delay the inode for some time to
447                          * avoid spinning on the CPU (100% iowait)
448                          * retrying writeback of the dirty page/inode
449                          * that cannot be performed immediately.
450                          */
451                         redirty_tail(inode, wb);
452                 }
453         } else if (inode->i_state & I_DIRTY) {
454                 /*
455                  * Filesystems can dirty the inode during writeback operations,
456                  * such as delayed allocation during submission or metadata
457                  * updates after data IO completion.
458                  */
459                 redirty_tail(inode, wb);
460         } else if (inode->i_state & I_DIRTY_TIME) {
461                 list_move(&inode->i_wb_list, &wb->b_dirty_time);
462         } else {
463                 /* The inode is clean. Remove from writeback lists. */
464                 list_del_init(&inode->i_wb_list);
465         }
466 }
467
468 /*
469  * Write out an inode and its dirty pages. Do not update the writeback list
470  * linkage. That is left to the caller. The caller is also responsible for
471  * setting I_SYNC flag and calling inode_sync_complete() to clear it.
472  */
473 static int
474 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
475 {
476         struct address_space *mapping = inode->i_mapping;
477         long nr_to_write = wbc->nr_to_write;
478         unsigned dirty;
479         int ret;
480
481         WARN_ON(!(inode->i_state & I_SYNC));
482
483         trace_writeback_single_inode_start(inode, wbc, nr_to_write);
484
485         ret = do_writepages(mapping, wbc);
486
487         /*
488          * Make sure to wait on the data before writing out the metadata.
489          * This is important for filesystems that modify metadata on data
490          * I/O completion. We don't do it for sync(2) writeback because it has a
491          * separate, external IO completion path and ->sync_fs for guaranteeing
492          * inode metadata is written back correctly.
493          */
494         if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
495                 int err = filemap_fdatawait(mapping);
496                 if (ret == 0)
497                         ret = err;
498         }
499
500         /*
501          * Some filesystems may redirty the inode during the writeback
502          * due to delalloc, clear dirty metadata flags right before
503          * write_inode()
504          */
505         spin_lock(&inode->i_lock);
506
507         dirty = inode->i_state & I_DIRTY;
508         if (((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) &&
509              (inode->i_state & I_DIRTY_TIME)) ||
510             (inode->i_state & I_DIRTY_TIME_EXPIRED)) {
511                 dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
512                 trace_writeback_lazytime(inode);
513         }
514         inode->i_state &= ~dirty;
515
516         /*
517          * Paired with smp_mb() in __mark_inode_dirty().  This allows
518          * __mark_inode_dirty() to test i_state without grabbing i_lock -
519          * either they see the I_DIRTY bits cleared or we see the dirtied
520          * inode.
521          *
522          * I_DIRTY_PAGES is always cleared together above even if @mapping
523          * still has dirty pages.  The flag is reinstated after smp_mb() if
524          * necessary.  This guarantees that either __mark_inode_dirty()
525          * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
526          */
527         smp_mb();
528
529         if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
530                 inode->i_state |= I_DIRTY_PAGES;
531
532         spin_unlock(&inode->i_lock);
533
534         if (dirty & I_DIRTY_TIME)
535                 mark_inode_dirty_sync(inode);
536         /* Don't write the inode if only I_DIRTY_PAGES was set */
537         if (dirty & ~I_DIRTY_PAGES) {
538                 int err = write_inode(inode, wbc);
539                 if (ret == 0)
540                         ret = err;
541         }
542         trace_writeback_single_inode(inode, wbc, nr_to_write);
543         return ret;
544 }
545
546 /*
547  * Write out an inode's dirty pages. Either the caller has an active reference
548  * on the inode or the inode has I_WILL_FREE set.
549  *
550  * This function is designed to be called for writing back one inode which
551  * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
552  * and does more profound writeback list handling in writeback_sb_inodes().
553  */
554 static int
555 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
556                        struct writeback_control *wbc)
557 {
558         int ret = 0;
559
560         spin_lock(&inode->i_lock);
561         if (!atomic_read(&inode->i_count))
562                 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
563         else
564                 WARN_ON(inode->i_state & I_WILL_FREE);
565
566         if (inode->i_state & I_SYNC) {
567                 if (wbc->sync_mode != WB_SYNC_ALL)
568                         goto out;
569                 /*
570                  * It's a data-integrity sync. We must wait. Since callers hold
571                  * inode reference or inode has I_WILL_FREE set, it cannot go
572                  * away under us.
573                  */
574                 __inode_wait_for_writeback(inode);
575         }
576         WARN_ON(inode->i_state & I_SYNC);
577         /*
578          * Skip inode if it is clean and we have no outstanding writeback in
579          * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
580          * function since flusher thread may be doing for example sync in
581          * parallel and if we move the inode, it could get skipped. So here we
582          * make sure inode is on some writeback list and leave it there unless
583          * we have completely cleaned the inode.
