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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 */
129static int
130xfs_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_mount(pag), 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 */
168int
169xfs_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
228int
229xfs_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
245static int
246xfs_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. */
284int
285xfs_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 */
309static int
310xfs_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
347static int
348xfs_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
380static int
381xfs_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
433convert:
434 return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
435
436out_trans_cancel:
437 xfs_trans_cancel(tp);
438 return error;
439}
440
441static int
442xfs_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
499out_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. */
505int
506xfs_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 */
563int
564xfs_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 }
624next_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 */
641int
642xfs_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
682out_cancel:
683 xfs_trans_cancel(tp);
684 xfs_iunlock(ip, XFS_ILOCK_EXCL);
685out:
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 */
700STATIC int
701xfs_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
823out_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 */
832int
833xfs_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 */
893int
894xfs_reflink_recover_cow(
895 struct xfs_mount *mp)
896{
897 struct xfs_perag *pag = NULL;
898 int error = 0;
899
900 if (!xfs_has_reflink(mp))
901 return 0;
902
903 while ((pag = xfs_perag_next(mp, pag))) {
904 error = xfs_refcount_recover_cow_leftovers(mp, pag);
905 if (error) {
906 xfs_perag_rele(pag);
907 break;
908 }
909 }
910
911 return error;
912}
913
914/*
915 * Reflinking (Block) Ranges of Two Files Together
916 *
917 * First, ensure that the reflink flag is set on both inodes. The flag is an
918 * optimization to avoid unnecessary refcount btree lookups in the write path.
919 *
920 * Now we can iteratively remap the range of extents (and holes) in src to the
921 * corresponding ranges in dest. Let drange and srange denote the ranges of
922 * logical blocks in dest and src touched by the reflink operation.
923 *
924 * While the length of drange is greater than zero,
925 * - Read src's bmbt at the start of srange ("imap")
926 * - If imap doesn't exist, make imap appear to start at the end of srange
927 * with zero length.
928 * - If imap starts before srange, advance imap to start at srange.
929 * - If imap goes beyond srange, truncate imap to end at the end of srange.
930 * - Punch (imap start - srange start + imap len) blocks from dest at
931 * offset (drange start).
932 * - If imap points to a real range of pblks,
933 * > Increase the refcount of the imap's pblks
934 * > Map imap's pblks into dest at the offset
935 * (drange start + imap start - srange start)
936 * - Advance drange and srange by (imap start - srange start + imap len)
937 *
938 * Finally, if the reflink made dest longer, update both the in-core and
939 * on-disk file sizes.
940 *
941 * ASCII Art Demonstration:
942 *
943 * Let's say we want to reflink this source file:
944 *
945 * ----SSSSSSS-SSSSS----SSSSSS (src file)
946 * <-------------------->
947 *
948 * into this destination file:
949 *
950 * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
951 * <-------------------->
952 * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
953 * Observe that the range has different logical offsets in either file.
954 *
955 * Consider that the first extent in the source file doesn't line up with our
956 * reflink range. Unmapping and remapping are separate operations, so we can
957 * unmap more blocks from the destination file than we remap.
958 *
959 * ----SSSSSSS-SSSSS----SSSSSS
960 * <------->
961 * --DDDDD---------DDDDD--DDD
962 * <------->
963 *
964 * Now remap the source extent into the destination file:
965 *
966 * ----SSSSSSS-SSSSS----SSSSSS
967 * <------->
968 * --DDDDD--SSSSSSSDDDDD--DDD
969 * <------->
970 *
971 * Do likewise with the second hole and extent in our range. Holes in the
972 * unmap range don't affect our operation.
973 *
974 * ----SSSSSSS-SSSSS----SSSSSS
975 * <---->
976 * --DDDDD--SSSSSSS-SSSSS-DDD
977 * <---->
978 *
979 * Finally, unmap and remap part of the third extent. This will increase the
980 * size of the destination file.
981 *
982 * ----SSSSSSS-SSSSS----SSSSSS
983 * <----->
984 * --DDDDD--SSSSSSS-SSSSS----SSS
985 * <----->
986 *
987 * Once we update the destination file's i_size, we're done.
988 */
989
990/*
991 * Ensure the reflink bit is set in both inodes.
