1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 2016 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
5 */
6 #include "xfs.h"
7 #include "xfs_fs.h"
8 #include "xfs_shared.h"
9 #include "xfs_format.h"
10 #include "xfs_log_format.h"
11 #include "xfs_trans_resv.h"
12 #include "xfs_mount.h"
13 #include "xfs_defer.h"
14 #include "xfs_inode.h"
15 #include "xfs_trans.h"
16 #include "xfs_bmap.h"
17 #include "xfs_bmap_util.h"
18 #include "xfs_trace.h"
19 #include "xfs_icache.h"
20 #include "xfs_btree.h"
21 #include "xfs_refcount_btree.h"
22 #include "xfs_refcount.h"
23 #include "xfs_bmap_btree.h"
24 #include "xfs_trans_space.h"
25 #include "xfs_bit.h"
26 #include "xfs_alloc.h"
27 #include "xfs_quota.h"
28 #include "xfs_reflink.h"
29 #include "xfs_iomap.h"
30 #include "xfs_ag.h"
31 #include "xfs_ag_resv.h"
32 #include "xfs_health.h"
33
34 /*
35 * Copy on Write of Shared Blocks
36 *
37 * XFS must preserve "the usual" file semantics even when two files share
38 * the same physical blocks. This means that a write to one file must not
39 * alter the blocks in a different file; the way that we'll do that is
40 * through the use of a copy-on-write mechanism. At a high level, that
41 * means that when we want to write to a shared block, we allocate a new
42 * block, write the data to the new block, and if that succeeds we map the
43 * new block into the file.
44 *
45 * XFS provides a "delayed allocation" mechanism that defers the allocation
46 * of disk blocks to dirty-but-not-yet-mapped file blocks as long as
47 * possible. This reduces fragmentation by enabling the filesystem to ask
48 * for bigger chunks less often, which is exactly what we want for CoW.
49 *
50 * The delalloc mechanism begins when the kernel wants to make a block
51 * writable (write_begin or page_mkwrite). If the offset is not mapped, we
52 * create a delalloc mapping, which is a regular in-core extent, but without
53 * a real startblock. (For delalloc mappings, the startblock encodes both
54 * a flag that this is a delalloc mapping, and a worst-case estimate of how
55 * many blocks might be required to put the mapping into the BMBT.) delalloc
56 * mappings are a reservation against the free space in the filesystem;
57 * adjacent mappings can also be combined into fewer larger mappings.
58 *
59 * As an optimization, the CoW extent size hint (cowextsz) creates
60 * outsized aligned delalloc reservations in the hope of landing out of
61 * order nearby CoW writes in a single extent on disk, thereby reducing
62 * fragmentation and improving future performance.
63 *
64 * D: --RRRRRRSSSRRRRRRRR--- (data fork)
65 * C: ------DDDDDDD--------- (CoW fork)
66 *
67 * When dirty pages are being written out (typically in writepage), the
68 * delalloc reservations are converted into unwritten mappings by
69 * allocating blocks and replacing the delalloc mapping with real ones.
70 * A delalloc mapping can be replaced by several unwritten ones if the
71 * free space is fragmented.
72 *
73 * D: --RRRRRRSSSRRRRRRRR---
74 * C: ------UUUUUUU---------
75 *
76 * We want to adapt the delalloc mechanism for copy-on-write, since the
77 * write paths are similar. The first two steps (creating the reservation
78 * and allocating the blocks) are exactly the same as delalloc except that
79 * the mappings must be stored in a separate CoW fork because we do not want
80 * to disturb the mapping in the data fork until we're sure that the write
81 * succeeded. IO completion in this case is the process of removing the old
82 * mapping from the data fork and moving the new mapping from the CoW fork to
83 * the data fork. This will be discussed shortly.
84 *
85 * For now, unaligned directio writes will be bounced back to the page cache.
86 * Block-aligned directio writes will use the same mechanism as buffered
87 * writes.
88 *
89 * Just prior to submitting the actual disk write requests, we convert
90 * the extents representing the range of the file actually being written
91 * (as opposed to extra pieces created for the cowextsize hint) to real
92 * extents. This will become important in the next step:
93 *
94 * D: --RRRRRRSSSRRRRRRRR---
95 * C: ------UUrrUUU---------
96 *
97 * CoW remapping must be done after the data block write completes,
98 * because we don't want to destroy the old data fork map until we're sure
99 * the new block has been written. Since the new mappings are kept in a
100 * separate fork, we can simply iterate these mappings to find the ones
101 * that cover the file blocks that we just CoW'd. For each extent, simply
102 * unmap the corresponding range in the data fork, map the new range into
103 * the data fork, and remove the extent from the CoW fork. Because of
104 * the presence of the cowextsize hint, however, we must be careful
105 * only to remap the blocks that we've actually written out -- we must
106 * never remap delalloc reservations nor CoW staging blocks that have
107 * yet to be written. This corresponds exactly to the real extents in
108 * the CoW fork:
109 *
110 * D: --RRRRRRrrSRRRRRRRR---
111 * C: ------UU--UUU---------
112 *
113 * Since the remapping operation can be applied to an arbitrary file
114 * range, we record the need for the remap step as a flag in the ioend
115 * instead of declaring a new IO type. This is required for direct io
116 * because we only have ioend for the whole dio, and we have to be able to
117 * remember the presence of unwritten blocks and CoW blocks with a single
118 * ioend structure. Better yet, the more ground we can cover with one
119 * ioend, the better.
120 */
121
122 /*
123 * Given an AG extent, find the lowest-numbered run of shared blocks
124 * within that range and return the range in fbno/flen. If
125 * find_end_of_shared is true, return the longest contiguous extent of
126 * shared blocks. If there are no shared extents, fbno and flen will
127 * be set to NULLAGBLOCK and 0, respectively.
128 */
129 static int
130 xfs_reflink_find_shared(
131 struct xfs_perag *pag,
132 struct xfs_trans *tp,
133 xfs_agblock_t agbno,
134 xfs_extlen_t aglen,
135 xfs_agblock_t *fbno,
136 xfs_extlen_t *flen,
137 bool find_end_of_shared)
138 {
139 struct xfs_buf *agbp;
140 struct xfs_btree_cur *cur;
141 int error;
142
143 error = xfs_alloc_read_agf(pag, tp, 0, &agbp);
144 if (error)
145 return error;
146
147 cur = xfs_refcountbt_init_cursor(pag->pag_mount, tp, agbp, pag);
148
149 error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen,
150 find_end_of_shared);
151
152 xfs_btree_del_cursor(cur, error);
153
154 xfs_trans_brelse(tp, agbp);
155 return error;
156 }
157
158 /*
159 * Trim the mapping to the next block where there's a change in the
160 * shared/unshared status. More specifically, this means that we
161 * find the lowest-numbered extent of shared blocks that coincides with
162 * the given block mapping. If the shared extent overlaps the start of
163 * the mapping, trim the mapping to the end of the shared extent. If
164 * the shared region intersects the mapping, trim the mapping to the
165 * start of the shared extent. If there are no shared regions that
166 * overlap, just return the original extent.