584          */
585         if (!(inode->i_state & I_DIRTY_ALL) &&
586             (wbc->sync_mode != WB_SYNC_ALL ||
587              !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
588                 goto out;
589         inode->i_state |= I_SYNC;
590         spin_unlock(&inode->i_lock);
591
592         ret = __writeback_single_inode(inode, wbc);
593
594         spin_lock(&wb->list_lock);
595         spin_lock(&inode->i_lock);
596         /*
597          * If inode is clean, remove it from writeback lists. Otherwise don't
598          * touch it. See comment above for explanation.
599          */
600         if (!(inode->i_state & I_DIRTY_ALL))
601                 list_del_init(&inode->i_wb_list);
602         spin_unlock(&wb->list_lock);
603         inode_sync_complete(inode);
604 out:
605         spin_unlock(&inode->i_lock);
606         return ret;
607 }
608
609 static long writeback_chunk_size(struct backing_dev_info *bdi,
610                                  struct wb_writeback_work *work)
611 {
612         long pages;
613
614         /*
615          * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
616          * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
617          * here avoids calling into writeback_inodes_wb() more than once.
618          *
619          * The intended call sequence for WB_SYNC_ALL writeback is:
620          *
621          *      wb_writeback()
622          *          writeback_sb_inodes()       <== called only once
623          *              write_cache_pages()     <== called once for each inode
624          *                   (quickly) tag currently dirty pages
625          *                   (maybe slowly) sync all tagged pages
626          */
627         if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
628                 pages = LONG_MAX;
629         else {
630                 pages = min(bdi->avg_write_bandwidth / 2,
631                             global_dirty_limit / DIRTY_SCOPE);
632                 pages = min(pages, work->nr_pages);
633                 pages = round_down(pages + MIN_WRITEBACK_PAGES,
634                                    MIN_WRITEBACK_PAGES);
635         }
636
637         return pages;
638 }
639
640 /*
641  * Write a portion of b_io inodes which belong to @sb.
642  *
643  * Return the number of pages and/or inodes written.
644  */
645 static long writeback_sb_inodes(struct super_block *sb,
646                                 struct bdi_writeback *wb,
647                                 struct wb_writeback_work *work)
648 {
649         struct writeback_control wbc = {
650                 .sync_mode              = work->sync_mode,
651                 .tagged_writepages      = work->tagged_writepages,
652                 .for_kupdate            = work->for_kupdate,
653                 .for_background         = work->for_background,
654                 .for_sync               = work->for_sync,
655                 .range_cyclic           = work->range_cyclic,
656                 .range_start            = 0,
657                 .range_end              = LLONG_MAX,
658         };
659         unsigned long start_time = jiffies;
660         long write_chunk;
661         long wrote = 0;  /* count both pages and inodes */
662
663         while (!list_empty(&wb->b_io)) {
664                 struct inode *inode = wb_inode(wb->b_io.prev);
665
666                 if (inode->i_sb != sb) {
667                         if (work->sb) {
668                                 /*
669                                  * We only want to write back data for this
670                                  * superblock, move all inodes not belonging
671                                  * to it back onto the dirty list.
672                                  */
673                                 redirty_tail(inode, wb);
674                                 continue;
675                         }
676
677                         /*
678                          * The inode belongs to a different superblock.
679                          * Bounce back to the caller to unpin this and
680                          * pin the next superblock.
681                          */
682                         break;
683                 }
684
685                 /*
686                  * Don't bother with new inodes or inodes being freed, first
687                  * kind does not need periodic writeout yet, and for the latter
688                  * kind writeout is handled by the freer.
689                  */
690                 spin_lock(&inode->i_lock);
691                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
692                         spin_unlock(&inode->i_lock);
693                         redirty_tail(inode, wb);
694                         continue;
695                 }
696                 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
697                         /*
698                          * If this inode is locked for writeback and we are not
699                          * doing writeback-for-data-integrity, move it to
700                          * b_more_io so that writeback can proceed with the
701                          * other inodes on s_io.
702                          *
703                          * We'll have another go at writing back this inode
704                          * when we completed a full scan of b_io.
705                          */
706                         spin_unlock(&inode->i_lock);
707                         requeue_io(inode, wb);
708                         trace_writeback_sb_inodes_requeue(inode);
709                         continue;
710                 }
711                 spin_unlock(&wb->list_lock);
712
713                 /*
714                  * We already requeued the inode if it had I_SYNC set and we
715                  * are doing WB_SYNC_NONE writeback. So this catches only the
716                  * WB_SYNC_ALL case.