992 */
993STATIC int
994xfs_reflink_set_inode_flag(
995 struct xfs_inode *src,
996 struct xfs_inode *dest)
997{
998 struct xfs_mount *mp = src->i_mount;
999 int error;
1000 struct xfs_trans *tp;
1001
1002 if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
1003 return 0;
1004
1005 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1006 if (error)
1007 goto out_error;
1008
1009 /* Lock both files against IO */
1010 if (src->i_ino == dest->i_ino)
1011 xfs_ilock(src, XFS_ILOCK_EXCL);
1012 else
1013 xfs_lock_two_inodes(src, XFS_ILOCK_EXCL, dest, XFS_ILOCK_EXCL);
1014
1015 if (!xfs_is_reflink_inode(src)) {
1016 trace_xfs_reflink_set_inode_flag(src);
1017 xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
1018 src->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1019 xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
1020 xfs_ifork_init_cow(src);
1021 } else
1022 xfs_iunlock(src, XFS_ILOCK_EXCL);
1023
1024 if (src->i_ino == dest->i_ino)
1025 goto commit_flags;
1026
1027 if (!xfs_is_reflink_inode(dest)) {
1028 trace_xfs_reflink_set_inode_flag(dest);
1029 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1030 dest->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1031 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1032 xfs_ifork_init_cow(dest);
1033 } else
1034 xfs_iunlock(dest, XFS_ILOCK_EXCL);
1035
1036commit_flags:
1037 error = xfs_trans_commit(tp);
1038 if (error)
1039 goto out_error;
1040 return error;
1041
1042out_error:
1043 trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
1044 return error;
1045}
1046
1047/*
1048 * Update destination inode size & cowextsize hint, if necessary.
1049 */
1050int
1051xfs_reflink_update_dest(
1052 struct xfs_inode *dest,
1053 xfs_off_t newlen,
1054 xfs_extlen_t cowextsize,
1055 unsigned int remap_flags)
1056{
1057 struct xfs_mount *mp = dest->i_mount;
1058 struct xfs_trans *tp;
1059 int error;
1060
1061 if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
1062 return 0;
1063
1064 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1065 if (error)
1066 goto out_error;
1067
1068 xfs_ilock(dest, XFS_ILOCK_EXCL);
1069 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1070
1071 if (newlen > i_size_read(VFS_I(dest))) {
1072 trace_xfs_reflink_update_inode_size(dest, newlen);
1073 i_size_write(VFS_I(dest), newlen);
1074 dest->i_disk_size = newlen;
1075 }
1076
1077 if (cowextsize) {
1078 dest->i_cowextsize = cowextsize;
1079 dest->i_diflags2 |= XFS_DIFLAG2_COWEXTSIZE;
1080 }
1081
1082 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1083
1084 error = xfs_trans_commit(tp);
1085 if (error)
1086 goto out_error;
1087 return error;
1088
1089out_error:
1090 trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
1091 return error;
1092}
1093
1094/*
1095 * Do we have enough reserve in this AG to handle a reflink? The refcount
1096 * btree already reserved all the space it needs, but the rmap btree can grow
1097 * infinitely, so we won't allow more reflinks when the AG is down to the
1098 * btree reserves.
1099 */
1100static int
1101xfs_reflink_ag_has_free_space(
1102 struct xfs_mount *mp,
1103 xfs_agnumber_t agno)
1104{
1105 struct xfs_perag *pag;
1106 int error = 0;
1107
1108 if (!xfs_has_rmapbt(mp))
1109 return 0;
1110
1111 pag = xfs_perag_get(mp, agno);
1112 if (xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) ||
1113 xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
1114 error = -ENOSPC;
1115 xfs_perag_put(pag);
1116 return error;
1117}
1118
1119/*
1120 * Remap the given extent into the file. The dmap blockcount will be set to
1121 * the number of blocks that were actually remapped.
