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Thu, 08 Oct 2026 14:43:54 -0700 (PDT) Received: from debian.lan ([172.245.89.240]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-91b5507646fsm903406d6.28.2026.10.08.14.43.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2026 14:43:53 -0700 (PDT) From: Maks To: axboe@kernel.dk Cc: Maks Ivanov , io-uring@vger.kernel.org, linux-block@vger.kernel.org Subject: Question about asynchronous blk-mq tag waiting for io_uring Date: Fri, 9 Oct 2026 00:41:37 +0300 Message-ID: <20261008214137.1267424-1-mi9992828@gmail.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable From: Maks Ivanov =0D Hi,=0D =0D I read your comment in liburing issue #1492 about callback-based retry=0D when storage tags are exhausted:=0D =0D https://github.com/axboe/liburing/issues/1492#issuecomment-4696489936=0D =0D I'm considering this direction for my bachelor's thesis and would like=0D to clarify its scope and design.=0D =0D The initial scope would be io_uring direct reads on raw block devices.=0D For requests without explicit RWF_NOWAIT, the mechanism would register=0D a continuation when tag allocation cannot complete immediately, then=0D retry submission when a tag becomes available.=0D Explicit RWF_NOWAIT requests would retain their existing=0D behaviour when tag allocation would require waiting.=0D =0D Could you clarify a few points?=0D =0D - Is this still an open direction worth investigating?=0D - Is there related work or an existing approach I should look at first?=0D - Which layer should own the continuation: io_uring, the block submission=0D path, or blk-mq?=0D - What lifetime and cancellation constraints would such a mechanism need=0D to satisfy?=0D =0D I would also appreciate pointers to other open problems in io_uring or=0D the block layer that could suit a focused implementation and validation=0D project. Existing bug reports, design discussions, or TODOs would be=0D very helpful.=0D =0D Thanks,=0D Maks Ivanov=0D