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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - fs/xfs/xfs_trans_ail.c
2 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
3 * Copyright (c) 2008 Dave Chinner
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.
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.
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
21 #include "xfs_types.h"
24 #include "xfs_trans.h"
27 #include "xfs_mount.h"
28 #include "xfs_trans_priv.h"
29 #include "xfs_error.h"
31 struct workqueue_struct
*xfs_ail_wq
; /* AIL workqueue */
35 * Check that the list is sorted as it should be.
42 xfs_log_item_t
*prev_lip
;
44 if (list_empty(&ailp
->xa_ail
))
48 * Check the next and previous entries are valid.
50 ASSERT((lip
->li_flags
& XFS_LI_IN_AIL
) != 0);
51 prev_lip
= list_entry(lip
->li_ail
.prev
, xfs_log_item_t
, li_ail
);
52 if (&prev_lip
->li_ail
!= &ailp
->xa_ail
)
53 ASSERT(XFS_LSN_CMP(prev_lip
->li_lsn
, lip
->li_lsn
) <= 0);
55 prev_lip
= list_entry(lip
->li_ail
.next
, xfs_log_item_t
, li_ail
);
56 if (&prev_lip
->li_ail
!= &ailp
->xa_ail
)
57 ASSERT(XFS_LSN_CMP(prev_lip
->li_lsn
, lip
->li_lsn
) >= 0);
60 #ifdef XFS_TRANS_DEBUG
62 * Walk the list checking lsn ordering, and that every entry has the
63 * XFS_LI_IN_AIL flag set. This is really expensive, so only do it
64 * when specifically debugging the transaction subsystem.
66 prev_lip
= list_entry(&ailp
->xa_ail
, xfs_log_item_t
, li_ail
);
67 list_for_each_entry(lip
, &ailp
->xa_ail
, li_ail
) {
68 if (&prev_lip
->li_ail
!= &ailp
->xa_ail
)
69 ASSERT(XFS_LSN_CMP(prev_lip
->li_lsn
, lip
->li_lsn
) <= 0);
70 ASSERT((lip
->li_flags
& XFS_LI_IN_AIL
) != 0);
73 #endif /* XFS_TRANS_DEBUG */
76 #define xfs_ail_check(a,l)
80 * Return a pointer to the first item in the AIL. If the AIL is empty, then
83 static xfs_log_item_t
*
87 if (list_empty(&ailp
->xa_ail
))
90 return list_first_entry(&ailp
->xa_ail
, xfs_log_item_t
, li_ail
);
94 * Return a pointer to the last item in the AIL. If the AIL is empty, then
97 static xfs_log_item_t
*
101 if (list_empty(&ailp
->xa_ail
))
104 return list_entry(ailp
->xa_ail
.prev
, xfs_log_item_t
, li_ail
);
108 * Return a pointer to the item which follows the given item in the AIL. If
109 * the given item is the last item in the list, then return NULL.
111 static xfs_log_item_t
*
113 struct xfs_ail
*ailp
,
116 if (lip
->li_ail
.next
== &ailp
->xa_ail
)
119 return list_first_entry(&lip
->li_ail
, xfs_log_item_t
, li_ail
);
123 * This is called by the log manager code to determine the LSN of the tail of
124 * the log. This is exactly the LSN of the first item in the AIL. If the AIL
125 * is empty, then this function returns 0.
127 * We need the AIL lock in order to get a coherent read of the lsn of the last
132 struct xfs_ail
*ailp
)
137 spin_lock(&ailp
->xa_lock
);
138 lip
= xfs_ail_min(ailp
);
141 spin_unlock(&ailp
->xa_lock
);
147 * Return the maximum lsn held in the AIL, or zero if the AIL is empty.
151 struct xfs_ail
*ailp
)
156 spin_lock(&ailp
->xa_lock
);
157 lip
= xfs_ail_max(ailp
);
160 spin_unlock(&ailp
->xa_lock
);
166 * The cursor keeps track of where our current traversal is up to by tracking
167 * the next item in the list for us. However, for this to be safe, removing an
168 * object from the AIL needs to invalidate any cursor that points to it. hence
169 * the traversal cursor needs to be linked to the struct xfs_ail so that
170 * deletion can search all the active cursors for invalidation.
