1 files changed, 16 insertions, 6 deletions

diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
index cd27c9d6c71f..5bba29a07812 100644
--- a/fs/xfs/xfs_dfrag.c
+++ b/fs/xfs/xfs_dfrag.c
@@ -177,16 +177,26 @@ xfs_swap_extents_check_format(
             XFS_IFORK_NEXTENTS(ip, XFS_DATA_FORK) > tip->i_df.if_ext_max)
                 return EINVAL;
 
-        /* Check root block of temp in btree form to max in target */
+        /*
+         * If we are in a btree format, check that the temp root block will fit
+         * in the target and that it has enough extents to be in btree format
+         * in the target.
+         *
+         * Note that we have to be careful to allow btree->extent conversions
+         * (a common defrag case) which will occur when the temp inode is in
+         * extent format...
+         */
         if (tip->i_d.di_format == XFS_DINODE_FMT_BTREE &&
-            XFS_IFORK_BOFF(ip) &&
-            tip->i_df.if_broot_bytes > XFS_IFORK_BOFF(ip))
+            ((XFS_IFORK_BOFF(ip) &&
+              tip->i_df.if_broot_bytes > XFS_IFORK_BOFF(ip)) ||
+             XFS_IFORK_NEXTENTS(tip, XFS_DATA_FORK) <= ip->i_df.if_ext_max))
                 return EINVAL;
 
-        /* Check root block of target in btree form to max in temp */
+        /* Reciprocal target->temp btree format checks */
         if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE &&
-            XFS_IFORK_BOFF(tip) &&
-            ip->i_df.if_broot_bytes > XFS_IFORK_BOFF(tip))
+            ((XFS_IFORK_BOFF(tip) &&
+              ip->i_df.if_broot_bytes > XFS_IFORK_BOFF(tip)) ||
+             XFS_IFORK_NEXTENTS(ip, XFS_DATA_FORK) <= tip->i_df.if_ext_max))
                 return EINVAL;
 
         return 0;