8e1d7b9e4a33afcf166eb77fcd5d387ad792e639
[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 EXPORT_SYMBOL(writeback_in_progress);
67
68 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
69 {
70         struct super_block *sb = inode->i_sb;
71
72         if (strcmp(sb->s_type->name, "bdev") == 0)
73                 return inode->i_mapping->backing_dev_info;
74
75         return sb->s_bdi;
76 }
77
78 static inline struct inode *wb_inode(struct list_head *head)
79 {
80         return list_entry(head, struct inode, i_wb_list);
81 }
82
83 /*
84  * Include the creation of the trace points after defining the
85  * wb_writeback_work structure and inline functions so that the definition
86  * remains local to this file.
87  */
88 #define CREATE_TRACE_POINTS
89 #include <trace/events/writeback.h>
90
91 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
92 static void bdi_wakeup_flusher(struct backing_dev_info *bdi)
93 {
94         if (bdi->wb.task) {
95                 wake_up_process(bdi->wb.task);
96         } else {
97                 /*
98                  * The bdi thread isn't there, wake up the forker thread which
99                  * will create and run it.
100                  */
101                 wake_up_process(default_backing_dev_info.wb.task);
102         }
103 }
104
105 static void bdi_queue_work(struct backing_dev_info *bdi,
106                            struct wb_writeback_work *work)
107 {
108         trace_writeback_queue(bdi, work);
109
110         spin_lock_bh(&bdi->wb_lock);
111         list_add_tail(&work->list, &bdi->work_list);
112         if (!bdi->wb.task)
113                 trace_writeback_nothread(bdi, work);
114         bdi_wakeup_flusher(bdi);
115         spin_unlock_bh(&bdi->wb_lock);
116 }
117
118 static void
119 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
120                       bool range_cyclic, enum wb_reason reason)
121 {
122         struct wb_writeback_work *work;
123
124         /*
125          * This is WB_SYNC_NONE writeback, so if allocation fails just
126          * wakeup the thread for old dirty data writeback
127          */
128         work = kzalloc(sizeof(*work), GFP_ATOMIC);
129         if (!work) {
130                 if (bdi->wb.task) {
131                         trace_writeback_nowork(bdi);
132                         wake_up_process(bdi->wb.task);
133                 }
134                 return;
135         }
136
137         work->sync_mode = WB_SYNC_NONE;
138         work->nr_pages  = nr_pages;
139         work->range_cyclic = range_cyclic;
140         work->reason    = reason;
141
142         bdi_queue_work(bdi, work);
143 }
144
145 /**
146  * bdi_start_writeback - start writeback
147  * @bdi: the backing device to write from
148  * @nr_pages: the number of pages to write
149  * @reason: reason why some writeback work was initiated
150  *
151  * Description:
152  *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
153  *   started when this function returns, we make no guarantees on
154  *   completion. Caller need not hold sb s_umount semaphore.
155  *
156  */
157 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
158                         enum wb_reason reason)
159 {
160         __bdi_start_writeback(bdi, nr_pages, true, reason);
161 }
162
163 /**
164  * bdi_start_background_writeback - start background writeback
165  * @bdi: the backing device to write from
166  *
167  * Description:
168  *   This makes sure WB_SYNC_NONE background writeback happens. When
169  *   this function returns, it is only guaranteed that for given BDI
170  *   some IO is happening if we are over background dirty threshold.
171  *   Caller need not hold sb s_umount semaphore.
172  */
173 void bdi_start_background_writeback(struct backing_dev_info *bdi)
174 {
175         /*
176          * We just wake up the flusher thread. It will perform background
177          * writeback as soon as there is no other work to do.
178          */
179         trace_writeback_wake_background(bdi);
180         spin_lock_bh(&bdi->wb_lock);
181         bdi_wakeup_flusher(bdi);
182         spin_unlock_bh(&bdi->wb_lock);
183 }
184
185 /*
186  * Remove the inode from the writeback list it is on.
187  */
188 void inode_wb_list_del(struct inode *inode)
189 {
190         struct backing_dev_info *bdi = inode_to_bdi(inode);
191
192         spin_lock(&bdi->wb.list_lock);
193         list_del_init(&inode->i_wb_list);
194         spin_unlock(&bdi->wb.list_lock);
195 }
196
197 /*
198  * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
199  * furthest end of its superblock's dirty-inode list.
200  *
201  * Before stamping the inode's ->dirtied_when, we check to see whether it is
202  * already the most-recently-dirtied inode on the b_dirty list.  If that is
203  * the case then the inode must have been redirtied while it was being written
204  * out and we don't reset its dirtied_when.
205  */
206 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
207 {
208         assert_spin_locked(&wb->list_lock);
209         if (!list_empty(&wb->b_dirty)) {
210                 struct inode *tail;
211
212                 tail = wb_inode(wb->b_dirty.next);
213                 if (time_before(inode->dirtied_when, tail->dirtied_when))
214                         inode->dirtied_when = jiffies;
215         }
216         list_move(&inode->i_wb_list, &wb->b_dirty);
217 }
218
219 /*
220  * requeue inode for re-scanning after bdi->b_io list is exhausted.
221  */
222 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
223 {
224         assert_spin_locked(&wb->list_lock);
225         list_move(&inode->i_wb_list, &wb->b_more_io);
226 }
227
228 static void inode_sync_complete(struct inode *inode)
229 {
230         inode->i_state &= ~I_SYNC;
231         /* Waiters must see I_SYNC cleared before being woken up */
232         smp_mb();
233         wake_up_bit(&inode->i_state, __I_SYNC);
234 }
235
236 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
237 {
238         bool ret = time_after(inode->dirtied_when, t);
239 #ifndef CONFIG_64BIT
240         /*
241          * For inodes being constantly redirtied, dirtied_when can get stuck.
242          * It _appears_ to be in the future, but is actually in distant past.
