linux-kernel - Re: [OOPS, 3.13-rc2] null ptr in dio

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Message-ID: <20131205212651.GP10988@dastard>
Date:	Fri, 6 Dec 2013 08:26:51 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Subject: Re: [OOPS, 3.13-rc2] null ptr in dio_complete()

On Thu, Dec 05, 2013 at 10:22:20PM +0800, Ming Lei wrote:
> On Wed, 4 Dec 2013 12:58:38 +1100
> Dave Chinner <david@...morbit.com> wrote:
> 
> > 
> > And I just hit this from running xfs_repair which is doing
> > multithreaded direct IO directly on /dev/vdc:
.....
> > So this is looking like another virtio+blk_mq problem....
> 
> This one might be caused by using-after-'free' request because the freed
> request may be allocated to another CPU immediately, and the below patch
> may be helpful, would you mind testing it?
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 6875736..2358bdf 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -311,12 +311,12 @@ void blk_mq_complete_request(struct request *rq, int error)
>  
>  	blk_account_io_completion(rq, bytes);
>  
> +	blk_account_io_done(rq);
> +
>  	if (rq->end_io)
>  		rq->end_io(rq, error);
>  	else
>  		blk_mq_free_request(rq);
> -
> -	blk_account_io_done(rq);
>  }
>  
>  void __blk_mq_end_io(struct request *rq, int error)

Testing it now. I'll let you know how it goes in couple of hours.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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