From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from acsinet15.oracle.com ([141.146.126.227]:16444 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750879Ab2HYCci (ORCPT ); Fri, 24 Aug 2012 22:32:38 -0400 Message-ID: <5038394B.9080106@oracle.com> Date: Sat, 25 Aug 2012 10:32:43 +0800 From: Liu Bo MIME-Version: 1.0 To: Josef Bacik CC: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: fix deadlock with freeze and sync V2 References: <1345834383-2172-1-git-send-email-jbacik@fusionio.com> In-Reply-To: <1345834383-2172-1-git-send-email-jbacik@fusionio.com> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 08/25/2012 02:53 AM, Josef Bacik wrote: > We can deadlock with freeze right now because we unconditionally start a > transaction in our ->sync_fs() call. To fix this just check and see if we > have a running transaction to commit. This saves us from the deadlock > because at this point we'll have the umount sem for the sb so we're safe > from freezes coming in after we've done our check. With this patch the > freeze xfstests no longer deadlocks. Thanks, > Actually I have a same patch pending to send... Anyway, I'm happy with the bug has been fixed. Reviewed-by: Liu Bo > Signed-off-by: Josef Bacik > --- > V1->V2: got a little overzealous and cleaned up the ret thing without actually > removing the now unused ret variable. > > fs/btrfs/super.c | 13 +++++++++---- > 1 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c > index 7b65fe8..83d6f9f 100644 > --- a/fs/btrfs/super.c > +++ b/fs/btrfs/super.c > @@ -838,7 +838,6 @@ int btrfs_sync_fs(struct super_block *sb, int wait) > struct btrfs_trans_handle *trans; > struct btrfs_fs_info *fs_info = btrfs_sb(sb); > struct btrfs_root *root = fs_info->tree_root; > - int ret; > > trace_btrfs_sync_fs(wait); > > @@ -849,11 +848,17 @@ int btrfs_sync_fs(struct super_block *sb, int wait) > > btrfs_wait_ordered_extents(root, 0, 0); > > - trans = btrfs_start_transaction(root, 0); > + spin_lock(&fs_info->trans_lock); > + if (!fs_info->running_transaction) { > + spin_unlock(&fs_info->trans_lock); > + return 0; > + } > + spin_unlock(&fs_info->trans_lock); > + > + trans = btrfs_join_transaction(root); > if (IS_ERR(trans)) > return PTR_ERR(trans); > - ret = btrfs_commit_transaction(trans, root); > - return ret; > + return btrfs_commit_transaction(trans, root); > } > > static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry) >