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1/*
2 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
3 * Copyright (c) 2008 Dave Chinner
4 * All Rights Reserved.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it would be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19#include "xfs.h"
20#include "xfs_fs.h"
21#include "xfs_format.h"
22#include "xfs_log_format.h"
23#include "xfs_trans_resv.h"
24#include "xfs_mount.h"
25#include "xfs_trans.h"
26#include "xfs_trans_priv.h"
27#include "xfs_trace.h"
28#include "xfs_errortag.h"
29#include "xfs_error.h"
30#include "xfs_log.h"
31
32#ifdef DEBUG
33/*
34 * Check that the list is sorted as it should be.
35 */
36STATIC void
37xfs_ail_check(
38 struct xfs_ail *ailp,
39 xfs_log_item_t *lip)
40{
41 xfs_log_item_t *prev_lip;
42
43 if (list_empty(&ailp->ail_head))
44 return;
45
46 /*
47 * Check the next and previous entries are valid.
48 */
49 ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
50 prev_lip = list_entry(lip->li_ail.prev, xfs_log_item_t, li_ail);
51 if (&prev_lip->li_ail != &ailp->ail_head)
52 ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
53
54 prev_lip = list_entry(lip->li_ail.next, xfs_log_item_t, li_ail);
55 if (&prev_lip->li_ail != &ailp->ail_head)
56 ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) >= 0);
57
58
59}
60#else /* !DEBUG */
61#define xfs_ail_check(a,l)
62#endif /* DEBUG */
63
64/*
65 * Return a pointer to the last item in the AIL. If the AIL is empty, then
66 * return NULL.
67 */
68static xfs_log_item_t *
69xfs_ail_max(
70 struct xfs_ail *ailp)
71{
72 if (list_empty(&ailp->ail_head))
73 return NULL;
74
75 return list_entry(ailp->ail_head.prev, xfs_log_item_t, li_ail);
76}
77
78/*
79 * Return a pointer to the item which follows the given item in the AIL. If
80 * the given item is the last item in the list, then return NULL.
81 */
82static xfs_log_item_t *
83xfs_ail_next(
84 struct xfs_ail *ailp,
85 xfs_log_item_t *lip)
86{
87 if (lip->li_ail.next == &ailp->ail_head)
88 return NULL;
89
90 return list_first_entry(&lip->li_ail, xfs_log_item_t, li_ail);
91}
92
93/*
94 * This is called by the log manager code to determine the LSN of the tail of
95 * the log. This is exactly the LSN of the first item in the AIL. If the AIL
96 * is empty, then this function returns 0.
97 *
98 * We need the AIL lock in order to get a coherent read of the lsn of the last
99 * item in the AIL.
100 */
101xfs_lsn_t
102xfs_ail_min_lsn(
103 struct xfs_ail *ailp)
104{
105 xfs_lsn_t lsn = 0;
106 xfs_log_item_t *lip;
107
108 spin_lock(&ailp->ail_lock);
109 lip = xfs_ail_min(ailp);
110 if (lip)
111 lsn = lip->li_lsn;
112 spin_unlock(&ailp->ail_lock);
113
114 return lsn;
115}
116
117/*
118 * Return the maximum lsn held in the AIL, or zero if the AIL is empty.
119 */
120static xfs_lsn_t
121xfs_ail_max_lsn(
122 struct xfs_ail *ailp)
123{
124 xfs_lsn_t lsn = 0;
125 xfs_log_item_t *lip;
126
127 spin_lock(&ailp->ail_lock);
128 lip = xfs_ail_max(ailp);
129 if (lip)
130 lsn = lip->li_lsn;
131 spin_unlock(&ailp->ail_lock);
132
133 return lsn;
134}
135
136/*
137 * The cursor keeps track of where our current traversal is up to by tracking
138 * the next item in the list for us. However, for this to be safe, removing an
139 * object from the AIL needs to invalidate any cursor that points to it. hence
140 * the traversal cursor needs to be linked to the struct xfs_ail so that
141 * deletion can search all the active cursors for invalidation.
142 */
143STATIC void
144xfs_trans_ail_cursor_init(
145 struct xfs_ail *ailp,
146 struct xfs_ail_cursor *cur)
147{
148 cur->item = NULL;
149 list_add_tail(&cur->list, &ailp->ail_cursors);
150}
151
152/*
153 * Get the next item in the traversal and advance the cursor. If the cursor
154 * was invalidated (indicated by a lip of 1), restart the traversal.
155 */
156struct xfs_log_item *
157xfs_trans_ail_cursor_next(
158 struct xfs_ail *ailp,
159 struct xfs_ail_cursor *cur)
160{
161 struct xfs_log_item *lip = cur->item;
162
163 if ((uintptr_t)lip & 1)
164 lip = xfs_ail_min(ailp);
165 if (lip)
166 cur->item = xfs_ail_next(ailp, lip);
167 return lip;
168}
169
170/*
171 * When the traversal is complete, we need to remove the cursor from the list
172 * of traversing cursors.
173 */
174void
175xfs_trans_ail_cursor_done(
176 struct xfs_ail_cursor *cur)
177{
178 cur->item = NULL;
179 list_del_init(&cur->list);
180}
181
182/*
183 * Invalidate any cursor that is pointing to this item. This is called when an
184 * item is removed from the AIL. Any cursor pointing to this object is now
185 * invalid and the traversal needs to be terminated so it doesn't reference a
186 * freed object. We set the low bit of the cursor item pointer so we can
187 * distinguish between an invalidation and the end of the list when getting the
188 * next item from the cursor.
189 */
190STATIC void
191xfs_trans_ail_cursor_clear(
192 struct xfs_ail *ailp,
193 struct xfs_log_item *lip)
194{
195 struct xfs_ail_cursor *cur;
196
197 list_for_each_entry(cur, &ailp->ail_cursors, list) {
198 if (cur->item == lip)
199 cur->item = (struct xfs_log_item *)
200 ((uintptr_t)cur->item | 1);
201 }
202}
203
204/*
205 * Find the first item in the AIL with the given @lsn by searching in ascending
206 * LSN order and initialise the cursor to point to the next item for a
207 * ascending traversal. Pass a @lsn of zero to initialise the cursor to the
208 * first item in the AIL. Returns NULL if the list is empty.
209 */
210xfs_log_item_t *
211xfs_trans_ail_cursor_first(
212 struct xfs_ail *ailp,
213 struct xfs_ail_cursor *cur,
214 xfs_lsn_t lsn)
215{
216 xfs_log_item_t *lip;
217
218 xfs_trans_ail_cursor_init(ailp, cur);
219
220 if (lsn == 0) {
221 lip = xfs_ail_min(ailp);
222 goto out;
223 }
224
225 list_for_each_entry(lip, &ailp->ail_head, li_ail) {
226 if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
227 goto out;
228 }
229 return NULL;
230
231out:
232 if (lip)
233 cur->item = xfs_ail_next(ailp, lip);
234 return lip;
235}
236
237static struct xfs_log_item *
238__xfs_trans_ail_cursor_last(
239 struct xfs_ail *ailp,
240 xfs_lsn_t lsn)
241{
242 xfs_log_item_t *lip;
243
244 list_for_each_entry_reverse(lip, &ailp->ail_head, li_ail) {
245 if (XFS_LSN_CMP(lip->li_lsn, lsn) <= 0)
246 return lip;
247 }
248 return NULL;
249}
250
251/*
252 * Find the last item in the AIL with the given @lsn by searching in descending
253 * LSN order and initialise the cursor to point to that item. If there is no
254 * item with the value of @lsn, then it sets the cursor to the last item with an
255 * LSN lower than @lsn. Returns NULL if the list is empty.