167 */
168 int
169 xfs_reflink_trim_around_shared(
170 struct xfs_inode *ip,
171 struct xfs_bmbt_irec *irec,
172 bool *shared)
173 {
174 struct xfs_mount *mp = ip->i_mount;
175 struct xfs_perag *pag;
176 xfs_agblock_t agbno;
177 xfs_extlen_t aglen;
178 xfs_agblock_t fbno;
179 xfs_extlen_t flen;
180 int error = 0;
181
182 /* Holes, unwritten, and delalloc extents cannot be shared */
183 if (!xfs_is_cow_inode(ip) || !xfs_bmap_is_written_extent(irec)) {
184 *shared = false;
185 return 0;
186 }
187
188 trace_xfs_reflink_trim_around_shared(ip, irec);
189
190 pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, irec->br_startblock));
191 agbno = XFS_FSB_TO_AGBNO(mp, irec->br_startblock);
192 aglen = irec->br_blockcount;
193
194 error = xfs_reflink_find_shared(pag, NULL, agbno, aglen, &fbno, &flen,
195 true);
196 xfs_perag_put(pag);
197 if (error)
198 return error;
199
200 *shared = false;
201 if (fbno == NULLAGBLOCK) {
202 /* No shared blocks at all. */
203 return 0;
204 }
205
206 if (fbno == agbno) {
207 /*
208 * The start of this extent is shared. Truncate the
209 * mapping at the end of the shared region so that a
210 * subsequent iteration starts at the start of the
211 * unshared region.
212 */
213 irec->br_blockcount = flen;
214 *shared = true;
215 return 0;
216 }
217
218 /*
219 * There's a shared extent midway through this extent.
220 * Truncate the mapping at the start of the shared
221 * extent so that a subsequent iteration starts at the
222 * start of the shared region.
223 */
224 irec->br_blockcount = fbno - agbno;
225 return 0;
226 }
227
228 int
229 xfs_bmap_trim_cow(
230 struct xfs_inode *ip,
231 struct xfs_bmbt_irec *imap,
232 bool *shared)
233 {
234 /* We can't update any real extents in always COW mode. */
235 if (xfs_is_always_cow_inode(ip) &&
236 !isnullstartblock(imap->br_startblock)) {
237 *shared = true;
238 return 0;
239 }
240
241 /* Trim the mapping to the nearest shared extent boundary. */
242 return xfs_reflink_trim_around_shared(ip, imap, shared);
243 }
244
245 static int
246 xfs_reflink_convert_cow_locked(
247 struct xfs_inode *ip,
248 xfs_fileoff_t offset_fsb,
249 xfs_filblks_t count_fsb)
250 {
251 struct xfs_iext_cursor icur;
252 struct xfs_bmbt_irec got;
253 struct xfs_btree_cur *dummy_cur = NULL;
254 int dummy_logflags;
255 int error = 0;
256
257 if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
258 return 0;
259
260 do {
261 if (got.br_startoff >= offset_fsb + count_fsb)
262 break;
263 if (got.br_state == XFS_EXT_NORM)
264 continue;
265 if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))
266 return -EIO;
267
268 xfs_trim_extent(&got, offset_fsb, count_fsb);
269 if (!got.br_blockcount)
270 continue;
271
272 got.br_state = XFS_EXT_NORM;
273 error = xfs_bmap_add_extent_unwritten_real(NULL, ip,
274 XFS_COW_FORK, &icur, &dummy_cur, &got,
275 &dummy_logflags);
276 if (error)
277 return error;
278 } while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));
279
280 return error;
281 }
282
283 /* Convert all of the unwritten CoW extents in a file's range to real ones. */
284 int
285 xfs_reflink_convert_cow(
286 struct xfs_inode *ip,
287 xfs_off_t offset,
288 xfs_off_t count)
289 {
290 struct xfs_mount *mp = ip->i_mount;
291 xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
292 xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
293 xfs_filblks_t count_fsb = end_fsb - offset_fsb;
294 int error;
295
296 ASSERT(count != 0);
297
298 xfs_ilock(ip, XFS_ILOCK_EXCL);
299 error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
300 xfs_iunlock(ip, XFS_ILOCK_EXCL);
301 return error;
302 }
303
304 /*
305 * Find the extent that maps the given range in the COW fork. Even if the extent
306 * is not shared we might have a preallocation for it in the COW fork. If so we
307 * use it that rather than trigger a new allocation.
308 */
309 static int
310 xfs_find_trim_cow_extent(
311 struct xfs_inode *ip,
312 struct xfs_bmbt_irec *imap,
313 struct xfs_bmbt_irec *cmap,
314 bool *shared,
315 bool *found)
316 {
317 xfs_fileoff_t offset_fsb = imap->br_startoff;
318 xfs_filblks_t count_fsb = imap->br_blockcount;
319 struct xfs_iext_cursor icur;
320
321 *found = false;
322
323 /*
324 * If we don't find an overlapping extent, trim the range we need to
325 * allocate to fit the hole we found.
326 */
327 if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, cmap))
328 cmap->br_startoff = offset_fsb + count_fsb;
329 if (cmap->br_startoff > offset_fsb) {
330 xfs_trim_extent(imap, imap->br_startoff,
331 cmap->br_startoff - imap->br_startoff);
332 return xfs_bmap_trim_cow(ip, imap, shared);
333 }
334
335 *shared = true;
336 if (isnullstartblock(cmap->br_startblock)) {
337 xfs_trim_extent(imap, cmap->br_startoff, cmap->br_blockcount);
338 return 0;
339 }
340
341 /* real extent found - no need to allocate */
342 xfs_trim_extent(cmap, offset_fsb, count_fsb);
343 *found = true;
344 return 0;
345 }
346
347 static int
348 xfs_reflink_convert_unwritten(
349 struct xfs_inode *ip,
350 struct xfs_bmbt_irec *imap,
351 struct xfs_bmbt_irec *cmap,
352 bool convert_now)
353 {
354 xfs_fileoff_t offset_fsb = imap->br_startoff;
355 xfs_filblks_t count_fsb = imap->br_blockcount;
356 int error;
357
358 /*
359 * cmap might larger than imap due to cowextsize hint.
360 */
361 xfs_trim_extent(cmap, offset_fsb, count_fsb);
362
363 /*
364 * COW fork extents are supposed to remain unwritten until we're ready
365 * to initiate a disk write. For direct I/O we are going to write the
366 * data and need the conversion, but for buffered writes we're done.
