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 ||
186 isnullstartblock(irec->br_startblock)) {
191 trace_xfs_reflink_trim_around_shared(ip, irec);
193 agno = XFS_FSB_TO_AGNO(ip->i_mount, irec->br_startblock);
194 agbno = XFS_FSB_TO_AGBNO(ip->i_mount, irec->br_startblock);
195 aglen = irec->br_blockcount;
197 error = xfs_reflink_find_shared(ip->i_mount, agno, agbno,
198 aglen, &fbno, &flen, true);
202 *shared = *trimmed = false;
203 if (fbno == NULLAGBLOCK) {
204 /* No shared blocks at all. */
206 } else if (fbno == agbno) {
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
213 irec->br_blockcount = flen;
220 * There's a shared extent midway through this extent.
221 * Truncate the mapping at the start of the shared
222 * extent so that a subsequent iteration starts at the
223 * start of the shared region.
225 irec->br_blockcount = fbno - agbno;
232 * Trim the passed in imap to the next shared/unshared extent boundary, and
233 * if imap->br_startoff points to a shared extent reserve space for it in the
234 * COW fork. In this case *shared is set to true, else to false.
236 * Note that imap will always contain the block numbers for the existing blocks
237 * in the data fork, as the upper layers need them for read-modify-write
241 xfs_reflink_reserve_cow(
242 struct xfs_inode *ip,
243 struct xfs_bmbt_irec *imap,
246 struct xfs_bmbt_irec got, prev;
247 xfs_fileoff_t end_fsb, orig_end_fsb;
248 int eof = 0, error = 0;
254 * Search the COW fork extent list first. This serves two purposes:
255 * first this implement the speculative preallocation using cowextisze,
256 * so that we also unshared block adjacent to shared blocks instead
257 * of just the shared blocks themselves. Second the lookup in the
258 * extent list is generally faster than going out to the shared extent
261 xfs_bmap_search_extents(ip, imap->br_startoff, XFS_COW_FORK, &eof, &idx,
263 if (!eof && got.br_startoff <= imap->br_startoff) {
264 trace_xfs_reflink_cow_found(ip, imap);
265 xfs_trim_extent(imap, got.br_startoff, got.br_blockcount);
271 /* Trim the mapping to the nearest shared extent boundary. */
272 error = xfs_reflink_trim_around_shared(ip, imap, shared, &trimmed);
276 /* Not shared? Just report the (potentially capped) extent. */
281 * Fork all the shared blocks from our write offset until the end of
284 error = xfs_qm_dqattach_locked(ip, 0);
288 end_fsb = orig_end_fsb = imap->br_startoff + imap->br_blockcount;
290 align = xfs_eof_alignment(ip, xfs_get_cowextsz_hint(ip));
292 end_fsb = roundup_64(end_fsb, align);
295 error = xfs_bmapi_reserve_delalloc(ip, XFS_COW_FORK, imap->br_startoff,
296 end_fsb - imap->br_startoff, &got, &prev, &idx, eof);
302 /* retry without any preallocation */
303 trace_xfs_reflink_cow_enospc(ip, imap);
304 if (end_fsb != orig_end_fsb) {
305 end_fsb = orig_end_fsb;
313 if (end_fsb != orig_end_fsb)
314 xfs_inode_set_cowblocks_tag(ip);
316 trace_xfs_reflink_cow_alloc(ip, &got);
320 /* Allocate all CoW reservations covering a range of blocks in a file. */
322 __xfs_reflink_allocate_cow(
323 struct xfs_inode *ip,
324 xfs_fileoff_t *offset_fsb,
325 xfs_fileoff_t end_fsb)
327 struct xfs_mount *mp = ip->i_mount;
328 struct xfs_bmbt_irec imap;
329 struct xfs_defer_ops dfops;
330 struct xfs_trans *tp;
331 xfs_fsblock_t first_block;
332 int nimaps = 1, error;
335 xfs_defer_init(&dfops, &first_block);
337 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0,
338 XFS_TRANS_RESERVE, &tp);
342 xfs_ilock(ip, XFS_ILOCK_EXCL);
344 /* Read extent from the source file. */
346 error = xfs_bmapi_read(ip, *offset_fsb, end_fsb - *offset_fsb,
352 error = xfs_reflink_reserve_cow(ip, &imap, &shared);
354 goto out_trans_cancel;
357 *offset_fsb = imap.br_startoff + imap.br_blockcount;
358 goto out_trans_cancel;
361 xfs_trans_ijoin(tp, ip, 0);
362 error = xfs_bmapi_write(tp, ip, imap.br_startoff, imap.br_blockcount,
363 XFS_BMAPI_COWFORK, &first_block,
364 XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK),
365 &imap, &nimaps, &dfops);
367 goto out_trans_cancel;
369 error = xfs_defer_finish(&tp, &dfops, NULL);
371 goto out_trans_cancel;
373 error = xfs_trans_commit(tp);
375 *offset_fsb = imap.br_startoff + imap.br_blockcount;
377 xfs_iunlock(ip, XFS_ILOCK_EXCL);
380 xfs_defer_cancel(&dfops);
381 xfs_trans_cancel(tp);
385 /* Allocate all CoW reservations covering a part of a file. */
387 xfs_reflink_allocate_cow_range(
388 struct xfs_inode *ip,
392 struct xfs_mount *mp = ip->i_mount;
393 xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
394 xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
397 ASSERT(xfs_is_reflink_inode(ip));
399 trace_xfs_reflink_allocate_cow_range(ip, offset, count);
402 * Make sure that the dquots are there.
