ocfs2: fix the end cluster offset of FIEMAP
[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/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/tracepoint.h>
29 #include "internal.h"
30
31 /*
32  * 4MB minimal write chunk size
33  */
34 #define MIN_WRITEBACK_PAGES     (4096UL >> (PAGE_CACHE_SHIFT - 10))
35
36 /*
37  * Passed into wb_writeback(), essentially a subset of writeback_control
38  */
39 struct wb_writeback_work {
40         long nr_pages;
41         struct super_block *sb;
42         unsigned long *older_than_this;
43         enum writeback_sync_modes sync_mode;
44         unsigned int tagged_writepages:1;
45         unsigned int for_kupdate:1;
46         unsigned int range_cyclic:1;
47         unsigned int for_background:1;
48         enum wb_reason reason;          /* why was writeback initiated? */
49
50         struct list_head list;          /* pending work list */
51         struct completion *done;        /* set if the caller waits */
52 };
53
54 /**
55  * writeback_in_progress - determine whether there is writeback in progress
56  * @bdi: the device's backing_dev_info structure.
57  *
58  * Determine whether there is writeback waiting to be handled against a
59  * backing device.
60  */
61 int writeback_in_progress(struct backing_dev_info *bdi)
62 {
63         return test_bit(BDI_writeback_running, &bdi->state);
64 }
65 EXPORT_SYMBOL(writeback_in_progress);
66
67 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
68 {
69         struct super_block *sb = inode->i_sb;
70
71         if (strcmp(sb->s_type->name, "bdev") == 0)
72                 return inode->i_mapping->backing_dev_info;
73
74         return sb->s_bdi;
75 }
76
77 static inline struct inode *wb_inode(struct list_head *head)
78 {
79         return list_entry(head, struct inode, i_wb_list);
80 }
81
82 /*
83  * Include the creation of the trace points after defining the
84  * wb_writeback_work structure and inline functions so that the definition
85  * remains local to this file.
86  */
87 #define CREATE_TRACE_POINTS
88 #include <trace/events/writeback.h>
89
90 static void bdi_queue_work(struct backing_dev_info *bdi,
91                            struct wb_writeback_work *work)
92 {
93         trace_writeback_queue(bdi, work);
94
95         spin_lock_bh(&bdi->wb_lock);
96         list_add_tail(&work->list, &bdi->work_list);
97         spin_unlock_bh(&bdi->wb_lock);
98
99         mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
100 }
101
102 static void
103 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
104                       bool range_cyclic, enum wb_reason reason)
105 {
106         struct wb_writeback_work *work;
107
108         /*
109          * This is WB_SYNC_NONE writeback, so if allocation fails just
110          * wakeup the thread for old dirty data writeback
111          */
112         work = kzalloc(sizeof(*work), GFP_ATOMIC);
113         if (!work) {
114                 trace_writeback_nowork(bdi);
115                 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
116                 return;
117         }
118
119         work->sync_mode = WB_SYNC_NONE;
120         work->nr_pages  = nr_pages;
121         work->range_cyclic = range_cyclic;
122         work->reason    = reason;
123
124         bdi_queue_work(bdi, work);
125 }
126
127 /**
128  * bdi_start_writeback - start writeback
129  * @bdi: the backing device to write from
130  * @nr_pages: the number of pages to write
131  * @reason: reason why some writeback work was initiated
132  *
133  * Description:
134  *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
135  *   started when this function returns, we make no guarantees on
136  *   completion. Caller need not hold sb s_umount semaphore.
137  *
138  */
139 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
140                         enum wb_reason reason)
141 {
142         __bdi_start_writeback(bdi, nr_pages, true, reason);
143 }
144
145 /**
146  * bdi_start_background_writeback - start background writeback
147  * @bdi: the backing device to write from
148  *
149  * Description:
150  *   This makes sure WB_SYNC_NONE background writeback happens. When
151  *   this function returns, it is only guaranteed that for given BDI
152  *   some IO is happening if we are over background dirty threshold.
153  *   Caller need not hold sb s_umount semaphore.
154  */
155 void bdi_start_background_writeback(struct backing_dev_info *bdi)
156 {
157         /*
158          * We just wake up the flusher thread. It will perform background
159          * writeback as soon as there is no other work to do.
160          */
161         trace_writeback_wake_background(bdi);
162         mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
163 }
164
165 /*
166  * Remove the inode from the writeback list it is on.
167  */
168 void inode_wb_list_del(struct inode *inode)
169 {
170         struct backing_dev_info *bdi = inode_to_bdi(inode);
171
172         spin_lock(&bdi->wb.list_lock);
173         list_del_init(&inode->i_wb_list);
174         spin_unlock(&bdi->wb.list_lock);
175 }
176
177 /*
178  * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
179  * furthest end of its superblock's dirty-inode list.
180  *
181  * Before stamping the inode's ->dirtied_when, we check to see whether it is
182  * already the most-recently-dirtied inode on the b_dirty list.  If that is
183  * the case then the inode must have been redirtied while it was being written
184  * out and we don't reset its dirtied_when.
185  */
186 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
187 {
188         assert_spin_locked(&wb->list_lock);
189         if (!list_empty(&wb->b_dirty)) {
190                 struct inode *tail;
191
192                 tail = wb_inode(wb->b_dirty.next);
193                 if (time_before(inode->dirtied_when, tail->dirtied_when))
194                         inode->dirtied_when = jiffies;
195         }
196         list_move(&inode->i_wb_list, &wb->b_dirty);
197 }
198
199 /*
200  * requeue inode for re-scanning after bdi->b_io list is exhausted.
201  */
202 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
203 {
204         assert_spin_locked(&wb->list_lock);
205         list_move(&inode->i_wb_list, &wb->b_more_io);
206 }
207
208 static void inode_sync_complete(struct inode *inode)
209 {
210         inode->i_state &= ~I_SYNC;
211         /* If inode is clean an unused, put it into LRU now... */
212         inode_add_lru(inode);
213         /* Waiters must see I_SYNC cleared before being woken up */
214         smp_mb();
215         wake_up_bit(&inode->i_state, __I_SYNC);
216 }
217
218 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
219 {
220         bool ret = time_after(inode->dirtied_when, t);
221 #ifndef CONFIG_64BIT
222         /*
223          * For inodes being constantly redirtied, dirtied_when can get stuck.
