1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
4 * Copyright (c) 2010 David Chinner.
5 * Copyright (c) 2011 Christoph Hellwig.
6 * All Rights Reserved.
7 */
8 #include "xfs.h"
9 #include "xfs_fs.h"
10 #include "xfs_format.h"
11 #include "xfs_log_format.h"
12 #include "xfs_shared.h"
13 #include "xfs_trans_resv.h"
14 #include "xfs_mount.h"
15 #include "xfs_alloc.h"
16 #include "xfs_extent_busy.h"
17 #include "xfs_trace.h"
18 #include "xfs_trans.h"
19 #include "xfs_log.h"
20 #include "xfs_ag.h"
21
22 static void
23 xfs_extent_busy_insert_list(
24 struct xfs_perag *pag,
25 xfs_agblock_t bno,
26 xfs_extlen_t len,
27 unsigned int flags,
28 struct list_head *busy_list)
29 {
30 struct xfs_extent_busy *new;
31 struct xfs_extent_busy *busyp;
32 struct rb_node **rbp;
33 struct rb_node *parent = NULL;
34
35 new = kzalloc(sizeof(struct xfs_extent_busy),
36 GFP_KERNEL | __GFP_NOFAIL);
37 new->agno = pag->pag_agno;
38 new->bno = bno;
39 new->length = len;
40 INIT_LIST_HEAD(&new->list);
41 new->flags = flags;
42
43 /* trace before insert to be able to see failed inserts */
44 trace_xfs_extent_busy(pag->pag_mount, pag->pag_agno, bno, len);
45
46 spin_lock(&pag->pagb_lock);
47 rbp = &pag->pagb_tree.rb_node;
48 while (*rbp) {
49 parent = *rbp;
50 busyp = rb_entry(parent, struct xfs_extent_busy, rb_node);
51
52 if (new->bno < busyp->bno) {
53 rbp = &(*rbp)->rb_left;
54 ASSERT(new->bno + new->length <= busyp->bno);
55 } else if (new->bno > busyp->bno) {
56 rbp = &(*rbp)->rb_right;
57 ASSERT(bno >= busyp->bno + busyp->length);
58 } else {
59 ASSERT(0);
60 }
61 }
62
63 rb_link_node(&new->rb_node, parent, rbp);
64 rb_insert_color(&new->rb_node, &pag->pagb_tree);
65
66 /* always process discard lists in fifo order */
67 list_add_tail(&new->list, busy_list);
68 spin_unlock(&pag->pagb_lock);
69 }
70
71 void
72 xfs_extent_busy_insert(
73 struct xfs_trans *tp,
74 struct xfs_perag *pag,
75 xfs_agblock_t bno,
76 xfs_extlen_t len,
77 unsigned int flags)
78 {
79 xfs_extent_busy_insert_list(pag, bno, len, flags, &tp->t_busy);
80 }
81
82 void
83 xfs_extent_busy_insert_discard(
84 struct xfs_perag *pag,
85 xfs_agblock_t bno,
86 xfs_extlen_t len,
87 struct list_head *busy_list)
88 {
89 xfs_extent_busy_insert_list(pag, bno, len, XFS_EXTENT_BUSY_DISCARDED,
90 busy_list);
91 }
92
93 /*
94 * Search for a busy extent within the range of the extent we are about to
95 * allocate. You need to be holding the busy extent tree lock when calling
96 * xfs_extent_busy_search(). This function returns 0 for no overlapping busy
97 * extent, -1 for an overlapping but not exact busy extent, and 1 for an exact
98 * match. This is done so that a non-zero return indicates an overlap that
99 * will require a synchronous transaction, but it can still be
100 * used to distinguish between a partial or exact match.
