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

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Message-ID: <43db8d24-aa70-3902-cee6-2879f8e8ff5e@huaweicloud.com>
Date:   Tue, 7 Nov 2023 17:44:52 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     "yebin (H)" <yebin10@...wei.com>,
        Yu Kuai <yukuai1@...weicloud.com>, hch@....de, axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com, yangerkun@...wei.com,
        Ming Lei <ming.lei@...hat.com>,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] blk-core: use pr_warn_ratelimited() in bio_check_ro()

Hi,

在 2023/11/07 11:50, yebin (H) 写道:
> 
> 
> On 2023/11/7 19:12, 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.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>>   block/blk-core.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index 9d51e9894ece..fdf25b8d6e78 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -501,8 +501,8 @@ static inline void bio_check_ro(struct bio *bio)
>>       if (op_is_write(bio_op(bio)) && bdev_read_only(bio->bi_bdev)) {
>>           if (op_is_flush(bio->bi_opf) && !bio_sectors(bio))
>>               return;
>> -        pr_warn("Trying to write to read-only block-device %pg\n",
>> -            bio->bi_bdev);
>> +        pr_warn_ratelimited("Trying to write to read-only 
>> block-device %pg\n",
>> +                    bio->bi_bdev);
> Acctually, before commit  57e95e4670d1 ("block: fix and cleanup 
> bio_check_ro") , there's only print warning once.
> I wrote a patch earlier, set GD_ROWR_WARNED flag for disk after emit 
> warning. You can look at the patch in the
> attachment, Is it possible to solve your problem.

Yes, this can work, other than that I think the flag should be in
block_device instead of gendisk.

However, I'm not sure which is better for now, hope Christoph or Ming
or anyone can give some advise.

Thanks,
Kuai
>>           /* Older lvm-tools actually trigger this */
>>       }
>>   }
>