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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/fs-writeback.c
4 *
5 * Copyright (C) 2002, Linus Torvalds.
6 *
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.
11 *
12 * 10Apr2002 Andrew Morton
13 * Split out of fs/inode.c
14 * Additions for address_space-based writeback
15 */
16
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>
22#include <linux/fs.h>
23#include <linux/mm.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>
32#include "internal.h"
33
34/*
35 * 4MB minimal write chunk size
36 */
37#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10))
38
39/*
40 * Passed into wb_writeback(), essentially a subset of writeback_control
41 */
42struct wb_writeback_work {
43 long nr_pages;
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? */
53
54 struct list_head list; /* pending work list */
55 struct wb_completion *done; /* set if the caller waits */
56};
57
58/*
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.
67 */
68unsigned int dirtytime_expire_interval = 12 * 60 * 60;
69
70static inline struct inode *wb_inode(struct list_head *head)
71{
72 return list_entry(head, struct inode, i_io_list);
73}
74
75/*
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.
79 */
80#define CREATE_TRACE_POINTS
81#include <trace/events/writeback.h>
82
83EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
84
85static bool wb_io_lists_populated(struct bdi_writeback *wb)
86{
87 if (wb_has_dirty_io(wb)) {
88 return false;
89 } else {
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);
94 return true;
95 }
96}
97
98static void wb_io_lists_depopulated(struct bdi_writeback *wb)
99{
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);
105 }
106}
107
108/**
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}
113 *
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.
117 */
118static bool inode_io_list_move_locked(struct inode *inode,
119 struct bdi_writeback *wb,
120 struct list_head *head)
121{
122 assert_spin_locked(&wb->list_lock);
123
124 list_move(&inode->i_io_list, head);
125
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);
129
130 wb_io_lists_depopulated(wb);
131 return false;
132}
133
134/**
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
138 *
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.
141 */
142static void inode_io_list_del_locked(struct inode *inode,
143 struct bdi_writeback *wb)
144{
145 assert_spin_locked(&wb->list_lock);
146 assert_spin_locked(&inode->i_lock);
147
148 inode->i_state &= ~I_SYNC_QUEUED;
149 list_del_init(&inode->i_io_list);
150 wb_io_lists_depopulated(wb);
151}
152
153static void wb_wakeup(struct bdi_writeback *wb)
154{
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);
159}
160
161static void finish_writeback_work(struct bdi_writeback *wb,
162 struct wb_writeback_work *work)
163{
164 struct wb_completion *done = work->done;
165
166 if (work->auto_free)
167 kfree(work);
168 if (done) {
169 wait_queue_head_t *waitq = done->waitq;
170
171 /* @done can't be accessed after the following dec */
172 if (atomic_dec_and_test(&done->cnt))
173 wake_up_all(waitq);
174 }
175}
176
177static void wb_queue_work(struct bdi_writeback *wb,
178 struct wb_writeback_work *work)
179{
180 trace_writeback_queue(wb, work);
181
182 if (work->done)
183 atomic_inc(&work->done->cnt);
184
185 spin_lock_bh(&wb->work_lock);
186
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);
190 } else
191 finish_writeback_work(wb, work);
192
193 spin_unlock_bh(&wb->work_lock);
194}
195
196/**
197 * wb_wait_for_completion - wait for completion of bdi_writeback_works
198 * @done: target wb_completion
199 *
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.
205 */
206void wb_wait_for_completion(struct wb_completion *done)
207{
208 atomic_dec(&done->cnt); /* put down the initial count */
209 wait_event(*done->waitq, !atomic_read(&done->cnt));
210}
211
212#ifdef CONFIG_CGROUP_WRITEBACK
213
214/*
215 * Parameters for foreign inode detection, see wbc_detach_inode() to see
216 * how they're used.
217 *
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.
221 *
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.
227 *
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.
232 */
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 */
237
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 */
246
247static atomic_t isw_nr_in_flight = ATOMIC_INIT(0);
248static struct workqueue_struct *isw_wq;
249
250void __inode_attach_wb(struct inode *inode, struct page *page)
251{
252 struct backing_dev_info *bdi = inode_to_bdi(inode);
253 struct bdi_writeback *wb = NULL;
254
255 if (inode_cgwb_enabled(inode)) {
256 struct cgroup_subsys_state *memcg_css;
257
258 if (page) {
259 memcg_css = mem_cgroup_css_from_page(page);
260 wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
261 } else {
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);
265 css_put(memcg_css);
266 }
267 }
268
269 if (!wb)
270 wb = &bdi->wb;
271
272 /*
273 * There may be multiple instances of this function racing to
274 * update the same inode. Use cmpxchg() to tell the winner.
275 */
276 if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
277 wb_put(wb);
278}
279EXPORT_SYMBOL_GPL(__inode_attach_wb);
280
281/**
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
284 *
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.
288 */
289static struct bdi_writeback *
290locked_inode_to_wb_and_lock_list(struct inode *inode)
291 __releases(&inode->i_lock)
292 __acquires(&wb->list_lock)
293{
294 while (true) {
295 struct bdi_writeback *wb = inode_to_wb(inode);
296
297 /*
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.
302 */
303 wb_get(wb);
304 spin_unlock(&inode->i_lock);
305 spin_lock(&wb->list_lock);
306
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 */
310 return wb;
311 }
312
313 spin_unlock(&wb->list_lock);
314 wb_put(wb);
315 cpu_relax();
316 spin_lock(&inode->i_lock);
317 }
318}
319
320/**
321 * inode_to_wb_and_lock_list - determine an inode's wb and lock it
322 * @inode: inode of interest
323 *
324 * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
325 * on entry.
326 */
327static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
328 __acquires(&wb->list_lock)
329{
330 spin_lock(&inode->i_lock);
331 return locked_inode_to_wb_and_lock_list(inode);
332}
333
334struct inode_switch_wbs_context {
335 struct inode *inode;
336 struct bdi_writeback *new_wb;
337
338 struct rcu_head rcu_head;
339 struct work_struct work;
340};
341
342static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi)
343{
344 down_write(&bdi->wb_switch_rwsem);
345}
346
347static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi)
348{
349 up_write(&bdi->wb_switch_rwsem);
350}
351
352static void inode_switch_wbs_work_fn(struct work_struct *work)
353{
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);
362 struct page *page;
363 bool switched = false;
364
365 /*
366 * If @inode switches cgwb membership while sync_inodes_sb() is
367 * being issued, sync_inodes_sb() might miss it. Synchronize.
368 */
369 down_read(&bdi->wb_switch_rwsem);
370
371 /*
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.
376 *
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.
380 */
381 if (old_wb < new_wb) {
382 spin_lock(&old_wb->list_lock);
383 spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING);
384 } else {
385 spin_lock(&new_wb->list_lock);
386 spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING);
387 }
388 spin_lock(&inode->i_lock);
389 xa_lock_irq(&mapping->i_pages);
390
391 /*
392 * Once I_FREEING is visible under i_lock, the eviction path owns
393 * the inode and we shouldn't modify ->i_io_list.
394 */
395 if (unlikely(inode->i_state & I_FREEING))
396 goto skip_switch;
397
398 trace_inode_switch_wbs(inode, old_wb, new_wb);
399
400 /*
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.
404 */
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);
409 }
410 }
411
412 xas_set(&xas, 0);
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);
417 }
418
419 wb_get(new_wb);
420
421 /*
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.
426 */
427 if (!list_empty(&inode->i_io_list)) {
428 struct inode *pos;
429
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,
434 pos->dirtied_when))
435 break;
436 inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev);
437 } else {
438 inode->i_wb = new_wb;
439 }
440
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;
445 switched = true;
446skip_switch:
447 /*
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.
450 */
451 smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH);
452
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);
457
458 up_read(&bdi->wb_switch_rwsem);
459
460 if (switched) {
461 wb_wakeup(new_wb);
462 wb_put(old_wb);
463 }
464 wb_put(new_wb);
465
466 iput(inode);
467 kfree(isw);
468
469 atomic_dec(&isw_nr_in_flight);
470}
471
472static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head)
473{
474 struct inode_switch_wbs_context *isw = container_of(rcu_head,
475 struct inode_switch_wbs_context, rcu_head);
476
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);
480}
481
482/**
483 * inode_switch_wbs - change the wb association of an inode
484 * @inode: target inode
485 * @new_wb_id: ID of the new wb
486 *
487 * Switch @inode's wb association to the wb identified by @new_wb_id. The
488 * switching is performed asynchronously and may fail silently.
489 */
490static void inode_switch_wbs(struct inode *inode, int new_wb_id)
491{
492 struct backing_dev_info *bdi = inode_to_bdi(inode);
493 struct cgroup_subsys_state *memcg_css;
494 struct inode_switch_wbs_context *isw;
495
496 /* noop if seems to be already in progress */
497 if (inode->i_state & I_WB_SWITCH)
498 return;
499
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)
502 return;
503
504 isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
505 if (!isw)
506 return;
507
508 /* find and pin the new wb */
509 rcu_read_lock();
510 memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys);
511 if (memcg_css)
512 isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
513 rcu_read_unlock();
514 if (!isw->new_wb)
515 goto out_free;
516
517 /* while holding I_WB_SWITCH, no one else can update the association */
518 spin_lock(&inode->i_lock);
519 if (!(inode->i_sb->s_flags & SB_ACTIVE) ||
520 inode->i_state & (I_WB_SWITCH | I_FREEING) ||
521 inode_to_wb(inode) == isw->new_wb) {
522 spin_unlock(&inode->i_lock);
523 goto out_free;
524 }
525 inode->i_state |= I_WB_SWITCH;
526 __iget(inode);
527 spin_unlock(&inode->i_lock);
528
529 isw->inode = inode;
530
531 /*
532 * In addition to synchronizing among switchers, I_WB_SWITCH tells
533 * the RCU protected stat update paths to grab the i_page
534 * lock so that stat transfer can synchronize against them.
535 * Let's continue after I_WB_SWITCH is guaranteed to be visible.
536 */
537 call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
538
539 atomic_inc(&isw_nr_in_flight);
540 return;
541
542out_free:
543 if (isw->new_wb)
544 wb_put(isw->new_wb);
545 kfree(isw);
546}
547
548/**
549 * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it
550 * @wbc: writeback_control of interest
551 * @inode: target inode
552 *
553 * @inode is locked and about to be written back under the control of @wbc.
554 * Record @inode's writeback context into @wbc and unlock the i_lock. On
555 * writeback completion, wbc_detach_inode() should be called. This is used
556 * to track the cgroup writeback context.
557 */
558void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
559 struct inode *inode)
560{
561 if (!inode_cgwb_enabled(inode)) {
562 spin_unlock(&inode->i_lock);
563 return;
564 }
565
566 wbc->wb = inode_to_wb(inode);
567 wbc->inode = inode;
568
569 wbc->wb_id = wbc->wb->memcg_css->id;
570 wbc->wb_lcand_id = inode->i_wb_frn_winner;
571 wbc->wb_tcand_id = 0;
572 wbc->wb_bytes = 0;
573 wbc->wb_lcand_bytes = 0;
574 wbc->wb_tcand_bytes = 0;
575
576 wb_get(wbc->wb);
577 spin_unlock(&inode->i_lock);
578
579 /*
580 * A dying wb indicates that either the blkcg associated with the
581 * memcg changed or the associated memcg is dying. In the first
582 * case, a replacement wb should already be available and we should
583 * refresh the wb immediately. In the second case, trying to
584 * refresh will keep failing.
585 */
586 if (unlikely(wb_dying(wbc->wb) && !css_is_dying(wbc->wb->memcg_css)))
587 inode_switch_wbs(inode, wbc->wb_id);
588}
589EXPORT_SYMBOL_GPL(wbc_attach_and_unlock_inode);
590
591/**
592 * wbc_detach_inode - disassociate wbc from inode and perform foreign detection
593 * @wbc: writeback_control of the just finished writeback
594 *
595 * To be called after a writeback attempt of an inode finishes and undoes
596 * wbc_attach_and_unlock_inode(). Can be called under any context.
597 *
598 * As concurrent write sharing of an inode is expected to be very rare and
599 * memcg only tracks page ownership on first-use basis severely confining
600 * the usefulness of such sharing, cgroup writeback tracks ownership
601 * per-inode. While the support for concurrent write sharing of an inode
602 * is deemed unnecessary, an inode being written to by different cgroups at
603 * different points in time is a lot more common, and, more importantly,
604 * charging only by first-use can too readily lead to grossly incorrect
605 * behaviors (single foreign page can lead to gigabytes of writeback to be
606 * incorrectly attributed).
607 *
608 * To resolve this issue, cgroup writeback detects the majority dirtier of
609 * an inode and transfers the ownership to it. To avoid unnnecessary
610 * oscillation, the detection mechanism keeps track of history and gives
611 * out the switch verdict only if the foreign usage pattern is stable over
612 * a certain amount of time and/or writeback attempts.
613 *
614 * On each writeback attempt, @wbc tries to detect the majority writer
615 * using Boyer-Moore majority vote algorithm. In addition to the byte
616 * count from the majority voting, it also counts the bytes written for the
617 * current wb and the last round's winner wb (max of last round's current
618 * wb, the winner from two rounds ago, and the last round's majority
619 * candidate). Keeping track of the historical winner helps the algorithm
620 * to semi-reliably detect the most active writer even when it's not the
621 * absolute majority.
622 *
623 * Once the winner of the round is determined, whether the winner is
624 * foreign or not and how much IO time the round consumed is recorded in
625 * inode->i_wb_frn_history. If the amount of recorded foreign IO time is
626 * over a certain threshold, the switch verdict is given.
627 */
628void wbc_detach_inode(struct writeback_control *wbc)
629{
630 struct bdi_writeback *wb = wbc->wb;
631 struct inode *inode = wbc->inode;
632 unsigned long avg_time, max_bytes, max_time;
633 u16 history;
634 int max_id;
635
636 if (!wb)
637 return;
638
639 history = inode->i_wb_frn_history;
640 avg_time = inode->i_wb_frn_avg_time;
641
642 /* pick the winner of this round */
643 if (wbc->wb_bytes >= wbc->wb_lcand_bytes &&
644 wbc->wb_bytes >= wbc->wb_tcand_bytes) {
645 max_id = wbc->wb_id;
646 max_bytes = wbc->wb_bytes;
647 } else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) {
648 max_id = wbc->wb_lcand_id;
649 max_bytes = wbc->wb_lcand_bytes;
650 } else {
651 max_id = wbc->wb_tcand_id;
652 max_bytes = wbc->wb_tcand_bytes;
653 }
654
655 /*
656 * Calculate the amount of IO time the winner consumed and fold it
657 * into the running average kept per inode. If the consumed IO
658 * time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
659 * deciding whether to switch or not. This is to prevent one-off
660 * small dirtiers from skewing the verdict.
661 */
662 max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT,
663 wb->avg_write_bandwidth);
664 if (avg_time)
665 avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) -
666 (avg_time >> WB_FRN_TIME_AVG_SHIFT);
667 else
668 avg_time = max_time; /* immediate catch up on first run */
669
670 if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) {
671 int slots;
672
673 /*
674 * The switch verdict is reached if foreign wb's consume
675 * more than a certain proportion of IO time in a
676 * WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
677 * history mask where each bit represents one sixteenth of
678 * the period. Determine the number of slots to shift into
679 * history from @max_time.
680 */
681 slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT),
682 (unsigned long)WB_FRN_HIST_MAX_SLOTS);
683 history <<= slots;
684 if (wbc->wb_id != max_id)
685 history |= (1U << slots) - 1;
686
687 if (history)
688 trace_inode_foreign_history(inode, wbc, history);
689
690 /*
691 * Switch if the current wb isn't the consistent winner.
692 * If there are multiple closely competing dirtiers, the
693 * inode may switch across them repeatedly over time, which
694 * is okay. The main goal is avoiding keeping an inode on
695 * the wrong wb for an extended period of time.