1122 */
1123STATIC int
1124xfs_reflink_remap_extent(
1125 struct xfs_inode *ip,
1126 struct xfs_bmbt_irec *dmap,
1127 xfs_off_t new_isize)
1128{
1129 struct xfs_bmbt_irec smap;
1130 struct xfs_mount *mp = ip->i_mount;
1131 struct xfs_trans *tp;
1132 xfs_off_t newlen;
1133 int64_t qdelta = 0;
1134 unsigned int resblks;
1135 bool quota_reserved = true;
1136 bool smap_real;
1137 bool dmap_written = xfs_bmap_is_written_extent(dmap);
1138 int iext_delta = 0;
1139 int nimaps;
1140 int error;
1141
1142 /*
1143 * Start a rolling transaction to switch the mappings.
1144 *
1145 * Adding a written extent to the extent map can cause a bmbt split,
1146 * and removing a mapped extent from the extent can cause a bmbt split.
1147 * The two operations cannot both cause a split since they operate on
1148 * the same index in the bmap btree, so we only need a reservation for
1149 * one bmbt split if either thing is happening. However, we haven't
1150 * locked the inode yet, so we reserve assuming this is the case.
1151 *
1152 * The first allocation call tries to reserve enough space to handle
1153 * mapping dmap into a sparse part of the file plus the bmbt split. We
1154 * haven't locked the inode or read the existing mapping yet, so we do
1155 * not know for sure that we need the space. This should succeed most
1156 * of the time.
1157 *
1158 * If the first attempt fails, try again but reserving only enough
1159 * space to handle a bmbt split. This is the hard minimum requirement,
1160 * and we revisit quota reservations later when we know more about what
1161 * we're remapping.
1162 */
1163 resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
1164 error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1165 resblks + dmap->br_blockcount, 0, false, &tp);
1166 if (error == -EDQUOT || error == -ENOSPC) {
1167 quota_reserved = false;
1168 error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1169 resblks, 0, false, &tp);
1170 }
1171 if (error)
1172 goto out;
1173
1174 /*
1175 * Read what's currently mapped in the destination file into smap.
1176 * If smap isn't a hole, we will have to remove it before we can add
1177 * dmap to the destination file.
1178 */
1179 nimaps = 1;
1180 error = xfs_bmapi_read(ip, dmap->br_startoff, dmap->br_blockcount,
1181 &smap, &nimaps, 0);
1182 if (error)
1183 goto out_cancel;
1184 ASSERT(nimaps == 1 && smap.br_startoff == dmap->br_startoff);
1185 smap_real = xfs_bmap_is_real_extent(&smap);
1186
1187 /*
1188 * We can only remap as many blocks as the smaller of the two extent
1189 * maps, because we can only remap one extent at a time.
1190 */
1191 dmap->br_blockcount = min(dmap->br_blockcount, smap.br_blockcount);
1192 ASSERT(dmap->br_blockcount == smap.br_blockcount);
1193
1194 trace_xfs_reflink_remap_extent_dest(ip, &smap);
1195
1196 /*
1197 * Two extents mapped to the same physical block must not have
1198 * different states; that's filesystem corruption. Move on to the next
1199 * extent if they're both holes or both the same physical extent.
1200 */
1201 if (dmap->br_startblock == smap.br_startblock) {
1202 if (dmap->br_state != smap.br_state) {
1203 xfs_bmap_mark_sick(ip, XFS_DATA_FORK);
1204 error = -EFSCORRUPTED;
1205 }
1206 goto out_cancel;
1207 }
1208
1209 /* If both extents are unwritten, leave them alone. */
1210 if (dmap->br_state == XFS_EXT_UNWRITTEN &&
1211 smap.br_state == XFS_EXT_UNWRITTEN)
1212 goto out_cancel;
1213
1214 /* No reflinking if the AG of the dest mapping is low on space. */
1215 if (dmap_written) {
1216 error = xfs_reflink_ag_has_free_space(mp,
1217 XFS_FSB_TO_AGNO(mp, dmap->br_startblock));
1218 if (error)
1219 goto out_cancel;
1220 }
1221
1222 /*
1223 * Increase quota reservation if we think the quota block counter for
1224 * this file could increase.
1225 *
1226 * If we are mapping a written extent into the file, we need to have
1227 * enough quota block count reservation to handle the blocks in that
1228 * extent. We log only the delta to the quota block counts, so if the
1229 * extent we're unmapping also has blocks allocated to it, we don't
1230 * need a quota reservation for the extent itself.
