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1 | /* | |
2 | * fs/fs-writeback.c | |
3 | * | |
4 | * Copyright (C) 2002, Linus Torvalds. | |
5 | * | |
6 | * Contains all the functions related to writing back and waiting | |
7 | * upon dirty inodes against superblocks, and writing back dirty | |
8 | * pages against inodes. ie: data writeback. Writeout of the | |
9 | * inode itself is not handled here. | |
10 | * | |
11 | * 10Apr2002 Andrew Morton | |
12 | * Split out of fs/inode.c | |
13 | * Additions for address_space-based writeback | |
14 | */ | |
15 | ||
16 | #include <linux/kernel.h> | |
17 | #include <linux/export.h> | |
18 | #include <linux/spinlock.h> | |
19 | #include <linux/slab.h> | |
20 | #include <linux/sched.h> | |
21 | #include <linux/fs.h> | |
22 | #include <linux/mm.h> | |
23 | #include <linux/pagemap.h> | |
24 | #include <linux/kthread.h> | |
25 | #include <linux/writeback.h> | |
26 | #include <linux/blkdev.h> | |
27 | #include <linux/backing-dev.h> | |
28 | #include <linux/tracepoint.h> | |
29 | #include <linux/device.h> | |
30 | #include <linux/memcontrol.h> | |
31 | #include "internal.h" | |
32 | ||
33 | /* | |
34 | * 4MB minimal write chunk size | |
35 | */ | |
36 | #define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10)) | |
37 | ||
38 | struct wb_completion { | |
39 | atomic_t cnt; | |
40 | }; | |
41 | ||
42 | /* | |
43 | * Passed into wb_writeback(), essentially a subset of writeback_control | |
44 | */ | |
45 | struct wb_writeback_work { | |
46 | long nr_pages; | |
47 | struct super_block *sb; | |
48 | unsigned long *older_than_this; | |
49 | enum writeback_sync_modes sync_mode; | |
50 | unsigned int tagged_writepages:1; | |
51 | unsigned int for_kupdate:1; | |
52 | unsigned int range_cyclic:1; | |
53 | unsigned int for_background:1; | |
54 | unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */ | |
55 | unsigned int auto_free:1; /* free on completion */ | |
56 | enum wb_reason reason; /* why was writeback initiated? */ | |
57 | ||
58 | struct list_head list; /* pending work list */ | |
59 | struct wb_completion *done; /* set if the caller waits */ | |
60 | }; | |
61 | ||
62 | /* | |
63 | * If one wants to wait for one or more wb_writeback_works, each work's | |
64 | * ->done should be set to a wb_completion defined using the following | |
65 | * macro. Once all work items are issued with wb_queue_work(), the caller | |
66 | * can wait for the completion of all using wb_wait_for_completion(). Work | |
67 | * items which are waited upon aren't freed automatically on completion. | |
68 | */ | |
69 | #define DEFINE_WB_COMPLETION_ONSTACK(cmpl) \ | |
70 | struct wb_completion cmpl = { \ | |
71 | .cnt = ATOMIC_INIT(1), \ | |
72 | } | |
73 | ||
74 | ||
75 | /* | |
76 | * If an inode is constantly having its pages dirtied, but then the | |
77 | * updates stop dirtytime_expire_interval seconds in the past, it's | |
78 | * possible for the worst case time between when an inode has its | |
79 | * timestamps updated and when they finally get written out to be two | |
80 | * dirtytime_expire_intervals. We set the default to 12 hours (in | |
81 | * seconds), which means most of the time inodes will have their | |
82 | * timestamps written to disk after 12 hours, but in the worst case a | |
83 | * few inodes might not their timestamps updated for 24 hours. | |
84 | */ | |
85 | unsigned int dirtytime_expire_interval = 12 * 60 * 60; | |
86 | ||
87 | static inline struct inode *wb_inode(struct list_head *head) | |
88 | { | |
89 | return list_entry(head, struct inode, i_io_list); | |
90 | } | |
91 | ||
92 | /* | |
93 | * Include the creation of the trace points after defining the | |
94 | * wb_writeback_work structure and inline functions so that the definition | |
95 | * remains local to this file. | |
96 | */ | |
97 | #define CREATE_TRACE_POINTS | |
98 | #include <trace/events/writeback.h> | |
99 | ||
100 | EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage); | |
101 | ||
102 | static bool wb_io_lists_populated(struct bdi_writeback *wb) | |
103 | { | |
104 | if (wb_has_dirty_io(wb)) { | |
105 | return false; | |
106 | } else { | |
107 | set_bit(WB_has_dirty_io, &wb->state); | |
108 | WARN_ON_ONCE(!wb->avg_write_bandwidth); | |
109 | atomic_long_add(wb->avg_write_bandwidth, | |
110 | &wb->bdi->tot_write_bandwidth); | |
111 | return true; | |
112 | } | |
113 | } | |
114 | ||
115 | static void wb_io_lists_depopulated(struct bdi_writeback *wb) | |
116 | { | |
117 | if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) && | |
118 | list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) { | |
119 | clear_bit(WB_has_dirty_io, &wb->state); | |
120 | WARN_ON_ONCE(atomic_long_sub_return(wb->avg_write_bandwidth, | |
121 | &wb->bdi->tot_write_bandwidth) < 0); | |
122 | } | |
123 | } | |
124 | ||
125 | /** | |
126 | * inode_io_list_move_locked - move an inode onto a bdi_writeback IO list | |
127 | * @inode: inode to be moved | |
128 | * @wb: target bdi_writeback | |
129 | * @head: one of @wb->b_{dirty|io|more_io|dirty_time} | |
130 | * | |
131 | * Move @inode->i_io_list to @list of @wb and set %WB_has_dirty_io. | |
132 | * Returns %true if @inode is the first occupant of the !dirty_time IO | |
133 | * lists; otherwise, %false. | |
134 | */ | |
135 | static bool inode_io_list_move_locked(struct inode *inode, | |
136 | struct bdi_writeback *wb, | |
137 | struct list_head *head) | |
138 | { | |
139 | assert_spin_locked(&wb->list_lock); | |
140 | ||
141 | list_move(&inode->i_io_list, head); | |
142 | ||
143 | /* dirty_time doesn't count as dirty_io until expiration */ | |
144 | if (head != &wb->b_dirty_time) | |
145 | return wb_io_lists_populated(wb); | |
146 | ||
147 | wb_io_lists_depopulated(wb); | |
148 | return false; | |
149 | } | |
150 | ||
151 | /** | |
152 | * inode_io_list_del_locked - remove an inode from its bdi_writeback IO list | |
153 | * @inode: inode to be removed | |
154 | * @wb: bdi_writeback @inode is being removed from | |
155 | * | |
156 | * Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and | |
157 | * clear %WB_has_dirty_io if all are empty afterwards. | |
158 | */ | |
159 | static void inode_io_list_del_locked(struct inode *inode, | |
160 | struct bdi_writeback *wb) | |
161 | { | |
162 | assert_spin_locked(&wb->list_lock); | |
163 | ||
164 | list_del_init(&inode->i_io_list); | |
165 | wb_io_lists_depopulated(wb); | |
166 | } | |
167 | ||
168 | static void wb_wakeup(struct bdi_writeback *wb) | |
169 | { | |
170 | spin_lock_bh(&wb->work_lock); | |
171 | if (test_bit(WB_registered, &wb->state)) | |
172 | mod_delayed_work(bdi_wq, &wb->dwork, 0); | |
173 | spin_unlock_bh(&wb->work_lock); | |
174 | } | |
175 | ||
176 | static void finish_writeback_work(struct bdi_writeback *wb, | |
177 | struct wb_writeback_work *work) | |
178 | { | |
179 | struct wb_completion *done = work->done; | |
180 | ||
181 | if (work->auto_free) | |
182 | kfree(work); | |
183 | if (done && atomic_dec_and_test(&done->cnt)) | |
184 | wake_up_all(&wb->bdi->wb_waitq); | |
185 | } | |
186 | ||
187 | static void wb_queue_work(struct bdi_writeback *wb, | |
188 | struct wb_writeback_work *work) | |
189 | { | |
190 | trace_writeback_queue(wb, work); | |
191 | ||
192 | if (work->done) | |
193 | atomic_inc(&work->done->cnt); | |
194 | ||
195 | spin_lock_bh(&wb->work_lock); | |
196 | ||
197 | if (test_bit(WB_registered, &wb->state)) { | |
198 | list_add_tail(&work->list, &wb->work_list); | |
199 | mod_delayed_work(bdi_wq, &wb->dwork, 0); | |
200 | } else | |
201 | finish_writeback_work(wb, work); | |
202 | ||
203 | spin_unlock_bh(&wb->work_lock); | |
204 | } | |
205 | ||
206 | /** | |
207 | * wb_wait_for_completion - wait for completion of bdi_writeback_works | |
208 | * @bdi: bdi work items were issued to | |
209 | * @done: target wb_completion | |
210 | * | |
211 | * Wait for one or more work items issued to @bdi with their ->done field | |
212 | * set to @done, which should have been defined with | |
213 | * DEFINE_WB_COMPLETION_ONSTACK(). This function returns after all such | |
214 | * work items are completed. Work items which are waited upon aren't freed | |
215 | * automatically on completion. | |
216 | */ | |
217 | static void wb_wait_for_completion(struct backing_dev_info *bdi, | |
218 | struct wb_completion *done) | |
219 | { | |
220 | atomic_dec(&done->cnt); /* put down the initial count */ | |
221 | wait_event(bdi->wb_waitq, !atomic_read(&done->cnt)); | |
222 | } | |
223 | ||
224 | #ifdef CONFIG_CGROUP_WRITEBACK | |
225 | ||
226 | /* parameters for foreign inode detection, see wb_detach_inode() */ | |
227 | #define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */ | |
228 | #define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */ | |
229 | #define WB_FRN_TIME_CUT_DIV 2 /* ignore rounds < avg / 2 */ | |
230 | #define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */ | |
231 | ||
232 | #define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */ | |
233 | #define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS) | |
234 | /* each slot's duration is 2s / 16 */ | |
235 | #define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2) | |
236 | /* if foreign slots >= 8, switch */ | |
237 | #define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1) | |
238 | /* one round can affect upto 5 slots */ | |
239 | ||
240 | static atomic_t isw_nr_in_flight = ATOMIC_INIT(0); | |
241 | static struct workqueue_struct *isw_wq; | |
242 | ||
243 | void __inode_attach_wb(struct inode *inode, struct page *page) | |
244 | { | |
245 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
246 | struct bdi_writeback *wb = NULL; | |
247 | ||
248 | if (inode_cgwb_enabled(inode)) { | |
249 | struct cgroup_subsys_state *memcg_css; | |
250 | ||
251 | if (page) { | |
252 | memcg_css = mem_cgroup_css_from_page(page); | |
253 | wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); | |
254 | } else { | |
255 | /* must pin memcg_css, see wb_get_create() */ | |
256 | memcg_css = task_get_css(current, memory_cgrp_id); | |
257 | wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); | |
258 | css_put(memcg_css); | |
259 | } | |
260 | } | |
261 | ||
262 | if (!wb) | |
263 | wb = &bdi->wb; | |
264 | ||
265 | /* | |
266 | * There may be multiple instances of this function racing to | |
267 | * update the same inode. Use cmpxchg() to tell the winner. | |
268 | */ | |
269 | if (unlikely(cmpxchg(&inode->i_wb, NULL, wb))) | |
270 | wb_put(wb); | |
271 | } | |
272 | ||
273 | /** | |
274 | * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it | |
275 | * @inode: inode of interest with i_lock held | |
276 | * | |
277 | * Returns @inode's wb with its list_lock held. @inode->i_lock must be | |
278 | * held on entry and is released on return. The returned wb is guaranteed | |
279 | * to stay @inode's associated wb until its list_lock is released. | |
280 | */ | |
281 | static struct bdi_writeback * | |
282 | locked_inode_to_wb_and_lock_list(struct inode *inode) | |
283 | __releases(&inode->i_lock) | |
284 | __acquires(&wb->list_lock) | |
285 | { | |
286 | while (true) { | |
287 | struct bdi_writeback *wb = inode_to_wb(inode); | |
288 | ||
289 | /* | |
290 | * inode_to_wb() association is protected by both | |
291 | * @inode->i_lock and @wb->list_lock but list_lock nests | |
292 | * outside i_lock. Drop i_lock and verify that the | |
293 | * association hasn't changed after acquiring list_lock. | |
294 | */ | |
295 | wb_get(wb); | |
296 | spin_unlock(&inode->i_lock); | |
297 | spin_lock(&wb->list_lock); | |
298 | ||
299 | /* i_wb may have changed inbetween, can't use inode_to_wb() */ | |
300 | if (likely(wb == inode->i_wb)) { | |
301 | wb_put(wb); /* @inode already has ref */ | |
302 | return wb; | |
303 | } | |
304 | ||
