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_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|dirty_time}
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 finish_writeback_work(struct bdi_writeback
*wb
,
177 struct wb_writeback_work
*work
)
179 struct wb_completion
*done
= work
->done
;
183 if (done
&& atomic_dec_and_test(&done
->cnt
))
184 wake_up_all(&wb
->bdi
->wb_waitq
);
187 static void wb_queue_work(struct bdi_writeback
*wb
,
188 struct wb_writeback_work
*work
)
190 trace_writeback_queue(wb
, work
);
193 atomic_inc(&work
->done
->cnt
);
195 spin_lock_bh(&wb
->work_lock
);
197 if (test_bit(WB_registered
, &wb
->state
)) {
198 list_add_tail(&work
->list
, &wb
->work_list
);
199 mod_delayed_work(bdi_wq
, &wb
->dwork
, 0);
201 finish_writeback_work(wb
, work
);
203 spin_unlock_bh(&wb
->work_lock
);
207 * wb_wait_for_completion - wait for completion of bdi_writeback_works
208 * @bdi: bdi work items were issued to
209 * @done: target wb_completion
211 * Wait for one or more work items issued to @bdi with their ->done field
212 * set to @done, which should have been defined with
213 * DEFINE_WB_COMPLETION_ONSTACK(). This function returns after all such
214 * work items are completed. Work items which are waited upon aren't freed
215 * automatically on completion.
217 static void wb_wait_for_completion(struct backing_dev_info
*bdi
,
218 struct wb_completion
*done
)
220 atomic_dec(&done
->cnt
); /* put down the initial count */
221 wait_event(bdi
->wb_waitq
, !atomic_read(&done
->cnt
));
224 #ifdef CONFIG_CGROUP_WRITEBACK
226 /* parameters for foreign inode detection, see wb_detach_inode() */
227 #define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */
228 #define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */
229 #define WB_FRN_TIME_CUT_DIV 2 /* ignore rounds < avg / 2 */
230 #define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */
232 #define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */
233 #define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS)
234 /* each slot's duration is 2s / 16 */
235 #define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2)
236 /* if foreign slots >= 8, switch */
237 #define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1)
238 /* one round can affect upto 5 slots */
240 static atomic_t isw_nr_in_flight
= ATOMIC_INIT(0);
241 static struct workqueue_struct
*isw_wq
;
243 void __inode_attach_wb(struct inode
*inode
, struct page
*page
)
245 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
246 struct bdi_writeback
*wb
= NULL
;
248 if (inode_cgwb_enabled(inode
)) {
249 struct cgroup_subsys_state
*memcg_css
;
252 memcg_css
= mem_cgroup_css_from_page(page
);
253 wb
= wb_get_create(bdi
, memcg_css
, GFP_ATOMIC
);
255 /* must pin memcg_css, see wb_get_create() */
256 memcg_css
= task_get_css(current
, memory_cgrp_id
);
257 wb
= wb_get_create(bdi
, memcg_css
, GFP_ATOMIC
);
266 * There may be multiple instances of this function racing to
267 * update the same inode. Use cmpxchg() to tell the winner.
269 if (unlikely(cmpxchg(&inode
->i_wb
, NULL
, wb
)))
272 EXPORT_SYMBOL_GPL(__inode_attach_wb
);
275 * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
276 * @inode: inode of interest with i_lock held
278 * Returns @inode's wb with its list_lock held. @inode->i_lock must be
279 * held on entry and is released on return. The returned wb is guaranteed
280 * to stay @inode's associated wb until its list_lock is released.
282 static struct bdi_writeback
*
283 locked_inode_to_wb_and_lock_list(struct inode
*inode
)
284 __releases(&inode
->i_lock
)
285 __acquires(&wb
->list_lock
)
288 struct bdi_writeback
*wb
= inode_to_wb(inode
);
291 * inode_to_wb() association is protected by both
292 * @inode->i_lock and @wb->list_lock but list_lock nests
293 * outside i_lock. Drop i_lock and verify that the
294 * association hasn't changed after acquiring list_lock.
297 spin_unlock(&inode
->i_lock
);
298 spin_lock(&wb
->list_lock
);
300 /* i_wb may have changed inbetween, can't use inode_to_wb() */
301 if (likely(wb
== inode
->i_wb
)) {
302 wb_put(wb
); /* @inode already has ref */
306 spin_unlock(&wb
->list_lock
);
309 spin_lock(&inode
->i_lock
);
314 * inode_to_wb_and_lock_list - determine an inode's wb and lock it
315 * @inode: inode of interest
317 * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
320 static struct bdi_writeback
*inode_to_wb_and_lock_list(struct inode
*inode
)
321 __acquires(&wb
->list_lock
)
323 spin_lock(&inode
->i_lock
);
324 return locked_inode_to_wb_and_lock_list(inode
);
327 struct inode_switch_wbs_context
{
329 struct bdi_writeback
*new_wb
;
331 struct rcu_head rcu_head
;
332 struct work_struct work
;
335 static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info
*bdi
)
337 down_write(&bdi
->wb_switch_rwsem
);
340 static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info
*bdi
)
342 up_write(&bdi
->wb_switch_rwsem
);
345 static void inode_switch_wbs_work_fn(struct work_struct
*work
)
347 struct inode_switch_wbs_context
*isw
=
348 container_of(work
, struct inode_switch_wbs_context
, work
);
349 struct inode
*inode
= isw
->inode
;
350 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
351 struct address_space
*mapping
= inode
->i_mapping
;
352 struct bdi_writeback
*old_wb
= inode
->i_wb
;
353 struct bdi_writeback
*new_wb
= isw
->new_wb
;
354 struct radix_tree_iter iter
;
355 bool switched
= false;
359 * If @inode switches cgwb membership while sync_inodes_sb() is
360 * being issued, sync_inodes_sb() might miss it. Synchronize.
362 down_read(&bdi
->wb_switch_rwsem
);
365 * By the time control reaches here, RCU grace period has passed
366 * since I_WB_SWITCH assertion and all wb stat update transactions
367 * between unlocked_inode_to_wb_begin/end() are guaranteed to be
368 * synchronizing against the i_pages lock.
370 * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock
371 * gives us exclusion against all wb related operations on @inode
372 * including IO list manipulations and stat updates.
374 if (old_wb
< new_wb
) {
375 spin_lock(&old_wb
->list_lock
);
376 spin_lock_nested(&new_wb
->list_lock
, SINGLE_DEPTH_NESTING
);
378 spin_lock(&new_wb
->list_lock
);
379 spin_lock_nested(&old_wb
->list_lock
, SINGLE_DEPTH_NESTING
);
381 spin_lock(&inode
->i_lock
);
382 xa_lock_irq(&mapping
->i_pages
);
385 * Once I_FREEING is visible under i_lock, the eviction path owns
386 * the inode and we shouldn't modify ->i_io_list.
388 if (unlikely(inode
->i_state
& I_FREEING
))
392 * Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points
393 * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
394 * pages actually under writeback.
396 radix_tree_for_each_tagged(slot
, &mapping
->i_pages
, &iter
, 0,
397 PAGECACHE_TAG_DIRTY
) {
398 struct page
*page
= radix_tree_deref_slot_protected(slot
,
399 &mapping
->i_pages
.xa_lock
);
400 if (likely(page
) && PageDirty(page
)) {
401 dec_wb_stat(old_wb
, WB_RECLAIMABLE
);
402 inc_wb_stat(new_wb
, WB_RECLAIMABLE
);
406 radix_tree_for_each_tagged(slot
, &mapping
->i_pages
, &iter
, 0,
407 PAGECACHE_TAG_WRITEBACK
) {
408 struct page
*page
= radix_tree_deref_slot_protected(slot
,
409 &mapping
->i_pages
.xa_lock
);
411 WARN_ON_ONCE(!PageWriteback(page
));
412 dec_wb_stat(old_wb
, WB_WRITEBACK
);
413 inc_wb_stat(new_wb
, WB_WRITEBACK
);
420 * Transfer to @new_wb's IO list if necessary. The specific list
421 * @inode was on is ignored and the inode is put on ->b_dirty which
422 * is always correct including from ->b_dirty_time. The transfer
423 * preserves @inode->dirtied_when ordering.
425 if (!list_empty(&inode
->i_io_list
)) {
428 inode_io_list_del_locked(inode
, old_wb
);
429 inode
->i_wb
= new_wb
;
430 list_for_each_entry(pos
, &new_wb
->b_dirty
, i_io_list
)
431 if (time_after_eq(inode
->dirtied_when
,
434 inode_io_list_move_locked(inode
, new_wb
, pos
->i_io_list
.prev
);
436 inode
->i_wb
= new_wb
;
439 /* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */
440 inode
->i_wb_frn_winner
= 0;
441 inode
->i_wb_frn_avg_time
= 0;
442 inode
->i_wb_frn_history
= 0;
446 * Paired with load_acquire in unlocked_inode_to_wb_begin() and
447 * ensures that the new wb is visible if they see !I_WB_SWITCH.