1231 *
1232 * Note that if we're replacing a delalloc reservation with a written
1233 * extent, we have to take the full quota reservation because removing
1234 * the delalloc reservation gives the block count back to the quota
1235 * count. This is suboptimal, but the VFS flushed the dest range
1236 * before we started. That should have removed all the delalloc
1237 * reservations, but we code defensively.
1238 *
1239 * xfs_trans_alloc_inode above already tried to grab an even larger
1240 * quota reservation, and kicked off a blockgc scan if it couldn't.
1241 * If we can't get a potentially smaller quota reservation now, we're
1242 * done.
1243 */
1244 if (!quota_reserved && !smap_real && dmap_written) {
1245 error = xfs_trans_reserve_quota_nblks(tp, ip,
1246 dmap->br_blockcount, 0, false);
1247 if (error)
1248 goto out_cancel;
1249 }
1250
1251 if (smap_real)
1252 ++iext_delta;
1253
1254 if (dmap_written)
1255 ++iext_delta;
1256
1257 error = xfs_iext_count_extend(tp, ip, XFS_DATA_FORK, iext_delta);
1258 if (error)
1259 goto out_cancel;
1260
1261 if (smap_real) {
1262 /*
1263 * If the extent we're unmapping is backed by storage (written
1264 * or not), unmap the extent and drop its refcount.
1265 */
1266 xfs_bmap_unmap_extent(tp, ip, XFS_DATA_FORK, &smap);
1267 xfs_refcount_decrease_extent(tp, &smap);
1268 qdelta -= smap.br_blockcount;
1269 } else if (smap.br_startblock == DELAYSTARTBLOCK) {
1270 int done;
1271
1272 /*
1273 * If the extent we're unmapping is a delalloc reservation,
1274 * we can use the regular bunmapi function to release the
1275 * incore state. Dropping the delalloc reservation takes care
1276 * of the quota reservation for us.
1277 */
1278 error = xfs_bunmapi(NULL, ip, smap.br_startoff,
1279 smap.br_blockcount, 0, 1, &done);
1280 if (error)
1281 goto out_cancel;
1282 ASSERT(done);
1283 }
1284
1285 /*
1286 * If the extent we're sharing is backed by written storage, increase
1287 * its refcount and map it into the file.
1288 */
1289 if (dmap_written) {
1290 xfs_refcount_increase_extent(tp, dmap);
1291 xfs_bmap_map_extent(tp, ip, XFS_DATA_FORK, dmap);
1292 qdelta += dmap->br_blockcount;
1293 }
1294
1295 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, qdelta);
1296
1297 /* Update dest isize if needed. */
1298 newlen = XFS_FSB_TO_B(mp, dmap->br_startoff + dmap->br_blockcount);
1299 newlen = min_t(xfs_off_t, newlen, new_isize);
1300 if (newlen > i_size_read(VFS_I(ip))) {
1301 trace_xfs_reflink_update_inode_size(ip, newlen);
1302 i_size_write(VFS_I(ip), newlen);
1303 ip->i_disk_size = newlen;
1304 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
1305 }
1306
1307 /* Commit everything and unlock. */
1308 error = xfs_trans_commit(tp);
1309 goto out_unlock;
1310
1311out_cancel:
1312 xfs_trans_cancel(tp);
1313out_unlock:
1314 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1315out:
1316 if (error)
1317 trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
1318 return error;
1319}
1320
1321/* Remap a range of one file to the other. */
1322int
1323xfs_reflink_remap_blocks(
1324 struct xfs_inode *src,
1325 loff_t pos_in,
1326 struct xfs_inode *dest,
1327 loff_t pos_out,
1328 loff_t remap_len,
1329 loff_t *remapped)
1330{
1331 struct xfs_bmbt_irec imap;
1332 struct xfs_mount *mp = src->i_mount;
1333 xfs_fileoff_t srcoff = XFS_B_TO_FSBT(mp, pos_in);
1334 xfs_fileoff_t destoff = XFS_B_TO_FSBT(mp, pos_out);
1335 xfs_filblks_t len;
1336 xfs_filblks_t remapped_len = 0;
1337 xfs_off_t new_isize = pos_out + remap_len;
1338 int nimaps;
1339 int error = 0;
1340
1341 len = min_t(xfs_filblks_t, XFS_B_TO_FSB(mp, remap_len),
1342 XFS_MAX_FILEOFF);
1343
1344 trace_xfs_reflink_remap_blocks(src, srcoff, len, dest, destoff);
1345
1346 while (len > 0) {
1347 unsigned int lock_mode;
1348
1349 /* Read extent from the source file */
1350 nimaps = 1;
1351 lock_mode = xfs_ilock_data_map_shared(src);
1352 error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
1353 xfs_iunlock(src, lock_mode);
1354 if (error)
1355 break;
1356 /*
1357 * The caller supposedly flushed all dirty pages in the source
1358 * file range, which means that writeback should have allocated
1359 * or deleted all delalloc reservations in that range. If we
1360 * find one, that's a good sign that something is seriously
1361 * wrong here.
