1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 2002, Linus Torvalds.
7 * Contains all the functions related to writing back and waiting
8 * upon dirty inodes against superblocks, and writing back dirty
9 * pages against inodes. ie: data writeback. Writeout of the
10 * inode itself is not handled here.
12 * 10Apr2002 Andrew Morton
13 * Split out of fs/inode.c
14 * Additions for address_space-based writeback
17 #include <linux/kernel.h>
18 #include <linux/export.h>
19 #include <linux/spinlock.h>
20 #include <linux/slab.h>
21 #include <linux/sched.h>
24 #include <linux/pagemap.h>
25 #include <linux/kthread.h>
26 #include <linux/writeback.h>
27 #include <linux/blkdev.h>
28 #include <linux/backing-dev.h>
29 #include <linux/tracepoint.h>
30 #include <linux/device.h>
31 #include <linux/memcontrol.h>
35 * 4MB minimal write chunk size
37 #define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10))
40 * Passed into wb_writeback(), essentially a subset of writeback_control
42 struct wb_writeback_work
{
44 struct super_block
*sb
;
45 enum writeback_sync_modes sync_mode
;
46 unsigned int tagged_writepages
:1;
47 unsigned int for_kupdate
:1;
48 unsigned int range_cyclic
:1;
49 unsigned int for_background
:1;
50 unsigned int for_sync
:1; /* sync(2) WB_SYNC_ALL writeback */
51 unsigned int auto_free
:1; /* free on completion */
52 enum wb_reason reason
; /* why was writeback initiated? */
54 struct list_head list
; /* pending work list */
55 struct wb_completion
*done
; /* set if the caller waits */
59 * If an inode is constantly having its pages dirtied, but then the
60 * updates stop dirtytime_expire_interval seconds in the past, it's
61 * possible for the worst case time between when an inode has its
62 * timestamps updated and when they finally get written out to be two
63 * dirtytime_expire_intervals. We set the default to 12 hours (in
64 * seconds), which means most of the time inodes will have their
65 * timestamps written to disk after 12 hours, but in the worst case a
66 * few inodes might not their timestamps updated for 24 hours.
68 unsigned int dirtytime_expire_interval
= 12 * 60 * 60;
70 static inline struct inode
*wb_inode(struct list_head
*head
)
72 return list_entry(head
, struct inode
, i_io_list
);
76 * Include the creation of the trace points after defining the
77 * wb_writeback_work structure and inline functions so that the definition
78 * remains local to this file.
80 #define CREATE_TRACE_POINTS
81 #include <trace/events/writeback.h>
83 EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage
);
85 static bool wb_io_lists_populated(struct bdi_writeback
*wb
)
87 if (wb_has_dirty_io(wb
)) {
90 set_bit(WB_has_dirty_io
, &wb
->state
);
91 WARN_ON_ONCE(!wb
->avg_write_bandwidth
);
92 atomic_long_add(wb
->avg_write_bandwidth
,
93 &wb
->bdi
->tot_write_bandwidth
);
98 static void wb_io_lists_depopulated(struct bdi_writeback
*wb
)
100 if (wb_has_dirty_io(wb
) && list_empty(&wb
->b_dirty
) &&
101 list_empty(&wb
->b_io
) && list_empty(&wb
->b_more_io
)) {
102 clear_bit(WB_has_dirty_io
, &wb
->state
);
103 WARN_ON_ONCE(atomic_long_sub_return(wb
->avg_write_bandwidth
,
104 &wb
->bdi
->tot_write_bandwidth
) < 0);
109 * inode_io_list_move_locked - move an inode onto a bdi_writeback IO list
110 * @inode: inode to be moved
111 * @wb: target bdi_writeback
112 * @head: one of @wb->b_{dirty|io|more_io|dirty_time}
114 * Move @inode->i_io_list to @list of @wb and set %WB_has_dirty_io.
115 * Returns %true if @inode is the first occupant of the !dirty_time IO
116 * lists; otherwise, %false.
118 static bool inode_io_list_move_locked(struct inode
*inode
,
119 struct bdi_writeback
*wb
,
120 struct list_head
*head
)
122 assert_spin_locked(&wb
->list_lock
);
124 list_move(&inode
->i_io_list
, head
);
126 /* dirty_time doesn't count as dirty_io until expiration */
127 if (head
!= &wb
->b_dirty_time
)
128 return wb_io_lists_populated(wb
);
130 wb_io_lists_depopulated(wb
);
135 * inode_io_list_del_locked - remove an inode from its bdi_writeback IO list
136 * @inode: inode to be removed
137 * @wb: bdi_writeback @inode is being removed from
139 * Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and
140 * clear %WB_has_dirty_io if all are empty afterwards.
142 static void inode_io_list_del_locked(struct inode
*inode
,
143 struct bdi_writeback
*wb
)
145 assert_spin_locked(&wb
->list_lock
);
146 assert_spin_locked(&inode
->i_lock
);
148 inode
->i_state
&= ~I_SYNC_QUEUED
;
149 list_del_init(&inode
->i_io_list
);
150 wb_io_lists_depopulated(wb
);
153 static void wb_wakeup(struct bdi_writeback
*wb
)
155 spin_lock_bh(&wb
->work_lock
);
156 if (test_bit(WB_registered
, &wb
->state
))
157 mod_delayed_work(bdi_wq
, &wb
->dwork
, 0);
158 spin_unlock_bh(&wb
->work_lock
);
161 static void finish_writeback_work(struct bdi_writeback
*wb
,
162 struct wb_writeback_work
*work
)
164 struct wb_completion
*done
= work
->done
;
169 wait_queue_head_t
*waitq
= done
->waitq
;
171 /* @done can't be accessed after the following dec */
172 if (atomic_dec_and_test(&done
->cnt
))
177 static void wb_queue_work(struct bdi_writeback
*wb
,
178 struct wb_writeback_work
*work
)
180 trace_writeback_queue(wb
, work
);
183 atomic_inc(&work
->done
->cnt
);
185 spin_lock_bh(&wb
->work_lock
);
187 if (test_bit(WB_registered
, &wb
->state
)) {
188 list_add_tail(&work
->list
, &wb
->work_list
);
189 mod_delayed_work(bdi_wq
, &wb
->dwork
, 0);
191 finish_writeback_work(wb
, work
);
193 spin_unlock_bh(&wb
->work_lock
);
197 * wb_wait_for_completion - wait for completion of bdi_writeback_works
198 * @done: target wb_completion
200 * Wait for one or more work items issued to @bdi with their ->done field
201 * set to @done, which should have been initialized with
202 * DEFINE_WB_COMPLETION(). This function returns after all such work items
203 * are completed. Work items which are waited upon aren't freed
204 * automatically on completion.
206 void wb_wait_for_completion(struct wb_completion
*done
)
208 atomic_dec(&done
->cnt
); /* put down the initial count */
209 wait_event(*done
->waitq
, !atomic_read(&done
->cnt
));
212 #ifdef CONFIG_CGROUP_WRITEBACK
215 * Parameters for foreign inode detection, see wbc_detach_inode() to see
218 * These paramters are inherently heuristical as the detection target
219 * itself is fuzzy. All we want to do is detaching an inode from the
220 * current owner if it's being written to by some other cgroups too much.
222 * The current cgroup writeback is built on the assumption that multiple
223 * cgroups writing to the same inode concurrently is very rare and a mode
224 * of operation which isn't well supported. As such, the goal is not
225 * taking too long when a different cgroup takes over an inode while
226 * avoiding too aggressive flip-flops from occasional foreign writes.
228 * We record, very roughly, 2s worth of IO time history and if more than
229 * half of that is foreign, trigger the switch. The recording is quantized
230 * to 16 slots. To avoid tiny writes from swinging the decision too much,
231 * writes smaller than 1/8 of avg size are ignored.
233 #define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */
234 #define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */
235 #define WB_FRN_TIME_CUT_DIV 8 /* ignore rounds < avg / 8 */
236 #define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */
238 #define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */
239 #define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS)
240 /* each slot's duration is 2s / 16 */
241 #define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2)
242 /* if foreign slots >= 8, switch */
243 #define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1)
244 /* one round can affect upto 5 slots */
245 #define WB_FRN_MAX_IN_FLIGHT 1024 /* don't queue too many concurrently */
247 static atomic_t isw_nr_in_flight
= ATOMIC_INIT(0);
248 static struct workqueue_struct
*isw_wq
;
250 void __inode_attach_wb(struct inode
*inode
, struct page
*page
)
252 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
253 struct bdi_writeback
*wb
= NULL
;
255 if (inode_cgwb_enabled(inode
)) {
256 struct cgroup_subsys_state
*memcg_css
;
259 memcg_css
= mem_cgroup_css_from_page(page
);
260 wb
= wb_get_create(bdi
, memcg_css
, GFP_ATOMIC
);
262 /* must pin memcg_css, see wb_get_create() */
263 memcg_css
= task_get_css(current
, memory_cgrp_id
);
264 wb
= wb_get_create(bdi
, memcg_css
, GFP_ATOMIC
);
273 * There may be multiple instances of this function racing to
274 * update the same inode. Use cmpxchg() to tell the winner.
276 if (unlikely(cmpxchg(&inode
->i_wb
, NULL
, wb
)))
279 EXPORT_SYMBOL_GPL(__inode_attach_wb
);
282 * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
283 * @inode: inode of interest with i_lock held
285 * Returns @inode's wb with its list_lock held. @inode->i_lock must be
286 * held on entry and is released on return. The returned wb is guaranteed
287 * to stay @inode's associated wb until its list_lock is released.
289 static struct bdi_writeback
*
290 locked_inode_to_wb_and_lock_list(struct inode
*inode
)
291 __releases(&inode
->i_lock
)
292 __acquires(&wb
->list_lock
)
295 struct bdi_writeback
*wb
= inode_to_wb(inode
);
298 * inode_to_wb() association is protected by both
299 * @inode->i_lock and @wb->list_lock but list_lock nests
300 * outside i_lock. Drop i_lock and verify that the
301 * association hasn't changed after acquiring list_lock.