449 smp_store_release(&inode
->i_state
, inode
->i_state
& ~I_WB_SWITCH
);
451 xa_unlock_irq(&mapping
->i_pages
);
452 spin_unlock(&inode
->i_lock
);
453 spin_unlock(&new_wb
->list_lock
);
454 spin_unlock(&old_wb
->list_lock
);
456 up_read(&bdi
->wb_switch_rwsem
);
467 atomic_dec(&isw_nr_in_flight
);
470 static void inode_switch_wbs_rcu_fn(struct rcu_head
*rcu_head
)
472 struct inode_switch_wbs_context
*isw
= container_of(rcu_head
,
473 struct inode_switch_wbs_context
, rcu_head
);
475 /* needs to grab bh-unsafe locks, bounce to work item */
476 INIT_WORK(&isw
->work
, inode_switch_wbs_work_fn
);
477 queue_work(isw_wq
, &isw
->work
);
481 * inode_switch_wbs - change the wb association of an inode
482 * @inode: target inode
483 * @new_wb_id: ID of the new wb
485 * Switch @inode's wb association to the wb identified by @new_wb_id. The
486 * switching is performed asynchronously and may fail silently.
488 static void inode_switch_wbs(struct inode
*inode
, int new_wb_id
)
490 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
491 struct cgroup_subsys_state
*memcg_css
;
492 struct inode_switch_wbs_context
*isw
;
494 /* noop if seems to be already in progress */
495 if (inode
->i_state
& I_WB_SWITCH
)
499 * Avoid starting new switches while sync_inodes_sb() is in
500 * progress. Otherwise, if the down_write protected issue path
501 * blocks heavily, we might end up starting a large number of
502 * switches which will block on the rwsem.
504 if (!down_read_trylock(&bdi
->wb_switch_rwsem
))
507 isw
= kzalloc(sizeof(*isw
), GFP_ATOMIC
);
511 /* find and pin the new wb */
513 memcg_css
= css_from_id(new_wb_id
, &memory_cgrp_subsys
);
515 isw
->new_wb
= wb_get_create(bdi
, memcg_css
, GFP_ATOMIC
);
520 /* while holding I_WB_SWITCH, no one else can update the association */
521 spin_lock(&inode
->i_lock
);
522 if (!(inode
->i_sb
->s_flags
& SB_ACTIVE
) ||
523 inode
->i_state
& (I_WB_SWITCH
| I_FREEING
) ||
524 inode_to_wb(inode
) == isw
->new_wb
) {
525 spin_unlock(&inode
->i_lock
);
528 inode
->i_state
|= I_WB_SWITCH
;
530 spin_unlock(&inode
->i_lock
);
535 * In addition to synchronizing among switchers, I_WB_SWITCH tells
536 * the RCU protected stat update paths to grab the i_page
537 * lock so that stat transfer can synchronize against them.
538 * Let's continue after I_WB_SWITCH is guaranteed to be visible.
540 call_rcu(&isw
->rcu_head
, inode_switch_wbs_rcu_fn
);
542 atomic_inc(&isw_nr_in_flight
);
551 up_read(&bdi
->wb_switch_rwsem
);
555 * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it
556 * @wbc: writeback_control of interest
557 * @inode: target inode
559 * @inode is locked and about to be written back under the control of @wbc.
560 * Record @inode's writeback context into @wbc and unlock the i_lock. On
561 * writeback completion, wbc_detach_inode() should be called. This is used
562 * to track the cgroup writeback context.
564 void wbc_attach_and_unlock_inode(struct writeback_control
*wbc
,
567 if (!inode_cgwb_enabled(inode
)) {
568 spin_unlock(&inode
->i_lock
);
572 wbc
->wb
= inode_to_wb(inode
);
575 wbc
->wb_id
= wbc
->wb
->memcg_css
->id
;
576 wbc
->wb_lcand_id
= inode
->i_wb_frn_winner
;
577 wbc
->wb_tcand_id
= 0;
579 wbc
->wb_lcand_bytes
= 0;
580 wbc
->wb_tcand_bytes
= 0;
583 spin_unlock(&inode
->i_lock
);
586 * A dying wb indicates that either the blkcg associated with the
587 * memcg changed or the associated memcg is dying. In the first
588 * case, a replacement wb should already be available and we should
589 * refresh the wb immediately. In the second case, trying to
590 * refresh will keep failing.
592 if (unlikely(wb_dying(wbc
->wb
) && !css_is_dying(wbc
->wb
->memcg_css
)))
593 inode_switch_wbs(inode
, wbc
->wb_id
);
597 * wbc_detach_inode - disassociate wbc from inode and perform foreign detection
598 * @wbc: writeback_control of the just finished writeback
600 * To be called after a writeback attempt of an inode finishes and undoes
601 * wbc_attach_and_unlock_inode(). Can be called under any context.
603 * As concurrent write sharing of an inode is expected to be very rare and
604 * memcg only tracks page ownership on first-use basis severely confining
605 * the usefulness of such sharing, cgroup writeback tracks ownership
606 * per-inode. While the support for concurrent write sharing of an inode
607 * is deemed unnecessary, an inode being written to by different cgroups at
608 * different points in time is a lot more common, and, more importantly,
609 * charging only by first-use can too readily lead to grossly incorrect
610 * behaviors (single foreign page can lead to gigabytes of writeback to be
611 * incorrectly attributed).
613 * To resolve this issue, cgroup writeback detects the majority dirtier of
614 * an inode and transfers the ownership to it. To avoid unnnecessary
615 * oscillation, the detection mechanism keeps track of history and gives
616 * out the switch verdict only if the foreign usage pattern is stable over
617 * a certain amount of time and/or writeback attempts.
619 * On each writeback attempt, @wbc tries to detect the majority writer
620 * using Boyer-Moore majority vote algorithm. In addition to the byte
621 * count from the majority voting, it also counts the bytes written for the
622 * current wb and the last round's winner wb (max of last round's current
623 * wb, the winner from two rounds ago, and the last round's majority
624 * candidate). Keeping track of the historical winner helps the algorithm
625 * to semi-reliably detect the most active writer even when it's not the
628 * Once the winner of the round is determined, whether the winner is
629 * foreign or not and how much IO time the round consumed is recorded in
630 * inode->i_wb_frn_history. If the amount of recorded foreign IO time is
631 * over a certain threshold, the switch verdict is given.
633 void wbc_detach_inode(struct writeback_control
*wbc
)
635 struct bdi_writeback
*wb
= wbc
->wb
;
636 struct inode
*inode
= wbc
->inode
;
637 unsigned long avg_time
, max_bytes
, max_time
;
644 history
= inode
->i_wb_frn_history
;
645 avg_time
= inode
->i_wb_frn_avg_time
;
647 /* pick the winner of this round */
648 if (wbc
->wb_bytes
>= wbc
->wb_lcand_bytes
&&
649 wbc
->wb_bytes
>= wbc
->wb_tcand_bytes
) {
651 max_bytes
= wbc
->wb_bytes
;
652 } else if (wbc
->wb_lcand_bytes
>= wbc
->wb_tcand_bytes
) {
653 max_id
= wbc
->wb_lcand_id
;
654 max_bytes
= wbc
->wb_lcand_bytes
;
656 max_id
= wbc
->wb_tcand_id
;
657 max_bytes
= wbc
->wb_tcand_bytes
;
661 * Calculate the amount of IO time the winner consumed and fold it
662 * into the running average kept per inode. If the consumed IO
663 * time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
664 * deciding whether to switch or not. This is to prevent one-off
665 * small dirtiers from skewing the verdict.
667 max_time
= DIV_ROUND_UP((max_bytes
>> PAGE_SHIFT
) << WB_FRN_TIME_SHIFT
,
668 wb
->avg_write_bandwidth
);
670 avg_time
+= (max_time
>> WB_FRN_TIME_AVG_SHIFT
) -
671 (avg_time
>> WB_FRN_TIME_AVG_SHIFT
);
673 avg_time
= max_time
; /* immediate catch up on first run */
675 if (max_time
>= avg_time
/ WB_FRN_TIME_CUT_DIV
) {
679 * The switch verdict is reached if foreign wb's consume
680 * more than a certain proportion of IO time in a
681 * WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
682 * history mask where each bit represents one sixteenth of
683 * the period. Determine the number of slots to shift into
684 * history from @max_time.
686 slots
= min(DIV_ROUND_UP(max_time
, WB_FRN_HIST_UNIT
),
687 (unsigned long)WB_FRN_HIST_MAX_SLOTS
);
689 if (wbc
->wb_id
!= max_id
)
690 history
|= (1U << slots
) - 1;
693 * Switch if the current wb isn't the consistent winner.
694 * If there are multiple closely competing dirtiers, the
695 * inode may switch across them repeatedly over time, which
696 * is okay. The main goal is avoiding keeping an inode on
697 * the wrong wb for an extended period of time.
699 if (hweight32(history
) > WB_FRN_HIST_THR_SLOTS
)
700 inode_switch_wbs(inode
, max_id
);
704 * Multiple instances of this function may race to update the
705 * following fields but we don't mind occassional inaccuracies.
707 inode
->i_wb_frn_winner
= max_id
;
708 inode
->i_wb_frn_avg_time
= min(avg_time
, (unsigned long)U16_MAX
);
709 inode
->i_wb_frn_history
= history
;
716 * wbc_account_io - account IO issued during writeback
717 * @wbc: writeback_control of the writeback in progress
718 * @page: page being written out
719 * @bytes: number of bytes being written out
721 * @bytes from @page are about to written out during the writeback
722 * controlled by @wbc. Keep the book for foreign inode detection. See
723 * wbc_detach_inode().
725 void wbc_account_io(struct writeback_control
*wbc
, struct page
*page
,
728 struct cgroup_subsys_state
*css
;
732 * pageout() path doesn't attach @wbc to the inode being written
733 * out. This is intentional as we don't want the function to block
734 * behind a slow cgroup. Ultimately, we want pageout() to kick off
735 * regular writeback instead of writing things out itself.
