1 /*
2 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
3 * Copyright (c) 2010 David Chinner.
4 * Copyright (c) 2011 Christoph Hellwig.
5 * All Rights Reserved.
6 *
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.
10 *
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.
15 *
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
19 */
20 #include "xfs.h"
21 #include "xfs_fs.h"
22 #include "xfs_format.h"
23 #include "xfs_log_format.h"
24 #include "xfs_shared.h"
25 #include "xfs_trans_resv.h"
26 #include "xfs_sb.h"
27 #include "xfs_mount.h"
28 #include "xfs_alloc.h"
29 #include "xfs_extent_busy.h"
30 #include "xfs_trace.h"
31 #include "xfs_trans.h"
32 #include "xfs_log.h"
33
34 void
xfs_extent_busy_insert(struct xfs_trans * tp,xfs_agnumber_t agno,xfs_agblock_t bno,xfs_extlen_t len,unsigned int flags)35 xfs_extent_busy_insert(
36 struct xfs_trans *tp,
37 xfs_agnumber_t agno,
38 xfs_agblock_t bno,
39 xfs_extlen_t len,
40 unsigned int flags)
41 {
42 struct xfs_extent_busy *new;
43 struct xfs_extent_busy *busyp;
44 struct xfs_perag *pag;
45 struct rb_node **rbp;
46 struct rb_node *parent = NULL;
47
48 new = kmem_zalloc(sizeof(struct xfs_extent_busy), KM_SLEEP);
49 new->agno = agno;
50 new->bno = bno;
51 new->length = len;
52 INIT_LIST_HEAD(&new->list);
53 new->flags = flags;
54
55 /* trace before insert to be able to see failed inserts */
56 trace_xfs_extent_busy(tp->t_mountp, agno, bno, len);
57
58 pag = xfs_perag_get(tp->t_mountp, new->agno);
59 spin_lock(&pag->pagb_lock);
60 rbp = &pag->pagb_tree.rb_node;
61 while (*rbp) {
62 parent = *rbp;
63 busyp = rb_entry(parent, struct xfs_extent_busy, rb_node);
64
65 if (new->bno < busyp->bno) {
66 rbp = &(*rbp)->rb_left;
67 ASSERT(new->bno + new->length <= busyp->bno);
68 } else if (new->bno > busyp->bno) {
69 rbp = &(*rbp)->rb_right;
70 ASSERT(bno >= busyp->bno + busyp->length);
71 } else {
72 ASSERT(0);
73 }
74 }
75
76 rb_link_node(&new->rb_node, parent, rbp);
77 rb_insert_color(&new->rb_node, &pag->pagb_tree);
78
79 list_add(&new->list, &tp->t_busy);
80 spin_unlock(&pag->pagb_lock);
81 xfs_perag_put(pag);
82 }
83
84 /*
85 * Search for a busy extent within the range of the extent we are about to
86 * allocate. You need to be holding the busy extent tree lock when calling
87 * xfs_extent_busy_search(). This function returns 0 for no overlapping busy
88 * extent, -1 for an overlapping but not exact busy extent, and 1 for an exact
89 * match. This is done so that a non-zero return indicates an overlap that
90 * will require a synchronous transaction, but it can still be
91 * used to distinguish between a partial or exact match.
