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Tue, 19 Aug 2025 07:43:59 -0700 (PDT) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-50c94998c07sm3489939173.49.2025.08.19.07.43.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 Aug 2025 07:43:58 -0700 (PDT) Message-ID: <06bd405d-c5dd-4f20-af90-775278686f5c@kernel.dk> Date: Tue, 19 Aug 2025 08:43:58 -0600 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] io_uring: uring_cmd: add multishot support without poll To: Ming Lei Cc: io-uring@vger.kernel.org, Pavel Begunkov , Caleb Sander Mateos References: <20250810025024.1659190-1-ming.lei@redhat.com> <393638fa-566a-4210-9f7e-79061de43bb4@kernel.dk> <91bc3fdf-880d-4b71-94b3-ac72ca0f3640@kernel.dk> <628449dc-45e7-4cdf-ad65-7c97e6b2bb6b@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/19/25 8:40 AM, Ming Lei wrote: > On Tue, Aug 19, 2025 at 08:31:32AM -0600, Jens Axboe wrote: >> On 8/19/25 8:28 AM, Ming Lei wrote: >>> On Tue, Aug 19, 2025 at 08:01:18AM -0600, Jens Axboe wrote: >>>> On 8/19/25 5:19 AM, Ming Lei wrote: >>>>>>> @@ -251,6 +264,11 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags) >>>>>>> } >>>>>>> >>>>>>> ret = file->f_op->uring_cmd(ioucmd, issue_flags); >>>>>>> + if (ioucmd->flags & IORING_URING_CMD_MULTISHOT) { >>>>>>> + if (ret >= 0) >>>>>>> + return IOU_ISSUE_SKIP_COMPLETE; >>>>>>> + io_kbuf_recycle(req, issue_flags); >>>>>>> + } >>>>>>> if (ret == -EAGAIN) { >>>>>>> ioucmd->flags |= IORING_URING_CMD_REISSUE; >>>>>>> return ret; >>>>>> >>>>>> Missing recycle for -EAGAIN? >>>>> >>>>> io_kbuf_recycle() is done above if `ret < 0` >>>> >>>> Inside the multishot case. I don't see anywhere where it's forbidden to >>>> use IOSQE_BUFFER_SELECT without having multishot set? Either that needs >>> >>> REQ_F_BUFFER_SELECT is supposed to be allowed for IORING_URING_CMD_MULTISHOT >>> only, and it is checked in io_uring_cmd_prep(). >>> >>>> to be explicit for now, or the recycling should happen generically. >>>> Probably the former I would suspect. >>> >>> Yes, the former is exactly what the patch is doing. >> >> Is it? Because looking at v2, you check if IORING_URING_CMD_FIXED is >> set, and you fail for that case if REQ_F_BUFFER_SELECT is set. Then you >> have a IORING_URING_CMD_MULTISHOT where the opposite is true, which >> obviously makes sense. >> >> But no checks if neither is set? > > Indeed, thanks for the catch, and the REQ_F_BUFFER_SELECT check in IORING_URING_CMD_FIXED > branch can be moved to the branch of !IORING_URING_CMD_MULTISHOT. > >> >> You could add that in io_uring_cmd_select_buffer(), eg fail if >> IORING_URING_CMD_MULTISHOT isn't set. Which if done, then the prep side >> checking could probably just go away. > > Looks this way is good too. Want to spin a v3 for this? -- Jens Axboe