243          * This test is necessary to prevent such wrapped-around relative times
244          * from permanently stopping the whole bdi writeback.
245          */
246         ret = ret && time_before_eq(inode->dirtied_when, jiffies);
247 #endif
248         return ret;
249 }
250
251 /*
252  * Move expired (dirtied after work->older_than_this) dirty inodes from
253  * @delaying_queue to @dispatch_queue.
254  */
255 static int move_expired_inodes(struct list_head *delaying_queue,
256                                struct list_head *dispatch_queue,
257                                struct wb_writeback_work *work)
258 {
259         LIST_HEAD(tmp);
260         struct list_head *pos, *node;
261         struct super_block *sb = NULL;
262         struct inode *inode;
263         int do_sb_sort = 0;
264         int moved = 0;
265
266         while (!list_empty(delaying_queue)) {
267                 inode = wb_inode(delaying_queue->prev);
268                 if (work->older_than_this &&
269                     inode_dirtied_after(inode, *work->older_than_this))
270                         break;
271                 if (sb && sb != inode->i_sb)
272                         do_sb_sort = 1;
273                 sb = inode->i_sb;
274                 list_move(&inode->i_wb_list, &tmp);
275                 moved++;
276         }
277
278         /* just one sb in list, splice to dispatch_queue and we're done */
279         if (!do_sb_sort) {
280                 list_splice(&tmp, dispatch_queue);
281                 goto out;
282         }
283
284         /* Move inodes from one superblock together */
285         while (!list_empty(&tmp)) {
286                 sb = wb_inode(tmp.prev)->i_sb;
287                 list_for_each_prev_safe(pos, node, &tmp) {
288                         inode = wb_inode(pos);
289                         if (inode->i_sb == sb)
290                                 list_move(&inode->i_wb_list, dispatch_queue);
291                 }
292         }
293 out:
294         return moved;
295 }
296
297 /*
298  * Queue all expired dirty inodes for io, eldest first.
299  * Before
300  *         newly dirtied     b_dirty    b_io    b_more_io
301  *         =============>    gf         edc     BA
302  * After
303  *         newly dirtied     b_dirty    b_io    b_more_io
304  *         =============>    g          fBAedc
305  *                                           |
306  *                                           +--> dequeue for IO
307  */
308 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
309 {
310         int moved;
311         assert_spin_locked(&wb->list_lock);
312         list_splice_init(&wb->b_more_io, &wb->b_io);
313         moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
314         trace_writeback_queue_io(wb, work, moved);
315 }
316
317 static int write_inode(struct inode *inode, struct writeback_control *wbc)
318 {
319         if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
320                 return inode->i_sb->s_op->write_inode(inode, wbc);
321         return 0;
322 }
323
324 /*
325  * Wait for writeback on an inode to complete. Called with i_lock held.
326  * Caller must make sure inode cannot go away when we drop i_lock.
327  */
328 static void __inode_wait_for_writeback(struct inode *inode)
329         __releases(inode->i_lock)
330         __acquires(inode->i_lock)
331 {
332         DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
333         wait_queue_head_t *wqh;
334
335         wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
336         while (inode->i_state & I_SYNC) {
337                 spin_unlock(&inode->i_lock);
338                 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
339                 spin_lock(&inode->i_lock);
340         }
341 }
342
343 /*
344  * Wait for writeback on an inode to complete. Caller must have inode pinned.
345  */
346 void inode_wait_for_writeback(struct inode *inode)
347 {
348         spin_lock(&inode->i_lock);
349         __inode_wait_for_writeback(inode);
350         spin_unlock(&inode->i_lock);
351 }
352
353 /*
354  * Sleep until I_SYNC is cleared. This function must be called with i_lock
355  * held and drops it. It is aimed for callers not holding any inode reference
356  * so once i_lock is dropped, inode can go away.
357  */
358 static void inode_sleep_on_writeback(struct inode *inode)
359         __releases(inode->i_lock)
360 {
361         DEFINE_WAIT(wait);
362         wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
363         int sleep;
364
365         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
366         sleep = inode->i_state & I_SYNC;
367         spin_unlock(&inode->i_lock);
368         if (sleep)
369                 schedule();
370         finish_wait(wqh, &wait);
371 }
372
373 /*
374  * Find proper writeback list for the inode depending on its current state and
375  * possibly also change of its state while we were doing writeback.  Here we
376  * handle things such as livelock prevention or fairness of writeback among
377  * inodes. This function can be called only by flusher thread - noone else
378  * processes all inodes in writeback lists and requeueing inodes behind flusher
379  * thread's back can have unexpected consequences.
380  */
381 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
382                           struct writeback_control *wbc)
383 {
384         if (inode->i_state & I_FREEING)
385                 return;
386
387         /*
388          * Sync livelock prevention. Each inode is tagged and synced in one
389          * shot. If still dirty, it will be redirty_tail()'ed below.  Update
390          * the dirty time to prevent enqueue and sync it again.
391          */
392         if ((inode->i_state & I_DIRTY) &&
393             (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
394                 inode->dirtied_when = jiffies;
395
396         if (wbc->pages_skipped) {
397                 /*
398                  * writeback is not making progress due to locked
399                  * buffers. Skip this inode for now.
400                  */
401                 redirty_tail(inode, wb);
402                 return;
403         }
404
405         if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
406                 /*
407                  * We didn't write back all the pages.  nfs_writepages()
408                  * sometimes bales out without doing anything.
409                  */
410                 if (wbc->nr_to_write <= 0) {
411                         /* Slice used up. Queue for next turn. */
412                         requeue_io(inode, wb);
413                 } else {
414                         /*
415                          * Writeback blocked by something other than
416                          * congestion. Delay the inode for some time to
417                          * avoid spinning on the CPU (100% iowait)
418                          * retrying writeback of the dirty page/inode
419                          * that cannot be performed immediately.
