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_sb.h"
31 #include "xfs_ag_resv.h"
32
33 /*
34 * Copy on Write of Shared Blocks
35 *
36 * XFS must preserve "the usual" file semantics even when two files share
37 * the same physical blocks. This means that a write to one file must not
38 * alter the blocks in a different file; the way that we'll do that is
39 * through the use of a copy-on-write mechanism. At a high level, that
40 * means that when we want to write to a shared block, we allocate a new
41 * block, write the data to the new block, and if that succeeds we map the
42 * new block into the file.
43 *
44 * XFS provides a "delayed allocation" mechanism that defers the allocation
45 * of disk blocks to dirty-but-not-yet-mapped file blocks as long as
46 * possible. This reduces fragmentation by enabling the filesystem to ask
47 * for bigger chunks less often, which is exactly what we want for CoW.
48 *
49 * The delalloc mechanism begins when the kernel wants to make a block
50 * writable (write_begin or page_mkwrite). If the offset is not mapped, we
51 * create a delalloc mapping, which is a regular in-core extent, but without
52 * a real startblock. (For delalloc mappings, the startblock encodes both
53 * a flag that this is a delalloc mapping, and a worst-case estimate of how
54 * many blocks might be required to put the mapping into the BMBT.) delalloc
55 * mappings are a reservation against the free space in the filesystem;
56 * adjacent mappings can also be combined into fewer larger mappings.
57 *
58 * As an optimization, the CoW extent size hint (cowextsz) creates
59 * outsized aligned delalloc reservations in the hope of landing out of
60 * order nearby CoW writes in a single extent on disk, thereby reducing
61 * fragmentation and improving future performance.
62 *
63 * D: --RRRRRRSSSRRRRRRRR--- (data fork)
64 * C: ------DDDDDDD--------- (CoW fork)
65 *
66 * When dirty pages are being written out (typically in writepage), the
67 * delalloc reservations are converted into unwritten mappings by
68 * allocating blocks and replacing the delalloc mapping with real ones.
69 * A delalloc mapping can be replaced by several unwritten ones if the
70 * free space is fragmented.
71 *
72 * D: --RRRRRRSSSRRRRRRRR---
73 * C: ------UUUUUUU---------
74 *
75 * We want to adapt the delalloc mechanism for copy-on-write, since the
76 * write paths are similar. The first two steps (creating the reservation
77 * and allocating the blocks) are exactly the same as delalloc except that
78 * the mappings must be stored in a separate CoW fork because we do not want
79 * to disturb the mapping in the data fork until we're sure that the write
80 * succeeded. IO completion in this case is the process of removing the old
81 * mapping from the data fork and moving the new mapping from the CoW fork to
82 * the data fork. This will be discussed shortly.
83 *
84 * For now, unaligned directio writes will be bounced back to the page cache.
85 * Block-aligned directio writes will use the same mechanism as buffered
86 * writes.
87 *
88 * Just prior to submitting the actual disk write requests, we convert
89 * the extents representing the range of the file actually being written
90 * (as opposed to extra pieces created for the cowextsize hint) to real
91 * extents. This will become important in the next step:
92 *
93 * D: --RRRRRRSSSRRRRRRRR---
94 * C: ------UUrrUUU---------
95 *
96 * CoW remapping must be done after the data block write completes,
97 * because we don't want to destroy the old data fork map until we're sure
98 * the new block has been written. Since the new mappings are kept in a
99 * separate fork, we can simply iterate these mappings to find the ones
100 * that cover the file blocks that we just CoW'd. For each extent, simply
101 * unmap the corresponding range in the data fork, map the new range into
102 * the data fork, and remove the extent from the CoW fork. Because of
103 * the presence of the cowextsize hint, however, we must be careful
104 * only to remap the blocks that we've actually written out -- we must
105 * never remap delalloc reservations nor CoW staging blocks that have
106 * yet to be written. This corresponds exactly to the real extents in
107 * the CoW fork:
108 *
109 * D: --RRRRRRrrSRRRRRRRR---
110 * C: ------UU--UUU---------
111 *
112 * Since the remapping operation can be applied to an arbitrary file
113 * range, we record the need for the remap step as a flag in the ioend
114 * instead of declaring a new IO type. This is required for direct io
115 * because we only have ioend for the whole dio, and we have to be able to
116 * remember the presence of unwritten blocks and CoW blocks with a single
117 * ioend structure. Better yet, the more ground we can cover with one
118 * ioend, the better.
119 */
120
121 /*
122 * Given an AG extent, find the lowest-numbered run of shared blocks
123 * within that range and return the range in fbno/flen. If
124 * find_end_of_shared is true, return the longest contiguous extent of
125 * shared blocks. If there are no shared extents, fbno and flen will
126 * be set to NULLAGBLOCK and 0, respectively.
127 */
128 int
129 xfs_reflink_find_shared(
130 struct xfs_mount *mp,
131 struct xfs_trans *tp,
132 xfs_agnumber_t agno,
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(mp, tp, agno, 0, &agbp);
144 if (error)
145 return error;
146 if (!agbp)
147 return -ENOMEM;
148
149 cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno);
150
151 error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen,
152 find_end_of_shared);
153
154 xfs_btree_del_cursor(cur, error);
155
156 xfs_trans_brelse(tp, agbp);
157 return error;
158 }
159
160 /*
161 * Trim the mapping to the next block where there's a change in the
162 * shared/unshared status. More specifically, this means that we
163 * find the lowest-numbered extent of shared blocks that coincides with
164 * the given block mapping. If the shared extent overlaps the start of
165 * the mapping, trim the mapping to the end of the shared extent. If
166 * the shared region intersects the mapping, trim the mapping to the
167 * start of the shared extent. If there are no shared regions that
168 * overlap, just return the original extent.
169 */
170 int
171 xfs_reflink_trim_around_shared(
172 struct xfs_inode *ip,
173 struct xfs_bmbt_irec *irec,
174 bool *shared)
175 {
176 xfs_agnumber_t agno;
177 xfs_agblock_t agbno;
178 xfs_extlen_t aglen;
179 xfs_agblock_t fbno;
180 xfs_extlen_t flen;
181 int error = 0;
182
183 /* Holes, unwritten, and delalloc extents cannot be shared */
184 if (!xfs_is_cow_inode(ip) || !xfs_bmap_is_real_extent(irec)) {
185 *shared = false;
186 return 0;
187 }
188
189 trace_xfs_reflink_trim_around_shared(ip, irec);
190
191 agno = XFS_FSB_TO_AGNO(ip->i_mount, irec->br_startblock);
192 agbno = XFS_FSB_TO_AGBNO(ip->i_mount, irec->br_startblock);
193 aglen = irec->br_blockcount;
194
195 error = xfs_reflink_find_shared(ip->i_mount, NULL, agno, agbno,
196 aglen, &fbno, &flen, true);
197 if (error)
198 return error;
199
200 *shared = false;
201 if (fbno == NULLAGBLOCK) {
202 /* No shared blocks at all. */
203 return 0;
204 } else if (fbno == agbno) {
205 /*
206 * The start of this extent is shared. Truncate the
207 * mapping at the end of the shared region so that a
208 * subsequent iteration starts at the start of the
209 * unshared region.