224          * It _appears_ to be in the future, but is actually in distant past.
225          * This test is necessary to prevent such wrapped-around relative times
226          * from permanently stopping the whole bdi writeback.
227          */
228         ret = ret && time_before_eq(inode->dirtied_when, jiffies);
229 #endif
230         return ret;
231 }
232
233 /*
234  * Move expired (dirtied before work->older_than_this) dirty inodes from
235  * @delaying_queue to @dispatch_queue.
236  */
237 static int move_expired_inodes(struct list_head *delaying_queue,
238                                struct list_head *dispatch_queue,
239                                struct wb_writeback_work *work)
240 {
241         LIST_HEAD(tmp);
242         struct list_head *pos, *node;
243         struct super_block *sb = NULL;
244         struct inode *inode;
245         int do_sb_sort = 0;
246         int moved = 0;
247
248         while (!list_empty(delaying_queue)) {
249                 inode = wb_inode(delaying_queue->prev);
250                 if (work->older_than_this &&
251                     inode_dirtied_after(inode, *work->older_than_this))
252                         break;
253                 if (sb && sb != inode->i_sb)
254                         do_sb_sort = 1;
255                 sb = inode->i_sb;
256                 list_move(&inode->i_wb_list, &tmp);
257                 moved++;
258         }
259
260         /* just one sb in list, splice to dispatch_queue and we're done */
261         if (!do_sb_sort) {
262                 list_splice(&tmp, dispatch_queue);
263                 goto out;
264         }
265
266         /* Move inodes from one superblock together */
267         while (!list_empty(&tmp)) {
268                 sb = wb_inode(tmp.prev)->i_sb;
269                 list_for_each_prev_safe(pos, node, &tmp) {
270                         inode = wb_inode(pos);
271                         if (inode->i_sb == sb)
272                                 list_move(&inode->i_wb_list, dispatch_queue);
273                 }
274         }
275 out:
276         return moved;
277 }
278
279 /*
280  * Queue all expired dirty inodes for io, eldest first.
281  * Before
282  *         newly dirtied     b_dirty    b_io    b_more_io
283  *         =============>    gf         edc     BA
284  * After
285  *         newly dirtied     b_dirty    b_io    b_more_io
286  *         =============>    g          fBAedc
287  *                                           |
288  *                                           +--> dequeue for IO
289  */
290 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
291 {
292         int moved;
293         assert_spin_locked(&wb->list_lock);
294         list_splice_init(&wb->b_more_io, &wb->b_io);
295         moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
296         trace_writeback_queue_io(wb, work, moved);
297 }
298
299 static int write_inode(struct inode *inode, struct writeback_control *wbc)
300 {
301         int ret;
302
303         if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
304                 trace_writeback_write_inode_start(inode, wbc);
305                 ret = inode->i_sb->s_op->write_inode(inode, wbc);
306                 trace_writeback_write_inode(inode, wbc);
307                 return ret;
308         }
309         return 0;
310 }
311
312 /*
313  * Wait for writeback on an inode to complete. Called with i_lock held.
314  * Caller must make sure inode cannot go away when we drop i_lock.
315  */
316 static void __inode_wait_for_writeback(struct inode *inode)
317         __releases(inode->i_lock)
318         __acquires(inode->i_lock)
319 {
320         DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
321         wait_queue_head_t *wqh;
322
323         wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
324         while (inode->i_state & I_SYNC) {
325                 spin_unlock(&inode->i_lock);
326                 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
327                 spin_lock(&inode->i_lock);
328         }
329 }
330
331 /*
332  * Wait for writeback on an inode to complete. Caller must have inode pinned.
333  */
334 void inode_wait_for_writeback(struct inode *inode)
335 {
336         spin_lock(&inode->i_lock);
337         __inode_wait_for_writeback(inode);
338         spin_unlock(&inode->i_lock);
339 }
340
341 /*
342  * Sleep until I_SYNC is cleared. This function must be called with i_lock
343  * held and drops it. It is aimed for callers not holding any inode reference
344  * so once i_lock is dropped, inode can go away.
345  */
346 static void inode_sleep_on_writeback(struct inode *inode)
347         __releases(inode->i_lock)
348 {
349         DEFINE_WAIT(wait);
350         wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
351         int sleep;
352
353         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
354         sleep = inode->i_state & I_SYNC;
355         spin_unlock(&inode->i_lock);
356         if (sleep)
357                 schedule();
358         finish_wait(wqh, &wait);
359 }
360
361 /*
362  * Find proper writeback list for the inode depending on its current state and
363  * possibly also change of its state while we were doing writeback.  Here we
364  * handle things such as livelock prevention or fairness of writeback among
365  * inodes. This function can be called only by flusher thread - noone else
366  * processes all inodes in writeback lists and requeueing inodes behind flusher
367  * thread's back can have unexpected consequences.
368  */
369 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
370                           struct writeback_control *wbc)
371 {
372         if (inode->i_state & I_FREEING)
373                 return;
374
375         /*
376          * Sync livelock prevention. Each inode is tagged and synced in one
377          * shot. If still dirty, it will be redirty_tail()'ed below.  Update
378          * the dirty time to prevent enqueue and sync it again.
379          */
380         if ((inode->i_state & I_DIRTY) &&
381             (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
382                 inode->dirtied_when = jiffies;
383
384         if (wbc->pages_skipped) {
385                 /*
386                  * writeback is not making progress due to locked
387                  * buffers. Skip this inode for now.
388                  */
389                 redirty_tail(inode, wb);
390                 return;
391         }
392
393         if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
394                 /*
395                  * We didn't write back all the pages.  nfs_writepages()
396                  * sometimes bales out without doing anything.