420                          */
421                         redirty_tail(inode, wb);
422                 }
423         } else if (inode->i_state & I_DIRTY) {
424                 /*
425                  * Filesystems can dirty the inode during writeback operations,
426                  * such as delayed allocation during submission or metadata
427                  * updates after data IO completion.
428                  */
429                 redirty_tail(inode, wb);
430         } else {
431                 /* The inode is clean. Remove from writeback lists. */
432                 list_del_init(&inode->i_wb_list);
433         }
434 }
435
436 /*
437  * Write out an inode and its dirty pages. Do not update the writeback list
438  * linkage. That is left to the caller. The caller is also responsible for
439  * setting I_SYNC flag and calling inode_sync_complete() to clear it.
440  */
441 static int
442 __writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
443                          struct writeback_control *wbc)
444 {
445         struct address_space *mapping = inode->i_mapping;
446         long nr_to_write = wbc->nr_to_write;
447         unsigned dirty;
448         int ret;
449
450         WARN_ON(!(inode->i_state & I_SYNC));
451
452         ret = do_writepages(mapping, wbc);
453
454         /*
455          * Make sure to wait on the data before writing out the metadata.
456          * This is important for filesystems that modify metadata on data
457          * I/O completion.
458          */
459         if (wbc->sync_mode == WB_SYNC_ALL) {
460                 int err = filemap_fdatawait(mapping);
461                 if (ret == 0)
462                         ret = err;
463         }
464
465         /*
466          * Some filesystems may redirty the inode during the writeback
467          * due to delalloc, clear dirty metadata flags right before
468          * write_inode()
469          */
470         spin_lock(&inode->i_lock);
471         /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
472         if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
473                 inode->i_state &= ~I_DIRTY_PAGES;
474         dirty = inode->i_state & I_DIRTY;
475         inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
476         spin_unlock(&inode->i_lock);
477         /* Don't write the inode if only I_DIRTY_PAGES was set */
478         if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
479                 int err = write_inode(inode, wbc);
480                 if (ret == 0)
481                         ret = err;
482         }
483         trace_writeback_single_inode(inode, wbc, nr_to_write);
484         return ret;
485 }
486
487 /*
488  * Write out an inode's dirty pages. Either the caller has an active reference
489  * on the inode or the inode has I_WILL_FREE set.
490  *
491  * This function is designed to be called for writing back one inode which
492  * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
493  * and does more profound writeback list handling in writeback_sb_inodes().
494  */
495 static int
496 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
497                        struct writeback_control *wbc)
498 {
499         int ret = 0;
500
501         spin_lock(&inode->i_lock);
502         if (!atomic_read(&inode->i_count))
503                 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
504         else
505                 WARN_ON(inode->i_state & I_WILL_FREE);
506
507         if (inode->i_state & I_SYNC) {
508                 if (wbc->sync_mode != WB_SYNC_ALL)
509                         goto out;
510                 /*
511                  * It's a data-integrity sync. We must wait. Since callers hold
512                  * inode reference or inode has I_WILL_FREE set, it cannot go
513                  * away under us.
514                  */
515                 __inode_wait_for_writeback(inode);
516         }
517         WARN_ON(inode->i_state & I_SYNC);
518         /*
519          * Skip inode if it is clean. We don't want to mess with writeback
520          * lists in this function since flusher thread may be doing for example
521          * sync in parallel and if we move the inode, it could get skipped. So
522          * here we make sure inode is on some writeback list and leave it there
523          * unless we have completely cleaned the inode.
524          */
525         if (!(inode->i_state & I_DIRTY))
526                 goto out;
527         inode->i_state |= I_SYNC;
528         spin_unlock(&inode->i_lock);
529
530         ret = __writeback_single_inode(inode, wb, wbc);
531
532         spin_lock(&wb->list_lock);
533         spin_lock(&inode->i_lock);
534         /*
535          * If inode is clean, remove it from writeback lists. Otherwise don't
536          * touch it. See comment above for explanation.
537          */
538         if (!(inode->i_state & I_DIRTY))
539                 list_del_init(&inode->i_wb_list);
540         spin_unlock(&wb->list_lock);
541         inode_sync_complete(inode);
542 out:
543         spin_unlock(&inode->i_lock);
544         return ret;
545 }
546
547 static long writeback_chunk_size(struct backing_dev_info *bdi,
548                                  struct wb_writeback_work *work)
549 {
550         long pages;
551
552         /*
553          * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
554          * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
555          * here avoids calling into writeback_inodes_wb() more than once.
556          *
557          * The intended call sequence for WB_SYNC_ALL writeback is:
558          *
559          *      wb_writeback()
560          *          writeback_sb_inodes()       <== called only once
561          *              write_cache_pages()     <== called once for each inode
562          *                   (quickly) tag currently dirty pages
563          *                   (maybe slowly) sync all tagged pages
564          */
565         if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
566                 pages = LONG_MAX;
567         else {
568                 pages = min(bdi->avg_write_bandwidth / 2,
569                             global_dirty_limit / DIRTY_SCOPE);
570                 pages = min(pages, work->nr_pages);
571                 pages = round_down(pages + MIN_WRITEBACK_PAGES,
572                                    MIN_WRITEBACK_PAGES);
573         }
574
575         return pages;
576 }
577
578 /*
579  * Write a portion of b_io inodes which belong to @sb.
580  *
581  * Return the number of pages and/or inodes written.
582  */
583 static long writeback_sb_inodes(struct super_block *sb,
584                                 struct bdi_writeback *wb,
585                                 struct wb_writeback_work *work)
586 {
587         struct writeback_control wbc = {
588                 .sync_mode              = work->sync_mode,
589                 .tagged_writepages      = work->tagged_writepages,
590                 .for_kupdate            = work->for_kupdate,
591                 .for_background         = work->for_background,
592                 .range_cyclic           = work->range_cyclic,
593                 .range_start            = 0,
594                 .range_end              = LLONG_MAX,
595         };
596         unsigned long start_time = jiffies;
597         long write_chunk;
598         long wrote = 0;  /* count both pages and inodes */
599
600         while (!list_empty(&wb->b_io)) {
601                 struct inode *inode = wb_inode(wb->b_io.prev);
602
603                 if (inode->i_sb != sb) {
604                         if (work->sb) {
605                                 /*
606                                  * We only want to write back data for this
607                                  * superblock, move all inodes not belonging
608                                  * to it back onto the dirty list.
