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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 : : */
42 : : struct wb_writeback_work {
43 : : long nr_pages;
44 : : struct super_block *sb;
45 : : unsigned long *older_than_this;
46 : : enum writeback_sync_modes sync_mode;
47 : : unsigned int tagged_writepages:1;
48 : : unsigned int for_kupdate:1;
49 : : unsigned int range_cyclic:1;
50 : : unsigned int for_background:1;
51 : : unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
52 : : unsigned int auto_free:1; /* free on completion */
53 : : enum wb_reason reason; /* why was writeback initiated? */
54 : :
55 : : struct list_head list; /* pending work list */
56 : : struct wb_completion *done; /* set if the caller waits */
57 : : };
58 : :
59 : : /*
60 : : * If an inode is constantly having its pages dirtied, but then the
61 : : * updates stop dirtytime_expire_interval seconds in the past, it's
62 : : * possible for the worst case time between when an inode has its
63 : : * timestamps updated and when they finally get written out to be two
64 : : * dirtytime_expire_intervals. We set the default to 12 hours (in
65 : : * seconds), which means most of the time inodes will have their
66 : : * timestamps written to disk after 12 hours, but in the worst case a
67 : : * few inodes might not their timestamps updated for 24 hours.
68 : : */
69 : : unsigned int dirtytime_expire_interval = 12 * 60 * 60;
70 : :
71 : : static inline struct inode *wb_inode(struct list_head *head)
72 : : {
73 : 44130 : return list_entry(head, struct inode, i_io_list);
74 : : }
75 : :
76 : : /*
77 : : * Include the creation of the trace points after defining the
78 : : * wb_writeback_work structure and inline functions so that the definition
79 : : * remains local to this file.
80 : : */
81 : : #define CREATE_TRACE_POINTS
82 : : #include <trace/events/writeback.h>
83 : :
84 : : EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
85 : :
86 : 250145 : static bool wb_io_lists_populated(struct bdi_writeback *wb)
87 : : {
88 [ + + ]: 250145 : if (wb_has_dirty_io(wb)) {
89 : : return false;
90 : : } else {
91 : 788 : set_bit(WB_has_dirty_io, &wb->state);
92 [ - + # # ]: 788 : WARN_ON_ONCE(!wb->avg_write_bandwidth);
93 : 1576 : atomic_long_add(wb->avg_write_bandwidth,
94 : 788 : &wb->bdi->tot_write_bandwidth);
95 : 788 : return true;
96 : : }
97 : : }
98 : :
99 : 65851 : static void wb_io_lists_depopulated(struct bdi_writeback *wb)
100 : : {
101 [ + - + + : 155008 : if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) &&
+ + ]
102 [ + - ]: 24054 : list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) {
103 : 374 : clear_bit(WB_has_dirty_io, &wb->state);
104 [ - + # # ]: 748 : WARN_ON_ONCE(atomic_long_sub_return(wb->avg_write_bandwidth,
105 : : &wb->bdi->tot_write_bandwidth) < 0);
106 : : }
107 : 65851 : }
108 : :
109 : : /**
110 : : * inode_io_list_move_locked - move an inode onto a bdi_writeback IO list
111 : : * @inode: inode to be moved
112 : : * @wb: target bdi_writeback
113 : : * @head: one of @wb->b_{dirty|io|more_io|dirty_time}
114 : : *
115 : : * Move @inode->i_io_list to @list of @wb and set %WB_has_dirty_io.
116 : : * Returns %true if @inode is the first occupant of the !dirty_time IO
117 : : * lists; otherwise, %false.
118 : : */
119 : 248171 : static bool inode_io_list_move_locked(struct inode *inode,
120 : : struct bdi_writeback *wb,
121 : : struct list_head *head)
122 : : {
123 [ - + ]: 248171 : assert_spin_locked(&wb->list_lock);
124 : :
125 : 248171 : list_move(&inode->i_io_list, head);
126 : :
127 : : /* dirty_time doesn't count as dirty_io until expiration */
128 [ + - ]: 248171 : if (head != &wb->b_dirty_time)
129 : 248171 : return wb_io_lists_populated(wb);
130 : :
131 : 0 : wb_io_lists_depopulated(wb);
132 : 0 : return false;
133 : : }
134 : :
135 : : /**
136 : : * inode_io_list_del_locked - remove an inode from its bdi_writeback IO list
137 : : * @inode: inode to be removed
138 : : * @wb: bdi_writeback @inode is being removed from
139 : : *
140 : : * Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and
141 : : * clear %WB_has_dirty_io if all are empty afterwards.
142 : : */
143 : 65851 : static void inode_io_list_del_locked(struct inode *inode,
144 : : struct bdi_writeback *wb)
145 : : {
146 [ - + ]: 65851 : assert_spin_locked(&wb->list_lock);
147 : :
148 : 65851 : list_del_init(&inode->i_io_list);
149 : 65851 : wb_io_lists_depopulated(wb);
150 : 65851 : }
151 : :
152 : 207 : static void wb_wakeup(struct bdi_writeback *wb)
153 : : {
154 : : spin_lock_bh(&wb->work_lock);
155 [ + - ]: 207 : if (test_bit(WB_registered, &wb->state))
156 : 207 : mod_delayed_work(bdi_wq, &wb->dwork, 0);
157 : : spin_unlock_bh(&wb->work_lock);
158 : 207 : }
159 : :
160 : 225 : static void finish_writeback_work(struct bdi_writeback *wb,
161 : : struct wb_writeback_work *work)
162 : : {
163 : 225 : struct wb_completion *done = work->done;
164 : :
165 [ + - ]: 225 : if (work->auto_free)
166 : 225 : kfree(work);
167 [ + - ]: 225 : if (done) {
168 : 225 : wait_queue_head_t *waitq = done->waitq;
169 : :
170 : : /* @done can't be accessed after the following dec */
171 [ + - ]: 450 : if (atomic_dec_and_test(&done->cnt))
172 : 225 : wake_up_all(waitq);
173 : : }
174 : 225 : }
175 : :
176 : 225 : static void wb_queue_work(struct bdi_writeback *wb,
177 : : struct wb_writeback_work *work)
178 : : {
179 : 225 : trace_writeback_queue(wb, work);
180 : :
181 [ + - ]: 225 : if (work->done)
182 : 225 : atomic_inc(&work->done->cnt);
183 : :
184 : : spin_lock_bh(&wb->work_lock);
185 : :
186 [ + - ]: 225 : if (test_bit(WB_registered, &wb->state)) {
187 : 225 : list_add_tail(&work->list, &wb->work_list);
188 : 225 : mod_delayed_work(bdi_wq, &wb->dwork, 0);
189 : : } else
190 : 0 : finish_writeback_work(wb, work);
191 : :
192 : : spin_unlock_bh(&wb->work_lock);
193 : 225 : }
194 : :
195 : : /**
196 : : * wb_wait_for_completion - wait for completion of bdi_writeback_works
197 : : * @done: target wb_completion
198 : : *
199 : : * Wait for one or more work items issued to @bdi with their ->done field
200 : : * set to @done, which should have been initialized with
201 : : * DEFINE_WB_COMPLETION(). This function returns after all such work items
202 : : * are completed. Work items which are waited upon aren't freed
203 : : * automatically on completion.
204 : : */
205 : 414 : void wb_wait_for_completion(struct wb_completion *done)
206 : : {
207 : 414 : atomic_dec(&done->cnt); /* put down the initial count */
208 [ + + + + ]: 1278 : wait_event(*done->waitq, !atomic_read(&done->cnt));
209 : 414 : }
210 : :
211 : : #ifdef CONFIG_CGROUP_WRITEBACK
212 : :
213 : : /*
214 : : * Parameters for foreign inode detection, see wbc_detach_inode() to see
215 : : * how they're used.
216 : : *
217 : : * These paramters are inherently heuristical as the detection target
218 : : * itself is fuzzy. All we want to do is detaching an inode from the
219 : : * current owner if it's being written to by some other cgroups too much.
220 : : *
221 : : * The current cgroup writeback is built on the assumption that multiple
222 : : * cgroups writing to the same inode concurrently is very rare and a mode
223 : : * of operation which isn't well supported. As such, the goal is not
224 : : * taking too long when a different cgroup takes over an inode while
225 : : * avoiding too aggressive flip-flops from occasional foreign writes.
226 : : *
227 : : * We record, very roughly, 2s worth of IO time history and if more than
228 : : * half of that is foreign, trigger the switch. The recording is quantized
229 : : * to 16 slots. To avoid tiny writes from swinging the decision too much,
230 : : * writes smaller than 1/8 of avg size are ignored.
231 : : */
232 : : #define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */
233 : : #define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */
234 : : #define WB_FRN_TIME_CUT_DIV 8 /* ignore rounds < avg / 8 */
235 : : #define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */
236 : :
237 : : #define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */
238 : : #define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS)
239 : : /* each slot's duration is 2s / 16 */
240 : : #define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2)
241 : : /* if foreign slots >= 8, switch */
242 : : #define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1)
243 : : /* one round can affect upto 5 slots */
244 : : #define WB_FRN_MAX_IN_FLIGHT 1024 /* don't queue too many concurrently */
245 : :
246 : : static atomic_t isw_nr_in_flight = ATOMIC_INIT(0);
247 : : static struct workqueue_struct *isw_wq;
248 : :
249 : 368975 : void __inode_attach_wb(struct inode *inode, struct page *page)
250 : : {
251 : 368975 : struct backing_dev_info *bdi = inode_to_bdi(inode);
252 : : struct bdi_writeback *wb = NULL;
253 : :
254 [ - + ]: 368663 : if (inode_cgwb_enabled(inode)) {
255 : : struct cgroup_subsys_state *memcg_css;
256 : :
257 [ # # ]: 0 : if (page) {
258 : 0 : memcg_css = mem_cgroup_css_from_page(page);
259 : 0 : wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
260 : : } else {
261 : : /* must pin memcg_css, see wb_get_create() */
262 : 0 : memcg_css = task_get_css(current, memory_cgrp_id);
263 : 0 : wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
264 : : css_put(memcg_css);
265 : : }
266 : : }
267 : :
268 [ + - ]: 368875 : if (!wb)
269 : 368875 : wb = &bdi->wb;
270 : :
271 : : /*
272 : : * There may be multiple instances of this function racing to
273 : : * update the same inode. Use cmpxchg() to tell the winner.
274 : : */
275 [ - + ]: 368875 : if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
276 : 0 : wb_put(wb);
277 : 368901 : }
278 : : EXPORT_SYMBOL_GPL(__inode_attach_wb);
279 : :
280 : : /**
281 : : * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
282 : : * @inode: inode of interest with i_lock held
283 : : *
284 : : * Returns @inode's wb with its list_lock held. @inode->i_lock must be
285 : : * held on entry and is released on return. The returned wb is guaranteed
286 : : * to stay @inode's associated wb until its list_lock is released.
287 : : */
288 : : static struct bdi_writeback *
289 : 313139 : locked_inode_to_wb_and_lock_list(struct inode *inode)
290 : : __releases(&inode->i_lock)
291 : : __acquires(&wb->list_lock)
292 : : {
293 : : while (true) {
294 : : struct bdi_writeback *wb = inode_to_wb(inode);
295 : :
296 : : /*
297 : : * inode_to_wb() association is protected by both
298 : : * @inode->i_lock and @wb->list_lock but list_lock nests
299 : : * outside i_lock. Drop i_lock and verify that the
300 : : * association hasn't changed after acquiring list_lock.
301 : : */
302 : : wb_get(wb);
303 : : spin_unlock(&inode->i_lock);
304 : : spin_lock(&wb->list_lock);
305 : :
306 : : /* i_wb may have changed inbetween, can't use inode_to_wb() */
307 [ + - ]: 313140 : if (likely(wb == inode->i_wb)) {
308 : 313140 : wb_put(wb); /* @inode already has ref */
309 : 313140 : return wb;
310 : : }
311 : :
312 : : spin_unlock(&wb->list_lock);
313 : 0 : wb_put(wb);
314 : 0 : cpu_relax();
315 : : spin_lock(&inode->i_lock);
316 : : }
317 : : }
318 : :
319 : : /**
320 : : * inode_to_wb_and_lock_list - determine an inode's wb and lock it
321 : : * @inode: inode of interest
322 : : *
323 : : * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
324 : : * on entry.
325 : : */
326 : : static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
327 : : __acquires(&wb->list_lock)
328 : : {
329 : : spin_lock(&inode->i_lock);
330 : 66286 : return locked_inode_to_wb_and_lock_list(inode);
331 : : }
332 : :
333 : : struct inode_switch_wbs_context {
334 : : struct inode *inode;
335 : : struct bdi_writeback *new_wb;
336 : :
337 : : struct rcu_head rcu_head;
338 : : struct work_struct work;
339 : : };
340 : :
341 : : static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi)
342 : : {
343 : 414 : down_write(&bdi->wb_switch_rwsem);
344 : : }
345 : :
346 : : static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi)
347 : : {
348 : 414 : up_write(&bdi->wb_switch_rwsem);
349 : : }
350 : :
351 : 0 : static void inode_switch_wbs_work_fn(struct work_struct *work)
352 : : {
353 : : struct inode_switch_wbs_context *isw =
354 : 0 : container_of(work, struct inode_switch_wbs_context, work);
355 : 0 : struct inode *inode = isw->inode;
356 : 0 : struct backing_dev_info *bdi = inode_to_bdi(inode);
357 : 0 : struct address_space *mapping = inode->i_mapping;
358 : 0 : struct bdi_writeback *old_wb = inode->i_wb;
359 : 0 : struct bdi_writeback *new_wb = isw->new_wb;
360 : 0 : XA_STATE(xas, &mapping->i_pages, 0);
361 : : struct page *page;
362 : : bool switched = false;
363 : :
364 : : /*
365 : : * If @inode switches cgwb membership while sync_inodes_sb() is
366 : : * being issued, sync_inodes_sb() might miss it. Synchronize.