256 */
257struct xfs_log_item *
258xfs_trans_ail_cursor_last(
259 struct xfs_ail *ailp,
260 struct xfs_ail_cursor *cur,
261 xfs_lsn_t lsn)
262{
263 xfs_trans_ail_cursor_init(ailp, cur);
264 cur->item = __xfs_trans_ail_cursor_last(ailp, lsn);
265 return cur->item;
266}
267
268/*
269 * Splice the log item list into the AIL at the given LSN. We splice to the
270 * tail of the given LSN to maintain insert order for push traversals. The
271 * cursor is optional, allowing repeated updates to the same LSN to avoid
272 * repeated traversals. This should not be called with an empty list.
273 */
274static void
275xfs_ail_splice(
276 struct xfs_ail *ailp,
277 struct xfs_ail_cursor *cur,
278 struct list_head *list,
279 xfs_lsn_t lsn)
280{
281 struct xfs_log_item *lip;
282
283 ASSERT(!list_empty(list));
284
285 /*
286 * Use the cursor to determine the insertion point if one is
287 * provided. If not, or if the one we got is not valid,
288 * find the place in the AIL where the items belong.
289 */
290 lip = cur ? cur->item : NULL;
291 if (!lip || (uintptr_t)lip & 1)
292 lip = __xfs_trans_ail_cursor_last(ailp, lsn);
293
294 /*
295 * If a cursor is provided, we know we're processing the AIL
296 * in lsn order, and future items to be spliced in will
297 * follow the last one being inserted now. Update the
298 * cursor to point to that last item, now while we have a
299 * reliable pointer to it.
300 */
301 if (cur)
302 cur->item = list_entry(list->prev, struct xfs_log_item, li_ail);
303
304 /*
305 * Finally perform the splice. Unless the AIL was empty,
306 * lip points to the item in the AIL _after_ which the new
307 * items should go. If lip is null the AIL was empty, so
308 * the new items go at the head of the AIL.
309 */
310 if (lip)
311 list_splice(list, &lip->li_ail);
312 else
313 list_splice(list, &ailp->ail_head);
314}
315
316/*
317 * Delete the given item from the AIL. Return a pointer to the item.
318 */
319static void
320xfs_ail_delete(
321 struct xfs_ail *ailp,
322 xfs_log_item_t *lip)
323{
324 xfs_ail_check(ailp, lip);
325 list_del(&lip->li_ail);
326 xfs_trans_ail_cursor_clear(ailp, lip);
327}
328
329static inline uint
330xfsaild_push_item(
331 struct xfs_ail *ailp,
332 struct xfs_log_item *lip)
333{
334 /*
335 * If log item pinning is enabled, skip the push and track the item as
336 * pinned. This can help induce head-behind-tail conditions.
337 */
338 if (XFS_TEST_ERROR(false, ailp->ail_mount, XFS_ERRTAG_LOG_ITEM_PIN))
339 return XFS_ITEM_PINNED;
340
341 return lip->li_ops->iop_push(lip, &ailp->ail_buf_list);
342}
343
344static long
345xfsaild_push(
346 struct xfs_ail *ailp)
347{
348 xfs_mount_t *mp = ailp->ail_mount;
349 struct xfs_ail_cursor cur;
350 xfs_log_item_t *lip;
351 xfs_lsn_t lsn;
352 xfs_lsn_t target;
353 long tout;
354 int stuck = 0;
355 int flushing = 0;
356 int count = 0;
357
358 /*
359 * If we encountered pinned items or did not finish writing out all
360 * buffers the last time we ran, force the log first and wait for it
361 * before pushing again.
362 */
363 if (ailp->ail_log_flush && ailp->ail_last_pushed_lsn == 0 &&
364 (!list_empty_careful(&ailp->ail_buf_list) ||
365 xfs_ail_min_lsn(ailp))) {
366 ailp->ail_log_flush = 0;
367
368 XFS_STATS_INC(mp, xs_push_ail_flush);
369 xfs_log_force(mp, XFS_LOG_SYNC);
370 }
371
372 spin_lock(&ailp->ail_lock);
373
374 /* barrier matches the ail_target update in xfs_ail_push() */
375 smp_rmb();
376 target = ailp->ail_target;
377 ailp->ail_target_prev = target;
378
379 lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->ail_last_pushed_lsn);
380 if (!lip) {
381 /*
382 * If the AIL is empty or our push has reached the end we are
383 * done now.
384 */
385 xfs_trans_ail_cursor_done(&cur);
386 spin_unlock(&ailp->ail_lock);
387 goto out_done;
388 }
389
390 XFS_STATS_INC(mp, xs_push_ail);
391
392 lsn = lip->li_lsn;
393 while ((XFS_LSN_CMP(lip->li_lsn, target) <= 0)) {
394 int lock_result;
395
396 /*
397 * Note that iop_push may unlock and reacquire the AIL lock. We
398 * rely on the AIL cursor implementation to be able to deal with
399 * the dropped lock.
400 */
401 lock_result = xfsaild_push_item(ailp, lip);
402 switch (lock_result) {
403 case XFS_ITEM_SUCCESS:
404 XFS_STATS_INC(mp, xs_push_ail_success);
405 trace_xfs_ail_push(lip);
406
407 ailp->ail_last_pushed_lsn = lsn;
408 break;
409
410 case XFS_ITEM_FLUSHING:
411 /*
412 * The item or its backing buffer is already beeing
413 * flushed. The typical reason for that is that an
414 * inode buffer is locked because we already pushed the
415 * updates to it as part of inode clustering.
416 *
417 * We do not want to to stop flushing just because lots
418 * of items are already beeing flushed, but we need to
419 * re-try the flushing relatively soon if most of the
420 * AIL is beeing flushed.
421 */
422 XFS_STATS_INC(mp, xs_push_ail_flushing);
423 trace_xfs_ail_flushing(lip);
424
425 flushing++;
426 ailp->ail_last_pushed_lsn = lsn;
427 break;
428
429 case XFS_ITEM_PINNED:
430 XFS_STATS_INC(mp, xs_push_ail_pinned);
431 trace_xfs_ail_pinned(lip);
432
433 stuck++;
434 ailp->ail_log_flush++;
435 break;
436 case XFS_ITEM_LOCKED:
437 XFS_STATS_INC(mp, xs_push_ail_locked);
438 trace_xfs_ail_locked(lip);
439
440 stuck++;
441 break;
442 default:
443 ASSERT(0);
444 break;
445 }
446
447 count++;
448
449 /*
450 * Are there too many items we can't do anything with?
451 *
452 * If we we are skipping too many items because we can't flush
453 * them or they are already being flushed, we back off and
454 * given them time to complete whatever operation is being
455 * done. i.e. remove pressure from the AIL while we can't make
456 * progress so traversals don't slow down further inserts and
457 * removals to/from the AIL.
458 *
459 * The value of 100 is an arbitrary magic number based on
460 * observation.
461 */
462 if (stuck > 100)
463 break;
464
465 lip = xfs_trans_ail_cursor_next(ailp, &cur);
466 if (lip == NULL)
467 break;
468 lsn = lip->li_lsn;
469 }
470 xfs_trans_ail_cursor_done(&cur);
471 spin_unlock(&ailp->ail_lock);
472
473 if (xfs_buf_delwri_submit_nowait(&ailp->ail_buf_list))
474 ailp->ail_log_flush++;
475
476 if (!count || XFS_LSN_CMP(lsn, target) >= 0) {
477out_done:
478 /*
479 * We reached the target or the AIL is empty, so wait a bit
480 * longer for I/O to complete and remove pushed items from the
481 * AIL before we start the next scan from the start of the AIL.