1362 */
1363 ASSERT(nimaps == 1 && imap.br_startoff == srcoff);
1364 if (imap.br_startblock == DELAYSTARTBLOCK) {
1365 ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
1366 xfs_bmap_mark_sick(src, XFS_DATA_FORK);
1367 error = -EFSCORRUPTED;
1368 break;
1369 }
1370
1371 trace_xfs_reflink_remap_extent_src(src, &imap);
1372
1373 /* Remap into the destination file at the given offset. */
1374 imap.br_startoff = destoff;
1375 error = xfs_reflink_remap_extent(dest, &imap, new_isize);
1376 if (error)
1377 break;
1378
1379 if (fatal_signal_pending(current)) {
1380 error = -EINTR;
1381 break;
1382 }
1383
1384 /* Advance drange/srange */
1385 srcoff += imap.br_blockcount;
1386 destoff += imap.br_blockcount;
1387 len -= imap.br_blockcount;
1388 remapped_len += imap.br_blockcount;
1389 cond_resched();
1390 }
1391
1392 if (error)
1393 trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
1394 *remapped = min_t(loff_t, remap_len,
1395 XFS_FSB_TO_B(src->i_mount, remapped_len));
1396 return error;
1397}
1398
1399/*
1400 * If we're reflinking to a point past the destination file's EOF, we must
1401 * zero any speculative post-EOF preallocations that sit between the old EOF
1402 * and the destination file offset.
1403 */
1404static int
1405xfs_reflink_zero_posteof(
1406 struct xfs_inode *ip,
1407 loff_t pos)
1408{
1409 loff_t isize = i_size_read(VFS_I(ip));
1410
1411 if (pos <= isize)
1412 return 0;
1413
1414 trace_xfs_zero_eof(ip, isize, pos - isize);
1415 return xfs_zero_range(ip, isize, pos - isize, NULL);
1416}
1417
1418/*
1419 * Prepare two files for range cloning. Upon a successful return both inodes
1420 * will have the iolock and mmaplock held, the page cache of the out file will
1421 * be truncated, and any leases on the out file will have been broken. This
1422 * function borrows heavily from xfs_file_aio_write_checks.
1423 *
1424 * The VFS allows partial EOF blocks to "match" for dedupe even though it hasn't
1425 * checked that the bytes beyond EOF physically match. Hence we cannot use the
1426 * EOF block in the source dedupe range because it's not a complete block match,
1427 * hence can introduce a corruption into the file that has it's block replaced.
1428 *
1429 * In similar fashion, the VFS file cloning also allows partial EOF blocks to be
1430 * "block aligned" for the purposes of cloning entire files. However, if the
1431 * source file range includes the EOF block and it lands within the existing EOF
1432 * of the destination file, then we can expose stale data from beyond the source
1433 * file EOF in the destination file.
1434 *
1435 * XFS doesn't support partial block sharing, so in both cases we have check
1436 * these cases ourselves. For dedupe, we can simply round the length to dedupe
1437 * down to the previous whole block and ignore the partial EOF block. While this
1438 * means we can't dedupe the last block of a file, this is an acceptible
1439 * tradeoff for simplicity on implementation.
1440 *
1441 * For cloning, we want to share the partial EOF block if it is also the new EOF
1442 * block of the destination file. If the partial EOF block lies inside the
1443 * existing destination EOF, then we have to abort the clone to avoid exposing
1444 * stale data in the destination file. Hence we reject these clone attempts with
1445 * -EINVAL in this case.