92 */
93 int
xfs_extent_busy_search(struct xfs_mount * mp,xfs_agnumber_t agno,xfs_agblock_t bno,xfs_extlen_t len)94 xfs_extent_busy_search(
95 struct xfs_mount *mp,
96 xfs_agnumber_t agno,
97 xfs_agblock_t bno,
98 xfs_extlen_t len)
99 {
100 struct xfs_perag *pag;
101 struct rb_node *rbp;
102 struct xfs_extent_busy *busyp;
103 int match = 0;
104
105 pag = xfs_perag_get(mp, agno);
106 spin_lock(&pag->pagb_lock);
107
108 rbp = pag->pagb_tree.rb_node;
109
110 /* find closest start bno overlap */
111 while (rbp) {
112 busyp = rb_entry(rbp, struct xfs_extent_busy, rb_node);
113 if (bno < busyp->bno) {
114 /* may overlap, but exact start block is lower */
115 if (bno + len > busyp->bno)
116 match = -1;
117 rbp = rbp->rb_left;
118 } else if (bno > busyp->bno) {
119 /* may overlap, but exact start block is higher */
120 if (bno < busyp->bno + busyp->length)
121 match = -1;
122 rbp = rbp->rb_right;
123 } else {
124 /* bno matches busyp, length determines exact match */
125 match = (busyp->length == len) ? 1 : -1;
126 break;
127 }
128 }
129 spin_unlock(&pag->pagb_lock);
130 xfs_perag_put(pag);
131 return match;
132 }
133
134 /*
135 * The found free extent [fbno, fend] overlaps part or all of the given busy
136 * extent. If the overlap covers the beginning, the end, or all of the busy
137 * extent, the overlapping portion can be made unbusy and used for the
138 * allocation. We can't split a busy extent because we can't modify a
139 * transaction/CIL context busy list, but we can update an entry's block
140 * number or length.
141 *
142 * Returns true if the extent can safely be reused, or false if the search
143 * needs to be restarted.
144 */
145 STATIC bool
xfs_extent_busy_update_extent(struct xfs_mount * mp,struct xfs_perag * pag,struct xfs_extent_busy * busyp,xfs_agblock_t fbno,xfs_extlen_t flen,bool userdata)146 xfs_extent_busy_update_extent(
147 struct xfs_mount *mp,
148 struct xfs_perag *pag,
149 struct xfs_extent_busy *busyp,
150 xfs_agblock_t fbno,
151 xfs_extlen_t flen,
152 bool userdata) __releases(&pag->pagb_lock)
153 __acquires(&pag->pagb_lock)
154 {
155 xfs_agblock_t fend = fbno + flen;
156 xfs_agblock_t bbno = busyp->bno;
157 xfs_agblock_t bend = bbno + busyp->length;
158
159 /*
160 * This extent is currently being discarded. Give the thread
161 * performing the discard a chance to mark the extent unbusy
162 * and retry.
163 */
164 if (busyp->flags & XFS_EXTENT_BUSY_DISCARDED) {
165 spin_unlock(&pag->pagb_lock);
166 delay(1);
167 spin_lock(&pag->pagb_lock);
168 return false;
169 }
170
171 /*
172 * If there is a busy extent overlapping a user allocation, we have
173 * no choice but to force the log and retry the search.
174 *
175 * Fortunately this does not happen during normal operation, but
176 * only if the filesystem is very low on space and has to dip into
177 * the AGFL for normal allocations.
178 */
179 if (userdata)
180 goto out_force_log;
181
182 if (bbno < fbno && bend > fend) {
183 /*
184 * Case 1:
185 * bbno bend
186 * +BBBBBBBBBBBBBBBBB+
187 * +---------+
188 * fbno fend
189 */
190
191 /*
192 * We would have to split the busy extent to be able to track
193 * it correct, which we cannot do because we would have to
194 * modify the list of busy extents attached to the transaction
195 * or CIL context, which is immutable.
196 *
197 * Force out the log to clear the busy extent and retry the
198 * search.
199 */
200 goto out_force_log;
201 } else if (bbno >= fbno && bend <= fend) {
202 /*
203 * Case 2:
204 * bbno bend
205 * +BBBBBBBBBBBBBBBBB+
206 * +-----------------+
207 * fbno fend
208 *
209 * Case 3:
210 * bbno bend
211 * +BBBBBBBBBBBBBBBBB+
212 * +--------------------------+
213 * fbno fend
214 *
215 * Case 4:
216 * bbno bend
217 * +BBBBBBBBBBBBBBBBB+
218 * +--------------------------+
219 * fbno fend
220 *
221 * Case 5:
222 * bbno bend
223 * +BBBBBBBBBBBBBBBBB+
224 * +-----------------------------------+
225 * fbno fend
226 *
227 */
228
229 /*
230 * The busy extent is fully covered by the extent we are
231 * allocating, and can simply be removed from the rbtree.
