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1/*
2 * Copyright (C) 2016 Oracle. All Rights Reserved.
3 *
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version 2
9 * of the License, or (at your option) any later version.
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_shared.h"
23#include "xfs_format.h"
24#include "xfs_log_format.h"
25#include "xfs_trans_resv.h"
26#include "xfs_sb.h"
27#include "xfs_mount.h"
28#include "xfs_defer.h"
29#include "xfs_btree.h"
30#include "xfs_bmap.h"
31#include "xfs_refcount_btree.h"
32#include "xfs_alloc.h"
33#include "xfs_errortag.h"
34#include "xfs_error.h"
35#include "xfs_trace.h"
36#include "xfs_cksum.h"
37#include "xfs_trans.h"
38#include "xfs_bit.h"
39#include "xfs_refcount.h"
40#include "xfs_rmap.h"
41
42/* Allowable refcount adjustment amounts. */
43enum xfs_refc_adjust_op {
44 XFS_REFCOUNT_ADJUST_INCREASE = 1,
45 XFS_REFCOUNT_ADJUST_DECREASE = -1,
46 XFS_REFCOUNT_ADJUST_COW_ALLOC = 0,
47 XFS_REFCOUNT_ADJUST_COW_FREE = -1,
48};
49
50STATIC int __xfs_refcount_cow_alloc(struct xfs_btree_cur *rcur,
51 xfs_agblock_t agbno, xfs_extlen_t aglen,
52 struct xfs_defer_ops *dfops);
53STATIC int __xfs_refcount_cow_free(struct xfs_btree_cur *rcur,
54 xfs_agblock_t agbno, xfs_extlen_t aglen,
55 struct xfs_defer_ops *dfops);
56
57/*
58 * Look up the first record less than or equal to [bno, len] in the btree
59 * given by cur.
60 */
61int
62xfs_refcount_lookup_le(
63 struct xfs_btree_cur *cur,
64 xfs_agblock_t bno,
65 int *stat)
66{
67 trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_private.a.agno, bno,
68 XFS_LOOKUP_LE);
69 cur->bc_rec.rc.rc_startblock = bno;
70 cur->bc_rec.rc.rc_blockcount = 0;
71 return xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
72}
73
74/*
75 * Look up the first record greater than or equal to [bno, len] in the btree
76 * given by cur.
77 */
78int
79xfs_refcount_lookup_ge(
80 struct xfs_btree_cur *cur,
81 xfs_agblock_t bno,
82 int *stat)
83{
84 trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_private.a.agno, bno,
85 XFS_LOOKUP_GE);
86 cur->bc_rec.rc.rc_startblock = bno;
87 cur->bc_rec.rc.rc_blockcount = 0;
88 return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
89}
90
91/* Convert on-disk record to in-core format. */
92static inline void
93xfs_refcount_btrec_to_irec(
94 union xfs_btree_rec *rec,
95 struct xfs_refcount_irec *irec)
96{
97 irec->rc_startblock = be32_to_cpu(rec->refc.rc_startblock);
98 irec->rc_blockcount = be32_to_cpu(rec->refc.rc_blockcount);
99 irec->rc_refcount = be32_to_cpu(rec->refc.rc_refcount);
100}
101
102/*
103 * Get the data from the pointed-to record.
104 */
105int
106xfs_refcount_get_rec(
107 struct xfs_btree_cur *cur,
108 struct xfs_refcount_irec *irec,
109 int *stat)
110{
111 union xfs_btree_rec *rec;
112 int error;
113
114 error = xfs_btree_get_rec(cur, &rec, stat);
115 if (!error && *stat == 1) {
116 xfs_refcount_btrec_to_irec(rec, irec);
117 trace_xfs_refcount_get(cur->bc_mp, cur->bc_private.a.agno,
118 irec);
119 }
120 return error;
121}
122
123/*
124 * Update the record referred to by cur to the value given
125 * by [bno, len, refcount].
126 * This either works (return 0) or gets an EFSCORRUPTED error.
127 */
128STATIC int
129xfs_refcount_update(
130 struct xfs_btree_cur *cur,
131 struct xfs_refcount_irec *irec)
132{
133 union xfs_btree_rec rec;
134 int error;
135
136 trace_xfs_refcount_update(cur->bc_mp, cur->bc_private.a.agno, irec);
137 rec.refc.rc_startblock = cpu_to_be32(irec->rc_startblock);
138 rec.refc.rc_blockcount = cpu_to_be32(irec->rc_blockcount);
139 rec.refc.rc_refcount = cpu_to_be32(irec->rc_refcount);
140 error = xfs_btree_update(cur, &rec);
141 if (error)
142 trace_xfs_refcount_update_error(cur->bc_mp,
143 cur->bc_private.a.agno, error, _RET_IP_);
144 return error;
145}
146
147/*
148 * Insert the record referred to by cur to the value given
149 * by [bno, len, refcount].
150 * This either works (return 0) or gets an EFSCORRUPTED error.
151 */
152STATIC int
153xfs_refcount_insert(
154 struct xfs_btree_cur *cur,
155 struct xfs_refcount_irec *irec,
156 int *i)
157{
158 int error;
159
160 trace_xfs_refcount_insert(cur->bc_mp, cur->bc_private.a.agno, irec);
161 cur->bc_rec.rc.rc_startblock = irec->rc_startblock;
162 cur->bc_rec.rc.rc_blockcount = irec->rc_blockcount;
163 cur->bc_rec.rc.rc_refcount = irec->rc_refcount;
164 error = xfs_btree_insert(cur, i);
165 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, *i == 1, out_error);
166out_error:
167 if (error)
168 trace_xfs_refcount_insert_error(cur->bc_mp,
169 cur->bc_private.a.agno, error, _RET_IP_);
170 return error;
171}
172
173/*
174 * Remove the record referred to by cur, then set the pointer to the spot
175 * where the record could be re-inserted, in case we want to increment or
176 * decrement the cursor.
177 * This either works (return 0) or gets an EFSCORRUPTED error.
178 */
179STATIC int
180xfs_refcount_delete(
181 struct xfs_btree_cur *cur,
182 int *i)
183{
184 struct xfs_refcount_irec irec;
185 int found_rec;
186 int error;
187
188 error = xfs_refcount_get_rec(cur, &irec, &found_rec);
189 if (error)
190 goto out_error;
191 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
192 trace_xfs_refcount_delete(cur->bc_mp, cur->bc_private.a.agno, &irec);
193 error = xfs_btree_delete(cur, i);
194 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, *i == 1, out_error);
195 if (error)
196 goto out_error;
197 error = xfs_refcount_lookup_ge(cur, irec.rc_startblock, &found_rec);
198out_error:
199 if (error)
200 trace_xfs_refcount_delete_error(cur->bc_mp,
201 cur->bc_private.a.agno, error, _RET_IP_);
202 return error;
203}
204
205/*
206 * Adjusting the Reference Count
207 *
208 * As stated elsewhere, the reference count btree (refcbt) stores
209 * >1 reference counts for extents of physical blocks. In this
210 * operation, we're either raising or lowering the reference count of
211 * some subrange stored in the tree:
212 *
213 * <------ adjustment range ------>
214 * ----+ +---+-----+ +--+--------+---------
215 * 2 | | 3 | 4 | |17| 55 | 10
216 * ----+ +---+-----+ +--+--------+---------
217 * X axis is physical blocks number;
218 * reference counts are the numbers inside the rectangles
219 *
220 * The first thing we need to do is to ensure that there are no
221 * refcount extents crossing either boundary of the range to be
222 * adjusted. For any extent that does cross a boundary, split it into
223 * two extents so that we can increment the refcount of one of the
224 * pieces later:
225 *
226 * <------ adjustment range ------>
227 * ----+ +---+-----+ +--+--------+----+----
228 * 2 | | 3 | 2 | |17| 55 | 10 | 10
229 * ----+ +---+-----+ +--+--------+----+----
230 *
231 * For this next step, let's assume that all the physical blocks in
232 * the adjustment range are mapped to a file and are therefore in use
233 * at least once. Therefore, we can infer that any gap in the
234 * refcount tree within the adjustment range represents a physical
235 * extent with refcount == 1:
236 *
237 * <------ adjustment range ------>
238 * ----+---+---+-----+-+--+--------+----+----
239 * 2 |"1"| 3 | 2 |1|17| 55 | 10 | 10
240 * ----+---+---+-----+-+--+--------+----+----
241 * ^
242 *
243 * For each extent that falls within the interval range, figure out
244 * which extent is to the left or the right of that extent. Now we
245 * have a left, current, and right extent. If the new reference count
246 * of the center extent enables us to merge left, center, and right
247 * into one record covering all three, do so. If the center extent is
248 * at the left end of the range, abuts the left extent, and its new
249 * reference count matches the left extent's record, then merge them.