482 */
483 tout = 50;
484 ailp->ail_last_pushed_lsn = 0;
485 } else if (((stuck + flushing) * 100) / count > 90) {
486 /*
487 * Either there is a lot of contention on the AIL or we are
488 * stuck due to operations in progress. "Stuck" in this case
489 * is defined as >90% of the items we tried to push were stuck.
490 *
491 * Backoff a bit more to allow some I/O to complete before
492 * restarting from the start of the AIL. This prevents us from
493 * spinning on the same items, and if they are pinned will all
494 * the restart to issue a log force to unpin the stuck items.
495 */
496 tout = 20;
497 ailp->ail_last_pushed_lsn = 0;
498 } else {
499 /*
500 * Assume we have more work to do in a short while.
501 */
502 tout = 10;
503 }
504
505 return tout;
506}
507
508static int
509xfsaild(
510 void *data)
511{
512 struct xfs_ail *ailp = data;
513 long tout = 0; /* milliseconds */
514
515 current->flags |= PF_MEMALLOC;
516 set_freezable();
517
518 while (1) {
519 if (tout && tout <= 20)
520 set_current_state(TASK_KILLABLE);
521 else
522 set_current_state(TASK_INTERRUPTIBLE);
523
524 /*
525 * Check kthread_should_stop() after we set the task state
526 * to guarantee that we either see the stop bit and exit or
527 * the task state is reset to runnable such that it's not
528 * scheduled out indefinitely and detects the stop bit at
529 * next iteration.
530 *
531 * A memory barrier is included in above task state set to
532 * serialize again kthread_stop().
533 */
534 if (kthread_should_stop()) {
535 __set_current_state(TASK_RUNNING);
536 break;
537 }
538
539 spin_lock(&ailp->ail_lock);
540
541 /*
542 * Idle if the AIL is empty and we are not racing with a target
543 * update. We check the AIL after we set the task to a sleep
544 * state to guarantee that we either catch an ail_target update
545 * or that a wake_up resets the state to TASK_RUNNING.
546 * Otherwise, we run the risk of sleeping indefinitely.
547 *
548 * The barrier matches the ail_target update in xfs_ail_push().
549 */
550 smp_rmb();
551 if (!xfs_ail_min(ailp) &&
552 ailp->ail_target == ailp->ail_target_prev) {
553 spin_unlock(&ailp->ail_lock);
554 freezable_schedule();
555 tout = 0;
556 continue;
557 }
558 spin_unlock(&ailp->ail_lock);
559
560 if (tout)
561 freezable_schedule_timeout(msecs_to_jiffies(tout));
562
563 __set_current_state(TASK_RUNNING);
564
565 try_to_freeze();
566
567 tout = xfsaild_push(ailp);
568 }
569
570 return 0;
571}
572
573/*
574 * This routine is called to move the tail of the AIL forward. It does this by
575 * trying to flush items in the AIL whose lsns are below the given
576 * threshold_lsn.
577 *
578 * The push is run asynchronously in a workqueue, which means the caller needs
579 * to handle waiting on the async flush for space to become available.
580 * We don't want to interrupt any push that is in progress, hence we only queue
581 * work if we set the pushing bit approriately.
582 *
583 * We do this unlocked - we only need to know whether there is anything in the
584 * AIL at the time we are called. We don't need to access the contents of
585 * any of the objects, so the lock is not needed.
586 */
587void
588xfs_ail_push(
589 struct xfs_ail *ailp,
590 xfs_lsn_t threshold_lsn)
591{
592 xfs_log_item_t *lip;
593
594 lip = xfs_ail_min(ailp);
595 if (!lip || XFS_FORCED_SHUTDOWN(ailp->ail_mount) ||
596 XFS_LSN_CMP(threshold_lsn, ailp->ail_target) <= 0)
597 return;
598
599 /*
600 * Ensure that the new target is noticed in push code before it clears
601 * the XFS_AIL_PUSHING_BIT.
602 */
603 smp_wmb();
604 xfs_trans_ail_copy_lsn(ailp, &ailp->ail_target, &threshold_lsn);
605 smp_wmb();
606
607 wake_up_process(ailp->ail_task);
608}
609
610/*
611 * Push out all items in the AIL immediately
612 */
613void
614xfs_ail_push_all(
615 struct xfs_ail *ailp)
616{
617 xfs_lsn_t threshold_lsn = xfs_ail_max_lsn(ailp);
618
619 if (threshold_lsn)
620 xfs_ail_push(ailp, threshold_lsn);
621}
622
623/*
624 * Push out all items in the AIL immediately and wait until the AIL is empty.
625 */
626void
627xfs_ail_push_all_sync(
628 struct xfs_ail *ailp)
629{
630 struct xfs_log_item *lip;
631 DEFINE_WAIT(wait);
632
633 spin_lock(&ailp->ail_lock);
634 while ((lip = xfs_ail_max(ailp)) != NULL) {
635 prepare_to_wait(&ailp->ail_empty, &wait, TASK_UNINTERRUPTIBLE);
636 ailp->ail_target = lip->li_lsn;
637 wake_up_process(ailp->ail_task);
638 spin_unlock(&ailp->ail_lock);
639 schedule();
640 spin_lock(&ailp->ail_lock);
641 }
642 spin_unlock(&ailp->ail_lock);
643
644 finish_wait(&ailp->ail_empty, &wait);
645}
646
647/*
648 * xfs_trans_ail_update - bulk AIL insertion operation.
649 *
650 * @xfs_trans_ail_update takes an array of log items that all need to be
651 * positioned at the same LSN in the AIL. If an item is not in the AIL, it will
652 * be added. Otherwise, it will be repositioned by removing it and re-adding
653 * it to the AIL. If we move the first item in the AIL, update the log tail to
654 * match the new minimum LSN in the AIL.
655 *
656 * This function takes the AIL lock once to execute the update operations on
657 * all the items in the array, and as such should not be called with the AIL
658 * lock held. As a result, once we have the AIL lock, we need to check each log
659 * item LSN to confirm it needs to be moved forward in the AIL.
660 *
661 * To optimise the insert operation, we delete all the items from the AIL in
662 * the first pass, moving them into a temporary list, then splice the temporary
663 * list into the correct position in the AIL. This avoids needing to do an
664 * insert operation on every item.
665 *
666 * This function must be called with the AIL lock held. The lock is dropped
667 * before returning.
668 */
669void
670xfs_trans_ail_update_bulk(
671 struct xfs_ail *ailp,
672 struct xfs_ail_cursor *cur,
673 struct xfs_log_item **log_items,
674 int nr_items,
675 xfs_lsn_t lsn) __releases(ailp->ail_lock)
676{
677 xfs_log_item_t *mlip;
678 int mlip_changed = 0;
679 int i;
680 LIST_HEAD(tmp);
681
682 ASSERT(nr_items > 0); /* Not required, but true. */
683 mlip = xfs_ail_min(ailp);
684
685 for (i = 0; i < nr_items; i++) {
686 struct xfs_log_item *lip = log_items[i];
687 if (lip->li_flags & XFS_LI_IN_AIL) {
688 /* check if we really need to move the item */
689 if (XFS_LSN_CMP(lsn, lip->li_lsn) <= 0)
690 continue;
691
692 trace_xfs_ail_move(lip, lip->li_lsn, lsn);
693 xfs_ail_delete(ailp, lip);
694 if (mlip == lip)
695 mlip_changed = 1;
696 } else {
697 lip->li_flags |= XFS_LI_IN_AIL;
698 trace_xfs_ail_insert(lip, 0, lsn);
699 }
700 lip->li_lsn = lsn;
701 list_add(&lip->li_ail, &tmp);
702 }
703
704 if (!list_empty(&tmp))
705 xfs_ail_splice(ailp, cur, &tmp, lsn);
706
707 if (mlip_changed) {
708 if (!XFS_FORCED_SHUTDOWN(ailp->ail_mount))
709 xlog_assign_tail_lsn_locked(ailp->ail_mount);
710 spin_unlock(&ailp->ail_lock);
711
712 xfs_log_space_wake(ailp->ail_mount);
713 } else {
714 spin_unlock(&ailp->ail_lock);
715 }
716}
717
718bool
719xfs_ail_delete_one(
720 struct xfs_ail *ailp,
721 struct xfs_log_item *lip)
722{
723 struct xfs_log_item *mlip = xfs_ail_min(ailp);
724
725 trace_xfs_ail_delete(lip, mlip->li_lsn, lip->li_lsn);
726 xfs_ail_delete(ailp, lip);
727 xfs_clear_li_failed(lip);
728 lip->li_flags &= ~XFS_LI_IN_AIL;
729 lip->li_lsn = 0;
730
731 return mlip == lip;
732}
733
734/**
735 * Remove a log items from the AIL
736 *
737 * @xfs_trans_ail_delete_bulk takes an array of log items that all need to
738 * removed from the AIL. The caller is already holding the AIL lock, and done
739 * all the checks necessary to ensure the items passed in via @log_items are
740 * ready for deletion. This includes checking that the items are in the AIL.