696 */
697 if (hweight32(history) > WB_FRN_HIST_THR_SLOTS)
698 inode_switch_wbs(inode, max_id);
699 }
700
701 /*
702 * Multiple instances of this function may race to update the
703 * following fields but we don't mind occassional inaccuracies.
704 */
705 inode->i_wb_frn_winner = max_id;
706 inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX);
707 inode->i_wb_frn_history = history;
708
709 wb_put(wbc->wb);
710 wbc->wb = NULL;
711}
712EXPORT_SYMBOL_GPL(wbc_detach_inode);
713
714/**
715 * wbc_account_cgroup_owner - account writeback to update inode cgroup ownership
716 * @wbc: writeback_control of the writeback in progress
717 * @page: page being written out
718 * @bytes: number of bytes being written out
719 *
720 * @bytes from @page are about to written out during the writeback
721 * controlled by @wbc. Keep the book for foreign inode detection. See
722 * wbc_detach_inode().
723 */
724void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
725 size_t bytes)
726{
727 struct cgroup_subsys_state *css;
728 int id;
729
730 /*
731 * pageout() path doesn't attach @wbc to the inode being written
732 * out. This is intentional as we don't want the function to block
733 * behind a slow cgroup. Ultimately, we want pageout() to kick off
734 * regular writeback instead of writing things out itself.
735 */
736 if (!wbc->wb || wbc->no_cgroup_owner)
737 return;
738
739 css = mem_cgroup_css_from_page(page);
740 /* dead cgroups shouldn't contribute to inode ownership arbitration */
741 if (!(css->flags & CSS_ONLINE))
742 return;
743
744 id = css->id;
745
746 if (id == wbc->wb_id) {
747 wbc->wb_bytes += bytes;
748 return;
749 }
750
751 if (id == wbc->wb_lcand_id)
752 wbc->wb_lcand_bytes += bytes;
753
754 /* Boyer-Moore majority vote algorithm */
755 if (!wbc->wb_tcand_bytes)
756 wbc->wb_tcand_id = id;
757 if (id == wbc->wb_tcand_id)
758 wbc->wb_tcand_bytes += bytes;
759 else
760 wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes);
761}
762EXPORT_SYMBOL_GPL(wbc_account_cgroup_owner);
763
764/**
765 * inode_congested - test whether an inode is congested
766 * @inode: inode to test for congestion (may be NULL)
767 * @cong_bits: mask of WB_[a]sync_congested bits to test
768 *
769 * Tests whether @inode is congested. @cong_bits is the mask of congestion
770 * bits to test and the return value is the mask of set bits.
771 *
772 * If cgroup writeback is enabled for @inode, the congestion state is
773 * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
774 * associated with @inode is congested; otherwise, the root wb's congestion
775 * state is used.
776 *
777 * @inode is allowed to be NULL as this function is often called on
778 * mapping->host which is NULL for the swapper space.
779 */
780int inode_congested(struct inode *inode, int cong_bits)
781{
782 /*
783 * Once set, ->i_wb never becomes NULL while the inode is alive.
784 * Start transaction iff ->i_wb is visible.
785 */
786 if (inode && inode_to_wb_is_valid(inode)) {
787 struct bdi_writeback *wb;
788 struct wb_lock_cookie lock_cookie = {};
789 bool congested;
790
791 wb = unlocked_inode_to_wb_begin(inode, &lock_cookie);
792 congested = wb_congested(wb, cong_bits);
793 unlocked_inode_to_wb_end(inode, &lock_cookie);
794 return congested;
795 }
796
797 return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
798}
799EXPORT_SYMBOL_GPL(inode_congested);
800
801/**
802 * wb_split_bdi_pages - split nr_pages to write according to bandwidth
803 * @wb: target bdi_writeback to split @nr_pages to
804 * @nr_pages: number of pages to write for the whole bdi
805 *
806 * Split @wb's portion of @nr_pages according to @wb's write bandwidth in
807 * relation to the total write bandwidth of all wb's w/ dirty inodes on
808 * @wb->bdi.
809 */
810static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
811{
812 unsigned long this_bw = wb->avg_write_bandwidth;
813 unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);
814
815 if (nr_pages == LONG_MAX)
816 return LONG_MAX;
817
818 /*
819 * This may be called on clean wb's and proportional distribution
820 * may not make sense, just use the original @nr_pages in those
821 * cases. In general, we wanna err on the side of writing more.
822 */
823 if (!tot_bw || this_bw >= tot_bw)
824 return nr_pages;
825 else
826 return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
827}
828
829/**
830 * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
831 * @bdi: target backing_dev_info
832 * @base_work: wb_writeback_work to issue
833 * @skip_if_busy: skip wb's which already have writeback in progress
834 *
835 * Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
836 * have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
837 * distributed to the busy wbs according to each wb's proportion in the
838 * total active write bandwidth of @bdi.
839 */
840static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
841 struct wb_writeback_work *base_work,
842 bool skip_if_busy)
843{
844 struct bdi_writeback *last_wb = NULL;
845 struct bdi_writeback *wb = list_entry(&bdi->wb_list,
846 struct bdi_writeback, bdi_node);
847
848 might_sleep();
849restart:
850 rcu_read_lock();
851 list_for_each_entry_continue_rcu(wb, &bdi->wb_list, bdi_node) {
852 DEFINE_WB_COMPLETION(fallback_work_done, bdi);
853 struct wb_writeback_work fallback_work;
854 struct wb_writeback_work *work;
855 long nr_pages;
856
857 if (last_wb) {
858 wb_put(last_wb);
859 last_wb = NULL;
860 }
861
862 /* SYNC_ALL writes out I_DIRTY_TIME too */
863 if (!wb_has_dirty_io(wb) &&
864 (base_work->sync_mode == WB_SYNC_NONE ||
865 list_empty(&wb->b_dirty_time)))
866 continue;
867 if (skip_if_busy && writeback_in_progress(wb))
868 continue;
869
870 nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages);
871
872 work = kmalloc(sizeof(*work), GFP_ATOMIC);
873 if (work) {
874 *work = *base_work;
875 work->nr_pages = nr_pages;
876 work->auto_free = 1;
877 wb_queue_work(wb, work);
878 continue;
879 }
880
881 /* alloc failed, execute synchronously using on-stack fallback */
882 work = &fallback_work;
883 *work = *base_work;
884 work->nr_pages = nr_pages;
885 work->auto_free = 0;
886 work->done = &fallback_work_done;
887
888 wb_queue_work(wb, work);
889
890 /*
891 * Pin @wb so that it stays on @bdi->wb_list. This allows
892 * continuing iteration from @wb after dropping and
893 * regrabbing rcu read lock.
894 */
895 wb_get(wb);
896 last_wb = wb;
897
898 rcu_read_unlock();
899 wb_wait_for_completion(&fallback_work_done);
900 goto restart;
901 }
902 rcu_read_unlock();
903
904 if (last_wb)
905 wb_put(last_wb);
906}
907
908/**
909 * cgroup_writeback_by_id - initiate cgroup writeback from bdi and memcg IDs
910 * @bdi_id: target bdi id
911 * @memcg_id: target memcg css id
912 * @nr: number of pages to write, 0 for best-effort dirty flushing
913 * @reason: reason why some writeback work initiated
914 * @done: target wb_completion
915 *
916 * Initiate flush of the bdi_writeback identified by @bdi_id and @memcg_id
917 * with the specified parameters.
918 */
919int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr,
920 enum wb_reason reason, struct wb_completion *done)
921{
922 struct backing_dev_info *bdi;
923 struct cgroup_subsys_state *memcg_css;
924 struct bdi_writeback *wb;
925 struct wb_writeback_work *work;
926 int ret;
927
928 /* lookup bdi and memcg */
929 bdi = bdi_get_by_id(bdi_id);
930 if (!bdi)
931 return -ENOENT;
932
933 rcu_read_lock();
934 memcg_css = css_from_id(memcg_id, &memory_cgrp_subsys);
935 if (memcg_css && !css_tryget(memcg_css))
936 memcg_css = NULL;
937 rcu_read_unlock();
938 if (!memcg_css) {
939 ret = -ENOENT;
940 goto out_bdi_put;
941 }
942
943 /*
944 * And find the associated wb. If the wb isn't there already
945 * there's nothing to flush, don't create one.
946 */
947 wb = wb_get_lookup(bdi, memcg_css);
948 if (!wb) {
949 ret = -ENOENT;
950 goto out_css_put;
951 }
952
953 /*
954 * If @nr is zero, the caller is attempting to write out most of
955 * the currently dirty pages. Let's take the current dirty page
956 * count and inflate it by 25% which should be large enough to
957 * flush out most dirty pages while avoiding getting livelocked by
958 * concurrent dirtiers.
959 */
960 if (!nr) {
961 unsigned long filepages, headroom, dirty, writeback;
962
963 mem_cgroup_wb_stats(wb, &filepages, &headroom, &dirty,
964 &writeback);
965 nr = dirty * 10 / 8;
966 }
967
968 /* issue the writeback work */
969 work = kzalloc(sizeof(*work), GFP_NOWAIT | __GFP_NOWARN);
970 if (work) {
971 work->nr_pages = nr;
972 work->sync_mode = WB_SYNC_NONE;
973 work->range_cyclic = 1;
974 work->reason = reason;
975 work->done = done;
976 work->auto_free = 1;
977 wb_queue_work(wb, work);
978 ret = 0;
979 } else {
980 ret = -ENOMEM;
981 }
982
983 wb_put(wb);
984out_css_put:
985 css_put(memcg_css);
986out_bdi_put:
987 bdi_put(bdi);
988 return ret;
989}
990
991/**
992 * cgroup_writeback_umount - flush inode wb switches for umount
993 *
994 * This function is called when a super_block is about to be destroyed and
995 * flushes in-flight inode wb switches. An inode wb switch goes through
996 * RCU and then workqueue, so the two need to be flushed in order to ensure
997 * that all previously scheduled switches are finished. As wb switches are
998 * rare occurrences and synchronize_rcu() can take a while, perform
999 * flushing iff wb switches are in flight.
1000 */
1001void cgroup_writeback_umount(void)
1002{
1003 if (atomic_read(&isw_nr_in_flight)) {
1004 /*
1005 * Use rcu_barrier() to wait for all pending callbacks to
1006 * ensure that all in-flight wb switches are in the workqueue.
1007 */
1008 rcu_barrier();
1009 flush_workqueue(isw_wq);
1010 }
1011}
1012
1013static int __init cgroup_writeback_init(void)
1014{
1015 isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0);
1016 if (!isw_wq)
1017 return -ENOMEM;
1018 return 0;
1019}
1020fs_initcall(cgroup_writeback_init);
1021
1022#else /* CONFIG_CGROUP_WRITEBACK */
1023
1024static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
1025static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
1026
1027static struct bdi_writeback *
1028locked_inode_to_wb_and_lock_list(struct inode *inode)
1029 __releases(&inode->i_lock)
1030 __acquires(&wb->list_lock)
1031{
1032 struct bdi_writeback *wb = inode_to_wb(inode);
1033
1034 spin_unlock(&inode->i_lock);
1035 spin_lock(&wb->list_lock);
1036 return wb;
1037}
1038
1039static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
1040 __acquires(&wb->list_lock)
1041{
1042 struct bdi_writeback *wb = inode_to_wb(inode);
1043
1044 spin_lock(&wb->list_lock);
1045 return wb;
1046}
1047
1048static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
1049{
1050 return nr_pages;
1051}
1052
1053static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
1054 struct wb_writeback_work *base_work,
1055 bool skip_if_busy)
1056{
1057 might_sleep();
1058
1059 if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
1060 base_work->auto_free = 0;
1061 wb_queue_work(&bdi->wb, base_work);
1062 }
1063}
1064
1065#endif /* CONFIG_CGROUP_WRITEBACK */
1066
1067/*
1068 * Add in the number of potentially dirty inodes, because each inode
1069 * write can dirty pagecache in the underlying blockdev.
1070 */
1071static unsigned long get_nr_dirty_pages(void)
1072{
1073 return global_node_page_state(NR_FILE_DIRTY) +
1074 get_nr_dirty_inodes();
1075}
1076
1077static void wb_start_writeback(struct bdi_writeback *wb, enum wb_reason reason)
1078{
1079 if (!wb_has_dirty_io(wb))
1080 return;
1081
1082 /*
1083 * All callers of this function want to start writeback of all
1084 * dirty pages. Places like vmscan can call this at a very
1085 * high frequency, causing pointless allocations of tons of
1086 * work items and keeping the flusher threads busy retrieving
1087 * that work. Ensure that we only allow one of them pending and
1088 * inflight at the time.
1089 */
1090 if (test_bit(WB_start_all, &wb->state) ||
1091 test_and_set_bit(WB_start_all, &wb->state))
1092 return;
1093
1094 wb->start_all_reason = reason;
1095 wb_wakeup(wb);
1096}
1097
1098/**
1099 * wb_start_background_writeback - start background writeback
1100 * @wb: bdi_writback to write from
1101 *
1102 * Description:
1103 * This makes sure WB_SYNC_NONE background writeback happens. When
1104 * this function returns, it is only guaranteed that for given wb
1105 * some IO is happening if we are over background dirty threshold.
1106 * Caller need not hold sb s_umount semaphore.
1107 */
1108void wb_start_background_writeback(struct bdi_writeback *wb)
1109{
1110 /*
1111 * We just wake up the flusher thread. It will perform background
1112 * writeback as soon as there is no other work to do.
1113 */
1114 trace_writeback_wake_background(wb);
1115 wb_wakeup(wb);
1116}
1117
1118/*
1119 * Remove the inode from the writeback list it is on.
1120 */
1121void inode_io_list_del(struct inode *inode)
1122{
1123 struct bdi_writeback *wb;
1124
1125 wb = inode_to_wb_and_lock_list(inode);
1126 spin_lock(&inode->i_lock);
1127 inode_io_list_del_locked(inode, wb);
1128 spin_unlock(&inode->i_lock);
1129 spin_unlock(&wb->list_lock);
1130}
1131EXPORT_SYMBOL(inode_io_list_del);
1132
1133/*
1134 * mark an inode as under writeback on the sb
1135 */
1136void sb_mark_inode_writeback(struct inode *inode)
1137{
1138 struct super_block *sb = inode->i_sb;
1139 unsigned long flags;
1140
1141 if (list_empty(&inode->i_wb_list)) {
1142 spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
1143 if (list_empty(&inode->i_wb_list)) {
1144 list_add_tail(&inode->i_wb_list, &sb->s_inodes_wb);
1145 trace_sb_mark_inode_writeback(inode);
1146 }
1147 spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
1148 }
1149}
1150
1151/*
1152 * clear an inode as under writeback on the sb
1153 */
1154void sb_clear_inode_writeback(struct inode *inode)
1155{
1156 struct super_block *sb = inode->i_sb;
1157 unsigned long flags;
1158
1159 if (!list_empty(&inode->i_wb_list)) {
1160 spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
1161 if (!list_empty(&inode->i_wb_list)) {
1162 list_del_init(&inode->i_wb_list);
1163 trace_sb_clear_inode_writeback(inode);
1164 }
1165 spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
1166 }
1167}
1168
1169/*
1170 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
1171 * furthest end of its superblock's dirty-inode list.
1172 *
1173 * Before stamping the inode's ->dirtied_when, we check to see whether it is
1174 * already the most-recently-dirtied inode on the b_dirty list. If that is
1175 * the case then the inode must have been redirtied while it was being written
1176 * out and we don't reset its dirtied_when.