101 */
102 int
103 xfs_extent_busy_search(
104 struct xfs_mount *mp,
105 struct xfs_perag *pag,
106 xfs_agblock_t bno,
107 xfs_extlen_t len)
108 {
109 struct rb_node *rbp;
110 struct xfs_extent_busy *busyp;
111 int match = 0;
112
113 /* find closest start bno overlap */
114 spin_lock(&pag->pagb_lock);
115 rbp = pag->pagb_tree.rb_node;
116 while (rbp) {
117 busyp = rb_entry(rbp, struct xfs_extent_busy, rb_node);
118 if (bno < busyp->bno) {
119 /* may overlap, but exact start block is lower */
120 if (bno + len > busyp->bno)
121 match = -1;
122 rbp = rbp->rb_left;
123 } else if (bno > busyp->bno) {
124 /* may overlap, but exact start block is higher */
125 if (bno < busyp->bno + busyp->length)
126 match = -1;
127 rbp = rbp->rb_right;
128 } else {
129 /* bno matches busyp, length determines exact match */
130 match = (busyp->length == len) ? 1 : -1;
131 break;
132 }
133 }
134 spin_unlock(&pag->pagb_lock);
135 return match;
136 }
137
138 /*
139 * The found free extent [fbno, fend] overlaps part or all of the given busy
140 * extent. If the overlap covers the beginning, the end, or all of the busy
141 * extent, the overlapping portion can be made unbusy and used for the
142 * allocation. We can't split a busy extent because we can't modify a
143 * transaction/CIL context busy list, but we can update an entry's block
144 * number or length.
145 *
146 * Returns true if the extent can safely be reused, or false if the search
147 * needs to be restarted.
148 */
149 STATIC bool
150 xfs_extent_busy_update_extent(
151 struct xfs_mount *mp,
152 struct xfs_perag *pag,
153 struct xfs_extent_busy *busyp,
154 xfs_agblock_t fbno,
155 xfs_extlen_t flen,
156 bool userdata) __releases(&pag->pagb_lock)
157 __acquires(&pag->pagb_lock)
158 {
159 xfs_agblock_t fend = fbno + flen;
160 xfs_agblock_t bbno = busyp->bno;
161 xfs_agblock_t bend = bbno + busyp->length;
162
163 /*
164 * This extent is currently being discarded. Give the thread
165 * performing the discard a chance to mark the extent unbusy
166 * and retry.
167 */
168 if (busyp->flags & XFS_EXTENT_BUSY_DISCARDED) {
169 spin_unlock(&pag->pagb_lock);
170 delay(1);
171 spin_lock(&pag->pagb_lock);
172 return false;
173 }
174
175 /*
176 * If there is a busy extent overlapping a user allocation, we have
177 * no choice but to force the log and retry the search.
178 *
179 * Fortunately this does not happen during normal operation, but
180 * only if the filesystem is very low on space and has to dip into
181 * the AGFL for normal allocations.
182 */
183 if (userdata)
184 goto out_force_log;
185
186 if (bbno < fbno && bend > fend) {
187 /*
188 * Case 1:
189 * bbno bend
190 * +BBBBBBBBBBBBBBBBB+
191 * +---------+
192 * fbno fend
193 */
194
195 /*
196 * We would have to split the busy extent to be able to track
197 * it correct, which we cannot do because we would have to
198 * modify the list of busy extents attached to the transaction
199 * or CIL context, which is immutable.
200 *
201 * Force out the log to clear the busy extent and retry the
202 * search.
203 */
204 goto out_force_log;
205 } else if (bbno >= fbno && bend <= fend) {
206 /*
207 * Case 2:
208 * bbno bend
209 * +BBBBBBBBBBBBBBBBB+
210 * +-----------------+
211 * fbno fend
212 *
213 * Case 3:
214 * bbno bend
215 * +BBBBBBBBBBBBBBBBB+
216 * +--------------------------+
217 * fbno fend
218 *
219 * Case 4:
220 * bbno bend
221 * +BBBBBBBBBBBBBBBBB+
222 * +--------------------------+
223 * fbno fend
224 *
225 * Case 5:
226 * bbno bend
227 * +BBBBBBBBBBBBBBBBB+
228 * +-----------------------------------+
229 * fbno fend
230 *
231 */
232
233 /*
234 * The busy extent is fully covered by the extent we are
235 * allocating, and can simply be removed from the rbtree.
236 * However we cannot remove it from the immutable list
237 * tracking busy extents in the transaction or CIL context,
238 * so set the length to zero to mark it invalid.
239 *
240 * We also need to restart the busy extent search from the
241 * tree root, because erasing the node can rearrange the
242 * tree topology.
