diff options
Diffstat (limited to 'fs/xfs/xfs_reflink.c')
| -rw-r--r-- | fs/xfs/xfs_reflink.c | 1520 |
1 files changed, 1520 insertions, 0 deletions
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c new file mode 100644 index 000000000..aa46b75d7 --- /dev/null +++ b/fs/xfs/xfs_reflink.c @@ -0,0 +1,1520 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2016 Oracle. All Rights Reserved. + * Author: Darrick J. Wong <darrick.wong@oracle.com> + */ +#include "xfs.h" +#include "xfs_fs.h" +#include "xfs_shared.h" +#include "xfs_format.h" +#include "xfs_log_format.h" +#include "xfs_trans_resv.h" +#include "xfs_mount.h" +#include "xfs_defer.h" +#include "xfs_inode.h" +#include "xfs_trans.h" +#include "xfs_bmap.h" +#include "xfs_bmap_util.h" +#include "xfs_trace.h" +#include "xfs_icache.h" +#include "xfs_btree.h" +#include "xfs_refcount_btree.h" +#include "xfs_refcount.h" +#include "xfs_bmap_btree.h" +#include "xfs_trans_space.h" +#include "xfs_bit.h" +#include "xfs_alloc.h" +#include "xfs_quota.h" +#include "xfs_reflink.h" +#include "xfs_iomap.h" +#include "xfs_sb.h" +#include "xfs_ag_resv.h" + +/* + * Copy on Write of Shared Blocks + * + * XFS must preserve "the usual" file semantics even when two files share + * the same physical blocks. This means that a write to one file must not + * alter the blocks in a different file; the way that we'll do that is + * through the use of a copy-on-write mechanism. At a high level, that + * means that when we want to write to a shared block, we allocate a new + * block, write the data to the new block, and if that succeeds we map the + * new block into the file. + * + * XFS provides a "delayed allocation" mechanism that defers the allocation + * of disk blocks to dirty-but-not-yet-mapped file blocks as long as + * possible. This reduces fragmentation by enabling the filesystem to ask + * for bigger chunks less often, which is exactly what we want for CoW. + * + * The delalloc mechanism begins when the kernel wants to make a block + * writable (write_begin or page_mkwrite). If the offset is not mapped, we + * create a delalloc mapping, which is a regular in-core extent, but without + * a real startblock. (For delalloc mappings, the startblock encodes both + * a flag that this is a delalloc mapping, and a worst-case estimate of how + * many blocks might be required to put the mapping into the BMBT.) delalloc + * mappings are a reservation against the free space in the filesystem; + * adjacent mappings can also be combined into fewer larger mappings. + * + * As an optimization, the CoW extent size hint (cowextsz) creates + * outsized aligned delalloc reservations in the hope of landing out of + * order nearby CoW writes in a single extent on disk, thereby reducing + * fragmentation and improving future performance. + * + * D: --RRRRRRSSSRRRRRRRR--- (data fork) + * C: ------DDDDDDD--------- (CoW fork) + * + * When dirty pages are being written out (typically in writepage), the + * delalloc reservations are converted into unwritten mappings by + * allocating blocks and replacing the delalloc mapping with real ones. + * A delalloc mapping can be replaced by several unwritten ones if the + * free space is fragmented. + * + * D: --RRRRRRSSSRRRRRRRR--- + * C: ------UUUUUUU--------- + * + * We want to adapt the delalloc mechanism for copy-on-write, since the + * write paths are similar. The first two steps (creating the reservation + * and allocating the blocks) are exactly the same as delalloc except that + * the mappings must be stored in a separate CoW fork because we do not want + * to disturb the mapping in the data fork until we're sure that the write + * succeeded. IO completion in this case is the process of removing the old + * mapping from the data fork and moving the new mapping from the CoW fork to + * the data fork. This will be discussed shortly. + * + * For now, unaligned directio writes will be bounced back to the page cache. + * Block-aligned directio writes will use the same mechanism as buffered + * writes. + * + * Just prior to submitting the actual disk write requests, we convert + * the extents representing the range of the file actually being written + * (as opposed to extra pieces created for the cowextsize hint) to real + * extents. This will become important in the next step: + * + * D: --RRRRRRSSSRRRRRRRR--- + * C: ------UUrrUUU--------- + * + * CoW remapping must be done after the data block write completes, + * because we don't want to destroy the old data fork map until we're sure + * the new block has been written. Since the new mappings are kept in a + * separate fork, we can simply iterate these mappings to find the ones + * that cover the file blocks that we just CoW'd. For each extent, simply + * unmap the corresponding range in the data fork, map the new range into + * the data fork, and remove the extent from the CoW fork. Because of + * the presence of the cowextsize hint, however, we must be careful + * only to remap the blocks that we've actually written out -- we must + * never remap delalloc reservations nor CoW staging blocks that have + * yet to be written. This corresponds exactly to the real extents in + * the CoW fork: + * + * D: --RRRRRRrrSRRRRRRRR--- + * C: ------UU--UUU--------- + * + * Since the remapping operation can be applied to an arbitrary file + * range, we record the need for the remap step as a flag in the ioend + * instead of declaring a new IO type. This is required for direct io + * because we only have ioend for the whole dio, and we have to be able to + * remember the presence of unwritten blocks and CoW blocks with a single + * ioend structure. Better yet, the more ground we can cover with one + * ioend, the better. + */ + +/* + * Given an AG extent, find the lowest-numbered run of shared blocks + * within that range and return the range in fbno/flen. If + * find_end_of_shared is true, return the longest contiguous extent of + * shared blocks. If there are no shared extents, fbno and flen will + * be set to NULLAGBLOCK and 0, respectively. + */ +int +xfs_reflink_find_shared( + struct xfs_mount *mp, + struct xfs_trans *tp, + xfs_agnumber_t agno, + xfs_agblock_t agbno, + xfs_extlen_t aglen, + xfs_agblock_t *fbno, + xfs_extlen_t *flen, + bool find_end_of_shared) +{ + struct xfs_buf *agbp; + struct xfs_btree_cur *cur; + int error; + + error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp); + if (error) + return error; + + cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno); + + error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen, + find_end_of_shared); + + xfs_btree_del_cursor(cur, error); + + xfs_trans_brelse(tp, agbp); + return error; +} + +/* + * Trim the mapping to the next block where there's a change in the + * shared/unshared status. More specifically, this means that we + * find the lowest-numbered extent of shared blocks that coincides with + * the given block mapping. If the shared extent overlaps the start of + * the mapping, trim the mapping to the end of the shared extent. If + * the shared region intersects the mapping, trim the mapping to the + * start of the shared extent. If there are no shared regions that + * overlap, just return the original extent. + */ +int +xfs_reflink_trim_around_shared( + struct xfs_inode *ip, + struct xfs_bmbt_irec *irec, + bool *shared) +{ + xfs_agnumber_t agno; + xfs_agblock_t agbno; + xfs_extlen_t aglen; + xfs_agblock_t fbno; + xfs_extlen_t flen; + int error = 0; + + /* Holes, unwritten, and delalloc extents cannot be shared */ + if (!xfs_is_cow_inode(ip) || !xfs_bmap_is_written_extent(irec)) { + *shared = false; + return 0; + } + + trace_xfs_reflink_trim_around_shared(ip, irec); + + agno = XFS_FSB_TO_AGNO(ip->i_mount, irec->br_startblock); + agbno = XFS_FSB_TO_AGBNO(ip->i_mount, irec->br_startblock); + aglen = irec->br_blockcount; + + error = xfs_reflink_find_shared(ip->i_mount, NULL, agno, agbno, + aglen, &fbno, &flen, true); + if (error) + return error; + + *shared = false; + if (fbno == NULLAGBLOCK) { + /* No shared blocks at all. */ + return 0; + } else if (fbno == agbno) { + /* + * The start of this extent is shared. Truncate the + * mapping at the end of the shared region so that a + * subsequent iteration starts at the start of the + * unshared region. + */ + irec->br_blockcount = flen; + *shared = true; + return 0; + } else { + /* + * There's a shared extent midway through this extent. + * Truncate the mapping at the start of the shared + * extent so that a subsequent iteration starts at the + * start of the shared region. + */ + irec->br_blockcount = fbno - agbno; + return 0; + } +} + +int +xfs_bmap_trim_cow( + struct xfs_inode *ip, + struct xfs_bmbt_irec *imap, + bool *shared) +{ + /* We can't update any real extents in always COW mode. */ + if (xfs_is_always_cow_inode(ip) && + !isnullstartblock(imap->br_startblock)) { + *shared = true; + return 0; + } + + /* Trim the mapping to the nearest shared extent boundary. */ + return xfs_reflink_trim_around_shared(ip, imap, shared); +} + +static int +xfs_reflink_convert_cow_locked( + struct xfs_inode *ip, + xfs_fileoff_t offset_fsb, + xfs_filblks_t count_fsb) +{ + struct xfs_iext_cursor icur; + struct xfs_bmbt_irec got; + struct xfs_btree_cur *dummy_cur = NULL; + int dummy_logflags; + int error = 0; + + if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got)) + return 0; + + do { + if (got.br_startoff >= offset_fsb + count_fsb) + break; + if (got.br_state == XFS_EXT_NORM) + continue; + if (WARN_ON_ONCE(isnullstartblock(got.br_startblock))) + return -EIO; + + xfs_trim_extent(&got, offset_fsb, count_fsb); + if (!got.br_blockcount) + continue; + + got.br_state = XFS_EXT_NORM; + error = xfs_bmap_add_extent_unwritten_real(NULL, ip, + XFS_COW_FORK, &icur, &dummy_cur, &got, + &dummy_logflags); + if (error) + return error; + } while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got)); + + return error; +} + +/* Convert all of the unwritten CoW extents in a file's range to real ones. */ +int +xfs_reflink_convert_cow( + struct xfs_inode *ip, + xfs_off_t offset, + xfs_off_t count) +{ + struct xfs_mount *mp = ip->i_mount; + xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset); + xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count); + xfs_filblks_t count_fsb = end_fsb - offset_fsb; + int error; + + ASSERT(count != 0); + + xfs_ilock(ip, XFS_ILOCK_EXCL); + error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb); + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return error; +} + +/* + * Find the extent that maps the given range in the COW fork. Even if the extent + * is not shared we might have a preallocation for it in the COW fork. If so we + * use it that rather than trigger a new allocation. + */ +static int +xfs_find_trim_cow_extent( + struct xfs_inode *ip, + struct xfs_bmbt_irec *imap, + struct xfs_bmbt_irec *cmap, + bool *shared, + bool *found) +{ + xfs_fileoff_t offset_fsb = imap->br_startoff; + xfs_filblks_t count_fsb = imap->br_blockcount; + struct xfs_iext_cursor icur; + + *found = false; + + /* + * If we don't find an overlapping extent, trim the range we need to + * allocate to fit the hole we found. + */ + if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, cmap)) + cmap->br_startoff = offset_fsb + count_fsb; + if (cmap->br_startoff > offset_fsb) { + xfs_trim_extent(imap, imap->br_startoff, + cmap->br_startoff - imap->br_startoff); + return