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

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