304 spin_unlock(&inode
->i_lock
);
305 spin_lock(&wb
->list_lock
);
307 /* i_wb may have changed inbetween, can't use inode_to_wb() */
308 if (likely(wb
== inode
->i_wb
)) {
309 wb_put(wb
); /* @inode already has ref */
313 spin_unlock(&wb
->list_lock
);
316 spin_lock(&inode
->i_lock
);
321 * inode_to_wb_and_lock_list - determine an inode's wb and lock it
322 * @inode: inode of interest
324 * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
327 static struct bdi_writeback
*inode_to_wb_and_lock_list(struct inode
*inode
)
328 __acquires(&wb
->list_lock
)
330 spin_lock(&inode
->i_lock
);
331 return locked_inode_to_wb_and_lock_list(inode
);
334 struct inode_switch_wbs_context
{
336 struct bdi_writeback
*new_wb
;
338 struct rcu_head rcu_head
;
339 struct work_struct work
;
342 static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info
*bdi
)
344 down_write(&bdi
->wb_switch_rwsem
);
347 static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info
*bdi
)
349 up_write(&bdi
->wb_switch_rwsem
);
352 static void inode_switch_wbs_work_fn(struct work_struct
*work
)
354 struct inode_switch_wbs_context
*isw
=
355 container_of(work
, struct inode_switch_wbs_context
, work
);
356 struct inode
*inode
= isw
->inode
;
357 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
358 struct address_space
*mapping
= inode
->i_mapping
;
359 struct bdi_writeback
*old_wb
= inode
->i_wb
;
360 struct bdi_writeback
*new_wb
= isw
->new_wb
;
361 XA_STATE(xas
, &mapping
->i_pages
, 0);
363 bool switched
= false;
366 * If @inode switches cgwb membership while sync_inodes_sb() is
367 * being issued, sync_inodes_sb() might miss it. Synchronize.
369 down_read(&bdi
->wb_switch_rwsem
);
372 * By the time control reaches here, RCU grace period has passed
373 * since I_WB_SWITCH assertion and all wb stat update transactions
374 * between unlocked_inode_to_wb_begin/end() are guaranteed to be
375 * synchronizing against the i_pages lock.
377 * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock
378 * gives us exclusion against all wb related operations on @inode
379 * including IO list manipulations and stat updates.
381 if (old_wb
< new_wb
) {
382 spin_lock(&old_wb
->list_lock
);
383 spin_lock_nested(&new_wb
->list_lock
, SINGLE_DEPTH_NESTING
);
385 spin_lock(&new_wb
->list_lock
);
386 spin_lock_nested(&old_wb
->list_lock
, SINGLE_DEPTH_NESTING
);
388 spin_lock(&inode
->i_lock
);
389 xa_lock_irq(&mapping
->i_pages
);
392 * Once I_FREEING is visible under i_lock, the eviction path owns
393 * the inode and we shouldn't modify ->i_io_list.
395 if (unlikely(inode
->i_state
& I_FREEING
))
398 trace_inode_switch_wbs(inode
, old_wb
, new_wb
);
401 * Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points
402 * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
403 * pages actually under writeback.
405 xas_for_each_marked(&xas
, page
, ULONG_MAX
, PAGECACHE_TAG_DIRTY
) {
406 if (PageDirty(page
)) {
407 dec_wb_stat(old_wb
, WB_RECLAIMABLE
);
408 inc_wb_stat(new_wb
, WB_RECLAIMABLE
);
413 xas_for_each_marked(&xas
, page
, ULONG_MAX
, PAGECACHE_TAG_WRITEBACK
) {
414 WARN_ON_ONCE(!PageWriteback(page
));
415 dec_wb_stat(old_wb
, WB_WRITEBACK
);
416 inc_wb_stat(new_wb
, WB_WRITEBACK
);
422 * Transfer to @new_wb's IO list if necessary. The specific list
423 * @inode was on is ignored and the inode is put on ->b_dirty which
424 * is always correct including from ->b_dirty_time. The transfer
425 * preserves @inode->dirtied_when ordering.
427 if (!list_empty(&inode
->i_io_list
)) {
430 inode_io_list_del_locked(inode
, old_wb
);
431 inode
->i_wb
= new_wb
;
432 list_for_each_entry(pos
, &new_wb
->b_dirty
, i_io_list
)
433 if (time_after_eq(inode
->dirtied_when
,
436 inode_io_list_move_locked(inode
, new_wb
, pos
->i_io_list
.prev
);
438 inode
->i_wb
= new_wb
;
441 /* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */
442 inode
->i_wb_frn_winner
= 0;
443 inode
->i_wb_frn_avg_time
= 0;
444 inode
->i_wb_frn_history
= 0;
448 * Paired with load_acquire in unlocked_inode_to_wb_begin() and
449 * ensures that the new wb is visible if they see !I_WB_SWITCH.
451 smp_store_release(&inode
->i_state
, inode
->i_state
& ~I_WB_SWITCH
);
453 xa_unlock_irq(&mapping
->i_pages
);
454 spin_unlock(&inode
->i_lock
);
455 spin_unlock(&new_wb
->list_lock
);
456 spin_unlock(&old_wb
->list_lock
);
458 up_read(&bdi
->wb_switch_rwsem
);
469 atomic_dec(&isw_nr_in_flight
);
472 static void inode_switch_wbs_rcu_fn(struct rcu_head
*rcu_head
)
474 struct inode_switch_wbs_context
*isw
= container_of(rcu_head
,
475 struct inode_switch_wbs_context
, rcu_head
);
477 /* needs to grab bh-unsafe locks, bounce to work item */
478 INIT_WORK(&isw
->work
, inode_switch_wbs_work_fn
);
479 queue_work(isw_wq
, &isw
->work
);
483 * inode_switch_wbs - change the wb association of an inode
484 * @inode: target inode
485 * @new_wb_id: ID of the new wb
487 * Switch @inode's wb association to the wb identified by @new_wb_id. The
488 * switching is performed asynchronously and may fail silently.
490 static void inode_switch_wbs(struct inode
*inode
, int new_wb_id
)
492 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
493 struct cgroup_subsys_state
*memcg_css
;
494 struct inode_switch_wbs_context
*isw
;
496 /* noop if seems to be already in progress */
497 if (inode
->i_state
& I_WB_SWITCH
)
500 /* avoid queueing a new switch if too many are already in flight */
501 if (atomic_read(&isw_nr_in_flight
) > WB_FRN_MAX_IN_FLIGHT
)
504 isw
= kzalloc(sizeof(*isw
), GFP_ATOMIC
);
508 atomic_inc(&isw_nr_in_flight
);
510 /* find and pin the new wb */
512 memcg_css
= css_from_id(new_wb_id
, &memory_cgrp_subsys
);
513 if (memcg_css
&& !css_tryget(memcg_css
))
519 isw
->new_wb
= wb_get_create(bdi
, memcg_css
, GFP_ATOMIC
);
524 /* while holding I_WB_SWITCH, no one else can update the association */
525 spin_lock(&inode
->i_lock
);
526 if (!(inode
->i_sb
->s_flags
& SB_ACTIVE
) ||
527 inode
->i_state
& (I_WB_SWITCH
| I_FREEING
) ||
528 inode_to_wb(inode
) == isw
->new_wb
) {
529 spin_unlock(&inode
->i_lock
);
532 inode
->i_state
|= I_WB_SWITCH
;
534 spin_unlock(&inode
->i_lock
);
539 * In addition to synchronizing among switchers, I_WB_SWITCH tells
540 * the RCU protected stat update paths to grab the i_page
541 * lock so that stat transfer can synchronize against them.
542 * Let's continue after I_WB_SWITCH is guaranteed to be visible.
544 call_rcu(&isw
->rcu_head
, inode_switch_wbs_rcu_fn
);
548 atomic_dec(&isw_nr_in_flight
);
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
);
595 EXPORT_SYMBOL_GPL(wbc_attach_and_unlock_inode
);
598 * wbc_detach_inode - disassociate wbc from inode and perform foreign detection
599 * @wbc: writeback_control of the just finished writeback
601 * To be called after a writeback attempt of an inode finishes and undoes
602 * wbc_attach_and_unlock_inode(). Can be called under any context.
604 * As concurrent write sharing of an inode is expected to be very rare and
605 * memcg only tracks page ownership on first-use basis severely confining
606 * the usefulness of such sharing, cgroup writeback tracks ownership
607 * per-inode. While the support for concurrent write sharing of an inode
608 * is deemed unnecessary, an inode being written to by different cgroups at
609 * different points in time is a lot more common, and, more importantly,
610 * charging only by first-use can too readily lead to grossly incorrect
611 * behaviors (single foreign page can lead to gigabytes of writeback to be
612 * incorrectly attributed).
614 * To resolve this issue, cgroup writeback detects the majority dirtier of
615 * an inode and transfers the ownership to it. To avoid unnnecessary
616 * oscillation, the detection mechanism keeps track of history and gives
617 * out the switch verdict only if the foreign usage pattern is stable over
618 * a certain amount of time and/or writeback attempts.
620 * On each writeback attempt, @wbc tries to detect the majority writer
621 * using Boyer-Moore majority vote algorithm. In addition to the byte
622 * count from the majority voting, it also counts the bytes written for the
623 * current wb and the last round's winner wb (max of last round's current
624 * wb, the winner from two rounds ago, and the last round's majority
625 * candidate). Keeping track of the historical winner helps the algorithm
626 * to semi-reliably detect the most active writer even when it's not the
629 * Once the winner of the round is determined, whether the winner is
630 * foreign or not and how much IO time the round consumed is recorded in
631 * inode->i_wb_frn_history. If the amount of recorded foreign IO time is
632 * over a certain threshold, the switch verdict is given.
634 void wbc_detach_inode(struct writeback_control
*wbc
)
636 struct bdi_writeback
*wb
= wbc
->wb
;
637 struct inode
*inode
= wbc
->inode
;
638 unsigned long avg_time
, max_bytes
, max_time
;
645 history
= inode
->i_wb_frn_history
;
646 avg_time
= inode
->i_wb_frn_avg_time
;
648 /* pick the winner of this round */
649 if (wbc
->wb_bytes
>= wbc
->wb_lcand_bytes
&&
650 wbc
->wb_bytes
>= wbc
->wb_tcand_bytes
) {
652 max_bytes
= wbc
->wb_bytes
;
653 } else if (wbc
->wb_lcand_bytes
>= wbc
->wb_tcand_bytes
) {
654 max_id
= wbc
->wb_lcand_id
;
655 max_bytes
= wbc
->wb_lcand_bytes
;
657 max_id
= wbc
->wb_tcand_id
;
658 max_bytes
= wbc
->wb_tcand_bytes
;
662 * Calculate the amount of IO time the winner consumed and fold it
663 * into the running average kept per inode. If the consumed IO
664 * time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
665 * deciding whether to switch or not. This is to prevent one-off
666 * small dirtiers from skewing the verdict.
