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 static atomic_t isw_nr_in_flight = ATOMIC_INIT(0);
227 static struct workqueue_struct *isw_wq;
229 void __inode_attach_wb(struct inode *inode, struct page *page)
231 struct backing_dev_info *bdi = inode_to_bdi(inode);
232 struct bdi_writeback *wb = NULL;
234 if (inode_cgwb_enabled(inode)) {
235 struct cgroup_subsys_state *memcg_css;
238 memcg_css = mem_cgroup_css_from_page(page);
239 wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
241 /* must pin memcg_css, see wb_get_create() */
242 memcg_css = task_get_css(current, memory_cgrp_id);
243 wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
252 * There may be multiple instances of this function racing to
253 * update the same inode. Use cmpxchg() to tell the winner.
255 if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
260 * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
261 * @inode: inode of interest with i_lock held
263 * Returns @inode's wb with its list_lock held. @inode->i_lock must be
264 * held on entry and is released on return. The returned wb is guaranteed
265 * to stay @inode's associated wb until its list_lock is released.
267 static struct bdi_writeback *
268 locked_inode_to_wb_and_lock_list(struct inode *inode)
269 __releases(&inode->i_lock)
270 __acquires(&wb->list_lock)
273 struct bdi_writeback *wb = inode_to_wb(inode);
276 * inode_to_wb() association is protected by both
277 * @inode->i_lock and @wb->list_lock but list_lock nests
278 * outside i_lock. Drop i_lock and verify that the
279 * association hasn't changed after acquiring list_lock.
282 spin_unlock(&inode->i_lock);
283 spin_lock(&wb->list_lock);
284 wb_put(wb); /* not gonna deref it anymore */
286 /* i_wb may have changed inbetween, can't use inode_to_wb() */
287 if (likely(wb == inode->i_wb))
288 return wb; /* @inode already has ref */
290 spin_unlock(&wb->list_lock);
292 spin_lock(&inode->i_lock);
297 * inode_to_wb_and_lock_list - determine an inode's wb and lock it
298 * @inode: inode of interest
300 * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
303 static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
304 __acquires(&wb->list_lock)
306 spin_lock(&inode->i_lock);
307 return locked_inode_to_wb_and_lock_list(inode);
310 struct inode_switch_wbs_context {
312 struct bdi_writeback *new_wb;
314 struct rcu_head rcu_head;
315 struct work_struct work;
318 static void inode_switch_wbs_work_fn(struct work_struct *work)
320 struct inode_switch_wbs_context *isw =
321 container_of(work, struct inode_switch_wbs_context, work);
322 struct inode *inode = isw->inode;
323 struct address_space *mapping = inode->i_mapping;
324 struct bdi_writeback *old_wb = inode->i_wb;
325 struct bdi_writeback *new_wb = isw->new_wb;
326 struct radix_tree_iter iter;
327 bool switched = false;
331 * By the time control reaches here, RCU grace period has passed
332 * since I_WB_SWITCH assertion and all wb stat update transactions
333 * between unlocked_inode_to_wb_begin/end() are guaranteed to be
334 * synchronizing against mapping->tree_lock.
336 * Grabbing old_wb->list_lock, inode->i_lock and mapping->tree_lock
337 * gives us exclusion against all wb related operations on @inode
338 * including IO list manipulations and stat updates.
340 if (old_wb < new_wb) {
341 spin_lock(&old_wb->list_lock);
342 spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING);
344 spin_lock(&new_wb->list_lock);
345 spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING);
347 spin_lock(&inode->i_lock);
348 spin_lock_irq(&mapping->tree_lock);
351 * Once I_FREEING is visible under i_lock, the eviction path owns
352 * the inode and we shouldn't modify ->i_io_list.
354 if (unlikely(inode->i_state & I_FREEING))
358 * Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points
359 * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
360 * pages actually under underwriteback.
362 radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, 0,
363 PAGECACHE_TAG_DIRTY) {
364 struct page *page = radix_tree_deref_slot_protected(slot,
365 &mapping->tree_lock);
366 if (likely(page) && PageDirty(page)) {
367 __dec_wb_stat(old_wb, WB_RECLAIMABLE);
368 __inc_wb_stat(new_wb, WB_RECLAIMABLE);
372 radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, 0,
373 PAGECACHE_TAG_WRITEBACK) {
374 struct page *page = radix_tree_deref_slot_protected(slot,
375 &mapping->tree_lock);
377 WARN_ON_ONCE(!PageWriteback(page));
378 __dec_wb_stat(old_wb, WB_WRITEBACK);
379 __inc_wb_stat(new_wb, WB_WRITEBACK);
386 * Transfer to @new_wb's IO list if necessary. The specific list
387 * @inode was on is ignored and the inode is put on ->b_dirty which
388 * is always correct including from ->b_dirty_time. The transfer
389 * preserves @inode->dirtied_when ordering.
391 if (!list_empty(&inode->i_io_list)) {
394 inode_io_list_del_locked(inode, old_wb);
395 inode->i_wb = new_wb;
396 list_for_each_entry(pos, &new_wb->b_dirty, i_io_list)
397 if (time_after_eq(inode->dirtied_when,
400 inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev);
402 inode->i_wb = new_wb;
405 /* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */
406 inode->i_wb_frn_winner = 0;
407 inode->i_wb_frn_avg_time = 0;
408 inode->i_wb_frn_history = 0;
412 * Paired with load_acquire in unlocked_inode_to_wb_begin() and
413 * ensures that the new wb is visible if they see !I_WB_SWITCH.
415 smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH);
417 spin_unlock_irq(&mapping->tree_lock);
418 spin_unlock(&inode->i_lock);
419 spin_unlock(&new_wb->list_lock);
420 spin_unlock(&old_wb->list_lock);
431 atomic_dec(&isw_nr_in_flight);
434 static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head)
436 struct inode_switch_wbs_context *isw = container_of(rcu_head,
437 struct inode_switch_wbs_context, rcu_head);
439 /* needs to grab bh-unsafe locks, bounce to work item */
440 INIT_WORK(&isw->work, inode_switch_wbs_work_fn);
441 queue_work(isw_wq, &isw->work);
445 * inode_switch_wbs - change the wb association of an inode
446 * @inode: target inode
447 * @new_wb_id: ID of the new wb
449 * Switch @inode's wb association to the wb identified by @new_wb_id. The
450 * switching is performed asynchronously and may fail silently.
452 static void inode_switch_wbs(struct inode *inode, int new_wb_id)
454 struct backing_dev_info *bdi = inode_to_bdi(inode);
455 struct cgroup_subsys_state *memcg_css;
456 struct inode_switch_wbs_context *isw;
458 /* noop if seems to be already in progress */
459 if (inode->i_state & I_WB_SWITCH)
462 isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
466 /* find and pin the new wb */
468 memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys);
470 isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
475 /* while holding I_WB_SWITCH, no one else can update the association */
476 spin_lock(&inode->i_lock);
477 if (!(inode->i_sb->s_flags & MS_ACTIVE) ||
478 inode->i_state & (I_WB_SWITCH | I_FREEING) ||
479 inode_to_wb(inode) == isw->new_wb) {
480 spin_unlock(&inode->i_lock);
483 inode->i_state |= I_WB_SWITCH;
484 spin_unlock(&inode->i_lock);
489 atomic_inc(&isw_nr_in_flight);
492 * In addition to synchronizing among switchers, I_WB_SWITCH tells
493 * the RCU protected stat update paths to grab the mapping's
494 * tree_lock so that stat transfer can synchronize against them.
