be3efc4f64f4b8c556e1d6de5c2ff400f05731ab
[linux-3.10.git] / fs / fs-writeback.c
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/freezer.h>
26 #include <linux/writeback.h>
27 #include <linux/blkdev.h>
28 #include <linux/backing-dev.h>
29 #include <linux/tracepoint.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         enum wb_reason reason;          /* why was writeback initiated? */
50
51         struct list_head list;          /* pending work list */
52         struct completion *done;        /* set if the caller waits */
53 };
54
55 /**
56  * writeback_in_progress - determine whether there is writeback in progress
57  * @bdi: the device's backing_dev_info structure.
58  *
59  * Determine whether there is writeback waiting to be handled against a
60  * backing device.
61  */
62 int writeback_in_progress(struct backing_dev_info *bdi)
63 {
64         return test_bit(BDI_writeback_running, &bdi->state);
65 }
66
67 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
68 {
69         struct super_block *sb = inode->i_sb;
70
71         if (strcmp(sb->s_type->name, "bdev") == 0)
72                 return inode->i_mapping->backing_dev_info;
73
74         return sb->s_bdi;
75 }
76
77 static inline struct inode *wb_inode(struct list_head *head)
78 {
79         return list_entry(head, struct inode, i_wb_list);
80 }
81
82 /*
83  * Include the creation of the trace points after defining the
84  * wb_writeback_work structure and inline functions so that the definition
85  * remains local to this file.
86  */
87 #define CREATE_TRACE_POINTS
88 #include <trace/events/writeback.h>
89
90 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
91 static void bdi_wakeup_flusher(struct backing_dev_info *bdi)
92 {
93         if (bdi->wb.task) {
94                 wake_up_process(bdi->wb.task);
95         } else {
96                 /*
97                  * The bdi thread isn't there, wake up the forker thread which
98                  * will create and run it.
99                  */
100                 wake_up_process(default_backing_dev_info.wb.task);
101         }
102 }
103
104 static void bdi_queue_work(struct backing_dev_info *bdi,
105                            struct wb_writeback_work *work)
106 {
107         trace_writeback_queue(bdi, work);
108
109         spin_lock_bh(&bdi->wb_lock);
110         list_add_tail(&work->list, &bdi->work_list);
111         if (!bdi->wb.task)
112                 trace_writeback_nothread(bdi, work);
113         bdi_wakeup_flusher(bdi);
114         spin_unlock_bh(&bdi->wb_lock);
115 }
116
117 static void
118 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
119                       bool range_cyclic, enum wb_reason reason)
120 {
121         struct wb_writeback_work *work;
122
123         /*
124          * This is WB_SYNC_NONE writeback, so if allocation fails just
125          * wakeup the thread for old dirty data writeback
126          */
127         work = kzalloc(sizeof(*work), GFP_ATOMIC);
128         if (!work) {
129                 if (bdi->wb.task) {
130                         trace_writeback_nowork(bdi);
131                         wake_up_process(bdi->wb.task);
132                 }
133                 return;
134         }
135
136         work->sync_mode = WB_SYNC_NONE;
137         work->nr_pages  = nr_pages;
138         work->range_cyclic = range_cyclic;
139         work->reason    = reason;
140
141         bdi_queue_work(bdi, work);
142 }
143
144 /**
145  * bdi_start_writeback - start writeback
146  * @bdi: the backing device to write from
147  * @nr_pages: the number of pages to write
148  * @reason: reason why some writeback work was initiated
149  *
150  * Description:
151  *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
152  *   started when this function returns, we make no guarantees on
153  *   completion. Caller need not hold sb s_umount semaphore.
154  *
155  */
156 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
157                         enum wb_reason reason)
158 {
159         __bdi_start_writeback(bdi, nr_pages, true, reason);
160 }
161
162 /**
163  * bdi_start_background_writeback - start background writeback
164  * @bdi: the backing device to write from
165  *
166  * Description:
167  *   This makes sure WB_SYNC_NONE background writeback happens. When
168  *   this function returns, it is only guaranteed that for given BDI
169  *   some IO is happening if we are over background dirty threshold.
170  *   Caller need not hold sb s_umount semaphore.
171  */
172 void bdi_start_background_writeback(struct backing_dev_info *bdi)
173 {
174         /*
175          * We just wake up the flusher thread. It will perform background
176          * writeback as soon as there is no other work to do.
177          */
178         trace_writeback_wake_background(bdi);
179         spin_lock_bh(&bdi->wb_lock);
180         bdi_wakeup_flusher(bdi);
181         spin_unlock_bh(&bdi->wb_lock);
182 }
183
184 /*
185  * Remove the inode from the writeback list it is on.
186  */
187 void inode_wb_list_del(struct inode *inode)
188 {
189         struct backing_dev_info *bdi = inode_to_bdi(inode);
190
191         spin_lock(&bdi->wb.list_lock);
192         list_del_init(&inode->i_wb_list);
193         spin_unlock(&bdi->wb.list_lock);
194 }
195
196 /*
197  * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
198  * furthest end of its superblock's dirty-inode list.
199  *
200  * Before stamping the inode's ->dirtied_when, we check to see whether it is
201  * already the most-recently-dirtied inode on the b_dirty list.  If that is
202  * the case then the inode must have been redirtied while it was being written
203  * out and we don't reset its dirtied_when.
204  */
205 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
206 {
207         assert_spin_locked(&wb->list_lock);
208         if (!list_empty(&wb->b_dirty)) {
209                 struct inode *tail;
210
211                 tail = wb_inode(wb->b_dirty.next);
212                 if (time_before(inode->dirtied_when, tail->dirtied_when))
213                         inode->dirtied_when = jiffies;
214         }
215         list_move(&inode->i_wb_list, &wb->b_dirty);
216 }
217
218 /*
219  * requeue inode for re-scanning after bdi->b_io list is exhausted.