210 */
211 irec->br_blockcount = flen;
212 *shared = true;
213 return 0;
214 } else {
215 /*
216 * There's a shared extent midway through this extent.
217 * Truncate the mapping at the start of the shared
218 * extent so that a subsequent iteration starts at the
219 * start of the shared region.
220 */
221 irec->br_blockcount = fbno - agbno;
222 return 0;
223 }
224 }
225
226 bool
227 xfs_inode_need_cow(
228 struct xfs_inode *ip,
229 struct xfs_bmbt_irec *imap,
230 bool *shared)
231 {
232 /* We can't update any real extents in always COW mode. */
233 if (xfs_is_always_cow_inode(ip) &&
234 !isnullstartblock(imap->br_startblock)) {
235 *shared = true;
236 return 0;
237 }
238
239 /* Trim the mapping to the nearest shared extent boundary. */
240 return xfs_reflink_trim_around_shared(ip, imap, shared);
241 }
242
243 static int
244 xfs_reflink_convert_cow_locked(
245 struct xfs_inode *ip,
246 xfs_fileoff_t offset_fsb,
247 xfs_filblks_t count_fsb)
248 {
249 struct xfs_iext_cursor icur;
250 struct xfs_bmbt_irec got;
251 struct xfs_btree_cur *dummy_cur = NULL;
252 int dummy_logflags;
253 int error = 0;
254
255 if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
256 return 0;
257
258 do {
259 if (got.br_startoff >= offset_fsb + count_fsb)
260 break;
261 if (got.br_state == XFS_EXT_NORM)
262 continue;
263 if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))
264 return -EIO;
265
266 xfs_trim_extent(&got, offset_fsb, count_fsb);
267 if (!got.br_blockcount)
268 continue;
269
270 got.br_state = XFS_EXT_NORM;
271 error = xfs_bmap_add_extent_unwritten_real(NULL, ip,
272 XFS_COW_FORK, &icur, &dummy_cur, &got,
273 &dummy_logflags);
274 if (error)
275 return error;
276 } while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));
277
278 return error;
279 }
280
281 /* Convert all of the unwritten CoW extents in a file's range to real ones. */
282 int
283 xfs_reflink_convert_cow(
284 struct xfs_inode *ip,
285 xfs_off_t offset,
286 xfs_off_t count)
287 {
288 struct xfs_mount *mp = ip->i_mount;
289 xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
290 xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
291 xfs_filblks_t count_fsb = end_fsb - offset_fsb;
292 int error;
293
294 ASSERT(count != 0);
295
296 xfs_ilock(ip, XFS_ILOCK_EXCL);
297 error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
298 xfs_iunlock(ip, XFS_ILOCK_EXCL);
299 return error;
300 }
301
302 /*
303 * Find the extent that maps the given range in the COW fork. Even if the extent
304 * is not shared we might have a preallocation for it in the COW fork. If so we
305 * use it that rather than trigger a new allocation.
306 */
307 static int
308 xfs_find_trim_cow_extent(
309 struct xfs_inode *ip,
310 struct xfs_bmbt_irec *imap,
311 bool *shared,
312 bool *found)
313 {
314 xfs_fileoff_t offset_fsb = imap->br_startoff;
315 xfs_filblks_t count_fsb = imap->br_blockcount;
316 struct xfs_iext_cursor icur;
317 struct xfs_bmbt_irec got;
318
319 *found = false;
320
321 /*
322 * If we don't find an overlapping extent, trim the range we need to
323 * allocate to fit the hole we found.
324 */
325 if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
326 got.br_startoff = offset_fsb + count_fsb;
327 if (got.br_startoff > offset_fsb) {
328 xfs_trim_extent(imap, imap->br_startoff,
329 got.br_startoff - imap->br_startoff);
330 return xfs_inode_need_cow(ip, imap, shared);
331 }
332
333 *shared = true;
334 if (isnullstartblock(got.br_startblock)) {
335 xfs_trim_extent(imap, got.br_startoff, got.br_blockcount);
336 return 0;
337 }
338
339 /* real extent found - no need to allocate */
340 xfs_trim_extent(&got, offset_fsb, count_fsb);
341 *imap = got;
342 *found = true;
343 return 0;
344 }
345
346 /* Allocate all CoW reservations covering a range of blocks in a file. */
347 int
348 xfs_reflink_allocate_cow(
349 struct xfs_inode *ip,
350 struct xfs_bmbt_irec *imap,
351 bool *shared,
352 uint *lockmode,
353 bool convert_now)
354 {
355 struct xfs_mount *mp = ip->i_mount;
356 xfs_fileoff_t offset_fsb = imap->br_startoff;
357 xfs_filblks_t count_fsb = imap->br_blockcount;
358 struct xfs_trans *tp;
359 int nimaps, error = 0;
360 bool found;
361 xfs_filblks_t resaligned;
362 xfs_extlen_t resblks = 0;
363
364 ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
365 if (!ip->i_cowfp) {
366 ASSERT(!xfs_is_reflink_inode(ip));
367 xfs_ifork_init_cow(ip);
368 }
369
370 error = xfs_find_trim_cow_extent(ip, imap, shared, &found);
371 if (error || !*shared)
372 return error;
373 if (found)
374 goto convert;
375
376 resaligned = xfs_aligned_fsb_count(imap->br_startoff,
377 imap->br_blockcount, xfs_get_cowextsz_hint(ip));
378 resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
379
380 xfs_iunlock(ip, *lockmode);
381 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
382 *lockmode = XFS_ILOCK_EXCL;
383 xfs_ilock(ip, *lockmode);
384
385 if (error)
386 return error;
387
388 error = xfs_qm_dqattach_locked(ip, false);
389 if (error)
390 goto out_trans_cancel;
391
392 /*
393 * Check for an overlapping extent again now that we dropped the ilock.
394 */
395 error = xfs_find_trim_cow_extent(ip, imap, shared, &found);
396 if (error || !*shared)
397 goto out_trans_cancel;
398 if (found) {
399 xfs_trans_cancel(tp);
400 goto convert;
401 }
402
403 error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0,
404 XFS_QMOPT_RES_REGBLKS);
405 if (error)
406 goto out_trans_cancel;
407
408 xfs_trans_ijoin(tp, ip, 0);
409
410 /* Allocate the entire reservation as unwritten blocks. */
411 nimaps = 1;
412 error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
413 XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC,
414 resblks, imap, &nimaps);
415 if (error)
416 goto out_unreserve;
417
418 xfs_inode_set_cowblocks_tag(ip);
419 error = xfs_trans_commit(tp);
420 if (error)
421 return error;
422
423 /*
424 * Allocation succeeded but the requested range was not even partially
425 * satisfied? Bail out!
