4 * Copyright (C) 2002, Linus Torvalds.
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.
11 * 10Apr2002 Andrew Morton
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
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>
23 #include <linux/pagemap.h>
24 #include <linux/kthread.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/tracepoint.h>
29 #include <linux/device.h>
30 #include <linux/memcontrol.h>
34 * 4MB minimal write chunk size
36 #define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
38 struct wb_completion {
43 * Passed into wb_writeback(), essentially a subset of writeback_control
45 struct wb_writeback_work {
47 struct super_block *sb;
48 unsigned long *older_than_this;
49 enum writeback_sync_modes sync_mode;
50 unsigned int tagged_writepages:1;
51 unsigned int for_kupdate:1;
52 unsigned int range_cyclic:1;
53 unsigned int for_background:1;
54 unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
55 unsigned int auto_free:1; /* free on completion */
56 enum wb_reason reason; /* why was writeback initiated? */
58 struct list_head list; /* pending work list */
59 struct wb_completion *done; /* set if the caller waits */
63 * If one wants to wait for one or more wb_writeback_works, each work's
64 * ->done should be set to a wb_completion defined using the following
65 * macro. Once all work items are issued with wb_queue_work(), the caller
66 * can wait for the completion of all using wb_wait_for_completion(). Work
67 * items which are waited upon aren't freed automatically on completion.
69 #define DEFINE_WB_COMPLETION_ONSTACK(cmpl) \
70 struct wb_completion cmpl = { \
71 .cnt = ATOMIC_INIT(1), \
76 * If an inode is constantly having its pages dirtied, but then the
77 * updates stop dirtytime_expire_interval seconds in the past, it's
78 * possible for the worst case time between when an inode has its
79 * timestamps updated and when they finally get written out to be two
80 * dirtytime_expire_intervals. We set the default to 12 hours (in
81 * seconds), which means most of the time inodes will have their
82 * timestamps written to disk after 12 hours, but in the worst case a
83 * few inodes might not their timestamps updated for 24 hours.
85 unsigned int dirtytime_expire_interval = 12 * 60 * 60;
87 static inline struct inode *wb_inode(struct list_head *head)
89 return list_entry(head, struct inode, i_io_list);
93 * Include the creation of the trace points after defining the
94 * wb_writeback_work structure and inline functions so that the definition
95 * remains local to this file.
97 #define CREATE_TRACE_POINTS
98 #include <trace/events/writeback.h>
100 EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
102 static bool wb_io_lists_populated(struct bdi_writeback *wb)
104 if (wb_has_dirty_io(wb)) {
107 set_bit(WB_has_dirty_io, &wb->state);
108 WARN_ON_ONCE(!wb->avg_write_bandwidth);
109 atomic_long_add(wb->avg_write_bandwidth,
110 &wb->bdi->tot_write_bandwidth);
115 static void wb_io_lists_depopulated(struct bdi_writeback *wb)
117 if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) &&
118 list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) {
119 clear_bit(WB_has_dirty_io, &wb->state);
120 WARN_ON_ONCE(atomic_long_sub_return(wb->avg_write_bandwidth,
121 &wb->bdi->tot_write_bandwidth) < 0);
126 * inode_io_list_move_locked - move an inode onto a bdi_writeback IO list
127 * @inode: inode to be moved
128 * @wb: target bdi_writeback
129 * @head: one of @wb->b_{dirty|io|more_io}
131 * Move @inode->i_io_list to @list of @wb and set %WB_has_dirty_io.
132 * Returns %true if @inode is the first occupant of the !dirty_time IO
133 * lists; otherwise, %false.
135 static bool inode_io_list_move_locked(struct inode *inode,
136 struct bdi_writeback *wb,
137 struct list_head *head)
139 assert_spin_locked(&wb->list_lock);
141 list_move(&inode->i_io_list, head);
143 /* dirty_time doesn't count as dirty_io until expiration */
144 if (head != &wb->b_dirty_time)
145 return wb_io_lists_populated(wb);
147 wb_io_lists_depopulated(wb);
152 * inode_io_list_del_locked - remove an inode from its bdi_writeback IO list
153 * @inode: inode to be removed
154 * @wb: bdi_writeback @inode is being removed from
156 * Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and
157 * clear %WB_has_dirty_io if all are empty afterwards.
159 static void inode_io_list_del_locked(struct inode *inode,
160 struct bdi_writeback *wb)
162 assert_spin_locked(&wb->list_lock);
164 list_del_init(&inode->i_io_list);
165 wb_io_lists_depopulated(wb);
168 static void wb_wakeup(struct bdi_writeback *wb)
170 spin_lock_bh(&wb->work_lock);
171 if (test_bit(WB_registered, &wb->state))
172 mod_delayed_work(bdi_wq, &wb->dwork, 0);
173 spin_unlock_bh(&wb->work_lock);
176 static void wb_queue_work(struct bdi_writeback *wb,
177 struct wb_writeback_work *work)
179 trace_writeback_queue(wb, work);
181 spin_lock_bh(&wb->work_lock);
182 if (!test_bit(WB_registered, &wb->state))
185 atomic_inc(&work->done->cnt);
186 list_add_tail(&work->list, &wb->work_list);
187 mod_delayed_work(bdi_wq, &wb->dwork, 0);
189 spin_unlock_bh(&wb->work_lock);
193 * wb_wait_for_completion - wait for completion of bdi_writeback_works
194 * @bdi: bdi work items were issued to
195 * @done: target wb_completion
197 * Wait for one or more work items issued to @bdi with their ->done field
198 * set to @done, which should have been defined with
199 * DEFINE_WB_COMPLETION_ONSTACK(). This function returns after all such
200 * work items are completed. Work items which are waited upon aren't freed
201 * automatically on completion.
203 static void wb_wait_for_completion(struct backing_dev_info *bdi,
204 struct wb_completion *done)
206 atomic_dec(&done->cnt); /* put down the initial count */
207 wait_event(bdi->wb_waitq, !atomic_read(&done->cnt));
210 #ifdef CONFIG_CGROUP_WRITEBACK
212 /* parameters for foreign inode detection, see wb_detach_inode() */
213 #define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */
214 #define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */
215 #define WB_FRN_TIME_CUT_DIV 2 /* ignore rounds < avg / 2 */
216 #define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */
218 #define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */
219 #define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS)
220 /* each slot's duration is 2s / 16 */
221 #define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2)
222 /* if foreign slots >= 8, switch */
223 #define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1)
224 /* one round can affect upto 5 slots */
226 void __inode_attach_wb(struct inode *inode, struct page *page)
228 struct backing_dev_info *bdi = inode_to_bdi(inode);
229 struct bdi_writeback *wb = NULL;
231 if (inode_cgwb_enabled(inode)) {
232 struct cgroup_subsys_state *memcg_css;
235 memcg_css = mem_cgroup_css_from_page(page);
236 wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
238 /* must pin memcg_css, see wb_get_create() */
239 memcg_css = task_get_css(current, memory_cgrp_id);
240 wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
249 * There may be multiple instances of this function racing to
250 * update the same inode. Use cmpxchg() to tell the winner.
252 if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
257 * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
258 * @inode: inode of interest with i_lock held
260 * Returns @inode's wb with its list_lock held. @inode->i_lock must be
261 * held on entry and is released on return. The returned wb is guaranteed
262 * to stay @inode's associated wb until its list_lock is released.
264 static struct bdi_writeback *
265 locked_inode_to_wb_and_lock_list(struct inode *inode)
266 __releases(&inode->i_lock)
267 __acquires(&wb->list_lock)
270 struct bdi_writeback *wb = inode_to_wb(inode);
273 * inode_to_wb() association is protected by both
274 * @inode->i_lock and @wb->list_lock but list_lock nests
275 * outside i_lock. Drop i_lock and verify that the
276 * association hasn't changed after acquiring list_lock.
