2 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License as
7 * published by the Free Software Foundation.
9 * This program is distributed in the hope that it would be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 #include "xfs_types.h"
23 #include "xfs_trans.h"
26 #include "xfs_dmapi.h"
27 #include "xfs_mount.h"
28 #include "xfs_trans_priv.h"
29 #include "xfs_error.h"
31 STATIC void xfs_ail_insert(struct xfs_ail *, xfs_log_item_t *);
32 STATIC xfs_log_item_t * xfs_ail_delete(struct xfs_ail *, xfs_log_item_t *);
33 STATIC xfs_log_item_t * xfs_ail_min(struct xfs_ail *);
34 STATIC xfs_log_item_t * xfs_ail_next(struct xfs_ail *, xfs_log_item_t *);
37 STATIC void xfs_ail_check(struct xfs_ail *, xfs_log_item_t *);
39 #define xfs_ail_check(a,l)
44 * This is called by the log manager code to determine the LSN
45 * of the tail of the log. This is exactly the LSN of the first
46 * item in the AIL. If the AIL is empty, then this function
49 * We need the AIL lock in order to get a coherent read of the
50 * lsn of the last item in the AIL.
59 spin_lock(&mp->m_ail_lock);
60 lip = xfs_ail_min(mp->m_ail);
66 spin_unlock(&mp->m_ail_lock);
74 * This routine is called to move the tail of the AIL forward. It does this by
75 * trying to flush items in the AIL whose lsns are below the given
78 * the push is run asynchronously in a separate thread, so we return the tail
79 * of the log right now instead of the tail after the push. This means we will
80 * either continue right away, or we will sleep waiting on the async thread to
83 * We do this unlocked - we only need to know whether there is anything in the
84 * AIL at the time we are called. We don't need to access the contents of
85 * any of the objects, so the lock is not needed.
90 xfs_lsn_t threshold_lsn)
94 lip = xfs_ail_min(mp->m_ail);
95 if (lip && !XFS_FORCED_SHUTDOWN(mp)) {
96 if (XFS_LSN_CMP(threshold_lsn, mp->m_ail->xa_target) > 0)
97 xfsaild_wakeup(mp->m_ail, threshold_lsn);
102 * Return the item in the AIL with the current lsn.
103 * Return the current tree generation number for use
104 * in calls to xfs_trans_next_ail().
106 STATIC xfs_log_item_t *
107 xfs_trans_first_push_ail(
114 lip = xfs_ail_min(mp->m_ail);
115 *gen = (int)mp->m_ail->xa_gen;
119 list_for_each_entry(lip, &mp->m_ail->xa_ail, li_ail) {
120 if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
128 * Function that does the work of pushing on the AIL
132 struct xfs_ail *ailp,
135 long tout = 1000; /* milliseconds */
136 xfs_lsn_t last_pushed_lsn = *last_lsn;
137 xfs_lsn_t target = ailp->xa_target;
142 int flush_log, count, stuck;
143 xfs_mount_t *mp = ailp->xa_mount;
145 #define XFS_TRANS_PUSH_AIL_RESTARTS 10
147 spin_lock(&mp->m_ail_lock);
148 lip = xfs_trans_first_push_ail(mp, &gen, *last_lsn);
149 if (!lip || XFS_FORCED_SHUTDOWN(mp)) {
151 * AIL is empty or our push has reached the end.
153 spin_unlock(&mp->m_ail_lock);
158 XFS_STATS_INC(xs_push_ail);
161 * While the item we are looking at is below the given threshold
162 * try to flush it out. We'd like not to stop until we've at least
163 * tried to push on everything in the AIL with an LSN less than
164 * the given threshold.
166 * However, we will stop after a certain number of pushes and wait
167 * for a reduced timeout to fire before pushing further. This
168 * prevents use from spinning when we can't do anything or there is
169 * lots of contention on the AIL lists.