250 * If the center extent is at the right end of the range, abuts the
251 * right extent, and the reference counts match, merge those. In the
252 * example, we can left merge (assuming an increment operation):
253 *
254 * <------ adjustment range ------>
255 * --------+---+-----+-+--+--------+----+----
256 * 2 | 3 | 2 |1|17| 55 | 10 | 10
257 * --------+---+-----+-+--+--------+----+----
258 * ^
259 *
260 * For all other extents within the range, adjust the reference count
261 * or delete it if the refcount falls below 2. If we were
262 * incrementing, the end result looks like this:
263 *
264 * <------ adjustment range ------>
265 * --------+---+-----+-+--+--------+----+----
266 * 2 | 4 | 3 |2|18| 56 | 11 | 10
267 * --------+---+-----+-+--+--------+----+----
268 *
269 * The result of a decrement operation looks as such:
270 *
271 * <------ adjustment range ------>
272 * ----+ +---+ +--+--------+----+----
273 * 2 | | 2 | |16| 54 | 9 | 10
274 * ----+ +---+ +--+--------+----+----
275 * DDDD 111111DD
276 *
277 * The blocks marked "D" are freed; the blocks marked "1" are only
278 * referenced once and therefore the record is removed from the
279 * refcount btree.
280 */
281
282/* Next block after this extent. */
283static inline xfs_agblock_t
284xfs_refc_next(
285 struct xfs_refcount_irec *rc)
286{
287 return rc->rc_startblock + rc->rc_blockcount;
288}
289
290/*
291 * Split a refcount extent that crosses agbno.
292 */
293STATIC int
294xfs_refcount_split_extent(
295 struct xfs_btree_cur *cur,
296 xfs_agblock_t agbno,
297 bool *shape_changed)
298{
299 struct xfs_refcount_irec rcext, tmp;
300 int found_rec;
301 int error;
302
303 *shape_changed = false;
304 error = xfs_refcount_lookup_le(cur, agbno, &found_rec);
305 if (error)
306 goto out_error;
307 if (!found_rec)
308 return 0;
309
310 error = xfs_refcount_get_rec(cur, &rcext, &found_rec);
311 if (error)
312 goto out_error;
313 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
314 if (rcext.rc_startblock == agbno || xfs_refc_next(&rcext) <= agbno)
315 return 0;
316
317 *shape_changed = true;
318 trace_xfs_refcount_split_extent(cur->bc_mp, cur->bc_private.a.agno,
319 &rcext, agbno);
320
321 /* Establish the right extent. */
322 tmp = rcext;
323 tmp.rc_startblock = agbno;
324 tmp.rc_blockcount -= (agbno - rcext.rc_startblock);
325 error = xfs_refcount_update(cur, &tmp);
326 if (error)
327 goto out_error;
328
329 /* Insert the left extent. */
330 tmp = rcext;
331 tmp.rc_blockcount = agbno - rcext.rc_startblock;
332 error = xfs_refcount_insert(cur, &tmp, &found_rec);
333 if (error)
334 goto out_error;
335 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
336 return error;
337
338out_error:
339 trace_xfs_refcount_split_extent_error(cur->bc_mp,
340 cur->bc_private.a.agno, error, _RET_IP_);
341 return error;
342}
343
344/*
345 * Merge the left, center, and right extents.
346 */
347STATIC int
348xfs_refcount_merge_center_extents(
349 struct xfs_btree_cur *cur,
350 struct xfs_refcount_irec *left,
351 struct xfs_refcount_irec *center,
352 struct xfs_refcount_irec *right,
353 unsigned long long extlen,
354 xfs_extlen_t *aglen)
355{
356 int error;
357 int found_rec;
358
359 trace_xfs_refcount_merge_center_extents(cur->bc_mp,
360 cur->bc_private.a.agno, left, center, right);
361
362 /*
363 * Make sure the center and right extents are not in the btree.
364 * If the center extent was synthesized, the first delete call
365 * removes the right extent and we skip the second deletion.
366 * If center and right were in the btree, then the first delete
367 * call removes the center and the second one removes the right
368 * extent.
369 */
370 error = xfs_refcount_lookup_ge(cur, center->rc_startblock,
371 &found_rec);
372 if (error)
373 goto out_error;
374 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
375
376 error = xfs_refcount_delete(cur, &found_rec);
377 if (error)
378 goto out_error;
379 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
380
381 if (center->rc_refcount > 1) {
382 error = xfs_refcount_delete(cur, &found_rec);
383 if (error)
384 goto out_error;
385 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
386 out_error);
387 }
388
389 /* Enlarge the left extent. */
390 error = xfs_refcount_lookup_le(cur, left->rc_startblock,
391 &found_rec);
392 if (error)
393 goto out_error;
394 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
395
396 left->rc_blockcount = extlen;
397 error = xfs_refcount_update(cur, left);
398 if (error)
399 goto out_error;
400
401 *aglen = 0;
402 return error;
403
404out_error:
405 trace_xfs_refcount_merge_center_extents_error(cur->bc_mp,
406 cur->bc_private.a.agno, error, _RET_IP_);
407 return error;
408}
409
410/*
411 * Merge with the left extent.
412 */
413STATIC int
414xfs_refcount_merge_left_extent(
415 struct xfs_btree_cur *cur,
416 struct xfs_refcount_irec *left,
417 struct xfs_refcount_irec *cleft,
418 xfs_agblock_t *agbno,
419 xfs_extlen_t *aglen)
420{
421 int error;
422 int found_rec;
423
424 trace_xfs_refcount_merge_left_extent(cur->bc_mp,
425 cur->bc_private.a.agno, left, cleft);
426
427 /* If the extent at agbno (cleft) wasn't synthesized, remove it. */
428 if (cleft->rc_refcount > 1) {
429 error = xfs_refcount_lookup_le(cur, cleft->rc_startblock,
430 &found_rec);
431 if (error)
432 goto out_error;
433 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
434 out_error);
435
436 error = xfs_refcount_delete(cur, &found_rec);
437 if (error)
438 goto out_error;
439 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
440 out_error);
441 }
442
443 /* Enlarge the left extent. */
444 error = xfs_refcount_lookup_le(cur, left->rc_startblock,
445 &found_rec);
446 if (error)
447 goto out_error;
448 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
449
450 left->rc_blockcount += cleft->rc_blockcount;
451 error = xfs_refcount_update(cur, left);
452 if (error)
453 goto out_error;
454
455 *agbno += cleft->rc_blockcount;
456 *aglen -= cleft->rc_blockcount;
457 return error;
458
459out_error:
460 trace_xfs_refcount_merge_left_extent_error(cur->bc_mp,
461 cur->bc_private.a.agno, error, _RET_IP_);
462 return error;
463}
464
465/*
466 * Merge with the right extent.
