[PATCH 3.10 73/77] btrfs: fix use of uninit "ret" in end_extent_writepage()

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Sandeen <sandeen@xxxxxxxxxx>

commit 3e2426bd0eb980648449e7a2f5a23e3cd3c7725c upstream.

If this condition in end_extent_writepage() is false:

	if (tree->ops && tree->ops->writepage_end_io_hook)

we will then test an uninitialized "ret" at:

	ret = ret < 0 ? ret : -EIO;

The test for ret is for the case where ->writepage_end_io_hook
failed, and we'd choose that ret as the error; but if
there is no ->writepage_end_io_hook, nothing sets ret.

Initializing ret to 0 should be sufficient; if
writepage_end_io_hook wasn't set, (!uptodate) means
non-zero err was passed in, so we choose -EIO in that case.

Signed-of-by: Eric Sandeen <sandeen@xxxxxxxxxx>

Signed-off-by: Chris Mason <clm@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/extent_io.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2357,7 +2357,7 @@ int end_extent_writepage(struct page *pa
 {
 	int uptodate = (err == 0);
 	struct extent_io_tree *tree;
-	int ret;
+	int ret = 0;
 
 	tree = &BTRFS_I(page->mapping->host)->io_tree;
 


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