2 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
3 * Copyright (c) 2010 David Chinner.
4 * Copyright (c) 2011 Christoph Hellwig.
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License as
9 * published by the Free Software Foundation.
11 * This program is distributed in the hope that it would be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 #include "xfs_types.h"
24 #include "xfs_trans.h"
27 #include "xfs_mount.h"
28 #include "xfs_bmap_btree.h"
29 #include "xfs_alloc.h"
30 #include "xfs_inode.h"
31 #include "xfs_extent_busy.h"
32 #include "xfs_trace.h"
35 xfs_extent_busy_insert(
42 struct xfs_extent_busy *new;
43 struct xfs_extent_busy *busyp;
44 struct xfs_perag *pag;
46 struct rb_node *parent = NULL;
48 new = kmem_zalloc(sizeof(struct xfs_extent_busy), KM_MAYFAIL);
51 * No Memory! Since it is now not possible to track the free
52 * block, make this a synchronous transaction to insure that
53 * the block is not reused before this transaction commits.
55 trace_xfs_extent_busy_enomem(tp->t_mountp, agno, bno, len);
56 xfs_trans_set_sync(tp);
63 INIT_LIST_HEAD(&new->list);
66 /* trace before insert to be able to see failed inserts */
67 trace_xfs_extent_busy(tp->t_mountp, agno, bno, len);
69 pag = xfs_perag_get(tp->t_mountp, new->agno);
70 spin_lock(&pag->pagb_lock);
71 rbp = &pag->pagb_tree.rb_node;
74 busyp = rb_entry(parent, struct xfs_extent_busy, rb_node);
76 if (new->bno < busyp->bno) {
77 rbp = &(*rbp)->rb_left;
78 ASSERT(new->bno + new->length <= busyp->bno);
79 } else if (new->bno > busyp->bno) {
80 rbp = &(*rbp)->rb_right;
81 ASSERT(bno >= busyp->bno + busyp->length);
87 rb_link_node(&new->rb_node, parent, rbp);
88 rb_insert_color(&new->rb_node, &pag->pagb_tree);
90 list_add(&new->list, &tp->t_busy);
91 spin_unlock(&pag->pagb_lock);
96 * Search for a busy extent within the range of the extent we are about to
97 * allocate. You need to be holding the busy extent tree lock when calling
98 * xfs_extent_busy_search(). This function returns 0 for no overlapping busy
99 * extent, -1 for an overlapping but not exact busy extent, and 1 for an exact
100 * match. This is done so that a non-zero return indicates an overlap that
101 * will require a synchronous transaction, but it can still be
102 * used to distinguish between a partial or exact match.
105 xfs_extent_busy_search(
106 struct xfs_mount *mp,
111 struct xfs_perag *pag;
113 struct xfs_extent_busy *busyp;
116 pag = xfs_perag_get(mp, agno);
117 spin_lock(&pag->pagb_lock);
119 rbp = pag->pagb_tree.rb_node;
121 /* find closest start bno overlap */
123 busyp = rb_entry(rbp, struct xfs_extent_busy, rb_node);
124 if (bno < busyp->bno) {
125 /* may overlap, but exact start block is lower */
126 if (bno + len > busyp->bno)
129 } else if (bno > busyp->bno) {
130 /* may overlap, but exact start block is higher */
131 if (bno < busyp->bno + busyp->length)
135 /* bno matches busyp, length determines exact match */
136 match = (busyp->length == len) ? 1 : -1;
140 spin_unlock(&pag->pagb_lock);
146 * The found free extent [fbno, fend] overlaps part or all of the given busy
147 * extent. If the overlap covers the beginning, the end, or all of the busy
148 * extent, the overlapping portion can be made unbusy and used for the
149 * allocation. We can't split a busy extent because we can't modify a
150 * transaction/CIL context busy list, but we can update an entry's block
153 * Returns true if the extent can safely be reused, or false if the search
154 * needs to be restarted.