397                  */
398                 if (wbc->nr_to_write <= 0) {
399                         /* Slice used up. Queue for next turn. */
400                         requeue_io(inode, wb);
401                 } else {
402                         /*
403                          * Writeback blocked by something other than
404                          * congestion. Delay the inode for some time to
405                          * avoid spinning on the CPU (100% iowait)
406                          * retrying writeback of the dirty page/inode
407                          * that cannot be performed immediately.
408                          */
409                         redirty_tail(inode, wb);
410                 }
411         } else if (inode->i_state & I_DIRTY) {
412                 /*
413                  * Filesystems can dirty the inode during writeback operations,
414                  * such as delayed allocation during submission or metadata
415                  * updates after data IO completion.
416                  */
417                 redirty_tail(inode, wb);
418         } else {
419                 /* The inode is clean. Remove from writeback lists. */
420                 list_del_init(&inode->i_wb_list);
421         }
422 }
423
424 /*
425  * Write out an inode and its dirty pages. Do not update the writeback list
426  * linkage. That is left to the caller. The caller is also responsible for
427  * setting I_SYNC flag and calling inode_sync_complete() to clear it.
428  */
429 static int
430 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
431 {
432         struct address_space *mapping = inode->i_mapping;
433         long nr_to_write = wbc->nr_to_write;
434         unsigned dirty;
435         int ret;
436
437         WARN_ON(!(inode->i_state & I_SYNC));
438
439         trace_writeback_single_inode_start(inode, wbc, nr_to_write);
440
441         ret = do_writepages(mapping, wbc);
442
443         /*
444          * Make sure to wait on the data before writing out the metadata.
445          * This is important for filesystems that modify metadata on data
446          * I/O completion.
447          */
448         if (wbc->sync_mode == WB_SYNC_ALL) {
449                 int err = filemap_fdatawait(mapping);
450                 if (ret == 0)
451                         ret = err;
452         }
453
454         /*
455          * Some filesystems may redirty the inode during the writeback
456          * due to delalloc, clear dirty metadata flags right before
457          * write_inode()
458          */
459         spin_lock(&inode->i_lock);
460         /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
461         if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
462                 inode->i_state &= ~I_DIRTY_PAGES;
463         dirty = inode->i_state & I_DIRTY;
464         inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
465         spin_unlock(&inode->i_lock);
466         /* Don't write the inode if only I_DIRTY_PAGES was set */
467         if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
468                 int err = write_inode(inode, wbc);
469                 if (ret == 0)
470                         ret = err;
471         }
472         trace_writeback_single_inode(inode, wbc, nr_to_write);
473         return ret;
474 }
475
476 /*
477  * Write out an inode's dirty pages. Either the caller has an active reference
478  * on the inode or the inode has I_WILL_FREE set.
479  *
480  * This function is designed to be called for writing back one inode which
481  * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
482  * and does more profound writeback list handling in writeback_sb_inodes().
483  */
484 static int
485 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
486                        struct writeback_control *wbc)
487 {
488         int ret = 0;
489
490         spin_lock(&inode->i_lock);
491         if (!atomic_read(&inode->i_count))
492                 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
493         else
494                 WARN_ON(inode->i_state & I_WILL_FREE);
495
496         if (inode->i_state & I_SYNC) {
497                 if (wbc->sync_mode != WB_SYNC_ALL)
498                         goto out;
499                 /*
500                  * It's a data-integrity sync. We must wait. Since callers hold
501                  * inode reference or inode has I_WILL_FREE set, it cannot go
502                  * away under us.
503                  */
504                 __inode_wait_for_writeback(inode);
505         }
506         WARN_ON(inode->i_state & I_SYNC);
507         /*
508          * Skip inode if it is clean. We don't want to mess with writeback
509          * lists in this function since flusher thread may be doing for example
510          * sync in parallel and if we move the inode, it could get skipped. So
511          * here we make sure inode is on some writeback list and leave it there
512          * unless we have completely cleaned the inode.
513          */
514         if (!(inode->i_state & I_DIRTY))
515                 goto out;
516         inode->i_state |= I_SYNC;
517         spin_unlock(&inode->i_lock);
518
519         ret = __writeback_single_inode(inode, wbc);
520
521         spin_lock(&wb->list_lock);
522         spin_lock(&inode->i_lock);
523         /*
524          * If inode is clean, remove it from writeback lists. Otherwise don't
525          * touch it. See comment above for explanation.
526          */
527         if (!(inode->i_state & I_DIRTY))
528                 list_del_init(&inode->i_wb_list);
529         spin_unlock(&wb->list_lock);
530         inode_sync_complete(inode);
531 out:
532         spin_unlock(&inode->i_lock);
533         return ret;
534 }
535
536 static long writeback_chunk_size(struct backing_dev_info *bdi,
537                                  struct wb_writeback_work *work)
538 {
539         long pages;
540
541         /*
542          * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
543          * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
544          * here avoids calling into writeback_inodes_wb() more than once.
545          *
546          * The intended call sequence for WB_SYNC_ALL writeback is:
547          *
548          *      wb_writeback()
549          *          writeback_sb_inodes()       <== called only once
550          *              write_cache_pages()     <== called once for each inode
551          *                   (quickly) tag currently dirty pages
552          *                   (maybe slowly) sync all tagged pages
553          */
554         if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
555                 pages = LONG_MAX;
556         else {
557                 pages = min(bdi->avg_write_bandwidth / 2,
558                             global_dirty_limit / DIRTY_SCOPE);
559                 pages = min(pages, work->nr_pages);
560                 pages = round_down(pages + MIN_WRITEBACK_PAGES,
561                                    MIN_WRITEBACK_PAGES);
562         }
563
564         return pages;
565 }
566
567 /*
568  * Write a portion of b_io inodes which belong to @sb.
569  *
570  * Return the number of pages and/or inodes written.