1177 */
1178static void redirty_tail_locked(struct inode *inode, struct bdi_writeback *wb)
1179{
1180 assert_spin_locked(&inode->i_lock);
1181
1182 if (!list_empty(&wb->b_dirty)) {
1183 struct inode *tail;
1184
1185 tail = wb_inode(wb->b_dirty.next);
1186 if (time_before(inode->dirtied_when, tail->dirtied_when))
1187 inode->dirtied_when = jiffies;
1188 }
1189 inode_io_list_move_locked(inode, wb, &wb->b_dirty);
1190 inode->i_state &= ~I_SYNC_QUEUED;
1191}
1192
1193static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
1194{
1195 spin_lock(&inode->i_lock);
1196 redirty_tail_locked(inode, wb);
1197 spin_unlock(&inode->i_lock);
1198}
1199
1200/*
1201 * requeue inode for re-scanning after bdi->b_io list is exhausted.
1202 */
1203static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
1204{
1205 inode_io_list_move_locked(inode, wb, &wb->b_more_io);
1206}
1207
1208static void inode_sync_complete(struct inode *inode)
1209{
1210 inode->i_state &= ~I_SYNC;
1211 /* If inode is clean an unused, put it into LRU now... */
1212 inode_add_lru(inode);
1213 /* Waiters must see I_SYNC cleared before being woken up */
1214 smp_mb();
1215 wake_up_bit(&inode->i_state, __I_SYNC);
1216}
1217
1218static bool inode_dirtied_after(struct inode *inode, unsigned long t)
1219{
1220 bool ret = time_after(inode->dirtied_when, t);
1221#ifndef CONFIG_64BIT
1222 /*
1223 * For inodes being constantly redirtied, dirtied_when can get stuck.
1224 * It _appears_ to be in the future, but is actually in distant past.
1225 * This test is necessary to prevent such wrapped-around relative times
1226 * from permanently stopping the whole bdi writeback.
1227 */
1228 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
1229#endif
1230 return ret;
1231}
1232
1233#define EXPIRE_DIRTY_ATIME 0x0001
1234
1235/*
1236 * Move expired (dirtied before dirtied_before) dirty inodes from
1237 * @delaying_queue to @dispatch_queue.
1238 */
1239static int move_expired_inodes(struct list_head *delaying_queue,
1240 struct list_head *dispatch_queue,
1241 unsigned long dirtied_before)
1242{
1243 LIST_HEAD(tmp);
1244 struct list_head *pos, *node;
1245 struct super_block *sb = NULL;
1246 struct inode *inode;
1247 int do_sb_sort = 0;
1248 int moved = 0;
1249
1250 while (!list_empty(delaying_queue)) {
1251 inode = wb_inode(delaying_queue->prev);
1252 if (inode_dirtied_after(inode, dirtied_before))
1253 break;
1254 list_move(&inode->i_io_list, &tmp);
1255 moved++;
1256 spin_lock(&inode->i_lock);
1257 inode->i_state |= I_SYNC_QUEUED;
1258 spin_unlock(&inode->i_lock);
1259 if (sb_is_blkdev_sb(inode->i_sb))
1260 continue;
1261 if (sb && sb != inode->i_sb)
1262 do_sb_sort = 1;
1263 sb = inode->i_sb;
1264 }
1265
1266 /* just one sb in list, splice to dispatch_queue and we're done */
1267 if (!do_sb_sort) {
1268 list_splice(&tmp, dispatch_queue);
1269 goto out;
1270 }
1271
1272 /* Move inodes from one superblock together */
1273 while (!list_empty(&tmp)) {
1274 sb = wb_inode(tmp.prev)->i_sb;
1275 list_for_each_prev_safe(pos, node, &tmp) {
1276 inode = wb_inode(pos);
1277 if (inode->i_sb == sb)
1278 list_move(&inode->i_io_list, dispatch_queue);
1279 }
1280 }
1281out:
1282 return moved;
1283}
1284
1285/*
1286 * Queue all expired dirty inodes for io, eldest first.
1287 * Before
1288 * newly dirtied b_dirty b_io b_more_io
1289 * =============> gf edc BA
1290 * After
1291 * newly dirtied b_dirty b_io b_more_io
1292 * =============> g fBAedc
1293 * |
1294 * +--> dequeue for IO
1295 */
1296static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work,
1297 unsigned long dirtied_before)
1298{
1299 int moved;
1300 unsigned long time_expire_jif = dirtied_before;
1301
1302 assert_spin_locked(&wb->list_lock);
1303 list_splice_init(&wb->b_more_io, &wb->b_io);
1304 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, dirtied_before);
1305 if (!work->for_sync)
1306 time_expire_jif = jiffies - dirtytime_expire_interval * HZ;
1307 moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
1308 time_expire_jif);
1309 if (moved)
1310 wb_io_lists_populated(wb);
1311 trace_writeback_queue_io(wb, work, dirtied_before, moved);
1312}
1313
1314static int write_inode(struct inode *inode, struct writeback_control *wbc)
1315{
1316 int ret;
1317
1318 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
1319 trace_writeback_write_inode_start(inode, wbc);
1320 ret = inode->i_sb->s_op->write_inode(inode, wbc);
1321 trace_writeback_write_inode(inode, wbc);
1322 return ret;
1323 }
1324 return 0;
1325}
1326
1327/*
1328 * Wait for writeback on an inode to complete. Called with i_lock held.
1329 * Caller must make sure inode cannot go away when we drop i_lock.
1330 */
1331static void __inode_wait_for_writeback(struct inode *inode)
1332 __releases(inode->i_lock)
1333 __acquires(inode->i_lock)
1334{
1335 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
1336 wait_queue_head_t *wqh;
1337
1338 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1339 while (inode->i_state & I_SYNC) {
1340 spin_unlock(&inode->i_lock);
1341 __wait_on_bit(wqh, &wq, bit_wait,
1342 TASK_UNINTERRUPTIBLE);
1343 spin_lock(&inode->i_lock);
1344 }
1345}
1346
1347/*
1348 * Wait for writeback on an inode to complete. Caller must have inode pinned.
1349 */
1350void inode_wait_for_writeback(struct inode *inode)
1351{
1352 spin_lock(&inode->i_lock);
1353 __inode_wait_for_writeback(inode);
1354 spin_unlock(&inode->i_lock);
1355}
1356
1357/*
1358 * Sleep until I_SYNC is cleared. This function must be called with i_lock
1359 * held and drops it. It is aimed for callers not holding any inode reference
1360 * so once i_lock is dropped, inode can go away.
1361 */
1362static void inode_sleep_on_writeback(struct inode *inode)
1363 __releases(inode->i_lock)
1364{
1365 DEFINE_WAIT(wait);
1366 wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1367 int sleep;
1368
1369 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1370 sleep = inode->i_state & I_SYNC;
1371 spin_unlock(&inode->i_lock);
1372 if (sleep)
1373 schedule();
1374 finish_wait(wqh, &wait);
1375}
1376
1377/*
1378 * Find proper writeback list for the inode depending on its current state and
1379 * possibly also change of its state while we were doing writeback. Here we
1380 * handle things such as livelock prevention or fairness of writeback among
1381 * inodes. This function can be called only by flusher thread - noone else
1382 * processes all inodes in writeback lists and requeueing inodes behind flusher
1383 * thread's back can have unexpected consequences.
1384 */
1385static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
1386 struct writeback_control *wbc)
1387{
1388 if (inode->i_state & I_FREEING)
1389 return;
1390
1391 /*
1392 * Sync livelock prevention. Each inode is tagged and synced in one
1393 * shot. If still dirty, it will be redirty_tail()'ed below. Update
1394 * the dirty time to prevent enqueue and sync it again.
1395 */
1396 if ((inode->i_state & I_DIRTY) &&
1397 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
1398 inode->dirtied_when = jiffies;
1399
1400 if (wbc->pages_skipped) {
1401 /*
1402 * writeback is not making progress due to locked
1403 * buffers. Skip this inode for now.
1404 */
1405 redirty_tail_locked(inode, wb);
1406 return;
1407 }
1408
1409 if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
1410 /*
1411 * We didn't write back all the pages. nfs_writepages()
1412 * sometimes bales out without doing anything.
1413 */
1414 if (wbc->nr_to_write <= 0) {
1415 /* Slice used up. Queue for next turn. */
1416 requeue_io(inode, wb);
1417 } else {
1418 /*
1419 * Writeback blocked by something other than
1420 * congestion. Delay the inode for some time to
1421 * avoid spinning on the CPU (100% iowait)
1422 * retrying writeback of the dirty page/inode
1423 * that cannot be performed immediately.
1424 */
1425 redirty_tail_locked(inode, wb);
1426 }
1427 } else if (inode->i_state & I_DIRTY) {
1428 /*
1429 * Filesystems can dirty the inode during writeback operations,
1430 * such as delayed allocation during submission or metadata
1431 * updates after data IO completion.
1432 */
1433 redirty_tail_locked(inode, wb);
1434 } else if (inode->i_state & I_DIRTY_TIME) {
1435 inode->dirtied_when = jiffies;
1436 inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
1437 inode->i_state &= ~I_SYNC_QUEUED;
1438 } else {
1439 /* The inode is clean. Remove from writeback lists. */
1440 inode_io_list_del_locked(inode, wb);
1441 }
1442}
1443
1444/*
1445 * Write out an inode and its dirty pages. Do not update the writeback list
1446 * linkage. That is left to the caller. The caller is also responsible for
1447 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
1448 */
1449static int
1450__writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
1451{
1452 struct address_space *mapping = inode->i_mapping;
1453 long nr_to_write = wbc->nr_to_write;
1454 unsigned dirty;
1455 int ret;
1456
1457 WARN_ON(!(inode->i_state & I_SYNC));
1458
1459 trace_writeback_single_inode_start(inode, wbc, nr_to_write);
1460
1461 ret = do_writepages(mapping, wbc);
1462
1463 /*
1464 * Make sure to wait on the data before writing out the metadata.
1465 * This is important for filesystems that modify metadata on data
1466 * I/O completion. We don't do it for sync(2) writeback because it has a
1467 * separate, external IO completion path and ->sync_fs for guaranteeing
1468 * inode metadata is written back correctly.
1469 */
1470 if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
1471 int err = filemap_fdatawait(mapping);
1472 if (ret == 0)
1473 ret = err;
1474 }
1475
1476 /*
1477 * Some filesystems may redirty the inode during the writeback
1478 * due to delalloc, clear dirty metadata flags right before
1479 * write_inode()
1480 */
1481 spin_lock(&inode->i_lock);
1482
1483 dirty = inode->i_state & I_DIRTY;
1484 if ((inode->i_state & I_DIRTY_TIME) &&
1485 ((dirty & I_DIRTY_INODE) ||
1486 wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
1487 time_after(jiffies, inode->dirtied_time_when +
1488 dirtytime_expire_interval * HZ))) {
1489 dirty |= I_DIRTY_TIME;
1490 trace_writeback_lazytime(inode);
1491 }
1492 inode->i_state &= ~dirty;
1493
1494 /*
1495 * Paired with smp_mb() in __mark_inode_dirty(). This allows
1496 * __mark_inode_dirty() to test i_state without grabbing i_lock -
1497 * either they see the I_DIRTY bits cleared or we see the dirtied
1498 * inode.
1499 *
1500 * I_DIRTY_PAGES is always cleared together above even if @mapping
1501 * still has dirty pages. The flag is reinstated after smp_mb() if
1502 * necessary. This guarantees that either __mark_inode_dirty()
1503 * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
1504 */
1505 smp_mb();
1506
1507 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
1508 inode->i_state |= I_DIRTY_PAGES;
1509
1510 spin_unlock(&inode->i_lock);
1511
1512 if (dirty & I_DIRTY_TIME)
1513 mark_inode_dirty_sync(inode);
1514 /* Don't write the inode if only I_DIRTY_PAGES was set */
1515 if (dirty & ~I_DIRTY_PAGES) {
1516 int err = write_inode(inode, wbc);
1517 if (ret == 0)
1518 ret = err;
1519 }
1520 trace_writeback_single_inode(inode, wbc, nr_to_write);
1521 return ret;
1522}
1523
1524/*
1525 * Write out an inode's dirty pages. Either the caller has an active reference
1526 * on the inode or the inode has I_WILL_FREE set.
1527 *
1528 * This function is designed to be called for writing back one inode which
1529 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
1530 * and does more profound writeback list handling in writeback_sb_inodes().
1531 */
1532static int writeback_single_inode(struct inode *inode,
1533 struct writeback_control *wbc)
1534{
1535 struct bdi_writeback *wb;
1536 int ret = 0;
1537
1538 spin_lock(&inode->i_lock);
1539 if (!atomic_read(&inode->i_count))
1540 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
1541 else
1542 WARN_ON(inode->i_state & I_WILL_FREE);
1543
1544 if (inode->i_state & I_SYNC) {
1545 if (wbc->sync_mode != WB_SYNC_ALL)
1546 goto out;
1547 /*
1548 * It's a data-integrity sync. We must wait. Since callers hold
1549 * inode reference or inode has I_WILL_FREE set, it cannot go
1550 * away under us.
1551 */
1552 __inode_wait_for_writeback(inode);
1553 }
1554 WARN_ON(inode->i_state & I_SYNC);
1555 /*
1556 * Skip inode if it is clean and we have no outstanding writeback in
1557 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
1558 * function since flusher thread may be doing for example sync in
1559 * parallel and if we move the inode, it could get skipped. So here we
1560 * make sure inode is on some writeback list and leave it there unless
1561 * we have completely cleaned the inode.
1562 */
1563 if (!(inode->i_state & I_DIRTY_ALL) &&
1564 (wbc->sync_mode != WB_SYNC_ALL ||
1565 !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
1566 goto out;
1567 inode->i_state |= I_SYNC;
1568 wbc_attach_and_unlock_inode(wbc, inode);
1569
1570 ret = __writeback_single_inode(inode, wbc);
1571
1572 wbc_detach_inode(wbc);
1573
1574 wb = inode_to_wb_and_lock_list(inode);
1575 spin_lock(&inode->i_lock);
1576 /*
1577 * If inode is clean, remove it from writeback lists. Otherwise don't
1578 * touch it. See comment above for explanation.
1579 */
1580 if (!(inode->i_state & I_DIRTY_ALL))
1581 inode_io_list_del_locked(inode, wb);
1582 spin_unlock(&wb->list_lock);
1583 inode_sync_complete(inode);
1584out:
1585 spin_unlock(&inode->i_lock);
1586 return ret;
1587}
1588
1589static long writeback_chunk_size(struct bdi_writeback *wb,
1590 struct wb_writeback_work *work)
1591{
1592 long pages;
1593
1594 /*
1595 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
1596 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
1597 * here avoids calling into writeback_inodes_wb() more than once.
1598 *
1599 * The intended call sequence for WB_SYNC_ALL writeback is:
1600 *
1601 * wb_writeback()
1602 * writeback_sb_inodes() <== called only once
1603 * write_cache_pages() <== called once for each inode
1604 * (quickly) tag currently dirty pages
1605 * (maybe slowly) sync all tagged pages
1606 */
1607 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
1608 pages = LONG_MAX;
1609 else {
1610 pages = min(wb->avg_write_bandwidth / 2,
1611 global_wb_domain.dirty_limit / DIRTY_SCOPE);
1612 pages = min(pages, work->nr_pages);
1613 pages = round_down(pages + MIN_WRITEBACK_PAGES,
1614 MIN_WRITEBACK_PAGES);
1615 }
1616
1617 return pages;
1618}
1619
1620/*
1621 * Write a portion of b_io inodes which belong to @sb.
1622 *
1623 * Return the number of pages and/or inodes written.
1624 *
1625 * NOTE! This is called with wb->list_lock held, and will
1626 * unlock and relock that for each inode it ends up doing
1627 * IO for.
