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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 715E7C43218 for ; Sun, 28 Apr 2019 15:41:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4BDE62067C for ; Sun, 28 Apr 2019 15:41:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726893AbfD1PlG (ORCPT ); Sun, 28 Apr 2019 11:41:06 -0400 Received: from mga07.intel.com ([134.134.136.100]:23705 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726801AbfD1PlF (ORCPT ); Sun, 28 Apr 2019 11:41:05 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Apr 2019 08:41:05 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,406,1549958400"; d="scan'208";a="138181779" Received: from smile.fi.intel.com (HELO smile) ([10.237.72.86]) by orsmga008.jf.intel.com with ESMTP; 28 Apr 2019 08:41:00 -0700 Received: from andy by smile with local (Exim 4.92) (envelope-from ) id 1hKlvF-0005io-ED; Sun, 28 Apr 2019 18:40:57 +0300 Date: Sun, 28 Apr 2019 18:40:57 +0300 From: Andy Shevchenko To: Yury Norov Cc: Andrew Morton , Rasmus Villemoes , Dmitry Torokhov , "David S . Miller" , Stephen Rothwell , Amritha Nambiar , Willem de Bruijn , Kees Cook , Matthew Wilcox , "Tobin C . Harding" , Will Deacon , Miklos Szeredi , Vineet Gupta , Chris Wilson , Arnaldo Carvalho de Melo , Yury Norov , linux-kernel@vger.kernel.org, Jens Axboe , Steffen Klassert Subject: Re: [PATCH 0/4] lib: rework bitmap_parse Message-ID: <20190428154057.GS9224@smile.fi.intel.com> References: <20190428032936.1317-1-ynorov@marvell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190428032936.1317-1-ynorov@marvell.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 27, 2019 at 08:29:30PM -0700, Yury Norov wrote: > On top of next-20190418. > > Similarly to recently revisited bitmap_parselist() [1], > bitmap_parse() is ineffective and overcomplicated. This > series reworks it, aligns its interface with bitmap_parselist() > and makes usage simpler. > > The series also adds a test for the function and fixes usage of it > in cpumask_parse() according to new design - drops the calculating > of length of an input string. > > The following users would also consider to drop the length argument, > if possible: > drivers/block/drbd/drbd_main.c:2608 > kernel/padata.c:924 > net/core/net-sysfs.c:726 > net/core/net-sysfs.c:1309 > net/core/net-sysfs.c:1391 > > bitmap_parse() takes the array of numbers to be put into the map in > the BE order which is reversed to the natural LE order for bitmaps. > For example, to construct bitmap containing a bit on the position 42, > we have to put a line '400,0'. Current implementation reads chunk > one by one from the beginning ('400' before '0') and makes bitmap > shift after each successful parse. It makes the complexity of the > whole process as O(n^2). We can do it in reverse direction ('0' > before '400') and avoid shifting, but it requires reverse parsing > helpers. Shouldn't test ceases pass on existing code base? I would rather start series with enabling tests and then we will have a proof that before and after at least tests have not been broken. > > Tested on arm64 and BE mips. > > [1] https://lkml.org/lkml/2019/4/16/66 > > Yury Norov (6): > lib/string: add strnchrnul() > bitops: more BITS_TO_* macros > lib/bitmap: make bitmap_parse_user a wrapper on bitmap_parse > lib: rework bitmap_parse() > lib: add test for bitmap_parse() > cpumask: don't calculate length of the input string > > include/linux/bitmap.h | 8 +- > include/linux/bitops.h | 3 + > include/linux/cpumask.h | 4 +- > include/linux/string.h | 3 + > lib/bitmap.c | 197 +++++++++++++++++------------------ > lib/string.c | 20 ++++ > lib/test_bitmap.c | 102 +++++++++++++++++- > tools/include/linux/bitops.h | 9 +- > 8 files changed, 230 insertions(+), 116 deletions(-) > > -- > 2.17.1 > -- With Best Regards, Andy Shevchenko