495 * Let's continue after I_WB_SWITCH is guaranteed to be visible.
497 call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
507 * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it
508 * @wbc: writeback_control of interest
509 * @inode: target inode
511 * @inode is locked and about to be written back under the control of @wbc.
512 * Record @inode's writeback context into @wbc and unlock the i_lock. On
513 * writeback completion, wbc_detach_inode() should be called. This is used
514 * to track the cgroup writeback context.
516 void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
519 if (!inode_cgwb_enabled(inode)) {
520 spin_unlock(&inode->i_lock);
524 wbc->wb = inode_to_wb(inode);
527 wbc->wb_id = wbc->wb->memcg_css->id;
528 wbc->wb_lcand_id = inode->i_wb_frn_winner;
529 wbc->wb_tcand_id = 0;
531 wbc->wb_lcand_bytes = 0;
532 wbc->wb_tcand_bytes = 0;
535 spin_unlock(&inode->i_lock);
538 * A dying wb indicates that the memcg-blkcg mapping has changed
539 * and a new wb is already serving the memcg. Switch immediately.
541 if (unlikely(wb_dying(wbc->wb)))
542 inode_switch_wbs(inode, wbc->wb_id);
546 * wbc_detach_inode - disassociate wbc from inode and perform foreign detection
547 * @wbc: writeback_control of the just finished writeback
549 * To be called after a writeback attempt of an inode finishes and undoes
550 * wbc_attach_and_unlock_inode(). Can be called under any context.
552 * As concurrent write sharing of an inode is expected to be very rare and
553 * memcg only tracks page ownership on first-use basis severely confining
554 * the usefulness of such sharing, cgroup writeback tracks ownership
555 * per-inode. While the support for concurrent write sharing of an inode
556 * is deemed unnecessary, an inode being written to by different cgroups at
557 * different points in time is a lot more common, and, more importantly,
558 * charging only by first-use can too readily lead to grossly incorrect
559 * behaviors (single foreign page can lead to gigabytes of writeback to be
560 * incorrectly attributed).
562 * To resolve this issue, cgroup writeback detects the majority dirtier of
563 * an inode and transfers the ownership to it. To avoid unnnecessary
564 * oscillation, the detection mechanism keeps track of history and gives
565 * out the switch verdict only if the foreign usage pattern is stable over
566 * a certain amount of time and/or writeback attempts.
568 * On each writeback attempt, @wbc tries to detect the majority writer
569 * using Boyer-Moore majority vote algorithm. In addition to the byte
570 * count from the majority voting, it also counts the bytes written for the
571 * current wb and the last round's winner wb (max of last round's current
572 * wb, the winner from two rounds ago, and the last round's majority
573 * candidate). Keeping track of the historical winner helps the algorithm
574 * to semi-reliably detect the most active writer even when it's not the
577 * Once the winner of the round is determined, whether the winner is
578 * foreign or not and how much IO time the round consumed is recorded in
579 * inode->i_wb_frn_history. If the amount of recorded foreign IO time is
580 * over a certain threshold, the switch verdict is given.
582 void wbc_detach_inode(struct writeback_control *wbc)
584 struct bdi_writeback *wb = wbc->wb;
585 struct inode *inode = wbc->inode;
586 unsigned long avg_time, max_bytes, max_time;
593 history = inode->i_wb_frn_history;
594 avg_time = inode->i_wb_frn_avg_time;
596 /* pick the winner of this round */
597 if (wbc->wb_bytes >= wbc->wb_lcand_bytes &&
598 wbc->wb_bytes >= wbc->wb_tcand_bytes) {
600 max_bytes = wbc->wb_bytes;
601 } else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) {
602 max_id = wbc->wb_lcand_id;
603 max_bytes = wbc->wb_lcand_bytes;
605 max_id = wbc->wb_tcand_id;
606 max_bytes = wbc->wb_tcand_bytes;
610 * Calculate the amount of IO time the winner consumed and fold it
611 * into the running average kept per inode. If the consumed IO
612 * time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
613 * deciding whether to switch or not. This is to prevent one-off
614 * small dirtiers from skewing the verdict.
616 max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT,
617 wb->avg_write_bandwidth);
619 avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) -
620 (avg_time >> WB_FRN_TIME_AVG_SHIFT);
622 avg_time = max_time; /* immediate catch up on first run */
624 if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) {
628 * The switch verdict is reached if foreign wb's consume
629 * more than a certain proportion of IO time in a
630 * WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
631 * history mask where each bit represents one sixteenth of
632 * the period. Determine the number of slots to shift into
633 * history from @max_time.
635 slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT),
636 (unsigned long)WB_FRN_HIST_MAX_SLOTS);
638 if (wbc->wb_id != max_id)
639 history |= (1U << slots) - 1;
642 * Switch if the current wb isn't the consistent winner.
643 * If there are multiple closely competing dirtiers, the
644 * inode may switch across them repeatedly over time, which
645 * is okay. The main goal is avoiding keeping an inode on
646 * the wrong wb for an extended period of time.
648 if (hweight32(history) > WB_FRN_HIST_THR_SLOTS)
649 inode_switch_wbs(inode, max_id);
653 * Multiple instances of this function may race to update the
654 * following fields but we don't mind occassional inaccuracies.
656 inode->i_wb_frn_winner = max_id;
657 inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX);
658 inode->i_wb_frn_history = history;
665 * wbc_account_io - account IO issued during writeback
666 * @wbc: writeback_control of the writeback in progress
667 * @page: page being written out
668 * @bytes: number of bytes being written out
670 * @bytes from @page are about to written out during the writeback
671 * controlled by @wbc. Keep the book for foreign inode detection. See
672 * wbc_detach_inode().
674 void wbc_account_io(struct writeback_control *wbc, struct page *page,
680 * pageout() path doesn't attach @wbc to the inode being written
681 * out. This is intentional as we don't want the function to block
682 * behind a slow cgroup. Ultimately, we want pageout() to kick off
683 * regular writeback instead of writing things out itself.
688 id = mem_cgroup_css_from_page(page)->id;
690 if (id == wbc->wb_id) {
691 wbc->wb_bytes += bytes;
695 if (id == wbc->wb_lcand_id)
696 wbc->wb_lcand_bytes += bytes;
698 /* Boyer-Moore majority vote algorithm */
699 if (!wbc->wb_tcand_bytes)
700 wbc->wb_tcand_id = id;
701 if (id == wbc->wb_tcand_id)
702 wbc->wb_tcand_bytes += bytes;
704 wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes);
706 EXPORT_SYMBOL_GPL(wbc_account_io);
709 * inode_congested - test whether an inode is congested
710 * @inode: inode to test for congestion (may be NULL)
711 * @cong_bits: mask of WB_[a]sync_congested bits to test
713 * Tests whether @inode is congested. @cong_bits is the mask of congestion
714 * bits to test and the return value is the mask of set bits.
716 * If cgroup writeback is enabled for @inode, the congestion state is
717 * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
718 * associated with @inode is congested; otherwise, the root wb's congestion
721 * @inode is allowed to be NULL as this function is often called on
722 * mapping->host which is NULL for the swapper space.
724 int inode_congested(struct inode *inode, int cong_bits)
727 * Once set, ->i_wb never becomes NULL while the inode is alive.
728 * Start transaction iff ->i_wb is visible.