220  */
221 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
222 {
223         assert_spin_locked(&wb->list_lock);
224         list_move(&inode->i_wb_list, &wb->b_more_io);
225 }
226
227 static void inode_sync_complete(struct inode *inode)
228 {
229         inode->i_state &= ~I_SYNC;
230         /* Waiters must see I_SYNC cleared before being woken up */
231         smp_mb();
232         wake_up_bit(&inode->i_state, __I_SYNC);
233 }
234
235 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
236 {
237         bool ret = time_after(inode->dirtied_when, t);
238 #ifndef CONFIG_64BIT
239         /*
240          * For inodes being constantly redirtied, dirtied_when can get stuck.
241          * It _appears_ to be in the future, but is actually in distant past.
242          * This test is necessary to prevent such wrapped-around relative times
243          * from permanently stopping the whole bdi writeback.
244          */
245         ret = ret && time_before_eq(inode->dirtied_when, jiffies);
246 #endif
247         return ret;
248 }
249
250 /*
251  * Move expired (dirtied after work->older_than_this) dirty inodes from
252  * @delaying_queue to @dispatch_queue.
253  */
254 static int move_expired_inodes(struct list_head *delaying_queue,
255                                struct list_head *dispatch_queue,
256                                struct wb_writeback_work *work)
257 {
258         LIST_HEAD(tmp);
259         struct list_head *pos, *node;
260         struct super_block *sb = NULL;
261         struct inode *inode;
262         int do_sb_sort = 0;
263         int moved = 0;
264
265         while (!list_empty(delaying_queue)) {
266                 inode = wb_inode(delaying_queue->prev);
267                 if (work->older_than_this &&
268                     inode_dirtied_after(inode, *work->older_than_this))
269                         break;
270                 if (sb && sb != inode->i_sb)
271                         do_sb_sort = 1;
272                 sb = inode->i_sb;
273                 list_move(&inode->i_wb_list, &tmp);
274                 moved++;
275         }
276
277         /* just one sb in list, splice to dispatch_queue and we're done */
278         if (!do_sb_sort) {
279                 list_splice(&tmp, dispatch_queue);
280                 goto out;
281         }
282
283         /* Move inodes from one superblock together */
284         while (!list_empty(&tmp)) {
285                 sb = wb_inode(tmp.prev)->i_sb;
286                 list_for_each_prev_safe(pos, node, &tmp) {
287                         inode = wb_inode(pos);
288                         if (inode->i_sb == sb)
289                                 list_move(&inode->i_wb_list, dispatch_queue);
290                 }
291         }
292 out:
293         return moved;
294 }
295
296 /*
297  * Queue all expired dirty inodes for io, eldest first.
298  * Before
299  *         newly dirtied     b_dirty    b_io    b_more_io
300  *         =============>    gf         edc     BA
301  * After
302  *         newly dirtied     b_dirty    b_io    b_more_io
303  *         =============>    g          fBAedc
304  *                                           |
305  *                                           +--> dequeue for IO
306  */
307 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
308 {
309         int moved;
310         assert_spin_locked(&wb->list_lock);
311         list_splice_init(&wb->b_more_io, &wb->b_io);
312         moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
313         trace_writeback_queue_io(wb, work, moved);
314 }
315
316 static int write_inode(struct inode *inode, struct writeback_control *wbc)
317 {
318         if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
319                 return inode->i_sb->s_op->write_inode(inode, wbc);
320         return 0;
321 }
322
323 /*
324  * Wait for writeback on an inode to complete. Called with i_lock held.
325  * Caller must make sure inode cannot go away when we drop i_lock.
326  */
327 static void __inode_wait_for_writeback(struct inode *inode)
328         __releases(inode->i_lock)
329         __acquires(inode->i_lock)
330 {
331         DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
332         wait_queue_head_t *wqh;
333
334         wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
335         while (inode->i_state & I_SYNC) {
336                 spin_unlock(&inode->i_lock);
337                 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
338                 spin_lock(&inode->i_lock);
339         }
340 }
341
342 /*
343  * Wait for writeback on an inode to complete. Caller must have inode pinned.
344  */
345 void inode_wait_for_writeback(struct inode *inode)
346 {
347         spin_lock(&inode->i_lock);
348         __inode_wait_for_writeback(inode);
349         spin_unlock(&inode->i_lock);
350 }
351
352 /*
353  * Sleep until I_SYNC is cleared. This function must be called with i_lock
354  * held and drops it. It is aimed for callers not holding any inode reference
355  * so once i_lock is dropped, inode can go away.
356  */
357 static void inode_sleep_on_writeback(struct inode *inode)
358         __releases(inode->i_lock)
359 {
360         DEFINE_WAIT(wait);
361         wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
362         int sleep;
363
364         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
365         sleep = inode->i_state & I_SYNC;
366         spin_unlock(&inode->i_lock);
367         if (sleep)
368                 schedule();
369         finish_wait(wqh, &wait);
370 }
371
372 /*
373  * Find proper writeback list for the inode depending on its current state and
374  * possibly also change of its state while we were doing writeback.  Here we
375  * handle things such as livelock prevention or fairness of writeback among
376  * inodes. This function can be called only by flusher thread - noone else
377  * processes all inodes in writeback lists and requeueing inodes behind flusher
378  * thread's back can have unexpected consequences.
379  */
380 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
381                           struct writeback_control *wbc)
382 {
383         if (inode->i_state & I_FREEING)
384                 return;
385
386         /*
387          * Sync livelock prevention. Each inode is tagged and synced in one
388          * shot. If still dirty, it will be redirty_tail()'ed below.  Update
389          * the dirty time to prevent enqueue and sync it again.
390          */
391         if ((inode->i_state & I_DIRTY) &&
392             (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
393                 inode->dirtied_when = jiffies;
394
395         if (wbc->pages_skipped) {
396                 /*
397                  * writeback is not making progress due to locked
398                  * buffers. Skip this inode for now.
399                  */
400                 redirty_tail(inode, wb);
401                 return;
402         }
403
404         if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
405                 /*
406                  * We didn't write back all the pages.  nfs_writepages()
407                  * sometimes bales out without doing anything.
