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Date: Fri, 21 Jan 2011 11:14:42 +0800
From: Wengang Wang <wen.gang.wang@oracle.com>
To: Chuck Lever <chuck.lever@oracle.com>
Cc: trond.myklebust@netapp.com, linux-nfs@vger.kernel.org
Subject: Re: [PATCH 1/4] NFS: Fix "kernel BUG at fs/aio.c:554!"
Message-ID: <20110121031442.GA10987@laptop.uk.oracle.com>
References: <20110121030314.1056.96774.stgit@matisse.1015granger.net>
 <20110121030508.1056.51625.stgit@matisse.1015granger.net>
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On 11-01-20 22:05, Chuck Lever wrote:
> Nick Piggin reports:
> 
> > I'm getting use after frees in aio code in NFS
> >
> > [ 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.
> 
> To address this, prevent the NFS direct I/O engine from completing
> async iocbs when the forward path returns an error without starting
> any I/O.
> 
> This fix appears to survive ^C during both "xfstest no. 208" and "fsx
> -Z."
> 
> It's likely this bug has existed for a very long while, as we are seeing
> very similar symptoms in OEL 5.  Copying stable.
> 
> Cc: Stable <stable@kernel.org>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> 
>  fs/nfs/direct.c |   30 ++++++++++++++++--------------
>  1 files changed, 16 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index e6ace0d..bde25ca 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c
> @@ -407,15 +407,16 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
>  		pos += vec->iov_len;
>  	}
>  
> +	/*
> +	 * If no bytes were started, return the error, and let the
> +	 * generic layer handle the completion.
> +	 */
> +	if (requested_bytes == 0)
> +		return result < 0 ? result : -EIO;
> +
>  	if (put_dreq(dreq))
>  		nfs_direct_complete(dreq);

Same comment as I wrote in another thread:

put_dreq() -> nfs_direct_complete() does more than complete the aio its self.
It also drops ref on dreq with put_dreq() and does

complete_all(&dreq->completion);
nfs_direct_req_release(dreq);

I think we still needs that called somewhere.

regards,
wengang.
> -
> -	if (requested_bytes != 0)
> -		return 0;
> -
> -	if (result < 0)
> -		return result;
> -	return -EIO;
> +	return 0;
>  }
>  
>  static ssize_t nfs_direct_read(struct kiocb *iocb, const struct iovec *iov,
> @@ -841,15 +842,16 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
>  		pos += vec->iov_len;
>  	}
>  
> +	/*
> +	 * If no bytes were started, return the error, and let the
> +	 * generic layer handle the completion.
> +	 */
> +	if (requested_bytes == 0)
> +		return result < 0 ? result : -EIO;
> +
>  	if (put_dreq(dreq))
>  		nfs_direct_write_complete(dreq, dreq->inode);
> -
> -	if (requested_bytes != 0)
> -		return 0;
> -
> -	if (result < 0)
> -		return result;
> -	return -EIO;
> +	return 0;
>  }
>  
>  static ssize_t nfs_direct_write(struct kiocb *iocb, const struct iovec *iov,
> 
> --
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