279 spin_unlock(&inode->i_lock);
280 spin_lock(&wb->list_lock);
281 wb_put(wb); /* not gonna deref it anymore */
283 /* i_wb may have changed inbetween, can't use inode_to_wb() */
284 if (likely(wb == inode->i_wb))
285 return wb; /* @inode already has ref */
287 spin_unlock(&wb->list_lock);
289 spin_lock(&inode->i_lock);
294 * inode_to_wb_and_lock_list - determine an inode's wb and lock it
295 * @inode: inode of interest
297 * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
300 static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
301 __acquires(&wb->list_lock)
303 spin_lock(&inode->i_lock);
304 return locked_inode_to_wb_and_lock_list(inode);
307 struct inode_switch_wbs_context {
309 struct bdi_writeback *new_wb;
311 struct rcu_head rcu_head;
312 struct work_struct work;
315 static void inode_switch_wbs_work_fn(struct work_struct *work)
317 struct inode_switch_wbs_context *isw =
318 container_of(work, struct inode_switch_wbs_context, work);
319 struct inode *inode = isw->inode;
320 struct address_space *mapping = inode->i_mapping;
321 struct bdi_writeback *old_wb = inode->i_wb;
322 struct bdi_writeback *new_wb = isw->new_wb;
323 struct radix_tree_iter iter;
324 bool switched = false;
328 * By the time control reaches here, RCU grace period has passed
329 * since I_WB_SWITCH assertion and all wb stat update transactions
330 * between unlocked_inode_to_wb_begin/end() are guaranteed to be
331 * synchronizing against mapping->tree_lock.
333 * Grabbing old_wb->list_lock, inode->i_lock and mapping->tree_lock
334 * gives us exclusion against all wb related operations on @inode
335 * including IO list manipulations and stat updates.
337 if (old_wb < new_wb) {
338 spin_lock(&old_wb->list_lock);
339 spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING);
341 spin_lock(&new_wb->list_lock);
342 spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING);
344 spin_lock(&inode->i_lock);
345 spin_lock_irq(&mapping->tree_lock);
348 * Once I_FREEING is visible under i_lock, the eviction path owns
349 * the inode and we shouldn't modify ->i_io_list.
351 if (unlikely(inode->i_state & I_FREEING))
355 * Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points
356 * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
357 * pages actually under underwriteback.
359 radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, 0,
360 PAGECACHE_TAG_DIRTY) {
361 struct page *page = radix_tree_deref_slot_protected(slot,
362 &mapping->tree_lock);
363 if (likely(page) && PageDirty(page)) {
364 __dec_wb_stat(old_wb, WB_RECLAIMABLE);
365 __inc_wb_stat(new_wb, WB_RECLAIMABLE);
369 radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, 0,
370 PAGECACHE_TAG_WRITEBACK) {
371 struct page *page = radix_tree_deref_slot_protected(slot,
372 &mapping->tree_lock);
374 WARN_ON_ONCE(!PageWriteback(page));
375 __dec_wb_stat(old_wb, WB_WRITEBACK);
376 __inc_wb_stat(new_wb, WB_WRITEBACK);
383 * Transfer to @new_wb's IO list if necessary. The specific list
384 * @inode was on is ignored and the inode is put on ->b_dirty which
385 * is always correct including from ->b_dirty_time. The transfer
386 * preserves @inode->dirtied_when ordering.
388 if (!list_empty(&inode->i_io_list)) {
391 inode_io_list_del_locked(inode, old_wb);
392 inode->i_wb = new_wb;
393 list_for_each_entry(pos, &new_wb->b_dirty, i_io_list)
394 if (time_after_eq(inode->dirtied_when,
397 inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev);
399 inode->i_wb = new_wb;
402 /* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */
403 inode->i_wb_frn_winner = 0;
404 inode->i_wb_frn_avg_time = 0;
405 inode->i_wb_frn_history = 0;
409 * Paired with load_acquire in unlocked_inode_to_wb_begin() and
410 * ensures that the new wb is visible if they see !I_WB_SWITCH.
412 smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH);
414 spin_unlock_irq(&mapping->tree_lock);
415 spin_unlock(&inode->i_lock);
416 spin_unlock(&new_wb->list_lock);
417 spin_unlock(&old_wb->list_lock);
429 static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head)
431 struct inode_switch_wbs_context *isw = container_of(rcu_head,
432 struct inode_switch_wbs_context, rcu_head);
434 /* needs to grab bh-unsafe locks, bounce to work item */
435 INIT_WORK(&isw->work, inode_switch_wbs_work_fn);
436 schedule_work(&isw->work);
440 * inode_switch_wbs - change the wb association of an inode
441 * @inode: target inode
442 * @new_wb_id: ID of the new wb
444 * Switch @inode's wb association to the wb identified by @new_wb_id. The
445 * switching is performed asynchronously and may fail silently.
447 static void inode_switch_wbs(struct inode *inode, int new_wb_id)
449 struct backing_dev_info *bdi = inode_to_bdi(inode);
450 struct cgroup_subsys_state *memcg_css;
451 struct inode_switch_wbs_context *isw;
453 /* noop if seems to be already in progress */
454 if (inode->i_state & I_WB_SWITCH)
457 isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
461 /* find and pin the new wb */
463 memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys);
465 isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
470 /* while holding I_WB_SWITCH, no one else can update the association */
471 spin_lock(&inode->i_lock);
472 if (inode->i_state & (I_WB_SWITCH | I_FREEING) ||
473 inode_to_wb(inode) == isw->new_wb) {
474 spin_unlock(&inode->i_lock);
477 inode->i_state |= I_WB_SWITCH;
478 spin_unlock(&inode->i_lock);
484 * In addition to synchronizing among switchers, I_WB_SWITCH tells
485 * the RCU protected stat update paths to grab the mapping's
486 * tree_lock so that stat transfer can synchronize against them.
487 * Let's continue after I_WB_SWITCH is guaranteed to be visible.
489 call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
499 * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it
500 * @wbc: writeback_control of interest
501 * @inode: target inode
503 * @inode is locked and about to be written back under the control of @wbc.
504 * Record @inode's writeback context into @wbc and unlock the i_lock. On
505 * writeback completion, wbc_detach_inode() should be called. This is used
506 * to track the cgroup writeback context.
508 void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
511 if (!inode_cgwb_enabled(inode)) {
512 spin_unlock(&inode->i_lock);
516 wbc->wb = inode_to_wb(inode);
519 wbc->wb_id = wbc->wb->memcg_css->id;
520 wbc->wb_lcand_id = inode->i_wb_frn_winner;
521 wbc->wb_tcand_id = 0;
523 wbc->wb_lcand_bytes = 0;
524 wbc->wb_tcand_bytes = 0;
527 spin_unlock(&inode->i_lock);
530 * A dying wb indicates that the memcg-blkcg mapping has changed
531 * and a new wb is already serving the memcg. Switch immediately.
533 if (unlikely(wb_dying(wbc->wb)))
534 inode_switch_wbs(inode, wbc->wb_id);
538 * wbc_detach_inode - disassociate wbc from inode and perform foreign detection
539 * @wbc: writeback_control of the just finished writeback
541 * To be called after a writeback attempt of an inode finishes and undoes
542 * wbc_attach_and_unlock_inode(). Can be called under any context.
544 * As concurrent write sharing of an inode is expected to be very rare and
545 * memcg only tracks page ownership on first-use basis severely confining
546 * the usefulness of such sharing, cgroup writeback tracks ownership
547 * per-inode. While the support for concurrent write sharing of an inode
548 * is deemed unnecessary, an inode being written to by different cgroups at
549 * different points in time is a lot more common, and, more importantly,
550 * charging only by first-use can too readily lead to grossly incorrect
551 * behaviors (single foreign page can lead to gigabytes of writeback to be
552 * incorrectly attributed).
554 * To resolve this issue, cgroup writeback detects the majority dirtier of
555 * an inode and transfers the ownership to it. To avoid unnnecessary
556 * oscillation, the detection mechanism keeps track of history and gives
557 * out the switch verdict only if the foreign usage pattern is stable over
558 * a certain amount of time and/or writeback attempts.