232 * However we cannot remove it from the immutable list
233 * tracking busy extents in the transaction or CIL context,
234 * so set the length to zero to mark it invalid.
235 *
236 * We also need to restart the busy extent search from the
237 * tree root, because erasing the node can rearrange the
238 * tree topology.
239 */
240 rb_erase(&busyp->rb_node, &pag->pagb_tree);
241 busyp->length = 0;
242 return false;
243 } else if (fend < bend) {
244 /*
245 * Case 6:
246 * bbno bend
247 * +BBBBBBBBBBBBBBBBB+
248 * +---------+
249 * fbno fend
250 *
251 * Case 7:
252 * bbno bend
253 * +BBBBBBBBBBBBBBBBB+
254 * +------------------+
255 * fbno fend
256 *
257 */
258 busyp->bno = fend;
259 } else if (bbno < fbno) {
260 /*
261 * Case 8:
262 * bbno bend
263 * +BBBBBBBBBBBBBBBBB+
264 * +-------------+
265 * fbno fend
266 *
267 * Case 9:
268 * bbno bend
269 * +BBBBBBBBBBBBBBBBB+
270 * +----------------------+
271 * fbno fend
272 */
273 busyp->length = fbno - busyp->bno;
274 } else {
275 ASSERT(0);
276 }
277
278 trace_xfs_extent_busy_reuse(mp, pag->pag_agno, fbno, flen);
279 return true;
280
281 out_force_log:
282 spin_unlock(&pag->pagb_lock);
283 xfs_log_force(mp, XFS_LOG_SYNC);
284 trace_xfs_extent_busy_force(mp, pag->pag_agno, fbno, flen);
285 spin_lock(&pag->pagb_lock);
286 return false;
287 }
288
289
290 /*
291 * For a given extent [fbno, flen], make sure we can reuse it safely.
292 */
293 void
xfs_extent_busy_reuse(struct xfs_mount * mp,xfs_agnumber_t agno,xfs_agblock_t fbno,xfs_extlen_t flen,bool userdata)294 xfs_extent_busy_reuse(
295 struct xfs_mount *mp,
296 xfs_agnumber_t agno,
297 xfs_agblock_t fbno,
298 xfs_extlen_t flen,
299 bool userdata)
300 {
301 struct xfs_perag *pag;
302 struct rb_node *rbp;
303
304 ASSERT(flen > 0);
305
306 pag = xfs_perag_get(mp, agno);
307 spin_lock(&pag->pagb_lock);
308 restart:
309 rbp = pag->pagb_tree.rb_node;
310 while (rbp) {
311 struct xfs_extent_busy *busyp =
312 rb_entry(rbp, struct xfs_extent_busy, rb_node);
313 xfs_agblock_t bbno = busyp->bno;
314 xfs_agblock_t bend = bbno + busyp->length;
315
316 if (fbno + flen <= bbno) {
317 rbp = rbp->rb_left;
318 continue;
319 } else if (fbno >= bend) {
320 rbp = rbp->rb_right;
321 continue;
322 }
323
324 if (!xfs_extent_busy_update_extent(mp, pag, busyp, fbno, flen,
325 userdata))
326 goto restart;
327 }
328 spin_unlock(&pag->pagb_lock);
329 xfs_perag_put(pag);
330 }
331
332 /*
333 * For a given extent [fbno, flen], search the busy extent list to find a
334 * subset of the extent that is not busy. If *rlen is smaller than
335 * args->minlen no suitable extent could be found, and the higher level
336 * code needs to force out the log and retry the allocation.
