linux-kernel - Re: [PATCH RFC 5/6] md/raid1: Handle bio

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Message-ID: <82a49b38-2732-4461-a714-908877714f35@oracle.com>
Date: Thu, 24 Oct 2024 10:56:36 +0100
From: John Garry <john.g.garry@...cle.com>
To: Yu Kuai <yukuai1@...weicloud.com>, Geoff Back <geoff@...onlair.co.uk>,
        axboe@...nel.dk, hch@....de
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, martin.petersen@...cle.com,
        "yangerkun@...wei.com" <yangerkun@...wei.com>,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH RFC 5/6] md/raid1: Handle bio_split() errors

On 24/10/2024 10:12, Yu Kuai wrote:
>>>
>>>>>>
>>>>>> Indeed, IMO, chance of encountering a device with BBs and supporting
>>>>>> atomic writes is low, so no need to try to make it work (if it were
>>>>>> possible) - I think that we just report EIO.
>>>
>>> If you want this, then make sure raid will set fail fast together with
>>> atomic write. This way disk will just faulty with IO error instead of
>>> marking with BB, hence make sure there are no BBs.
>>
>> To be clear, you mean to set the r1/r10 bio failfast flag, right? 
>> There are rdev and also r1/r10 bio failfast flags.
> 
> I mean the rdev flag, all underlying disks should set FailFast, so that
> no BB will be present. rdev will just become faulty for the case IO
> error.
> 
> r1/r10 bio failfast flags is for internal usage to handle IO error.

I am not familiar with all consequences of FailFast for an rdev, but it 
seems a bit drastic to set it just because the rdev supports atomic 
writes. If we support atomic writes, then not all writes will 
necessarily be atomic.

Thanks,
John