560 * On each writeback attempt, @wbc tries to detect the majority writer
561 * using Boyer-Moore majority vote algorithm. In addition to the byte
562 * count from the majority voting, it also counts the bytes written for the
563 * current wb and the last round's winner wb (max of last round's current
564 * wb, the winner from two rounds ago, and the last round's majority
565 * candidate). Keeping track of the historical winner helps the algorithm
566 * to semi-reliably detect the most active writer even when it's not the
569 * Once the winner of the round is determined, whether the winner is
570 * foreign or not and how much IO time the round consumed is recorded in
571 * inode->i_wb_frn_history. If the amount of recorded foreign IO time is
572 * over a certain threshold, the switch verdict is given.
574 void wbc_detach_inode(struct writeback_control *wbc)
576 struct bdi_writeback *wb = wbc->wb;
577 struct inode *inode = wbc->inode;
578 unsigned long avg_time, max_bytes, max_time;
585 history = inode->i_wb_frn_history;
586 avg_time = inode->i_wb_frn_avg_time;
588 /* pick the winner of this round */
589 if (wbc->wb_bytes >= wbc->wb_lcand_bytes &&
590 wbc->wb_bytes >= wbc->wb_tcand_bytes) {
592 max_bytes = wbc->wb_bytes;
593 } else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) {
594 max_id = wbc->wb_lcand_id;
595 max_bytes = wbc->wb_lcand_bytes;
597 max_id = wbc->wb_tcand_id;
598 max_bytes = wbc->wb_tcand_bytes;
602 * Calculate the amount of IO time the winner consumed and fold it
603 * into the running average kept per inode. If the consumed IO
604 * time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
605 * deciding whether to switch or not. This is to prevent one-off
606 * small dirtiers from skewing the verdict.
608 max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT,
609 wb->avg_write_bandwidth);
611 avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) -
612 (avg_time >> WB_FRN_TIME_AVG_SHIFT);
614 avg_time = max_time; /* immediate catch up on first run */
616 if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) {
620 * The switch verdict is reached if foreign wb's consume
621 * more than a certain proportion of IO time in a
622 * WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
623 * history mask where each bit represents one sixteenth of
624 * the period. Determine the number of slots to shift into
625 * history from @max_time.
627 slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT),
628 (unsigned long)WB_FRN_HIST_MAX_SLOTS);
630 if (wbc->wb_id != max_id)
631 history |= (1U << slots) - 1;
634 * Switch if the current wb isn't the consistent winner.
635 * If there are multiple closely competing dirtiers, the
636 * inode may switch across them repeatedly over time, which
637 * is okay. The main goal is avoiding keeping an inode on
638 * the wrong wb for an extended period of time.
640 if (hweight32(history) > WB_FRN_HIST_THR_SLOTS)
641 inode_switch_wbs(inode, max_id);
645 * Multiple instances of this function may race to update the
646 * following fields but we don't mind occassional inaccuracies.
648 inode->i_wb_frn_winner = max_id;
649 inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX);
650 inode->i_wb_frn_history = history;
657 * wbc_account_io - account IO issued during writeback
658 * @wbc: writeback_control of the writeback in progress
659 * @page: page being written out
660 * @bytes: number of bytes being written out
662 * @bytes from @page are about to written out during the writeback
663 * controlled by @wbc. Keep the book for foreign inode detection. See
664 * wbc_detach_inode().
666 void wbc_account_io(struct writeback_control *wbc, struct page *page,
672 * pageout() path doesn't attach @wbc to the inode being written
673 * out. This is intentional as we don't want the function to block
674 * behind a slow cgroup. Ultimately, we want pageout() to kick off
675 * regular writeback instead of writing things out itself.
681 id = mem_cgroup_css_from_page(page)->id;
684 if (id == wbc->wb_id) {
685 wbc->wb_bytes += bytes;
689 if (id == wbc->wb_lcand_id)
690 wbc->wb_lcand_bytes += bytes;
692 /* Boyer-Moore majority vote algorithm */
693 if (!wbc->wb_tcand_bytes)
694 wbc->wb_tcand_id = id;
695 if (id == wbc->wb_tcand_id)
696 wbc->wb_tcand_bytes += bytes;
698 wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes);
700 EXPORT_SYMBOL_GPL(wbc_account_io);
703 * inode_congested - test whether an inode is congested
704 * @inode: inode to test for congestion (may be NULL)
705 * @cong_bits: mask of WB_[a]sync_congested bits to test
707 * Tests whether @inode is congested. @cong_bits is the mask of congestion
708 * bits to test and the return value is the mask of set bits.
710 * If cgroup writeback is enabled for @inode, the congestion state is
711 * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
712 * associated with @inode is congested; otherwise, the root wb's congestion
715 * @inode is allowed to be NULL as this function is often called on
716 * mapping->host which is NULL for the swapper space.
718 int inode_congested(struct inode *inode, int cong_bits)
721 * Once set, ->i_wb never becomes NULL while the inode is alive.
722 * Start transaction iff ->i_wb is visible.
724 if (inode && inode_to_wb_is_valid(inode)) {
725 struct bdi_writeback *wb;
726 bool locked, congested;
728 wb = unlocked_inode_to_wb_begin(inode, &locked);
729 congested = wb_congested(wb, cong_bits);
730 unlocked_inode_to_wb_end(inode, locked);
734 return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
736 EXPORT_SYMBOL_GPL(inode_congested);
739 * wb_split_bdi_pages - split nr_pages to write according to bandwidth
740 * @wb: target bdi_writeback to split @nr_pages to
741 * @nr_pages: number of pages to write for the whole bdi
743 * Split @wb's portion of @nr_pages according to @wb's write bandwidth in
744 * relation to the total write bandwidth of all wb's w/ dirty inodes on
747 static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
749 unsigned long this_bw = wb->avg_write_bandwidth;
750 unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);
752 if (nr_pages == LONG_MAX)
756 * This may be called on clean wb's and proportional distribution
757 * may not make sense, just use the original @nr_pages in those
758 * cases. In general, we wanna err on the side of writing more.
760 if (!tot_bw || this_bw >= tot_bw)
763 return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
767 * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
768 * @bdi: target backing_dev_info
769 * @base_work: wb_writeback_work to issue
770 * @skip_if_busy: skip wb's which already have writeback in progress
772 * Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
773 * have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
774 * distributed to the busy wbs according to each wb's proportion in the
775 * total active write bandwidth of @bdi.
777 static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
778 struct wb_writeback_work *base_work,
781 struct bdi_writeback *last_wb = NULL;
782 struct bdi_writeback *wb = list_entry_rcu(&bdi->wb_list,
783 struct bdi_writeback, bdi_node);
788 list_for_each_entry_continue_rcu(wb, &bdi->wb_list, bdi_node) {
789 DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done);
790 struct wb_writeback_work fallback_work;
791 struct wb_writeback_work *work;
799 /* SYNC_ALL writes out I_DIRTY_TIME too */
800 if (!wb_has_dirty_io(wb) &&
801 (base_work->sync_mode == WB_SYNC_NONE ||
802 list_empty(&wb->b_dirty_time)))
804 if (skip_if_busy && writeback_in_progress(wb))
807 nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages);
809 work = kmalloc(sizeof(*work), GFP_ATOMIC);
812 work->nr_pages = nr_pages;
814 wb_queue_work(wb, work);
818 /* alloc failed, execute synchronously using on-stack fallback */
819 work = &fallback_work;
821 work->nr_pages = nr_pages;
823 work->done = &fallback_work_done;
825 wb_queue_work(wb, work);
828 * Pin @wb so that it stays on @bdi->wb_list. This allows
829 * continuing iteration from @wb after dropping and
830 * regrabbing rcu read lock.