367 : : */
368 : 0 : down_read(&bdi->wb_switch_rwsem);
369 : :
370 : : /*
371 : : * By the time control reaches here, RCU grace period has passed
372 : : * since I_WB_SWITCH assertion and all wb stat update transactions
373 : : * between unlocked_inode_to_wb_begin/end() are guaranteed to be
374 : : * synchronizing against the i_pages lock.
375 : : *
376 : : * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock
377 : : * gives us exclusion against all wb related operations on @inode
378 : : * including IO list manipulations and stat updates.
379 : : */
380 [ # # ]: 0 : if (old_wb < new_wb) {
381 : : spin_lock(&old_wb->list_lock);
382 : 0 : spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING);
383 : : } else {
384 : : spin_lock(&new_wb->list_lock);
385 : 0 : spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING);
386 : : }
387 : : spin_lock(&inode->i_lock);
388 : : xa_lock_irq(&mapping->i_pages);
389 : :
390 : : /*
391 : : * Once I_FREEING is visible under i_lock, the eviction path owns
392 : : * the inode and we shouldn't modify ->i_io_list.
393 : : */
394 [ # # ]: 0 : if (unlikely(inode->i_state & I_FREEING))
395 : : goto skip_switch;
396 : :
397 : 0 : trace_inode_switch_wbs(inode, old_wb, new_wb);
398 : :
399 : : /*
400 : : * Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points
401 : : * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
402 : : * pages actually under writeback.
403 : : */
404 [ # # ]: 0 : xas_for_each_marked(&xas, page, ULONG_MAX, PAGECACHE_TAG_DIRTY) {
405 [ # # ]: 0 : if (PageDirty(page)) {
406 : : dec_wb_stat(old_wb, WB_RECLAIMABLE);
407 : : inc_wb_stat(new_wb, WB_RECLAIMABLE);
408 : : }
409 : : }
410 : :
411 : : xas_set(&xas, 0);
412 [ # # ]: 0 : xas_for_each_marked(&xas, page, ULONG_MAX, PAGECACHE_TAG_WRITEBACK) {
413 [ # # # # ]: 0 : WARN_ON_ONCE(!PageWriteback(page));
414 : : dec_wb_stat(old_wb, WB_WRITEBACK);
415 : : inc_wb_stat(new_wb, WB_WRITEBACK);
416 : : }
417 : :
418 : : wb_get(new_wb);
419 : :
420 : : /*
421 : : * Transfer to @new_wb's IO list if necessary. The specific list
422 : : * @inode was on is ignored and the inode is put on ->b_dirty which
423 : : * is always correct including from ->b_dirty_time. The transfer
424 : : * preserves @inode->dirtied_when ordering.
425 : : */
426 [ # # ]: 0 : if (!list_empty(&inode->i_io_list)) {
427 : : struct inode *pos;
428 : :
429 : 0 : inode_io_list_del_locked(inode, old_wb);
430 : 0 : inode->i_wb = new_wb;
431 [ # # ]: 0 : list_for_each_entry(pos, &new_wb->b_dirty, i_io_list)
432 [ # # ]: 0 : if (time_after_eq(inode->dirtied_when,
433 : : pos->dirtied_when))
434 : : break;
435 : 0 : inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev);
436 : : } else {
437 : 0 : inode->i_wb = new_wb;
438 : : }
439 : :
440 : : /* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */
441 : 0 : inode->i_wb_frn_winner = 0;
442 : 0 : inode->i_wb_frn_avg_time = 0;
443 : 0 : inode->i_wb_frn_history = 0;
444 : : switched = true;
445 : : skip_switch:
446 : : /*
447 : : * Paired with load_acquire in unlocked_inode_to_wb_begin() and
448 : : * ensures that the new wb is visible if they see !I_WB_SWITCH.
449 : : */
450 : 0 : smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH);
451 : :
452 : : xa_unlock_irq(&mapping->i_pages);
453 : : spin_unlock(&inode->i_lock);
454 : : spin_unlock(&new_wb->list_lock);
455 : : spin_unlock(&old_wb->list_lock);
456 : :
457 : 0 : up_read(&bdi->wb_switch_rwsem);
458 : :
459 [ # # ]: 0 : if (switched) {
460 : 0 : wb_wakeup(new_wb);
461 : 0 : wb_put(old_wb);
462 : : }
463 : 0 : wb_put(new_wb);
464 : :
465 : 0 : iput(inode);
466 : 0 : kfree(isw);
467 : :
468 : : atomic_dec(&isw_nr_in_flight);
469 : 0 : }
470 : :
471 : 0 : static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head)
472 : : {
473 : : struct inode_switch_wbs_context *isw = container_of(rcu_head,
474 : : struct inode_switch_wbs_context, rcu_head);
475 : :
476 : : /* needs to grab bh-unsafe locks, bounce to work item */
477 : 0 : INIT_WORK(&isw->work, inode_switch_wbs_work_fn);
478 : 0 : queue_work(isw_wq, &isw->work);
479 : 0 : }
480 : :
481 : : /**
482 : : * inode_switch_wbs - change the wb association of an inode
483 : : * @inode: target inode
484 : : * @new_wb_id: ID of the new wb
485 : : *
486 : : * Switch @inode's wb association to the wb identified by @new_wb_id. The
487 : : * switching is performed asynchronously and may fail silently.
488 : : */
489 : 0 : static void inode_switch_wbs(struct inode *inode, int new_wb_id)
490 : : {
491 : 0 : struct backing_dev_info *bdi = inode_to_bdi(inode);
492 : : struct cgroup_subsys_state *memcg_css;
493 : : struct inode_switch_wbs_context *isw;
494 : :
495 : : /* noop if seems to be already in progress */
496 [ # # ]: 0 : if (inode->i_state & I_WB_SWITCH)
497 : : return;
498 : :
499 : : /* avoid queueing a new switch if too many are already in flight */
500 [ # # ]: 0 : if (atomic_read(&isw_nr_in_flight) > WB_FRN_MAX_IN_FLIGHT)
501 : : return;
502 : :
503 : 0 : isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
504 [ # # ]: 0 : if (!isw)
505 : : return;
506 : :
507 : : /* find and pin the new wb */
508 : : rcu_read_lock();
509 : 0 : memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys);
510 [ # # ]: 0 : if (memcg_css)
511 : 0 : isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
512 : : rcu_read_unlock();
513 [ # # ]: 0 : if (!isw->new_wb)
514 : : goto out_free;
515 : :
516 : : /* while holding I_WB_SWITCH, no one else can update the association */
517 : : spin_lock(&inode->i_lock);
518 [ # # # # ]: 0 : if (!(inode->i_sb->s_flags & SB_ACTIVE) ||
519 [ # # ]: 0 : inode->i_state & (I_WB_SWITCH | I_FREEING) ||
520 : 0 : inode_to_wb(inode) == isw->new_wb) {
521 : : spin_unlock(&inode->i_lock);
522 : : goto out_free;
523 : : }
524 : 0 : inode->i_state |= I_WB_SWITCH;
525 : 0 : __iget(inode);
526 : : spin_unlock(&inode->i_lock);
527 : :
528 : 0 : isw->inode = inode;
529 : :
530 : : /*
531 : : * In addition to synchronizing among switchers, I_WB_SWITCH tells
532 : : * the RCU protected stat update paths to grab the i_page
533 : : * lock so that stat transfer can synchronize against them.
534 : : * Let's continue after I_WB_SWITCH is guaranteed to be visible.
535 : : */
536 : 0 : call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
537 : :
538 : : atomic_inc(&isw_nr_in_flight);
539 : : return;
540 : :
541 : : out_free:
542 [ # # ]: 0 : if (isw->new_wb)
543 : 0 : wb_put(isw->new_wb);
544 : 0 : kfree(isw);
545 : : }
546 : :
547 : : /**
548 : : * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it
549 : : * @wbc: writeback_control of interest
550 : : * @inode: target inode
551 : : *
552 : : * @inode is locked and about to be written back under the control of @wbc.
553 : : * Record @inode's writeback context into @wbc and unlock the i_lock. On
554 : : * writeback completion, wbc_detach_inode() should be called. This is used
555 : : * to track the cgroup writeback context.
556 : : */
557 : 41661 : void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
558 : : struct inode *inode)
559 : : {
560 [ + - ]: 41661 : if (!inode_cgwb_enabled(inode)) {
561 : : spin_unlock(&inode->i_lock);
562 : 41661 : return;
563 : : }
564 : :
565 : 0 : wbc->wb = inode_to_wb(inode);
566 : 0 : wbc->inode = inode;
567 : :
568 : 0 : wbc->wb_id = wbc->wb->memcg_css->id;
569 : 0 : wbc->wb_lcand_id = inode->i_wb_frn_winner;
570 : 0 : wbc->wb_tcand_id = 0;
571 : 0 : wbc->wb_bytes = 0;
572 : 0 : wbc->wb_lcand_bytes = 0;
573 : 0 : wbc->wb_tcand_bytes = 0;
574 : :
575 : : wb_get(wbc->wb);
576 : : spin_unlock(&inode->i_lock);
577 : :
578 : : /*
579 : : * A dying wb indicates that either the blkcg associated with the
580 : : * memcg changed or the associated memcg is dying. In the first
581 : : * case, a replacement wb should already be available and we should
582 : : * refresh the wb immediately. In the second case, trying to
583 : : * refresh will keep failing.
584 : : */
585 [ # # # # ]: 0 : if (unlikely(wb_dying(wbc->wb) && !css_is_dying(wbc->wb->memcg_css)))
586 : 0 : inode_switch_wbs(inode, wbc->wb_id);
587 : : }
588 : : EXPORT_SYMBOL_GPL(wbc_attach_and_unlock_inode);
589 : :
590 : : /**
591 : : * wbc_detach_inode - disassociate wbc from inode and perform foreign detection
592 : : * @wbc: writeback_control of the just finished writeback
593 : : *
594 : : * To be called after a writeback attempt of an inode finishes and undoes
595 : : * wbc_attach_and_unlock_inode(). Can be called under any context.
596 : : *
597 : : * As concurrent write sharing of an inode is expected to be very rare and
598 : : * memcg only tracks page ownership on first-use basis severely confining
599 : : * the usefulness of such sharing, cgroup writeback tracks ownership
600 : : * per-inode. While the support for concurrent write sharing of an inode
601 : : * is deemed unnecessary, an inode being written to by different cgroups at
602 : : * different points in time is a lot more common, and, more importantly,
603 : : * charging only by first-use can too readily lead to grossly incorrect
604 : : * behaviors (single foreign page can lead to gigabytes of writeback to be
605 : : * incorrectly attributed).
606 : : *
607 : : * To resolve this issue, cgroup writeback detects the majority dirtier of
608 : : * an inode and transfers the ownership to it. To avoid unnnecessary
609 : : * oscillation, the detection mechanism keeps track of history and gives
610 : : * out the switch verdict only if the foreign usage pattern is stable over
611 : : * a certain amount of time and/or writeback attempts.
612 : : *
613 : : * On each writeback attempt, @wbc tries to detect the majority writer
614 : : * using Boyer-Moore majority vote algorithm. In addition to the byte
615 : : * count from the majority voting, it also counts the bytes written for the
616 : : * current wb and the last round's winner wb (max of last round's current
617 : : * wb, the winner from two rounds ago, and the last round's majority
618 : : * candidate). Keeping track of the historical winner helps the algorithm
619 : : * to semi-reliably detect the most active writer even when it's not the
620 : : * absolute majority.
621 : : *
622 : : * Once the winner of the round is determined, whether the winner is
623 : : * foreign or not and how much IO time the round consumed is recorded in
624 : : * inode->i_wb_frn_history. If the amount of recorded foreign IO time is
625 : : * over a certain threshold, the switch verdict is given.
626 : : */
627 : 41661 : void wbc_detach_inode(struct writeback_control *wbc)
628 : : {
629 : 41661 : struct bdi_writeback *wb = wbc->wb;
630 : 41661 : struct inode *inode = wbc->inode;
631 : : unsigned long avg_time, max_bytes, max_time;
632 : : u16 history;
633 : : int max_id;
634 : :
635 [ - + ]: 41661 : if (!wb)
636 : 41661 : return;
637 : :
638 : 0 : history = inode->i_wb_frn_history;
639 : 0 : avg_time = inode->i_wb_frn_avg_time;
640 : :
641 : : /* pick the winner of this round */
642 [ # # # # ]: 0 : if (wbc->wb_bytes >= wbc->wb_lcand_bytes &&
643 : 0 : wbc->wb_bytes >= wbc->wb_tcand_bytes) {
644 : 0 : max_id = wbc->wb_id;
645 : 0 : max_bytes = wbc->wb_bytes;
646 [ # # ]: 0 : } else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) {
647 : 0 : max_id = wbc->wb_lcand_id;
648 : : max_bytes = wbc->wb_lcand_bytes;
649 : : } else {
650 : 0 : max_id = wbc->wb_tcand_id;
651 : : max_bytes = wbc->wb_tcand_bytes;
652 : : }
653 : :
654 : : /*
655 : : * Calculate the amount of IO time the winner consumed and fold it
656 : : * into the running average kept per inode. If the consumed IO
657 : : * time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
658 : : * deciding whether to switch or not. This is to prevent one-off
659 : : * small dirtiers from skewing the verdict.
660 : : */
661 : 0 : max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT,
662 : : wb->avg_write_bandwidth);
663 [ # # ]: 0 : if (avg_time)
664 : 0 : avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) -
665 : 0 : (avg_time >> WB_FRN_TIME_AVG_SHIFT);
666 : : else
667 : : avg_time = max_time; /* immediate catch up on first run */
668 : :
669 [ # # ]: 0 : if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) {
670 : : int slots;
671 : :
672 : : /*
673 : : * The switch verdict is reached if foreign wb's consume
674 : : * more than a certain proportion of IO time in a
675 : : * WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
676 : : * history mask where each bit represents one sixteenth of
677 : : * the period. Determine the number of slots to shift into
678 : : * history from @max_time.
