From: Pavel Begunkov <asml.silence@gmail.com>
To: Kanchan Joshi <joshi.k@samsung.com>,
axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me
Cc: selvakuma.s1@samsung.com, linux-kernel@vger.kernel.org,
linux-nvme@lists.infradead.org, io-uring@vger.kernel.org,
linux-fsdevel@vger.kernel.org, javier.gonz@samsung.com,
nj.shetty@samsung.com
Subject: Re: [RFC PATCH 0/4] Asynchronous passthrough ioctl
Date: Wed, 27 Jan 2021 15:53:19 +0000 [thread overview]
Message-ID: <a287bd9e-3474-83a4-e5c2-98df17214dc7@gmail.com> (raw)
In-Reply-To: <489691ce-3b1e-30ce-9f72-d32389e33901@gmail.com>
On 27/01/2021 15:42, Pavel Begunkov wrote:
> On 27/01/2021 15:00, Kanchan Joshi wrote:
>> This RFC patchset adds asynchronous ioctl capability for NVMe devices.
>> Purpose of RFC is to get the feedback and optimize the path.
>>
>> At the uppermost io-uring layer, a new opcode IORING_OP_IOCTL_PT is
>> presented to user-space applications. Like regular-ioctl, it takes
>> ioctl opcode and an optional argument (ioctl-specific input/output
>> parameter). Unlike regular-ioctl, it is made to skip the block-layer
>> and reach directly to the underlying driver (nvme in the case of this
>> patchset). This path between io-uring and nvme is via a newly
>> introduced block-device operation "async_ioctl". This operation
>> expects io-uring to supply a callback function which can be used to
>> report completion at later stage.
>>
>> For a regular ioctl, NVMe driver submits the command to the device and
>> the submitter (task) is made to wait until completion arrives. For
>> async-ioctl, completion is decoupled from submission. Submitter goes
>> back to its business without waiting for nvme-completion. When
>> nvme-completion arrives, it informs io-uring via the registered
>> completion-handler. But some ioctls may require updating certain
>> ioctl-specific fields which can be accessed only in context of the
>> submitter task. For that reason, NVMe driver uses task-work infra for
>> that ioctl-specific update. Since task-work is not exported, it cannot
>> be referenced when nvme is compiled as a module. Therefore, one of the
>> patch exports task-work API.
>>
>> Here goes example of usage (pseudo-code).
>> Actual nvme-cli source, modified to issue all ioctls via this opcode
>> is present at-
>> https://github.com/joshkan/nvme-cli/commit/a008a733f24ab5593e7874cfbc69ee04e88068c5
>
> see https://git.kernel.dk/cgit/linux-block/log/?h=io_uring-fops
>
> Looks like good time to bring that branch/discussion back
a bit more context:
https://github.com/axboe/liburing/issues/270
--
Pavel Begunkov
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next prev parent reply other threads:[~2021-01-27 15:57 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20210127150134epcas5p251fc1de3ff3581dd4c68b3fbe0b9dd91@epcas5p2.samsung.com>
2021-01-27 15:00 ` [RFC PATCH 0/4] Asynchronous passthrough ioctl Kanchan Joshi
[not found] ` <CGME20210127150140epcas5p32832cc0c0db953db199eb9dd326f2d4c@epcas5p3.samsung.com>
2021-01-27 15:00 ` [RFC PATCH 1/4] block: introduce async ioctl operation Kanchan Joshi
[not found] ` <CGME20210127150144epcas5p29ccb35d7e7170aba7947b5ee16fd2db0@epcas5p2.samsung.com>
2021-01-27 15:00 ` [RFC PATCH 2/4] kernel: export task_work_add Kanchan Joshi
[not found] ` <CGME20210127150149epcas5p4fa8edd47712f28ccdd9bac5139fc6e61@epcas5p4.samsung.com>
2021-01-27 15:00 ` [RFC PATCH 3/4] nvme: add async ioctl support Kanchan Joshi
[not found] ` <CGME20210127150156epcas5p26cdf368e4ff6bffb132fa1c7f9430653@epcas5p2.samsung.com>
2021-01-27 15:00 ` [RFC PATCH 4/4] io_uring: add async passthrough " Kanchan Joshi
2021-01-27 15:42 ` [RFC PATCH 0/4] Asynchronous passthrough ioctl Pavel Begunkov
2021-01-27 15:53 ` Pavel Begunkov [this message]
2021-01-28 12:04 ` Kanchan Joshi
2021-01-28 14:38 ` Jens Axboe
2021-01-28 17:13 ` Kanchan Joshi
2021-01-28 17:24 ` Jens Axboe
2021-02-22 13:42 ` Kanchan Joshi
2021-02-22 14:33 ` Jens Axboe
2021-02-23 4:41 ` Kanchan Joshi
2021-01-28 14:50 ` Jens Axboe
2021-01-28 17:25 ` Kanchan Joshi
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