571  */
572 static long writeback_sb_inodes(struct super_block *sb,
573                                 struct bdi_writeback *wb,
574                                 struct wb_writeback_work *work)
575 {
576         struct writeback_control wbc = {
577                 .sync_mode              = work->sync_mode,
578                 .tagged_writepages      = work->tagged_writepages,
579                 .for_kupdate            = work->for_kupdate,
580                 .for_background         = work->for_background,
581                 .range_cyclic           = work->range_cyclic,
582                 .range_start            = 0,
583                 .range_end              = LLONG_MAX,
584         };
585         unsigned long start_time = jiffies;
586         long write_chunk;
587         long wrote = 0;  /* count both pages and inodes */
588
589         while (!list_empty(&wb->b_io)) {
590                 struct inode *inode = wb_inode(wb->b_io.prev);
591
592                 if (inode->i_sb != sb) {
593                         if (work->sb) {
594                                 /*
595                                  * We only want to write back data for this
596                                  * superblock, move all inodes not belonging
597                                  * to it back onto the dirty list.
598                                  */
599                                 redirty_tail(inode, wb);
600                                 continue;
601                         }
602
603                         /*
604                          * The inode belongs to a different superblock.
605                          * Bounce back to the caller to unpin this and
606                          * pin the next superblock.
607                          */
608                         break;
609                 }
610
611                 /*
612                  * Don't bother with new inodes or inodes being freed, first
613                  * kind does not need periodic writeout yet, and for the latter
614                  * kind writeout is handled by the freer.
615                  */
616                 spin_lock(&inode->i_lock);
617                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
618                         spin_unlock(&inode->i_lock);
619                         redirty_tail(inode, wb);
620                         continue;
621                 }
622                 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
623                         /*
624                          * If this inode is locked for writeback and we are not
625                          * doing writeback-for-data-integrity, move it to
626                          * b_more_io so that writeback can proceed with the
627                          * other inodes on s_io.
628                          *
629                          * We'll have another go at writing back this inode
630                          * when we completed a full scan of b_io.
631                          */
632                         spin_unlock(&inode->i_lock);
633                         requeue_io(inode, wb);
634                         trace_writeback_sb_inodes_requeue(inode);
635                         continue;
636                 }
637                 spin_unlock(&wb->list_lock);
638
639                 /*
640                  * We already requeued the inode if it had I_SYNC set and we
641                  * are doing WB_SYNC_NONE writeback. So this catches only the
642                  * WB_SYNC_ALL case.
643                  */
644                 if (inode->i_state & I_SYNC) {
645                         /* Wait for I_SYNC. This function drops i_lock... */
646                         inode_sleep_on_writeback(inode);
647                         /* Inode may be gone, start again */
648                         spin_lock(&wb->list_lock);
649                         continue;
650                 }
651                 inode->i_state |= I_SYNC;
652                 spin_unlock(&inode->i_lock);
653
654                 write_chunk = writeback_chunk_size(wb->bdi, work);
655                 wbc.nr_to_write = write_chunk;
656                 wbc.pages_skipped = 0;
657
658                 /*
659                  * We use I_SYNC to pin the inode in memory. While it is set
660                  * evict_inode() will wait so the inode cannot be freed.
661                  */
662                 __writeback_single_inode(inode, &wbc);
663
664                 work->nr_pages -= write_chunk - wbc.nr_to_write;
665                 wrote += write_chunk - wbc.nr_to_write;
666                 spin_lock(&wb->list_lock);
667                 spin_lock(&inode->i_lock);
668                 if (!(inode->i_state & I_DIRTY))
669                         wrote++;
670                 requeue_inode(inode, wb, &wbc);
671                 inode_sync_complete(inode);
672                 spin_unlock(&inode->i_lock);
673                 cond_resched_lock(&wb->list_lock);
674                 /*
675                  * bail out to wb_writeback() often enough to check
676                  * background threshold and other termination conditions.
677                  */
678                 if (wrote) {
679                         if (time_is_before_jiffies(start_time + HZ / 10UL))
680                                 break;
681                         if (work->nr_pages <= 0)
682                                 break;
683                 }
684         }
685         return wrote;
686 }
687
688 static long __writeback_inodes_wb(struct bdi_writeback *wb,
689                                   struct wb_writeback_work *work)
690 {
691         unsigned long start_time = jiffies;
692         long wrote = 0;
693
694         while (!list_empty(&wb->b_io)) {
695                 struct inode *inode = wb_inode(wb->b_io.prev);
696                 struct super_block *sb = inode->i_sb;
697
698                 if (!grab_super_passive(sb)) {
699                         /*
700                          * grab_super_passive() may fail consistently due to
701                          * s_umount being grabbed by someone else. Don't use
702                          * requeue_io() to avoid busy retrying the inode/sb.
703                          */
704                         redirty_tail(inode, wb);
705                         continue;
706                 }
707                 wrote += writeback_sb_inodes(sb, wb, work);
708                 drop_super(sb);
709
710                 /* refer to the same tests at the end of writeback_sb_inodes */
711                 if (wrote) {
712                         if (time_is_before_jiffies(start_time + HZ / 10UL))
713                                 break;
714                         if (work->nr_pages <= 0)
715                                 break;
716                 }
717         }
718         /* Leave any unwritten inodes on b_io */
719         return wrote;
720 }
721
722 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
723                                 enum wb_reason reason)
724 {
725         struct wb_writeback_work work = {
726                 .nr_pages       = nr_pages,
727                 .sync_mode      = WB_SYNC_NONE,
728                 .range_cyclic   = 1,
729                 .reason         = reason,
730         };
731
732         spin_lock(&wb->list_lock);
733         if (list_empty(&wb->b_io))
734                 queue_io(wb, &work);
735         __writeback_inodes_wb(wb, &work);
736         spin_unlock(&wb->list_lock);
737
738         return nr_pages - work.nr_pages;
739 }
740
741 static bool over_bground_thresh(struct backing_dev_info *bdi)
742 {
743         unsigned long background_thresh, dirty_thresh;
744
745         global_dirty_limits(&background_thresh, &dirty_thresh);
746
747         if (global_page_state(NR_FILE_DIRTY) +
748             global_page_state(NR_UNSTABLE_NFS) > background_thresh)
749                 return true;
750
751         if (bdi_stat(bdi, BDI_RECLAIMABLE) >
752                                 bdi_dirty_limit(bdi, background_thresh))
753                 return true;
754
755         return false;
756 }
757
758 /*
759  * Called under wb->list_lock. If there are multiple wb per bdi,
760  * only the flusher working on the first wb should do it.