741 *
742 * For each log item to be removed, unlink it from the AIL, clear the IN_AIL
743 * flag from the item and reset the item's lsn to 0. If we remove the first
744 * item in the AIL, update the log tail to match the new minimum LSN in the
745 * AIL.
746 *
747 * This function will not drop the AIL lock until all items are removed from
748 * the AIL to minimise the amount of lock traffic on the AIL. This does not
749 * greatly increase the AIL hold time, but does significantly reduce the amount
750 * of traffic on the lock, especially during IO completion.
751 *
752 * This function must be called with the AIL lock held. The lock is dropped
753 * before returning.
754 */
755void
756xfs_trans_ail_delete(
757 struct xfs_ail *ailp,
758 struct xfs_log_item *lip,
759 int shutdown_type) __releases(ailp->ail_lock)
760{
761 struct xfs_mount *mp = ailp->ail_mount;
762 bool mlip_changed;
763
764 if (!(lip->li_flags & XFS_LI_IN_AIL)) {
765 spin_unlock(&ailp->ail_lock);
766 if (!XFS_FORCED_SHUTDOWN(mp)) {
767 xfs_alert_tag(mp, XFS_PTAG_AILDELETE,
768 "%s: attempting to delete a log item that is not in the AIL",
769 __func__);
770 xfs_force_shutdown(mp, shutdown_type);
771 }
772 return;
773 }
774
775 mlip_changed = xfs_ail_delete_one(ailp, lip);
776 if (mlip_changed) {
777 if (!XFS_FORCED_SHUTDOWN(mp))
778 xlog_assign_tail_lsn_locked(mp);
779 if (list_empty(&ailp->ail_head))
780 wake_up_all(&ailp->ail_empty);
781 }
782
783 spin_unlock(&ailp->ail_lock);
784 if (mlip_changed)
785 xfs_log_space_wake(ailp->ail_mount);
786}
787
788int
789xfs_trans_ail_init(
790 xfs_mount_t *mp)
791{
792 struct xfs_ail *ailp;
793
794 ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
795 if (!ailp)
796 return -ENOMEM;
797
798 ailp->ail_mount = mp;
799 INIT_LIST_HEAD(&ailp->ail_head);
800 INIT_LIST_HEAD(&ailp->ail_cursors);
801 spin_lock_init(&ailp->ail_lock);
802 INIT_LIST_HEAD(&ailp->ail_buf_list);
803 init_waitqueue_head(&ailp->ail_empty);
804
805 ailp->ail_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
806 ailp->ail_mount->m_fsname);
807 if (IS_ERR(ailp->ail_task))
808 goto out_free_ailp;
809
810 mp->m_ail = ailp;
811 return 0;
812
813out_free_ailp:
814 kmem_free(ailp);
815 return -ENOMEM;
816}
817
818void
819xfs_trans_ail_destroy(
820 xfs_mount_t *mp)
821{
822 struct xfs_ail *ailp = mp->m_ail;
823
824 kthread_stop(ailp->ail_task);
825 kmem_free(ailp);
826}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
4 * Copyright (c) 2008 Dave Chinner
5 * All Rights Reserved.
6 */
7#include "xfs.h"
8#include "xfs_fs.h"
9#include "xfs_shared.h"
10#include "xfs_format.h"
11#include "xfs_log_format.h"
12#include "xfs_trans_resv.h"
13#include "xfs_mount.h"
14#include "xfs_trans.h"
15#include "xfs_trans_priv.h"
16#include "xfs_trace.h"
17#include "xfs_errortag.h"
18#include "xfs_error.h"
19#include "xfs_log.h"
20#include "xfs_log_priv.h"
21
22#ifdef DEBUG
23/*
24 * Check that the list is sorted as it should be.
25 *
26 * Called with the ail lock held, but we don't want to assert fail with it
27 * held otherwise we'll lock everything up and won't be able to debug the
28 * cause. Hence we sample and check the state under the AIL lock and return if
29 * everything is fine, otherwise we drop the lock and run the ASSERT checks.
30 * Asserts may not be fatal, so pick the lock back up and continue onwards.
31 */
32STATIC void
33xfs_ail_check(
34 struct xfs_ail *ailp,
35 struct xfs_log_item *lip)
36 __must_hold(&ailp->ail_lock)
37{
38 struct xfs_log_item *prev_lip;
39 struct xfs_log_item *next_lip;
40 xfs_lsn_t prev_lsn = NULLCOMMITLSN;
41 xfs_lsn_t next_lsn = NULLCOMMITLSN;
42 xfs_lsn_t lsn;
43 bool in_ail;
44
45
46 if (list_empty(&ailp->ail_head))
47 return;
48
49 /*
50 * Sample then check the next and previous entries are valid.
51 */
52 in_ail = test_bit(XFS_LI_IN_AIL, &lip->li_flags);
53 prev_lip = list_entry(lip->li_ail.prev, struct xfs_log_item, li_ail);
54 if (&prev_lip->li_ail != &ailp->ail_head)
55 prev_lsn = prev_lip->li_lsn;
56 next_lip = list_entry(lip->li_ail.next, struct xfs_log_item, li_ail);
57 if (&next_lip->li_ail != &ailp->ail_head)
58 next_lsn = next_lip->li_lsn;
59 lsn = lip->li_lsn;
60
61 if (in_ail &&
62 (prev_lsn == NULLCOMMITLSN || XFS_LSN_CMP(prev_lsn, lsn) <= 0) &&
63 (next_lsn == NULLCOMMITLSN || XFS_LSN_CMP(next_lsn, lsn) >= 0))
64 return;
65
66 spin_unlock(&ailp->ail_lock);
67 ASSERT(in_ail);
68 ASSERT(prev_lsn == NULLCOMMITLSN || XFS_LSN_CMP(prev_lsn, lsn) <= 0);
69 ASSERT(next_lsn == NULLCOMMITLSN || XFS_LSN_CMP(next_lsn, lsn) >= 0);
70 spin_lock(&ailp->ail_lock);
71}
72#else /* !DEBUG */
73#define xfs_ail_check(a,l)
74#endif /* DEBUG */
75
76/*
77 * Return a pointer to the last item in the AIL. If the AIL is empty, then
78 * return NULL.
79 */
80static struct xfs_log_item *
81xfs_ail_max(
82 struct xfs_ail *ailp)
83{
84 if (list_empty(&ailp->ail_head))
85 return NULL;
86
87 return list_entry(ailp->ail_head.prev, struct xfs_log_item, li_ail);
88}
89
90/*
91 * Return a pointer to the item which follows the given item in the AIL. If
92 * the given item is the last item in the list, then return NULL.