836 wb_wait_for_completion(bdi, &fallback_work_done);
845 #else /* CONFIG_CGROUP_WRITEBACK */
847 static struct bdi_writeback *
848 locked_inode_to_wb_and_lock_list(struct inode *inode)
849 __releases(&inode->i_lock)
850 __acquires(&wb->list_lock)
852 struct bdi_writeback *wb = inode_to_wb(inode);
854 spin_unlock(&inode->i_lock);
855 spin_lock(&wb->list_lock);
859 static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
860 __acquires(&wb->list_lock)
862 struct bdi_writeback *wb = inode_to_wb(inode);
864 spin_lock(&wb->list_lock);
868 static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
873 static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
874 struct wb_writeback_work *base_work,
879 if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
880 base_work->auto_free = 0;
881 wb_queue_work(&bdi->wb, base_work);
885 #endif /* CONFIG_CGROUP_WRITEBACK */
887 void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
888 bool range_cyclic, enum wb_reason reason)
890 struct wb_writeback_work *work;
892 if (!wb_has_dirty_io(wb))
896 * This is WB_SYNC_NONE writeback, so if allocation fails just
897 * wakeup the thread for old dirty data writeback
899 work = kzalloc(sizeof(*work), GFP_ATOMIC);
901 trace_writeback_nowork(wb);
906 work->sync_mode = WB_SYNC_NONE;
907 work->nr_pages = nr_pages;
908 work->range_cyclic = range_cyclic;
909 work->reason = reason;
912 wb_queue_work(wb, work);
916 * wb_start_background_writeback - start background writeback
917 * @wb: bdi_writback to write from
920 * This makes sure WB_SYNC_NONE background writeback happens. When
921 * this function returns, it is only guaranteed that for given wb
922 * some IO is happening if we are over background dirty threshold.
923 * Caller need not hold sb s_umount semaphore.
925 void wb_start_background_writeback(struct bdi_writeback *wb)
928 * We just wake up the flusher thread. It will perform background
929 * writeback as soon as there is no other work to do.
931 trace_writeback_wake_background(wb);
936 * Remove the inode from the writeback list it is on.
938 void inode_io_list_del(struct inode *inode)
940 struct bdi_writeback *wb;
942 wb = inode_to_wb_and_lock_list(inode);
943 inode_io_list_del_locked(inode, wb);
944 spin_unlock(&wb->list_lock);
948 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
949 * furthest end of its superblock's dirty-inode list.
951 * Before stamping the inode's ->dirtied_when, we check to see whether it is
952 * already the most-recently-dirtied inode on the b_dirty list. If that is
953 * the case then the inode must have been redirtied while it was being written
954 * out and we don't reset its dirtied_when.
956 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
958 if (!list_empty(&wb->b_dirty)) {
961 tail = wb_inode(wb->b_dirty.next);
962 if (time_before(inode->dirtied_when, tail->dirtied_when))
963 inode->dirtied_when = jiffies;
965 inode_io_list_move_locked(inode, wb, &wb->b_dirty);
969 * requeue inode for re-scanning after bdi->b_io list is exhausted.
971 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
973 inode_io_list_move_locked(inode, wb, &wb->b_more_io);
976 static void inode_sync_complete(struct inode *inode)
978 inode->i_state &= ~I_SYNC;
979 /* If inode is clean an unused, put it into LRU now... */
980 inode_add_lru(inode);
981 /* Waiters must see I_SYNC cleared before being woken up */
983 wake_up_bit(&inode->i_state, __I_SYNC);
986 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
988 bool ret = time_after(inode->dirtied_when, t);
991 * For inodes being constantly redirtied, dirtied_when can get stuck.
992 * It _appears_ to be in the future, but is actually in distant past.
993 * This test is necessary to prevent such wrapped-around relative times
994 * from permanently stopping the whole bdi writeback.
996 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
1001 #define EXPIRE_DIRTY_ATIME 0x0001
1004 * Move expired (dirtied before work->older_than_this) dirty inodes from
1005 * @delaying_queue to @dispatch_queue.
1007 static int move_expired_inodes(struct list_head *delaying_queue,
1008 struct list_head *dispatch_queue,
1010 struct wb_writeback_work *work)
1012 unsigned long *older_than_this = NULL;
1013 unsigned long expire_time;
1015 struct list_head *pos, *node;
1016 struct super_block *sb = NULL;
1017 struct inode *inode;
1021 if ((flags & EXPIRE_DIRTY_ATIME) == 0)
1022 older_than_this = work->older_than_this;
1023 else if (!work->for_sync) {
1024 expire_time = jiffies - (dirtytime_expire_interval * HZ);
1025 older_than_this = &expire_time;
1027 while (!list_empty(delaying_queue)) {
1028 inode = wb_inode(delaying_queue->prev);
1029 if (older_than_this &&
1030 inode_dirtied_after(inode, *older_than_this))
1032 list_move(&inode->i_io_list, &tmp);
1034 if (flags & EXPIRE_DIRTY_ATIME)
1035 set_bit(__I_DIRTY_TIME_EXPIRED, &inode->i_state);
1036 if (sb_is_blkdev_sb(inode->i_sb))
1038 if (sb && sb != inode->i_sb)
1043 /* just one sb in list, splice to dispatch_queue and we're done */
1045 list_splice(&tmp, dispatch_queue);
1049 /* Move inodes from one superblock together */
1050 while (!list_empty(&tmp)) {
1051 sb = wb_inode(tmp.prev)->i_sb;
1052 list_for_each_prev_safe(pos, node, &tmp) {
1053 inode = wb_inode(pos);
1054 if (inode->i_sb == sb)
1055 list_move(&inode->i_io_list, dispatch_queue);
1063 * Queue all expired dirty inodes for io, eldest first.
1065 * newly dirtied b_dirty b_io b_more_io
1066 * =============> gf edc BA
1068 * newly dirtied b_dirty b_io b_more_io
1069 * =============> g fBAedc
1071 * +--> dequeue for IO
1073 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
1077 assert_spin_locked(&wb->list_lock);
1078 list_splice_init(&wb->b_more_io, &wb->b_io);
1079 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work);
1080 moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
1081 EXPIRE_DIRTY_ATIME, work);
1083 wb_io_lists_populated(wb);
1084 trace_writeback_queue_io(wb, work, moved);
1087 static int write_inode(struct inode *inode, struct writeback_control *wbc)
1091 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
1092 trace_writeback_write_inode_start(inode, wbc);
1093 ret = inode->i_sb->s_op->write_inode(inode, wbc);
1094 trace_writeback_write_inode(inode, wbc);
1101 * Wait for writeback on an inode to complete. Called with i_lock held.
1102 * Caller must make sure inode cannot go away when we drop i_lock.
1104 static void __inode_wait_for_writeback(struct inode *inode)
1105 __releases(inode->i_lock)
1106 __acquires(inode->i_lock)
1108 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
1109 wait_queue_head_t *wqh;
1111 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1112 while (inode->i_state & I_SYNC) {
1113 spin_unlock(&inode->i_lock);
1114 __wait_on_bit(wqh, &wq, bit_wait,
1115 TASK_UNINTERRUPTIBLE);
1116 spin_lock(&inode->i_lock);
1121 * Wait for writeback on an inode to complete. Caller must have inode pinned.
1123 void inode_wait_for_writeback(struct inode *inode)
1125 spin_lock(&inode->i_lock);
1126 __inode_wait_for_writeback(inode);
1127 spin_unlock(&inode->i_lock);
1131 * Sleep until I_SYNC is cleared. This function must be called with i_lock
1132 * held and drops it. It is aimed for callers not holding any inode reference
1133 * so once i_lock is dropped, inode can go away.
1135 static void inode_sleep_on_writeback(struct inode *inode)
1136 __releases(inode->i_lock)
1139 wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1142 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1143 sleep = inode->i_state & I_SYNC;
1144 spin_unlock(&inode->i_lock);
1147 finish_wait(wqh, &wait);
1151 * Find proper writeback list for the inode depending on its current state and
1152 * possibly also change of its state while we were doing writeback. Here we
1153 * handle things such as livelock prevention or fairness of writeback among
1154 * inodes. This function can be called only by flusher thread - noone else
1155 * processes all inodes in writeback lists and requeueing inodes behind flusher
1156 * thread's back can have unexpected consequences.
1158 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
1159 struct writeback_control *wbc)
1161 if (inode->i_state & I_FREEING)
1165 * Sync livelock prevention. Each inode is tagged and synced in one
1166 * shot. If still dirty, it will be redirty_tail()'ed below. Update
1167 * the dirty time to prevent enqueue and sync it again.
1169 if ((inode->i_state & I_DIRTY) &&
1170 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
1171 inode->dirtied_when = jiffies;
1173 if (wbc->pages_skipped) {
1175 * writeback is not making progress due to locked
1176 * buffers. Skip this inode for now.
