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Thu, 21 Aug 2025 05:25:32 +0000 (GMT) Message-ID: Date: Thu, 21 Aug 2025 10:55:31 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] nvme: add an opt-in to use AWUPF To: Keith Busch , John Garry Cc: axboe@kernel.dk, hch@lst.de, sagi@grimberg.me, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, tytso@mit.edu, martin.petersen@oracle.com, djwong@kernel.org, mcgrof@infradead.org References: <20250820150220.1923826-1-john.g.garry@oracle.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODE5MDIyMiBTYWx0ZWRfXw8zxww9smSiF pN80EtrZVprrZOl8SgTAkDo+XM1Xa0sVE8b0j5a5RXOuZrJ8yj+n7KyNbwySdv6dEpel03H9HEK 4vR37rUfE9fNEhEE/vq6NXA9cSOOMnkfz29YoBB/kYgdms2fJ56YMLoZMmLTSUd3AkrrAnaHXB0 jQz9gQtvixthLqh6zYkUCuMfq7onKipBwPZGidJ9+a9cNlTL5iPqWEg3elJceIa5L+ZM4VEQaTq RtrY78wYrSvDwQGkz3McvOpVqocUnflLkwOqpxoRpBMzUlWjpM03WWOrQASde2snr7d9/QrtZGa 7OqCYi2Bb0nAxJtwbnbeaVKz3oTjS+zwkHtiV71+RMfknBcOYBfKyzBsZrotQVIprl/4oWRIFdL nD6jROKL4JScvGuebrd/9mV+Q5zwoQ== X-Authority-Analysis: v=2.4 cv=PMlWOfqC c=1 sm=1 tr=0 ts=68a6add3 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=VwQbUJbxAAAA:8 a=xiRpjWrZGW_SbaGU0d0A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-GUID: FdsaARlXUgnrR_MZ-4H1Ngj0Qr7UKuy0 X-Proofpoint-ORIG-GUID: FdsaARlXUgnrR_MZ-4H1Ngj0Qr7UKuy0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-20_06,2025-08-20_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 bulkscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 spamscore=0 phishscore=0 suspectscore=0 clxscore=1011 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2508110000 definitions=main-2508190222 On 8/21/25 3:21 AM, Keith Busch wrote: > On Wed, Aug 20, 2025 at 03:02:20PM +0000, John Garry wrote: >> It would be preferred to stop honouring AWUPF altogether, but this may >> needlessly disable atomic write support for many "good" devices which >> only specify AWUPF. Currently all validation of controller-related >> atomics limits is dropped. > > These "good" devices that only report AWUPF, is there some set of > characteristics that generally applies to all of them? Yes, I know of such “good” devices. Typically, they report a consistent AWUPF value across all controllers, and that value does not change when the namespaces attached to those controllers are reformatted. As we know, though, validating this in code is difficult. A past attempt to implement such validation failed because there are disks in the field that do change the AWUPF value when reformatting namespaces. > I tried to list out conditions for when I think the value could be counted on here: > > https://lore.kernel.org/linux-nvme/aGvuRS8VmC0JXAR3@kbusch-mbp/ > Regarding the checks you listed, they seem too restrictive. They only support AWUPF for single-controller devices and for disks that either have only one namespace or support formatting all namespaces together (i.e., do not support formatting individual namespaces). > I just don't know if you know of any devices where that criteria doesn't > git. If not, maybe we can work with that without introducing more user > knobs. Given this, IMO, an opt-in approach should be considered, letting users decide whether they want to enable atomic write support or not. Thanks, --Nilay