93 */
94static struct xfs_log_item *
95xfs_ail_next(
96 struct xfs_ail *ailp,
97 struct xfs_log_item *lip)
98{
99 if (lip->li_ail.next == &ailp->ail_head)
100 return NULL;
101
102 return list_first_entry(&lip->li_ail, struct xfs_log_item, li_ail);
103}
104
105/*
106 * This is called by the log manager code to determine the LSN of the tail of
107 * the log. This is exactly the LSN of the first item in the AIL. If the AIL
108 * is empty, then this function returns 0.
109 *
110 * We need the AIL lock in order to get a coherent read of the lsn of the last
111 * item in the AIL.
112 */
113static xfs_lsn_t
114__xfs_ail_min_lsn(
115 struct xfs_ail *ailp)
116{
117 struct xfs_log_item *lip = xfs_ail_min(ailp);
118
119 if (lip)
120 return lip->li_lsn;
121 return 0;
122}
123
124xfs_lsn_t
125xfs_ail_min_lsn(
126 struct xfs_ail *ailp)
127{
128 xfs_lsn_t lsn;
129
130 spin_lock(&ailp->ail_lock);
131 lsn = __xfs_ail_min_lsn(ailp);
132 spin_unlock(&ailp->ail_lock);
133
134 return lsn;
135}
136
137/*
138 * The cursor keeps track of where our current traversal is up to by tracking
139 * the next item in the list for us. However, for this to be safe, removing an
140 * object from the AIL needs to invalidate any cursor that points to it. hence
141 * the traversal cursor needs to be linked to the struct xfs_ail so that
142 * deletion can search all the active cursors for invalidation.
143 */
144STATIC void
145xfs_trans_ail_cursor_init(
146 struct xfs_ail *ailp,
147 struct xfs_ail_cursor *cur)
148{
149 cur->item = NULL;
150 list_add_tail(&cur->list, &ailp->ail_cursors);
151}
152
153/*
154 * Get the next item in the traversal and advance the cursor. If the cursor
155 * was invalidated (indicated by a lip of 1), restart the traversal.
156 */
157struct xfs_log_item *
158xfs_trans_ail_cursor_next(
159 struct xfs_ail *ailp,
160 struct xfs_ail_cursor *cur)
161{
162 struct xfs_log_item *lip = cur->item;
163
164 if ((uintptr_t)lip & 1)
165 lip = xfs_ail_min(ailp);
166 if (lip)
167 cur->item = xfs_ail_next(ailp, lip);
168 return lip;
169}
170
171/*
172 * When the traversal is complete, we need to remove the cursor from the list
173 * of traversing cursors.
174 */
175void
176xfs_trans_ail_cursor_done(
177 struct xfs_ail_cursor *cur)
178{
179 cur->item = NULL;
180 list_del_init(&cur->list);
181}
182
183/*
184 * Invalidate any cursor that is pointing to this item. This is called when an
185 * item is removed from the AIL. Any cursor pointing to this object is now
186 * invalid and the traversal needs to be terminated so it doesn't reference a
187 * freed object. We set the low bit of the cursor item pointer so we can
188 * distinguish between an invalidation and the end of the list when getting the
189 * next item from the cursor.
190 */
191STATIC void
192xfs_trans_ail_cursor_clear(
193 struct xfs_ail *ailp,
194 struct xfs_log_item *lip)
195{
196 struct xfs_ail_cursor *cur;
197
198 list_for_each_entry(cur, &ailp->ail_cursors, list) {
199 if (cur->item == lip)
200 cur->item = (struct xfs_log_item *)
201 ((uintptr_t)cur->item | 1);
202 }
203}
204
205/*
206 * Find the first item in the AIL with the given @lsn by searching in ascending
207 * LSN order and initialise the cursor to point to the next item for a
208 * ascending traversal. Pass a @lsn of zero to initialise the cursor to the
209 * first item in the AIL. Returns NULL if the list is empty.
210 */
211struct xfs_log_item *
212xfs_trans_ail_cursor_first(
213 struct xfs_ail *ailp,
214 struct xfs_ail_cursor *cur,
215 xfs_lsn_t lsn)
216{
217 struct xfs_log_item *lip;
218
219 xfs_trans_ail_cursor_init(ailp, cur);
220
221 if (lsn == 0) {
222 lip = xfs_ail_min(ailp);
223 goto out;
224 }
225
226 list_for_each_entry(lip, &ailp->ail_head, li_ail) {
227 if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
228 goto out;
229 }
230 return NULL;
231
232out:
233 if (lip)
234 cur->item = xfs_ail_next(ailp, lip);
235 return lip;
236}
237
238static struct xfs_log_item *
239__xfs_trans_ail_cursor_last(
240 struct xfs_ail *ailp,
241 xfs_lsn_t lsn)
242{
243 struct xfs_log_item *lip;
244
245 list_for_each_entry_reverse(lip, &ailp->ail_head, li_ail) {
246 if (XFS_LSN_CMP(lip->li_lsn, lsn) <= 0)
247 return lip;
248 }
249 return NULL;
250}
251
252/*
253 * Find the last item in the AIL with the given @lsn by searching in descending
254 * LSN order and initialise the cursor to point to that item. If there is no
255 * item with the value of @lsn, then it sets the cursor to the last item with an
256 * LSN lower than @lsn. Returns NULL if the list is empty.
257 */
258struct xfs_log_item *
259xfs_trans_ail_cursor_last(
260 struct xfs_ail *ailp,
261 struct xfs_ail_cursor *cur,
262 xfs_lsn_t lsn)
263{
264 xfs_trans_ail_cursor_init(ailp, cur);
265 cur->item = __xfs_trans_ail_cursor_last(ailp, lsn);
266 return cur->item;
267}
268
269/*
270 * Splice the log item list into the AIL at the given LSN. We splice to the
271 * tail of the given LSN to maintain insert order for push traversals. The
272 * cursor is optional, allowing repeated updates to the same LSN to avoid
273 * repeated traversals. This should not be called with an empty list.
274 */
275static void
276xfs_ail_splice(
277 struct xfs_ail *ailp,
278 struct xfs_ail_cursor *cur,
279 struct list_head *list,
280 xfs_lsn_t lsn)
281{
282 struct xfs_log_item *lip;
283
284 ASSERT(!list_empty(list));
285
286 /*
287 * Use the cursor to determine the insertion point if one is
288 * provided. If not, or if the one we got is not valid,
289 * find the place in the AIL where the items belong.
290 */
291 lip = cur ? cur->item : NULL;
292 if (!lip || (uintptr_t)lip & 1)
293 lip = __xfs_trans_ail_cursor_last(ailp, lsn);
294
295 /*
296 * If a cursor is provided, we know we're processing the AIL
297 * in lsn order, and future items to be spliced in will
298 * follow the last one being inserted now. Update the
299 * cursor to point to that last item, now while we have a
300 * reliable pointer to it.
301 */
302 if (cur)
303 cur->item = list_entry(list->prev, struct xfs_log_item, li_ail);
304
305 /*
306 * Finally perform the splice. Unless the AIL was empty,
307 * lip points to the item in the AIL _after_ which the new
308 * items should go. If lip is null the AIL was empty, so
309 * the new items go at the head of the AIL.
310 */
311 if (lip)
312 list_splice(list, &lip->li_ail);
313 else
314 list_splice(list, &ailp->ail_head);
315}
316
317/*
318 * Delete the given item from the AIL. Return a pointer to the item.
319 */
320static void
321xfs_ail_delete(
322 struct xfs_ail *ailp,
323 struct xfs_log_item *lip)
324{
325 xfs_ail_check(ailp, lip);
326 list_del(&lip->li_ail);
327 xfs_trans_ail_cursor_clear(ailp, lip);
328}
329
330/*
331 * Requeue a failed buffer for writeback.
