From: Jan Kara <jack@suse.cz>
Subject: Re: WARNING at fs/ext4/inode.c ext4_evict_inode() triggers on 4.0
Date: Thu, 30 Jun 2016 09:00:32 +0200
Message-ID: <20160630070032.GA19671@quack2.suse.cz>
References: <20160615204939.GA52455@calvinowens-mba.dhcp.thefacebook.com>
 <20160616083304.GD22835@quack2.suse.cz>
 <20160617174033.GC72696@calvinowens-mba.dhcp.thefacebook.com>
 <20160617180434.GA427@quack2.suse.cz>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Jan Kara <jack@suse.cz>, linux-ext4@vger.kernel.org,
	kernel-team@fb.com
To: Calvin Owens <calvinowens@fb.com>
Return-path: <linux-ext4-owner@vger.kernel.org>
Received: from mx2.suse.de ([195.135.220.15]:53519 "EHLO mx2.suse.de"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1750969AbcF3HAg (ORCPT <rfc822;linux-ext4@vger.kernel.org>);
	Thu, 30 Jun 2016 03:00:36 -0400
Content-Disposition: inline
In-Reply-To: <20160617180434.GA427@quack2.suse.cz>
Sender: linux-ext4-owner@vger.kernel.org
List-ID: <linux-ext4.vger.kernel.org>

On Fri 17-06-16 20:04:34, Jan Kara wrote:
> On Fri 17-06-16 13:40:33, Calvin Owens wrote:
> > On Thursday 06/16 at 10:33 +0200, Jan Kara wrote:
> > > Hi Calvin,
> > > 
> > > On Wed 15-06-16 16:49:39, Calvin Owens wrote:
> > > > I'm hitting the following warning on a 4.0 kernel:
> > > > 
> > > >   WARNING: CPU: 15 PID: 1005611 at fs/ext4/inode.c:233 ext4_evict_inode+0x4be/0x4d0()
> > > >   CPU: 15 PID: 1005611 Comm: rocksdb:bg0 Not tainted 4.0.9-60_fbk10_rc1_3974_g796b9b6 #1
> > > >   Call Trace: 
> > > >   [<ffffffff8176af8e>] dump_stack+0x4d/0x63
> > > >   [<ffffffff8106c4dc>] warn_slowpath_common+0x8c/0xd0
> > > >   [<ffffffff8106c5da>] warn_slowpath_null+0x1a/0x20
> > > >   [<ffffffff81242c0e>] ext4_evict_inode+0x4be/0x4d0
> > > >   [<ffffffff811d248b>] evict+0xbb/0x190 
> > > >   [<ffffffff811d2d6d>] iput+0x17d/0x1e0
> > > >   [<ffffffff811ce0e0>] __dentry_kill+0x190/0x1e0
> > > >   [<ffffffff811ce2d1>] dput+0x1a1/0x1f0
> > > >   [<ffffffff811b952a>] __fput+0x17a/0x210
> > > >   [<ffffffff811b960e>] ____fput+0xe/0x10
> > > >   [<ffffffff81086dbf>] task_work_run+0xbf/0x100 
> > > >   [<ffffffff81002bcc>] do_notify_resume+0x7c/0x90
> > > >   [<ffffffff81771529>] int_signal+0x12/0x17
> > > > 
> > > > Commit 822dbba ("ext4: fix warning in ext4_evict_inode()") proportedly fixed
> > > > this in 3.11. The check was entirely removed in 4.6.
> > > 
> > > OK, so this is the warning:
> > > 
> > > WARN_ON(atomic_read(&EXT4_I(inode)->i_ioend_count));
> > > 
> > > It was removed in 4.6 since we maintained i_ioend_count only to be able to
> > > do this check and it didn't trigger for a long time. So it is interesting
> > > that it actually triggered for you with 4.0.
> > > 
> > > > Is it interesting to you that this triggers on 4.0? I can revert 600be30 and
> > > > see if I can reproduce it on upstream, but since the check got removed I
> > > > was wondering if there was post-4.0 work that makes it obsolete?
> > > 
> > > It would be great. I'm attaching a revert and an additional debug patch. If
> > > you can run with these two on the latest kernel (or even just apply the debug
> > > patch on top of 4.0) and reproduce the issue with it, I would be grateful.
> > 
> > Forgot to attach the patches? Or did my mailserver eat them? :)
> 
> Sorry, probably forgot to attach. Here they are.

Any luck with the patch?

									Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR