btrfs: do not write corrupted metadata blocks to disk

commit 0f805531daa2ebfb5706422dc2ead1cff9e53e65 upstream.

csum_dirty_buffer was issuing a warning in case the extent buffer
did not look alright, but was still returning success.
Let's return error in this case, and also add an additional sanity
check on the extent buffer header.
The caller up the chain may BUG_ON on this, for example flush_epd_write_bio will,
but it is better than to have a silent metadata corruption on disk.

Signed-off-by: Alex Lyakas <alex@zadarastorage.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 87946c69c68fc0a0f2deb3f9e6ddb5a718f281b5..ae6e3e36fdf0632b6bc6a693d8fb63cff72b6494 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -513,9 +513,20 @@ static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
        eb = (struct extent_buffer *)page->private;
        if (page != eb->pages[0])
                return 0;
+
        found_start = btrfs_header_bytenr(eb);
-       if (WARN_ON(found_start != start || !PageUptodate(page)))
-               return 0;
+       /*
+        * Please do not consolidate these warnings into a single if.
+        * It is useful to know what went wrong.
+        */
+       if (WARN_ON(found_start != start))
+               return -EUCLEAN;
+       if (WARN_ON(!PageUptodate(page)))
+               return -EUCLEAN;
+
+       ASSERT(memcmp_extent_buffer(eb, fs_info->fsid,
+                       btrfs_header_fsid(), BTRFS_FSID_SIZE) == 0);
+
        return csum_tree_block(fs_info, eb, 0);
 }