1178 redirty_tail(inode, wb);
1182 if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
1184 * We didn't write back all the pages. nfs_writepages()
1185 * sometimes bales out without doing anything.
1187 if (wbc->nr_to_write <= 0) {
1188 /* Slice used up. Queue for next turn. */
1189 requeue_io(inode, wb);
1192 * Writeback blocked by something other than
1193 * congestion. Delay the inode for some time to
1194 * avoid spinning on the CPU (100% iowait)
1195 * retrying writeback of the dirty page/inode
1196 * that cannot be performed immediately.
1198 redirty_tail(inode, wb);
1200 } else if (inode->i_state & I_DIRTY) {
1202 * Filesystems can dirty the inode during writeback operations,
1203 * such as delayed allocation during submission or metadata
1204 * updates after data IO completion.
1206 redirty_tail(inode, wb);
1207 } else if (inode->i_state & I_DIRTY_TIME) {
1208 inode->dirtied_when = jiffies;
1209 inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
1211 /* The inode is clean. Remove from writeback lists. */
1212 inode_io_list_del_locked(inode, wb);
1217 * Write out an inode and its dirty pages. Do not update the writeback list
1218 * linkage. That is left to the caller. The caller is also responsible for
1219 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
1222 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
1224 struct address_space *mapping = inode->i_mapping;
1225 long nr_to_write = wbc->nr_to_write;
1229 WARN_ON(!(inode->i_state & I_SYNC));
1231 trace_writeback_single_inode_start(inode, wbc, nr_to_write);
1233 ret = do_writepages(mapping, wbc);
1236 * Make sure to wait on the data before writing out the metadata.
1237 * This is important for filesystems that modify metadata on data
1238 * I/O completion. We don't do it for sync(2) writeback because it has a
1239 * separate, external IO completion path and ->sync_fs for guaranteeing
1240 * inode metadata is written back correctly.
1242 if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
1243 int err = filemap_fdatawait(mapping);
1249 * Some filesystems may redirty the inode during the writeback
1250 * due to delalloc, clear dirty metadata flags right before
1253 spin_lock(&inode->i_lock);
1255 dirty = inode->i_state & I_DIRTY;
1256 if (inode->i_state & I_DIRTY_TIME) {
1257 if ((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) ||
1258 unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) ||
1259 unlikely(time_after(jiffies,
1260 (inode->dirtied_time_when +
1261 dirtytime_expire_interval * HZ)))) {
1262 dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
1263 trace_writeback_lazytime(inode);
1266 inode->i_state &= ~I_DIRTY_TIME_EXPIRED;
1267 inode->i_state &= ~dirty;
1270 * Paired with smp_mb() in __mark_inode_dirty(). This allows
1271 * __mark_inode_dirty() to test i_state without grabbing i_lock -
1272 * either they see the I_DIRTY bits cleared or we see the dirtied
1275 * I_DIRTY_PAGES is always cleared together above even if @mapping
1276 * still has dirty pages. The flag is reinstated after smp_mb() if
1277 * necessary. This guarantees that either __mark_inode_dirty()
1278 * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
1282 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
1283 inode->i_state |= I_DIRTY_PAGES;
1285 spin_unlock(&inode->i_lock);
1287 if (dirty & I_DIRTY_TIME)
1288 mark_inode_dirty_sync(inode);
1289 /* Don't write the inode if only I_DIRTY_PAGES was set */
1290 if (dirty & ~I_DIRTY_PAGES) {
1291 int err = write_inode(inode, wbc);
1295 trace_writeback_single_inode(inode, wbc, nr_to_write);
1300 * Write out an inode's dirty pages. Either the caller has an active reference
1301 * on the inode or the inode has I_WILL_FREE set.
1303 * This function is designed to be called for writing back one inode which
1304 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
1305 * and does more profound writeback list handling in writeback_sb_inodes().
1308 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
1309 struct writeback_control *wbc)
1313 spin_lock(&inode->i_lock);
1314 if (!atomic_read(&inode->i_count))
1315 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
1317 WARN_ON(inode->i_state & I_WILL_FREE);
1319 if (inode->i_state & I_SYNC) {
1320 if (wbc->sync_mode != WB_SYNC_ALL)
1323 * It's a data-integrity sync. We must wait. Since callers hold
1324 * inode reference or inode has I_WILL_FREE set, it cannot go
1327 __inode_wait_for_writeback(inode);
1329 WARN_ON(inode->i_state & I_SYNC);
1331 * Skip inode if it is clean and we have no outstanding writeback in
1332 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
1333 * function since flusher thread may be doing for example sync in
1334 * parallel and if we move the inode, it could get skipped. So here we
1335 * make sure inode is on some writeback list and leave it there unless
1336 * we have completely cleaned the inode.
1338 if (!(inode->i_state & I_DIRTY_ALL) &&
1339 (wbc->sync_mode != WB_SYNC_ALL ||
1340 !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
1342 inode->i_state |= I_SYNC;
1343 wbc_attach_and_unlock_inode(wbc, inode);
1345 ret = __writeback_single_inode(inode, wbc);
1347 wbc_detach_inode(wbc);
1348 spin_lock(&wb->list_lock);
1349 spin_lock(&inode->i_lock);
1351 * If inode is clean, remove it from writeback lists. Otherwise don't
1352 * touch it. See comment above for explanation.
1354 if (!(inode->i_state & I_DIRTY_ALL))
1355 inode_io_list_del_locked(inode, wb);
1356 spin_unlock(&wb->list_lock);
1357 inode_sync_complete(inode);
1359 spin_unlock(&inode->i_lock);
1363 static long writeback_chunk_size(struct bdi_writeback *wb,
1364 struct wb_writeback_work *work)
1369 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
1370 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
1371 * here avoids calling into writeback_inodes_wb() more than once.
1373 * The intended call sequence for WB_SYNC_ALL writeback is:
1376 * writeback_sb_inodes() <== called only once
1377 * write_cache_pages() <== called once for each inode
1378 * (quickly) tag currently dirty pages
1379 * (maybe slowly) sync all tagged pages
1381 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
1384 pages = min(wb->avg_write_bandwidth / 2,
1385 global_wb_domain.dirty_limit / DIRTY_SCOPE);
1386 pages = min(pages, work->nr_pages);
1387 pages = round_down(pages + MIN_WRITEBACK_PAGES,
1388 MIN_WRITEBACK_PAGES);
1395 * Write a portion of b_io inodes which belong to @sb.
1397 * Return the number of pages and/or inodes written.
1399 * NOTE! This is called with wb->list_lock held, and will
1400 * unlock and relock that for each inode it ends up doing
1403 static long writeback_sb_inodes(struct super_block *sb,
1404 struct bdi_writeback *wb,
1405 struct wb_writeback_work *work)
1407 struct writeback_control wbc = {
1408 .sync_mode = work->sync_mode,
1409 .tagged_writepages = work->tagged_writepages,
1410 .for_kupdate = work->for_kupdate,
1411 .for_background = work->for_background,
1412 .for_sync = work->for_sync,
1413 .range_cyclic = work->range_cyclic,
1415 .range_end = LLONG_MAX,
1417 unsigned long start_time = jiffies;
1419 long wrote = 0; /* count both pages and inodes */
1421 while (!list_empty(&wb->b_io)) {
1422 struct inode *inode = wb_inode(wb->b_io.prev);
1424 if (inode->i_sb != sb) {
1427 * We only want to write back data for this
1428 * superblock, move all inodes not belonging
1429 * to it back onto the dirty list.
1431 redirty_tail(inode, wb);
1436 * The inode belongs to a different superblock.
1437 * Bounce back to the caller to unpin this and
1438 * pin the next superblock.
1444 * Don't bother with new inodes or inodes being freed, first
1445 * kind does not need periodic writeout yet, and for the latter
1446 * kind writeout is handled by the freer.
1448 spin_lock(&inode->i_lock);
1449 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
1450 spin_unlock(&inode->i_lock);
1451 redirty_tail(inode, wb);
1454 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
1456 * If this inode is locked for writeback and we are not
1457 * doing writeback-for-data-integrity, move it to
1458 * b_more_io so that writeback can proceed with the
1459 * other inodes on s_io.
1461 * We'll have another go at writing back this inode
1462 * when we completed a full scan of b_io.