679 : : */
680 : 0 : slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT),
681 : : (unsigned long)WB_FRN_HIST_MAX_SLOTS);
682 : 0 : history <<= slots;
683 [ # # ]: 0 : if (wbc->wb_id != max_id)
684 : 0 : history |= (1U << slots) - 1;
685 : :
686 [ # # ]: 0 : if (history)
687 : 0 : trace_inode_foreign_history(inode, wbc, history);
688 : :
689 : : /*
690 : : * Switch if the current wb isn't the consistent winner.
691 : : * If there are multiple closely competing dirtiers, the
692 : : * inode may switch across them repeatedly over time, which
693 : : * is okay. The main goal is avoiding keeping an inode on
694 : : * the wrong wb for an extended period of time.
695 : : */
696 [ # # # # ]: 0 : if (hweight32(history) > WB_FRN_HIST_THR_SLOTS)
697 : 0 : inode_switch_wbs(inode, max_id);
698 : : }
699 : :
700 : : /*
701 : : * Multiple instances of this function may race to update the
702 : : * following fields but we don't mind occassional inaccuracies.
703 : : */
704 : 0 : inode->i_wb_frn_winner = max_id;
705 : 0 : inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX);
706 : 0 : inode->i_wb_frn_history = history;
707 : :
708 : 0 : wb_put(wbc->wb);
709 : 0 : wbc->wb = NULL;
710 : : }
711 : : EXPORT_SYMBOL_GPL(wbc_detach_inode);
712 : :
713 : : /**
714 : : * wbc_account_cgroup_owner - account writeback to update inode cgroup ownership
715 : : * @wbc: writeback_control of the writeback in progress
716 : : * @page: page being written out
717 : : * @bytes: number of bytes being written out
718 : : *
719 : : * @bytes from @page are about to written out during the writeback
720 : : * controlled by @wbc. Keep the book for foreign inode detection. See
721 : : * wbc_detach_inode().
722 : : */
723 : 95396 : void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
724 : : size_t bytes)
725 : : {
726 : : struct cgroup_subsys_state *css;
727 : : int id;
728 : :
729 : : /*
730 : : * pageout() path doesn't attach @wbc to the inode being written
731 : : * out. This is intentional as we don't want the function to block
732 : : * behind a slow cgroup. Ultimately, we want pageout() to kick off
733 : : * regular writeback instead of writing things out itself.
734 : : */
735 [ - + # # ]: 95396 : if (!wbc->wb || wbc->no_cgroup_owner)
736 : : return;
737 : :
738 : 0 : css = mem_cgroup_css_from_page(page);
739 : : /* dead cgroups shouldn't contribute to inode ownership arbitration */
740 [ # # ]: 0 : if (!(css->flags & CSS_ONLINE))
741 : : return;
742 : :
743 : 0 : id = css->id;
744 : :
745 [ # # ]: 0 : if (id == wbc->wb_id) {
746 : 0 : wbc->wb_bytes += bytes;
747 : 0 : return;
748 : : }
749 : :
750 [ # # ]: 0 : if (id == wbc->wb_lcand_id)
751 : 0 : wbc->wb_lcand_bytes += bytes;
752 : :
753 : : /* Boyer-Moore majority vote algorithm */
754 [ # # ]: 0 : if (!wbc->wb_tcand_bytes)
755 : 0 : wbc->wb_tcand_id = id;
756 [ # # ]: 0 : if (id == wbc->wb_tcand_id)
757 : 0 : wbc->wb_tcand_bytes += bytes;
758 : : else
759 : 0 : wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes);
760 : : }
761 : : EXPORT_SYMBOL_GPL(wbc_account_cgroup_owner);
762 : :
763 : : /**
764 : : * inode_congested - test whether an inode is congested
765 : : * @inode: inode to test for congestion (may be NULL)
766 : : * @cong_bits: mask of WB_[a]sync_congested bits to test
767 : : *
768 : : * Tests whether @inode is congested. @cong_bits is the mask of congestion
769 : : * bits to test and the return value is the mask of set bits.
770 : : *
771 : : * If cgroup writeback is enabled for @inode, the congestion state is
772 : : * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
773 : : * associated with @inode is congested; otherwise, the root wb's congestion
774 : : * state is used.
775 : : *
776 : : * @inode is allowed to be NULL as this function is often called on
777 : : * mapping->host which is NULL for the swapper space.
778 : : */
779 : 211510 : int inode_congested(struct inode *inode, int cong_bits)
780 : : {
781 : : /*
782 : : * Once set, ->i_wb never becomes NULL while the inode is alive.
783 : : * Start transaction iff ->i_wb is visible.
784 : : */
785 [ + + - + ]: 422168 : if (inode && inode_to_wb_is_valid(inode)) {
786 : : struct bdi_writeback *wb;
787 : 0 : struct wb_lock_cookie lock_cookie = {};
788 : : bool congested;
789 : :
790 : 0 : wb = unlocked_inode_to_wb_begin(inode, &lock_cookie);
791 : 0 : congested = wb_congested(wb, cong_bits);
792 : : unlocked_inode_to_wb_end(inode, &lock_cookie);
793 : 0 : return congested;
794 : : }
795 : :
796 : 422954 : return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
797 : : }
798 : : EXPORT_SYMBOL_GPL(inode_congested);
799 : :
800 : : /**
801 : : * wb_split_bdi_pages - split nr_pages to write according to bandwidth
802 : : * @wb: target bdi_writeback to split @nr_pages to
803 : : * @nr_pages: number of pages to write for the whole bdi
804 : : *
805 : : * Split @wb's portion of @nr_pages according to @wb's write bandwidth in
806 : : * relation to the total write bandwidth of all wb's w/ dirty inodes on
807 : : * @wb->bdi.
808 : : */
809 : 432 : static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
810 : : {
811 : 432 : unsigned long this_bw = wb->avg_write_bandwidth;
812 : 864 : unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);
813 : :
814 [ + + ]: 432 : if (nr_pages == LONG_MAX)
815 : : return LONG_MAX;
816 : :
817 : : /*
818 : : * This may be called on clean wb's and proportional distribution
819 : : * may not make sense, just use the original @nr_pages in those
820 : : * cases. In general, we wanna err on the side of writing more.
821 : : */
822 [ - + ]: 207 : if (!tot_bw || this_bw >= tot_bw)
823 : : return nr_pages;
824 : : else
825 [ # # # # : 0 : return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
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826 : : }
827 : :
828 : : /**
829 : : * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
830 : : * @bdi: target backing_dev_info
831 : : * @base_work: wb_writeback_work to issue
832 : : * @skip_if_busy: skip wb's which already have writeback in progress
833 : : *
834 : : * Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
835 : : * have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
836 : : * distributed to the busy wbs according to each wb's proportion in the
837 : : * total active write bandwidth of @bdi.
838 : : */
839 : 414 : static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
840 : : struct wb_writeback_work *base_work,
841 : : bool skip_if_busy)
842 : : {
843 : : struct bdi_writeback *last_wb = NULL;
844 : 414 : struct bdi_writeback *wb = list_entry(&bdi->wb_list,
845 : : struct bdi_writeback, bdi_node);
846 : :
847 : 414 : might_sleep();
848 : : restart:
849 : : rcu_read_lock();
850 [ + + ]: 828 : list_for_each_entry_continue_rcu(wb, &bdi->wb_list, bdi_node) {
851 : 414 : DEFINE_WB_COMPLETION(fallback_work_done, bdi);
852 : : struct wb_writeback_work fallback_work;
853 : : struct wb_writeback_work *work;
854 : : long nr_pages;
855 : :
856 [ - + ]: 414 : if (last_wb) {
857 : 0 : wb_put(last_wb);
858 : : last_wb = NULL;
859 : : }
860 : :
861 : : /* SYNC_ALL writes out I_DIRTY_TIME too */
862 [ + + + - ]: 603 : if (!wb_has_dirty_io(wb) &&
863 [ + - ]: 378 : (base_work->sync_mode == WB_SYNC_NONE ||
864 : 189 : list_empty(&wb->b_dirty_time)))
865 : 603 : continue;
866 [ - + # # ]: 225 : if (skip_if_busy && writeback_in_progress(wb))
867 : 0 : continue;
868 : :
869 : 225 : nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages);
870 : :
871 : : work = kmalloc(sizeof(*work), GFP_ATOMIC);
872 [ + - ]: 225 : if (work) {
873 : 225 : *work = *base_work;
874 : 225 : work->nr_pages = nr_pages;
875 : 225 : work->auto_free = 1;
876 : 225 : wb_queue_work(wb, work);
877 : 225 : continue;
878 : : }
879 : :
880 : : /* alloc failed, execute synchronously using on-stack fallback */
881 : : work = &fallback_work;
882 : 0 : *work = *base_work;
883 : 0 : work->nr_pages = nr_pages;
884 : 0 : work->auto_free = 0;
885 : 0 : work->done = &fallback_work_done;
886 : :
887 : 0 : wb_queue_work(wb, work);
888 : :
889 : : /*
890 : : * Pin @wb so that it stays on @bdi->wb_list. This allows
891 : : * continuing iteration from @wb after dropping and
892 : : * regrabbing rcu read lock.
893 : : */
894 : : wb_get(wb);
895 : 0 : last_wb = wb;
896 : :
897 : : rcu_read_unlock();
898 : 0 : wb_wait_for_completion(&fallback_work_done);
899 : 0 : goto restart;
900 : : }
901 : : rcu_read_unlock();
902 : :
903 [ - + ]: 414 : if (last_wb)
904 : 0 : wb_put(last_wb);
905 : 414 : }
906 : :
907 : : /**
908 : : * cgroup_writeback_by_id - initiate cgroup writeback from bdi and memcg IDs
909 : : * @bdi_id: target bdi id
910 : : * @memcg_id: target memcg css id
911 : : * @nr: number of pages to write, 0 for best-effort dirty flushing
912 : : * @reason: reason why some writeback work initiated
913 : : * @done: target wb_completion
914 : : *
915 : : * Initiate flush of the bdi_writeback identified by @bdi_id and @memcg_id
916 : : * with the specified parameters.
917 : : */
918 : 0 : int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr,
919 : : enum wb_reason reason, struct wb_completion *done)
920 : : {
921 : : struct backing_dev_info *bdi;
922 : : struct cgroup_subsys_state *memcg_css;
923 : : struct bdi_writeback *wb;
924 : : struct wb_writeback_work *work;
925 : : int ret;
926 : :
927 : : /* lookup bdi and memcg */
928 : 0 : bdi = bdi_get_by_id(bdi_id);
929 [ # # ]: 0 : if (!bdi)
930 : : return -ENOENT;
931 : :
932 : : rcu_read_lock();
933 : 0 : memcg_css = css_from_id(memcg_id, &memory_cgrp_subsys);
934 [ # # # # ]: 0 : if (memcg_css && !css_tryget(memcg_css))
935 : : memcg_css = NULL;
936 : : rcu_read_unlock();
937 [ # # ]: 0 : if (!memcg_css) {
938 : : ret = -ENOENT;
939 : : goto out_bdi_put;
940 : : }
941 : :
942 : : /*
943 : : * And find the associated wb. If the wb isn't there already
944 : : * there's nothing to flush, don't create one.
945 : : */
946 : 0 : wb = wb_get_lookup(bdi, memcg_css);
947 [ # # ]: 0 : if (!wb) {
948 : : ret = -ENOENT;
949 : : goto out_css_put;
950 : : }
951 : :
952 : : /*
953 : : * If @nr is zero, the caller is attempting to write out most of
954 : : * the currently dirty pages. Let's take the current dirty page
955 : : * count and inflate it by 25% which should be large enough to
956 : : * flush out most dirty pages while avoiding getting livelocked by
957 : : * concurrent dirtiers.
958 : : */
959 [ # # ]: 0 : if (!nr) {
960 : : unsigned long filepages, headroom, dirty, writeback;
961 : :
962 : 0 : mem_cgroup_wb_stats(wb, &filepages, &headroom, &dirty,
963 : : &writeback);
964 : 0 : nr = dirty * 10 / 8;
965 : : }
966 : :
967 : : /* issue the writeback work */
968 : 0 : work = kzalloc(sizeof(*work), GFP_NOWAIT | __GFP_NOWARN);
969 [ # # ]: 0 : if (work) {
970 : 0 : work->nr_pages = nr;
971 : 0 : work->sync_mode = WB_SYNC_NONE;
972 : 0 : work->range_cyclic = 1;
973 : 0 : work->reason = reason;
974 : 0 : work->done = done;
975 : 0 : work->auto_free = 1;
976 : 0 : wb_queue_work(wb, work);
977 : : ret = 0;
978 : : } else {
979 : : ret = -ENOMEM;
980 : : }
981 : :
982 : 0 : wb_put(wb);
983 : : out_css_put:
984 : : css_put(memcg_css);
985 : : out_bdi_put:
986 : 0 : bdi_put(bdi);
987 : 0 : return ret;
988 : : }
989 : :
990 : : /**
991 : : * cgroup_writeback_umount - flush inode wb switches for umount
992 : : *
993 : : * This function is called when a super_block is about to be destroyed and
994 : : * flushes in-flight inode wb switches. An inode wb switch goes through
995 : : * RCU and then workqueue, so the two need to be flushed in order to ensure
996 : : * that all previously scheduled switches are finished. As wb switches are
997 : : * rare occurrences and synchronize_rcu() can take a while, perform
998 : : * flushing iff wb switches are in flight.
999 : : */
1000 : 2 : void cgroup_writeback_umount(void)
1001 : : {
1002 [ - + ]: 2 : if (atomic_read(&isw_nr_in_flight)) {
1003 : : /*
1004 : : * Use rcu_barrier() to wait for all pending callbacks to
1005 : : * ensure that all in-flight wb switches are in the workqueue.