367 */
368 if (!convert_now || cmap->br_state == XFS_EXT_NORM)
369 return 0;
370
371 trace_xfs_reflink_convert_cow(ip, cmap);
372
373 error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
374 if (!error)
375 cmap->br_state = XFS_EXT_NORM;
376
377 return error;
378 }
379
380 static int
381 xfs_reflink_fill_cow_hole(
382 struct xfs_inode *ip,
383 struct xfs_bmbt_irec *imap,
384 struct xfs_bmbt_irec *cmap,
385 bool *shared,
386 uint *lockmode,
387 bool convert_now)
388 {
389 struct xfs_mount *mp = ip->i_mount;
390 struct xfs_trans *tp;
391 xfs_filblks_t resaligned;
392 xfs_extlen_t resblks;
393 int nimaps;
394 int error;
395 bool found;
396
397 resaligned = xfs_aligned_fsb_count(imap->br_startoff,
398 imap->br_blockcount, xfs_get_cowextsz_hint(ip));
399 resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
400
401 xfs_iunlock(ip, *lockmode);
402 *lockmode = 0;
403
404 error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, resblks, 0,
405 false, &tp);
406 if (error)
407 return error;
408
409 *lockmode = XFS_ILOCK_EXCL;
410
411 error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
412 if (error || !*shared)
413 goto out_trans_cancel;
414
415 if (found) {
416 xfs_trans_cancel(tp);
417 goto convert;
418 }
419
420 /* Allocate the entire reservation as unwritten blocks. */
421 nimaps = 1;
422 error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
423 XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0, cmap,
424 &nimaps);
425 if (error)
426 goto out_trans_cancel;
427
428 xfs_inode_set_cowblocks_tag(ip);
429 error = xfs_trans_commit(tp);
430 if (error)
431 return error;
432
433 convert:
434 return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
435
436 out_trans_cancel:
437 xfs_trans_cancel(tp);
438 return error;
439 }
440
441 static int
442 xfs_reflink_fill_delalloc(
443 struct xfs_inode *ip,
444 struct xfs_bmbt_irec *imap,
445 struct xfs_bmbt_irec *cmap,
446 bool *shared,
447 uint *lockmode,
448 bool convert_now)
449 {
450 struct xfs_mount *mp = ip->i_mount;
451 struct xfs_trans *tp;
452 int nimaps;
453 int error;
454 bool found;
455
456 do {
457 xfs_iunlock(ip, *lockmode);
458 *lockmode = 0;
459
460 error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, 0, 0,
461 false, &tp);
462 if (error)
463 return error;
464
465 *lockmode = XFS_ILOCK_EXCL;
466
467 error = xfs_find_trim_cow_extent(ip, imap, cmap, shared,
468 &found);
469 if (error || !*shared)
470 goto out_trans_cancel;
471
472 if (found) {
473 xfs_trans_cancel(tp);
474 break;
475 }
476
477 ASSERT(isnullstartblock(cmap->br_startblock) ||
478 cmap->br_startblock == DELAYSTARTBLOCK);
479
480 /*
481 * Replace delalloc reservation with an unwritten extent.
482 */
483 nimaps = 1;
484 error = xfs_bmapi_write(tp, ip, cmap->br_startoff,
485 cmap->br_blockcount,
486 XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0,
487 cmap, &nimaps);
488 if (error)
489 goto out_trans_cancel;
490
491 xfs_inode_set_cowblocks_tag(ip);
492 error = xfs_trans_commit(tp);
493 if (error)
494 return error;
495 } while (cmap->br_startoff + cmap->br_blockcount <= imap->br_startoff);
496
497 return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
498
499 out_trans_cancel:
500 xfs_trans_cancel(tp);
501 return error;
502 }
503
504 /* Allocate all CoW reservations covering a range of blocks in a file. */
505 int
506 xfs_reflink_allocate_cow(
507 struct xfs_inode *ip,
508 struct xfs_bmbt_irec *imap,
509 struct xfs_bmbt_irec *cmap,
510 bool *shared,
511 uint *lockmode,
512 bool convert_now)
513 {
514 int error;
515 bool found;
516
517 xfs_assert_ilocked(ip, XFS_ILOCK_EXCL);
518 if (!ip->i_cowfp) {
519 ASSERT(!xfs_is_reflink_inode(ip));
520 xfs_ifork_init_cow(ip);
521 }
522
523 error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
524 if (error || !*shared)
525 return error;
526
527 /* CoW fork has a real extent */
528 if (found)
529 return xfs_reflink_convert_unwritten(ip, imap, cmap,
530 convert_now);
531
532 /*
533 * CoW fork does not have an extent and data extent is shared.
534 * Allocate a real extent in the CoW fork.
535 */
536 if (cmap->br_startoff > imap->br_startoff)
537 return xfs_reflink_fill_cow_hole(ip, imap, cmap, shared,
538 lockmode, convert_now);
539
540 /*
541 * CoW fork has a delalloc reservation. Replace it with a real extent.
542 * There may or may not be a data fork mapping.
543 */
544 if (isnullstartblock(cmap->br_startblock) ||
545 cmap->br_startblock == DELAYSTARTBLOCK)
546 return xfs_reflink_fill_delalloc(ip, imap, cmap, shared,
547 lockmode, convert_now);
548
549 /* Shouldn't get here. */
550 ASSERT(0);
551 return -EFSCORRUPTED;
552 }
553
554 /*
555 * Cancel CoW reservations for some block range of an inode.
556 *
557 * If cancel_real is true this function cancels all COW fork extents for the
558 * inode; if cancel_real is false, real extents are not cleared.
559 *
560 * Caller must have already joined the inode to the current transaction. The
561 * inode will be joined to the transaction returned to the caller.
562 */
563 int
564 xfs_reflink_cancel_cow_blocks(
565 struct xfs_inode *ip,
566 struct xfs_trans **tpp,
567 xfs_fileoff_t offset_fsb,
568 xfs_fileoff_t end_fsb,
569 bool cancel_real)
570 {
571 struct xfs_ifork *ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
572 struct xfs_bmbt_irec got, del;
573 struct xfs_iext_cursor icur;
574 int error = 0;
575
576 if (!xfs_inode_has_cow_data(ip))
577 return 0;
578 if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got))
579 return 0;
580
581 /* Walk backwards until we're out of the I/O range... */
582 while (got.br_startoff + got.br_blockcount > offset_fsb) {
583 del = got;
584 xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
585
586 /* Extent delete may have bumped ext forward */
587 if (!del.br_blockcount) {
588 xfs_iext_prev(ifp, &icur);
589 goto next_extent;
590 }
591
592 trace_xfs_reflink_cancel_cow(ip, &del);
593
594 if (isnullstartblock(del.br_startblock)) {
595 xfs_bmap_del_extent_delay(ip, XFS_COW_FORK, &icur, &got,
596 &del);
597 } else if (del.br_state == XFS_EXT_UNWRITTEN || cancel_real) {
598 ASSERT((*tpp)->t_highest_agno == NULLAGNUMBER);
599
600 /* Free the CoW orphan record. */
601 xfs_refcount_free_cow_extent(*tpp, del.br_startblock,
602 del.br_blockcount);
603
604 error = xfs_free_extent_later(*tpp, del.br_startblock,
605 del.br_blockcount, NULL,
606 XFS_AG_RESV_NONE, 0);
607 if (error)
608 break;
609
610 /* Roll the transaction */
611 error = xfs_defer_finish(tpp);
612 if (error)
613 break;
614
615 /* Remove the mapping from the CoW fork. */
616 xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
617
618 /* Remove the quota reservation */
619 xfs_quota_unreserve_blkres(ip, del.br_blockcount);
620 } else {
621 /* Didn't do anything, push cursor back. */
622 xfs_iext_prev(ifp, &icur);
623 }
624 next_extent:
625 if (!xfs_iext_get_extent(ifp, &icur, &got))
626 break;
627 }
628
629 /* clear tag if cow fork is emptied */
630 if (!ifp->if_bytes)
631 xfs_inode_clear_cowblocks_tag(ip);
632 return error;
633 }
634
635 /*
636 * Cancel CoW reservations for some byte range of an inode.
637 *
638 * If cancel_real is true this function cancels all COW fork extents for the
639 * inode; if cancel_real is false, real extents are not cleared.