305 | spin_unlock(&wb->list_lock); | |
306 | wb_put(wb); | |
307 | cpu_relax(); | |
308 | spin_lock(&inode->i_lock); | |
309 | } | |
310 | } | |
311 | ||
312 | /** | |
313 | * inode_to_wb_and_lock_list - determine an inode's wb and lock it | |
314 | * @inode: inode of interest | |
315 | * | |
316 | * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held | |
317 | * on entry. | |
318 | */ | |
319 | static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode) | |
320 | __acquires(&wb->list_lock) | |
321 | { | |
322 | spin_lock(&inode->i_lock); | |
323 | return locked_inode_to_wb_and_lock_list(inode); | |
324 | } | |
325 | ||
326 | struct inode_switch_wbs_context { | |
327 | struct inode *inode; | |
328 | struct bdi_writeback *new_wb; | |
329 | ||
330 | struct rcu_head rcu_head; | |
331 | struct work_struct work; | |
332 | }; | |
333 | ||
334 | static void inode_switch_wbs_work_fn(struct work_struct *work) | |
335 | { | |
336 | struct inode_switch_wbs_context *isw = | |
337 | container_of(work, struct inode_switch_wbs_context, work); | |
338 | struct inode *inode = isw->inode; | |
339 | struct address_space *mapping = inode->i_mapping; | |
340 | struct bdi_writeback *old_wb = inode->i_wb; | |
341 | struct bdi_writeback *new_wb = isw->new_wb; | |
342 | struct radix_tree_iter iter; | |
343 | bool switched = false; | |
344 | void **slot; | |
345 | ||
346 | /* | |
347 | * By the time control reaches here, RCU grace period has passed | |
348 | * since I_WB_SWITCH assertion and all wb stat update transactions | |
349 | * between unlocked_inode_to_wb_begin/end() are guaranteed to be | |
350 | * synchronizing against the i_pages lock. | |
351 | * | |
352 | * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock | |
353 | * gives us exclusion against all wb related operations on @inode | |
354 | * including IO list manipulations and stat updates. | |
355 | */ | |
356 | if (old_wb < new_wb) { | |
357 | spin_lock(&old_wb->list_lock); | |
358 | spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING); | |
359 | } else { | |
360 | spin_lock(&new_wb->list_lock); | |
361 | spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING); | |
362 | } | |
363 | spin_lock(&inode->i_lock); | |
364 | xa_lock_irq(&mapping->i_pages); | |
365 | ||
366 | /* | |
367 | * Once I_FREEING is visible under i_lock, the eviction path owns | |
368 | * the inode and we shouldn't modify ->i_io_list. | |
369 | */ | |
370 | if (unlikely(inode->i_state & I_FREEING)) | |
371 | goto skip_switch; | |
372 | ||
373 | /* | |
374 | * Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points | |
375 | * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to | |
376 | * pages actually under writeback. | |
377 | */ | |
378 | radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, 0, | |
379 | PAGECACHE_TAG_DIRTY) { | |
380 | struct page *page = radix_tree_deref_slot_protected(slot, | |
381 | &mapping->i_pages.xa_lock); | |
382 | if (likely(page) && PageDirty(page)) { | |
383 | dec_wb_stat(old_wb, WB_RECLAIMABLE); | |
384 | inc_wb_stat(new_wb, WB_RECLAIMABLE); | |
385 | } | |
386 | } | |
387 | ||
388 | radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, 0, | |
389 | PAGECACHE_TAG_WRITEBACK) { | |
390 | struct page *page = radix_tree_deref_slot_protected(slot, | |
391 | &mapping->i_pages.xa_lock); | |
392 | if (likely(page)) { | |
393 | WARN_ON_ONCE(!PageWriteback(page)); | |
394 | dec_wb_stat(old_wb, WB_WRITEBACK); | |
395 | inc_wb_stat(new_wb, WB_WRITEBACK); | |
396 | } | |
397 | } | |
398 | ||
399 | wb_get(new_wb); | |
400 | ||
401 | /* | |
402 | * Transfer to @new_wb's IO list if necessary. The specific list | |
403 | * @inode was on is ignored and the inode is put on ->b_dirty which | |
404 | * is always correct including from ->b_dirty_time. The transfer | |
405 | * preserves @inode->dirtied_when ordering. | |
406 | */ | |
407 | if (!list_empty(&inode->i_io_list)) { | |
408 | struct inode *pos; | |
409 | ||
410 | inode_io_list_del_locked(inode, old_wb); | |
411 | inode->i_wb = new_wb; | |
412 | list_for_each_entry(pos, &new_wb->b_dirty, i_io_list) | |
413 | if (time_after_eq(inode->dirtied_when, | |
414 | pos->dirtied_when)) | |
415 | break; | |
416 | inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev); | |
417 | } else { | |
418 | inode->i_wb = new_wb; | |
419 | } | |
420 | ||
421 | /* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */ | |
422 | inode->i_wb_frn_winner = 0; | |
423 | inode->i_wb_frn_avg_time = 0; | |
424 | inode->i_wb_frn_history = 0; | |
425 | switched = true; | |
426 | skip_switch: | |
427 | /* | |
428 | * Paired with load_acquire in unlocked_inode_to_wb_begin() and | |
429 | * ensures that the new wb is visible if they see !I_WB_SWITCH. | |
430 | */ | |
431 | smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH); | |
432 | ||
433 | xa_unlock_irq(&mapping->i_pages); | |
434 | spin_unlock(&inode->i_lock); | |
435 | spin_unlock(&new_wb->list_lock); | |
436 | spin_unlock(&old_wb->list_lock); | |
437 | ||
438 | if (switched) { | |
439 | wb_wakeup(new_wb); | |
440 | wb_put(old_wb); | |
441 | } | |
442 | wb_put(new_wb); | |
443 | ||
444 | iput(inode); | |
445 | kfree(isw); | |
446 | ||
447 | atomic_dec(&isw_nr_in_flight); | |
448 | } | |
449 | ||
450 | static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head) | |
451 | { | |
452 | struct inode_switch_wbs_context *isw = container_of(rcu_head, | |
453 | struct inode_switch_wbs_context, rcu_head); | |
454 | ||
455 | /* needs to grab bh-unsafe locks, bounce to work item */ | |
456 | INIT_WORK(&isw->work, inode_switch_wbs_work_fn); | |
457 | queue_work(isw_wq, &isw->work); | |
458 | } | |
459 | ||
460 | /** | |
461 | * inode_switch_wbs - change the wb association of an inode | |
462 | * @inode: target inode | |
463 | * @new_wb_id: ID of the new wb | |
464 | * | |
465 | * Switch @inode's wb association to the wb identified by @new_wb_id. The | |
466 | * switching is performed asynchronously and may fail silently. | |
467 | */ | |
468 | static void inode_switch_wbs(struct inode *inode, int new_wb_id) | |
469 | { | |
470 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
471 | struct cgroup_subsys_state *memcg_css; | |
472 | struct inode_switch_wbs_context *isw; | |
473 | ||
474 | /* noop if seems to be already in progress */ | |
475 | if (inode->i_state & I_WB_SWITCH) | |
476 | return; | |
477 | ||
478 | isw = kzalloc(sizeof(*isw), GFP_ATOMIC); | |
479 | if (!isw) | |
480 | return; | |
481 | ||
482 | /* find and pin the new wb */ | |
483 | rcu_read_lock(); | |
484 | memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys); | |
485 | if (memcg_css) | |
486 | isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); | |
487 | rcu_read_unlock(); | |
488 | if (!isw->new_wb) | |
489 | goto out_free; | |
490 | ||
491 | /* while holding I_WB_SWITCH, no one else can update the association */ | |
492 | spin_lock(&inode->i_lock); | |
493 | if (!(inode->i_sb->s_flags & SB_ACTIVE) || | |
494 | inode->i_state & (I_WB_SWITCH | I_FREEING) || | |
495 | inode_to_wb(inode) == isw->new_wb) { | |
496 | spin_unlock(&inode->i_lock); | |
497 | goto out_free; | |
498 | } | |
499 | inode->i_state |= I_WB_SWITCH; | |
500 | __iget(inode); | |
501 | spin_unlock(&inode->i_lock); | |
502 | ||
503 | isw->inode = inode; | |
504 | ||
505 | atomic_inc(&isw_nr_in_flight); | |
506 | ||
507 | /* | |
508 | * In addition to synchronizing among switchers, I_WB_SWITCH tells | |
509 | * the RCU protected stat update paths to grab the i_page | |
510 | * lock so that stat transfer can synchronize against them. | |
511 | * Let's continue after I_WB_SWITCH is guaranteed to be visible. | |
512 | */ | |
513 | call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn); | |
514 | return; | |
515 | ||
516 | out_free: | |
517 | if (isw->new_wb) | |
518 | wb_put(isw->new_wb); | |
519 | kfree(isw); | |
520 | } | |
521 | ||
522 | /** | |
523 | * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it | |
524 | * @wbc: writeback_control of interest | |
525 | * @inode: target inode | |
526 | * | |
527 | * @inode is locked and about to be written back under the control of @wbc. | |
528 | * Record @inode's writeback context into @wbc and unlock the i_lock. On | |
529 | * writeback completion, wbc_detach_inode() should be called. This is used | |
530 | * to track the cgroup writeback context. | |
531 | */ | |
532 | void wbc_attach_and_unlock_inode(struct writeback_control *wbc, | |
533 | struct inode *inode) | |
534 | { | |
535 | if (!inode_cgwb_enabled(inode)) { | |
536 | spin_unlock(&inode->i_lock); | |
537 | return; | |
538 | } | |
539 | ||
540 | wbc->wb = inode_to_wb(inode); | |
541 | wbc->inode = inode; | |
542 | ||
543 | wbc->wb_id = wbc->wb->memcg_css->id; | |
544 | wbc->wb_lcand_id = inode->i_wb_frn_winner; | |
545 | wbc->wb_tcand_id = 0; | |
546 | wbc->wb_bytes = 0; | |
547 | wbc->wb_lcand_bytes = 0; | |
548 | wbc->wb_tcand_bytes = 0; | |
549 | ||
550 | wb_get(wbc->wb); | |
551 | spin_unlock(&inode->i_lock); | |
552 | ||
553 | /* | |
554 | * A dying wb indicates that the memcg-blkcg mapping has changed | |
555 | * and a new wb is already serving the memcg. Switch immediately. | |
556 | */ | |
557 | if (unlikely(wb_dying(wbc->wb))) | |
558 | inode_switch_wbs(inode, wbc->wb_id); | |
559 | } | |
560 | ||
561 | /** | |
562 | * wbc_detach_inode - disassociate wbc from inode and perform foreign detection | |
563 | * @wbc: writeback_control of the just finished writeback | |
564 | * | |
565 | * To be called after a writeback attempt of an inode finishes and undoes | |
566 | * wbc_attach_and_unlock_inode(). Can be called under any context. | |
567 | * | |
568 | * As concurrent write sharing of an inode is expected to be very rare and | |
569 | * memcg only tracks page ownership on first-use basis severely confining | |
570 | * the usefulness of such sharing, cgroup writeback tracks ownership | |
571 | * per-inode. While the support for concurrent write sharing of an inode | |
572 | * is deemed unnecessary, an inode being written to by different cgroups at | |
573 | * different points in time is a lot more common, and, more importantly, | |
574 | * charging only by first-use can too readily lead to grossly incorrect | |
575 | * behaviors (single foreign page can lead to gigabytes of writeback to be | |
576 | * incorrectly attributed). | |
577 | * | |
578 | * To resolve this issue, cgroup writeback detects the majority dirtier of | |
579 | * an inode and transfers the ownership to it. To avoid unnnecessary | |
580 | * oscillation, the detection mechanism keeps track of history and gives | |
581 | * out the switch verdict only if the foreign usage pattern is stable over | |
582 | * a certain amount of time and/or writeback attempts. | |
583 | * | |
584 | * On each writeback attempt, @wbc tries to detect the majority writer | |
585 | * using Boyer-Moore majority vote algorithm. In addition to the byte | |
586 | * count from the majority voting, it also counts the bytes written for the | |
587 | * current wb and the last round's winner wb (max of last round's current | |
588 | * wb, the winner from two rounds ago, and the last round's majority | |
589 | * candidate). Keeping track of the historical winner helps the algorithm | |
590 | * to semi-reliably detect the most active writer even when it's not the | |
591 | * absolute majority. | |
592 | * | |
593 | * Once the winner of the round is determined, whether the winner is | |
594 | * foreign or not and how much IO time the round consumed is recorded in | |
595 | * inode->i_wb_frn_history. If the amount of recorded foreign IO time is | |
596 | * over a certain threshold, the switch verdict is given. | |
597 | */ | |
598 | void wbc_detach_inode(struct writeback_control *wbc) | |