1446 */
1447int
1448xfs_reflink_remap_prep(
1449 struct file *file_in,
1450 loff_t pos_in,
1451 struct file *file_out,
1452 loff_t pos_out,
1453 loff_t *len,
1454 unsigned int remap_flags)
1455{
1456 struct inode *inode_in = file_inode(file_in);
1457 struct xfs_inode *src = XFS_I(inode_in);
1458 struct inode *inode_out = file_inode(file_out);
1459 struct xfs_inode *dest = XFS_I(inode_out);
1460 int ret;
1461
1462 /* Lock both files against IO */
1463 ret = xfs_ilock2_io_mmap(src, dest);
1464 if (ret)
1465 return ret;
1466
1467 /* Check file eligibility and prepare for block sharing. */
1468 ret = -EINVAL;
1469 /* Don't reflink realtime inodes */
1470 if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
1471 goto out_unlock;
1472
1473 /* Don't share DAX file data with non-DAX file. */
1474 if (IS_DAX(inode_in) != IS_DAX(inode_out))
1475 goto out_unlock;
1476
1477 if (!IS_DAX(inode_in))
1478 ret = generic_remap_file_range_prep(file_in, pos_in, file_out,
1479 pos_out, len, remap_flags);
1480 else
1481 ret = dax_remap_file_range_prep(file_in, pos_in, file_out,
1482 pos_out, len, remap_flags, &xfs_read_iomap_ops);
1483 if (ret || *len == 0)
1484 goto out_unlock;
1485
1486 /* Attach dquots to dest inode before changing block map */
1487 ret = xfs_qm_dqattach(dest);
1488 if (ret)
1489 goto out_unlock;
1490
1491 /*
1492 * Zero existing post-eof speculative preallocations in the destination
1493 * file.
1494 */
1495 ret = xfs_reflink_zero_posteof(dest, pos_out);
1496 if (ret)
1497 goto out_unlock;
1498
1499 /* Set flags and remap blocks. */
1500 ret = xfs_reflink_set_inode_flag(src, dest);
1501 if (ret)
1502 goto out_unlock;
1503
1504 /*
1505 * If pos_out > EOF, we may have dirtied blocks between EOF and
1506 * pos_out. In that case, we need to extend the flush and unmap to cover
1507 * from EOF to the end of the copy length.
1508 */
1509 if (pos_out > XFS_ISIZE(dest)) {
1510 loff_t flen = *len + (pos_out - XFS_ISIZE(dest));
1511 ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen);
1512 } else {
1513 ret = xfs_flush_unmap_range(dest, pos_out, *len);
1514 }
1515 if (ret)
1516 goto out_unlock;
1517
1518 xfs_iflags_set(src, XFS_IREMAPPING);
1519 if (inode_in != inode_out)
1520 xfs_ilock_demote(src, XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL);
1521
1522 return 0;
1523out_unlock:
1524 xfs_iunlock2_io_mmap(src, dest);
1525 return ret;
1526}
1527
1528/* Does this inode need the reflink flag? */
1529int
1530xfs_reflink_inode_has_shared_extents(
1531 struct xfs_trans *tp,
1532 struct xfs_inode *ip,
1533 bool *has_shared)
1534{
1535 struct xfs_bmbt_irec got;
1536 struct xfs_mount *mp = ip->i_mount;
1537 struct xfs_ifork *ifp;
1538 struct xfs_iext_cursor icur;
1539 bool found;
1540 int error;
1541
1542 ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
1543 error = xfs_iread_extents(tp, ip, XFS_DATA_FORK);
1544 if (error)
1545 return error;
1546
1547 *has_shared = false;
1548 found = xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got);
1549 while (found) {
1550 struct xfs_perag *pag;
1551 xfs_agblock_t agbno;
1552 xfs_extlen_t aglen;
1553 xfs_agblock_t rbno;
1554 xfs_extlen_t rlen;
1555
1556 if (isnullstartblock(got.br_startblock) ||
1557 got.br_state != XFS_EXT_NORM)
1558 goto next;
1559
1560 pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, got.br_startblock));
1561 agbno = XFS_FSB_TO_AGBNO(mp, got.br_startblock);
1562 aglen = got.br_blockcount;
1563 error = xfs_reflink_find_shared(pag, tp, agbno, aglen,
1564 &rbno, &rlen, false);
1565 xfs_perag_put(pag);
1566 if (error)
1567 return error;
1568
1569 /* Is there still a shared block here? */
1570 if (rbno != NULLAGBLOCK) {
1571 *has_shared = true;
1572 return 0;
1573 }
1574next:
1575 found = xfs_iext_next_extent(ifp, &icur, &got);
1576 }
1577
1578 return 0;
1579}
1580
1581/*
1582 * Clear the inode reflink flag if there are no shared extents.
