Btrfs: [PATCH] extent_map: make the writepage_io hook optional

The writepage_io is not mandatory, e.g. my port of xfs to the extent_map
code does not have one for now.  So handle a NULL pointer gracefully
here.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index ff2b1dd25bf9..162766773a32 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1607,7 +1607,12 @@ int extent_write_full_page(struct extent_map_tree *tree, struct page *page,
                         continue;
                 }
                 clear_extent_dirty(tree, cur, cur + iosize - 1, GFP_NOFS);
-                ret = tree->ops->writepage_io_hook(page, cur, cur + iosize - 1);
+                if (tree->ops && tree->ops->writepage_io_hook) {
+                        ret = tree->ops->writepage_io_hook(page, cur,
+                                                cur + iosize - 1);
+                } else {
+                        ret = 0;
+                }
                 if (ret)
                         SetPageError(page);
                 else {