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Date:   Mon, 10 Dec 2018 06:48:23 -0600
From:   Goldwyn Rodrigues <rgoldwyn@suse.de>
To:     Avi Kivity <avi@scylladb.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>, linux-aio@kvack.org
Subject: Re: Spurious EIO on AIO+DIO+RWF_NOWAIT
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On 13:19 09/12, Avi Kivity wrote:
> I have an application that receives spurious EIO when running with
> RWF_NOWAIT enabled. Removing RWF_NOWAIT causes those EIOs to disappear. The
> application uses AIO+DIO, and errors were seen on both xfs and ext4.
> 
> 
> I suspect the following code:
> 
> 
> /*
> ?* Process one completed BIO.? No locks are held.
> ?*/
> static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
> {
> ??????? struct bio_vec *bvec;
> ??????? unsigned i;
> ??????? blk_status_t err = bio->bi_status;
> 
> ??????? if (err) {
> ??????????????? if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))
> ??????????????????????? dio->io_error = -EAGAIN;
> ??????????????? else
> ??????????????????????? dio->io_error = -EIO;
> ??????? }
> 
> Could it be that REQ_NOWAIT was dropped from bio->bi_opf? or that
> bio->bi_status got changed along the way?
> 

I don't think REQ_NOWAIT is dropped. I am assuming bio->bi_status error
is set differently. Is the blk queue being stopped? Is it possible to
instrument the kernel in your testcase?

-- 
Goldwyn