1464 spin_unlock(&inode->i_lock);
1465 requeue_io(inode, wb);
1466 trace_writeback_sb_inodes_requeue(inode);
1469 spin_unlock(&wb->list_lock);
1472 * We already requeued the inode if it had I_SYNC set and we
1473 * are doing WB_SYNC_NONE writeback. So this catches only the
1476 if (inode->i_state & I_SYNC) {
1477 /* Wait for I_SYNC. This function drops i_lock... */
1478 inode_sleep_on_writeback(inode);
1479 /* Inode may be gone, start again */
1480 spin_lock(&wb->list_lock);
1483 inode->i_state |= I_SYNC;
1484 wbc_attach_and_unlock_inode(&wbc, inode);
1486 write_chunk = writeback_chunk_size(wb, work);
1487 wbc.nr_to_write = write_chunk;
1488 wbc.pages_skipped = 0;
1491 * We use I_SYNC to pin the inode in memory. While it is set
1492 * evict_inode() will wait so the inode cannot be freed.
1494 __writeback_single_inode(inode, &wbc);
1496 wbc_detach_inode(&wbc);
1497 work->nr_pages -= write_chunk - wbc.nr_to_write;
1498 wrote += write_chunk - wbc.nr_to_write;
1500 if (need_resched()) {
1502 * We're trying to balance between building up a nice
1503 * long list of IOs to improve our merge rate, and
1504 * getting those IOs out quickly for anyone throttling
1505 * in balance_dirty_pages(). cond_resched() doesn't
1506 * unplug, so get our IOs out the door before we
1509 blk_flush_plug(current);
1514 spin_lock(&wb->list_lock);
1515 spin_lock(&inode->i_lock);
1516 if (!(inode->i_state & I_DIRTY_ALL))
1518 requeue_inode(inode, wb, &wbc);
1519 inode_sync_complete(inode);
1520 spin_unlock(&inode->i_lock);
1523 * bail out to wb_writeback() often enough to check
1524 * background threshold and other termination conditions.
1527 if (time_is_before_jiffies(start_time + HZ / 10UL))
1529 if (work->nr_pages <= 0)
1536 static long __writeback_inodes_wb(struct bdi_writeback *wb,
1537 struct wb_writeback_work *work)
1539 unsigned long start_time = jiffies;
1542 while (!list_empty(&wb->b_io)) {
1543 struct inode *inode = wb_inode(wb->b_io.prev);
1544 struct super_block *sb = inode->i_sb;
1546 if (!trylock_super(sb)) {
1548 * trylock_super() may fail consistently due to
1549 * s_umount being grabbed by someone else. Don't use
1550 * requeue_io() to avoid busy retrying the inode/sb.
1552 redirty_tail(inode, wb);
1555 wrote += writeback_sb_inodes(sb, wb, work);
1556 up_read(&sb->s_umount);
1558 /* refer to the same tests at the end of writeback_sb_inodes */
1560 if (time_is_before_jiffies(start_time + HZ / 10UL))
1562 if (work->nr_pages <= 0)
1566 /* Leave any unwritten inodes on b_io */
1570 static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
1571 enum wb_reason reason)
1573 struct wb_writeback_work work = {
1574 .nr_pages = nr_pages,
1575 .sync_mode = WB_SYNC_NONE,
1579 struct blk_plug plug;
1581 blk_start_plug(&plug);
1582 spin_lock(&wb->list_lock);
1583 if (list_empty(&wb->b_io))
1584 queue_io(wb, &work);
1585 __writeback_inodes_wb(wb, &work);
1586 spin_unlock(&wb->list_lock);
1587 blk_finish_plug(&plug);
1589 return nr_pages - work.nr_pages;
1593 * Explicit flushing or periodic writeback of "old" data.
1595 * Define "old": the first time one of an inode's pages is dirtied, we mark the
1596 * dirtying-time in the inode's address_space. So this periodic writeback code
1597 * just walks the superblock inode list, writing back any inodes which are
1598 * older than a specific point in time.
1600 * Try to run once per dirty_writeback_interval. But if a writeback event
1601 * takes longer than a dirty_writeback_interval interval, then leave a
1604 * older_than_this takes precedence over nr_to_write. So we'll only write back
1605 * all dirty pages if they are all attached to "old" mappings.
1607 static long wb_writeback(struct bdi_writeback *wb,
1608 struct wb_writeback_work *work)
1610 unsigned long wb_start = jiffies;
1611 long nr_pages = work->nr_pages;
1612 unsigned long oldest_jif;
1613 struct inode *inode;
1615 struct blk_plug plug;
1617 oldest_jif = jiffies;
1618 work->older_than_this = &oldest_jif;
1620 blk_start_plug(&plug);
1621 spin_lock(&wb->list_lock);
1624 * Stop writeback when nr_pages has been consumed
1626 if (work->nr_pages <= 0)
1630 * Background writeout and kupdate-style writeback may
1631 * run forever. Stop them if there is other work to do
1632 * so that e.g. sync can proceed. They'll be restarted
1633 * after the other works are all done.
1635 if ((work->for_background || work->for_kupdate) &&
1636 !list_empty(&wb->work_list))
1640 * For background writeout, stop when we are below the
1641 * background dirty threshold
1643 if (work->for_background && !wb_over_bg_thresh(wb))
1647 * Kupdate and background works are special and we want to
1648 * include all inodes that need writing. Livelock avoidance is
1649 * handled by these works yielding to any other work so we are
1652 if (work->for_kupdate) {
1653 oldest_jif = jiffies -
1654 msecs_to_jiffies(dirty_expire_interval * 10);
1655 } else if (work->for_background)
1656 oldest_jif = jiffies;
1658 trace_writeback_start(wb, work);
1659 if (list_empty(&wb->b_io))
1662 progress = writeback_sb_inodes(work->sb, wb, work);
1664 progress = __writeback_inodes_wb(wb, work);
1665 trace_writeback_written(wb, work);
1667 wb_update_bandwidth(wb, wb_start);
1670 * Did we write something? Try for more
1672 * Dirty inodes are moved to b_io for writeback in batches.
1673 * The completion of the current batch does not necessarily
1674 * mean the overall work is done. So we keep looping as long
1675 * as made some progress on cleaning pages or inodes.
1680 * No more inodes for IO, bail
1682 if (list_empty(&wb->b_more_io))
1685 * Nothing written. Wait for some inode to
1686 * become available for writeback. Otherwise
1687 * we'll just busyloop.
1689 if (!list_empty(&wb->b_more_io)) {
1690 trace_writeback_wait(wb, work);
1691 inode = wb_inode(wb->b_more_io.prev);
1692 spin_lock(&inode->i_lock);
1693 spin_unlock(&wb->list_lock);
1694 /* This function drops i_lock... */
1695 inode_sleep_on_writeback(inode);
1696 spin_lock(&wb->list_lock);
1699 spin_unlock(&wb->list_lock);
1700 blk_finish_plug(&plug);
1702 return nr_pages - work->nr_pages;
1706 * Return the next wb_writeback_work struct that hasn't been processed yet.
1708 static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
1710 struct wb_writeback_work *work = NULL;
1712 spin_lock_bh(&wb->work_lock);
1713 if (!list_empty(&wb->work_list)) {
1714 work = list_entry(wb->work_list.next,
1715 struct wb_writeback_work, list);
1716 list_del_init(&work->list);
1718 spin_unlock_bh(&wb->work_lock);
1723 * Add in the number of potentially dirty inodes, because each inode
1724 * write can dirty pagecache in the underlying blockdev.