599 | { | |
600 | struct bdi_writeback *wb = wbc->wb; | |
601 | struct inode *inode = wbc->inode; | |
602 | unsigned long avg_time, max_bytes, max_time; | |
603 | u16 history; | |
604 | int max_id; | |
605 | ||
606 | if (!wb) | |
607 | return; | |
608 | ||
609 | history = inode->i_wb_frn_history; | |
610 | avg_time = inode->i_wb_frn_avg_time; | |
611 | ||
612 | /* pick the winner of this round */ | |
613 | if (wbc->wb_bytes >= wbc->wb_lcand_bytes && | |
614 | wbc->wb_bytes >= wbc->wb_tcand_bytes) { | |
615 | max_id = wbc->wb_id; | |
616 | max_bytes = wbc->wb_bytes; | |
617 | } else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) { | |
618 | max_id = wbc->wb_lcand_id; | |
619 | max_bytes = wbc->wb_lcand_bytes; | |
620 | } else { | |
621 | max_id = wbc->wb_tcand_id; | |
622 | max_bytes = wbc->wb_tcand_bytes; | |
623 | } | |
624 | ||
625 | /* | |
626 | * Calculate the amount of IO time the winner consumed and fold it | |
627 | * into the running average kept per inode. If the consumed IO | |
628 | * time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for | |
629 | * deciding whether to switch or not. This is to prevent one-off | |
630 | * small dirtiers from skewing the verdict. | |
631 | */ | |
632 | max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT, | |
633 | wb->avg_write_bandwidth); | |
634 | if (avg_time) | |
635 | avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) - | |
636 | (avg_time >> WB_FRN_TIME_AVG_SHIFT); | |
637 | else | |
638 | avg_time = max_time; /* immediate catch up on first run */ | |
639 | ||
640 | if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) { | |
641 | int slots; | |
642 | ||
643 | /* | |
644 | * The switch verdict is reached if foreign wb's consume | |
645 | * more than a certain proportion of IO time in a | |
646 | * WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot | |
647 | * history mask where each bit represents one sixteenth of | |
648 | * the period. Determine the number of slots to shift into | |
649 | * history from @max_time. | |
650 | */ | |
651 | slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT), | |
652 | (unsigned long)WB_FRN_HIST_MAX_SLOTS); | |
653 | history <<= slots; | |
654 | if (wbc->wb_id != max_id) | |
655 | history |= (1U << slots) - 1; | |
656 | ||
657 | /* | |
658 | * Switch if the current wb isn't the consistent winner. | |
659 | * If there are multiple closely competing dirtiers, the | |
660 | * inode may switch across them repeatedly over time, which | |
661 | * is okay. The main goal is avoiding keeping an inode on | |
662 | * the wrong wb for an extended period of time. | |
663 | */ | |
664 | if (hweight32(history) > WB_FRN_HIST_THR_SLOTS) | |
665 | inode_switch_wbs(inode, max_id); | |
666 | } | |
667 | ||
668 | /* | |
669 | * Multiple instances of this function may race to update the | |
670 | * following fields but we don't mind occassional inaccuracies. | |
671 | */ | |
672 | inode->i_wb_frn_winner = max_id; | |
673 | inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX); | |
674 | inode->i_wb_frn_history = history; | |
675 | ||
676 | wb_put(wbc->wb); | |
677 | wbc->wb = NULL; | |
678 | } | |
679 | ||
680 | /** | |
681 | * wbc_account_io - account IO issued during writeback | |
682 | * @wbc: writeback_control of the writeback in progress | |
683 | * @page: page being written out | |
684 | * @bytes: number of bytes being written out | |
685 | * | |
686 | * @bytes from @page are about to written out during the writeback | |
687 | * controlled by @wbc. Keep the book for foreign inode detection. See | |
688 | * wbc_detach_inode(). | |
689 | */ | |
690 | void wbc_account_io(struct writeback_control *wbc, struct page *page, | |
691 | size_t bytes) | |
692 | { | |
693 | int id; | |
694 | ||
695 | /* | |
696 | * pageout() path doesn't attach @wbc to the inode being written | |
697 | * out. This is intentional as we don't want the function to block | |
698 | * behind a slow cgroup. Ultimately, we want pageout() to kick off | |
699 | * regular writeback instead of writing things out itself. | |
700 | */ | |
701 | if (!wbc->wb) | |
702 | return; | |
703 | ||
704 | id = mem_cgroup_css_from_page(page)->id; | |
705 | ||
706 | if (id == wbc->wb_id) { | |
707 | wbc->wb_bytes += bytes; | |
708 | return; | |
709 | } | |
710 | ||
711 | if (id == wbc->wb_lcand_id) | |
712 | wbc->wb_lcand_bytes += bytes; | |
713 | ||
714 | /* Boyer-Moore majority vote algorithm */ | |
715 | if (!wbc->wb_tcand_bytes) | |
716 | wbc->wb_tcand_id = id; | |
717 | if (id == wbc->wb_tcand_id) | |
718 | wbc->wb_tcand_bytes += bytes; | |
719 | else | |
720 | wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes); | |
721 | } | |
722 | EXPORT_SYMBOL_GPL(wbc_account_io); | |
723 | ||
724 | /** | |
725 | * inode_congested - test whether an inode is congested | |
726 | * @inode: inode to test for congestion (may be NULL) | |
727 | * @cong_bits: mask of WB_[a]sync_congested bits to test | |
728 | * | |
729 | * Tests whether @inode is congested. @cong_bits is the mask of congestion | |
730 | * bits to test and the return value is the mask of set bits. | |
731 | * | |
732 | * If cgroup writeback is enabled for @inode, the congestion state is | |
733 | * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg | |
734 | * associated with @inode is congested; otherwise, the root wb's congestion | |
735 | * state is used. | |
736 | * | |
737 | * @inode is allowed to be NULL as this function is often called on | |
738 | * mapping->host which is NULL for the swapper space. | |
739 | */ | |
740 | int inode_congested(struct inode *inode, int cong_bits) | |
741 | { | |
742 | /* | |
743 | * Once set, ->i_wb never becomes NULL while the inode is alive. | |
744 | * Start transaction iff ->i_wb is visible. | |
745 | */ | |
746 | if (inode && inode_to_wb_is_valid(inode)) { | |
747 | struct bdi_writeback *wb; | |
748 | bool locked, congested; | |
749 | ||
750 | wb = unlocked_inode_to_wb_begin(inode, &locked); | |
751 | congested = wb_congested(wb, cong_bits); | |
752 | unlocked_inode_to_wb_end(inode, locked); | |
753 | return congested; | |
754 | } | |
755 | ||
756 | return wb_congested(&inode_to_bdi(inode)->wb, cong_bits); | |
757 | } | |
758 | EXPORT_SYMBOL_GPL(inode_congested); | |
759 | ||
760 | /** | |
761 | * wb_split_bdi_pages - split nr_pages to write according to bandwidth | |
762 | * @wb: target bdi_writeback to split @nr_pages to | |
763 | * @nr_pages: number of pages to write for the whole bdi | |
764 | * | |
765 | * Split @wb's portion of @nr_pages according to @wb's write bandwidth in | |
766 | * relation to the total write bandwidth of all wb's w/ dirty inodes on | |
767 | * @wb->bdi. | |
768 | */ | |
769 | static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages) | |
770 | { | |
771 | unsigned long this_bw = wb->avg_write_bandwidth; | |
772 | unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth); | |
773 | ||
774 | if (nr_pages == LONG_MAX) | |
775 | return LONG_MAX; | |
776 | ||
777 | /* | |
778 | * This may be called on clean wb's and proportional distribution | |
779 | * may not make sense, just use the original @nr_pages in those | |
780 | * cases. In general, we wanna err on the side of writing more. | |
781 | */ | |
782 | if (!tot_bw || this_bw >= tot_bw) | |
783 | return nr_pages; | |
784 | else | |
785 | return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw); | |
786 | } | |
787 | ||
788 | /** | |
789 | * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi | |
790 | * @bdi: target backing_dev_info | |
791 | * @base_work: wb_writeback_work to issue | |
792 | * @skip_if_busy: skip wb's which already have writeback in progress | |
793 | * | |
794 | * Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which | |
795 | * have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's | |
796 | * distributed to the busy wbs according to each wb's proportion in the | |
797 | * total active write bandwidth of @bdi. | |
798 | */ | |
799 | static void bdi_split_work_to_wbs(struct backing_dev_info *bdi, | |
800 | struct wb_writeback_work *base_work, | |
801 | bool skip_if_busy) | |
802 | { | |
803 | struct bdi_writeback *last_wb = NULL; | |
804 | struct bdi_writeback *wb = list_entry(&bdi->wb_list, | |
805 | struct bdi_writeback, bdi_node); | |
806 | ||
807 | might_sleep(); | |
808 | restart: | |
809 | rcu_read_lock(); | |
810 | list_for_each_entry_continue_rcu(wb, &bdi->wb_list, bdi_node) { | |
811 | DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done); | |
812 | struct wb_writeback_work fallback_work; | |
813 | struct wb_writeback_work *work; | |
814 | long nr_pages; | |
815 | ||
816 | if (last_wb) { | |
817 | wb_put(last_wb); | |
818 | last_wb = NULL; | |
819 | } | |
820 | ||
821 | /* SYNC_ALL writes out I_DIRTY_TIME too */ | |
822 | if (!wb_has_dirty_io(wb) && | |
823 | (base_work->sync_mode == WB_SYNC_NONE || | |
824 | list_empty(&wb->b_dirty_time))) | |
825 | continue; | |
826 | if (skip_if_busy && writeback_in_progress(wb)) | |
827 | continue; | |
828 | ||
829 | nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages); | |
830 | ||
831 | work = kmalloc(sizeof(*work), GFP_ATOMIC); | |
832 | if (work) { | |
833 | *work = *base_work; | |
834 | work->nr_pages = nr_pages; | |
835 | work->auto_free = 1; | |
836 | wb_queue_work(wb, work); | |
837 | continue; | |
838 | } | |
839 | ||
840 | /* alloc failed, execute synchronously using on-stack fallback */ | |
841 | work = &fallback_work; | |
842 | *work = *base_work; | |
843 | work->nr_pages = nr_pages; | |
844 | work->auto_free = 0; | |
845 | work->done = &fallback_work_done; | |
846 | ||
847 | wb_queue_work(wb, work); | |
848 | ||
849 | /* | |
850 | * Pin @wb so that it stays on @bdi->wb_list. This allows | |
851 | * continuing iteration from @wb after dropping and | |
852 | * regrabbing rcu read lock. | |
853 | */ | |
854 | wb_get(wb); | |
855 | last_wb = wb; | |
856 | ||
857 | rcu_read_unlock(); | |
858 | wb_wait_for_completion(bdi, &fallback_work_done); | |
859 | goto restart; | |
860 | } | |
861 | rcu_read_unlock(); | |
862 | ||
863 | if (last_wb) | |
864 | wb_put(last_wb); | |
865 | } | |
866 | ||
867 | /** | |
868 | * cgroup_writeback_umount - flush inode wb switches for umount | |
869 | * | |
870 | * This function is called when a super_block is about to be destroyed and | |
871 | * flushes in-flight inode wb switches. An inode wb switch goes through | |
872 | * RCU and then workqueue, so the two need to be flushed in order to ensure | |
873 | * that all previously scheduled switches are finished. As wb switches are | |
874 | * rare occurrences and synchronize_rcu() can take a while, perform | |
875 | * flushing iff wb switches are in flight. | |
876 | */ | |
877 | void cgroup_writeback_umount(void) | |
878 | { | |
879 | if (atomic_read(&isw_nr_in_flight)) { | |
880 | synchronize_rcu(); | |
881 | flush_workqueue(isw_wq); | |
882 | } | |
883 | } | |
884 | ||
885 | static int __init cgroup_writeback_init(void) | |
886 | { | |
887 | isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0); | |
888 | if (!isw_wq) | |
889 | return -ENOMEM; | |
890 | return 0; | |
891 | } | |
892 | fs_initcall(cgroup_writeback_init); | |
893 | ||
894 | #else /* CONFIG_CGROUP_WRITEBACK */ | |
895 | ||
896 | static struct bdi_writeback * | |
897 | locked_inode_to_wb_and_lock_list(struct inode *inode) | |
898 | __releases(&inode->i_lock) | |
899 | __acquires(&wb->list_lock) | |
900 | { | |
901 | struct bdi_writeback *wb = inode_to_wb(inode); | |
902 | ||
903 | spin_unlock(&inode->i_lock); | |
904 | spin_lock(&wb->list_lock); | |
905 | return wb; | |
906 | } | |
907 | ||
908 | static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode) | |
909 | __acquires(&wb->list_lock) | |
910 | { | |