761  */
762 static void wb_update_bandwidth(struct bdi_writeback *wb,
763                                 unsigned long start_time)
764 {
765         __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
766 }
767
768 /*
769  * Explicit flushing or periodic writeback of "old" data.
770  *
771  * Define "old": the first time one of an inode's pages is dirtied, we mark the
772  * dirtying-time in the inode's address_space.  So this periodic writeback code
773  * just walks the superblock inode list, writing back any inodes which are
774  * older than a specific point in time.
775  *
776  * Try to run once per dirty_writeback_interval.  But if a writeback event
777  * takes longer than a dirty_writeback_interval interval, then leave a
778  * one-second gap.
779  *
780  * older_than_this takes precedence over nr_to_write.  So we'll only write back
781  * all dirty pages if they are all attached to "old" mappings.
782  */
783 static long wb_writeback(struct bdi_writeback *wb,
784                          struct wb_writeback_work *work)
785 {
786         unsigned long wb_start = jiffies;
787         long nr_pages = work->nr_pages;
788         unsigned long oldest_jif;
789         struct inode *inode;
790         long progress;
791
792         oldest_jif = jiffies;
793         work->older_than_this = &oldest_jif;
794
795         spin_lock(&wb->list_lock);
796         for (;;) {
797                 /*
798                  * Stop writeback when nr_pages has been consumed
799                  */
800                 if (work->nr_pages <= 0)
801                         break;
802
803                 /*
804                  * Background writeout and kupdate-style writeback may
805                  * run forever. Stop them if there is other work to do
806                  * so that e.g. sync can proceed. They'll be restarted
807                  * after the other works are all done.
808                  */
809                 if ((work->for_background || work->for_kupdate) &&
810                     !list_empty(&wb->bdi->work_list))
811                         break;
812
813                 /*
814                  * For background writeout, stop when we are below the
815                  * background dirty threshold
816                  */
817                 if (work->for_background && !over_bground_thresh(wb->bdi))
818                         break;
819
820                 /*
821                  * Kupdate and background works are special and we want to
822                  * include all inodes that need writing. Livelock avoidance is
823                  * handled by these works yielding to any other work so we are
824                  * safe.
825                  */
826                 if (work->for_kupdate) {
827                         oldest_jif = jiffies -
828                                 msecs_to_jiffies(dirty_expire_interval * 10);
829                 } else if (work->for_background)
830                         oldest_jif = jiffies;
831
832                 trace_writeback_start(wb->bdi, work);
833                 if (list_empty(&wb->b_io))
834                         queue_io(wb, work);
835                 if (work->sb)
836                         progress = writeback_sb_inodes(work->sb, wb, work);
837                 else
838                         progress = __writeback_inodes_wb(wb, work);
839                 trace_writeback_written(wb->bdi, work);
840
841                 wb_update_bandwidth(wb, wb_start);
842
843                 /*
844                  * Did we write something? Try for more
845                  *
846                  * Dirty inodes are moved to b_io for writeback in batches.
847                  * The completion of the current batch does not necessarily
848                  * mean the overall work is done. So we keep looping as long
849                  * as made some progress on cleaning pages or inodes.
850                  */
851                 if (progress)
852                         continue;
853                 /*
854                  * No more inodes for IO, bail
855                  */
856                 if (list_empty(&wb->b_more_io))
857                         break;
858                 /*
859                  * Nothing written. Wait for some inode to
860                  * become available for writeback. Otherwise
861                  * we'll just busyloop.
862                  */
863                 if (!list_empty(&wb->b_more_io))  {
864                         trace_writeback_wait(wb->bdi, work);
865                         inode = wb_inode(wb->b_more_io.prev);
866                         spin_lock(&inode->i_lock);
867                         spin_unlock(&wb->list_lock);
868                         /* This function drops i_lock... */
869                         inode_sleep_on_writeback(inode);
870                         spin_lock(&wb->list_lock);
871                 }
872         }
873         spin_unlock(&wb->list_lock);
874
875         return nr_pages - work->nr_pages;
876 }
877
878 /*
879  * Return the next wb_writeback_work struct that hasn't been processed yet.
880  */
881 static struct wb_writeback_work *
882 get_next_work_item(struct backing_dev_info *bdi)
883 {
884         struct wb_writeback_work *work = NULL;
885
886         spin_lock_bh(&bdi->wb_lock);
887         if (!list_empty(&bdi->work_list)) {
888                 work = list_entry(bdi->work_list.next,
889                                   struct wb_writeback_work, list);
890                 list_del_init(&work->list);
891         }
892         spin_unlock_bh(&bdi->wb_lock);
893         return work;
894 }
895
896 /*
897  * Add in the number of potentially dirty inodes, because each inode
898  * write can dirty pagecache in the underlying blockdev.
