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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_error.h"
 29 #include "xfs_log.h"
 30 
 31 #ifdef DEBUG
 32 /*
 33  * Check that the list is sorted as it should be.
 34  */
 35 STATIC void
 36 xfs_ail_check(
 37         struct xfs_ail  *ailp,
 38         xfs_log_item_t  *lip)
 39 {
 40         xfs_log_item_t  *prev_lip;
 41 
 42         if (list_empty(&ailp->xa_ail))
 43                 return;
 44 
 45         /*
 46          * Check the next and previous entries are valid.
 47          */
 48         ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
 49         prev_lip = list_entry(lip->li_ail.prev, xfs_log_item_t, li_ail);
 50         if (&prev_lip->li_ail != &ailp->xa_ail)
 51                 ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
 52 
 53         prev_lip = list_entry(lip->li_ail.next, xfs_log_item_t, li_ail);
 54         if (&prev_lip->li_ail != &ailp->xa_ail)
 55                 ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) >= 0);
 56 
 57 
 58 }
 59 #else /* !DEBUG */
 60 #define xfs_ail_check(a,l)
 61 #endif /* DEBUG */
 62 
 63 /*
 64  * Return a pointer to the last item in the AIL.  If the AIL is empty, then
 65  * return NULL.
 66  */
 67 static xfs_log_item_t *
 68 xfs_ail_max(
 69         struct xfs_ail  *ailp)
 70 {
 71         if (list_empty(&ailp->xa_ail))
 72                 return NULL;
 73 
 74         return list_entry(ailp->xa_ail.prev, xfs_log_item_t, li_ail);
 75 }
 76 
 77 /*
 78  * Return a pointer to the item which follows the given item in the AIL.  If
 79  * the given item is the last item in the list, then return NULL.
 80  */
 81 static xfs_log_item_t *
 82 xfs_ail_next(
 83         struct xfs_ail  *ailp,
 84         xfs_log_item_t  *lip)
 85 {
 86         if (lip->li_ail.next == &ailp->xa_ail)
 87                 return NULL;
 88 
 89         return list_first_entry(&lip->li_ail, xfs_log_item_t, li_ail);
 90 }
 91 
 92 /*
 93  * This is called by the log manager code to determine the LSN of the tail of
 94  * the log.  This is exactly the LSN of the first item in the AIL.  If the AIL
 95  * is empty, then this function returns 0.
 96  *
 97  * We need the AIL lock in order to get a coherent read of the lsn of the last
 98  * item in the AIL.
 99  */
100 xfs_lsn_t
101 xfs_ail_min_lsn(
102         struct xfs_ail  *ailp)
103 {
104         xfs_lsn_t       lsn = 0;
105         xfs_log_item_t  *lip;
106 
107         spin_lock(&ailp->xa_lock);
108         lip = xfs_ail_min(ailp);
109         if (lip)
110                 lsn = lip->li_lsn;
111         spin_unlock(&ailp->xa_lock);
112 
113         return lsn;
114 }
115 
116 /*
117  * Return the maximum lsn held in the AIL, or zero if the AIL is empty.
118  */
119 static xfs_lsn_t
120 xfs_ail_max_lsn(
121         struct xfs_ail  *ailp)
122 {
123         xfs_lsn_t       lsn = 0;
124         xfs_log_item_t  *lip;
125 
126         spin_lock(&ailp->xa_lock);
127         lip = xfs_ail_max(ailp);
128         if (lip)
129                 lsn = lip->li_lsn;
130         spin_unlock(&ailp->xa_lock);
131 
132         return lsn;
133 }
134 
135 /*
136  * The cursor keeps track of where our current traversal is up to by tracking
137  * the next item in the list for us. However, for this to be safe, removing an
138  * object from the AIL needs to invalidate any cursor that points to it. hence
139  * the traversal cursor needs to be linked to the struct xfs_ail so that
140  * deletion can search all the active cursors for invalidation.