1628 */
1629static long writeback_sb_inodes(struct super_block *sb,
1630 struct bdi_writeback *wb,
1631 struct wb_writeback_work *work)
1632{
1633 struct writeback_control wbc = {
1634 .sync_mode = work->sync_mode,
1635 .tagged_writepages = work->tagged_writepages,
1636 .for_kupdate = work->for_kupdate,
1637 .for_background = work->for_background,
1638 .for_sync = work->for_sync,
1639 .range_cyclic = work->range_cyclic,
1640 .range_start = 0,
1641 .range_end = LLONG_MAX,
1642 };
1643 unsigned long start_time = jiffies;
1644 long write_chunk;
1645 long wrote = 0; /* count both pages and inodes */
1646
1647 while (!list_empty(&wb->b_io)) {
1648 struct inode *inode = wb_inode(wb->b_io.prev);
1649 struct bdi_writeback *tmp_wb;
1650
1651 if (inode->i_sb != sb) {
1652 if (work->sb) {
1653 /*
1654 * We only want to write back data for this
1655 * superblock, move all inodes not belonging
1656 * to it back onto the dirty list.
1657 */
1658 redirty_tail(inode, wb);
1659 continue;
1660 }
1661
1662 /*
1663 * The inode belongs to a different superblock.
1664 * Bounce back to the caller to unpin this and
1665 * pin the next superblock.
1666 */
1667 break;
1668 }
1669
1670 /*
1671 * Don't bother with new inodes or inodes being freed, first
1672 * kind does not need periodic writeout yet, and for the latter
1673 * kind writeout is handled by the freer.
1674 */
1675 spin_lock(&inode->i_lock);
1676 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
1677 redirty_tail_locked(inode, wb);
1678 spin_unlock(&inode->i_lock);
1679 continue;
1680 }
1681 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
1682 /*
1683 * If this inode is locked for writeback and we are not
1684 * doing writeback-for-data-integrity, move it to
1685 * b_more_io so that writeback can proceed with the
1686 * other inodes on s_io.
1687 *
1688 * We'll have another go at writing back this inode
1689 * when we completed a full scan of b_io.
1690 */
1691 spin_unlock(&inode->i_lock);
1692 requeue_io(inode, wb);
1693 trace_writeback_sb_inodes_requeue(inode);
1694 continue;
1695 }
1696 spin_unlock(&wb->list_lock);
1697
1698 /*
1699 * We already requeued the inode if it had I_SYNC set and we
1700 * are doing WB_SYNC_NONE writeback. So this catches only the
1701 * WB_SYNC_ALL case.
1702 */
1703 if (inode->i_state & I_SYNC) {
1704 /* Wait for I_SYNC. This function drops i_lock... */
1705 inode_sleep_on_writeback(inode);
1706 /* Inode may be gone, start again */
1707 spin_lock(&wb->list_lock);
1708 continue;
1709 }
1710 inode->i_state |= I_SYNC;
1711 wbc_attach_and_unlock_inode(&wbc, inode);
1712
1713 write_chunk = writeback_chunk_size(wb, work);
1714 wbc.nr_to_write = write_chunk;
1715 wbc.pages_skipped = 0;
1716
1717 /*
1718 * We use I_SYNC to pin the inode in memory. While it is set
1719 * evict_inode() will wait so the inode cannot be freed.
1720 */
1721 __writeback_single_inode(inode, &wbc);
1722
1723 wbc_detach_inode(&wbc);
1724 work->nr_pages -= write_chunk - wbc.nr_to_write;
1725 wrote += write_chunk - wbc.nr_to_write;
1726
1727 if (need_resched()) {
1728 /*
1729 * We're trying to balance between building up a nice
1730 * long list of IOs to improve our merge rate, and
1731 * getting those IOs out quickly for anyone throttling
1732 * in balance_dirty_pages(). cond_resched() doesn't
1733 * unplug, so get our IOs out the door before we
1734 * give up the CPU.
1735 */
1736 blk_flush_plug(current);
1737 cond_resched();
1738 }
1739
1740 /*
1741 * Requeue @inode if still dirty. Be careful as @inode may
1742 * have been switched to another wb in the meantime.
1743 */
1744 tmp_wb = inode_to_wb_and_lock_list(inode);
1745 spin_lock(&inode->i_lock);
1746 if (!(inode->i_state & I_DIRTY_ALL))
1747 wrote++;
1748 requeue_inode(inode, tmp_wb, &wbc);
1749 inode_sync_complete(inode);
1750 spin_unlock(&inode->i_lock);
1751
1752 if (unlikely(tmp_wb != wb)) {
1753 spin_unlock(&tmp_wb->list_lock);
1754 spin_lock(&wb->list_lock);
1755 }
1756
1757 /*
1758 * bail out to wb_writeback() often enough to check
1759 * background threshold and other termination conditions.
1760 */
1761 if (wrote) {
1762 if (time_is_before_jiffies(start_time + HZ / 10UL))
1763 break;
1764 if (work->nr_pages <= 0)
1765 break;
1766 }
1767 }
1768 return wrote;
1769}
1770
1771static long __writeback_inodes_wb(struct bdi_writeback *wb,
1772 struct wb_writeback_work *work)
1773{
1774 unsigned long start_time = jiffies;
1775 long wrote = 0;
1776
1777 while (!list_empty(&wb->b_io)) {
1778 struct inode *inode = wb_inode(wb->b_io.prev);
1779 struct super_block *sb = inode->i_sb;
1780
1781 if (!trylock_super(sb)) {
1782 /*
1783 * trylock_super() may fail consistently due to
1784 * s_umount being grabbed by someone else. Don't use
1785 * requeue_io() to avoid busy retrying the inode/sb.
1786 */
1787 redirty_tail(inode, wb);
1788 continue;
1789 }
1790 wrote += writeback_sb_inodes(sb, wb, work);
1791 up_read(&sb->s_umount);
1792
1793 /* refer to the same tests at the end of writeback_sb_inodes */
1794 if (wrote) {
1795 if (time_is_before_jiffies(start_time + HZ / 10UL))
1796 break;
1797 if (work->nr_pages <= 0)
1798 break;
1799 }
1800 }
1801 /* Leave any unwritten inodes on b_io */
1802 return wrote;
1803}
1804
1805static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
1806 enum wb_reason reason)
1807{
1808 struct wb_writeback_work work = {
1809 .nr_pages = nr_pages,
1810 .sync_mode = WB_SYNC_NONE,
1811 .range_cyclic = 1,
1812 .reason = reason,
1813 };
1814 struct blk_plug plug;
1815
1816 blk_start_plug(&plug);
1817 spin_lock(&wb->list_lock);
1818 if (list_empty(&wb->b_io))
1819 queue_io(wb, &work, jiffies);
1820 __writeback_inodes_wb(wb, &work);
1821 spin_unlock(&wb->list_lock);
1822 blk_finish_plug(&plug);
1823
1824 return nr_pages - work.nr_pages;
1825}
1826
1827/*
1828 * Explicit flushing or periodic writeback of "old" data.
1829 *
1830 * Define "old": the first time one of an inode's pages is dirtied, we mark the
1831 * dirtying-time in the inode's address_space. So this periodic writeback code
1832 * just walks the superblock inode list, writing back any inodes which are
1833 * older than a specific point in time.
1834 *
1835 * Try to run once per dirty_writeback_interval. But if a writeback event
1836 * takes longer than a dirty_writeback_interval interval, then leave a
1837 * one-second gap.
1838 *
1839 * dirtied_before takes precedence over nr_to_write. So we'll only write back
1840 * all dirty pages if they are all attached to "old" mappings.
1841 */
1842static long wb_writeback(struct bdi_writeback *wb,
1843 struct wb_writeback_work *work)
1844{
1845 unsigned long wb_start = jiffies;
1846 long nr_pages = work->nr_pages;
1847 unsigned long dirtied_before = jiffies;
1848 struct inode *inode;
1849 long progress;
1850 struct blk_plug plug;
1851
1852 blk_start_plug(&plug);
1853 spin_lock(&wb->list_lock);
1854 for (;;) {
1855 /*
1856 * Stop writeback when nr_pages has been consumed
1857 */
1858 if (work->nr_pages <= 0)
1859 break;
1860
1861 /*
1862 * Background writeout and kupdate-style writeback may
1863 * run forever. Stop them if there is other work to do
1864 * so that e.g. sync can proceed. They'll be restarted
1865 * after the other works are all done.
1866 */
1867 if ((work->for_background || work->for_kupdate) &&
1868 !list_empty(&wb->work_list))
1869 break;
1870
1871 /*
1872 * For background writeout, stop when we are below the
1873 * background dirty threshold
1874 */
1875 if (work->for_background && !wb_over_bg_thresh(wb))
1876 break;
1877
1878 /*
1879 * Kupdate and background works are special and we want to
1880 * include all inodes that need writing. Livelock avoidance is
1881 * handled by these works yielding to any other work so we are
1882 * safe.
1883 */
1884 if (work->for_kupdate) {
1885 dirtied_before = jiffies -
1886 msecs_to_jiffies(dirty_expire_interval * 10);
1887 } else if (work->for_background)
1888 dirtied_before = jiffies;
1889
1890 trace_writeback_start(wb, work);
1891 if (list_empty(&wb->b_io))
1892 queue_io(wb, work, dirtied_before);
1893 if (work->sb)
1894 progress = writeback_sb_inodes(work->sb, wb, work);
1895 else
1896 progress = __writeback_inodes_wb(wb, work);
1897 trace_writeback_written(wb, work);
1898
1899 wb_update_bandwidth(wb, wb_start);
1900
1901 /*
1902 * Did we write something? Try for more
1903 *
1904 * Dirty inodes are moved to b_io for writeback in batches.
1905 * The completion of the current batch does not necessarily
1906 * mean the overall work is done. So we keep looping as long
1907 * as made some progress on cleaning pages or inodes.
1908 */
1909 if (progress)
1910 continue;
1911 /*
1912 * No more inodes for IO, bail
1913 */
1914 if (list_empty(&wb->b_more_io))
1915 break;
1916 /*
1917 * Nothing written. Wait for some inode to
1918 * become available for writeback. Otherwise
1919 * we'll just busyloop.
1920 */
1921 trace_writeback_wait(wb, work);
1922 inode = wb_inode(wb->b_more_io.prev);
1923 spin_lock(&inode->i_lock);
1924 spin_unlock(&wb->list_lock);
1925 /* This function drops i_lock... */
1926 inode_sleep_on_writeback(inode);
1927 spin_lock(&wb->list_lock);
1928 }
1929 spin_unlock(&wb->list_lock);
1930 blk_finish_plug(&plug);
1931
1932 return nr_pages - work->nr_pages;
1933}
1934
1935/*
1936 * Return the next wb_writeback_work struct that hasn't been processed yet.
1937 */
1938static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
1939{
1940 struct wb_writeback_work *work = NULL;
1941
1942 spin_lock_bh(&wb->work_lock);
1943 if (!list_empty(&wb->work_list)) {
1944 work = list_entry(wb->work_list.next,
1945 struct wb_writeback_work, list);
1946 list_del_init(&work->list);
1947 }
1948 spin_unlock_bh(&wb->work_lock);
1949 return work;
1950}
1951
1952static long wb_check_background_flush(struct bdi_writeback *wb)
1953{
1954 if (wb_over_bg_thresh(wb)) {
1955
1956 struct wb_writeback_work work = {
1957 .nr_pages = LONG_MAX,
1958 .sync_mode = WB_SYNC_NONE,
1959 .for_background = 1,
1960 .range_cyclic = 1,
1961 .reason = WB_REASON_BACKGROUND,
1962 };
1963
1964 return wb_writeback(wb, &work);
1965 }
1966
1967 return 0;
1968}
1969
1970static long wb_check_old_data_flush(struct bdi_writeback *wb)
1971{
1972 unsigned long expired;
1973 long nr_pages;
1974
1975 /*
1976 * When set to zero, disable periodic writeback
1977 */
1978 if (!dirty_writeback_interval)
1979 return 0;
1980
1981 expired = wb->last_old_flush +
1982 msecs_to_jiffies(dirty_writeback_interval * 10);
1983 if (time_before(jiffies, expired))
1984 return 0;
1985
1986 wb->last_old_flush = jiffies;
1987 nr_pages = get_nr_dirty_pages();
1988
1989 if (nr_pages) {
1990 struct wb_writeback_work work = {
1991 .nr_pages = nr_pages,
1992 .sync_mode = WB_SYNC_NONE,
1993 .for_kupdate = 1,
1994 .range_cyclic = 1,
1995 .reason = WB_REASON_PERIODIC,
1996 };
1997
1998 return wb_writeback(wb, &work);
1999 }
2000
2001 return 0;
2002}
2003
2004static long wb_check_start_all(struct bdi_writeback *wb)
2005{
2006 long nr_pages;
2007
2008 if (!test_bit(WB_start_all, &wb->state))
2009 return 0;
2010
2011 nr_pages = get_nr_dirty_pages();
2012 if (nr_pages) {
2013 struct wb_writeback_work work = {
2014 .nr_pages = wb_split_bdi_pages(wb, nr_pages),
2015 .sync_mode = WB_SYNC_NONE,
2016 .range_cyclic = 1,
2017 .reason = wb->start_all_reason,
2018 };
2019
2020 nr_pages = wb_writeback(wb, &work);
2021 }
2022
2023 clear_bit(WB_start_all, &wb->state);
2024 return nr_pages;
2025}
2026
2027
2028/*
2029 * Retrieve work items and do the writeback they describe
2030 */
2031static long wb_do_writeback(struct bdi_writeback *wb)
2032{
2033 struct wb_writeback_work *work;
2034 long wrote = 0;
2035
2036 set_bit(WB_writeback_running, &wb->state);
2037 while ((work = get_next_work_item(wb)) != NULL) {
2038 trace_writeback_exec(wb, work);
2039 wrote += wb_writeback(wb, work);
2040 finish_writeback_work(wb, work);
2041 }
2042
2043 /*
2044 * Check for a flush-everything request
2045 */
2046 wrote += wb_check_start_all(wb);
2047
2048 /*
2049 * Check for periodic writeback, kupdated() style
2050 */
2051 wrote += wb_check_old_data_flush(wb);
2052 wrote += wb_check_background_flush(wb);
2053 clear_bit(WB_writeback_running, &wb->state);
2054
2055 return wrote;
2056}
2057
2058/*
2059 * Handle writeback of dirty data for the device backed by this bdi. Also
2060 * reschedules periodically and does kupdated style flushing.
2061 */
2062void wb_workfn(struct work_struct *work)
2063{
2064 struct bdi_writeback *wb = container_of(to_delayed_work(work),
2065 struct bdi_writeback, dwork);
2066 long pages_written;
2067
2068 set_worker_desc("flush-%s", bdi_dev_name(wb->bdi));
2069 current->flags |= PF_SWAPWRITE;
2070
2071 if (likely(!current_is_workqueue_rescuer() ||
2072 !test_bit(WB_registered, &wb->state))) {
2073 /*
2074 * The normal path. Keep writing back @wb until its
2075 * work_list is empty. Note that this path is also taken
2076 * if @wb is shutting down even when we're running off the
2077 * rescuer as work_list needs to be drained.
2078 */
2079 do {
2080 pages_written = wb_do_writeback(wb);
2081 trace_writeback_pages_written(pages_written);
2082 } while (!list_empty(&wb->work_list));
2083 } else {
2084 /*
2085 * bdi_wq can't get enough workers and we're running off
2086 * the emergency worker. Don't hog it. Hopefully, 1024 is
2087 * enough for efficient IO.
2088 */
2089 pages_written = writeback_inodes_wb(wb, 1024,
2090 WB_REASON_FORKER_THREAD);
2091 trace_writeback_pages_written(pages_written);
2092 }
2093
2094 if (!list_empty(&wb->work_list))
2095 wb_wakeup(wb);
2096 else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
2097 wb_wakeup_delayed(wb);
2098
2099 current->flags &= ~PF_SWAPWRITE;
2100}
2101
2102/*
2103 * Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero,
2104 * write back the whole world.