408                  */
409                 if (wbc->nr_to_write <= 0) {
410                         /* Slice used up. Queue for next turn. */
411                         requeue_io(inode, wb);
412                 } else {
413                         /*
414                          * Writeback blocked by something other than
415                          * congestion. Delay the inode for some time to
416                          * avoid spinning on the CPU (100% iowait)
417                          * retrying writeback of the dirty page/inode
418                          * that cannot be performed immediately.
419                          */
420                         redirty_tail(inode, wb);
421                 }
422         } else if (inode->i_state & I_DIRTY) {
423                 /*
424                  * Filesystems can dirty the inode during writeback operations,
425                  * such as delayed allocation during submission or metadata
426                  * updates after data IO completion.
427                  */
428                 redirty_tail(inode, wb);
429         } else {
430                 /* The inode is clean. Remove from writeback lists. */
431                 list_del_init(&inode->i_wb_list);
432         }
433 }
434
435 /*
436  * Write out an inode and its dirty pages. Do not update the writeback list
437  * linkage. That is left to the caller. The caller is also responsible for
438  * setting I_SYNC flag and calling inode_sync_complete() to clear it.
439  */
440 static int
441 __writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
442                          struct writeback_control *wbc)
443 {
444         struct address_space *mapping = inode->i_mapping;
445         long nr_to_write = wbc->nr_to_write;
446         unsigned dirty;
447         int ret;
448
449         WARN_ON(!(inode->i_state & I_SYNC));
450
451         ret = do_writepages(mapping, wbc);
452
453         /*
454          * Make sure to wait on the data before writing out the metadata.
455          * This is important for filesystems that modify metadata on data
456          * I/O completion.
457          */
458         if (wbc->sync_mode == WB_SYNC_ALL) {
459                 int err = filemap_fdatawait(mapping);
460                 if (ret == 0)
461                         ret = err;
462         }
463
464         /*
465          * Some filesystems may redirty the inode during the writeback
466          * due to delalloc, clear dirty metadata flags right before
467          * write_inode()
468          */
469         spin_lock(&inode->i_lock);
470         /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
471         if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
472                 inode->i_state &= ~I_DIRTY_PAGES;
473         dirty = inode->i_state & I_DIRTY;
474         inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
475         spin_unlock(&inode->i_lock);
476         /* Don't write the inode if only I_DIRTY_PAGES was set */
477         if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
478                 int err = write_inode(inode, wbc);
479                 if (ret == 0)
480                         ret = err;
481         }
482         trace_writeback_single_inode(inode, wbc, nr_to_write);
483         return ret;
484 }
485
486 /*
487  * Write out an inode's dirty pages. Either the caller has an active reference
488  * on the inode or the inode has I_WILL_FREE set.
489  *
490  * This function is designed to be called for writing back one inode which
491  * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
492  * and does more profound writeback list handling in writeback_sb_inodes().
493  */
494 static int
495 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
496                        struct writeback_control *wbc)
497 {
498         int ret = 0;
499
500         spin_lock(&inode->i_lock);
501         if (!atomic_read(&inode->i_count))
502                 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
503         else
504                 WARN_ON(inode->i_state & I_WILL_FREE);
505
506         if (inode->i_state & I_SYNC) {
507                 if (wbc->sync_mode != WB_SYNC_ALL)
508                         goto out;
509                 /*
510                  * It's a data-integrity sync. We must wait. Since callers hold
511                  * inode reference or inode has I_WILL_FREE set, it cannot go
512                  * away under us.
513                  */
514                 __inode_wait_for_writeback(inode);
515         }
516         WARN_ON(inode->i_state & I_SYNC);
517         /*
518          * Skip inode if it is clean. We don't want to mess with writeback
519          * lists in this function since flusher thread may be doing for example
520          * sync in parallel and if we move the inode, it could get skipped. So
521          * here we make sure inode is on some writeback list and leave it there
522          * unless we have completely cleaned the inode.
523          */
524         if (!(inode->i_state & I_DIRTY))
525                 goto out;
526         inode->i_state |= I_SYNC;
527         spin_unlock(&inode->i_lock);
528
529         ret = __writeback_single_inode(inode, wb, wbc);
530
531         spin_lock(&wb->list_lock);
532         spin_lock(&inode->i_lock);
533         /*
534          * If inode is clean, remove it from writeback lists. Otherwise don't
535          * touch it. See comment above for explanation.
536          */
537         if (!(inode->i_state & I_DIRTY))
538                 list_del_init(&inode->i_wb_list);
539         spin_unlock(&wb->list_lock);
540         inode_sync_complete(inode);
541 out:
542         spin_unlock(&inode->i_lock);
543         return ret;
544 }
545
546 static long writeback_chunk_size(struct backing_dev_info *bdi,
547                                  struct wb_writeback_work *work)
548 {
549         long pages;
550
551         /*
552          * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
553          * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
554          * here avoids calling into writeback_inodes_wb() more than once.
555          *
556          * The intended call sequence for WB_SYNC_ALL writeback is:
557          *
558          *      wb_writeback()
559          *          writeback_sb_inodes()       <== called only once
560          *              write_cache_pages()     <== called once for each inode
561          *                   (quickly) tag currently dirty pages
562          *                   (maybe slowly) sync all tagged pages
563          */
564         if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
565                 pages = LONG_MAX;
566         else {
567                 pages = min(bdi->avg_write_bandwidth / 2,
568                             global_dirty_limit / DIRTY_SCOPE);
569                 pages = min(pages, work->nr_pages);
570                 pages = round_down(pages + MIN_WRITEBACK_PAGES,
571                                    MIN_WRITEBACK_PAGES);
572         }
573
574         return pages;
575 }
576
577 /*
578  * Write a portion of b_io inodes which belong to @sb.
579  *
580  * If @only_this_sb is true, then find and write all such
581  * inodes. Otherwise write only ones which go sequentially
582  * in reverse order.
583  *
584  * Return the number of pages and/or inodes written.