668 max_time
= DIV_ROUND_UP((max_bytes
>> PAGE_SHIFT
) << WB_FRN_TIME_SHIFT
,
669 wb
->avg_write_bandwidth
);
671 avg_time
+= (max_time
>> WB_FRN_TIME_AVG_SHIFT
) -
672 (avg_time
>> WB_FRN_TIME_AVG_SHIFT
);
674 avg_time
= max_time
; /* immediate catch up on first run */
676 if (max_time
>= avg_time
/ WB_FRN_TIME_CUT_DIV
) {
680 * The switch verdict is reached if foreign wb's consume
681 * more than a certain proportion of IO time in a
682 * WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
683 * history mask where each bit represents one sixteenth of
684 * the period. Determine the number of slots to shift into
685 * history from @max_time.
687 slots
= min(DIV_ROUND_UP(max_time
, WB_FRN_HIST_UNIT
),
688 (unsigned long)WB_FRN_HIST_MAX_SLOTS
);
690 if (wbc
->wb_id
!= max_id
)
691 history
|= (1U << slots
) - 1;
694 trace_inode_foreign_history(inode
, wbc
, history
);
697 * Switch if the current wb isn't the consistent winner.
698 * If there are multiple closely competing dirtiers, the
699 * inode may switch across them repeatedly over time, which
700 * is okay. The main goal is avoiding keeping an inode on
701 * the wrong wb for an extended period of time.
703 if (hweight32(history
) > WB_FRN_HIST_THR_SLOTS
)
704 inode_switch_wbs(inode
, max_id
);
708 * Multiple instances of this function may race to update the
709 * following fields but we don't mind occassional inaccuracies.
711 inode
->i_wb_frn_winner
= max_id
;
712 inode
->i_wb_frn_avg_time
= min(avg_time
, (unsigned long)U16_MAX
);
713 inode
->i_wb_frn_history
= history
;
718 EXPORT_SYMBOL_GPL(wbc_detach_inode
);
721 * wbc_account_cgroup_owner - account writeback to update inode cgroup ownership
722 * @wbc: writeback_control of the writeback in progress
723 * @page: page being written out
724 * @bytes: number of bytes being written out
726 * @bytes from @page are about to written out during the writeback
727 * controlled by @wbc. Keep the book for foreign inode detection. See
728 * wbc_detach_inode().
730 void wbc_account_cgroup_owner(struct writeback_control
*wbc
, struct page
*page
,
733 struct cgroup_subsys_state
*css
;
737 * pageout() path doesn't attach @wbc to the inode being written
738 * out. This is intentional as we don't want the function to block
739 * behind a slow cgroup. Ultimately, we want pageout() to kick off
740 * regular writeback instead of writing things out itself.
742 if (!wbc
->wb
|| wbc
->no_cgroup_owner
)
745 css
= mem_cgroup_css_from_page(page
);
746 /* dead cgroups shouldn't contribute to inode ownership arbitration */
747 if (!(css
->flags
& CSS_ONLINE
))
752 if (id
== wbc
->wb_id
) {
753 wbc
->wb_bytes
+= bytes
;
757 if (id
== wbc
->wb_lcand_id
)
758 wbc
->wb_lcand_bytes
+= bytes
;
760 /* Boyer-Moore majority vote algorithm */
761 if (!wbc
->wb_tcand_bytes
)
762 wbc
->wb_tcand_id
= id
;
763 if (id
== wbc
->wb_tcand_id
)
764 wbc
->wb_tcand_bytes
+= bytes
;
766 wbc
->wb_tcand_bytes
-= min(bytes
, wbc
->wb_tcand_bytes
);
768 EXPORT_SYMBOL_GPL(wbc_account_cgroup_owner
);
771 * inode_congested - test whether an inode is congested
772 * @inode: inode to test for congestion (may be NULL)
773 * @cong_bits: mask of WB_[a]sync_congested bits to test
775 * Tests whether @inode is congested. @cong_bits is the mask of congestion
776 * bits to test and the return value is the mask of set bits.
778 * If cgroup writeback is enabled for @inode, the congestion state is
779 * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
780 * associated with @inode is congested; otherwise, the root wb's congestion
783 * @inode is allowed to be NULL as this function is often called on
784 * mapping->host which is NULL for the swapper space.
786 int inode_congested(struct inode
*inode
, int cong_bits
)
789 * Once set, ->i_wb never becomes NULL while the inode is alive.
790 * Start transaction iff ->i_wb is visible.
792 if (inode
&& inode_to_wb_is_valid(inode
)) {
793 struct bdi_writeback
*wb
;
794 struct wb_lock_cookie lock_cookie
= {};
797 wb
= unlocked_inode_to_wb_begin(inode
, &lock_cookie
);
798 congested
= wb_congested(wb
, cong_bits
);
799 unlocked_inode_to_wb_end(inode
, &lock_cookie
);
803 return wb_congested(&inode_to_bdi(inode
)->wb
, cong_bits
);
805 EXPORT_SYMBOL_GPL(inode_congested
);
808 * wb_split_bdi_pages - split nr_pages to write according to bandwidth
809 * @wb: target bdi_writeback to split @nr_pages to
810 * @nr_pages: number of pages to write for the whole bdi
812 * Split @wb's portion of @nr_pages according to @wb's write bandwidth in
813 * relation to the total write bandwidth of all wb's w/ dirty inodes on
816 static long wb_split_bdi_pages(struct bdi_writeback
*wb
, long nr_pages
)
818 unsigned long this_bw
= wb
->avg_write_bandwidth
;
819 unsigned long tot_bw
= atomic_long_read(&wb
->bdi
->tot_write_bandwidth
);
821 if (nr_pages
== LONG_MAX
)
825 * This may be called on clean wb's and proportional distribution
826 * may not make sense, just use the original @nr_pages in those
827 * cases. In general, we wanna err on the side of writing more.
829 if (!tot_bw
|| this_bw
>= tot_bw
)
832 return DIV_ROUND_UP_ULL((u64
)nr_pages
* this_bw
, tot_bw
);
836 * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
837 * @bdi: target backing_dev_info
838 * @base_work: wb_writeback_work to issue
839 * @skip_if_busy: skip wb's which already have writeback in progress
841 * Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
842 * have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
843 * distributed to the busy wbs according to each wb's proportion in the
844 * total active write bandwidth of @bdi.
846 static void bdi_split_work_to_wbs(struct backing_dev_info
*bdi
,
847 struct wb_writeback_work
*base_work
,
850 struct bdi_writeback
*last_wb
= NULL
;
851 struct bdi_writeback
*wb
= list_entry(&bdi
->wb_list
,
852 struct bdi_writeback
, bdi_node
);
857 list_for_each_entry_continue_rcu(wb
, &bdi
->wb_list
, bdi_node
) {
858 DEFINE_WB_COMPLETION(fallback_work_done
, bdi
);
859 struct wb_writeback_work fallback_work
;
860 struct wb_writeback_work
*work
;
868 /* SYNC_ALL writes out I_DIRTY_TIME too */
869 if (!wb_has_dirty_io(wb
) &&
870 (base_work
->sync_mode
== WB_SYNC_NONE
||
871 list_empty(&wb
->b_dirty_time
)))
873 if (skip_if_busy
&& writeback_in_progress(wb
))
876 nr_pages
= wb_split_bdi_pages(wb
, base_work
->nr_pages
);
878 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
881 work
->nr_pages
= nr_pages
;
883 wb_queue_work(wb
, work
);
887 /* alloc failed, execute synchronously using on-stack fallback */
888 work
= &fallback_work
;
890 work
->nr_pages
= nr_pages
;
892 work
->done
= &fallback_work_done
;
894 wb_queue_work(wb
, work
);
897 * Pin @wb so that it stays on @bdi->wb_list. This allows
898 * continuing iteration from @wb after dropping and
899 * regrabbing rcu read lock.
905 wb_wait_for_completion(&fallback_work_done
);
915 * cgroup_writeback_by_id - initiate cgroup writeback from bdi and memcg IDs
916 * @bdi_id: target bdi id
917 * @memcg_id: target memcg css id
918 * @nr: number of pages to write, 0 for best-effort dirty flushing
919 * @reason: reason why some writeback work initiated
920 * @done: target wb_completion
922 * Initiate flush of the bdi_writeback identified by @bdi_id and @memcg_id
923 * with the specified parameters.
925 int cgroup_writeback_by_id(u64 bdi_id
, int memcg_id
, unsigned long nr
,
926 enum wb_reason reason
, struct wb_completion
*done
)
928 struct backing_dev_info
*bdi
;
929 struct cgroup_subsys_state
*memcg_css
;
930 struct bdi_writeback
*wb
;
931 struct wb_writeback_work
*work
;
934 /* lookup bdi and memcg */
935 bdi
= bdi_get_by_id(bdi_id
);
940 memcg_css
= css_from_id(memcg_id
, &memory_cgrp_subsys
);
941 if (memcg_css
&& !css_tryget(memcg_css
))
950 * And find the associated wb. If the wb isn't there already
951 * there's nothing to flush, don't create one.
953 wb
= wb_get_lookup(bdi
, memcg_css
);
960 * If @nr is zero, the caller is attempting to write out most of
961 * the currently dirty pages. Let's take the current dirty page
962 * count and inflate it by 25% which should be large enough to
963 * flush out most dirty pages while avoiding getting livelocked by
964 * concurrent dirtiers.