1583 *
1584 * The caller is responsible for joining the inode to the transaction passed in.
1585 * The inode will be joined to the transaction that is returned to the caller.
1586 */
1587int
1588xfs_reflink_clear_inode_flag(
1589 struct xfs_inode *ip,
1590 struct xfs_trans **tpp)
1591{
1592 bool needs_flag;
1593 int error = 0;
1594
1595 ASSERT(xfs_is_reflink_inode(ip));
1596
1597 if (!xfs_can_free_cowblocks(ip))
1598 return 0;
1599
1600 error = xfs_reflink_inode_has_shared_extents(*tpp, ip, &needs_flag);
1601 if (error || needs_flag)
1602 return error;
1603
1604 /*
1605 * We didn't find any shared blocks so turn off the reflink flag.
1606 * First, get rid of any leftover CoW mappings.
1607 */
1608 error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, XFS_MAX_FILEOFF,
1609 true);
1610 if (error)
1611 return error;
1612
1613 /* Clear the inode flag. */
1614 trace_xfs_reflink_unset_inode_flag(ip);
1615 ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
1616 xfs_inode_clear_cowblocks_tag(ip);
1617 xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
1618
1619 return error;
1620}
1621
1622/*
1623 * Clear the inode reflink flag if there are no shared extents and the size
1624 * hasn't changed.
1625 */
1626STATIC int
1627xfs_reflink_try_clear_inode_flag(
1628 struct xfs_inode *ip)
1629{
1630 struct xfs_mount *mp = ip->i_mount;
1631 struct xfs_trans *tp;
1632 int error = 0;
1633
1634 /* Start a rolling transaction to remove the mappings */
1635 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1636 if (error)
1637 return error;
1638
1639 xfs_ilock(ip, XFS_ILOCK_EXCL);
1640 xfs_trans_ijoin(tp, ip, 0);
1641
1642 error = xfs_reflink_clear_inode_flag(ip, &tp);
1643 if (error)
1644 goto cancel;
1645
1646 error = xfs_trans_commit(tp);
1647 if (error)
1648 goto out;
1649
1650 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1651 return 0;
1652cancel:
1653 xfs_trans_cancel(tp);
1654out:
1655 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1656 return error;
1657}
1658
1659/*
1660 * Pre-COW all shared blocks within a given byte range of a file and turn off
1661 * the reflink flag if we unshare all of the file's blocks.
1662 */
1663int
1664xfs_reflink_unshare(
1665 struct xfs_inode *ip,
1666 xfs_off_t offset,
1667 xfs_off_t len)
1668{
1669 struct inode *inode = VFS_I(ip);
1670 int error;
1671
1672 if (!xfs_is_reflink_inode(ip))
1673 return 0;
1674
1675 trace_xfs_reflink_unshare(ip, offset, len);
1676
1677 inode_dio_wait(inode);
1678
1679 if (IS_DAX(inode))
1680 error = dax_file_unshare(inode, offset, len,
1681 &xfs_dax_write_iomap_ops);
1682 else
1683 error = iomap_file_unshare(inode, offset, len,
1684 &xfs_buffered_write_iomap_ops);
1685 if (error)
1686 goto out;
1687
1688 error = filemap_write_and_wait_range(inode->i_mapping, offset,
1689 offset + len - 1);
1690 if (error)
1691 goto out;
1692
1693 /* Turn off the reflink flag if possible. */
1694 error = xfs_reflink_try_clear_inode_flag(ip);
1695 if (error)
1696 goto out;
1697 return 0;
1698
1699out:
1700 trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
1701 return error;
1702}