From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mo-p00-ob.rzone.de ([81.169.146.160]:53672 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751270Ab3JSIuo (ORCPT ); Sat, 19 Oct 2013 04:50:44 -0400 Message-ID: <526247E3.9000804@giantdisaster.de> Date: Sat, 19 Oct 2013 10:50:43 +0200 From: Stefan Behrens MIME-Version: 1.0 To: Wang Shilong , linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: fix race condition between writting and scrubing supers References: <1382156250-2336-1-git-send-email-wangshilong1991@gmail.com> In-Reply-To: <1382156250-2336-1-git-send-email-wangshilong1991@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 10/19/2013 06:17, Wang Shilong wrote: > From: Wang Shilong > > Scrubing supers is not in a transaction context, when trying to > write supers to disk, we should check if we are trying to > scrub supers.Fix it. > > Signed-off-by: Wang Shilong > --- > fs/btrfs/disk-io.c | 2 ++ > fs/btrfs/transaction.c | 2 ++ > 2 files changed, 4 insertions(+) > > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index 419968e..0debb19 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -3582,7 +3582,9 @@ int btrfs_commit_super(struct btrfs_root *root) > return ret; > } > > + btrfs_scrub_pause_super(root); > ret = write_ctree_super(NULL, root, 0); > + btrfs_scrub_continue_super(root); > return ret; > } > > diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c > index 277fe81..3ebcbbd 100644 > --- a/fs/btrfs/transaction.c > +++ b/fs/btrfs/transaction.c > @@ -1892,7 +1892,9 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans, > goto cleanup_transaction; > } > > + btrfs_scrub_pause_super(root); > ret = write_ctree_super(trans, root, 0); > + btrfs_scrub_continue_super(root); > if (ret) { > mutex_unlock(&root->fs_info->tree_log_mutex); > goto cleanup_transaction; > What kind of race do you see between writing the 4K superblock and scrub checking its checksum? Or in other words, what could happen?