967 unsigned long filepages
, headroom
, dirty
, writeback
;
969 mem_cgroup_wb_stats(wb
, &filepages
, &headroom
, &dirty
,
974 /* issue the writeback work */
975 work
= kzalloc(sizeof(*work
), GFP_NOWAIT
| __GFP_NOWARN
);
978 work
->sync_mode
= WB_SYNC_NONE
;
979 work
->range_cyclic
= 1;
980 work
->reason
= reason
;
983 wb_queue_work(wb
, work
);
998 * cgroup_writeback_umount - flush inode wb switches for umount
1000 * This function is called when a super_block is about to be destroyed and
1001 * flushes in-flight inode wb switches. An inode wb switch goes through
1002 * RCU and then workqueue, so the two need to be flushed in order to ensure
1003 * that all previously scheduled switches are finished. As wb switches are
1004 * rare occurrences and synchronize_rcu() can take a while, perform
1005 * flushing iff wb switches are in flight.
1007 void cgroup_writeback_umount(void)
1009 if (atomic_read(&isw_nr_in_flight
)) {
1011 * Use rcu_barrier() to wait for all pending callbacks to
1012 * ensure that all in-flight wb switches are in the workqueue.
1015 flush_workqueue(isw_wq
);
1019 static int __init
cgroup_writeback_init(void)
1021 isw_wq
= alloc_workqueue("inode_switch_wbs", 0, 0);
1026 fs_initcall(cgroup_writeback_init
);
1028 #else /* CONFIG_CGROUP_WRITEBACK */
1030 static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info
*bdi
) { }
1031 static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info
*bdi
) { }
1033 static struct bdi_writeback
*
1034 locked_inode_to_wb_and_lock_list(struct inode
*inode
)
1035 __releases(&inode
->i_lock
)
1036 __acquires(&wb
->list_lock
)
1038 struct bdi_writeback
*wb
= inode_to_wb(inode
);
1040 spin_unlock(&inode
->i_lock
);
1041 spin_lock(&wb
->list_lock
);
1045 static struct bdi_writeback
*inode_to_wb_and_lock_list(struct inode
*inode
)
1046 __acquires(&wb
->list_lock
)
1048 struct bdi_writeback
*wb
= inode_to_wb(inode
);
1050 spin_lock(&wb
->list_lock
);
1054 static long wb_split_bdi_pages(struct bdi_writeback
*wb
, long nr_pages
)
1059 static void bdi_split_work_to_wbs(struct backing_dev_info
*bdi
,
1060 struct wb_writeback_work
*base_work
,
1065 if (!skip_if_busy
|| !writeback_in_progress(&bdi
->wb
)) {
1066 base_work
->auto_free
= 0;
1067 wb_queue_work(&bdi
->wb
, base_work
);
1071 #endif /* CONFIG_CGROUP_WRITEBACK */
1074 * Add in the number of potentially dirty inodes, because each inode
1075 * write can dirty pagecache in the underlying blockdev.
1077 static unsigned long get_nr_dirty_pages(void)
1079 return global_node_page_state(NR_FILE_DIRTY
) +
1080 global_node_page_state(NR_UNSTABLE_NFS
) +
1081 get_nr_dirty_inodes();
1084 static void wb_start_writeback(struct bdi_writeback
*wb
, enum wb_reason reason
)
1086 if (!wb_has_dirty_io(wb
))
1090 * All callers of this function want to start writeback of all
1091 * dirty pages. Places like vmscan can call this at a very
1092 * high frequency, causing pointless allocations of tons of
1093 * work items and keeping the flusher threads busy retrieving
1094 * that work. Ensure that we only allow one of them pending and
1095 * inflight at the time.
1097 if (test_bit(WB_start_all
, &wb
->state
) ||
1098 test_and_set_bit(WB_start_all
, &wb
->state
))
1101 wb
->start_all_reason
= reason
;
1106 * wb_start_background_writeback - start background writeback
1107 * @wb: bdi_writback to write from
1110 * This makes sure WB_SYNC_NONE background writeback happens. When
1111 * this function returns, it is only guaranteed that for given wb
1112 * some IO is happening if we are over background dirty threshold.
1113 * Caller need not hold sb s_umount semaphore.
1115 void wb_start_background_writeback(struct bdi_writeback
*wb
)
1118 * We just wake up the flusher thread. It will perform background
1119 * writeback as soon as there is no other work to do.
1121 trace_writeback_wake_background(wb
);
1126 * Remove the inode from the writeback list it is on.
1128 void inode_io_list_del(struct inode
*inode
)
1130 struct bdi_writeback
*wb
;
1132 wb
= inode_to_wb_and_lock_list(inode
);
1133 spin_lock(&inode
->i_lock
);
1134 inode_io_list_del_locked(inode
, wb
);
1135 spin_unlock(&inode
->i_lock
);
1136 spin_unlock(&wb
->list_lock
);
1140 * mark an inode as under writeback on the sb
1142 void sb_mark_inode_writeback(struct inode
*inode
)
1144 struct super_block
*sb
= inode
->i_sb
;
1145 unsigned long flags
;
1147 if (list_empty(&inode
->i_wb_list
)) {
1148 spin_lock_irqsave(&sb
->s_inode_wblist_lock
, flags
);
1149 if (list_empty(&inode
->i_wb_list
)) {
1150 list_add_tail(&inode
->i_wb_list
, &sb
->s_inodes_wb
);
1151 trace_sb_mark_inode_writeback(inode
);
1153 spin_unlock_irqrestore(&sb
->s_inode_wblist_lock
, flags
);
1158 * clear an inode as under writeback on the sb
1160 void sb_clear_inode_writeback(struct inode
*inode
)
1162 struct super_block
*sb
= inode
->i_sb
;
1163 unsigned long flags
;
1165 if (!list_empty(&inode
->i_wb_list
)) {
1166 spin_lock_irqsave(&sb
->s_inode_wblist_lock
, flags
);
1167 if (!list_empty(&inode
->i_wb_list
)) {
1168 list_del_init(&inode
->i_wb_list
);
1169 trace_sb_clear_inode_writeback(inode
);
1171 spin_unlock_irqrestore(&sb
->s_inode_wblist_lock
, flags
);
1176 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
1177 * furthest end of its superblock's dirty-inode list.
1179 * Before stamping the inode's ->dirtied_when, we check to see whether it is
1180 * already the most-recently-dirtied inode on the b_dirty list. If that is
1181 * the case then the inode must have been redirtied while it was being written
1182 * out and we don't reset its dirtied_when.
1184 static void redirty_tail_locked(struct inode
*inode
, struct bdi_writeback
*wb
)
1186 assert_spin_locked(&inode
->i_lock
);
1188 if (!list_empty(&wb
->b_dirty
)) {
1191 tail
= wb_inode(wb
->b_dirty
.next
);
1192 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
1193 inode
->dirtied_when
= jiffies
;
1195 inode_io_list_move_locked(inode
, wb
, &wb
->b_dirty
);
1196 inode
->i_state
&= ~I_SYNC_QUEUED
;
1199 static void redirty_tail(struct inode
*inode
, struct bdi_writeback
*wb
)
1201 spin_lock(&inode
->i_lock
);
1202 redirty_tail_locked(inode
, wb
);
1203 spin_unlock(&inode
->i_lock
);
1207 * requeue inode for re-scanning after bdi->b_io list is exhausted.
1209 static void requeue_io(struct inode
*inode
, struct bdi_writeback
*wb
)
1211 inode_io_list_move_locked(inode
, wb
, &wb
->b_more_io
);
1214 static void inode_sync_complete(struct inode
*inode
)
1216 inode
->i_state
&= ~I_SYNC
;
1217 /* If inode is clean an unused, put it into LRU now... */
1218 inode_add_lru(inode
);
1219 /* Waiters must see I_SYNC cleared before being woken up */
1221 wake_up_bit(&inode
->i_state
, __I_SYNC
);
1224 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
1226 bool ret
= time_after(inode
->dirtied_when
, t
);
1227 #ifndef CONFIG_64BIT
1229 * For inodes being constantly redirtied, dirtied_when can get stuck.
1230 * It _appears_ to be in the future, but is actually in distant past.
1231 * This test is necessary to prevent such wrapped-around relative times
1232 * from permanently stopping the whole bdi writeback.
1234 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
1239 #define EXPIRE_DIRTY_ATIME 0x0001
1242 * Move expired (dirtied before dirtied_before) dirty inodes from
1243 * @delaying_queue to @dispatch_queue.
1245 static int move_expired_inodes(struct list_head
*delaying_queue
,
1246 struct list_head
*dispatch_queue
,
1247 unsigned long dirtied_before
)
1250 struct list_head
*pos
, *node
;
1251 struct super_block
*sb
= NULL
;
1252 struct inode
*inode
;
1256 while (!list_empty(delaying_queue
)) {
1257 inode
= wb_inode(delaying_queue
->prev
);
1258 if (inode_dirtied_after(inode
, dirtied_before
))
1260 list_move(&inode
->i_io_list
, &tmp
);
1262 spin_lock(&inode
->i_lock
);
1263 inode
->i_state
|= I_SYNC_QUEUED
;
1264 spin_unlock(&inode
->i_lock
);
1265 if (sb_is_blkdev_sb(inode
->i_sb
))
1267 if (sb
&& sb
!= inode
->i_sb
)
1272 /* just one sb in list, splice to dispatch_queue and we're done */
1274 list_splice(&tmp
, dispatch_queue
);
1278 /* Move inodes from one superblock together */
1279 while (!list_empty(&tmp
)) {
1280 sb
= wb_inode(tmp
.prev
)->i_sb
;
1281 list_for_each_prev_safe(pos
, node
, &tmp
) {
1282 inode
= wb_inode(pos
);
1283 if (inode
->i_sb
== sb
)
1284 list_move(&inode
->i_io_list
, dispatch_queue
);
1292 * Queue all expired dirty inodes for io, eldest first.
1294 * newly dirtied b_dirty b_io b_more_io
1295 * =============> gf edc BA
1297 * newly dirtied b_dirty b_io b_more_io
1298 * =============> g fBAedc
1300 * +--> dequeue for IO
1302 static void queue_io(struct bdi_writeback
*wb
, struct wb_writeback_work
*work
,
1303 unsigned long dirtied_before
)
1306 unsigned long time_expire_jif
= dirtied_before
;
1308 assert_spin_locked(&wb
->list_lock
);
1309 list_splice_init(&wb
->b_more_io
, &wb
->b_io
);
1310 moved
= move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, dirtied_before
);
1311 if (!work
->for_sync
)
1312 time_expire_jif
= jiffies
- dirtytime_expire_interval
* HZ
;
1313 moved
+= move_expired_inodes(&wb
->b_dirty_time
, &wb
->b_io
,
1316 wb_io_lists_populated(wb
);
1317 trace_writeback_queue_io(wb
, work
, dirtied_before
, moved
);
1320 static int write_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1324 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
)) {
1325 trace_writeback_write_inode_start(inode
, wbc
);
1326 ret
= inode
->i_sb
->s_op
->write_inode(inode
, wbc
);
1327 trace_writeback_write_inode(inode
, wbc
);
1334 * Wait for writeback on an inode to complete. Called with i_lock held.