911 | struct bdi_writeback *wb = inode_to_wb(inode); | |
912 | ||
913 | spin_lock(&wb->list_lock); | |
914 | return wb; | |
915 | } | |
916 | ||
917 | static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages) | |
918 | { | |
919 | return nr_pages; | |
920 | } | |
921 | ||
922 | static void bdi_split_work_to_wbs(struct backing_dev_info *bdi, | |
923 | struct wb_writeback_work *base_work, | |
924 | bool skip_if_busy) | |
925 | { | |
926 | might_sleep(); | |
927 | ||
928 | if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) { | |
929 | base_work->auto_free = 0; | |
930 | wb_queue_work(&bdi->wb, base_work); | |
931 | } | |
932 | } | |
933 | ||
934 | #endif /* CONFIG_CGROUP_WRITEBACK */ | |
935 | ||
936 | /* | |
937 | * Add in the number of potentially dirty inodes, because each inode | |
938 | * write can dirty pagecache in the underlying blockdev. | |
939 | */ | |
940 | static unsigned long get_nr_dirty_pages(void) | |
941 | { | |
942 | return global_node_page_state(NR_FILE_DIRTY) + | |
943 | global_node_page_state(NR_UNSTABLE_NFS) + | |
944 | get_nr_dirty_inodes(); | |
945 | } | |
946 | ||
947 | static void wb_start_writeback(struct bdi_writeback *wb, enum wb_reason reason) | |
948 | { | |
949 | if (!wb_has_dirty_io(wb)) | |
950 | return; | |
951 | ||
952 | /* | |
953 | * All callers of this function want to start writeback of all | |
954 | * dirty pages. Places like vmscan can call this at a very | |
955 | * high frequency, causing pointless allocations of tons of | |
956 | * work items and keeping the flusher threads busy retrieving | |
957 | * that work. Ensure that we only allow one of them pending and | |
958 | * inflight at the time. | |
959 | */ | |
960 | if (test_bit(WB_start_all, &wb->state) || | |
961 | test_and_set_bit(WB_start_all, &wb->state)) | |
962 | return; | |
963 | ||
964 | wb->start_all_reason = reason; | |
965 | wb_wakeup(wb); | |
966 | } | |
967 | ||
968 | /** | |
969 | * wb_start_background_writeback - start background writeback | |
970 | * @wb: bdi_writback to write from | |
971 | * | |
972 | * Description: | |
973 | * This makes sure WB_SYNC_NONE background writeback happens. When | |
974 | * this function returns, it is only guaranteed that for given wb | |
975 | * some IO is happening if we are over background dirty threshold. | |
976 | * Caller need not hold sb s_umount semaphore. | |
977 | */ | |
978 | void wb_start_background_writeback(struct bdi_writeback *wb) | |
979 | { | |
980 | /* | |
981 | * We just wake up the flusher thread. It will perform background | |
982 | * writeback as soon as there is no other work to do. | |
983 | */ | |
984 | trace_writeback_wake_background(wb); | |
985 | wb_wakeup(wb); | |
986 | } | |
987 | ||
988 | /* | |
989 | * Remove the inode from the writeback list it is on. | |
990 | */ | |
991 | void inode_io_list_del(struct inode *inode) | |
992 | { | |
993 | struct bdi_writeback *wb; | |
994 | ||
995 | wb = inode_to_wb_and_lock_list(inode); | |
996 | inode_io_list_del_locked(inode, wb); | |
997 | spin_unlock(&wb->list_lock); | |
998 | } | |
999 | ||
1000 | /* | |
1001 | * mark an inode as under writeback on the sb | |
1002 | */ | |
1003 | void sb_mark_inode_writeback(struct inode *inode) | |
1004 | { | |
1005 | struct super_block *sb = inode->i_sb; | |
1006 | unsigned long flags; | |
1007 | ||
1008 | if (list_empty(&inode->i_wb_list)) { | |
1009 | spin_lock_irqsave(&sb->s_inode_wblist_lock, flags); | |
1010 | if (list_empty(&inode->i_wb_list)) { | |
1011 | list_add_tail(&inode->i_wb_list, &sb->s_inodes_wb); | |
1012 | trace_sb_mark_inode_writeback(inode); | |
1013 | } | |
1014 | spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags); | |
1015 | } | |
1016 | } | |
1017 | ||
1018 | /* | |
1019 | * clear an inode as under writeback on the sb | |
1020 | */ | |
1021 | void sb_clear_inode_writeback(struct inode *inode) | |
1022 | { | |
1023 | struct super_block *sb = inode->i_sb; | |
1024 | unsigned long flags; | |
1025 | ||
1026 | if (!list_empty(&inode->i_wb_list)) { | |
1027 | spin_lock_irqsave(&sb->s_inode_wblist_lock, flags); | |
1028 | if (!list_empty(&inode->i_wb_list)) { | |
1029 | list_del_init(&inode->i_wb_list); | |
1030 | trace_sb_clear_inode_writeback(inode); | |
1031 | } | |
1032 | spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags); | |
1033 | } | |
1034 | } | |
1035 | ||
1036 | /* | |
1037 | * Redirty an inode: set its when-it-was dirtied timestamp and move it to the | |
1038 | * furthest end of its superblock's dirty-inode list. | |
1039 | * | |
1040 | * Before stamping the inode's ->dirtied_when, we check to see whether it is | |
1041 | * already the most-recently-dirtied inode on the b_dirty list. If that is | |
1042 | * the case then the inode must have been redirtied while it was being written | |
1043 | * out and we don't reset its dirtied_when. | |
1044 | */ | |
1045 | static void redirty_tail(struct inode *inode, struct bdi_writeback *wb) | |
1046 | { | |
1047 | if (!list_empty(&wb->b_dirty)) { | |
1048 | struct inode *tail; | |
1049 | ||
1050 | tail = wb_inode(wb->b_dirty.next); | |
1051 | if (time_before(inode->dirtied_when, tail->dirtied_when)) | |
1052 | inode->dirtied_when = jiffies; | |
1053 | } | |
1054 | inode_io_list_move_locked(inode, wb, &wb->b_dirty); | |
1055 | } | |
1056 | ||
1057 | /* | |
1058 | * requeue inode for re-scanning after bdi->b_io list is exhausted. | |
1059 | */ | |
1060 | static void requeue_io(struct inode *inode, struct bdi_writeback *wb) | |
1061 | { | |
1062 | inode_io_list_move_locked(inode, wb, &wb->b_more_io); | |
1063 | } | |
1064 | ||
1065 | static void inode_sync_complete(struct inode *inode) | |
1066 | { | |
1067 | inode->i_state &= ~I_SYNC; | |
1068 | /* If inode is clean an unused, put it into LRU now... */ | |
1069 | inode_add_lru(inode); | |
1070 | /* Waiters must see I_SYNC cleared before being woken up */ | |
1071 | smp_mb(); | |
1072 | wake_up_bit(&inode->i_state, __I_SYNC); | |
1073 | } | |
1074 | ||
1075 | static bool inode_dirtied_after(struct inode *inode, unsigned long t) | |
1076 | { | |
1077 | bool ret = time_after(inode->dirtied_when, t); | |
1078 | #ifndef CONFIG_64BIT | |
1079 | /* | |
1080 | * For inodes being constantly redirtied, dirtied_when can get stuck. | |
1081 | * It _appears_ to be in the future, but is actually in distant past. | |
1082 | * This test is necessary to prevent such wrapped-around relative times | |
1083 | * from permanently stopping the whole bdi writeback. | |
1084 | */ | |
1085 | ret = ret && time_before_eq(inode->dirtied_when, jiffies); | |
1086 | #endif | |
1087 | return ret; | |
1088 | } | |
1089 | ||
1090 | #define EXPIRE_DIRTY_ATIME 0x0001 | |
1091 | ||
1092 | /* | |
1093 | * Move expired (dirtied before work->older_than_this) dirty inodes from | |
1094 | * @delaying_queue to @dispatch_queue. | |
1095 | */ | |
1096 | static int move_expired_inodes(struct list_head *delaying_queue, | |
1097 | struct list_head *dispatch_queue, | |
1098 | int flags, | |
1099 | struct wb_writeback_work *work) | |
1100 | { | |
1101 | unsigned long *older_than_this = NULL; | |
1102 | unsigned long expire_time; | |
1103 | LIST_HEAD(tmp); | |
1104 | struct list_head *pos, *node; | |
1105 | struct super_block *sb = NULL; | |
1106 | struct inode *inode; | |
1107 | int do_sb_sort = 0; | |
1108 | int moved = 0; | |
1109 | ||
1110 | if ((flags & EXPIRE_DIRTY_ATIME) == 0) | |
1111 | older_than_this = work->older_than_this; | |
1112 | else if (!work->for_sync) { | |
1113 | expire_time = jiffies - (dirtytime_expire_interval * HZ); | |
1114 | older_than_this = &expire_time; | |
1115 | } | |
1116 | while (!list_empty(delaying_queue)) { | |
1117 | inode = wb_inode(delaying_queue->prev); | |
1118 | if (older_than_this && | |
1119 | inode_dirtied_after(inode, *older_than_this)) | |
1120 | break; | |
1121 | list_move(&inode->i_io_list, &tmp); | |
1122 | moved++; | |
1123 | if (flags & EXPIRE_DIRTY_ATIME) | |
1124 | set_bit(__I_DIRTY_TIME_EXPIRED, &inode->i_state); | |
1125 | if (sb_is_blkdev_sb(inode->i_sb)) | |
1126 | continue; | |
1127 | if (sb && sb != inode->i_sb) | |
1128 | do_sb_sort = 1; | |
1129 | sb = inode->i_sb; | |
1130 | } | |
1131 | ||
1132 | /* just one sb in list, splice to dispatch_queue and we're done */ | |
1133 | if (!do_sb_sort) { | |
1134 | list_splice(&tmp, dispatch_queue); | |
1135 | goto out; | |
1136 | } | |
1137 | ||
1138 | /* Move inodes from one superblock together */ | |
1139 | while (!list_empty(&tmp)) { | |
1140 | sb = wb_inode(tmp.prev)->i_sb; | |
1141 | list_for_each_prev_safe(pos, node, &tmp) { | |
1142 | inode = wb_inode(pos); | |
1143 | if (inode->i_sb == sb) | |
1144 | list_move(&inode->i_io_list, dispatch_queue); | |
1145 | } | |
1146 | } | |
1147 | out: | |
1148 | return moved; | |
1149 | } | |
1150 | ||
1151 | /* | |
1152 | * Queue all expired dirty inodes for io, eldest first. | |
1153 | * Before | |
1154 | * newly dirtied b_dirty b_io b_more_io | |
1155 | * =============> gf edc BA | |
1156 | * After | |
1157 | * newly dirtied b_dirty b_io b_more_io | |
1158 | * =============> g fBAedc | |
1159 | * | | |
1160 | * +--> dequeue for IO | |
1161 | */ | |
1162 | static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work) | |
1163 | { | |
1164 | int moved; | |
1165 | ||
1166 | assert_spin_locked(&wb->list_lock); | |
1167 | list_splice_init(&wb->b_more_io, &wb->b_io); | |
1168 | moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work); | |
1169 | moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io, | |
1170 | EXPIRE_DIRTY_ATIME, work); | |
1171 | if (moved) | |
1172 | wb_io_lists_populated(wb); | |
1173 | trace_writeback_queue_io(wb, work, moved); | |
1174 | } | |
1175 | ||
1176 | static int write_inode(struct inode *inode, struct writeback_control *wbc) | |
1177 | { | |
1178 | int ret; | |
1179 | ||
1180 | if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) { | |
1181 | trace_writeback_write_inode_start(inode, wbc); | |
1182 | ret = inode->i_sb->s_op->write_inode(inode, wbc); | |
1183 | trace_writeback_write_inode(inode, wbc); | |
1184 | return ret; | |
1185 | } | |
1186 | return 0; | |
1187 | } | |
1188 | ||
1189 | /* | |
1190 | * Wait for writeback on an inode to complete. Called with i_lock held. | |
1191 | * Caller must make sure inode cannot go away when we drop i_lock. | |
1192 | */ | |
1193 | static void __inode_wait_for_writeback(struct inode *inode) | |
1194 | __releases(inode->i_lock) | |
1195 | __acquires(inode->i_lock) | |
1196 | { | |
1197 | DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC); | |
1198 | wait_queue_head_t *wqh; | |
1199 | ||
1200 | wqh = bit_waitqueue(&inode->i_state, __I_SYNC); | |
1201 | while (inode->i_state & I_SYNC) { | |
1202 | spin_unlock(&inode->i_lock); | |
1203 | __wait_on_bit(wqh, &wq, bit_wait, | |
1204 | TASK_UNINTERRUPTIBLE); | |
1205 | spin_lock(&inode->i_lock); | |
1206 | } | |
1207 | } | |
1208 | ||
1209 | /* | |
1210 | * Wait for writeback on an inode to complete. Caller must have inode pinned. | |
1211 | */ | |
1212 | void inode_wait_for_writeback(struct inode *inode) | |
1213 | { | |
1214 | spin_lock(&inode->i_lock); | |
1215 | __inode_wait_for_writeback(inode); | |
1216 | spin_unlock(&inode->i_lock); | |
1217 | } | |
1218 | ||
1219 | /* | |
1220 | * Sleep until I_SYNC is cleared. This function must be called with i_lock | |
1221 | * held and drops it. It is aimed for callers not holding any inode reference | |
1222 | * so once i_lock is dropped, inode can go away. | |
1223 | */ | |
1224 | static void inode_sleep_on_writeback(struct inode *inode) | |
1225 | __releases(inode->i_lock) | |
1226 | { | |
1227 | DEFINE_WAIT(wait); | |
1228 | wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC); | |
1229 | int sleep; | |
1230 | ||
1231 | prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); | |
