linux-kernel - Re: [PATCH 3/9] blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr

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Message-ID: <49151de5-0505-6cbd-d368-e032676232b9@huawei.com>
Date:   Tue, 20 Jul 2021 09:06:00 +0100
From:   John Garry <john.garry@...wei.com>
To:     Ming Lei <ming.lei@...hat.com>
CC:     <axboe@...nel.dk>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <kashyap.desai@...adcom.com>, <hare@...e.de>
Subject: Re: [PATCH 3/9] blk-mq: Relocate shared sbitmap resize in
 blk_mq_update_nr_requests()

On 20/07/2021 08:50, Ming Lei wrote:
>> Signed-off-by: John Garry<john.garry@...wei.com>
>> ---
>>   block/blk-mq.c | 13 ++++++++-----
>>   1 file changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index ae28f470893c..56e3c6fdba60 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -3624,8 +3624,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
>>   		if (!hctx->sched_tags) {
>>   			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
>>   							false);
>> -			if (!ret && blk_mq_is_sbitmap_shared(set->flags))
>> -				blk_mq_tag_resize_shared_sbitmap(set, nr);
>>   		} else {
>>   			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
>>   							nr, true);
>> @@ -3643,9 +3641,14 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
>>   	}
>>   	if (!ret) {
>>   		q->nr_requests = nr;
>> -		if (q->elevator && blk_mq_is_sbitmap_shared(set->flags))
>> -			sbitmap_queue_resize(&q->sched_bitmap_tags,
>> -					     nr - set->reserved_tags);
>> +		if (blk_mq_is_sbitmap_shared(set->flags)) {

Hi Ming,

>> +			if (q->elevator) {
>> +				sbitmap_queue_resize(&q->sched_bitmap_tags,
>> +						     nr - set->reserved_tags);

I have learned that some people prefer {} for multi-line single 
statements, like this.

Anyway, more code is added here later in the series, so better to add {} 
now, rather than re-arrange code later.

>> +			} else {
>> +				blk_mq_tag_resize_shared_sbitmap(set, nr);
>> +			}
> The above two {} can be removed.

Thanks,
John