730 if (inode && inode_to_wb_is_valid(inode)) {
731 struct bdi_writeback *wb;
732 bool locked, congested;
734 wb = unlocked_inode_to_wb_begin(inode, &locked);
735 congested = wb_congested(wb, cong_bits);
736 unlocked_inode_to_wb_end(inode, locked);
740 return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
742 EXPORT_SYMBOL_GPL(inode_congested);
745 * wb_split_bdi_pages - split nr_pages to write according to bandwidth
746 * @wb: target bdi_writeback to split @nr_pages to
747 * @nr_pages: number of pages to write for the whole bdi
749 * Split @wb's portion of @nr_pages according to @wb's write bandwidth in
750 * relation to the total write bandwidth of all wb's w/ dirty inodes on
753 static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
755 unsigned long this_bw = wb->avg_write_bandwidth;
756 unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);
758 if (nr_pages == LONG_MAX)
762 * This may be called on clean wb's and proportional distribution
763 * may not make sense, just use the original @nr_pages in those
764 * cases. In general, we wanna err on the side of writing more.
766 if (!tot_bw || this_bw >= tot_bw)
769 return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
773 * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
774 * @bdi: target backing_dev_info
775 * @base_work: wb_writeback_work to issue
776 * @skip_if_busy: skip wb's which already have writeback in progress
778 * Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
779 * have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
780 * distributed to the busy wbs according to each wb's proportion in the
781 * total active write bandwidth of @bdi.
783 static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
784 struct wb_writeback_work *base_work,
787 struct bdi_writeback *last_wb = NULL;
788 struct bdi_writeback *wb = list_entry(&bdi->wb_list,
789 struct bdi_writeback, bdi_node);
794 list_for_each_entry_continue_rcu(wb, &bdi->wb_list, bdi_node) {
795 DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done);
796 struct wb_writeback_work fallback_work;
797 struct wb_writeback_work *work;
805 /* SYNC_ALL writes out I_DIRTY_TIME too */
806 if (!wb_has_dirty_io(wb) &&
807 (base_work->sync_mode == WB_SYNC_NONE ||
808 list_empty(&wb->b_dirty_time)))
810 if (skip_if_busy && writeback_in_progress(wb))
813 nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages);
815 work = kmalloc(sizeof(*work), GFP_ATOMIC);
818 work->nr_pages = nr_pages;
820 wb_queue_work(wb, work);
824 /* alloc failed, execute synchronously using on-stack fallback */
825 work = &fallback_work;
827 work->nr_pages = nr_pages;
829 work->done = &fallback_work_done;
831 wb_queue_work(wb, work);
834 * Pin @wb so that it stays on @bdi->wb_list. This allows
835 * continuing iteration from @wb after dropping and
836 * regrabbing rcu read lock.
842 wb_wait_for_completion(bdi, &fallback_work_done);
852 * cgroup_writeback_umount - flush inode wb switches for umount
854 * This function is called when a super_block is about to be destroyed and
855 * flushes in-flight inode wb switches. An inode wb switch goes through
856 * RCU and then workqueue, so the two need to be flushed in order to ensure
857 * that all previously scheduled switches are finished. As wb switches are
858 * rare occurrences and synchronize_rcu() can take a while, perform
859 * flushing iff wb switches are in flight.
861 void cgroup_writeback_umount(void)
863 if (atomic_read(&isw_nr_in_flight)) {
865 flush_workqueue(isw_wq);
869 static int __init cgroup_writeback_init(void)
871 isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0);
876 fs_initcall(cgroup_writeback_init);
878 #else /* CONFIG_CGROUP_WRITEBACK */
880 static struct bdi_writeback *
881 locked_inode_to_wb_and_lock_list(struct inode *inode)
882 __releases(&inode->i_lock)
883 __acquires(&wb->list_lock)
885 struct bdi_writeback *wb = inode_to_wb(inode);
887 spin_unlock(&inode->i_lock);
888 spin_lock(&wb->list_lock);
892 static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
893 __acquires(&wb->list_lock)
895 struct bdi_writeback *wb = inode_to_wb(inode);
897 spin_lock(&wb->list_lock);
901 static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
906 static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
907 struct wb_writeback_work *base_work,
912 if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
913 base_work->auto_free = 0;
914 wb_queue_work(&bdi->wb, base_work);
918 #endif /* CONFIG_CGROUP_WRITEBACK */
920 void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
921 bool range_cyclic, enum wb_reason reason)
923 struct wb_writeback_work *work;
925 if (!wb_has_dirty_io(wb))
929 * This is WB_SYNC_NONE writeback, so if allocation fails just
930 * wakeup the thread for old dirty data writeback
932 work = kzalloc(sizeof(*work), GFP_ATOMIC);
934 trace_writeback_nowork(wb);
939 work->sync_mode = WB_SYNC_NONE;
940 work->nr_pages = nr_pages;
941 work->range_cyclic = range_cyclic;
942 work->reason = reason;
945 wb_queue_work(wb, work);
949 * wb_start_background_writeback - start background writeback
950 * @wb: bdi_writback to write from
953 * This makes sure WB_SYNC_NONE background writeback happens. When
954 * this function returns, it is only guaranteed that for given wb
955 * some IO is happening if we are over background dirty threshold.
956 * Caller need not hold sb s_umount semaphore.
958 void wb_start_background_writeback(struct bdi_writeback *wb)
961 * We just wake up the flusher thread. It will perform background
962 * writeback as soon as there is no other work to do.
964 trace_writeback_wake_background(wb);
969 * Remove the inode from the writeback list it is on.
971 void inode_io_list_del(struct inode *inode)
973 struct bdi_writeback *wb;
975 wb = inode_to_wb_and_lock_list(inode);
976 inode_io_list_del_locked(inode, wb);
977 spin_unlock(&wb->list_lock);
981 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
982 * furthest end of its superblock's dirty-inode list.
984 * Before stamping the inode's ->dirtied_when, we check to see whether it is
985 * already the most-recently-dirtied inode on the b_dirty list. If that is
986 * the case then the inode must have been redirtied while it was being written
987 * out and we don't reset its dirtied_when.
989 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
991 if (!list_empty(&wb->b_dirty)) {
994 tail = wb_inode(wb->b_dirty.next);
995 if (time_before(inode->dirtied_when, tail->dirtied_when))
996 inode->dirtied_when = jiffies;
998 inode_io_list_move_locked(inode, wb, &wb->b_dirty);
1002 * requeue inode for re-scanning after bdi->b_io list is exhausted.
1004 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
1006 inode_io_list_move_locked(inode, wb, &wb->b_more_io);
1009 static void inode_sync_complete(struct inode *inode)
1011 inode->i_state &= ~I_SYNC;
1012 /* If inode is clean an unused, put it into LRU now... */
1013 inode_add_lru(inode);
1014 /* Waiters must see I_SYNC cleared before being woken up */
1016 wake_up_bit(&inode->i_state, __I_SYNC);
1019 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
1021 bool ret = time_after(inode->dirtied_when, t);
1022 #ifndef CONFIG_64BIT
1024 * For inodes being constantly redirtied, dirtied_when can get stuck.
1025 * It _appears_ to be in the future, but is actually in distant past.
1026 * This test is necessary to prevent such wrapped-around relative times
1027 * from permanently stopping the whole bdi writeback.
1029 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
1034 #define EXPIRE_DIRTY_ATIME 0x0001
1037 * Move expired (dirtied before work->older_than_this) dirty inodes from
1038 * @delaying_queue to @dispatch_queue.
