linux-kernel - Re: [16/32] kernfs, sysfs, cgroup, intel_rdt: Support fs

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Message-ID: <20180622165715.GA5361@outlook.office365.com>
Date:   Fri, 22 Jun 2018 09:57:16 -0700
From:   Andrei Vagin <avagin@...tuozzo.com>
To:     David Howells <dhowells@...hat.com>
Cc:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, Tejun Heo <tj@...nel.org>
Subject: Re: [16/32] kernfs, sysfs, cgroup, intel_rdt: Support fs_context
 [ver #8]

On Fri, Jun 22, 2018 at 08:30:29AM -0700, Andrei Vagin wrote:
> On Fri, Jun 22, 2018 at 01:52:16PM +0100, David Howells wrote:
> > Andrei Vagin <avagin@...tuozzo.com> wrote:
> > 
> > >                 ret = 0;
> > > +               ctx->root = root;
> > >                 goto out_unlock;
> > 
> > Okay, I can see that.
> > 
> > >                 percpu_ref_reinit(&root->cgrp.self.refcnt);
> > >                 mutex_unlock(&cgroup_mutex);
> > >         }
> > > +       cgroup_get(&root->cgrp);
> > 
> > This probably needs to be conditional on ret == 0.
> 
> yes, you are right


I've read the code and I think it isn't obvious. A reference will be
released id cgroup_fs_context_free() even if ret isn't zero here.

I look at do_new_mount()

vfs_new_fs_context()
...
if (vfs_get_tree()) 
	goto out_fc;
....
out_fc:
put_fs_context(fc);
	fc->ops->free(fc);
		cgroup_fs_context_free()
			cgroup_put(&ctx->root->cgrp);

> 
> > 
> > Which version are you testing btw?  The patches in git have been fixed a
> > little from what was last posted.
> 
> I'm testing linux-next-20180621
> 
> commit 8439c34f07a3f58245e933ca2703239417288363 (tag: next-20180621,
> linux-next/master)
> Author: Stephen Rothwell <sfr@...b.auug.org.au>
> Date:   Thu Jun 21 14:09:41 2018 +1000
> 
>     Add linux-next specific files for 20180621
>     
>     Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
> 
> > 
> > David