609                                  */
610                                 redirty_tail(inode, wb);
611                                 continue;
612                         }
613
614                         /*
615                          * The inode belongs to a different superblock.
616                          * Bounce back to the caller to unpin this and
617                          * pin the next superblock.
618                          */
619                         break;
620                 }
621
622                 /*
623                  * Don't bother with new inodes or inodes being freed, first
624                  * kind does not need periodic writeout yet, and for the latter
625                  * kind writeout is handled by the freer.
626                  */
627                 spin_lock(&inode->i_lock);
628                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
629                         spin_unlock(&inode->i_lock);
630                         redirty_tail(inode, wb);
631                         continue;
632                 }
633                 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
634                         /*
635                          * If this inode is locked for writeback and we are not
636                          * doing writeback-for-data-integrity, move it to
637                          * b_more_io so that writeback can proceed with the
638                          * other inodes on s_io.
639                          *
640                          * We'll have another go at writing back this inode
641                          * when we completed a full scan of b_io.
642                          */
643                         spin_unlock(&inode->i_lock);
644                         requeue_io(inode, wb);
645                         trace_writeback_sb_inodes_requeue(inode);
646                         continue;
647                 }
648                 spin_unlock(&wb->list_lock);
649
650                 /*
651                  * We already requeued the inode if it had I_SYNC set and we
652                  * are doing WB_SYNC_NONE writeback. So this catches only the
653                  * WB_SYNC_ALL case.
654                  */
655                 if (inode->i_state & I_SYNC) {
656                         /* Wait for I_SYNC. This function drops i_lock... */
657                         inode_sleep_on_writeback(inode);
658                         /* Inode may be gone, start again */
659                         spin_lock(&wb->list_lock);
660                         continue;
661                 }
662                 inode->i_state |= I_SYNC;
663                 spin_unlock(&inode->i_lock);
664
665                 write_chunk = writeback_chunk_size(wb->bdi, work);
666                 wbc.nr_to_write = write_chunk;
667                 wbc.pages_skipped = 0;
668
669                 /*
670                  * We use I_SYNC to pin the inode in memory. While it is set
671                  * evict_inode() will wait so the inode cannot be freed.
672                  */
673                 __writeback_single_inode(inode, wb, &wbc);
674
675                 work->nr_pages -= write_chunk - wbc.nr_to_write;
676                 wrote += write_chunk - wbc.nr_to_write;
677                 spin_lock(&wb->list_lock);
678                 spin_lock(&inode->i_lock);
679                 if (!(inode->i_state & I_DIRTY))
680                         wrote++;
681                 requeue_inode(inode, wb, &wbc);
682                 inode_sync_complete(inode);
683                 spin_unlock(&inode->i_lock);
684                 cond_resched_lock(&wb->list_lock);
685                 /*
686                  * bail out to wb_writeback() often enough to check
687                  * background threshold and other termination conditions.
688                  */
689                 if (wrote) {
690                         if (time_is_before_jiffies(start_time + HZ / 10UL))
691                                 break;
692                         if (work->nr_pages <= 0)
693                                 break;
694                 }
695         }
696         return wrote;
697 }
698
699 static long __writeback_inodes_wb(struct bdi_writeback *wb,
700                                   struct wb_writeback_work *work)
701 {
702         unsigned long start_time = jiffies;
703         long wrote = 0;
704
705         while (!list_empty(&wb->b_io)) {
706                 struct inode *inode = wb_inode(wb->b_io.prev);
707                 struct super_block *sb = inode->i_sb;
708
709                 if (!grab_super_passive(sb)) {
710                         /*
711                          * grab_super_passive() may fail consistently due to
712                          * s_umount being grabbed by someone else. Don't use
713                          * requeue_io() to avoid busy retrying the inode/sb.
714                          */
715                         redirty_tail(inode, wb);
716                         continue;
717                 }
718                 wrote += writeback_sb_inodes(sb, wb, work);
719                 drop_super(sb);
720
721                 /* refer to the same tests at the end of writeback_sb_inodes */
722                 if (wrote) {
723                         if (time_is_before_jiffies(start_time + HZ / 10UL))
724                                 break;
725                         if (work->nr_pages <= 0)
726                                 break;
727                 }
728         }
729         /* Leave any unwritten inodes on b_io */
730         return wrote;
731 }
732
733 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
734                                 enum wb_reason reason)
735 {
736         struct wb_writeback_work work = {
737                 .nr_pages       = nr_pages,
738                 .sync_mode      = WB_SYNC_NONE,
739                 .range_cyclic   = 1,
740                 .reason         = reason,
741         };
742
743         spin_lock(&wb->list_lock);
744         if (list_empty(&wb->b_io))
745                 queue_io(wb, &work);
746         __writeback_inodes_wb(wb, &work);
747         spin_unlock(&wb->list_lock);
748
749         return nr_pages - work.nr_pages;
750 }
751
752 static bool over_bground_thresh(struct backing_dev_info *bdi)
753 {
754         unsigned long background_thresh, dirty_thresh;
755
756         global_dirty_limits(&background_thresh, &dirty_thresh);
757
758         if (global_page_state(NR_FILE_DIRTY) +
759             global_page_state(NR_UNSTABLE_NFS) > background_thresh)
760                 return true;
761
762         if (bdi_stat(bdi, BDI_RECLAIMABLE) >
763                                 bdi_dirty_limit(bdi, background_thresh))
764                 return true;
765
766         return false;
767 }
768
769 /*
770  * Called under wb->list_lock. If there are multiple wb per bdi,
771  * only the flusher working on the first wb should do it.