717                  */
718                 if (inode->i_state & I_SYNC) {
719                         /* Wait for I_SYNC. This function drops i_lock... */
720                         inode_sleep_on_writeback(inode);
721                         /* Inode may be gone, start again */
722                         spin_lock(&wb->list_lock);
723                         continue;
724                 }
725                 inode->i_state |= I_SYNC;
726                 spin_unlock(&inode->i_lock);
727
728                 write_chunk = writeback_chunk_size(wb->bdi, work);
729                 wbc.nr_to_write = write_chunk;
730                 wbc.pages_skipped = 0;
731
732                 /*
733                  * We use I_SYNC to pin the inode in memory. While it is set
734                  * evict_inode() will wait so the inode cannot be freed.
735                  */
736                 __writeback_single_inode(inode, &wbc);
737
738                 work->nr_pages -= write_chunk - wbc.nr_to_write;
739                 wrote += write_chunk - wbc.nr_to_write;
740                 spin_lock(&wb->list_lock);
741                 spin_lock(&inode->i_lock);
742                 if (!(inode->i_state & I_DIRTY_ALL))
743                         wrote++;
744                 requeue_inode(inode, wb, &wbc);
745                 inode_sync_complete(inode);
746                 spin_unlock(&inode->i_lock);
747                 cond_resched_lock(&wb->list_lock);
748                 /*
749                  * bail out to wb_writeback() often enough to check
750                  * background threshold and other termination conditions.
751                  */
752                 if (wrote) {
753                         if (time_is_before_jiffies(start_time + HZ / 10UL))
754                                 break;
755                         if (work->nr_pages <= 0)
756                                 break;
757                 }
758         }
759         return wrote;
760 }
761
762 static long __writeback_inodes_wb(struct bdi_writeback *wb,
763                                   struct wb_writeback_work *work)
764 {
765         unsigned long start_time = jiffies;
766         long wrote = 0;
767
768         while (!list_empty(&wb->b_io)) {
769                 struct inode *inode = wb_inode(wb->b_io.prev);
770                 struct super_block *sb = inode->i_sb;
771
772                 if (!trylock_super(sb)) {
773                         /*
774                          * trylock_super() may fail consistently due to
775                          * s_umount being grabbed by someone else. Don't use
776                          * requeue_io() to avoid busy retrying the inode/sb.
777                          */
778                         redirty_tail(inode, wb);
779                         continue;
780                 }
781                 wrote += writeback_sb_inodes(sb, wb, work);
782                 up_read(&sb->s_umount);
783
784                 /* refer to the same tests at the end of writeback_sb_inodes */
785                 if (wrote) {
786                         if (time_is_before_jiffies(start_time + HZ / 10UL))
787                                 break;
788                         if (work->nr_pages <= 0)
789                                 break;
790                 }
791         }
792         /* Leave any unwritten inodes on b_io */
793         return wrote;
794 }
795
796 static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
797                                 enum wb_reason reason)
798 {
799         struct wb_writeback_work work = {
800                 .nr_pages       = nr_pages,
801                 .sync_mode      = WB_SYNC_NONE,
802                 .range_cyclic   = 1,
803                 .reason         = reason,
804         };
805
806         spin_lock(&wb->list_lock);
807         if (list_empty(&wb->b_io))
808                 queue_io(wb, &work);
809         __writeback_inodes_wb(wb, &work);
810         spin_unlock(&wb->list_lock);
811
812         return nr_pages - work.nr_pages;
813 }
814
815 static bool over_bground_thresh(struct backing_dev_info *bdi)
816 {
817         unsigned long background_thresh, dirty_thresh;
818
819         global_dirty_limits(&background_thresh, &dirty_thresh);
820
821         if (global_page_state(NR_FILE_DIRTY) +
822             global_page_state(NR_UNSTABLE_NFS) > background_thresh)
823                 return true;
824
825         if (bdi_stat(bdi, BDI_RECLAIMABLE) >
826                                 bdi_dirty_limit(bdi, background_thresh))
827                 return true;
828
829         return false;
830 }
831
832 /*
833  * Called under wb->list_lock. If there are multiple wb per bdi,
834  * only the flusher working on the first wb should do it.
835  */
836 static void wb_update_bandwidth(struct bdi_writeback *wb,
837                                 unsigned long start_time)
838 {
839         __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
840 }
841
842 /*
843  * Explicit flushing or periodic writeback of "old" data.
844  *
845  * Define "old": the first time one of an inode's pages is dirtied, we mark the
846  * dirtying-time in the inode's address_space.  So this periodic writeback code
847  * just walks the superblock inode list, writing back any inodes which are
848  * older than a specific point in time.
