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Subject: Re: NFS dio aio bug
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From: Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <AANLkTinjkvVySCA93F+p66KrTuqMfMF064ggNSg0yauX@mail.gmail.com>
Date: Fri, 14 Jan 2011 11:08:52 -0500
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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References: <AANLkTinjkvVySCA93F+p66KrTuqMfMF064ggNSg0yauX@mail.gmail.com>
To: Nick Piggin <npiggin@gmail.com>
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Hi Nick-

On Jan 13, 2011, at 8:29 PM, Nick Piggin wrote:

> Hi Trond,
> 
> I'm getting use after frees in aio code in NFS

Can you describe how to reproduce this?

> [ 2703.396766] Call Trace:
> [ 2703.396858]  [<ffffffff8100b057>] ? native_sched_clock+0x27/0x80
> [ 2703.396959]  [<ffffffff8108509e>] ? put_lock_stats+0xe/0x40
> [ 2703.397058]  [<ffffffff81088348>] ? lock_release_holdtime+0xa8/0x140
> [ 2703.397159]  [<ffffffff8108a2a5>] lock_acquire+0x95/0x1b0
> [ 2703.397260]  [<ffffffff811627db>] ? aio_put_req+0x2b/0x60
> [ 2703.397361]  [<ffffffff81039701>] ? get_parent_ip+0x11/0x50
> [ 2703.397464]  [<ffffffff81612a31>] _raw_spin_lock_irq+0x41/0x80
> [ 2703.397564]  [<ffffffff811627db>] ? aio_put_req+0x2b/0x60
> [ 2703.397662]  [<ffffffff811627db>] aio_put_req+0x2b/0x60
> [ 2703.397761]  [<ffffffff811647fe>] do_io_submit+0x2be/0x7c0
> [ 2703.397895]  [<ffffffff81164d0b>] sys_io_submit+0xb/0x10
> [ 2703.397995]  [<ffffffff8100307b>] system_call_fastpath+0x16/0x1b
> 
> Adding some tracing, it is due to nfs completing the request then
> returning something other than -EIOCBQUEUED, so aio.c
> also completes the request.

Is this with reads, writes, or both?  Are the I/O requests smaller than, equal to, or larger than rsize or wsize?

We have a related bug report: hitting the BUG at fs/aio.c:552 (OEL5) and similar for more recent kernels.  Looks like dreq refcounting is faulty somehow.

-- 
Chuck Lever
chuck[dot]lever[at]oracle[dot]com