899  */
900 static unsigned long get_nr_dirty_pages(void)
901 {
902         return global_page_state(NR_FILE_DIRTY) +
903                 global_page_state(NR_UNSTABLE_NFS) +
904                 get_nr_dirty_inodes();
905 }
906
907 static long wb_check_background_flush(struct bdi_writeback *wb)
908 {
909         if (over_bground_thresh(wb->bdi)) {
910
911                 struct wb_writeback_work work = {
912                         .nr_pages       = LONG_MAX,
913                         .sync_mode      = WB_SYNC_NONE,
914                         .for_background = 1,
915                         .range_cyclic   = 1,
916                         .reason         = WB_REASON_BACKGROUND,
917                 };
918
919                 return wb_writeback(wb, &work);
920         }
921
922         return 0;
923 }
924
925 static long wb_check_old_data_flush(struct bdi_writeback *wb)
926 {
927         unsigned long expired;
928         long nr_pages;
929
930         /*
931          * When set to zero, disable periodic writeback
932          */
933         if (!dirty_writeback_interval)
934                 return 0;
935
936         expired = wb->last_old_flush +
937                         msecs_to_jiffies(dirty_writeback_interval * 10);
938         if (time_before(jiffies, expired))
939                 return 0;
940
941         wb->last_old_flush = jiffies;
942         nr_pages = get_nr_dirty_pages();
943
944         if (nr_pages) {
945                 struct wb_writeback_work work = {
946                         .nr_pages       = nr_pages,
947                         .sync_mode      = WB_SYNC_NONE,
948                         .for_kupdate    = 1,
949                         .range_cyclic   = 1,
950                         .reason         = WB_REASON_PERIODIC,
951                 };
952
953                 return wb_writeback(wb, &work);
954         }
955
956         return 0;
957 }
958
959 /*
960  * Retrieve work items and do the writeback they describe
961  */
962 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
963 {
964         struct backing_dev_info *bdi = wb->bdi;
965         struct wb_writeback_work *work;
966         long wrote = 0;
967
968         set_bit(BDI_writeback_running, &wb->bdi->state);
969         while ((work = get_next_work_item(bdi)) != NULL) {
970                 /*
971                  * Override sync mode, in case we must wait for completion
972                  * because this thread is exiting now.
973                  */
974                 if (force_wait)
975                         work->sync_mode = WB_SYNC_ALL;
976
977                 trace_writeback_exec(bdi, work);
978
979                 wrote += wb_writeback(wb, work);
980
981                 /*
982                  * Notify the caller of completion if this is a synchronous
983                  * work item, otherwise just free it.
984                  */
985                 if (work->done)
986                         complete(work->done);
987                 else
988                         kfree(work);
989         }
990
991         /*
992          * Check for periodic writeback, kupdated() style
993          */
994         wrote += wb_check_old_data_flush(wb);
995         wrote += wb_check_background_flush(wb);
996         clear_bit(BDI_writeback_running, &wb->bdi->state);
997
998         return wrote;
999 }
1000
1001 /*
1002  * Handle writeback of dirty data for the device backed by this bdi. Also
1003  * reschedules periodically and does kupdated style flushing.
1004  */
1005 void bdi_writeback_workfn(struct work_struct *work)
1006 {
1007         struct bdi_writeback *wb = container_of(to_delayed_work(work),
1008                                                 struct bdi_writeback, dwork);
1009         struct backing_dev_info *bdi = wb->bdi;
1010         long pages_written;
1011
1012         set_worker_desc("flush-%s", dev_name(bdi->dev));
1013         current->flags |= PF_SWAPWRITE;
1014
1015         if (likely(!current_is_workqueue_rescuer() ||
1016                    list_empty(&bdi->bdi_list))) {
1017                 /*
1018                  * The normal path.  Keep writing back @bdi until its
1019                  * work_list is empty.  Note that this path is also taken
1020                  * if @bdi is shutting down even when we're running off the
1021                  * rescuer as work_list needs to be drained.
1022                  */
1023                 do {
1024                         pages_written = wb_do_writeback(wb, 0);
1025                         trace_writeback_pages_written(pages_written);
1026                 } while (!list_empty(&bdi->work_list));
1027         } else {
1028                 /*
1029                  * bdi_wq can't get enough workers and we're running off
1030                  * the emergency worker.  Don't hog it.  Hopefully, 1024 is
1031                  * enough for efficient IO.
1032                  */
1033                 pages_written = writeback_inodes_wb(&bdi->wb, 1024,
1034                                                     WB_REASON_FORKER_THREAD);
1035                 trace_writeback_pages_written(pages_written);
1036         }
1037
1038         if (!list_empty(&bdi->work_list) ||
1039             (wb_has_dirty_io(wb) && dirty_writeback_interval))
1040                 queue_delayed_work(bdi_wq, &wb->dwork,
1041                         msecs_to_jiffies(dirty_writeback_interval * 10));
1042
1043         current->flags &= ~PF_SWAPWRITE;
1044 }
1045
1046 /*
1047  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
1048  * the whole world.
1049  */
1050 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1051 {
1052         struct backing_dev_info *bdi;
1053
1054         if (!nr_pages) {
1055                 nr_pages = global_page_state(NR_FILE_DIRTY) +
1056                                 global_page_state(NR_UNSTABLE_NFS);
1057         }
1058
1059         rcu_read_lock();
1060         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1061                 if (!bdi_has_dirty_io(bdi))
1062                         continue;
1063                 __bdi_start_writeback(bdi, nr_pages, false, reason);
1064         }
1065         rcu_read_unlock();
1066 }
1067
1068 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1069 {
1070         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1071                 struct dentry *dentry;
1072                 const char *name = "?";
1073
1074                 dentry = d_find_alias(inode);
1075                 if (dentry) {
1076                         spin_lock(&dentry->d_lock);
1077                         name = (const char *) dentry->d_name.name;
1078                 }
1079                 printk(KERN_DEBUG
1080                        "%s(%d): dirtied inode %lu (%s) on %s\n",
1081                        current->comm, task_pid_nr(current), inode->i_ino,
1082                        name, inode->i_sb->s_id);
1083                 if (dentry) {
1084                         spin_unlock(&dentry->d_lock);
1085                         dput(dentry);
1086                 }
1087         }
1088 }
1089
1090 /**
1091  *      __mark_inode_dirty -    internal function
1092  *      @inode: inode to mark
1093  *      @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1094  *      Mark an inode as dirty. Callers should use mark_inode_dirty or
1095  *      mark_inode_dirty_sync.
1096  *
1097  * Put the inode on the super block's dirty list.
