linux-kernel - Re: [PATCH 1/3] block: don't show disk stats if io accounting is disabled

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Date:   Fri, 18 Mar 2022 09:36:39 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Bart Van Assche <bvanassche@....org>, <axboe@...nel.dk>,
        <mpatocka@...hat.com>, <snitzer@...hat.com>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yi.zhang@...wei.com>
Subject: Re: [PATCH 1/3] block: don't show disk stats if io accounting is
 disabled

在 2022/03/17 22:06, Bart Van Assche 写道:
> On 3/17/22 04:26, Yu Kuai wrote:
>> If io accounting is disabled, there is no point to handle such device
>> in diskstats_show(), and it can be confused for users because all fields
>> in iostat are zero while the disk is handling io.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>>   block/genhd.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/block/genhd.c b/block/genhd.c
>> index c3b32c665aec..e5307f512185 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -937,6 +937,9 @@ ssize_t part_stat_show(struct device *dev,
>>       struct disk_stats stat;
>>       unsigned int inflight;
>> +    if (!blk_queue_io_stat(q))
>> +        return sprintf(buf, "io accounting is disabled\n");
>> +
> 
> Hmm ... the above looks sub-optimal to me. Has it been considered to 
> return an error code instead or even better to hide the stat attribute 
> if I/O accounting is disabled? The latter can be achieved by modifying 
> disk_visible().

Hi,

It's right this way is much better, i'll hide the 'stat' in next
iteration.

BTW, do you have any suggestion about patch 3?

Thanks,
Kuai