332 *
333 * We clear the log item failed state here as well, but we have to be careful
334 * about reference counts because the only active reference counts on the buffer
335 * may be the failed log items. Hence if we clear the log item failed state
336 * before queuing the buffer for IO we can release all active references to
337 * the buffer and free it, leading to use after free problems in
338 * xfs_buf_delwri_queue. It makes no difference to the buffer or log items which
339 * order we process them in - the buffer is locked, and we own the buffer list
340 * so nothing on them is going to change while we are performing this action.
341 *
342 * Hence we can safely queue the buffer for IO before we clear the failed log
343 * item state, therefore always having an active reference to the buffer and
344 * avoiding the transient zero-reference state that leads to use-after-free.
345 */
346static inline int
347xfsaild_resubmit_item(
348 struct xfs_log_item *lip,
349 struct list_head *buffer_list)
350{
351 struct xfs_buf *bp = lip->li_buf;
352
353 if (!xfs_buf_trylock(bp))
354 return XFS_ITEM_LOCKED;
355
356 if (!xfs_buf_delwri_queue(bp, buffer_list)) {
357 xfs_buf_unlock(bp);
358 return XFS_ITEM_FLUSHING;
359 }
360
361 /* protected by ail_lock */
362 list_for_each_entry(lip, &bp->b_li_list, li_bio_list) {
363 if (bp->b_flags & (_XBF_INODES | _XBF_DQUOTS))
364 clear_bit(XFS_LI_FAILED, &lip->li_flags);
365 else
366 xfs_clear_li_failed(lip);
367 }
368
369 xfs_buf_unlock(bp);
370 return XFS_ITEM_SUCCESS;
371}
372
373static inline uint
374xfsaild_push_item(
375 struct xfs_ail *ailp,
376 struct xfs_log_item *lip)
377{
378 /*
379 * If log item pinning is enabled, skip the push and track the item as
380 * pinned. This can help induce head-behind-tail conditions.
381 */
382 if (XFS_TEST_ERROR(false, ailp->ail_log->l_mp, XFS_ERRTAG_LOG_ITEM_PIN))
383 return XFS_ITEM_PINNED;
384
385 /*
386 * Consider the item pinned if a push callback is not defined so the
387 * caller will force the log. This should only happen for intent items
388 * as they are unpinned once the associated done item is committed to
389 * the on-disk log.
390 */
391 if (!lip->li_ops->iop_push)
392 return XFS_ITEM_PINNED;
393 if (test_bit(XFS_LI_FAILED, &lip->li_flags))
394 return xfsaild_resubmit_item(lip, &ailp->ail_buf_list);
395 return lip->li_ops->iop_push(lip, &ailp->ail_buf_list);
396}
397
398/*
399 * Compute the LSN that we'd need to push the log tail towards in order to have
400 * at least 25% of the log space free. If the log free space already meets this
401 * threshold, this function returns the lowest LSN in the AIL to slowly keep
402 * writeback ticking over and the tail of the log moving forward.
403 */
404static xfs_lsn_t
405xfs_ail_calc_push_target(
406 struct xfs_ail *ailp)
407{
408 struct xlog *log = ailp->ail_log;
409 struct xfs_log_item *lip;
410 xfs_lsn_t target_lsn;
411 xfs_lsn_t max_lsn;
412 xfs_lsn_t min_lsn;
413 int32_t free_bytes;
414 uint32_t target_block;
415 uint32_t target_cycle;
416
417 lockdep_assert_held(&ailp->ail_lock);
418
419 lip = xfs_ail_max(ailp);
420 if (!lip)
421 return NULLCOMMITLSN;
422
423 max_lsn = lip->li_lsn;
424 min_lsn = __xfs_ail_min_lsn(ailp);
425
426 /*
427 * If we are supposed to push all the items in the AIL, we want to push
428 * to the current head. We then clear the push flag so that we don't
429 * keep pushing newly queued items beyond where the push all command was
430 * run. If the push waiter wants to empty the ail, it should queue
431 * itself on the ail_empty wait queue.
432 */
433 if (test_and_clear_bit(XFS_AIL_OPSTATE_PUSH_ALL, &ailp->ail_opstate))
434 return max_lsn;
435
436 /* If someone wants the AIL empty, keep pushing everything we have. */
437 if (waitqueue_active(&ailp->ail_empty))
438 return max_lsn;
439
440 /*
441 * Background pushing - attempt to keep 25% of the log free and if we
442 * have that much free retain the existing target.
443 */
444 free_bytes = log->l_logsize - xlog_lsn_sub(log, max_lsn, min_lsn);
445 if (free_bytes >= log->l_logsize >> 2)
446 return ailp->ail_target;
447
448 target_cycle = CYCLE_LSN(min_lsn);
449 target_block = BLOCK_LSN(min_lsn) + (log->l_logBBsize >> 2);
450 if (target_block >= log->l_logBBsize) {
451 target_block -= log->l_logBBsize;
452 target_cycle += 1;
453 }
454 target_lsn = xlog_assign_lsn(target_cycle, target_block);
455
456 /* Cap the target to the highest LSN known to be in the AIL. */
457 if (XFS_LSN_CMP(target_lsn, max_lsn) > 0)
458 return max_lsn;
459
460 /* If the existing target is higher than the new target, keep it. */
461 if (XFS_LSN_CMP(ailp->ail_target, target_lsn) >= 0)
462 return ailp->ail_target;
463 return target_lsn;
464}
465
466static long
467xfsaild_push(
468 struct xfs_ail *ailp)
469{
470 struct xfs_mount *mp = ailp->ail_log->l_mp;
471 struct xfs_ail_cursor cur;
472 struct xfs_log_item *lip;
473 xfs_lsn_t lsn;
474 long tout;
475 int stuck = 0;
476 int flushing = 0;
477 int count = 0;
478
479 /*
480 * If we encountered pinned items or did not finish writing out all
481 * buffers the last time we ran, force a background CIL push to get the
482 * items unpinned in the near future. We do not wait on the CIL push as
483 * that could stall us for seconds if there is enough background IO
484 * load. Stalling for that long when the tail of the log is pinned and
485 * needs flushing will hard stop the transaction subsystem when log
486 * space runs out.
487 */
488 if (ailp->ail_log_flush && ailp->ail_last_pushed_lsn == 0 &&
489 (!list_empty_careful(&ailp->ail_buf_list) ||
490 xfs_ail_min_lsn(ailp))) {
491 ailp->ail_log_flush = 0;
492
493 XFS_STATS_INC(mp, xs_push_ail_flush);
494 xlog_cil_flush(ailp->ail_log);
495 }
496
497 spin_lock(&ailp->ail_lock);
498 WRITE_ONCE(ailp->ail_target, xfs_ail_calc_push_target(ailp));
499 if (ailp->ail_target == NULLCOMMITLSN)
500 goto out_done;
501
502 /* we're done if the AIL is empty or our push has reached the end */
503 lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->ail_last_pushed_lsn);
504 if (!lip)
505 goto out_done_cursor;
506
507 XFS_STATS_INC(mp, xs_push_ail);
508
509 ASSERT(ailp->ail_target != NULLCOMMITLSN);
510
511 lsn = lip->li_lsn;
512 while ((XFS_LSN_CMP(lip->li_lsn, ailp->ail_target) <= 0)) {
513 int lock_result;
514
515 if (test_bit(XFS_LI_FLUSHING, &lip->li_flags))
516 goto next_item;
517
518 /*
519 * Note that iop_push may unlock and reacquire the AIL lock. We
520 * rely on the AIL cursor implementation to be able to deal with
521 * the dropped lock.