2105 */
2106static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
2107 enum wb_reason reason)
2108{
2109 struct bdi_writeback *wb;
2110
2111 if (!bdi_has_dirty_io(bdi))
2112 return;
2113
2114 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
2115 wb_start_writeback(wb, reason);
2116}
2117
2118void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
2119 enum wb_reason reason)
2120{
2121 rcu_read_lock();
2122 __wakeup_flusher_threads_bdi(bdi, reason);
2123 rcu_read_unlock();
2124}
2125
2126/*
2127 * Wakeup the flusher threads to start writeback of all currently dirty pages
2128 */
2129void wakeup_flusher_threads(enum wb_reason reason)
2130{
2131 struct backing_dev_info *bdi;
2132
2133 /*
2134 * If we are expecting writeback progress we must submit plugged IO.
2135 */
2136 if (blk_needs_flush_plug(current))
2137 blk_schedule_flush_plug(current);
2138
2139 rcu_read_lock();
2140 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
2141 __wakeup_flusher_threads_bdi(bdi, reason);
2142 rcu_read_unlock();
2143}
2144
2145/*
2146 * Wake up bdi's periodically to make sure dirtytime inodes gets
2147 * written back periodically. We deliberately do *not* check the
2148 * b_dirtytime list in wb_has_dirty_io(), since this would cause the
2149 * kernel to be constantly waking up once there are any dirtytime
2150 * inodes on the system. So instead we define a separate delayed work
2151 * function which gets called much more rarely. (By default, only
2152 * once every 12 hours.)
2153 *
2154 * If there is any other write activity going on in the file system,
2155 * this function won't be necessary. But if the only thing that has
2156 * happened on the file system is a dirtytime inode caused by an atime
2157 * update, we need this infrastructure below to make sure that inode
2158 * eventually gets pushed out to disk.
2159 */
2160static void wakeup_dirtytime_writeback(struct work_struct *w);
2161static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback);
2162
2163static void wakeup_dirtytime_writeback(struct work_struct *w)
2164{
2165 struct backing_dev_info *bdi;
2166
2167 rcu_read_lock();
2168 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
2169 struct bdi_writeback *wb;
2170
2171 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
2172 if (!list_empty(&wb->b_dirty_time))
2173 wb_wakeup(wb);
2174 }
2175 rcu_read_unlock();
2176 schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
2177}
2178
2179static int __init start_dirtytime_writeback(void)
2180{
2181 schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
2182 return 0;
2183}
2184__initcall(start_dirtytime_writeback);
2185
2186int dirtytime_interval_handler(struct ctl_table *table, int write,
2187 void *buffer, size_t *lenp, loff_t *ppos)
2188{
2189 int ret;
2190
2191 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
2192 if (ret == 0 && write)
2193 mod_delayed_work(system_wq, &dirtytime_work, 0);
2194 return ret;
2195}
2196
2197static noinline void block_dump___mark_inode_dirty(struct inode *inode)
2198{
2199 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
2200 struct dentry *dentry;
2201 const char *name = "?";
2202
2203 dentry = d_find_alias(inode);
2204 if (dentry) {
2205 spin_lock(&dentry->d_lock);
2206 name = (const char *) dentry->d_name.name;
2207 }
2208 printk(KERN_DEBUG
2209 "%s(%d): dirtied inode %lu (%s) on %s\n",
2210 current->comm, task_pid_nr(current), inode->i_ino,
2211 name, inode->i_sb->s_id);
2212 if (dentry) {
2213 spin_unlock(&dentry->d_lock);
2214 dput(dentry);
2215 }
2216 }
2217}
2218
2219/**
2220 * __mark_inode_dirty - internal function
2221 *
2222 * @inode: inode to mark
2223 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
2224 *
2225 * Mark an inode as dirty. Callers should use mark_inode_dirty or
2226 * mark_inode_dirty_sync.
2227 *
2228 * Put the inode on the super block's dirty list.
2229 *
2230 * CAREFUL! We mark it dirty unconditionally, but move it onto the
2231 * dirty list only if it is hashed or if it refers to a blockdev.
2232 * If it was not hashed, it will never be added to the dirty list
2233 * even if it is later hashed, as it will have been marked dirty already.
2234 *
2235 * In short, make sure you hash any inodes _before_ you start marking
2236 * them dirty.
2237 *
2238 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
2239 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
2240 * the kernel-internal blockdev inode represents the dirtying time of the
2241 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
2242 * page->mapping->host, so the page-dirtying time is recorded in the internal
2243 * blockdev inode.
2244 */
2245void __mark_inode_dirty(struct inode *inode, int flags)
2246{
2247 struct super_block *sb = inode->i_sb;
2248 int dirtytime;
2249
2250 trace_writeback_mark_inode_dirty(inode, flags);
2251
2252 /*
2253 * Don't do this for I_DIRTY_PAGES - that doesn't actually
2254 * dirty the inode itself
2255 */
2256 if (flags & (I_DIRTY_INODE | I_DIRTY_TIME)) {
2257 trace_writeback_dirty_inode_start(inode, flags);
2258
2259 if (sb->s_op->dirty_inode)
2260 sb->s_op->dirty_inode(inode, flags);
2261
2262 trace_writeback_dirty_inode(inode, flags);
2263 }
2264 if (flags & I_DIRTY_INODE)
2265 flags &= ~I_DIRTY_TIME;
2266 dirtytime = flags & I_DIRTY_TIME;
2267
2268 /*
2269 * Paired with smp_mb() in __writeback_single_inode() for the
2270 * following lockless i_state test. See there for details.
2271 */
2272 smp_mb();
2273
2274 if (((inode->i_state & flags) == flags) ||
2275 (dirtytime && (inode->i_state & I_DIRTY_INODE)))
2276 return;
2277
2278 if (unlikely(block_dump))
2279 block_dump___mark_inode_dirty(inode);
2280
2281 spin_lock(&inode->i_lock);
2282 if (dirtytime && (inode->i_state & I_DIRTY_INODE))
2283 goto out_unlock_inode;
2284 if ((inode->i_state & flags) != flags) {
2285 const int was_dirty = inode->i_state & I_DIRTY;
2286
2287 inode_attach_wb(inode, NULL);
2288
2289 if (flags & I_DIRTY_INODE)
2290 inode->i_state &= ~I_DIRTY_TIME;
2291 inode->i_state |= flags;
2292
2293 /*
2294 * If the inode is queued for writeback by flush worker, just
2295 * update its dirty state. Once the flush worker is done with
2296 * the inode it will place it on the appropriate superblock
2297 * list, based upon its state.
2298 */
2299 if (inode->i_state & I_SYNC_QUEUED)
2300 goto out_unlock_inode;
2301
2302 /*
2303 * Only add valid (hashed) inodes to the superblock's
2304 * dirty list. Add blockdev inodes as well.
2305 */
2306 if (!S_ISBLK(inode->i_mode)) {
2307 if (inode_unhashed(inode))
2308 goto out_unlock_inode;
2309 }
2310 if (inode->i_state & I_FREEING)
2311 goto out_unlock_inode;
2312
2313 /*
2314 * If the inode was already on b_dirty/b_io/b_more_io, don't
2315 * reposition it (that would break b_dirty time-ordering).
2316 */
2317 if (!was_dirty) {
2318 struct bdi_writeback *wb;
2319 struct list_head *dirty_list;
2320 bool wakeup_bdi = false;
2321
2322 wb = locked_inode_to_wb_and_lock_list(inode);
2323
2324 WARN(bdi_cap_writeback_dirty(wb->bdi) &&
2325 !test_bit(WB_registered, &wb->state),
2326 "bdi-%s not registered\n", bdi_dev_name(wb->bdi));
2327
2328 inode->dirtied_when = jiffies;
2329 if (dirtytime)
2330 inode->dirtied_time_when = jiffies;
2331
2332 if (inode->i_state & I_DIRTY)
2333 dirty_list = &wb->b_dirty;
2334 else
2335 dirty_list = &wb->b_dirty_time;
2336
2337 wakeup_bdi = inode_io_list_move_locked(inode, wb,
2338 dirty_list);
2339
2340 spin_unlock(&wb->list_lock);
2341 trace_writeback_dirty_inode_enqueue(inode);
2342
2343 /*
2344 * If this is the first dirty inode for this bdi,
2345 * we have to wake-up the corresponding bdi thread
2346 * to make sure background write-back happens
2347 * later.
2348 */
2349 if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
2350 wb_wakeup_delayed(wb);
2351 return;
2352 }
2353 }
2354out_unlock_inode:
2355 spin_unlock(&inode->i_lock);
2356}
2357EXPORT_SYMBOL(__mark_inode_dirty);
2358
2359/*
2360 * The @s_sync_lock is used to serialise concurrent sync operations
2361 * to avoid lock contention problems with concurrent wait_sb_inodes() calls.
2362 * Concurrent callers will block on the s_sync_lock rather than doing contending
2363 * walks. The queueing maintains sync(2) required behaviour as all the IO that
2364 * has been issued up to the time this function is enter is guaranteed to be
2365 * completed by the time we have gained the lock and waited for all IO that is
2366 * in progress regardless of the order callers are granted the lock.
2367 */
2368static void wait_sb_inodes(struct super_block *sb)
2369{
2370 LIST_HEAD(sync_list);
2371
2372 /*
2373 * We need to be protected against the filesystem going from
2374 * r/o to r/w or vice versa.
2375 */
2376 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2377
2378 mutex_lock(&sb->s_sync_lock);
2379
2380 /*
2381 * Splice the writeback list onto a temporary list to avoid waiting on
2382 * inodes that have started writeback after this point.
2383 *
2384 * Use rcu_read_lock() to keep the inodes around until we have a
2385 * reference. s_inode_wblist_lock protects sb->s_inodes_wb as well as
2386 * the local list because inodes can be dropped from either by writeback
2387 * completion.
2388 */
2389 rcu_read_lock();
2390 spin_lock_irq(&sb->s_inode_wblist_lock);
2391 list_splice_init(&sb->s_inodes_wb, &sync_list);
2392
2393 /*
2394 * Data integrity sync. Must wait for all pages under writeback, because
2395 * there may have been pages dirtied before our sync call, but which had
2396 * writeout started before we write it out. In which case, the inode
2397 * may not be on the dirty list, but we still have to wait for that
2398 * writeout.
2399 */
2400 while (!list_empty(&sync_list)) {
2401 struct inode *inode = list_first_entry(&sync_list, struct inode,
2402 i_wb_list);
2403 struct address_space *mapping = inode->i_mapping;
2404
2405 /*
2406 * Move each inode back to the wb list before we drop the lock
2407 * to preserve consistency between i_wb_list and the mapping
2408 * writeback tag. Writeback completion is responsible to remove
2409 * the inode from either list once the writeback tag is cleared.
2410 */
2411 list_move_tail(&inode->i_wb_list, &sb->s_inodes_wb);
2412
2413 /*
2414 * The mapping can appear untagged while still on-list since we
2415 * do not have the mapping lock. Skip it here, wb completion
2416 * will remove it.
2417 */
2418 if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
2419 continue;
2420
2421 spin_unlock_irq(&sb->s_inode_wblist_lock);
2422
2423 spin_lock(&inode->i_lock);
2424 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
2425 spin_unlock(&inode->i_lock);
2426
2427 spin_lock_irq(&sb->s_inode_wblist_lock);
2428 continue;
2429 }
2430 __iget(inode);
2431 spin_unlock(&inode->i_lock);
2432 rcu_read_unlock();
2433
2434 /*
2435 * We keep the error status of individual mapping so that
2436 * applications can catch the writeback error using fsync(2).
2437 * See filemap_fdatawait_keep_errors() for details.
2438 */
2439 filemap_fdatawait_keep_errors(mapping);
2440
2441 cond_resched();
2442
2443 iput(inode);
2444
2445 rcu_read_lock();
2446 spin_lock_irq(&sb->s_inode_wblist_lock);
2447 }
2448 spin_unlock_irq(&sb->s_inode_wblist_lock);
2449 rcu_read_unlock();
2450 mutex_unlock(&sb->s_sync_lock);
2451}
2452
2453static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
2454 enum wb_reason reason, bool skip_if_busy)
2455{
2456 struct backing_dev_info *bdi = sb->s_bdi;
2457 DEFINE_WB_COMPLETION(done, bdi);
2458 struct wb_writeback_work work = {
2459 .sb = sb,
2460 .sync_mode = WB_SYNC_NONE,
2461 .tagged_writepages = 1,
2462 .done = &done,
2463 .nr_pages = nr,
2464 .reason = reason,
2465 };
2466
2467 if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info)
2468 return;
2469 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2470
2471 bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy);
2472 wb_wait_for_completion(&done);
2473}
2474
2475/**
2476 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
2477 * @sb: the superblock
2478 * @nr: the number of pages to write
2479 * @reason: reason why some writeback work initiated
2480 *
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.
2484 */
2485void writeback_inodes_sb_nr(struct super_block *sb,
2486 unsigned long nr,
2487 enum wb_reason reason)
2488{
2489 __writeback_inodes_sb_nr(sb, nr, reason, false);
2490}
2491EXPORT_SYMBOL(writeback_inodes_sb_nr);
2492
2493/**
2494 * writeback_inodes_sb - writeback dirty inodes from given super_block
2495 * @sb: the superblock
2496 * @reason: reason why some writeback work was initiated
2497 *
2498 * Start writeback on some inodes on this super_block. No guarantees are made
2499 * on how many (if any) will be written, and this function does not wait
2500 * for IO completion of submitted IO.
2501 */
2502void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2503{
2504 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
2505}
2506EXPORT_SYMBOL(writeback_inodes_sb);
2507
2508/**
2509 * try_to_writeback_inodes_sb - try to start writeback if none underway
2510 * @sb: the superblock
2511 * @reason: reason why some writeback work was initiated
2512 *
2513 * Invoke __writeback_inodes_sb_nr if no writeback is currently underway.
2514 */
2515void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2516{
2517 if (!down_read_trylock(&sb->s_umount))
2518 return;
2519
2520 __writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason, true);
2521 up_read(&sb->s_umount);
2522}
2523EXPORT_SYMBOL(try_to_writeback_inodes_sb);
2524
2525/**
2526 * sync_inodes_sb - sync sb inode pages
2527 * @sb: the superblock
2528 *
2529 * This function writes and waits on any dirty inode belonging to this
2530 * super_block.
2531 */
2532void sync_inodes_sb(struct super_block *sb)
2533{
2534 struct backing_dev_info *bdi = sb->s_bdi;
2535 DEFINE_WB_COMPLETION(done, bdi);
2536 struct wb_writeback_work work = {
2537 .sb = sb,
2538 .sync_mode = WB_SYNC_ALL,
2539 .nr_pages = LONG_MAX,
2540 .range_cyclic = 0,
2541 .done = &done,
2542 .reason = WB_REASON_SYNC,
2543 .for_sync = 1,
2544 };
2545
2546 /*
2547 * Can't skip on !bdi_has_dirty() because we should wait for !dirty
2548 * inodes under writeback and I_DIRTY_TIME inodes ignored by
2549 * bdi_has_dirty() need to be written out too.
2550 */
2551 if (bdi == &noop_backing_dev_info)
2552 return;
2553 WARN_ON(!rwsem_is_locked(&sb->s_umount));
2554
2555 /* protect against inode wb switch, see inode_switch_wbs_work_fn() */
2556 bdi_down_write_wb_switch_rwsem(bdi);
2557 bdi_split_work_to_wbs(bdi, &work, false);
2558 wb_wait_for_completion(&done);
2559 bdi_up_write_wb_switch_rwsem(bdi);
2560
2561 wait_sb_inodes(sb);
2562}
2563EXPORT_SYMBOL(sync_inodes_sb);
2564
2565/**
2566 * write_inode_now - write an inode to disk
2567 * @inode: inode to write to disk
2568 * @sync: whether the write should be synchronous or not
2569 *
2570 * This function commits an inode to disk immediately if it is dirty. This is
2571 * primarily needed by knfsd.