173 xfs_trans_ail_cursor_init(
174 struct xfs_ail
*ailp
,
175 struct xfs_ail_cursor
*cur
)
178 list_add_tail(&cur
->list
, &ailp
->xa_cursors
);
182 * Get the next item in the traversal and advance the cursor. If the cursor
183 * was invalidated (indicated by a lip of 1), restart the traversal.
185 struct xfs_log_item
*
186 xfs_trans_ail_cursor_next(
187 struct xfs_ail
*ailp
,
188 struct xfs_ail_cursor
*cur
)
190 struct xfs_log_item
*lip
= cur
->item
;
192 if ((__psint_t
)lip
& 1)
193 lip
= xfs_ail_min(ailp
);
195 cur
->item
= xfs_ail_next(ailp
, lip
);
200 * When the traversal is complete, we need to remove the cursor from the list
201 * of traversing cursors.
204 xfs_trans_ail_cursor_done(
205 struct xfs_ail
*ailp
,
206 struct xfs_ail_cursor
*cur
)
209 list_del_init(&cur
->list
);
213 * Invalidate any cursor that is pointing to this item. This is called when an
214 * item is removed from the AIL. Any cursor pointing to this object is now
215 * invalid and the traversal needs to be terminated so it doesn't reference a
216 * freed object. We set the low bit of the cursor item pointer so we can
217 * distinguish between an invalidation and the end of the list when getting the
218 * next item from the cursor.
221 xfs_trans_ail_cursor_clear(
222 struct xfs_ail
*ailp
,
223 struct xfs_log_item
*lip
)
225 struct xfs_ail_cursor
*cur
;
227 list_for_each_entry(cur
, &ailp
->xa_cursors
, list
) {
228 if (cur
->item
== lip
)
229 cur
->item
= (struct xfs_log_item
*)
230 ((__psint_t
)cur
->item
| 1);
235 * Find the first item in the AIL with the given @lsn by searching in ascending
236 * LSN order and initialise the cursor to point to the next item for a
237 * ascending traversal. Pass a @lsn of zero to initialise the cursor to the
238 * first item in the AIL. Returns NULL if the list is empty.
241 xfs_trans_ail_cursor_first(
242 struct xfs_ail
*ailp
,
243 struct xfs_ail_cursor
*cur
,
248 xfs_trans_ail_cursor_init(ailp
, cur
);
251 lip
= xfs_ail_min(ailp
);
255 list_for_each_entry(lip
, &ailp
->xa_ail
, li_ail
) {
256 if (XFS_LSN_CMP(lip
->li_lsn
, lsn
) >= 0)
263 cur
->item
= xfs_ail_next(ailp
, lip
);
267 static struct xfs_log_item
*
268 __xfs_trans_ail_cursor_last(
269 struct xfs_ail
*ailp
,
274 list_for_each_entry_reverse(lip
, &ailp
->xa_ail
, li_ail
) {
275 if (XFS_LSN_CMP(lip
->li_lsn
, lsn
) <= 0)
282 * Find the last item in the AIL with the given @lsn by searching in descending
283 * LSN order and initialise the cursor to point to that item. If there is no
284 * item with the value of @lsn, then it sets the cursor to the last item with an
285 * LSN lower than @lsn. Returns NULL if the list is empty.
287 struct xfs_log_item
*
288 xfs_trans_ail_cursor_last(
289 struct xfs_ail
*ailp
,
290 struct xfs_ail_cursor
*cur
,
293 xfs_trans_ail_cursor_init(ailp
, cur
);
294 cur
->item
= __xfs_trans_ail_cursor_last(ailp
, lsn
);
299 * Splice the log item list into the AIL at the given LSN. We splice to the
300 * tail of the given LSN to maintain insert order for push traversals. The
301 * cursor is optional, allowing repeated updates to the same LSN to avoid
302 * repeated traversals.
306 struct xfs_ail
*ailp
,
307 struct xfs_ail_cursor
*cur
,
308 struct list_head
*list
,
311 struct xfs_log_item
*lip
= cur
? cur
->item
: NULL
;
312 struct xfs_log_item
*next_lip
;
315 * Get a new cursor if we don't have a placeholder or the existing one
316 * has been invalidated.
318 if (!lip
|| (__psint_t
)lip
& 1) {
319 lip
= __xfs_trans_ail_cursor_last(ailp
, lsn
);
322 /* The list is empty, so just splice and return. */
325 list_splice(list
, &ailp
->xa_ail
);
331 * Our cursor points to the item we want to insert _after_, so we have
332 * to update the cursor to point to the end of the list we are splicing
333 * in so that it points to the correct location for the next splice.
334 * i.e. before the splice
336 * lsn -> lsn -> lsn + x -> lsn + x ...
338 * | cursor points here
340 * After the splice we have:
342 * lsn -> lsn -> lsn -> lsn -> .... -> lsn -> lsn + x -> lsn + x ...
344 * | cursor points here | needs to move here
346 * So we set the cursor to the last item in the list to be spliced
347 * before we execute the splice, resulting in the cursor pointing to
348 * the correct item after the splice occurs.
351 next_lip
= list_entry(list
->prev
, struct xfs_log_item
, li_ail
);
352 cur
->item
= next_lip
;
354 list_splice(list
, &lip
->li_ail
);
358 * Delete the given item from the AIL. Return a pointer to the item.
362 struct xfs_ail
*ailp
,
365 xfs_ail_check(ailp
, lip
);
366 list_del(&lip
->li_ail
);
367 xfs_trans_ail_cursor_clear(ailp
, lip
);
371 * xfs_ail_worker does the work of pushing on the AIL. It will requeue itself
372 * to run at a later time if there is more work to do to complete the push.
376 struct work_struct
*work
)
378 struct xfs_ail
*ailp
= container_of(to_delayed_work(work
),
379 struct xfs_ail
, xa_work
);
380 xfs_mount_t
*mp
= ailp
->xa_mount
;
381 struct xfs_ail_cursor cur
;
389 int push_xfsbufd
= 0;
391 spin_lock(&ailp
->xa_lock
);
392 target
= ailp
->xa_target
;
393 lip
= xfs_trans_ail_cursor_first(ailp
, &cur
, ailp
->xa_last_pushed_lsn
);
394 if (!lip
|| XFS_FORCED_SHUTDOWN(mp
)) {
396 * AIL is empty or our push has reached the end.
398 xfs_trans_ail_cursor_done(ailp
, &cur
);
399 spin_unlock(&ailp
->xa_lock
);
403 XFS_STATS_INC(xs_push_ail
);
406 * While the item we are looking at is below the given threshold
407 * try to flush it out. We'd like not to stop until we've at least
408 * tried to push on everything in the AIL with an LSN less than
409 * the given threshold.
411 * However, we will stop after a certain number of pushes and wait
412 * for a reduced timeout to fire before pushing further. This
413 * prevents use from spinning when we can't do anything or there is
414 * lots of contention on the AIL lists.
417 while ((XFS_LSN_CMP(lip
->li_lsn
, target
) <= 0)) {
420 * If we can lock the item without sleeping, unlock the AIL
421 * lock and flush the item. Then re-grab the AIL lock so we
422 * can look for the next item on the AIL. List changes are
423 * handled by the AIL lookup functions internally
425 * If we can't lock the item, either its holder will flush it
426 * or it is already being flushed or it is being relogged. In
427 * any of these case it is being taken care of and we can just
428 * skip to the next item in the list.
430 lock_result
= IOP_TRYLOCK(lip
);
431 spin_unlock(&ailp
->xa_lock
);
432 switch (lock_result
) {
433 case XFS_ITEM_SUCCESS
:
434 XFS_STATS_INC(xs_push_ail_success
);
436 ailp
->xa_last_pushed_lsn
= lsn
;
439 case XFS_ITEM_PUSHBUF
:
440 XFS_STATS_INC(xs_push_ail_pushbuf
);
442 ailp
->xa_last_pushed_lsn
= lsn
;
446 case XFS_ITEM_PINNED
:
447 XFS_STATS_INC(xs_push_ail_pinned
);
452 case XFS_ITEM_LOCKED
:
453 XFS_STATS_INC(xs_push_ail_locked
);
454 ailp
->xa_last_pushed_lsn
= lsn
;
463 spin_lock(&ailp
->xa_lock
);
464 /* should we bother continuing? */
465 if (XFS_FORCED_SHUTDOWN(mp
))
472 * Are there too many items we can't do anything with?