585  */
586 static long writeback_sb_inodes(struct super_block *sb,
587                                 struct bdi_writeback *wb,
588                                 struct wb_writeback_work *work)
589 {
590         struct writeback_control wbc = {
591                 .sync_mode              = work->sync_mode,
592                 .tagged_writepages      = work->tagged_writepages,
593                 .for_kupdate            = work->for_kupdate,
594                 .for_background         = work->for_background,
595                 .range_cyclic           = work->range_cyclic,
596                 .range_start            = 0,
597                 .range_end              = LLONG_MAX,
598         };
599         unsigned long start_time = jiffies;
600         long write_chunk;
601         long wrote = 0;  /* count both pages and inodes */
602
603         while (!list_empty(&wb->b_io)) {
604                 struct inode *inode = wb_inode(wb->b_io.prev);
605
606                 if (inode->i_sb != sb) {
607                         if (work->sb) {
608                                 /*
609                                  * We only want to write back data for this
610                                  * superblock, move all inodes not belonging
611                                  * to it back onto the dirty list.
612                                  */
613                                 redirty_tail(inode, wb);
614                                 continue;
615                         }
616
617                         /*
618                          * The inode belongs to a different superblock.
619                          * Bounce back to the caller to unpin this and
620                          * pin the next superblock.
621                          */
622                         break;
623                 }
624
625                 /*
626                  * Don't bother with new inodes or inodes being freed, first
627                  * kind does not need periodic writeout yet, and for the latter
628                  * kind writeout is handled by the freer.
629                  */
630                 spin_lock(&inode->i_lock);
631                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
632                         spin_unlock(&inode->i_lock);
633                         redirty_tail(inode, wb);
634                         continue;
635                 }
636                 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
637                         /*
638                          * If this inode is locked for writeback and we are not
639                          * doing writeback-for-data-integrity, move it to
640                          * b_more_io so that writeback can proceed with the
641                          * other inodes on s_io.
642                          *
643                          * We'll have another go at writing back this inode
644                          * when we completed a full scan of b_io.
645                          */
646                         spin_unlock(&inode->i_lock);
647                         requeue_io(inode, wb);
648                         trace_writeback_sb_inodes_requeue(inode);
649                         continue;
650                 }
651                 spin_unlock(&wb->list_lock);
652
653                 /*
654                  * We already requeued the inode if it had I_SYNC set and we
655                  * are doing WB_SYNC_NONE writeback. So this catches only the
656                  * WB_SYNC_ALL case.
657                  */
658                 if (inode->i_state & I_SYNC) {
659                         /* Wait for I_SYNC. This function drops i_lock... */
660                         inode_sleep_on_writeback(inode);
661                         /* Inode may be gone, start again */
662                         spin_lock(&wb->list_lock);
663                         continue;
664                 }
665                 inode->i_state |= I_SYNC;
666                 spin_unlock(&inode->i_lock);
667
668                 write_chunk = writeback_chunk_size(wb->bdi, work);
669                 wbc.nr_to_write = write_chunk;
670                 wbc.pages_skipped = 0;
671
672                 /*
673                  * We use I_SYNC to pin the inode in memory. While it is set
674                  * evict_inode() will wait so the inode cannot be freed.
675                  */
676                 __writeback_single_inode(inode, wb, &wbc);
677
678                 work->nr_pages -= write_chunk - wbc.nr_to_write;
679                 wrote += write_chunk - wbc.nr_to_write;
680                 spin_lock(&wb->list_lock);
681                 spin_lock(&inode->i_lock);
682                 if (!(inode->i_state & I_DIRTY))
683                         wrote++;
684                 requeue_inode(inode, wb, &wbc);
685                 inode_sync_complete(inode);
686                 spin_unlock(&inode->i_lock);
687                 cond_resched_lock(&wb->list_lock);
688                 /*
689                  * bail out to wb_writeback() often enough to check
690                  * background threshold and other termination conditions.
691                  */
692                 if (wrote) {
693                         if (time_is_before_jiffies(start_time + HZ / 10UL))
694                                 break;
695                         if (work->nr_pages <= 0)
696                                 break;
697                 }
698         }
699         return wrote;
700 }
701
702 static long __writeback_inodes_wb(struct bdi_writeback *wb,
703                                   struct wb_writeback_work *work)
704 {
705         unsigned long start_time = jiffies;
706         long wrote = 0;
707
708         while (!list_empty(&wb->b_io)) {
709                 struct inode *inode = wb_inode(wb->b_io.prev);
710                 struct super_block *sb = inode->i_sb;
711
712                 if (!grab_super_passive(sb)) {
713                         /*
714                          * grab_super_passive() may fail consistently due to
715                          * s_umount being grabbed by someone else. Don't use
716                          * requeue_io() to avoid busy retrying the inode/sb.
717                          */
718                         redirty_tail(inode, wb);
719                         continue;
720                 }
721                 wrote += writeback_sb_inodes(sb, wb, work);
722                 drop_super(sb);
723
724                 /* refer to the same tests at the end of writeback_sb_inodes */
725                 if (wrote) {
726                         if (time_is_before_jiffies(start_time + HZ / 10UL))
727                                 break;
728                         if (work->nr_pages <= 0)
729                                 break;
730                 }
731         }
732         /* Leave any unwritten inodes on b_io */
733         return wrote;
734 }
735
736 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
737                                 enum wb_reason reason)
738 {
739         struct wb_writeback_work work = {
740                 .nr_pages       = nr_pages,
741                 .sync_mode      = WB_SYNC_NONE,
742                 .range_cyclic   = 1,
743                 .reason         = reason,
744         };
745
746         spin_lock(&wb->list_lock);
747         if (list_empty(&wb->b_io))
748                 queue_io(wb, &work);
749         __writeback_inodes_wb(wb, &work);
750         spin_unlock(&wb->list_lock);
751
752         return nr_pages - work.nr_pages;
753 }
754
755 static bool over_bground_thresh(struct backing_dev_info *bdi)
756 {
757         unsigned long background_thresh, dirty_thresh;
758
759         global_dirty_limits(&background_thresh, &dirty_thresh);
760
761         if (global_page_state(NR_FILE_DIRTY) +
762             global_page_state(NR_UNSTABLE_NFS) > background_thresh)
763                 return true;
764
765         if (bdi_stat(bdi, BDI_RECLAIMABLE) >
766                                 bdi_dirty_limit(bdi, background_thresh))
767                 return true;
768
769         return false;
770 }
771
772 /*
773  * Called under wb->list_lock. If there are multiple wb per bdi,
774  * only the flusher working on the first wb should do it.