772  */
773 static void wb_update_bandwidth(struct bdi_writeback *wb,
774                                 unsigned long start_time)
775 {
776         __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
777 }
778
779 /*
780  * Explicit flushing or periodic writeback of "old" data.
781  *
782  * Define "old": the first time one of an inode's pages is dirtied, we mark the
783  * dirtying-time in the inode's address_space.  So this periodic writeback code
784  * just walks the superblock inode list, writing back any inodes which are
785  * older than a specific point in time.
786  *
787  * Try to run once per dirty_writeback_interval.  But if a writeback event
788  * takes longer than a dirty_writeback_interval interval, then leave a
789  * one-second gap.
790  *
791  * older_than_this takes precedence over nr_to_write.  So we'll only write back
792  * all dirty pages if they are all attached to "old" mappings.
793  */
794 static long wb_writeback(struct bdi_writeback *wb,
795                          struct wb_writeback_work *work)
796 {
797         unsigned long wb_start = jiffies;
798         long nr_pages = work->nr_pages;
799         unsigned long oldest_jif;
800         struct inode *inode;
801         long progress;
802
803         oldest_jif = jiffies;
804         work->older_than_this = &oldest_jif;
805
806         spin_lock(&wb->list_lock);
807         for (;;) {
808                 /*
809                  * Stop writeback when nr_pages has been consumed
810                  */
811                 if (work->nr_pages <= 0)
812                         break;
813
814                 /*
815                  * Background writeout and kupdate-style writeback may
816                  * run forever. Stop them if there is other work to do
817                  * so that e.g. sync can proceed. They'll be restarted
818                  * after the other works are all done.
819                  */
820                 if ((work->for_background || work->for_kupdate) &&
821                     !list_empty(&wb->bdi->work_list))
822                         break;
823
824                 /*
825                  * For background writeout, stop when we are below the
826                  * background dirty threshold
827                  */
828                 if (work->for_background && !over_bground_thresh(wb->bdi))
829                         break;
830
831                 /*
832                  * Kupdate and background works are special and we want to
833                  * include all inodes that need writing. Livelock avoidance is
834                  * handled by these works yielding to any other work so we are
835                  * safe.
836                  */
837                 if (work->for_kupdate) {
838                         oldest_jif = jiffies -
839                                 msecs_to_jiffies(dirty_expire_interval * 10);
840                 } else if (work->for_background)
841                         oldest_jif = jiffies;
842
843                 trace_writeback_start(wb->bdi, work);
844                 if (list_empty(&wb->b_io))
845                         queue_io(wb, work);
846                 if (work->sb)
847                         progress = writeback_sb_inodes(work->sb, wb, work);
848                 else
849                         progress = __writeback_inodes_wb(wb, work);
850                 trace_writeback_written(wb->bdi, work);
851
852                 wb_update_bandwidth(wb, wb_start);
853
854                 /*
855                  * Did we write something? Try for more
856                  *
857                  * Dirty inodes are moved to b_io for writeback in batches.
858                  * The completion of the current batch does not necessarily
859                  * mean the overall work is done. So we keep looping as long
860                  * as made some progress on cleaning pages or inodes.
861                  */
862                 if (progress)
863                         continue;
864                 /*
865                  * No more inodes for IO, bail
866                  */
867                 if (list_empty(&wb->b_more_io))
868                         break;
869                 /*
870                  * Nothing written. Wait for some inode to
871                  * become available for writeback. Otherwise
872                  * we'll just busyloop.
873                  */
874                 if (!list_empty(&wb->b_more_io))  {
875                         trace_writeback_wait(wb->bdi, work);
876                         inode = wb_inode(wb->b_more_io.prev);
877                         spin_lock(&inode->i_lock);
878                         spin_unlock(&wb->list_lock);
879                         /* This function drops i_lock... */
880                         inode_sleep_on_writeback(inode);
881                         spin_lock(&wb->list_lock);
882                 }
883         }
884         spin_unlock(&wb->list_lock);
885
886         return nr_pages - work->nr_pages;
887 }
888
889 /*
890  * Return the next wb_writeback_work struct that hasn't been processed yet.
891  */
892 static struct wb_writeback_work *
893 get_next_work_item(struct backing_dev_info *bdi)
894 {
895         struct wb_writeback_work *work = NULL;
896
897         spin_lock_bh(&bdi->wb_lock);
898         if (!list_empty(&bdi->work_list)) {
899                 work = list_entry(bdi->work_list.next,
900                                   struct wb_writeback_work, list);
901                 list_del_init(&work->list);
902         }
903         spin_unlock_bh(&bdi->wb_lock);
904         return work;
905 }
906
907 /*
908  * Add in the number of potentially dirty inodes, because each inode
909  * write can dirty pagecache in the underlying blockdev.