157 xfs_extent_busy_update_extent(
158 struct xfs_mount *mp,
159 struct xfs_perag *pag,
160 struct xfs_extent_busy *busyp,
165 xfs_agblock_t fend = fbno + flen;
166 xfs_agblock_t bbno = busyp->bno;
167 xfs_agblock_t bend = bbno + busyp->length;
170 * This extent is currently being discarded. Give the thread
171 * performing the discard a chance to mark the extent unbusy
174 if (busyp->flags & XFS_EXTENT_BUSY_DISCARDED) {
175 spin_unlock(&pag->pagb_lock);
177 spin_lock(&pag->pagb_lock);
182 * If there is a busy extent overlapping a user allocation, we have
183 * no choice but to force the log and retry the search.
185 * Fortunately this does not happen during normal operation, but
186 * only if the filesystem is very low on space and has to dip into
187 * the AGFL for normal allocations.
192 if (bbno < fbno && bend > fend) {
196 * +BBBBBBBBBBBBBBBBB+
202 * We would have to split the busy extent to be able to track
203 * it correct, which we cannot do because we would have to
204 * modify the list of busy extents attached to the transaction
205 * or CIL context, which is immutable.
207 * Force out the log to clear the busy extent and retry the
211 } else if (bbno >= fbno && bend <= fend) {
215 * +BBBBBBBBBBBBBBBBB+
216 * +-----------------+
221 * +BBBBBBBBBBBBBBBBB+
222 * +--------------------------+
227 * +BBBBBBBBBBBBBBBBB+
228 * +--------------------------+
233 * +BBBBBBBBBBBBBBBBB+
234 * +-----------------------------------+
240 * The busy extent is fully covered by the extent we are
241 * allocating, and can simply be removed from the rbtree.
242 * However we cannot remove it from the immutable list
243 * tracking busy extents in the transaction or CIL context,
244 * so set the length to zero to mark it invalid.
246 * We also need to restart the busy extent search from the
247 * tree root, because erasing the node can rearrange the
250 rb_erase(&busyp->rb_node, &pag->pagb_tree);
253 } else if (fend < bend) {
257 * +BBBBBBBBBBBBBBBBB+
263 * +BBBBBBBBBBBBBBBBB+
264 * +------------------+
269 } else if (bbno < fbno) {
273 * +BBBBBBBBBBBBBBBBB+
279 * +BBBBBBBBBBBBBBBBB+
280 * +----------------------+
283 busyp->length = fbno - busyp->bno;
288 trace_xfs_extent_busy_reuse(mp, pag->pag_agno, fbno, flen);
292 spin_unlock(&pag->pagb_lock);
293 xfs_log_force(mp, XFS_LOG_SYNC);
294 trace_xfs_extent_busy_force(mp, pag->pag_agno, fbno, flen);
295 spin_lock(&pag->pagb_lock);
301 * For a given extent [fbno, flen], make sure we can reuse it safely.
304 xfs_extent_busy_reuse(
305 struct xfs_mount *mp,
311 struct xfs_perag *pag;
316 pag = xfs_perag_get(mp, agno);
317 spin_lock(&pag->pagb_lock);
319 rbp = pag->pagb_tree.rb_node;
321 struct xfs_extent_busy *busyp =
322 rb_entry(rbp, struct xfs_extent_busy, rb_node);
323 xfs_agblock_t bbno = busyp->bno;
324 xfs_agblock_t bend = bbno + busyp->length;
326 if (fbno + flen <= bbno) {
329 } else if (fbno >= bend) {
334 if (!xfs_extent_busy_update_extent(mp, pag, busyp, fbno, flen,
338 spin_unlock(&pag->pagb_lock);
343 * For a given extent [fbno, flen], search the busy extent list to find a
344 * subset of the extent that is not busy. If *rlen is smaller than
345 * args->minlen no suitable extent could be found, and the higher level
346 * code needs to force out the log and retry the allocation.
349 xfs_extent_busy_trim(
350 struct xfs_alloc_arg *args,
362 spin_lock(&args->pag->pagb_lock);
366 rbp = args->pag->pagb_tree.rb_node;
367 while (rbp && flen >= args->minlen) {
368 struct xfs_extent_busy *busyp =
369 rb_entry(rbp, struct xfs_extent_busy, rb_node);
370 xfs_agblock_t fend = fbno + flen;
371 xfs_agblock_t bbno = busyp->bno;
372 xfs_agblock_t bend = bbno + busyp->length;
377 } else if (fbno >= bend) {
383 * If this is a metadata allocation, try to reuse the busy
384 * extent instead of trimming the allocation.