141  */
142 STATIC void
143 xfs_trans_ail_cursor_init(
144         struct xfs_ail          *ailp,
145         struct xfs_ail_cursor   *cur)
146 {
147         cur->item = NULL;
148         list_add_tail(&cur->list, &ailp->xa_cursors);
149 }
150 
151 /*
152  * Get the next item in the traversal and advance the cursor.  If the cursor
153  * was invalidated (indicated by a lip of 1), restart the traversal.
154  */
155 struct xfs_log_item *
156 xfs_trans_ail_cursor_next(
157         struct xfs_ail          *ailp,
158         struct xfs_ail_cursor   *cur)
159 {
160         struct xfs_log_item     *lip = cur->item;
161 
162         if ((uintptr_t)lip & 1)
163                 lip = xfs_ail_min(ailp);
164         if (lip)
165                 cur->item = xfs_ail_next(ailp, lip);
166         return lip;
167 }
168 
169 /*
170  * When the traversal is complete, we need to remove the cursor from the list
171  * of traversing cursors.
172  */
173 void
174 xfs_trans_ail_cursor_done(
175         struct xfs_ail_cursor   *cur)
176 {
177         cur->item = NULL;
178         list_del_init(&cur->list);
179 }
180 
181 /*
182  * Invalidate any cursor that is pointing to this item. This is called when an
183  * item is removed from the AIL. Any cursor pointing to this object is now
184  * invalid and the traversal needs to be terminated so it doesn't reference a
185  * freed object. We set the low bit of the cursor item pointer so we can
186  * distinguish between an invalidation and the end of the list when getting the
187  * next item from the cursor.
188  */
189 STATIC void
190 xfs_trans_ail_cursor_clear(
191         struct xfs_ail          *ailp,
192         struct xfs_log_item     *lip)
193 {
194         struct xfs_ail_cursor   *cur;
195 
196         list_for_each_entry(cur, &ailp->xa_cursors, list) {
197                 if (cur->item == lip)
198                         cur->item = (struct xfs_log_item *)
199                                         ((uintptr_t)cur->item | 1);
200         }
201 }
202 
203 /*
204  * Find the first item in the AIL with the given @lsn by searching in ascending
205  * LSN order and initialise the cursor to point to the next item for a
206  * ascending traversal.  Pass a @lsn of zero to initialise the cursor to the
207  * first item in the AIL. Returns NULL if the list is empty.
208  */
209 xfs_log_item_t *
210 xfs_trans_ail_cursor_first(
211         struct xfs_ail          *ailp,
212         struct xfs_ail_cursor   *cur,
213         xfs_lsn_t               lsn)
214 {
215         xfs_log_item_t          *lip;
216 
217         xfs_trans_ail_cursor_init(ailp, cur);
218 
219         if (lsn == 0) {
220                 lip = xfs_ail_min(ailp);
221                 goto out;
222         }
223 
224         list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
225                 if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
226                         goto out;
227         }
228         return NULL;
229 
230 out:
231         if (lip)
232                 cur->item = xfs_ail_next(ailp, lip);
233         return lip;
234 }
235 
236 static struct xfs_log_item *
237 __xfs_trans_ail_cursor_last(
238         struct xfs_ail          *ailp,
239         xfs_lsn_t               lsn)
240 {
241         xfs_log_item_t          *lip;
242 
243         list_for_each_entry_reverse(lip, &ailp->xa_ail, li_ail) {
244                 if (XFS_LSN_CMP(lip->li_lsn, lsn) <= 0)
245                         return lip;
246         }
247         return NULL;
248 }
249 
250 /*
251  * Find the last item in the AIL with the given @lsn by searching in descending
252  * LSN order and initialise the cursor to point to that item.  If there is no
253  * item with the value of @lsn, then it sets the cursor to the last item with an
254  * LSN lower than @lsn.  Returns NULL if the list is empty.