522 */
523 lock_result = xfsaild_push_item(ailp, lip);
524 switch (lock_result) {
525 case XFS_ITEM_SUCCESS:
526 XFS_STATS_INC(mp, xs_push_ail_success);
527 trace_xfs_ail_push(lip);
528
529 ailp->ail_last_pushed_lsn = lsn;
530 break;
531
532 case XFS_ITEM_FLUSHING:
533 /*
534 * The item or its backing buffer is already being
535 * flushed. The typical reason for that is that an
536 * inode buffer is locked because we already pushed the
537 * updates to it as part of inode clustering.
538 *
539 * We do not want to stop flushing just because lots
540 * of items are already being flushed, but we need to
541 * re-try the flushing relatively soon if most of the
542 * AIL is being flushed.
543 */
544 XFS_STATS_INC(mp, xs_push_ail_flushing);
545 trace_xfs_ail_flushing(lip);
546
547 flushing++;
548 ailp->ail_last_pushed_lsn = lsn;
549 break;
550
551 case XFS_ITEM_PINNED:
552 XFS_STATS_INC(mp, xs_push_ail_pinned);
553 trace_xfs_ail_pinned(lip);
554
555 stuck++;
556 ailp->ail_log_flush++;
557 break;
558 case XFS_ITEM_LOCKED:
559 XFS_STATS_INC(mp, xs_push_ail_locked);
560 trace_xfs_ail_locked(lip);
561
562 stuck++;
563 break;
564 default:
565 ASSERT(0);
566 break;
567 }
568
569 count++;
570
571 /*
572 * Are there too many items we can't do anything with?
573 *
574 * If we are skipping too many items because we can't flush
575 * them or they are already being flushed, we back off and
576 * given them time to complete whatever operation is being
577 * done. i.e. remove pressure from the AIL while we can't make
578 * progress so traversals don't slow down further inserts and
579 * removals to/from the AIL.
580 *
581 * The value of 100 is an arbitrary magic number based on
582 * observation.
583 */
584 if (stuck > 100)
585 break;
586
587next_item:
588 lip = xfs_trans_ail_cursor_next(ailp, &cur);
589 if (lip == NULL)
590 break;
591 if (lip->li_lsn != lsn && count > 1000)
592 break;
593 lsn = lip->li_lsn;
594 }
595
596out_done_cursor:
597 xfs_trans_ail_cursor_done(&cur);
598out_done:
599 spin_unlock(&ailp->ail_lock);
600
601 if (xfs_buf_delwri_submit_nowait(&ailp->ail_buf_list))
602 ailp->ail_log_flush++;
603
604 if (!count || XFS_LSN_CMP(lsn, ailp->ail_target) >= 0) {
605 /*
606 * We reached the target or the AIL is empty, so wait a bit
607 * longer for I/O to complete and remove pushed items from the
608 * AIL before we start the next scan from the start of the AIL.
609 */
610 tout = 50;
611 ailp->ail_last_pushed_lsn = 0;
612 } else if (((stuck + flushing) * 100) / count > 90) {
613 /*
614 * Either there is a lot of contention on the AIL or we are
615 * stuck due to operations in progress. "Stuck" in this case
616 * is defined as >90% of the items we tried to push were stuck.
617 *
618 * Backoff a bit more to allow some I/O to complete before
619 * restarting from the start of the AIL. This prevents us from
620 * spinning on the same items, and if they are pinned will all
621 * the restart to issue a log force to unpin the stuck items.
622 */
623 tout = 20;
624 ailp->ail_last_pushed_lsn = 0;
625 } else {
626 /*
627 * Assume we have more work to do in a short while.
628 */
629 tout = 0;
630 }
631
632 return tout;
633}
634
635static int
636xfsaild(
637 void *data)
638{
639 struct xfs_ail *ailp = data;
640 long tout = 0; /* milliseconds */
641 unsigned int noreclaim_flag;
642
643 noreclaim_flag = memalloc_noreclaim_save();
644 set_freezable();
645
646 while (1) {
647 /*
648 * Long waits of 50ms or more occur when we've run out of items
649 * to push, so we only want uninterruptible state if we're
650 * actually blocked on something.
651 */
652 if (tout && tout <= 20)
653 set_current_state(TASK_KILLABLE|TASK_FREEZABLE);
654 else
655 set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
656
657 /*
658 * Check kthread_should_stop() after we set the task state to
659 * guarantee that we either see the stop bit and exit or the
660 * task state is reset to runnable such that it's not scheduled
661 * out indefinitely and detects the stop bit at next iteration.
662 * A memory barrier is included in above task state set to
663 * serialize again kthread_stop().
664 */
665 if (kthread_should_stop()) {
666 __set_current_state(TASK_RUNNING);
667
668 /*
669 * The caller forces out the AIL before stopping the
670 * thread in the common case, which means the delwri
671 * queue is drained. In the shutdown case, the queue may
672 * still hold relogged buffers that haven't been
673 * submitted because they were pinned since added to the
674 * queue.
675 *
676 * Log I/O error processing stales the underlying buffer
677 * and clears the delwri state, expecting the buf to be
678 * removed on the next submission attempt. That won't
679 * happen if we're shutting down, so this is the last
680 * opportunity to release such buffers from the queue.
681 */
682 ASSERT(list_empty(&ailp->ail_buf_list) ||
683 xlog_is_shutdown(ailp->ail_log));
684 xfs_buf_delwri_cancel(&ailp->ail_buf_list);
685 break;
686 }
687
688 /* Idle if the AIL is empty. */
689 spin_lock(&ailp->ail_lock);
690 if (!xfs_ail_min(ailp) && list_empty(&ailp->ail_buf_list)) {
691 spin_unlock(&ailp->ail_lock);
692 schedule();
693 tout = 0;
694 continue;
695 }
696 spin_unlock(&ailp->ail_lock);
697
698 if (tout)
699 schedule_timeout(msecs_to_jiffies(tout));
700
701 __set_current_state(TASK_RUNNING);
702
703 try_to_freeze();
704
705 tout = xfsaild_push(ailp);
706 }
707
708 memalloc_noreclaim_restore(noreclaim_flag);
709 return 0;
710}
711
712/*
713 * Push out all items in the AIL immediately and wait until the AIL is empty.
714 */
715void
716xfs_ail_push_all_sync(
717 struct xfs_ail *ailp)
718{
719 DEFINE_WAIT(wait);
720
721 spin_lock(&ailp->ail_lock);
722 while (xfs_ail_max(ailp) != NULL) {
723 prepare_to_wait(&ailp->ail_empty, &wait, TASK_UNINTERRUPTIBLE);
724 wake_up_process(ailp->ail_task);
725 spin_unlock(&ailp->ail_lock);
726 schedule();
727 spin_lock(&ailp->ail_lock);
728 }
729 spin_unlock(&ailp->ail_lock);
730
731 finish_wait(&ailp->ail_empty, &wait);
732}
733
734void
735__xfs_ail_assign_tail_lsn(
736 struct xfs_ail *ailp)
737{
738 struct xlog *log = ailp->ail_log;
739 xfs_lsn_t tail_lsn;
740
741 assert_spin_locked(&ailp->ail_lock);
742
743 if (xlog_is_shutdown(log))
744 return;
745
746 tail_lsn = __xfs_ail_min_lsn(ailp);
747 if (!tail_lsn)
748 tail_lsn = ailp->ail_head_lsn;
749
750 WRITE_ONCE(log->l_tail_space,
751 xlog_lsn_sub(log, ailp->ail_head_lsn, tail_lsn));
752 trace_xfs_log_assign_tail_lsn(log, tail_lsn);
753 atomic64_set(&log->l_tail_lsn, tail_lsn);
754}
755
756/*
757 * Callers should pass the original tail lsn so that we can detect if the tail
758 * has moved as a result of the operation that was performed. If the caller
759 * needs to force a tail space update, it should pass NULLCOMMITLSN to bypass
760 * the "did the tail LSN change?" checks. If the caller wants to avoid a tail
761 * update (e.g. it knows the tail did not change) it should pass an @old_lsn of
762 * 0.