426 */
427 if (nimaps == 0)
428 return -ENOSPC;
429 convert:
430 xfs_trim_extent(imap, offset_fsb, count_fsb);
431 /*
432 * COW fork extents are supposed to remain unwritten until we're ready
433 * to initiate a disk write. For direct I/O we are going to write the
434 * data and need the conversion, but for buffered writes we're done.
435 */
436 if (!convert_now || imap->br_state == XFS_EXT_NORM)
437 return 0;
438 trace_xfs_reflink_convert_cow(ip, imap);
439 return xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
440
441 out_unreserve:
442 xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,
443 XFS_QMOPT_RES_REGBLKS);
444 out_trans_cancel:
445 xfs_trans_cancel(tp);
446 return error;
447 }
448
449 /*
450 * Cancel CoW reservations for some block range of an inode.
451 *
452 * If cancel_real is true this function cancels all COW fork extents for the
453 * inode; if cancel_real is false, real extents are not cleared.
454 *
455 * Caller must have already joined the inode to the current transaction. The
456 * inode will be joined to the transaction returned to the caller.
457 */
458 int
459 xfs_reflink_cancel_cow_blocks(
460 struct xfs_inode *ip,
461 struct xfs_trans **tpp,
462 xfs_fileoff_t offset_fsb,
463 xfs_fileoff_t end_fsb,
464 bool cancel_real)
465 {
466 struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
467 struct xfs_bmbt_irec got, del;
468 struct xfs_iext_cursor icur;
469 int error = 0;
470
471 if (!xfs_inode_has_cow_data(ip))
472 return 0;
473 if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got))
474 return 0;
475
476 /* Walk backwards until we're out of the I/O range... */
477 while (got.br_startoff + got.br_blockcount > offset_fsb) {
478 del = got;
479 xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
480
481 /* Extent delete may have bumped ext forward */
482 if (!del.br_blockcount) {
483 xfs_iext_prev(ifp, &icur);
484 goto next_extent;
485 }
486
487 trace_xfs_reflink_cancel_cow(ip, &del);
488
489 if (isnullstartblock(del.br_startblock)) {
490 error = xfs_bmap_del_extent_delay(ip, XFS_COW_FORK,
491 &icur, &got, &del);
492 if (error)
493 break;
494 } else if (del.br_state == XFS_EXT_UNWRITTEN || cancel_real) {
495 ASSERT((*tpp)->t_firstblock == NULLFSBLOCK);
496
497 /* Free the CoW orphan record. */
498 xfs_refcount_free_cow_extent(*tpp, del.br_startblock,
499 del.br_blockcount);
500
501 xfs_bmap_add_free(*tpp, del.br_startblock,
502 del.br_blockcount, NULL);
503
504 /* Roll the transaction */
505 error = xfs_defer_finish(tpp);
506 if (error)
507 break;
508
509 /* Remove the mapping from the CoW fork. */
510 xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
511
512 /* Remove the quota reservation */
513 error = xfs_trans_reserve_quota_nblks(NULL, ip,
514 -(long)del.br_blockcount, 0,
515 XFS_QMOPT_RES_REGBLKS);
516 if (error)
517 break;
518 } else {
519 /* Didn't do anything, push cursor back. */
520 xfs_iext_prev(ifp, &icur);
521 }
522 next_extent:
523 if (!xfs_iext_get_extent(ifp, &icur, &got))
524 break;
525 }
526
527 /* clear tag if cow fork is emptied */
528 if (!ifp->if_bytes)
529 xfs_inode_clear_cowblocks_tag(ip);
530 return error;
531 }
532
533 /*
534 * Cancel CoW reservations for some byte range of an inode.
535 *
536 * If cancel_real is true this function cancels all COW fork extents for the
537 * inode; if cancel_real is false, real extents are not cleared.
538 */
539 int
540 xfs_reflink_cancel_cow_range(
541 struct xfs_inode *ip,
542 xfs_off_t offset,
543 xfs_off_t count,
544 bool cancel_real)
545 {
546 struct xfs_trans *tp;
547 xfs_fileoff_t offset_fsb;
548 xfs_fileoff_t end_fsb;
549 int error;
550
551 trace_xfs_reflink_cancel_cow_range(ip, offset, count);
552 ASSERT(ip->i_cowfp);
553
554 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
555 if (count == NULLFILEOFF)
556 end_fsb = NULLFILEOFF;
557 else
558 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
559
560 /* Start a rolling transaction to remove the mappings */
561 error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
562 0, 0, 0, &tp);
563 if (error)
564 goto out;
565
566 xfs_ilock(ip, XFS_ILOCK_EXCL);
567 xfs_trans_ijoin(tp, ip, 0);
568
569 /* Scrape out the old CoW reservations */
570 error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb,
571 cancel_real);
572 if (error)
573 goto out_cancel;
574
575 error = xfs_trans_commit(tp);
576
577 xfs_iunlock(ip, XFS_ILOCK_EXCL);
578 return error;
579
580 out_cancel:
581 xfs_trans_cancel(tp);
582 xfs_iunlock(ip, XFS_ILOCK_EXCL);
583 out:
584 trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_);
585 return error;
586 }
587
588 /*
589 * Remap part of the CoW fork into the data fork.
590 *
591 * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
592 * into the data fork; this function will remap what it can (at the end of the
593 * range) and update @end_fsb appropriately. Each remap gets its own
594 * transaction because we can end up merging and splitting bmbt blocks for
595 * every remap operation and we'd like to keep the block reservation
596 * requirements as low as possible.
597 */
598 STATIC int
599 xfs_reflink_end_cow_extent(
600 struct xfs_inode *ip,
601 xfs_fileoff_t offset_fsb,
602 xfs_fileoff_t *end_fsb)
603 {
604 struct xfs_bmbt_irec got, del;
605 struct xfs_iext_cursor icur;
606 struct xfs_mount *mp = ip->i_mount;
607 struct xfs_trans *tp;
608 struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
609 xfs_filblks_t rlen;
610 unsigned int resblks;
611 int error;
612
613 /* No COW extents? That's easy! */
614 if (ifp->if_bytes == 0) {
615 *end_fsb = offset_fsb;
616 return 0;
617 }
618
619 resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
620 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
621 XFS_TRANS_RESERVE, &tp);
622 if (error)
623 return error;
624
625 /*
626 * Lock the inode. We have to ijoin without automatic unlock because
627 * the lead transaction is the refcountbt record deletion; the data
628 * fork update follows as a deferred log item.
629 */
630 xfs_ilock(ip, XFS_ILOCK_EXCL);
631 xfs_trans_ijoin(tp, ip, 0);
632
633 /*
634 * In case of racing, overlapping AIO writes no COW extents might be
635 * left by the time I/O completes for the loser of the race. In that
636 * case we are done.