1726 static unsigned long get_nr_dirty_pages(void)
1728 return global_page_state(NR_FILE_DIRTY) +
1729 global_page_state(NR_UNSTABLE_NFS) +
1730 get_nr_dirty_inodes();
1733 static long wb_check_background_flush(struct bdi_writeback *wb)
1735 if (wb_over_bg_thresh(wb)) {
1737 struct wb_writeback_work work = {
1738 .nr_pages = LONG_MAX,
1739 .sync_mode = WB_SYNC_NONE,
1740 .for_background = 1,
1742 .reason = WB_REASON_BACKGROUND,
1745 return wb_writeback(wb, &work);
1751 static long wb_check_old_data_flush(struct bdi_writeback *wb)
1753 unsigned long expired;
1757 * When set to zero, disable periodic writeback
1759 if (!dirty_writeback_interval)
1762 expired = wb->last_old_flush +
1763 msecs_to_jiffies(dirty_writeback_interval * 10);
1764 if (time_before(jiffies, expired))
1767 wb->last_old_flush = jiffies;
1768 nr_pages = get_nr_dirty_pages();
1771 struct wb_writeback_work work = {
1772 .nr_pages = nr_pages,
1773 .sync_mode = WB_SYNC_NONE,
1776 .reason = WB_REASON_PERIODIC,
1779 return wb_writeback(wb, &work);
1786 * Retrieve work items and do the writeback they describe
1788 static long wb_do_writeback(struct bdi_writeback *wb)
1790 struct wb_writeback_work *work;
1793 set_bit(WB_writeback_running, &wb->state);
1794 while ((work = get_next_work_item(wb)) != NULL) {
1795 struct wb_completion *done = work->done;
1797 trace_writeback_exec(wb, work);
1799 wrote += wb_writeback(wb, work);
1801 if (work->auto_free)
1803 if (done && atomic_dec_and_test(&done->cnt))
1804 wake_up_all(&wb->bdi->wb_waitq);
1808 * Check for periodic writeback, kupdated() style
1810 wrote += wb_check_old_data_flush(wb);
1811 wrote += wb_check_background_flush(wb);
1812 clear_bit(WB_writeback_running, &wb->state);
1818 * Handle writeback of dirty data for the device backed by this bdi. Also
1819 * reschedules periodically and does kupdated style flushing.
1821 void wb_workfn(struct work_struct *work)
1823 struct bdi_writeback *wb = container_of(to_delayed_work(work),
1824 struct bdi_writeback, dwork);
1827 set_worker_desc("flush-%s", dev_name(wb->bdi->dev));
1828 current->flags |= PF_SWAPWRITE;
1830 if (likely(!current_is_workqueue_rescuer() ||
1831 !test_bit(WB_registered, &wb->state))) {
1833 * The normal path. Keep writing back @wb until its
1834 * work_list is empty. Note that this path is also taken
1835 * if @wb is shutting down even when we're running off the
1836 * rescuer as work_list needs to be drained.
1839 pages_written = wb_do_writeback(wb);
1840 trace_writeback_pages_written(pages_written);
1841 } while (!list_empty(&wb->work_list));
1844 * bdi_wq can't get enough workers and we're running off
1845 * the emergency worker. Don't hog it. Hopefully, 1024 is
1846 * enough for efficient IO.
1848 pages_written = writeback_inodes_wb(wb, 1024,
1849 WB_REASON_FORKER_THREAD);
1850 trace_writeback_pages_written(pages_written);
1853 if (!list_empty(&wb->work_list))
1854 mod_delayed_work(bdi_wq, &wb->dwork, 0);
1855 else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1856 wb_wakeup_delayed(wb);
1858 current->flags &= ~PF_SWAPWRITE;
1862 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
1865 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1867 struct backing_dev_info *bdi;
1870 nr_pages = get_nr_dirty_pages();
1873 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1874 struct bdi_writeback *wb;
1876 if (!bdi_has_dirty_io(bdi))
1879 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
1880 wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
1887 * Wake up bdi's periodically to make sure dirtytime inodes gets
1888 * written back periodically. We deliberately do *not* check the
1889 * b_dirtytime list in wb_has_dirty_io(), since this would cause the
1890 * kernel to be constantly waking up once there are any dirtytime
1891 * inodes on the system. So instead we define a separate delayed work
1892 * function which gets called much more rarely. (By default, only
1893 * once every 12 hours.)
1895 * If there is any other write activity going on in the file system,
1896 * this function won't be necessary. But if the only thing that has
1897 * happened on the file system is a dirtytime inode caused by an atime
1898 * update, we need this infrastructure below to make sure that inode
1899 * eventually gets pushed out to disk.
1901 static void wakeup_dirtytime_writeback(struct work_struct *w);
1902 static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback);
1904 static void wakeup_dirtytime_writeback(struct work_struct *w)
1906 struct backing_dev_info *bdi;
1909 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1910 struct bdi_writeback *wb;
1912 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
1913 if (!list_empty(&wb->b_dirty_time))
1917 schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
1920 static int __init start_dirtytime_writeback(void)
1922 schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
1925 __initcall(start_dirtytime_writeback);
1927 int dirtytime_interval_handler(struct ctl_table *table, int write,
1928 void __user *buffer, size_t *lenp, loff_t *ppos)
1932 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1933 if (ret == 0 && write)
1934 mod_delayed_work(system_wq, &dirtytime_work, 0);
1938 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1940 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1941 struct dentry *dentry;
1942 const char *name = "?";
1944 dentry = d_find_alias(inode);
1946 spin_lock(&dentry->d_lock);
1947 name = (const char *) dentry->d_name.name;
1950 "%s(%d): dirtied inode %lu (%s) on %s\n",
1951 current->comm, task_pid_nr(current), inode->i_ino,
1952 name, inode->i_sb->s_id);
1954 spin_unlock(&dentry->d_lock);
1961 * __mark_inode_dirty - internal function
1962 * @inode: inode to mark
1963 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1964 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1965 * mark_inode_dirty_sync.
1967 * Put the inode on the super block's dirty list.
1969 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1970 * dirty list only if it is hashed or if it refers to a blockdev.
1971 * If it was not hashed, it will never be added to the dirty list
1972 * even if it is later hashed, as it will have been marked dirty already.
1974 * In short, make sure you hash any inodes _before_ you start marking
1977 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1978 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1979 * the kernel-internal blockdev inode represents the dirtying time of the
1980 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1981 * page->mapping->host, so the page-dirtying time is recorded in the internal
1984 #define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
1985 void __mark_inode_dirty(struct inode *inode, int flags)
1987 struct super_block *sb = inode->i_sb;
1990 trace_writeback_mark_inode_dirty(inode, flags);
1993 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1994 * dirty the inode itself
1996 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_TIME)) {
1997 trace_writeback_dirty_inode_start(inode, flags);
1999 if (sb->s_op->dirty_inode)
2000 sb->s_op->dirty_inode(inode, flags);
2002 trace_writeback_dirty_inode(inode, flags);
2004 if (flags & I_DIRTY_INODE)
2005 flags &= ~I_DIRTY_TIME;
2006 dirtytime = flags & I_DIRTY_TIME;
2009 * Paired with smp_mb() in __writeback_single_inode() for the
2010 * following lockless i_state test. See there for details.
2014 if (((inode->i_state & flags) == flags) ||
2015 (dirtytime && (inode->i_state & I_DIRTY_INODE)))
2018 if (unlikely(block_dump))
2019 block_dump___mark_inode_dirty(inode);
2021 spin_lock(&inode->i_lock);
2022 if (dirtytime && (inode->i_state & I_DIRTY_INODE))
2023 goto out_unlock_inode;
2024 if ((inode->i_state & flags) != flags) {
2025 const int was_dirty = inode->i_state & I_DIRTY;
2027 inode_attach_wb(inode, NULL);
2029 if (flags & I_DIRTY_INODE)
2030 inode->i_state &= ~I_DIRTY_TIME;
2031 inode->i_state |= flags;
2034 * If the inode is being synced, just update its dirty state.
2035 * The unlocker will place the inode on the appropriate
2036 * superblock list, based upon its state.
2038 if (inode->i_state & I_SYNC)
2039 goto out_unlock_inode;
2042 * Only add valid (hashed) inodes to the superblock's
2043 * dirty list. Add blockdev inodes as well.
2045 if (!S_ISBLK(inode->i_mode)) {
2046 if (inode_unhashed(inode))
2047 goto out_unlock_inode;
2049 if (inode->i_state & I_FREEING)
2050 goto out_unlock_inode;
2053 * If the inode was already on b_dirty/b_io/b_more_io, don't
2054 * reposition it (that would break b_dirty time-ordering).