775  */
776 static void wb_update_bandwidth(struct bdi_writeback *wb,
777                                 unsigned long start_time)
778 {
779         __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
780 }
781
782 /*
783  * Explicit flushing or periodic writeback of "old" data.
784  *
785  * Define "old": the first time one of an inode's pages is dirtied, we mark the
786  * dirtying-time in the inode's address_space.  So this periodic writeback code
787  * just walks the superblock inode list, writing back any inodes which are
788  * older than a specific point in time.
789  *
790  * Try to run once per dirty_writeback_interval.  But if a writeback event
791  * takes longer than a dirty_writeback_interval interval, then leave a
792  * one-second gap.
793  *
794  * older_than_this takes precedence over nr_to_write.  So we'll only write back
795  * all dirty pages if they are all attached to "old" mappings.
796  */
797 static long wb_writeback(struct bdi_writeback *wb,
798                          struct wb_writeback_work *work)
799 {
800         unsigned long wb_start = jiffies;
801         long nr_pages = work->nr_pages;
802         unsigned long oldest_jif;
803         struct inode *inode;
804         long progress;
805
806         oldest_jif = jiffies;
807         work->older_than_this = &oldest_jif;
808
809         spin_lock(&wb->list_lock);
810         for (;;) {
811                 /*
812                  * Stop writeback when nr_pages has been consumed
813                  */
814                 if (work->nr_pages <= 0)
815                         break;
816
817                 /*
818                  * Background writeout and kupdate-style writeback may
819                  * run forever. Stop them if there is other work to do
820                  * so that e.g. sync can proceed. They'll be restarted
821                  * after the other works are all done.
822                  */
823                 if ((work->for_background || work->for_kupdate) &&
824                     !list_empty(&wb->bdi->work_list))
825                         break;
826
827                 /*
828                  * For background writeout, stop when we are below the
829                  * background dirty threshold
830                  */
831                 if (work->for_background && !over_bground_thresh(wb->bdi))
832                         break;
833
834                 /*
835                  * Kupdate and background works are special and we want to
836                  * include all inodes that need writing. Livelock avoidance is
837                  * handled by these works yielding to any other work so we are
838                  * safe.
839                  */
840                 if (work->for_kupdate) {
841                         oldest_jif = jiffies -
842                                 msecs_to_jiffies(dirty_expire_interval * 10);
843                 } else if (work->for_background)
844                         oldest_jif = jiffies;
845
846                 trace_writeback_start(wb->bdi, work);
847                 if (list_empty(&wb->b_io))
848                         queue_io(wb, work);
849                 if (work->sb)
850                         progress = writeback_sb_inodes(work->sb, wb, work);
851                 else
852                         progress = __writeback_inodes_wb(wb, work);
853                 trace_writeback_written(wb->bdi, work);
854
855                 wb_update_bandwidth(wb, wb_start);
856
857                 /*
858                  * Did we write something? Try for more
859                  *
860                  * Dirty inodes are moved to b_io for writeback in batches.
861                  * The completion of the current batch does not necessarily
862                  * mean the overall work is done. So we keep looping as long
863                  * as made some progress on cleaning pages or inodes.
864                  */
865                 if (progress)
866                         continue;
867                 /*
868                  * No more inodes for IO, bail
869                  */
870                 if (list_empty(&wb->b_more_io))
871                         break;
872                 /*
873                  * Nothing written. Wait for some inode to
874                  * become available for writeback. Otherwise
875                  * we'll just busyloop.
876                  */
877                 if (!list_empty(&wb->b_more_io))  {
878                         trace_writeback_wait(wb->bdi, work);
879                         inode = wb_inode(wb->b_more_io.prev);
880                         spin_lock(&inode->i_lock);
881                         spin_unlock(&wb->list_lock);
882                         /* This function drops i_lock... */
883                         inode_sleep_on_writeback(inode);
884                         spin_lock(&wb->list_lock);
885                 }
886         }
887         spin_unlock(&wb->list_lock);
888
889         return nr_pages - work->nr_pages;
890 }
891
892 /*
893  * Return the next wb_writeback_work struct that hasn't been processed yet.
894  */
895 static struct wb_writeback_work *
896 get_next_work_item(struct backing_dev_info *bdi)
897 {
898         struct wb_writeback_work *work = NULL;
899
900         spin_lock_bh(&bdi->wb_lock);
901         if (!list_empty(&bdi->work_list)) {
902                 work = list_entry(bdi->work_list.next,
903                                   struct wb_writeback_work, list);
904                 list_del_init(&work->list);
905         }
906         spin_unlock_bh(&bdi->wb_lock);
907         return work;
908 }
909
910 /*
911  * Add in the number of potentially dirty inodes, because each inode
912  * write can dirty pagecache in the underlying blockdev.
