linux-kernel - Re: [PATCH RFC 4/7] md/raid10: convert read/write to use bio_submit

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Message-ID: <bcdb3af6-44b4-44f8-b03f-a89f98d8a71b@oracle.com>
Date: Tue, 2 Sep 2025 07:58:48 +0100
From: John Garry <john.g.garry@...cle.com>
To: Christoph Hellwig <hch@...radead.org>, Yu Kuai <yukuai1@...weicloud.com>
Cc: anthony <antmbox@...ngman.org.uk>, colyli@...nel.org, hare@...e.de,
        tieren@...as.com, axboe@...nel.dk, tj@...nel.org, josef@...icpanda.com,
        song@...nel.org, akpm@...ux-foundation.org, neil@...wn.name,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-raid@...r.kernel.org,
        yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH RFC 4/7] md/raid10: convert read/write to use
 bio_submit_split()

On 02/09/2025 07:30, Christoph Hellwig wrote:
> On Tue, Sep 02, 2025 at 07:18:01AM +0100, John Garry wrote:
>> BTW, do we realistically expect atomic writes HW support and bad blocks ever
>> to meet?
> 
> That's the point I'm trying to make.  bad block tracking is stupid
> with modern hardware.  Both SSDs and HDDs are overprovisioned on
> physical "blocks", and once they run out fine grained bad block tracking
> is not going to help.  І really do not understand why md even tries
> to do this bad block tracking, 

Just because they can try to deal with bad blocks for some (mirroring) 
personalities, I suppose.

> but claiming to support atomic writes
> while it does is actively harmful.
> 

There does not look to be some switch to turn off bad block support. 
That's from briefly checking raid10.c anyway. Kuai, any thoughts on 
whether we should allow this to be disabled?

Thanks,
John