740 css
= mem_cgroup_css_from_page(page
);
741 /* dead cgroups shouldn't contribute to inode ownership arbitration */
742 if (!(css
->flags
& CSS_ONLINE
))
747 if (id
== wbc
->wb_id
) {
748 wbc
->wb_bytes
+= bytes
;
752 if (id
== wbc
->wb_lcand_id
)
753 wbc
->wb_lcand_bytes
+= bytes
;
755 /* Boyer-Moore majority vote algorithm */
756 if (!wbc
->wb_tcand_bytes
)
757 wbc
->wb_tcand_id
= id
;
758 if (id
== wbc
->wb_tcand_id
)
759 wbc
->wb_tcand_bytes
+= bytes
;
761 wbc
->wb_tcand_bytes
-= min(bytes
, wbc
->wb_tcand_bytes
);
763 EXPORT_SYMBOL_GPL(wbc_account_io
);
766 * inode_congested - test whether an inode is congested
767 * @inode: inode to test for congestion (may be NULL)
768 * @cong_bits: mask of WB_[a]sync_congested bits to test
770 * Tests whether @inode is congested. @cong_bits is the mask of congestion
771 * bits to test and the return value is the mask of set bits.
773 * If cgroup writeback is enabled for @inode, the congestion state is
774 * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
775 * associated with @inode is congested; otherwise, the root wb's congestion
778 * @inode is allowed to be NULL as this function is often called on
779 * mapping->host which is NULL for the swapper space.
781 int inode_congested(struct inode
*inode
, int cong_bits
)
784 * Once set, ->i_wb never becomes NULL while the inode is alive.
785 * Start transaction iff ->i_wb is visible.
787 if (inode
&& inode_to_wb_is_valid(inode
)) {
788 struct bdi_writeback
*wb
;
789 struct wb_lock_cookie lock_cookie
= {};
792 wb
= unlocked_inode_to_wb_begin(inode
, &lock_cookie
);
793 congested
= wb_congested(wb
, cong_bits
);
794 unlocked_inode_to_wb_end(inode
, &lock_cookie
);
798 return wb_congested(&inode_to_bdi(inode
)->wb
, cong_bits
);
800 EXPORT_SYMBOL_GPL(inode_congested
);
803 * wb_split_bdi_pages - split nr_pages to write according to bandwidth
804 * @wb: target bdi_writeback to split @nr_pages to
805 * @nr_pages: number of pages to write for the whole bdi
807 * Split @wb's portion of @nr_pages according to @wb's write bandwidth in
808 * relation to the total write bandwidth of all wb's w/ dirty inodes on
811 static long wb_split_bdi_pages(struct bdi_writeback
*wb
, long nr_pages
)
813 unsigned long this_bw
= wb
->avg_write_bandwidth
;
814 unsigned long tot_bw
= atomic_long_read(&wb
->bdi
->tot_write_bandwidth
);
816 if (nr_pages
== LONG_MAX
)
820 * This may be called on clean wb's and proportional distribution
821 * may not make sense, just use the original @nr_pages in those
822 * cases. In general, we wanna err on the side of writing more.
824 if (!tot_bw
|| this_bw
>= tot_bw
)
827 return DIV_ROUND_UP_ULL((u64
)nr_pages
* this_bw
, tot_bw
);
831 * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
832 * @bdi: target backing_dev_info
833 * @base_work: wb_writeback_work to issue
834 * @skip_if_busy: skip wb's which already have writeback in progress
836 * Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
837 * have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
838 * distributed to the busy wbs according to each wb's proportion in the
839 * total active write bandwidth of @bdi.
841 static void bdi_split_work_to_wbs(struct backing_dev_info
*bdi
,
842 struct wb_writeback_work
*base_work
,
845 struct bdi_writeback
*last_wb
= NULL
;
846 struct bdi_writeback
*wb
= list_entry(&bdi
->wb_list
,
847 struct bdi_writeback
, bdi_node
);
852 list_for_each_entry_continue_rcu(wb
, &bdi
->wb_list
, bdi_node
) {
853 DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done
);
854 struct wb_writeback_work fallback_work
;
855 struct wb_writeback_work
*work
;
863 /* SYNC_ALL writes out I_DIRTY_TIME too */
864 if (!wb_has_dirty_io(wb
) &&
865 (base_work
->sync_mode
== WB_SYNC_NONE
||
866 list_empty(&wb
->b_dirty_time
)))
868 if (skip_if_busy
&& writeback_in_progress(wb
))
871 nr_pages
= wb_split_bdi_pages(wb
, base_work
->nr_pages
);
873 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
876 work
->nr_pages
= nr_pages
;
878 wb_queue_work(wb
, work
);
882 /* alloc failed, execute synchronously using on-stack fallback */
883 work
= &fallback_work
;
885 work
->nr_pages
= nr_pages
;
887 work
->done
= &fallback_work_done
;
889 wb_queue_work(wb
, work
);
892 * Pin @wb so that it stays on @bdi->wb_list. This allows
893 * continuing iteration from @wb after dropping and
894 * regrabbing rcu read lock.
900 wb_wait_for_completion(bdi
, &fallback_work_done
);
910 * cgroup_writeback_umount - flush inode wb switches for umount
912 * This function is called when a super_block is about to be destroyed and
913 * flushes in-flight inode wb switches. An inode wb switch goes through
914 * RCU and then workqueue, so the two need to be flushed in order to ensure
915 * that all previously scheduled switches are finished. As wb switches are
916 * rare occurrences and synchronize_rcu() can take a while, perform
917 * flushing iff wb switches are in flight.
919 void cgroup_writeback_umount(void)
921 if (atomic_read(&isw_nr_in_flight
)) {
923 * Use rcu_barrier() to wait for all pending callbacks to
924 * ensure that all in-flight wb switches are in the workqueue.
927 flush_workqueue(isw_wq
);
931 static int __init
cgroup_writeback_init(void)
933 isw_wq
= alloc_workqueue("inode_switch_wbs", 0, 0);
938 fs_initcall(cgroup_writeback_init
);
940 #else /* CONFIG_CGROUP_WRITEBACK */
942 static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info
*bdi
) { }
943 static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info
*bdi
) { }
945 static struct bdi_writeback
*
946 locked_inode_to_wb_and_lock_list(struct inode
*inode
)
947 __releases(&inode
->i_lock
)
948 __acquires(&wb
->list_lock
)
950 struct bdi_writeback
*wb
= inode_to_wb(inode
);
952 spin_unlock(&inode
->i_lock
);
953 spin_lock(&wb
->list_lock
);
957 static struct bdi_writeback
*inode_to_wb_and_lock_list(struct inode
*inode
)
958 __acquires(&wb
->list_lock
)
960 struct bdi_writeback
*wb
= inode_to_wb(inode
);
962 spin_lock(&wb
->list_lock
);
966 static long wb_split_bdi_pages(struct bdi_writeback
*wb
, long nr_pages
)
971 static void bdi_split_work_to_wbs(struct backing_dev_info
*bdi
,
972 struct wb_writeback_work
*base_work
,
977 if (!skip_if_busy
|| !writeback_in_progress(&bdi
->wb
)) {
978 base_work
->auto_free
= 0;
979 wb_queue_work(&bdi
->wb
, base_work
);
983 #endif /* CONFIG_CGROUP_WRITEBACK */
986 * Add in the number of potentially dirty inodes, because each inode
987 * write can dirty pagecache in the underlying blockdev.
989 static unsigned long get_nr_dirty_pages(void)
991 return global_node_page_state(NR_FILE_DIRTY
) +
992 global_node_page_state(NR_UNSTABLE_NFS
) +
993 get_nr_dirty_inodes();
996 static void wb_start_writeback(struct bdi_writeback
*wb
, enum wb_reason reason
)
998 if (!wb_has_dirty_io(wb
))
1002 * All callers of this function want to start writeback of all
1003 * dirty pages. Places like vmscan can call this at a very
1004 * high frequency, causing pointless allocations of tons of
1005 * work items and keeping the flusher threads busy retrieving
1006 * that work. Ensure that we only allow one of them pending and
1007 * inflight at the time.
1009 if (test_bit(WB_start_all
, &wb
->state
) ||
1010 test_and_set_bit(WB_start_all
, &wb
->state
))
1013 wb
->start_all_reason
= reason
;
1018 * wb_start_background_writeback - start background writeback
1019 * @wb: bdi_writback to write from
1022 * This makes sure WB_SYNC_NONE background writeback happens. When
1023 * this function returns, it is only guaranteed that for given wb
1024 * some IO is happening if we are over background dirty threshold.
1025 * Caller need not hold sb s_umount semaphore.
1027 void wb_start_background_writeback(struct bdi_writeback
*wb
)
1030 * We just wake up the flusher thread. It will perform background
1031 * writeback as soon as there is no other work to do.
1033 trace_writeback_wake_background(wb
);
1038 * Remove the inode from the writeback list it is on.