255  */
256 struct xfs_log_item *
257 xfs_trans_ail_cursor_last(
258         struct xfs_ail          *ailp,
259         struct xfs_ail_cursor   *cur,
260         xfs_lsn_t               lsn)
261 {
262         xfs_trans_ail_cursor_init(ailp, cur);
263         cur->item = __xfs_trans_ail_cursor_last(ailp, lsn);
264         return cur->item;
265 }
266 
267 /*
268  * Splice the log item list into the AIL at the given LSN. We splice to the
269  * tail of the given LSN to maintain insert order for push traversals. The
270  * cursor is optional, allowing repeated updates to the same LSN to avoid
271  * repeated traversals.  This should not be called with an empty list.
272  */
273 static void
274 xfs_ail_splice(
275         struct xfs_ail          *ailp,
276         struct xfs_ail_cursor   *cur,
277         struct list_head        *list,
278         xfs_lsn_t               lsn)
279 {
280         struct xfs_log_item     *lip;
281 
282         ASSERT(!list_empty(list));
283 
284         /*
285          * Use the cursor to determine the insertion point if one is
286          * provided.  If not, or if the one we got is not valid,
287          * find the place in the AIL where the items belong.
288          */
289         lip = cur ? cur->item : NULL;
290         if (!lip || (uintptr_t)lip & 1)
291                 lip = __xfs_trans_ail_cursor_last(ailp, lsn);
292 
293         /*
294          * If a cursor is provided, we know we're processing the AIL
295          * in lsn order, and future items to be spliced in will
296          * follow the last one being inserted now.  Update the
297          * cursor to point to that last item, now while we have a
298          * reliable pointer to it.
299          */
300         if (cur)
301                 cur->item = list_entry(list->prev, struct xfs_log_item, li_ail);
302 
303         /*
304          * Finally perform the splice.  Unless the AIL was empty,
305          * lip points to the item in the AIL _after_ which the new
306          * items should go.  If lip is null the AIL was empty, so
307          * the new items go at the head of the AIL.
308          */
309         if (lip)
310                 list_splice(list, &lip->li_ail);
311         else
312                 list_splice(list, &ailp->xa_ail);
313 }
314 
315 /*
316  * Delete the given item from the AIL.  Return a pointer to the item.
317  */
318 static void
319 xfs_ail_delete(
320         struct xfs_ail  *ailp,
321         xfs_log_item_t  *lip)
322 {
323         xfs_ail_check(ailp, lip);
324         list_del(&lip->li_ail);
325         xfs_trans_ail_cursor_clear(ailp, lip);
326 }
327 
328 static long
329 xfsaild_push(
330         struct xfs_ail          *ailp)
331 {
332         xfs_mount_t             *mp = ailp->xa_mount;
333         struct xfs_ail_cursor   cur;
334         xfs_log_item_t          *lip;
335         xfs_lsn_t               lsn;
336         xfs_lsn_t               target;
337         long                    tout;
338         int                     stuck = 0;
339         int                     flushing = 0;
340         int                     count = 0;
341 
342         /*
343          * If we encountered pinned items or did not finish writing out all
344          * buffers the last time we ran, force the log first and wait for it
345          * before pushing again.
346          */
347         if (ailp->xa_log_flush && ailp->xa_last_pushed_lsn == 0 &&
348             (!list_empty_careful(&ailp->xa_buf_list) ||
349              xfs_ail_min_lsn(ailp))) {
350                 ailp->xa_log_flush = 0;
351 
352                 XFS_STATS_INC(mp, xs_push_ail_flush);
353                 xfs_log_force(mp, XFS_LOG_SYNC);
354         }
355 
356         spin_lock(&ailp->xa_lock);
357 
358         /* barrier matches the xa_target update in xfs_ail_push() */
359         smp_rmb();
360         target = ailp->xa_target;
361         ailp->xa_target_prev = target;
362 
363         lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->xa_last_pushed_lsn);
364         if (!lip) {
365                 /*
366                  * If the AIL is empty or our push has reached the end we are
367                  * done now.