1098  *
1099  * CAREFUL! We mark it dirty unconditionally, but move it onto the
1100  * dirty list only if it is hashed or if it refers to a blockdev.
1101  * If it was not hashed, it will never be added to the dirty list
1102  * even if it is later hashed, as it will have been marked dirty already.
1103  *
1104  * In short, make sure you hash any inodes _before_ you start marking
1105  * them dirty.
1106  *
1107  * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1108  * the block-special inode (/dev/hda1) itself.  And the ->dirtied_when field of
1109  * the kernel-internal blockdev inode represents the dirtying time of the
1110  * blockdev's pages.  This is why for I_DIRTY_PAGES we always use
1111  * page->mapping->host, so the page-dirtying time is recorded in the internal
1112  * blockdev inode.
1113  */
1114 void __mark_inode_dirty(struct inode *inode, int flags)
1115 {
1116         struct super_block *sb = inode->i_sb;
1117         struct backing_dev_info *bdi = NULL;
1118
1119         /*
1120          * Don't do this for I_DIRTY_PAGES - that doesn't actually
1121          * dirty the inode itself
1122          */
1123         if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1124                 trace_writeback_dirty_inode_start(inode, flags);
1125
1126                 if (sb->s_op->dirty_inode)
1127                         sb->s_op->dirty_inode(inode, flags);
1128
1129                 trace_writeback_dirty_inode(inode, flags);
1130         }
1131
1132         /*
1133          * make sure that changes are seen by all cpus before we test i_state
1134          * -- mikulas
1135          */
1136         smp_mb();
1137
1138         /* avoid the locking if we can */
1139         if ((inode->i_state & flags) == flags)
1140                 return;
1141
1142         if (unlikely(block_dump))
1143                 block_dump___mark_inode_dirty(inode);
1144
1145         spin_lock(&inode->i_lock);
1146         if ((inode->i_state & flags) != flags) {
1147                 const int was_dirty = inode->i_state & I_DIRTY;
1148
1149                 inode->i_state |= flags;
1150
1151                 /*
1152                  * If the inode is being synced, just update its dirty state.
1153                  * The unlocker will place the inode on the appropriate
1154                  * superblock list, based upon its state.
1155                  */
1156                 if (inode->i_state & I_SYNC)
1157                         goto out_unlock_inode;
1158
1159                 /*
1160                  * Only add valid (hashed) inodes to the superblock's
1161                  * dirty list.  Add blockdev inodes as well.
1162                  */
1163                 if (!S_ISBLK(inode->i_mode)) {
1164                         if (inode_unhashed(inode))
1165                                 goto out_unlock_inode;
1166                 }
1167                 if (inode->i_state & I_FREEING)
1168                         goto out_unlock_inode;
1169
1170                 /*
1171                  * If the inode was already on b_dirty/b_io/b_more_io, don't
1172                  * reposition it (that would break b_dirty time-ordering).
1173                  */
1174                 if (!was_dirty) {
1175                         bool wakeup_bdi = false;
1176                         bdi = inode_to_bdi(inode);
1177
1178                         if (bdi_cap_writeback_dirty(bdi)) {
1179                                 WARN(!test_bit(BDI_registered, &bdi->state),
1180                                      "bdi-%s not registered\n", bdi->name);
1181
1182                                 /*
1183                                  * If this is the first dirty inode for this
1184                                  * bdi, we have to wake-up the corresponding
1185                                  * bdi thread to make sure background
1186                                  * write-back happens later.
1187                                  */
1188                                 if (!wb_has_dirty_io(&bdi->wb))
1189                                         wakeup_bdi = true;
1190                         }
1191
1192                         spin_unlock(&inode->i_lock);
1193                         spin_lock(&bdi->wb.list_lock);
1194                         inode->dirtied_when = jiffies;
1195                         list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1196                         spin_unlock(&bdi->wb.list_lock);
1197
1198                         if (wakeup_bdi)
1199                                 bdi_wakeup_thread_delayed(bdi);
1200                         return;
1201                 }
1202         }
1203 out_unlock_inode:
1204         spin_unlock(&inode->i_lock);
1205
1206 }
1207 EXPORT_SYMBOL(__mark_inode_dirty);
1208
1209 static void wait_sb_inodes(struct super_block *sb)
1210 {
1211         struct inode *inode, *old_inode = NULL;
1212
1213         /*
1214          * We need to be protected against the filesystem going from
1215          * r/o to r/w or vice versa.
1216          */
1217         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1218
1219         spin_lock(&inode_sb_list_lock);
1220
1221         /*
1222          * Data integrity sync. Must wait for all pages under writeback,
1223          * because there may have been pages dirtied before our sync
1224          * call, but which had writeout started before we write it out.
1225          * In which case, the inode may not be on the dirty list, but
1226          * we still have to wait for that writeout.
1227          */
1228         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1229                 struct address_space *mapping = inode->i_mapping;
1230
1231                 spin_lock(&inode->i_lock);
1232                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1233                     (mapping->nrpages == 0)) {
1234                         spin_unlock(&inode->i_lock);
1235                         continue;
1236                 }
1237                 __iget(inode);
1238                 spin_unlock(&inode->i_lock);
1239                 spin_unlock(&inode_sb_list_lock);
1240
1241                 /*
1242                  * We hold a reference to 'inode' so it couldn't have been
1243                  * removed from s_inodes list while we dropped the
1244                  * inode_sb_list_lock.  We cannot iput the inode now as we can
1245                  * be holding the last reference and we cannot iput it under
1246                  * inode_sb_list_lock. So we keep the reference and iput it
1247                  * later.
1248                  */
1249                 iput(old_inode);
1250                 old_inode = inode;
1251
1252                 filemap_fdatawait(mapping);
1253
1254                 cond_resched();
1255
1256                 spin_lock(&inode_sb_list_lock);
1257         }
1258         spin_unlock(&inode_sb_list_lock);
1259         iput(old_inode);
1260 }
1261
1262 /**
1263  * writeback_inodes_sb_nr -     writeback dirty inodes from given super_block
1264  * @sb: the superblock
1265  * @nr: the number of pages to write
1266  * @reason: reason why some writeback work initiated
1267  *
1268  * Start writeback on some inodes on this super_block. No guarantees are made
1269  * on how many (if any) will be written, and this function does not wait
1270  * for IO completion of submitted IO.
