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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Wed, 27 Sep 2023 10:46:58 +0200
Message-ID: <CAJfpegu3BKXE+b51cj3=QwAsxe3QyKOEG_10muEsAsGD=_vkAA@mail.gmail.com>
Subject: Re: [RFC PATCH 2/3] add statmnt(2) syscall
To:     Christian Brauner <brauner@kernel.org>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Miklos Szeredi <mszeredi@redhat.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-api@vger.kernel.org, linux-man@vger.kernel.org,
        linux-security-module@vger.kernel.org, Karel Zak <kzak@redhat.com>,
        Ian Kent <raven@themaw.net>,
        David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <christian@brauner.io>,
        Amir Goldstein <amir73il@gmail.com>
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On Mon, 25 Sept 2023 at 15:20, Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> On Mon, 25 Sept 2023 at 15:19, Christian Brauner <brauner@kernel.org> wrote:
> >
> > > How about passing u64 *?
> >
> > struct statmnt_req {
> >         __u64 mnt_id;
> >         __u64 mask;
> > };
> >
> > ?
>
> I'm fine with that as well.

So after a bit more thinking: this is okay to make life easier for
32bit archs, but only on the kernel ABI.

On the library API the args should *not* be multiplexed, as it's just
a pointless complication.  This is just an internal implementation
detail for the sake of legacy architectures, instead of being good API
design.

And because it's an internal thingy, my feeling is that this struct
could be reused for passing mnt_id to listmount(2) as well, despite
the fact that the mask would be unused.   But I'm ready to be
convinced otherwise...

Thanks,
Miklos