1006 : : */
1007 : 0 : rcu_barrier();
1008 : 0 : flush_workqueue(isw_wq);
1009 : : }
1010 : 2 : }
1011 : :
1012 : 207 : static int __init cgroup_writeback_init(void)
1013 : : {
1014 : 207 : isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0);
1015 [ + - ]: 207 : if (!isw_wq)
1016 : : return -ENOMEM;
1017 : 207 : return 0;
1018 : : }
1019 : : fs_initcall(cgroup_writeback_init);
1020 : :
1021 : : #else /* CONFIG_CGROUP_WRITEBACK */
1022 : :
1023 : : static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
1024 : : static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
1025 : :
1026 : : static struct bdi_writeback *
1027 : : locked_inode_to_wb_and_lock_list(struct inode *inode)
1028 : : __releases(&inode->i_lock)
1029 : : __acquires(&wb->list_lock)
1030 : : {
1031 : : struct bdi_writeback *wb = inode_to_wb(inode);
1032 : :
1033 : : spin_unlock(&inode->i_lock);
1034 : : spin_lock(&wb->list_lock);
1035 : : return wb;
1036 : : }
1037 : :
1038 : : static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
1039 : : __acquires(&wb->list_lock)
1040 : : {
1041 : : struct bdi_writeback *wb = inode_to_wb(inode);
1042 : :
1043 : : spin_lock(&wb->list_lock);
1044 : : return wb;
1045 : : }
1046 : :
1047 : : static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
1048 : : {
1049 : : return nr_pages;
1050 : : }
1051 : :
1052 : : static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
1053 : : struct wb_writeback_work *base_work,
1054 : : bool skip_if_busy)
1055 : : {
1056 : : might_sleep();
1057 : :
1058 : : if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
1059 : : base_work->auto_free = 0;
1060 : : wb_queue_work(&bdi->wb, base_work);
1061 : : }
1062 : : }
1063 : :
1064 : : #endif /* CONFIG_CGROUP_WRITEBACK */
1065 : :
1066 : : /*
1067 : : * Add in the number of potentially dirty inodes, because each inode
1068 : : * write can dirty pagecache in the underlying blockdev.
1069 : : */
1070 : 3631 : static unsigned long get_nr_dirty_pages(void)
1071 : : {
1072 : 7262 : return global_node_page_state(NR_FILE_DIRTY) +
1073 : 3631 : global_node_page_state(NR_UNSTABLE_NFS) +
1074 : 3631 : get_nr_dirty_inodes();
1075 : : }
1076 : :
1077 : 207 : static void wb_start_writeback(struct bdi_writeback *wb, enum wb_reason reason)
1078 : : {
1079 [ + - ]: 207 : 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 [ + - + - ]: 414 : if (test_bit(WB_start_all, &wb->state) ||
1091 : 207 : test_and_set_bit(WB_start_all, &wb->state))
1092 : : return;
1093 : :
1094 : 207 : wb->start_all_reason = reason;
1095 : 207 : 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 : : */
1108 : 0 : void 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 : 0 : trace_writeback_wake_background(wb);
1115 : 0 : wb_wakeup(wb);
1116 : 0 : }
1117 : :
1118 : : /*
1119 : : * Remove the inode from the writeback list it is on.
1120 : : */
1121 : 26210 : void inode_io_list_del(struct inode *inode)
1122 : : {
1123 : : struct bdi_writeback *wb;
1124 : :
1125 : : wb = inode_to_wb_and_lock_list(inode);
1126 : 26210 : inode_io_list_del_locked(inode, wb);
1127 : : spin_unlock(&wb->list_lock);
1128 : 26210 : }
1129 : :
1130 : : /*
1131 : : * mark an inode as under writeback on the sb
1132 : : */
1133 : 17860 : void sb_mark_inode_writeback(struct inode *inode)
1134 : : {
1135 : 17860 : struct super_block *sb = inode->i_sb;
1136 : : unsigned long flags;
1137 : :
1138 [ + - ]: 35720 : if (list_empty(&inode->i_wb_list)) {
1139 : 17860 : spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
1140 [ + - ]: 17860 : if (list_empty(&inode->i_wb_list)) {
1141 : 17860 : list_add_tail(&inode->i_wb_list, &sb->s_inodes_wb);
1142 : 17860 : trace_sb_mark_inode_writeback(inode);
1143 : : }
1144 : : spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
1145 : : }
1146 : 17860 : }
1147 : :
1148 : : /*
1149 : : * clear an inode as under writeback on the sb
1150 : : */
1151 : 17860 : void sb_clear_inode_writeback(struct inode *inode)
1152 : : {
1153 : 17860 : struct super_block *sb = inode->i_sb;
1154 : : unsigned long flags;
1155 : :
1156 [ + - ]: 35720 : if (!list_empty(&inode->i_wb_list)) {
1157 : 17860 : spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
1158 [ + - ]: 17860 : if (!list_empty(&inode->i_wb_list)) {
1159 : : list_del_init(&inode->i_wb_list);
1160 : 17860 : trace_sb_clear_inode_writeback(inode);
1161 : : }
1162 : : spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
1163 : : }
1164 : 17860 : }
1165 : :
1166 : : /*
1167 : : * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
1168 : : * furthest end of its superblock's dirty-inode list.
1169 : : *
1170 : : * Before stamping the inode's ->dirtied_when, we check to see whether it is
1171 : : * already the most-recently-dirtied inode on the b_dirty list. If that is
1172 : : * the case then the inode must have been redirtied while it was being written
1173 : : * out and we don't reset its dirtied_when.
1174 : : */
1175 : 1317 : static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
1176 : : {
1177 [ + + ]: 2634 : if (!list_empty(&wb->b_dirty)) {
1178 : : struct inode *tail;
1179 : :
1180 : 648 : tail = wb_inode(wb->b_dirty.next);
1181 [ + + ]: 648 : if (time_before(inode->dirtied_when, tail->dirtied_when))
1182 : 138 : inode->dirtied_when = jiffies;
1183 : : }
1184 : 1317 : inode_io_list_move_locked(inode, wb, &wb->b_dirty);
1185 : 1317 : }
1186 : :
1187 : : /*
1188 : : * requeue inode for re-scanning after bdi->b_io list is exhausted.
1189 : : */
1190 : : static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
1191 : : {
1192 : 0 : inode_io_list_move_locked(inode, wb, &wb->b_more_io);
1193 : : }
1194 : :
1195 : 40076 : static void inode_sync_complete(struct inode *inode)
1196 : : {
1197 : 40076 : inode->i_state &= ~I_SYNC;
1198 : : /* If inode is clean an unused, put it into LRU now... */
1199 : 40076 : inode_add_lru(inode);
1200 : : /* Waiters must see I_SYNC cleared before being woken up */
1201 : 40076 : smp_mb();
1202 : 40076 : wake_up_bit(&inode->i_state, __I_SYNC);
1203 : 40076 : }
1204 : :
1205 : : static bool inode_dirtied_after(struct inode *inode, unsigned long t)
1206 : : {
1207 [ + + ]: 46187 : bool ret = time_after(inode->dirtied_when, t);
1208 : : #ifndef CONFIG_64BIT
1209 : : /*
1210 : : * For inodes being constantly redirtied, dirtied_when can get stuck.
1211 : : * It _appears_ to be in the future, but is actually in distant past.
1212 : : * This test is necessary to prevent such wrapped-around relative times
1213 : : * from permanently stopping the whole bdi writeback.
1214 : : */
1215 [ + + - + ]: 46187 : ret = ret && time_before_eq(inode->dirtied_when, jiffies);
1216 : : #endif
1217 : : return ret;
1218 : : }
1219 : :
1220 : : #define EXPIRE_DIRTY_ATIME 0x0001
1221 : :
1222 : : /*
1223 : : * Move expired (dirtied before work->older_than_this) dirty inodes from
1224 : : * @delaying_queue to @dispatch_queue.
1225 : : */
1226 : 10572 : static int move_expired_inodes(struct list_head *delaying_queue,
1227 : : struct list_head *dispatch_queue,
1228 : : int flags,
1229 : : struct wb_writeback_work *work)
1230 : : {
1231 : : unsigned long *older_than_this = NULL;
1232 : : unsigned long expire_time;
1233 : 10572 : LIST_HEAD(tmp);
1234 : : struct list_head *pos, *node;
1235 : : struct super_block *sb = NULL;
1236 : : struct inode *inode;
1237 : : int do_sb_sort = 0;
1238 : : int moved = 0;
1239 : :
1240 [ + + ]: 10572 : if ((flags & EXPIRE_DIRTY_ATIME) == 0)
1241 : 5286 : older_than_this = work->older_than_this;
1242 [ + + ]: 5286 : else if (!work->for_sync) {
1243 : 4897 : expire_time = jiffies - (dirtytime_expire_interval * HZ);
1244 : : older_than_this = &expire_time;
1245 : : }
1246 [ + + ]: 52992 : while (!list_empty(delaying_queue)) {
1247 : 46187 : inode = wb_inode(delaying_queue->prev);
1248 [ + - + + ]: 92374 : if (older_than_this &&
1249 : 46187 : inode_dirtied_after(inode, *older_than_this))
1250 : : break;
1251 : 42420 : list_move(&inode->i_io_list, &tmp);
1252 : 42420 : moved++;
1253 [ - + ]: 42420 : if (flags & EXPIRE_DIRTY_ATIME)
1254 : 0 : set_bit(__I_DIRTY_TIME_EXPIRED, &inode->i_state);
1255 [ + + ]: 84840 : if (sb_is_blkdev_sb(inode->i_sb))
1256 : 2199 : continue;
1257 [ + + + + ]: 40221 : if (sb && sb != inode->i_sb)
1258 : : do_sb_sort = 1;
1259 : : sb = inode->i_sb;
1260 : : }
1261 : :
1262 : : /* just one sb in list, splice to dispatch_queue and we're done */
1263 [ + + ]: 10572 : if (!do_sb_sort) {
1264 : : list_splice(&tmp, dispatch_queue);
1265 : : goto out;
1266 : : }
1267 : :
1268 : : /* Move inodes from one superblock together */
1269 [ + + ]: 832 : while (!list_empty(&tmp)) {
1270 : 624 : sb = wb_inode(tmp.prev)->i_sb;
1271 [ + + ]: 13213 : list_for_each_prev_safe(pos, node, &tmp) {
1272 : : inode = wb_inode(pos);
1273 [ + + ]: 12589 : if (inode->i_sb == sb)
1274 : 6398 : list_move(&inode->i_io_list, dispatch_queue);
1275 : : }
1276 : : }
1277 : : out:
1278 : 10572 : return moved;
1279 : : }
1280 : :
1281 : : /*
1282 : : * Queue all expired dirty inodes for io, eldest first.
1283 : : * Before
1284 : : * newly dirtied b_dirty b_io b_more_io
1285 : : * =============> gf edc BA
1286 : : * After
1287 : : * newly dirtied b_dirty b_io b_more_io
1288 : : * =============> g fBAedc
1289 : : * |
1290 : : * +--> dequeue for IO
1291 : : */
1292 : 5286 : static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
1293 : : {
1294 : : int moved;
1295 : :
1296 [ - + ]: 5286 : assert_spin_locked(&wb->list_lock);
1297 : 5286 : list_splice_init(&wb->b_more_io, &wb->b_io);
1298 : 5286 : moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work);
1299 : 5286 : moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
1300 : : EXPIRE_DIRTY_ATIME, work);
1301 [ + + ]: 5286 : if (moved)
1302 : 1974 : wb_io_lists_populated(wb);
1303 : 5286 : trace_writeback_queue_io(wb, work, moved);
1304 : 5286 : }
1305 : :
1306 : 38560 : static int write_inode(struct inode *inode, struct writeback_control *wbc)
1307 : : {
1308 : : int ret;
1309 : :
1310 [ + - + - ]: 38560 : if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
1311 : 38560 : trace_writeback_write_inode_start(inode, wbc);
1312 : 38560 : ret = inode->i_sb->s_op->write_inode(inode, wbc);
1313 : 38560 : trace_writeback_write_inode(inode, wbc);
1314 : 38560 : return ret;
1315 : : }
1316 : : return 0;
1317 : : }
1318 : :
1319 : : /*
1320 : : * Wait for writeback on an inode to complete. Called with i_lock held.
1321 : : * Caller must make sure inode cannot go away when we drop i_lock.
1322 : : */
1323 : 1734142 : static void __inode_wait_for_writeback(struct inode *inode)
1324 : : __releases(inode->i_lock)
1325 : : __acquires(inode->i_lock)
1326 : : {
1327 : 3468284 : DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
1328 : : wait_queue_head_t *wqh;
1329 : :
1330 : 1734142 : wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1331 [ - + ]: 3468599 : while (inode->i_state & I_SYNC) {
1332 : : spin_unlock(&inode->i_lock);
1333 : 0 : __wait_on_bit(wqh, &wq, bit_wait,
1334 : : TASK_UNINTERRUPTIBLE);
1335 : : spin_lock(&inode->i_lock);
1336 : : }
1337 : 1734608 : }
1338 : :
1339 : : /*
1340 : : * Wait for writeback on an inode to complete. Caller must have inode pinned.
1341 : : */
1342 : 1734684 : void inode_wait_for_writeback(struct inode *inode)
1343 : : {
1344 : : spin_lock(&inode->i_lock);
1345 : 1734680 : __inode_wait_for_writeback(inode);
1346 : : spin_unlock(&inode->i_lock);
1347 : 1734599 : }
1348 : :
1349 : : /*
1350 : : * Sleep until I_SYNC is cleared. This function must be called with i_lock
1351 : : * held and drops it. It is aimed for callers not holding any inode reference
1352 : : * so once i_lock is dropped, inode can go away.
