xfs: Check for extent overflow when remapping an extent

Remapping an extent involves unmapping the existing extent and mapping
in the new extent. When unmapping, an extent containing the entire unmap
range can be split into two extents,
i.e. | Old extent | hole | Old extent |
Hence extent count increases by 1.

Mapping in the new extent into the destination file can increase the
extent count by 1.

Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index ca0ac14..e1c98db 100644 (file)
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1006,6 +1006,7 @@ xfs_reflink_remap_extent(
        unsigned int            resblks;
        bool                    smap_real;
        bool                    dmap_written = xfs_bmap_is_written_extent(dmap);
+       int                     iext_delta = 0;
        int                     nimaps;
        int                     error;
 
@@ -1099,6 +1100,16 @@ xfs_reflink_remap_extent(
                        goto out_cancel;
        }
 
+       if (smap_real)
+               ++iext_delta;
+
+       if (dmap_written)
+               ++iext_delta;
+
+       error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, iext_delta);
+       if (error)
+               goto out_cancel;
+
        if (smap_real) {
                /*
                 * If the extent we're unmapping is backed by storage (written