467 */
468STATIC int
469xfs_refcount_merge_right_extent(
470 struct xfs_btree_cur *cur,
471 struct xfs_refcount_irec *right,
472 struct xfs_refcount_irec *cright,
473 xfs_extlen_t *aglen)
474{
475 int error;
476 int found_rec;
477
478 trace_xfs_refcount_merge_right_extent(cur->bc_mp,
479 cur->bc_private.a.agno, cright, right);
480
481 /*
482 * If the extent ending at agbno+aglen (cright) wasn't synthesized,
483 * remove it.
484 */
485 if (cright->rc_refcount > 1) {
486 error = xfs_refcount_lookup_le(cur, cright->rc_startblock,
487 &found_rec);
488 if (error)
489 goto out_error;
490 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
491 out_error);
492
493 error = xfs_refcount_delete(cur, &found_rec);
494 if (error)
495 goto out_error;
496 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
497 out_error);
498 }
499
500 /* Enlarge the right extent. */
501 error = xfs_refcount_lookup_le(cur, right->rc_startblock,
502 &found_rec);
503 if (error)
504 goto out_error;
505 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
506
507 right->rc_startblock -= cright->rc_blockcount;
508 right->rc_blockcount += cright->rc_blockcount;
509 error = xfs_refcount_update(cur, right);
510 if (error)
511 goto out_error;
512
513 *aglen -= cright->rc_blockcount;
514 return error;
515
516out_error:
517 trace_xfs_refcount_merge_right_extent_error(cur->bc_mp,
518 cur->bc_private.a.agno, error, _RET_IP_);
519 return error;
520}
521
522#define XFS_FIND_RCEXT_SHARED 1
523#define XFS_FIND_RCEXT_COW 2
524/*
525 * Find the left extent and the one after it (cleft). This function assumes
526 * that we've already split any extent crossing agbno.
527 */
528STATIC int
529xfs_refcount_find_left_extents(
530 struct xfs_btree_cur *cur,
531 struct xfs_refcount_irec *left,
532 struct xfs_refcount_irec *cleft,
533 xfs_agblock_t agbno,
534 xfs_extlen_t aglen,
535 int flags)
536{
537 struct xfs_refcount_irec tmp;
538 int error;
539 int found_rec;
540
541 left->rc_startblock = cleft->rc_startblock = NULLAGBLOCK;
542 error = xfs_refcount_lookup_le(cur, agbno - 1, &found_rec);
543 if (error)
544 goto out_error;
545 if (!found_rec)
546 return 0;
547
548 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
549 if (error)
550 goto out_error;
551 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
552
553 if (xfs_refc_next(&tmp) != agbno)
554 return 0;
555 if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
556 return 0;
557 if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
558 return 0;
559 /* We have a left extent; retrieve (or invent) the next right one */
560 *left = tmp;
561
562 error = xfs_btree_increment(cur, 0, &found_rec);
563 if (error)
564 goto out_error;
565 if (found_rec) {
566 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
567 if (error)
568 goto out_error;
569 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
570 out_error);
571
572 /* if tmp starts at the end of our range, just use that */
573 if (tmp.rc_startblock == agbno)
574 *cleft = tmp;
575 else {
576 /*
577 * There's a gap in the refcntbt at the start of the
578 * range we're interested in (refcount == 1) so
579 * synthesize the implied extent and pass it back.
580 * We assume here that the agbno/aglen range was
581 * passed in from a data fork extent mapping and
582 * therefore is allocated to exactly one owner.
583 */
584 cleft->rc_startblock = agbno;
585 cleft->rc_blockcount = min(aglen,
586 tmp.rc_startblock - agbno);
587 cleft->rc_refcount = 1;
588 }
589 } else {
590 /*
591 * No extents, so pretend that there's one covering the whole
592 * range.
593 */
594 cleft->rc_startblock = agbno;
595 cleft->rc_blockcount = aglen;
596 cleft->rc_refcount = 1;
597 }
598 trace_xfs_refcount_find_left_extent(cur->bc_mp, cur->bc_private.a.agno,
599 left, cleft, agbno);
600 return error;
601
602out_error:
603 trace_xfs_refcount_find_left_extent_error(cur->bc_mp,
604 cur->bc_private.a.agno, error, _RET_IP_);
605 return error;
606}
607
608/*
609 * Find the right extent and the one before it (cright). This function
610 * assumes that we've already split any extents crossing agbno + aglen.
611 */
612STATIC int
613xfs_refcount_find_right_extents(
614 struct xfs_btree_cur *cur,
615 struct xfs_refcount_irec *right,
616 struct xfs_refcount_irec *cright,
617 xfs_agblock_t agbno,
618 xfs_extlen_t aglen,
619 int flags)
620{
621 struct xfs_refcount_irec tmp;
622 int error;
623 int found_rec;
624
625 right->rc_startblock = cright->rc_startblock = NULLAGBLOCK;
626 error = xfs_refcount_lookup_ge(cur, agbno + aglen, &found_rec);
627 if (error)
628 goto out_error;
629 if (!found_rec)
630 return 0;
631
632 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
633 if (error)
634 goto out_error;
635 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1, out_error);
636
637 if (tmp.rc_startblock != agbno + aglen)
638 return 0;
639 if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
640 return 0;
641 if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
642 return 0;
643 /* We have a right extent; retrieve (or invent) the next left one */
644 *right = tmp;
645
646 error = xfs_btree_decrement(cur, 0, &found_rec);
647 if (error)
648 goto out_error;
649 if (found_rec) {
650 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
651 if (error)
652 goto out_error;
653 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, found_rec == 1,
654 out_error);
655
656 /* if tmp ends at the end of our range, just use that */
657 if (xfs_refc_next(&tmp) == agbno + aglen)
658 *cright = tmp;
659 else {
660 /*
661 * There's a gap in the refcntbt at the end of the
662 * range we're interested in (refcount == 1) so
663 * create the implied extent and pass it back.
664 * We assume here that the agbno/aglen range was
665 * passed in from a data fork extent mapping and
666 * therefore is allocated to exactly one owner.
667 */
668 cright->rc_startblock = max(agbno, xfs_refc_next(&tmp));
669 cright->rc_blockcount = right->rc_startblock -
670 cright->rc_startblock;
671 cright->rc_refcount = 1;
672 }
673 } else {
674 /*
675 * No extents, so pretend that there's one covering the whole
676 * range.
677 */
678 cright->rc_startblock = agbno;
679 cright->rc_blockcount = aglen;
680 cright->rc_refcount = 1;
681 }
682 trace_xfs_refcount_find_right_extent(cur->bc_mp, cur->bc_private.a.agno,
683 cright, right, agbno + aglen);
684 return error;
685
686out_error:
687 trace_xfs_refcount_find_right_extent_error(cur->bc_mp,
688 cur->bc_private.a.agno, error, _RET_IP_);
689 return error;
690}
691
692/* Is this extent valid? */
693static inline bool
694xfs_refc_valid(
695 struct xfs_refcount_irec *rc)
696{
697 return rc->rc_startblock != NULLAGBLOCK;
698}
699
700/*
701 * Try to merge with any extents on the boundaries of the adjustment range.