404 error = xfs_qm_dqattach(ip, 0);
408 while (offset_fsb < end_fsb) {
409 error = __xfs_reflink_allocate_cow(ip, &offset_fsb, end_fsb);
411 trace_xfs_reflink_allocate_cow_range_error(ip, error,
421 * Find the CoW reservation (and whether or not it needs block allocation)
422 * for a given byte offset of a file.
425 xfs_reflink_find_cow_mapping(
426 struct xfs_inode *ip,
428 struct xfs_bmbt_irec *imap,
431 struct xfs_bmbt_irec irec;
432 struct xfs_ifork *ifp;
433 struct xfs_bmbt_rec_host *gotp;
437 ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
438 ASSERT(xfs_is_reflink_inode(ip));
440 /* Find the extent in the CoW fork. */
441 ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
442 bno = XFS_B_TO_FSBT(ip->i_mount, offset);
443 gotp = xfs_iext_bno_to_ext(ifp, bno, &idx);
447 xfs_bmbt_get_all(gotp, &irec);
448 if (bno >= irec.br_startoff + irec.br_blockcount ||
449 bno < irec.br_startoff)
452 trace_xfs_reflink_find_cow_mapping(ip, offset, 1, XFS_IO_OVERWRITE,
455 /* If it's still delalloc, we must allocate later. */
457 *need_alloc = !!(isnullstartblock(irec.br_startblock));
463 * Trim an extent to end at the next CoW reservation past offset_fsb.
466 xfs_reflink_trim_irec_to_next_cow(
467 struct xfs_inode *ip,
468 xfs_fileoff_t offset_fsb,
469 struct xfs_bmbt_irec *imap)
471 struct xfs_bmbt_irec irec;
472 struct xfs_ifork *ifp;
473 struct xfs_bmbt_rec_host *gotp;
476 if (!xfs_is_reflink_inode(ip))
479 /* Find the extent in the CoW fork. */
480 ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
481 gotp = xfs_iext_bno_to_ext(ifp, offset_fsb, &idx);
484 xfs_bmbt_get_all(gotp, &irec);
486 /* This is the extent before; try sliding up one. */
487 if (irec.br_startoff < offset_fsb) {
489 if (idx >= ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
491 gotp = xfs_iext_get_ext(ifp, idx);
492 xfs_bmbt_get_all(gotp, &irec);
495 if (irec.br_startoff >= imap->br_startoff + imap->br_blockcount)
498 imap->br_blockcount = irec.br_startoff - imap->br_startoff;
499 trace_xfs_reflink_trim_irec(ip, imap);
505 * Cancel all pending CoW reservations for some block range of an inode.
508 xfs_reflink_cancel_cow_blocks(
509 struct xfs_inode *ip,
510 struct xfs_trans **tpp,
511 xfs_fileoff_t offset_fsb,
512 xfs_fileoff_t end_fsb)
514 struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
515 struct xfs_bmbt_irec got, prev, del;
517 xfs_fsblock_t firstfsb;
518 struct xfs_defer_ops dfops;
519 int error = 0, eof = 0;
521 if (!xfs_is_reflink_inode(ip))
524 xfs_bmap_search_extents(ip, offset_fsb, XFS_COW_FORK, &eof, &idx,
529 while (got.br_startoff < end_fsb) {
531 xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
532 trace_xfs_reflink_cancel_cow(ip, &del);
534 if (isnullstartblock(del.br_startblock)) {
535 error = xfs_bmap_del_extent_delay(ip, XFS_COW_FORK,
540 xfs_trans_ijoin(*tpp, ip, 0);
541 xfs_defer_init(&dfops, &firstfsb);
543 /* Free the CoW orphan record. */
544 error = xfs_refcount_free_cow_extent(ip->i_mount,
545 &dfops, del.br_startblock,
550 xfs_bmap_add_free(ip->i_mount, &dfops,
551 del.br_startblock, del.br_blockcount,
554 /* Update quota accounting */
555 xfs_trans_mod_dquot_byino(*tpp, ip, XFS_TRANS_DQ_BCOUNT,
556 -(long)del.br_blockcount);
558 /* Roll the transaction */
559 error = xfs_defer_finish(tpp, &dfops, ip);
561 xfs_defer_cancel(&dfops);
565 /* Remove the mapping from the CoW fork. */
566 xfs_bmap_del_extent_cow(ip, &idx, &got, &del);
569 if (++idx >= ifp->if_bytes / sizeof(struct xfs_bmbt_rec))
571 xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), &got);
574 /* clear tag if cow fork is emptied */
576 xfs_inode_clear_cowblocks_tag(ip);
582 * Cancel all pending CoW reservations for some byte range of an inode.