637 */
638 if (!xfs_iext_lookup_extent_before(ip, ifp, end_fsb, &icur, &got) ||
639 got.br_startoff + got.br_blockcount <= offset_fsb) {
640 *end_fsb = offset_fsb;
641 goto out_cancel;
642 }
643
644 /*
645 * Structure copy @got into @del, then trim @del to the range that we
646 * were asked to remap. We preserve @got for the eventual CoW fork
647 * deletion; from now on @del represents the mapping that we're
648 * actually remapping.
649 */
650 del = got;
651 xfs_trim_extent(&del, offset_fsb, *end_fsb - offset_fsb);
652
653 ASSERT(del.br_blockcount > 0);
654
655 /*
656 * Only remap real extents that contain data. With AIO, speculative
657 * preallocations can leak into the range we are called upon, and we
658 * need to skip them.
659 */
660 if (!xfs_bmap_is_real_extent(&got)) {
661 *end_fsb = del.br_startoff;
662 goto out_cancel;
663 }
664
665 /* Unmap the old blocks in the data fork. */
666 rlen = del.br_blockcount;
667 error = __xfs_bunmapi(tp, ip, del.br_startoff, &rlen, 0, 1);
668 if (error)
669 goto out_cancel;
670
671 /* Trim the extent to whatever got unmapped. */
672 xfs_trim_extent(&del, del.br_startoff + rlen, del.br_blockcount - rlen);
673 trace_xfs_reflink_cow_remap(ip, &del);
674
675 /* Free the CoW orphan record. */
676 xfs_refcount_free_cow_extent(tp, del.br_startblock, del.br_blockcount);
677
678 /* Map the new blocks into the data fork. */
679 xfs_bmap_map_extent(tp, ip, &del);
680
681 /* Charge this new data fork mapping to the on-disk quota. */
682 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
683 (long)del.br_blockcount);
684
685 /* Remove the mapping from the CoW fork. */
686 xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
687
688 error = xfs_trans_commit(tp);
689 xfs_iunlock(ip, XFS_ILOCK_EXCL);
690 if (error)
691 return error;
692
693 /* Update the caller about how much progress we made. */
694 *end_fsb = del.br_startoff;
695 return 0;
696
697 out_cancel:
698 xfs_trans_cancel(tp);
699 xfs_iunlock(ip, XFS_ILOCK_EXCL);
700 return error;
701 }
702
703 /*
704 * Remap parts of a file's data fork after a successful CoW.
705 */
706 int
707 xfs_reflink_end_cow(
708 struct xfs_inode *ip,
709 xfs_off_t offset,
710 xfs_off_t count)
711 {
712 xfs_fileoff_t offset_fsb;
713 xfs_fileoff_t end_fsb;
714 int error = 0;
715
716 trace_xfs_reflink_end_cow(ip, offset, count);
717
718 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
719 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
720
721 /*
722 * Walk backwards until we're out of the I/O range. The loop function
723 * repeatedly cycles the ILOCK to allocate one transaction per remapped
724 * extent.
725 *
726 * If we're being called by writeback then the the pages will still
727 * have PageWriteback set, which prevents races with reflink remapping
728 * and truncate. Reflink remapping prevents races with writeback by
729 * taking the iolock and mmaplock before flushing the pages and
730 * remapping, which means there won't be any further writeback or page
731 * cache dirtying until the reflink completes.
732 *
733 * We should never have two threads issuing writeback for the same file
734 * region. There are also have post-eof checks in the writeback
735 * preparation code so that we don't bother writing out pages that are
736 * about to be truncated.
737 *
738 * If we're being called as part of directio write completion, the dio
739 * count is still elevated, which reflink and truncate will wait for.
740 * Reflink remapping takes the iolock and mmaplock and waits for
741 * pending dio to finish, which should prevent any directio until the
742 * remap completes. Multiple concurrent directio writes to the same
743 * region are handled by end_cow processing only occurring for the
744 * threads which succeed; the outcome of multiple overlapping direct
745 * writes is not well defined anyway.
746 *
747 * It's possible that a buffered write and a direct write could collide
748 * here (the buffered write stumbles in after the dio flushes and
749 * invalidates the page cache and immediately queues writeback), but we
750 * have never supported this 100%. If either disk write succeeds the
751 * blocks will be remapped.
752 */
753 while (end_fsb > offset_fsb && !error)
754 error = xfs_reflink_end_cow_extent(ip, offset_fsb, &end_fsb);
755
756 if (error)
757 trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
758 return error;
759 }
760
761 /*
762 * Free leftover CoW reservations that didn't get cleaned out.
763 */
764 int
765 xfs_reflink_recover_cow(
766 struct xfs_mount *mp)
767 {
768 xfs_agnumber_t agno;
769 int error = 0;
770
771 if (!xfs_sb_version_hasreflink(&mp->m_sb))
772 return 0;
773
774 for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
775 error = xfs_refcount_recover_cow_leftovers(mp, agno);
776 if (error)
777 break;
778 }
779
780 return error;
781 }
782
783 /*
784 * Reflinking (Block) Ranges of Two Files Together
785 *
786 * First, ensure that the reflink flag is set on both inodes. The flag is an
787 * optimization to avoid unnecessary refcount btree lookups in the write path.
788 *
789 * Now we can iteratively remap the range of extents (and holes) in src to the
790 * corresponding ranges in dest. Let drange and srange denote the ranges of
791 * logical blocks in dest and src touched by the reflink operation.
792 *
793 * While the length of drange is greater than zero,
794 * - Read src's bmbt at the start of srange ("imap")
795 * - If imap doesn't exist, make imap appear to start at the end of srange
796 * with zero length.
797 * - If imap starts before srange, advance imap to start at srange.
798 * - If imap goes beyond srange, truncate imap to end at the end of srange.
799 * - Punch (imap start - srange start + imap len) blocks from dest at
800 * offset (drange start).
801 * - If imap points to a real range of pblks,
802 * > Increase the refcount of the imap's pblks
803 * > Map imap's pblks into dest at the offset
804 * (drange start + imap start - srange start)
805 * - Advance drange and srange by (imap start - srange start + imap len)
806 *
807 * Finally, if the reflink made dest longer, update both the in-core and
808 * on-disk file sizes.
809 *
810 * ASCII Art Demonstration:
811 *
812 * Let's say we want to reflink this source file:
813 *
814 * ----SSSSSSS-SSSSS----SSSSSS (src file)
815 * <-------------------->
816 *
817 * into this destination file:
818 *
819 * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
820 * <-------------------->
821 * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
822 * Observe that the range has different logical offsets in either file.
823 *
824 * Consider that the first extent in the source file doesn't line up with our
825 * reflink range. Unmapping and remapping are separate operations, so we can
826 * unmap more blocks from the destination file than we remap.
827 *
828 * ----SSSSSSS-SSSSS----SSSSSS
829 * <------->
830 * --DDDDD---------DDDDD--DDD
831 * <------->
832 *
833 * Now remap the source extent into the destination file:
834 *
835 * ----SSSSSSS-SSSSS----SSSSSS
836 * <------->
837 * --DDDDD--SSSSSSSDDDDD--DDD
838 * <------->
839 *
840 * Do likewise with the second hole and extent in our range. Holes in the
841 * unmap range don't affect our operation.