1353 : : */
1354 : 0 : static void inode_sleep_on_writeback(struct inode *inode)
1355 : : __releases(inode->i_lock)
1356 : : {
1357 : 0 : DEFINE_WAIT(wait);
1358 : 0 : wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
1359 : : int sleep;
1360 : :
1361 : 0 : prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1362 : 0 : sleep = inode->i_state & I_SYNC;
1363 : : spin_unlock(&inode->i_lock);
1364 [ # # ]: 0 : if (sleep)
1365 : 0 : schedule();
1366 : 0 : finish_wait(wqh, &wait);
1367 : 0 : }
1368 : :
1369 : : /*
1370 : : * Find proper writeback list for the inode depending on its current state and
1371 : : * possibly also change of its state while we were doing writeback. Here we
1372 : : * handle things such as livelock prevention or fairness of writeback among
1373 : : * inodes. This function can be called only by flusher thread - noone else
1374 : : * processes all inodes in writeback lists and requeueing inodes behind flusher
1375 : : * thread's back can have unexpected consequences.
1376 : : */
1377 : 40076 : static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
1378 : : struct writeback_control *wbc)
1379 : : {
1380 [ + - ]: 40076 : if (inode->i_state & I_FREEING)
1381 : : return;
1382 : :
1383 : : /*
1384 : : * Sync livelock prevention. Each inode is tagged and synced in one
1385 : : * shot. If still dirty, it will be redirty_tail()'ed below. Update
1386 : : * the dirty time to prevent enqueue and sync it again.
1387 : : */
1388 [ + + + - ]: 40509 : if ((inode->i_state & I_DIRTY) &&
1389 [ - + ]: 866 : (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
1390 : 0 : inode->dirtied_when = jiffies;
1391 : :
1392 [ - + ]: 40076 : if (wbc->pages_skipped) {
1393 : : /*
1394 : : * writeback is not making progress due to locked
1395 : : * buffers. Skip this inode for now.
1396 : : */
1397 : 0 : redirty_tail(inode, wb);
1398 : 0 : return;
1399 : : }
1400 : :
1401 [ + + ]: 80152 : if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
1402 : : /*
1403 : : * We didn't write back all the pages. nfs_writepages()
1404 : : * sometimes bales out without doing anything.
1405 : : */
1406 [ - + ]: 435 : if (wbc->nr_to_write <= 0) {
1407 : : /* Slice used up. Queue for next turn. */
1408 : : requeue_io(inode, wb);
1409 : : } else {
1410 : : /*
1411 : : * Writeback blocked by something other than
1412 : : * congestion. Delay the inode for some time to
1413 : : * avoid spinning on the CPU (100% iowait)
1414 : : * retrying writeback of the dirty page/inode
1415 : : * that cannot be performed immediately.
1416 : : */
1417 : 435 : redirty_tail(inode, wb);
1418 : : }
1419 [ - + ]: 39641 : } else if (inode->i_state & I_DIRTY) {
1420 : : /*
1421 : : * Filesystems can dirty the inode during writeback operations,
1422 : : * such as delayed allocation during submission or metadata
1423 : : * updates after data IO completion.
1424 : : */
1425 : 0 : redirty_tail(inode, wb);
1426 [ - + ]: 39641 : } else if (inode->i_state & I_DIRTY_TIME) {
1427 : 0 : inode->dirtied_when = jiffies;
1428 : 0 : inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
1429 : : } else {
1430 : : /* The inode is clean. Remove from writeback lists. */
1431 : 39641 : inode_io_list_del_locked(inode, wb);
1432 : : }
1433 : : }
1434 : :
1435 : : /*
1436 : : * Write out an inode and its dirty pages. Do not update the writeback list
1437 : : * linkage. That is left to the caller. The caller is also responsible for
1438 : : * setting I_SYNC flag and calling inode_sync_complete() to clear it.
1439 : : */
1440 : : static int
1441 : 40076 : __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
1442 : : {
1443 : 40076 : struct address_space *mapping = inode->i_mapping;
1444 : 40076 : long nr_to_write = wbc->nr_to_write;
1445 : : unsigned dirty;
1446 : : int ret;
1447 : :
1448 [ - + ]: 40076 : WARN_ON(!(inode->i_state & I_SYNC));
1449 : :
1450 : 40076 : trace_writeback_single_inode_start(inode, wbc, nr_to_write);
1451 : :
1452 : 40076 : ret = do_writepages(mapping, wbc);
1453 : :
1454 : : /*
1455 : : * Make sure to wait on the data before writing out the metadata.
1456 : : * This is important for filesystems that modify metadata on data
1457 : : * I/O completion. We don't do it for sync(2) writeback because it has a
1458 : : * separate, external IO completion path and ->sync_fs for guaranteeing
1459 : : * inode metadata is written back correctly.
1460 : : */
1461 [ + + - + ]: 40076 : if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
1462 : : int err = filemap_fdatawait(mapping);
1463 [ # # ]: 0 : if (ret == 0)
1464 : : ret = err;
1465 : : }
1466 : :
1467 : : /*
1468 : : * Some filesystems may redirty the inode during the writeback
1469 : : * due to delalloc, clear dirty metadata flags right before
1470 : : * write_inode()
1471 : : */
1472 : : spin_lock(&inode->i_lock);
1473 : :
1474 : 40076 : dirty = inode->i_state & I_DIRTY;
1475 [ - + ]: 40076 : if (inode->i_state & I_DIRTY_TIME) {
1476 [ # # # # ]: 0 : if ((dirty & I_DIRTY_INODE) ||
1477 [ # # ]: 0 : wbc->sync_mode == WB_SYNC_ALL ||
1478 [ # # ]: 0 : unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) ||
1479 : 0 : unlikely(time_after(jiffies,
1480 : : (inode->dirtied_time_when +
1481 : : dirtytime_expire_interval * HZ)))) {
1482 : 0 : dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
1483 : 0 : trace_writeback_lazytime(inode);
1484 : : }
1485 : : } else
1486 : 40076 : inode->i_state &= ~I_DIRTY_TIME_EXPIRED;
1487 : 40076 : inode->i_state &= ~dirty;
1488 : :
1489 : : /*
1490 : : * Paired with smp_mb() in __mark_inode_dirty(). This allows
1491 : : * __mark_inode_dirty() to test i_state without grabbing i_lock -
1492 : : * either they see the I_DIRTY bits cleared or we see the dirtied
1493 : : * inode.
1494 : : *
1495 : : * I_DIRTY_PAGES is always cleared together above even if @mapping
1496 : : * still has dirty pages. The flag is reinstated after smp_mb() if
1497 : : * necessary. This guarantees that either __mark_inode_dirty()
1498 : : * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
1499 : : */
1500 : 40076 : smp_mb();
1501 : :
1502 [ + + ]: 40076 : if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
1503 : 432 : inode->i_state |= I_DIRTY_PAGES;
1504 : :
1505 : : spin_unlock(&inode->i_lock);
1506 : :
1507 [ - + ]: 40076 : if (dirty & I_DIRTY_TIME)
1508 : : mark_inode_dirty_sync(inode);
1509 : : /* Don't write the inode if only I_DIRTY_PAGES was set */
1510 [ + + ]: 40076 : if (dirty & ~I_DIRTY_PAGES) {
1511 : 38560 : int err = write_inode(inode, wbc);
1512 [ + - ]: 38560 : if (ret == 0)
1513 : : ret = err;
1514 : : }
1515 : 40076 : trace_writeback_single_inode(inode, wbc, nr_to_write);
1516 : 40076 : return ret;
1517 : : }
1518 : :
1519 : : /*
1520 : : * Write out an inode's dirty pages. Either the caller has an active reference
1521 : : * on the inode or the inode has I_WILL_FREE set.
1522 : : *
1523 : : * This function is designed to be called for writing back one inode which
1524 : : * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
1525 : : * and does more profound writeback list handling in writeback_sb_inodes().
1526 : : */
1527 : 0 : static int writeback_single_inode(struct inode *inode,
1528 : : struct writeback_control *wbc)
1529 : : {
1530 : : struct bdi_writeback *wb;
1531 : : int ret = 0;
1532 : :
1533 : : spin_lock(&inode->i_lock);
1534 [ # # ]: 0 : if (!atomic_read(&inode->i_count))
1535 [ # # ]: 0 : WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
1536 : : else
1537 [ # # ]: 0 : WARN_ON(inode->i_state & I_WILL_FREE);
1538 : :
1539 [ # # ]: 0 : if (inode->i_state & I_SYNC) {
1540 [ # # ]: 0 : if (wbc->sync_mode != WB_SYNC_ALL)
1541 : : goto out;
1542 : : /*
1543 : : * It's a data-integrity sync. We must wait. Since callers hold
1544 : : * inode reference or inode has I_WILL_FREE set, it cannot go
1545 : : * away under us.
1546 : : */
1547 : 0 : __inode_wait_for_writeback(inode);
1548 : : }
1549 [ # # ]: 0 : WARN_ON(inode->i_state & I_SYNC);
1550 : : /*
1551 : : * Skip inode if it is clean and we have no outstanding writeback in
1552 : : * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
1553 : : * function since flusher thread may be doing for example sync in
1554 : : * parallel and if we move the inode, it could get skipped. So here we
1555 : : * make sure inode is on some writeback list and leave it there unless
1556 : : * we have completely cleaned the inode.
1557 : : */
1558 [ # # # # ]: 0 : if (!(inode->i_state & I_DIRTY_ALL) &&
1559 [ # # ]: 0 : (wbc->sync_mode != WB_SYNC_ALL ||
1560 : 0 : !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
1561 : : goto out;
1562 : 0 : inode->i_state |= I_SYNC;
1563 : 0 : wbc_attach_and_unlock_inode(wbc, inode);
1564 : :
1565 : 0 : ret = __writeback_single_inode(inode, wbc);
1566 : :
1567 : 0 : wbc_detach_inode(wbc);
1568 : :
1569 : : wb = inode_to_wb_and_lock_list(inode);
1570 : : spin_lock(&inode->i_lock);
1571 : : /*
1572 : : * If inode is clean, remove it from writeback lists. Otherwise don't
1573 : : * touch it. See comment above for explanation.
1574 : : */
1575 [ # # ]: 0 : if (!(inode->i_state & I_DIRTY_ALL))
1576 : 0 : inode_io_list_del_locked(inode, wb);
1577 : : spin_unlock(&wb->list_lock);
1578 : 0 : inode_sync_complete(inode);
1579 : : out:
1580 : : spin_unlock(&inode->i_lock);
1581 : 0 : return ret;
1582 : : }
1583 : :
1584 : : static long writeback_chunk_size(struct bdi_writeback *wb,
1585 : : struct wb_writeback_work *work)
1586 : : {
1587 : : long pages;
1588 : :
1589 : : /*
1590 : : * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
1591 : : * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
1592 : : * here avoids calling into writeback_inodes_wb() more than once.
1593 : : *
1594 : : * The intended call sequence for WB_SYNC_ALL writeback is:
1595 : : *
1596 : : * wb_writeback()
1597 : : * writeback_sb_inodes() <== called only once
1598 : : * write_cache_pages() <== called once for each inode
1599 : : * (quickly) tag currently dirty pages
1600 : : * (maybe slowly) sync all tagged pages
1601 : : */
1602 [ + + + - ]: 40076 : if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
1603 : : pages = LONG_MAX;
1604 : : else {
1605 : 35549 : pages = min(wb->avg_write_bandwidth / 2,
1606 : : global_wb_domain.dirty_limit / DIRTY_SCOPE);
1607 : 35549 : pages = min(pages, work->nr_pages);
1608 : 35549 : pages = round_down(pages + MIN_WRITEBACK_PAGES,
1609 : : MIN_WRITEBACK_PAGES);
1610 : : }
1611 : :
1612 : : return pages;
1613 : : }
1614 : :
1615 : : /*
1616 : : * Write a portion of b_io inodes which belong to @sb.
1617 : : *
1618 : : * Return the number of pages and/or inodes written.
1619 : : *
1620 : : * NOTE! This is called with wb->list_lock held, and will
1621 : : * unlock and relock that for each inode it ends up doing
1622 : : * IO for.
1623 : : */
1624 : 2784 : static long writeback_sb_inodes(struct super_block *sb,
1625 : : struct bdi_writeback *wb,
1626 : : struct wb_writeback_work *work)
1627 : : {
1628 : 19488 : struct writeback_control wbc = {
1629 : 2784 : .sync_mode = work->sync_mode,
1630 : 2784 : .tagged_writepages = work->tagged_writepages,
1631 : 2784 : .for_kupdate = work->for_kupdate,
1632 : 2784 : .for_background = work->for_background,
1633 : 2784 : .for_sync = work->for_sync,
1634 : 2784 : .range_cyclic = work->range_cyclic,
1635 : : .range_start = 0,
1636 : : .range_end = LLONG_MAX,
1637 : : };
1638 : 2784 : unsigned long start_time = jiffies;
1639 : : long write_chunk;
1640 : : long wrote = 0; /* count both pages and inodes */
1641 : :
1642 [ + + ]: 90198 : while (!list_empty(&wb->b_io)) {
1643 : 41735 : struct inode *inode = wb_inode(wb->b_io.prev);
1644 : : struct bdi_writeback *tmp_wb;
1645 : :
1646 [ + + ]: 41735 : if (inode->i_sb != sb) {
1647 [ + + ]: 1659 : if (work->sb) {
1648 : : /*
1649 : : * We only want to write back data for this
1650 : : * superblock, move all inodes not belonging
1651 : : * to it back onto the dirty list.
1652 : : */
1653 : 882 : redirty_tail(inode, wb);
1654 : 882 : continue;
1655 : : }
1656 : :
1657 : : /*
1658 : : * The inode belongs to a different superblock.
1659 : : * Bounce back to the caller to unpin this and
1660 : : * pin the next superblock.
1661 : : */
1662 : : break;
1663 : : }
1664 : :
1665 : : /*
1666 : : * Don't bother with new inodes or inodes being freed, first
1667 : : * kind does not need periodic writeout yet, and for the latter
1668 : : * kind writeout is handled by the freer.