702 */
703STATIC int
704xfs_refcount_merge_extents(
705 struct xfs_btree_cur *cur,
706 xfs_agblock_t *agbno,
707 xfs_extlen_t *aglen,
708 enum xfs_refc_adjust_op adjust,
709 int flags,
710 bool *shape_changed)
711{
712 struct xfs_refcount_irec left = {0}, cleft = {0};
713 struct xfs_refcount_irec cright = {0}, right = {0};
714 int error;
715 unsigned long long ulen;
716 bool cequal;
717
718 *shape_changed = false;
719 /*
720 * Find the extent just below agbno [left], just above agbno [cleft],
721 * just below (agbno + aglen) [cright], and just above (agbno + aglen)
722 * [right].
723 */
724 error = xfs_refcount_find_left_extents(cur, &left, &cleft, *agbno,
725 *aglen, flags);
726 if (error)
727 return error;
728 error = xfs_refcount_find_right_extents(cur, &right, &cright, *agbno,
729 *aglen, flags);
730 if (error)
731 return error;
732
733 /* No left or right extent to merge; exit. */
734 if (!xfs_refc_valid(&left) && !xfs_refc_valid(&right))
735 return 0;
736
737 cequal = (cleft.rc_startblock == cright.rc_startblock) &&
738 (cleft.rc_blockcount == cright.rc_blockcount);
739
740 /* Try to merge left, cleft, and right. cleft must == cright. */
741 ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount +
742 right.rc_blockcount;
743 if (xfs_refc_valid(&left) && xfs_refc_valid(&right) &&
744 xfs_refc_valid(&cleft) && xfs_refc_valid(&cright) && cequal &&
745 left.rc_refcount == cleft.rc_refcount + adjust &&
746 right.rc_refcount == cleft.rc_refcount + adjust &&
747 ulen < MAXREFCEXTLEN) {
748 *shape_changed = true;
749 return xfs_refcount_merge_center_extents(cur, &left, &cleft,
750 &right, ulen, aglen);
751 }
752
753 /* Try to merge left and cleft. */
754 ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount;
755 if (xfs_refc_valid(&left) && xfs_refc_valid(&cleft) &&
756 left.rc_refcount == cleft.rc_refcount + adjust &&
757 ulen < MAXREFCEXTLEN) {
758 *shape_changed = true;
759 error = xfs_refcount_merge_left_extent(cur, &left, &cleft,
760 agbno, aglen);
761 if (error)
762 return error;
763
764 /*
765 * If we just merged left + cleft and cleft == cright,
766 * we no longer have a cright to merge with right. We're done.
767 */
768 if (cequal)
769 return 0;
770 }
771
772 /* Try to merge cright and right. */
773 ulen = (unsigned long long)right.rc_blockcount + cright.rc_blockcount;
774 if (xfs_refc_valid(&right) && xfs_refc_valid(&cright) &&
775 right.rc_refcount == cright.rc_refcount + adjust &&
776 ulen < MAXREFCEXTLEN) {
777 *shape_changed = true;
778 return xfs_refcount_merge_right_extent(cur, &right, &cright,
779 aglen);
780 }
781
782 return error;
783}
784
785/*
786 * XXX: This is a pretty hand-wavy estimate. The penalty for guessing
787 * true incorrectly is a shutdown FS; the penalty for guessing false
788 * incorrectly is more transaction rolls than might be necessary.
789 * Be conservative here.
790 */
791static bool
792xfs_refcount_still_have_space(
793 struct xfs_btree_cur *cur)
794{
795 unsigned long overhead;
796
797 overhead = cur->bc_private.a.priv.refc.shape_changes *
798 xfs_allocfree_log_count(cur->bc_mp, 1);
799 overhead *= cur->bc_mp->m_sb.sb_blocksize;
800
801 /*
802 * Only allow 2 refcount extent updates per transaction if the
803 * refcount continue update "error" has been injected.
804 */
805 if (cur->bc_private.a.priv.refc.nr_ops > 2 &&
806 XFS_TEST_ERROR(false, cur->bc_mp,
807 XFS_ERRTAG_REFCOUNT_CONTINUE_UPDATE))
808 return false;
809
810 if (cur->bc_private.a.priv.refc.nr_ops == 0)
811 return true;
812 else if (overhead > cur->bc_tp->t_log_res)
813 return false;
814 return cur->bc_tp->t_log_res - overhead >
815 cur->bc_private.a.priv.refc.nr_ops * XFS_REFCOUNT_ITEM_OVERHEAD;
816}
817
818/*
819 * Adjust the refcounts of middle extents. At this point we should have
820 * split extents that crossed the adjustment range; merged with adjacent
821 * extents; and updated agbno/aglen to reflect the merges. Therefore,
822 * all we have to do is update the extents inside [agbno, agbno + aglen].
823 */
824STATIC int
825xfs_refcount_adjust_extents(
826 struct xfs_btree_cur *cur,
827 xfs_agblock_t *agbno,
828 xfs_extlen_t *aglen,
829 enum xfs_refc_adjust_op adj,
830 struct xfs_defer_ops *dfops,
831 struct xfs_owner_info *oinfo)
832{
833 struct xfs_refcount_irec ext, tmp;
834 int error;
835 int found_rec, found_tmp;
836 xfs_fsblock_t fsbno;
837
838 /* Merging did all the work already. */
839 if (*aglen == 0)
840 return 0;
841
842 error = xfs_refcount_lookup_ge(cur, *agbno, &found_rec);
843 if (error)
844 goto out_error;
845
846 while (*aglen > 0 && xfs_refcount_still_have_space(cur)) {
847 error = xfs_refcount_get_rec(cur, &ext, &found_rec);
848 if (error)
849 goto out_error;
850 if (!found_rec) {
851 ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks;
852 ext.rc_blockcount = 0;
853 ext.rc_refcount = 0;
854 }
855
856 /*
857 * Deal with a hole in the refcount tree; if a file maps to
858 * these blocks and there's no refcountbt record, pretend that
859 * there is one with refcount == 1.
860 */
861 if (ext.rc_startblock != *agbno) {
862 tmp.rc_startblock = *agbno;
863 tmp.rc_blockcount = min(*aglen,
864 ext.rc_startblock - *agbno);
865 tmp.rc_refcount = 1 + adj;
866 trace_xfs_refcount_modify_extent(cur->bc_mp,
867 cur->bc_private.a.agno, &tmp);
868
869 /*
870 * Either cover the hole (increment) or
871 * delete the range (decrement).
872 */
873 if (tmp.rc_refcount) {
874 error = xfs_refcount_insert(cur, &tmp,
875 &found_tmp);
876 if (error)
877 goto out_error;
878 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
879 found_tmp == 1, out_error);
880 cur->bc_private.a.priv.refc.nr_ops++;
881 } else {
882 fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
883 cur->bc_private.a.agno,
884 tmp.rc_startblock);
885 xfs_bmap_add_free(cur->bc_mp, dfops, fsbno,
886 tmp.rc_blockcount, oinfo);
887 }
888
889 (*agbno) += tmp.rc_blockcount;
890 (*aglen) -= tmp.rc_blockcount;
891
892 error = xfs_refcount_lookup_ge(cur, *agbno,
893 &found_rec);
894 if (error)
895 goto out_error;
896 }
897
898 /* Stop if there's nothing left to modify */
899 if (*aglen == 0 || !xfs_refcount_still_have_space(cur))
900 break;
901
902 /*
903 * Adjust the reference count and either update the tree
904 * (incr) or free the blocks (decr).