842 *
843 * ----SSSSSSS-SSSSS----SSSSSS
844 * <---->
845 * --DDDDD--SSSSSSS-SSSSS-DDD
846 * <---->
847 *
848 * Finally, unmap and remap part of the third extent. This will increase the
849 * size of the destination file.
850 *
851 * ----SSSSSSS-SSSSS----SSSSSS
852 * <----->
853 * --DDDDD--SSSSSSS-SSSSS----SSS
854 * <----->
855 *
856 * Once we update the destination file's i_size, we're done.
857 */
858
859 /*
860 * Ensure the reflink bit is set in both inodes.
861 */
862 STATIC int
863 xfs_reflink_set_inode_flag(
864 struct xfs_inode *src,
865 struct xfs_inode *dest)
866 {
867 struct xfs_mount *mp = src->i_mount;
868 int error;
869 struct xfs_trans *tp;
870
871 if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
872 return 0;
873
874 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
875 if (error)
876 goto out_error;
877
878 /* Lock both files against IO */
879 if (src->i_ino == dest->i_ino)
880 xfs_ilock(src, XFS_ILOCK_EXCL);
881 else
882 xfs_lock_two_inodes(src, XFS_ILOCK_EXCL, dest, XFS_ILOCK_EXCL);
883
884 if (!xfs_is_reflink_inode(src)) {
885 trace_xfs_reflink_set_inode_flag(src);
886 xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
887 src->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK;
888 xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
889 xfs_ifork_init_cow(src);
890 } else
891 xfs_iunlock(src, XFS_ILOCK_EXCL);
892
893 if (src->i_ino == dest->i_ino)
894 goto commit_flags;
895
896 if (!xfs_is_reflink_inode(dest)) {
897 trace_xfs_reflink_set_inode_flag(dest);
898 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
899 dest->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK;
900 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
901 xfs_ifork_init_cow(dest);
902 } else
903 xfs_iunlock(dest, XFS_ILOCK_EXCL);
904
905 commit_flags:
906 error = xfs_trans_commit(tp);
907 if (error)
908 goto out_error;
909 return error;
910
911 out_error:
912 trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
913 return error;
914 }
915
916 /*
917 * Update destination inode size & cowextsize hint, if necessary.
918 */
919 int
920 xfs_reflink_update_dest(
921 struct xfs_inode *dest,
922 xfs_off_t newlen,
923 xfs_extlen_t cowextsize,
924 unsigned int remap_flags)
925 {
926 struct xfs_mount *mp = dest->i_mount;
927 struct xfs_trans *tp;
928 int error;
929
930 if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
931 return 0;
932
933 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
934 if (error)
935 goto out_error;
936
937 xfs_ilock(dest, XFS_ILOCK_EXCL);
938 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
939
940 if (newlen > i_size_read(VFS_I(dest))) {
941 trace_xfs_reflink_update_inode_size(dest, newlen);
942 i_size_write(VFS_I(dest), newlen);
943 dest->i_d.di_size = newlen;
944 }
945
946 if (cowextsize) {
947 dest->i_d.di_cowextsize = cowextsize;
948 dest->i_d.di_flags2 |= XFS_DIFLAG2_COWEXTSIZE;
949 }
950
951 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
952
953 error = xfs_trans_commit(tp);
954 if (error)
955 goto out_error;
956 return error;
957
958 out_error:
959 trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
960 return error;
961 }
962
963 /*
964 * Do we have enough reserve in this AG to handle a reflink? The refcount
965 * btree already reserved all the space it needs, but the rmap btree can grow
966 * infinitely, so we won't allow more reflinks when the AG is down to the
967 * btree reserves.
968 */
969 static int
970 xfs_reflink_ag_has_free_space(
971 struct xfs_mount *mp,
972 xfs_agnumber_t agno)
973 {
974 struct xfs_perag *pag;
975 int error = 0;
976
977 if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
978 return 0;
979
980 pag = xfs_perag_get(mp, agno);
981 if (xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) ||
982 xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
983 error = -ENOSPC;
984 xfs_perag_put(pag);
985 return error;
986 }
987
988 /*
989 * Unmap a range of blocks from a file, then map other blocks into the hole.
990 * The range to unmap is (destoff : destoff + srcioff + irec->br_blockcount).
991 * The extent irec is mapped into dest at irec->br_startoff.
992 */
993 STATIC int
994 xfs_reflink_remap_extent(
995 struct xfs_inode *ip,
996 struct xfs_bmbt_irec *irec,
997 xfs_fileoff_t destoff,
998 xfs_off_t new_isize)
999 {
1000 struct xfs_mount *mp = ip->i_mount;
1001 bool real_extent = xfs_bmap_is_real_extent(irec);
1002 struct xfs_trans *tp;
1003 unsigned int resblks;
1004 struct xfs_bmbt_irec uirec;
1005 xfs_filblks_t rlen;
1006 xfs_filblks_t unmap_len;
1007 xfs_off_t newlen;
1008 int error;
1009
1010 unmap_len = irec->br_startoff + irec->br_blockcount - destoff;
1011 trace_xfs_reflink_punch_range(ip, destoff, unmap_len);
1012
1013 /* No reflinking if we're low on space */
1014 if (real_extent) {
1015 error = xfs_reflink_ag_has_free_space(mp,
1016 XFS_FSB_TO_AGNO(mp, irec->br_startblock));
1017 if (error)
1018 goto out;
1019 }
1020
1021 /* Start a rolling transaction to switch the mappings */
1022 resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);
1023 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
1024 if (error)
1025 goto out;
1026
1027 xfs_ilock(ip, XFS_ILOCK_EXCL);
1028 xfs_trans_ijoin(tp, ip, 0);
1029
1030 /* If we're not just clearing space, then do we have enough quota? */
1031 if (real_extent) {
1032 error = xfs_trans_reserve_quota_nblks(tp, ip,
1033 irec->br_blockcount, 0, XFS_QMOPT_RES_REGBLKS);
1034 if (error)
1035 goto out_cancel;
1036 }
1037
1038 trace_xfs_reflink_remap(ip, irec->br_startoff,
1039 irec->br_blockcount, irec->br_startblock);
1040
1041 /* Unmap the old blocks in the data fork. */
1042 rlen = unmap_len;
1043 while (rlen) {
1044 ASSERT(tp->t_firstblock == NULLFSBLOCK);
1045 error = __xfs_bunmapi(tp, ip, destoff, &rlen, 0, 1);
1046 if (error)
1047 goto out_cancel;
1048
1049 /*
1050 * Trim the extent to whatever got unmapped.
1051 * Remember, bunmapi works backwards.
