linux-kernel - Re: [PATCH v2 3/4] blk-flush: kill the flush state machine

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Message-ID: <1f9f6c41-6b67-ef33-f7d0-9c0e42a231c9@linux.dev>
Date:   Mon, 31 Jul 2023 22:27:25 +0800
From:   Chengming Zhou <chengming.zhou@...ux.dev>
To:     Christoph Hellwig <hch@....de>
Cc:     axboe@...nel.dk, ming.lei@...hat.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, zhouchengming@...edance.com
Subject: Re: [PATCH v2 3/4] blk-flush: kill the flush state machine

On 2023/7/31 14:19, Christoph Hellwig wrote:
> On Tue, Jul 25, 2023 at 09:01:01PM +0800, chengming.zhou@...ux.dev wrote:
>> From: Chengming Zhou <zhouchengming@...edance.com>
>>
>> Since now we put preflush and postflush requests in separate queues,
>> we don't need the flush sequence to record anymore.
>>
>> REQ_FSEQ_PREFLUSH: blk_enqueue_preflush()
>> REQ_FSEQ_POSTFLUSH: blk_enqueue_postflush()
>> REQ_FSEQ_DONE: blk_end_flush()
>>
>> In blk_flush_complete(), we have two list to handle: preflush_running
>> and postflush_running. We just blk_end_flush() directly for postflush
>> requests, but need to move preflush requests to requeue_list to
>> dispatch.
>>
>> This patch just kill the flush state machine and directly call these
>> functions, in preparation for the next patch.
> 
>> +static void blk_enqueue_postflush(struct request *rq, struct blk_flush_queue *fq)
> 
> Please avoid the overly long here.  Maybe just rename enqueue to queue
> here and for the preflush version as we don't really use enqueue in
> the flush code anyway.

Ok, will rename to queue.

> 
>> +{
>> +	unsigned int nr_requeue = 0;
>> +	struct list_head *preflush_running;
>> +	struct list_head *postflush_running;
>> +	struct request *rq, *n;
>> +
>> +	preflush_running = &fq->preflush_queue[fq->flush_running_idx];
>> +	postflush_running = &fq->postflush_queue[fq->flush_running_idx];
> 
> I'd initialize these ad declaration time:
> 
> 	struct list_head *preflush_running =
> 		&fq->preflush_queue[fq->flush_running_idx];
> 	struct list_head *postflush_running =
> 		&fq->postflush_queue[fq->flush_running_idx];
> 	unsigned int nr_requeue = 0;
> 	struct request *rq, *n;
> 

LGTM, will change these.

Thanks for your review!

>> +
>> +	list_for_each_entry_safe(rq, n, postflush_running, queuelist) {
>> +		blk_end_flush(rq, fq, error);
>>  	}
> 
> No need for the braces.
>