From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:52557 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934775AbcIZQ4x (ORCPT ); Mon, 26 Sep 2016 12:56:53 -0400 Date: Mon, 26 Sep 2016 18:54:44 +0200 From: David Sterba To: Liu Bo Cc: linux-btrfs@vger.kernel.org, David Sterba , Chris Mason Subject: Re: [PATCH] Btrfs: memset to avoid stale content in btree leaf Message-ID: <20160926165444.GD16983@twin.jikos.cz> Reply-To: dsterba@suse.cz References: <1474663484-23245-1-git-send-email-bo.li.liu@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1474663484-23245-1-git-send-email-bo.li.liu@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, Sep 23, 2016 at 01:44:44PM -0700, Liu Bo wrote: > @@ -3732,15 +3734,21 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb, > if (btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID) > bio_flags = EXTENT_BIO_TREE_LOG; > > - /* set btree node beyond nritems with 0 to avoid stale content */ > + /* set btree blocks beyond nritems with 0 to avoid stale content. */ > + nritems = btrfs_header_nritems(eb); > if (btrfs_header_level(eb) > 0) { > - u32 nritems; > - unsigned long end; > - > - nritems = btrfs_header_nritems(eb); > end = btrfs_node_key_ptr_offset(nritems); > > memset_extent_buffer(eb, 0, end, eb->len - end); > + } else { > + /* > + * leaf: > + * header 0 1 2 .. N ... data_N .. data_2 data_1 data_0 > + */ > + start = btrfs_item_nr_offset(nritems); So, AFAICS this also works for empty root nodes (nritems == 0). It's hidden in leaf_data_end that actually looks at nritems and decides. Reviewed-by: David Sterba > + end = btrfs_leaf_data(eb) + > + leaf_data_end(fs_info->tree_root, eb); > + memset_extent_buffer(eb, 0, start, end - start);