1040 static int move_expired_inodes(struct list_head *delaying_queue,
1041 struct list_head *dispatch_queue,
1043 struct wb_writeback_work *work)
1045 unsigned long *older_than_this = NULL;
1046 unsigned long expire_time;
1048 struct list_head *pos, *node;
1049 struct super_block *sb = NULL;
1050 struct inode *inode;
1054 if ((flags & EXPIRE_DIRTY_ATIME) == 0)
1055 older_than_this = work->older_than_this;
1056 else if (!work->for_sync) {
1057 expire_time = jiffies - (dirtytime_expire_interval * HZ);
1058 older_than_this = &expire_time;
1060 while (!list_empty(delaying_queue)) {
1061 inode = wb_inode(delaying_queue->prev);
1062 if (older_than_this &&
1063 inode_dirtied_after(inode, *older_than_this))
1065 list_move(&inode->i_io_list, &tmp);
1067 if (flags & EXPIRE_DIRTY_ATIME)
1068 set_bit(__I_DIRTY_TIME_EXPIRED, &inode->i_state);
1069 if (sb_is_blkdev_sb(inode->i_sb))
1071 if (sb && sb != inode->i_sb)
1076 /* just one sb in list, splice to dispatch_queue and we're done */
1078 list_splice(&tmp, dispatch_queue);
1082 /* Move inodes from one superblock together */
1083 while (!list_empty(&tmp)) {
1084 sb = wb_inode(tmp.prev)->i_sb;
1085 list_for_each_prev_safe(pos, node, &tmp) {
1086 inode = wb_inode(pos);
1087 if (inode->i_sb == sb)
1088 list_move(&inode->i_io_list, dispatch_queue);
1096 * Queue all expired dirty inodes for io, eldest first.
1098 * newly dirtied b_dirty b_io b_more_io
1099 * =============> gf edc BA
1101 * newly dirtied b_dirty b_io b_more_io
1102 * =============> g fBAedc
1104 * +--> dequeue for IO
1106 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
1110 assert_spin_locked(&wb->list_lock);
1111 list_splice_init(&wb->b_more_io, &wb->b_io);
1112 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work);
1113 moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
1114 EXPIRE_DIRTY_ATIME, work);
1116 wb_io_lists_populated(wb);
1117 trace_writeback_queue_io(wb, work, moved);
1120 static int write_inode(struct inode *inode, struct writeback_control *wbc)
1124 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
1125 trace_writeback_write_inode_start(inode, wbc);
1126 ret = inode->i_sb->s_op->write_inode(inode, wbc);
1127 trace_writeback_write_inode(inode, wbc);
1134 * Wait for writeback on an inode to complete. Called with i_lock held.
1135 * Caller must make sure inode cannot go away when we drop i_lock.
1137 static void __inode_wait_for_writeback(struct inode *inode)
1138 __releases(inode->i_lock)
1139 __acquires(inode->i_lock)
1141 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
1142 wait_queue_head_t *wqh;
1144 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1145 while (inode->i_state & I_SYNC) {
1146 spin_unlock(&inode->i_lock);
1147 __wait_on_bit(wqh, &wq, bit_wait,
1148 TASK_UNINTERRUPTIBLE);
1149 spin_lock(&inode->i_lock);
1154 * Wait for writeback on an inode to complete. Caller must have inode pinned.
1156 void inode_wait_for_writeback(struct inode *inode)
1158 spin_lock(&inode->i_lock);
1159 __inode_wait_for_writeback(inode);
1160 spin_unlock(&inode->i_lock);
1164 * Sleep until I_SYNC is cleared. This function must be called with i_lock
1165 * held and drops it. It is aimed for callers not holding any inode reference
1166 * so once i_lock is dropped, inode can go away.
1168 static void inode_sleep_on_writeback(struct inode *inode)
1169 __releases(inode->i_lock)
1172 wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1175 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1176 sleep = inode->i_state & I_SYNC;
1177 spin_unlock(&inode->i_lock);
1180 finish_wait(wqh, &wait);
1184 * Find proper writeback list for the inode depending on its current state and
1185 * possibly also change of its state while we were doing writeback. Here we
1186 * handle things such as livelock prevention or fairness of writeback among
1187 * inodes. This function can be called only by flusher thread - noone else
1188 * processes all inodes in writeback lists and requeueing inodes behind flusher
1189 * thread's back can have unexpected consequences.
1191 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
1192 struct writeback_control *wbc)
1194 if (inode->i_state & I_FREEING)
1198 * Sync livelock prevention. Each inode is tagged and synced in one
1199 * shot. If still dirty, it will be redirty_tail()'ed below. Update
1200 * the dirty time to prevent enqueue and sync it again.
1202 if ((inode->i_state & I_DIRTY) &&
1203 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
1204 inode->dirtied_when = jiffies;
1206 if (wbc->pages_skipped) {
1208 * writeback is not making progress due to locked
1209 * buffers. Skip this inode for now.
1211 redirty_tail(inode, wb);
1215 if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
1217 * We didn't write back all the pages. nfs_writepages()
1218 * sometimes bales out without doing anything.
1220 if (wbc->nr_to_write <= 0) {
1221 /* Slice used up. Queue for next turn. */
1222 requeue_io(inode, wb);
1225 * Writeback blocked by something other than
1226 * congestion. Delay the inode for some time to
1227 * avoid spinning on the CPU (100% iowait)
1228 * retrying writeback of the dirty page/inode
1229 * that cannot be performed immediately.
1231 redirty_tail(inode, wb);
1233 } else if (inode->i_state & I_DIRTY) {
1235 * Filesystems can dirty the inode during writeback operations,
1236 * such as delayed allocation during submission or metadata
1237 * updates after data IO completion.
1239 redirty_tail(inode, wb);
1240 } else if (inode->i_state & I_DIRTY_TIME) {
1241 inode->dirtied_when = jiffies;
1242 inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
1244 /* The inode is clean. Remove from writeback lists. */
1245 inode_io_list_del_locked(inode, wb);
1250 * Write out an inode and its dirty pages. Do not update the writeback list
1251 * linkage. That is left to the caller. The caller is also responsible for
1252 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
1255 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
1257 struct address_space *mapping = inode->i_mapping;
1258 long nr_to_write = wbc->nr_to_write;
1262 WARN_ON(!(inode->i_state & I_SYNC));
1264 trace_writeback_single_inode_start(inode, wbc, nr_to_write);
1266 ret = do_writepages(mapping, wbc);
1269 * Make sure to wait on the data before writing out the metadata.
1270 * This is important for filesystems that modify metadata on data
1271 * I/O completion. We don't do it for sync(2) writeback because it has a
1272 * separate, external IO completion path and ->sync_fs for guaranteeing
1273 * inode metadata is written back correctly.
1275 if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
1276 int err = filemap_fdatawait(mapping);
1282 * Some filesystems may redirty the inode during the writeback
1283 * due to delalloc, clear dirty metadata flags right before
1286 spin_lock(&inode->i_lock);
1288 dirty = inode->i_state & I_DIRTY;
1289 if (inode->i_state & I_DIRTY_TIME) {
1290 if ((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) ||
1291 unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) ||
1292 unlikely(time_after(jiffies,
1293 (inode->dirtied_time_when +
1294 dirtytime_expire_interval * HZ)))) {
1295 dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
1296 trace_writeback_lazytime(inode);
1299 inode->i_state &= ~I_DIRTY_TIME_EXPIRED;
1300 inode->i_state &= ~dirty;
1303 * Paired with smp_mb() in __mark_inode_dirty(). This allows
1304 * __mark_inode_dirty() to test i_state without grabbing i_lock -
1305 * either they see the I_DIRTY bits cleared or we see the dirtied
1308 * I_DIRTY_PAGES is always cleared together above even if @mapping
1309 * still has dirty pages. The flag is reinstated after smp_mb() if
1310 * necessary. This guarantees that either __mark_inode_dirty()
1311 * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
1315 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
1316 inode->i_state |= I_DIRTY_PAGES;
1318 spin_unlock(&inode->i_lock);
1320 if (dirty & I_DIRTY_TIME)
1321 mark_inode_dirty_sync(inode);
1322 /* Don't write the inode if only I_DIRTY_PAGES was set */
1323 if (dirty & ~I_DIRTY_PAGES) {
1324 int err = write_inode(inode, wbc);
1328 trace_writeback_single_inode(inode, wbc, nr_to_write);
1333 * Write out an inode's dirty pages. Either the caller has an active reference
1334 * on the inode or the inode has I_WILL_FREE set.
