On Tue, Nov 29, 2022 at 02:01:36PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Upon enabling fsdax + reflink for XFS, xfs/179 began to report refcount
> metadata corruptions after being run. Specifically, xfs_repair noticed
> single-block refcount records that could be combined but had not been.
>
> The root cause of this is improper MAXREFCOUNT edge case handling in
> xfs_refcount_merge_extents. When we're trying to find candidates for a
> refcount btree record merge, we compute the refcount attribute of the
> merged record, but we fail to account for the fact that once a record
> hits rc_refcount == MAXREFCOUNT, it is pinned that way forever. Hence
> the computed refcount is wrong, and we fail to merge the extents.
>
> Fix this by adjusting the merge predicates to compute the adjusted
> refcount correctly.
>
> Fixes: 3172725814f9 ("xfs: adjust refcount of an extent of blocks in refcount btree")
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_refcount.c | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
Looks good to me.
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
--
Dave Chinner
david@xxxxxxxxxxxxx
