linux-kernel - Re: [PATCH 27/27] kernfs, sysfs, cgroup: Support fs

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Message-ID: <20170614175426.GA26229@htj.duckdns.org>
Date:   Wed, 14 Jun 2017 13:54:26 -0400
From:   Tejun Heo <tj@...nel.org>
To:     David Howells <dhowells@...hat.com>
Cc:     mszeredi@...hat.com, viro@...iv.linux.org.uk,
        linux-nfs@...r.kernel.org, jlayton@...hat.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org
Subject: Re: [PATCH 27/27] kernfs, sysfs, cgroup: Support fs_context [ver #5]

Hello, David.

On Wed, Jun 14, 2017 at 04:19:19PM +0100, David Howells wrote:
> Make kernfs support superblock creation/mount/remount with fs_context.
> 
> This requires that sysfs and cgroup, which are built on kernfs, be made to
> support fs_context also.

Can you please include a brief rationale for doing this and include a
pointer to the fuller description on what's going on?

> Weirdies:
> 
>  (*) cgroup_do_get_tree() calls cset_cgroup_from_root() with locks held,
>      but then uses the resulting pointer after dropping the locks.  I'm
>      told this is okay and needs commenting.

Yeah, will add the comment.

>  (*) The cgroup refcount web.  This really needs documenting.

If you're talking about the mount refcnt part, yeah, it's confusing to
me too and we definitely need to document it better.

>  (*) cgroup2 only has one root?

Yeap.

Thanks.

-- 
tejun