913  */
914 static unsigned long get_nr_dirty_pages(void)
915 {
916         return global_page_state(NR_FILE_DIRTY) +
917                 global_page_state(NR_UNSTABLE_NFS) +
918                 get_nr_dirty_inodes();
919 }
920
921 static long wb_check_background_flush(struct bdi_writeback *wb)
922 {
923         if (over_bground_thresh(wb->bdi)) {
924
925                 struct wb_writeback_work work = {
926                         .nr_pages       = LONG_MAX,
927                         .sync_mode      = WB_SYNC_NONE,
928                         .for_background = 1,
929                         .range_cyclic   = 1,
930                         .reason         = WB_REASON_BACKGROUND,
931                 };
932
933                 return wb_writeback(wb, &work);
934         }
935
936         return 0;
937 }
938
939 static long wb_check_old_data_flush(struct bdi_writeback *wb)
940 {
941         unsigned long expired;
942         long nr_pages;
943
944         /*
945          * When set to zero, disable periodic writeback
946          */
947         if (!dirty_writeback_interval)
948                 return 0;
949
950         expired = wb->last_old_flush +
951                         msecs_to_jiffies(dirty_writeback_interval * 10);
952         if (time_before(jiffies, expired))
953                 return 0;
954
955         wb->last_old_flush = jiffies;
956         nr_pages = get_nr_dirty_pages();
957
958         if (nr_pages) {
959                 struct wb_writeback_work work = {
960                         .nr_pages       = nr_pages,
961                         .sync_mode      = WB_SYNC_NONE,
962                         .for_kupdate    = 1,
963                         .range_cyclic   = 1,
964                         .reason         = WB_REASON_PERIODIC,
965                 };
966
967                 return wb_writeback(wb, &work);
968         }
969
970         return 0;
971 }
972
973 /*
974  * Retrieve work items and do the writeback they describe
975  */
976 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
977 {
978         struct backing_dev_info *bdi = wb->bdi;
979         struct wb_writeback_work *work;
980         long wrote = 0;
981
982         set_bit(BDI_writeback_running, &wb->bdi->state);
983         while ((work = get_next_work_item(bdi)) != NULL) {
984                 /*
985                  * Override sync mode, in case we must wait for completion
986                  * because this thread is exiting now.
987                  */
988                 if (force_wait)
989                         work->sync_mode = WB_SYNC_ALL;
990
991                 trace_writeback_exec(bdi, work);
992
993                 wrote += wb_writeback(wb, work);
994
995                 /*
996                  * Notify the caller of completion if this is a synchronous
997                  * work item, otherwise just free it.
998                  */
999                 if (work->done)
1000                         complete(work->done);
1001                 else
1002                         kfree(work);
1003         }
1004
1005         /*
1006          * Check for periodic writeback, kupdated() style
1007          */
1008         wrote += wb_check_old_data_flush(wb);
1009         wrote += wb_check_background_flush(wb);
1010         clear_bit(BDI_writeback_running, &wb->bdi->state);
1011
1012         return wrote;
1013 }
1014
1015 /*
1016  * Handle writeback of dirty data for the device backed by this bdi. Also
1017  * wakes up periodically and does kupdated style flushing.
1018  */
1019 int bdi_writeback_thread(void *data)
1020 {
1021         struct bdi_writeback *wb = data;
1022         struct backing_dev_info *bdi = wb->bdi;
1023         long pages_written;
1024
1025         current->flags |= PF_SWAPWRITE;
1026         set_freezable();
1027         wb->last_active = jiffies;
1028
1029         /*
1030          * Our parent may run at a different priority, just set us to normal
1031          */
1032         set_user_nice(current, 0);
1033
1034         trace_writeback_thread_start(bdi);
1035
1036         while (!kthread_freezable_should_stop(NULL)) {
1037                 /*
1038                  * Remove own delayed wake-up timer, since we are already awake
1039                  * and we'll take care of the preriodic write-back.
1040                  */
1041                 del_timer(&wb->wakeup_timer);
1042
1043                 pages_written = wb_do_writeback(wb, 0);
1044
1045                 trace_writeback_pages_written(pages_written);
1046
1047                 if (pages_written)
1048                         wb->last_active = jiffies;
1049
1050                 set_current_state(TASK_INTERRUPTIBLE);
1051                 if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
1052                         __set_current_state(TASK_RUNNING);
1053                         continue;
1054                 }
1055
1056                 if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1057                         schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
1058                 else {
1059                         /*
1060                          * We have nothing to do, so can go sleep without any
1061                          * timeout and save power. When a work is queued or
1062                          * something is made dirty - we will be woken up.
1063                          */
1064                         schedule();
1065                 }
1066         }
1067
1068         /* Flush any work that raced with us exiting */
1069         if (!list_empty(&bdi->work_list))
1070                 wb_do_writeback(wb, 1);
1071
1072         trace_writeback_thread_stop(bdi);
1073         return 0;
1074 }
1075
1076
1077 /*
1078  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
1079  * the whole world.
1080  */
1081 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1082 {
1083         struct backing_dev_info *bdi;
1084
1085         if (!nr_pages) {
1086                 nr_pages = global_page_state(NR_FILE_DIRTY) +
1087                                 global_page_state(NR_UNSTABLE_NFS);
1088         }
1089
1090         rcu_read_lock();
1091         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1092                 if (!bdi_has_dirty_io(bdi))
1093                         continue;
1094                 __bdi_start_writeback(bdi, nr_pages, false, reason);
1095         }
1096         rcu_read_unlock();
1097 }
1098
1099 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1100 {
1101         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1102                 struct dentry *dentry;
1103                 const char *name = "?";
1104
1105                 dentry = d_find_alias(inode);
1106                 if (dentry) {
1107                         spin_lock(&dentry->d_lock);
1108                         name = (const char *) dentry->d_name.name;
1109                 }
1110                 printk(KERN_DEBUG
1111                        "%s(%d): dirtied inode %lu (%s) on %s\n",
1112                        current->comm, task_pid_nr(current), inode->i_ino,
1113                        name, inode->i_sb->s_id);
1114                 if (dentry) {
1115                         spin_unlock(&dentry->d_lock);
1116                         dput(dentry);
1117                 }
1118         }
1119 }
1120
1121 /**
1122  *      __mark_inode_dirty -    internal function
1123  *      @inode: inode to mark
1124  *      @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1125  *      Mark an inode as dirty. Callers should use mark_inode_dirty or
1126  *      mark_inode_dirty_sync.
1127  *
1128  * Put the inode on the super block's dirty list.
1129  *
1130  * CAREFUL! We mark it dirty unconditionally, but move it onto the
1131  * dirty list only if it is hashed or if it refers to a blockdev.