1336 * This function is designed to be called for writing back one inode which
1337 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
1338 * and does more profound writeback list handling in writeback_sb_inodes().
1341 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
1342 struct writeback_control *wbc)
1346 spin_lock(&inode->i_lock);
1347 if (!atomic_read(&inode->i_count))
1348 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
1350 WARN_ON(inode->i_state & I_WILL_FREE);
1352 if (inode->i_state & I_SYNC) {
1353 if (wbc->sync_mode != WB_SYNC_ALL)
1356 * It's a data-integrity sync. We must wait. Since callers hold
1357 * inode reference or inode has I_WILL_FREE set, it cannot go
1360 __inode_wait_for_writeback(inode);
1362 WARN_ON(inode->i_state & I_SYNC);
1364 * Skip inode if it is clean and we have no outstanding writeback in
1365 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
1366 * function since flusher thread may be doing for example sync in
1367 * parallel and if we move the inode, it could get skipped. So here we
1368 * make sure inode is on some writeback list and leave it there unless
1369 * we have completely cleaned the inode.
1371 if (!(inode->i_state & I_DIRTY_ALL) &&
1372 (wbc->sync_mode != WB_SYNC_ALL ||
1373 !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
1375 inode->i_state |= I_SYNC;
1376 wbc_attach_and_unlock_inode(wbc, inode);
1378 ret = __writeback_single_inode(inode, wbc);
1380 wbc_detach_inode(wbc);
1381 spin_lock(&wb->list_lock);
1382 spin_lock(&inode->i_lock);
1384 * If inode is clean, remove it from writeback lists. Otherwise don't
1385 * touch it. See comment above for explanation.
1387 if (!(inode->i_state & I_DIRTY_ALL))
1388 inode_io_list_del_locked(inode, wb);
1389 spin_unlock(&wb->list_lock);
1390 inode_sync_complete(inode);
1392 spin_unlock(&inode->i_lock);
1396 static long writeback_chunk_size(struct bdi_writeback *wb,
1397 struct wb_writeback_work *work)
1402 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
1403 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
1404 * here avoids calling into writeback_inodes_wb() more than once.
1406 * The intended call sequence for WB_SYNC_ALL writeback is:
1409 * writeback_sb_inodes() <== called only once
1410 * write_cache_pages() <== called once for each inode
1411 * (quickly) tag currently dirty pages
1412 * (maybe slowly) sync all tagged pages
1414 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
1417 pages = min(wb->avg_write_bandwidth / 2,
1418 global_wb_domain.dirty_limit / DIRTY_SCOPE);
1419 pages = min(pages, work->nr_pages);
1420 pages = round_down(pages + MIN_WRITEBACK_PAGES,
1421 MIN_WRITEBACK_PAGES);
1428 * Write a portion of b_io inodes which belong to @sb.
1430 * Return the number of pages and/or inodes written.
1432 * NOTE! This is called with wb->list_lock held, and will
1433 * unlock and relock that for each inode it ends up doing
1436 static long writeback_sb_inodes(struct super_block *sb,
1437 struct bdi_writeback *wb,
1438 struct wb_writeback_work *work)
1440 struct writeback_control wbc = {
1441 .sync_mode = work->sync_mode,
1442 .tagged_writepages = work->tagged_writepages,
1443 .for_kupdate = work->for_kupdate,
1444 .for_background = work->for_background,
1445 .for_sync = work->for_sync,
1446 .range_cyclic = work->range_cyclic,
1448 .range_end = LLONG_MAX,
1450 unsigned long start_time = jiffies;
1452 long wrote = 0; /* count both pages and inodes */
1454 while (!list_empty(&wb->b_io)) {
1455 struct inode *inode = wb_inode(wb->b_io.prev);
1457 if (inode->i_sb != sb) {
1460 * We only want to write back data for this
1461 * superblock, move all inodes not belonging
1462 * to it back onto the dirty list.
1464 redirty_tail(inode, wb);
1469 * The inode belongs to a different superblock.
1470 * Bounce back to the caller to unpin this and
1471 * pin the next superblock.
1477 * Don't bother with new inodes or inodes being freed, first
1478 * kind does not need periodic writeout yet, and for the latter
1479 * kind writeout is handled by the freer.
1481 spin_lock(&inode->i_lock);
1482 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
1483 spin_unlock(&inode->i_lock);
1484 redirty_tail(inode, wb);
1487 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
1489 * If this inode is locked for writeback and we are not
1490 * doing writeback-for-data-integrity, move it to
1491 * b_more_io so that writeback can proceed with the
1492 * other inodes on s_io.
1494 * We'll have another go at writing back this inode
1495 * when we completed a full scan of b_io.
1497 spin_unlock(&inode->i_lock);
1498 requeue_io(inode, wb);
1499 trace_writeback_sb_inodes_requeue(inode);
1502 spin_unlock(&wb->list_lock);
1505 * We already requeued the inode if it had I_SYNC set and we
1506 * are doing WB_SYNC_NONE writeback. So this catches only the
1509 if (inode->i_state & I_SYNC) {
1510 /* Wait for I_SYNC. This function drops i_lock... */
1511 inode_sleep_on_writeback(inode);
1512 /* Inode may be gone, start again */
1513 spin_lock(&wb->list_lock);
1516 inode->i_state |= I_SYNC;
1517 wbc_attach_and_unlock_inode(&wbc, inode);
1519 write_chunk = writeback_chunk_size(wb, work);
1520 wbc.nr_to_write = write_chunk;
1521 wbc.pages_skipped = 0;
1524 * We use I_SYNC to pin the inode in memory. While it is set
1525 * evict_inode() will wait so the inode cannot be freed.
1527 __writeback_single_inode(inode, &wbc);
1529 wbc_detach_inode(&wbc);
1530 work->nr_pages -= write_chunk - wbc.nr_to_write;
1531 wrote += write_chunk - wbc.nr_to_write;
1533 if (need_resched()) {
1535 * We're trying to balance between building up a nice
1536 * long list of IOs to improve our merge rate, and
1537 * getting those IOs out quickly for anyone throttling
1538 * in balance_dirty_pages(). cond_resched() doesn't
1539 * unplug, so get our IOs out the door before we
1542 blk_flush_plug(current);
1547 spin_lock(&wb->list_lock);
1548 spin_lock(&inode->i_lock);
1549 if (!(inode->i_state & I_DIRTY_ALL))
1551 requeue_inode(inode, wb, &wbc);
1552 inode_sync_complete(inode);
1553 spin_unlock(&inode->i_lock);
1556 * bail out to wb_writeback() often enough to check
1557 * background threshold and other termination conditions.