640 */
641 int
642 xfs_reflink_cancel_cow_range(
643 struct xfs_inode *ip,
644 xfs_off_t offset,
645 xfs_off_t count,
646 bool cancel_real)
647 {
648 struct xfs_trans *tp;
649 xfs_fileoff_t offset_fsb;
650 xfs_fileoff_t end_fsb;
651 int error;
652
653 trace_xfs_reflink_cancel_cow_range(ip, offset, count);
654 ASSERT(ip->i_cowfp);
655
656 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
657 if (count == NULLFILEOFF)
658 end_fsb = NULLFILEOFF;
659 else
660 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
661
662 /* Start a rolling transaction to remove the mappings */
663 error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
664 0, 0, 0, &tp);
665 if (error)
666 goto out;
667
668 xfs_ilock(ip, XFS_ILOCK_EXCL);
669 xfs_trans_ijoin(tp, ip, 0);
670
671 /* Scrape out the old CoW reservations */
672 error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb,
673 cancel_real);
674 if (error)
675 goto out_cancel;
676
677 error = xfs_trans_commit(tp);
678
679 xfs_iunlock(ip, XFS_ILOCK_EXCL);
680 return error;
681
682 out_cancel:
683 xfs_trans_cancel(tp);
684 xfs_iunlock(ip, XFS_ILOCK_EXCL);
685 out:
686 trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_);
687 return error;
688 }
689
690 /*
691 * Remap part of the CoW fork into the data fork.
692 *
693 * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
694 * into the data fork; this function will remap what it can (at the end of the
695 * range) and update @end_fsb appropriately. Each remap gets its own
696 * transaction because we can end up merging and splitting bmbt blocks for
697 * every remap operation and we'd like to keep the block reservation
698 * requirements as low as possible.
699 */
700 STATIC int
701 xfs_reflink_end_cow_extent(
702 struct xfs_inode *ip,
703 xfs_fileoff_t *offset_fsb,
704 xfs_fileoff_t end_fsb)
705 {
706 struct xfs_iext_cursor icur;
707 struct xfs_bmbt_irec got, del, data;
708 struct xfs_mount *mp = ip->i_mount;
709 struct xfs_trans *tp;
710 struct xfs_ifork *ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
711 unsigned int resblks;
712 int nmaps;
713 int error;
714
715 resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
716 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
717 XFS_TRANS_RESERVE, &tp);
718 if (error)
719 return error;
720
721 /*
722 * Lock the inode. We have to ijoin without automatic unlock because
723 * the lead transaction is the refcountbt record deletion; the data
724 * fork update follows as a deferred log item.
725 */
726 xfs_ilock(ip, XFS_ILOCK_EXCL);
727 xfs_trans_ijoin(tp, ip, 0);
728
729 /*
730 * In case of racing, overlapping AIO writes no COW extents might be
731 * left by the time I/O completes for the loser of the race. In that
732 * case we are done.
733 */
734 if (!xfs_iext_lookup_extent(ip, ifp, *offset_fsb, &icur, &got) ||
735 got.br_startoff >= end_fsb) {
736 *offset_fsb = end_fsb;
737 goto out_cancel;
738 }
739
740 /*
741 * Only remap real extents that contain data. With AIO, speculative
742 * preallocations can leak into the range we are called upon, and we
743 * need to skip them. Preserve @got for the eventual CoW fork
744 * deletion; from now on @del represents the mapping that we're
745 * actually remapping.
746 */
747 while (!xfs_bmap_is_written_extent(&got)) {
748 if (!xfs_iext_next_extent(ifp, &icur, &got) ||
749 got.br_startoff >= end_fsb) {
750 *offset_fsb = end_fsb;
751 goto out_cancel;
752 }
753 }
754 del = got;
755 xfs_trim_extent(&del, *offset_fsb, end_fsb - *offset_fsb);
756
757 error = xfs_iext_count_extend(tp, ip, XFS_DATA_FORK,
758 XFS_IEXT_REFLINK_END_COW_CNT);
759 if (error)
760 goto out_cancel;
761
762 /* Grab the corresponding mapping in the data fork. */
763 nmaps = 1;
764 error = xfs_bmapi_read(ip, del.br_startoff, del.br_blockcount, &data,
765 &nmaps, 0);
766 if (error)
767 goto out_cancel;
768
769 /* We can only remap the smaller of the two extent sizes. */
770 data.br_blockcount = min(data.br_blockcount, del.br_blockcount);
771 del.br_blockcount = data.br_blockcount;
772
773 trace_xfs_reflink_cow_remap_from(ip, &del);
774 trace_xfs_reflink_cow_remap_to(ip, &data);
775
776 if (xfs_bmap_is_real_extent(&data)) {
777 /*
778 * If the extent we're remapping is backed by storage (written
779 * or not), unmap the extent and drop its refcount.
780 */
781 xfs_bmap_unmap_extent(tp, ip, XFS_DATA_FORK, &data);
782 xfs_refcount_decrease_extent(tp, &data);
783 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
784 -data.br_blockcount);
785 } else if (data.br_startblock == DELAYSTARTBLOCK) {
786 int done;
787
788 /*
789 * If the extent we're remapping is a delalloc reservation,
790 * we can use the regular bunmapi function to release the
791 * incore state. Dropping the delalloc reservation takes care
792 * of the quota reservation for us.
793 */
794 error = xfs_bunmapi(NULL, ip, data.br_startoff,
795 data.br_blockcount, 0, 1, &done);
796 if (error)
797 goto out_cancel;
798 ASSERT(done);
799 }
800
801 /* Free the CoW orphan record. */
802 xfs_refcount_free_cow_extent(tp, del.br_startblock, del.br_blockcount);
803
804 /* Map the new blocks into the data fork. */
805 xfs_bmap_map_extent(tp, ip, XFS_DATA_FORK, &del);
806
807 /* Charge this new data fork mapping to the on-disk quota. */
808 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
809 (long)del.br_blockcount);
810
811 /* Remove the mapping from the CoW fork. */
812 xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
813
814 error = xfs_trans_commit(tp);
815 xfs_iunlock(ip, XFS_ILOCK_EXCL);
816 if (error)
817 return error;
818
819 /* Update the caller about how much progress we made. */
820 *offset_fsb = del.br_startoff + del.br_blockcount;
821 return 0;
822
823 out_cancel:
824 xfs_trans_cancel(tp);
825 xfs_iunlock(ip, XFS_ILOCK_EXCL);
826 return error;
827 }
828
829 /*
830 * Remap parts of a file's data fork after a successful CoW.
831 */
832 int
833 xfs_reflink_end_cow(
834 struct xfs_inode *ip,
835 xfs_off_t offset,
836 xfs_off_t count)
837 {
838 xfs_fileoff_t offset_fsb;
839 xfs_fileoff_t end_fsb;
840 int error = 0;
841
842 trace_xfs_reflink_end_cow(ip, offset, count);
843
844 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
845 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
846
847 /*
848 * Walk forwards until we've remapped the I/O range. The loop function
849 * repeatedly cycles the ILOCK to allocate one transaction per remapped
850 * extent.
851 *
852 * If we're being called by writeback then the pages will still
853 * have PageWriteback set, which prevents races with reflink remapping
854 * and truncate. Reflink remapping prevents races with writeback by
855 * taking the iolock and mmaplock before flushing the pages and
856 * remapping, which means there won't be any further writeback or page
857 * cache dirtying until the reflink completes.
858 *
859 * We should never have two threads issuing writeback for the same file
860 * region. There are also have post-eof checks in the writeback
861 * preparation code so that we don't bother writing out pages that are
862 * about to be truncated.
863 *
864 * If we're being called as part of directio write completion, the dio
865 * count is still elevated, which reflink and truncate will wait for.
