Online defragmentation does not currently support inodes that using
iomap buffered I/O path, as it still relies on buffer_head for the
management of sub-folio blocks.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/ext4/move_extent.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index ce1f738dff93..fd8dabdfd962 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -476,6 +476,17 @@ static int mext_check_validity(struct inode *orig_inode,
 		return -EOPNOTSUPP;
 	}
 
+	/*
+	 * TODO: support online defrag for inodes that using the buffered
+	 * I/O iomap path.
+	 */
+	if (ext4_inode_buffered_iomap(orig_inode) ||
+	    ext4_inode_buffered_iomap(donor_inode)) {
+		ext4_msg(sb, KERN_ERR,
+			 "Online defrag not supported for inode with iomap buffered IO path");
+		return -EOPNOTSUPP;
+	}
+
 	if (donor_inode->i_mode & (S_ISUID|S_ISGID)) {
 		ext4_debug("ext4 move extent: suid or sgid is set to donor file [ino:orig %lu, donor %lu]\n",
 			   orig_inode->i_ino, donor_inode->i_ino);
-- 
2.52.0