Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
To:     linux-kernel <linux-kernel@vger.kernel.org>, linux-aio@kvack.org,
        Goldwyn Rodrigues <rgoldwyn@suse.de>
From:   Avi Kivity <avi@scylladb.com>
Subject: Spurious EIO on AIO+DIO+RWF_NOWAIT
Organization: ScyllaDB
Message-ID: <9bab0f40-5748-f147-efeb-5aac4fd44533@scylladb.com>
Date:   Sun, 9 Dec 2018 13:19:51 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.3.1
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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?


Reducing the test case may be a lot of work, but I can package a binary 
using docker if a reproducer is needed. Seen on 4.18.19 and 4.19.something.