866 * Reflink remapping takes the iolock and mmaplock and waits for
867 * pending dio to finish, which should prevent any directio until the
868 * remap completes. Multiple concurrent directio writes to the same
869 * region are handled by end_cow processing only occurring for the
870 * threads which succeed; the outcome of multiple overlapping direct
871 * writes is not well defined anyway.
872 *
873 * It's possible that a buffered write and a direct write could collide
874 * here (the buffered write stumbles in after the dio flushes and
875 * invalidates the page cache and immediately queues writeback), but we
876 * have never supported this 100%. If either disk write succeeds the
877 * blocks will be remapped.
878 */
879 while (end_fsb > offset_fsb && !error)
880 error = xfs_reflink_end_cow_extent(ip, &offset_fsb, end_fsb);
881
882 if (error)
883 trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
884 return error;
885 }
886
887 /*
888 * Free all CoW staging blocks that are still referenced by the ondisk refcount
889 * metadata. The ondisk metadata does not track which inode created the
890 * staging extent, so callers must ensure that there are no cached inodes with
891 * live CoW staging extents.
892 */
893 int
894 xfs_reflink_recover_cow(
895 struct xfs_mount *mp)
896 {
897 struct xfs_perag *pag;
898 xfs_agnumber_t agno;
899 int error = 0;
900
901 if (!xfs_has_reflink(mp))
902 return 0;
903
904 for_each_perag(mp, agno, pag) {
905 error = xfs_refcount_recover_cow_leftovers(mp, pag);
906 if (error) {
907 xfs_perag_rele(pag);
908 break;
909 }
910 }
911
912 return error;
913 }
914
915 /*
916 * Reflinking (Block) Ranges of Two Files Together
917 *
918 * First, ensure that the reflink flag is set on both inodes. The flag is an
919 * optimization to avoid unnecessary refcount btree lookups in the write path.
920 *
921 * Now we can iteratively remap the range of extents (and holes) in src to the
922 * corresponding ranges in dest. Let drange and srange denote the ranges of
923 * logical blocks in dest and src touched by the reflink operation.
924 *
925 * While the length of drange is greater than zero,
926 * - Read src's bmbt at the start of srange ("imap")
927 * - If imap doesn't exist, make imap appear to start at the end of srange
928 * with zero length.
929 * - If imap starts before srange, advance imap to start at srange.
930 * - If imap goes beyond srange, truncate imap to end at the end of srange.
931 * - Punch (imap start - srange start + imap len) blocks from dest at
932 * offset (drange start).
933 * - If imap points to a real range of pblks,
934 * > Increase the refcount of the imap's pblks
935 * > Map imap's pblks into dest at the offset
936 * (drange start + imap start - srange start)
937 * - Advance drange and srange by (imap start - srange start + imap len)
938 *
939 * Finally, if the reflink made dest longer, update both the in-core and
940 * on-disk file sizes.
941 *
942 * ASCII Art Demonstration:
943 *
944 * Let's say we want to reflink this source file:
945 *
946 * ----SSSSSSS-SSSSS----SSSSSS (src file)
947 * <-------------------->
948 *
949 * into this destination file:
950 *
951 * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
952 * <-------------------->
953 * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
954 * Observe that the range has different logical offsets in either file.
955 *
956 * Consider that the first extent in the source file doesn't line up with our
957 * reflink range. Unmapping and remapping are separate operations, so we can
958 * unmap more blocks from the destination file than we remap.
959 *
960 * ----SSSSSSS-SSSSS----SSSSSS
961 * <------->
962 * --DDDDD---------DDDDD--DDD
963 * <------->
964 *
965 * Now remap the source extent into the destination file:
966 *
967 * ----SSSSSSS-SSSSS----SSSSSS
968 * <------->
969 * --DDDDD--SSSSSSSDDDDD--DDD
970 * <------->
971 *
972 * Do likewise with the second hole and extent in our range. Holes in the
973 * unmap range don't affect our operation.
974 *
975 * ----SSSSSSS-SSSSS----SSSSSS
976 * <---->
977 * --DDDDD--SSSSSSS-SSSSS-DDD
978 * <---->
979 *
980 * Finally, unmap and remap part of the third extent. This will increase the
981 * size of the destination file.
982 *
983 * ----SSSSSSS-SSSSS----SSSSSS
984 * <----->
985 * --DDDDD--SSSSSSS-SSSSS----SSS
986 * <----->
987 *
988 * Once we update the destination file's i_size, we're done.
989 */
990
991 /*
992 * Ensure the reflink bit is set in both inodes.
993 */
994 STATIC int
995 xfs_reflink_set_inode_flag(
996 struct xfs_inode *src,
997 struct xfs_inode *dest)
998 {
999 struct xfs_mount *mp = src->i_mount;
1000 int error;
1001 struct xfs_trans *tp;
1002
1003 if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
1004 return 0;
1005
1006 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1007 if (error)
1008 goto out_error;
1009
1010 /* Lock both files against IO */
1011 if (src->i_ino == dest->i_ino)
1012 xfs_ilock(src, XFS_ILOCK_EXCL);
1013 else
1014 xfs_lock_two_inodes(src, XFS_ILOCK_EXCL, dest, XFS_ILOCK_EXCL);
1015
1016 if (!xfs_is_reflink_inode(src)) {
1017 trace_xfs_reflink_set_inode_flag(src);
1018 xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
1019 src->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1020 xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
1021 xfs_ifork_init_cow(src);
1022 } else
1023 xfs_iunlock(src, XFS_ILOCK_EXCL);
1024
1025 if (src->i_ino == dest->i_ino)
1026 goto commit_flags;
1027
1028 if (!xfs_is_reflink_inode(dest)) {
1029 trace_xfs_reflink_set_inode_flag(dest);
1030 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1031 dest->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1032 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1033 xfs_ifork_init_cow(dest);
1034 } else
1035 xfs_iunlock(dest, XFS_ILOCK_EXCL);
1036
1037 commit_flags:
1038 error = xfs_trans_commit(tp);
1039 if (error)
1040 goto out_error;
1041 return error;
1042
1043 out_error:
1044 trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
1045 return error;
1046 }
1047
1048 /*
1049 * Update destination inode size & cowextsize hint, if necessary.
1050 */
1051 int
1052 xfs_reflink_update_dest(
1053 struct xfs_inode *dest,
1054 xfs_off_t newlen,
1055 xfs_extlen_t cowextsize,
1056 unsigned int remap_flags)
1057 {
1058 struct xfs_mount *mp = dest->i_mount;
1059 struct xfs_trans *tp;
1060 int error;
1061
1062 if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
1063 return 0;
1064
1065 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1066 if (error)
1067 goto out_error;
1068
1069 xfs_ilock(dest, XFS_ILOCK_EXCL);
1070 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1071
1072 if (newlen > i_size_read(VFS_I(dest))) {
1073 trace_xfs_reflink_update_inode_size(dest, newlen);
1074 i_size_write(VFS_I(dest), newlen);
1075 dest->i_disk_size = newlen;
1076 }
1077
1078 if (cowextsize) {
1079 dest->i_cowextsize = cowextsize;
1080 dest->i_diflags2 |= XFS_DIFLAG2_COWEXTSIZE;
1081 }
1082
1083 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1084
1085 error = xfs_trans_commit(tp);
1086 if (error)
1087 goto out_error;
1088 return error;
1089
1090 out_error:
1091 trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
1092 return error;
1093 }
1094
1095 /*
1096 * Do we have enough reserve in this AG to handle a reflink? The refcount
1097 * btree already reserved all the space it needs, but the rmap btree can grow
1098 * infinitely, so we won't allow more reflinks when the AG is down to the
1099 * btree reserves.