905 */
906 if (ext.rc_refcount == MAXREFCOUNT)
907 goto skip;
908 ext.rc_refcount += adj;
909 trace_xfs_refcount_modify_extent(cur->bc_mp,
910 cur->bc_private.a.agno, &ext);
911 if (ext.rc_refcount > 1) {
912 error = xfs_refcount_update(cur, &ext);
913 if (error)
914 goto out_error;
915 cur->bc_private.a.priv.refc.nr_ops++;
916 } else if (ext.rc_refcount == 1) {
917 error = xfs_refcount_delete(cur, &found_rec);
918 if (error)
919 goto out_error;
920 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
921 found_rec == 1, out_error);
922 cur->bc_private.a.priv.refc.nr_ops++;
923 goto advloop;
924 } else {
925 fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
926 cur->bc_private.a.agno,
927 ext.rc_startblock);
928 xfs_bmap_add_free(cur->bc_mp, dfops, fsbno,
929 ext.rc_blockcount, oinfo);
930 }
931
932skip:
933 error = xfs_btree_increment(cur, 0, &found_rec);
934 if (error)
935 goto out_error;
936
937advloop:
938 (*agbno) += ext.rc_blockcount;
939 (*aglen) -= ext.rc_blockcount;
940 }
941
942 return error;
943out_error:
944 trace_xfs_refcount_modify_extent_error(cur->bc_mp,
945 cur->bc_private.a.agno, error, _RET_IP_);
946 return error;
947}
948
949/* Adjust the reference count of a range of AG blocks. */
950STATIC int
951xfs_refcount_adjust(
952 struct xfs_btree_cur *cur,
953 xfs_agblock_t agbno,
954 xfs_extlen_t aglen,
955 xfs_agblock_t *new_agbno,
956 xfs_extlen_t *new_aglen,
957 enum xfs_refc_adjust_op adj,
958 struct xfs_defer_ops *dfops,
959 struct xfs_owner_info *oinfo)
960{
961 bool shape_changed;
962 int shape_changes = 0;
963 int error;
964
965 *new_agbno = agbno;
966 *new_aglen = aglen;
967 if (adj == XFS_REFCOUNT_ADJUST_INCREASE)
968 trace_xfs_refcount_increase(cur->bc_mp, cur->bc_private.a.agno,
969 agbno, aglen);
970 else
971 trace_xfs_refcount_decrease(cur->bc_mp, cur->bc_private.a.agno,
972 agbno, aglen);
973
974 /*
975 * Ensure that no rcextents cross the boundary of the adjustment range.
976 */
977 error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
978 if (error)
979 goto out_error;
980 if (shape_changed)
981 shape_changes++;
982
983 error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
984 if (error)
985 goto out_error;
986 if (shape_changed)
987 shape_changes++;
988
989 /*
990 * Try to merge with the left or right extents of the range.
991 */
992 error = xfs_refcount_merge_extents(cur, new_agbno, new_aglen, adj,
993 XFS_FIND_RCEXT_SHARED, &shape_changed);
994 if (error)
995 goto out_error;
996 if (shape_changed)
997 shape_changes++;
998 if (shape_changes)
999 cur->bc_private.a.priv.refc.shape_changes++;
1000
1001 /* Now that we've taken care of the ends, adjust the middle extents */
1002 error = xfs_refcount_adjust_extents(cur, new_agbno, new_aglen,
1003 adj, dfops, oinfo);
1004 if (error)
1005 goto out_error;
1006
1007 return 0;
1008
1009out_error:
1010 trace_xfs_refcount_adjust_error(cur->bc_mp, cur->bc_private.a.agno,
1011 error, _RET_IP_);
1012 return error;
1013}
1014
1015/* Clean up after calling xfs_refcount_finish_one. */
1016void
1017xfs_refcount_finish_one_cleanup(
1018 struct xfs_trans *tp,
1019 struct xfs_btree_cur *rcur,
1020 int error)
1021{
1022 struct xfs_buf *agbp;
1023
1024 if (rcur == NULL)
1025 return;
1026 agbp = rcur->bc_private.a.agbp;
1027 xfs_btree_del_cursor(rcur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
1028 if (error)
1029 xfs_trans_brelse(tp, agbp);
1030}
1031
1032/*
1033 * Process one of the deferred refcount operations. We pass back the
1034 * btree cursor to maintain our lock on the btree between calls.
1035 * This saves time and eliminates a buffer deadlock between the
1036 * superblock and the AGF because we'll always grab them in the same
1037 * order.
1038 */
1039int
1040xfs_refcount_finish_one(
1041 struct xfs_trans *tp,
1042 struct xfs_defer_ops *dfops,
1043 enum xfs_refcount_intent_type type,
1044 xfs_fsblock_t startblock,
1045 xfs_extlen_t blockcount,
1046 xfs_fsblock_t *new_fsb,
1047 xfs_extlen_t *new_len,
1048 struct xfs_btree_cur **pcur)
1049{
1050 struct xfs_mount *mp = tp->t_mountp;
1051 struct xfs_btree_cur *rcur;
1052 struct xfs_buf *agbp = NULL;
1053 int error = 0;
1054 xfs_agnumber_t agno;
1055 xfs_agblock_t bno;
1056 xfs_agblock_t new_agbno;
1057 unsigned long nr_ops = 0;
1058 int shape_changes = 0;
1059
1060 agno = XFS_FSB_TO_AGNO(mp, startblock);
1061 ASSERT(agno != NULLAGNUMBER);
1062 bno = XFS_FSB_TO_AGBNO(mp, startblock);
1063
1064 trace_xfs_refcount_deferred(mp, XFS_FSB_TO_AGNO(mp, startblock),
1065 type, XFS_FSB_TO_AGBNO(mp, startblock),
1066 blockcount);
1067
1068 if (XFS_TEST_ERROR(false, mp,
1069 XFS_ERRTAG_REFCOUNT_FINISH_ONE))
1070 return -EIO;
1071
1072 /*
1073 * If we haven't gotten a cursor or the cursor AG doesn't match
1074 * the startblock, get one now.
