From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754894AbcESM0K (ORCPT <rfc822;w@1wt.eu>);
	Thu, 19 May 2016 08:26:10 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:46318 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754430AbcESM0E (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 19 May 2016 08:26:04 -0400
Date: Thu, 19 May 2016 14:25:58 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Darren Hart <darren@dvhart.com>, Ingo Molnar <mingo@kernel.org>,
        Michael Kerrisk <mtk.manpages@googlemail.com>,
        Davidlohr Bueso <dave@stgolabs.net>, Chris Mason <clm@fb.com>,
        "Carlos O'Donell" <carlos@redhat.com>,
        Torvald Riegel <triegel@redhat.com>,
        Eric Dumazet <edumazet@google.com>
Subject: Re: [patch V2 3/7] futex: Add op for hash preallocation
Message-ID: <20160519122558.GC3192@twins.programming.kicks-ass.net>
References: <20160505204230.932454245@linutronix.de>
 <20160505204354.051976225@linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20160505204354.051976225@linutronix.de>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, May 05, 2016 at 08:44:05PM -0000, Thomas Gleixner wrote:
> +static int futex_preallocate_hash(unsigned int slots)
> +{
> +#ifdef CONFIG_FUTEX_PRIVATE_HASH
> +	struct mm_struct *mm = current->mm;
> +	struct futex_hash_bucket *hb;
> +	unsigned int bits;
> +
> +	/* Try to allocate the requested nr of slots */
> +	bits = order_base_2(slots);
> +
> +	if (bits < FUTEX_MIN_HASH_BITS)
> +		bits = FUTEX_MIN_HASH_BITS;
> +
> +	if (bits > futex_max_hash_bits)
> +		bits = futex_max_hash_bits;
> +
> +	futex_populate_hash(bits);

Should we not simply fail if the provided number of slots is not a power
of 2 ?