From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F413C43334 for ; Mon, 18 Jul 2022 21:06:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 97C156B0075; Mon, 18 Jul 2022 17:06:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 928C46B0078; Mon, 18 Jul 2022 17:06:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F0746B007B; Mon, 18 Jul 2022 17:06:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 6C76B6B0075 for ; Mon, 18 Jul 2022 17:06:41 -0400 (EDT) Received: from smtpin31.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 30F96EA0 for ; Mon, 18 Jul 2022 21:06:41 +0000 (UTC) X-FDA: 79701454602.31.5D9B883 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf15.hostedemail.com (Postfix) with ESMTP id 12B43A0072 for ; Mon, 18 Jul 2022 21:06:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1658178400; x=1689714400; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=AZnZ+ju1Gy0QlCJrVsdsFb6+tvlthvRhSGGs0i/zWLc=; b=UseLEK6s4yIDKt7w+J0NN3eQePeCV5EnHP7fNyT7WjH135OmOZmJOYb1 ob38BXTJCWU11UAtCljf1rYyrPtxHJzaJ1RjnOeSC1/QTFCo++P0tV6ro SHuuWo3rUPCCHlpNj2dZfhEdviX3xstcNNYnyQHZv73kM66e3prQNV9v1 VXoVyT/NpLzzme0a4S/HWUr4s0+XMrlcU4BX7rtx+8gVo7YGltlYwxbmI 8FylsjzKwyfwzpmwQcVjw1nhN8m9kJv7Li6VFfcqG2aOZQQuNG+HJUqcR wggT7NCP3tr63KNdupFPy7KrJuGCVvbGXf8MYqaoSVR8SXO1gIa/EpJiu g==; X-IronPort-AV: E=McAfee;i="6400,9594,10412"; a="312007387" X-IronPort-AV: E=Sophos;i="5.92,282,1650956400"; d="scan'208";a="312007387" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2022 14:06:38 -0700 X-IronPort-AV: E=Sophos;i="5.92,282,1650956400"; d="scan'208";a="700173485" Received: from smile.fi.intel.com ([10.237.72.54]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2022 14:06:29 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1oDXwe-001OYR-1W; Tue, 19 Jul 2022 00:06:24 +0300 Date: Tue, 19 Jul 2022 00:06:24 +0300 From: Andy Shevchenko To: Yury Norov Cc: linux-kernel@vger.kernel.org, Alexander Lobakin , Alexei Starovoitov , Alexey Klimov , Andrew Morton , Andrii Nakryiko , Ben Segall , Christoph Lameter , Dan Williams , Daniel Borkmann , Daniel Bristot de Oliveira , Dennis Zhou , Dietmar Eggemann , Eric Dumazet , Frederic Weisbecker , Guenter Roeck , Ingo Molnar , Isabella Basso , John Fastabend , Josh Poimboeuf , Juergen Gross , Juri Lelli , KP Singh , Kees Cook , Martin KaFai Lau , Mel Gorman , Miroslav Benes , Nathan Chancellor , "Paul E . McKenney" , Peter Zijlstra , Randy Dunlap , Rasmus Villemoes , Sebastian Andrzej Siewior , Song Liu , Steven Rostedt , Tejun Heo , Thomas Gleixner , Valentin Schneider , Vincent Guittot , Vlastimil Babka , Yonghong Song , linux-mm@kvack.org, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH 02/16] lib/bitmap: don't call bitmap_set() with len == 0 Message-ID: References: <20220718192844.1805158-1-yury.norov@gmail.com> <20220718192844.1805158-3-yury.norov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220718192844.1805158-3-yury.norov@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=UseLEK6s; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf15.hostedemail.com: domain of andriy.shevchenko@linux.intel.com has no SPF policy when checking 192.55.52.88) smtp.mailfrom=andriy.shevchenko@linux.intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658178400; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=PV2vECMosaxS8EX/xlQd16D3MsfmixwCeYPHsXarhuo=; b=BZqWe1utba5rHOmAITwUe49taFKGpUWMtdV0xvi+0s+4pAx4NNSUbk1O4XhmrcoYuBCIJN aJAihHsR7wEwsQJ4Wp9GcgZGCsIQpRy/4KlyFlP4xxnGCIhn7Xu/a/RxlZMlOf1AY3ZV/m erBh4n/7oXJnmHyKw+XfVhCwi3TssPE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658178400; a=rsa-sha256; cv=none; b=H0bZGPjrJ6xSkrPouAuxTpClk3CrLjJzzMGC8ZEvQpijS7VqjoJYMx8zZWvdXjaqiGXpI8 Cn4uCKrGxL6SW66+dqI3OKq78BuUGVyWOHHpxIr0UnH7/cJw3Mok+WaSQqLAV/bqDJaBsX q7qHMC/W4s8lJAYI+FXOpmlivXsHMeI= X-Rspamd-Queue-Id: 12B43A0072 Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=UseLEK6s; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf15.hostedemail.com: domain of andriy.shevchenko@linux.intel.com has no SPF policy when checking 192.55.52.88) smtp.mailfrom=andriy.shevchenko@linux.intel.com X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: dw36odmautoasa3rr3px37aiw8f8pgin X-HE-Tag: 1658178399-454683 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 18, 2022 at 12:28:30PM -0700, Yury Norov wrote: > bitmap_parselist() format allows passing 0-length regions, but because > len == 0 is not covered by small_const_nbits() macro, we have to call > __bitmap_set() and do some prologue calculations just for nothing. ... > static void bitmap_set_region(const struct region *r, unsigned long *bitmap) > { > - unsigned int start; > + unsigned int start, len; > > - for (start = r->start; start <= r->end; start += r->group_len) > - bitmap_set(bitmap, start, min(r->end - start + 1, r->off)); > + for (start = r->start; start <= r->end; start += r->group_len) { > + len = min(r->end - start + 1, r->off); > + if (len > 0) > + bitmap_set(bitmap, start, len); Maybe I'm missing something, but how small_const_nbits() can possible be useful here? I mean in which cases the compiler would be able to prove that len is a const with < sizeof(unsigned long) bits? > + } > } -- With Best Regards, Andy Shevchenko