linux-kernel - Re: [PATCH] block: remove redundant empty check of mq

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Date:   Wed, 9 Sep 2020 08:21:29 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Xianting Tian <tian.xianting@....com>, ast@...nel.org,
        daniel@...earbox.net, kafai@...com, songliubraving@...com,
        yhs@...com, andriin@...com, john.fastabend@...il.com,
        kpsingh@...omium.org
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] block: remove redundant empty check of mq_list

On 9/9/20 12:48 AM, Xianting Tian wrote:
> blk_mq_flush_plug_list() itself will do the empty check of mq_list,
> so remove such check in blk_flush_plug_list().
> Actually normally mq_list is not empty when blk_flush_plug_list is
> called.

It's cheaper to do in the caller, instead of doing the function call
and then aborting if it's empty. So I'd suggest just leaving it alone.
Right now this is the only caller, but it's nicer to assume we can
be called in any state vs not having the check.

-- 
Jens Axboe