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Date:   Wed, 2 Dec 2020 10:47:51 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Christian Brauner <christian.brauner@ubuntu.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
        linux-fsdevel@vger.kernel.org,
        John Johansen <john.johansen@canonical.com>,
        James Morris <jmorris@namei.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
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        Mrunal Patel <mpatel@redhat.com>,
        Josh Triplett <josh@joshtriplett.org>,
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        Theodore Tso <tytso@mit.edu>, Alban Crequy <alban@kinvolk.io>,
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Subject: Re: [PATCH v3 04/38] fs: add mount_setattr()
Message-ID: <20201202094751.GA6129@lst.de>
References: <20201128213527.2669807-1-christian.brauner@ubuntu.com> <20201128213527.2669807-5-christian.brauner@ubuntu.com> <20201201104907.GD27730@lst.de> <20201202094218.ym5zqnulwz6gj6eo@wittgenstein>
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On Wed, Dec 02, 2020 at 10:42:18AM +0100, Christian Brauner wrote:
> > > +	if (upper_32_bits(attr->attr_set))
> > > +		return -EINVAL;
> > > +	if (build_attr_flags(lower_32_bits(attr->attr_set), &kattr->attr_set))
> > > +		return -EINVAL;
> > > +
> > > +	if (upper_32_bits(attr->attr_clr))
> > > +		return -EINVAL;
> > > +	if (build_attr_flags(lower_32_bits(attr->attr_clr), &kattr->attr_clr))
> > > +		return -EINVAL;
> > 
> > What is so magic about the upper and lower 32 bits?
> 
> Nothing apart from the fact that they arent't currently valid. I can
> think about reworking these lines. Or do you already have a preferred
> way of doing this in mind?

Just turn the attr_flags argument to build_attr_flags into a u64 and
the first sanity check there will catch all invalid flags, no matter
where they are places.  That should also generate more efficient code.