xfs_bmap_trim_cow(ip, imap, shared); + } + + *shared = true; + if (isnullstartblock(cmap->br_startblock)) { + xfs_trim_extent(imap, cmap->br_startoff, cmap->br_blockcount); + return 0; + } + + /* real extent found - no need to allocate */ + xfs_trim_extent(cmap, offset_fsb, count_fsb); + *found = true; + return 0; +} + +/* Allocate all CoW reservations covering a range of blocks in a file. */ +int +xfs_reflink_allocate_cow( + struct xfs_inode *ip, + struct xfs_bmbt_irec *imap, + struct xfs_bmbt_irec *cmap, + bool *shared, + uint *lockmode, + bool convert_now) +{ + struct xfs_mount *mp = ip->i_mount; + xfs_fileoff_t offset_fsb = imap->br_startoff; + xfs_filblks_t count_fsb = imap->br_blockcount; + struct xfs_trans *tp; + int nimaps, error = 0; + bool found; + xfs_filblks_t resaligned; + xfs_extlen_t resblks = 0; + + ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL)); + if (!ip->i_cowfp) { + ASSERT(!xfs_is_reflink_inode(ip)); + xfs_ifork_init_cow(ip); + } + + error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found); + if (error || !*shared) + return error; + if (found) + goto convert; + + resaligned = xfs_aligned_fsb_count(imap->br_startoff, + imap->br_blockcount, xfs_get_cowextsz_hint(ip)); + resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned); + + xfs_iunlock(ip, *lockmode); + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp); + *lockmode = XFS_ILOCK_EXCL; + xfs_ilock(ip, *lockmode); + + if (error) + return error; + + error = xfs_qm_dqattach_locked(ip, false); + if (error) + goto out_trans_cancel; + + /* + * Check for an overlapping extent again now that we dropped the ilock. + */ + error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found); + if (error || !*shared) + goto out_trans_cancel; + if (found) { + xfs_trans_cancel(tp); + goto convert; + } + + error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0, + XFS_QMOPT_RES_REGBLKS); + if (error) + goto out_trans_cancel; + + xfs_trans_ijoin(tp, ip, 0); + + /* Allocate the entire reservation as unwritten blocks. */ + nimaps = 1; + error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount, + XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0, cmap, + &nimaps); + if (error) + goto out_unreserve; + + xfs_inode_set_cowblocks_tag(ip); + error = xfs_trans_commit(tp); + if (error) + return error; + + /* + * Allocation succeeded but the requested range was not even partially + * satisfied? Bail out! + */ + if (nimaps == 0) + return -ENOSPC; +convert: + xfs_trim_extent(cmap, offset_fsb, count_fsb); + /* + * COW fork extents are supposed to remain unwritten until we're ready + * to initiate a disk write. For direct I/O we are going to write the + * data and need the conversion, but for buffered writes we're done. + */ + if (!convert_now || cmap->br_state == XFS_EXT_NORM) + return 0; + trace_xfs_reflink_convert_cow(ip, cmap); + return xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb); + +out_unreserve: + xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0, + XFS_QMOPT_RES_REGBLKS); +out_trans_cancel: + xfs_trans_cancel(tp); + return error; +} + +/* + * Cancel CoW reservations for some block range of an inode. + * + * If cancel_real is true this function cancels all COW fork extents for the + * inode; if cancel_real is false, real extents are not cleared. + * + * Caller must have already joined the inode to the current transaction. The + * inode will be joined to the transaction returned to the caller. + */ +int +xfs_reflink_cancel_cow_blocks( + struct xfs_inode *ip, + struct xfs_trans **tpp, + xfs_fileoff_t offset_fsb, + xfs_fileoff_t end_fsb, + bool cancel_real) +{ + struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK); + struct xfs_bmbt_irec got, del; + struct xfs_iext_cursor icur; + int error = 0; + + if (!xfs_inode_has_cow_data(ip)) + return 0; + if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got)) + return 0; + + /* Walk backwards until we're out of the I/O range... */ + while (got.br_startoff + got.br_blockcount > offset_fsb) { + del = got; + xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb); + + /* Extent delete may have bumped ext forward */ + if (!del.br_blockcount) { + xfs_iext_prev(ifp, &icur); + goto next_extent; + } + + trace_xfs_reflink_cancel_cow(ip, &del); + + if (isnullstartblock(del.br_startblock)) { + error = xfs_bmap_del_extent_delay(ip, XFS_COW_FORK, + &icur, &got, &del); + if (error) + break; + } else if (del.br_state == XFS_EXT_UNWRITTEN || cancel_real) { + ASSERT((*tpp)->t_firstblock == NULLFSBLOCK); + + /* Free the CoW orphan record. */ + xfs_refcount_free_cow_extent(*tpp, del.br_startblock, + del.br_blockcount); + + xfs_bmap_add_free(*tpp, del.br_startblock, + del.br_blockcount, NULL); + + /* Roll the transaction */ + error = xfs_defer_finish(tpp); + if (error) + break; + + /* Remove the mapping from the CoW fork. */ + xfs_bmap_del_extent_cow(ip, &icur, &got, &del); + + /* Remove the quota reservation */ + error = xfs_trans_reserve_quota_nblks(NULL, ip, + -(long)del.br_blockcount, 0, + XFS_QMOPT_RES_REGBLKS); + if (error) + break; + } else { + /* Didn't do anything, push cursor back. */ + xfs_iext_prev(ifp, &icur); + } +next_extent: + if (!xfs_iext_get_extent(ifp, &icur, &got)) + break; + } + + /* clear tag if cow fork is emptied */ + if (!ifp->if_bytes) + xfs_inode_clear_cowblocks_tag(ip); + return error; +} + +/* + * Cancel CoW reservations for some byte range of an inode. + * + * If cancel_real is true this function cancels all COW fork extents for the + * inode; if cancel_real is false, real extents are not cleared. + */ +int +xfs_reflink_cancel_cow_range( + struct xfs_inode *ip, + xfs_off_t offset, + xfs_off_t count, + bool cancel_real) +{ + struct xfs_trans *tp; + xfs_fileoff_t offset_fsb; + xfs_fileoff_t end_fsb; + int error; + + trace_xfs_reflink_cancel_cow_range(ip, offset, count); + ASSERT(ip->i_cowfp); + + offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset); + if (count == NULLFILEOFF) + end_fsb = NULLFILEOFF; + else + end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count); + + /* Start a rolling transaction to remove the mappings */ + error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write, + 0, 0, 0, &tp); + if (error) + goto out; + + xfs_ilock(ip, XFS_ILOCK_EXCL); + xfs_trans_ijoin(tp, ip, 0); + + /* Scrape out the old CoW reservations */ + error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb, + cancel_real); + if (error) + goto out_cancel; + + error = xfs_trans_commit(tp); + + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return error; + +out_cancel: + xfs_trans_cancel(tp); + xfs_iunlock(ip, XFS_ILOCK_EXCL); +out: + trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_); + return error; +} + +/* + * Remap part of the CoW fork into the data fork. + * + * We aim to remap the range starting at @offset_fsb and ending at @end_fsb + * into the data fork; this function will remap what it can (at the end of the + * range) and update @end_fsb appropriately. Each remap gets its own + * transaction because we can end up merging and splitting bmbt blocks for + * every remap operation and we'd like to keep the block reservation + * requirements as low as possible. + */ +STATIC int +xfs_reflink_end_cow_extent( + struct xfs_inode *ip, + xfs_fileoff_t offset_fsb, + xfs_fileoff_t *end_fsb) +{ + struct xfs_bmbt_irec got, del; + struct xfs_iext_cursor icur; + struct xfs_mount *mp = ip->i_mount; + struct xfs_trans *tp; + struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK); + xfs_filblks_t rlen; + unsigned int resblks; + int error; + + /* No COW extents? That's easy! */ + if (ifp->if_bytes == 0) { + *end_fsb = offset_fsb; + return 0; + } + + resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK); + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, + XFS_TRANS_RESERVE, &tp); + if (error) + return error; + + /* + * Lock the inode. We have to ijoin without automatic unlock because + * the lead transaction is the refcountbt record deletion; the data + * fork update follows as a deferred log item. + */ + xfs_ilock(ip, XFS_ILOCK_EXCL); + xfs_trans_ijoin(tp, ip, 0); + + /* + * In case of racing, overlapping AIO writes no COW extents might be + * left by the time I/O completes for the loser of the race. In that + * case we are done. + */ + if (!xfs_iext_lookup_extent_before(ip, ifp, end_fsb, &icur, &got) || + got.br_startoff + got.br_blockcount <= offset_fsb) { + *end_fsb = offset_fsb; + goto out_cancel; + } + + /* + * Structure copy @got into @del, then trim @del to the range that we + * were asked to remap. We preserve @got for the eventual CoW fork + * deletion; from now on @del represents the mapping that we're + * actually remapping. + */ + del = got; + xfs_trim_extent(&del, offset_fsb, *end_fsb - offset_fsb); + + ASSERT(del.br_blockcount > 0); + + /* + * Only remap real extents that contain data. With AIO, speculative + * preallocations can leak into the range we are called upon, and we + * need to skip them. + */ + if (!xfs_bmap_is_written_extent(&got)) { + *end_fsb = del.br_startoff; + goto out_cancel; + } + + /* Unmap the old blocks in the data fork. */ + rlen = del.br_blockcount; + error = __xfs_bunmapi(tp, ip, del.br_startoff, &rlen, 0, 1); + if (error) + goto out_cancel; + + /* Trim the extent to whatever got unmapped. */ + xfs_trim_extent(&del, del.br_startoff + rlen, del.br_blockcount - rlen); + trace_xfs_reflink_cow_remap(ip, &del); + + /* Free the CoW orphan record. */ + xfs_refcount_free_cow_extent(tp, del.br_startblock, del.br_blockcount); + + /* Map the new blocks into the data fork. */ + xfs_bmap_map_extent(tp, ip, &del); + + /* Charge this new data fork mapping to the on-disk quota. */ + xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT, + (long)del.br_blockcount); + + /* Remove the mapping from the CoW fork. */ + xfs_bmap_del_extent_cow(ip, &icur, &got, &del); + + error = xfs_trans_commit(tp); + xfs_iunlock(ip, XFS_ILOCK_EXCL); + if (error) + return error; + + /* Update the caller about how much progress we made. */ + *end_fsb = del.br_startoff; + return 0; + +out_cancel: + xfs_trans_cancel(tp); + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return error; +} + +/* + * Remap parts of a file's data fork after a successful CoW. + */ +int +xfs_reflink_end_cow( + struct xfs_inode *ip, + xfs_off_t offset, + xfs_off_t count) +{ + xfs_fileoff_t offset_fsb; + xfs_fileoff_t end_fsb; + int error = 0; + + trace_xfs_reflink_end_cow(ip, offset, count); + + offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset); + end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count); + + /* + * Walk backwards until we're out of the I/O range. The loop function + * repeatedly cycles the ILOCK to allocate one transaction per remapped + * extent. + * + * If we're being called by writeback then the pages will still + * have PageWriteback set, which prevents races with reflink remapping + * and truncate. Reflink remapping prevents races with writeback by + * taking the iolock and mmaplock before flushing the pages and + * remapping, which means there won't be any further writeback or page + * cache dirtying until the reflink completes. + * + * We should never have two threads issuing writeback for the same file + * region. There are also have post-eof checks in the writeback + * preparation code so that we don't bother writing out pages that are + * about to be