2572 *
2573 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
2574 */
2575int write_inode_now(struct inode *inode, int sync)
2576{
2577 struct writeback_control wbc = {
2578 .nr_to_write = LONG_MAX,
2579 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
2580 .range_start = 0,
2581 .range_end = LLONG_MAX,
2582 };
2583
2584 if (!mapping_cap_writeback_dirty(inode->i_mapping))
2585 wbc.nr_to_write = 0;
2586
2587 might_sleep();
2588 return writeback_single_inode(inode, &wbc);
2589}
2590EXPORT_SYMBOL(write_inode_now);
2591
2592/**
2593 * sync_inode - write an inode and its pages to disk.
2594 * @inode: the inode to sync
2595 * @wbc: controls the writeback mode
2596 *
2597 * sync_inode() will write an inode and its pages to disk. It will also
2598 * correctly update the inode on its superblock's dirty inode lists and will
2599 * update inode->i_state.
2600 *
2601 * The caller must have a ref on the inode.
2602 */
2603int sync_inode(struct inode *inode, struct writeback_control *wbc)
2604{
2605 return writeback_single_inode(inode, wbc);
2606}
2607EXPORT_SYMBOL(sync_inode);
2608
2609/**
2610 * sync_inode_metadata - write an inode to disk
2611 * @inode: the inode to sync
2612 * @wait: wait for I/O to complete.
2613 *
2614 * Write an inode to disk and adjust its dirty state after completion.
2615 *
2616 * Note: only writes the actual inode, no associated data or other metadata.
2617 */
2618int sync_inode_metadata(struct inode *inode, int wait)
2619{
2620 struct writeback_control wbc = {
2621 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
2622 .nr_to_write = 0, /* metadata-only */
2623 };
2624
2625 return sync_inode(inode, &wbc);
2626}
2627EXPORT_SYMBOL(sync_inode_metadata);
1/*
2 * fs/fs-writeback.c
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * Contains all the functions related to writing back and waiting
7 * upon dirty inodes against superblocks, and writing back dirty
8 * pages against inodes. ie: data writeback. Writeout of the
9 * inode itself is not handled here.
10 *
11 * 10Apr2002 Andrew Morton
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
14 */
15
16#include <linux/kernel.h>
17#include <linux/export.h>
18#include <linux/spinlock.h>
19#include <linux/slab.h>
20#include <linux/sched.h>
21#include <linux/fs.h>
22#include <linux/mm.h>
23#include <linux/pagemap.h>
24#include <linux/kthread.h>
25#include <linux/writeback.h>
26#include <linux/blkdev.h>
27#include <linux/backing-dev.h>
28#include <linux/tracepoint.h>
29#include <linux/device.h>
30#include "internal.h"
31
32/*
33 * 4MB minimal write chunk size
34 */
35#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
36
37/*
38 * Passed into wb_writeback(), essentially a subset of writeback_control
39 */
40struct wb_writeback_work {
41 long nr_pages;
42 struct super_block *sb;
43 unsigned long *older_than_this;
44 enum writeback_sync_modes sync_mode;
45 unsigned int tagged_writepages:1;
46 unsigned int for_kupdate:1;
47 unsigned int range_cyclic:1;
48 unsigned int for_background:1;
49 unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
50 enum wb_reason reason; /* why was writeback initiated? */
51
52 struct list_head list; /* pending work list */
53 struct completion *done; /* set if the caller waits */
54};
55
56/**
57 * writeback_in_progress - determine whether there is writeback in progress
58 * @bdi: the device's backing_dev_info structure.
59 *
60 * Determine whether there is writeback waiting to be handled against a
61 * backing device.
62 */
63int writeback_in_progress(struct backing_dev_info *bdi)
64{
65 return test_bit(BDI_writeback_running, &bdi->state);
66}
67EXPORT_SYMBOL(writeback_in_progress);
68
69static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
70{
71 struct super_block *sb = inode->i_sb;
72
73 if (sb_is_blkdev_sb(sb))
74 return inode->i_mapping->backing_dev_info;
75
76 return sb->s_bdi;
77}
78
79static inline struct inode *wb_inode(struct list_head *head)
80{
81 return list_entry(head, struct inode, i_wb_list);
82}
83
84/*
85 * Include the creation of the trace points after defining the
86 * wb_writeback_work structure and inline functions so that the definition
87 * remains local to this file.
88 */
89#define CREATE_TRACE_POINTS
90#include <trace/events/writeback.h>
91
92EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
93
94static void bdi_wakeup_thread(struct backing_dev_info *bdi)
95{
96 spin_lock_bh(&bdi->wb_lock);
97 if (test_bit(BDI_registered, &bdi->state))
98 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
99 spin_unlock_bh(&bdi->wb_lock);
100}
101
102static void bdi_queue_work(struct backing_dev_info *bdi,
103 struct wb_writeback_work *work)
104{
105 trace_writeback_queue(bdi, work);
106
107 spin_lock_bh(&bdi->wb_lock);
108 if (!test_bit(BDI_registered, &bdi->state)) {
109 if (work->done)
110 complete(work->done);
111 goto out_unlock;
112 }
113 list_add_tail(&work->list, &bdi->work_list);
114 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
115out_unlock:
116 spin_unlock_bh(&bdi->wb_lock);
117}
118
119static void
120__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
121 bool range_cyclic, enum wb_reason reason)
122{
123 struct wb_writeback_work *work;
124
125 /*
126 * This is WB_SYNC_NONE writeback, so if allocation fails just
127 * wakeup the thread for old dirty data writeback
128 */
129 work = kzalloc(sizeof(*work), GFP_ATOMIC);
130 if (!work) {
131 trace_writeback_nowork(bdi);
132 bdi_wakeup_thread(bdi);
133 return;
134 }
135
136 work->sync_mode = WB_SYNC_NONE;
137 work->nr_pages = nr_pages;
138 work->range_cyclic = range_cyclic;
139 work->reason = reason;
140
141 bdi_queue_work(bdi, work);
142}
143
144/**
145 * bdi_start_writeback - start writeback
146 * @bdi: the backing device to write from
147 * @nr_pages: the number of pages to write
148 * @reason: reason why some writeback work was initiated
149 *
150 * Description:
151 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
152 * started when this function returns, we make no guarantees on
153 * completion. Caller need not hold sb s_umount semaphore.
154 *
155 */
156void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
157 enum wb_reason reason)
158{
159 __bdi_start_writeback(bdi, nr_pages, true, reason);
160}
161
162/**
163 * bdi_start_background_writeback - start background writeback
164 * @bdi: the backing device to write from
165 *
166 * Description:
167 * This makes sure WB_SYNC_NONE background writeback happens. When
168 * this function returns, it is only guaranteed that for given BDI
169 * some IO is happening if we are over background dirty threshold.
170 * Caller need not hold sb s_umount semaphore.
171 */
172void bdi_start_background_writeback(struct backing_dev_info *bdi)
173{
174 /*
175 * We just wake up the flusher thread. It will perform background
176 * writeback as soon as there is no other work to do.
177 */
178 trace_writeback_wake_background(bdi);
179 bdi_wakeup_thread(bdi);
180}
181
182/*
183 * Remove the inode from the writeback list it is on.
184 */
185void inode_wb_list_del(struct inode *inode)
186{
187 struct backing_dev_info *bdi = inode_to_bdi(inode);
188
189 spin_lock(&bdi->wb.list_lock);
190 list_del_init(&inode->i_wb_list);
191 spin_unlock(&bdi->wb.list_lock);
192}
193
194/*
195 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
196 * furthest end of its superblock's dirty-inode list.
197 *
198 * Before stamping the inode's ->dirtied_when, we check to see whether it is
199 * already the most-recently-dirtied inode on the b_dirty list. If that is
200 * the case then the inode must have been redirtied while it was being written
201 * out and we don't reset its dirtied_when.
202 */
203static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
204{
205 assert_spin_locked(&wb->list_lock);
206 if (!list_empty(&wb->b_dirty)) {
207 struct inode *tail;
208
209 tail = wb_inode(wb->b_dirty.next);
210 if (time_before(inode->dirtied_when, tail->dirtied_when))
211 inode->dirtied_when = jiffies;
212 }
213 list_move(&inode->i_wb_list, &wb->b_dirty);
214}
215
216/*
217 * requeue inode for re-scanning after bdi->b_io list is exhausted.
218 */
219static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
220{
221 assert_spin_locked(&wb->list_lock);
222 list_move(&inode->i_wb_list, &wb->b_more_io);
223}
224
225static void inode_sync_complete(struct inode *inode)
226{
227 inode->i_state &= ~I_SYNC;
228 /* If inode is clean an unused, put it into LRU now... */
229 inode_add_lru(inode);
230 /* Waiters must see I_SYNC cleared before being woken up */
231 smp_mb();
232 wake_up_bit(&inode->i_state, __I_SYNC);
233}
234
235static bool inode_dirtied_after(struct inode *inode, unsigned long t)
236{
237 bool ret = time_after(inode->dirtied_when, t);
238#ifndef CONFIG_64BIT
239 /*
240 * For inodes being constantly redirtied, dirtied_when can get stuck.
241 * It _appears_ to be in the future, but is actually in distant past.
242 * This test is necessary to prevent such wrapped-around relative times
243 * from permanently stopping the whole bdi writeback.
244 */
245 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
246#endif
247 return ret;
248}
249
250/*
251 * Move expired (dirtied before work->older_than_this) dirty inodes from
252 * @delaying_queue to @dispatch_queue.
253 */
254static int move_expired_inodes(struct list_head *delaying_queue,
255 struct list_head *dispatch_queue,
256 struct wb_writeback_work *work)
257{
258 LIST_HEAD(tmp);
259 struct list_head *pos, *node;
260 struct super_block *sb = NULL;
261 struct inode *inode;
262 int do_sb_sort = 0;
263 int moved = 0;
264
265 while (!list_empty(delaying_queue)) {
266 inode = wb_inode(delaying_queue->prev);
267 if (work->older_than_this &&
268 inode_dirtied_after(inode, *work->older_than_this))
269 break;
270 list_move(&inode->i_wb_list, &tmp);
271 moved++;
272 if (sb_is_blkdev_sb(inode->i_sb))
273 continue;
274 if (sb && sb != inode->i_sb)
275 do_sb_sort = 1;
276 sb = inode->i_sb;
277 }
278
279 /* just one sb in list, splice to dispatch_queue and we're done */
280 if (!do_sb_sort) {
281 list_splice(&tmp, dispatch_queue);
282 goto out;
283 }
284
285 /* Move inodes from one superblock together */
286 while (!list_empty(&tmp)) {
287 sb = wb_inode(tmp.prev)->i_sb;
288 list_for_each_prev_safe(pos, node, &tmp) {
289 inode = wb_inode(pos);
290 if (inode->i_sb == sb)
291 list_move(&inode->i_wb_list, dispatch_queue);
292 }
293 }
294out:
295 return moved;
296}
297
298/*
299 * Queue all expired dirty inodes for io, eldest first.
300 * Before
301 * newly dirtied b_dirty b_io b_more_io
302 * =============> gf edc BA
303 * After
304 * newly dirtied b_dirty b_io b_more_io
305 * =============> g fBAedc
306 * |
307 * +--> dequeue for IO
308 */
309static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
310{
311 int moved;
312 assert_spin_locked(&wb->list_lock);
313 list_splice_init(&wb->b_more_io, &wb->b_io);
314 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
315 trace_writeback_queue_io(wb, work, moved);
316}
317
318static int write_inode(struct inode *inode, struct writeback_control *wbc)
319{
320 int ret;
321
322 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
323 trace_writeback_write_inode_start(inode, wbc);
324 ret = inode->i_sb->s_op->write_inode(inode, wbc);
325 trace_writeback_write_inode(inode, wbc);
326 return ret;
327 }
328 return 0;
329}
330
331/*
332 * Wait for writeback on an inode to complete. Called with i_lock held.
333 * Caller must make sure inode cannot go away when we drop i_lock.
334 */
335static void __inode_wait_for_writeback(struct inode *inode)
336 __releases(inode->i_lock)
337 __acquires(inode->i_lock)
338{
339 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
340 wait_queue_head_t *wqh;
341
342 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
343 while (inode->i_state & I_SYNC) {
344 spin_unlock(&inode->i_lock);
345 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
346 spin_lock(&inode->i_lock);
347 }
348}
349
350/*
351 * Wait for writeback on an inode to complete. Caller must have inode pinned.
352 */
353void inode_wait_for_writeback(struct inode *inode)
354{
355 spin_lock(&inode->i_lock);
356 __inode_wait_for_writeback(inode);
357 spin_unlock(&inode->i_lock);
358}
359
360/*
361 * Sleep until I_SYNC is cleared. This function must be called with i_lock
362 * held and drops it. It is aimed for callers not holding any inode reference
363 * so once i_lock is dropped, inode can go away.
364 */
365static void inode_sleep_on_writeback(struct inode *inode)
366 __releases(inode->i_lock)
367{
368 DEFINE_WAIT(wait);
369 wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
370 int sleep;
371
372 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
373 sleep = inode->i_state & I_SYNC;
374 spin_unlock(&inode->i_lock);
375 if (sleep)
376 schedule();
377 finish_wait(wqh, &wait);
378}
379
380/*
381 * Find proper writeback list for the inode depending on its current state and
382 * possibly also change of its state while we were doing writeback. Here we
383 * handle things such as livelock prevention or fairness of writeback among
384 * inodes. This function can be called only by flusher thread - noone else
385 * processes all inodes in writeback lists and requeueing inodes behind flusher
386 * thread's back can have unexpected consequences.
387 */
388static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
389 struct writeback_control *wbc)
390{
391 if (inode->i_state & I_FREEING)
392 return;
393
394 /*
395 * Sync livelock prevention. Each inode is tagged and synced in one
396 * shot. If still dirty, it will be redirty_tail()'ed below. Update
397 * the dirty time to prevent enqueue and sync it again.
398 */
399 if ((inode->i_state & I_DIRTY) &&
400 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
401 inode->dirtied_when = jiffies;
402
403 if (wbc->pages_skipped) {
404 /*
405 * writeback is not making progress due to locked
406 * buffers. Skip this inode for now.
407 */
408 redirty_tail(inode, wb);
409 return;
410 }
411
412 if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
413 /*
414 * We didn't write back all the pages. nfs_writepages()
415 * sometimes bales out without doing anything.
416 */
417 if (wbc->nr_to_write <= 0) {
418 /* Slice used up. Queue for next turn. */
419 requeue_io(inode, wb);
420 } else {
421 /*
422 * Writeback blocked by something other than
423 * congestion. Delay the inode for some time to
424 * avoid spinning on the CPU (100% iowait)
425 * retrying writeback of the dirty page/inode
426 * that cannot be performed immediately.
427 */
428 redirty_tail(inode, wb);
429 }
430 } else if (inode->i_state & I_DIRTY) {
431 /*
432 * Filesystems can dirty the inode during writeback operations,
433 * such as delayed allocation during submission or metadata
434 * updates after data IO completion.
435 */
436 redirty_tail(inode, wb);
437 } else {
438 /* The inode is clean. Remove from writeback lists. */
439 list_del_init(&inode->i_wb_list);
440 }
441}
442
443/*
444 * Write out an inode and its dirty pages. Do not update the writeback list
445 * linkage. That is left to the caller. The caller is also responsible for
446 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
447 */
448static int
449__writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
450{
451 struct address_space *mapping = inode->i_mapping;
452 long nr_to_write = wbc->nr_to_write;
453 unsigned dirty;
454 int ret;
455
456 WARN_ON(!(inode->i_state & I_SYNC));
457
458 trace_writeback_single_inode_start(inode, wbc, nr_to_write);
459
460 ret = do_writepages(mapping, wbc);
461
462 /*
463 * Make sure to wait on the data before writing out the metadata.
