linux-kernel - Re: WARNING at fs/nfs/write.c:743 nfs_inode_remove

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Date:	Tue, 23 Sep 2014 11:02:26 -0400
From:	Weston Andros Adamson <dros@...marydata.com>
To:	Will Deacon <will.deacon@....com>
Cc:	Peng Tao <tao.peng@...marydata.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	linux-nfs list <linux-nfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: WARNING at fs/nfs/write.c:743 nfs_inode_remove_request with -rc6

On Sep 23, 2014, at 10:59 AM, Weston Andros Adamson <dros@...marydata.com> wrote:

> On Sep 23, 2014, at 10:53 AM, Will Deacon <will.deacon@....com> wrote:
> 
>> On Tue, Sep 23, 2014 at 02:59:38PM +0100, Will Deacon wrote:
>>> On Tue, Sep 23, 2014 at 02:33:06PM +0100, Weston Andros Adamson wrote:
>>>> Any more info on how to reproduce this would be really great. Unfortunately I don’t
>>>> have access to an arm64 system.
>>> 
>>> I've not spotted a pattern other than using 64k pages, yet. If I manage to
>>> get a reproducer, I'll let you know.
>>> 
>>>> If it’s possible, could we get a packet trace around when this happens? This is pure
>>>> speculation, but this might have something to do the resend path - a commit fails
>>>> and all the requests on the commit list have to be resent.
>>> 
>>> Sure, once I can reproduce it reliably, then I'll try to do that.
>> 
>> Right, a bunch of DDing from /dev/zero over an ssh session triggers this
>> very quickly. I've put a binary tcpdump here:
>> 
>> http://www.willdeacon.ukfsn.org/bitbucket/oopsen/nfs/tcpdump.bin
>> 
>> You may want to filter out the ssh packets. The only `interesting' thing to
>> me is a retransmission about half way through, but I don't know what I'm
>> looking for.
>> 
>> The NFS server is 10.1.203.204 and the client is 10.1.203.24.
> 
> Thanks! You are using NFSv2, so there are no commits - that rules out my hunch.

Wait a second - the whole point of this extra reference (that the WARN_ON_ONCE is
related to) is to handle the pass off to commit lists.

Maybe I’m just doing the wrong thing here with NFSv2!

More soon.

-dros

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