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

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Message-ID: <fa43e80c-0aab-b4bf-039f-c3b70856335b@huaweicloud.com>
Date: Fri, 25 Oct 2024 09:39:11 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: John Garry <john.g.garry@...cle.com>, 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

Hi,

在 2024/10/24 17:56, John Garry 写道:
> 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.

I don't see there is other option for now.

1) set failfast and make sure no BB will be present;
2) handle BB and don't split it for the good disks for atomic writes.

Thanks,
Kuai

> 
> Thanks,
> John
> 
> .
>