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xfs: punch out data fork delalloc blocks on COW writeback failure 

[tapd]
https://tapd.woa.com/69992352/bugtrace/bugs/view/1069992352125111747

commit 5ca5916b6b upstream.

If writeback I/O to a COW extent fails, the COW fork blocks are
punched out and the data fork blocks left alone. It is possible for
COW fork blocks to overlap non-shared data fork blocks (due to
cowextsz hint prealloc), however, and writeback unconditionally maps
to the COW fork whenever blocks exist at the corresponding offset of
the page undergoing writeback. This means it's quite possible for a
COW fork extent to overlap delalloc data fork blocks, writeback to
convert and map to the COW fork blocks, writeback to fail, and
finally for ioend completion to cancel the COW fork blocks and leave
stale data fork delalloc blocks around in the inode. The blocks are
effectively stale because writeback failure also discards dirty page
state.

If this occurs, it is likely to trigger assert failures, free space
accounting corruption and failures in unrelated file operations. For
example, a subsequent reflink attempt of the affected file to a new
target file will trip over the stale delalloc in the source file and
fail. Several of these issues are occasionally reproduced by
generic/648, but are reproducible on demand with the right sequence
of operations and timely I/O error injection.

To fix this problem, update the ioend failure path to also punch out
underlying data fork delalloc blocks on I/O error. This is analogous
to the writeback submission failure path in xfs_discard_page() where
we might fail to map data fork delalloc blocks and consistent with
the successful COW writeback completion path, which is responsible
for unmapping from the data fork and remapping in COW fork blocks.

Fixes: 787eb48550 ("xfs: fix and streamline error handling in xfs_end_io")
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Juntong Deng <juntongdeng@tencent.com>
Signed-off-by: Jianping Liu <frankjpliu@tencent.com>
This commit is contained in:
Brian Foster 2021-10-21 14:11:55 -07:00 committed by Jianping Liu
parent fb48a99d11
commit 8bf1cece5c
1 changed files with 7 additions and 2 deletions
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9
fs/xfs/xfs_aops.c
View File

@ -232,6 +232,7 @@ xfs_end_ioend(
{
struct list_head ioend_list;
struct xfs_inode *ip = XFS_I(ioend->io_inode);
struct xfs_mount *mp = ip->i_mount;
xfs_off_t offset = ioend->io_offset;
size_t size = ioend->io_size;
unsigned int nofs_flag;
@ -247,7 +248,7 @@ xfs_end_ioend(
/*
* Just clean up the in-memory strutures if the fs has been shut down.
*/
if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
if (XFS_FORCED_SHUTDOWN(mp)) {
error = -EIO;
goto done;
}
@ -257,8 +258,12 @@ xfs_end_ioend(
*/
error = blk_status_to_errno(ioend->io_bio->bi_status);
if (unlikely(error)) {
if (ioend->io_fork == XFS_COW_FORK)
if (ioend->io_fork == XFS_COW_FORK) {
xfs_reflink_cancel_cow_range(ip, offset, size, true);
xfs_bmap_punch_delalloc_range(ip,
XFS_B_TO_FSBT(mp, offset),
XFS_B_TO_FSB(mp, size));
}
goto done;
}