585 xfs_reflink_cancel_cow_range(
586 struct xfs_inode *ip,
590 struct xfs_trans *tp;
591 xfs_fileoff_t offset_fsb;
592 xfs_fileoff_t end_fsb;
595 trace_xfs_reflink_cancel_cow_range(ip, offset, count);
596 ASSERT(xfs_is_reflink_inode(ip));
598 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
599 if (count == NULLFILEOFF)
600 end_fsb = NULLFILEOFF;
602 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
604 /* Start a rolling transaction to remove the mappings */
605 error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
610 xfs_ilock(ip, XFS_ILOCK_EXCL);
611 xfs_trans_ijoin(tp, ip, 0);
613 /* Scrape out the old CoW reservations */
614 error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb);
618 error = xfs_trans_commit(tp);
620 xfs_iunlock(ip, XFS_ILOCK_EXCL);
624 xfs_trans_cancel(tp);
625 xfs_iunlock(ip, XFS_ILOCK_EXCL);
627 trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_);
632 * Remap parts of a file's data fork after a successful CoW.
636 struct xfs_inode *ip,
640 struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
641 struct xfs_bmbt_irec got, prev, del;
642 struct xfs_trans *tp;
643 xfs_fileoff_t offset_fsb;
644 xfs_fileoff_t end_fsb;
645 xfs_fsblock_t firstfsb;
646 struct xfs_defer_ops dfops;
648 unsigned int resblks;
652 trace_xfs_reflink_end_cow(ip, offset, count);
654 /* No COW extents? That's easy! */
655 if (ifp->if_bytes == 0)
658 offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
659 end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
661 /* Start a rolling transaction to switch the mappings */
662 resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);
663 error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
668 xfs_ilock(ip, XFS_ILOCK_EXCL);
669 xfs_trans_ijoin(tp, ip, 0);
671 xfs_bmap_search_extents(ip, end_fsb - 1, XFS_COW_FORK, &eof, &idx,
674 /* If there is a hole at end_fsb - 1 go to the previous extent */
675 if (eof || got.br_startoff > end_fsb) {
677 xfs_bmbt_get_all(xfs_iext_get_ext(ifp, --idx), &got);
680 /* Walk backwards until we're out of the I/O range... */
681 while (got.br_startoff + got.br_blockcount > offset_fsb) {
683 xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
685 /* Extent delete may have bumped idx forward */
686 if (!del.br_blockcount) {
691 ASSERT(!isnullstartblock(got.br_startblock));
693 /* Unmap the old blocks in the data fork. */
694 xfs_defer_init(&dfops, &firstfsb);
695 rlen = del.br_blockcount;
696 error = __xfs_bunmapi(tp, ip, del.br_startoff, &rlen, 0, 1,
701 /* Trim the extent to whatever got unmapped. */
703 xfs_trim_extent(&del, del.br_startoff + rlen,
704 del.br_blockcount - rlen);
706 trace_xfs_reflink_cow_remap(ip, &del);
708 /* Free the CoW orphan record. */
709 error = xfs_refcount_free_cow_extent(tp->t_mountp, &dfops,
710 del.br_startblock, del.br_blockcount);
714 /* Map the new blocks into the data fork. */
715 error = xfs_bmap_map_extent(tp->t_mountp, &dfops, ip, &del);
719 /* Remove the mapping from the CoW fork. */
720 xfs_bmap_del_extent_cow(ip, &idx, &got, &del);
722 error = xfs_defer_finish(&tp, &dfops, ip);
729 xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), &got);
732 error = xfs_trans_commit(tp);
733 xfs_iunlock(ip, XFS_ILOCK_EXCL);
739 xfs_defer_cancel(&dfops);
740 xfs_trans_cancel(tp);
741 xfs_iunlock(ip, XFS_ILOCK_EXCL);
743 trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
748 * Free leftover CoW reservations that didn't get cleaned out.
751 xfs_reflink_recover_cow(
752 struct xfs_mount *mp)
757 if (!xfs_sb_version_hasreflink(&mp->m_sb))
760 for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
761 error = xfs_refcount_recover_cow_leftovers(mp, agno);
770 * Reflinking (Block) Ranges of Two Files Together
772 * First, ensure that the reflink flag is set on both inodes. The flag is an
773 * optimization to avoid unnecessary refcount btree lookups in the write path.