1560 if (time_is_before_jiffies(start_time + HZ / 10UL))
1562 if (work->nr_pages <= 0)
1569 static long __writeback_inodes_wb(struct bdi_writeback *wb,
1570 struct wb_writeback_work *work)
1572 unsigned long start_time = jiffies;
1575 while (!list_empty(&wb->b_io)) {
1576 struct inode *inode = wb_inode(wb->b_io.prev);
1577 struct super_block *sb = inode->i_sb;
1579 if (!trylock_super(sb)) {
1581 * trylock_super() may fail consistently due to
1582 * s_umount being grabbed by someone else. Don't use
1583 * requeue_io() to avoid busy retrying the inode/sb.
1585 redirty_tail(inode, wb);
1588 wrote += writeback_sb_inodes(sb, wb, work);
1589 up_read(&sb->s_umount);
1591 /* refer to the same tests at the end of writeback_sb_inodes */
1593 if (time_is_before_jiffies(start_time + HZ / 10UL))
1595 if (work->nr_pages <= 0)
1599 /* Leave any unwritten inodes on b_io */
1603 static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
1604 enum wb_reason reason)
1606 struct wb_writeback_work work = {
1607 .nr_pages = nr_pages,
1608 .sync_mode = WB_SYNC_NONE,
1612 struct blk_plug plug;
1614 blk_start_plug(&plug);
1615 spin_lock(&wb->list_lock);
1616 if (list_empty(&wb->b_io))
1617 queue_io(wb, &work);
1618 __writeback_inodes_wb(wb, &work);
1619 spin_unlock(&wb->list_lock);
1620 blk_finish_plug(&plug);
1622 return nr_pages - work.nr_pages;
1626 * Explicit flushing or periodic writeback of "old" data.
1628 * Define "old": the first time one of an inode's pages is dirtied, we mark the
1629 * dirtying-time in the inode's address_space. So this periodic writeback code
1630 * just walks the superblock inode list, writing back any inodes which are
1631 * older than a specific point in time.
1633 * Try to run once per dirty_writeback_interval. But if a writeback event
1634 * takes longer than a dirty_writeback_interval interval, then leave a
1637 * older_than_this takes precedence over nr_to_write. So we'll only write back
1638 * all dirty pages if they are all attached to "old" mappings.
1640 static long wb_writeback(struct bdi_writeback *wb,
1641 struct wb_writeback_work *work)
1643 unsigned long wb_start = jiffies;
1644 long nr_pages = work->nr_pages;
1645 unsigned long oldest_jif;
1646 struct inode *inode;
1648 struct blk_plug plug;
1650 oldest_jif = jiffies;
1651 work->older_than_this = &oldest_jif;
1653 blk_start_plug(&plug);
1654 spin_lock(&wb->list_lock);
1657 * Stop writeback when nr_pages has been consumed
1659 if (work->nr_pages <= 0)
1663 * Background writeout and kupdate-style writeback may
1664 * run forever. Stop them if there is other work to do
1665 * so that e.g. sync can proceed. They'll be restarted
1666 * after the other works are all done.
1668 if ((work->for_background || work->for_kupdate) &&
1669 !list_empty(&wb->work_list))
1673 * For background writeout, stop when we are below the
1674 * background dirty threshold
1676 if (work->for_background && !wb_over_bg_thresh(wb))
1680 * Kupdate and background works are special and we want to
1681 * include all inodes that need writing. Livelock avoidance is
1682 * handled by these works yielding to any other work so we are
1685 if (work->for_kupdate) {
1686 oldest_jif = jiffies -
1687 msecs_to_jiffies(dirty_expire_interval * 10);
1688 } else if (work->for_background)
1689 oldest_jif = jiffies;
1691 trace_writeback_start(wb, work);
1692 if (list_empty(&wb->b_io))
1695 progress = writeback_sb_inodes(work->sb, wb, work);
1697 progress = __writeback_inodes_wb(wb, work);
1698 trace_writeback_written(wb, work);
1700 wb_update_bandwidth(wb, wb_start);
1703 * Did we write something? Try for more
1705 * Dirty inodes are moved to b_io for writeback in batches.
1706 * The completion of the current batch does not necessarily
1707 * mean the overall work is done. So we keep looping as long
1708 * as made some progress on cleaning pages or inodes.
1713 * No more inodes for IO, bail
1715 if (list_empty(&wb->b_more_io))
1718 * Nothing written. Wait for some inode to
1719 * become available for writeback. Otherwise
1720 * we'll just busyloop.
1722 if (!list_empty(&wb->b_more_io)) {
1723 trace_writeback_wait(wb, work);
1724 inode = wb_inode(wb->b_more_io.prev);
1725 spin_lock(&inode->i_lock);
1726 spin_unlock(&wb->list_lock);
1727 /* This function drops i_lock... */
1728 inode_sleep_on_writeback(inode);
1729 spin_lock(&wb->list_lock);
1732 spin_unlock(&wb->list_lock);
1733 blk_finish_plug(&plug);
1735 return nr_pages - work->nr_pages;
1739 * Return the next wb_writeback_work struct that hasn't been processed yet.
1741 static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
1743 struct wb_writeback_work *work = NULL;
1745 spin_lock_bh(&wb->work_lock);
1746 if (!list_empty(&wb->work_list)) {
1747 work = list_entry(wb->work_list.next,
1748 struct wb_writeback_work, list);
1749 list_del_init(&work->list);
1751 spin_unlock_bh(&wb->work_lock);
1756 * Add in the number of potentially dirty inodes, because each inode
1757 * write can dirty pagecache in the underlying blockdev.
1759 static unsigned long get_nr_dirty_pages(void)
1761 return global_page_state(NR_FILE_DIRTY) +
1762 global_page_state(NR_UNSTABLE_NFS) +
1763 get_nr_dirty_inodes();
1766 static long wb_check_background_flush(struct bdi_writeback *wb)
1768 if (wb_over_bg_thresh(wb)) {
1770 struct wb_writeback_work work = {
1771 .nr_pages = LONG_MAX,
1772 .sync_mode = WB_SYNC_NONE,
1773 .for_background = 1,
1775 .reason = WB_REASON_BACKGROUND,
1778 return wb_writeback(wb, &work);
1784 static long wb_check_old_data_flush(struct bdi_writeback *wb)
1786 unsigned long expired;
1790 * When set to zero, disable periodic writeback
1792 if (!dirty_writeback_interval)
1795 expired = wb->last_old_flush +
1796 msecs_to_jiffies(dirty_writeback_interval * 10);
1797 if (time_before(jiffies, expired))
1800 wb->last_old_flush = jiffies;
1801 nr_pages = get_nr_dirty_pages();
1804 struct wb_writeback_work work = {
1805 .nr_pages = nr_pages,
1806 .sync_mode = WB_SYNC_NONE,
1809 .reason = WB_REASON_PERIODIC,
1812 return wb_writeback(wb, &work);
1819 * Retrieve work items and do the writeback they describe
1821 static long wb_do_writeback(struct bdi_writeback *wb)
1823 struct wb_writeback_work *work;
1826 set_bit(WB_writeback_running, &wb->state);
1827 while ((work = get_next_work_item(wb)) != NULL) {
1828 struct wb_completion *done = work->done;
1830 trace_writeback_exec(wb, work);
1832 wrote += wb_writeback(wb, work);
1834 if (work->auto_free)
1836 if (done && atomic_dec_and_test(&done->cnt))
1837 wake_up_all(&wb->bdi->wb_waitq);
1841 * Check for periodic writeback, kupdated() style
1843 wrote += wb_check_old_data_flush(wb);
1844 wrote += wb_check_background_flush(wb);
1845 clear_bit(WB_writeback_running, &wb->state);
1851 * Handle writeback of dirty data for the device backed by this bdi. Also
1852 * reschedules periodically and does kupdated style flushing.