1232 | sleep = inode->i_state & I_SYNC; | |
1233 | spin_unlock(&inode->i_lock); | |
1234 | if (sleep) | |
1235 | schedule(); | |
1236 | finish_wait(wqh, &wait); | |
1237 | } | |
1238 | ||
1239 | /* | |
1240 | * Find proper writeback list for the inode depending on its current state and | |
1241 | * possibly also change of its state while we were doing writeback. Here we | |
1242 | * handle things such as livelock prevention or fairness of writeback among | |
1243 | * inodes. This function can be called only by flusher thread - noone else | |
1244 | * processes all inodes in writeback lists and requeueing inodes behind flusher | |
1245 | * thread's back can have unexpected consequences. | |
1246 | */ | |
1247 | static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, | |
1248 | struct writeback_control *wbc) | |
1249 | { | |
1250 | if (inode->i_state & I_FREEING) | |
1251 | return; | |
1252 | ||
1253 | /* | |
1254 | * Sync livelock prevention. Each inode is tagged and synced in one | |
1255 | * shot. If still dirty, it will be redirty_tail()'ed below. Update | |
1256 | * the dirty time to prevent enqueue and sync it again. | |
1257 | */ | |
1258 | if ((inode->i_state & I_DIRTY) && | |
1259 | (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)) | |
1260 | inode->dirtied_when = jiffies; | |
1261 | ||
1262 | if (wbc->pages_skipped) { | |
1263 | /* | |
1264 | * writeback is not making progress due to locked | |
1265 | * buffers. Skip this inode for now. | |
1266 | */ | |
1267 | redirty_tail(inode, wb); | |
1268 | return; | |
1269 | } | |
1270 | ||
1271 | if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) { | |
1272 | /* | |
1273 | * We didn't write back all the pages. nfs_writepages() | |
1274 | * sometimes bales out without doing anything. | |
1275 | */ | |
1276 | if (wbc->nr_to_write <= 0) { | |
1277 | /* Slice used up. Queue for next turn. */ | |
1278 | requeue_io(inode, wb); | |
1279 | } else { | |
1280 | /* | |
1281 | * Writeback blocked by something other than | |
1282 | * congestion. Delay the inode for some time to | |
1283 | * avoid spinning on the CPU (100% iowait) | |
1284 | * retrying writeback of the dirty page/inode | |
1285 | * that cannot be performed immediately. | |
1286 | */ | |
1287 | redirty_tail(inode, wb); | |
1288 | } | |
1289 | } else if (inode->i_state & I_DIRTY) { | |
1290 | /* | |
1291 | * Filesystems can dirty the inode during writeback operations, | |
1292 | * such as delayed allocation during submission or metadata | |
1293 | * updates after data IO completion. | |
1294 | */ | |
1295 | redirty_tail(inode, wb); | |
1296 | } else if (inode->i_state & I_DIRTY_TIME) { | |
1297 | inode->dirtied_when = jiffies; | |
1298 | inode_io_list_move_locked(inode, wb, &wb->b_dirty_time); | |
1299 | } else { | |
1300 | /* The inode is clean. Remove from writeback lists. */ | |
1301 | inode_io_list_del_locked(inode, wb); | |
1302 | } | |
1303 | } | |
1304 | ||
1305 | /* | |
1306 | * Write out an inode and its dirty pages. Do not update the writeback list | |
1307 | * linkage. That is left to the caller. The caller is also responsible for | |
1308 | * setting I_SYNC flag and calling inode_sync_complete() to clear it. | |
1309 | */ | |
1310 | static int | |
1311 | __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) | |
1312 | { | |
1313 | struct address_space *mapping = inode->i_mapping; | |
1314 | long nr_to_write = wbc->nr_to_write; | |
1315 | unsigned dirty; | |
1316 | int ret; | |
1317 | ||
1318 | WARN_ON(!(inode->i_state & I_SYNC)); | |
1319 | ||
1320 | trace_writeback_single_inode_start(inode, wbc, nr_to_write); | |
1321 | ||
1322 | ret = do_writepages(mapping, wbc); | |
1323 | ||
1324 | /* | |
1325 | * Make sure to wait on the data before writing out the metadata. | |
1326 | * This is important for filesystems that modify metadata on data | |
1327 | * I/O completion. We don't do it for sync(2) writeback because it has a | |
1328 | * separate, external IO completion path and ->sync_fs for guaranteeing | |
1329 | * inode metadata is written back correctly. | |
1330 | */ | |
1331 | if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) { | |
1332 | int err = filemap_fdatawait(mapping); | |
1333 | if (ret == 0) | |
1334 | ret = err; | |
1335 | } | |
1336 | ||
1337 | /* | |
1338 | * Some filesystems may redirty the inode during the writeback | |
1339 | * due to delalloc, clear dirty metadata flags right before | |
1340 | * write_inode() | |
1341 | */ | |
1342 | spin_lock(&inode->i_lock); | |
1343 | ||
1344 | dirty = inode->i_state & I_DIRTY; | |
1345 | if (inode->i_state & I_DIRTY_TIME) { | |
1346 | if ((dirty & I_DIRTY_INODE) || | |
1347 | wbc->sync_mode == WB_SYNC_ALL || | |
1348 | unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) || | |
1349 | unlikely(time_after(jiffies, | |
1350 | (inode->dirtied_time_when + | |
1351 | dirtytime_expire_interval * HZ)))) { | |
1352 | dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED; | |
1353 | trace_writeback_lazytime(inode); | |
1354 | } | |
1355 | } else | |
1356 | inode->i_state &= ~I_DIRTY_TIME_EXPIRED; | |
1357 | inode->i_state &= ~dirty; | |
1358 | ||
1359 | /* | |
1360 | * Paired with smp_mb() in __mark_inode_dirty(). This allows | |
1361 | * __mark_inode_dirty() to test i_state without grabbing i_lock - | |
1362 | * either they see the I_DIRTY bits cleared or we see the dirtied | |
1363 | * inode. | |
1364 | * | |
1365 | * I_DIRTY_PAGES is always cleared together above even if @mapping | |
1366 | * still has dirty pages. The flag is reinstated after smp_mb() if | |
1367 | * necessary. This guarantees that either __mark_inode_dirty() | |
1368 | * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY. | |
1369 | */ | |
1370 | smp_mb(); | |
1371 | ||
1372 | if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) | |
1373 | inode->i_state |= I_DIRTY_PAGES; | |
1374 | ||
1375 | spin_unlock(&inode->i_lock); | |
1376 | ||
1377 | if (dirty & I_DIRTY_TIME) | |
1378 | mark_inode_dirty_sync(inode); | |
1379 | /* Don't write the inode if only I_DIRTY_PAGES was set */ | |
1380 | if (dirty & ~I_DIRTY_PAGES) { | |
1381 | int err = write_inode(inode, wbc); | |
1382 | if (ret == 0) | |
1383 | ret = err; | |
1384 | } | |
1385 | trace_writeback_single_inode(inode, wbc, nr_to_write); | |
1386 | return ret; | |
1387 | } | |
1388 | ||
1389 | /* | |
1390 | * Write out an inode's dirty pages. Either the caller has an active reference | |
1391 | * on the inode or the inode has I_WILL_FREE set. | |
1392 | * | |
1393 | * This function is designed to be called for writing back one inode which | |
1394 | * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode() | |
1395 | * and does more profound writeback list handling in writeback_sb_inodes(). | |
1396 | */ | |
1397 | static int writeback_single_inode(struct inode *inode, | |
1398 | struct writeback_control *wbc) | |
1399 | { | |
1400 | struct bdi_writeback *wb; | |
1401 | int ret = 0; | |
1402 | ||
1403 | spin_lock(&inode->i_lock); | |
1404 | if (!atomic_read(&inode->i_count)) | |
1405 | WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING))); | |
1406 | else | |
1407 | WARN_ON(inode->i_state & I_WILL_FREE); | |
1408 | ||
1409 | if (inode->i_state & I_SYNC) { | |
1410 | if (wbc->sync_mode != WB_SYNC_ALL) | |
1411 | goto out; | |
1412 | /* | |
1413 | * It's a data-integrity sync. We must wait. Since callers hold | |
1414 | * inode reference or inode has I_WILL_FREE set, it cannot go | |
1415 | * away under us. | |
1416 | */ | |
1417 | __inode_wait_for_writeback(inode); | |
1418 | } | |
1419 | WARN_ON(inode->i_state & I_SYNC); | |
1420 | /* | |
1421 | * Skip inode if it is clean and we have no outstanding writeback in | |
1422 | * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this | |
1423 | * function since flusher thread may be doing for example sync in | |
1424 | * parallel and if we move the inode, it could get skipped. So here we | |
1425 | * make sure inode is on some writeback list and leave it there unless | |
1426 | * we have completely cleaned the inode. | |
1427 | */ | |
1428 | if (!(inode->i_state & I_DIRTY_ALL) && | |
1429 | (wbc->sync_mode != WB_SYNC_ALL || | |
1430 | !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK))) | |
1431 | goto out; | |
1432 | inode->i_state |= I_SYNC; | |
1433 | wbc_attach_and_unlock_inode(wbc, inode); | |
1434 | ||
1435 | ret = __writeback_single_inode(inode, wbc); | |
1436 | ||
1437 | wbc_detach_inode(wbc); | |
1438 | ||
1439 | wb = inode_to_wb_and_lock_list(inode); | |
1440 | spin_lock(&inode->i_lock); | |
1441 | /* | |
1442 | * If inode is clean, remove it from writeback lists. Otherwise don't | |
1443 | * touch it. See comment above for explanation. | |
1444 | */ | |
1445 | if (!(inode->i_state & I_DIRTY_ALL)) | |
1446 | inode_io_list_del_locked(inode, wb); | |
1447 | spin_unlock(&wb->list_lock); | |
1448 | inode_sync_complete(inode); | |
1449 | out: | |
1450 | spin_unlock(&inode->i_lock); | |
1451 | return ret; | |
1452 | } | |
1453 | ||
1454 | static long writeback_chunk_size(struct bdi_writeback *wb, | |
1455 | struct wb_writeback_work *work) | |
1456 | { | |
1457 | long pages; | |
1458 | ||
1459 | /* | |
1460 | * WB_SYNC_ALL mode does livelock avoidance by syncing dirty | |
1461 | * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX | |
1462 | * here avoids calling into writeback_inodes_wb() more than once. | |
1463 | * | |
1464 | * The intended call sequence for WB_SYNC_ALL writeback is: | |
1465 | * | |
1466 | * wb_writeback() | |
1467 | * writeback_sb_inodes() <== called only once | |
1468 | * write_cache_pages() <== called once for each inode | |
1469 | * (quickly) tag currently dirty pages | |
1470 | * (maybe slowly) sync all tagged pages | |
1471 | */ | |
1472 | if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages) | |
1473 | pages = LONG_MAX; | |
1474 | else { | |
1475 | pages = min(wb->avg_write_bandwidth / 2, | |
1476 | global_wb_domain.dirty_limit / DIRTY_SCOPE); | |
1477 | pages = min(pages, work->nr_pages); | |
1478 | pages = round_down(pages + MIN_WRITEBACK_PAGES, | |
1479 | MIN_WRITEBACK_PAGES); | |
1480 | } | |
1481 | ||
1482 | return pages; | |
1483 | } | |
1484 | ||
1485 | /* | |
1486 | * Write a portion of b_io inodes which belong to @sb. | |
1487 | * | |
1488 | * Return the number of pages and/or inodes written. | |
1489 | * | |
1490 | * NOTE! This is called with wb->list_lock held, and will | |
1491 | * unlock and relock that for each inode it ends up doing | |
1492 | * IO for. | |
1493 | */ | |
1494 | static long writeback_sb_inodes(struct super_block *sb, | |
1495 | struct bdi_writeback *wb, | |
1496 | struct wb_writeback_work *work) | |
1497 | { | |
1498 | struct writeback_control wbc = { | |
1499 | .sync_mode = work->sync_mode, | |
1500 | .tagged_writepages = work->tagged_writepages, | |
1501 | .for_kupdate = work->for_kupdate, | |
1502 | .for_background = work->for_background, | |
1503 | .for_sync = work->for_sync, | |
1504 | .range_cyclic = work->range_cyclic, | |
1505 | .range_start = 0, | |
1506 | .range_end = LLONG_MAX, | |
1507 | }; | |
1508 | unsigned long start_time = jiffies; | |
1509 | long write_chunk; | |
1510 | long wrote = 0; /* count both pages and inodes */ | |
1511 | ||
1512 | while (!list_empty(&wb->b_io)) { | |
1513 | struct inode *inode = wb_inode(wb->b_io.prev); | |
1514 | struct bdi_writeback *tmp_wb; | |
1515 | ||
1516 | if (inode->i_sb != sb) { | |
1517 | if (work->sb) { | |
1518 | /* | |
1519 | * We only want to write back data for this | |
1520 | * superblock, move all inodes not belonging | |
1521 | * to it back onto the dirty list. | |
1522 | */ | |
1523 | redirty_tail(inode, wb); | |
1524 | continue; | |
1525 | } | |
1526 | ||
1527 | /* | |
