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From:   "Frank Filz" <ffilzlnx@mindspring.com>
To:     <hch@infradead.org>, "'Trond Myklebust'" <trondmy@hammerspace.com>
Cc:     <pgoetz@math.utexas.edu>, <wangzhibei1999@gmail.com>,
        <chuck.lever@oracle.com>, <greg@kroah.com>, <w@1wt.eu>,
        <security@kernel.org>, <bfields@fieldses.org>,
        <linux-nfs@vger.kernel.org>
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Subject: RE: nfsd vurlerability submit
Date:   Wed, 13 Jan 2021 07:45:34 -0800
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> On Wed, Jan 13, 2021 at 03:16:52PM +0000, Trond Myklebust wrote:
> > How would that work then? Would you just look at the project ID of the
> > directory identified by the filehandle as the export point, and then
> > match to the project ID on the target inode? That sounds like it
> > doesn't even need to encode anything special in the filehandle.
> 
> True, we would not even have to encode them.
> 
> > How do you set a project ID in XFS?
> 
> With the XFS_IOC_SETXFLAGS ioctl.
> 
> On the command line side people usually do it using the xfs_quota tool as
part
> of setting up the tree quotas, but it can also be done separately using
the chproj
> subcommand of xfs_io.

Is this also queried via the ioctl? If this is a viable way of specifying
sub-trees, nfs-ganesha could also use it, though making an ioctl call for
each file system object would add some metadata performance hit.

Frank