From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:17562 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757319Ab3APBHu (ORCPT ); Tue, 15 Jan 2013 20:07:50 -0500 Date: Wed, 16 Jan 2013 09:05:30 +0800 From: Liu Bo To: Ilya Dryomov Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: fix crash of starting balance Message-ID: <20130116010529.GC3942@liubo> Reply-To: bo.li.liu@oracle.com References: <1358261277-3566-1-git-send-email-bo.li.liu@oracle.com> <20130115165903.GB2040@zambezi.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20130115165903.GB2040@zambezi.lan> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Tue, Jan 15, 2013 at 06:59:04PM +0200, Ilya Dryomov wrote: > On Tue, Jan 15, 2013 at 10:47:57PM +0800, Liu Bo wrote: > > We will crash on BUG_ON(ret == -EEXIST) when we do not resume the existing > > balance but attempt to start a new one. > > > > The steps can be: > > 1. start balance > > 2. pause balance > > 3. start balance > > > > Signed-off-by: Liu Bo > > --- > > fs/btrfs/volumes.c | 7 ++++++- > > 1 files changed, 6 insertions(+), 1 deletions(-) > > > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > > index 5cce6aa..3901654 100644 > > --- a/fs/btrfs/volumes.c > > +++ b/fs/btrfs/volumes.c > > @@ -3100,7 +3100,12 @@ int btrfs_balance(struct btrfs_balance_control *bctl, > > goto out; > > > > if (!(bctl->flags & BTRFS_BALANCE_RESUME)) { > > - BUG_ON(ret == -EEXIST); > > + /* > > + * This can happen when we do not resume the existing balance > > + * but try to start a new one instead. > > + */ > > + if (ret == -EEXIST) > > + goto out; > > set_balance_control(bctl); > > } else { > > BUG_ON(ret != -EEXIST); > > OK, it seems balance pause/resume logic got broken by dev-replace code > (5ac00addc7ac09110995fe967071d191b5981cc1), which went into v3.8-rc1. > This is most certainly not the right way to fix it, that BUG_ON is there > for a reason. I'll send a fix in a couple of days. Okay, right here waiting for test ;) thanks, liubo