2 * Copyright (C) 2016 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version 2
9 * of the License, or (at your option) any later version.
11 * This program is distributed in the hope that it would be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
22 #include "xfs_shared.h"
23 #include "xfs_format.h"
24 #include "xfs_log_format.h"
25 #include "xfs_trans_resv.h"
26 #include "xfs_mount.h"
27 #include "xfs_defer.h"
28 #include "xfs_da_format.h"
29 #include "xfs_da_btree.h"
30 #include "xfs_inode.h"
31 #include "xfs_trans.h"
32 #include "xfs_inode_item.h"
34 #include "xfs_bmap_util.h"
35 #include "xfs_error.h"
37 #include "xfs_dir2_priv.h"
38 #include "xfs_ioctl.h"
39 #include "xfs_trace.h"
41 #include "xfs_icache.h"
43 #include "xfs_btree.h"
44 #include "xfs_refcount_btree.h"
45 #include "xfs_refcount.h"
46 #include "xfs_bmap_btree.h"
47 #include "xfs_trans_space.h"
49 #include "xfs_alloc.h"
50 #include "xfs_quota_defs.h"
51 #include "xfs_quota.h"
52 #include "xfs_btree.h"
53 #include "xfs_bmap_btree.h"
54 #include "xfs_reflink.h"
55 #include "xfs_iomap.h"
56 #include "xfs_rmap_btree.h"
58 #include "xfs_ag_resv.h"
61 * Copy on Write of Shared Blocks
63 * XFS must preserve "the usual" file semantics even when two files share
64 * the same physical blocks. This means that a write to one file must not
65 * alter the blocks in a different file; the way that we'll do that is
66 * through the use of a copy-on-write mechanism. At a high level, that
67 * means that when we want to write to a shared block, we allocate a new
68 * block, write the data to the new block, and if that succeeds we map the
69 * new block into the file.
71 * XFS provides a "delayed allocation" mechanism that defers the allocation
72 * of disk blocks to dirty-but-not-yet-mapped file blocks as long as
73 * possible. This reduces fragmentation by enabling the filesystem to ask
74 * for bigger chunks less often, which is exactly what we want for CoW.
76 * The delalloc mechanism begins when the kernel wants to make a block
77 * writable (write_begin or page_mkwrite). If the offset is not mapped, we
78 * create a delalloc mapping, which is a regular in-core extent, but without
79 * a real startblock. (For delalloc mappings, the startblock encodes both
80 * a flag that this is a delalloc mapping, and a worst-case estimate of how
81 * many blocks might be required to put the mapping into the BMBT.) delalloc
82 * mappings are a reservation against the free space in the filesystem;
83 * adjacent mappings can also be combined into fewer larger mappings.
85 * When dirty pages are being written out (typically in writepage), the
86 * delalloc reservations are converted into real mappings by allocating
87 * blocks and replacing the delalloc mapping with real ones. A delalloc
88 * mapping can be replaced by several real ones if the free space is
91 * We want to adapt the delalloc mechanism for copy-on-write, since the
92 * write paths are similar. The first two steps (creating the reservation
93 * and allocating the blocks) are exactly the same as delalloc except that
94 * the mappings must be stored in a separate CoW fork because we do not want
95 * to disturb the mapping in the data fork until we're sure that the write
96 * succeeded. IO completion in this case is the process of removing the old
97 * mapping from the data fork and moving the new mapping from the CoW fork to
98 * the data fork. This will be discussed shortly.
100 * For now, unaligned directio writes will be bounced back to the page cache.
101 * Block-aligned directio writes will use the same mechanism as buffered
104 * CoW remapping must be done after the data block write completes,
105 * because we don't want to destroy the old data fork map until we're sure
106 * the new block has been written. Since the new mappings are kept in a
107 * separate fork, we can simply iterate these mappings to find the ones
108 * that cover the file blocks that we just CoW'd. For each extent, simply
109 * unmap the corresponding range in the data fork, map the new range into
110 * the data fork, and remove the extent from the CoW fork.
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
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.
129 xfs_reflink_find_shared(
130 struct xfs_mount *mp,
136 bool find_end_of_shared)
138 struct xfs_buf *agbp;
139 struct xfs_btree_cur *cur;
142 error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);
146 cur = xfs_refcountbt_init_cursor(mp, NULL, agbp, agno, NULL);
148 error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen,
151 xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
158 * Trim the mapping to the next block where there's a change in the
159 * shared/unshared status. More specifically, this means that we
160 * find the lowest-numbered extent of shared blocks that coincides with
161 * the given block mapping. If the shared extent overlaps the start of
162 * the mapping, trim the mapping to the end of the shared extent. If
163 * the shared region intersects the mapping, trim the mapping to the
164 * start of the shared extent. If there are no shared regions that
165 * overlap, just return the original extent.