1528 | * The inode belongs to a different superblock. | |
1529 | * Bounce back to the caller to unpin this and | |
1530 | * pin the next superblock. | |
1531 | */ | |
1532 | break; | |
1533 | } | |
1534 | ||
1535 | /* | |
1536 | * Don't bother with new inodes or inodes being freed, first | |
1537 | * kind does not need periodic writeout yet, and for the latter | |
1538 | * kind writeout is handled by the freer. | |
1539 | */ | |
1540 | spin_lock(&inode->i_lock); | |
1541 | if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) { | |
1542 | spin_unlock(&inode->i_lock); | |
1543 | redirty_tail(inode, wb); | |
1544 | continue; | |
1545 | } | |
1546 | if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) { | |
1547 | /* | |
1548 | * If this inode is locked for writeback and we are not | |
1549 | * doing writeback-for-data-integrity, move it to | |
1550 | * b_more_io so that writeback can proceed with the | |
1551 | * other inodes on s_io. | |
1552 | * | |
1553 | * We'll have another go at writing back this inode | |
1554 | * when we completed a full scan of b_io. | |
1555 | */ | |
1556 | spin_unlock(&inode->i_lock); | |
1557 | requeue_io(inode, wb); | |
1558 | trace_writeback_sb_inodes_requeue(inode); | |
1559 | continue; | |
1560 | } | |
1561 | spin_unlock(&wb->list_lock); | |
1562 | ||
1563 | /* | |
1564 | * We already requeued the inode if it had I_SYNC set and we | |
1565 | * are doing WB_SYNC_NONE writeback. So this catches only the | |
1566 | * WB_SYNC_ALL case. | |
1567 | */ | |
1568 | if (inode->i_state & I_SYNC) { | |
1569 | /* Wait for I_SYNC. This function drops i_lock... */ | |
1570 | inode_sleep_on_writeback(inode); | |
1571 | /* Inode may be gone, start again */ | |
1572 | spin_lock(&wb->list_lock); | |
1573 | continue; | |
1574 | } | |
1575 | inode->i_state |= I_SYNC; | |
1576 | wbc_attach_and_unlock_inode(&wbc, inode); | |
1577 | ||
1578 | write_chunk = writeback_chunk_size(wb, work); | |
1579 | wbc.nr_to_write = write_chunk; | |
1580 | wbc.pages_skipped = 0; | |
1581 | ||
1582 | /* | |
1583 | * We use I_SYNC to pin the inode in memory. While it is set | |
1584 | * evict_inode() will wait so the inode cannot be freed. | |
1585 | */ | |
1586 | __writeback_single_inode(inode, &wbc); | |
1587 | ||
1588 | wbc_detach_inode(&wbc); | |
1589 | work->nr_pages -= write_chunk - wbc.nr_to_write; | |
1590 | wrote += write_chunk - wbc.nr_to_write; | |
1591 | ||
1592 | if (need_resched()) { | |
1593 | /* | |
1594 | * We're trying to balance between building up a nice | |
1595 | * long list of IOs to improve our merge rate, and | |
1596 | * getting those IOs out quickly for anyone throttling | |
1597 | * in balance_dirty_pages(). cond_resched() doesn't | |
1598 | * unplug, so get our IOs out the door before we | |
1599 | * give up the CPU. | |
1600 | */ | |
1601 | blk_flush_plug(current); | |
1602 | cond_resched(); | |
1603 | } | |
1604 | ||
1605 | /* | |
1606 | * Requeue @inode if still dirty. Be careful as @inode may | |
1607 | * have been switched to another wb in the meantime. | |
1608 | */ | |
1609 | tmp_wb = inode_to_wb_and_lock_list(inode); | |
1610 | spin_lock(&inode->i_lock); | |
1611 | if (!(inode->i_state & I_DIRTY_ALL)) | |
1612 | wrote++; | |
1613 | requeue_inode(inode, tmp_wb, &wbc); | |
1614 | inode_sync_complete(inode); | |
1615 | spin_unlock(&inode->i_lock); | |
1616 | ||
1617 | if (unlikely(tmp_wb != wb)) { | |
1618 | spin_unlock(&tmp_wb->list_lock); | |
1619 | spin_lock(&wb->list_lock); | |
1620 | } | |
1621 | ||
1622 | /* | |
1623 | * bail out to wb_writeback() often enough to check | |
1624 | * background threshold and other termination conditions. | |
1625 | */ | |
1626 | if (wrote) { | |
1627 | if (time_is_before_jiffies(start_time + HZ / 10UL)) | |
1628 | break; | |
1629 | if (work->nr_pages <= 0) | |
1630 | break; | |
1631 | } | |
1632 | } | |
1633 | return wrote; | |
1634 | } | |
1635 | ||
1636 | static long __writeback_inodes_wb(struct bdi_writeback *wb, | |
1637 | struct wb_writeback_work *work) | |
1638 | { | |
1639 | unsigned long start_time = jiffies; | |
1640 | long wrote = 0; | |
1641 | ||
1642 | while (!list_empty(&wb->b_io)) { | |
1643 | struct inode *inode = wb_inode(wb->b_io.prev); | |
1644 | struct super_block *sb = inode->i_sb; | |
1645 | ||
1646 | if (!trylock_super(sb)) { | |
1647 | /* | |
1648 | * trylock_super() may fail consistently due to | |
1649 | * s_umount being grabbed by someone else. Don't use | |
1650 | * requeue_io() to avoid busy retrying the inode/sb. | |
1651 | */ | |
1652 | redirty_tail(inode, wb); | |
1653 | continue; | |
1654 | } | |
1655 | wrote += writeback_sb_inodes(sb, wb, work); | |
1656 | up_read(&sb->s_umount); | |
1657 | ||
1658 | /* refer to the same tests at the end of writeback_sb_inodes */ | |
1659 | if (wrote) { | |
1660 | if (time_is_before_jiffies(start_time + HZ / 10UL)) | |
1661 | break; | |
1662 | if (work->nr_pages <= 0) | |
1663 | break; | |
1664 | } | |
1665 | } | |
1666 | /* Leave any unwritten inodes on b_io */ | |
1667 | return wrote; | |
1668 | } | |
1669 | ||
1670 | static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages, | |
1671 | enum wb_reason reason) | |
1672 | { | |
1673 | struct wb_writeback_work work = { | |
1674 | .nr_pages = nr_pages, | |
1675 | .sync_mode = WB_SYNC_NONE, | |
1676 | .range_cyclic = 1, | |
1677 | .reason = reason, | |
1678 | }; | |
1679 | struct blk_plug plug; | |
1680 | ||
1681 | blk_start_plug(&plug); | |
1682 | spin_lock(&wb->list_lock); | |
1683 | if (list_empty(&wb->b_io)) | |
1684 | queue_io(wb, &work); | |
1685 | __writeback_inodes_wb(wb, &work); | |
1686 | spin_unlock(&wb->list_lock); | |
1687 | blk_finish_plug(&plug); | |
1688 | ||
1689 | return nr_pages - work.nr_pages; | |
1690 | } | |
1691 | ||
1692 | /* | |
1693 | * Explicit flushing or periodic writeback of "old" data. | |
1694 | * | |
1695 | * Define "old": the first time one of an inode's pages is dirtied, we mark the | |
1696 | * dirtying-time in the inode's address_space. So this periodic writeback code | |
1697 | * just walks the superblock inode list, writing back any inodes which are | |
1698 | * older than a specific point in time. | |
1699 | * | |
1700 | * Try to run once per dirty_writeback_interval. But if a writeback event | |
1701 | * takes longer than a dirty_writeback_interval interval, then leave a | |
1702 | * one-second gap. | |
1703 | * | |
1704 | * older_than_this takes precedence over nr_to_write. So we'll only write back | |
1705 | * all dirty pages if they are all attached to "old" mappings. | |
1706 | */ | |
1707 | static long wb_writeback(struct bdi_writeback *wb, | |
1708 | struct wb_writeback_work *work) | |
1709 | { | |
1710 | unsigned long wb_start = jiffies; | |
1711 | long nr_pages = work->nr_pages; | |
1712 | unsigned long oldest_jif; | |
1713 | struct inode *inode; | |
1714 | long progress; | |
1715 | struct blk_plug plug; | |
1716 | ||
1717 | oldest_jif = jiffies; | |
1718 | work->older_than_this = &oldest_jif; | |
1719 | ||
1720 | blk_start_plug(&plug); | |
1721 | spin_lock(&wb->list_lock); | |
1722 | for (;;) { | |
1723 | /* | |
1724 | * Stop writeback when nr_pages has been consumed | |
1725 | */ | |
1726 | if (work->nr_pages <= 0) | |
1727 | break; | |
1728 | ||
1729 | /* | |
1730 | * Background writeout and kupdate-style writeback may | |
1731 | * run forever. Stop them if there is other work to do | |
1732 | * so that e.g. sync can proceed. They'll be restarted | |
1733 | * after the other works are all done. | |
1734 | */ | |
1735 | if ((work->for_background || work->for_kupdate) && | |
1736 | !list_empty(&wb->work_list)) | |
1737 | break; | |
1738 | ||
1739 | /* | |
1740 | * For background writeout, stop when we are below the | |
1741 | * background dirty threshold | |
1742 | */ | |
1743 | if (work->for_background && !wb_over_bg_thresh(wb)) | |
1744 | break; | |
1745 | ||
1746 | /* | |
1747 | * Kupdate and background works are special and we want to | |
1748 | * include all inodes that need writing. Livelock avoidance is | |
1749 | * handled by these works yielding to any other work so we are | |
1750 | * safe. | |
1751 | */ | |
1752 | if (work->for_kupdate) { | |
1753 | oldest_jif = jiffies - | |
1754 | msecs_to_jiffies(dirty_expire_interval * 10); | |
1755 | } else if (work->for_background) | |
1756 | oldest_jif = jiffies; | |
1757 | ||
1758 | trace_writeback_start(wb, work); | |
1759 | if (list_empty(&wb->b_io)) | |
1760 | queue_io(wb, work); | |
1761 | if (work->sb) | |
1762 | progress = writeback_sb_inodes(work->sb, wb, work); | |
1763 | else | |
1764 | progress = __writeback_inodes_wb(wb, work); | |
1765 | trace_writeback_written(wb, work); | |
1766 | ||
1767 | wb_update_bandwidth(wb, wb_start); | |
1768 | ||
1769 | /* | |
1770 | * Did we write something? Try for more | |
1771 | * | |
1772 | * Dirty inodes are moved to b_io for writeback in batches. | |
1773 | * The completion of the current batch does not necessarily | |
1774 | * mean the overall work is done. So we keep looping as long | |
1775 | * as made some progress on cleaning pages or inodes. | |
1776 | */ | |
1777 | if (progress) | |
1778 | continue; | |
1779 | /* | |
1780 | * No more inodes for IO, bail | |
1781 | */ | |
1782 | if (list_empty(&wb->b_more_io)) | |
1783 | break; | |
1784 | /* | |
1785 | * Nothing written. Wait for some inode to | |
1786 | * become available for writeback. Otherwise | |
1787 | * we'll just busyloop. | |
1788 | */ | |
1789 | trace_writeback_wait(wb, work); | |
1790 | inode = wb_inode(wb->b_more_io.prev); | |
1791 | spin_lock(&inode->i_lock); | |
1792 | spin_unlock(&wb->list_lock); | |
1793 | /* This function drops i_lock... */ | |
1794 | inode_sleep_on_writeback(inode); | |
1795 | spin_lock(&wb->list_lock); | |
1796 | } | |
1797 | spin_unlock(&wb->list_lock); | |
1798 | blk_finish_plug(&plug); | |
1799 | ||
1800 | return nr_pages - work->nr_pages; | |
1801 | } | |
1802 | ||
1803 | /* | |
1804 | * Return the next wb_writeback_work struct that hasn't been processed yet. | |
1805 | */ | |
1806 | static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb) | |
1807 | { | |
1808 | struct wb_writeback_work *work = NULL; | |
1809 | ||
1810 | spin_lock_bh(&wb->work_lock); | |
1811 | if (!list_empty(&wb->work_list)) { | |
1812 | work = list_entry(wb->work_list.next, | |
1813 | struct wb_writeback_work, list); | |
1814 | list_del_init(&work->list); | |
1815 | } | |
1816 | spin_unlock_bh(&wb->work_lock); | |
1817 | return work; | |
1818 | } | |
1819 | ||
1820 | static long wb_check_background_flush(struct bdi_writeback *wb) | |
1821 | { | |
1822 | if (wb_over_bg_thresh(wb)) { | |
1823 | ||
1824 | struct wb_writeback_work work = { | |
1825 | .nr_pages = LONG_MAX, | |
1826 | .sync_mode = WB_SYNC_NONE, | |
1827 | .for_background = 1, | |
1828 | .range_cyclic = 1, | |
1829 | .reason = WB_REASON_BACKGROUND, | |
1830 | }; | |
1831 | ||
1832 | return wb_writeback(wb, &work); | |
1833 | } | |
1834 | ||
1835 | return 0; | |
1836 | } | |
1837 | ||
1838 | static long wb_check_old_data_flush(struct bdi_writeback *wb) | |
1839 | { | |
1840 | unsigned long expired; | |
1841 | long nr_pages; | |
1842 | ||
1843 | /* | |
1844 | * When set to zero, disable periodic writeback | |
1845 | */ | |
1846 | if (!dirty_writeback_interval) | |
1847 | return 0; | |
1848 | ||
1849 | expired = wb->last_old_flush + | |
1850 | msecs_to_jiffies(dirty_writeback_interval * 10); | |
1851 | if (time_before(jiffies, expired)) | |
1852 | return 0; | |
1853 | ||
1854 | wb->last_old_flush = jiffies; | |
1855 | nr_pages = get_nr_dirty_pages(); | |
1856 | ||
1857 | if (nr_pages) { | |
1858 | struct wb_writeback_work work = { | |
1859 | .nr_pages = nr_pages, | |
1860 | .sync_mode = WB_SYNC_NONE, | |
1861 | .for_kupdate = 1, | |
1862 | .range_cyclic = 1, | |
1863 | .reason = WB_REASON_PERIODIC, | |