243 */
244 rb_erase(&busyp->rb_node, &pag->pagb_tree);
245 busyp->length = 0;
246 return false;
247 } else if (fend < bend) {
248 /*
249 * Case 6:
250 * bbno bend
251 * +BBBBBBBBBBBBBBBBB+
252 * +---------+
253 * fbno fend
254 *
255 * Case 7:
256 * bbno bend
257 * +BBBBBBBBBBBBBBBBB+
258 * +------------------+
259 * fbno fend
260 *
261 */
262 busyp->bno = fend;
263 busyp->length = bend - fend;
264 } else if (bbno < fbno) {
265 /*
266 * Case 8:
267 * bbno bend
268 * +BBBBBBBBBBBBBBBBB+
269 * +-------------+
270 * fbno fend
271 *
272 * Case 9:
273 * bbno bend
274 * +BBBBBBBBBBBBBBBBB+
275 * +----------------------+
276 * fbno fend
277 */
278 busyp->length = fbno - busyp->bno;
279 } else {
280 ASSERT(0);
281 }
282
283 trace_xfs_extent_busy_reuse(mp, pag->pag_agno, fbno, flen);
284 return true;
285
286 out_force_log:
287 spin_unlock(&pag->pagb_lock);
288 xfs_log_force(mp, XFS_LOG_SYNC);
289 trace_xfs_extent_busy_force(mp, pag->pag_agno, fbno, flen);
290 spin_lock(&pag->pagb_lock);
291 return false;
292 }
293
294
295 /*
296 * For a given extent [fbno, flen], make sure we can reuse it safely.
297 */
298 void
299 xfs_extent_busy_reuse(
300 struct xfs_mount *mp,
301 struct xfs_perag *pag,
302 xfs_agblock_t fbno,
303 xfs_extlen_t flen,
304 bool userdata)
305 {
306 struct rb_node *rbp;
307
308 ASSERT(flen > 0);
309 spin_lock(&pag->pagb_lock);
310 restart:
311 rbp = pag->pagb_tree.rb_node;
312 while (rbp) {
313 struct xfs_extent_busy *busyp =
314 rb_entry(rbp, struct xfs_extent_busy, rb_node);
315 xfs_agblock_t bbno = busyp->bno;
316 xfs_agblock_t bend = bbno + busyp->length;
317
318 if (fbno + flen <= bbno) {
319 rbp = rbp->rb_left;
320 continue;
321 } else if (fbno >= bend) {
322 rbp = rbp->rb_right;
323 continue;
324 }
325
326 if (!xfs_extent_busy_update_extent(mp, pag, busyp, fbno, flen,
327 userdata))
328 goto restart;
329 }
330 spin_unlock(&pag->pagb_lock);
331 }
332
333 /*
334 * For a given extent [fbno, flen], search the busy extent list to find a
335 * subset of the extent that is not busy. If *rlen is smaller than
336 * args->minlen no suitable extent could be found, and the higher level
337 * code needs to force out the log and retry the allocation.
338 *
339 * Return the current busy generation for the AG if the extent is busy. This
340 * value can be used to wait for at least one of the currently busy extents
341 * to be cleared. Note that the busy list is not guaranteed to be empty after
342 * the gen is woken. The state of a specific extent must always be confirmed
343 * with another call to xfs_extent_busy_trim() before it can be used.
344 */
345 bool
346 xfs_extent_busy_trim(
347 struct xfs_alloc_arg *args,
348 xfs_agblock_t *bno,
349 xfs_extlen_t *len,
350 unsigned *busy_gen)
351 {
352 xfs_agblock_t fbno;
353 xfs_extlen_t flen;
354 struct rb_node *rbp;
355 bool ret = false;
356
357 ASSERT(*len > 0);
358
359 spin_lock(&args->pag->pagb_lock);
360 fbno = *bno;
361 flen = *len;
362 rbp = args->pag->pagb_tree.rb_node;
363 while (rbp && flen >= args->minlen) {
364 struct xfs_extent_busy *busyp =
365 rb_entry(rbp, struct xfs_extent_busy, rb_node);
366 xfs_agblock_t fend = fbno + flen;
367 xfs_agblock_t bbno = busyp->bno;
368 xfs_agblock_t bend = bbno + busyp->length;
369
370 if (fend <= bbno) {
371 rbp = rbp->rb_left;
372 continue;
373 } else if (fbno >= bend) {
374 rbp = rbp->rb_right;
375 continue;
376 }
377
378 if (bbno <= fbno) {
379 /* start overlap */
380
381 /*
382 * Case 1:
383 * bbno bend
384 * +BBBBBBBBBBBBBBBBB+
385 * +---------+
386 * fbno fend
387 *
388 * Case 2:
389 * bbno bend
390 * +BBBBBBBBBBBBBBBBB+
391 * +-------------+
392 * fbno fend
393 *
394 * Case 3:
395 * bbno bend
396 * +BBBBBBBBBBBBBBBBB+
397 * +-------------+
398 * fbno fend
399 *
400 * Case 4:
401 * bbno bend
402 * +BBBBBBBBBBBBBBBBB+
403 * +-----------------+
404 * fbno fend
405 *
406 * No unbusy region in extent, return failure.
