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Mon, 3 Feb 2025 22:25:40 +0900 (KST) Received: from [107.122.11.51] (unknown [107.122.11.51]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20250203132539epsmtip1589e5dc6851fa5ef8adba0afe090ee70~gtZxL5cA52891528915epsmtip1K; Mon, 3 Feb 2025 13:25:38 +0000 (GMT) Message-ID: <8e548c8f-7a05-4e82-aed7-6044a0d247c9@samsung.com> Date: Mon, 3 Feb 2025 18:55:38 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/3] Btrfs checksum offload To: Johannes Thumshirn , "josef@toxicpanda.com" , "dsterba@suse.com" , "clm@fb.com" , "axboe@kernel.dk" , "kbusch@kernel.org" , hch Cc: "linux-btrfs@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , "gost.dev@samsung.com" Content-Language: en-US From: Kanchan Joshi In-Reply-To: <73ba28f4-0588-4ca8-b64f-2a6dd593606b@wdc.com> Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrPJsWRmVeSWpSXmKPExsWy7bCmhu7VwwvSDdbs5LRYfbefzWJS/wx2 iws/Gpksbh7YyWSxcvVRJou/XfeYLP48NLSYdOgao8XeW9oWlx6vYLeYv+wpuwO3x8Tmd+we l8+Wemxa1cnmsXlJvcfumw1sHn1bVjF6rN9ylcVjwuaNrB6fN8l5tB/oZgrgisq2yUhNTEkt UkjNS85PycxLt1XyDo53jjc1MzDUNbS0MFdSyEvMTbVVcvEJ0HXLzAG6V0mhLDGnFCgUkFhc rKRvZ1OUX1qSqpCRX1xiq5RakJJTYFKgV5yYW1yal66Xl1piZWhgYGQKVJiQnTH38ByWginc Fc9W9LE2MH7n6GLk4JAQMJG4s8Wxi5GLQ0hgN6NES+MfdgjnE6PEvcUfmboYOYGcb4wS56+A 2SANa9dfgorvZZRY0SUF0fCWUWJ2fzs7SIJXwE5i0poH7CAbWARUJL4+MoEIC0qcnPmEBcQW FZCXuH9rBlAJO4ewgK7EjmiQKSICXUwSh9csZwVxmAW+MEr8eH6EFaSeWUBc4taT+UwgI9kE NCUuTC4FCXMKWEs0f1zPDFEiL7H97RxmkF4JgTMcEnOv32CBuNlF4szsGWwQtrDEq+Nb2CFs KYnP7/ZCxbMlHjx6AFVfI7Fjcx8rhG0v0fDnBivIXmagvet36UPs4pPo/f2ECRKGvBIdbUIQ 1YoS9yY9heoUl3g4YwmU7SHxYsIxNkioLWaSaDjuPoFRYRZSoMxC8uQsJN/MQli8gJFlFaNk akFxbnpqsmmBYV5qOTyuk/NzNzGCU7KWyw7GG/P/6R1iZOJgPMQowcGsJMJ7evuCdCHelMTK qtSi/Pii0pzU4kOMpsDImcgsJZqcD8wKeSXxhiaWBiZmZmYmlsZmhkrivM07W9KFBNITS1Kz U1MLUotg+pg4OKUamG4xcIXt29n5z41hpf6ZR+tOFjNlHL/zhUPT3/dI9FdL1p6tqZetX1ZX rLry02/C3bqHPFXTNbK2zEr/qXb6wP8rnj2hockq8wT61ym8rlhymE3IyJcrr/HvmZPv175V EnPZ/a5UMPPvEe4NbglG+5S8NZ/aZC61TPnyQKtlxuwXF47ZsfPuDZ4ppLHK3PPcz+j5Wzu2 6GicmnVfzsdVaNV2CZcnjxUqWT97vv7vqSe3ub2190v1BsGmmPMm/P9PqahxT5oVp1LbmDF1 9xORk4kdj2alTv9VGjPtY1S6F8s7yfVqCW6dMxL/VXjoL178uC1W5N/5N17BM5XK82+apHnG pi64arLA5XShonRavxJLcUaioRZzUXEiAGm48rJSBAAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprPIsWRmVeSWpSXmKPExsWy7bCSnO6VwwvSDc63G1isvtvPZjGpfwa7 xYUfjUwWNw/sZLJYufook8XfrntMFn8eGlpMOnSN0WLvLW2LS49XsFvMX/aU3YHbY2LzO3aP y2dLPTat6mTz2Lyk3mP3zQY2j74tqxg91m+5yuIxYfNGVo/Pm+Q82g90MwVwRXHZpKTmZJal FunbJXBlzD08h6VgCnfFsxV9rA2M3zm6GDk5JARMJNauv8TUxcjFISSwm1Hi9aa/7BAJcYnm az+gbGGJlf+es0MUvWaUuHbxOBtIglfATmLSmgdACQ4OFgEVia+PTCDCghInZz5hAbFFBeQl 