Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH V10 3/4] blk-mq: issue directly with bypass 'false' in
 blk_mq_sched_insert_requests
To:     Jianchao Wang <jianchao.w.wang@oracle.com>
Cc:     ming.lei@redhat.com, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1544067160-20564-1-git-send-email-jianchao.w.wang@oracle.com>
 <1544067160-20564-4-git-send-email-jianchao.w.wang@oracle.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <840accff-5050-744d-9c95-febce5433ab2@kernel.dk>
Date:   Thu, 6 Dec 2018 08:19:26 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: <1544067160-20564-4-git-send-email-jianchao.w.wang@oracle.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 12/5/18 8:32 PM, Jianchao Wang wrote:
> It is not necessary to issue request directly with bypass 'true'
> in blk_mq_sched_insert_requests and handle the non-issued requests
> itself. Just set bypass to 'false' and let blk_mq_try_issue_directly
> handle them totally. Remove the blk_rq_can_direct_dispatch check,
> because blk_mq_try_issue_directly can handle it well.
> 
> With respect to commit_rqs hook, we only need to care about the last
> request's result. If it is inserted, invoke commit_rqs.

I don't think there's anything wrong, functionally, with this patch,
but I question the logic of continuing to attempt direct dispatch
if we fail one. If we get busy on one, for instance, we should just
insert that one to the dispatch list, and insert the rest of the list
normally.


-- 
Jens Axboe