775 * Now we can iteratively remap the range of extents (and holes) in src to the
776 * corresponding ranges in dest. Let drange and srange denote the ranges of
777 * logical blocks in dest and src touched by the reflink operation.
779 * While the length of drange is greater than zero,
780 * - Read src's bmbt at the start of srange ("imap")
781 * - If imap doesn't exist, make imap appear to start at the end of srange
783 * - If imap starts before srange, advance imap to start at srange.
784 * - If imap goes beyond srange, truncate imap to end at the end of srange.
785 * - Punch (imap start - srange start + imap len) blocks from dest at
786 * offset (drange start).
787 * - If imap points to a real range of pblks,
788 * > Increase the refcount of the imap's pblks
789 * > Map imap's pblks into dest at the offset
790 * (drange start + imap start - srange start)
791 * - Advance drange and srange by (imap start - srange start + imap len)
793 * Finally, if the reflink made dest longer, update both the in-core and
794 * on-disk file sizes.
796 * ASCII Art Demonstration:
798 * Let's say we want to reflink this source file:
800 * ----SSSSSSS-SSSSS----SSSSSS (src file)
801 * <-------------------->
803 * into this destination file:
805 * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
806 * <-------------------->
807 * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
808 * Observe that the range has different logical offsets in either file.
810 * Consider that the first extent in the source file doesn't line up with our
811 * reflink range. Unmapping and remapping are separate operations, so we can
812 * unmap more blocks from the destination file than we remap.
814 * ----SSSSSSS-SSSSS----SSSSSS
816 * --DDDDD---------DDDDD--DDD
819 * Now remap the source extent into the destination file:
821 * ----SSSSSSS-SSSSS----SSSSSS
823 * --DDDDD--SSSSSSSDDDDD--DDD
826 * Do likewise with the second hole and extent in our range. Holes in the
827 * unmap range don't affect our operation.
829 * ----SSSSSSS-SSSSS----SSSSSS
831 * --DDDDD--SSSSSSS-SSSSS-DDD
834 * Finally, unmap and remap part of the third extent. This will increase the
835 * size of the destination file.
837 * ----SSSSSSS-SSSSS----SSSSSS
839 * --DDDDD--SSSSSSS-SSSSS----SSS
842 * Once we update the destination file's i_size, we're done.
846 * Ensure the reflink bit is set in both inodes.
849 xfs_reflink_set_inode_flag(
850 struct xfs_inode *src,
851 struct xfs_inode *dest)
853 struct xfs_mount *mp = src->i_mount;
855 struct xfs_trans *tp;
857 if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
860 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
864 /* Lock both files against IO */
865 if (src->i_ino == dest->i_ino)
866 xfs_ilock(src, XFS_ILOCK_EXCL);
868 xfs_lock_two_inodes(src, dest, XFS_ILOCK_EXCL);
870 if (!xfs_is_reflink_inode(src)) {
871 trace_xfs_reflink_set_inode_flag(src);
872 xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
873 src->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK;
874 xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
875 xfs_ifork_init_cow(src);
877 xfs_iunlock(src, XFS_ILOCK_EXCL);
879 if (src->i_ino == dest->i_ino)
882 if (!xfs_is_reflink_inode(dest)) {
883 trace_xfs_reflink_set_inode_flag(dest);
884 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
885 dest->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK;
886 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
887 xfs_ifork_init_cow(dest);
889 xfs_iunlock(dest, XFS_ILOCK_EXCL);
892 error = xfs_trans_commit(tp);
898 trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
903 * Update destination inode size & cowextsize hint, if necessary.
906 xfs_reflink_update_dest(
907 struct xfs_inode *dest,
909 xfs_extlen_t cowextsize)
911 struct xfs_mount *mp = dest->i_mount;
912 struct xfs_trans *tp;
915 if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
918 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
922 xfs_ilock(dest, XFS_ILOCK_EXCL);
923 xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
925 if (newlen > i_size_read(VFS_I(dest))) {
926 trace_xfs_reflink_update_inode_size(dest, newlen);
927 i_size_write(VFS_I(dest), newlen);
928 dest->i_d.di_size = newlen;
932 dest->i_d.di_cowextsize = cowextsize;
933 dest->i_d.di_flags2 |= XFS_DIFLAG2_COWEXTSIZE;
936 xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
938 error = xfs_trans_commit(tp);
944 trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
949 * Do we have enough reserve in this AG to handle a reflink? The refcount
950 * btree already reserved all the space it needs, but the rmap btree can grow
951 * infinitely, so we won't allow more reflinks when the AG is down to the
955 xfs_reflink_ag_has_free_space(
956 struct xfs_mount *mp,
959 struct xfs_perag *pag;
962 if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
965 pag = xfs_perag_get(mp, agno);
966 if (xfs_ag_resv_critical(pag, XFS_AG_RESV_AGFL) ||
967 xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
974 * Unmap a range of blocks from a file, then map other blocks into the hole.