truncated. + * + * If we're being called as part of directio write completion, the dio + * count is still elevated, which reflink and truncate will wait for. + * Reflink remapping takes the iolock and mmaplock and waits for + * pending dio to finish, which should prevent any directio until the + * remap completes. Multiple concurrent directio writes to the same + * region are handled by end_cow processing only occurring for the + * threads which succeed; the outcome of multiple overlapping direct + * writes is not well defined anyway. + * + * It's possible that a buffered write and a direct write could collide + * here (the buffered write stumbles in after the dio flushes and + * invalidates the page cache and immediately queues writeback), but we + * have never supported this 100%. If either disk write succeeds the + * blocks will be remapped. + */ + while (end_fsb > offset_fsb && !error) + error = xfs_reflink_end_cow_extent(ip, offset_fsb, &end_fsb); + + if (error) + trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_); + return error; +} + +/* + * Free leftover CoW reservations that didn't get cleaned out. + */ +int +xfs_reflink_recover_cow( + struct xfs_mount *mp) +{ + xfs_agnumber_t agno; + int error = 0; + + if (!xfs_sb_version_hasreflink(&mp->m_sb)) + return 0; + + for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) { + error = xfs_refcount_recover_cow_leftovers(mp, agno); + if (error) + break; + } + + return error; +} + +/* + * Reflinking (Block) Ranges of Two Files Together + * + * First, ensure that the reflink flag is set on both inodes. The flag is an + * optimization to avoid unnecessary refcount btree lookups in the write path. + * + * Now we can iteratively remap the range of extents (and holes) in src to the + * corresponding ranges in dest. Let drange and srange denote the ranges of + * logical blocks in dest and src touched by the reflink operation. + * + * While the length of drange is greater than zero, + * - Read src's bmbt at the start of srange ("imap") + * - If imap doesn't exist, make imap appear to start at the end of srange + * with zero length. + * - If imap starts before srange, advance imap to start at srange. + * - If imap goes beyond srange, truncate imap to end at the end of srange. + * - Punch (imap start - srange start + imap len) blocks from dest at + * offset (drange start). + * - If imap points to a real range of pblks, + * > Increase the refcount of the imap's pblks + * > Map imap's pblks into dest at the offset + * (drange start + imap start - srange start) + * - Advance drange and srange by (imap start - srange start + imap len) + * + * Finally, if the reflink made dest longer, update both the in-core and + * on-disk file sizes. + * + * ASCII Art Demonstration: + * + * Let's say we want to reflink this source file: + * + * ----SSSSSSS-SSSSS----SSSSSS (src file) + * <--------------------> + * + * into this destination file: + * + * --DDDDDDDDDDDDDDDDDDD--DDD (dest file) + * <--------------------> + * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest. + * Observe that the range has different logical offsets in either file. + * + * Consider that the first extent in the source file doesn't line up with our + * reflink range. Unmapping and remapping are separate operations, so we can + * unmap more blocks from the destination file than we remap. + * + * ----SSSSSSS-SSSSS----SSSSSS + * <-------> + * --DDDDD---------DDDDD--DDD + * <-------> + * + * Now remap the source extent into the destination file: + * + * ----SSSSSSS-SSSSS----SSSSSS + * <-------> + * --DDDDD--SSSSSSSDDDDD--DDD + * <-------> + * + * Do likewise with the second hole and extent in our range. Holes in the + * unmap range don't affect our operation. + * + * ----SSSSSSS-SSSSS----SSSSSS + * <----> + * --DDDDD--SSSSSSS-SSSSS-DDD + * <----> + * + * Finally, unmap and remap part of the third extent. This will increase the + * size of the destination file. + * + * ----SSSSSSS-SSSSS----SSSSSS + * <-----> + * --DDDDD--SSSSSSS-SSSSS----SSS + * <-----> + * + * Once we update the destination file's i_size, we're done. + */ + +/* + * Ensure the reflink bit is set in both inodes. + */ +STATIC int +xfs_reflink_set_inode_flag( + struct xfs_inode *src, + struct xfs_inode *dest) +{ + struct xfs_mount *mp = src->i_mount; + int error; + struct xfs_trans *tp; + + if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest)) + return 0; + + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp); + if (error) + goto out_error; + + /* Lock both files against IO */ + if (src->i_ino == dest->i_ino) + xfs_ilock(src, XFS_ILOCK_EXCL); + else + xfs_lock_two_inodes(src, XFS_ILOCK_EXCL, dest, XFS_ILOCK_EXCL); + + if (!xfs_is_reflink_inode(src)) { + trace_xfs_reflink_set_inode_flag(src); + xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL); + src->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK; + xfs_trans_log_inode(tp, src, XFS_ILOG_CORE); + xfs_ifork_init_cow(src); + } else + xfs_iunlock(src, XFS_ILOCK_EXCL); + + if (src->i_ino == dest->i_ino) + goto commit_flags; + + if (!xfs_is_reflink_inode(dest)) { + trace_xfs_reflink_set_inode_flag(dest); + xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL); + dest->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK; + xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE); + xfs_ifork_init_cow(dest); + } else + xfs_iunlock(dest, XFS_ILOCK_EXCL); + +commit_flags: + error = xfs_trans_commit(tp); + if (error) + goto out_error; + return error; + +out_error: + trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_); + return error; +} + +/* + * Update destination inode size & cowextsize hint, if necessary. + */ +int +xfs_reflink_update_dest( + struct