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([2620:15c:211:201:fc96:5ba7:a6f5:b187]) by smtp.gmail.com with ESMTPSA id v9-20020a170902b7c900b001c41e1e9ca7sm1790448plz.215.2023.10.03.09.40.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Oct 2023 09:40:47 -0700 (PDT) Message-ID: <7f031c7a-1830-4331-86f9-4d5fbca94b8a@acm.org> Date: Tue, 3 Oct 2023 09:40:45 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/21] block: Add atomic write operations to request_queue limits Content-Language: en-US To: John Garry , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, jejb@linux.ibm.com, martin.petersen@oracle.com, djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, chandan.babu@oracle.com, dchinner@redhat.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com, linux-api@vger.kernel.org, Himanshu Madhani References: <20230929102726.2985188-1-john.g.garry@oracle.com> <20230929102726.2985188-2-john.g.garry@oracle.com> From: Bart Van Assche In-Reply-To: <20230929102726.2985188-2-john.g.garry@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231003_094050_753486_1525D2A4 X-CRM114-Status: GOOD ( 11.91 ) 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 9/29/23 03:27, John Garry wrote: > +What: /sys/block//atomic_write_unit_min_bytes > +Date: May 2023 > +Contact: Himanshu Madhani > +Description: > + [RO] This parameter specifies the smallest block which can > + be written atomically with an atomic write operation. All > + atomic write operations must begin at a > + atomic_write_unit_min boundary and must be multiples of > + atomic_write_unit_min. This value must be a power-of-two. I have two comments about these descriptions: - Referring to "atomic writes" only is not sufficient. It should be explained that in this context "atomic" means "indivisible" only and also that there are no guarantees that the data written by an atomic write will survive a power failure. See also the difference between the NVMe parameters AWUN and AWUPF. - atomic_write_unit_min_bytes will always be the logical block size so I don't think it is useful to make the block layer track this value nor to export this value through sysfs. Thanks, Bart.