1335 * Caller must make sure inode cannot go away when we drop i_lock.
1337 static void __inode_wait_for_writeback(struct inode
*inode
)
1338 __releases(inode
->i_lock
)
1339 __acquires(inode
->i_lock
)
1341 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
1342 wait_queue_head_t
*wqh
;
1344 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
1345 while (inode
->i_state
& I_SYNC
) {
1346 spin_unlock(&inode
->i_lock
);
1347 __wait_on_bit(wqh
, &wq
, bit_wait
,
1348 TASK_UNINTERRUPTIBLE
);
1349 spin_lock(&inode
->i_lock
);
1354 * Wait for writeback on an inode to complete. Caller must have inode pinned.
1356 void inode_wait_for_writeback(struct inode
*inode
)
1358 spin_lock(&inode
->i_lock
);
1359 __inode_wait_for_writeback(inode
);
1360 spin_unlock(&inode
->i_lock
);
1364 * Sleep until I_SYNC is cleared. This function must be called with i_lock
1365 * held and drops it. It is aimed for callers not holding any inode reference
1366 * so once i_lock is dropped, inode can go away.
1368 static void inode_sleep_on_writeback(struct inode
*inode
)
1369 __releases(inode
->i_lock
)
1372 wait_queue_head_t
*wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
1375 prepare_to_wait(wqh
, &wait
, TASK_UNINTERRUPTIBLE
);
1376 sleep
= inode
->i_state
& I_SYNC
;
1377 spin_unlock(&inode
->i_lock
);
1380 finish_wait(wqh
, &wait
);
1384 * Find proper writeback list for the inode depending on its current state and
1385 * possibly also change of its state while we were doing writeback. Here we
1386 * handle things such as livelock prevention or fairness of writeback among
1387 * inodes. This function can be called only by flusher thread - noone else
1388 * processes all inodes in writeback lists and requeueing inodes behind flusher
1389 * thread's back can have unexpected consequences.
1391 static void requeue_inode(struct inode
*inode
, struct bdi_writeback
*wb
,
1392 struct writeback_control
*wbc
)
1394 if (inode
->i_state
& I_FREEING
)
1398 * Sync livelock prevention. Each inode is tagged and synced in one
1399 * shot. If still dirty, it will be redirty_tail()'ed below. Update
1400 * the dirty time to prevent enqueue and sync it again.
1402 if ((inode
->i_state
& I_DIRTY
) &&
1403 (wbc
->sync_mode
== WB_SYNC_ALL
|| wbc
->tagged_writepages
))
1404 inode
->dirtied_when
= jiffies
;
1406 if (wbc
->pages_skipped
) {
1408 * writeback is not making progress due to locked
1409 * buffers. Skip this inode for now.
1411 redirty_tail_locked(inode
, wb
);
1415 if (mapping_tagged(inode
->i_mapping
, PAGECACHE_TAG_DIRTY
)) {
1417 * We didn't write back all the pages. nfs_writepages()
1418 * sometimes bales out without doing anything.
1420 if (wbc
->nr_to_write
<= 0) {
1421 /* Slice used up. Queue for next turn. */
1422 requeue_io(inode
, wb
);
1425 * Writeback blocked by something other than
1426 * congestion. Delay the inode for some time to
1427 * avoid spinning on the CPU (100% iowait)
1428 * retrying writeback of the dirty page/inode
1429 * that cannot be performed immediately.
1431 redirty_tail_locked(inode
, wb
);
1433 } else if (inode
->i_state
& I_DIRTY
) {
1435 * Filesystems can dirty the inode during writeback operations,
1436 * such as delayed allocation during submission or metadata
1437 * updates after data IO completion.
1439 redirty_tail_locked(inode
, wb
);
1440 } else if (inode
->i_state
& I_DIRTY_TIME
) {
1441 inode
->dirtied_when
= jiffies
;
1442 inode_io_list_move_locked(inode
, wb
, &wb
->b_dirty_time
);
1443 inode
->i_state
&= ~I_SYNC_QUEUED
;
1445 /* The inode is clean. Remove from writeback lists. */
1446 inode_io_list_del_locked(inode
, wb
);
1451 * Write out an inode and its dirty pages. Do not update the writeback list
1452 * linkage. That is left to the caller. The caller is also responsible for
1453 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
1456 __writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1458 struct address_space
*mapping
= inode
->i_mapping
;
1459 long nr_to_write
= wbc
->nr_to_write
;
1463 WARN_ON(!(inode
->i_state
& I_SYNC
));
1465 trace_writeback_single_inode_start(inode
, wbc
, nr_to_write
);
1467 ret
= do_writepages(mapping
, wbc
);
1470 * Make sure to wait on the data before writing out the metadata.
1471 * This is important for filesystems that modify metadata on data
1472 * I/O completion. We don't do it for sync(2) writeback because it has a
1473 * separate, external IO completion path and ->sync_fs for guaranteeing
1474 * inode metadata is written back correctly.
1476 if (wbc
->sync_mode
== WB_SYNC_ALL
&& !wbc
->for_sync
) {
1477 int err
= filemap_fdatawait(mapping
);
1483 * If the inode has dirty timestamps and we need to write them, call
1484 * mark_inode_dirty_sync() to notify the filesystem about it and to
1485 * change I_DIRTY_TIME into I_DIRTY_SYNC.
1487 if ((inode
->i_state
& I_DIRTY_TIME
) &&
1488 (wbc
->sync_mode
== WB_SYNC_ALL
|| wbc
->for_sync
||
1489 time_after(jiffies
, inode
->dirtied_time_when
+
1490 dirtytime_expire_interval
* HZ
))) {
1491 trace_writeback_lazytime(inode
);
1492 mark_inode_dirty_sync(inode
);
1496 * Some filesystems may redirty the inode during the writeback
1497 * due to delalloc, clear dirty metadata flags right before
1500 spin_lock(&inode
->i_lock
);
1501 dirty
= inode
->i_state
& I_DIRTY
;
1502 inode
->i_state
&= ~dirty
;
1505 * Paired with smp_mb() in __mark_inode_dirty(). This allows
1506 * __mark_inode_dirty() to test i_state without grabbing i_lock -
1507 * either they see the I_DIRTY bits cleared or we see the dirtied
1510 * I_DIRTY_PAGES is always cleared together above even if @mapping
1511 * still has dirty pages. The flag is reinstated after smp_mb() if
1512 * necessary. This guarantees that either __mark_inode_dirty()
1513 * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
1517 if (mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
))
1518 inode
->i_state
|= I_DIRTY_PAGES
;
1520 spin_unlock(&inode
->i_lock
);
1522 /* Don't write the inode if only I_DIRTY_PAGES was set */
1523 if (dirty
& ~I_DIRTY_PAGES
) {
1524 int err
= write_inode(inode
, wbc
);
1528 trace_writeback_single_inode(inode
, wbc
, nr_to_write
);
1533 * Write out an inode's dirty pages. Either the caller has an active reference
1534 * on the inode or the inode has I_WILL_FREE set.
1536 * This function is designed to be called for writing back one inode which
1537 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
1538 * and does more profound writeback list handling in writeback_sb_inodes().
1540 static int writeback_single_inode(struct inode
*inode
,
1541 struct writeback_control
*wbc
)
1543 struct bdi_writeback
*wb
;
1546 spin_lock(&inode
->i_lock
);
1547 if (!atomic_read(&inode
->i_count
))
1548 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
1550 WARN_ON(inode
->i_state
& I_WILL_FREE
);
1552 if (inode
->i_state
& I_SYNC
) {
1553 if (wbc
->sync_mode
!= WB_SYNC_ALL
)
1556 * It's a data-integrity sync. We must wait. Since callers hold
1557 * inode reference or inode has I_WILL_FREE set, it cannot go
1560 __inode_wait_for_writeback(inode
);
1562 WARN_ON(inode
->i_state
& I_SYNC
);
1564 * Skip inode if it is clean and we have no outstanding writeback in
1565 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
1566 * function since flusher thread may be doing for example sync in
1567 * parallel and if we move the inode, it could get skipped. So here we
1568 * make sure inode is on some writeback list and leave it there unless
1569 * we have completely cleaned the inode.
1571 if (!(inode
->i_state
& I_DIRTY_ALL
) &&
1572 (wbc
->sync_mode
!= WB_SYNC_ALL
||
1573 !mapping_tagged(inode
->i_mapping
, PAGECACHE_TAG_WRITEBACK
)))
1575 inode
->i_state
|= I_SYNC
;
1576 wbc_attach_and_unlock_inode(wbc
, inode
);
1578 ret
= __writeback_single_inode(inode
, wbc
);
1580 wbc_detach_inode(wbc
);
1582 wb
= inode_to_wb_and_lock_list(inode
);
1583 spin_lock(&inode
->i_lock
);
1585 * If inode is clean, remove it from writeback lists. Otherwise don't
1586 * touch it. See comment above for explanation.
1588 if (!(inode
->i_state
& I_DIRTY_ALL
))
1589 inode_io_list_del_locked(inode
, wb
);
1590 spin_unlock(&wb
->list_lock
);
1591 inode_sync_complete(inode
);
1593 spin_unlock(&inode
->i_lock
);
1597 static long writeback_chunk_size(struct bdi_writeback
*wb
,
1598 struct wb_writeback_work
*work
)
1603 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
1604 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
1605 * here avoids calling into writeback_inodes_wb() more than once.
