linux-kernel - Re: [PATCH 1/2] kernfs: add kernfs_ops.free operation to free resources tied to the file

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Message-ID: <CAJuCfpGt8Bg1VLkx-aMw7_JTvh=co4QSM9B=fvikp0mQ-6rvjg@mail.gmail.com>
Date:   Mon, 26 Jun 2023 13:39:18 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     gregkh@...uxfoundation.org, peterz@...radead.org,
        lujialin4@...wei.com, lizefan.x@...edance.com, hannes@...xchg.org,
        mingo@...hat.com, ebiggers@...nel.org, oleg@...hat.com,
        akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
        brauner@...nel.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH 1/2] kernfs: add kernfs_ops.free operation to free
 resources tied to the file

On Mon, Jun 26, 2023 at 1:31 PM Tejun Heo <tj@...nel.org> wrote:
>
> On Mon, Jun 26, 2023 at 01:17:12PM -0700, Suren Baghdasaryan wrote:
> > diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> > index 73f5c120def8..a7e404ff31bb 100644
> > --- a/include/linux/kernfs.h
> > +++ b/include/linux/kernfs.h
> > @@ -273,6 +273,11 @@ struct kernfs_ops {
> >        */
> >       int (*open)(struct kernfs_open_file *of);
> >       void (*release)(struct kernfs_open_file *of);
> > +     /*
> > +      * Free resources tied to the lifecycle of the file, like a
> > +      * waitqueue used for polling.
> > +      */
> > +     void (*free)(struct kernfs_open_file *of);
>
> I think this can use a bit more commenting - ie. explain that release may be
> called earlier than the actual freeing of the file and how that can lead to
> problems. Othre than that, looks fine to me.

Sure, once I get more feedback I'll post the next version with
expanded description.
Thanks!

>
> Greg, as Suren suggested, I can route both patches through the cgroup tree
> if you're okay with it.
>
> Thanks.
>
> --
> tejun