473 * If we we are skipping too many items because we can't flush
474 * them or they are already being flushed, we back off and
475 * given them time to complete whatever operation is being
476 * done. i.e. remove pressure from the AIL while we can't make
477 * progress so traversals don't slow down further inserts and
478 * removals to/from the AIL.
480 * The value of 100 is an arbitrary magic number based on
486 lip
= xfs_trans_ail_cursor_next(ailp
, &cur
);
491 xfs_trans_ail_cursor_done(ailp
, &cur
);
492 spin_unlock(&ailp
->xa_lock
);
496 * If something we need to push out was pinned, then
497 * push out the log so it will become unpinned and
498 * move forward in the AIL.
500 XFS_STATS_INC(xs_push_ail_flush
);
501 xfs_log_force(mp
, 0);
505 /* we've got delayed write buffers to flush */
506 wake_up_process(mp
->m_ddev_targp
->bt_task
);
509 /* assume we have more work to do in a short while */
512 /* We're past our target or empty, so idle */
513 ailp
->xa_last_pushed_lsn
= 0;
516 * We clear the XFS_AIL_PUSHING_BIT first before checking
517 * whether the target has changed. If the target has changed,
518 * this pushes the requeue race directly onto the result of the
519 * atomic test/set bit, so we are guaranteed that either the
520 * the pusher that changed the target or ourselves will requeue
521 * the work (but not both).
523 clear_bit(XFS_AIL_PUSHING_BIT
, &ailp
->xa_flags
);
525 if (XFS_LSN_CMP(ailp
->xa_target
, target
) == 0 ||
526 test_and_set_bit(XFS_AIL_PUSHING_BIT
, &ailp
->xa_flags
))
530 } else if (XFS_LSN_CMP(lsn
, target
) >= 0) {
532 * We reached the target so wait a bit longer for I/O to
533 * complete and remove pushed items from the AIL before we
534 * start the next scan from the start of the AIL.
537 ailp
->xa_last_pushed_lsn
= 0;
538 } else if ((stuck
* 100) / count
> 90) {
540 * Either there is a lot of contention on the AIL or we
541 * are stuck due to operations in progress. "Stuck" in this
542 * case is defined as >90% of the items we tried to push
545 * Backoff a bit more to allow some I/O to complete before
546 * continuing from where we were.
551 /* There is more to do, requeue us. */
552 queue_delayed_work(xfs_syncd_wq
, &ailp
->xa_work
,
553 msecs_to_jiffies(tout
));
557 * This routine is called to move the tail of the AIL forward. It does this by
558 * trying to flush items in the AIL whose lsns are below the given
561 * The push is run asynchronously in a workqueue, which means the caller needs
562 * to handle waiting on the async flush for space to become available.
563 * We don't want to interrupt any push that is in progress, hence we only queue
564 * work if we set the pushing bit approriately.
566 * We do this unlocked - we only need to know whether there is anything in the
567 * AIL at the time we are called. We don't need to access the contents of
568 * any of the objects, so the lock is not needed.
572 struct xfs_ail
*ailp
,
573 xfs_lsn_t threshold_lsn
)
577 lip
= xfs_ail_min(ailp
);
578 if (!lip
|| XFS_FORCED_SHUTDOWN(ailp
->xa_mount
) ||
579 XFS_LSN_CMP(threshold_lsn
, ailp
->xa_target
) <= 0)
583 * Ensure that the new target is noticed in push code before it clears
584 * the XFS_AIL_PUSHING_BIT.