849  *
850  * Try to run once per dirty_writeback_interval.  But if a writeback event
851  * takes longer than a dirty_writeback_interval interval, then leave a
852  * one-second gap.
853  *
854  * older_than_this takes precedence over nr_to_write.  So we'll only write back
855  * all dirty pages if they are all attached to "old" mappings.
856  */
857 static long wb_writeback(struct bdi_writeback *wb,
858                          struct wb_writeback_work *work)
859 {
860         unsigned long wb_start = jiffies;
861         long nr_pages = work->nr_pages;
862         unsigned long oldest_jif;
863         struct inode *inode;
864         long progress;
865
866         oldest_jif = jiffies;
867         work->older_than_this = &oldest_jif;
868
869         spin_lock(&wb->list_lock);
870         for (;;) {
871                 /*
872                  * Stop writeback when nr_pages has been consumed
873                  */
874                 if (work->nr_pages <= 0)
875                         break;
876
877                 /*
878                  * Background writeout and kupdate-style writeback may
879                  * run forever. Stop them if there is other work to do
880                  * so that e.g. sync can proceed. They'll be restarted
881                  * after the other works are all done.
882                  */
883                 if ((work->for_background || work->for_kupdate) &&
884                     !list_empty(&wb->bdi->work_list))
885                         break;
886
887                 /*
888                  * For background writeout, stop when we are below the
889                  * background dirty threshold
890                  */
891                 if (work->for_background && !over_bground_thresh(wb->bdi))
892                         break;
893
894                 /*
895                  * Kupdate and background works are special and we want to
896                  * include all inodes that need writing. Livelock avoidance is
897                  * handled by these works yielding to any other work so we are
898                  * safe.
899                  */
900                 if (work->for_kupdate) {
901                         oldest_jif = jiffies -
902                                 msecs_to_jiffies(dirty_expire_interval * 10);
903                 } else if (work->for_background)
904                         oldest_jif = jiffies;
905
906                 trace_writeback_start(wb->bdi, work);
907                 if (list_empty(&wb->b_io))
908                         queue_io(wb, work);
909                 if (work->sb)
910                         progress = writeback_sb_inodes(work->sb, wb, work);
911                 else
912                         progress = __writeback_inodes_wb(wb, work);
913                 trace_writeback_written(wb->bdi, work);
914
915                 wb_update_bandwidth(wb, wb_start);
916
917                 /*
918                  * Did we write something? Try for more
919                  *
920                  * Dirty inodes are moved to b_io for writeback in batches.
921                  * The completion of the current batch does not necessarily
922                  * mean the overall work is done. So we keep looping as long
923                  * as made some progress on cleaning pages or inodes.
924                  */
925                 if (progress)
926                         continue;
927                 /*
928                  * No more inodes for IO, bail
929                  */
930                 if (list_empty(&wb->b_more_io))
931                         break;
932                 /*
933                  * Nothing written. Wait for some inode to
934                  * become available for writeback. Otherwise
935                  * we'll just busyloop.
936                  */
937                 if (!list_empty(&wb->b_more_io))  {
938                         trace_writeback_wait(wb->bdi, work);
939                         inode = wb_inode(wb->b_more_io.prev);
940                         spin_lock(&inode->i_lock);
941                         spin_unlock(&wb->list_lock);
942                         /* This function drops i_lock... */
943                         inode_sleep_on_writeback(inode);
944                         spin_lock(&wb->list_lock);
945                 }
946         }
947         spin_unlock(&wb->list_lock);
948
949         return nr_pages - work->nr_pages;
950 }
951
952 /*
953  * Return the next wb_writeback_work struct that hasn't been processed yet.
954  */
955 static struct wb_writeback_work *
956 get_next_work_item(struct backing_dev_info *bdi)
957 {
958         struct wb_writeback_work *work = NULL;
959
960         spin_lock_bh(&bdi->wb_lock);
961         if (!list_empty(&bdi->work_list)) {
962                 work = list_entry(bdi->work_list.next,
963                                   struct wb_writeback_work, list);
964                 list_del_init(&work->list);
965         }
966         spin_unlock_bh(&bdi->wb_lock);
967         return work;
968 }
969
970 /*
971  * Add in the number of potentially dirty inodes, because each inode
972  * write can dirty pagecache in the underlying blockdev.