337 */
338 void
xfs_extent_busy_trim(struct xfs_alloc_arg * args,xfs_agblock_t bno,xfs_extlen_t len,xfs_agblock_t * rbno,xfs_extlen_t * rlen)339 xfs_extent_busy_trim(
340 struct xfs_alloc_arg *args,
341 xfs_agblock_t bno,
342 xfs_extlen_t len,
343 xfs_agblock_t *rbno,
344 xfs_extlen_t *rlen)
345 {
346 xfs_agblock_t fbno;
347 xfs_extlen_t flen;
348 struct rb_node *rbp;
349
350 ASSERT(len > 0);
351
352 spin_lock(&args->pag->pagb_lock);
353 restart:
354 fbno = bno;
355 flen = len;
356 rbp = args->pag->pagb_tree.rb_node;
357 while (rbp && flen >= args->minlen) {
358 struct xfs_extent_busy *busyp =
359 rb_entry(rbp, struct xfs_extent_busy, rb_node);
360 xfs_agblock_t fend = fbno + flen;
361 xfs_agblock_t bbno = busyp->bno;
362 xfs_agblock_t bend = bbno + busyp->length;
363
364 if (fend <= bbno) {
365 rbp = rbp->rb_left;
366 continue;
367 } else if (fbno >= bend) {
368 rbp = rbp->rb_right;
369 continue;
370 }
371
372 /*
373 * If this is a metadata allocation, try to reuse the busy
374 * extent instead of trimming the allocation.
375 */
376 if (!xfs_alloc_is_userdata(args->datatype) &&
377 !(busyp->flags & XFS_EXTENT_BUSY_DISCARDED)) {
378 if (!xfs_extent_busy_update_extent(args->mp, args->pag,
379 busyp, fbno, flen,
380 false))
381 goto restart;
382 continue;
383 }
384
385 if (bbno <= fbno) {
386 /* start overlap */
387
388 /*
389 * Case 1:
390 * bbno bend
391 * +BBBBBBBBBBBBBBBBB+
392 * +---------+
393 * fbno fend
394 *
395 * Case 2:
396 * bbno bend
397 * +BBBBBBBBBBBBBBBBB+
398 * +-------------+
399 * fbno fend
400 *
401 * Case 3:
402 * bbno bend
403 * +BBBBBBBBBBBBBBBBB+
404 * +-------------+
405 * fbno fend
406 *
407 * Case 4:
408 * bbno bend
409 * +BBBBBBBBBBBBBBBBB+
410 * +-----------------+
411 * fbno fend
412 *
413 * No unbusy region in extent, return failure.
414 */
415 if (fend <= bend)
416 goto fail;
417
418 /*
419 * Case 5:
420 * bbno bend
421 * +BBBBBBBBBBBBBBBBB+
422 * +----------------------+
423 * fbno fend
424 *
425 * Case 6:
426 * bbno bend
427 * +BBBBBBBBBBBBBBBBB+
428 * +--------------------------+
429 * fbno fend
430 *
431 * Needs to be trimmed to:
432 * +-------+
433 * fbno fend
434 */
435 fbno = bend;
436 } else if (bend >= fend) {
437 /* end overlap */
438
439 /*
440 * Case 7:
441 * bbno bend
442 * +BBBBBBBBBBBBBBBBB+
443 * +------------------+
444 * fbno fend
445 *
446 * Case 8:
447 * bbno bend
448 * +BBBBBBBBBBBBBBBBB+
449 * +--------------------------+
450 * fbno fend
451 *
452 * Needs to be trimmed to:
453 * +-------+
454 * fbno fend
455 */
456 fend = bbno;
457 } else {
458 /* middle overlap */
459
460 /*
461 * Case 9:
462 * bbno bend
463 * +BBBBBBBBBBBBBBBBB+
464 * +-----------------------------------+
465 * fbno fend
466 *
467 * Can be trimmed to:
468 * +-------+ OR +-------+
469 * fbno fend fbno fend
470 *
471 * Backward allocation leads to significant
472 * fragmentation of directories, which degrades
473 * directory performance, therefore we always want to
474 * choose the option that produces forward allocation
475 * patterns.
476 * Preferring the lower bno extent will make the next
477 * request use "fend" as the start of the next
478 * allocation; if the segment is no longer busy at
479 * that point, we'll get a contiguous allocation, but
480 * even if it is still busy, we will get a forward
481 * allocation.