1854 void wb_workfn(struct work_struct *work)
1856 struct bdi_writeback *wb = container_of(to_delayed_work(work),
1857 struct bdi_writeback, dwork);
1860 set_worker_desc("flush-%s", dev_name(wb->bdi->dev));
1861 current->flags |= PF_SWAPWRITE;
1863 if (likely(!current_is_workqueue_rescuer() ||
1864 !test_bit(WB_registered, &wb->state))) {
1866 * The normal path. Keep writing back @wb until its
1867 * work_list is empty. Note that this path is also taken
1868 * if @wb is shutting down even when we're running off the
1869 * rescuer as work_list needs to be drained.
1872 pages_written = wb_do_writeback(wb);
1873 trace_writeback_pages_written(pages_written);
1874 } while (!list_empty(&wb->work_list));
1877 * bdi_wq can't get enough workers and we're running off
1878 * the emergency worker. Don't hog it. Hopefully, 1024 is
1879 * enough for efficient IO.
1881 pages_written = writeback_inodes_wb(wb, 1024,
1882 WB_REASON_FORKER_THREAD);
1883 trace_writeback_pages_written(pages_written);
1886 if (!list_empty(&wb->work_list))
1887 mod_delayed_work(bdi_wq, &wb->dwork, 0);
1888 else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1889 wb_wakeup_delayed(wb);
1891 current->flags &= ~PF_SWAPWRITE;
1895 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
1898 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1900 struct backing_dev_info *bdi;
1903 nr_pages = get_nr_dirty_pages();
1906 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1907 struct bdi_writeback *wb;
1909 if (!bdi_has_dirty_io(bdi))
1912 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
1913 wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
1920 * Wake up bdi's periodically to make sure dirtytime inodes gets
1921 * written back periodically. We deliberately do *not* check the
1922 * b_dirtytime list in wb_has_dirty_io(), since this would cause the
1923 * kernel to be constantly waking up once there are any dirtytime
1924 * inodes on the system. So instead we define a separate delayed work
1925 * function which gets called much more rarely. (By default, only
1926 * once every 12 hours.)
1928 * If there is any other write activity going on in the file system,
1929 * this function won't be necessary. But if the only thing that has
1930 * happened on the file system is a dirtytime inode caused by an atime
1931 * update, we need this infrastructure below to make sure that inode
1932 * eventually gets pushed out to disk.
1934 static void wakeup_dirtytime_writeback(struct work_struct *w);
1935 static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback);
1937 static void wakeup_dirtytime_writeback(struct work_struct *w)
1939 struct backing_dev_info *bdi;
1942 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1943 struct bdi_writeback *wb;
1945 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
1946 if (!list_empty(&wb->b_dirty_time))
1950 schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
1953 static int __init start_dirtytime_writeback(void)
1955 schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
1958 __initcall(start_dirtytime_writeback);
1960 int dirtytime_interval_handler(struct ctl_table *table, int write,
1961 void __user *buffer, size_t *lenp, loff_t *ppos)
1965 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1966 if (ret == 0 && write)
1967 mod_delayed_work(system_wq, &dirtytime_work, 0);
1971 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1973 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1974 struct dentry *dentry;
1975 const char *name = "?";
1977 dentry = d_find_alias(inode);
1979 spin_lock(&dentry->d_lock);
1980 name = (const char *) dentry->d_name.name;
1983 "%s(%d): dirtied inode %lu (%s) on %s\n",
1984 current->comm, task_pid_nr(current), inode->i_ino,
1985 name, inode->i_sb->s_id);
1987 spin_unlock(&dentry->d_lock);
1994 * __mark_inode_dirty - internal function
1995 * @inode: inode to mark
1996 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1997 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1998 * mark_inode_dirty_sync.
2000 * Put the inode on the super block's dirty list.
2002 * CAREFUL! We mark it dirty unconditionally, but move it onto the
2003 * dirty list only if it is hashed or if it refers to a blockdev.
2004 * If it was not hashed, it will never be added to the dirty list
2005 * even if it is later hashed, as it will have been marked dirty already.
2007 * In short, make sure you hash any inodes _before_ you start marking
2010 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
2011 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
2012 * the kernel-internal blockdev inode represents the dirtying time of the
2013 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
2014 * page->mapping->host, so the page-dirtying time is recorded in the internal
2017 void __mark_inode_dirty(struct inode *inode, int flags)
2019 #define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
2020 struct super_block *sb = inode->i_sb;
2023 trace_writeback_mark_inode_dirty(inode, flags);
2026 * Don't do this for I_DIRTY_PAGES - that doesn't actually
2027 * dirty the inode itself
2029 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_TIME)) {
2030 trace_writeback_dirty_inode_start(inode, flags);
2032 if (sb->s_op->dirty_inode)
2033 sb->s_op->dirty_inode(inode, flags);
2035 trace_writeback_dirty_inode(inode, flags);
2037 if (flags & I_DIRTY_INODE)
2038 flags &= ~I_DIRTY_TIME;
2039 dirtytime = flags & I_DIRTY_TIME;
2042 * Paired with smp_mb() in __writeback_single_inode() for the
2043 * following lockless i_state test. See there for details.
2047 if (((inode->i_state & flags) == flags) ||
2048 (dirtytime && (inode->i_state & I_DIRTY_INODE)))
2051 if (unlikely(block_dump))
2052 block_dump___mark_inode_dirty(inode);
2054 spin_lock(&inode->i_lock);
2055 if (dirtytime && (inode->i_state & I_DIRTY_INODE))
2056 goto out_unlock_inode;
2057 if ((inode->i_state & flags) != flags) {
2058 const int was_dirty = inode->i_state & I_DIRTY;
2060 inode_attach_wb(inode, NULL);
2062 if (flags & I_DIRTY_INODE)
2063 inode->i_state &= ~I_DIRTY_TIME;
2064 inode->i_state |= flags;
2067 * If the inode is being synced, just update its dirty state.
2068 * The unlocker will place the inode on the appropriate
2069 * superblock list, based upon its state.
2071 if (inode->i_state & I_SYNC)
2072 goto out_unlock_inode;
2075 * Only add valid (hashed) inodes to the superblock's
2076 * dirty list. Add blockdev inodes as well.
2078 if (!S_ISBLK(inode->i_mode)) {
2079 if (inode_unhashed(inode))
2080 goto out_unlock_inode;
2082 if (inode->i_state & I_FREEING)
2083 goto out_unlock_inode;
2086 * If the inode was already on b_dirty/b_io/b_more_io, don't
2087 * reposition it (that would break b_dirty time-ordering).
2090 struct bdi_writeback *wb;
2091 struct list_head *dirty_list;
2092 bool wakeup_bdi = false;
2094 wb = locked_inode_to_wb_and_lock_list(inode);
2096 WARN(bdi_cap_writeback_dirty(wb->bdi) &&
2097 !test_bit(WB_registered, &wb->state),
2098 "bdi-%s not registered\n", wb->bdi->name);
2100 inode->dirtied_when = jiffies;
2102 inode->dirtied_time_when = jiffies;
2104 if (inode->i_state & (I_DIRTY_INODE | I_DIRTY_PAGES))
2105 dirty_list = &wb->b_dirty;
2107 dirty_list = &wb->b_dirty_time;
2109 wakeup_bdi = inode_io_list_move_locked(inode, wb,
2112 spin_unlock(&wb->list_lock);
2113 trace_writeback_dirty_inode_enqueue(inode);
2116 * If this is the first dirty inode for this bdi,
2117 * we have to wake-up the corresponding bdi thread
2118 * to make sure background write-back happens
2121 if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
2122 wb_wakeup_delayed(wb);
2127 spin_unlock(&inode->i_lock);
2129 #undef I_DIRTY_INODE
2131 EXPORT_SYMBOL(__mark_inode_dirty);
2134 * The @s_sync_lock is used to serialise concurrent sync operations
2135 * to avoid lock contention problems with concurrent wait_sb_inodes() calls.