1100 */
1101 static int
1102 xfs_reflink_ag_has_free_space(
1103 struct xfs_mount *mp,
1104 xfs_agnumber_t agno)
1105 {
1106 struct xfs_perag *pag;
1107 int error = 0;
1108
1109 if (!xfs_has_rmapbt(mp))
1110 return 0;
1111
1112 pag = xfs_perag_get(mp, agno);
1113 if (xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) ||
1114 xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
1115 error = -ENOSPC;
1116 xfs_perag_put(pag);
1117 return error;
1118 }
1119
1120 /*
1121 * Remap the given extent into the file. The dmap blockcount will be set to
1122 * the number of blocks that were actually remapped.
1123 */
1124 STATIC int
1125 xfs_reflink_remap_extent(
1126 struct xfs_inode *ip,
1127 struct xfs_bmbt_irec *dmap,
1128 xfs_off_t new_isize)
1129 {
1130 struct xfs_bmbt_irec smap;
1131 struct xfs_mount *mp = ip->i_mount;
1132 struct xfs_trans *tp;
1133 xfs_off_t newlen;
1134 int64_t qdelta = 0;
1135 unsigned int resblks;
1136 bool quota_reserved = true;
1137 bool smap_real;
1138 bool dmap_written = xfs_bmap_is_written_extent(dmap);
1139 int iext_delta = 0;
1140 int nimaps;
1141 int error;
1142
1143 /*
1144 * Start a rolling transaction to switch the mappings.
1145 *
1146 * Adding a written extent to the extent map can cause a bmbt split,
1147 * and removing a mapped extent from the extent can cause a bmbt split.
1148 * The two operations cannot both cause a split since they operate on
1149 * the same index in the bmap btree, so we only need a reservation for
1150 * one bmbt split if either thing is happening. However, we haven't
1151 * locked the inode yet, so we reserve assuming this is the case.
1152 *
1153 * The first allocation call tries to reserve enough space to handle
1154 * mapping dmap into a sparse part of the file plus the bmbt split. We
1155 * haven't locked the inode or read the existing mapping yet, so we do
1156 * not know for sure that we need the space. This should succeed most
1157 * of the time.
1158 *
1159 * If the first attempt fails, try again but reserving only enough
1160 * space to handle a bmbt split. This is the hard minimum requirement,
1161 * and we revisit quota reservations later when we know more about what
1162 * we're remapping.
1163 */
1164 resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
1165 error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1166 resblks + dmap->br_blockcount, 0, false, &tp);
1167 if (error == -EDQUOT || error == -ENOSPC) {
1168 quota_reserved = false;
1169 error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1170 resblks, 0, false, &tp);
1171 }
1172 if (error)
1173 goto out;
1174
1175 /*
1176 * Read what's currently mapped in the destination file into smap.
1177 * If smap isn't a hole, we will have to remove it before we can add
1178 * dmap to the destination file.
1179 */
1180 nimaps = 1;
1181 error = xfs_bmapi_read(ip, dmap->br_startoff, dmap->br_blockcount,
1182 &smap, &nimaps, 0);
1183 if (error)
1184 goto out_cancel;
1185 ASSERT(nimaps == 1 && smap.br_startoff == dmap->br_startoff);
1186 smap_real = xfs_bmap_is_real_extent(&smap);
1187
1188 /*
1189 * We can only remap as many blocks as the smaller of the two extent
1190 * maps, because we can only remap one extent at a time.
1191 */
1192 dmap->br_blockcount = min(dmap->br_blockcount, smap.br_blockcount);
1193 ASSERT(dmap->br_blockcount == smap.br_blockcount);
1194
1195 trace_xfs_reflink_remap_extent_dest(ip, &smap);
1196
1197 /*
1198 * Two extents mapped to the same physical block must not have
1199 * different states; that's filesystem corruption. Move on to the next
1200 * extent if they're both holes or both the same physical extent.
1201 */
1202 if (dmap->br_startblock == smap.br_startblock) {
1203 if (dmap->br_state != smap.br_state) {
1204 xfs_bmap_mark_sick(ip, XFS_DATA_FORK);
1205 error = -EFSCORRUPTED;
1206 }
1207 goto out_cancel;
1208 }
1209
1210 /* If both extents are unwritten, leave them alone. */
1211 if (dmap->br_state == XFS_EXT_UNWRITTEN &&
1212 smap.br_state == XFS_EXT_UNWRITTEN)
1213 goto out_cancel;
1214
1215 /* No reflinking if the AG of the dest mapping is low on space. */
1216 if (dmap_written) {
1217 error = xfs_reflink_ag_has_free_space(mp,
1218 XFS_FSB_TO_AGNO(mp, dmap->br_startblock));
1219 if (error)
1220 goto out_cancel;
1221 }
1222
1223 /*
1224 * Increase quota reservation if we think the quota block counter for
1225 * this file could increase.
1226 *
1227 * If we are mapping a written extent into the file, we need to have
1228 * enough quota block count reservation to handle the blocks in that
1229 * extent. We log only the delta to the quota block counts, so if the
1230 * extent we're unmapping also has blocks allocated to it, we don't
1231 * need a quota reservation for the extent itself.
1232 *
1233 * Note that if we're replacing a delalloc reservation with a written
1234 * extent, we have to take the full quota reservation because removing
1235 * the delalloc reservation gives the block count back to the quota
1236 * count. This is suboptimal, but the VFS flushed the dest range
1237 * before we started. That should have removed all the delalloc
1238 * reservations, but we code defensively.
1239 *
1240 * xfs_trans_alloc_inode above already tried to grab an even larger
1241 * quota reservation, and kicked off a blockgc scan if it couldn't.
1242 * If we can't get a potentially smaller quota reservation now, we're
1243 * done.
1244 */
1245 if (!quota_reserved && !smap_real && dmap_written) {
1246 error = xfs_trans_reserve_quota_nblks(tp, ip,
1247 dmap->br_blockcount, 0, false);
1248 if (error)
1249 goto out_cancel;
1250 }
1251
1252 if (smap_real)
1253 ++iext_delta;
1254
1255 if (dmap_written)
1256 ++iext_delta;
1257
1258 error = xfs_iext_count_extend(tp, ip, XFS_DATA_FORK, iext_delta);
1259 if (error)
1260 goto out_cancel;
1261
1262 if (smap_real) {
1263 /*
1264 * If the extent we're unmapping is backed by storage (written
1265 * or not), unmap the extent and drop its refcount.
1266 */
1267 xfs_bmap_unmap_extent(tp, ip, XFS_DATA_FORK, &smap);
1268 xfs_refcount_decrease_extent(tp, &smap);
1269 qdelta -= smap.br_blockcount;
1270 } else if (smap.br_startblock == DELAYSTARTBLOCK) {
1271 int done;
1272
1273 /*
1274 * If the extent we're unmapping is a delalloc reservation,
1275 * we can use the regular bunmapi function to release the
1276 * incore state. Dropping the delalloc reservation takes care
1277 * of the quota reservation for us.
