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Date:   Wed, 20 Jan 2021 13:03:10 +0100
From:   Christian Brauner <christian.brauner@ubuntu.com>
To:     Jann Horn <jannh@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        John Johansen <john.johansen@canonical.com>,
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        Mimi Zohar <zohar@linux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
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        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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        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 15/42] fs: add file_user_ns() helper
Message-ID: <20210120120310.6tczonwl3rdtnyu3@wittgenstein>
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On Tue, Jan 19, 2021 at 04:05:00PM +0100, Jann Horn wrote:
> On Wed, Jan 13, 2021 at 1:52 AM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
> > Add a simple helper to retrieve the user namespace associated with the
> > vfsmount of a file. Christoph correctly points out that this makes
> > codepaths (e.g. ioctls) way easier to follow that would otherwise
> > dereference via mnt_user_ns(file->f_path.mnt).
> >
> > In order to make file_user_ns() static inline we'd need to include
> > mount.h in either file.h or fs.h which seems undesirable so let's simply
> > not force file_user_ns() to be inline.
> [...]
> > +struct user_namespace *file_user_ns(struct file *file)
> > +{
> > +       return mnt_user_ns(file->f_path.mnt);
> > +}
> 
> That name is confusing to me, because when I think of "the userns of a
> file", it's file->f_cred->user_ns. There are a bunch of places that
> look at that, as you can see from grepping for "f_cred->user_ns".
> 
> If you really want this to be a separate helper, can you maybe give it
> a clearer name? file_mnt_user_ns(), or something like that, idk.

Done.