From: John Garry <john.g.garry@oracle.com>
To: david@fromorbit.com, djwong@kernel.org, hch@lst.de,
linux-xfs@vger.kernel.org
Subject: Storing bdev request_queue limits in xfs_buftarg
Date: Thu, 21 Mar 2024 10:46:11 +0000 [thread overview]
Message-ID: <881d7dfc-c11a-4d19-9c2e-4bf8d9f607dd@oracle.com> (raw)
This is a question regarding the atomic writes work, and whether it is
proper to store atomic write-related bdev request_queue limits in
xfs_buftarg, as already discussed in
https://lore.kernel.org/linux-xfs/6430d813-cb30-4a66-94e1-ea89bdc921da@oracle.com/
(and also in the v2 series).
I can't get a conclusion, so I am sending a separate mail.
A suggestion is to store atomic_write_unit_{min, max} in xfs_buftarg,
like we do for bdev logical block size. But the concern is "geometry of
the device can change underneath", see
https://lore.kernel.org/linux-xfs/20231003161029.GG21298@frogsfrogsfrogs/#t
(so do not do it).
We only need those limits in XFS for statx reporting of
atomic_write_unit_{min, max}, as in that series the block layer will
reject out-of-limit atomic writes.
If those limits did change after mount, then the worst that happens is
that we report incorrect atomic_write_unit_{min, max} values and the
user may have IOs rejected unexpectedly.
I assume that we would not normally consider adding other bdev
request_queue limits to xfs_buftarg, and we rely on the block layer to
handle all sizes of BIOs submitted.
Please advise.
John
reply other threads:[~2024-03-21 10:46 UTC|newest]
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