168 xfs_reflink_trim_around_shared(
169 struct xfs_inode *ip,
170 struct xfs_bmbt_irec *irec,
181 /* Holes, unwritten, and delalloc extents cannot be shared */
182 if (!xfs_is_reflink_inode(ip) ||
184 irec->br_startblock == HOLESTARTBLOCK ||
185 irec->br_startblock == DELAYSTARTBLOCK) {
190 trace_xfs_reflink_trim_around_shared(ip, irec);
192 agno = XFS_FSB_TO_AGNO(ip->i_mount, irec->br_startblock);
193 agbno = XFS_FSB_TO_AGBNO(ip->i_mount, irec->br_startblock);
194 aglen = irec->br_blockcount;
196 error = xfs_reflink_find_shared(ip->i_mount, agno, agbno,
197 aglen, &fbno, &flen, true);
201 *shared = *trimmed = false;
202 if (fbno == NULLAGBLOCK) {
203 /* No shared blocks at all. */
205 } else if (fbno == agbno) {
207 * The start of this extent is shared. Truncate the
208 * mapping at the end of the shared region so that a
209 * subsequent iteration starts at the start of the
212 irec->br_blockcount = flen;
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.
224 irec->br_blockcount = fbno - agbno;
230 /* Create a CoW reservation for a range of blocks within a file. */
232 __xfs_reflink_reserve_cow(
233 struct xfs_inode *ip,
234 xfs_fileoff_t *offset_fsb,
235 xfs_fileoff_t end_fsb,
238 struct xfs_bmbt_irec got, prev, imap;
239 xfs_fileoff_t orig_end_fsb;
240 int nimaps, eof = 0, error = 0;
241 bool shared = false, trimmed = false;
245 /* Already reserved? Skip the refcount btree access. */
246 xfs_bmap_search_extents(ip, *offset_fsb, XFS_COW_FORK, &eof, &idx,
248 if (!eof && got.br_startoff <= *offset_fsb) {
249 end_fsb = orig_end_fsb = got.br_startoff + got.br_blockcount;
250 trace_xfs_reflink_cow_found(ip, &got);
254 /* Read extent from the source file. */
256 error = xfs_bmapi_read(ip, *offset_fsb, end_fsb - *offset_fsb,
262 /* Trim the mapping to the nearest shared extent boundary. */
263 error = xfs_reflink_trim_around_shared(ip, &imap, &shared, &trimmed);
267 end_fsb = orig_end_fsb = imap.br_startoff + imap.br_blockcount;
269 /* Not shared? Just report the (potentially capped) extent. */
276 * Fork all the shared blocks from our write offset until the end of
279 error = xfs_qm_dqattach_locked(ip, 0);
283 align = xfs_eof_alignment(ip, xfs_get_cowextsz_hint(ip));
285 end_fsb = roundup_64(end_fsb, align);
288 error = xfs_bmapi_reserve_delalloc(ip, XFS_COW_FORK, *offset_fsb,
289 end_fsb - *offset_fsb, &got,
296 /* retry without any preallocation */
297 trace_xfs_reflink_cow_enospc(ip, &imap);
298 if (end_fsb != orig_end_fsb) {
299 end_fsb = orig_end_fsb;
307 if (end_fsb != orig_end_fsb)
308 xfs_inode_set_cowblocks_tag(ip);
310 trace_xfs_reflink_cow_alloc(ip, &got);
312 *offset_fsb = end_fsb;
317 /* Create a CoW reservation for part of a file. */
319 xfs_reflink_reserve_cow_range(
320 struct xfs_inode *ip,
324 struct xfs_mount *mp = ip->i_mount;
325 xfs_fileoff_t offset_fsb, end_fsb;
326 bool skipped = false;
329 trace_xfs_reflink_reserve_cow_range(ip, offset, count);
331 offset_fsb = XFS_B_TO_FSBT(mp, offset);
332 end_fsb = XFS_B_TO_FSB(mp, offset + count);
334 xfs_ilock(ip, XFS_ILOCK_EXCL);
335 while (offset_fsb < end_fsb) {
336 error = __xfs_reflink_reserve_cow(ip, &offset_fsb, end_fsb,
339 trace_xfs_reflink_reserve_cow_range_error(ip, error,
344 xfs_iunlock(ip, XFS_ILOCK_EXCL);
349 /* Allocate all CoW reservations covering a range of blocks in a file. */
351 __xfs_reflink_allocate_cow(
352 struct xfs_inode *ip,
353 xfs_fileoff_t *offset_fsb,
354 xfs_fileoff_t end_fsb)
356 struct xfs_mount *mp = ip->i_mount;
357 struct xfs_bmbt_irec imap;
358 struct xfs_defer_ops dfops;
359 struct xfs_trans *tp;
360 xfs_fsblock_t first_block;
361 xfs_fileoff_t next_fsb;
362 int nimaps = 1, error;
363 bool skipped = false;
365 xfs_defer_init(&dfops, &first_block);
367 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0,
368 XFS_TRANS_RESERVE, &tp);
372 xfs_ilock(ip, XFS_ILOCK_EXCL);
374 next_fsb = *offset_fsb;
375 error = __xfs_reflink_reserve_cow(ip, &next_fsb, end_fsb, &skipped);
377 goto out_trans_cancel;
380 *offset_fsb = next_fsb;
381 goto out_trans_cancel;
384 xfs_trans_ijoin(tp, ip, 0);
385 error = xfs_bmapi_write(tp, ip, *offset_fsb, next_fsb - *offset_fsb,
386 XFS_BMAPI_COWFORK, &first_block,
387 XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK),
388 &imap, &nimaps, &dfops);
390 goto out_trans_cancel;
392 /* We might not have been able to map the whole delalloc extent */
393 *offset_fsb = min(*offset_fsb + imap.br_blockcount, next_fsb);
395 error = xfs_defer_finish(&tp, &dfops, NULL);
397 goto out_trans_cancel;
399 error = xfs_trans_commit(tp);
402 xfs_iunlock(ip, XFS_ILOCK_EXCL);
405 xfs_defer_cancel(&dfops);
406 xfs_trans_cancel(tp);
410 /* Allocate all CoW reservations covering a part of a file. */
412 xfs_reflink_allocate_cow_range(
413 struct xfs_inode *ip,
417 struct xfs_mount *mp = ip->i_mount;
418 xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
419 xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
422 ASSERT(xfs_is_reflink_inode(ip));
424 trace_xfs_reflink_allocate_cow_range(ip, offset, count);
427 * Make sure that the dquots are there.