386 if (!args->userdata &&
387 !(busyp->flags & XFS_EXTENT_BUSY_DISCARDED)) {
388 if (!xfs_extent_busy_update_extent(args->mp, args->pag,
401 * +BBBBBBBBBBBBBBBBB+
407 * +BBBBBBBBBBBBBBBBB+
413 * +BBBBBBBBBBBBBBBBB+
419 * +BBBBBBBBBBBBBBBBB+
420 * +-----------------+
423 * No unbusy region in extent, return failure.
431 * +BBBBBBBBBBBBBBBBB+
432 * +----------------------+
437 * +BBBBBBBBBBBBBBBBB+
438 * +--------------------------+
441 * Needs to be trimmed to:
446 } else if (bend >= fend) {
452 * +BBBBBBBBBBBBBBBBB+
453 * +------------------+
458 * +BBBBBBBBBBBBBBBBB+
459 * +--------------------------+
462 * Needs to be trimmed to:
473 * +BBBBBBBBBBBBBBBBB+
474 * +-----------------------------------+
478 * +-------+ OR +-------+
479 * fbno fend fbno fend
481 * Backward allocation leads to significant
482 * fragmentation of directories, which degrades
483 * directory performance, therefore we always want to
484 * choose the option that produces forward allocation
486 * Preferring the lower bno extent will make the next
487 * request use "fend" as the start of the next
488 * allocation; if the segment is no longer busy at
489 * that point, we'll get a contiguous allocation, but
490 * even if it is still busy, we will get a forward
492 * We try to avoid choosing the segment at "bend",
493 * because that can lead to the next allocation
494 * taking the segment at "fbno", which would be a
495 * backward allocation. We only use the segment at
496 * "fbno" if it is much larger than the current
497 * requested size, because in that case there's a
498 * good chance subsequent allocations will be
501 if (bbno - fbno >= args->maxlen) {
502 /* left candidate fits perfect */
504 } else if (fend - bend >= args->maxlen * 4) {
505 /* right candidate has enough free space */
507 } else if (bbno - fbno >= args->minlen) {
508 /* left candidate fits minimum requirement */
517 spin_unlock(&args->pag->pagb_lock);
519 if (fbno != bno || flen != len) {
520 trace_xfs_extent_busy_trim(args->mp, args->agno, bno, len,
528 * Return a zero extent length as failure indications. All callers
529 * re-check if the trimmed extent satisfies the minlen requirement.
531 spin_unlock(&args->pag->pagb_lock);
532 trace_xfs_extent_busy_trim(args->mp, args->agno, bno, len, fbno, 0);
538 xfs_extent_busy_clear_one(
539 struct xfs_mount *mp,
540 struct xfs_perag *pag,
541 struct xfs_extent_busy *busyp)
544 trace_xfs_extent_busy_clear(mp, busyp->agno, busyp->bno,
546 rb_erase(&busyp->rb_node, &pag->pagb_tree);
549 list_del_init(&busyp->list);
554 * Remove all extents on the passed in list from the busy extents tree.
555 * If do_discard is set skip extents that need to be discarded, and mark
556 * these as undergoing a discard operation instead.
559 xfs_extent_busy_clear(
560 struct xfs_mount *mp,
561 struct list_head *list,
564 struct xfs_extent_busy *busyp, *n;
565 struct xfs_perag *pag = NULL;
566 xfs_agnumber_t agno = NULLAGNUMBER;
568 list_for_each_entry_safe(busyp, n, list, list) {
569 if (busyp->agno != agno) {
571 spin_unlock(&pag->pagb_lock);
574 pag = xfs_perag_get(mp, busyp->agno);
575 spin_lock(&pag->pagb_lock);
579 if (do_discard && busyp->length &&
580 !(busyp->flags & XFS_EXTENT_BUSY_SKIP_DISCARD))
581 busyp->flags = XFS_EXTENT_BUSY_DISCARDED;
583 xfs_extent_busy_clear_one(mp, pag, busyp);
587 spin_unlock(&pag->pagb_lock);
593 * Callback for list_sort to sort busy extents by the AG they reside in.
596 xfs_extent_busy_ag_cmp(
601 return container_of(a, struct xfs_extent_busy, list)->agno -
602 container_of(b, struct xfs_extent_busy, list)->agno;