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