482 * We try to avoid choosing the segment at "bend",
483 * because that can lead to the next allocation
484 * taking the segment at "fbno", which would be a
485 * backward allocation. We only use the segment at
486 * "fbno" if it is much larger than the current
487 * requested size, because in that case there's a
488 * good chance subsequent allocations will be
489 * contiguous.
490 */
491 if (bbno - fbno >= args->maxlen) {
492 /* left candidate fits perfect */
493 fend = bbno;
494 } else if (fend - bend >= args->maxlen * 4) {
495 /* right candidate has enough free space */
496 fbno = bend;
497 } else if (bbno - fbno >= args->minlen) {
498 /* left candidate fits minimum requirement */
499 fend = bbno;
500 } else {
501 goto fail;
502 }
503 }
504
505 flen = fend - fbno;
506 }
507 spin_unlock(&args->pag->pagb_lock);
508
509 if (fbno != bno || flen != len) {
510 trace_xfs_extent_busy_trim(args->mp, args->agno, bno, len,
511 fbno, flen);
512 }
513 *rbno = fbno;
514 *rlen = flen;
515 return;
516 fail:
517 /*
518 * Return a zero extent length as failure indications. All callers
519 * re-check if the trimmed extent satisfies the minlen requirement.
520 */
521 spin_unlock(&args->pag->pagb_lock);
522 trace_xfs_extent_busy_trim(args->mp, args->agno, bno, len, fbno, 0);
523 *rbno = fbno;
524 *rlen = 0;
525 }
526
527 STATIC void
xfs_extent_busy_clear_one(struct xfs_mount * mp,struct xfs_perag * pag,struct xfs_extent_busy * busyp)528 xfs_extent_busy_clear_one(
529 struct xfs_mount *mp,
530 struct xfs_perag *pag,
531 struct xfs_extent_busy *busyp)
532 {
533 if (busyp->length) {
534 trace_xfs_extent_busy_clear(mp, busyp->agno, busyp->bno,
535 busyp->length);
536 rb_erase(&busyp->rb_node, &pag->pagb_tree);
537 }
538
539 list_del_init(&busyp->list);
540 kmem_free(busyp);
541 }
542
543 /*
544 * Remove all extents on the passed in list from the busy extents tree.
545 * If do_discard is set skip extents that need to be discarded, and mark
546 * these as undergoing a discard operation instead.
547 */
548 void
xfs_extent_busy_clear(struct xfs_mount * mp,struct list_head * list,bool do_discard)549 xfs_extent_busy_clear(
550 struct xfs_mount *mp,
551 struct list_head *list,
552 bool do_discard)
553 {
554 struct xfs_extent_busy *busyp, *n;
555 struct xfs_perag *pag = NULL;
556 xfs_agnumber_t agno = NULLAGNUMBER;
557
558 list_for_each_entry_safe(busyp, n, list, list) {
559 if (busyp->agno != agno) {
560 if (pag) {
561 spin_unlock(&pag->pagb_lock);
562 xfs_perag_put(pag);
563 }
564 pag = xfs_perag_get(mp, busyp->agno);
565 spin_lock(&pag->pagb_lock);
566 agno = busyp->agno;
567 }
568
569 if (do_discard && busyp->length &&
570 !(busyp->flags & XFS_EXTENT_BUSY_SKIP_DISCARD))
571 busyp->flags = XFS_EXTENT_BUSY_DISCARDED;
572 else
573 xfs_extent_busy_clear_one(mp, pag, busyp);
574 }
575
576 if (pag) {
577 spin_unlock(&pag->pagb_lock);
578 xfs_perag_put(pag);
579 }
580 }
581
582 /*
583 * Callback for list_sort to sort busy extents by the AG they reside in.
584 */
585 int
xfs_extent_busy_ag_cmp(void * priv,struct list_head * a,struct list_head * b)586 xfs_extent_busy_ag_cmp(
587 void *priv,
588 struct list_head *a,
589 struct list_head *b)
590 {
591 return container_of(a, struct xfs_extent_busy, list)->agno -
592 container_of(b, struct xfs_extent_busy, list)->agno;
593 }
594