1132  * If it was not hashed, it will never be added to the dirty list
1133  * even if it is later hashed, as it will have been marked dirty already.
1134  *
1135  * In short, make sure you hash any inodes _before_ you start marking
1136  * them dirty.
1137  *
1138  * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1139  * the block-special inode (/dev/hda1) itself.  And the ->dirtied_when field of
1140  * the kernel-internal blockdev inode represents the dirtying time of the
1141  * blockdev's pages.  This is why for I_DIRTY_PAGES we always use
1142  * page->mapping->host, so the page-dirtying time is recorded in the internal
1143  * blockdev inode.
1144  */
1145 void __mark_inode_dirty(struct inode *inode, int flags)
1146 {
1147         struct super_block *sb = inode->i_sb;
1148         struct backing_dev_info *bdi = NULL;
1149
1150         /*
1151          * Don't do this for I_DIRTY_PAGES - that doesn't actually
1152          * dirty the inode itself
1153          */
1154         if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1155                 if (sb->s_op->dirty_inode)
1156                         sb->s_op->dirty_inode(inode, flags);
1157         }
1158
1159         /*
1160          * make sure that changes are seen by all cpus before we test i_state
1161          * -- mikulas
1162          */
1163         smp_mb();
1164
1165         /* avoid the locking if we can */
1166         if ((inode->i_state & flags) == flags)
1167                 return;
1168
1169         if (unlikely(block_dump))
1170                 block_dump___mark_inode_dirty(inode);
1171
1172         spin_lock(&inode->i_lock);
1173         if ((inode->i_state & flags) != flags) {
1174                 const int was_dirty = inode->i_state & I_DIRTY;
1175
1176                 inode->i_state |= flags;
1177
1178                 /*
1179                  * If the inode is being synced, just update its dirty state.
1180                  * The unlocker will place the inode on the appropriate
1181                  * superblock list, based upon its state.
1182                  */
1183                 if (inode->i_state & I_SYNC)
1184                         goto out_unlock_inode;
1185
1186                 /*
1187                  * Only add valid (hashed) inodes to the superblock's
1188                  * dirty list.  Add blockdev inodes as well.
1189                  */
1190                 if (!S_ISBLK(inode->i_mode)) {
1191                         if (inode_unhashed(inode))
1192                                 goto out_unlock_inode;
1193                 }
1194                 if (inode->i_state & I_FREEING)
1195                         goto out_unlock_inode;
1196
1197                 /*
1198                  * If the inode was already on b_dirty/b_io/b_more_io, don't
1199                  * reposition it (that would break b_dirty time-ordering).
1200                  */
1201                 if (!was_dirty) {
1202                         bool wakeup_bdi = false;
1203                         bdi = inode_to_bdi(inode);
1204
1205                         if (bdi_cap_writeback_dirty(bdi)) {
1206                                 WARN(!test_bit(BDI_registered, &bdi->state),
1207                                      "bdi-%s not registered\n", bdi->name);
1208
1209                                 /*
1210                                  * If this is the first dirty inode for this
1211                                  * bdi, we have to wake-up the corresponding
1212                                  * bdi thread to make sure background
1213                                  * write-back happens later.
1214                                  */
1215                                 if (!wb_has_dirty_io(&bdi->wb))
1216                                         wakeup_bdi = true;
1217                         }
1218
1219                         spin_unlock(&inode->i_lock);
1220                         spin_lock(&bdi->wb.list_lock);
1221                         inode->dirtied_when = jiffies;
1222                         list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1223                         spin_unlock(&bdi->wb.list_lock);
1224
1225                         if (wakeup_bdi)
1226                                 bdi_wakeup_thread_delayed(bdi);
1227                         return;
1228                 }
1229         }
1230 out_unlock_inode:
1231         spin_unlock(&inode->i_lock);
1232
1233 }
1234 EXPORT_SYMBOL(__mark_inode_dirty);
1235
1236 static void wait_sb_inodes(struct super_block *sb)
1237 {
1238         struct inode *inode, *old_inode = NULL;
1239
1240         /*
1241          * We need to be protected against the filesystem going from
1242          * r/o to r/w or vice versa.
1243          */
1244         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1245
1246         spin_lock(&inode_sb_list_lock);
1247
1248         /*
1249          * Data integrity sync. Must wait for all pages under writeback,
1250          * because there may have been pages dirtied before our sync
1251          * call, but which had writeout started before we write it out.
1252          * In which case, the inode may not be on the dirty list, but
1253          * we still have to wait for that writeout.
1254          */
1255         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1256                 struct address_space *mapping = inode->i_mapping;
1257
1258                 spin_lock(&inode->i_lock);
1259                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1260                     (mapping->nrpages == 0)) {
1261                         spin_unlock(&inode->i_lock);
1262                         continue;
1263                 }
1264                 __iget(inode);
1265                 spin_unlock(&inode->i_lock);
1266                 spin_unlock(&inode_sb_list_lock);
1267
1268                 /*
1269                  * We hold a reference to 'inode' so it couldn't have been
1270                  * removed from s_inodes list while we dropped the
1271                  * inode_sb_list_lock.  We cannot iput the inode now as we can
1272                  * be holding the last reference and we cannot iput it under
1273                  * inode_sb_list_lock. So we keep the reference and iput it
1274                  * later.
1275                  */
1276                 iput(old_inode);
1277                 old_inode = inode;
1278
1279                 filemap_fdatawait(mapping);
1280
1281                 cond_resched();
1282
1283                 spin_lock(&inode_sb_list_lock);
1284         }
1285         spin_unlock(&inode_sb_list_lock);
1286         iput(old_inode);
1287 }
1288
1289 /**
1290  * writeback_inodes_sb_nr -     writeback dirty inodes from given super_block
1291  * @sb: the superblock
1292  * @nr: the number of pages to write
1293  * @reason: reason why some writeback work initiated
1294  *
1295  * Start writeback on some inodes on this super_block. No guarantees are made
1296  * on how many (if any) will be written, and this function does not wait
1297  * for IO completion of submitted IO.
