Btrfs: set error return value in btrfs_get_blocks_direct

We were returning with 0 (success) because we weren't extracting the
error code from em (PTR_ERR(em)). Fix it.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/inode.c

@@ -7143,8 +7143,10 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
 						       block_start, len,
 						       orig_block_len,
 						       ram_bytes, type);
-				if (IS_ERR(em))
+				if (IS_ERR(em)) {
+					ret = PTR_ERR(em);
 					goto unlock_err;
+				}
 			}
 
 			ret = btrfs_add_ordered_extent_dio(inode, start,