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Wed, 11 Nov 2026 15:05:45 -0800 (PST) Received: from brian--MacBookPro18.purestorage.com ([170.85.204.93]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37520bfb58dsm36388538eec.18.2026.11.11.15.05.44 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 11 Nov 2026 15:05:44 -0800 (PST) From: Brian Bunker To: Martin Wilck Cc: Benjamin Marzinski , Christophe Varoqui , dm-devel@lists.linux.dev Subject: Re: [PATCH v3 0/1] multipathd: check re-added paths' WWIDs against sysfs Date: Wed, 11 Nov 2026 15:05:34 -0800 Message-ID: <20261111230535.12947-1-brian@purestorage.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: References: <20261109185556.27139-1-brian@purestorage.com> <214d18ebabeca8318352dfa5456bc5b37cdefdeb.camel@suse.com> <20261111174259.41911-1-brian@purestorage.com> X-Mailing-List: dm-devel@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Wed, 2026-11-11, Martin Wilck wrote: > Right, but "newer" doesn't mean "more accurate". You write below that > there is no indication that anything actually changed, so time > shouldn't be a factor. If a wrong VPD reply is possible once, it can > also occur multiple times. If it's just an unlikely failure, a purely > stochastical thing, it would help to simply repeat the same request; > if the probability for error is 1e-4, the probability for two errors > in succession would be 1e-8. However we don't know if it's > stochastical. Fair, "newer" was the wrong word, and we can't show what caused the bad reply. I think the patch stands without that, though. recheck_wwid already exists to stop a path whose WWID has changed from staying in, or going into, the wrong map: multipathd checks the WWID with the device when a failed path comes back, and when a path is added with "multipathd add path". The re-add in uev_update_path() is a third place where a path is put into a map because of a WWID change, and the only one of the three that acts purely on the udev value. v4 applies the same check there, under the same option. It also costs little: nothing unless recheck_wwid is set, and with it set, one INQUIRY on a re-add that only happens after udev reports a changed WWID. If it ever refuses an add, it logs the udev WWID and the one the device returned. We'll run with recheck_wwid enabled on our test initiators and watch for that message. If it shows up more than once, we'll come back with those logs, which would be better evidence than the one run we have, where we didn't know at the time that our test tool was flooding udev. > I'd go one step further and say that it tells us nothing at all. Agreed. > However from the time line you provided, it makes sense that your > patch would have been effective in the error case. Thanks. Brian