2057 struct bdi_writeback *wb;
2058 struct list_head *dirty_list;
2059 bool wakeup_bdi = false;
2061 wb = locked_inode_to_wb_and_lock_list(inode);
2063 WARN(bdi_cap_writeback_dirty(wb->bdi) &&
2064 !test_bit(WB_registered, &wb->state),
2065 "bdi-%s not registered\n", wb->bdi->name);
2067 inode->dirtied_when = jiffies;
2069 inode->dirtied_time_when = jiffies;
2071 if (inode->i_state & (I_DIRTY_INODE | I_DIRTY_PAGES))
2072 dirty_list = &wb->b_dirty;
2074 dirty_list = &wb->b_dirty_time;
2076 wakeup_bdi = inode_io_list_move_locked(inode, wb,
2079 spin_unlock(&wb->list_lock);
2080 trace_writeback_dirty_inode_enqueue(inode);
2083 * If this is the first dirty inode for this bdi,
2084 * we have to wake-up the corresponding bdi thread
2085 * to make sure background write-back happens
2088 if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
2089 wb_wakeup_delayed(wb);
2094 spin_unlock(&inode->i_lock);
2097 EXPORT_SYMBOL(__mark_inode_dirty);
2100 * The @s_sync_lock is used to serialise concurrent sync operations
2101 * to avoid lock contention problems with concurrent wait_sb_inodes() calls.
2102 * Concurrent callers will block on the s_sync_lock rather than doing contending
2103 * walks. The queueing maintains sync(2) required behaviour as all the IO that
2104 * has been issued up to the time this function is enter is guaranteed to be
2105 * completed by the time we have gained the lock and waited for all IO that is
2106 * in progress regardless of the order callers are granted the lock.
2108 static void wait_sb_inodes(struct super_block *sb)
2110 struct inode *inode, *old_inode = NULL;
2113 * We need to be protected against the filesystem going from
2114 * r/o to r/w or vice versa.
2116 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2118 mutex_lock(&sb->s_sync_lock);
2119 spin_lock(&sb->s_inode_list_lock);
2122 * Data integrity sync. Must wait for all pages under writeback,
2123 * because there may have been pages dirtied before our sync
2124 * call, but which had writeout started before we write it out.
2125 * In which case, the inode may not be on the dirty list, but
2126 * we still have to wait for that writeout.
2128 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
2129 struct address_space *mapping = inode->i_mapping;
2131 spin_lock(&inode->i_lock);
2132 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
2133 (mapping->nrpages == 0)) {
2134 spin_unlock(&inode->i_lock);
2138 spin_unlock(&inode->i_lock);
2139 spin_unlock(&sb->s_inode_list_lock);
2142 * We hold a reference to 'inode' so it couldn't have been
2143 * removed from s_inodes list while we dropped the
2144 * s_inode_list_lock. We cannot iput the inode now as we can
2145 * be holding the last reference and we cannot iput it under
2146 * s_inode_list_lock. So we keep the reference and iput it
2152 filemap_fdatawait(mapping);
2156 spin_lock(&sb->s_inode_list_lock);
2158 spin_unlock(&sb->s_inode_list_lock);
2160 mutex_unlock(&sb->s_sync_lock);
2163 static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
2164 enum wb_reason reason, bool skip_if_busy)
2166 DEFINE_WB_COMPLETION_ONSTACK(done);
2167 struct wb_writeback_work work = {
2169 .sync_mode = WB_SYNC_NONE,
2170 .tagged_writepages = 1,
2175 struct backing_dev_info *bdi = sb->s_bdi;
2177 if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info)
2179 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2181 bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy);
2182 wb_wait_for_completion(bdi, &done);
2186 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
2187 * @sb: the superblock
2188 * @nr: the number of pages to write
2189 * @reason: reason why some writeback work initiated
2191 * Start writeback on some inodes on this super_block. No guarantees are made
2192 * on how many (if any) will be written, and this function does not wait
2193 * for IO completion of submitted IO.
2195 void writeback_inodes_sb_nr(struct super_block *sb,
2197 enum wb_reason reason)
2199 __writeback_inodes_sb_nr(sb, nr, reason, false);
2201 EXPORT_SYMBOL(writeback_inodes_sb_nr);
2204 * writeback_inodes_sb - writeback dirty inodes from given super_block
2205 * @sb: the superblock
2206 * @reason: reason why some writeback work was initiated
2208 * Start writeback on some inodes on this super_block. No guarantees are made
2209 * on how many (if any) will be written, and this function does not wait
2210 * for IO completion of submitted IO.
2212 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2214 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
2216 EXPORT_SYMBOL(writeback_inodes_sb);
2219 * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
2220 * @sb: the superblock
2221 * @nr: the number of pages to write
2222 * @reason: the reason of writeback
2224 * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
2225 * Returns 1 if writeback was started, 0 if not.
2227 bool try_to_writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
2228 enum wb_reason reason)
2230 if (!down_read_trylock(&sb->s_umount))
2233 __writeback_inodes_sb_nr(sb, nr, reason, true);
2234 up_read(&sb->s_umount);
2237 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
2240 * try_to_writeback_inodes_sb - try to start writeback if none underway
2241 * @sb: the superblock
2242 * @reason: reason why some writeback work was initiated
2244 * Implement by try_to_writeback_inodes_sb_nr()
2245 * Returns 1 if writeback was started, 0 if not.
2247 bool try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2249 return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
2251 EXPORT_SYMBOL(try_to_writeback_inodes_sb);
2254 * sync_inodes_sb - sync sb inode pages
2255 * @sb: the superblock
2257 * This function writes and waits on any dirty inode belonging to this
2260 void sync_inodes_sb(struct super_block *sb)
2262 DEFINE_WB_COMPLETION_ONSTACK(done);
2263 struct wb_writeback_work work = {
2265 .sync_mode = WB_SYNC_ALL,
2266 .nr_pages = LONG_MAX,
2269 .reason = WB_REASON_SYNC,
2272 struct backing_dev_info *bdi = sb->s_bdi;
2275 * Can't skip on !bdi_has_dirty() because we should wait for !dirty
2276 * inodes under writeback and I_DIRTY_TIME inodes ignored by
2277 * bdi_has_dirty() need to be written out too.
2279 if (bdi == &noop_backing_dev_info)
2281 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2283 bdi_split_work_to_wbs(bdi, &work, false);
2284 wb_wait_for_completion(bdi, &done);
2288 EXPORT_SYMBOL(sync_inodes_sb);
2291 * write_inode_now - write an inode to disk
2292 * @inode: inode to write to disk
2293 * @sync: whether the write should be synchronous or not
2295 * This function commits an inode to disk immediately if it is dirty. This is
2296 * primarily needed by knfsd.
2298 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
2300 int write_inode_now(struct inode *inode, int sync)
2302 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
2303 struct writeback_control wbc = {
2304 .nr_to_write = LONG_MAX,
2305 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
2307 .range_end = LLONG_MAX,
2310 if (!mapping_cap_writeback_dirty(inode->i_mapping))
2311 wbc.nr_to_write = 0;
2314 return writeback_single_inode(inode, wb, &wbc);
2316 EXPORT_SYMBOL(write_inode_now);
2319 * sync_inode - write an inode and its pages to disk.
2320 * @inode: the inode to sync
2321 * @wbc: controls the writeback mode
2323 * sync_inode() will write an inode and its pages to disk. It will also
2324 * correctly update the inode on its superblock's dirty inode lists and will
2325 * update inode->i_state.
2327 * The caller must have a ref on the inode.
2329 int sync_inode(struct inode *inode, struct writeback_control *wbc)
2331 return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
2333 EXPORT_SYMBOL(sync_inode);
2336 * sync_inode_metadata - write an inode to disk
2337 * @inode: the inode to sync
2338 * @wait: wait for I/O to complete.
2340 * Write an inode to disk and adjust its dirty state after completion.
2342 * Note: only writes the actual inode, no associated data or other metadata.
2344 int sync_inode_metadata(struct inode *inode, int wait)
2346 struct writeback_control wbc = {
2347 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
2348 .nr_to_write = 0, /* metadata-only */
2351 return sync_inode(inode, &wbc);
2353 EXPORT_SYMBOL(sync_inode_metadata);