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;
Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley
        Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United
        Kingdom.
        Registered in England and Wales under Company Registration No. 3798903
From:   David Howells <dhowells@redhat.com>
In-Reply-To: <20180922161406.6beo2ob6ki2otrjx@brauner.io>
References: <20180922161406.6beo2ob6ki2otrjx@brauner.io> <20180922132106.wfa6xaxwbu276qka@brauner.io> <20180921155455.flkf5vdrm3vgn6do@brauner.io> <20180920151214.15484-6-mszeredi@redhat.com> <20180920151214.15484-1-mszeredi@redhat.com> <17157.1537542475@warthog.procyon.org.uk> <20311.1537548756@warthog.procyon.org.uk> <8221.1537631312@warthog.procyon.org.uk>
To:     Christian Brauner <christian@brauner.io>
Cc:     dhowells@redhat.com, Miklos Szeredi <mszeredi@redhat.com>,
        Al Viro <viro@ZenIV.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/6] fsmount: do not use legacy MS_ flags
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <3867.1537742717.1@warthog.procyon.org.uk>
Date:   Sun, 23 Sep 2018 23:45:17 +0100
Message-ID: <3868.1537742717@warthog.procyon.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Christian Brauner <christian@brauner.io> wrote:

> Of course, I'm not sure what the reasons for all of the other arguments to
> this function are since it's not yet implemented.

Well, dfd, path and atflags are pretty standard.  atflags conveys things like
AT_EMPTY_PATH or AT_SYMLINK_NOFOLLOW and dfd conveys a file descriptor
pointing to a vfs object or AT_FDCWD.

> Seems that attr_values and attr_mask could be compacted to a single
> attr_mask maybe?

If you don't have a mask, you can't really do recursion.  Without the mask,
you have to supply the entire set of options absolutely - and this would get
stamped on everything in the target range.

With a mask in combination with the set of desired values, you can turn on or
off a specific subset of the attributes without affecting the rest - without
needing to know the rest.

David