975 * The range to unmap is (destoff : destoff + srcioff + irec->br_blockcount).
976 * The extent irec is mapped into dest at irec->br_startoff.
979 xfs_reflink_remap_extent(
980 struct xfs_inode *ip,
981 struct xfs_bmbt_irec *irec,
982 xfs_fileoff_t destoff,
985 struct xfs_mount *mp = ip->i_mount;
986 struct xfs_trans *tp;
987 xfs_fsblock_t firstfsb;
988 unsigned int resblks;
989 struct xfs_defer_ops dfops;
990 struct xfs_bmbt_irec uirec;
993 xfs_filblks_t unmap_len;
997 unmap_len = irec->br_startoff + irec->br_blockcount - destoff;
998 trace_xfs_reflink_punch_range(ip, destoff, unmap_len);
1000 /* Only remap normal extents. */
1001 real_extent = (irec->br_startblock != HOLESTARTBLOCK &&
1002 irec->br_startblock != DELAYSTARTBLOCK &&
1003 !ISUNWRITTEN(irec));
1005 /* No reflinking if we're low on space */
1007 error = xfs_reflink_ag_has_free_space(mp,
1008 XFS_FSB_TO_AGNO(mp, irec->br_startblock));
1013 /* Start a rolling transaction to switch the mappings */
1014 resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);
1015 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
1019 xfs_ilock(ip, XFS_ILOCK_EXCL);
1020 xfs_trans_ijoin(tp, ip, 0);
1022 /* If we're not just clearing space, then do we have enough quota? */
1024 error = xfs_trans_reserve_quota_nblks(tp, ip,
1025 irec->br_blockcount, 0, XFS_QMOPT_RES_REGBLKS);
1030 trace_xfs_reflink_remap(ip, irec->br_startoff,
1031 irec->br_blockcount, irec->br_startblock);
1033 /* Unmap the old blocks in the data fork. */
1036 xfs_defer_init(&dfops, &firstfsb);
1037 error = __xfs_bunmapi(tp, ip, destoff, &rlen, 0, 1,
1043 * Trim the extent to whatever got unmapped.
1044 * Remember, bunmapi works backwards.
1046 uirec.br_startblock = irec->br_startblock + rlen;
1047 uirec.br_startoff = irec->br_startoff + rlen;
1048 uirec.br_blockcount = unmap_len - rlen;
1051 /* If this isn't a real mapping, we're done. */
1052 if (!real_extent || uirec.br_blockcount == 0)
1055 trace_xfs_reflink_remap(ip, uirec.br_startoff,
1056 uirec.br_blockcount, uirec.br_startblock);
1058 /* Update the refcount tree */
1059 error = xfs_refcount_increase_extent(mp, &dfops, &uirec);
1063 /* Map the new blocks into the data fork. */
1064 error = xfs_bmap_map_extent(mp, &dfops, ip, &uirec);
1068 /* Update quota accounting. */
1069 xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
1070 uirec.br_blockcount);
1072 /* Update dest isize if needed. */
1073 newlen = XFS_FSB_TO_B(mp,
1074 uirec.br_startoff + uirec.br_blockcount);
1075 newlen = min_t(xfs_off_t, newlen, new_isize);
1076 if (newlen > i_size_read(VFS_I(ip))) {
1077 trace_xfs_reflink_update_inode_size(ip, newlen);
1078 i_size_write(VFS_I(ip), newlen);
1079 ip->i_d.di_size = newlen;
1080 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
1084 /* Process all the deferred stuff. */
1085 error = xfs_defer_finish(&tp, &dfops, ip);
1090 error = xfs_trans_commit(tp);
1091 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1097 xfs_defer_cancel(&dfops);
1099 xfs_trans_cancel(tp);
1100 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1102 trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
1107 * Iteratively remap one file's extents (and holes) to another's.