1607 * The intended call sequence for WB_SYNC_ALL writeback is:
1610 * writeback_sb_inodes() <== called only once
1611 * write_cache_pages() <== called once for each inode
1612 * (quickly) tag currently dirty pages
1613 * (maybe slowly) sync all tagged pages
1615 if (work
->sync_mode
== WB_SYNC_ALL
|| work
->tagged_writepages
)
1618 pages
= min(wb
->avg_write_bandwidth
/ 2,
1619 global_wb_domain
.dirty_limit
/ DIRTY_SCOPE
);
1620 pages
= min(pages
, work
->nr_pages
);
1621 pages
= round_down(pages
+ MIN_WRITEBACK_PAGES
,
1622 MIN_WRITEBACK_PAGES
);
1629 * Write a portion of b_io inodes which belong to @sb.
1631 * Return the number of pages and/or inodes written.
1633 * NOTE! This is called with wb->list_lock held, and will
1634 * unlock and relock that for each inode it ends up doing
1637 static long writeback_sb_inodes(struct super_block
*sb
,
1638 struct bdi_writeback
*wb
,
1639 struct wb_writeback_work
*work
)
1641 struct writeback_control wbc
= {
1642 .sync_mode
= work
->sync_mode
,
1643 .tagged_writepages
= work
->tagged_writepages
,
1644 .for_kupdate
= work
->for_kupdate
,
1645 .for_background
= work
->for_background
,
1646 .for_sync
= work
->for_sync
,
1647 .range_cyclic
= work
->range_cyclic
,
1649 .range_end
= LLONG_MAX
,
1651 unsigned long start_time
= jiffies
;
1653 long wrote
= 0; /* count both pages and inodes */
1655 while (!list_empty(&wb
->b_io
)) {
1656 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
1657 struct bdi_writeback
*tmp_wb
;
1659 if (inode
->i_sb
!= sb
) {
1662 * We only want to write back data for this
1663 * superblock, move all inodes not belonging
1664 * to it back onto the dirty list.
1666 redirty_tail(inode
, wb
);
1671 * The inode belongs to a different superblock.
1672 * Bounce back to the caller to unpin this and
1673 * pin the next superblock.
1679 * Don't bother with new inodes or inodes being freed, first
1680 * kind does not need periodic writeout yet, and for the latter
1681 * kind writeout is handled by the freer.
1683 spin_lock(&inode
->i_lock
);
1684 if (inode
->i_state
& (I_NEW
| I_FREEING
| I_WILL_FREE
)) {
1685 redirty_tail_locked(inode
, wb
);
1686 spin_unlock(&inode
->i_lock
);
1689 if ((inode
->i_state
& I_SYNC
) && wbc
.sync_mode
!= WB_SYNC_ALL
) {
1691 * If this inode is locked for writeback and we are not
1692 * doing writeback-for-data-integrity, move it to
1693 * b_more_io so that writeback can proceed with the
1694 * other inodes on s_io.
1696 * We'll have another go at writing back this inode
1697 * when we completed a full scan of b_io.
1699 spin_unlock(&inode
->i_lock
);
1700 requeue_io(inode
, wb
);
1701 trace_writeback_sb_inodes_requeue(inode
);
1704 spin_unlock(&wb
->list_lock
);
1707 * We already requeued the inode if it had I_SYNC set and we
1708 * are doing WB_SYNC_NONE writeback. So this catches only the
1711 if (inode
->i_state
& I_SYNC
) {
1712 /* Wait for I_SYNC. This function drops i_lock... */
1713 inode_sleep_on_writeback(inode
);
1714 /* Inode may be gone, start again */
1715 spin_lock(&wb
->list_lock
);
1718 inode
->i_state
|= I_SYNC
;
1719 wbc_attach_and_unlock_inode(&wbc
, inode
);
1721 write_chunk
= writeback_chunk_size(wb
, work
);
1722 wbc
.nr_to_write
= write_chunk
;
1723 wbc
.pages_skipped
= 0;
1726 * We use I_SYNC to pin the inode in memory. While it is set
1727 * evict_inode() will wait so the inode cannot be freed.
1729 __writeback_single_inode(inode
, &wbc
);
1731 wbc_detach_inode(&wbc
);
1732 work
->nr_pages
-= write_chunk
- wbc
.nr_to_write
;
1733 wrote
+= write_chunk
- wbc
.nr_to_write
;
1735 if (need_resched()) {
1737 * We're trying to balance between building up a nice
1738 * long list of IOs to improve our merge rate, and
1739 * getting those IOs out quickly for anyone throttling
1740 * in balance_dirty_pages(). cond_resched() doesn't
1741 * unplug, so get our IOs out the door before we
1744 blk_flush_plug(current
);
1749 * Requeue @inode if still dirty. Be careful as @inode may
1750 * have been switched to another wb in the meantime.
1752 tmp_wb
= inode_to_wb_and_lock_list(inode
);
1753 spin_lock(&inode
->i_lock
);
1754 if (!(inode
->i_state
& I_DIRTY_ALL
))
1756 requeue_inode(inode
, tmp_wb
, &wbc
);
1757 inode_sync_complete(inode
);
1758 spin_unlock(&inode
->i_lock
);
1760 if (unlikely(tmp_wb
!= wb
)) {
1761 spin_unlock(&tmp_wb
->list_lock
);
1762 spin_lock(&wb
->list_lock
);
1766 * bail out to wb_writeback() often enough to check
1767 * background threshold and other termination conditions.
1770 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
1772 if (work
->nr_pages
<= 0)
1779 static long __writeback_inodes_wb(struct bdi_writeback
*wb
,
1780 struct wb_writeback_work
*work
)
1782 unsigned long start_time
= jiffies
;
1785 while (!list_empty(&wb
->b_io
)) {
1786 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
1787 struct super_block
*sb
= inode
->i_sb
;
1789 if (!trylock_super(sb
)) {
1791 * trylock_super() may fail consistently due to
1792 * s_umount being grabbed by someone else. Don't use
1793 * requeue_io() to avoid busy retrying the inode/sb.
1795 redirty_tail(inode
, wb
);
1798 wrote
+= writeback_sb_inodes(sb
, wb
, work
);
1799 up_read(&sb
->s_umount
);
1801 /* refer to the same tests at the end of writeback_sb_inodes */
1803 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
1805 if (work
->nr_pages
<= 0)
1809 /* Leave any unwritten inodes on b_io */
1813 static long writeback_inodes_wb(struct bdi_writeback
*wb
, long nr_pages
,
1814 enum wb_reason reason
)
1816 struct wb_writeback_work work
= {
1817 .nr_pages
= nr_pages
,
1818 .sync_mode
= WB_SYNC_NONE
,
1822 struct blk_plug plug
;
1824 blk_start_plug(&plug
);
1825 spin_lock(&wb
->list_lock
);
1826 if (list_empty(&wb
->b_io
))
1827 queue_io(wb
, &work
, jiffies
);
1828 __writeback_inodes_wb(wb
, &work
);
1829 spin_unlock(&wb
->list_lock
);
1830 blk_finish_plug(&plug
);
1832 return nr_pages
- work
.nr_pages
;
1836 * Explicit flushing or periodic writeback of "old" data.
1838 * Define "old": the first time one of an inode's pages is dirtied, we mark the
1839 * dirtying-time in the inode's address_space. So this periodic writeback code
1840 * just walks the superblock inode list, writing back any inodes which are
1841 * older than a specific point in time.
1843 * Try to run once per dirty_writeback_interval. But if a writeback event
1844 * takes longer than a dirty_writeback_interval interval, then leave a
1847 * dirtied_before takes precedence over nr_to_write. So we'll only write back
1848 * all dirty pages if they are all attached to "old" mappings.
1850 static long wb_writeback(struct bdi_writeback
*wb
,
1851 struct wb_writeback_work
*work
)
1853 unsigned long wb_start
= jiffies
;
1854 long nr_pages
= work
->nr_pages
;
1855 unsigned long dirtied_before
= jiffies
;
1856 struct inode
*inode
;
1858 struct blk_plug plug
;
1860 blk_start_plug(&plug
);
1861 spin_lock(&wb
->list_lock
);
1864 * Stop writeback when nr_pages has been consumed
1866 if (work
->nr_pages
<= 0)
1870 * Background writeout and kupdate-style writeback may
1871 * run forever. Stop them if there is other work to do
1872 * so that e.g. sync can proceed. They'll be restarted
1873 * after the other works are all done.
1875 if ((work
->for_background
|| work
->for_kupdate
) &&
1876 !list_empty(&wb
->work_list
))
1880 * For background writeout, stop when we are below the
1881 * background dirty threshold
1883 if (work
->for_background
&& !wb_over_bg_thresh(wb
))
1887 * Kupdate and background works are special and we want to
1888 * include all inodes that need writing. Livelock avoidance is
1889 * handled by these works yielding to any other work so we are
1892 if (work
->for_kupdate
) {
1893 dirtied_before
= jiffies
-
1894 msecs_to_jiffies(dirty_expire_interval
* 10);
1895 } else if (work
->for_background
)
1896 dirtied_before
= jiffies
;
1898 trace_writeback_start(wb
, work
);
1899 if (list_empty(&wb
->b_io
))
1900 queue_io(wb
, work
, dirtied_before
);
1902 progress
= writeback_sb_inodes(work
->sb
, wb
, work
);
1904 progress
= __writeback_inodes_wb(wb
, work
);
1905 trace_writeback_written(wb
, work
);
1907 wb_update_bandwidth(wb
, wb_start
);
1910 * Did we write something? Try for more
1912 * Dirty inodes are moved to b_io for writeback in batches.
1913 * The completion of the current batch does not necessarily
1914 * mean the overall work is done. So we keep looping as long
1915 * as made some progress on cleaning pages or inodes.
1920 * No more inodes for IO, bail
1922 if (list_empty(&wb
->b_more_io
))
1925 * Nothing written. Wait for some inode to
1926 * become available for writeback. Otherwise
1927 * we'll just busyloop.
1929 trace_writeback_wait(wb
, work
);
1930 inode
= wb_inode(wb
->b_more_io
.prev
);
1931 spin_lock(&inode
->i_lock
);
1932 spin_unlock(&wb
->list_lock
);
1933 /* This function drops i_lock... */
1934 inode_sleep_on_writeback(inode
);
1935 spin_lock(&wb
->list_lock
);
1937 spin_unlock(&wb
->list_lock
);
1938 blk_finish_plug(&plug
);
1940 return nr_pages
- work
->nr_pages
;
1944 * Return the next wb_writeback_work struct that hasn't been processed yet.