173 flush_log = stuck = count = restarts = 0;
174 while ((XFS_LSN_CMP(lip->li_lsn, target) < 0)) {
177 * If we can lock the item without sleeping, unlock the AIL
178 * lock and flush the item. Then re-grab the AIL lock so we
179 * can look for the next item on the AIL. List changes are
180 * handled by the AIL lookup functions internally
182 * If we can't lock the item, either its holder will flush it
183 * or it is already being flushed or it is being relogged. In
184 * any of these case it is being taken care of and we can just
185 * skip to the next item in the list.
187 lock_result = IOP_TRYLOCK(lip);
188 spin_unlock(&mp->m_ail_lock);
189 switch (lock_result) {
190 case XFS_ITEM_SUCCESS:
191 XFS_STATS_INC(xs_push_ail_success);
193 last_pushed_lsn = lsn;
196 case XFS_ITEM_PUSHBUF:
197 XFS_STATS_INC(xs_push_ail_pushbuf);
199 last_pushed_lsn = lsn;
202 case XFS_ITEM_PINNED:
203 XFS_STATS_INC(xs_push_ail_pinned);
208 case XFS_ITEM_LOCKED:
209 XFS_STATS_INC(xs_push_ail_locked);
210 last_pushed_lsn = lsn;
214 case XFS_ITEM_FLUSHING:
215 XFS_STATS_INC(xs_push_ail_flushing);
216 last_pushed_lsn = lsn;
225 spin_lock(&mp->m_ail_lock);
226 /* should we bother continuing? */
227 if (XFS_FORCED_SHUTDOWN(mp))
234 * Are there too many items we can't do anything with?
235 * If we we are skipping too many items because we can't flush
236 * them or they are already being flushed, we back off and
237 * given them time to complete whatever operation is being
238 * done. i.e. remove pressure from the AIL while we can't make
239 * progress so traversals don't slow down further inserts and
240 * removals to/from the AIL.
242 * The value of 100 is an arbitrary magic number based on
248 lip = xfs_trans_next_ail(mp, lip, &gen, &restarts);
251 if (restarts > XFS_TRANS_PUSH_AIL_RESTARTS)
255 spin_unlock(&mp->m_ail_lock);
259 * If something we need to push out was pinned, then
260 * push out the log so it will become unpinned and
261 * move forward in the AIL.
263 XFS_STATS_INC(xs_push_ail_flush);
264 xfs_log_force(mp, (xfs_lsn_t)0, XFS_LOG_FORCE);
268 /* We're past our target or empty, so idle */
270 } else if (XFS_LSN_CMP(lsn, target) >= 0) {
272 * We reached the target so wait a bit longer for I/O to
273 * complete and remove pushed items from the AIL before we
274 * start the next scan from the start of the AIL.
278 } else if ((restarts > XFS_TRANS_PUSH_AIL_RESTARTS) ||
279 ((stuck * 100) / count > 90)) {
281 * Either there is a lot of contention on the AIL or we
282 * are stuck due to operations in progress. "Stuck" in this
283 * case is defined as >90% of the items we tried to push
286 * Backoff a bit more to allow some I/O to complete before
287 * continuing from where we were.
292 *last_lsn = last_pushed_lsn;
298 * This is to be called when an item is unlocked that may have
299 * been in the AIL. It will wake up the first member of the AIL
300 * wait list if this item's unlocking might allow it to progress.
301 * If the item is in the AIL, then we need to get the AIL lock
302 * while doing our checking so we don't race with someone going
303 * to sleep waiting for this event in xfs_trans_push_ail().
306 xfs_trans_unlocked_item(
310 xfs_log_item_t *min_lip;
313 * If we're forcibly shutting down, we may have
314 * unlocked log items arbitrarily. The last thing
315 * we want to do is to move the tail of the log
316 * over some potentially valid data.
