Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 2 Mar 2020 13:55:31 +0100
From:   Christian Brauner <christian.brauner@ubuntu.com>
To:     Florian Weimer <fweimer@redhat.com>
Cc:     David Howells <dhowells@redhat.com>, linux-api@vger.kernel.org,
        viro@zeniv.linux.org.uk, metze@samba.org,
        torvalds@linux-foundation.org, cyphar@cyphar.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Have RESOLVE_* flags superseded AT_* flags for new syscalls?
Message-ID: <20200302125531.7z2viveb3zxhqkuj@wittgenstein>
References: <96563.1582901612@warthog.procyon.org.uk>
 <20200228152427.rv3crd7akwdhta2r@wittgenstein>
 <87h7z7ngd4.fsf@oldenburg2.str.redhat.com>
 <20200302115239.pcxvej3szmricxzu@wittgenstein>
 <8736arnel9.fsf@oldenburg2.str.redhat.com>
 <20200302121959.it3iophjavbhtoyp@wittgenstein>
 <20200302123510.bm3a2zssohwvkaa4@wittgenstein>
 <87y2sjlygl.fsf@oldenburg2.str.redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <87y2sjlygl.fsf@oldenburg2.str.redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Mar 02, 2020 at 01:42:50PM +0100, Florian Weimer wrote:
> * Christian Brauner:
> 
> > One difference to openat() is that openat2() doesn't silently ignore
> > unknown flags. But I'm not sure that would matter for iplementing
> > openat() via openat2() since there are no flags that openat() knows about
> > that openat2() doesn't know about afaict. So the only risks would be
> > programs that accidently have a bit set that isn't used yet.
> 
> Will there be any new flags for openat in the future?  If not, we can
> just use a constant mask in an openat2-based implementation of openat.

From past experiences with other syscalls I would expect that any new
features would only be available through openat2().
The way I see it in general is that a revised version of a syscall
basically deprecates the old syscall _wrt to new features_, i.e. new
features will only be available through the revised version unless there
are very strong reasons to also allow it in the old version (security
bug or whatever).
(But I don't want to be presumptuous here and pretend I can make any
definiteve statement. Ultimately it's up to the community, I guess. :))

Christian