1040 void inode_io_list_del(struct inode
*inode
)
1042 struct bdi_writeback
*wb
;
1044 wb
= inode_to_wb_and_lock_list(inode
);
1045 inode_io_list_del_locked(inode
, wb
);
1046 spin_unlock(&wb
->list_lock
);
1050 * mark an inode as under writeback on the sb
1052 void sb_mark_inode_writeback(struct inode
*inode
)
1054 struct super_block
*sb
= inode
->i_sb
;
1055 unsigned long flags
;
1057 if (list_empty(&inode
->i_wb_list
)) {
1058 spin_lock_irqsave(&sb
->s_inode_wblist_lock
, flags
);
1059 if (list_empty(&inode
->i_wb_list
)) {
1060 list_add_tail(&inode
->i_wb_list
, &sb
->s_inodes_wb
);
1061 trace_sb_mark_inode_writeback(inode
);
1063 spin_unlock_irqrestore(&sb
->s_inode_wblist_lock
, flags
);
1068 * clear an inode as under writeback on the sb
1070 void sb_clear_inode_writeback(struct inode
*inode
)
1072 struct super_block
*sb
= inode
->i_sb
;
1073 unsigned long flags
;
1075 if (!list_empty(&inode
->i_wb_list
)) {
1076 spin_lock_irqsave(&sb
->s_inode_wblist_lock
, flags
);
1077 if (!list_empty(&inode
->i_wb_list
)) {
1078 list_del_init(&inode
->i_wb_list
);
1079 trace_sb_clear_inode_writeback(inode
);
1081 spin_unlock_irqrestore(&sb
->s_inode_wblist_lock
, flags
);
1086 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
1087 * furthest end of its superblock's dirty-inode list.
1089 * Before stamping the inode's ->dirtied_when, we check to see whether it is
1090 * already the most-recently-dirtied inode on the b_dirty list. If that is
1091 * the case then the inode must have been redirtied while it was being written
1092 * out and we don't reset its dirtied_when.
1094 static void redirty_tail(struct inode
*inode
, struct bdi_writeback
*wb
)
1096 if (!list_empty(&wb
->b_dirty
)) {
1099 tail
= wb_inode(wb
->b_dirty
.next
);
1100 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
1101 inode
->dirtied_when
= jiffies
;
1103 inode_io_list_move_locked(inode
, wb
, &wb
->b_dirty
);
1107 * requeue inode for re-scanning after bdi->b_io list is exhausted.
1109 static void requeue_io(struct inode
*inode
, struct bdi_writeback
*wb
)
1111 inode_io_list_move_locked(inode
, wb
, &wb
->b_more_io
);
1114 static void inode_sync_complete(struct inode
*inode
)
1116 inode
->i_state
&= ~I_SYNC
;
1117 /* If inode is clean an unused, put it into LRU now... */
1118 inode_add_lru(inode
);
1119 /* Waiters must see I_SYNC cleared before being woken up */
1121 wake_up_bit(&inode
->i_state
, __I_SYNC
);
1124 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
1126 bool ret
= time_after(inode
->dirtied_when
, t
);
1127 #ifndef CONFIG_64BIT
1129 * For inodes being constantly redirtied, dirtied_when can get stuck.
1130 * It _appears_ to be in the future, but is actually in distant past.
1131 * This test is necessary to prevent such wrapped-around relative times
1132 * from permanently stopping the whole bdi writeback.
1134 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
1139 #define EXPIRE_DIRTY_ATIME 0x0001
1142 * Move expired (dirtied before work->older_than_this) dirty inodes from
1143 * @delaying_queue to @dispatch_queue.
1145 static int move_expired_inodes(struct list_head
*delaying_queue
,
1146 struct list_head
*dispatch_queue
,
1148 struct wb_writeback_work
*work
)
1150 unsigned long *older_than_this
= NULL
;
1151 unsigned long expire_time
;
1153 struct list_head
*pos
, *node
;
1154 struct super_block
*sb
= NULL
;
1155 struct inode
*inode
;
1159 if ((flags
& EXPIRE_DIRTY_ATIME
) == 0)
1160 older_than_this
= work
->older_than_this
;
1161 else if (!work
->for_sync
) {
1162 expire_time
= jiffies
- (dirtytime_expire_interval
* HZ
);
1163 older_than_this
= &expire_time
;
1165 while (!list_empty(delaying_queue
)) {
1166 inode
= wb_inode(delaying_queue
->prev
);
1167 if (older_than_this
&&
1168 inode_dirtied_after(inode
, *older_than_this
))
1170 list_move(&inode
->i_io_list
, &tmp
);
1172 if (flags
& EXPIRE_DIRTY_ATIME
)
1173 set_bit(__I_DIRTY_TIME_EXPIRED
, &inode
->i_state
);
1174 if (sb_is_blkdev_sb(inode
->i_sb
))
1176 if (sb
&& sb
!= inode
->i_sb
)
1181 /* just one sb in list, splice to dispatch_queue and we're done */
1183 list_splice(&tmp
, dispatch_queue
);
1187 /* Move inodes from one superblock together */
1188 while (!list_empty(&tmp
)) {
1189 sb
= wb_inode(tmp
.prev
)->i_sb
;
1190 list_for_each_prev_safe(pos
, node
, &tmp
) {
1191 inode
= wb_inode(pos
);
1192 if (inode
->i_sb
== sb
)
1193 list_move(&inode
->i_io_list
, dispatch_queue
);
1201 * Queue all expired dirty inodes for io, eldest first.
1203 * newly dirtied b_dirty b_io b_more_io
1204 * =============> gf edc BA
1206 * newly dirtied b_dirty b_io b_more_io
1207 * =============> g fBAedc
1209 * +--> dequeue for IO
1211 static void queue_io(struct bdi_writeback
*wb
, struct wb_writeback_work
*work
)
1215 assert_spin_locked(&wb
->list_lock
);
1216 list_splice_init(&wb
->b_more_io
, &wb
->b_io
);
1217 moved
= move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, 0, work
);
1218 moved
+= move_expired_inodes(&wb
->b_dirty_time
, &wb
->b_io
,
1219 EXPIRE_DIRTY_ATIME
, work
);
1221 wb_io_lists_populated(wb
);
1222 trace_writeback_queue_io(wb
, work
, moved
);
1225 static int write_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1229 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
)) {
1230 trace_writeback_write_inode_start(inode
, wbc
);
1231 ret
= inode
->i_sb
->s_op
->write_inode(inode
, wbc
);
1232 trace_writeback_write_inode(inode
, wbc
);
1239 * Wait for writeback on an inode to complete. Called with i_lock held.
1240 * Caller must make sure inode cannot go away when we drop i_lock.
1242 static void __inode_wait_for_writeback(struct inode
*inode
)
1243 __releases(inode
->i_lock
)
1244 __acquires(inode
->i_lock
)
1246 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
1247 wait_queue_head_t
*wqh
;
1249 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
1250 while (inode
->i_state
& I_SYNC
) {
1251 spin_unlock(&inode
->i_lock
);
1252 __wait_on_bit(wqh
, &wq
, bit_wait
,
1253 TASK_UNINTERRUPTIBLE
);
1254 spin_lock(&inode
->i_lock
);
1259 * Wait for writeback on an inode to complete. Caller must have inode pinned.
1261 void inode_wait_for_writeback(struct inode
*inode
)
1263 spin_lock(&inode
->i_lock
);
1264 __inode_wait_for_writeback(inode
);
1265 spin_unlock(&inode
->i_lock
);
1269 * Sleep until I_SYNC is cleared. This function must be called with i_lock
1270 * held and drops it. It is aimed for callers not holding any inode reference
1271 * so once i_lock is dropped, inode can go away.
1273 static void inode_sleep_on_writeback(struct inode
*inode
)
1274 __releases(inode
->i_lock
)
1277 wait_queue_head_t
*wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
1280 prepare_to_wait(wqh
, &wait
, TASK_UNINTERRUPTIBLE
);
1281 sleep
= inode
->i_state
& I_SYNC
;
1282 spin_unlock(&inode
->i_lock
);
1285 finish_wait(wqh
, &wait
);
1289 * Find proper writeback list for the inode depending on its current state and
1290 * possibly also change of its state while we were doing writeback. Here we
1291 * handle things such as livelock prevention or fairness of writeback among
1292 * inodes. This function can be called only by flusher thread - noone else
1293 * processes all inodes in writeback lists and requeueing inodes behind flusher
1294 * thread's back can have unexpected consequences.
1296 static void requeue_inode(struct inode
*inode
, struct bdi_writeback
*wb
,
1297 struct writeback_control
*wbc
)
1299 if (inode
->i_state
& I_FREEING
)
1303 * Sync livelock prevention. Each inode is tagged and synced in one
1304 * shot. If still dirty, it will be redirty_tail()'ed below. Update
1305 * the dirty time to prevent enqueue and sync it again.
1307 if ((inode
->i_state
& I_DIRTY
) &&
1308 (wbc
->sync_mode
== WB_SYNC_ALL
|| wbc
->tagged_writepages
))
1309 inode
->dirtied_when
= jiffies
;
1311 if (wbc
->pages_skipped
) {
1313 * writeback is not making progress due to locked
1314 * buffers. Skip this inode for now.
1316 redirty_tail(inode
, wb
);
1320 if (mapping_tagged(inode
->i_mapping
, PAGECACHE_TAG_DIRTY
)) {
1322 * We didn't write back all the pages. nfs_writepages()
1323 * sometimes bales out without doing anything.
1325 if (wbc
->nr_to_write
<= 0) {
1326 /* Slice used up. Queue for next turn. */
1327 requeue_io(inode
, wb
);
1330 * Writeback blocked by something other than
1331 * congestion. Delay the inode for some time to
1332 * avoid spinning on the CPU (100% iowait)
1333 * retrying writeback of the dirty page/inode
1334 * that cannot be performed immediately.