429 error = xfs_qm_dqattach(ip, 0);
433 while (offset_fsb < end_fsb) {
434 error = __xfs_reflink_allocate_cow(ip, &offset_fsb, end_fsb);
436 trace_xfs_reflink_allocate_cow_range_error(ip, error,
446 * Find the CoW reservation (and whether or not it needs block allocation)
447 * for a given byte offset of a file.
450 xfs_reflink_find_cow_mapping(
451 struct xfs_inode *ip,
453 struct xfs_bmbt_irec *imap,
456 struct xfs_bmbt_irec irec;
457 struct xfs_ifork *ifp;
458 struct xfs_bmbt_rec_host *gotp;
462 ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
463 ASSERT(xfs_is_reflink_inode(ip));
465 /* Find the extent in the CoW fork. */
466 ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
467 bno = XFS_B_TO_FSBT(ip->i_mount, offset);
468 gotp = xfs_iext_bno_to_ext(ifp, bno, &idx);
472 xfs_bmbt_get_all(gotp, &irec);
473 if (bno >= irec.br_startoff + irec.br_blockcount ||
474 bno < irec.br_startoff)
477 trace_xfs_reflink_find_cow_mapping(ip, offset, 1, XFS_IO_OVERWRITE,
480 /* If it's still delalloc, we must allocate later. */
482 *need_alloc = !!(isnullstartblock(irec.br_startblock));
488 * Trim an extent to end at the next CoW reservation past offset_fsb.
491 xfs_reflink_trim_irec_to_next_cow(
492 struct xfs_inode *ip,
493 xfs_fileoff_t offset_fsb,
494 struct xfs_bmbt_irec *imap)
496 struct xfs_bmbt_irec irec;
497 struct xfs_ifork *ifp;
498 struct xfs_bmbt_rec_host *gotp;
501 if (!xfs_is_reflink_inode(ip))
504 /* Find the extent in the CoW fork. */
505 ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
506 gotp = xfs_iext_bno_to_ext(ifp, offset_fsb, &idx);
509 xfs_bmbt_get_all(gotp, &irec);
511 /* This is the extent before; try sliding up one. */
512 if (irec.br_startoff < offset_fsb) {
514 if (idx >= ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
516 gotp = xfs_iext_get_ext(ifp, idx);
517 xfs_bmbt_get_all(gotp, &irec);
520 if (irec.br_startoff >= imap->br_startoff + imap->br_blockcount)
523 imap->br_blockcount = irec.br_startoff - imap->br_startoff;
524 trace_xfs_reflink_trim_irec(ip, imap);
530 * Cancel all pending CoW reservations for some block range of an inode.
533 xfs_reflink_cancel_cow_blocks(
534 struct xfs_inode *ip,
535 struct xfs_trans **tpp,
536 xfs_fileoff_t offset_fsb,
537 xfs_fileoff_t end_fsb)
539 struct xfs_bmbt_irec irec;
540 xfs_filblks_t count_fsb;
541 xfs_fsblock_t firstfsb;
542 struct xfs_defer_ops dfops;
546 if (!xfs_is_reflink_inode(ip))
549 /* Go find the old extent in the CoW fork. */
550 while (offset_fsb < end_fsb) {
552 count_fsb = (xfs_filblks_t)(end_fsb - offset_fsb);
553 error = xfs_bmapi_read(ip, offset_fsb, count_fsb, &irec,
554 &nimaps, XFS_BMAPI_COWFORK);
559 trace_xfs_reflink_cancel_cow(ip, &irec);
561 if (irec.br_startblock == DELAYSTARTBLOCK) {
562 /* Free a delayed allocation. */
563 xfs_mod_fdblocks(ip->i_mount, irec.br_blockcount,
565 ip->i_delayed_blks -= irec.br_blockcount;
567 /* Remove the mapping from the CoW fork. */
568 error = xfs_bunmapi_cow(ip, &irec);
571 } else if (irec.br_startblock == HOLESTARTBLOCK) {
574 xfs_trans_ijoin(*tpp, ip, 0);
575 xfs_defer_init(&dfops, &firstfsb);
577 /* Free the CoW orphan record. */
578 error = xfs_refcount_free_cow_extent(ip->i_mount,
579 &dfops, irec.br_startblock,
584 xfs_bmap_add_free(ip->i_mount, &dfops,
585 irec.br_startblock, irec.br_blockcount,
588 /* Update quota accounting */
589 xfs_trans_mod_dquot_byino(*tpp, ip, XFS_TRANS_DQ_BCOUNT,
590 -(long)irec.br_blockcount);
592 /* Roll the transaction */
593 error = xfs_defer_finish(tpp, &dfops, ip);
595 xfs_defer_cancel(&dfops);
599 /* Remove the mapping from the CoW fork. */
600 error = xfs_bunmapi_cow(ip, &irec);
606 offset_fsb = irec.br_startoff + irec.br_blockcount;
613 * Cancel all pending CoW reservations for some byte range of an inode.
