diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 7011ac9..f1aca06 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1959,6 +1959,11 @@ cleanup:
 	return err;
 }
 
+/*
+ * ext4_ext_walk_space() should be called with i_data_sem locked. If we're
+ * not modifying found extents, or extent tree in callback function, then
+ * read lock is ok.
+ */
 static int ext4_ext_walk_space(struct inode *inode, ext4_lblk_t block,
 			       ext4_lblk_t num, ext_prepare_callback func,
 			       void *cbdata)
@@ -1976,9 +1981,7 @@ static int ext4_ext_walk_space(struct inode *inode, ext4_lblk_t block,
 	while (block < last && block != EXT_MAX_BLOCKS) {
 		num = last - block;
 		/* find extent for this block */
-		down_read(&EXT4_I(inode)->i_data_sem);
 		path = ext4_ext_find_extent(inode, block, path);
-		up_read(&EXT4_I(inode)->i_data_sem);
 		if (IS_ERR(path)) {
 			err = PTR_ERR(path);
 			path = NULL;
@@ -5021,8 +5024,10 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		 * Walk the extent tree gathering extent information.
 		 * ext4_ext_fiemap_cb will push extents back to user.
 		 */
+		down_read(&EXT4_I(inode)->i_data_sem);
 		error = ext4_ext_walk_space(inode, start_blk, len_blks,
 					  ext4_ext_fiemap_cb, fieinfo);
+		up_read(&EXT4_I(inode)->i_data_sem);
 	}
 
 	return error;