368                  */
369                 xfs_trans_ail_cursor_done(&cur);
370                 spin_unlock(&ailp->xa_lock);
371                 goto out_done;
372         }
373 
374         XFS_STATS_INC(mp, xs_push_ail);
375 
376         lsn = lip->li_lsn;
377         while ((XFS_LSN_CMP(lip->li_lsn, target) <= 0)) {
378                 int     lock_result;
379 
380                 /*
381                  * Note that iop_push may unlock and reacquire the AIL lock.  We
382                  * rely on the AIL cursor implementation to be able to deal with
383                  * the dropped lock.
384                  */
385                 lock_result = lip->li_ops->iop_push(lip, &ailp->xa_buf_list);
386                 switch (lock_result) {
387                 case XFS_ITEM_SUCCESS:
388                         XFS_STATS_INC(mp, xs_push_ail_success);
389                         trace_xfs_ail_push(lip);
390 
391                         ailp->xa_last_pushed_lsn = lsn;
392                         break;
393 
394                 case XFS_ITEM_FLUSHING:
395                         /*
396                          * The item or its backing buffer is already beeing
397                          * flushed.  The typical reason for that is that an
398                          * inode buffer is locked because we already pushed the
399                          * updates to it as part of inode clustering.
400                          *
401                          * We do not want to to stop flushing just because lots
402                          * of items are already beeing flushed, but we need to
403                          * re-try the flushing relatively soon if most of the
404                          * AIL is beeing flushed.
405                          */
406                         XFS_STATS_INC(mp, xs_push_ail_flushing);
407                         trace_xfs_ail_flushing(lip);
408 
409                         flushing++;
410                         ailp->xa_last_pushed_lsn = lsn;
411                         break;
412 
413                 case XFS_ITEM_PINNED:
414                         XFS_STATS_INC(mp, xs_push_ail_pinned);
415                         trace_xfs_ail_pinned(lip);
416 
417                         stuck++;
418                         ailp->xa_log_flush++;
419                         break;
420                 case XFS_ITEM_LOCKED:
421                         XFS_STATS_INC(mp, xs_push_ail_locked);
422                         trace_xfs_ail_locked(lip);
423 
424                         stuck++;
425                         break;
426                 default:
427                         ASSERT(0);
428                         break;
429                 }
430 
431                 count++;
432 
433                 /*
434                  * Are there too many items we can't do anything with?
435                  *
436                  * If we we are skipping too many items because we can't flush
437                  * them or they are already being flushed, we back off and
438                  * given them time to complete whatever operation is being
439                  * done. i.e. remove pressure from the AIL while we can't make
440                  * progress so traversals don't slow down further inserts and
441                  * removals to/from the AIL.
442                  *
443                  * The value of 100 is an arbitrary magic number based on
444                  * observation.
445                  */
446                 if (stuck > 100)
447                         break;
448 
449                 lip = xfs_trans_ail_cursor_next(ailp, &cur);
450                 if (lip == NULL)
451                         break;
452                 lsn = lip->li_lsn;
453         }
454         xfs_trans_ail_cursor_done(&cur);
455         spin_unlock(&ailp->xa_lock);
456 
457         if (xfs_buf_delwri_submit_nowait(&ailp->xa_buf_list))
458                 ailp->xa_log_flush++;
459 
460         if (!count || XFS_LSN_CMP(lsn, target) >= 0) {
461 out_done:
462                 /*
463                  * We reached the target or the AIL is empty, so wait a bit
464                  * longer for I/O to complete and remove pushed items from the
465                  * AIL before we start the next scan from the start of the AIL.
466                  */
467                 tout = 50;
468                 ailp->xa_last_pushed_lsn = 0;
469         } else if (((stuck + flushing) * 100) / count > 90) {
470                 /*
471                  * Either there is a lot of contention on the AIL or we are
472                  * stuck due to operations in progress. "Stuck" in this case
473                  * is defined as >90% of the items we tried to push were stuck.
