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Mon, 11 Jul 2022 10:19:07 -0700 (PDT) Message-ID: <7ce5175e-c4dc-3af1-e47a-5966a999fdfe@kernel.dk> Date: Mon, 11 Jul 2022 11:19:07 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH for-next 3/4] io_uring: grow a field in struct io_uring_cmd Content-Language: en-US To: Sagi Grimberg , Kanchan Joshi , hch@lst.de, kbusch@kernel.org Cc: io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, asml.silence@gmail.com, joshiiitr@gmail.com, anuj20.g@samsung.com, gost.dev@samsung.com References: <20220711110155.649153-1-joshi.k@samsung.com> <20220711110155.649153-4-joshi.k@samsung.com> <11db8ab2-b41a-967e-8653-7a84b8a984c0@grimberg.me> From: Jens Axboe In-Reply-To: <11db8ab2-b41a-967e-8653-7a84b8a984c0@grimberg.me> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220711_101910_201389_875B1B63 X-CRM114-Status: GOOD ( 16.41 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 7/11/22 11:00 AM, Sagi Grimberg wrote: > >> Use the leftover space to carve 'next' field that enables linking of >> io_uring_cmd structs. Also introduce a list head and few helpers. >> >> This is in preparation to support nvme-mulitpath, allowing multiple >> uring passthrough commands to be queued. >> >> Signed-off-by: Kanchan Joshi >> Signed-off-by: Anuj Gupta >> --- >>   include/linux/io_uring.h | 38 ++++++++++++++++++++++++++++++++++++-- >>   1 file changed, 36 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h >> index 54063d67506b..d734599cbcd7 100644 >> --- a/include/linux/io_uring.h >> +++ b/include/linux/io_uring.h >> @@ -22,9 +22,14 @@ struct io_uring_cmd { >>       const void    *cmd; >>       /* callback to defer completions to task context */ >>       void (*task_work_cb)(struct io_uring_cmd *cmd); >> +    struct io_uring_cmd    *next; >>       u32        cmd_op; >> -    u32        pad; >> -    u8        pdu[32]; /* available inline for free use */ >> +    u8        pdu[28]; /* available inline for free use */ >> +}; > > I think io_uring_cmd will at some point become two cachelines and may > not be worth the effort to limit a pdu to 28 bytes... -- Jens Axboe