Btrfs: do error checking in btrfs_del_csums

Got a report of a box panicing because we got a NULL eb in read_extent_buffer.
His fs was borked and btrfs_search_path returned EIO, but we don't check for
errors so the box paniced.  Yes I know this will just make something higher up
the stack panic, but that's a problem for future Josef.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index d0bc72657cd7..4f19a3e1bf32 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -550,7 +550,10 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
                         if (path->slots[0] == 0)
                                 goto out;
                         path->slots[0]--;
+                } else if (ret < 0) {
+                        goto out;
                 }
+
                 leaf = path->nodes[0];
                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);