From: JeffleXu <jefflexu@linux.alibaba.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
joseph.qi@linux.alibaba.com, dm-devel@redhat.com,
io-uring@vger.kernel.org, koct9i@gmail.com
Subject: Re: [dm-devel] dm: add support for DM_TARGET_NOWAIT for various targets
Date: Thu, 12 Nov 2020 15:58:27 +0800 [thread overview]
Message-ID: <8e958749-3954-a041-e6a9-ec13c328e9b6@linux.alibaba.com> (raw)
In-Reply-To: <533a3b6b-146b-afe6-2e3e-d1bc2180a8c8@linux.alibaba.com>
On 11/12/20 2:05 PM, JeffleXu wrote:
>>
>> dm-table.c:dm_table_set_restrictions() has:
>>
>> if (dm_table_supports_nowait(t))
>> blk_queue_flag_set(QUEUE_FLAG_NOWAIT, q);
>> else
>> blk_queue_flag_clear(QUEUE_FLAG_NOWAIT, q);
>>
>>> This patch adds support for DM_TARGET_NOWAIT for those dm targets, the
>>> .map() algorithm of which just involves sector recalculation.
>> So you're looking to constrain which targets will properly support
>> REQ_NOWAIT, based on whether they do a simple remapping?
>
> To be honest, I'm a little confused about the semantics of REQ_NOWAIT.
> Jens may had ever
>
> explained it in block or io_uring mailing list, but I can't find the
> specific mail.
>
I find it here
https://lore.kernel.org/linux-block/f1a6ae88-1436-e947-1124-41e10b3ea9bc@kernel.dk/
So if the IO is offloaded to workqueue and the current process context
will not get blocked,
then is this device capable of handling REQ_NOWAIT or not?
--
Thanks,
Jeffle
--
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next prev parent reply other threads:[~2020-11-13 8:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 6:55 [dm-devel] [PATCH] dm: add support for DM_TARGET_NOWAIT for various targets Jeffle Xu
2020-11-11 15:38 ` [dm-devel] " Mike Snitzer
2020-11-12 6:05 ` JeffleXu
2020-11-12 7:58 ` JeffleXu [this message]
2020-11-12 16:11 ` Mike Snitzer
2020-11-13 2:05 ` [dm-devel] [PATCH v2] " Jeffle Xu
2020-11-13 2:12 ` JeffleXu
2020-11-18 2:01 ` JeffleXu
2020-11-18 15:38 ` Mike Snitzer
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