2136 * Concurrent callers will block on the s_sync_lock rather than doing contending
2137 * walks. The queueing maintains sync(2) required behaviour as all the IO that
2138 * has been issued up to the time this function is enter is guaranteed to be
2139 * completed by the time we have gained the lock and waited for all IO that is
2140 * in progress regardless of the order callers are granted the lock.
2142 static void wait_sb_inodes(struct super_block *sb)
2144 struct inode *inode, *old_inode = NULL;
2147 * We need to be protected against the filesystem going from
2148 * r/o to r/w or vice versa.
2150 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2152 mutex_lock(&sb->s_sync_lock);
2153 spin_lock(&sb->s_inode_list_lock);
2156 * Data integrity sync. Must wait for all pages under writeback,
2157 * because there may have been pages dirtied before our sync
2158 * call, but which had writeout started before we write it out.
2159 * In which case, the inode may not be on the dirty list, but
2160 * we still have to wait for that writeout.
2162 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
2163 struct address_space *mapping = inode->i_mapping;
2165 spin_lock(&inode->i_lock);
2166 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
2167 (mapping->nrpages == 0)) {
2168 spin_unlock(&inode->i_lock);
2172 spin_unlock(&inode->i_lock);
2173 spin_unlock(&sb->s_inode_list_lock);
2176 * We hold a reference to 'inode' so it couldn't have been
2177 * removed from s_inodes list while we dropped the
2178 * s_inode_list_lock. We cannot iput the inode now as we can
2179 * be holding the last reference and we cannot iput it under
2180 * s_inode_list_lock. So we keep the reference and iput it
2187 * We keep the error status of individual mapping so that
2188 * applications can catch the writeback error using fsync(2).
2189 * See filemap_fdatawait_keep_errors() for details.
2191 filemap_fdatawait_keep_errors(mapping);
2195 spin_lock(&sb->s_inode_list_lock);
2197 spin_unlock(&sb->s_inode_list_lock);
2199 mutex_unlock(&sb->s_sync_lock);
2202 static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
2203 enum wb_reason reason, bool skip_if_busy)
2205 DEFINE_WB_COMPLETION_ONSTACK(done);
2206 struct wb_writeback_work work = {
2208 .sync_mode = WB_SYNC_NONE,
2209 .tagged_writepages = 1,
2214 struct backing_dev_info *bdi = sb->s_bdi;
2216 if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info)
2218 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2220 bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy);
2221 wb_wait_for_completion(bdi, &done);
2225 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
2226 * @sb: the superblock
2227 * @nr: the number of pages to write
2228 * @reason: reason why some writeback work initiated
2230 * Start writeback on some inodes on this super_block. No guarantees are made
2231 * on how many (if any) will be written, and this function does not wait
2232 * for IO completion of submitted IO.
2234 void writeback_inodes_sb_nr(struct super_block *sb,
2236 enum wb_reason reason)
2238 __writeback_inodes_sb_nr(sb, nr, reason, false);
2240 EXPORT_SYMBOL(writeback_inodes_sb_nr);
2243 * writeback_inodes_sb - writeback dirty inodes from given super_block
2244 * @sb: the superblock
2245 * @reason: reason why some writeback work was initiated
2247 * Start writeback on some inodes on this super_block. No guarantees are made
2248 * on how many (if any) will be written, and this function does not wait
2249 * for IO completion of submitted IO.
2251 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2253 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
2255 EXPORT_SYMBOL(writeback_inodes_sb);
2258 * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
2259 * @sb: the superblock
2260 * @nr: the number of pages to write
2261 * @reason: the reason of writeback
2263 * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
2264 * Returns 1 if writeback was started, 0 if not.
2266 bool try_to_writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
2267 enum wb_reason reason)
2269 if (!down_read_trylock(&sb->s_umount))
2272 __writeback_inodes_sb_nr(sb, nr, reason, true);
2273 up_read(&sb->s_umount);
2276 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
2279 * try_to_writeback_inodes_sb - try to start writeback if none underway
2280 * @sb: the superblock
2281 * @reason: reason why some writeback work was initiated
2283 * Implement by try_to_writeback_inodes_sb_nr()
2284 * Returns 1 if writeback was started, 0 if not.
2286 bool try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2288 return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
2290 EXPORT_SYMBOL(try_to_writeback_inodes_sb);
2293 * sync_inodes_sb - sync sb inode pages
2294 * @sb: the superblock
2296 * This function writes and waits on any dirty inode belonging to this
2299 void sync_inodes_sb(struct super_block *sb)
2301 DEFINE_WB_COMPLETION_ONSTACK(done);
2302 struct wb_writeback_work work = {
2304 .sync_mode = WB_SYNC_ALL,
2305 .nr_pages = LONG_MAX,
2308 .reason = WB_REASON_SYNC,
2311 struct backing_dev_info *bdi = sb->s_bdi;
2314 * Can't skip on !bdi_has_dirty() because we should wait for !dirty
2315 * inodes under writeback and I_DIRTY_TIME inodes ignored by
2316 * bdi_has_dirty() need to be written out too.
2318 if (bdi == &noop_backing_dev_info)
2320 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2322 bdi_split_work_to_wbs(bdi, &work, false);
2323 wb_wait_for_completion(bdi, &done);
2327 EXPORT_SYMBOL(sync_inodes_sb);
2330 * write_inode_now - write an inode to disk
2331 * @inode: inode to write to disk
2332 * @sync: whether the write should be synchronous or not
2334 * This function commits an inode to disk immediately if it is dirty. This is
2335 * primarily needed by knfsd.
2337 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
2339 int write_inode_now(struct inode *inode, int sync)
2341 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
2342 struct writeback_control wbc = {
2343 .nr_to_write = LONG_MAX,
2344 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
2346 .range_end = LLONG_MAX,
2349 if (!mapping_cap_writeback_dirty(inode->i_mapping))
2350 wbc.nr_to_write = 0;
2353 return writeback_single_inode(inode, wb, &wbc);
2355 EXPORT_SYMBOL(write_inode_now);
2358 * sync_inode - write an inode and its pages to disk.
2359 * @inode: the inode to sync
2360 * @wbc: controls the writeback mode
2362 * sync_inode() will write an inode and its pages to disk. It will also
2363 * correctly update the inode on its superblock's dirty inode lists and will
2364 * update inode->i_state.
2366 * The caller must have a ref on the inode.
2368 int sync_inode(struct inode *inode, struct writeback_control *wbc)
2370 return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
2372 EXPORT_SYMBOL(sync_inode);
2375 * sync_inode_metadata - write an inode to disk
2376 * @inode: the inode to sync
2377 * @wait: wait for I/O to complete.
2379 * Write an inode to disk and adjust its dirty state after completion.
2381 * Note: only writes the actual inode, no associated data or other metadata.
2383 int sync_inode_metadata(struct inode *inode, int wait)
2385 struct writeback_control wbc = {
2386 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
2387 .nr_to_write = 0, /* metadata-only */
2390 return sync_inode(inode, &wbc);
2392 EXPORT_SYMBOL(sync_inode_metadata);