1336 redirty_tail(inode
, wb
);
1338 } else if (inode
->i_state
& I_DIRTY
) {
1340 * Filesystems can dirty the inode during writeback operations,
1341 * such as delayed allocation during submission or metadata
1342 * updates after data IO completion.
1344 redirty_tail(inode
, wb
);
1345 } else if (inode
->i_state
& I_DIRTY_TIME
) {
1346 inode
->dirtied_when
= jiffies
;
1347 inode_io_list_move_locked(inode
, wb
, &wb
->b_dirty_time
);
1349 /* The inode is clean. Remove from writeback lists. */
1350 inode_io_list_del_locked(inode
, wb
);
1355 * Write out an inode and its dirty pages. Do not update the writeback list
1356 * linkage. That is left to the caller. The caller is also responsible for
1357 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
1360 __writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1362 struct address_space
*mapping
= inode
->i_mapping
;
1363 long nr_to_write
= wbc
->nr_to_write
;
1367 WARN_ON(!(inode
->i_state
& I_SYNC
));
1369 trace_writeback_single_inode_start(inode
, wbc
, nr_to_write
);
1371 ret
= do_writepages(mapping
, wbc
);
1374 * Make sure to wait on the data before writing out the metadata.
1375 * This is important for filesystems that modify metadata on data
1376 * I/O completion. We don't do it for sync(2) writeback because it has a
1377 * separate, external IO completion path and ->sync_fs for guaranteeing
1378 * inode metadata is written back correctly.
1380 if (wbc
->sync_mode
== WB_SYNC_ALL
&& !wbc
->for_sync
) {
1381 int err
= filemap_fdatawait(mapping
);
1387 * Some filesystems may redirty the inode during the writeback
1388 * due to delalloc, clear dirty metadata flags right before
1391 spin_lock(&inode
->i_lock
);
1393 dirty
= inode
->i_state
& I_DIRTY
;
1394 if (inode
->i_state
& I_DIRTY_TIME
) {
1395 if ((dirty
& I_DIRTY_INODE
) ||
1396 wbc
->sync_mode
== WB_SYNC_ALL
||
1397 unlikely(inode
->i_state
& I_DIRTY_TIME_EXPIRED
) ||
1398 unlikely(time_after(jiffies
,
1399 (inode
->dirtied_time_when
+
1400 dirtytime_expire_interval
* HZ
)))) {
1401 dirty
|= I_DIRTY_TIME
| I_DIRTY_TIME_EXPIRED
;
1402 trace_writeback_lazytime(inode
);
1405 inode
->i_state
&= ~I_DIRTY_TIME_EXPIRED
;
1406 inode
->i_state
&= ~dirty
;
1409 * Paired with smp_mb() in __mark_inode_dirty(). This allows
1410 * __mark_inode_dirty() to test i_state without grabbing i_lock -
1411 * either they see the I_DIRTY bits cleared or we see the dirtied
1414 * I_DIRTY_PAGES is always cleared together above even if @mapping
1415 * still has dirty pages. The flag is reinstated after smp_mb() if
1416 * necessary. This guarantees that either __mark_inode_dirty()
1417 * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
1421 if (mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
))
1422 inode
->i_state
|= I_DIRTY_PAGES
;
1424 spin_unlock(&inode
->i_lock
);
1426 if (dirty
& I_DIRTY_TIME
)
1427 mark_inode_dirty_sync(inode
);
1428 /* Don't write the inode if only I_DIRTY_PAGES was set */
1429 if (dirty
& ~I_DIRTY_PAGES
) {
1430 int err
= write_inode(inode
, wbc
);
1434 trace_writeback_single_inode(inode
, wbc
, nr_to_write
);
1439 * Write out an inode's dirty pages. Either the caller has an active reference
1440 * on the inode or the inode has I_WILL_FREE set.
1442 * This function is designed to be called for writing back one inode which
1443 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
1444 * and does more profound writeback list handling in writeback_sb_inodes().
1446 static int writeback_single_inode(struct inode
*inode
,
1447 struct writeback_control
*wbc
)
1449 struct bdi_writeback
*wb
;
1452 spin_lock(&inode
->i_lock
);
1453 if (!atomic_read(&inode
->i_count
))
1454 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
1456 WARN_ON(inode
->i_state
& I_WILL_FREE
);
1458 if (inode
->i_state
& I_SYNC
) {
1459 if (wbc
->sync_mode
!= WB_SYNC_ALL
)
1462 * It's a data-integrity sync. We must wait. Since callers hold
1463 * inode reference or inode has I_WILL_FREE set, it cannot go
1466 __inode_wait_for_writeback(inode
);
1468 WARN_ON(inode
->i_state
& I_SYNC
);
1470 * Skip inode if it is clean and we have no outstanding writeback in
1471 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
1472 * function since flusher thread may be doing for example sync in
1473 * parallel and if we move the inode, it could get skipped. So here we
1474 * make sure inode is on some writeback list and leave it there unless
1475 * we have completely cleaned the inode.
1477 if (!(inode
->i_state
& I_DIRTY_ALL
) &&
1478 (wbc
->sync_mode
!= WB_SYNC_ALL
||
1479 !mapping_tagged(inode
->i_mapping
, PAGECACHE_TAG_WRITEBACK
)))
1481 inode
->i_state
|= I_SYNC
;
1482 wbc_attach_and_unlock_inode(wbc
, inode
);
1484 ret
= __writeback_single_inode(inode
, wbc
);
1486 wbc_detach_inode(wbc
);
1488 wb
= inode_to_wb_and_lock_list(inode
);
1489 spin_lock(&inode
->i_lock
);
1491 * If inode is clean, remove it from writeback lists. Otherwise don't
1492 * touch it. See comment above for explanation.
1494 if (!(inode
->i_state
& I_DIRTY_ALL
))
1495 inode_io_list_del_locked(inode
, wb
);
1496 spin_unlock(&wb
->list_lock
);
1497 inode_sync_complete(inode
);
1499 spin_unlock(&inode
->i_lock
);
1503 static long writeback_chunk_size(struct bdi_writeback
*wb
,
1504 struct wb_writeback_work
*work
)
1509 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
1510 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
1511 * here avoids calling into writeback_inodes_wb() more than once.
1513 * The intended call sequence for WB_SYNC_ALL writeback is:
1516 * writeback_sb_inodes() <== called only once
1517 * write_cache_pages() <== called once for each inode
1518 * (quickly) tag currently dirty pages
1519 * (maybe slowly) sync all tagged pages
1521 if (work
->sync_mode
== WB_SYNC_ALL
|| work
->tagged_writepages
)
1524 pages
= min(wb
->avg_write_bandwidth
/ 2,
1525 global_wb_domain
.dirty_limit
/ DIRTY_SCOPE
);
1526 pages
= min(pages
, work
->nr_pages
);
1527 pages
= round_down(pages
+ MIN_WRITEBACK_PAGES
,
1528 MIN_WRITEBACK_PAGES
);
1535 * Write a portion of b_io inodes which belong to @sb.
1537 * Return the number of pages and/or inodes written.
1539 * NOTE! This is called with wb->list_lock held, and will
1540 * unlock and relock that for each inode it ends up doing
1543 static long writeback_sb_inodes(struct super_block
*sb
,
1544 struct bdi_writeback
*wb
,
1545 struct wb_writeback_work
*work
)
1547 struct writeback_control wbc
= {
1548 .sync_mode
= work
->sync_mode
,
1549 .tagged_writepages
= work
->tagged_writepages
,
1550 .for_kupdate
= work
->for_kupdate
,
1551 .for_background
= work
->for_background
,
1552 .for_sync
= work
->for_sync
,
1553 .range_cyclic
= work
->range_cyclic
,
1555 .range_end
= LLONG_MAX
,
1557 unsigned long start_time
= jiffies
;
1559 long wrote
= 0; /* count both pages and inodes */
1561 while (!list_empty(&wb
->b_io
)) {
1562 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
1563 struct bdi_writeback
*tmp_wb
;
1565 if (inode
->i_sb
!= sb
) {
1568 * We only want to write back data for this
1569 * superblock, move all inodes not belonging
1570 * to it back onto the dirty list.
1572 redirty_tail(inode
, wb
);
1577 * The inode belongs to a different superblock.
1578 * Bounce back to the caller to unpin this and
1579 * pin the next superblock.
1585 * Don't bother with new inodes or inodes being freed, first
1586 * kind does not need periodic writeout yet, and for the latter
1587 * kind writeout is handled by the freer.
1589 spin_lock(&inode
->i_lock
);
1590 if (inode
->i_state
& (I_NEW
| I_FREEING
| I_WILL_FREE
)) {
1591 spin_unlock(&inode
->i_lock
);
1592 redirty_tail(inode
, wb
);
1595 if ((inode
->i_state
& I_SYNC
) && wbc
.sync_mode
!= WB_SYNC_ALL
) {
1597 * If this inode is locked for writeback and we are not
1598 * doing writeback-for-data-integrity, move it to
1599 * b_more_io so that writeback can proceed with the
1600 * other inodes on s_io.
1602 * We'll have another go at writing back this inode
1603 * when we completed a full scan of b_io.