587 xfs_trans_ail_copy_lsn(ailp
, &ailp
->xa_target
, &threshold_lsn
);
588 if (!test_and_set_bit(XFS_AIL_PUSHING_BIT
, &ailp
->xa_flags
))
589 queue_delayed_work(xfs_syncd_wq
, &ailp
->xa_work
, 0);
593 * Push out all items in the AIL immediately
597 struct xfs_ail
*ailp
)
599 xfs_lsn_t threshold_lsn
= xfs_ail_max_lsn(ailp
);
602 xfs_ail_push(ailp
, threshold_lsn
);
606 * This is to be called when an item is unlocked that may have
607 * been in the AIL. It will wake up the first member of the AIL
608 * wait list if this item's unlocking might allow it to progress.
609 * If the item is in the AIL, then we need to get the AIL lock
610 * while doing our checking so we don't race with someone going
611 * to sleep waiting for this event in xfs_trans_push_ail().
614 xfs_trans_unlocked_item(
615 struct xfs_ail
*ailp
,
618 xfs_log_item_t
*min_lip
;
621 * If we're forcibly shutting down, we may have
622 * unlocked log items arbitrarily. The last thing
623 * we want to do is to move the tail of the log
624 * over some potentially valid data.
626 if (!(lip
->li_flags
& XFS_LI_IN_AIL
) ||
627 XFS_FORCED_SHUTDOWN(ailp
->xa_mount
)) {
632 * This is the one case where we can call into xfs_ail_min()
633 * without holding the AIL lock because we only care about the
634 * case where we are at the tail of the AIL. If the object isn't
635 * at the tail, it doesn't matter what result we get back. This
636 * is slightly racy because since we were just unlocked, we could
637 * go to sleep between the call to xfs_ail_min and the call to
638 * xfs_log_move_tail, have someone else lock us, commit to us disk,
639 * move us out of the tail of the AIL, and then we wake up. However,
640 * the call to xfs_log_move_tail() doesn't do anything if there's
641 * not enough free space to wake people up so we're safe calling it.
643 min_lip
= xfs_ail_min(ailp
);
646 xfs_log_move_tail(ailp
->xa_mount
, 1);
647 } /* xfs_trans_unlocked_item */
650 * xfs_trans_ail_update - bulk AIL insertion operation.
652 * @xfs_trans_ail_update takes an array of log items that all need to be
653 * positioned at the same LSN in the AIL. If an item is not in the AIL, it will
654 * be added. Otherwise, it will be repositioned by removing it and re-adding
655 * it to the AIL. If we move the first item in the AIL, update the log tail to
656 * match the new minimum LSN in the AIL.
658 * This function takes the AIL lock once to execute the update operations on
659 * all the items in the array, and as such should not be called with the AIL
660 * lock held. As a result, once we have the AIL lock, we need to check each log
661 * item LSN to confirm it needs to be moved forward in the AIL.
663 * To optimise the insert operation, we delete all the items from the AIL in
664 * the first pass, moving them into a temporary list, then splice the temporary
665 * list into the correct position in the AIL. This avoids needing to do an
666 * insert operation on every item.
668 * This function must be called with the AIL lock held. The lock is dropped
672 xfs_trans_ail_update_bulk(
673 struct xfs_ail
*ailp
,
674 struct xfs_ail_cursor
*cur
,
675 struct xfs_log_item
**log_items
,
677 xfs_lsn_t lsn
) __releases(ailp
->xa_lock
)
679 xfs_log_item_t
*mlip
;
681 int mlip_changed
= 0;
685 mlip
= xfs_ail_min(ailp
);
687 for (i
= 0; i
< nr_items
; i
++) {
688 struct xfs_log_item
*lip
= log_items
[i
];
689 if (lip
->li_flags
& XFS_LI_IN_AIL
) {
690 /* check if we really need to move the item */
691 if (XFS_LSN_CMP(lsn
, lip
->li_lsn
) <= 0)
694 xfs_ail_delete(ailp
, lip
);
698 lip
->li_flags
|= XFS_LI_IN_AIL
;
701 list_add(&lip
->li_ail
, &tmp
);
704 xfs_ail_splice(ailp
, cur
, &tmp
, lsn
);
707 spin_unlock(&ailp
->xa_lock
);
712 * It is not safe to access mlip after the AIL lock is dropped, so we
713 * must get a copy of li_lsn before we do so. This is especially
714 * important on 32-bit platforms where accessing and updating 64-bit
715 * values like li_lsn is not atomic.