616 xfs_reflink_cancel_cow_range(
617 struct xfs_inode *ip,
621 struct xfs_trans *tp;
622 xfs_fileoff_t offset_fsb;
623 xfs_fileoff_t end_fsb;
626 trace_xfs_reflink_cancel_cow_range(ip, offset, count);
627 ASSERT(xfs_is_reflink_inode(ip));
629 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
630 if (count == NULLFILEOFF)
631 end_fsb = NULLFILEOFF;
633 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
635 /* Start a rolling transaction to remove the mappings */
636 error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
641 xfs_ilock(ip, XFS_ILOCK_EXCL);
642 xfs_trans_ijoin(tp, ip, 0);
644 /* Scrape out the old CoW reservations */
645 error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb);
649 error = xfs_trans_commit(tp);
651 xfs_iunlock(ip, XFS_ILOCK_EXCL);
655 xfs_trans_cancel(tp);
656 xfs_iunlock(ip, XFS_ILOCK_EXCL);
658 trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_);
663 * Remap parts of a file's data fork after a successful CoW.
667 struct xfs_inode *ip,
671 struct xfs_bmbt_irec irec;
672 struct xfs_bmbt_irec uirec;
673 struct xfs_trans *tp;
674 xfs_fileoff_t offset_fsb;
675 xfs_fileoff_t end_fsb;
676 xfs_filblks_t count_fsb;
677 xfs_fsblock_t firstfsb;
678 struct xfs_defer_ops dfops;
680 unsigned int resblks;
685 trace_xfs_reflink_end_cow(ip, offset, count);
687 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
688 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
689 count_fsb = (xfs_filblks_t)(end_fsb - offset_fsb);
691 /* Start a rolling transaction to switch the mappings */
692 resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);
693 error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
698 xfs_ilock(ip, XFS_ILOCK_EXCL);
699 xfs_trans_ijoin(tp, ip, 0);
701 /* Go find the old extent in the CoW fork. */
702 while (offset_fsb < end_fsb) {
703 /* Read extent from the source file */
705 count_fsb = (xfs_filblks_t)(end_fsb - offset_fsb);
706 error = xfs_bmapi_read(ip, offset_fsb, count_fsb, &irec,
707 &nimaps, XFS_BMAPI_COWFORK);
712 ASSERT(irec.br_startblock != DELAYSTARTBLOCK);
713 trace_xfs_reflink_cow_remap(ip, &irec);
716 * We can have a hole in the CoW fork if part of a directio
717 * write is CoW but part of it isn't.
719 rlen = ilen = irec.br_blockcount;
720 if (irec.br_startblock == HOLESTARTBLOCK)
723 /* Unmap the old blocks in the data fork. */
725 xfs_defer_init(&dfops, &firstfsb);
726 error = __xfs_bunmapi(tp, ip, irec.br_startoff,
727 &rlen, 0, 1, &firstfsb, &dfops);
732 * Trim the extent to whatever got unmapped.
733 * Remember, bunmapi works backwards.
735 uirec.br_startblock = irec.br_startblock + rlen;
736 uirec.br_startoff = irec.br_startoff + rlen;
737 uirec.br_blockcount = irec.br_blockcount - rlen;
738 irec.br_blockcount = rlen;
739 trace_xfs_reflink_cow_remap_piece(ip, &uirec);
741 /* Free the CoW orphan record. */
742 error = xfs_refcount_free_cow_extent(tp->t_mountp,
743 &dfops, uirec.br_startblock,
744 uirec.br_blockcount);
748 /* Map the new blocks into the data fork. */
749 error = xfs_bmap_map_extent(tp->t_mountp, &dfops,
754 /* Remove the mapping from the CoW fork. */
755 error = xfs_bunmapi_cow(ip, &uirec);
759 error = xfs_defer_finish(&tp, &dfops, ip);
766 offset_fsb = irec.br_startoff + ilen;
769 error = xfs_trans_commit(tp);
770 xfs_iunlock(ip, XFS_ILOCK_EXCL);
776 xfs_defer_cancel(&dfops);
778 xfs_trans_cancel(tp);
779 xfs_iunlock(ip, XFS_ILOCK_EXCL);
781 trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
786 * Free leftover CoW reservations that didn't get cleaned out.
789 xfs_reflink_recover_cow(
790 struct xfs_mount *mp)
795 if (!xfs_sb_version_hasreflink(&mp->m_sb))
798 for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
799 error = xfs_refcount_recover_cow_leftovers(mp, agno);
808 * Reflinking (Block) Ranges of Two Files Together
810 * First, ensure that the reflink flag is set on both inodes. The flag is an
811 * optimization to avoid unnecessary refcount btree lookups in the write path.
813 * Now we can iteratively remap the range of extents (and holes) in src to the
814 * corresponding ranges in dest. Let drange and srange denote the ranges of
815 * logical blocks in dest and src touched by the reflink operation.
817 * While the length of drange is greater than zero,
818 * - Read src's bmbt at the start of srange ("imap")
819 * - If imap doesn't exist, make imap appear to start at the end of srange
821 * - If imap starts before srange, advance imap to start at srange.
822 * - If imap goes beyond srange, truncate imap to end at the end of srange.