1605 spin_unlock(&inode
->i_lock
);
1606 requeue_io(inode
, wb
);
1607 trace_writeback_sb_inodes_requeue(inode
);
1610 spin_unlock(&wb
->list_lock
);
1613 * We already requeued the inode if it had I_SYNC set and we
1614 * are doing WB_SYNC_NONE writeback. So this catches only the
1617 if (inode
->i_state
& I_SYNC
) {
1618 /* Wait for I_SYNC. This function drops i_lock... */
1619 inode_sleep_on_writeback(inode
);
1620 /* Inode may be gone, start again */
1621 spin_lock(&wb
->list_lock
);
1624 inode
->i_state
|= I_SYNC
;
1625 wbc_attach_and_unlock_inode(&wbc
, inode
);
1627 write_chunk
= writeback_chunk_size(wb
, work
);
1628 wbc
.nr_to_write
= write_chunk
;
1629 wbc
.pages_skipped
= 0;
1632 * We use I_SYNC to pin the inode in memory. While it is set
1633 * evict_inode() will wait so the inode cannot be freed.
1635 __writeback_single_inode(inode
, &wbc
);
1637 wbc_detach_inode(&wbc
);
1638 work
->nr_pages
-= write_chunk
- wbc
.nr_to_write
;
1639 wrote
+= write_chunk
- wbc
.nr_to_write
;
1641 if (need_resched()) {
1643 * We're trying to balance between building up a nice
1644 * long list of IOs to improve our merge rate, and
1645 * getting those IOs out quickly for anyone throttling
1646 * in balance_dirty_pages(). cond_resched() doesn't
1647 * unplug, so get our IOs out the door before we
1650 blk_flush_plug(current
);
1655 * Requeue @inode if still dirty. Be careful as @inode may
1656 * have been switched to another wb in the meantime.
1658 tmp_wb
= inode_to_wb_and_lock_list(inode
);
1659 spin_lock(&inode
->i_lock
);
1660 if (!(inode
->i_state
& I_DIRTY_ALL
))
1662 requeue_inode(inode
, tmp_wb
, &wbc
);
1663 inode_sync_complete(inode
);
1664 spin_unlock(&inode
->i_lock
);
1666 if (unlikely(tmp_wb
!= wb
)) {
1667 spin_unlock(&tmp_wb
->list_lock
);
1668 spin_lock(&wb
->list_lock
);
1672 * bail out to wb_writeback() often enough to check
1673 * background threshold and other termination conditions.
1676 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
1678 if (work
->nr_pages
<= 0)
1685 static long __writeback_inodes_wb(struct bdi_writeback
*wb
,
1686 struct wb_writeback_work
*work
)
1688 unsigned long start_time
= jiffies
;
1691 while (!list_empty(&wb
->b_io
)) {
1692 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
1693 struct super_block
*sb
= inode
->i_sb
;
1695 if (!trylock_super(sb
)) {
1697 * trylock_super() may fail consistently due to
1698 * s_umount being grabbed by someone else. Don't use
1699 * requeue_io() to avoid busy retrying the inode/sb.
1701 redirty_tail(inode
, wb
);
1704 wrote
+= writeback_sb_inodes(sb
, wb
, work
);
1705 up_read(&sb
->s_umount
);
1707 /* refer to the same tests at the end of writeback_sb_inodes */
1709 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
1711 if (work
->nr_pages
<= 0)
1715 /* Leave any unwritten inodes on b_io */
1719 static long writeback_inodes_wb(struct bdi_writeback
*wb
, long nr_pages
,
1720 enum wb_reason reason
)
1722 struct wb_writeback_work work
= {
1723 .nr_pages
= nr_pages
,
1724 .sync_mode
= WB_SYNC_NONE
,
1728 struct blk_plug plug
;
1730 blk_start_plug(&plug
);
1731 spin_lock(&wb
->list_lock
);
1732 if (list_empty(&wb
->b_io
))
1733 queue_io(wb
, &work
);
1734 __writeback_inodes_wb(wb
, &work
);
1735 spin_unlock(&wb
->list_lock
);
1736 blk_finish_plug(&plug
);
1738 return nr_pages
- work
.nr_pages
;
1742 * Explicit flushing or periodic writeback of "old" data.
1744 * Define "old": the first time one of an inode's pages is dirtied, we mark the
1745 * dirtying-time in the inode's address_space. So this periodic writeback code
1746 * just walks the superblock inode list, writing back any inodes which are
1747 * older than a specific point in time.
1749 * Try to run once per dirty_writeback_interval. But if a writeback event
1750 * takes longer than a dirty_writeback_interval interval, then leave a
1753 * older_than_this takes precedence over nr_to_write. So we'll only write back
1754 * all dirty pages if they are all attached to "old" mappings.
1756 static long wb_writeback(struct bdi_writeback
*wb
,
1757 struct wb_writeback_work
*work
)
1759 unsigned long wb_start
= jiffies
;
1760 long nr_pages
= work
->nr_pages
;
1761 unsigned long oldest_jif
;
1762 struct inode
*inode
;
1764 struct blk_plug plug
;
1766 oldest_jif
= jiffies
;
1767 work
->older_than_this
= &oldest_jif
;
1769 blk_start_plug(&plug
);
1770 spin_lock(&wb
->list_lock
);
1773 * Stop writeback when nr_pages has been consumed
1775 if (work
->nr_pages
<= 0)
1779 * Background writeout and kupdate-style writeback may
1780 * run forever. Stop them if there is other work to do
1781 * so that e.g. sync can proceed. They'll be restarted
1782 * after the other works are all done.
1784 if ((work
->for_background
|| work
->for_kupdate
) &&
1785 !list_empty(&wb
->work_list
))
1789 * For background writeout, stop when we are below the
1790 * background dirty threshold
1792 if (work
->for_background
&& !wb_over_bg_thresh(wb
))
1796 * Kupdate and background works are special and we want to
1797 * include all inodes that need writing. Livelock avoidance is
1798 * handled by these works yielding to any other work so we are
1801 if (work
->for_kupdate
) {
1802 oldest_jif
= jiffies
-
1803 msecs_to_jiffies(dirty_expire_interval
* 10);
1804 } else if (work
->for_background
)
1805 oldest_jif
= jiffies
;
1807 trace_writeback_start(wb
, work
);
1808 if (list_empty(&wb
->b_io
))
1811 progress
= writeback_sb_inodes(work
->sb
, wb
, work
);
1813 progress
= __writeback_inodes_wb(wb
, work
);
1814 trace_writeback_written(wb
, work
);
1816 wb_update_bandwidth(wb
, wb_start
);
1819 * Did we write something? Try for more
1821 * Dirty inodes are moved to b_io for writeback in batches.
1822 * The completion of the current batch does not necessarily
1823 * mean the overall work is done. So we keep looping as long
1824 * as made some progress on cleaning pages or inodes.
1829 * No more inodes for IO, bail
1831 if (list_empty(&wb
->b_more_io
))
1834 * Nothing written. Wait for some inode to
1835 * become available for writeback. Otherwise
1836 * we'll just busyloop.
1838 trace_writeback_wait(wb
, work
);
1839 inode
= wb_inode(wb
->b_more_io
.prev
);
1840 spin_lock(&inode
->i_lock
);
1841 spin_unlock(&wb
->list_lock
);
1842 /* This function drops i_lock... */
1843 inode_sleep_on_writeback(inode
);
1844 spin_lock(&wb
->list_lock
);
1846 spin_unlock(&wb
->list_lock
);
1847 blk_finish_plug(&plug
);
1849 return nr_pages
- work
->nr_pages
;
1853 * Return the next wb_writeback_work struct that hasn't been processed yet.
1855 static struct wb_writeback_work
*get_next_work_item(struct bdi_writeback
*wb
)
1857 struct wb_writeback_work
*work
= NULL
;
1859 spin_lock_bh(&wb
->work_lock
);
1860 if (!list_empty(&wb
->work_list
)) {
1861 work
= list_entry(wb
->work_list
.next
,
1862 struct wb_writeback_work
, list
);
1863 list_del_init(&work
->list
);
1865 spin_unlock_bh(&wb
->work_lock
);
1869 static long wb_check_background_flush(struct bdi_writeback
*wb
)
1871 if (wb_over_bg_thresh(wb
)) {
1873 struct wb_writeback_work work
= {
1874 .nr_pages
= LONG_MAX
,
1875 .sync_mode
= WB_SYNC_NONE
,
1876 .for_background
= 1,
1878 .reason
= WB_REASON_BACKGROUND
,
1881 return wb_writeback(wb
, &work
);
1887 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
1889 unsigned long expired
;
1893 * When set to zero, disable periodic writeback
1895 if (!dirty_writeback_interval
)
1898 expired
= wb
->last_old_flush
+
1899 msecs_to_jiffies(dirty_writeback_interval
* 10);
1900 if (time_before(jiffies
, expired
))
1903 wb
->last_old_flush
= jiffies
;
1904 nr_pages
= get_nr_dirty_pages();
1907 struct wb_writeback_work work
= {
1908 .nr_pages
= nr_pages
,
1909 .sync_mode
= WB_SYNC_NONE
,
1912 .reason
= WB_REASON_PERIODIC
,
1915 return wb_writeback(wb
, &work
);
1921 static long wb_check_start_all(struct bdi_writeback
*wb
)
1925 if (!test_bit(WB_start_all
, &wb
->state
))
1928 nr_pages
= get_nr_dirty_pages();
1930 struct wb_writeback_work work
= {
1931 .nr_pages
= wb_split_bdi_pages(wb
, nr_pages
),
1932 .sync_mode
= WB_SYNC_NONE
,
1934 .reason
= wb
->start_all_reason
,
1937 nr_pages
= wb_writeback(wb
, &work
);
1940 clear_bit(WB_start_all
, &wb
->state
);
1946 * Retrieve work items and do the writeback they describe
1948 static long wb_do_writeback(struct bdi_writeback
*wb
)
1950 struct wb_writeback_work
*work
;
1953 set_bit(WB_writeback_running
, &wb
->state
);
1954 while ((work
= get_next_work_item(wb
)) != NULL
) {
1955 trace_writeback_exec(wb
, work
);
1956 wrote
+= wb_writeback(wb
, work
);
1957 finish_writeback_work(wb
, work
);
1961 * Check for a flush-everything request
1963 wrote
+= wb_check_start_all(wb
);
1966 * Check for periodic writeback, kupdated() style
1968 wrote
+= wb_check_old_data_flush(wb
);
1969 wrote
+= wb_check_background_flush(wb
);
1970 clear_bit(WB_writeback_running
, &wb
->state
);
1976 * Handle writeback of dirty data for the device backed by this bdi. Also
1977 * reschedules periodically and does kupdated style flushing.
