btrfs: fix use of uninit "ret" in end_extent_writepage()

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@redhat.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 2d391ce71ea40876d20caac11aa4c99a01710376..84ceff6abbc11f66e8e3f96d24740d67cbacd1ed 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2357,7 +2357,7 @@ int end_extent_writepage(struct page *page, int err, u64 start, u64 end)
 {
        int uptodate = (err == 0);
        struct extent_io_tree *tree;
-       int ret;
+       int ret = 0;
 
        tree = &BTRFS_I(page->mapping->host)->io_tree;