1271  */
1272 void writeback_inodes_sb_nr(struct super_block *sb,
1273                             unsigned long nr,
1274                             enum wb_reason reason)
1275 {
1276         DECLARE_COMPLETION_ONSTACK(done);
1277         struct wb_writeback_work work = {
1278                 .sb                     = sb,
1279                 .sync_mode              = WB_SYNC_NONE,
1280                 .tagged_writepages      = 1,
1281                 .done                   = &done,
1282                 .nr_pages               = nr,
1283                 .reason                 = reason,
1284         };
1285
1286         if (sb->s_bdi == &noop_backing_dev_info)
1287                 return;
1288         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1289         bdi_queue_work(sb->s_bdi, &work);
1290         wait_for_completion(&done);
1291 }
1292 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1293
1294 /**
1295  * writeback_inodes_sb  -       writeback dirty inodes from given super_block
1296  * @sb: the superblock
1297  * @reason: reason why some writeback work was initiated
1298  *
1299  * Start writeback on some inodes on this super_block. No guarantees are made
1300  * on how many (if any) will be written, and this function does not wait
1301  * for IO completion of submitted IO.
1302  */
1303 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1304 {
1305         return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1306 }
1307 EXPORT_SYMBOL(writeback_inodes_sb);
1308
1309 /**
1310  * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
1311  * @sb: the superblock
1312  * @nr: the number of pages to write
1313  * @reason: the reason of writeback
1314  *
1315  * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
1316  * Returns 1 if writeback was started, 0 if not.
1317  */
1318 int try_to_writeback_inodes_sb_nr(struct super_block *sb,
1319                                   unsigned long nr,
1320                                   enum wb_reason reason)
1321 {
1322         if (writeback_in_progress(sb->s_bdi))
1323                 return 1;
1324
1325         if (!down_read_trylock(&sb->s_umount))
1326                 return 0;
1327
1328         writeback_inodes_sb_nr(sb, nr, reason);
1329         up_read(&sb->s_umount);
1330         return 1;
1331 }
1332 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
1333
1334 /**
1335  * try_to_writeback_inodes_sb - try to start writeback if none underway
1336  * @sb: the superblock
1337  * @reason: reason why some writeback work was initiated
1338  *
1339  * Implement by try_to_writeback_inodes_sb_nr()
1340  * Returns 1 if writeback was started, 0 if not.
1341  */
1342 int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1343 {
1344         return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1345 }
1346 EXPORT_SYMBOL(try_to_writeback_inodes_sb);
1347
1348 /**
1349  * sync_inodes_sb       -       sync sb inode pages
1350  * @sb: the superblock
1351  *
1352  * This function writes and waits on any dirty inode belonging to this
1353  * super_block.
1354  */
1355 void sync_inodes_sb(struct super_block *sb)
1356 {
1357         DECLARE_COMPLETION_ONSTACK(done);
1358         struct wb_writeback_work work = {
1359                 .sb             = sb,
1360                 .sync_mode      = WB_SYNC_ALL,
1361                 .nr_pages       = LONG_MAX,
1362                 .range_cyclic   = 0,
1363                 .done           = &done,
1364                 .reason         = WB_REASON_SYNC,
1365         };
1366
1367         /* Nothing to do? */
1368         if (sb->s_bdi == &noop_backing_dev_info)
1369                 return;
1370         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1371
1372         bdi_queue_work(sb->s_bdi, &work);
1373         wait_for_completion(&done);
1374
1375         wait_sb_inodes(sb);
1376 }
1377 EXPORT_SYMBOL(sync_inodes_sb);
1378
1379 /**
1380  * write_inode_now      -       write an inode to disk
1381  * @inode: inode to write to disk
1382  * @sync: whether the write should be synchronous or not
1383  *
1384  * This function commits an inode to disk immediately if it is dirty. This is
1385  * primarily needed by knfsd.
1386  *
1387  * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1388  */
1389 int write_inode_now(struct inode *inode, int sync)
1390 {
1391         struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1392         struct writeback_control wbc = {
1393                 .nr_to_write = LONG_MAX,
1394                 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1395                 .range_start = 0,
1396                 .range_end = LLONG_MAX,
1397         };
1398
1399         if (!mapping_cap_writeback_dirty(inode->i_mapping))
1400                 wbc.nr_to_write = 0;
1401
1402         might_sleep();
1403         return writeback_single_inode(inode, wb, &wbc);
1404 }
1405 EXPORT_SYMBOL(write_inode_now);
1406
1407 /**
1408  * sync_inode - write an inode and its pages to disk.
1409  * @inode: the inode to sync
1410  * @wbc: controls the writeback mode
1411  *
1412  * sync_inode() will write an inode and its pages to disk.  It will also
1413  * correctly update the inode on its superblock's dirty inode lists and will
1414  * update inode->i_state.
1415  *
1416  * The caller must have a ref on the inode.
1417  */
1418 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1419 {
1420         return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1421 }
1422 EXPORT_SYMBOL(sync_inode);
1423
1424 /**
1425  * sync_inode_metadata - write an inode to disk
1426  * @inode: the inode to sync
1427  * @wait: wait for I/O to complete.
1428  *
1429  * Write an inode to disk and adjust its dirty state after completion.
1430  *
1431  * Note: only writes the actual inode, no associated data or other metadata.
1432  */
1433 int sync_inode_metadata(struct inode *inode, int wait)
1434 {
1435         struct writeback_control wbc = {
1436                 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1437                 .nr_to_write = 0, /* metadata-only */
1438         };
1439
1440         return sync_inode(inode, &wbc);
1441 }
1442 EXPORT_SYMBOL(sync_inode_metadata);