1669 : : */
1670 : : spin_lock(&inode->i_lock);
1671 [ - + ]: 40076 : if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
1672 : : spin_unlock(&inode->i_lock);
1673 : 0 : redirty_tail(inode, wb);
1674 : 0 : continue;
1675 : : }
1676 [ - + # # ]: 40076 : if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
1677 : : /*
1678 : : * If this inode is locked for writeback and we are not
1679 : : * doing writeback-for-data-integrity, move it to
1680 : : * b_more_io so that writeback can proceed with the
1681 : : * other inodes on s_io.
1682 : : *
1683 : : * We'll have another go at writing back this inode
1684 : : * when we completed a full scan of b_io.
1685 : : */
1686 : : spin_unlock(&inode->i_lock);
1687 : : requeue_io(inode, wb);
1688 : 0 : trace_writeback_sb_inodes_requeue(inode);
1689 : 0 : continue;
1690 : : }
1691 : : spin_unlock(&wb->list_lock);
1692 : :
1693 : : /*
1694 : : * We already requeued the inode if it had I_SYNC set and we
1695 : : * are doing WB_SYNC_NONE writeback. So this catches only the
1696 : : * WB_SYNC_ALL case.
1697 : : */
1698 [ - + ]: 40076 : if (inode->i_state & I_SYNC) {
1699 : : /* Wait for I_SYNC. This function drops i_lock... */
1700 : 0 : inode_sleep_on_writeback(inode);
1701 : : /* Inode may be gone, start again */
1702 : : spin_lock(&wb->list_lock);
1703 : 0 : continue;
1704 : : }
1705 : 40076 : inode->i_state |= I_SYNC;
1706 : 40076 : wbc_attach_and_unlock_inode(&wbc, inode);
1707 : :
1708 : : write_chunk = writeback_chunk_size(wb, work);
1709 : 40076 : wbc.nr_to_write = write_chunk;
1710 : 40076 : wbc.pages_skipped = 0;
1711 : :
1712 : : /*
1713 : : * We use I_SYNC to pin the inode in memory. While it is set
1714 : : * evict_inode() will wait so the inode cannot be freed.
1715 : : */
1716 : 40076 : __writeback_single_inode(inode, &wbc);
1717 : :
1718 : 40076 : wbc_detach_inode(&wbc);
1719 : 40076 : work->nr_pages -= write_chunk - wbc.nr_to_write;
1720 : 40076 : wrote += write_chunk - wbc.nr_to_write;
1721 : :
1722 [ + + ]: 40076 : if (need_resched()) {
1723 : : /*
1724 : : * We're trying to balance between building up a nice
1725 : : * long list of IOs to improve our merge rate, and
1726 : : * getting those IOs out quickly for anyone throttling
1727 : : * in balance_dirty_pages(). cond_resched() doesn't
1728 : : * unplug, so get our IOs out the door before we
1729 : : * give up the CPU.
1730 : : */
1731 : 161 : blk_flush_plug(current);
1732 : 161 : cond_resched();
1733 : : }
1734 : :
1735 : : /*
1736 : : * Requeue @inode if still dirty. Be careful as @inode may
1737 : : * have been switched to another wb in the meantime.
1738 : : */
1739 : : tmp_wb = inode_to_wb_and_lock_list(inode);
1740 : : spin_lock(&inode->i_lock);
1741 [ + + ]: 40076 : if (!(inode->i_state & I_DIRTY_ALL))
1742 : 39643 : wrote++;
1743 : 40076 : requeue_inode(inode, tmp_wb, &wbc);
1744 : 40076 : inode_sync_complete(inode);
1745 : : spin_unlock(&inode->i_lock);
1746 : :
1747 [ - + ]: 40076 : if (unlikely(tmp_wb != wb)) {
1748 : : spin_unlock(&tmp_wb->list_lock);
1749 : : spin_lock(&wb->list_lock);
1750 : : }
1751 : :
1752 : : /*
1753 : : * bail out to wb_writeback() often enough to check
1754 : : * background threshold and other termination conditions.
1755 : : */
1756 [ + + ]: 40076 : if (wrote) {
1757 [ + + ]: 39997 : if (time_is_before_jiffies(start_time + HZ / 10UL))
1758 : : break;
1759 [ + - ]: 39962 : if (work->nr_pages <= 0)
1760 : : break;
1761 : : }
1762 : : }
1763 : 2784 : return wrote;
1764 : : }
1765 : :
1766 : 4916 : static long __writeback_inodes_wb(struct bdi_writeback *wb,
1767 : : struct wb_writeback_work *work)
1768 : : {
1769 : 4916 : unsigned long start_time = jiffies;
1770 : : long wrote = 0;
1771 : :
1772 [ + + ]: 19458 : while (!list_empty(&wb->b_io)) {
1773 : 2395 : struct inode *inode = wb_inode(wb->b_io.prev);
1774 : 2395 : struct super_block *sb = inode->i_sb;
1775 : :
1776 [ - + ]: 2395 : if (!trylock_super(sb)) {
1777 : : /*
1778 : : * trylock_super() may fail consistently due to
1779 : : * s_umount being grabbed by someone else. Don't use
1780 : : * requeue_io() to avoid busy retrying the inode/sb.
1781 : : */
1782 : 0 : redirty_tail(inode, wb);
1783 : 0 : continue;
1784 : : }
1785 : 2395 : wrote += writeback_sb_inodes(sb, wb, work);
1786 : 2395 : up_read(&sb->s_umount);
1787 : :
1788 : : /* refer to the same tests at the end of writeback_sb_inodes */
1789 [ + + ]: 2395 : if (wrote) {
1790 [ + + ]: 2353 : if (time_is_before_jiffies(start_time + HZ / 10UL))
1791 : : break;
1792 [ + - ]: 2313 : if (work->nr_pages <= 0)
1793 : : break;
1794 : : }
1795 : : }
1796 : : /* Leave any unwritten inodes on b_io */
1797 : 4916 : return wrote;
1798 : : }
1799 : :
1800 : 0 : static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
1801 : : enum wb_reason reason)
1802 : : {
1803 : 0 : struct wb_writeback_work work = {
1804 : : .nr_pages = nr_pages,
1805 : : .sync_mode = WB_SYNC_NONE,
1806 : : .range_cyclic = 1,
1807 : : .reason = reason,
1808 : : };
1809 : : struct blk_plug plug;
1810 : :
1811 : 0 : blk_start_plug(&plug);
1812 : : spin_lock(&wb->list_lock);
1813 [ # # ]: 0 : if (list_empty(&wb->b_io))
1814 : 0 : queue_io(wb, &work);
1815 : 0 : __writeback_inodes_wb(wb, &work);
1816 : : spin_unlock(&wb->list_lock);
1817 : 0 : blk_finish_plug(&plug);
1818 : :
1819 : 0 : return nr_pages - work.nr_pages;
1820 : : }
1821 : :
1822 : : /*
1823 : : * Explicit flushing or periodic writeback of "old" data.
1824 : : *
1825 : : * Define "old": the first time one of an inode's pages is dirtied, we mark the
1826 : : * dirtying-time in the inode's address_space. So this periodic writeback code
1827 : : * just walks the superblock inode list, writing back any inodes which are
1828 : : * older than a specific point in time.
1829 : : *
1830 : : * Try to run once per dirty_writeback_interval. But if a writeback event
1831 : : * takes longer than a dirty_writeback_interval interval, then leave a
1832 : : * one-second gap.
1833 : : *
1834 : : * older_than_this takes precedence over nr_to_write. So we'll only write back
1835 : : * all dirty pages if they are all attached to "old" mappings.
1836 : : */
1837 : 3794 : static long wb_writeback(struct bdi_writeback *wb,
1838 : : struct wb_writeback_work *work)
1839 : : {
1840 : 3794 : unsigned long wb_start = jiffies;
1841 : 3794 : long nr_pages = work->nr_pages;
1842 : : unsigned long oldest_jif;
1843 : : struct inode *inode;
1844 : : long progress;
1845 : : struct blk_plug plug;
1846 : :
1847 : 3794 : oldest_jif = jiffies;
1848 : 3794 : work->older_than_this = &oldest_jif;
1849 : :
1850 : 3794 : blk_start_plug(&plug);
1851 : : spin_lock(&wb->list_lock);
1852 : : for (;;) {
1853 : : /*
1854 : : * Stop writeback when nr_pages has been consumed
1855 : : */
1856 [ + - ]: 5566 : if (work->nr_pages <= 0)
1857 : : break;
1858 : :
1859 : : /*
1860 : : * Background writeout and kupdate-style writeback may
1861 : : * run forever. Stop them if there is other work to do
1862 : : * so that e.g. sync can proceed. They'll be restarted
1863 : : * after the other works are all done.
1864 : : */
1865 [ + + + + ]: 10128 : if ((work->for_background || work->for_kupdate) &&
1866 : 4562 : !list_empty(&wb->work_list))
1867 : : break;
1868 : :
1869 : : /*
1870 : : * For background writeout, stop when we are below the
1871 : : * background dirty threshold
1872 : : */
1873 [ + + + + ]: 5565 : if (work->for_background && !wb_over_bg_thresh(wb))
1874 : : break;
1875 : :
1876 : : /*
1877 : : * Kupdate and background works are special and we want to
1878 : : * include all inodes that need writing. Livelock avoidance is
1879 : : * handled by these works yielding to any other work so we are
1880 : : * safe.
1881 : : */
1882 [ + + ]: 5305 : if (work->for_kupdate) {
1883 : 7480 : oldest_jif = jiffies -
1884 : 3740 : msecs_to_jiffies(dirty_expire_interval * 10);
1885 [ + + ]: 1565 : } else if (work->for_background)
1886 : 561 : oldest_jif = jiffies;
1887 : :
1888 : 5305 : trace_writeback_start(wb, work);
1889 [ + + ]: 10610 : if (list_empty(&wb->b_io))
1890 : 5286 : queue_io(wb, work);
1891 [ + + ]: 5305 : if (work->sb)
1892 : 389 : progress = writeback_sb_inodes(work->sb, wb, work);
1893 : : else
1894 : 4916 : progress = __writeback_inodes_wb(wb, work);
1895 : 5305 : trace_writeback_written(wb, work);
1896 : :
1897 : 5305 : wb_update_bandwidth(wb, wb_start);
1898 : :
1899 : : /*
1900 : : * Did we write something? Try for more
1901 : : *
1902 : : * Dirty inodes are moved to b_io for writeback in batches.
1903 : : * The completion of the current batch does not necessarily
1904 : : * mean the overall work is done. So we keep looping as long
1905 : : * as made some progress on cleaning pages or inodes.
1906 : : */
1907 [ + + ]: 5305 : if (progress)
1908 : 1772 : continue;
1909 : : /*
1910 : : * No more inodes for IO, bail
1911 : : */
1912 [ - + ]: 7066 : if (list_empty(&wb->b_more_io))
1913 : : break;
1914 : : /*
1915 : : * Nothing written. Wait for some inode to
1916 : : * become available for writeback. Otherwise
1917 : : * we'll just busyloop.
1918 : : */
1919 : 0 : trace_writeback_wait(wb, work);
1920 : 0 : inode = wb_inode(wb->b_more_io.prev);
1921 : : spin_lock(&inode->i_lock);
1922 : : spin_unlock(&wb->list_lock);
1923 : : /* This function drops i_lock... */
1924 : 0 : inode_sleep_on_writeback(inode);
1925 : : spin_lock(&wb->list_lock);
1926 : : }
1927 : : spin_unlock(&wb->list_lock);
1928 : 3794 : blk_finish_plug(&plug);
1929 : :
1930 : 3794 : return nr_pages - work->nr_pages;
1931 : : }
1932 : :
1933 : : /*
1934 : : * Return the next wb_writeback_work struct that hasn't been processed yet.
