linux-kernel - Re: [PATCH 12/19] btrfs: expire submit buffer on timeout

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Message-ID: <BYAPR04MB5816CFF901A5BF10A2E51A52E7EB0@BYAPR04MB5816.namprd04.prod.outlook.com>
Date:   Mon, 17 Jun 2019 03:19:10 +0000
From:   Damien Le Moal <Damien.LeMoal@....com>
To:     Josef Bacik <josef@...icpanda.com>,
        Naohiro Aota <Naohiro.Aota@....com>
CC:     "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        David Sterba <dsterba@...e.com>, Chris Mason <clm@...com>,
        Qu Wenruo <wqu@...e.com>, Nikolay Borisov <nborisov@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Hannes Reinecke <hare@...e.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Matias Bjørling <mb@...htnvm.io>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Bart Van Assche <bvanassche@....org>
Subject: Re: [PATCH 12/19] btrfs: expire submit buffer on timeout

On 2019/06/13 23:15, Josef Bacik wrote:
> On Fri, Jun 07, 2019 at 10:10:18PM +0900, Naohiro Aota wrote:
>> It is possible to have bios stalled in the submit buffer due to some bug or
>> device problem. In such situation, btrfs stops working waiting for buffered
>> bios completions. To avoid such hang, add a worker that will cancel the
>> stalled bios after a timeout.
>>
> 
> The block layer does this with it's request timeouts right?  So it'll timeout
> and we'll get an EIO?  If that's not working then we need to fix the block
> layer.  Thanks,

Joseph,

The block layer timeout is started only when the request is dispatched. The
timeout is not started on BIO/request allocation and so will not trigger for
bios stalled inside btrfs scheduler.


-- 
Damien Le Moal
Western Digital Research