318 if (!(lip->li_flags & XFS_LI_IN_AIL) ||
319 XFS_FORCED_SHUTDOWN(mp)) {
324 * This is the one case where we can call into xfs_ail_min()
325 * without holding the AIL lock because we only care about the
326 * case where we are at the tail of the AIL. If the object isn't
327 * at the tail, it doesn't matter what result we get back. This
328 * is slightly racy because since we were just unlocked, we could
329 * go to sleep between the call to xfs_ail_min and the call to
330 * xfs_log_move_tail, have someone else lock us, commit to us disk,
331 * move us out of the tail of the AIL, and then we wake up. However,
332 * the call to xfs_log_move_tail() doesn't do anything if there's
333 * not enough free space to wake people up so we're safe calling it.
335 min_lip = xfs_ail_min(mp->m_ail);
338 xfs_log_move_tail(mp, 1);
339 } /* xfs_trans_unlocked_item */
343 * Update the position of the item in the AIL with the new
344 * lsn. If it is not yet in the AIL, add it. Otherwise, move
345 * it to its new position by removing it and re-adding it.
347 * Wakeup anyone with an lsn less than the item's lsn. If the item
348 * we move in the AIL is the minimum one, update the tail lsn in the
351 * Increment the AIL's generation count to indicate that the tree
354 * This function must be called with the AIL lock held. The lock
355 * is dropped before returning.
358 xfs_trans_update_ail(
361 xfs_lsn_t lsn) __releases(mp->m_ail_lock)
363 xfs_log_item_t *dlip=NULL;
364 xfs_log_item_t *mlip; /* ptr to minimum lip */
366 mlip = xfs_ail_min(mp->m_ail);
368 if (lip->li_flags & XFS_LI_IN_AIL) {
369 dlip = xfs_ail_delete(mp->m_ail, lip);
372 lip->li_flags |= XFS_LI_IN_AIL;
377 xfs_ail_insert(mp->m_ail, lip);
381 mlip = xfs_ail_min(mp->m_ail);
382 spin_unlock(&mp->m_ail_lock);
383 xfs_log_move_tail(mp, mlip->li_lsn);
385 spin_unlock(&mp->m_ail_lock);
389 } /* xfs_trans_update_ail */
392 * Delete the given item from the AIL. It must already be in
395 * Wakeup anyone with an lsn less than item's lsn. If the item
396 * we delete in the AIL is the minimum one, update the tail lsn in the
399 * Clear the IN_AIL flag from the item, reset its lsn to 0, and
400 * bump the AIL's generation count to indicate that the tree
403 * This function must be called with the AIL lock held. The lock
404 * is dropped before returning.
407 xfs_trans_delete_ail(
409 xfs_log_item_t *lip) __releases(mp->m_ail_lock)
411 xfs_log_item_t *dlip;
412 xfs_log_item_t *mlip;
414 if (lip->li_flags & XFS_LI_IN_AIL) {
415 mlip = xfs_ail_min(mp->m_ail);
416 dlip = xfs_ail_delete(mp->m_ail, lip);
420 lip->li_flags &= ~XFS_LI_IN_AIL;
425 mlip = xfs_ail_min(mp->m_ail);
426 spin_unlock(&mp->m_ail_lock);
427 xfs_log_move_tail(mp, (mlip ? mlip->li_lsn : 0));
429 spin_unlock(&mp->m_ail_lock);
434 * If the file system is not being shutdown, we are in
435 * serious trouble if we get to this stage.
437 if (XFS_FORCED_SHUTDOWN(mp))
438 spin_unlock(&mp->m_ail_lock);
440 xfs_cmn_err(XFS_PTAG_AILDELETE, CE_ALERT, mp,
441 "%s: attempting to delete a log item that is not in the AIL",
443 spin_unlock(&mp->m_ail_lock);
444 xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
452 * Return the item in the AIL with the smallest lsn.
453 * Return the current tree generation number for use
454 * in calls to xfs_trans_next_ail().
