Btrfs: Use invalidatepage when writepage finds a page outside of i_size

With all the recent fixes to the delalloc locking, it is now safe
again to use invalidatepage inside the writepage code for
pages outside of i_size.  This used to deadlock against some of the
code to write locked ranges of pages, but all of that has been fixed.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/file-item.c

@@ -185,6 +185,7 @@ int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 				       "%llu\n", inode->i_ino,
 				       (unsigned long long)offset);
 				item = NULL;
+				btrfs_release_path(root, path);
 				goto found;
 			}
 			btrfs_item_key_to_cpu(path->nodes[0], &found_key,