1946 static struct wb_writeback_work
*get_next_work_item(struct bdi_writeback
*wb
)
1948 struct wb_writeback_work
*work
= NULL
;
1950 spin_lock_bh(&wb
->work_lock
);
1951 if (!list_empty(&wb
->work_list
)) {
1952 work
= list_entry(wb
->work_list
.next
,
1953 struct wb_writeback_work
, list
);
1954 list_del_init(&work
->list
);
1956 spin_unlock_bh(&wb
->work_lock
);
1960 static long wb_check_background_flush(struct bdi_writeback
*wb
)
1962 if (wb_over_bg_thresh(wb
)) {
1964 struct wb_writeback_work work
= {
1965 .nr_pages
= LONG_MAX
,
1966 .sync_mode
= WB_SYNC_NONE
,
1967 .for_background
= 1,
1969 .reason
= WB_REASON_BACKGROUND
,
1972 return wb_writeback(wb
, &work
);
1978 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
1980 unsigned long expired
;
1984 * When set to zero, disable periodic writeback
1986 if (!dirty_writeback_interval
)
1989 expired
= wb
->last_old_flush
+
1990 msecs_to_jiffies(dirty_writeback_interval
* 10);
1991 if (time_before(jiffies
, expired
))
1994 wb
->last_old_flush
= jiffies
;
1995 nr_pages
= get_nr_dirty_pages();
1998 struct wb_writeback_work work
= {
1999 .nr_pages
= nr_pages
,
2000 .sync_mode
= WB_SYNC_NONE
,
2003 .reason
= WB_REASON_PERIODIC
,
2006 return wb_writeback(wb
, &work
);
2012 static long wb_check_start_all(struct bdi_writeback
*wb
)
2016 if (!test_bit(WB_start_all
, &wb
->state
))
2019 nr_pages
= get_nr_dirty_pages();
2021 struct wb_writeback_work work
= {
2022 .nr_pages
= wb_split_bdi_pages(wb
, nr_pages
),
2023 .sync_mode
= WB_SYNC_NONE
,
2025 .reason
= wb
->start_all_reason
,
2028 nr_pages
= wb_writeback(wb
, &work
);
2031 clear_bit(WB_start_all
, &wb
->state
);
2037 * Retrieve work items and do the writeback they describe
2039 static long wb_do_writeback(struct bdi_writeback
*wb
)
2041 struct wb_writeback_work
*work
;
2044 set_bit(WB_writeback_running
, &wb
->state
);
2045 while ((work
= get_next_work_item(wb
)) != NULL
) {
2046 trace_writeback_exec(wb
, work
);
2047 wrote
+= wb_writeback(wb
, work
);
2048 finish_writeback_work(wb
, work
);
2052 * Check for a flush-everything request
2054 wrote
+= wb_check_start_all(wb
);
2057 * Check for periodic writeback, kupdated() style
2059 wrote
+= wb_check_old_data_flush(wb
);
2060 wrote
+= wb_check_background_flush(wb
);
2061 clear_bit(WB_writeback_running
, &wb
->state
);
2067 * Handle writeback of dirty data for the device backed by this bdi. Also
2068 * reschedules periodically and does kupdated style flushing.
2070 void wb_workfn(struct work_struct
*work
)
2072 struct bdi_writeback
*wb
= container_of(to_delayed_work(work
),
2073 struct bdi_writeback
, dwork
);
2076 set_worker_desc("flush-%s", bdi_dev_name(wb
->bdi
));
2077 current
->flags
|= PF_SWAPWRITE
;
2079 if (likely(!current_is_workqueue_rescuer() ||
2080 !test_bit(WB_registered
, &wb
->state
))) {
2082 * The normal path. Keep writing back @wb until its
2083 * work_list is empty. Note that this path is also taken
2084 * if @wb is shutting down even when we're running off the
2085 * rescuer as work_list needs to be drained.
2088 pages_written
= wb_do_writeback(wb
);
2089 trace_writeback_pages_written(pages_written
);
2090 } while (!list_empty(&wb
->work_list
));
2093 * bdi_wq can't get enough workers and we're running off
2094 * the emergency worker. Don't hog it. Hopefully, 1024 is
2095 * enough for efficient IO.
2097 pages_written
= writeback_inodes_wb(wb
, 1024,
2098 WB_REASON_FORKER_THREAD
);
2099 trace_writeback_pages_written(pages_written
);
2102 if (!list_empty(&wb
->work_list
))
2104 else if (wb_has_dirty_io(wb
) && dirty_writeback_interval
)
2105 wb_wakeup_delayed(wb
);
2107 current
->flags
&= ~PF_SWAPWRITE
;
2111 * Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero,
2112 * write back the whole world.
2114 static void __wakeup_flusher_threads_bdi(struct backing_dev_info
*bdi
,
2115 enum wb_reason reason
)
2117 struct bdi_writeback
*wb
;
2119 if (!bdi_has_dirty_io(bdi
))
2122 list_for_each_entry_rcu(wb
, &bdi
->wb_list
, bdi_node
)
2123 wb_start_writeback(wb
, reason
);
2126 void wakeup_flusher_threads_bdi(struct backing_dev_info
*bdi
,
2127 enum wb_reason reason
)
2130 __wakeup_flusher_threads_bdi(bdi
, reason
);
2135 * Wakeup the flusher threads to start writeback of all currently dirty pages
2137 void wakeup_flusher_threads(enum wb_reason reason
)
2139 struct backing_dev_info
*bdi
;
2142 * If we are expecting writeback progress we must submit plugged IO.
2144 if (blk_needs_flush_plug(current
))
2145 blk_schedule_flush_plug(current
);
2148 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
)
2149 __wakeup_flusher_threads_bdi(bdi
, reason
);
2154 * Wake up bdi's periodically to make sure dirtytime inodes gets
2155 * written back periodically. We deliberately do *not* check the
2156 * b_dirtytime list in wb_has_dirty_io(), since this would cause the
2157 * kernel to be constantly waking up once there are any dirtytime
2158 * inodes on the system. So instead we define a separate delayed work
2159 * function which gets called much more rarely. (By default, only
2160 * once every 12 hours.)
2162 * If there is any other write activity going on in the file system,
2163 * this function won't be necessary. But if the only thing that has
2164 * happened on the file system is a dirtytime inode caused by an atime
2165 * update, we need this infrastructure below to make sure that inode
2166 * eventually gets pushed out to disk.
2168 static void wakeup_dirtytime_writeback(struct work_struct
*w
);
2169 static DECLARE_DELAYED_WORK(dirtytime_work
, wakeup_dirtytime_writeback
);
2171 static void wakeup_dirtytime_writeback(struct work_struct
*w
)
2173 struct backing_dev_info
*bdi
;
2176 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
2177 struct bdi_writeback
*wb
;
2179 list_for_each_entry_rcu(wb
, &bdi
->wb_list
, bdi_node
)
2180 if (!list_empty(&wb
->b_dirty_time
))
2184 schedule_delayed_work(&dirtytime_work
, dirtytime_expire_interval
* HZ
);
2187 static int __init
start_dirtytime_writeback(void)
2189 schedule_delayed_work(&dirtytime_work
, dirtytime_expire_interval
* HZ
);
2192 __initcall(start_dirtytime_writeback
);
2194 int dirtytime_interval_handler(struct ctl_table
*table
, int write
,
2195 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2199 ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
2200 if (ret
== 0 && write
)
2201 mod_delayed_work(system_wq
, &dirtytime_work
, 0);
2206 * __mark_inode_dirty - internal function
2208 * @inode: inode to mark
2209 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
2211 * Mark an inode as dirty. Callers should use mark_inode_dirty or
2212 * mark_inode_dirty_sync.
2214 * Put the inode on the super block's dirty list.
2216 * CAREFUL! We mark it dirty unconditionally, but move it onto the
2217 * dirty list only if it is hashed or if it refers to a blockdev.
2218 * If it was not hashed, it will never be added to the dirty list
2219 * even if it is later hashed, as it will have been marked dirty already.
2221 * In short, make sure you hash any inodes _before_ you start marking
2224 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
2225 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
2226 * the kernel-internal blockdev inode represents the dirtying time of the
2227 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
2228 * page->mapping->host, so the page-dirtying time is recorded in the internal
2231 void __mark_inode_dirty(struct inode
*inode
, int flags
)
2233 struct super_block
*sb
= inode
->i_sb
;
2236 trace_writeback_mark_inode_dirty(inode
, flags
);
2239 * Don't do this for I_DIRTY_PAGES - that doesn't actually
2240 * dirty the inode itself
2242 if (flags
& (I_DIRTY_INODE
| I_DIRTY_TIME
)) {
2243 trace_writeback_dirty_inode_start(inode
, flags
);
2245 if (sb
->s_op
->dirty_inode
)
2246 sb
->s_op
->dirty_inode(inode
, flags
);
2248 trace_writeback_dirty_inode(inode
, flags
);
2250 if (flags
& I_DIRTY_INODE
)
2251 flags
&= ~I_DIRTY_TIME
;
2252 dirtytime
= flags
& I_DIRTY_TIME
;
2255 * Paired with smp_mb() in __writeback_single_inode() for the
2256 * following lockless i_state test. See there for details.
2260 if (((inode
->i_state
& flags
) == flags
) ||
2261 (dirtytime
&& (inode
->i_state
& I_DIRTY_INODE
)))
2264 spin_lock(&inode
->i_lock
);
2265 if (dirtytime
&& (inode
->i_state
& I_DIRTY_INODE
))
2266 goto out_unlock_inode
;
2267 if ((inode
->i_state
& flags
) != flags
) {
2268 const int was_dirty
= inode
->i_state
& I_DIRTY
;
2270 inode_attach_wb(inode
, NULL
);
2272 if (flags
& I_DIRTY_INODE
)
2273 inode
->i_state
&= ~I_DIRTY_TIME
;
2274 inode
->i_state
|= flags
;
2277 * If the inode is queued for writeback by flush worker, just
2278 * update its dirty state. Once the flush worker is done with
2279 * the inode it will place it on the appropriate superblock
2280 * list, based upon its state.
2282 if (inode
->i_state
& I_SYNC_QUEUED
)
2283 goto out_unlock_inode
;
2286 * Only add valid (hashed) inodes to the superblock's
2287 * dirty list. Add blockdev inodes as well.