474                  *
475                  * Backoff a bit more to allow some I/O to complete before
476                  * restarting from the start of the AIL. This prevents us from
477                  * spinning on the same items, and if they are pinned will all
478                  * the restart to issue a log force to unpin the stuck items.
479                  */
480                 tout = 20;
481                 ailp->xa_last_pushed_lsn = 0;
482         } else {
483                 /*
484                  * Assume we have more work to do in a short while.
485                  */
486                 tout = 10;
487         }
488 
489         return tout;
490 }
491 
492 static int
493 xfsaild(
494         void            *data)
495 {
496         struct xfs_ail  *ailp = data;
497         long            tout = 0;       /* milliseconds */
498 
499         current->flags |= PF_MEMALLOC;
500         set_freezable();
501 
502         while (!kthread_should_stop()) {
503                 if (tout && tout <= 20)
504                         __set_current_state(TASK_KILLABLE);
505                 else
506                         __set_current_state(TASK_INTERRUPTIBLE);
507 
508                 spin_lock(&ailp->xa_lock);
509 
510                 /*
511                  * Idle if the AIL is empty and we are not racing with a target
512                  * update. We check the AIL after we set the task to a sleep
513                  * state to guarantee that we either catch an xa_target update
514                  * or that a wake_up resets the state to TASK_RUNNING.
515                  * Otherwise, we run the risk of sleeping indefinitely.
516                  *
517                  * The barrier matches the xa_target update in xfs_ail_push().
518                  */
519                 smp_rmb();
520                 if (!xfs_ail_min(ailp) &&
521                     ailp->xa_target == ailp->xa_target_prev) {
522                         spin_unlock(&ailp->xa_lock);
523                         freezable_schedule();
524                         tout = 0;
525                         continue;
526                 }
527                 spin_unlock(&ailp->xa_lock);
528 
529                 if (tout)
530                         freezable_schedule_timeout(msecs_to_jiffies(tout));
531 
532                 __set_current_state(TASK_RUNNING);
533 
534                 try_to_freeze();
535 
536                 tout = xfsaild_push(ailp);
537         }
538 
539         return 0;
540 }
541 
542 /*
543  * This routine is called to move the tail of the AIL forward.  It does this by
544  * trying to flush items in the AIL whose lsns are below the given
545  * threshold_lsn.
546  *
547  * The push is run asynchronously in a workqueue, which means the caller needs
548  * to handle waiting on the async flush for space to become available.
549  * We don't want to interrupt any push that is in progress, hence we only queue
550  * work if we set the pushing bit approriately.
551  *
552  * We do this unlocked - we only need to know whether there is anything in the
553  * AIL at the time we are called. We don't need to access the contents of
554  * any of the objects, so the lock is not needed.
555  */
556 void
557 xfs_ail_push(
558         struct xfs_ail  *ailp,
559         xfs_lsn_t       threshold_lsn)
560 {
561         xfs_log_item_t  *lip;
562 
563         lip = xfs_ail_min(ailp);
564         if (!lip || XFS_FORCED_SHUTDOWN(ailp->xa_mount) ||
565             XFS_LSN_CMP(threshold_lsn, ailp->xa_target) <= 0)
566                 return;
567 
568         /*
569          * Ensure that the new target is noticed in push code before it clears
570          * the XFS_AIL_PUSHING_BIT.
571          */
572         smp_wmb();
573         xfs_trans_ail_copy_lsn(ailp, &ailp->xa_target, &threshold_lsn);
574         smp_wmb();
575 
576         wake_up_process(ailp->xa_task);
577 }
578 
579 /*
580  * Push out all items in the AIL immediately
581  */
582 void
583 xfs_ail_push_all(
584         struct xfs_ail  *ailp)
585 {
586         xfs_lsn_t       threshold_lsn = xfs_ail_max_lsn(ailp);
587 
588         if (threshold_lsn)
589                 xfs_ail_push(ailp, threshold_lsn);
590 }
591 
592 /*
593  * Push out all items in the AIL immediately and wait until the AIL is empty.