910  */
911 static unsigned long get_nr_dirty_pages(void)
912 {
913         return global_page_state(NR_FILE_DIRTY) +
914                 global_page_state(NR_UNSTABLE_NFS) +
915                 get_nr_dirty_inodes();
916 }
917
918 static long wb_check_background_flush(struct bdi_writeback *wb)
919 {
920         if (over_bground_thresh(wb->bdi)) {
921
922                 struct wb_writeback_work work = {
923                         .nr_pages       = LONG_MAX,
924                         .sync_mode      = WB_SYNC_NONE,
925                         .for_background = 1,
926                         .range_cyclic   = 1,
927                         .reason         = WB_REASON_BACKGROUND,
928                 };
929
930                 return wb_writeback(wb, &work);
931         }
932
933         return 0;
934 }
935
936 static long wb_check_old_data_flush(struct bdi_writeback *wb)
937 {
938         unsigned long expired;
939         long nr_pages;
940
941         /*
942          * When set to zero, disable periodic writeback
943          */
944         if (!dirty_writeback_interval)
945                 return 0;
946
947         expired = wb->last_old_flush +
948                         msecs_to_jiffies(dirty_writeback_interval * 10);
949         if (time_before(jiffies, expired))
950                 return 0;
951
952         wb->last_old_flush = jiffies;
953         nr_pages = get_nr_dirty_pages();
954
955         if (nr_pages) {
956                 struct wb_writeback_work work = {
957                         .nr_pages       = nr_pages,
958                         .sync_mode      = WB_SYNC_NONE,
959                         .for_kupdate    = 1,
960                         .range_cyclic   = 1,
961                         .reason         = WB_REASON_PERIODIC,
962                 };
963
964                 return wb_writeback(wb, &work);
965         }
966
967         return 0;
968 }
969
970 /*
971  * Retrieve work items and do the writeback they describe
972  */
973 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
974 {
975         struct backing_dev_info *bdi = wb->bdi;
976         struct wb_writeback_work *work;
977         long wrote = 0;
978
979         set_bit(BDI_writeback_running, &wb->bdi->state);
980         while ((work = get_next_work_item(bdi)) != NULL) {
981                 /*
982                  * Override sync mode, in case we must wait for completion
983                  * because this thread is exiting now.
984                  */
985                 if (force_wait)
986                         work->sync_mode = WB_SYNC_ALL;
987
988                 trace_writeback_exec(bdi, work);
989
990                 wrote += wb_writeback(wb, work);
991
992                 /*
993                  * Notify the caller of completion if this is a synchronous
994                  * work item, otherwise just free it.
995                  */
996                 if (work->done)
997                         complete(work->done);
998                 else
999                         kfree(work);
1000         }
1001
1002         /*
1003          * Check for periodic writeback, kupdated() style
1004          */
1005         wrote += wb_check_old_data_flush(wb);
1006         wrote += wb_check_background_flush(wb);
1007         clear_bit(BDI_writeback_running, &wb->bdi->state);
1008
1009         return wrote;
1010 }
1011
1012 /*
1013  * Handle writeback of dirty data for the device backed by this bdi. Also
1014  * wakes up periodically and does kupdated style flushing.
1015  */
1016 int bdi_writeback_thread(void *data)
1017 {
1018         struct bdi_writeback *wb = data;
1019         struct backing_dev_info *bdi = wb->bdi;
1020         long pages_written;
1021
1022         current->flags |= PF_SWAPWRITE;
1023         set_freezable();
1024         wb->last_active = jiffies;
1025
1026         /*
1027          * Our parent may run at a different priority, just set us to normal
1028          */
1029         set_user_nice(current, 0);
1030
1031         trace_writeback_thread_start(bdi);
1032
1033         while (!kthread_freezable_should_stop(NULL)) {
1034                 /*
1035                  * Remove own delayed wake-up timer, since we are already awake
1036                  * and we'll take care of the preriodic write-back.
1037                  */
1038                 del_timer(&wb->wakeup_timer);
1039
1040                 pages_written = wb_do_writeback(wb, 0);
1041
1042                 trace_writeback_pages_written(pages_written);
1043
1044                 if (pages_written)
1045                         wb->last_active = jiffies;
1046
1047                 set_current_state(TASK_INTERRUPTIBLE);
1048                 if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
1049                         __set_current_state(TASK_RUNNING);
1050                         continue;
1051                 }
1052
1053                 if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1054                         schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
1055                 else {
1056                         /*
1057                          * We have nothing to do, so can go sleep without any
1058                          * timeout and save power. When a work is queued or
1059                          * something is made dirty - we will be woken up.
1060                          */
1061                         schedule();
1062                 }
1063         }
1064
1065         /* Flush any work that raced with us exiting */
1066         if (!list_empty(&bdi->work_list))
1067                 wb_do_writeback(wb, 1);
1068
1069         trace_writeback_thread_stop(bdi);
1070         return 0;
1071 }
1072
1073
1074 /*
1075  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
1076  * the whole world.
1077  */
1078 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1079 {
1080         struct backing_dev_info *bdi;
1081
1082         if (!nr_pages) {
1083                 nr_pages = global_page_state(NR_FILE_DIRTY) +
1084                                 global_page_state(NR_UNSTABLE_NFS);
1085         }
1086
1087         rcu_read_lock();
1088         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1089                 if (!bdi_has_dirty_io(bdi))
1090                         continue;
1091                 __bdi_start_writeback(bdi, nr_pages, false, reason);
1092         }
1093         rcu_read_unlock();
1094 }
1095
1096 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1097 {
1098         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1099                 struct dentry *dentry;
1100                 const char *name = "?";
1101
1102                 dentry = d_find_alias(inode);
1103                 if (dentry) {
1104                         spin_lock(&dentry->d_lock);
1105                         name = (const char *) dentry->d_name.name;
1106                 }
1107                 printk(KERN_DEBUG
1108                        "%s(%d): dirtied inode %lu (%s) on %s\n",
1109                        current->comm, task_pid_nr(current), inode->i_ino,
1110                        name, inode->i_sb->s_id);
1111                 if (dentry) {
1112                         spin_unlock(&dentry->d_lock);
1113                         dput(dentry);
1114                 }
1115         }
1116 }
1117
1118 /**
1119  *      __mark_inode_dirty -    internal function
1120  *      @inode: inode to mark
1121  *      @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1122  *      Mark an inode as dirty. Callers should use mark_inode_dirty or
1123  *      mark_inode_dirty_sync.
1124  *
1125  * Put the inode on the super block's dirty list.
1126  *
1127  * CAREFUL! We mark it dirty unconditionally, but move it onto the
1128  * dirty list only if it is hashed or if it refers to a blockdev.
1129  * If it was not hashed, it will never be added to the dirty list
1130  * even if it is later hashed, as it will have been marked dirty already.