1110 xfs_reflink_remap_blocks(
1111 struct xfs_inode *src,
1112 xfs_fileoff_t srcoff,
1113 struct xfs_inode *dest,
1114 xfs_fileoff_t destoff,
1116 xfs_off_t new_isize)
1118 struct xfs_bmbt_irec imap;
1121 xfs_filblks_t range_len;
1123 /* drange = (destoff, destoff + len); srange = (srcoff, srcoff + len) */
1125 trace_xfs_reflink_remap_blocks_loop(src, srcoff, len,
1127 /* Read extent from the source file */
1129 xfs_ilock(src, XFS_ILOCK_EXCL);
1130 error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
1131 xfs_iunlock(src, XFS_ILOCK_EXCL);
1134 ASSERT(nimaps == 1);
1136 trace_xfs_reflink_remap_imap(src, srcoff, len, XFS_IO_OVERWRITE,
1139 /* Translate imap into the destination file. */
1140 range_len = imap.br_startoff + imap.br_blockcount - srcoff;
1141 imap.br_startoff += destoff - srcoff;
1143 /* Clear dest from destoff to the end of imap and map it in. */
1144 error = xfs_reflink_remap_extent(dest, &imap, destoff,
1149 if (fatal_signal_pending(current)) {
1154 /* Advance drange/srange */
1155 srcoff += range_len;
1156 destoff += range_len;
1163 trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
1168 * Read a page's worth of file data into the page cache. Return the page
1171 static struct page *
1173 struct inode *inode,
1176 struct address_space *mapping;
1180 n = offset >> PAGE_SHIFT;
1181 mapping = inode->i_mapping;
1182 page = read_mapping_page(mapping, n, NULL);
1185 if (!PageUptodate(page)) {
1187 return ERR_PTR(-EIO);
1194 * Compare extents of two files to see if they are the same.
1197 xfs_compare_extents(
1206 xfs_off_t dest_poff;
1209 struct page *src_page;
1210 struct page *dest_page;
1218 src_poff = srcoff & (PAGE_SIZE - 1);
1219 dest_poff = destoff & (PAGE_SIZE - 1);
1220 cmp_len = min(PAGE_SIZE - src_poff,
1221 PAGE_SIZE - dest_poff);
1222 cmp_len = min(cmp_len, len);
1223 ASSERT(cmp_len > 0);
1225 trace_xfs_reflink_compare_extents(XFS_I(src), srcoff, cmp_len,
1226 XFS_I(dest), destoff);
1228 src_page = xfs_get_page(src, srcoff);
1229 if (IS_ERR(src_page)) {
1230 error = PTR_ERR(src_page);
1233 dest_page = xfs_get_page(dest, destoff);
1234 if (IS_ERR(dest_page)) {
1235 error = PTR_ERR(dest_page);
1236 unlock_page(src_page);
1240 src_addr = kmap_atomic(src_page);
1241 dest_addr = kmap_atomic(dest_page);
1243 flush_dcache_page(src_page);
1244 flush_dcache_page(dest_page);
1246 if (memcmp(src_addr + src_poff, dest_addr + dest_poff, cmp_len))
1249 kunmap_atomic(dest_addr);
1250 kunmap_atomic(src_addr);
1251 unlock_page(dest_page);
1252 unlock_page(src_page);
1253 put_page(dest_page);
1268 trace_xfs_reflink_compare_extents_error(XFS_I(dest), error, _RET_IP_);
1273 * Link a range of blocks from one file to another.
1276 xfs_reflink_remap_range(
1277 struct file *file_in,
1279 struct file *file_out,
1284 struct inode *inode_in = file_inode(file_in);
1285 struct xfs_inode *src = XFS_I(inode_in);
1286 struct inode *inode_out = file_inode(file_out);
1287 struct xfs_inode *dest = XFS_I(inode_out);
1288 struct xfs_mount *mp = src->i_mount;
1289 loff_t bs = inode_out->i_sb->s_blocksize;
1290 bool same_inode = (inode_in == inode_out);
1291 xfs_fileoff_t sfsbno, dfsbno;
1292 xfs_filblks_t fsblen;
1293 xfs_extlen_t cowextsize;
1298 if (!xfs_sb_version_hasreflink(&mp->m_sb))
1301 if (XFS_FORCED_SHUTDOWN(mp))
1304 /* Lock both files against IO */
1306 xfs_ilock(src, XFS_IOLOCK_EXCL);
1307 xfs_ilock(src, XFS_MMAPLOCK_EXCL);
1309 xfs_lock_two_inodes(src, dest, XFS_IOLOCK_EXCL);
1310 xfs_lock_two_inodes(src, dest, XFS_MMAPLOCK_EXCL);
1313 /* Don't touch certain kinds of inodes */
1315 if (IS_IMMUTABLE(inode_out))
1319 if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
1323 /* Don't reflink dirs, pipes, sockets... */
1325 if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
1328 if (S_ISFIFO(inode_in->i_mode) || S_ISFIFO(inode_out->i_mode))
1330 if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
1333 /* Don't reflink realtime inodes */
1334 if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
1337 /* Don't share DAX file data for now. */
1338 if (IS_DAX(inode_in) || IS_DAX(inode_out))
1341 /* Are we going all the way to the end? */
1342 isize = i_size_read(inode_in);
1349 len = isize - pos_in;
1351 /* Ensure offsets don't wrap and the input is inside i_size */
1352 if (pos_in + len < pos_in || pos_out + len < pos_out ||
1353 pos_in + len > isize)
1356 /* Don't allow dedupe past EOF in the dest file */
1360 disize = i_size_read(inode_out);
1361 if (pos_out >= disize || pos_out + len > disize)
1365 /* If we're linking to EOF, continue to the block boundary. */
1366 if (pos_in + len == isize)
1367 blen = ALIGN(isize, bs) - pos_in;
1371 /* Only reflink if we're aligned to block boundaries */
1372 if (!IS_ALIGNED(pos_in, bs) || !IS_ALIGNED(pos_in + blen, bs) ||
1373 !IS_ALIGNED(pos_out, bs) || !IS_ALIGNED(pos_out + blen, bs))
1376 /* Don't allow overlapped reflink within the same file */
1378 if (pos_out + blen > pos_in && pos_out < pos_in + blen)
1382 /* Wait for the completion of any pending IOs on both files */
1383 inode_dio_wait(inode_in);
1385 inode_dio_wait(inode_out);
1387 ret = filemap_write_and_wait_range(inode_in->i_mapping,
1388 pos_in, pos_in + len - 1);
1392 ret = filemap_write_and_wait_range(inode_out->i_mapping,
1393 pos_out, pos_out + len - 1);
1397 trace_xfs_reflink_remap_range(src, pos_in, len, dest, pos_out);
1400 * Check that the extents are the same.
