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Wed, 12 Nov 2025 07:26:02 -0800 (PST) From: Jens Axboe To: Ming Lei , Keith Busch , Chaitanya Kulkarni , Caleb Sander Mateos Cc: linux-block@vger.kernel.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20251111191530.1268875-1-csander@purestorage.com> References: <20251111191530.1268875-1-csander@purestorage.com> Subject: Re: [PATCH] io_uring/rsrc: don't use blk_rq_nr_phys_segments() as number of bvecs Message-Id: <176296116216.24001.10740596505863921319.b4-ty@kernel.dk> Date: Wed, 12 Nov 2025 08:26:02 -0700 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Mailer: b4 0.14.3 On Tue, 11 Nov 2025 12:15:29 -0700, Caleb Sander Mateos wrote: > io_buffer_register_bvec() currently uses blk_rq_nr_phys_segments() as > the number of bvecs in the request. However, bvecs may be split into > multiple segments depending on the queue limits. Thus, the number of > segments may overestimate the number of bvecs. For ublk devices, the > only current users of io_buffer_register_bvec(), virt_boundary_mask, > seg_boundary_mask, max_segments, and max_segment_size can all be set > arbitrarily by the ublk server process. > Set imu->nr_bvecs based on the number of bvecs the rq_for_each_bvec() > loop actually yields. However, continue using blk_rq_nr_phys_segments() > as an upper bound on the number of bvecs when allocating imu to avoid > needing to iterate the bvecs a second time. > > [...] Applied, thanks! [1/1] io_uring/rsrc: don't use blk_rq_nr_phys_segments() as number of bvecs commit: 2d0e88f3fd1dcb37072d499c36162baf5b009d41 Best regards, -- Jens Axboe