1864 | }; | |
1865 | ||
1866 | return wb_writeback(wb, &work); | |
1867 | } | |
1868 | ||
1869 | return 0; | |
1870 | } | |
1871 | ||
1872 | static long wb_check_start_all(struct bdi_writeback *wb) | |
1873 | { | |
1874 | long nr_pages; | |
1875 | ||
1876 | if (!test_bit(WB_start_all, &wb->state)) | |
1877 | return 0; | |
1878 | ||
1879 | nr_pages = get_nr_dirty_pages(); | |
1880 | if (nr_pages) { | |
1881 | struct wb_writeback_work work = { | |
1882 | .nr_pages = wb_split_bdi_pages(wb, nr_pages), | |
1883 | .sync_mode = WB_SYNC_NONE, | |
1884 | .range_cyclic = 1, | |
1885 | .reason = wb->start_all_reason, | |
1886 | }; | |
1887 | ||
1888 | nr_pages = wb_writeback(wb, &work); | |
1889 | } | |
1890 | ||
1891 | clear_bit(WB_start_all, &wb->state); | |
1892 | return nr_pages; | |
1893 | } | |
1894 | ||
1895 | ||
1896 | /* | |
1897 | * Retrieve work items and do the writeback they describe | |
1898 | */ | |
1899 | static long wb_do_writeback(struct bdi_writeback *wb) | |
1900 | { | |
1901 | struct wb_writeback_work *work; | |
1902 | long wrote = 0; | |
1903 | ||
1904 | set_bit(WB_writeback_running, &wb->state); | |
1905 | while ((work = get_next_work_item(wb)) != NULL) { | |
1906 | trace_writeback_exec(wb, work); | |
1907 | wrote += wb_writeback(wb, work); | |
1908 | finish_writeback_work(wb, work); | |
1909 | } | |
1910 | ||
1911 | /* | |
1912 | * Check for a flush-everything request | |
1913 | */ | |
1914 | wrote += wb_check_start_all(wb); | |
1915 | ||
1916 | /* | |
1917 | * Check for periodic writeback, kupdated() style | |
1918 | */ | |
1919 | wrote += wb_check_old_data_flush(wb); | |
1920 | wrote += wb_check_background_flush(wb); | |
1921 | clear_bit(WB_writeback_running, &wb->state); | |
1922 | ||
1923 | return wrote; | |
1924 | } | |
1925 | ||
1926 | /* | |
1927 | * Handle writeback of dirty data for the device backed by this bdi. Also | |
1928 | * reschedules periodically and does kupdated style flushing. | |
1929 | */ | |
1930 | void wb_workfn(struct work_struct *work) | |
1931 | { | |
1932 | struct bdi_writeback *wb = container_of(to_delayed_work(work), | |
1933 | struct bdi_writeback, dwork); | |
1934 | long pages_written; | |
1935 | ||
1936 | set_worker_desc("flush-%s", dev_name(wb->bdi->dev)); | |
1937 | current->flags |= PF_SWAPWRITE; | |
1938 | ||
1939 | if (likely(!current_is_workqueue_rescuer() || | |
1940 | !test_bit(WB_registered, &wb->state))) { | |
1941 | /* | |
1942 | * The normal path. Keep writing back @wb until its | |
1943 | * work_list is empty. Note that this path is also taken | |
1944 | * if @wb is shutting down even when we're running off the | |
1945 | * rescuer as work_list needs to be drained. | |
1946 | */ | |
1947 | do { | |
1948 | pages_written = wb_do_writeback(wb); | |
1949 | trace_writeback_pages_written(pages_written); | |
1950 | } while (!list_empty(&wb->work_list)); | |
1951 | } else { | |
1952 | /* | |
1953 | * bdi_wq can't get enough workers and we're running off | |
1954 | * the emergency worker. Don't hog it. Hopefully, 1024 is | |
1955 | * enough for efficient IO. | |
1956 | */ | |
1957 | pages_written = writeback_inodes_wb(wb, 1024, | |
1958 | WB_REASON_FORKER_THREAD); | |
1959 | trace_writeback_pages_written(pages_written); | |
1960 | } | |
1961 | ||
1962 | if (!list_empty(&wb->work_list)) | |
1963 | mod_delayed_work(bdi_wq, &wb->dwork, 0); | |
1964 | else if (wb_has_dirty_io(wb) && dirty_writeback_interval) | |
1965 | wb_wakeup_delayed(wb); | |
1966 | ||
1967 | current->flags &= ~PF_SWAPWRITE; | |
1968 | } | |
1969 | ||
1970 | /* | |
1971 | * Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero, | |
1972 | * write back the whole world. | |
1973 | */ | |
1974 | static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, | |
1975 | enum wb_reason reason) | |
1976 | { | |
1977 | struct bdi_writeback *wb; | |
1978 | ||
1979 | if (!bdi_has_dirty_io(bdi)) | |
1980 | return; | |
1981 | ||
1982 | list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node) | |
1983 | wb_start_writeback(wb, reason); | |
1984 | } | |
1985 | ||
1986 | void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, | |
1987 | enum wb_reason reason) | |
1988 | { | |
1989 | rcu_read_lock(); | |
1990 | __wakeup_flusher_threads_bdi(bdi, reason); | |
1991 | rcu_read_unlock(); | |
1992 | } | |
1993 | ||
1994 | /* | |
1995 | * Wakeup the flusher threads to start writeback of all currently dirty pages | |
1996 | */ | |
1997 | void wakeup_flusher_threads(enum wb_reason reason) | |
1998 | { | |
1999 | struct backing_dev_info *bdi; | |
2000 | ||
2001 | /* | |
2002 | * If we are expecting writeback progress we must submit plugged IO. | |
2003 | */ | |
2004 | if (blk_needs_flush_plug(current)) | |
2005 | blk_schedule_flush_plug(current); | |
2006 | ||
2007 | rcu_read_lock(); | |
2008 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
2009 | __wakeup_flusher_threads_bdi(bdi, reason); | |
2010 | rcu_read_unlock(); | |
2011 | } | |
2012 | ||
2013 | /* | |
2014 | * Wake up bdi's periodically to make sure dirtytime inodes gets | |
2015 | * written back periodically. We deliberately do *not* check the | |
2016 | * b_dirtytime list in wb_has_dirty_io(), since this would cause the | |
2017 | * kernel to be constantly waking up once there are any dirtytime | |
2018 | * inodes on the system. So instead we define a separate delayed work | |
2019 | * function which gets called much more rarely. (By default, only | |
2020 | * once every 12 hours.) | |
2021 | * | |
2022 | * If there is any other write activity going on in the file system, | |
2023 | * this function won't be necessary. But if the only thing that has | |
2024 | * happened on the file system is a dirtytime inode caused by an atime | |
2025 | * update, we need this infrastructure below to make sure that inode | |
2026 | * eventually gets pushed out to disk. | |
2027 | */ | |
2028 | static void wakeup_dirtytime_writeback(struct work_struct *w); | |
2029 | static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback); | |
2030 | ||
2031 | static void wakeup_dirtytime_writeback(struct work_struct *w) | |
2032 | { | |
2033 | struct backing_dev_info *bdi; | |
2034 | ||
2035 | rcu_read_lock(); | |
2036 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { | |
2037 | struct bdi_writeback *wb; | |
2038 | ||
2039 | list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node) | |
2040 | if (!list_empty(&wb->b_dirty_time)) | |
2041 | wb_wakeup(wb); | |
2042 | } | |
2043 | rcu_read_unlock(); | |
2044 | schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); | |
2045 | } | |
2046 | ||
2047 | static int __init start_dirtytime_writeback(void) | |
2048 | { | |
2049 | schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); | |
2050 | return 0; | |
2051 | } | |
2052 | __initcall(start_dirtytime_writeback); | |
2053 | ||
2054 | int dirtytime_interval_handler(struct ctl_table *table, int write, | |
2055 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
2056 | { | |
2057 | int ret; | |
2058 | ||
2059 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
2060 | if (ret == 0 && write) | |
2061 | mod_delayed_work(system_wq, &dirtytime_work, 0); | |
2062 | return ret; | |
2063 | } | |
2064 | ||
2065 | static noinline void block_dump___mark_inode_dirty(struct inode *inode) | |
2066 | { | |
2067 | if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) { | |
2068 | struct dentry *dentry; | |
2069 | const char *name = "?"; | |
2070 | ||
2071 | dentry = d_find_alias(inode); | |
2072 | if (dentry) { | |
2073 | spin_lock(&dentry->d_lock); | |
2074 | name = (const char *) dentry->d_name.name; | |
2075 | } | |
2076 | printk(KERN_DEBUG | |
2077 | "%s(%d): dirtied inode %lu (%s) on %s\n", | |
2078 | current->comm, task_pid_nr(current), inode->i_ino, | |
2079 | name, inode->i_sb->s_id); | |
2080 | if (dentry) { | |
2081 | spin_unlock(&dentry->d_lock); | |
2082 | dput(dentry); | |
2083 | } | |
2084 | } | |
2085 | } | |
2086 | ||
2087 | /** | |
2088 | * __mark_inode_dirty - internal function | |
2089 | * | |
2090 | * @inode: inode to mark | |
2091 | * @flags: what kind of dirty (i.e. I_DIRTY_SYNC) | |
2092 | * | |
2093 | * Mark an inode as dirty. Callers should use mark_inode_dirty or | |
2094 | * mark_inode_dirty_sync. | |
2095 | * | |
2096 | * Put the inode on the super block's dirty list. | |
2097 | * | |
2098 | * CAREFUL! We mark it dirty unconditionally, but move it onto the | |
2099 | * dirty list only if it is hashed or if it refers to a blockdev. | |
2100 | * If it was not hashed, it will never be added to the dirty list | |
2101 | * even if it is later hashed, as it will have been marked dirty already. | |
2102 | * | |
2103 | * In short, make sure you hash any inodes _before_ you start marking | |
2104 | * them dirty. | |
2105 | * | |
2106 | * Note that for blockdevs, inode->dirtied_when represents the dirtying time of | |
2107 | * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of | |
2108 | * the kernel-internal blockdev inode represents the dirtying time of the | |
2109 | * blockdev's pages. This is why for I_DIRTY_PAGES we always use | |
2110 | * page->mapping->host, so the page-dirtying time is recorded in the internal | |
2111 | * blockdev inode. | |
2112 | */ | |
2113 | void __mark_inode_dirty(struct inode *inode, int flags) | |
2114 | { | |
2115 | struct super_block *sb = inode->i_sb; | |
2116 | int dirtytime; | |
2117 | ||
2118 | trace_writeback_mark_inode_dirty(inode, flags); | |
2119 | ||
2120 | /* | |
2121 | * Don't do this for I_DIRTY_PAGES - that doesn't actually | |
2122 | * dirty the inode itself | |
2123 | */ | |
2124 | if (flags & (I_DIRTY_INODE | I_DIRTY_TIME)) { | |
2125 | trace_writeback_dirty_inode_start(inode, flags); | |
2126 | ||
2127 | if (sb->s_op->dirty_inode) | |
2128 | sb->s_op->dirty_inode(inode, flags); | |
2129 | ||
2130 | trace_writeback_dirty_inode(inode, flags); | |
2131 | } | |
2132 | if (flags & I_DIRTY_INODE) | |
2133 | flags &= ~I_DIRTY_TIME; | |
2134 | dirtytime = flags & I_DIRTY_TIME; | |
2135 | ||
2136 | /* | |
2137 | * Paired with smp_mb() in __writeback_single_inode() for the | |
2138 | * following lockless i_state test. See there for details. | |
2139 | */ | |
2140 | smp_mb(); | |
2141 | ||
2142 | if (((inode->i_state & flags) == flags) || | |
2143 | (dirtytime && (inode->i_state & I_DIRTY_INODE))) | |
2144 | return; | |
2145 | ||
2146 | if (unlikely(block_dump)) | |
2147 | block_dump___mark_inode_dirty(inode); | |
2148 | ||
2149 | spin_lock(&inode->i_lock); | |
2150 | if (dirtytime && (inode->i_state & I_DIRTY_INODE)) | |
2151 | goto out_unlock_inode; | |
2152 | if ((inode->i_state & flags) != flags) { | |
2153 | const int was_dirty = inode->i_state & I_DIRTY; | |
2154 | ||
2155 | inode_attach_wb(inode, NULL); | |
2156 | ||
2157 | if (flags & I_DIRTY_INODE) | |
2158 | inode->i_state &= ~I_DIRTY_TIME; | |
2159 | inode->i_state |= flags; | |
2160 | ||
2161 | /* | |
2162 | * If the inode is being synced, just update its dirty state. | |
2163 | * The unlocker will place the inode on the appropriate | |
2164 | * superblock list, based upon its state. | |
2165 | */ | |
2166 | if (inode->i_state & I_SYNC) | |
2167 | goto out_unlock_inode; | |
2168 | ||
2169 | /* | |
2170 | * Only add valid (hashed) inodes to the superblock's | |
2171 | * dirty list. Add blockdev inodes as well. | |
2172 | */ | |
2173 | if (!S_ISBLK(inode->i_mode)) { | |
2174 | if (inode_unhashed(inode)) | |
2175 | goto out_unlock_inode; | |
2176 | } | |
2177 | if (inode->i_state & I_FREEING) | |
2178 | goto out_unlock_inode; | |
2179 | ||
2180 | /* | |
2181 | * If the inode was already on b_dirty/b_io/b_more_io, don't | |
2182 | * reposition it (that would break b_dirty time-ordering). | |
2183 | */ | |
2184 | if (!was_dirty) { | |