1979 void wb_workfn(struct work_struct
*work
)
1981 struct bdi_writeback
*wb
= container_of(to_delayed_work(work
),
1982 struct bdi_writeback
, dwork
);
1985 set_worker_desc("flush-%s", dev_name(wb
->bdi
->dev
));
1986 current
->flags
|= PF_SWAPWRITE
;
1988 if (likely(!current_is_workqueue_rescuer() ||
1989 !test_bit(WB_registered
, &wb
->state
))) {
1991 * The normal path. Keep writing back @wb until its
1992 * work_list is empty. Note that this path is also taken
1993 * if @wb is shutting down even when we're running off the
1994 * rescuer as work_list needs to be drained.
1997 pages_written
= wb_do_writeback(wb
);
1998 trace_writeback_pages_written(pages_written
);
1999 } while (!list_empty(&wb
->work_list
));
2002 * bdi_wq can't get enough workers and we're running off
2003 * the emergency worker. Don't hog it. Hopefully, 1024 is
2004 * enough for efficient IO.
2006 pages_written
= writeback_inodes_wb(wb
, 1024,
2007 WB_REASON_FORKER_THREAD
);
2008 trace_writeback_pages_written(pages_written
);
2011 if (!list_empty(&wb
->work_list
))
2013 else if (wb_has_dirty_io(wb
) && dirty_writeback_interval
)
2014 wb_wakeup_delayed(wb
);
2016 current
->flags
&= ~PF_SWAPWRITE
;
2020 * Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero,
2021 * write back the whole world.
2023 static void __wakeup_flusher_threads_bdi(struct backing_dev_info
*bdi
,
2024 enum wb_reason reason
)
2026 struct bdi_writeback
*wb
;
2028 if (!bdi_has_dirty_io(bdi
))
2031 list_for_each_entry_rcu(wb
, &bdi
->wb_list
, bdi_node
)
2032 wb_start_writeback(wb
, reason
);
2035 void wakeup_flusher_threads_bdi(struct backing_dev_info
*bdi
,
2036 enum wb_reason reason
)
2039 __wakeup_flusher_threads_bdi(bdi
, reason
);
2044 * Wakeup the flusher threads to start writeback of all currently dirty pages
2046 void wakeup_flusher_threads(enum wb_reason reason
)
2048 struct backing_dev_info
*bdi
;
2051 * If we are expecting writeback progress we must submit plugged IO.
2053 if (blk_needs_flush_plug(current
))
2054 blk_schedule_flush_plug(current
);
2057 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
)
2058 __wakeup_flusher_threads_bdi(bdi
, reason
);
2063 * Wake up bdi's periodically to make sure dirtytime inodes gets
2064 * written back periodically. We deliberately do *not* check the
2065 * b_dirtytime list in wb_has_dirty_io(), since this would cause the
2066 * kernel to be constantly waking up once there are any dirtytime
2067 * inodes on the system. So instead we define a separate delayed work
2068 * function which gets called much more rarely. (By default, only
2069 * once every 12 hours.)
2071 * If there is any other write activity going on in the file system,
2072 * this function won't be necessary. But if the only thing that has
2073 * happened on the file system is a dirtytime inode caused by an atime
2074 * update, we need this infrastructure below to make sure that inode
2075 * eventually gets pushed out to disk.
2077 static void wakeup_dirtytime_writeback(struct work_struct
*w
);
2078 static DECLARE_DELAYED_WORK(dirtytime_work
, wakeup_dirtytime_writeback
);
2080 static void wakeup_dirtytime_writeback(struct work_struct
*w
)
2082 struct backing_dev_info
*bdi
;
2085 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
2086 struct bdi_writeback
*wb
;
2088 list_for_each_entry_rcu(wb
, &bdi
->wb_list
, bdi_node
)
2089 if (!list_empty(&wb
->b_dirty_time
))
2093 schedule_delayed_work(&dirtytime_work
, dirtytime_expire_interval
* HZ
);
2096 static int __init
start_dirtytime_writeback(void)
2098 schedule_delayed_work(&dirtytime_work
, dirtytime_expire_interval
* HZ
);
2101 __initcall(start_dirtytime_writeback
);
2103 int dirtytime_interval_handler(struct ctl_table
*table
, int write
,
2104 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2108 ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
2109 if (ret
== 0 && write
)
2110 mod_delayed_work(system_wq
, &dirtytime_work
, 0);
2114 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
2116 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
2117 struct dentry
*dentry
;
2118 const char *name
= "?";
2120 dentry
= d_find_alias(inode
);
2122 spin_lock(&dentry
->d_lock
);
2123 name
= (const char *) dentry
->d_name
.name
;
2126 "%s(%d): dirtied inode %lu (%s) on %s\n",
2127 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
2128 name
, inode
->i_sb
->s_id
);
2130 spin_unlock(&dentry
->d_lock
);
2137 * __mark_inode_dirty - internal function
2139 * @inode: inode to mark
2140 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
2142 * Mark an inode as dirty. Callers should use mark_inode_dirty or
2143 * mark_inode_dirty_sync.
2145 * Put the inode on the super block's dirty list.
2147 * CAREFUL! We mark it dirty unconditionally, but move it onto the
2148 * dirty list only if it is hashed or if it refers to a blockdev.
2149 * If it was not hashed, it will never be added to the dirty list
2150 * even if it is later hashed, as it will have been marked dirty already.
2152 * In short, make sure you hash any inodes _before_ you start marking
2155 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
2156 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
2157 * the kernel-internal blockdev inode represents the dirtying time of the
2158 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
2159 * page->mapping->host, so the page-dirtying time is recorded in the internal
2162 void __mark_inode_dirty(struct inode
*inode
, int flags
)
2164 struct super_block
*sb
= inode
->i_sb
;
2167 trace_writeback_mark_inode_dirty(inode
, flags
);
2170 * Don't do this for I_DIRTY_PAGES - that doesn't actually
2171 * dirty the inode itself
2173 if (flags
& (I_DIRTY_INODE
| I_DIRTY_TIME
)) {
2174 trace_writeback_dirty_inode_start(inode
, flags
);
2176 if (sb
->s_op
->dirty_inode
)
2177 sb
->s_op
->dirty_inode(inode
, flags
);
2179 trace_writeback_dirty_inode(inode
, flags
);
2181 if (flags
& I_DIRTY_INODE
)
2182 flags
&= ~I_DIRTY_TIME
;
2183 dirtytime
= flags
& I_DIRTY_TIME
;
2186 * Paired with smp_mb() in __writeback_single_inode() for the
2187 * following lockless i_state test. See there for details.
2191 if (((inode
->i_state
& flags
) == flags
) ||
2192 (dirtytime
&& (inode
->i_state
& I_DIRTY_INODE
)))
2195 if (unlikely(block_dump
))
2196 block_dump___mark_inode_dirty(inode
);
2198 spin_lock(&inode
->i_lock
);
2199 if (dirtytime
&& (inode
->i_state
& I_DIRTY_INODE
))
2200 goto out_unlock_inode
;
2201 if ((inode
->i_state
& flags
) != flags
) {
2202 const int was_dirty
= inode
->i_state
& I_DIRTY
;
2204 inode_attach_wb(inode
, NULL
);
2206 if (flags
& I_DIRTY_INODE
)
2207 inode
->i_state
&= ~I_DIRTY_TIME
;
2208 inode
->i_state
|= flags
;
2211 * If the inode is being synced, just update its dirty state.
2212 * The unlocker will place the inode on the appropriate
2213 * superblock list, based upon its state.
2215 if (inode
->i_state
& I_SYNC
)
2216 goto out_unlock_inode
;
2219 * Only add valid (hashed) inodes to the superblock's
2220 * dirty list. Add blockdev inodes as well.
2222 if (!S_ISBLK(inode
->i_mode
)) {
2223 if (inode_unhashed(inode
))
2224 goto out_unlock_inode
;
2226 if (inode
->i_state
& I_FREEING
)
2227 goto out_unlock_inode
;
2230 * If the inode was already on b_dirty/b_io/b_more_io, don't
2231 * reposition it (that would break b_dirty time-ordering).