1278 */
1279 error = xfs_bunmapi(NULL, ip, smap.br_startoff,
1280 smap.br_blockcount, 0, 1, &done);
1281 if (error)
1282 goto out_cancel;
1283 ASSERT(done);
1284 }
1285
1286 /*
1287 * If the extent we're sharing is backed by written storage, increase
1288 * its refcount and map it into the file.
1289 */
1290 if (dmap_written) {
1291 xfs_refcount_increase_extent(tp, dmap);
1292 xfs_bmap_map_extent(tp, ip, XFS_DATA_FORK, dmap);
1293 qdelta += dmap->br_blockcount;
1294 }
1295
1296 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, qdelta);
1297
1298 /* Update dest isize if needed. */
1299 newlen = XFS_FSB_TO_B(mp, dmap->br_startoff + dmap->br_blockcount);
1300 newlen = min_t(xfs_off_t, newlen, new_isize);
1301 if (newlen > i_size_read(VFS_I(ip))) {
1302 trace_xfs_reflink_update_inode_size(ip, newlen);
1303 i_size_write(VFS_I(ip), newlen);
1304 ip->i_disk_size = newlen;
1305 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
1306 }
1307
1308 /* Commit everything and unlock. */
1309 error = xfs_trans_commit(tp);
1310 goto out_unlock;
1311
1312 out_cancel:
1313 xfs_trans_cancel(tp);
1314 out_unlock:
1315 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1316 out:
1317 if (error)
1318 trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
1319 return error;
1320 }
1321
1322 /* Remap a range of one file to the other. */
1323 int
1324 xfs_reflink_remap_blocks(
1325 struct xfs_inode *src,
1326 loff_t pos_in,
1327 struct xfs_inode *dest,
1328 loff_t pos_out,
1329 loff_t remap_len,
1330 loff_t *remapped)
1331 {
1332 struct xfs_bmbt_irec imap;
1333 struct xfs_mount *mp = src->i_mount;
1334 xfs_fileoff_t srcoff = XFS_B_TO_FSBT(mp, pos_in);
1335 xfs_fileoff_t destoff = XFS_B_TO_FSBT(mp, pos_out);
1336 xfs_filblks_t len;
1337 xfs_filblks_t remapped_len = 0;
1338 xfs_off_t new_isize = pos_out + remap_len;
1339 int nimaps;
1340 int error = 0;
1341
1342 len = min_t(xfs_filblks_t, XFS_B_TO_FSB(mp, remap_len),
1343 XFS_MAX_FILEOFF);
1344
1345 trace_xfs_reflink_remap_blocks(src, srcoff, len, dest, destoff);
1346
1347 while (len > 0) {
1348 unsigned int lock_mode;
1349
1350 /* Read extent from the source file */
1351 nimaps = 1;
1352 lock_mode = xfs_ilock_data_map_shared(src);
1353 error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
1354 xfs_iunlock(src, lock_mode);
1355 if (error)
1356 break;
1357 /*
1358 * The caller supposedly flushed all dirty pages in the source
1359 * file range, which means that writeback should have allocated
1360 * or deleted all delalloc reservations in that range. If we
1361 * find one, that's a good sign that something is seriously
1362 * wrong here.
1363 */
1364 ASSERT(nimaps == 1 && imap.br_startoff == srcoff);
1365 if (imap.br_startblock == DELAYSTARTBLOCK) {
1366 ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
1367 xfs_bmap_mark_sick(src, XFS_DATA_FORK);
1368 error = -EFSCORRUPTED;
1369 break;
1370 }
1371
1372 trace_xfs_reflink_remap_extent_src(src, &imap);
1373
1374 /* Remap into the destination file at the given offset. */
1375 imap.br_startoff = destoff;
1376 error = xfs_reflink_remap_extent(dest, &imap, new_isize);
1377 if (error)
1378 break;
1379
1380 if (fatal_signal_pending(current)) {
1381 error = -EINTR;
1382 break;
1383 }
1384
1385 /* Advance drange/srange */
1386 srcoff += imap.br_blockcount;
1387 destoff += imap.br_blockcount;
1388 len -= imap.br_blockcount;
1389 remapped_len += imap.br_blockcount;
1390 cond_resched();
1391 }
1392
1393 if (error)
1394 trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
1395 *remapped = min_t(loff_t, remap_len,
1396 XFS_FSB_TO_B(src->i_mount, remapped_len));
1397 return error;
1398 }
1399
1400 /*
1401 * If we're reflinking to a point past the destination file's EOF, we must
1402 * zero any speculative post-EOF preallocations that sit between the old EOF
1403 * and the destination file offset.
1404 */
1405 static int
1406 xfs_reflink_zero_posteof(
1407 struct xfs_inode *ip,
1408 loff_t pos)
1409 {
1410 loff_t isize = i_size_read(VFS_I(ip));
1411
1412 if (pos <= isize)
1413 return 0;
1414
1415 trace_xfs_zero_eof(ip, isize, pos - isize);
1416 return xfs_zero_range(ip, isize, pos - isize, NULL);
1417 }
1418
1419 /*
1420 * Prepare two files for range cloning. Upon a successful return both inodes
1421 * will have the iolock and mmaplock held, the page cache of the out file will
1422 * be truncated, and any leases on the out file will have been broken. This
1423 * function borrows heavily from xfs_file_aio_write_checks.
1424 *
1425 * The VFS allows partial EOF blocks to "match" for dedupe even though it hasn't
1426 * checked that the bytes beyond EOF physically match. Hence we cannot use the
1427 * EOF block in the source dedupe range because it's not a complete block match,
1428 * hence can introduce a corruption into the file that has it's block replaced.
1429 *
1430 * In similar fashion, the VFS file cloning also allows partial EOF blocks to be
1431 * "block aligned" for the purposes of cloning entire files. However, if the
1432 * source file range includes the EOF block and it lands within the existing EOF
1433 * of the destination file, then we can expose stale data from beyond the source
1434 * file EOF in the destination file.
1435 *
1436 * XFS doesn't support partial block sharing, so in both cases we have check
1437 * these cases ourselves. For dedupe, we can simply round the length to dedupe
1438 * down to the previous whole block and ignore the partial EOF block. While this
1439 * means we can't dedupe the last block of a file, this is an acceptible
1440 * tradeoff for simplicity on implementation.
1441 *
1442 * For cloning, we want to share the partial EOF block if it is also the new EOF
1443 * block of the destination file. If the partial EOF block lies inside the
1444 * existing destination EOF, then we have to abort the clone to avoid exposing
1445 * stale data in the destination file. Hence we reject these clone attempts with
1446 * -EINVAL in this case.