1403 bool is_same = false;
1405 ret = xfs_compare_extents(inode_in, pos_in, inode_out, pos_out,
1415 ret = xfs_reflink_set_inode_flag(src, dest);
1420 * Invalidate the page cache so that we can clear any CoW mappings
1421 * in the destination file.
1423 truncate_inode_pages_range(&inode_out->i_data, pos_out,
1424 PAGE_ALIGN(pos_out + len) - 1);
1426 dfsbno = XFS_B_TO_FSBT(mp, pos_out);
1427 sfsbno = XFS_B_TO_FSBT(mp, pos_in);
1428 fsblen = XFS_B_TO_FSB(mp, len);
1429 ret = xfs_reflink_remap_blocks(src, sfsbno, dest, dfsbno, fsblen,
1435 * Carry the cowextsize hint from src to dest if we're sharing the
1436 * entire source file to the entire destination file, the source file
1437 * has a cowextsize hint, and the destination file does not.
1440 if (pos_in == 0 && len == i_size_read(inode_in) &&
1441 (src->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE) &&
1442 pos_out == 0 && len >= i_size_read(inode_out) &&
1443 !(dest->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE))
1444 cowextsize = src->i_d.di_cowextsize;
1446 ret = xfs_reflink_update_dest(dest, pos_out + len, cowextsize);
1449 xfs_iunlock(src, XFS_MMAPLOCK_EXCL);
1450 xfs_iunlock(src, XFS_IOLOCK_EXCL);
1451 if (src->i_ino != dest->i_ino) {
1452 xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
1453 xfs_iunlock(dest, XFS_IOLOCK_EXCL);
1456 trace_xfs_reflink_remap_range_error(dest, ret, _RET_IP_);
1461 * The user wants to preemptively CoW all shared blocks in this file,
1462 * which enables us to turn off the reflink flag. Iterate all
1463 * extents which are not prealloc/delalloc to see which ranges are
1464 * mentioned in the refcount tree, then read those blocks into the
1465 * pagecache, dirty them, fsync them back out, and then we can update
1466 * the inode flag. What happens if we run out of memory? :)
1469 xfs_reflink_dirty_extents(
1470 struct xfs_inode *ip,
1475 struct xfs_mount *mp = ip->i_mount;
1476 xfs_agnumber_t agno;
1477 xfs_agblock_t agbno;
1483 struct xfs_bmbt_irec map[2];
1487 while (end - fbno > 0) {
1490 * Look for extents in the file. Skip holes, delalloc, or
1491 * unwritten extents; they can't be reflinked.