973  */
974 static unsigned long get_nr_dirty_pages(void)
975 {
976         return global_page_state(NR_FILE_DIRTY) +
977                 global_page_state(NR_UNSTABLE_NFS) +
978                 get_nr_dirty_inodes();
979 }
980
981 static long wb_check_background_flush(struct bdi_writeback *wb)
982 {
983         if (over_bground_thresh(wb->bdi)) {
984
985                 struct wb_writeback_work work = {
986                         .nr_pages       = LONG_MAX,
987                         .sync_mode      = WB_SYNC_NONE,
988                         .for_background = 1,
989                         .range_cyclic   = 1,
990                         .reason         = WB_REASON_BACKGROUND,
991                 };
992
993                 return wb_writeback(wb, &work);
994         }
995
996         return 0;
997 }
998
999 static long wb_check_old_data_flush(struct bdi_writeback *wb)
1000 {
1001         unsigned long expired;
1002         long nr_pages;
1003
1004         /*
1005          * When set to zero, disable periodic writeback
1006          */
1007         if (!dirty_writeback_interval)
1008                 return 0;
1009
1010         expired = wb->last_old_flush +
1011                         msecs_to_jiffies(dirty_writeback_interval * 10);
1012         if (time_before(jiffies, expired))
1013                 return 0;
1014
1015         wb->last_old_flush = jiffies;
1016         nr_pages = get_nr_dirty_pages();
1017
1018         if (nr_pages) {
1019                 struct wb_writeback_work work = {
1020                         .nr_pages       = nr_pages,
1021                         .sync_mode      = WB_SYNC_NONE,
1022                         .for_kupdate    = 1,
1023                         .range_cyclic   = 1,
1024                         .reason         = WB_REASON_PERIODIC,
1025                 };
1026
1027                 return wb_writeback(wb, &work);
1028         }
1029
1030         return 0;
1031 }
1032
1033 /*
1034  * Retrieve work items and do the writeback they describe
1035  */
1036 static long wb_do_writeback(struct bdi_writeback *wb)
1037 {
1038         struct backing_dev_info *bdi = wb->bdi;
1039         struct wb_writeback_work *work;
1040         long wrote = 0;
1041
1042         set_bit(BDI_writeback_running, &wb->bdi->state);
1043         while ((work = get_next_work_item(bdi)) != NULL) {
1044
1045                 trace_writeback_exec(bdi, work);
1046
1047                 wrote += wb_writeback(wb, work);
1048
1049                 /*
1050                  * Notify the caller of completion if this is a synchronous
1051                  * work item, otherwise just free it.
1052                  */
1053                 if (work->done)
1054                         complete(work->done);
1055                 else
1056                         kfree(work);
1057         }
1058
1059         /*
1060          * Check for periodic writeback, kupdated() style
1061          */
1062         wrote += wb_check_old_data_flush(wb);
1063         wrote += wb_check_background_flush(wb);
1064         clear_bit(BDI_writeback_running, &wb->bdi->state);
1065
1066         return wrote;
1067 }
1068
1069 /*
1070  * Handle writeback of dirty data for the device backed by this bdi. Also
1071  * reschedules periodically and does kupdated style flushing.
1072  */
1073 void bdi_writeback_workfn(struct work_struct *work)
1074 {
1075         struct bdi_writeback *wb = container_of(to_delayed_work(work),
1076                                                 struct bdi_writeback, dwork);
1077         struct backing_dev_info *bdi = wb->bdi;
1078         long pages_written;
1079
1080         set_worker_desc("flush-%s", dev_name(bdi->dev));
1081         current->flags |= PF_SWAPWRITE;
1082
1083         if (likely(!current_is_workqueue_rescuer() ||
1084                    !test_bit(BDI_registered, &bdi->state))) {
1085                 /*
1086                  * The normal path.  Keep writing back @bdi until its
1087                  * work_list is empty.  Note that this path is also taken
1088                  * if @bdi is shutting down even when we're running off the
1089                  * rescuer as work_list needs to be drained.
1090                  */
1091                 do {
1092                         pages_written = wb_do_writeback(wb);
1093                         trace_writeback_pages_written(pages_written);
1094                 } while (!list_empty(&bdi->work_list));
1095         } else {
1096                 /*
1097                  * bdi_wq can't get enough workers and we're running off
1098                  * the emergency worker.  Don't hog it.  Hopefully, 1024 is
1099                  * enough for efficient IO.
1100                  */
1101                 pages_written = writeback_inodes_wb(&bdi->wb, 1024,
1102                                                     WB_REASON_FORKER_THREAD);
1103                 trace_writeback_pages_written(pages_written);
1104         }
1105
1106         if (!list_empty(&bdi->work_list))
1107                 mod_delayed_work(bdi_wq, &wb->dwork, 0);
1108         else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1109                 bdi_wakeup_thread_delayed(bdi);
1110
1111         current->flags &= ~PF_SWAPWRITE;
1112 }
1113
1114 /*
1115  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
1116  * the whole world.
