From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36204 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933081AbeCPP3h (ORCPT ); Fri, 16 Mar 2018 11:29:37 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tahsin Erdogan , Theodore Tso , Andreas Dilger , Tommi Rantala Subject: [PATCH 4.4 45/63] ext4: inplace xattr block update fails to deduplicate blocks Date: Fri, 16 Mar 2018 16:23:17 +0100 Message-Id: <20180316152304.770115727@linuxfoundation.org> In-Reply-To: <20180316152259.964532775@linuxfoundation.org> References: <20180316152259.964532775@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tahsin Erdogan commit ec00022030da5761518476096626338bd67df57a upstream. When an xattr block has a single reference, block is updated inplace and it is reinserted to the cache. Later, a cache lookup is performed to see whether an existing block has the same contents. This cache lookup will most of the time return the just inserted entry so deduplication is not achieved. Running the following test script will produce two xattr blocks which can be observed in "File ACL: " line of debugfs output: mke2fs -b 1024 -I 128 -F -O extent /dev/sdb 1G mount /dev/sdb /mnt/sdb touch /mnt/sdb/{x,y} setfattr -n user.1 -v aaa /mnt/sdb/x setfattr -n user.2 -v bbb /mnt/sdb/x setfattr -n user.1 -v aaa /mnt/sdb/y setfattr -n user.2 -v bbb /mnt/sdb/y debugfs -R 'stat x' /dev/sdb | cat debugfs -R 'stat y' /dev/sdb | cat This patch defers the reinsertion to the cache so that we can locate other blocks with the same contents. Signed-off-by: Tahsin Erdogan Signed-off-by: Theodore Ts'o Reviewed-by: Andreas Dilger Signed-off-by: Tommi Rantala Signed-off-by: Greg Kroah-Hartman --- fs/ext4/xattr.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -828,8 +828,6 @@ ext4_xattr_block_set(handle_t *handle, s if (!IS_LAST_ENTRY(s->first)) ext4_xattr_rehash(header(s->base), s->here); - ext4_xattr_cache_insert(ext4_mb_cache, - bs->bh); } unlock_buffer(bs->bh); if (error == -EFSCORRUPTED) @@ -918,6 +916,7 @@ inserted: } else if (bs->bh && s->base == bs->bh->b_data) { /* We were modifying this block in-place. */ ea_bdebug(bs->bh, "keeping this block"); + ext4_xattr_cache_insert(ext4_mb_cache, bs->bh); new_bh = bs->bh; get_bh(new_bh); } else {