464 * This is important for filesystems that modify metadata on data
465 * I/O completion. We don't do it for sync(2) writeback because it has a
466 * separate, external IO completion path and ->sync_fs for guaranteeing
467 * inode metadata is written back correctly.
468 */
469 if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
470 int err = filemap_fdatawait(mapping);
471 if (ret == 0)
472 ret = err;
473 }
474
475 /*
476 * Some filesystems may redirty the inode during the writeback
477 * due to delalloc, clear dirty metadata flags right before
478 * write_inode()
479 */
480 spin_lock(&inode->i_lock);
481 /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
482 if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
483 inode->i_state &= ~I_DIRTY_PAGES;
484 dirty = inode->i_state & I_DIRTY;
485 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
486 spin_unlock(&inode->i_lock);
487 /* Don't write the inode if only I_DIRTY_PAGES was set */
488 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
489 int err = write_inode(inode, wbc);
490 if (ret == 0)
491 ret = err;
492 }
493 trace_writeback_single_inode(inode, wbc, nr_to_write);
494 return ret;
495}
496
497/*
498 * Write out an inode's dirty pages. Either the caller has an active reference
499 * on the inode or the inode has I_WILL_FREE set.
500 *
501 * This function is designed to be called for writing back one inode which
502 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
503 * and does more profound writeback list handling in writeback_sb_inodes().
504 */
505static int
506writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
507 struct writeback_control *wbc)
508{
509 int ret = 0;
510
511 spin_lock(&inode->i_lock);
512 if (!atomic_read(&inode->i_count))
513 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
514 else
515 WARN_ON(inode->i_state & I_WILL_FREE);
516
517 if (inode->i_state & I_SYNC) {
518 if (wbc->sync_mode != WB_SYNC_ALL)
519 goto out;
520 /*
521 * It's a data-integrity sync. We must wait. Since callers hold
522 * inode reference or inode has I_WILL_FREE set, it cannot go
523 * away under us.
524 */
525 __inode_wait_for_writeback(inode);
526 }
527 WARN_ON(inode->i_state & I_SYNC);
528 /*
529 * Skip inode if it is clean and we have no outstanding writeback in
530 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
531 * function since flusher thread may be doing for example sync in
532 * parallel and if we move the inode, it could get skipped. So here we
533 * make sure inode is on some writeback list and leave it there unless
534 * we have completely cleaned the inode.
535 */
536 if (!(inode->i_state & I_DIRTY) &&
537 (wbc->sync_mode != WB_SYNC_ALL ||
538 !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
539 goto out;
540 inode->i_state |= I_SYNC;
541 spin_unlock(&inode->i_lock);
542
543 ret = __writeback_single_inode(inode, wbc);
544
545 spin_lock(&wb->list_lock);
546 spin_lock(&inode->i_lock);
547 /*
548 * If inode is clean, remove it from writeback lists. Otherwise don't
549 * touch it. See comment above for explanation.
550 */
551 if (!(inode->i_state & I_DIRTY))
552 list_del_init(&inode->i_wb_list);
553 spin_unlock(&wb->list_lock);
554 inode_sync_complete(inode);
555out:
556 spin_unlock(&inode->i_lock);
557 return ret;
558}
559
560static long writeback_chunk_size(struct backing_dev_info *bdi,
561 struct wb_writeback_work *work)
562{
563 long pages;
564
565 /*
566 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
567 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
568 * here avoids calling into writeback_inodes_wb() more than once.
569 *
570 * The intended call sequence for WB_SYNC_ALL writeback is:
571 *
572 * wb_writeback()
573 * writeback_sb_inodes() <== called only once
574 * write_cache_pages() <== called once for each inode
575 * (quickly) tag currently dirty pages
576 * (maybe slowly) sync all tagged pages
577 */
578 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
579 pages = LONG_MAX;
580 else {
581 pages = min(bdi->avg_write_bandwidth / 2,
582 global_dirty_limit / DIRTY_SCOPE);
583 pages = min(pages, work->nr_pages);
584 pages = round_down(pages + MIN_WRITEBACK_PAGES,
585 MIN_WRITEBACK_PAGES);
586 }
587
588 return pages;
589}
590
591/*
592 * Write a portion of b_io inodes which belong to @sb.
593 *
594 * Return the number of pages and/or inodes written.
595 */
596static long writeback_sb_inodes(struct super_block *sb,
597 struct bdi_writeback *wb,
598 struct wb_writeback_work *work)
599{
600 struct writeback_control wbc = {
601 .sync_mode = work->sync_mode,
602 .tagged_writepages = work->tagged_writepages,
603 .for_kupdate = work->for_kupdate,
604 .for_background = work->for_background,
605 .for_sync = work->for_sync,
606 .range_cyclic = work->range_cyclic,
607 .range_start = 0,
608 .range_end = LLONG_MAX,
609 };
610 unsigned long start_time = jiffies;
611 long write_chunk;
612 long wrote = 0; /* count both pages and inodes */
613
614 while (!list_empty(&wb->b_io)) {
615 struct inode *inode = wb_inode(wb->b_io.prev);
616
617 if (inode->i_sb != sb) {
618 if (work->sb) {
619 /*
620 * We only want to write back data for this
621 * superblock, move all inodes not belonging
622 * to it back onto the dirty list.
623 */
624 redirty_tail(inode, wb);
625 continue;
626 }
627
628 /*
629 * The inode belongs to a different superblock.
630 * Bounce back to the caller to unpin this and
631 * pin the next superblock.
632 */
633 break;
634 }
635
636 /*
637 * Don't bother with new inodes or inodes being freed, first
638 * kind does not need periodic writeout yet, and for the latter
639 * kind writeout is handled by the freer.
640 */
641 spin_lock(&inode->i_lock);
642 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
643 spin_unlock(&inode->i_lock);
644 redirty_tail(inode, wb);
645 continue;
646 }
647 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
648 /*
649 * If this inode is locked for writeback and we are not
650 * doing writeback-for-data-integrity, move it to
651 * b_more_io so that writeback can proceed with the
652 * other inodes on s_io.
653 *
654 * We'll have another go at writing back this inode
655 * when we completed a full scan of b_io.
656 */
657 spin_unlock(&inode->i_lock);
658 requeue_io(inode, wb);
659 trace_writeback_sb_inodes_requeue(inode);
660 continue;
661 }
662 spin_unlock(&wb->list_lock);
663
664 /*
665 * We already requeued the inode if it had I_SYNC set and we
666 * are doing WB_SYNC_NONE writeback. So this catches only the
667 * WB_SYNC_ALL case.
668 */
669 if (inode->i_state & I_SYNC) {
670 /* Wait for I_SYNC. This function drops i_lock... */
671 inode_sleep_on_writeback(inode);
672 /* Inode may be gone, start again */
673 spin_lock(&wb->list_lock);
674 continue;
675 }
676 inode->i_state |= I_SYNC;
677 spin_unlock(&inode->i_lock);
678
679 write_chunk = writeback_chunk_size(wb->bdi, work);
680 wbc.nr_to_write = write_chunk;
681 wbc.pages_skipped = 0;
682
683 /*
684 * We use I_SYNC to pin the inode in memory. While it is set
685 * evict_inode() will wait so the inode cannot be freed.
686 */
687 __writeback_single_inode(inode, &wbc);
688
689 work->nr_pages -= write_chunk - wbc.nr_to_write;
690 wrote += write_chunk - wbc.nr_to_write;
691 spin_lock(&wb->list_lock);
692 spin_lock(&inode->i_lock);
693 if (!(inode->i_state & I_DIRTY))
694 wrote++;
695 requeue_inode(inode, wb, &wbc);
696 inode_sync_complete(inode);
697 spin_unlock(&inode->i_lock);
698 cond_resched_lock(&wb->list_lock);
699 /*
700 * bail out to wb_writeback() often enough to check
701 * background threshold and other termination conditions.
702 */
703 if (wrote) {
704 if (time_is_before_jiffies(start_time + HZ / 10UL))
705 break;
706 if (work->nr_pages <= 0)
707 break;
708 }
709 }
710 return wrote;
711}
712
713static long __writeback_inodes_wb(struct bdi_writeback *wb,
714 struct wb_writeback_work *work)
715{
716 unsigned long start_time = jiffies;
717 long wrote = 0;
718
719 while (!list_empty(&wb->b_io)) {
720 struct inode *inode = wb_inode(wb->b_io.prev);
721 struct super_block *sb = inode->i_sb;
722
723 if (!grab_super_passive(sb)) {
724 /*
725 * grab_super_passive() may fail consistently due to
726 * s_umount being grabbed by someone else. Don't use
727 * requeue_io() to avoid busy retrying the inode/sb.
728 */
729 redirty_tail(inode, wb);
730 continue;
731 }
732 wrote += writeback_sb_inodes(sb, wb, work);
733 drop_super(sb);
734
735 /* refer to the same tests at the end of writeback_sb_inodes */
736 if (wrote) {
737 if (time_is_before_jiffies(start_time + HZ / 10UL))
738 break;
739 if (work->nr_pages <= 0)
740 break;
741 }
742 }
743 /* Leave any unwritten inodes on b_io */
744 return wrote;
745}
746
747static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
748 enum wb_reason reason)
749{
750 struct wb_writeback_work work = {
751 .nr_pages = nr_pages,
752 .sync_mode = WB_SYNC_NONE,
753 .range_cyclic = 1,
754 .reason = reason,
755 };
756
757 spin_lock(&wb->list_lock);
758 if (list_empty(&wb->b_io))
759 queue_io(wb, &work);
760 __writeback_inodes_wb(wb, &work);
761 spin_unlock(&wb->list_lock);
762
763 return nr_pages - work.nr_pages;
764}
765
766static bool over_bground_thresh(struct backing_dev_info *bdi)
767{
768 unsigned long background_thresh, dirty_thresh;
769
770 global_dirty_limits(&background_thresh, &dirty_thresh);
771
772 if (global_page_state(NR_FILE_DIRTY) +
773 global_page_state(NR_UNSTABLE_NFS) > background_thresh)
774 return true;
775
776 if (bdi_stat(bdi, BDI_RECLAIMABLE) >
777 bdi_dirty_limit(bdi, background_thresh))
778 return true;
779
780 return false;
781}
782
783/*
784 * Called under wb->list_lock. If there are multiple wb per bdi,
785 * only the flusher working on the first wb should do it.
786 */
787static void wb_update_bandwidth(struct bdi_writeback *wb,
788 unsigned long start_time)
789{
790 __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
791}
792
793/*
794 * Explicit flushing or periodic writeback of "old" data.
795 *
796 * Define "old": the first time one of an inode's pages is dirtied, we mark the
797 * dirtying-time in the inode's address_space. So this periodic writeback code
798 * just walks the superblock inode list, writing back any inodes which are
799 * older than a specific point in time.
800 *
801 * Try to run once per dirty_writeback_interval. But if a writeback event
802 * takes longer than a dirty_writeback_interval interval, then leave a
803 * one-second gap.
804 *
805 * older_than_this takes precedence over nr_to_write. So we'll only write back
806 * all dirty pages if they are all attached to "old" mappings.
807 */
808static long wb_writeback(struct bdi_writeback *wb,
809 struct wb_writeback_work *work)
810{
811 unsigned long wb_start = jiffies;
812 long nr_pages = work->nr_pages;
813 unsigned long oldest_jif;
814 struct inode *inode;
815 long progress;
816
817 oldest_jif = jiffies;
818 work->older_than_this = &oldest_jif;
819
820 spin_lock(&wb->list_lock);
821 for (;;) {
822 /*
823 * Stop writeback when nr_pages has been consumed
824 */
825 if (work->nr_pages <= 0)
826 break;
827
828 /*
829 * Background writeout and kupdate-style writeback may
830 * run forever. Stop them if there is other work to do
831 * so that e.g. sync can proceed. They'll be restarted
832 * after the other works are all done.
833 */
834 if ((work->for_background || work->for_kupdate) &&
835 !list_empty(&wb->bdi->work_list))
836 break;
837
838 /*
839 * For background writeout, stop when we are below the
840 * background dirty threshold
841 */
842 if (work->for_background && !over_bground_thresh(wb->bdi))
843 break;
844
845 /*
846 * Kupdate and background works are special and we want to
847 * include all inodes that need writing. Livelock avoidance is
848 * handled by these works yielding to any other work so we are
849 * safe.
850 */
851 if (work->for_kupdate) {
852 oldest_jif = jiffies -
853 msecs_to_jiffies(dirty_expire_interval * 10);
854 } else if (work->for_background)
855 oldest_jif = jiffies;
856
857 trace_writeback_start(wb->bdi, work);
858 if (list_empty(&wb->b_io))
859 queue_io(wb, work);
860 if (work->sb)
861 progress = writeback_sb_inodes(work->sb, wb, work);
862 else
863 progress = __writeback_inodes_wb(wb, work);
864 trace_writeback_written(wb->bdi, work);
865
866 wb_update_bandwidth(wb, wb_start);
867
868 /*
869 * Did we write something? Try for more
870 *
871 * Dirty inodes are moved to b_io for writeback in batches.
872 * The completion of the current batch does not necessarily
873 * mean the overall work is done. So we keep looping as long
874 * as made some progress on cleaning pages or inodes.
875 */
876 if (progress)
877 continue;
878 /*
879 * No more inodes for IO, bail
880 */
881 if (list_empty(&wb->b_more_io))
882 break;
883 /*
884 * Nothing written. Wait for some inode to
885 * become available for writeback. Otherwise
886 * we'll just busyloop.
887 */
888 if (!list_empty(&wb->b_more_io)) {
889 trace_writeback_wait(wb->bdi, work);
890 inode = wb_inode(wb->b_more_io.prev);
891 spin_lock(&inode->i_lock);
892 spin_unlock(&wb->list_lock);
893 /* This function drops i_lock... */
894 inode_sleep_on_writeback(inode);
895 spin_lock(&wb->list_lock);
896 }
897 }
898 spin_unlock(&wb->list_lock);
899
900 return nr_pages - work->nr_pages;
901}
902
903/*
904 * Return the next wb_writeback_work struct that hasn't been processed yet.
905 */
906static struct wb_writeback_work *
907get_next_work_item(struct backing_dev_info *bdi)
908{
909 struct wb_writeback_work *work = NULL;
910
911 spin_lock_bh(&bdi->wb_lock);
912 if (!list_empty(&bdi->work_list)) {
913 work = list_entry(bdi->work_list.next,
914 struct wb_writeback_work, list);
915 list_del_init(&work->list);
916 }
917 spin_unlock_bh(&bdi->wb_lock);
918 return work;
919}
920
921/*
922 * Add in the number of potentially dirty inodes, because each inode
923 * write can dirty pagecache in the underlying blockdev.
