From: "Darrick J. Wong" djwong@kernel.org
[ Upstream commit 8d54eacd82a0623a963e0c150ad3b02970638b0d ]
With the 20 Oct 2025 release of fstests, generic/521 fails for me on regular (aka non-block-atomic-writes) storage:
QA output created by 521 dowrite: write: Input/output error LOG DUMP (8553 total operations): 1( 1 mod 256): SKIPPED (no operation) 2( 2 mod 256): WRITE 0x7e000 thru 0x8dfff (0x10000 bytes) HOLE 3( 3 mod 256): READ 0x69000 thru 0x79fff (0x11000 bytes) 4( 4 mod 256): FALLOC 0x53c38 thru 0x5e853 (0xac1b bytes) INTERIOR 5( 5 mod 256): COPY 0x55000 thru 0x59fff (0x5000 bytes) to 0x25000 thru 0x29fff 6( 6 mod 256): WRITE 0x74000 thru 0x88fff (0x15000 bytes) 7( 7 mod 256): ZERO 0xedb1 thru 0x11693 (0x28e3 bytes)
with a warning in dmesg from iomap about XFS trying to give it a delalloc mapping for a directio write. Fix the software atomic write iomap_begin code to convert the reservation into a written mapping. This doesn't fix the data corruption problems reported by generic/760, but it's a start.
Cc: stable@vger.kernel.org # v6.16 Fixes: bd1d2c21d5d249 ("xfs: add xfs_atomic_write_cow_iomap_begin()") Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: John Garry john.g.garry@oracle.com Signed-off-by: Carlos Maiolino cem@kernel.org Stable-dep-of: 8d7bba1e8314 ("xfs: fix various problems in xfs_atomic_write_cow_iomap_begin") Signed-off-by: Sasha Levin sashal@kernel.org --- fs/xfs/xfs_iomap.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 2a74f29573410..a4a22975c7cc9 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -1121,7 +1121,7 @@ xfs_atomic_write_cow_iomap_begin( return -EAGAIN;
trace_xfs_iomap_atomic_write_cow(ip, offset, length); - +retry: xfs_ilock(ip, XFS_ILOCK_EXCL);
if (!ip->i_cowfp) { @@ -1132,6 +1132,8 @@ xfs_atomic_write_cow_iomap_begin( if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap)) cmap.br_startoff = end_fsb; if (cmap.br_startoff <= offset_fsb) { + if (isnullstartblock(cmap.br_startblock)) + goto convert_delay; xfs_trim_extent(&cmap, offset_fsb, count_fsb); goto found; } @@ -1160,8 +1162,10 @@ xfs_atomic_write_cow_iomap_begin( if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap)) cmap.br_startoff = end_fsb; if (cmap.br_startoff <= offset_fsb) { - xfs_trim_extent(&cmap, offset_fsb, count_fsb); xfs_trans_cancel(tp); + if (isnullstartblock(cmap.br_startblock)) + goto convert_delay; + xfs_trim_extent(&cmap, offset_fsb, count_fsb); goto found; }
@@ -1201,6 +1205,19 @@ xfs_atomic_write_cow_iomap_begin( xfs_iunlock(ip, XFS_ILOCK_EXCL); return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, IOMAP_F_SHARED, seq);
+convert_delay: + xfs_iunlock(ip, XFS_ILOCK_EXCL); + error = xfs_bmapi_convert_delalloc(ip, XFS_COW_FORK, offset, iomap, + NULL); + if (error) + return error; + + /* + * Try the lookup again, because the delalloc conversion might have + * turned the COW mapping into unwritten, but we need it to be in + * written state. + */ + goto retry; out_unlock: xfs_iunlock(ip, XFS_ILOCK_EXCL); return error;