2185 | struct bdi_writeback *wb; | |
2186 | struct list_head *dirty_list; | |
2187 | bool wakeup_bdi = false; | |
2188 | ||
2189 | wb = locked_inode_to_wb_and_lock_list(inode); | |
2190 | ||
2191 | WARN(bdi_cap_writeback_dirty(wb->bdi) && | |
2192 | !test_bit(WB_registered, &wb->state), | |
2193 | "bdi-%s not registered\n", wb->bdi->name); | |
2194 | ||
2195 | inode->dirtied_when = jiffies; | |
2196 | if (dirtytime) | |
2197 | inode->dirtied_time_when = jiffies; | |
2198 | ||
2199 | if (inode->i_state & I_DIRTY) | |
2200 | dirty_list = &wb->b_dirty; | |
2201 | else | |
2202 | dirty_list = &wb->b_dirty_time; | |
2203 | ||
2204 | wakeup_bdi = inode_io_list_move_locked(inode, wb, | |
2205 | dirty_list); | |
2206 | ||
2207 | spin_unlock(&wb->list_lock); | |
2208 | trace_writeback_dirty_inode_enqueue(inode); | |
2209 | ||
2210 | /* | |
2211 | * If this is the first dirty inode for this bdi, | |
2212 | * we have to wake-up the corresponding bdi thread | |
2213 | * to make sure background write-back happens | |
2214 | * later. | |
2215 | */ | |
2216 | if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi) | |
2217 | wb_wakeup_delayed(wb); | |
2218 | return; | |
2219 | } | |
2220 | } | |
2221 | out_unlock_inode: | |
2222 | spin_unlock(&inode->i_lock); | |
2223 | } | |
2224 | EXPORT_SYMBOL(__mark_inode_dirty); | |
2225 | ||
2226 | /* | |
2227 | * The @s_sync_lock is used to serialise concurrent sync operations | |
2228 | * to avoid lock contention problems with concurrent wait_sb_inodes() calls. | |
2229 | * Concurrent callers will block on the s_sync_lock rather than doing contending | |
2230 | * walks. The queueing maintains sync(2) required behaviour as all the IO that | |
2231 | * has been issued up to the time this function is enter is guaranteed to be | |
2232 | * completed by the time we have gained the lock and waited for all IO that is | |
2233 | * in progress regardless of the order callers are granted the lock. | |
2234 | */ | |
2235 | static void wait_sb_inodes(struct super_block *sb) | |
2236 | { | |
2237 | LIST_HEAD(sync_list); | |
2238 | ||
2239 | /* | |
2240 | * We need to be protected against the filesystem going from | |
2241 | * r/o to r/w or vice versa. | |
2242 | */ | |
2243 | WARN_ON(!rwsem_is_locked(&sb->s_umount)); | |
2244 | ||
2245 | mutex_lock(&sb->s_sync_lock); | |
2246 | ||
2247 | /* | |
2248 | * Splice the writeback list onto a temporary list to avoid waiting on | |
2249 | * inodes that have started writeback after this point. | |
2250 | * | |
2251 | * Use rcu_read_lock() to keep the inodes around until we have a | |
2252 | * reference. s_inode_wblist_lock protects sb->s_inodes_wb as well as | |
2253 | * the local list because inodes can be dropped from either by writeback | |
2254 | * completion. | |
2255 | */ | |
2256 | rcu_read_lock(); | |
2257 | spin_lock_irq(&sb->s_inode_wblist_lock); | |
2258 | list_splice_init(&sb->s_inodes_wb, &sync_list); | |
2259 | ||
2260 | /* | |
2261 | * Data integrity sync. Must wait for all pages under writeback, because | |
2262 | * there may have been pages dirtied before our sync call, but which had | |
2263 | * writeout started before we write it out. In which case, the inode | |
2264 | * may not be on the dirty list, but we still have to wait for that | |
2265 | * writeout. | |
2266 | */ | |
2267 | while (!list_empty(&sync_list)) { | |
2268 | struct inode *inode = list_first_entry(&sync_list, struct inode, | |
2269 | i_wb_list); | |
2270 | struct address_space *mapping = inode->i_mapping; | |
2271 | ||
2272 | /* | |
2273 | * Move each inode back to the wb list before we drop the lock | |
2274 | * to preserve consistency between i_wb_list and the mapping | |
2275 | * writeback tag. Writeback completion is responsible to remove | |
2276 | * the inode from either list once the writeback tag is cleared. | |
2277 | */ | |
2278 | list_move_tail(&inode->i_wb_list, &sb->s_inodes_wb); | |
2279 | ||
2280 | /* | |
2281 | * The mapping can appear untagged while still on-list since we | |
2282 | * do not have the mapping lock. Skip it here, wb completion | |
2283 | * will remove it. | |
2284 | */ | |
2285 | if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) | |
2286 | continue; | |
2287 | ||
2288 | spin_unlock_irq(&sb->s_inode_wblist_lock); | |
2289 | ||
2290 | spin_lock(&inode->i_lock); | |
2291 | if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) { | |
2292 | spin_unlock(&inode->i_lock); | |
2293 | ||
2294 | spin_lock_irq(&sb->s_inode_wblist_lock); | |
2295 | continue; | |
2296 | } | |
2297 | __iget(inode); | |
2298 | spin_unlock(&inode->i_lock); | |
2299 | rcu_read_unlock(); | |
2300 | ||
2301 | /* | |
2302 | * We keep the error status of individual mapping so that | |
2303 | * applications can catch the writeback error using fsync(2). | |
2304 | * See filemap_fdatawait_keep_errors() for details. | |
2305 | */ | |
2306 | filemap_fdatawait_keep_errors(mapping); | |
2307 | ||
2308 | cond_resched(); | |
2309 | ||
2310 | iput(inode); | |
2311 | ||
2312 | rcu_read_lock(); | |
2313 | spin_lock_irq(&sb->s_inode_wblist_lock); | |
2314 | } | |
2315 | spin_unlock_irq(&sb->s_inode_wblist_lock); | |
2316 | rcu_read_unlock(); | |
2317 | mutex_unlock(&sb->s_sync_lock); | |
2318 | } | |
2319 | ||
2320 | static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr, | |
2321 | enum wb_reason reason, bool skip_if_busy) | |
2322 | { | |
2323 | DEFINE_WB_COMPLETION_ONSTACK(done); | |
2324 | struct wb_writeback_work work = { | |
2325 | .sb = sb, | |
2326 | .sync_mode = WB_SYNC_NONE, | |
2327 | .tagged_writepages = 1, | |
2328 | .done = &done, | |
2329 | .nr_pages = nr, | |
2330 | .reason = reason, | |
2331 | }; | |
2332 | struct backing_dev_info *bdi = sb->s_bdi; | |
2333 | ||
2334 | if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info) | |
2335 | return; | |
2336 | WARN_ON(!rwsem_is_locked(&sb->s_umount)); | |
2337 | ||
2338 | bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy); | |
2339 | wb_wait_for_completion(bdi, &done); | |
2340 | } | |
2341 | ||
2342 | /** | |
2343 | * writeback_inodes_sb_nr - writeback dirty inodes from given super_block | |
2344 | * @sb: the superblock | |
2345 | * @nr: the number of pages to write | |
2346 | * @reason: reason why some writeback work initiated | |
2347 | * | |
2348 | * Start writeback on some inodes on this super_block. No guarantees are made | |
2349 | * on how many (if any) will be written, and this function does not wait | |
2350 | * for IO completion of submitted IO. | |
2351 | */ | |
2352 | void writeback_inodes_sb_nr(struct super_block *sb, | |
2353 | unsigned long nr, | |
2354 | enum wb_reason reason) | |
2355 | { | |
2356 | __writeback_inodes_sb_nr(sb, nr, reason, false); | |
2357 | } | |
2358 | EXPORT_SYMBOL(writeback_inodes_sb_nr); | |
2359 | ||
2360 | /** | |
2361 | * writeback_inodes_sb - writeback dirty inodes from given super_block | |
2362 | * @sb: the superblock | |
2363 | * @reason: reason why some writeback work was initiated | |
2364 | * | |
2365 | * Start writeback on some inodes on this super_block. No guarantees are made | |
2366 | * on how many (if any) will be written, and this function does not wait | |
2367 | * for IO completion of submitted IO. | |
2368 | */ | |
2369 | void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) | |
2370 | { | |
2371 | return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason); | |
2372 | } | |
2373 | EXPORT_SYMBOL(writeback_inodes_sb); | |
2374 | ||
2375 | /** | |
2376 | * try_to_writeback_inodes_sb - try to start writeback if none underway | |
2377 | * @sb: the superblock | |
2378 | * @reason: reason why some writeback work was initiated | |
2379 | * | |
2380 | * Invoke __writeback_inodes_sb_nr if no writeback is currently underway. | |
2381 | */ | |
2382 | void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) | |
2383 | { | |
2384 | if (!down_read_trylock(&sb->s_umount)) | |
2385 | return; | |
2386 | ||
2387 | __writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason, true); | |
2388 | up_read(&sb->s_umount); | |
2389 | } | |
2390 | EXPORT_SYMBOL(try_to_writeback_inodes_sb); | |
2391 | ||
2392 | /** | |
2393 | * sync_inodes_sb - sync sb inode pages | |
2394 | * @sb: the superblock | |
2395 | * | |
2396 | * This function writes and waits on any dirty inode belonging to this | |
2397 | * super_block. | |
2398 | */ | |
2399 | void sync_inodes_sb(struct super_block *sb) | |
2400 | { | |
2401 | DEFINE_WB_COMPLETION_ONSTACK(done); | |
2402 | struct wb_writeback_work work = { | |
2403 | .sb = sb, | |
2404 | .sync_mode = WB_SYNC_ALL, | |
2405 | .nr_pages = LONG_MAX, | |
2406 | .range_cyclic = 0, | |
2407 | .done = &done, | |
2408 | .reason = WB_REASON_SYNC, | |
2409 | .for_sync = 1, | |
2410 | }; | |
2411 | struct backing_dev_info *bdi = sb->s_bdi; | |
2412 | ||
2413 | /* | |
2414 | * Can't skip on !bdi_has_dirty() because we should wait for !dirty | |
2415 | * inodes under writeback and I_DIRTY_TIME inodes ignored by | |
2416 | * bdi_has_dirty() need to be written out too. | |
2417 | */ | |
2418 | if (bdi == &noop_backing_dev_info) | |
2419 | return; | |
2420 | WARN_ON(!rwsem_is_locked(&sb->s_umount)); | |
2421 | ||
2422 | bdi_split_work_to_wbs(bdi, &work, false); | |
2423 | wb_wait_for_completion(bdi, &done); | |
2424 | ||
2425 | wait_sb_inodes(sb); | |
2426 | } | |
2427 | EXPORT_SYMBOL(sync_inodes_sb); | |
2428 | ||
2429 | /** | |
2430 | * write_inode_now - write an inode to disk | |
2431 | * @inode: inode to write to disk | |
2432 | * @sync: whether the write should be synchronous or not | |
2433 | * | |
2434 | * This function commits an inode to disk immediately if it is dirty. This is | |
2435 | * primarily needed by knfsd. | |
2436 | * | |
2437 | * The caller must either have a ref on the inode or must have set I_WILL_FREE. | |
2438 | */ | |
2439 | int write_inode_now(struct inode *inode, int sync) | |
2440 | { | |
2441 | struct writeback_control wbc = { | |
2442 | .nr_to_write = LONG_MAX, | |
2443 | .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE, | |
2444 | .range_start = 0, | |
2445 | .range_end = LLONG_MAX, | |
2446 | }; | |
2447 | ||
2448 | if (!mapping_cap_writeback_dirty(inode->i_mapping)) | |
2449 | wbc.nr_to_write = 0; | |
2450 | ||
2451 | might_sleep(); | |
2452 | return writeback_single_inode(inode, &wbc); | |
2453 | } | |
2454 | EXPORT_SYMBOL(write_inode_now); | |
2455 | ||
2456 | /** | |
2457 | * sync_inode - write an inode and its pages to disk. | |
2458 | * @inode: the inode to sync | |
2459 | * @wbc: controls the writeback mode | |
2460 | * | |
2461 | * sync_inode() will write an inode and its pages to disk. It will also | |
2462 | * correctly update the inode on its superblock's dirty inode lists and will | |
2463 | * update inode->i_state. | |
2464 | * | |
2465 | * The caller must have a ref on the inode. | |
2466 | */ | |
2467 | int sync_inode(struct inode *inode, struct writeback_control *wbc) | |
2468 | { | |
2469 | return writeback_single_inode(inode, wbc); | |
2470 | } | |
2471 | EXPORT_SYMBOL(sync_inode); | |
2472 | ||
2473 | /** | |
2474 | * sync_inode_metadata - write an inode to disk | |
2475 | * @inode: the inode to sync | |
2476 | * @wait: wait for I/O to complete. | |
2477 | * | |
2478 | * Write an inode to disk and adjust its dirty state after completion. | |
2479 | * | |
2480 | * Note: only writes the actual inode, no associated data or other metadata. | |
2481 | */ | |
2482 | int sync_inode_metadata(struct inode *inode, int wait) | |
2483 | { | |
2484 | struct writeback_control wbc = { | |
2485 | .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE, | |
2486 | .nr_to_write = 0, /* metadata-only */ | |
2487 | }; | |
2488 | ||
2489 | return sync_inode(inode, &wbc); | |
2490 | } | |
2491 | EXPORT_SYMBOL(sync_inode_metadata); |