1052 */
1053 uirec.br_startblock = irec->br_startblock + rlen;
1054 uirec.br_startoff = irec->br_startoff + rlen;
1055 uirec.br_blockcount = unmap_len - rlen;
1056 uirec.br_state = irec->br_state;
1057 unmap_len = rlen;
1058
1059 /* If this isn't a real mapping, we're done. */
1060 if (!real_extent || uirec.br_blockcount == 0)
1061 goto next_extent;
1062
1063 trace_xfs_reflink_remap(ip, uirec.br_startoff,
1064 uirec.br_blockcount, uirec.br_startblock);
1065
1066 /* Update the refcount tree */
1067 xfs_refcount_increase_extent(tp, &uirec);
1068
1069 /* Map the new blocks into the data fork. */
1070 xfs_bmap_map_extent(tp, ip, &uirec);
1071
1072 /* Update quota accounting. */
1073 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
1074 uirec.br_blockcount);
1075
1076 /* Update dest isize if needed. */
1077 newlen = XFS_FSB_TO_B(mp,
1078 uirec.br_startoff + uirec.br_blockcount);
1079 newlen = min_t(xfs_off_t, newlen, new_isize);
1080 if (newlen > i_size_read(VFS_I(ip))) {
1081 trace_xfs_reflink_update_inode_size(ip, newlen);
1082 i_size_write(VFS_I(ip), newlen);
1083 ip->i_d.di_size = newlen;
1084 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
1085 }
1086
1087 next_extent:
1088 /* Process all the deferred stuff. */
1089 error = xfs_defer_finish(&tp);
1090 if (error)
1091 goto out_cancel;
1092 }
1093
1094 error = xfs_trans_commit(tp);
1095 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1096 if (error)
1097 goto out;
1098 return 0;
1099
1100 out_cancel:
1101 xfs_trans_cancel(tp);
1102 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1103 out:
1104 trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
1105 return error;
1106 }
1107
1108 /*
1109 * Iteratively remap one file's extents (and holes) to another's.
1110 */
1111 int
1112 xfs_reflink_remap_blocks(
1113 struct xfs_inode *src,
1114 loff_t pos_in,
1115 struct xfs_inode *dest,
1116 loff_t pos_out,
1117 loff_t remap_len,
1118 loff_t *remapped)
1119 {
1120 struct xfs_bmbt_irec imap;
1121 xfs_fileoff_t srcoff;
1122 xfs_fileoff_t destoff;
1123 xfs_filblks_t len;
1124 xfs_filblks_t range_len;
1125 xfs_filblks_t remapped_len = 0;
1126 xfs_off_t new_isize = pos_out + remap_len;
1127 int nimaps;
1128 int error = 0;
1129
1130 destoff = XFS_B_TO_FSBT(src->i_mount, pos_out);
1131 srcoff = XFS_B_TO_FSBT(src->i_mount, pos_in);
1132 len = XFS_B_TO_FSB(src->i_mount, remap_len);
1133
1134 /* drange = (destoff, destoff + len); srange = (srcoff, srcoff + len) */
1135 while (len) {
1136 uint lock_mode;
1137
1138 trace_xfs_reflink_remap_blocks_loop(src, srcoff, len,
1139 dest, destoff);
1140
1141 /* Read extent from the source file */
1142 nimaps = 1;
1143 lock_mode = xfs_ilock_data_map_shared(src);
1144 error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
1145 xfs_iunlock(src, lock_mode);
1146 if (error)
1147 break;
1148 ASSERT(nimaps == 1);
1149
1150 trace_xfs_reflink_remap_imap(src, srcoff, len, XFS_DATA_FORK,
1151 &imap);
1152
1153 /* Translate imap into the destination file. */
1154 range_len = imap.br_startoff + imap.br_blockcount - srcoff;
1155 imap.br_startoff += destoff - srcoff;
1156
1157 /* Clear dest from destoff to the end of imap and map it in. */
1158 error = xfs_reflink_remap_extent(dest, &imap, destoff,
1159 new_isize);
1160 if (error)
1161 break;
1162
1163 if (fatal_signal_pending(current)) {
1164 error = -EINTR;
1165 break;
1166 }
1167
1168 /* Advance drange/srange */
1169 srcoff += range_len;
1170 destoff += range_len;
1171 len -= range_len;
1172 remapped_len += range_len;
1173 }
1174
1175 if (error)
1176 trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
1177 *remapped = min_t(loff_t, remap_len,
1178 XFS_FSB_TO_B(src->i_mount, remapped_len));
1179 return error;
1180 }
1181
1182 /*
1183 * Grab the exclusive iolock for a data copy from src to dest, making sure to
1184 * abide vfs locking order (lowest pointer value goes first) and breaking the
1185 * layout leases before proceeding. The loop is needed because we cannot call
1186 * the blocking break_layout() with the iolocks held, and therefore have to
1187 * back out both locks.
1188 */
1189 static int
1190 xfs_iolock_two_inodes_and_break_layout(
1191 struct inode *src,
1192 struct inode *dest)
1193 {
1194 int error;
1195
1196 if (src > dest)
1197 swap(src, dest);
1198
1199 retry:
1200 /* Wait to break both inodes' layouts before we start locking. */
1201 error = break_layout(src, true);
1202 if (error)
1203 return error;
1204 if (src != dest) {
1205 error = break_layout(dest, true);
1206 if (error)
1207 return error;
1208 }
1209
1210 /* Lock one inode and make sure nobody got in and leased it. */
1211 inode_lock(src);
1212 error = break_layout(src, false);
1213 if (error) {
1214 inode_unlock(src);
1215 if (error == -EWOULDBLOCK)
1216 goto retry;
1217 return error;
1218 }
1219
1220 if (src == dest)
1221 return 0;
1222
1223 /* Lock the other inode and make sure nobody got in and leased it. */
1224 inode_lock_nested(dest, I_MUTEX_NONDIR2);
1225 error = break_layout(dest, false);
1226 if (error) {
1227 inode_unlock(src);
1228 inode_unlock(dest);
1229 if (error == -EWOULDBLOCK)
1230 goto retry;
1231 return error;
1232 }
1233
1234 return 0;
1235 }
1236
1237 /* Unlock both inodes after they've been prepped for a range clone. */
1238 void
1239 xfs_reflink_remap_unlock(
1240 struct file *file_in,
1241 struct file *file_out)
1242 {
1243 struct inode *inode_in = file_inode(file_in);
1244 struct xfs_inode *src = XFS_I(inode_in);
1245 struct inode *inode_out = file_inode(file_out);
1246 struct xfs_inode *dest = XFS_I(inode_out);
1247 bool same_inode = (inode_in == inode_out);
1248
1249 xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
1250 if (!same_inode)
1251 xfs_iunlock(src, XFS_MMAPLOCK_EXCL);
1252 inode_unlock(inode_out);
1253 if (!same_inode)
1254 inode_unlock(inode_in);
1255 }
1256
1257 /*
1258 * If we're reflinking to a point past the destination file's EOF, we must
1259 * zero any speculative post-EOF preallocations that sit between the old EOF
1260 * and the destination file offset.
