From: Kemeng Shi <shikemeng@huaweicloud.com>
To: Christoph Hellwig <hch@lst.de>
Cc: axboe@kernel.dk, dwagner@suse.de, hare@suse.de,
ming.lei@redhat.com, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, john.garry@huawei.com,
jack@suse.cz
Subject: Re: [PATCH v4 12/14] blk-mq: remove set of bd->last when get driver tag for next request fails
Date: Thu, 19 Jan 2023 09:45:04 +0800 [thread overview]
Message-ID: <1f116b9b-8194-54c8-eedb-7f2c9cd493c6@huaweicloud.com> (raw)
In-Reply-To: <20230118174208.GH12399@lst.de>
on 1/19/2023 1:42 AM, Christoph Hellwig wrote:
> On Wed, Jan 18, 2023 at 05:37:24PM +0800, Kemeng Shi wrote:
>> Commit 113285b473824 ("blk-mq: ensure that bd->last is always set
>> correctly") will set last if we failed to get driver tag for next
>> request to avoid flush miss as we break the list walk and will not
>> send the last request in the list which will be sent with last set
>> normally.
>> This code seems stale now becase the flush introduced is always
>> redundant as:
>> For case tag is really out, we will send a extra flush if we find
>> list is not empty after list walk.
>> For case some tag is freed before retry in blk_mq_prep_dispatch_rq for
>> next, then we can get a tag for next request in retry and flush notified
>> already is not necessary.
>
> I think Ming will know this code better than me, but aren't we
> losing the blk_mq_get_driver_tag call entirely here now. Where
> is getting the driver tag covered now?
>
We will get driver tag in blk_mq_prep_dispatch_rq at beginning of dispatch
loop, so it's fine to remove blk_mq_get_driver_tag here. Thanks.
--
Best wishes
Kemeng Shi
next prev parent reply other threads:[~2023-01-19 1:48 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-18 9:37 [PATCH v4 01/14] blk-mq: avoid sleep in blk_mq_alloc_request_hctx Kemeng Shi
2023-01-18 9:37 ` [PATCH v4 02/14] blk-mq: remove stale comment for blk_mq_sched_mark_restart_hctx Kemeng Shi
2023-01-18 9:37 ` [PATCH v4 03/14] blk-mq: wait on correct sbitmap_queue in blk_mq_mark_tag_wait Kemeng Shi
2023-01-18 9:37 ` [PATCH v4 04/14] blk-mq: Fix potential io hung for shared sbitmap per tagset Kemeng Shi
2023-02-06 15:52 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 05/14] blk-mq: remove unnecessary list_empty check in blk_mq_try_issue_list_directly Kemeng Shi
2023-01-18 9:37 ` [PATCH v4 06/14] blk-mq: remove unncessary from_schedule parameter in blk_mq_plug_issue_direct Kemeng Shi
2023-01-18 17:36 ` Christoph Hellwig
2023-02-06 15:52 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 07/14] blk-mq: make blk_mq_commit_rqs a general function for all commits Kemeng Shi
2023-01-18 17:37 ` Christoph Hellwig
2023-01-19 1:40 ` Kemeng Shi
2023-01-28 1:55 ` Kemeng Shi
2023-02-06 15:53 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 08/14] blk-mq: remove unncessary error count and commit in blk_mq_plug_issue_direct Kemeng Shi
2023-01-18 17:38 ` Christoph Hellwig
2023-02-06 15:53 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 09/14] blk-mq: use blk_mq_commit_rqs helper in blk_mq_try_issue_list_directly Kemeng Shi
2023-01-18 17:38 ` Christoph Hellwig
2023-02-06 15:53 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 10/14] blk-mq: simplify flush check in blk_mq_dispatch_rq_list Kemeng Shi
2023-01-18 17:38 ` Christoph Hellwig
2023-02-06 15:53 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 11/14] blk-mq: remove unnecessary error count and " Kemeng Shi
2023-01-18 17:39 ` Christoph Hellwig
2023-02-06 15:54 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 12/14] blk-mq: remove set of bd->last when get driver tag for next request fails Kemeng Shi
2023-01-18 17:42 ` Christoph Hellwig
2023-01-19 1:45 ` Kemeng Shi [this message]
2023-01-28 2:03 ` Kemeng Shi
2023-02-06 1:05 ` Kemeng Shi
2023-02-06 16:06 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 13/14] blk-mq: use switch/case to improve readability in blk_mq_try_issue_list_directly Kemeng Shi
2023-01-18 17:42 ` Christoph Hellwig
2023-01-18 9:37 ` [PATCH v4 14/14] blk-mq: correct stale comment of .get_budget Kemeng Shi
2023-01-18 17:42 ` Christoph Hellwig
2023-02-06 16:22 ` [PATCH v4 01/14] blk-mq: avoid sleep in blk_mq_alloc_request_hctx Jens Axboe
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