1117  */
1118 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1119 {
1120         struct backing_dev_info *bdi;
1121
1122         if (!nr_pages)
1123                 nr_pages = get_nr_dirty_pages();
1124
1125         rcu_read_lock();
1126         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1127                 if (!bdi_has_dirty_io(bdi))
1128                         continue;
1129                 __bdi_start_writeback(bdi, nr_pages, false, reason);
1130         }
1131         rcu_read_unlock();
1132 }
1133
1134 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1135 {
1136         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1137                 struct dentry *dentry;
1138                 const char *name = "?";
1139
1140                 dentry = d_find_alias(inode);
1141                 if (dentry) {
1142                         spin_lock(&dentry->d_lock);
1143                         name = (const char *) dentry->d_name.name;
1144                 }
1145                 printk(KERN_DEBUG
1146                        "%s(%d): dirtied inode %lu (%s) on %s\n",
1147                        current->comm, task_pid_nr(current), inode->i_ino,
1148                        name, inode->i_sb->s_id);
1149                 if (dentry) {
1150                         spin_unlock(&dentry->d_lock);
1151                         dput(dentry);
1152                 }
1153         }
1154 }
1155
1156 /**
1157  *      __mark_inode_dirty -    internal function
1158  *      @inode: inode to mark
1159  *      @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1160  *      Mark an inode as dirty. Callers should use mark_inode_dirty or
1161  *      mark_inode_dirty_sync.
1162  *
1163  * Put the inode on the super block's dirty list.
1164  *
1165  * CAREFUL! We mark it dirty unconditionally, but move it onto the
1166  * dirty list only if it is hashed or if it refers to a blockdev.
1167  * If it was not hashed, it will never be added to the dirty list
1168  * even if it is later hashed, as it will have been marked dirty already.
1169  *
1170  * In short, make sure you hash any inodes _before_ you start marking
1171  * them dirty.
1172  *
1173  * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1174  * the block-special inode (/dev/hda1) itself.  And the ->dirtied_when field of
1175  * the kernel-internal blockdev inode represents the dirtying time of the
1176  * blockdev's pages.  This is why for I_DIRTY_PAGES we always use
1177  * page->mapping->host, so the page-dirtying time is recorded in the internal
1178  * blockdev inode.
1179  */
1180 #define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
1181 void __mark_inode_dirty(struct inode *inode, int flags)
1182 {
1183         struct super_block *sb = inode->i_sb;
1184         struct backing_dev_info *bdi = NULL;
1185         int dirtytime;
1186
1187         trace_writeback_mark_inode_dirty(inode, flags);
1188
1189         /*
1190          * Don't do this for I_DIRTY_PAGES - that doesn't actually
1191          * dirty the inode itself
1192          */
1193         if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_TIME)) {
1194                 trace_writeback_dirty_inode_start(inode, flags);
1195
1196                 if (sb->s_op->dirty_inode)
1197                         sb->s_op->dirty_inode(inode, flags);
1198
1199                 trace_writeback_dirty_inode(inode, flags);
1200         }
1201         if (flags & I_DIRTY_INODE)
1202                 flags &= ~I_DIRTY_TIME;
1203         dirtytime = flags & I_DIRTY_TIME;
1204
1205         /*
1206          * Paired with smp_mb() in __writeback_single_inode() for the
1207          * following lockless i_state test.  See there for details.
1208          */
1209         smp_mb();
1210
1211         if (((inode->i_state & flags) == flags) ||
1212             (dirtytime && (inode->i_state & I_DIRTY_INODE)))
1213                 return;
1214
1215         if (unlikely(block_dump))
1216                 block_dump___mark_inode_dirty(inode);
1217
1218         spin_lock(&inode->i_lock);
1219         if (dirtytime && (inode->i_state & I_DIRTY_INODE))
1220                 goto out_unlock_inode;
1221         if ((inode->i_state & flags) != flags) {
1222                 const int was_dirty = inode->i_state & I_DIRTY;
1223
1224                 if (flags & I_DIRTY_INODE)
1225                         inode->i_state &= ~I_DIRTY_TIME;
1226                 inode->i_state |= flags;
1227
1228                 /*
1229                  * If the inode is being synced, just update its dirty state.
1230                  * The unlocker will place the inode on the appropriate
1231                  * superblock list, based upon its state.
1232                  */
1233                 if (inode->i_state & I_SYNC)
1234                         goto out_unlock_inode;
1235
1236                 /*
1237                  * Only add valid (hashed) inodes to the superblock's
1238                  * dirty list.  Add blockdev inodes as well.
1239                  */
1240                 if (!S_ISBLK(inode->i_mode)) {
1241                         if (inode_unhashed(inode))
1242                                 goto out_unlock_inode;
1243                 }
1244                 if (inode->i_state & I_FREEING)
1245                         goto out_unlock_inode;
1246
1247                 /*
1248                  * If the inode was already on b_dirty/b_io/b_more_io, don't
1249                  * reposition it (that would break b_dirty time-ordering).
