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

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Date:   Sun, 24 Jun 2018 00:34:36 +0100
From:   David Howells <dhowells@...hat.com>
To:     Andrei Vagin <avagin@...tuozzo.com>
Cc:     dhowells@...hat.com, 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]

Andrei Vagin <avagin@...tuozzo.com> wrote:

> > > >                 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);

Yeah, you're right: ctx->root is set above, so the put will trigger anyway.
I'll fold both of these changes in.

David