1261 */
1262 static int
1263 xfs_reflink_zero_posteof(
1264 struct xfs_inode *ip,
1265 loff_t pos)
1266 {
1267 loff_t isize = i_size_read(VFS_I(ip));
1268
1269 if (pos <= isize)
1270 return 0;
1271
1272 trace_xfs_zero_eof(ip, isize, pos - isize);
1273 return iomap_zero_range(VFS_I(ip), isize, pos - isize, NULL,
1274 &xfs_iomap_ops);
1275 }
1276
1277 /*
1278 * Prepare two files for range cloning. Upon a successful return both inodes
1279 * will have the iolock and mmaplock held, the page cache of the out file will
1280 * be truncated, and any leases on the out file will have been broken. This
1281 * function borrows heavily from xfs_file_aio_write_checks.
1282 *
1283 * The VFS allows partial EOF blocks to "match" for dedupe even though it hasn't
1284 * checked that the bytes beyond EOF physically match. Hence we cannot use the
1285 * EOF block in the source dedupe range because it's not a complete block match,
1286 * hence can introduce a corruption into the file that has it's block replaced.
1287 *
1288 * In similar fashion, the VFS file cloning also allows partial EOF blocks to be
1289 * "block aligned" for the purposes of cloning entire files. However, if the
1290 * source file range includes the EOF block and it lands within the existing EOF
1291 * of the destination file, then we can expose stale data from beyond the source
1292 * file EOF in the destination file.
1293 *
1294 * XFS doesn't support partial block sharing, so in both cases we have check
1295 * these cases ourselves. For dedupe, we can simply round the length to dedupe
1296 * down to the previous whole block and ignore the partial EOF block. While this
1297 * means we can't dedupe the last block of a file, this is an acceptible
1298 * tradeoff for simplicity on implementation.
1299 *
1300 * For cloning, we want to share the partial EOF block if it is also the new EOF
1301 * block of the destination file. If the partial EOF block lies inside the
1302 * existing destination EOF, then we have to abort the clone to avoid exposing
1303 * stale data in the destination file. Hence we reject these clone attempts with
1304 * -EINVAL in this case.
1305 */
1306 int
1307 xfs_reflink_remap_prep(
1308 struct file *file_in,
1309 loff_t pos_in,
1310 struct file *file_out,
1311 loff_t pos_out,
1312 loff_t *len,
1313 unsigned int remap_flags)
1314 {
1315 struct inode *inode_in = file_inode(file_in);
1316 struct xfs_inode *src = XFS_I(inode_in);
1317 struct inode *inode_out = file_inode(file_out);
1318 struct xfs_inode *dest = XFS_I(inode_out);
1319 bool same_inode = (inode_in == inode_out);
1320 ssize_t ret;
1321
1322 /* Lock both files against IO */
1323 ret = xfs_iolock_two_inodes_and_break_layout(inode_in, inode_out);
1324 if (ret)
1325 return ret;
1326 if (same_inode)
1327 xfs_ilock(src, XFS_MMAPLOCK_EXCL);
1328 else
1329 xfs_lock_two_inodes(src, XFS_MMAPLOCK_EXCL, dest,
1330 XFS_MMAPLOCK_EXCL);
1331
1332 /* Check file eligibility and prepare for block sharing. */
1333 ret = -EINVAL;
1334 /* Don't reflink realtime inodes */
1335 if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
1336 goto out_unlock;
1337
1338 /* Don't share DAX file data for now. */
1339 if (IS_DAX(inode_in) || IS_DAX(inode_out))
1340 goto out_unlock;
1341
1342 ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
1343 len, remap_flags);
1344 if (ret < 0 || *len == 0)
1345 goto out_unlock;
1346
1347 /* Attach dquots to dest inode before changing block map */
1348 ret = xfs_qm_dqattach(dest);
1349 if (ret)
1350 goto out_unlock;
1351
1352 /*
1353 * Zero existing post-eof speculative preallocations in the destination
1354 * file.
1355 */
1356 ret = xfs_reflink_zero_posteof(dest, pos_out);
1357 if (ret)
1358 goto out_unlock;
1359
1360 /* Set flags and remap blocks. */
1361 ret = xfs_reflink_set_inode_flag(src, dest);
1362 if (ret)
1363 goto out_unlock;
1364
1365 /*
1366 * If pos_out > EOF, we may have dirtied blocks between EOF and
1367 * pos_out. In that case, we need to extend the flush and unmap to cover
1368 * from EOF to the end of the copy length.
1369 */
1370 if (pos_out > XFS_ISIZE(dest)) {
1371 loff_t flen = *len + (pos_out - XFS_ISIZE(dest));
1372 ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen);
1373 } else {
1374 ret = xfs_flush_unmap_range(dest, pos_out, *len);
1375 }
1376 if (ret)
1377 goto out_unlock;
1378
1379 return 1;
1380 out_unlock:
1381 xfs_reflink_remap_unlock(file_in, file_out);
1382 return ret;
1383 }
1384
1385 /*
1386 * The user wants to preemptively CoW all shared blocks in this file,
1387 * which enables us to turn off the reflink flag. Iterate all
1388 * extents which are not prealloc/delalloc to see which ranges are
1389 * mentioned in the refcount tree, then read those blocks into the
1390 * pagecache, dirty them, fsync them back out, and then we can update
1391 * the inode flag. What happens if we run out of memory? :)
1392 */
1393 STATIC int
1394 xfs_reflink_dirty_extents(
1395 struct xfs_inode *ip,
1396 xfs_fileoff_t fbno,
1397 xfs_filblks_t end,
1398 xfs_off_t isize)
1399 {
1400 struct xfs_mount *mp = ip->i_mount;
1401 xfs_agnumber_t agno;
1402 xfs_agblock_t agbno;
1403 xfs_extlen_t aglen;
1404 xfs_agblock_t rbno;
1405 xfs_extlen_t rlen;
1406 xfs_off_t fpos;
1407 xfs_off_t flen;
1408 struct xfs_bmbt_irec map[2];
1409 int nmaps;
1410 int error = 0;
1411
1412 while (end - fbno > 0) {
1413 nmaps = 1;
1414 /*
1415 * Look for extents in the file. Skip holes, delalloc, or
1416 * unwritten extents; they can't be reflinked.