1075 */
1076 rcur = *pcur;
1077 if (rcur != NULL && rcur->bc_private.a.agno != agno) {
1078 nr_ops = rcur->bc_private.a.priv.refc.nr_ops;
1079 shape_changes = rcur->bc_private.a.priv.refc.shape_changes;
1080 xfs_refcount_finish_one_cleanup(tp, rcur, 0);
1081 rcur = NULL;
1082 *pcur = NULL;
1083 }
1084 if (rcur == NULL) {
1085 error = xfs_alloc_read_agf(tp->t_mountp, tp, agno,
1086 XFS_ALLOC_FLAG_FREEING, &agbp);
1087 if (error)
1088 return error;
1089 if (!agbp)
1090 return -EFSCORRUPTED;
1091
1092 rcur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno, dfops);
1093 if (!rcur) {
1094 error = -ENOMEM;
1095 goto out_cur;
1096 }
1097 rcur->bc_private.a.priv.refc.nr_ops = nr_ops;
1098 rcur->bc_private.a.priv.refc.shape_changes = shape_changes;
1099 }
1100 *pcur = rcur;
1101
1102 switch (type) {
1103 case XFS_REFCOUNT_INCREASE:
1104 error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1105 new_len, XFS_REFCOUNT_ADJUST_INCREASE, dfops, NULL);
1106 *new_fsb = XFS_AGB_TO_FSB(mp, agno, new_agbno);
1107 break;
1108 case XFS_REFCOUNT_DECREASE:
1109 error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1110 new_len, XFS_REFCOUNT_ADJUST_DECREASE, dfops, NULL);
1111 *new_fsb = XFS_AGB_TO_FSB(mp, agno, new_agbno);
1112 break;
1113 case XFS_REFCOUNT_ALLOC_COW:
1114 *new_fsb = startblock + blockcount;
1115 *new_len = 0;
1116 error = __xfs_refcount_cow_alloc(rcur, bno, blockcount, dfops);
1117 break;
1118 case XFS_REFCOUNT_FREE_COW:
1119 *new_fsb = startblock + blockcount;
1120 *new_len = 0;
1121 error = __xfs_refcount_cow_free(rcur, bno, blockcount, dfops);
1122 break;
1123 default:
1124 ASSERT(0);
1125 error = -EFSCORRUPTED;
1126 }
1127 if (!error && *new_len > 0)
1128 trace_xfs_refcount_finish_one_leftover(mp, agno, type,
1129 bno, blockcount, new_agbno, *new_len);
1130 return error;
1131
1132out_cur:
1133 xfs_trans_brelse(tp, agbp);
1134
1135 return error;
1136}
1137
1138/*
1139 * Record a refcount intent for later processing.
1140 */
1141static int
1142__xfs_refcount_add(
1143 struct xfs_mount *mp,
1144 struct xfs_defer_ops *dfops,
1145 enum xfs_refcount_intent_type type,
1146 xfs_fsblock_t startblock,
1147 xfs_extlen_t blockcount)
1148{
1149 struct xfs_refcount_intent *ri;
1150
1151 trace_xfs_refcount_defer(mp, XFS_FSB_TO_AGNO(mp, startblock),
1152 type, XFS_FSB_TO_AGBNO(mp, startblock),
1153 blockcount);
1154
1155 ri = kmem_alloc(sizeof(struct xfs_refcount_intent),
1156 KM_SLEEP | KM_NOFS);
1157 INIT_LIST_HEAD(&ri->ri_list);
1158 ri->ri_type = type;
1159 ri->ri_startblock = startblock;
1160 ri->ri_blockcount = blockcount;
1161
1162 xfs_defer_add(dfops, XFS_DEFER_OPS_TYPE_REFCOUNT, &ri->ri_list);
1163 return 0;
1164}
1165
1166/*
1167 * Increase the reference count of the blocks backing a file's extent.
1168 */
1169int
1170xfs_refcount_increase_extent(
1171 struct xfs_mount *mp,
1172 struct xfs_defer_ops *dfops,
1173 struct xfs_bmbt_irec *PREV)
1174{
1175 if (!xfs_sb_version_hasreflink(&mp->m_sb))
1176 return 0;
1177
1178 return __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_INCREASE,
1179 PREV->br_startblock, PREV->br_blockcount);
1180}
1181
1182/*
1183 * Decrease the reference count of the blocks backing a file's extent.
1184 */
1185int
1186xfs_refcount_decrease_extent(
1187 struct xfs_mount *mp,
1188 struct xfs_defer_ops *dfops,
1189 struct xfs_bmbt_irec *PREV)
1190{
1191 if (!xfs_sb_version_hasreflink(&mp->m_sb))
1192 return 0;
1193
1194 return __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_DECREASE,
1195 PREV->br_startblock, PREV->br_blockcount);
1196}
1197
1198/*
1199 * Given an AG extent, find the lowest-numbered run of shared blocks
1200 * within that range and return the range in fbno/flen. If
1201 * find_end_of_shared is set, return the longest contiguous extent of
1202 * shared blocks; if not, just return the first extent we find. If no
1203 * shared blocks are found, fbno and flen will be set to NULLAGBLOCK
1204 * and 0, respectively.
1205 */
1206int
1207xfs_refcount_find_shared(
1208 struct xfs_btree_cur *cur,
1209 xfs_agblock_t agbno,
1210 xfs_extlen_t aglen,
1211 xfs_agblock_t *fbno,
1212 xfs_extlen_t *flen,
1213 bool find_end_of_shared)
1214{
1215 struct xfs_refcount_irec tmp;
1216 int i;
1217 int have;
1218 int error;
1219
1220 trace_xfs_refcount_find_shared(cur->bc_mp, cur->bc_private.a.agno,
1221 agbno, aglen);
1222
1223 /* By default, skip the whole range */
1224 *fbno = NULLAGBLOCK;
1225 *flen = 0;
1226
1227 /* Try to find a refcount extent that crosses the start */
1228 error = xfs_refcount_lookup_le(cur, agbno, &have);
1229 if (error)
1230 goto out_error;
1231 if (!have) {
1232 /* No left extent, look at the next one */
1233 error = xfs_btree_increment(cur, 0, &have);
1234 if (error)
1235 goto out_error;
1236 if (!have)
1237 goto done;
1238 }
1239 error = xfs_refcount_get_rec(cur, &tmp, &i);
1240 if (error)
1241 goto out_error;
1242 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);
1243
1244 /* If the extent ends before the start, look at the next one */
1245 if (tmp.rc_startblock + tmp.rc_blockcount <= agbno) {
1246 error = xfs_btree_increment(cur, 0, &have);
1247 if (error)
1248 goto out_error;
1249 if (!have)
1250 goto done;
1251 error = xfs_refcount_get_rec(cur, &tmp, &i);
1252 if (error)
1253 goto out_error;
1254 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);
1255 }
1256
1257 /* If the extent starts after the range we want, bail out */
1258 if (tmp.rc_startblock >= agbno + aglen)
1259 goto done;
1260
1261 /* We found the start of a shared extent! */
1262 if (tmp.rc_startblock < agbno) {
1263 tmp.rc_blockcount -= (agbno - tmp.rc_startblock);
1264 tmp.rc_startblock = agbno;
1265 }
1266
1267 *fbno = tmp.rc_startblock;
1268 *flen = min(tmp.rc_blockcount, agbno + aglen - *fbno);
1269 if (!find_end_of_shared)
1270 goto done;
1271
1272 /* Otherwise, find the end of this shared extent */
1273 while (*fbno + *flen < agbno + aglen) {
1274 error = xfs_btree_increment(cur, 0, &have);
1275 if (error)
1276 goto out_error;
1277 if (!have)
1278 break;
1279 error = xfs_refcount_get_rec(cur, &tmp, &i);
1280 if (error)
1281 goto out_error;
1282 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, out_error);
1283 if (tmp.rc_startblock >= agbno + aglen ||
1284 tmp.rc_startblock != *fbno + *flen)
1285 break;
1286 *flen = min(*flen + tmp.rc_blockcount, agbno + aglen - *fbno);
1287 }
1288
1289done:
1290 trace_xfs_refcount_find_shared_result(cur->bc_mp,
1291 cur->bc_private.a.agno, *fbno, *flen);
1292
1293out_error:
1294 if (error)
1295 trace_xfs_refcount_find_shared_error(cur->bc_mp,
1296 cur->bc_private.a.agno, error, _RET_IP_);
1297 return error;
1298}
1299
1300/*
1301 * Recovering CoW Blocks After a Crash
1302 *
1303 * Due to the way that the copy on write mechanism works, there's a window of
1304 * opportunity in which we can lose track of allocated blocks during a crash.