1447 */
1448 int
1449 xfs_reflink_remap_prep(
1450 struct file *file_in,
1451 loff_t pos_in,
1452 struct file *file_out,
1453 loff_t pos_out,
1454 loff_t *len,
1455 unsigned int remap_flags)
1456 {
1457 struct inode *inode_in = file_inode(file_in);
1458 struct xfs_inode *src = XFS_I(inode_in);
1459 struct inode *inode_out = file_inode(file_out);
1460 struct xfs_inode *dest = XFS_I(inode_out);
1461 int ret;
1462
1463 /* Lock both files against IO */
1464 ret = xfs_ilock2_io_mmap(src, dest);
1465 if (ret)
1466 return ret;
1467
1468 /* Check file eligibility and prepare for block sharing. */
1469 ret = -EINVAL;
1470 /* Don't reflink realtime inodes */
1471 if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
1472 goto out_unlock;
1473
1474 /* Don't share DAX file data with non-DAX file. */
1475 if (IS_DAX(inode_in) != IS_DAX(inode_out))
1476 goto out_unlock;
1477
1478 if (!IS_DAX(inode_in))
1479 ret = generic_remap_file_range_prep(file_in, pos_in, file_out,
1480 pos_out, len, remap_flags);
1481 else
1482 ret = dax_remap_file_range_prep(file_in, pos_in, file_out,
1483 pos_out, len, remap_flags, &xfs_read_iomap_ops);
1484 if (ret || *len == 0)
1485 goto out_unlock;
1486
1487 /* Attach dquots to dest inode before changing block map */
1488 ret = xfs_qm_dqattach(dest);
1489 if (ret)
1490 goto out_unlock;
1491
1492 /*
1493 * Zero existing post-eof speculative preallocations in the destination
1494 * file.
1495 */
1496 ret = xfs_reflink_zero_posteof(dest, pos_out);
1497 if (ret)
1498 goto out_unlock;
1499
1500 /* Set flags and remap blocks. */
1501 ret = xfs_reflink_set_inode_flag(src, dest);
1502 if (ret)
1503 goto out_unlock;
1504
1505 /*
1506 * If pos_out > EOF, we may have dirtied blocks between EOF and
1507 * pos_out. In that case, we need to extend the flush and unmap to cover
1508 * from EOF to the end of the copy length.
1509 */
1510 if (pos_out > XFS_ISIZE(dest)) {
1511 loff_t flen = *len + (pos_out - XFS_ISIZE(dest));
1512 ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen);
1513 } else {
1514 ret = xfs_flush_unmap_range(dest, pos_out, *len);
1515 }
1516 if (ret)
1517 goto out_unlock;
1518
1519 xfs_iflags_set(src, XFS_IREMAPPING);
1520 if (inode_in != inode_out)
1521 xfs_ilock_demote(src, XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL);
1522
1523 return 0;
1524 out_unlock:
1525 xfs_iunlock2_io_mmap(src, dest);
1526 return ret;
1527 }
1528
1529 /* Does this inode need the reflink flag? */
1530 int
1531 xfs_reflink_inode_has_shared_extents(
1532 struct xfs_trans *tp,
1533 struct xfs_inode *ip,
1534 bool *has_shared)
1535 {
1536 struct xfs_bmbt_irec got;
1537 struct xfs_mount *mp = ip->i_mount;
1538 struct xfs_ifork *ifp;
1539 struct xfs_iext_cursor icur;
1540 bool found;
1541 int error;
1542
1543 ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
1544 error = xfs_iread_extents(tp, ip, XFS_DATA_FORK);
1545 if (error)
1546 return error;
1547
1548 *has_shared = false;
1549 found = xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got);
1550 while (found) {
1551 struct xfs_perag *pag;
1552 xfs_agblock_t agbno;
1553 xfs_extlen_t aglen;
1554 xfs_agblock_t rbno;
1555 xfs_extlen_t rlen;
1556
1557 if (isnullstartblock(got.br_startblock) ||
1558 got.br_state != XFS_EXT_NORM)
1559 goto next;
1560
1561 pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, got.br_startblock));
1562 agbno = XFS_FSB_TO_AGBNO(mp, got.br_startblock);
1563 aglen = got.br_blockcount;
1564 error = xfs_reflink_find_shared(pag, tp, agbno, aglen,
1565 &rbno, &rlen, false);
1566 xfs_perag_put(pag);
1567 if (error)
1568 return error;
1569
1570 /* Is there still a shared block here? */
1571 if (rbno != NULLAGBLOCK) {
1572 *has_shared = true;
1573 return 0;
1574 }
1575 next:
1576 found = xfs_iext_next_extent(ifp, &icur, &got);
1577 }
1578
1579 return 0;
1580 }
1581
1582 /*
1583 * Clear the inode reflink flag if there are no shared extents.
1584 *
1585 * The caller is responsible for joining the inode to the transaction passed in.
1586 * The inode will be joined to the transaction that is returned to the caller.
1587 */
1588 int
1589 xfs_reflink_clear_inode_flag(
1590 struct xfs_inode *ip,
1591 struct xfs_trans **tpp)
1592 {
1593 bool needs_flag;
1594 int error = 0;
1595
1596 ASSERT(xfs_is_reflink_inode(ip));
1597
1598 error = xfs_reflink_inode_has_shared_extents(*tpp, ip, &needs_flag);
1599 if (error || needs_flag)
1600 return error;
1601
1602 /*
1603 * We didn't find any shared blocks so turn off the reflink flag.
1604 * First, get rid of any leftover CoW mappings.
1605 */
1606 error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, XFS_MAX_FILEOFF,
1607 true);
1608 if (error)
1609 return error;
1610
1611 /* Clear the inode flag. */
1612 trace_xfs_reflink_unset_inode_flag(ip);
1613 ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
1614 xfs_inode_clear_cowblocks_tag(ip);
1615 xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
1616
1617 return error;
1618 }
1619
1620 /*
1621 * Clear the inode reflink flag if there are no shared extents and the size
1622 * hasn't changed.
1623 */
1624 STATIC int
1625 xfs_reflink_try_clear_inode_flag(
1626 struct xfs_inode *ip)
1627 {
1628 struct xfs_mount *mp = ip->i_mount;
1629 struct xfs_trans *tp;
1630 int error = 0;
1631
1632 /* Start a rolling transaction to remove the mappings */
1633 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1634 if (error)
1635 return error;
1636
1637 xfs_ilock(ip, XFS_ILOCK_EXCL);
1638 xfs_trans_ijoin(tp, ip, 0);
1639
1640 error = xfs_reflink_clear_inode_flag(ip, &tp);
1641 if (error)
1642 goto cancel;
1643
1644 error = xfs_trans_commit(tp);
1645 if (error)
1646 goto out;
1647
1648 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1649 return 0;
1650 cancel:
1651 xfs_trans_cancel(tp);
1652 out:
1653 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1654 return error;
1655 }
1656
1657 /*
1658 * Pre-COW all shared blocks within a given byte range of a file and turn off
1659 * the reflink flag if we unshare all of the file's blocks.
1660 */
1661 int
1662 xfs_reflink_unshare(
1663 struct xfs_inode *ip,
1664 xfs_off_t offset,
1665 xfs_off_t len)
1666 {
1667 struct inode *inode = VFS_I(ip);
1668 int error;
1669
1670 if (!xfs_is_reflink_inode(ip))
1671 return 0;
1672
1673 trace_xfs_reflink_unshare(ip, offset, len);
1674
1675 inode_dio_wait(inode);
1676
1677 if (IS_DAX(inode))
1678 error = dax_file_unshare(inode, offset, len,
1679 &xfs_dax_write_iomap_ops);
1680 else
1681 error = iomap_file_unshare(inode, offset, len,
1682 &xfs_buffered_write_iomap_ops);
1683 if (error)
1684 goto out;
1685
1686 error = filemap_write_and_wait_range(inode->i_mapping, offset,
1687 offset + len - 1);
1688 if (error)
1689 goto out;
1690
1691 /* Turn off the reflink flag if possible. */
1692 error = xfs_reflink_try_clear_inode_flag(ip);
1693 if (error)
1694 goto out;
1695 return 0;
1696
1697 out:
1698 trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
1699 return error;
1700 }
1701
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