1298  */
1299 void writeback_inodes_sb_nr(struct super_block *sb,
1300                             unsigned long nr,
1301                             enum wb_reason reason)
1302 {
1303         DECLARE_COMPLETION_ONSTACK(done);
1304         struct wb_writeback_work work = {
1305                 .sb                     = sb,
1306                 .sync_mode              = WB_SYNC_NONE,
1307                 .tagged_writepages      = 1,
1308                 .done                   = &done,
1309                 .nr_pages               = nr,
1310                 .reason                 = reason,
1311         };
1312
1313         if (sb->s_bdi == &noop_backing_dev_info)
1314                 return;
1315         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1316         bdi_queue_work(sb->s_bdi, &work);
1317         wait_for_completion(&done);
1318 }
1319 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1320
1321 /**
1322  * writeback_inodes_sb  -       writeback dirty inodes from given super_block
1323  * @sb: the superblock
1324  * @reason: reason why some writeback work was initiated
1325  *
1326  * Start writeback on some inodes on this super_block. No guarantees are made
1327  * on how many (if any) will be written, and this function does not wait
1328  * for IO completion of submitted IO.
1329  */
1330 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1331 {
1332         return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1333 }
1334 EXPORT_SYMBOL(writeback_inodes_sb);
1335
1336 /**
1337  * writeback_inodes_sb_if_idle  -       start writeback if none underway
1338  * @sb: the superblock
1339  * @reason: reason why some writeback work was initiated
1340  *
1341  * Invoke writeback_inodes_sb if no writeback is currently underway.
1342  * Returns 1 if writeback was started, 0 if not.
1343  */
1344 int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
1345 {
1346         if (!writeback_in_progress(sb->s_bdi)) {
1347                 down_read(&sb->s_umount);
1348                 writeback_inodes_sb(sb, reason);
1349                 up_read(&sb->s_umount);
1350                 return 1;
1351         } else
1352                 return 0;
1353 }
1354 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1355
1356 /**
1357  * writeback_inodes_sb_nr_if_idle       -       start writeback if none underway
1358  * @sb: the superblock
1359  * @nr: the number of pages to write
1360  * @reason: reason why some writeback work was initiated
1361  *
1362  * Invoke writeback_inodes_sb if no writeback is currently underway.
1363  * Returns 1 if writeback was started, 0 if not.
1364  */
1365 int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
1366                                    unsigned long nr,
1367                                    enum wb_reason reason)
1368 {
1369         if (!writeback_in_progress(sb->s_bdi)) {
1370                 down_read(&sb->s_umount);
1371                 writeback_inodes_sb_nr(sb, nr, reason);
1372                 up_read(&sb->s_umount);
1373                 return 1;
1374         } else
1375                 return 0;
1376 }
1377 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
1378
1379 /**
1380  * sync_inodes_sb       -       sync sb inode pages
1381  * @sb: the superblock
1382  *
1383  * This function writes and waits on any dirty inode belonging to this
1384  * super_block.
1385  */
1386 void sync_inodes_sb(struct super_block *sb)
1387 {
1388         DECLARE_COMPLETION_ONSTACK(done);
1389         struct wb_writeback_work work = {
1390                 .sb             = sb,
1391                 .sync_mode      = WB_SYNC_ALL,
1392                 .nr_pages       = LONG_MAX,
1393                 .range_cyclic   = 0,
1394                 .done           = &done,
1395                 .reason         = WB_REASON_SYNC,
1396         };
1397
1398         /* Nothing to do? */
1399         if (sb->s_bdi == &noop_backing_dev_info)
1400                 return;
1401         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1402
1403         bdi_queue_work(sb->s_bdi, &work);
1404         wait_for_completion(&done);
1405
1406         wait_sb_inodes(sb);
1407 }
1408 EXPORT_SYMBOL(sync_inodes_sb);
1409
1410 /**
1411  * write_inode_now      -       write an inode to disk
1412  * @inode: inode to write to disk
1413  * @sync: whether the write should be synchronous or not
1414  *
1415  * This function commits an inode to disk immediately if it is dirty. This is
1416  * primarily needed by knfsd.
1417  *
1418  * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1419  */
1420 int write_inode_now(struct inode *inode, int sync)
1421 {
1422         struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1423         struct writeback_control wbc = {
1424                 .nr_to_write = LONG_MAX,
1425                 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1426                 .range_start = 0,
1427                 .range_end = LLONG_MAX,
1428         };
1429
1430         if (!mapping_cap_writeback_dirty(inode->i_mapping))
1431                 wbc.nr_to_write = 0;
1432
1433         might_sleep();
1434         return writeback_single_inode(inode, wb, &wbc);
1435 }
1436 EXPORT_SYMBOL(write_inode_now);
1437
1438 /**
1439  * sync_inode - write an inode and its pages to disk.
1440  * @inode: the inode to sync
1441  * @wbc: controls the writeback mode
1442  *
1443  * sync_inode() will write an inode and its pages to disk.  It will also
1444  * correctly update the inode on its superblock's dirty inode lists and will
1445  * update inode->i_state.
1446  *
1447  * The caller must have a ref on the inode.
1448  */
1449 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1450 {
1451         return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1452 }
1453 EXPORT_SYMBOL(sync_inode);
1454
1455 /**
1456  * sync_inode_metadata - write an inode to disk
1457  * @inode: the inode to sync
1458  * @wait: wait for I/O to complete.
1459  *
1460  * Write an inode to disk and adjust its dirty state after completion.
1461  *
1462  * Note: only writes the actual inode, no associated data or other metadata.
1463  */
1464 int sync_inode_metadata(struct inode *inode, int wait)
1465 {
1466         struct writeback_control wbc = {
1467                 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1468                 .nr_to_write = 0, /* metadata-only */
1469         };
1470
1471         return sync_inode(inode, &wbc);
1472 }
1473 EXPORT_SYMBOL(sync_inode_metadata);