1305 * Because CoW uses delayed allocation in the in-core CoW fork, writeback
1306 * causes blocks to be allocated and stored in the CoW fork. The blocks are
1307 * no longer in the free space btree but are not otherwise recorded anywhere
1308 * until the write completes and the blocks are mapped into the file. A crash
1309 * in between allocation and remapping results in the replacement blocks being
1310 * lost. This situation is exacerbated by the CoW extent size hint because
1311 * allocations can hang around for long time.
1312 *
1313 * However, there is a place where we can record these allocations before they
1314 * become mappings -- the reference count btree. The btree does not record
1315 * extents with refcount == 1, so we can record allocations with a refcount of
1316 * 1. Blocks being used for CoW writeout cannot be shared, so there should be
1317 * no conflict with shared block records. These mappings should be created
1318 * when we allocate blocks to the CoW fork and deleted when they're removed
1319 * from the CoW fork.
1320 *
1321 * Minor nit: records for in-progress CoW allocations and records for shared
1322 * extents must never be merged, to preserve the property that (except for CoW
1323 * allocations) there are no refcount btree entries with refcount == 1. The
1324 * only time this could potentially happen is when unsharing a block that's
1325 * adjacent to CoW allocations, so we must be careful to avoid this.
1326 *
1327 * At mount time we recover lost CoW allocations by searching the refcount
1328 * btree for these refcount == 1 mappings. These represent CoW allocations
1329 * that were in progress at the time the filesystem went down, so we can free
1330 * them to get the space back.
1331 *
1332 * This mechanism is superior to creating EFIs for unmapped CoW extents for
1333 * several reasons -- first, EFIs pin the tail of the log and would have to be
1334 * periodically relogged to avoid filling up the log. Second, CoW completions
1335 * will have to file an EFD and create new EFIs for whatever remains in the
1336 * CoW fork; this partially takes care of (1) but extent-size reservations
1337 * will have to periodically relog even if there's no writeout in progress.
1338 * This can happen if the CoW extent size hint is set, which you really want.
1339 * Third, EFIs cannot currently be automatically relogged into newer
1340 * transactions to advance the log tail. Fourth, stuffing the log full of
1341 * EFIs places an upper bound on the number of CoW allocations that can be
1342 * held filesystem-wide at any given time. Recording them in the refcount
1343 * btree doesn't require us to maintain any state in memory and doesn't pin
1344 * the log.
1345 */
1346/*
1347 * Adjust the refcounts of CoW allocations. These allocations are "magic"
1348 * in that they're not referenced anywhere else in the filesystem, so we
1349 * stash them in the refcount btree with a refcount of 1 until either file
1350 * remapping (or CoW cancellation) happens.
1351 */
1352STATIC int
1353xfs_refcount_adjust_cow_extents(
1354 struct xfs_btree_cur *cur,
1355 xfs_agblock_t agbno,
1356 xfs_extlen_t aglen,
1357 enum xfs_refc_adjust_op adj)
1358{
1359 struct xfs_refcount_irec ext, tmp;
1360 int error;
1361 int found_rec, found_tmp;
1362
1363 if (aglen == 0)
1364 return 0;
1365
1366 /* Find any overlapping refcount records */
1367 error = xfs_refcount_lookup_ge(cur, agbno, &found_rec);
1368 if (error)
1369 goto out_error;
1370 error = xfs_refcount_get_rec(cur, &ext, &found_rec);
1371 if (error)
1372 goto out_error;
1373 if (!found_rec) {
1374 ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks +
1375 XFS_REFC_COW_START;
1376 ext.rc_blockcount = 0;
1377 ext.rc_refcount = 0;
1378 }
1379
1380 switch (adj) {
1381 case XFS_REFCOUNT_ADJUST_COW_ALLOC:
1382 /* Adding a CoW reservation, there should be nothing here. */
1383 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
1384 ext.rc_startblock >= agbno + aglen, out_error);
1385
1386 tmp.rc_startblock = agbno;
1387 tmp.rc_blockcount = aglen;
1388 tmp.rc_refcount = 1;
1389 trace_xfs_refcount_modify_extent(cur->bc_mp,
1390 cur->bc_private.a.agno, &tmp);
1391
1392 error = xfs_refcount_insert(cur, &tmp,
1393 &found_tmp);
1394 if (error)
1395 goto out_error;
1396 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
1397 found_tmp == 1, out_error);
1398 break;
1399 case XFS_REFCOUNT_ADJUST_COW_FREE:
1400 /* Removing a CoW reservation, there should be one extent. */
1401 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
1402 ext.rc_startblock == agbno, out_error);
1403 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
1404 ext.rc_blockcount == aglen, out_error);
1405 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
1406 ext.rc_refcount == 1, out_error);
1407
1408 ext.rc_refcount = 0;
1409 trace_xfs_refcount_modify_extent(cur->bc_mp,
1410 cur->bc_private.a.agno, &ext);
1411 error = xfs_refcount_delete(cur, &found_rec);
1412 if (error)
1413 goto out_error;
1414 XFS_WANT_CORRUPTED_GOTO(cur->bc_mp,
1415 found_rec == 1, out_error);
1416 break;
1417 default:
1418 ASSERT(0);
1419 }
1420
1421 return error;
1422out_error:
1423 trace_xfs_refcount_modify_extent_error(cur->bc_mp,
1424 cur->bc_private.a.agno, error, _RET_IP_);
1425 return error;
1426}
1427
1428/*
1429 * Add or remove refcount btree entries for CoW reservations.
1430 */
1431STATIC int
1432xfs_refcount_adjust_cow(
1433 struct xfs_btree_cur *cur,
1434 xfs_agblock_t agbno,
1435 xfs_extlen_t aglen,
1436 enum xfs_refc_adjust_op adj)
1437{
1438 bool shape_changed;
1439 int error;
1440
1441 agbno += XFS_REFC_COW_START;
1442
1443 /*
1444 * Ensure that no rcextents cross the boundary of the adjustment range.
1445 */
1446 error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
1447 if (error)
1448 goto out_error;
1449
1450 error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
1451 if (error)
1452 goto out_error;
1453
1454 /*
1455 * Try to merge with the left or right extents of the range.
1456 */
1457 error = xfs_refcount_merge_extents(cur, &agbno, &aglen, adj,
1458 XFS_FIND_RCEXT_COW, &shape_changed);
1459 if (error)
1460 goto out_error;
1461
1462 /* Now that we've taken care of the ends, adjust the middle extents */
1463 error = xfs_refcount_adjust_cow_extents(cur, agbno, aglen, adj);
1464 if (error)
1465 goto out_error;
1466
1467 return 0;
1468
1469out_error:
1470 trace_xfs_refcount_adjust_cow_error(cur->bc_mp, cur->bc_private.a.agno,
1471 error, _RET_IP_);
1472 return error;
1473}
1474
1475/*
1476 * Record a CoW allocation in the refcount btree.
1477 */
1478STATIC int
1479__xfs_refcount_cow_alloc(
1480 struct xfs_btree_cur *rcur,
1481 xfs_agblock_t agbno,
1482 xfs_extlen_t aglen,
1483 struct xfs_defer_ops *dfops)
1484{
1485 trace_xfs_refcount_cow_increase(rcur->bc_mp, rcur->bc_private.a.agno,
1486 agbno, aglen);
1487
1488 /* Add refcount btree reservation */
1489 return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1490 XFS_REFCOUNT_ADJUST_COW_ALLOC);
1491}
1492
1493/*
1494 * Remove a CoW allocation from the refcount btree.
