linux-kernel - Re: [PATCH 3/9] async: Extend kfence to allow struct embedding

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Date:	Wed, 13 Jul 2016 12:31:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	linux-kernel@...r.kernel.org,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Shuah Khan <shuahkh@....samsung.com>,
	Tejun Heo <tj@...nel.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
	"David S. Miller" <davem@...emloft.net>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH 3/9] async: Extend kfence to allow struct embedding

On Fri, Jun 24, 2016 at 10:08:47AM +0100, Chris Wilson wrote:
> @@ -151,7 +161,11 @@ static void kfence_free(struct kref *kref)
>  
>  	WARN_ON(atomic_read(&fence->pending) > 0);
>  
> -	kfree(fence);
> +	if (fence->flags) {
> +		kfence_notify_t fn = (kfence_notify_t)fence->flags;

Maybe provide an inline helper for that conversion and also mask out the
low bits, just to be careful. You're assuming they're not set here,
which seems like a dangerous thing.

> +		fn(fence);
> +	} else
> +		kfree(fence);

Also Codingstyle wants braces on both branches if its on one.