407 */
408 if (fend <= bend)
409 goto fail;
410
411 /*
412 * Case 5:
413 * bbno bend
414 * +BBBBBBBBBBBBBBBBB+
415 * +----------------------+
416 * fbno fend
417 *
418 * Case 6:
419 * bbno bend
420 * +BBBBBBBBBBBBBBBBB+
421 * +--------------------------+
422 * fbno fend
423 *
424 * Needs to be trimmed to:
425 * +-------+
426 * fbno fend
427 */
428 fbno = bend;
429 } else if (bend >= fend) {
430 /* end overlap */
431
432 /*
433 * Case 7:
434 * bbno bend
435 * +BBBBBBBBBBBBBBBBB+
436 * +------------------+
437 * fbno fend
438 *
439 * Case 8:
440 * bbno bend
441 * +BBBBBBBBBBBBBBBBB+
442 * +--------------------------+
443 * fbno fend
444 *
445 * Needs to be trimmed to:
446 * +-------+
447 * fbno fend
448 */
449 fend = bbno;
450 } else {
451 /* middle overlap */
452
453 /*
454 * Case 9:
455 * bbno bend
456 * +BBBBBBBBBBBBBBBBB+
457 * +-----------------------------------+
458 * fbno fend
459 *
460 * Can be trimmed to:
461 * +-------+ OR +-------+
462 * fbno fend fbno fend
463 *
464 * Backward allocation leads to significant
465 * fragmentation of directories, which degrades
466 * directory performance, therefore we always want to
467 * choose the option that produces forward allocation
468 * patterns.
469 * Preferring the lower bno extent will make the next
470 * request use "fend" as the start of the next
471 * allocation; if the segment is no longer busy at
472 * that point, we'll get a contiguous allocation, but
473 * even if it is still busy, we will get a forward
474 * allocation.
475 * We try to avoid choosing the segment at "bend",
476 * because that can lead to the next allocation
477 * taking the segment at "fbno", which would be a
478 * backward allocation. We only use the segment at
479 * "fbno" if it is much larger than the current
480 * requested size, because in that case there's a
481 * good chance subsequent allocations will be
482 * contiguous.
483 */
484 if (bbno - fbno >= args->maxlen) {
485 /* left candidate fits perfect */
486 fend = bbno;
487 } else if (fend - bend >= args->maxlen * 4) {
488 /* right candidate has enough free space */
489 fbno = bend;
490 } else if (bbno - fbno >= args->minlen) {
491 /* left candidate fits minimum requirement */
492 fend = bbno;
493 } else {
494 goto fail;
495 }
496 }
497
498 flen = fend - fbno;
499 }
500 out:
501
502 if (fbno != *bno || flen != *len) {
503 trace_xfs_extent_busy_trim(args->mp, args->agno, *bno, *len,
504 fbno, flen);
505 *bno = fbno;
506 *len = flen;
507 *busy_gen = args->pag->pagb_gen;
508 ret = true;
509 }
510 spin_unlock(&args->pag->pagb_lock);
511 return ret;
512 fail:
513 /*
514 * Return a zero extent length as failure indications. All callers
515 * re-check if the trimmed extent satisfies the minlen requirement.