2234 struct bdi_writeback
*wb
;
2235 struct list_head
*dirty_list
;
2236 bool wakeup_bdi
= false;
2238 wb
= locked_inode_to_wb_and_lock_list(inode
);
2240 WARN(bdi_cap_writeback_dirty(wb
->bdi
) &&
2241 !test_bit(WB_registered
, &wb
->state
),
2242 "bdi-%s not registered\n", wb
->bdi
->name
);
2244 inode
->dirtied_when
= jiffies
;
2246 inode
->dirtied_time_when
= jiffies
;
2248 if (inode
->i_state
& I_DIRTY
)
2249 dirty_list
= &wb
->b_dirty
;
2251 dirty_list
= &wb
->b_dirty_time
;
2253 wakeup_bdi
= inode_io_list_move_locked(inode
, wb
,
2256 spin_unlock(&wb
->list_lock
);
2257 trace_writeback_dirty_inode_enqueue(inode
);
2260 * If this is the first dirty inode for this bdi,
2261 * we have to wake-up the corresponding bdi thread
2262 * to make sure background write-back happens
2265 if (bdi_cap_writeback_dirty(wb
->bdi
) && wakeup_bdi
)
2266 wb_wakeup_delayed(wb
);
2271 spin_unlock(&inode
->i_lock
);
2273 EXPORT_SYMBOL(__mark_inode_dirty
);
2276 * The @s_sync_lock is used to serialise concurrent sync operations
2277 * to avoid lock contention problems with concurrent wait_sb_inodes() calls.
2278 * Concurrent callers will block on the s_sync_lock rather than doing contending
2279 * walks. The queueing maintains sync(2) required behaviour as all the IO that
2280 * has been issued up to the time this function is enter is guaranteed to be
2281 * completed by the time we have gained the lock and waited for all IO that is
2282 * in progress regardless of the order callers are granted the lock.
2284 static void wait_sb_inodes(struct super_block
*sb
)
2286 LIST_HEAD(sync_list
);
2289 * We need to be protected against the filesystem going from
2290 * r/o to r/w or vice versa.
2292 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
2294 mutex_lock(&sb
->s_sync_lock
);
2297 * Splice the writeback list onto a temporary list to avoid waiting on
2298 * inodes that have started writeback after this point.
2300 * Use rcu_read_lock() to keep the inodes around until we have a
2301 * reference. s_inode_wblist_lock protects sb->s_inodes_wb as well as
2302 * the local list because inodes can be dropped from either by writeback
2306 spin_lock_irq(&sb
->s_inode_wblist_lock
);
2307 list_splice_init(&sb
->s_inodes_wb
, &sync_list
);
2310 * Data integrity sync. Must wait for all pages under writeback, because
2311 * there may have been pages dirtied before our sync call, but which had
2312 * writeout started before we write it out. In which case, the inode
2313 * may not be on the dirty list, but we still have to wait for that
2316 while (!list_empty(&sync_list
)) {
2317 struct inode
*inode
= list_first_entry(&sync_list
, struct inode
,
2319 struct address_space
*mapping
= inode
->i_mapping
;
2322 * Move each inode back to the wb list before we drop the lock
2323 * to preserve consistency between i_wb_list and the mapping
2324 * writeback tag. Writeback completion is responsible to remove
2325 * the inode from either list once the writeback tag is cleared.
2327 list_move_tail(&inode
->i_wb_list
, &sb
->s_inodes_wb
);
2330 * The mapping can appear untagged while still on-list since we
2331 * do not have the mapping lock. Skip it here, wb completion
2334 if (!mapping_tagged(mapping
, PAGECACHE_TAG_WRITEBACK
))
2337 spin_unlock_irq(&sb
->s_inode_wblist_lock
);
2339 spin_lock(&inode
->i_lock
);
2340 if (inode
->i_state
& (I_FREEING
|I_WILL_FREE
|I_NEW
)) {
2341 spin_unlock(&inode
->i_lock
);
2343 spin_lock_irq(&sb
->s_inode_wblist_lock
);
2347 spin_unlock(&inode
->i_lock
);
2351 * We keep the error status of individual mapping so that
2352 * applications can catch the writeback error using fsync(2).
2353 * See filemap_fdatawait_keep_errors() for details.
2355 filemap_fdatawait_keep_errors(mapping
);
2362 spin_lock_irq(&sb
->s_inode_wblist_lock
);
2364 spin_unlock_irq(&sb
->s_inode_wblist_lock
);
2366 mutex_unlock(&sb
->s_sync_lock
);
2369 static void __writeback_inodes_sb_nr(struct super_block
*sb
, unsigned long nr
,
2370 enum wb_reason reason
, bool skip_if_busy
)
2372 DEFINE_WB_COMPLETION_ONSTACK(done
);
2373 struct wb_writeback_work work
= {
2375 .sync_mode
= WB_SYNC_NONE
,
2376 .tagged_writepages
= 1,
2381 struct backing_dev_info
*bdi
= sb
->s_bdi
;
2383 if (!bdi_has_dirty_io(bdi
) || bdi
== &noop_backing_dev_info
)
2385 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
2387 bdi_split_work_to_wbs(sb
->s_bdi
, &work
, skip_if_busy
);
2388 wb_wait_for_completion(bdi
, &done
);
2392 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
2393 * @sb: the superblock
2394 * @nr: the number of pages to write
2395 * @reason: reason why some writeback work initiated
2397 * Start writeback on some inodes on this super_block. No guarantees are made
2398 * on how many (if any) will be written, and this function does not wait
2399 * for IO completion of submitted IO.
2401 void writeback_inodes_sb_nr(struct super_block
*sb
,
2403 enum wb_reason reason
)
2405 __writeback_inodes_sb_nr(sb
, nr
, reason
, false);
2407 EXPORT_SYMBOL(writeback_inodes_sb_nr
);
2410 * writeback_inodes_sb - writeback dirty inodes from given super_block
2411 * @sb: the superblock
2412 * @reason: reason why some writeback work was initiated
2414 * Start writeback on some inodes on this super_block. No guarantees are made
2415 * on how many (if any) will be written, and this function does not wait
2416 * for IO completion of submitted IO.
2418 void writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
)
2420 return writeback_inodes_sb_nr(sb
, get_nr_dirty_pages(), reason
);
2422 EXPORT_SYMBOL(writeback_inodes_sb
);
2425 * try_to_writeback_inodes_sb - try to start writeback if none underway
2426 * @sb: the superblock
2427 * @reason: reason why some writeback work was initiated
2429 * Invoke __writeback_inodes_sb_nr if no writeback is currently underway.
2431 void try_to_writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
)
2433 if (!down_read_trylock(&sb
->s_umount
))
2436 __writeback_inodes_sb_nr(sb
, get_nr_dirty_pages(), reason
, true);
2437 up_read(&sb
->s_umount
);
2439 EXPORT_SYMBOL(try_to_writeback_inodes_sb
);
2442 * sync_inodes_sb - sync sb inode pages
2443 * @sb: the superblock
2445 * This function writes and waits on any dirty inode belonging to this
2448 void sync_inodes_sb(struct super_block
*sb
)
2450 DEFINE_WB_COMPLETION_ONSTACK(done
);
2451 struct wb_writeback_work work
= {
2453 .sync_mode
= WB_SYNC_ALL
,
2454 .nr_pages
= LONG_MAX
,
2457 .reason
= WB_REASON_SYNC
,
2460 struct backing_dev_info
*bdi
= sb
->s_bdi
;
2463 * Can't skip on !bdi_has_dirty() because we should wait for !dirty
2464 * inodes under writeback and I_DIRTY_TIME inodes ignored by
2465 * bdi_has_dirty() need to be written out too.
2467 if (bdi
== &noop_backing_dev_info
)
2469 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
2471 /* protect against inode wb switch, see inode_switch_wbs_work_fn() */
2472 bdi_down_write_wb_switch_rwsem(bdi
);
2473 bdi_split_work_to_wbs(bdi
, &work
, false);
2474 wb_wait_for_completion(bdi
, &done
);
2475 bdi_up_write_wb_switch_rwsem(bdi
);
2479 EXPORT_SYMBOL(sync_inodes_sb
);
2482 * write_inode_now - write an inode to disk
2483 * @inode: inode to write to disk
2484 * @sync: whether the write should be synchronous or not
2486 * This function commits an inode to disk immediately if it is dirty. This is
2487 * primarily needed by knfsd.
2489 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
2491 int write_inode_now(struct inode
*inode
, int sync
)
2493 struct writeback_control wbc
= {
2494 .nr_to_write
= LONG_MAX
,
2495 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
2497 .range_end
= LLONG_MAX
,
2500 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
2501 wbc
.nr_to_write
= 0;
2504 return writeback_single_inode(inode
, &wbc
);
2506 EXPORT_SYMBOL(write_inode_now
);
2509 * sync_inode - write an inode and its pages to disk.
2510 * @inode: the inode to sync
2511 * @wbc: controls the writeback mode
2513 * sync_inode() will write an inode and its pages to disk. It will also
2514 * correctly update the inode on its superblock's dirty inode lists and will
2515 * update inode->i_state.
2517 * The caller must have a ref on the inode.
2519 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
2521 return writeback_single_inode(inode
, wbc
);
2523 EXPORT_SYMBOL(sync_inode
);
2526 * sync_inode_metadata - write an inode to disk
2527 * @inode: the inode to sync
2528 * @wait: wait for I/O to complete.
2530 * Write an inode to disk and adjust its dirty state after completion.
2532 * Note: only writes the actual inode, no associated data or other metadata.
2534 int sync_inode_metadata(struct inode
*inode
, int wait
)
2536 struct writeback_control wbc
= {
2537 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_NONE
,
2538 .nr_to_write
= 0, /* metadata-only */
2541 return sync_inode(inode
, &wbc
);
2543 EXPORT_SYMBOL(sync_inode_metadata
);