717 mlip
= xfs_ail_min(ailp
);
718 tail_lsn
= mlip
->li_lsn
;
719 spin_unlock(&ailp
->xa_lock
);
720 xfs_log_move_tail(ailp
->xa_mount
, tail_lsn
);
724 * xfs_trans_ail_delete_bulk - remove multiple log items from the AIL
726 * @xfs_trans_ail_delete_bulk takes an array of log items that all need to
727 * removed from the AIL. The caller is already holding the AIL lock, and done
728 * all the checks necessary to ensure the items passed in via @log_items are
729 * ready for deletion. This includes checking that the items are in the AIL.
731 * For each log item to be removed, unlink it from the AIL, clear the IN_AIL
732 * flag from the item and reset the item's lsn to 0. If we remove the first
733 * item in the AIL, update the log tail to match the new minimum LSN in the
736 * This function will not drop the AIL lock until all items are removed from
737 * the AIL to minimise the amount of lock traffic on the AIL. This does not
738 * greatly increase the AIL hold time, but does significantly reduce the amount
739 * of traffic on the lock, especially during IO completion.
741 * This function must be called with the AIL lock held. The lock is dropped
745 xfs_trans_ail_delete_bulk(
746 struct xfs_ail
*ailp
,
747 struct xfs_log_item
**log_items
,
748 int nr_items
) __releases(ailp
->xa_lock
)
750 xfs_log_item_t
*mlip
;
752 int mlip_changed
= 0;
755 mlip
= xfs_ail_min(ailp
);
757 for (i
= 0; i
< nr_items
; i
++) {
758 struct xfs_log_item
*lip
= log_items
[i
];
759 if (!(lip
->li_flags
& XFS_LI_IN_AIL
)) {
760 struct xfs_mount
*mp
= ailp
->xa_mount
;
762 spin_unlock(&ailp
->xa_lock
);
763 if (!XFS_FORCED_SHUTDOWN(mp
)) {
764 xfs_alert_tag(mp
, XFS_PTAG_AILDELETE
,
765 "%s: attempting to delete a log item that is not in the AIL",
767 xfs_force_shutdown(mp
, SHUTDOWN_CORRUPT_INCORE
);
772 xfs_ail_delete(ailp
, lip
);
773 lip
->li_flags
&= ~XFS_LI_IN_AIL
;
780 spin_unlock(&ailp
->xa_lock
);
785 * It is not safe to access mlip after the AIL lock is dropped, so we
786 * must get a copy of li_lsn before we do so. This is especially
787 * important on 32-bit platforms where accessing and updating 64-bit
788 * values like li_lsn is not atomic. It is possible we've emptied the
789 * AIL here, so if that is the case, pass an LSN of 0 to the tail move.
791 mlip
= xfs_ail_min(ailp
);
792 tail_lsn
= mlip
? mlip
->li_lsn
: 0;
793 spin_unlock(&ailp
->xa_lock
);
794 xfs_log_move_tail(ailp
->xa_mount
, tail_lsn
);
798 * The active item list (AIL) is a doubly linked list of log
799 * items sorted by ascending lsn. The base of the list is
800 * a forw/back pointer pair embedded in the xfs mount structure.
801 * The base is initialized with both pointers pointing to the
802 * base. This case always needs to be distinguished, because
803 * the base has no lsn to look at. We almost always insert
804 * at the end of the list, so on inserts we search from the
805 * end of the list to find where the new item belongs.
809 * Initialize the doubly linked list to point only to itself.
815 struct xfs_ail
*ailp
;
817 ailp
= kmem_zalloc(sizeof(struct xfs_ail
), KM_MAYFAIL
);
822 INIT_LIST_HEAD(&ailp
->xa_ail
);
823 INIT_LIST_HEAD(&ailp
->xa_cursors
);
824 spin_lock_init(&ailp
->xa_lock
);
825 INIT_DELAYED_WORK(&ailp
->xa_work
, xfs_ail_worker
);
831 xfs_trans_ail_destroy(
834 struct xfs_ail
*ailp
= mp
->m_ail
;
836 cancel_delayed_work_sync(&ailp
->xa_work
);