1250                  */
1251                 if (!was_dirty) {
1252                         bool wakeup_bdi = false;
1253                         bdi = inode_to_bdi(inode);
1254
1255                         spin_unlock(&inode->i_lock);
1256                         spin_lock(&bdi->wb.list_lock);
1257                         if (bdi_cap_writeback_dirty(bdi)) {
1258                                 WARN(!test_bit(BDI_registered, &bdi->state),
1259                                      "bdi-%s not registered\n", bdi->name);
1260
1261                                 /*
1262                                  * If this is the first dirty inode for this
1263                                  * bdi, we have to wake-up the corresponding
1264                                  * bdi thread to make sure background
1265                                  * write-back happens later.
1266                                  */
1267                                 if (!wb_has_dirty_io(&bdi->wb))
1268                                         wakeup_bdi = true;
1269                         }
1270
1271                         inode->dirtied_when = jiffies;
1272                         list_move(&inode->i_wb_list, dirtytime ?
1273                                   &bdi->wb.b_dirty_time : &bdi->wb.b_dirty);
1274                         spin_unlock(&bdi->wb.list_lock);
1275                         trace_writeback_dirty_inode_enqueue(inode);
1276
1277                         if (wakeup_bdi)
1278                                 bdi_wakeup_thread_delayed(bdi);
1279                         return;
1280                 }
1281         }
1282 out_unlock_inode:
1283         spin_unlock(&inode->i_lock);
1284
1285 }
1286 EXPORT_SYMBOL(__mark_inode_dirty);
1287
1288 static void wait_sb_inodes(struct super_block *sb)
1289 {
1290         struct inode *inode, *old_inode = NULL;
1291
1292         /*
1293          * We need to be protected against the filesystem going from
1294          * r/o to r/w or vice versa.
1295          */
1296         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1297
1298         spin_lock(&inode_sb_list_lock);
1299
1300         /*
1301          * Data integrity sync. Must wait for all pages under writeback,
1302          * because there may have been pages dirtied before our sync
1303          * call, but which had writeout started before we write it out.
1304          * In which case, the inode may not be on the dirty list, but
1305          * we still have to wait for that writeout.
1306          */
1307         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1308                 struct address_space *mapping = inode->i_mapping;
1309
1310                 spin_lock(&inode->i_lock);
1311                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1312                     (mapping->nrpages == 0)) {
1313                         spin_unlock(&inode->i_lock);
1314                         continue;
1315                 }
1316                 __iget(inode);
1317                 spin_unlock(&inode->i_lock);
1318                 spin_unlock(&inode_sb_list_lock);
1319
1320                 /*
1321                  * We hold a reference to 'inode' so it couldn't have been
1322                  * removed from s_inodes list while we dropped the
1323                  * inode_sb_list_lock.  We cannot iput the inode now as we can
1324                  * be holding the last reference and we cannot iput it under
1325                  * inode_sb_list_lock. So we keep the reference and iput it
1326                  * later.
1327                  */
1328                 iput(old_inode);
1329                 old_inode = inode;
1330
1331                 filemap_fdatawait(mapping);
1332
1333                 cond_resched();
1334
1335                 spin_lock(&inode_sb_list_lock);
1336         }
1337         spin_unlock(&inode_sb_list_lock);
1338         iput(old_inode);
1339 }
1340
1341 /**
1342  * writeback_inodes_sb_nr -     writeback dirty inodes from given super_block
1343  * @sb: the superblock
1344  * @nr: the number of pages to write
1345  * @reason: reason why some writeback work initiated
1346  *
1347  * Start writeback on some inodes on this super_block. No guarantees are made
1348  * on how many (if any) will be written, and this function does not wait
1349  * for IO completion of submitted IO.
1350  */
1351 void writeback_inodes_sb_nr(struct super_block *sb,
1352                             unsigned long nr,
1353                             enum wb_reason reason)
1354 {
1355         DECLARE_COMPLETION_ONSTACK(done);
1356         struct wb_writeback_work work = {
1357                 .sb                     = sb,
1358                 .sync_mode              = WB_SYNC_NONE,
1359                 .tagged_writepages      = 1,
1360                 .done                   = &done,
1361                 .nr_pages               = nr,
1362                 .reason                 = reason,
1363         };
1364
1365         if (sb->s_bdi == &noop_backing_dev_info)
1366                 return;
1367         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1368         bdi_queue_work(sb->s_bdi, &work);
1369         wait_for_completion(&done);
1370 }
1371 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1372
1373 /**
1374  * writeback_inodes_sb  -       writeback dirty inodes from given super_block
1375  * @sb: the superblock
1376  * @reason: reason why some writeback work was initiated
1377  *
1378  * Start writeback on some inodes on this super_block. No guarantees are made
1379  * on how many (if any) will be written, and this function does not wait
1380  * for IO completion of submitted IO.