823 * - Punch (imap start - srange start + imap len) blocks from dest at
824 * offset (drange start).
825 * - If imap points to a real range of pblks,
826 * > Increase the refcount of the imap's pblks
827 * > Map imap's pblks into dest at the offset
828 * (drange start + imap start - srange start)
829 * - Advance drange and srange by (imap start - srange start + imap len)
831 * Finally, if the reflink made dest longer, update both the in-core and
832 * on-disk file sizes.
834 * ASCII Art Demonstration:
836 * Let's say we want to reflink this source file:
838 * ----SSSSSSS-SSSSS----SSSSSS (src file)
839 * <-------------------->
841 * into this destination file:
843 * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
844 * <-------------------->
845 * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
846 * Observe that the range has different logical offsets in either file.
848 * Consider that the first extent in the source file doesn't line up with our
849 * reflink range. Unmapping and remapping are separate operations, so we can
850 * unmap more blocks from the destination file than we remap.
852 * ----SSSSSSS-SSSSS----SSSSSS
854 * --DDDDD---------DDDDD--DDD
857 * Now remap the source extent into the destination file:
859 * ----SSSSSSS-SSSSS----SSSSSS
861 * --DDDDD--SSSSSSSDDDDD--DDD
864 * Do likewise with the second hole and extent in our range. Holes in the
865 * unmap range don't affect our operation.
867 * ----SSSSSSS-SSSSS----SSSSSS
869 * --DDDDD--SSSSSSS-SSSSS-DDD
872 * Finally, unmap and remap part of the third extent. This will increase the
873 * size of the destination file.
875 * ----SSSSSSS-SSSSS----SSSSSS
877 * --DDDDD--SSSSSSS-SSSSS----SSS
880 * Once we update the destination file's i_size, we're done.
884 * Ensure the reflink bit is set in both inodes.
887 xfs_reflink_set_inode_flag(
888 struct xfs_inode *src,
889 struct xfs_inode *dest)
891 struct xfs_mount *mp = src->i_mount;
893 struct xfs_trans *tp;
895 if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
898 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
902 /* Lock both files against IO */
903 if (src->i_ino == dest->i_ino)
904 xfs_ilock(src, XFS_ILOCK_EXCL);
906 xfs_lock_two_inodes(src, dest, XFS_ILOCK_EXCL);
908 if (!xfs_is_reflink_inode(src)) {
909 trace_xfs_reflink_set_inode_flag(src);
910 xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
911 src->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK;
912 xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
913 xfs_ifork_init_cow(src);
915 xfs_iunlock(src, XFS_ILOCK_EXCL);
917 if (src->i_ino == dest->i_ino)
920 if (!xfs_is_reflink_inode(dest)) {
921 trace_xfs_reflink_set_inode_flag(dest);
922 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
923 dest->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK;
924 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
925 xfs_ifork_init_cow(dest);
927 xfs_iunlock(dest, XFS_ILOCK_EXCL);
930 error = xfs_trans_commit(tp);
936 trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
941 * Update destination inode size & cowextsize hint, if necessary.
944 xfs_reflink_update_dest(
945 struct xfs_inode *dest,
947 xfs_extlen_t cowextsize)
949 struct xfs_mount *mp = dest->i_mount;
950 struct xfs_trans *tp;
953 if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
956 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
960 xfs_ilock(dest, XFS_ILOCK_EXCL);
961 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
963 if (newlen > i_size_read(VFS_I(dest))) {
964 trace_xfs_reflink_update_inode_size(dest, newlen);
965 i_size_write(VFS_I(dest), newlen);
966 dest->i_d.di_size = newlen;
970 dest->i_d.di_cowextsize = cowextsize;
971 dest->i_d.di_flags2 |= XFS_DIFLAG2_COWEXTSIZE;
974 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
976 error = xfs_trans_commit(tp);
982 trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
987 * Do we have enough reserve in this AG to handle a reflink? The refcount
988 * btree already reserved all the space it needs, but the rmap btree can grow
989 * infinitely, so we won't allow more reflinks when the AG is down to the
993 xfs_reflink_ag_has_free_space(
994 struct xfs_mount *mp,
997 struct xfs_perag *pag;
1000 if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
1003 pag = xfs_perag_get(mp, agno);
1004 if (xfs_ag_resv_critical(pag, XFS_AG_RESV_AGFL) ||
1005 xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
1012 * Unmap a range of blocks from a file, then map other blocks into the hole.
1013 * The range to unmap is (destoff : destoff + srcioff + irec->br_blockcount).
1014 * The extent irec is mapped into dest at irec->br_startoff.