2289 if (!S_ISBLK(inode
->i_mode
)) {
2290 if (inode_unhashed(inode
))
2291 goto out_unlock_inode
;
2293 if (inode
->i_state
& I_FREEING
)
2294 goto out_unlock_inode
;
2297 * If the inode was already on b_dirty/b_io/b_more_io, don't
2298 * reposition it (that would break b_dirty time-ordering).
2301 struct bdi_writeback
*wb
;
2302 struct list_head
*dirty_list
;
2303 bool wakeup_bdi
= false;
2305 wb
= locked_inode_to_wb_and_lock_list(inode
);
2307 WARN(bdi_cap_writeback_dirty(wb
->bdi
) &&
2308 !test_bit(WB_registered
, &wb
->state
),
2309 "bdi-%s not registered\n", wb
->bdi
->name
);
2311 inode
->dirtied_when
= jiffies
;
2313 inode
->dirtied_time_when
= jiffies
;
2315 if (inode
->i_state
& I_DIRTY
)
2316 dirty_list
= &wb
->b_dirty
;
2318 dirty_list
= &wb
->b_dirty_time
;
2320 wakeup_bdi
= inode_io_list_move_locked(inode
, wb
,
2323 spin_unlock(&wb
->list_lock
);
2324 trace_writeback_dirty_inode_enqueue(inode
);
2327 * If this is the first dirty inode for this bdi,
2328 * we have to wake-up the corresponding bdi thread
2329 * to make sure background write-back happens
2332 if (bdi_cap_writeback_dirty(wb
->bdi
) && wakeup_bdi
)
2333 wb_wakeup_delayed(wb
);
2338 spin_unlock(&inode
->i_lock
);
2340 EXPORT_SYMBOL(__mark_inode_dirty
);
2343 * The @s_sync_lock is used to serialise concurrent sync operations
2344 * to avoid lock contention problems with concurrent wait_sb_inodes() calls.
2345 * Concurrent callers will block on the s_sync_lock rather than doing contending
2346 * walks. The queueing maintains sync(2) required behaviour as all the IO that
2347 * has been issued up to the time this function is enter is guaranteed to be
2348 * completed by the time we have gained the lock and waited for all IO that is
2349 * in progress regardless of the order callers are granted the lock.
2351 static void wait_sb_inodes(struct super_block
*sb
)
2353 LIST_HEAD(sync_list
);
2356 * We need to be protected against the filesystem going from
2357 * r/o to r/w or vice versa.
2359 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
2361 mutex_lock(&sb
->s_sync_lock
);
2364 * Splice the writeback list onto a temporary list to avoid waiting on
2365 * inodes that have started writeback after this point.
2367 * Use rcu_read_lock() to keep the inodes around until we have a
2368 * reference. s_inode_wblist_lock protects sb->s_inodes_wb as well as
2369 * the local list because inodes can be dropped from either by writeback
2373 spin_lock_irq(&sb
->s_inode_wblist_lock
);
2374 list_splice_init(&sb
->s_inodes_wb
, &sync_list
);
2377 * Data integrity sync. Must wait for all pages under writeback, because
2378 * there may have been pages dirtied before our sync call, but which had
2379 * writeout started before we write it out. In which case, the inode
2380 * may not be on the dirty list, but we still have to wait for that
2383 while (!list_empty(&sync_list
)) {
2384 struct inode
*inode
= list_first_entry(&sync_list
, struct inode
,
2386 struct address_space
*mapping
= inode
->i_mapping
;
2389 * Move each inode back to the wb list before we drop the lock
2390 * to preserve consistency between i_wb_list and the mapping
2391 * writeback tag. Writeback completion is responsible to remove
2392 * the inode from either list once the writeback tag is cleared.
2394 list_move_tail(&inode
->i_wb_list
, &sb
->s_inodes_wb
);
2397 * The mapping can appear untagged while still on-list since we
2398 * do not have the mapping lock. Skip it here, wb completion
2401 if (!mapping_tagged(mapping
, PAGECACHE_TAG_WRITEBACK
))
2404 spin_unlock_irq(&sb
->s_inode_wblist_lock
);
2406 spin_lock(&inode
->i_lock
);
2407 if (inode
->i_state
& (I_FREEING
|I_WILL_FREE
|I_NEW
)) {
2408 spin_unlock(&inode
->i_lock
);
2410 spin_lock_irq(&sb
->s_inode_wblist_lock
);
2414 spin_unlock(&inode
->i_lock
);
2418 * We keep the error status of individual mapping so that
2419 * applications can catch the writeback error using fsync(2).
2420 * See filemap_fdatawait_keep_errors() for details.
2422 filemap_fdatawait_keep_errors(mapping
);
2429 spin_lock_irq(&sb
->s_inode_wblist_lock
);
2431 spin_unlock_irq(&sb
->s_inode_wblist_lock
);
2433 mutex_unlock(&sb
->s_sync_lock
);
2436 static void __writeback_inodes_sb_nr(struct super_block
*sb
, unsigned long nr
,
2437 enum wb_reason reason
, bool skip_if_busy
)
2439 struct backing_dev_info
*bdi
= sb
->s_bdi
;
2440 DEFINE_WB_COMPLETION(done
, bdi
);
2441 struct wb_writeback_work work
= {
2443 .sync_mode
= WB_SYNC_NONE
,
2444 .tagged_writepages
= 1,
2450 if (!bdi_has_dirty_io(bdi
) || bdi
== &noop_backing_dev_info
)
2452 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
2454 bdi_split_work_to_wbs(sb
->s_bdi
, &work
, skip_if_busy
);
2455 wb_wait_for_completion(&done
);
2459 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
2460 * @sb: the superblock
2461 * @nr: the number of pages to write
2462 * @reason: reason why some writeback work initiated
2464 * Start writeback on some inodes on this super_block. No guarantees are made
2465 * on how many (if any) will be written, and this function does not wait
2466 * for IO completion of submitted IO.
2468 void writeback_inodes_sb_nr(struct super_block
*sb
,
2470 enum wb_reason reason
)
2472 __writeback_inodes_sb_nr(sb
, nr
, reason
, false);
2474 EXPORT_SYMBOL(writeback_inodes_sb_nr
);
2477 * writeback_inodes_sb - writeback dirty inodes from given super_block
2478 * @sb: the superblock
2479 * @reason: reason why some writeback work was initiated
2481 * Start writeback on some inodes on this super_block. No guarantees are made
2482 * on how many (if any) will be written, and this function does not wait
2483 * for IO completion of submitted IO.
2485 void writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
)
2487 return writeback_inodes_sb_nr(sb
, get_nr_dirty_pages(), reason
);
2489 EXPORT_SYMBOL(writeback_inodes_sb
);
2492 * try_to_writeback_inodes_sb - try to start writeback if none underway
2493 * @sb: the superblock
2494 * @reason: reason why some writeback work was initiated
2496 * Invoke __writeback_inodes_sb_nr if no writeback is currently underway.
2498 void try_to_writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
)
2500 if (!down_read_trylock(&sb
->s_umount
))
2503 __writeback_inodes_sb_nr(sb
, get_nr_dirty_pages(), reason
, true);
2504 up_read(&sb
->s_umount
);
2506 EXPORT_SYMBOL(try_to_writeback_inodes_sb
);
2509 * sync_inodes_sb - sync sb inode pages
2510 * @sb: the superblock
2512 * This function writes and waits on any dirty inode belonging to this
2515 void sync_inodes_sb(struct super_block
*sb
)
2517 struct backing_dev_info
*bdi
= sb
->s_bdi
;
2518 DEFINE_WB_COMPLETION(done
, bdi
);
2519 struct wb_writeback_work work
= {
2521 .sync_mode
= WB_SYNC_ALL
,
2522 .nr_pages
= LONG_MAX
,
2525 .reason
= WB_REASON_SYNC
,
2530 * Can't skip on !bdi_has_dirty() because we should wait for !dirty
2531 * inodes under writeback and I_DIRTY_TIME inodes ignored by
2532 * bdi_has_dirty() need to be written out too.
2534 if (bdi
== &noop_backing_dev_info
)
2536 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
2538 /* protect against inode wb switch, see inode_switch_wbs_work_fn() */
2539 bdi_down_write_wb_switch_rwsem(bdi
);
2540 bdi_split_work_to_wbs(bdi
, &work
, false);
2541 wb_wait_for_completion(&done
);
2542 bdi_up_write_wb_switch_rwsem(bdi
);
2546 EXPORT_SYMBOL(sync_inodes_sb
);
2549 * write_inode_now - write an inode to disk
2550 * @inode: inode to write to disk
2551 * @sync: whether the write should be synchronous or not
2553 * This function commits an inode to disk immediately if it is dirty. This is
2554 * primarily needed by knfsd.
2556 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
2558 int write_inode_now(struct inode
*inode
, int sync
)
2560 struct writeback_control wbc
= {
2561 .nr_to_write
= LONG_MAX
,
2562 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
2564 .range_end
= LLONG_MAX
,
2567 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
2568 wbc
.nr_to_write
= 0;
2571 return writeback_single_inode(inode
, &wbc
);
2573 EXPORT_SYMBOL(write_inode_now
);
2576 * sync_inode - write an inode and its pages to disk.
2577 * @inode: the inode to sync
2578 * @wbc: controls the writeback mode
2580 * sync_inode() will write an inode and its pages to disk. It will also
2581 * correctly update the inode on its superblock's dirty inode lists and will
2582 * update inode->i_state.
2584 * The caller must have a ref on the inode.
2586 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
2588 return writeback_single_inode(inode
, wbc
);
2590 EXPORT_SYMBOL(sync_inode
);
2593 * sync_inode_metadata - write an inode to disk
2594 * @inode: the inode to sync
2595 * @wait: wait for I/O to complete.
2597 * Write an inode to disk and adjust its dirty state after completion.
2599 * Note: only writes the actual inode, no associated data or other metadata.
2601 int sync_inode_metadata(struct inode
*inode
, int wait
)
2603 struct writeback_control wbc
= {
2604 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_NONE
,
2605 .nr_to_write
= 0, /* metadata-only */
2608 return sync_inode(inode
, &wbc
);
2610 EXPORT_SYMBOL(sync_inode_metadata
);