[PATCH V7 08/14] xfs: Check for extent overflow when remapping an extent

Chandan Babu R
2020-10-19T06:41:35Z

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.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
---
fs/xfs/xfs_reflink.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 4f0198f636ad..856fe755a5e9 100644
--- 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
--
2.28.0