Re: [RFC PATCH 1/2] quota: allow DQF_ROOT_SQUASH on all quota formats

[sashiko-bot@kernel.org]

> ignore_hardlimit() exempts CAP_SYS_RESOURCE holders from enforcement of
> hard limits and of soft limits whose grace time expired.
> DQF_ROOT_SQUASH disables that exemption, but it has been confined to the
> old v1 quota format since the quota format abstraction was introduced,
> and commit ca6cb0918e87 ("quota: Verify flags passed to Q_SETINFO")
> later made Q_SETINFO reject it explicitly on other formats.
> 
> That confinement predates generic project quota support. Project limits
> bound the size of a directory tree rather than restrict a user, and are
> commonly used for capacity isolation of container volumes and NFS
> exports. There the exemption defeats the purpose: knfsd raises
> CAP_SYS_RESOURCE for requests mapped to root on no_root_squash exports
> (CAP_NFSD_SET), so any remote root write silently exceeds project hard
> limits. XFS enforces project limits regardless of capabilities.
> 
> Lift the format restriction so the flag can be set per quota type
> through Q_SETINFO on journaled quota as well. Existing setups keep their
> behaviour: the flag stays clear unless explicitly set, and setting it
> was previously rejected with -EINVAL on anything but QFMT_VFS_OLD -
> accepting it there is the user-visible ABI change this patch makes.
> 
> Signed-off-by: Kitae Yoo <kitaeyoo777@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260814114649.51253-1-kitaeyoo777@gmail.com?part=1