1495 */
1496STATIC int
1497__xfs_refcount_cow_free(
1498 struct xfs_btree_cur *rcur,
1499 xfs_agblock_t agbno,
1500 xfs_extlen_t aglen,
1501 struct xfs_defer_ops *dfops)
1502{
1503 trace_xfs_refcount_cow_decrease(rcur->bc_mp, rcur->bc_private.a.agno,
1504 agbno, aglen);
1505
1506 /* Remove refcount btree reservation */
1507 return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1508 XFS_REFCOUNT_ADJUST_COW_FREE);
1509}
1510
1511/* Record a CoW staging extent in the refcount btree. */
1512int
1513xfs_refcount_alloc_cow_extent(
1514 struct xfs_mount *mp,
1515 struct xfs_defer_ops *dfops,
1516 xfs_fsblock_t fsb,
1517 xfs_extlen_t len)
1518{
1519 int error;
1520
1521 if (!xfs_sb_version_hasreflink(&mp->m_sb))
1522 return 0;
1523
1524 error = __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_ALLOC_COW,
1525 fsb, len);
1526 if (error)
1527 return error;
1528
1529 /* Add rmap entry */
1530 return xfs_rmap_alloc_extent(mp, dfops, XFS_FSB_TO_AGNO(mp, fsb),
1531 XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1532}
1533
1534/* Forget a CoW staging event in the refcount btree. */
1535int
1536xfs_refcount_free_cow_extent(
1537 struct xfs_mount *mp,
1538 struct xfs_defer_ops *dfops,
1539 xfs_fsblock_t fsb,
1540 xfs_extlen_t len)
1541{
1542 int error;
1543
1544 if (!xfs_sb_version_hasreflink(&mp->m_sb))
1545 return 0;
1546
1547 /* Remove rmap entry */
1548 error = xfs_rmap_free_extent(mp, dfops, XFS_FSB_TO_AGNO(mp, fsb),
1549 XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1550 if (error)
1551 return error;
1552
1553 return __xfs_refcount_add(mp, dfops, XFS_REFCOUNT_FREE_COW,
1554 fsb, len);
1555}
1556
1557struct xfs_refcount_recovery {
1558 struct list_head rr_list;
1559 struct xfs_refcount_irec rr_rrec;
1560};
1561
1562/* Stuff an extent on the recovery list. */
1563STATIC int
1564xfs_refcount_recover_extent(
1565 struct xfs_btree_cur *cur,
1566 union xfs_btree_rec *rec,
1567 void *priv)
1568{
1569 struct list_head *debris = priv;
1570 struct xfs_refcount_recovery *rr;
1571
1572 if (be32_to_cpu(rec->refc.rc_refcount) != 1)
1573 return -EFSCORRUPTED;
1574
1575 rr = kmem_alloc(sizeof(struct xfs_refcount_recovery), KM_SLEEP);
1576 xfs_refcount_btrec_to_irec(rec, &rr->rr_rrec);
1577 list_add_tail(&rr->rr_list, debris);
1578
1579 return 0;
1580}
1581
1582/* Find and remove leftover CoW reservations. */
1583int
1584xfs_refcount_recover_cow_leftovers(
1585 struct xfs_mount *mp,
1586 xfs_agnumber_t agno)
1587{
1588 struct xfs_trans *tp;
1589 struct xfs_btree_cur *cur;
1590 struct xfs_buf *agbp;
1591 struct xfs_refcount_recovery *rr, *n;
1592 struct list_head debris;
1593 union xfs_btree_irec low;
1594 union xfs_btree_irec high;
1595 struct xfs_defer_ops dfops;
1596 xfs_fsblock_t fsb;
1597 xfs_agblock_t agbno;
1598 int error;
1599
1600 if (mp->m_sb.sb_agblocks >= XFS_REFC_COW_START)
1601 return -EOPNOTSUPP;
1602
1603 INIT_LIST_HEAD(&debris);
1604
1605 /*
1606 * In this first part, we use an empty transaction to gather up
1607 * all the leftover CoW extents so that we can subsequently
1608 * delete them. The empty transaction is used to avoid
1609 * a buffer lock deadlock if there happens to be a loop in the
1610 * refcountbt because we're allowed to re-grab a buffer that is
1611 * already attached to our transaction. When we're done
1612 * recording the CoW debris we cancel the (empty) transaction
1613 * and everything goes away cleanly.
1614 */
1615 error = xfs_trans_alloc_empty(mp, &tp);
1616 if (error)
1617 return error;
1618
1619 error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp);
1620 if (error)
1621 goto out_trans;
1622 if (!agbp) {
1623 error = -ENOMEM;
1624 goto out_trans;
1625 }
1626 cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno, NULL);
1627
1628 /* Find all the leftover CoW staging extents. */
1629 memset(&low, 0, sizeof(low));
1630 memset(&high, 0, sizeof(high));
1631 low.rc.rc_startblock = XFS_REFC_COW_START;
1632 high.rc.rc_startblock = -1U;
1633 error = xfs_btree_query_range(cur, &low, &high,
1634 xfs_refcount_recover_extent, &debris);
1635 if (error)
1636 goto out_cursor;
1637 xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
1638 xfs_trans_brelse(tp, agbp);
1639 xfs_trans_cancel(tp);
1640
1641 /* Now iterate the list to free the leftovers */
1642 list_for_each_entry_safe(rr, n, &debris, rr_list) {
1643 /* Set up transaction. */
1644 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1645 if (error)
1646 goto out_free;
1647
1648 trace_xfs_refcount_recover_extent(mp, agno, &rr->rr_rrec);
1649
1650 /* Free the orphan record */
1651 xfs_defer_init(&dfops, &fsb);
1652 agbno = rr->rr_rrec.rc_startblock - XFS_REFC_COW_START;
1653 fsb = XFS_AGB_TO_FSB(mp, agno, agbno);
1654 error = xfs_refcount_free_cow_extent(mp, &dfops, fsb,
1655 rr->rr_rrec.rc_blockcount);
1656 if (error)
1657 goto out_defer;
1658
1659 /* Free the block. */
1660 xfs_bmap_add_free(mp, &dfops, fsb,
1661 rr->rr_rrec.rc_blockcount, NULL);
1662
1663 error = xfs_defer_finish(&tp, &dfops);
1664 if (error)
1665 goto out_defer;
1666
1667 error = xfs_trans_commit(tp);
1668 if (error)
1669 goto out_free;
1670
1671 list_del(&rr->rr_list);
1672 kmem_free(rr);
1673 }
1674
1675 return error;
1676out_defer:
1677 xfs_defer_cancel(&dfops);
1678out_trans:
1679 xfs_trans_cancel(tp);
1680out_free:
1681 /* Free the leftover list */
1682 list_for_each_entry_safe(rr, n, &debris, rr_list) {
1683 list_del(&rr->rr_list);
1684 kmem_free(rr);
1685 }
1686 return error;
1687
1688out_cursor:
1689 xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
1690 xfs_trans_brelse(tp, agbp);
1691 goto out_trans;
1692}
1693
1694/* Is there a record covering a given extent? */
1695int
1696xfs_refcount_has_record(
1697 struct xfs_btree_cur *cur,
1698 xfs_agblock_t bno,
1699 xfs_extlen_t len,
1700 bool *exists)
1701{
1702 union xfs_btree_irec low;
1703 union xfs_btree_irec high;
1704
1705 memset(&low, 0, sizeof(low));
1706 low.rc.rc_startblock = bno;
1707 memset(&high, 0xFF, sizeof(high));
1708 high.rc.rc_startblock = bno + len - 1;
1709
1710 return xfs_btree_has_record(cur, &low, &high, exists);
1711}