linux-kernel - Re: [PATCH] blk-core: use pr_warn_ratelimited() in bio_check

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Date:   Wed, 8 Nov 2023 16:17:49 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Christoph Hellwig <hch@....de>, Yu Kuai <yukuai1@...weicloud.com>
Cc:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] blk-core: use pr_warn_ratelimited() in bio_check_ro()

Hi,

在 2023/11/08 15:16, Christoph Hellwig 写道:
> On Tue, Nov 07, 2023 at 07:12:47PM +0800, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> If one of the underlying disks of raid or dm is set to read-only, then
>> each io will generate new log, which will cause message storm. This
>> environment is indeed problematic, however we can't make sure our
>> naive custormer won't do this, hence use pr_warn_ratelimited() to
>> prevent message storm in this case.
> 
> Reducing the log spam sounds good, and I guess the single warning
> would be even better.

Got it.

Jens, I see that you already apply this version, do you want me to send
a new version to generate single warning for each block_device?
> 
> That being said, why/how is the underlying device set to read-only?
> If there is a good reason we should probably add a holder op to tell
> the user about it so that it stop sending writes.
> 
Our custormer use blockdev --getro to underlying device directly,
they're trying to forbid other users to write underlying device, so
in this case I think set underlying device to read-only is not okay
because it's already write opened, however I'm not sure if we want the
ioctl to fail.

Thanks,
Kuai
> 
> .
>