Date: Thu, 9 Oct 2025 04:57:13 +1100 From: Peter Jeremy <peterj@freebsd.org> To: Dave Cottlehuber <dch@skunkwerks.at> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: getfsstat(2) MNT_NOWAIT & stale data for zpool Message-ID: <aOal-ZA6K7OOAMsV@server.rulingia.com> In-Reply-To: <2706a6b0-ef12-440d-9f29-da5b9e597f9b@app.fastmail.com>
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[-- Attachment #1 --] On 2025-Oct-08 15:59:12 +0000, Dave Cottlehuber <dch@skunkwerks.at> wrote: >When does getfsstat(2) stale info get updated? It seems this can >be easily more than 15 minutes, based on experiments in prod. It >can be triggered by running `/bin/df` but not `/bin/df /`, which >would be preferable. > >Background: > >I'm using prometheus node_exporter on a zpool to monitor disk usage. >Right now this is broken, as a zpool can fill up, and node_exporter >continues to return the old data. > >It loops over all filesystems, doing unix.Getfsstat(buf, unix.MNT_NOWAIT), >which is a wrapper around getfsstat(2) which clearly states: > > Normally mode should be specified as MNT_WAIT. If mode is set to MNT_NOWAIT, getfsstat() will return the information it has > available without requesting an update from each file system. Thus, some of the information will be out of date, but getfsstat() > will not block waiting for information from a file system that is unable to respond. It will also skip any file system that is in > the process of being unmounted, even if the unmount would eventually fail. > >Is node_exporter just broken and should be fixed to use MNT_WAIT? > >Is there some tunable to refresh this stale data more frequently, >or should I just add `/bin/df` to a regular crontab? See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=273094 and https://github.com/prometheus/node_exporter/issues/1498 -- Peter Jeremy [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE7rKYbDBnHnTmXCJ+FqWXoOSiCzQFAmjmpfBfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEVF QjI5ODZDMzA2NzFFNzRFNjVDMjI3RTE2QTU5N0EwRTRBMjBCMzQACgkQFqWXoOSi CzSY3A/+M76VD0qvmx1LH21k9zD3AtMJ7B5lKCwtw3+n5KrTUpks+3IzGo46LrjM 7KmMx+ubP4soG6N/d1r9qXnkm1PE7d9pReQ8WN8859j5EqEFKAFDDGFGQwWRKj/i 5Kr8QJtimb6ocrqXCc4gUOZOeuO6X49CHOr6coqwZQ1qcqLj2nod2YMrVIvxWs7q 4de6T54UTM19kP88+bRXWoJ+uRpG02aAayyEIp4Njg+emj+MhNpDmEnNQRO8CSmw k6BKpQrajyCr3iLQ+TQ6ffQwZippniobTbFJf39O6NM205bXH4CWQ1/sNsQKgUZR 606NA3L0qDPRQV9jvpua1eYlPBZVeun7PFZUi582Z/y//mUeo2HKfiqUjL2qZUdW 0cVcCf4hpaCpbrXo9xvABE8Yll1/YOWohclA/M7qgsE0EBz+W1GJ7/WeZ9jCyL7t nnX0LnuN9gol/bTmI2WQ2kvf4DAdkNES+9ZQxcKoud2HMP6Og/uPmaRdIISKu5xl Ukh8TqzsspRjw9XvraNMB2G90/LExxCcihf3/hCi0UFH7J9OvU2/M9wUqmJWSB0O NlknMaVxS2iyztHU+AVEb7ciGvGl1A52SWhsZVVmwEp91FZ6pQT6JF8A1IURCZhk p6TD0B2RfQR11RmmI6p/DuMZIvlDXvsWjE2DZ2FliTkdL1oNDn8= =45km -----END PGP SIGNATURE-----home | help
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