linux-kernel - Re: [PATCH net] net: mvpp2: debugfs: fix problem with previous memory leak fix

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Message-ID: <CAPv3WKcEa69vhrfE9h2XeuckDjvB=Y-HT7Y3fjV1W6gqYRmyjw@mail.gmail.com>
Date:   Sun, 25 Sep 2022 01:27:06 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, stable <stable@...nel.org>
Subject: Re: [PATCH net] net: mvpp2: debugfs: fix problem with previous memory
 leak fix

Hi Russell,

czw., 22 wrz 2022 o 19:08 Marcin Wojtas <mw@...ihalf.com> napisał(a):
>
> Hi,
>
> Thank you both for the patches.
>
>
> czw., 22 wrz 2022 o 18:05 Russell King (Oracle)
> <linux@...linux.org.uk> napisał(a):
> >
> > On Wed, Sep 21, 2022 at 01:44:44PM +0200, Greg Kroah-Hartman wrote:
> > > In commit fe2c9c61f668 ("net: mvpp2: debugfs: fix memory leak when using
> > > debugfs_lookup()"), if the module is unloaded, the directory will still
> > > be present if the module is loaded again and creating the directory will
> > > fail, causing the creation of additional child debugfs entries for the
> > > individual devices to fail.
> > >
> > > As this module never cleaned up the root directory it created, even when
> > > loaded, and unloading/loading a module is not a normal operation, none
> > > of would normally happen.
> > >
> > > To clean all of this up, use a tiny reference counted structure to hold
> > > the root debugfs directory for the driver, and then clean it up when the
> > > last user of it is removed from the system.  This should resolve the
> > > previously reported problems, and the original memory leak that
> > > fe2c9c61f668 ("net: mvpp2: debugfs: fix memory leak when using
> > > debugfs_lookup()") was attempting to fix.
> >
> > For the record... I have a better fix for this, but I haven't been able
> > to get it into a state suitable for submission yet.
> >
> > http://www.home.armlinux.org.uk/~rmk/misc/mvpp2-debugfs.diff
> >
> > Not yet against the net tree. Might have time tomorrow to do that, not
> > sure at the moment. Medical stuff is getting in the way. :(
> >
>
> I'd lean towards this version - it is a bit more compact. I'll try to
> test that tomorrow or during the weekend.
>

I improved the patch compile and work (tested on my CN913x board).
Feel free to submit (if you wish, I can do it too - please let me know
your preference):
https://github.com/semihalf-wojtas-marcin/Linux-Kernel/commit/0abb75115ffb2772f595bb3346573e27e650018b

Best regards,
Marcin