1131  *
1132  * In short, make sure you hash any inodes _before_ you start marking
1133  * them dirty.
1134  *
1135  * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1136  * the block-special inode (/dev/hda1) itself.  And the ->dirtied_when field of
1137  * the kernel-internal blockdev inode represents the dirtying time of the
1138  * blockdev's pages.  This is why for I_DIRTY_PAGES we always use
1139  * page->mapping->host, so the page-dirtying time is recorded in the internal
1140  * blockdev inode.
1141  */
1142 void __mark_inode_dirty(struct inode *inode, int flags)
1143 {
1144         struct super_block *sb = inode->i_sb;
1145         struct backing_dev_info *bdi = NULL;
1146
1147         /*
1148          * Don't do this for I_DIRTY_PAGES - that doesn't actually
1149          * dirty the inode itself
1150          */
1151         if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1152                 if (sb->s_op->dirty_inode)
1153                         sb->s_op->dirty_inode(inode, flags);
1154         }
1155
1156         /*
1157          * make sure that changes are seen by all cpus before we test i_state
1158          * -- mikulas
1159          */
1160         smp_mb();
1161
1162         /* avoid the locking if we can */
1163         if ((inode->i_state & flags) == flags)
1164                 return;
1165
1166         if (unlikely(block_dump))
1167                 block_dump___mark_inode_dirty(inode);
1168
1169         spin_lock(&inode->i_lock);
1170         if ((inode->i_state & flags) != flags) {
1171                 const int was_dirty = inode->i_state & I_DIRTY;
1172
1173                 inode->i_state |= flags;
1174
1175                 /*
1176                  * If the inode is being synced, just update its dirty state.
1177                  * The unlocker will place the inode on the appropriate
1178                  * superblock list, based upon its state.
1179                  */
1180                 if (inode->i_state & I_SYNC)
1181                         goto out_unlock_inode;
1182
1183                 /*
1184                  * Only add valid (hashed) inodes to the superblock's
1185                  * dirty list.  Add blockdev inodes as well.
1186                  */
1187                 if (!S_ISBLK(inode->i_mode)) {
1188                         if (inode_unhashed(inode))
1189                                 goto out_unlock_inode;
1190                 }
1191                 if (inode->i_state & I_FREEING)
1192                         goto out_unlock_inode;
1193
1194                 /*
1195                  * If the inode was already on b_dirty/b_io/b_more_io, don't
1196                  * reposition it (that would break b_dirty time-ordering).
1197                  */
1198                 if (!was_dirty) {
1199                         bool wakeup_bdi = false;
1200                         bdi = inode_to_bdi(inode);
1201
1202                         if (bdi_cap_writeback_dirty(bdi)) {
1203                                 WARN(!test_bit(BDI_registered, &bdi->state),
1204                                      "bdi-%s not registered\n", bdi->name);
1205
1206                                 /*
1207                                  * If this is the first dirty inode for this
1208                                  * bdi, we have to wake-up the corresponding
1209                                  * bdi thread to make sure background
1210                                  * write-back happens later.
1211                                  */
1212                                 if (!wb_has_dirty_io(&bdi->wb))
1213                                         wakeup_bdi = true;
1214                         }
1215
1216                         spin_unlock(&inode->i_lock);
1217                         spin_lock(&bdi->wb.list_lock);
1218                         inode->dirtied_when = jiffies;
1219                         list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1220                         spin_unlock(&bdi->wb.list_lock);
1221
1222                         if (wakeup_bdi)
1223                                 bdi_wakeup_thread_delayed(bdi);
1224                         return;
1225                 }
1226         }
1227 out_unlock_inode:
1228         spin_unlock(&inode->i_lock);
1229
1230 }
1231 EXPORT_SYMBOL(__mark_inode_dirty);
1232
1233 static void wait_sb_inodes(struct super_block *sb)
1234 {
1235         struct inode *inode, *old_inode = NULL;
1236
1237         /*
1238          * We need to be protected against the filesystem going from
1239          * r/o to r/w or vice versa.
1240          */
1241         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1242
1243         spin_lock(&inode_sb_list_lock);
1244
1245         /*
1246          * Data integrity sync. Must wait for all pages under writeback,
1247          * because there may have been pages dirtied before our sync
1248          * call, but which had writeout started before we write it out.
1249          * In which case, the inode may not be on the dirty list, but
1250          * we still have to wait for that writeout.
1251          */
1252         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1253                 struct address_space *mapping = inode->i_mapping;
1254
1255                 spin_lock(&inode->i_lock);
1256                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1257                     (mapping->nrpages == 0)) {
1258                         spin_unlock(&inode->i_lock);
1259                         continue;
1260                 }
1261                 __iget(inode);
1262                 spin_unlock(&inode->i_lock);
1263                 spin_unlock(&inode_sb_list_lock);
1264
1265                 /*
1266                  * We hold a reference to 'inode' so it couldn't have been
1267                  * removed from s_inodes list while we dropped the
1268                  * inode_sb_list_lock.  We cannot iput the inode now as we can
1269                  * be holding the last reference and we cannot iput it under
1270                  * inode_sb_list_lock. So we keep the reference and iput it
1271                  * later.
1272                  */
1273                 iput(old_inode);
1274                 old_inode = inode;
1275
1276                 filemap_fdatawait(mapping);
1277
1278                 cond_resched();
1279
1280                 spin_lock(&inode_sb_list_lock);
1281         }
1282         spin_unlock(&inode_sb_list_lock);
1283         iput(old_inode);
1284 }
1285
1286 /**
1287  * writeback_inodes_sb_nr -     writeback dirty inodes from given super_block
1288  * @sb: the superblock
1289  * @nr: the number of pages to write
1290  * @reason: reason why some writeback work initiated
1291  *
1292  * Start writeback on some inodes on this super_block. No guarantees are made
1293  * on how many (if any) will be written, and this function does not wait
1294  * for IO completion of submitted IO.