594  */
595 void
596 xfs_ail_push_all_sync(
597         struct xfs_ail  *ailp)
598 {
599         struct xfs_log_item     *lip;
600         DEFINE_WAIT(wait);
601 
602         spin_lock(&ailp->xa_lock);
603         while ((lip = xfs_ail_max(ailp)) != NULL) {
604                 prepare_to_wait(&ailp->xa_empty, &wait, TASK_UNINTERRUPTIBLE);
605                 ailp->xa_target = lip->li_lsn;
606                 wake_up_process(ailp->xa_task);
607                 spin_unlock(&ailp->xa_lock);
608                 schedule();
609                 spin_lock(&ailp->xa_lock);
610         }
611         spin_unlock(&ailp->xa_lock);
612 
613         finish_wait(&ailp->xa_empty, &wait);
614 }
615 
616 /*
617  * xfs_trans_ail_update - bulk AIL insertion operation.
618  *
619  * @xfs_trans_ail_update takes an array of log items that all need to be
620  * positioned at the same LSN in the AIL. If an item is not in the AIL, it will
621  * be added.  Otherwise, it will be repositioned  by removing it and re-adding
622  * it to the AIL. If we move the first item in the AIL, update the log tail to
623  * match the new minimum LSN in the AIL.
624  *
625  * This function takes the AIL lock once to execute the update operations on
626  * all the items in the array, and as such should not be called with the AIL
627  * lock held. As a result, once we have the AIL lock, we need to check each log
628  * item LSN to confirm it needs to be moved forward in the AIL.
629  *
630  * To optimise the insert operation, we delete all the items from the AIL in
631  * the first pass, moving them into a temporary list, then splice the temporary
632  * list into the correct position in the AIL. This avoids needing to do an
633  * insert operation on every item.
634  *
635  * This function must be called with the AIL lock held.  The lock is dropped
636  * before returning.
637  */
638 void
639 xfs_trans_ail_update_bulk(
640         struct xfs_ail          *ailp,
641         struct xfs_ail_cursor   *cur,
642         struct xfs_log_item     **log_items,
643         int                     nr_items,
644         xfs_lsn_t               lsn) __releases(ailp->xa_lock)
645 {
646         xfs_log_item_t          *mlip;
647         int                     mlip_changed = 0;
648         int                     i;
649         LIST_HEAD(tmp);
650 
651         ASSERT(nr_items > 0);           /* Not required, but true. */
652         mlip = xfs_ail_min(ailp);
653 
654         for (i = 0; i < nr_items; i++) {
655                 struct xfs_log_item *lip = log_items[i];
656                 if (lip->li_flags & XFS_LI_IN_AIL) {
657                         /* check if we really need to move the item */
658                         if (XFS_LSN_CMP(lsn, lip->li_lsn) <= 0)
659                                 continue;
660 
661                         trace_xfs_ail_move(lip, lip->li_lsn, lsn);
662                         xfs_ail_delete(ailp, lip);
663                         if (mlip == lip)
664                                 mlip_changed = 1;
665                 } else {
666                         lip->li_flags |= XFS_LI_IN_AIL;
667                         trace_xfs_ail_insert(lip, 0, lsn);
668                 }
669                 lip->li_lsn = lsn;
670                 list_add(&lip->li_ail, &tmp);
671         }
672 
673         if (!list_empty(&tmp))
674                 xfs_ail_splice(ailp, cur, &tmp, lsn);
675 
676         if (mlip_changed) {
677                 if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount))
678                         xlog_assign_tail_lsn_locked(ailp->xa_mount);
679                 spin_unlock(&ailp->xa_lock);
680 
681                 xfs_log_space_wake(ailp->xa_mount);
682         } else {
683                 spin_unlock(&ailp->xa_lock);
684         }
685 }
686 
687 /*
688  * xfs_trans_ail_delete_bulk - remove multiple log items from the AIL
689  *
690  * @xfs_trans_ail_delete_bulk takes an array of log items that all need to
691  * removed from the AIL. The caller is already holding the AIL lock, and done
692  * all the checks necessary to ensure the items passed in via @log_items are
693  * ready for deletion. This includes checking that the items are in the AIL.