924 */
925static unsigned long get_nr_dirty_pages(void)
926{
927 return global_page_state(NR_FILE_DIRTY) +
928 global_page_state(NR_UNSTABLE_NFS) +
929 get_nr_dirty_inodes();
930}
931
932static long wb_check_background_flush(struct bdi_writeback *wb)
933{
934 if (over_bground_thresh(wb->bdi)) {
935
936 struct wb_writeback_work work = {
937 .nr_pages = LONG_MAX,
938 .sync_mode = WB_SYNC_NONE,
939 .for_background = 1,
940 .range_cyclic = 1,
941 .reason = WB_REASON_BACKGROUND,
942 };
943
944 return wb_writeback(wb, &work);
945 }
946
947 return 0;
948}
949
950static long wb_check_old_data_flush(struct bdi_writeback *wb)
951{
952 unsigned long expired;
953 long nr_pages;
954
955 /*
956 * When set to zero, disable periodic writeback
957 */
958 if (!dirty_writeback_interval)
959 return 0;
960
961 expired = wb->last_old_flush +
962 msecs_to_jiffies(dirty_writeback_interval * 10);
963 if (time_before(jiffies, expired))
964 return 0;
965
966 wb->last_old_flush = jiffies;
967 nr_pages = get_nr_dirty_pages();
968
969 if (nr_pages) {
970 struct wb_writeback_work work = {
971 .nr_pages = nr_pages,
972 .sync_mode = WB_SYNC_NONE,
973 .for_kupdate = 1,
974 .range_cyclic = 1,
975 .reason = WB_REASON_PERIODIC,
976 };
977
978 return wb_writeback(wb, &work);
979 }
980
981 return 0;
982}
983
984/*
985 * Retrieve work items and do the writeback they describe
986 */
987static long wb_do_writeback(struct bdi_writeback *wb)
988{
989 struct backing_dev_info *bdi = wb->bdi;
990 struct wb_writeback_work *work;
991 long wrote = 0;
992
993 set_bit(BDI_writeback_running, &wb->bdi->state);
994 while ((work = get_next_work_item(bdi)) != NULL) {
995
996 trace_writeback_exec(bdi, work);
997
998 wrote += wb_writeback(wb, work);
999
1000 /*
1001 * Notify the caller of completion if this is a synchronous
1002 * work item, otherwise just free it.
1003 */
1004 if (work->done)
1005 complete(work->done);
1006 else
1007 kfree(work);
1008 }
1009
1010 /*
1011 * Check for periodic writeback, kupdated() style
1012 */
1013 wrote += wb_check_old_data_flush(wb);
1014 wrote += wb_check_background_flush(wb);
1015 clear_bit(BDI_writeback_running, &wb->bdi->state);
1016
1017 return wrote;
1018}
1019
1020/*
1021 * Handle writeback of dirty data for the device backed by this bdi. Also
1022 * reschedules periodically and does kupdated style flushing.
1023 */
1024void bdi_writeback_workfn(struct work_struct *work)
1025{
1026 struct bdi_writeback *wb = container_of(to_delayed_work(work),
1027 struct bdi_writeback, dwork);
1028 struct backing_dev_info *bdi = wb->bdi;
1029 long pages_written;
1030
1031 set_worker_desc("flush-%s", dev_name(bdi->dev));
1032 current->flags |= PF_SWAPWRITE;
1033
1034 if (likely(!current_is_workqueue_rescuer() ||
1035 !test_bit(BDI_registered, &bdi->state))) {
1036 /*
1037 * The normal path. Keep writing back @bdi until its
1038 * work_list is empty. Note that this path is also taken
1039 * if @bdi is shutting down even when we're running off the
1040 * rescuer as work_list needs to be drained.
1041 */
1042 do {
1043 pages_written = wb_do_writeback(wb);
1044 trace_writeback_pages_written(pages_written);
1045 } while (!list_empty(&bdi->work_list));
1046 } else {
1047 /*
1048 * bdi_wq can't get enough workers and we're running off
1049 * the emergency worker. Don't hog it. Hopefully, 1024 is
1050 * enough for efficient IO.
1051 */
1052 pages_written = writeback_inodes_wb(&bdi->wb, 1024,
1053 WB_REASON_FORKER_THREAD);
1054 trace_writeback_pages_written(pages_written);
1055 }
1056
1057 if (!list_empty(&bdi->work_list))
1058 mod_delayed_work(bdi_wq, &wb->dwork, 0);
1059 else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1060 bdi_wakeup_thread_delayed(bdi);
1061
1062 current->flags &= ~PF_SWAPWRITE;
1063}
1064
1065/*
1066 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
1067 * the whole world.
1068 */
1069void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1070{
1071 struct backing_dev_info *bdi;
1072
1073 if (!nr_pages)
1074 nr_pages = get_nr_dirty_pages();
1075
1076 rcu_read_lock();
1077 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1078 if (!bdi_has_dirty_io(bdi))
1079 continue;
1080 __bdi_start_writeback(bdi, nr_pages, false, reason);
1081 }
1082 rcu_read_unlock();
1083}
1084
1085static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1086{
1087 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1088 struct dentry *dentry;
1089 const char *name = "?";
1090
1091 dentry = d_find_alias(inode);
1092 if (dentry) {
1093 spin_lock(&dentry->d_lock);
1094 name = (const char *) dentry->d_name.name;
1095 }
1096 printk(KERN_DEBUG
1097 "%s(%d): dirtied inode %lu (%s) on %s\n",
1098 current->comm, task_pid_nr(current), inode->i_ino,
1099 name, inode->i_sb->s_id);
1100 if (dentry) {
1101 spin_unlock(&dentry->d_lock);
1102 dput(dentry);
1103 }
1104 }
1105}
1106
1107/**
1108 * __mark_inode_dirty - internal function
1109 * @inode: inode to mark
1110 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1111 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1112 * mark_inode_dirty_sync.
1113 *
1114 * Put the inode on the super block's dirty list.
1115 *
1116 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1117 * dirty list only if it is hashed or if it refers to a blockdev.
1118 * If it was not hashed, it will never be added to the dirty list
1119 * even if it is later hashed, as it will have been marked dirty already.
1120 *
1121 * In short, make sure you hash any inodes _before_ you start marking
1122 * them dirty.
1123 *
1124 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1125 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1126 * the kernel-internal blockdev inode represents the dirtying time of the
1127 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1128 * page->mapping->host, so the page-dirtying time is recorded in the internal
1129 * blockdev inode.
1130 */
1131void __mark_inode_dirty(struct inode *inode, int flags)
1132{
1133 struct super_block *sb = inode->i_sb;
1134 struct backing_dev_info *bdi = NULL;
1135
1136 /*
1137 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1138 * dirty the inode itself
1139 */
1140 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1141 trace_writeback_dirty_inode_start(inode, flags);
1142
1143 if (sb->s_op->dirty_inode)
1144 sb->s_op->dirty_inode(inode, flags);
1145
1146 trace_writeback_dirty_inode(inode, flags);
1147 }
1148
1149 /*
1150 * make sure that changes are seen by all cpus before we test i_state
1151 * -- mikulas
1152 */
1153 smp_mb();
1154
1155 /* avoid the locking if we can */
1156 if ((inode->i_state & flags) == flags)
1157 return;
1158
1159 if (unlikely(block_dump))
1160 block_dump___mark_inode_dirty(inode);
1161
1162 spin_lock(&inode->i_lock);
1163 if ((inode->i_state & flags) != flags) {
1164 const int was_dirty = inode->i_state & I_DIRTY;
1165
1166 inode->i_state |= flags;
1167
1168 /*
1169 * If the inode is being synced, just update its dirty state.
1170 * The unlocker will place the inode on the appropriate
1171 * superblock list, based upon its state.
1172 */
1173 if (inode->i_state & I_SYNC)
1174 goto out_unlock_inode;
1175
1176 /*
1177 * Only add valid (hashed) inodes to the superblock's
1178 * dirty list. Add blockdev inodes as well.
1179 */
1180 if (!S_ISBLK(inode->i_mode)) {
1181 if (inode_unhashed(inode))
1182 goto out_unlock_inode;
1183 }
1184 if (inode->i_state & I_FREEING)
1185 goto out_unlock_inode;
1186
1187 /*
1188 * If the inode was already on b_dirty/b_io/b_more_io, don't
1189 * reposition it (that would break b_dirty time-ordering).
1190 */
1191 if (!was_dirty) {
1192 bool wakeup_bdi = false;
1193 bdi = inode_to_bdi(inode);
1194
1195 spin_unlock(&inode->i_lock);
1196 spin_lock(&bdi->wb.list_lock);
1197 if (bdi_cap_writeback_dirty(bdi)) {
1198 WARN(!test_bit(BDI_registered, &bdi->state),
1199 "bdi-%s not registered\n", bdi->name);
1200
1201 /*
1202 * If this is the first dirty inode for this
1203 * bdi, we have to wake-up the corresponding
1204 * bdi thread to make sure background
1205 * write-back happens later.
1206 */
1207 if (!wb_has_dirty_io(&bdi->wb))
1208 wakeup_bdi = true;
1209 }
1210
1211 inode->dirtied_when = jiffies;
1212 list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1213 spin_unlock(&bdi->wb.list_lock);
1214
1215 if (wakeup_bdi)
1216 bdi_wakeup_thread_delayed(bdi);
1217 return;
1218 }
1219 }
1220out_unlock_inode:
1221 spin_unlock(&inode->i_lock);
1222
1223}
1224EXPORT_SYMBOL(__mark_inode_dirty);
1225
1226static void wait_sb_inodes(struct super_block *sb)
1227{
1228 struct inode *inode, *old_inode = NULL;
1229
1230 /*
1231 * We need to be protected against the filesystem going from
1232 * r/o to r/w or vice versa.
1233 */
1234 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1235
1236 spin_lock(&inode_sb_list_lock);
1237
1238 /*
1239 * Data integrity sync. Must wait for all pages under writeback,
1240 * because there may have been pages dirtied before our sync
1241 * call, but which had writeout started before we write it out.
1242 * In which case, the inode may not be on the dirty list, but
1243 * we still have to wait for that writeout.
1244 */
1245 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1246 struct address_space *mapping = inode->i_mapping;
1247
1248 spin_lock(&inode->i_lock);
1249 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1250 (mapping->nrpages == 0)) {
1251 spin_unlock(&inode->i_lock);
1252 continue;
1253 }
1254 __iget(inode);
1255 spin_unlock(&inode->i_lock);
1256 spin_unlock(&inode_sb_list_lock);
1257
1258 /*
1259 * We hold a reference to 'inode' so it couldn't have been
1260 * removed from s_inodes list while we dropped the
1261 * inode_sb_list_lock. We cannot iput the inode now as we can
1262 * be holding the last reference and we cannot iput it under
1263 * inode_sb_list_lock. So we keep the reference and iput it
1264 * later.
1265 */
1266 iput(old_inode);
1267 old_inode = inode;
1268
1269 filemap_fdatawait(mapping);
1270
1271 cond_resched();
1272
1273 spin_lock(&inode_sb_list_lock);
1274 }
1275 spin_unlock(&inode_sb_list_lock);
1276 iput(old_inode);
1277}
1278
1279/**
1280 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1281 * @sb: the superblock
1282 * @nr: the number of pages to write
1283 * @reason: reason why some writeback work initiated
1284 *
1285 * Start writeback on some inodes on this super_block. No guarantees are made
1286 * on how many (if any) will be written, and this function does not wait
1287 * for IO completion of submitted IO.
1288 */
1289void writeback_inodes_sb_nr(struct super_block *sb,
1290 unsigned long nr,
1291 enum wb_reason reason)
1292{
1293 DECLARE_COMPLETION_ONSTACK(done);
1294 struct wb_writeback_work work = {
1295 .sb = sb,
1296 .sync_mode = WB_SYNC_NONE,
1297 .tagged_writepages = 1,
1298 .done = &done,
1299 .nr_pages = nr,
1300 .reason = reason,
1301 };
1302
1303 if (sb->s_bdi == &noop_backing_dev_info)
1304 return;
1305 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1306 bdi_queue_work(sb->s_bdi, &work);
1307 wait_for_completion(&done);
1308}
1309EXPORT_SYMBOL(writeback_inodes_sb_nr);
1310
1311/**
1312 * writeback_inodes_sb - writeback dirty inodes from given super_block
1313 * @sb: the superblock
1314 * @reason: reason why some writeback work was initiated
1315 *
1316 * Start writeback on some inodes on this super_block. No guarantees are made
1317 * on how many (if any) will be written, and this function does not wait
1318 * for IO completion of submitted IO.
1319 */
1320void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1321{
1322 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1323}
1324EXPORT_SYMBOL(writeback_inodes_sb);
1325
1326/**
1327 * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
1328 * @sb: the superblock
1329 * @nr: the number of pages to write
1330 * @reason: the reason of writeback
1331 *
1332 * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
1333 * Returns 1 if writeback was started, 0 if not.
1334 */
1335int try_to_writeback_inodes_sb_nr(struct super_block *sb,
1336 unsigned long nr,
1337 enum wb_reason reason)
1338{
1339 if (writeback_in_progress(sb->s_bdi))
1340 return 1;
1341
1342 if (!down_read_trylock(&sb->s_umount))
1343 return 0;
1344
1345 writeback_inodes_sb_nr(sb, nr, reason);
1346 up_read(&sb->s_umount);
1347 return 1;
1348}
1349EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
1350
1351/**
1352 * try_to_writeback_inodes_sb - try to start writeback if none underway
1353 * @sb: the superblock
1354 * @reason: reason why some writeback work was initiated
1355 *
1356 * Implement by try_to_writeback_inodes_sb_nr()
1357 * Returns 1 if writeback was started, 0 if not.
1358 */
1359int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1360{
1361 return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1362}
1363EXPORT_SYMBOL(try_to_writeback_inodes_sb);
1364
1365/**
1366 * sync_inodes_sb - sync sb inode pages
1367 * @sb: the superblock
1368 *
1369 * This function writes and waits on any dirty inode belonging to this
1370 * super_block.
1371 */
1372void sync_inodes_sb(struct super_block *sb)
1373{
1374 DECLARE_COMPLETION_ONSTACK(done);
1375 struct wb_writeback_work work = {
1376 .sb = sb,
1377 .sync_mode = WB_SYNC_ALL,
1378 .nr_pages = LONG_MAX,
1379 .range_cyclic = 0,
1380 .done = &done,
1381 .reason = WB_REASON_SYNC,
1382 .for_sync = 1,
1383 };
1384
1385 /* Nothing to do? */
1386 if (sb->s_bdi == &noop_backing_dev_info)
1387 return;
1388 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1389
1390 bdi_queue_work(sb->s_bdi, &work);
1391 wait_for_completion(&done);
1392
1393 wait_sb_inodes(sb);
1394}
1395EXPORT_SYMBOL(sync_inodes_sb);
1396
1397/**
1398 * write_inode_now - write an inode to disk
1399 * @inode: inode to write to disk
1400 * @sync: whether the write should be synchronous or not
1401 *
1402 * This function commits an inode to disk immediately if it is dirty. This is
1403 * primarily needed by knfsd.
1404 *
1405 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1406 */
1407int write_inode_now(struct inode *inode, int sync)
1408{
1409 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1410 struct writeback_control wbc = {
1411 .nr_to_write = LONG_MAX,
1412 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1413 .range_start = 0,
1414 .range_end = LLONG_MAX,
1415 };
1416
1417 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1418 wbc.nr_to_write = 0;
1419
1420 might_sleep();
1421 return writeback_single_inode(inode, wb, &wbc);
1422}
1423EXPORT_SYMBOL(write_inode_now);
1424
1425/**
1426 * sync_inode - write an inode and its pages to disk.
1427 * @inode: the inode to sync
1428 * @wbc: controls the writeback mode
1429 *
1430 * sync_inode() will write an inode and its pages to disk. It will also
1431 * correctly update the inode on its superblock's dirty inode lists and will
1432 * update inode->i_state.
1433 *
1434 * The caller must have a ref on the inode.
1435 */
1436int sync_inode(struct inode *inode, struct writeback_control *wbc)
1437{
1438 return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1439}
1440EXPORT_SYMBOL(sync_inode);
1441
1442/**
1443 * sync_inode_metadata - write an inode to disk
1444 * @inode: the inode to sync
1445 * @wait: wait for I/O to complete.
1446 *
1447 * Write an inode to disk and adjust its dirty state after completion.
1448 *
1449 * Note: only writes the actual inode, no associated data or other metadata.
1450 */
1451int sync_inode_metadata(struct inode *inode, int wait)
1452{
1453 struct writeback_control wbc = {
1454 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1455 .nr_to_write = 0, /* metadata-only */
1456 };
1457
1458 return sync_inode(inode, &wbc);
1459}
1460EXPORT_SYMBOL(sync_inode_metadata);