xfs_inode *dest, + xfs_off_t newlen, + xfs_extlen_t cowextsize, + unsigned int remap_flags) +{ + struct xfs_mount *mp = dest->i_mount; + struct xfs_trans *tp; + int error; + + if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0) + return 0; + + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp); + if (error) + goto out_error; + + xfs_ilock(dest, XFS_ILOCK_EXCL); + xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL); + + if (newlen > i_size_read(VFS_I(dest))) { + trace_xfs_reflink_update_inode_size(dest, newlen); + i_size_write(VFS_I(dest), newlen); + dest->i_d.di_size = newlen; + } + + if (cowextsize) { + dest->i_d.di_cowextsize = cowextsize; + dest->i_d.di_flags2 |= XFS_DIFLAG2_COWEXTSIZE; + } + + xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE); + + error = xfs_trans_commit(tp); + if (error) + goto out_error; + return error; + +out_error: + trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_); + return error; +} + +/* + * Do we have enough reserve in this AG to handle a reflink? The refcount + * btree already reserved all the space it needs, but the rmap btree can grow + * infinitely, so we won't allow more reflinks when the AG is down to the + * btree reserves. + */ +static int +xfs_reflink_ag_has_free_space( + struct xfs_mount *mp, + xfs_agnumber_t agno) +{ + struct xfs_perag *pag; + int error = 0; + + if (!xfs_sb_version_hasrmapbt(&mp->m_sb)) + return 0; + + pag = xfs_perag_get(mp, agno); + if (xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) || + xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA)) + error = -ENOSPC; + xfs_perag_put(pag); + return error; +} + +/* + * Remap the given extent into the file. The dmap blockcount will be set to + * the number of blocks that were actually remapped. + */ +STATIC int +xfs_reflink_remap_extent( + struct xfs_inode *ip, + struct xfs_bmbt_irec *dmap, + xfs_off_t new_isize) +{ + struct xfs_bmbt_irec smap; + struct xfs_mount *mp = ip->i_mount; + struct xfs_trans *tp; + xfs_off_t newlen; + int64_t qres, qdelta; + unsigned int resblks; + bool smap_real; + bool dmap_written = xfs_bmap_is_written_extent(dmap); + int nimaps; + int error; + + /* Start a rolling transaction to switch the mappings */ + resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK); + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp); + if (error) + goto out; + + xfs_ilock(ip, XFS_ILOCK_EXCL); + xfs_trans_ijoin(tp, ip, 0); + + /* + * Read what's currently mapped in the destination file into smap. + * If smap isn't a hole, we will have to remove it before we can add + * dmap to the destination file. + */ + nimaps = 1; + error = xfs_bmapi_read(ip, dmap->br_startoff, dmap->br_blockcount, + &smap, &nimaps, 0); + if (error) + goto out_cancel; + ASSERT(nimaps == 1 && smap.br_startoff == dmap->br_startoff); + smap_real = xfs_bmap_is_real_extent(&smap); + + /* + * We can only remap as many blocks as the smaller of the two extent + * maps, because we can only remap one extent at a time. + */ + dmap->br_blockcount = min(dmap->br_blockcount, smap.br_blockcount); + ASSERT(dmap->br_blockcount == smap.br_blockcount); + + trace_xfs_reflink_remap_extent_dest(ip, &smap); + + /* + * Two extents mapped to the same physical block must not have + * different states; that's filesystem corruption. Move on to the next + * extent if they're both holes or both the same physical extent. + */ + if (dmap->br_startblock == smap.br_startblock) { + if (dmap->br_state != smap.br_state) + error = -EFSCORRUPTED; + goto out_cancel; + } + + /* If both extents are unwritten, leave them alone. */ + if (dmap->br_state == XFS_EXT_UNWRITTEN && + smap.br_state == XFS_EXT_UNWRITTEN) + goto out_cancel; + + /* No reflinking if the AG of the dest mapping is low on space. */ + if (dmap_written) { + error = xfs_reflink_ag_has_free_space(mp, + XFS_FSB_TO_AGNO(mp, dmap->br_startblock)); + if (error) + goto out_cancel; + } + + /* + * Compute quota reservation if we think the quota block counter for + * this file could increase. + * + * Adding a written extent to the extent map can cause a bmbt split, + * and removing a mapped extent from the extent can cause a bmbt split. + * The two operations cannot both cause a split since they operate on + * the same index in the bmap btree, so we only need a reservation for + * one bmbt split if either thing is happening. + * + * If we are mapping a written extent into the file, we need to have + * enough quota block count reservation to handle the blocks in that + * extent. We log only the delta to the quota block counts, so if the + * extent we're unmapping also has blocks allocated to it, we don't + * need a quota reservation for the extent itself. + * + * Note that if we're replacing a delalloc reservation with a written + * extent, we have to take the full quota reservation because removing + * the delalloc reservation gives the block count back to the quota + * count. This is suboptimal, but the VFS flushed the dest range + * before we started. That should have removed all the delalloc + * reservations, but we code defensively. + */ + qres = qdelta = 0; + if (smap_real || dmap_written) + qres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK); + if (!smap_real && dmap_written) + qres += dmap->br_blockcount; + if (qres > 0) { + error = xfs_trans_reserve_quota_nblks(tp, ip, qres, 0, + XFS_QMOPT_RES_REGBLKS); + if (error) + goto out_cancel; + } + + if (smap_real) { + /* + * If the extent we're unmapping is backed by storage (written + * or not), unmap the extent and drop its refcount. + */ + xfs_bmap_unmap_extent(tp, ip, &smap); + xfs_refcount_decrease_extent(tp, &smap); + qdelta -= smap.br_blockcount; + } else if (smap.br_startblock == DELAYSTARTBLOCK) { + xfs_filblks_t len = smap.br_blockcount; + + /* + * If the extent we're unmapping is a delalloc reservation, + * we can use the regular bunmapi function to release the + * incore state. Dropping the delalloc reservation takes care + * of the quota reservation for us. + */ + error = __xfs_bunmapi(NULL, ip, smap.br_startoff, &len, 0, 1); + if (error) + goto out_cancel; + ASSERT(len == 0); + } + + /* + * If the extent we're sharing is backed by written storage, increase + * its refcount and map it into the file. + */ + if (dmap_written) { + xfs_refcount_increase_extent(tp, dmap); + xfs_bmap_map_extent(tp, ip, dmap); + qdelta += dmap->br_blockcount; + } + + xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, qdelta); + + /* Update dest isize if needed. */ + newlen = XFS_FSB_TO_B(mp, dmap->br_startoff + dmap->br_blockcount); + newlen = min_t(xfs_off_t, newlen, new_isize); + if (newlen > i_size_read(VFS_I(ip))) { + trace_xfs_reflink_update_inode_size(ip, newlen); + i_size_write(VFS_I(ip), newlen); + ip->i_d.di_size = newlen; + xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE); + } + + /* Commit everything and unlock. */ + error = xfs_trans_commit(tp); + goto out_unlock; + +out_cancel: + xfs_trans_cancel(tp); +out_unlock: + xfs_iunlock(ip, XFS_ILOCK_EXCL); +out: + if (error) + trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_); + return error; +} + +/* Remap a range of one file to the other. */ +int +xfs_reflink_remap_blocks( + struct xfs_inode *src, + loff_t pos_in, + struct xfs_inode *dest, + loff_t pos_out, + loff_t remap_len, + loff_t *remapped) +{ + struct xfs_bmbt_irec imap; + struct xfs_mount *mp = src->i_mount; + xfs_fileoff_t srcoff = XFS_B_TO_FSBT(mp, pos_in); + xfs_fileoff_t destoff = XFS_B_TO_FSBT(mp, pos_out); + xfs_filblks_t len; + xfs_filblks_t remapped_len = 0; + xfs_off_t new_isize = pos_out + remap_len; + int nimaps; + int error = 0; + + len = min_t(xfs_filblks_t, XFS_B_TO_FSB(mp, remap_len), + XFS_MAX_FILEOFF); + + trace_xfs_reflink_remap_blocks(src, srcoff, len, dest, destoff); + + while (len > 0) { + unsigned int lock_mode; + + /* Read extent from the source file */ + nimaps = 1; + lock_mode = xfs_ilock_data_map_shared(src); + error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0); + xfs_iunlock(src, lock_mode); + if (error) + break; + /* + * The caller supposedly flushed all dirty pages in the source + * file range, which means that writeback should have allocated + * or deleted all delalloc reservations in that range. If we + * find one, that's a good sign that something is seriously + * wrong here. + */ + ASSERT(nimaps == 1 && imap.br_startoff == srcoff); + if (imap.br_startblock == DELAYSTARTBLOCK) { + ASSERT(imap.br_startblock != DELAYSTARTBLOCK); + error = -EFSCORRUPTED; + break; + } + + trace_xfs_reflink_remap_extent_src(src, &imap); + + /* Remap into the destination file at the given offset. */ + imap.br_startoff = destoff; + error = xfs_reflink_remap_extent(dest, &imap, new_isize); + if (error) + break; + + if (fatal_signal_pending(current)) { + error = -EINTR; + break; + } + + /* Advance drange/srange */ + srcoff += imap.br_blockcount; + destoff += imap.br_blockcount; + len -= imap.br_blockcount; + remapped_len += imap.br_blockcount; + } + + if (error) + trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_); + *remapped = min_t(loff_t, remap_len, + XFS_FSB_TO_B(src->i_mount, remapped_len)); + return error; +} + +/* + * If we're reflinking to a point past the destination file's EOF, we must + * zero any speculative post-EOF preallocations that sit between the old EOF + * and the destination file offset. + */ +static int +xfs_reflink_zero_posteof( + struct xfs_inode *ip, + loff_t pos) +{ + loff_t isize = i_size_read(VFS_I(ip)); + + if (pos <= isize) + return 0; + + trace_xfs_zero_eof(ip, isize, pos - isize); + return iomap_zero_range(VFS_I(ip), isize, pos - isize, NULL, + &xfs_buffered_write_iomap_ops); +} + +/* + * Prepare two files for range cloning. Upon a successful return both inodes + * will have the iolock and mmaplock held, the page cache of the out file will + * be truncated, and any leases on the out file will have been broken. This + * function borrows heavily from xfs_file_aio_write_checks. + * + * The VFS allows partial EOF blocks to "match" for dedupe even though it hasn't + * checked that the bytes beyond EOF physically match. Hence we cannot use the + * EOF block in the source dedupe range because it's not a complete block match, + * hence can introduce a corruption into the file that has it's block replaced. + * + * In similar fashion, the VFS file cloning also allows partial EOF blocks to be + * "block aligned" for the purposes of cloning entire files. However, if the + * source file range includes the EOF block and it lands within the existing EOF + * of the destination file, then we can expose stale data from beyond the source + * file EOF in the destination file. + * + * XFS doesn't support partial block sharing, so in both cases we have check + * these cases ourselves. For dedupe, we can simply round the length to dedupe + * down to the previous whole block and ignore the partial EOF block. While this + * means we can't dedupe the last block of a file, this is an acceptible + * tradeoff for simplicity on implementation. + * + * For cloning, we want to share the partial EOF block if it is also the new EOF + * block of the destination file. If the partial EOF block lies inside the + * existing destination EOF, then we have to abort the clone to avoid exposing + * stale data in the destination file. Hence we reject these clone attempts with + * -EINVAL in this case. + */ +int +xfs_reflink_remap_prep( + struct