1017 xfs_reflink_remap_extent(
1018 struct xfs_inode *ip,
1019 struct xfs_bmbt_irec *irec,
1020 xfs_fileoff_t destoff,
1021 xfs_off_t new_isize)
1023 struct xfs_mount *mp = ip->i_mount;
1024 struct xfs_trans *tp;
1025 xfs_fsblock_t firstfsb;
1026 unsigned int resblks;
1027 struct xfs_defer_ops dfops;
1028 struct xfs_bmbt_irec uirec;
1031 xfs_filblks_t unmap_len;
1035 unmap_len = irec->br_startoff + irec->br_blockcount - destoff;
1036 trace_xfs_reflink_punch_range(ip, destoff, unmap_len);
1038 /* Only remap normal extents. */
1039 real_extent = (irec->br_startblock != HOLESTARTBLOCK &&
1040 irec->br_startblock != DELAYSTARTBLOCK &&
1041 !ISUNWRITTEN(irec));
1043 /* No reflinking if we're low on space */
1045 error = xfs_reflink_ag_has_free_space(mp,
1046 XFS_FSB_TO_AGNO(mp, irec->br_startblock));
1051 /* Start a rolling transaction to switch the mappings */
1052 resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);
1053 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
1057 xfs_ilock(ip, XFS_ILOCK_EXCL);
1058 xfs_trans_ijoin(tp, ip, 0);
1060 /* If we're not just clearing space, then do we have enough quota? */
1062 error = xfs_trans_reserve_quota_nblks(tp, ip,
1063 irec->br_blockcount, 0, XFS_QMOPT_RES_REGBLKS);
1068 trace_xfs_reflink_remap(ip, irec->br_startoff,
1069 irec->br_blockcount, irec->br_startblock);
1071 /* Unmap the old blocks in the data fork. */
1074 xfs_defer_init(&dfops, &firstfsb);
1075 error = __xfs_bunmapi(tp, ip, destoff, &rlen, 0, 1,
1081 * Trim the extent to whatever got unmapped.
1082 * Remember, bunmapi works backwards.
1084 uirec.br_startblock = irec->br_startblock + rlen;
1085 uirec.br_startoff = irec->br_startoff + rlen;
1086 uirec.br_blockcount = unmap_len - rlen;
1089 /* If this isn't a real mapping, we're done. */
1090 if (!real_extent || uirec.br_blockcount == 0)
1093 trace_xfs_reflink_remap(ip, uirec.br_startoff,
1094 uirec.br_blockcount, uirec.br_startblock);
1096 /* Update the refcount tree */
1097 error = xfs_refcount_increase_extent(mp, &dfops, &uirec);
1101 /* Map the new blocks into the data fork. */
1102 error = xfs_bmap_map_extent(mp, &dfops, ip, &uirec);
1106 /* Update quota accounting. */
1107 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
1108 uirec.br_blockcount);
1110 /* Update dest isize if needed. */
1111 newlen = XFS_FSB_TO_B(mp,
1112 uirec.br_startoff + uirec.br_blockcount);
1113 newlen = min_t(xfs_off_t, newlen, new_isize);
1114 if (newlen > i_size_read(VFS_I(ip))) {
1115 trace_xfs_reflink_update_inode_size(ip, newlen);
1116 i_size_write(VFS_I(ip), newlen);
1117 ip->i_d.di_size = newlen;
1118 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
1122 /* Process all the deferred stuff. */
1123 error = xfs_defer_finish(&tp, &dfops, ip);
1128 error = xfs_trans_commit(tp);
1129 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1135 xfs_defer_cancel(&dfops);
1137 xfs_trans_cancel(tp);
1138 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1140 trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
1145 * Iteratively remap one file's extents (and holes) to another's.
1148 xfs_reflink_remap_blocks(
1149 struct xfs_inode *src,
1150 xfs_fileoff_t srcoff,
1151 struct xfs_inode *dest,
1152 xfs_fileoff_t destoff,
1154 xfs_off_t new_isize)
1156 struct xfs_bmbt_irec imap;
1159 xfs_filblks_t range_len;
1161 /* drange = (destoff, destoff + len); srange = (srcoff, srcoff + len) */
1163 trace_xfs_reflink_remap_blocks_loop(src, srcoff, len,
1165 /* Read extent from the source file */
1167 xfs_ilock(src, XFS_ILOCK_EXCL);
1168 error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
1169 xfs_iunlock(src, XFS_ILOCK_EXCL);
1172 ASSERT(nimaps == 1);
1174 trace_xfs_reflink_remap_imap(src, srcoff, len, XFS_IO_OVERWRITE,
1177 /* Translate imap into the destination file. */
1178 range_len = imap.br_startoff + imap.br_blockcount - srcoff;
1179 imap.br_startoff += destoff - srcoff;
1181 /* Clear dest from destoff to the end of imap and map it in. */
1182 error = xfs_reflink_remap_extent(dest, &imap, destoff,
1187 if (fatal_signal_pending(current)) {
1192 /* Advance drange/srange */
1193 srcoff += range_len;
1194 destoff += range_len;
1201 trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
1206 * Read a page's worth of file data into the page cache. Return the page
1209 static struct page *
1211 struct inode *inode,
1214 struct address_space *mapping;
1218 n = offset >> PAGE_SHIFT;
1219 mapping = inode->i_mapping;
1220 page = read_mapping_page(mapping, n, NULL);
1223 if (!PageUptodate(page)) {
1225 return ERR_PTR(-EIO);
1232 * Compare extents of two files to see if they are the same.