463 lip = xfs_ail_min(mp->m_ail);
464 *gen = (int)mp->m_ail->xa_gen;
470 * If the generation count of the tree has not changed since the
471 * caller last took something from the AIL, then return the elmt
472 * in the tree which follows the one given. If the count has changed,
473 * then return the minimum elmt of the AIL and bump the restarts counter
483 xfs_log_item_t *nlip;
485 ASSERT(mp && lip && gen);
486 if (mp->m_ail->xa_gen == *gen) {
487 nlip = xfs_ail_next(mp->m_ail, lip);
489 nlip = xfs_ail_min(mp->m_ail);
490 *gen = (int)mp->m_ail->xa_gen;
491 if (restarts != NULL) {
492 XFS_STATS_INC(xs_push_ail_restarts);
502 * The active item list (AIL) is a doubly linked list of log
503 * items sorted by ascending lsn. The base of the list is
504 * a forw/back pointer pair embedded in the xfs mount structure.
505 * The base is initialized with both pointers pointing to the
506 * base. This case always needs to be distinguished, because
507 * the base has no lsn to look at. We almost always insert
508 * at the end of the list, so on inserts we search from the
509 * end of the list to find where the new item belongs.
513 * Initialize the doubly linked list to point only to itself.
519 struct xfs_ail *ailp;
521 ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
526 INIT_LIST_HEAD(&ailp->xa_ail);
527 return xfsaild_start(ailp);
531 xfs_trans_ail_destroy(
534 struct xfs_ail *ailp = mp->m_ail;
541 * Insert the given log item into the AIL.
542 * We almost always insert at the end of the list, so on inserts
543 * we search from the end of the list to find where the
548 struct xfs_ail *ailp,
552 xfs_log_item_t *next_lip;
555 * If the list is empty, just insert the item.
557 if (list_empty(&ailp->xa_ail)) {
558 list_add(&lip->li_ail, &ailp->xa_ail);
562 list_for_each_entry_reverse(next_lip, &ailp->xa_ail, li_ail) {
563 if (XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) <= 0)
567 ASSERT((&next_lip->li_ail == &ailp->xa_ail) ||
568 (XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) <= 0));
570 list_add(&lip->li_ail, &next_lip->li_ail);
572 xfs_ail_check(ailp, lip);
577 * Delete the given item from the AIL. Return a pointer to the item.
580 STATIC xfs_log_item_t *
582 struct xfs_ail *ailp,
586 xfs_ail_check(ailp, lip);
588 list_del(&lip->li_ail);
594 * Return a pointer to the first item in the AIL.
595 * If the AIL is empty, then return NULL.
597 STATIC xfs_log_item_t *
599 struct xfs_ail *ailp)
602 if (list_empty(&ailp->xa_ail))
605 return list_first_entry(&ailp->xa_ail, xfs_log_item_t, li_ail);
609 * Return a pointer to the item which follows
610 * the given item in the AIL. If the given item
611 * is the last item in the list, then return NULL.
613 STATIC xfs_log_item_t *
615 struct xfs_ail *ailp,
619 if (lip->li_ail.next == &ailp->xa_ail)
622 return list_first_entry(&lip->li_ail, xfs_log_item_t, li_ail);
627 * Check that the list is sorted as it should be.
631 struct xfs_ail *ailp,
634 xfs_log_item_t *prev_lip;
636 if (list_empty(&ailp->xa_ail))
640 * Check the next and previous entries are valid.
642 ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
643 prev_lip = list_entry(lip->li_ail.prev, xfs_log_item_t, li_ail);
644 if (&prev_lip->li_ail != &ailp->xa_ail)
645 ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
647 prev_lip = list_entry(lip->li_ail.next, xfs_log_item_t, li_ail);
648 if (&prev_lip->li_ail != &ailp->xa_ail)
649 ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) >= 0);
652 #ifdef XFS_TRANS_DEBUG
654 * Walk the list checking lsn ordering, and that every entry has the
655 * XFS_LI_IN_AIL flag set. This is really expensive, so only do it
656 * when specifically debugging the transaction subsystem.
658 prev_lip = list_entry(&ailp->xa_ail, xfs_log_item_t, li_ail);
659 list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
660 if (&prev_lip->li_ail != &ailp->xa_ail)
661 ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
662 ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
665 #endif /* XFS_TRANS_DEBUG */