7t+aAVTCziEsoCuxIxpkiohAD5PEufO7GEEcZoEvjBI7r11lhJi/mEni8auvYIuZgY649WQ+ E8h8NgFNiQuTS0HCnALWEs0f1zNDlJhJdG3tYoSw5SW2v53DPIFRaBaSM2YhmTQLScssJC0L GFlWMUqmFhTnpucmGxYY5qWW6xUn5haX5qXrJefnbmIEx6GWxg7Gd9+a9A8xMnEwHmKU4GBW EuE9vX1BuhBvSmJlVWpRfnxRaU5q8SFGaQ4WJXHelYYR6UIC6YklqdmpqQWpRTBZJg5OqQYm vW6BY8z+tb/mbOP8LKukXeW6zFJOJyVx+dIz6g1/AjU5dW27Oeyt2Z+c2L78oou07ce5683a +bQ32ez11ygp+zx18T4l5u673UvUtneeC/tb/uink7D7et7i/OkSMtoFOScnPvhqlfxujWt7 +y8G0fsnFT72SZ14LSAqUPs9g/Oi0luuX4f3HpjxRiZm1b7K80dmburM+WJ9PyLW1+uWKb+i wy2J6ld3F8w1/bb4hL/qvMx9+SwTxQ1/pq4U+7UqeO7ESwurtq8rsJS8OtNTs26Tv0jEvIlL FPdtm336zd3NkQl//zhMlRbauS5kknBnM0ftyenPW90XeLj9Ltt3U8OmykhPpfb6Pr/IOU+F lViKMxINtZiLihMBam5g6TIDAAA= X-CMS-MailID: 20250203132540epcas5p3108da1d357572d2569b2daacd0ff6e2a X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" CMS-TYPE: 105P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20250129141039epcas5p11feb1be4124c0db3c5223325924183a3 References: <20250129140207.22718-1-joshi.k@samsung.com> <299a886d-c065-4b75-b0be-625710f7348c@wdc.com> <572e0418-de26-47ec-b536-b63291acff52@samsung.com> <73ba28f4-0588-4ca8-b64f-2a6dd593606b@wdc.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250203_052550_905067_ED7E3E65 X-CRM114-Status: GOOD ( 17.18 ) 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 1/31/2025 3:59 PM, Johannes Thumshirn wrote: >> I tested the series for read, but only the success cases. In this case >> checksum generation/verification happens only within the device. It was >> slightly tricky to inject an error and I skipped that. >> >> Since separate checksum I/Os are omitted, this is about handling the >> error condition in data read I/O path itself. I have not yet checked if >> repair code triggers when Btrfs is working with existing 'nodatasum' >> mount option. But I get your point that this needs to be handled. >> > So this as of now disables one of the most useful features of the FS, > repairing bad data. The whole "story" for the RAID code in the FS is > build around this assumption, that we can repair bad data, unlike say MD > RAID. Does repairing-bad-data work when Btrfs is mounted with NODATASUM? If not, should not the proposed option be seen as an upgrade over that? You might be knowing, but I do not know how does Btrfs currently decide to apply NODATSUM! With these patches it becomes possible to know if checksum-offload is supported by the underlying hardware. And that makes it possible to apply NODATASUM in an informed manner. I have not reduced anything, but added an opt-in for deployments that may have a different definition of what is useful. Not all planets are Mars. The cost of checksum tree will be different (say on QLC vs SLC).