file *file_in, + loff_t pos_in, + struct file *file_out, + loff_t pos_out, + loff_t *len, + unsigned int remap_flags) +{ + struct inode *inode_in = file_inode(file_in); + struct xfs_inode *src = XFS_I(inode_in); + struct inode *inode_out = file_inode(file_out); + struct xfs_inode *dest = XFS_I(inode_out); + int ret; + + /* Lock both files against IO */ + ret = xfs_ilock2_io_mmap(src, dest); + if (ret) + return ret; + + /* Check file eligibility and prepare for block sharing. */ + ret = -EINVAL; + /* Don't reflink realtime inodes */ + if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest)) + goto out_unlock; + + /* Don't share DAX file data for now. */ + if (IS_DAX(inode_in) || IS_DAX(inode_out)) + goto out_unlock; + + ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out, + len, remap_flags); + if (ret || *len == 0) + goto out_unlock; + + /* Attach dquots to dest inode before changing block map */ + ret = xfs_qm_dqattach(dest); + if (ret) + goto out_unlock; + + /* + * Zero existing post-eof speculative preallocations in the destination + * file. + */ + ret = xfs_reflink_zero_posteof(dest, pos_out); + if (ret) + goto out_unlock; + + /* Set flags and remap blocks. */ + ret = xfs_reflink_set_inode_flag(src, dest); + if (ret) + goto out_unlock; + + /* + * If pos_out > EOF, we may have dirtied blocks between EOF and + * pos_out. In that case, we need to extend the flush and unmap to cover + * from EOF to the end of the copy length. + */ + if (pos_out > XFS_ISIZE(dest)) { + loff_t flen = *len + (pos_out - XFS_ISIZE(dest)); + ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen); + } else { + ret = xfs_flush_unmap_range(dest, pos_out, *len); + } + if (ret) + goto out_unlock; + + return 0; +out_unlock: + xfs_iunlock2_io_mmap(src, dest); + return ret; +} + +/* Does this inode need the reflink flag? */ +int +xfs_reflink_inode_has_shared_extents( + struct xfs_trans *tp, + struct xfs_inode *ip, + bool *has_shared) +{ + struct xfs_bmbt_irec got; + struct xfs_mount *mp = ip->i_mount; + struct xfs_ifork *ifp; + xfs_agnumber_t agno; + xfs_agblock_t agbno; + xfs_extlen_t aglen; + xfs_agblock_t rbno; + xfs_extlen_t rlen; + struct xfs_iext_cursor icur; + bool found; + int error; + + ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK); + if (!(ifp->if_flags & XFS_IFEXTENTS)) { + error = xfs_iread_extents(tp, ip, XFS_DATA_FORK); + if (error) + return error; + } + + *has_shared = false; + found = xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got); + while (found) { + if (isnullstartblock(got.br_startblock) || + got.br_state != XFS_EXT_NORM) + goto next; + agno = XFS_FSB_TO_AGNO(mp, got.br_startblock); + agbno = XFS_FSB_TO_AGBNO(mp, got.br_startblock); + aglen = got.br_blockcount; + + error = xfs_reflink_find_shared(mp, tp, agno, agbno, aglen, + &rbno, &rlen, false); + if (error) + return error; + /* Is there still a shared block here? */ + if (rbno != NULLAGBLOCK) { + *has_shared = true; + return 0; + } +next: + found = xfs_iext_next_extent(ifp, &icur, &got); + } + + return 0; +} + +/* + * Clear the inode reflink flag if there are no shared extents. + * + * The caller is responsible for joining the inode to the transaction passed in. + * The inode will be joined to the transaction that is returned to the caller. + */ +int +xfs_reflink_clear_inode_flag( + struct xfs_inode *ip, + struct xfs_trans **tpp) +{ + bool needs_flag; + int error = 0; + + ASSERT(xfs_is_reflink_inode(ip)); + + error = xfs_reflink_inode_has_shared_extents(*tpp, ip, &needs_flag); + if (error || needs_flag) + return error; + + /* + * We didn't find any shared blocks so turn off the reflink flag. + * First, get rid of any leftover CoW mappings. + */ + error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, XFS_MAX_FILEOFF, + true); + if (error) + return error; + + /* Clear the inode flag. */ + trace_xfs_reflink_unset_inode_flag(ip); + ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK; + xfs_inode_clear_cowblocks_tag(ip); + xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE); + + return error; +} + +/* + * Clear the inode reflink flag if there are no shared extents and the size + * hasn't changed. + */ +STATIC int +xfs_reflink_try_clear_inode_flag( + struct xfs_inode *ip) +{ + struct xfs_mount *mp = ip->i_mount; + struct xfs_trans *tp; + int error = 0; + + /* Start a rolling transaction to remove the mappings */ + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp); + if (error) + return error; + + xfs_ilock(ip, XFS_ILOCK_EXCL); + xfs_trans_ijoin(tp, ip, 0); + + error = xfs_reflink_clear_inode_flag(ip, &tp); + if (error) + goto cancel; + + error = xfs_trans_commit(tp); + if (error) + goto out; + + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return 0; +cancel: + xfs_trans_cancel(tp); +out: + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return error; +} + +/* + * Pre-COW all shared blocks within a given byte range of a file and turn off + * the reflink flag if we unshare all of the file's blocks. + */ +int +xfs_reflink_unshare( + struct xfs_inode *ip, + xfs_off_t offset, + xfs_off_t len) +{ + struct inode *inode = VFS_I(ip); + int error; + + if (!xfs_is_reflink_inode(ip)) + return 0; + + trace_xfs_reflink_unshare(ip, offset, len); + + inode_dio_wait(inode); + + error = iomap_file_unshare(inode, offset, len, + &xfs_buffered_write_iomap_ops); + if (error) + goto out; + + error = filemap_write_and_wait_range(inode->i_mapping, offset, + offset + len - 1); + if (error) + goto out; + + /* Turn off the reflink flag if possible. */ + error = xfs_reflink_try_clear_inode_flag(ip); + if (error) + goto out; + return 0; + +out: + trace_xfs_reflink_unshare_error(ip, error, _RET_IP_); + return error; +} |