linux-kernel - Re: [PATCH 5/5] blk-mq: Drop 'reserved' member of busy_tag_iter

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Message-ID: <a18fa379-5a9b-ff45-3be4-b253efd96a50@huawei.com>
Date:   Fri, 17 Jun 2022 17:42:36 +0100
From:   John Garry <john.garry@...wei.com>
To:     Bart Van Assche <bvanassche@....org>, <axboe@...nel.dk>,
        <damien.lemoal@...nsource.wdc.com>, <hch@....de>,
        <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>, <hare@...e.de>,
        <satishkh@...co.com>, <sebaddel@...co.com>, <kartilak@...co.com>
CC:     <linux-rdma@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
        <linux-nvme@...ts.infradead.org>, <linux-s390@...r.kernel.org>,
        <linux-scsi@...r.kernel.org>, <mpi3mr-linuxdrv.pdl@...adcom.com>,
        <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <nbd@...er.debian.org>
Subject: Re: [PATCH 5/5] blk-mq: Drop 'reserved' member of busy_tag_iter_fn

On 17/06/2022 17:33, Bart Van Assche wrote:
> On 6/17/22 03:55, John Garry wrote:
>> We no longer use the 'reserved' member in for any iter function so it
>                                           ^^^^^^
> One of these two words probably should be removed.

Yeah, it's a typo - I can fix it.

> 
>> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
>> index 2dcd738c6952..b8cc8b41553f 100644
>> --- a/block/blk-mq-tag.c
>> +++ b/block/blk-mq-tag.c
>> @@ -266,7 +266,6 @@ static bool bt_iter(struct sbitmap *bitmap, 
>> unsigned int bitnr, void *data)
>>       struct blk_mq_hw_ctx *hctx = iter_data->hctx;
>>       struct request_queue *q = iter_data->q;
>>       struct blk_mq_tag_set *set = q->tag_set;
>> -    bool reserved = iter_data->reserved;
>>       struct blk_mq_tags *tags;
>>       struct request *rq;
>>       bool ret = true;
>> @@ -276,7 +275,7 @@ static bool bt_iter(struct sbitmap *bitmap, 
>> unsigned int bitnr, void *data)
>>       else
>>           tags = hctx->tags;
>> -    if (!reserved)
>> +    if (!iter_data->reserved)
>>           bitnr += tags->nr_reserved_tags;
>>       /*
>>        * We can hit rq == NULL here, because the tagging functions
> 
> Is the above change really necessary?

It's not totally necessary. Since local variable 'reserved' would now 
only be used once I thought it was better to get rid of it.

I can keep it if you really think that is better.

>> @@ -337,12 +336,11 @@ static bool bt_tags_iter(struct sbitmap *bitmap, 
>> unsigned int bitnr, void *data)
>>   {
>>       struct bt_tags_iter_data *iter_data = data;
>>       struct blk_mq_tags *tags = iter_data->tags;
>> -    bool reserved = iter_data->flags & BT_TAG_ITER_RESERVED;
>>       struct request *rq;
>>       bool ret = true;
>>       bool iter_static_rqs = !!(iter_data->flags & 
>> BT_TAG_ITER_STATIC_RQS);
>> -    if (!reserved)
>> +    if (!(iter_data->flags & BT_TAG_ITER_RESERVED))
>>           bitnr += tags->nr_reserved_tags;
>>       /*
> 
> Same question here: is the above change really necessary?

As above.

Thanks,
john