694  *
695  * For each log item to be removed, unlink it  from the AIL, clear the IN_AIL
696  * flag from the item and reset the item's lsn to 0. If we remove the first
697  * item in the AIL, update the log tail to match the new minimum LSN in the
698  * AIL.
699  *
700  * This function will not drop the AIL lock until all items are removed from
701  * the AIL to minimise the amount of lock traffic on the AIL. This does not
702  * greatly increase the AIL hold time, but does significantly reduce the amount
703  * of traffic on the lock, especially during IO completion.
704  *
705  * This function must be called with the AIL lock held.  The lock is dropped
706  * before returning.
707  */
708 void
709 xfs_trans_ail_delete_bulk(
710         struct xfs_ail          *ailp,
711         struct xfs_log_item     **log_items,
712         int                     nr_items,
713         int                     shutdown_type) __releases(ailp->xa_lock)
714 {
715         xfs_log_item_t          *mlip;
716         int                     mlip_changed = 0;
717         int                     i;
718 
719         mlip = xfs_ail_min(ailp);
720 
721         for (i = 0; i < nr_items; i++) {
722                 struct xfs_log_item *lip = log_items[i];
723                 if (!(lip->li_flags & XFS_LI_IN_AIL)) {
724                         struct xfs_mount        *mp = ailp->xa_mount;
725 
726                         spin_unlock(&ailp->xa_lock);
727                         if (!XFS_FORCED_SHUTDOWN(mp)) {
728                                 xfs_alert_tag(mp, XFS_PTAG_AILDELETE,
729                 "%s: attempting to delete a log item that is not in the AIL",
730                                                 __func__);
731                                 xfs_force_shutdown(mp, shutdown_type);
732                         }
733                         return;
734                 }
735 
736                 trace_xfs_ail_delete(lip, mlip->li_lsn, lip->li_lsn);
737                 xfs_ail_delete(ailp, lip);
738                 lip->li_flags &= ~XFS_LI_IN_AIL;
739                 lip->li_lsn = 0;
740                 if (mlip == lip)
741                         mlip_changed = 1;
742         }
743 
744         if (mlip_changed) {
745                 if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount))
746                         xlog_assign_tail_lsn_locked(ailp->xa_mount);
747                 if (list_empty(&ailp->xa_ail))
748                         wake_up_all(&ailp->xa_empty);
749                 spin_unlock(&ailp->xa_lock);
750 
751                 xfs_log_space_wake(ailp->xa_mount);
752         } else {
753                 spin_unlock(&ailp->xa_lock);
754         }
755 }
756 
757 int
758 xfs_trans_ail_init(
759         xfs_mount_t     *mp)
760 {
761         struct xfs_ail  *ailp;
762 
763         ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
764         if (!ailp)
765                 return -ENOMEM;
766 
767         ailp->xa_mount = mp;
768         INIT_LIST_HEAD(&ailp->xa_ail);
769         INIT_LIST_HEAD(&ailp->xa_cursors);
770         spin_lock_init(&ailp->xa_lock);
771         INIT_LIST_HEAD(&ailp->xa_buf_list);
772         init_waitqueue_head(&ailp->xa_empty);
773 
774         ailp->xa_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
775                         ailp->xa_mount->m_fsname);
776         if (IS_ERR(ailp->xa_task))
777                 goto out_free_ailp;
778 
779         mp->m_ail = ailp;
780         return 0;
781 
782 out_free_ailp:
783         kmem_free(ailp);
784         return -ENOMEM;
785 }
786 
787 void
788 xfs_trans_ail_destroy(
789         xfs_mount_t     *mp)
790 {
791         struct xfs_ail  *ailp = mp->m_ail;
792 
793         kthread_stop(ailp->xa_task);
794         kmem_free(ailp);
795 }
796 

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