1235 xfs_compare_extents(
1244 xfs_off_t dest_poff;
1247 struct page *src_page;
1248 struct page *dest_page;
1256 src_poff = srcoff & (PAGE_SIZE - 1);
1257 dest_poff = destoff & (PAGE_SIZE - 1);
1258 cmp_len = min(PAGE_SIZE - src_poff,
1259 PAGE_SIZE - dest_poff);
1260 cmp_len = min(cmp_len, len);
1261 ASSERT(cmp_len > 0);
1263 trace_xfs_reflink_compare_extents(XFS_I(src), srcoff, cmp_len,
1264 XFS_I(dest), destoff);
1266 src_page = xfs_get_page(src, srcoff);
1267 if (IS_ERR(src_page)) {
1268 error = PTR_ERR(src_page);
1271 dest_page = xfs_get_page(dest, destoff);
1272 if (IS_ERR(dest_page)) {
1273 error = PTR_ERR(dest_page);
1274 unlock_page(src_page);
1278 src_addr = kmap_atomic(src_page);
1279 dest_addr = kmap_atomic(dest_page);
1281 flush_dcache_page(src_page);
1282 flush_dcache_page(dest_page);
1284 if (memcmp(src_addr + src_poff, dest_addr + dest_poff, cmp_len))
1287 kunmap_atomic(dest_addr);
1288 kunmap_atomic(src_addr);
1289 unlock_page(dest_page);
1290 unlock_page(src_page);
1291 put_page(dest_page);
1306 trace_xfs_reflink_compare_extents_error(XFS_I(dest), error, _RET_IP_);
1311 * Link a range of blocks from one file to another.
1314 xfs_reflink_remap_range(
1315 struct xfs_inode *src,
1317 struct xfs_inode *dest,
1322 struct xfs_mount *mp = src->i_mount;
1323 xfs_fileoff_t sfsbno, dfsbno;
1324 xfs_filblks_t fsblen;
1326 xfs_extlen_t cowextsize;
1329 if (!xfs_sb_version_hasreflink(&mp->m_sb))
1332 if (XFS_FORCED_SHUTDOWN(mp))
1335 /* Don't reflink realtime inodes */
1336 if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
1339 if (flags & ~XFS_REFLINK_ALL)
1342 trace_xfs_reflink_remap_range(src, srcoff, len, dest, destoff);
1344 /* Lock both files against IO */
1345 if (src->i_ino == dest->i_ino) {
1346 xfs_ilock(src, XFS_IOLOCK_EXCL);
1347 xfs_ilock(src, XFS_MMAPLOCK_EXCL);
1349 xfs_lock_two_inodes(src, dest, XFS_IOLOCK_EXCL);
1350 xfs_lock_two_inodes(src, dest, XFS_MMAPLOCK_EXCL);
1354 * Check that the extents are the same.
1356 if (flags & XFS_REFLINK_DEDUPE) {
1358 error = xfs_compare_extents(VFS_I(src), srcoff, VFS_I(dest),
1359 destoff, len, &is_same);
1368 error = xfs_reflink_set_inode_flag(src, dest);
1373 * Invalidate the page cache so that we can clear any CoW mappings
1374 * in the destination file.
1376 truncate_inode_pages_range(&VFS_I(dest)->i_data, destoff,
1377 PAGE_ALIGN(destoff + len) - 1);
1379 dfsbno = XFS_B_TO_FSBT(mp, destoff);
1380 sfsbno = XFS_B_TO_FSBT(mp, srcoff);
1381 fsblen = XFS_B_TO_FSB(mp, len);
1382 error = xfs_reflink_remap_blocks(src, sfsbno, dest, dfsbno, fsblen,
1388 * Carry the cowextsize hint from src to dest if we're sharing the
1389 * entire source file to the entire destination file, the source file
1390 * has a cowextsize hint, and the destination file does not.
1393 if (srcoff == 0 && len == i_size_read(VFS_I(src)) &&
1394 (src->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE) &&
1395 destoff == 0 && len >= i_size_read(VFS_I(dest)) &&
1396 !(dest->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE))
1397 cowextsize = src->i_d.di_cowextsize;
1399 error = xfs_reflink_update_dest(dest, destoff + len, cowextsize);
1404 xfs_iunlock(src, XFS_MMAPLOCK_EXCL);
1405 xfs_iunlock(src, XFS_IOLOCK_EXCL);
1406 if (src->i_ino != dest->i_ino) {
1407 xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
1408 xfs_iunlock(dest, XFS_IOLOCK_EXCL);
1411 trace_xfs_reflink_remap_range_error(dest, error, _RET_IP_);
1416 * The user wants to preemptively CoW all shared blocks in this file,
1417 * which enables us to turn off the reflink flag. Iterate all
1418 * extents which are not prealloc/delalloc to see which ranges are
1419 * mentioned in the refcount tree, then read those blocks into the
1420 * pagecache, dirty them, fsync them back out, and then we can update
1421 * the inode flag. What happens if we run out of memory? :)
1424 xfs_reflink_dirty_extents(
1425 struct xfs_inode *ip,
1430 struct xfs_mount *mp = ip->i_mount;
1431 xfs_agnumber_t agno;
1432 xfs_agblock_t agbno;
1438 struct xfs_bmbt_irec map[2];
1442 while (end - fbno > 0) {
1445 * Look for extents in the file. Skip holes, delalloc, or
1446 * unwritten extents; they can't be reflinked.
