xfs: set format back to extents if xfs_bmap_extents_to_btree

If xfs_bmap_extents_to_btree fails in a mode where we call
xfs_iroot_realloc(-1) to de-allocate the root, set the
format back to extents.

Otherwise we can assume we can dereference ifp->if_broot
based on the XFS_DINODE_FMT_BTREE format, and crash.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199423
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 6a7c2f03ea11..040eeda8426f 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -725,12 +725,16 @@ xfs_bmap_extents_to_btree(
         *logflagsp = 0;
         if ((error = xfs_alloc_vextent(&args))) {
                 xfs_iroot_realloc(ip, -1, whichfork);
+                ASSERT(ifp->if_broot == NULL);
+                XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_EXTENTS);
                 xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
                 return error;
         }
 
         if (WARN_ON_ONCE(args.fsbno == NULLFSBLOCK)) {
                 xfs_iroot_realloc(ip, -1, whichfork);
+                ASSERT(ifp->if_broot == NULL);
+                XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_EXTENTS);
                 xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
                 return -ENOSPC;
         }