From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.fusionio.com ([66.114.96.30]:52289 "EHLO mx1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752317Ab2IQNiR (ORCPT ); Mon, 17 Sep 2012 09:38:17 -0400 Date: Mon, 17 Sep 2012 09:38:14 -0400 From: Josef Bacik To: Miao Xie CC: Josef Bacik , "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH] Btrfs: fix race with freeze and free space inodes Message-ID: <20120917133814.GA3143@localhost.localdomain> References: <1347636380-30185-1-git-send-email-jbacik@fusionio.com> <5056B6F9.4000708@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <5056B6F9.4000708@cn.fujitsu.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Sun, Sep 16, 2012 at 11:36:57PM -0600, Miao Xie wrote: > On fri, 14 Sep 2012 11:26:20 -0400, Josef Bacik wrote: > > So we start our freeze, somebody comes in and does an fsync() on a file > > where we have to commit a transaction for whatever reason, and we will > > deadlock because the freeze is waiting on FS_FREEZE people to stop writing > > to the file system, but the transaction is waiting for its free space inodes > > to be written out, which are in turn waiting on sb_start_intwrite while > > trying to write the file extents. To fix this we'll just skip the > > sb_start_intwrite() if we TRANS_JOIN_NOLOCK since we're being waited on by a > > transaction commit so we're safe wrt to freeze and this will keep us from > > deadlocking. Thanks, > > > > Signed-off-by: Josef Bacik > > --- > > fs/btrfs/transaction.c | 10 +++++++++- > > 1 files changed, 9 insertions(+), 1 deletions(-) > > > > diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c > > index c9265a6..ba74dfb 100644 > > --- a/fs/btrfs/transaction.c > > +++ b/fs/btrfs/transaction.c > > @@ -342,7 +342,15 @@ again: > > if (!h) > > return ERR_PTR(-ENOMEM); > > > > - if (!__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) { > > + /* > > + * If we are JOIN_NOLOCK we're already committing a transaction and > > + * waiting on this guy, so we don't need to do the sb_start_intwrite > > + * because we're already holding a ref. We need this because we could > > + * have raced in and did an fsync() on a file which can kick a commit > > + * and then we deadlock with somebody doing a freeze. > > + */ > > + if (type != TRANS_JOIN_NOLOCK && > > + !__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) { > > if (type == TRANS_JOIN_FREEZE) > > return ERR_PTR(-EPERM); > > sb_start_intwrite(root->fs_info->sb); > > > > This patch forgets to deal with it in __btrfs_end_transaction(), or the freeze counter > will be wrong. > This was fixed locally I just sent the wrong patch, thanks, Josef