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Wed, 11 Nov 2026 10:16:52 -0800 (PST) Received: from brian--MacBookPro18.purestorage.com ([170.85.204.93]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-375212ec002sm20565706eec.26.2026.11.11.10.16.51 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 11 Nov 2026 10:16:52 -0800 (PST) From: Brian Bunker To: Martin Wilck Cc: Benjamin Marzinski , Christophe Varoqui , dm-devel@lists.linux.dev Subject: [PATCH v4 0/1] multipathd: recheck WWIDs of re-added paths with the device Date: Wed, 11 Nov 2026 10:16:41 -0800 Message-ID: <20261111181642.51912-1-brian@purestorage.com> X-Mailer: git-send-email 2.56.0 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 During an array controller failover on an iSCSI host, multipathd briefly put a path to one LUN into the map of another LUN, and I/O meant for the first LUN landed on the second. See the v1 cover letter for the full sequence, and my reply to Martin on v3 for the open questions about it. In short: a change uevent reported the wrong WWID for one path. The removal of the path from its map then blocked for 4.4 seconds while the map was suspended, and the re-add used that same, by then 4.4 second old, uevent to put the path into the wrong map. The next INQUIRY on the path, 140 ms after the re-add, returned the correct WWID. Changes in v4, after Martin's and Ben's review of v3: - Back to SG_IO, as in v2. The re-add check reads VPD page 0x83 from the device with check_path_wwid_change(), the same function recheck_wwid already uses, instead of comparing with the cached sysfs page. The cached page can be stale, so it isn't a better reference than udev's own INQUIRY. - The check only runs if recheck_wwid is set. It is off by default, so nothing changes for users who don't enable it. - Still only on PATH_ADD_REINIT, i.e. only for the re-add at the end of uev_update_path(). Ordinary adds never run it. - No changes to libmultipath. get_sysfs_wwid() and the ABI version bump from v3 are gone. - The uev_update_path() check from v2 that ignored a changed udev WWID stays dropped. - multipath.conf(5) documents the new case under recheck_wwid. We've seen the problem once and haven't reproduced it. We have been running a v1-style patch on our test initiators since then without a recurrence, which at this rate doesn't prove much either way. Brian Bunker (1): multipathd: recheck WWIDs of re-added paths with the device multipath/multipath.conf.5.in | 8 +++++--- multipathd/cli_handlers.c | 2 +- multipathd/main.c | 37 ++++++++++++++++++++++++----------- multipathd/main.h | 13 +++++++++++- 4 files changed, 44 insertions(+), 16 deletions(-) -- 2.56.0