diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index e910720..2e061df 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3644,6 +3644,10 @@
 	struct ext4_map_blocks map;
 	unsigned int credits, blkbits = inode->i_blkbits;
 
+	/* We only support the FALLOC_FL_KEEP_SIZE mode */
+	if (mode && (mode != FALLOC_FL_KEEP_SIZE))
+		return -EOPNOTSUPP;
+
 	/*
 	 * currently supporting (pre)allocate mode for extent-based
 	 * files _only_