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Linux/fs/xfs/xfs_trans_ail.c

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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  */
 36 STATIC void
 37 xfs_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  */
 68 static xfs_log_item_t *
 69 xfs_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  */
 82 static xfs_log_item_t *
 83 xfs_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  */
101 xfs_lsn_t
102 xfs_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  */
120 static xfs_lsn_t
121 xfs_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  */
143 STATIC void
144 xfs_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  */
156 struct xfs_log_item *
157 xfs_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  */
174 void
175 xfs_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  */
190 STATIC void
191 xfs_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  */
210 xfs_log_item_t *
211 xfs_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 
231 out:
232         if (lip)
233                 cur->item = xfs_ail_next(ailp, lip);
234         return lip;
235 }
236 
237 static 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  */
257 struct xfs_log_item *
258 xfs_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  */
274 static void
275 xfs_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  */
319 static void
320 xfs_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 
329 static inline uint
330 xfsaild_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 
344 static long
345 xfsaild_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) {
477 out_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 
508 static int
509 xfsaild(
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  */
587 void
588 xfs_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  */
613 void
614 xfs_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  */
626 void
627 xfs_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  */
669 void
670 xfs_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 
718 bool
719 xfs_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  */
755 void
756 xfs_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 
788 int
789 xfs_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 
813 out_free_ailp:
814         kmem_free(ailp);
815         return -ENOMEM;
816 }
817 
818 void
819 xfs_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 }
827 

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