1295  */
1296 void writeback_inodes_sb_nr(struct super_block *sb,
1297                             unsigned long nr,
1298                             enum wb_reason reason)
1299 {
1300         DECLARE_COMPLETION_ONSTACK(done);
1301         struct wb_writeback_work work = {
1302                 .sb                     = sb,
1303                 .sync_mode              = WB_SYNC_NONE,
1304                 .tagged_writepages      = 1,
1305                 .done                   = &done,
1306                 .nr_pages               = nr,
1307                 .reason                 = reason,
1308         };
1309
1310         if (sb->s_bdi == &noop_backing_dev_info)
1311                 return;
1312         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1313         bdi_queue_work(sb->s_bdi, &work);
1314         wait_for_completion(&done);
1315 }
1316 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1317
1318 /**
1319  * writeback_inodes_sb  -       writeback dirty inodes from given super_block
1320  * @sb: the superblock
1321  * @reason: reason why some writeback work was initiated
1322  *
1323  * Start writeback on some inodes on this super_block. No guarantees are made
1324  * on how many (if any) will be written, and this function does not wait
1325  * for IO completion of submitted IO.
1326  */
1327 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1328 {
1329         return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1330 }
1331 EXPORT_SYMBOL(writeback_inodes_sb);
1332
1333 /**
1334  * writeback_inodes_sb_if_idle  -       start writeback if none underway
1335  * @sb: the superblock
1336  * @reason: reason why some writeback work was initiated
1337  *
1338  * Invoke writeback_inodes_sb if no writeback is currently underway.
1339  * Returns 1 if writeback was started, 0 if not.
1340  */
1341 int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
1342 {
1343         if (!writeback_in_progress(sb->s_bdi)) {
1344                 down_read(&sb->s_umount);
1345                 writeback_inodes_sb(sb, reason);
1346                 up_read(&sb->s_umount);
1347                 return 1;
1348         } else
1349                 return 0;
1350 }
1351 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1352
1353 /**
1354  * writeback_inodes_sb_nr_if_idle       -       start writeback if none underway
1355  * @sb: the superblock
1356  * @nr: the number of pages to write
1357  * @reason: reason why some writeback work was initiated
1358  *
1359  * Invoke writeback_inodes_sb if no writeback is currently underway.
1360  * Returns 1 if writeback was started, 0 if not.
1361  */
1362 int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
1363                                    unsigned long nr,
1364                                    enum wb_reason reason)
1365 {
1366         if (!writeback_in_progress(sb->s_bdi)) {
1367                 down_read(&sb->s_umount);
1368                 writeback_inodes_sb_nr(sb, nr, reason);
1369                 up_read(&sb->s_umount);
1370                 return 1;
1371         } else
1372                 return 0;
1373 }
1374 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
1375
1376 /**
1377  * sync_inodes_sb       -       sync sb inode pages
1378  * @sb: the superblock
1379  *
1380  * This function writes and waits on any dirty inode belonging to this
1381  * super_block.
1382  */
1383 void sync_inodes_sb(struct super_block *sb)
1384 {
1385         DECLARE_COMPLETION_ONSTACK(done);
1386         struct wb_writeback_work work = {
1387                 .sb             = sb,
1388                 .sync_mode      = WB_SYNC_ALL,
1389                 .nr_pages       = LONG_MAX,
1390                 .range_cyclic   = 0,
1391                 .done           = &done,
1392                 .reason         = WB_REASON_SYNC,
1393         };
1394
1395         /* Nothing to do? */
1396         if (sb->s_bdi == &noop_backing_dev_info)
1397                 return;
1398         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1399
1400         bdi_queue_work(sb->s_bdi, &work);
1401         wait_for_completion(&done);
1402
1403         wait_sb_inodes(sb);
1404 }
1405 EXPORT_SYMBOL(sync_inodes_sb);
1406
1407 /**
1408  * write_inode_now      -       write an inode to disk
1409  * @inode: inode to write to disk
1410  * @sync: whether the write should be synchronous or not
1411  *
1412  * This function commits an inode to disk immediately if it is dirty. This is
1413  * primarily needed by knfsd.
1414  *
1415  * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1416  */
1417 int write_inode_now(struct inode *inode, int sync)
1418 {
1419         struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1420         struct writeback_control wbc = {
1421                 .nr_to_write = LONG_MAX,
1422                 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1423                 .range_start = 0,
1424                 .range_end = LLONG_MAX,
1425         };
1426
1427         if (!mapping_cap_writeback_dirty(inode->i_mapping))
1428                 wbc.nr_to_write = 0;
1429
1430         might_sleep();
1431         return writeback_single_inode(inode, wb, &wbc);
1432 }
1433 EXPORT_SYMBOL(write_inode_now);
1434
1435 /**
1436  * sync_inode - write an inode and its pages to disk.
1437  * @inode: the inode to sync
1438  * @wbc: controls the writeback mode
1439  *
1440  * sync_inode() will write an inode and its pages to disk.  It will also
1441  * correctly update the inode on its superblock's dirty inode lists and will
1442  * update inode->i_state.
1443  *
1444  * The caller must have a ref on the inode.
1445  */
1446 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1447 {
1448         return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1449 }
1450 EXPORT_SYMBOL(sync_inode);
1451
1452 /**
1453  * sync_inode_metadata - write an inode to disk
1454  * @inode: the inode to sync
1455  * @wait: wait for I/O to complete.
1456  *
1457  * Write an inode to disk and adjust its dirty state after completion.
1458  *
1459  * Note: only writes the actual inode, no associated data or other metadata.
1460  */
1461 int sync_inode_metadata(struct inode *inode, int wait)
1462 {
1463         struct writeback_control wbc = {
1464                 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1465                 .nr_to_write = 0, /* metadata-only */
1466         };
1467
1468         return sync_inode(inode, &wbc);
1469 }
1470 EXPORT_SYMBOL(sync_inode_metadata);