1448 error = xfs_bmapi_read(ip, fbno, end - fbno, map, &nmaps, 0);
1453 if (map[0].br_startblock == HOLESTARTBLOCK ||
1454 map[0].br_startblock == DELAYSTARTBLOCK ||
1455 ISUNWRITTEN(&map[0]))
1459 while (map[1].br_blockcount) {
1460 agno = XFS_FSB_TO_AGNO(mp, map[1].br_startblock);
1461 agbno = XFS_FSB_TO_AGBNO(mp, map[1].br_startblock);
1462 aglen = map[1].br_blockcount;
1464 error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
1465 &rbno, &rlen, true);
1468 if (rbno == NULLAGBLOCK)
1471 /* Dirty the pages */
1472 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1473 fpos = XFS_FSB_TO_B(mp, map[1].br_startoff +
1475 flen = XFS_FSB_TO_B(mp, rlen);
1476 if (fpos + flen > isize)
1477 flen = isize - fpos;
1478 error = iomap_file_dirty(VFS_I(ip), fpos, flen,
1480 xfs_ilock(ip, XFS_ILOCK_EXCL);
1484 map[1].br_blockcount -= (rbno - agbno + rlen);
1485 map[1].br_startoff += (rbno - agbno + rlen);
1486 map[1].br_startblock += (rbno - agbno + rlen);
1490 fbno = map[0].br_startoff + map[0].br_blockcount;
1496 /* Clear the inode reflink flag if there are no shared extents. */
1498 xfs_reflink_clear_inode_flag(
1499 struct xfs_inode *ip,
1500 struct xfs_trans **tpp)
1502 struct xfs_mount *mp = ip->i_mount;
1505 xfs_agnumber_t agno;
1506 xfs_agblock_t agbno;
1510 struct xfs_bmbt_irec map;
1514 ASSERT(xfs_is_reflink_inode(ip));
1517 end = XFS_B_TO_FSB(mp, i_size_read(VFS_I(ip)));
1518 while (end - fbno > 0) {
1521 * Look for extents in the file. Skip holes, delalloc, or
1522 * unwritten extents; they can't be reflinked.
1524 error = xfs_bmapi_read(ip, fbno, end - fbno, &map, &nmaps, 0);
1529 if (map.br_startblock == HOLESTARTBLOCK ||
1530 map.br_startblock == DELAYSTARTBLOCK ||
1534 agno = XFS_FSB_TO_AGNO(mp, map.br_startblock);
1535 agbno = XFS_FSB_TO_AGBNO(mp, map.br_startblock);
1536 aglen = map.br_blockcount;
1538 error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
1539 &rbno, &rlen, false);
1542 /* Is there still a shared block here? */
1543 if (rbno != NULLAGBLOCK)
1546 fbno = map.br_startoff + map.br_blockcount;
1550 * We didn't find any shared blocks so turn off the reflink flag.
1551 * First, get rid of any leftover CoW mappings.
1553 error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, NULLFILEOFF);
1557 /* Clear the inode flag. */
1558 trace_xfs_reflink_unset_inode_flag(ip);
1559 ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
1560 xfs_inode_clear_cowblocks_tag(ip);
1561 xfs_trans_ijoin(*tpp, ip, 0);
1562 xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
1568 * Clear the inode reflink flag if there are no shared extents and the size
1572 xfs_reflink_try_clear_inode_flag(
1573 struct xfs_inode *ip,
1574 xfs_off_t old_isize)
1576 struct xfs_mount *mp = ip->i_mount;
1577 struct xfs_trans *tp;
1580 /* Start a rolling transaction to remove the mappings */
1581 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1585 xfs_ilock(ip, XFS_ILOCK_EXCL);
1586 xfs_trans_ijoin(tp, ip, 0);
1588 if (old_isize != i_size_read(VFS_I(ip)))
1591 error = xfs_reflink_clear_inode_flag(ip, &tp);
1595 error = xfs_trans_commit(tp);
1599 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1602 xfs_trans_cancel(tp);
1604 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1609 * Pre-COW all shared blocks within a given byte range of a file and turn off
1610 * the reflink flag if we unshare all of the file's blocks.
1613 xfs_reflink_unshare(
1614 struct xfs_inode *ip,
1618 struct xfs_mount *mp = ip->i_mount;
1624 if (!xfs_is_reflink_inode(ip))
1627 trace_xfs_reflink_unshare(ip, offset, len);
1629 inode_dio_wait(VFS_I(ip));
1631 /* Try to CoW the selected ranges */
1632 xfs_ilock(ip, XFS_ILOCK_EXCL);
1633 fbno = XFS_B_TO_FSB(mp, offset);
1634 isize = i_size_read(VFS_I(ip));
1635 end = XFS_B_TO_FSB(mp, offset + len);
1636 error = xfs_reflink_dirty_extents(ip, fbno, end, isize);
1639 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1641 /* Wait for the IO to finish */
1642 error = filemap_write_and_wait(VFS_I(ip)->i_mapping);
1646 /* Turn off the reflink flag if we unshared the whole file */
1647 if (offset == 0 && len == isize) {
1648 error = xfs_reflink_try_clear_inode_flag(ip, isize);
1656 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1658 trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
1663 * Does this inode have any real CoW reservations?
1666 xfs_reflink_has_real_cow_blocks(
1667 struct xfs_inode *ip)
1669 struct xfs_bmbt_irec irec;
1670 struct xfs_ifork *ifp;
1671 struct xfs_bmbt_rec_host *gotp;
1674 if (!xfs_is_reflink_inode(ip))
1677 /* Go find the old extent in the CoW fork. */
1678 ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
1679 gotp = xfs_iext_bno_to_ext(ifp, 0, &idx);
1681 xfs_bmbt_get_all(gotp, &irec);
1683 if (!isnullstartblock(irec.br_startblock))
1688 if (idx >= ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
1690 gotp = xfs_iext_get_ext(ifp, idx);