763 */
764void
765xfs_ail_update_finish(
766 struct xfs_ail *ailp,
767 xfs_lsn_t old_lsn) __releases(ailp->ail_lock)
768{
769 struct xlog *log = ailp->ail_log;
770
771 /* If the tail lsn hasn't changed, don't do updates or wakeups. */
772 if (!old_lsn || old_lsn == __xfs_ail_min_lsn(ailp)) {
773 spin_unlock(&ailp->ail_lock);
774 return;
775 }
776
777 __xfs_ail_assign_tail_lsn(ailp);
778 if (list_empty(&ailp->ail_head))
779 wake_up_all(&ailp->ail_empty);
780 spin_unlock(&ailp->ail_lock);
781 xfs_log_space_wake(log->l_mp);
782}
783
784/*
785 * xfs_trans_ail_update - bulk AIL insertion operation.
786 *
787 * @xfs_trans_ail_update takes an array of log items that all need to be
788 * positioned at the same LSN in the AIL. If an item is not in the AIL, it will
789 * be added. Otherwise, it will be repositioned by removing it and re-adding
790 * it to the AIL. If we move the first item in the AIL, update the log tail to
791 * match the new minimum LSN in the AIL.
792 *
793 * This function takes the AIL lock once to execute the update operations on
794 * all the items in the array, and as such should not be called with the AIL
795 * lock held. As a result, once we have the AIL lock, we need to check each log
796 * item LSN to confirm it needs to be moved forward in the AIL.
797 *
798 * To optimise the insert operation, we delete all the items from the AIL in
799 * the first pass, moving them into a temporary list, then splice the temporary
800 * list into the correct position in the AIL. This avoids needing to do an
801 * insert operation on every item.
802 *
803 * This function must be called with the AIL lock held. The lock is dropped
804 * before returning.
805 */
806void
807xfs_trans_ail_update_bulk(
808 struct xfs_ail *ailp,
809 struct xfs_ail_cursor *cur,
810 struct xfs_log_item **log_items,
811 int nr_items,
812 xfs_lsn_t lsn) __releases(ailp->ail_lock)
813{
814 struct xfs_log_item *mlip;
815 xfs_lsn_t tail_lsn = 0;
816 int i;
817 LIST_HEAD(tmp);
818
819 ASSERT(nr_items > 0); /* Not required, but true. */
820 mlip = xfs_ail_min(ailp);
821
822 for (i = 0; i < nr_items; i++) {
823 struct xfs_log_item *lip = log_items[i];
824 if (test_and_set_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
825 /* check if we really need to move the item */
826 if (XFS_LSN_CMP(lsn, lip->li_lsn) <= 0)
827 continue;
828
829 trace_xfs_ail_move(lip, lip->li_lsn, lsn);
830 if (mlip == lip && !tail_lsn)
831 tail_lsn = lip->li_lsn;
832
833 xfs_ail_delete(ailp, lip);
834 } else {
835 trace_xfs_ail_insert(lip, 0, lsn);
836 }
837 lip->li_lsn = lsn;
838 list_add_tail(&lip->li_ail, &tmp);
839 }
840
841 if (!list_empty(&tmp))
842 xfs_ail_splice(ailp, cur, &tmp, lsn);
843
844 /*
845 * If this is the first insert, wake up the push daemon so it can
846 * actively scan for items to push. We also need to do a log tail
847 * LSN update to ensure that it is correctly tracked by the log, so
848 * set the tail_lsn to NULLCOMMITLSN so that xfs_ail_update_finish()
849 * will see that the tail lsn has changed and will update the tail
850 * appropriately.
851 */
852 if (!mlip) {
853 wake_up_process(ailp->ail_task);
854 tail_lsn = NULLCOMMITLSN;
855 }
856
857 xfs_ail_update_finish(ailp, tail_lsn);
858}
859
860/* Insert a log item into the AIL. */
861void
862xfs_trans_ail_insert(
863 struct xfs_ail *ailp,
864 struct xfs_log_item *lip,
865 xfs_lsn_t lsn)
866{
867 spin_lock(&ailp->ail_lock);
868 xfs_trans_ail_update_bulk(ailp, NULL, &lip, 1, lsn);
869}
870
871/*
872 * Delete one log item from the AIL.
873 *
874 * If this item was at the tail of the AIL, return the LSN of the log item so
875 * that we can use it to check if the LSN of the tail of the log has moved
876 * when finishing up the AIL delete process in xfs_ail_update_finish().
877 */
878xfs_lsn_t
879xfs_ail_delete_one(
880 struct xfs_ail *ailp,
881 struct xfs_log_item *lip)
882{
883 struct xfs_log_item *mlip = xfs_ail_min(ailp);
884 xfs_lsn_t lsn = lip->li_lsn;
885
886 trace_xfs_ail_delete(lip, mlip->li_lsn, lip->li_lsn);
887 xfs_ail_delete(ailp, lip);
888 clear_bit(XFS_LI_IN_AIL, &lip->li_flags);
889 lip->li_lsn = 0;
890
891 if (mlip == lip)
892 return lsn;
893 return 0;
894}
895
896void
897xfs_trans_ail_delete(
898 struct xfs_log_item *lip,
899 int shutdown_type)
900{
901 struct xfs_ail *ailp = lip->li_ailp;
902 struct xlog *log = ailp->ail_log;
903 xfs_lsn_t tail_lsn;
904
905 spin_lock(&ailp->ail_lock);
906 if (!test_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
907 spin_unlock(&ailp->ail_lock);
908 if (shutdown_type && !xlog_is_shutdown(log)) {
909 xfs_alert_tag(log->l_mp, XFS_PTAG_AILDELETE,
910 "%s: attempting to delete a log item that is not in the AIL",
911 __func__);
912 xlog_force_shutdown(log, shutdown_type);
913 }
914 return;
915 }
916
917 /* xfs_ail_update_finish() drops the AIL lock */
918 xfs_clear_li_failed(lip);
919 tail_lsn = xfs_ail_delete_one(ailp, lip);
920 xfs_ail_update_finish(ailp, tail_lsn);
921}
922
923int
924xfs_trans_ail_init(
925 xfs_mount_t *mp)
926{
927 struct xfs_ail *ailp;
928
929 ailp = kzalloc(sizeof(struct xfs_ail),
930 GFP_KERNEL | __GFP_RETRY_MAYFAIL);
931 if (!ailp)
932 return -ENOMEM;
933
934 ailp->ail_log = mp->m_log;
935 INIT_LIST_HEAD(&ailp->ail_head);
936 INIT_LIST_HEAD(&ailp->ail_cursors);
937 spin_lock_init(&ailp->ail_lock);
938 INIT_LIST_HEAD(&ailp->ail_buf_list);
939 init_waitqueue_head(&ailp->ail_empty);
940
941 ailp->ail_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
942 mp->m_super->s_id);
943 if (IS_ERR(ailp->ail_task))
944 goto out_free_ailp;
945
946 mp->m_ail = ailp;
947 return 0;
948
949out_free_ailp:
950 kfree(ailp);
951 return -ENOMEM;
952}
953
954void
955xfs_trans_ail_destroy(
956 xfs_mount_t *mp)
957{
958 struct xfs_ail *ailp = mp->m_ail;
959
960 kthread_stop(ailp->ail_task);
961 kfree(ailp);
962}