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Tue, 29 Sep 2026 18:35:02 -0700 (PDT) From: Prashant Singh To: CC: , , , , , , , , <93sam@debian.org>, , , , , Prashant Singh Subject: Re: [PATCH v4] efivarfs: add nostatfs mount option to skip QueryVariableInfo() Date: Tue, 29 Sep 2026 18:35:00 -0700 Message-ID: <20260930013500.10273-1-singhpra@juniper.net> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260929151401.doOQX7D0@linutronix.de> References: <20260928203445.72318-1-singhpra@juniper.net> <20260929074312.v3jT8uel@linutronix.de> <59d5452c-42b1-4784-a593-5e549a2a0f12@app.fastmail.com> <20260929151401.doOQX7D0@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B077:EE_|MN6PR05MB10210:EE_ X-MS-Office365-Filtering-Correlation-Id: 557ac903-0f1a-4a02-d99f-08df1e930d16 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|35950700016|376014|82310400026|7416014|1800799024|10067099003|56012099006|11063799006|4143699003|22082099003|18002099003|13003099007; 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Noted, and apologies for sending v4 without first finalizing the v3 discussion. >I asked you an honest question, and it seems Sashiko spotted an >issue here too. >Is there a problem with how the current code deals with uid and gid >on a remount? No, I checked and did not find a problem. I mentioned this in my response to your query on v3: https://lore.kernel.org/all/20260925113145.7396-1-singhpra@juniper.net/ >This until the end looks extremely verbose. I can drop the strace data from the commit message if that reads cleaner; I had included it to highlight the issue. >could this be, I don't know something smaller not including the >commandline where I would expect that people know how to use it. > >=================== ========================================================= >(no)statfs Control whether ``statfs(2)`` reports the variable-store > used/ available. Disabling it skips the EFI runtime > service call, which might block the CPU for a few milliseconds, > reporting 0 for used and capacity. Enabled by default on > PREEMPT_RT. >=================== ========================================================= > >It might make sense to add this knob to Documentation/core-api/real-time/hardware.rst. Thanks, I will use this wording and move it to Documentation/core-api/real-time/hardware.rst. >Here and below you add a comment to every change you make. What about >focusing on the important parts, that deserve an explanation why a >change has been made. For instance why nostatfs has the READ_ONCE/ >WRITE_ONCE accessors and sometimes it does not. Apologies, that was a miss on my part, and I saw that sashiko-bot flagged it too. I wanted to gather any additional comments before addressing it. >Yeah the most severe issue is that entering SMM requires a rendez-vous >of all the cores, and so whether preemption is enabled or not is >actually kind of irrelevant, given that all the other cores just >disappear. Yes, I observed the same behavior. I was not sure whether this is x86-specific, so I refrained from mentioning it in the commit log. >Right. So if anything, there could be a data_race() in one place >instead inconsistent READ/ WRITE once as we have it now. I would use data_race() on the write for nostatfs. Please let me know if the below looks OK: /* nostatfs is read locklessly by statfs()/show_options(); the racy update is benign. */ data_race(sfi->mount_opts.nostatfs = new_sfi->mount_opts.nostatfs); Thanks, Prashant