1381  */
1382 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1383 {
1384         return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1385 }
1386 EXPORT_SYMBOL(writeback_inodes_sb);
1387
1388 /**
1389  * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
1390  * @sb: the superblock
1391  * @nr: the number of pages to write
1392  * @reason: the reason of writeback
1393  *
1394  * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
1395  * Returns 1 if writeback was started, 0 if not.
1396  */
1397 int try_to_writeback_inodes_sb_nr(struct super_block *sb,
1398                                   unsigned long nr,
1399                                   enum wb_reason reason)
1400 {
1401         if (writeback_in_progress(sb->s_bdi))
1402                 return 1;
1403
1404         if (!down_read_trylock(&sb->s_umount))
1405                 return 0;
1406
1407         writeback_inodes_sb_nr(sb, nr, reason);
1408         up_read(&sb->s_umount);
1409         return 1;
1410 }
1411 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
1412
1413 /**
1414  * try_to_writeback_inodes_sb - try to start writeback if none underway
1415  * @sb: the superblock
1416  * @reason: reason why some writeback work was initiated
1417  *
1418  * Implement by try_to_writeback_inodes_sb_nr()
1419  * Returns 1 if writeback was started, 0 if not.
1420  */
1421 int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1422 {
1423         return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1424 }
1425 EXPORT_SYMBOL(try_to_writeback_inodes_sb);
1426
1427 /**
1428  * sync_inodes_sb       -       sync sb inode pages
1429  * @sb: the superblock
1430  *
1431  * This function writes and waits on any dirty inode belonging to this
1432  * super_block.
1433  */
1434 void sync_inodes_sb(struct super_block *sb)
1435 {
1436         DECLARE_COMPLETION_ONSTACK(done);
1437         struct wb_writeback_work work = {
1438                 .sb             = sb,
1439                 .sync_mode      = WB_SYNC_ALL,
1440                 .nr_pages       = LONG_MAX,
1441                 .range_cyclic   = 0,
1442                 .done           = &done,
1443                 .reason         = WB_REASON_SYNC,
1444                 .for_sync       = 1,
1445         };
1446
1447         /* Nothing to do? */
1448         if (sb->s_bdi == &noop_backing_dev_info)
1449                 return;
1450         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1451
1452         bdi_queue_work(sb->s_bdi, &work);
1453         wait_for_completion(&done);
1454
1455         wait_sb_inodes(sb);
1456 }
1457 EXPORT_SYMBOL(sync_inodes_sb);
1458
1459 /**
1460  * write_inode_now      -       write an inode to disk
1461  * @inode: inode to write to disk
1462  * @sync: whether the write should be synchronous or not
1463  *
1464  * This function commits an inode to disk immediately if it is dirty. This is
1465  * primarily needed by knfsd.
1466  *
1467  * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1468  */
1469 int write_inode_now(struct inode *inode, int sync)
1470 {
1471         struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1472         struct writeback_control wbc = {
1473                 .nr_to_write = LONG_MAX,
1474                 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1475                 .range_start = 0,
1476                 .range_end = LLONG_MAX,
1477         };
1478
1479         if (!mapping_cap_writeback_dirty(inode->i_mapping))
1480                 wbc.nr_to_write = 0;
1481
1482         might_sleep();
1483         return writeback_single_inode(inode, wb, &wbc);
1484 }
1485 EXPORT_SYMBOL(write_inode_now);
1486
1487 /**
1488  * sync_inode - write an inode and its pages to disk.
1489  * @inode: the inode to sync
1490  * @wbc: controls the writeback mode
1491  *
1492  * sync_inode() will write an inode and its pages to disk.  It will also
1493  * correctly update the inode on its superblock's dirty inode lists and will
1494  * update inode->i_state.
1495  *
1496  * The caller must have a ref on the inode.
1497  */
1498 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1499 {
1500         return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1501 }
1502 EXPORT_SYMBOL(sync_inode);
1503
1504 /**
1505  * sync_inode_metadata - write an inode to disk
1506  * @inode: the inode to sync
1507  * @wait: wait for I/O to complete.
1508  *
1509  * Write an inode to disk and adjust its dirty state after completion.
1510  *
1511  * Note: only writes the actual inode, no associated data or other metadata.
1512  */
1513 int sync_inode_metadata(struct inode *inode, int wait)
1514 {
1515         struct writeback_control wbc = {
1516                 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1517                 .nr_to_write = 0, /* metadata-only */
1518         };
1519
1520         return sync_inode(inode, &wbc);
1521 }
1522 EXPORT_SYMBOL(sync_inode_metadata);