1935 : : */
1936 : 3539 : static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
1937 : : {
1938 : : struct wb_writeback_work *work = NULL;
1939 : :
1940 : : spin_lock_bh(&wb->work_lock);
1941 [ + + ]: 7078 : if (!list_empty(&wb->work_list)) {
1942 : 225 : work = list_entry(wb->work_list.next,
1943 : : struct wb_writeback_work, list);
1944 : 225 : list_del_init(&work->list);
1945 : : }
1946 : : spin_unlock_bh(&wb->work_lock);
1947 : 3539 : return work;
1948 : : }
1949 : :
1950 : 3314 : static long wb_check_background_flush(struct bdi_writeback *wb)
1951 : : {
1952 [ + + ]: 3314 : if (wb_over_bg_thresh(wb)) {
1953 : :
1954 : 354 : struct wb_writeback_work work = {
1955 : : .nr_pages = LONG_MAX,
1956 : : .sync_mode = WB_SYNC_NONE,
1957 : : .for_background = 1,
1958 : : .range_cyclic = 1,
1959 : : .reason = WB_REASON_BACKGROUND,
1960 : : };
1961 : :
1962 : 354 : return wb_writeback(wb, &work);
1963 : : }
1964 : :
1965 : : return 0;
1966 : : }
1967 : :
1968 : 3314 : static long wb_check_old_data_flush(struct bdi_writeback *wb)
1969 : : {
1970 : : unsigned long expired;
1971 : : long nr_pages;
1972 : :
1973 : : /*
1974 : : * When set to zero, disable periodic writeback
1975 : : */
1976 [ + - ]: 3314 : if (!dirty_writeback_interval)
1977 : : return 0;
1978 : :
1979 : 6628 : expired = wb->last_old_flush +
1980 : 3314 : msecs_to_jiffies(dirty_writeback_interval * 10);
1981 [ + + ]: 3314 : if (time_before(jiffies, expired))
1982 : : return 0;
1983 : :
1984 : 3008 : wb->last_old_flush = jiffies;
1985 : 3008 : nr_pages = get_nr_dirty_pages();
1986 : :
1987 [ + - ]: 3008 : if (nr_pages) {
1988 : 3008 : struct wb_writeback_work work = {
1989 : : .nr_pages = nr_pages,
1990 : : .sync_mode = WB_SYNC_NONE,
1991 : : .for_kupdate = 1,
1992 : : .range_cyclic = 1,
1993 : : .reason = WB_REASON_PERIODIC,
1994 : : };
1995 : :
1996 : 3008 : return wb_writeback(wb, &work);
1997 : : }
1998 : :
1999 : : return 0;
2000 : : }
2001 : :
2002 : 3314 : static long wb_check_start_all(struct bdi_writeback *wb)
2003 : : {
2004 : : long nr_pages;
2005 : :
2006 [ + + ]: 3314 : if (!test_bit(WB_start_all, &wb->state))
2007 : : return 0;
2008 : :
2009 : 207 : nr_pages = get_nr_dirty_pages();
2010 [ + - ]: 207 : if (nr_pages) {
2011 : 621 : struct wb_writeback_work work = {
2012 : 207 : .nr_pages = wb_split_bdi_pages(wb, nr_pages),
2013 : : .sync_mode = WB_SYNC_NONE,
2014 : : .range_cyclic = 1,
2015 : 207 : .reason = wb->start_all_reason,
2016 : : };
2017 : :
2018 : 207 : nr_pages = wb_writeback(wb, &work);
2019 : : }
2020 : :
2021 : 207 : clear_bit(WB_start_all, &wb->state);
2022 : 207 : return nr_pages;
2023 : : }
2024 : :
2025 : :
2026 : : /*
2027 : : * Retrieve work items and do the writeback they describe
2028 : : */
2029 : 3314 : static long wb_do_writeback(struct bdi_writeback *wb)
2030 : : {
2031 : : struct wb_writeback_work *work;
2032 : : long wrote = 0;
2033 : :
2034 : 3314 : set_bit(WB_writeback_running, &wb->state);
2035 [ + + ]: 6853 : while ((work = get_next_work_item(wb)) != NULL) {
2036 : 225 : trace_writeback_exec(wb, work);
2037 : 225 : wrote += wb_writeback(wb, work);
2038 : 225 : finish_writeback_work(wb, work);
2039 : : }
2040 : :
2041 : : /*
2042 : : * Check for a flush-everything request
2043 : : */
2044 : 3314 : wrote += wb_check_start_all(wb);
2045 : :
2046 : : /*
2047 : : * Check for periodic writeback, kupdated() style
2048 : : */
2049 : 3314 : wrote += wb_check_old_data_flush(wb);
2050 : 3314 : wrote += wb_check_background_flush(wb);
2051 : 3314 : clear_bit(WB_writeback_running, &wb->state);
2052 : :
2053 : 3314 : return wrote;
2054 : : }
2055 : :
2056 : : /*
2057 : : * Handle writeback of dirty data for the device backed by this bdi. Also
2058 : : * reschedules periodically and does kupdated style flushing.
2059 : : */
2060 : 3279 : void wb_workfn(struct work_struct *work)
2061 : : {
2062 : 3279 : struct bdi_writeback *wb = container_of(to_delayed_work(work),
2063 : : struct bdi_writeback, dwork);
2064 : : long pages_written;
2065 : :
2066 : 3279 : set_worker_desc("flush-%s", bdi_dev_name(wb->bdi));
2067 : 3279 : current->flags |= PF_SWAPWRITE;
2068 : :
2069 [ - + # # ]: 3279 : if (likely(!current_is_workqueue_rescuer() ||
2070 : : !test_bit(WB_registered, &wb->state))) {
2071 : : /*
2072 : : * The normal path. Keep writing back @wb until its
2073 : : * work_list is empty. Note that this path is also taken
2074 : : * if @wb is shutting down even when we're running off the
2075 : : * rescuer as work_list needs to be drained.
2076 : : */
2077 : : do {
2078 : 3314 : pages_written = wb_do_writeback(wb);
2079 : 3314 : trace_writeback_pages_written(pages_written);
2080 [ + + ]: 6628 : } while (!list_empty(&wb->work_list));
2081 : : } else {
2082 : : /*
2083 : : * bdi_wq can't get enough workers and we're running off
2084 : : * the emergency worker. Don't hog it. Hopefully, 1024 is
2085 : : * enough for efficient IO.
2086 : : */
2087 : 0 : pages_written = writeback_inodes_wb(wb, 1024,
2088 : : WB_REASON_FORKER_THREAD);
2089 : 0 : trace_writeback_pages_written(pages_written);
2090 : : }
2091 : :
2092 [ - + ]: 6558 : if (!list_empty(&wb->work_list))
2093 : 0 : wb_wakeup(wb);
2094 [ + + + - ]: 3279 : else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
2095 : 2888 : wb_wakeup_delayed(wb);
2096 : :
2097 : 3279 : current->flags &= ~PF_SWAPWRITE;
2098 : 3279 : }
2099 : :
2100 : : /*
2101 : : * Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero,
2102 : : * write back the whole world.
2103 : : */
2104 : 5175 : static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
2105 : : enum wb_reason reason)
2106 : : {
2107 : : struct bdi_writeback *wb;
2108 : :
2109 [ + + ]: 5175 : if (!bdi_has_dirty_io(bdi))
2110 : 5175 : return;
2111 : :
2112 [ + + ]: 414 : list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
2113 : 207 : wb_start_writeback(wb, reason);
2114 : : }
2115 : :
2116 : 0 : void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
2117 : : enum wb_reason reason)
2118 : : {
2119 : : rcu_read_lock();
2120 : 0 : __wakeup_flusher_threads_bdi(bdi, reason);
2121 : : rcu_read_unlock();
2122 : 0 : }
2123 : :
2124 : : /*
2125 : : * Wakeup the flusher threads to start writeback of all currently dirty pages
2126 : : */
2127 : 207 : void wakeup_flusher_threads(enum wb_reason reason)
2128 : : {
2129 : : struct backing_dev_info *bdi;
2130 : :
2131 : : /*
2132 : : * If we are expecting writeback progress we must submit plugged IO.
2133 : : */
2134 [ - + ]: 414 : if (blk_needs_flush_plug(current))
2135 : : blk_schedule_flush_plug(current);
2136 : :
2137 : : rcu_read_lock();
2138 [ + + ]: 5382 : list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
2139 : 5175 : __wakeup_flusher_threads_bdi(bdi, reason);
2140 : : rcu_read_unlock();
2141 : 207 : }
2142 : :
2143 : : /*
2144 : : * Wake up bdi's periodically to make sure dirtytime inodes gets
2145 : : * written back periodically. We deliberately do *not* check the
2146 : : * b_dirtytime list in wb_has_dirty_io(), since this would cause the
2147 : : * kernel to be constantly waking up once there are any dirtytime
2148 : : * inodes on the system. So instead we define a separate delayed work
2149 : : * function which gets called much more rarely. (By default, only
2150 : : * once every 12 hours.)
2151 : : *
2152 : : * If there is any other write activity going on in the file system,
2153 : : * this function won't be necessary. But if the only thing that has
2154 : : * happened on the file system is a dirtytime inode caused by an atime
2155 : : * update, we need this infrastructure below to make sure that inode
2156 : : * eventually gets pushed out to disk.
2157 : : */
2158 : : static void wakeup_dirtytime_writeback(struct work_struct *w);
2159 : : static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback);
2160 : :
2161 : 0 : static void wakeup_dirtytime_writeback(struct work_struct *w)
2162 : : {
2163 : : struct backing_dev_info *bdi;
2164 : :
2165 : : rcu_read_lock();
2166 [ # # ]: 0 : list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
2167 : : struct bdi_writeback *wb;
2168 : :
2169 [ # # ]: 0 : list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
2170 [ # # ]: 0 : if (!list_empty(&wb->b_dirty_time))
2171 : 0 : wb_wakeup(wb);
2172 : : }
2173 : : rcu_read_unlock();
2174 : 0 : schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
2175 : 0 : }
2176 : :
2177 : 207 : static int __init start_dirtytime_writeback(void)
2178 : : {
2179 : 207 : schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
2180 : 207 : return 0;
2181 : : }
2182 : : __initcall(start_dirtytime_writeback);
2183 : :
2184 : 0 : int dirtytime_interval_handler(struct ctl_table *table, int write,
2185 : : void __user *buffer, size_t *lenp, loff_t *ppos)
2186 : : {
2187 : : int ret;
2188 : :
2189 : 0 : ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
2190 [ # # ]: 0 : if (ret == 0 && write)
2191 : 0 : mod_delayed_work(system_wq, &dirtytime_work, 0);
2192 : 0 : return ret;
2193 : : }
2194 : :
2195 : 0 : static noinline void block_dump___mark_inode_dirty(struct inode *inode)
2196 : : {
2197 [ # # # # ]: 0 : if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
2198 : : struct dentry *dentry;
2199 : : const char *name = "?";
2200 : :
2201 : 0 : dentry = d_find_alias(inode);
2202 [ # # ]: 0 : if (dentry) {
2203 : : spin_lock(&dentry->d_lock);
2204 : 0 : name = (const char *) dentry->d_name.name;
2205 : : }
2206 : 0 : printk(KERN_DEBUG
2207 : : "%s(%d): dirtied inode %lu (%s) on %s\n",
2208 : 0 : current->comm, task_pid_nr(current), inode->i_ino,
2209 : 0 : name, inode->i_sb->s_id);
2210 [ # # ]: 0 : if (dentry) {
2211 : : spin_unlock(&dentry->d_lock);
2212 : 0 : dput(dentry);
2213 : : }
2214 : : }
2215 : 0 : }
2216 : :
2217 : : /**
2218 : : * __mark_inode_dirty - internal function
2219 : : *
2220 : : * @inode: inode to mark
2221 : : * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
2222 : : *
2223 : : * Mark an inode as dirty. Callers should use mark_inode_dirty or
2224 : : * mark_inode_dirty_sync.
2225 : : *
2226 : : * Put the inode on the super block's dirty list.
2227 : : *
2228 : : * CAREFUL! We mark it dirty unconditionally, but move it onto the
2229 : : * dirty list only if it is hashed or if it refers to a blockdev.
2230 : : * If it was not hashed, it will never be added to the dirty list
2231 : : * even if it is later hashed, as it will have been marked dirty already.
2232 : : *
2233 : : * In short, make sure you hash any inodes _before_ you start marking
2234 : : * them dirty.
2235 : : *
2236 : : * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
2237 : : * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
2238 : : * the kernel-internal blockdev inode represents the dirtying time of the
2239 : : * blockdev's pages. This is why for I_DIRTY_PAGES we always use
2240 : : * page->mapping->host, so the page-dirtying time is recorded in the internal
2241 : : * blockdev inode.
2242 : : */
2243 : 1375164 : void __mark_inode_dirty(struct inode *inode, int flags)
2244 : : {
2245 : 1375164 : struct super_block *sb = inode->i_sb;
2246 : : int dirtytime;
2247 : :
2248 : 1375164 : trace_writeback_mark_inode_dirty(inode, flags);
2249 : :
2250 : : /*
2251 : : * Don't do this for I_DIRTY_PAGES - that doesn't actually
2252 : : * dirty the inode itself
2253 : : */
2254 [ + + ]: 1376114 : if (flags & (I_DIRTY_INODE | I_DIRTY_TIME)) {
2255 : 1150646 : trace_writeback_dirty_inode_start(inode, flags);
2256 : :
2257 [ + + ]: 1150219 : if (sb->s_op->dirty_inode)
2258 : 580772 : sb->s_op->dirty_inode(inode, flags);
2259 : :
2260 : 1150233 : trace_writeback_dirty_inode(inode, flags);
2261 : : }
2262 [ + + ]: 1375344 : if (flags & I_DIRTY_INODE)
2263 : 1150420 : flags &= ~I_DIRTY_TIME;
2264 : 1375344 : dirtytime = flags & I_DIRTY_TIME;
2265 : :
2266 : : /*
2267 : : * Paired with smp_mb() in __writeback_single_inode() for the
2268 : : * following lockless i_state test. See there for details.
2269 : : */
2270 : 1375344 : smp_mb();
2271 : :
2272 [ + + - + ]: 1375715 : if (((inode->i_state & flags) == flags) ||
2273 [ # # ]: 0 : (dirtytime && (inode->i_state & I_DIRTY_INODE)))
2274 : : return;
2275 : :
2276 [ - + ]: 521241 : if (unlikely(block_dump))
2277 : 0 : block_dump___mark_inode_dirty(inode);
2278 : :
2279 : : spin_lock(&inode->i_lock);
2280 [ - + # # ]: 521434 : if (dirtytime && (inode->i_state & I_DIRTY_INODE))
2281 : : goto out_unlock_inode;
2282 [ + + ]: 521181 : if ((inode->i_state & flags) != flags) {
2283 : 521012 : const int was_dirty = inode->i_state & I_DIRTY;
2284 : :
2285 : : inode_attach_wb(inode, NULL);
2286 : :
2287 [ + + ]: 521008 : if (flags & I_DIRTY_INODE)
2288 : 445374 : inode->i_state &= ~I_DIRTY_TIME;
2289 : 521008 : inode->i_state |= flags;
2290 : :
2291 : : /*
2292 : : * If the inode is being synced, just update its dirty state.
2293 : : * The unlocker will place the inode on the appropriate
2294 : : * superblock list, based upon its state.
2295 : : */
2296 [ + + ]: 521008 : if (inode->i_state & I_SYNC)
2297 : : goto out_unlock_inode;
2298 : :
2299 : : /*
2300 : : * Only add valid (hashed) inodes to the superblock's
2301 : : * dirty list. Add blockdev inodes as well.
2302 : : */
2303 [ + + ]: 521004 : if (!S_ISBLK(inode->i_mode)) {
2304 [ + + ]: 515897 : if (inode_unhashed(inode))
2305 : : goto out_unlock_inode;
2306 : : }
2307 [ + + ]: 394065 : if (inode->i_state & I_FREEING)
2308 : : goto out_unlock_inode;
2309 : :
2310 : : /*
2311 : : * If the inode was already on b_dirty/b_io/b_more_io, don't
2312 : : * reposition it (that would break b_dirty time-ordering).