1493 error = xfs_bmapi_read(ip, fbno, end - fbno, map, &nmaps, 0);
1498 if (map[0].br_startblock == HOLESTARTBLOCK ||
1499 map[0].br_startblock == DELAYSTARTBLOCK ||
1500 ISUNWRITTEN(&map[0]))
1504 while (map[1].br_blockcount) {
1505 agno = XFS_FSB_TO_AGNO(mp, map[1].br_startblock);
1506 agbno = XFS_FSB_TO_AGBNO(mp, map[1].br_startblock);
1507 aglen = map[1].br_blockcount;
1509 error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
1510 &rbno, &rlen, true);
1513 if (rbno == NULLAGBLOCK)
1516 /* Dirty the pages */
1517 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1518 fpos = XFS_FSB_TO_B(mp, map[1].br_startoff +
1520 flen = XFS_FSB_TO_B(mp, rlen);
1521 if (fpos + flen > isize)
1522 flen = isize - fpos;
1523 error = iomap_file_dirty(VFS_I(ip), fpos, flen,
1525 xfs_ilock(ip, XFS_ILOCK_EXCL);
1529 map[1].br_blockcount -= (rbno - agbno + rlen);
1530 map[1].br_startoff += (rbno - agbno + rlen);
1531 map[1].br_startblock += (rbno - agbno + rlen);
1535 fbno = map[0].br_startoff + map[0].br_blockcount;
1541 /* Clear the inode reflink flag if there are no shared extents. */
1543 xfs_reflink_clear_inode_flag(
1544 struct xfs_inode *ip,
1545 struct xfs_trans **tpp)
1547 struct xfs_mount *mp = ip->i_mount;
1550 xfs_agnumber_t agno;
1551 xfs_agblock_t agbno;
1555 struct xfs_bmbt_irec map;
1559 ASSERT(xfs_is_reflink_inode(ip));
1562 end = XFS_B_TO_FSB(mp, i_size_read(VFS_I(ip)));
1563 while (end - fbno > 0) {
1566 * Look for extents in the file. Skip holes, delalloc, or
1567 * unwritten extents; they can't be reflinked.
1569 error = xfs_bmapi_read(ip, fbno, end - fbno, &map, &nmaps, 0);
1574 if (map.br_startblock == HOLESTARTBLOCK ||
1575 map.br_startblock == DELAYSTARTBLOCK ||
1579 agno = XFS_FSB_TO_AGNO(mp, map.br_startblock);
1580 agbno = XFS_FSB_TO_AGBNO(mp, map.br_startblock);
1581 aglen = map.br_blockcount;
1583 error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
1584 &rbno, &rlen, false);
1587 /* Is there still a shared block here? */
1588 if (rbno != NULLAGBLOCK)
1591 fbno = map.br_startoff + map.br_blockcount;
1595 * We didn't find any shared blocks so turn off the reflink flag.
1596 * First, get rid of any leftover CoW mappings.
1598 error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, NULLFILEOFF);
1602 /* Clear the inode flag. */
1603 trace_xfs_reflink_unset_inode_flag(ip);
1604 ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
1605 xfs_inode_clear_cowblocks_tag(ip);
1606 xfs_trans_ijoin(*tpp, ip, 0);
1607 xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
1613 * Clear the inode reflink flag if there are no shared extents and the size
1617 xfs_reflink_try_clear_inode_flag(
1618 struct xfs_inode *ip)
1620 struct xfs_mount *mp = ip->i_mount;
1621 struct xfs_trans *tp;
1624 /* Start a rolling transaction to remove the mappings */
1625 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1629 xfs_ilock(ip, XFS_ILOCK_EXCL);
1630 xfs_trans_ijoin(tp, ip, 0);
1632 error = xfs_reflink_clear_inode_flag(ip, &tp);
1636 error = xfs_trans_commit(tp);
1640 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1643 xfs_trans_cancel(tp);
1645 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1650 * Pre-COW all shared blocks within a given byte range of a file and turn off
1651 * the reflink flag if we unshare all of the file's blocks.
1654 xfs_reflink_unshare(
1655 struct xfs_inode *ip,
1659 struct xfs_mount *mp = ip->i_mount;
1665 if (!xfs_is_reflink_inode(ip))
1668 trace_xfs_reflink_unshare(ip, offset, len);
1670 inode_dio_wait(VFS_I(ip));
1672 /* Try to CoW the selected ranges */
1673 xfs_ilock(ip, XFS_ILOCK_EXCL);
1674 fbno = XFS_B_TO_FSBT(mp, offset);
1675 isize = i_size_read(VFS_I(ip));
1676 end = XFS_B_TO_FSB(mp, offset + len);
1677 error = xfs_reflink_dirty_extents(ip, fbno, end, isize);
1680 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1682 /* Wait for the IO to finish */
1683 error = filemap_write_and_wait(VFS_I(ip)->i_mapping);
1687 /* Turn off the reflink flag if possible. */
1688 error = xfs_reflink_try_clear_inode_flag(ip);
1695 xfs_iunlock(ip, XFS_ILOCK_EXCL);
1697 trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
1702 * Does this inode have any real CoW reservations?
1705 xfs_reflink_has_real_cow_blocks(
1706 struct xfs_inode *ip)
1708 struct xfs_bmbt_irec irec;
1709 struct xfs_ifork *ifp;
1710 struct xfs_bmbt_rec_host *gotp;
1713 if (!xfs_is_reflink_inode(ip))
1716 /* Go find the old extent in the CoW fork. */
1717 ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
1718 gotp = xfs_iext_bno_to_ext(ifp, 0, &idx);
1720 xfs_bmbt_get_all(gotp, &irec);
1722 if (!isnullstartblock(irec.br_startblock))
1727 if (idx >= ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
1729 gotp = xfs_iext_get_ext(ifp, idx);