1417 */
1418 error = xfs_bmapi_read(ip, fbno, end - fbno, map, &nmaps, 0);
1419 if (error)
1420 goto out;
1421 if (nmaps == 0)
1422 break;
1423 if (!xfs_bmap_is_real_extent(&map[0]))
1424 goto next;
1425
1426 map[1] = map[0];
1427 while (map[1].br_blockcount) {
1428 agno = XFS_FSB_TO_AGNO(mp, map[1].br_startblock);
1429 agbno = XFS_FSB_TO_AGBNO(mp, map[1].br_startblock);
1430 aglen = map[1].br_blockcount;
1431
1432 error = xfs_reflink_find_shared(mp, NULL, agno, agbno,
1433 aglen, &rbno, &rlen, true);
1434 if (error)
1435 goto out;
1436 if (rbno == NULLAGBLOCK)
1437 break;
1438
1439 /* Dirty the pages */
1440 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1441 fpos = XFS_FSB_TO_B(mp, map[1].br_startoff +
1442 (rbno - agbno));
1443 flen = XFS_FSB_TO_B(mp, rlen);
1444 if (fpos + flen > isize)
1445 flen = isize - fpos;
1446 error = iomap_file_dirty(VFS_I(ip), fpos, flen,
1447 &xfs_iomap_ops);
1448 xfs_ilock(ip, XFS_ILOCK_EXCL);
1449 if (error)
1450 goto out;
1451
1452 map[1].br_blockcount -= (rbno - agbno + rlen);
1453 map[1].br_startoff += (rbno - agbno + rlen);
1454 map[1].br_startblock += (rbno - agbno + rlen);
1455 }
1456
1457 next:
1458 fbno = map[0].br_startoff + map[0].br_blockcount;
1459 }
1460 out:
1461 return error;
1462 }
1463
1464 /* Does this inode need the reflink flag? */
1465 int
1466 xfs_reflink_inode_has_shared_extents(
1467 struct xfs_trans *tp,
1468 struct xfs_inode *ip,
1469 bool *has_shared)
1470 {
1471 struct xfs_bmbt_irec got;
1472 struct xfs_mount *mp = ip->i_mount;
1473 struct xfs_ifork *ifp;
1474 xfs_agnumber_t agno;
1475 xfs_agblock_t agbno;
1476 xfs_extlen_t aglen;
1477 xfs_agblock_t rbno;
1478 xfs_extlen_t rlen;
1479 struct xfs_iext_cursor icur;
1480 bool found;
1481 int error;
1482
1483 ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
1484 if (!(ifp->if_flags & XFS_IFEXTENTS)) {
1485 error = xfs_iread_extents(tp, ip, XFS_DATA_FORK);
1486 if (error)
1487 return error;
1488 }
1489
1490 *has_shared = false;
1491 found = xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got);
1492 while (found) {
1493 if (isnullstartblock(got.br_startblock) ||
1494 got.br_state != XFS_EXT_NORM)
1495 goto next;
1496 agno = XFS_FSB_TO_AGNO(mp, got.br_startblock);
1497 agbno = XFS_FSB_TO_AGBNO(mp, got.br_startblock);
1498 aglen = got.br_blockcount;
1499
1500 error = xfs_reflink_find_shared(mp, tp, agno, agbno, aglen,
1501 &rbno, &rlen, false);
1502 if (error)
1503 return error;
1504 /* Is there still a shared block here? */
1505 if (rbno != NULLAGBLOCK) {
1506 *has_shared = true;
1507 return 0;
1508 }
1509 next:
1510 found = xfs_iext_next_extent(ifp, &icur, &got);
1511 }
1512
1513 return 0;
1514 }
1515
1516 /*
1517 * Clear the inode reflink flag if there are no shared extents.
1518 *
1519 * The caller is responsible for joining the inode to the transaction passed in.
1520 * The inode will be joined to the transaction that is returned to the caller.
1521 */
1522 int
1523 xfs_reflink_clear_inode_flag(
1524 struct xfs_inode *ip,
1525 struct xfs_trans **tpp)
1526 {
1527 bool needs_flag;
1528 int error = 0;
1529
1530 ASSERT(xfs_is_reflink_inode(ip));
1531
1532 error = xfs_reflink_inode_has_shared_extents(*tpp, ip, &needs_flag);
1533 if (error || needs_flag)
1534 return error;
1535
1536 /*
1537 * We didn't find any shared blocks so turn off the reflink flag.
1538 * First, get rid of any leftover CoW mappings.
1539 */
1540 error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, NULLFILEOFF, true);
1541 if (error)
1542 return error;
1543
1544 /* Clear the inode flag. */
1545 trace_xfs_reflink_unset_inode_flag(ip);
1546 ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
1547 xfs_inode_clear_cowblocks_tag(ip);
1548 xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
1549
1550 return error;
1551 }
1552
1553 /*
1554 * Clear the inode reflink flag if there are no shared extents and the size
1555 * hasn't changed.
1556 */
1557 STATIC int
1558 xfs_reflink_try_clear_inode_flag(
1559 struct xfs_inode *ip)
1560 {
1561 struct xfs_mount *mp = ip->i_mount;
1562 struct xfs_trans *tp;
1563 int error = 0;
1564
1565 /* Start a rolling transaction to remove the mappings */
1566 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1567 if (error)
1568 return error;
1569
1570 xfs_ilock(ip, XFS_ILOCK_EXCL);
1571 xfs_trans_ijoin(tp, ip, 0);
1572
1573 error = xfs_reflink_clear_inode_flag(ip, &tp);
1574 if (error)
1575 goto cancel;
1576
1577 error = xfs_trans_commit(tp);
1578 if (error)
1579 goto out;
1580
1581 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1582 return 0;
1583 cancel:
1584 xfs_trans_cancel(tp);
1585 out:
1586 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1587 return error;
1588 }
1589
1590 /*
1591 * Pre-COW all shared blocks within a given byte range of a file and turn off
1592 * the reflink flag if we unshare all of the file's blocks.
1593 */
1594 int
1595 xfs_reflink_unshare(
1596 struct xfs_inode *ip,
1597 xfs_off_t offset,
1598 xfs_off_t len)
1599 {
1600 struct xfs_mount *mp = ip->i_mount;
1601 xfs_fileoff_t fbno;
1602 xfs_filblks_t end;
1603 xfs_off_t isize;
1604 int error;
1605
1606 if (!xfs_is_reflink_inode(ip))
1607 return 0;
1608
1609 trace_xfs_reflink_unshare(ip, offset, len);
1610
1611 inode_dio_wait(VFS_I(ip));
1612
1613 /* Try to CoW the selected ranges */
1614 xfs_ilock(ip, XFS_ILOCK_EXCL);
1615 fbno = XFS_B_TO_FSBT(mp, offset);
1616 isize = i_size_read(VFS_I(ip));
1617 end = XFS_B_TO_FSB(mp, offset + len);
1618 error = xfs_reflink_dirty_extents(ip, fbno, end, isize);
1619 if (error)
1620 goto out_unlock;
1621 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1622
1623 /* Wait for the IO to finish */
1624 error = filemap_write_and_wait(VFS_I(ip)->i_mapping);
1625 if (error)
1626 goto out;
1627
1628 /* Turn off the reflink flag if possible. */
1629 error = xfs_reflink_try_clear_inode_flag(ip);
1630 if (error)
1631 goto out;
1632
1633 return 0;
1634
1635 out_unlock:
1636 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1637 out:
1638 trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
1639 return error;
1640 }