2313 : : */
2314 [ + + ]: 391708 : if (!was_dirty) {
2315 : : struct bdi_writeback *wb;
2316 : : struct list_head *dirty_list;
2317 : : bool wakeup_bdi = false;
2318 : :
2319 : 246853 : wb = locked_inode_to_wb_and_lock_list(inode);
2320 : :
2321 [ + + + - : 618280 : WARN(bdi_cap_writeback_dirty(wb->bdi) &&
- + ]
2322 : : !test_bit(WB_registered, &wb->state),
2323 : : "bdi-%s not registered\n", wb->bdi->name);
2324 : :
2325 : 246854 : inode->dirtied_when = jiffies;
2326 [ - + ]: 246854 : if (dirtytime)
2327 : 0 : inode->dirtied_time_when = jiffies;
2328 : :
2329 [ + - ]: 246854 : if (inode->i_state & I_DIRTY)
2330 : 246854 : dirty_list = &wb->b_dirty;
2331 : : else
2332 : 0 : dirty_list = &wb->b_dirty_time;
2333 : :
2334 : 246854 : wakeup_bdi = inode_io_list_move_locked(inode, wb,
2335 : : dirty_list);
2336 : :
2337 : : spin_unlock(&wb->list_lock);
2338 : 246854 : trace_writeback_dirty_inode_enqueue(inode);
2339 : :
2340 : : /*
2341 : : * If this is the first dirty inode for this bdi,
2342 : : * we have to wake-up the corresponding bdi thread
2343 : : * to make sure background write-back happens
2344 : : * later.
2345 : : */
2346 [ + + + + ]: 493696 : if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
2347 : 581 : wb_wakeup_delayed(wb);
2348 : : return;
2349 : : }
2350 : : }
2351 : : out_unlock_inode:
2352 : : spin_unlock(&inode->i_lock);
2353 : : }
2354 : : EXPORT_SYMBOL(__mark_inode_dirty);
2355 : :
2356 : : /*
2357 : : * The @s_sync_lock is used to serialise concurrent sync operations
2358 : : * to avoid lock contention problems with concurrent wait_sb_inodes() calls.
2359 : : * Concurrent callers will block on the s_sync_lock rather than doing contending
2360 : : * walks. The queueing maintains sync(2) required behaviour as all the IO that
2361 : : * has been issued up to the time this function is enter is guaranteed to be
2362 : : * completed by the time we have gained the lock and waited for all IO that is
2363 : : * in progress regardless of the order callers are granted the lock.
2364 : : */
2365 : 414 : static void wait_sb_inodes(struct super_block *sb)
2366 : : {
2367 : 414 : LIST_HEAD(sync_list);
2368 : :
2369 : : /*
2370 : : * We need to be protected against the filesystem going from
2371 : : * r/o to r/w or vice versa.
2372 : : */
2373 [ - + ]: 414 : WARN_ON(!rwsem_is_locked(&sb->s_umount));
2374 : :
2375 : 414 : mutex_lock(&sb->s_sync_lock);
2376 : :
2377 : : /*
2378 : : * Splice the writeback list onto a temporary list to avoid waiting on
2379 : : * inodes that have started writeback after this point.
2380 : : *
2381 : : * Use rcu_read_lock() to keep the inodes around until we have a
2382 : : * reference. s_inode_wblist_lock protects sb->s_inodes_wb as well as
2383 : : * the local list because inodes can be dropped from either by writeback
2384 : : * completion.
2385 : : */
2386 : : rcu_read_lock();
2387 : : spin_lock_irq(&sb->s_inode_wblist_lock);
2388 : 414 : list_splice_init(&sb->s_inodes_wb, &sync_list);
2389 : :
2390 : : /*
2391 : : * Data integrity sync. Must wait for all pages under writeback, because
2392 : : * there may have been pages dirtied before our sync call, but which had
2393 : : * writeout started before we write it out. In which case, the inode
2394 : : * may not be on the dirty list, but we still have to wait for that
2395 : : * writeout.
2396 : : */
2397 [ + + ]: 1386 : while (!list_empty(&sync_list)) {
2398 : 972 : struct inode *inode = list_first_entry(&sync_list, struct inode,
2399 : : i_wb_list);
2400 : 972 : struct address_space *mapping = inode->i_mapping;
2401 : :
2402 : : /*
2403 : : * Move each inode back to the wb list before we drop the lock
2404 : : * to preserve consistency between i_wb_list and the mapping
2405 : : * writeback tag. Writeback completion is responsible to remove
2406 : : * the inode from either list once the writeback tag is cleared.
2407 : : */
2408 : 972 : list_move_tail(&inode->i_wb_list, &sb->s_inodes_wb);
2409 : :
2410 : : /*
2411 : : * The mapping can appear untagged while still on-list since we
2412 : : * do not have the mapping lock. Skip it here, wb completion
2413 : : * will remove it.
2414 : : */
2415 [ + + ]: 972 : if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
2416 : 1 : continue;
2417 : :
2418 : : spin_unlock_irq(&sb->s_inode_wblist_lock);
2419 : :
2420 : : spin_lock(&inode->i_lock);
2421 [ - + ]: 971 : if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
2422 : : spin_unlock(&inode->i_lock);
2423 : :
2424 : : spin_lock_irq(&sb->s_inode_wblist_lock);
2425 : 0 : continue;
2426 : : }
2427 : 971 : __iget(inode);
2428 : : spin_unlock(&inode->i_lock);
2429 : : rcu_read_unlock();
2430 : :
2431 : : /*
2432 : : * We keep the error status of individual mapping so that
2433 : : * applications can catch the writeback error using fsync(2).
2434 : : * See filemap_fdatawait_keep_errors() for details.
2435 : : */
2436 : 971 : filemap_fdatawait_keep_errors(mapping);
2437 : :
2438 : 971 : cond_resched();
2439 : :
2440 : 971 : iput(inode);
2441 : :
2442 : : rcu_read_lock();
2443 : : spin_lock_irq(&sb->s_inode_wblist_lock);
2444 : : }
2445 : : spin_unlock_irq(&sb->s_inode_wblist_lock);
2446 : : rcu_read_unlock();
2447 : 414 : mutex_unlock(&sb->s_sync_lock);
2448 : 414 : }
2449 : :
2450 : 416 : static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
2451 : : enum wb_reason reason, bool skip_if_busy)
2452 : : {
2453 : 416 : struct backing_dev_info *bdi = sb->s_bdi;
2454 : 416 : DEFINE_WB_COMPLETION(done, bdi);
2455 : 416 : struct wb_writeback_work work = {
2456 : : .sb = sb,
2457 : : .sync_mode = WB_SYNC_NONE,
2458 : : .tagged_writepages = 1,
2459 : : .done = &done,
2460 : : .nr_pages = nr,
2461 : : .reason = reason,
2462 : : };
2463 : :
2464 [ + - - + ]: 416 : if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info)
2465 : 416 : return;
2466 [ # # ]: 0 : WARN_ON(!rwsem_is_locked(&sb->s_umount));
2467 : :
2468 : 0 : bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy);
2469 : 0 : wb_wait_for_completion(&done);
2470 : : }
2471 : :
2472 : : /**
2473 : : * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
2474 : : * @sb: the superblock
2475 : : * @nr: the number of pages to write
2476 : : * @reason: reason why some writeback work initiated
2477 : : *
2478 : : * Start writeback on some inodes on this super_block. No guarantees are made
2479 : : * on how many (if any) will be written, and this function does not wait
2480 : : * for IO completion of submitted IO.
2481 : : */
2482 : 0 : void writeback_inodes_sb_nr(struct super_block *sb,
2483 : : unsigned long nr,
2484 : : enum wb_reason reason)
2485 : : {
2486 : 416 : __writeback_inodes_sb_nr(sb, nr, reason, false);
2487 : 0 : }
2488 : : EXPORT_SYMBOL(writeback_inodes_sb_nr);
2489 : :
2490 : : /**
2491 : : * writeback_inodes_sb - writeback dirty inodes from given super_block
2492 : : * @sb: the superblock
2493 : : * @reason: reason why some writeback work was initiated
2494 : : *
2495 : : * Start writeback on some inodes on this super_block. No guarantees are made
2496 : : * on how many (if any) will be written, and this function does not wait
2497 : : * for IO completion of submitted IO.
2498 : : */
2499 : 416 : void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2500 : : {
2501 : 832 : return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
2502 : : }
2503 : : EXPORT_SYMBOL(writeback_inodes_sb);
2504 : :
2505 : : /**
2506 : : * try_to_writeback_inodes_sb - try to start writeback if none underway
2507 : : * @sb: the superblock
2508 : : * @reason: reason why some writeback work was initiated
2509 : : *
2510 : : * Invoke __writeback_inodes_sb_nr if no writeback is currently underway.
2511 : : */
2512 : 0 : void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
2513 : : {
2514 [ # # ]: 0 : if (!down_read_trylock(&sb->s_umount))
2515 : 0 : return;
2516 : :
2517 : 0 : __writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason, true);
2518 : 0 : up_read(&sb->s_umount);
2519 : : }
2520 : : EXPORT_SYMBOL(try_to_writeback_inodes_sb);
2521 : :
2522 : : /**
2523 : : * sync_inodes_sb - sync sb inode pages
2524 : : * @sb: the superblock
2525 : : *
2526 : : * This function writes and waits on any dirty inode belonging to this
2527 : : * super_block.
2528 : : */
2529 : 8489 : void sync_inodes_sb(struct super_block *sb)
2530 : : {
2531 : 8489 : struct backing_dev_info *bdi = sb->s_bdi;
2532 : 8489 : DEFINE_WB_COMPLETION(done, bdi);
2533 : 8489 : struct wb_writeback_work work = {
2534 : : .sb = sb,
2535 : : .sync_mode = WB_SYNC_ALL,
2536 : : .nr_pages = LONG_MAX,
2537 : : .range_cyclic = 0,
2538 : : .done = &done,
2539 : : .reason = WB_REASON_SYNC,
2540 : : .for_sync = 1,
2541 : : };
2542 : :
2543 : : /*
2544 : : * Can't skip on !bdi_has_dirty() because we should wait for !dirty
2545 : : * inodes under writeback and I_DIRTY_TIME inodes ignored by
2546 : : * bdi_has_dirty() need to be written out too.
2547 : : */
2548 [ + + ]: 8489 : if (bdi == &noop_backing_dev_info)
2549 : 8075 : return;
2550 [ - + ]: 414 : WARN_ON(!rwsem_is_locked(&sb->s_umount));
2551 : :
2552 : : /* protect against inode wb switch, see inode_switch_wbs_work_fn() */
2553 : : bdi_down_write_wb_switch_rwsem(bdi);
2554 : 414 : bdi_split_work_to_wbs(bdi, &work, false);
2555 : 414 : wb_wait_for_completion(&done);
2556 : : bdi_up_write_wb_switch_rwsem(bdi);
2557 : :
2558 : 414 : wait_sb_inodes(sb);
2559 : : }
2560 : : EXPORT_SYMBOL(sync_inodes_sb);
2561 : :
2562 : : /**
2563 : : * write_inode_now - write an inode to disk
2564 : : * @inode: inode to write to disk
2565 : : * @sync: whether the write should be synchronous or not
2566 : : *
2567 : : * This function commits an inode to disk immediately if it is dirty. This is
2568 : : * primarily needed by knfsd.
2569 : : *
2570 : : * The caller must either have a ref on the inode or must have set I_WILL_FREE.
2571 : : */
2572 : 0 : int write_inode_now(struct inode *inode, int sync)
2573 : : {
2574 : 0 : struct writeback_control wbc = {
2575 : : .nr_to_write = LONG_MAX,
2576 : 0 : .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
2577 : : .range_start = 0,
2578 : : .range_end = LLONG_MAX,
2579 : : };
2580 : :
2581 [ # # ]: 0 : if (!mapping_cap_writeback_dirty(inode->i_mapping))
2582 : 0 : wbc.nr_to_write = 0;
2583 : :
2584 : 0 : might_sleep();
2585 : 0 : return writeback_single_inode(inode, &wbc);
2586 : : }
2587 : : EXPORT_SYMBOL(write_inode_now);
2588 : :
2589 : : /**
2590 : : * sync_inode - write an inode and its pages to disk.
2591 : : * @inode: the inode to sync
2592 : : * @wbc: controls the writeback mode
2593 : : *
2594 : : * sync_inode() will write an inode and its pages to disk. It will also
2595 : : * correctly update the inode on its superblock's dirty inode lists and will
2596 : : * update inode->i_state.
2597 : : *
2598 : : * The caller must have a ref on the inode.
2599 : : */
2600 : 0 : int sync_inode(struct inode *inode, struct writeback_control *wbc)
2601 : : {
2602 : 0 : return writeback_single_inode(inode, wbc);
2603 : : }
2604 : : EXPORT_SYMBOL(sync_inode);
2605 : :
2606 : : /**
2607 : : * sync_inode_metadata - write an inode to disk
2608 : : * @inode: the inode to sync
2609 : : * @wait: wait for I/O to complete.
2610 : : *
2611 : : * Write an inode to disk and adjust its dirty state after completion.
2612 : : *
2613 : : * Note: only writes the actual inode, no associated data or other metadata.
2614 : : */
2615 : 0 : int sync_inode_metadata(struct inode *inode, int wait)
2616 : : {
2617 : 0 : struct writeback_control wbc = {
2618 : 0 : .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
2619 : : .nr_to_write = 0, /* metadata-only */
2620 : : };
2621 : :
2622 : 0 : return sync_inode(inode, &wbc);
2623 : : }
2624 : : EXPORT_SYMBOL(sync_inode_metadata);
|