516 */
517 flen = 0;
518 goto out;
519 }
520
521 static bool
522 xfs_extent_busy_clear_one(
523 struct xfs_perag *pag,
524 struct xfs_extent_busy *busyp,
525 bool do_discard)
526 {
527 if (busyp->length) {
528 if (do_discard &&
529 !(busyp->flags & XFS_EXTENT_BUSY_SKIP_DISCARD)) {
530 busyp->flags = XFS_EXTENT_BUSY_DISCARDED;
531 return false;
532 }
533 trace_xfs_extent_busy_clear(pag->pag_mount, busyp->agno,
534 busyp->bno, busyp->length);
535 rb_erase(&busyp->rb_node, &pag->pagb_tree);
536 }
537
538 list_del_init(&busyp->list);
539 kfree(busyp);
540 return true;
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
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, *next;
555
556 busyp = list_first_entry_or_null(list, typeof(*busyp), list);
557 if (!busyp)
558 return;
559
560 do {
561 bool wakeup = false;
562 struct xfs_perag *pag;
563
564 pag = xfs_perag_get(mp, busyp->agno);
565 spin_lock(&pag->pagb_lock);
566 do {
567 next = list_next_entry(busyp, list);
568 if (xfs_extent_busy_clear_one(pag, busyp, do_discard))
569 wakeup = true;
570 busyp = next;
571 } while (!list_entry_is_head(busyp, list, list) &&
572 busyp->agno == pag->pag_agno);
573
574 if (wakeup) {
575 pag->pagb_gen++;
576 wake_up_all(&pag->pagb_wait);
577 }
578 spin_unlock(&pag->pagb_lock);
579 xfs_perag_put(pag);
580 } while (!list_entry_is_head(busyp, list, list));
581 }
582
583 /*
584 * Flush out all busy extents for this AG.
585 *
586 * If the current transaction is holding busy extents, the caller may not want
587 * to wait for committed busy extents to resolve. If we are being told just to
588 * try a flush or progress has been made since we last skipped a busy extent,
589 * return immediately to allow the caller to try again.
590 *
591 * If we are freeing extents, we might actually be holding the only free extents
592 * in the transaction busy list and the log force won't resolve that situation.
593 * In this case, we must return -EAGAIN to avoid a deadlock by informing the
594 * caller it needs to commit the busy extents it holds before retrying the
595 * extent free operation.
596 */
597 int
598 xfs_extent_busy_flush(
599 struct xfs_trans *tp,
600 struct xfs_perag *pag,
601 unsigned busy_gen,
602 uint32_t alloc_flags)
603 {
604 DEFINE_WAIT (wait);
605 int error;
606
607 error = xfs_log_force(tp->t_mountp, XFS_LOG_SYNC);
608 if (error)
609 return error;
610
611 /* Avoid deadlocks on uncommitted busy extents. */
612 if (!list_empty(&tp->t_busy)) {
613 if (alloc_flags & XFS_ALLOC_FLAG_TRYFLUSH)
614 return 0;
615
616 if (busy_gen != READ_ONCE(pag->pagb_gen))
617 return 0;
618
619 if (alloc_flags & XFS_ALLOC_FLAG_FREEING)
620 return -EAGAIN;
621 }
622
623 /* Wait for committed busy extents to resolve. */
624 do {
625 prepare_to_wait(&pag->pagb_wait, &wait, TASK_KILLABLE);
626 if (busy_gen != READ_ONCE(pag->pagb_gen))
627 break;
628 schedule();
629 } while (1);
630
631 finish_wait(&pag->pagb_wait, &wait);
632 return 0;
633 }
634
635 void
636 xfs_extent_busy_wait_all(
637 struct xfs_mount *mp)
638 {
639 struct xfs_perag *pag;
640 DEFINE_WAIT (wait);
641 xfs_agnumber_t agno;
642
643 for_each_perag(mp, agno, pag) {
644 do {
645 prepare_to_wait(&pag->pagb_wait, &wait, TASK_KILLABLE);
646 if (RB_EMPTY_ROOT(&pag->pagb_tree))
647 break;
648 schedule();
649 } while (1);
650 finish_wait(&pag->pagb_wait, &wait);
651 }
652 }
653
654 /*
655 * Callback for list_sort to sort busy extents by the AG they reside in.
656 */
657 int
658 xfs_extent_busy_ag_cmp(
659 void *priv,
660 const struct list_head *l1,
661 const struct list_head *l2)
662 {
663 struct xfs_extent_busy *b1 =
664 container_of(l1, struct xfs_extent_busy, list);
665 struct xfs_extent_busy *b2 =
666 container_of(l2, struct xfs_extent_busy, list);
667 s32 diff;
668
669 diff = b1->agno - b2->agno;
670 if (!diff)
671 diff = b1->bno - b2->bno;
672 return diff;
673 }
674
675 /* Are there any busy extents in this AG? */
676 bool
677 xfs_extent_busy_list_empty(
678 struct xfs_perag *pag)
679 {
680 bool res;
681
682 spin_lock(&pag->pagb_lock);
683 res = RB_EMPTY_ROOT(&pag->pagb_tree);
684 spin_unlock(&pag->pagb_lock);
685 return res;
686 }
687
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.