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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 09F4FC43141 for ; Mon, 18 Nov 2019 12:02:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E06A22084D for ; Mon, 18 Nov 2019 12:01:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727128AbfKRMB0 (ORCPT ); Mon, 18 Nov 2019 07:01:26 -0500 Received: from mx2.suse.de ([195.135.220.15]:37228 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726506AbfKRMBX (ORCPT ); Mon, 18 Nov 2019 07:01:23 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 956F2B021; Mon, 18 Nov 2019 12:01:20 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 2A7271E4AF8; Mon, 18 Nov 2019 10:46:04 +0100 (CET) Date: Mon, 18 Nov 2019 10:46:04 +0100 From: Jan Kara To: John Hubbard Cc: Andrew Morton , Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Christoph Hellwig , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?iso-8859-1?B?Suly9G1l?= Glisse , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , bpf@vger.kernel.org, dri-devel@lists.freedesktop.org, kvm@vger.kernel.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-mm@kvack.org, LKML , Christoph Hellwig , "Aneesh Kumar K . V" Subject: Re: [PATCH v5 02/24] mm/gup: factor out duplicate code from four routines Message-ID: <20191118094604.GC17319@quack2.suse.cz> References: <20191115055340.1825745-1-jhubbard@nvidia.com> <20191115055340.1825745-3-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20191115055340.1825745-3-jhubbard@nvidia.com> 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 Thu 14-11-19 21:53:18, John Hubbard wrote: > There are four locations in gup.c that have a fair amount of code > duplication. This means that changing one requires making the same > changes in four places, not to mention reading the same code four > times, and wondering if there are subtle differences. > > Factor out the common code into static functions, thus reducing the > overall line count and the code's complexity. > > Also, take the opportunity to slightly improve the efficiency of the > error cases, by doing a mass subtraction of the refcount, surrounded > by get_page()/put_page(). > > Also, further simplify (slightly), by waiting until the the successful > end of each routine, to increment *nr. > > Reviewed-by: Jérôme Glisse > Cc: Jan Kara > Cc: Ira Weiny > Cc: Christoph Hellwig > Cc: Aneesh Kumar K.V > Signed-off-by: John Hubbard > --- > mm/gup.c | 95 ++++++++++++++++++++++++-------------------------------- > 1 file changed, 40 insertions(+), 55 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 85caf76b3012..858541ea30ce 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1969,6 +1969,29 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr, > } > #endif > > +static int __record_subpages(struct page *page, unsigned long addr, > + unsigned long end, struct page **pages) > +{ > + int nr = 0; > + int nr_recorded_pages = 0; > + > + do { > + pages[nr] = page; > + nr++; > + page++; > + nr_recorded_pages++; > + } while (addr += PAGE_SIZE, addr != end); > + return nr_recorded_pages; nr == nr_recorded_pages so no need for both... BTW, structuring this as a for loop would be probably more logical and shorter now: for (nr = 0; addr != end; addr += PAGE_SIZE) pages[nr++] = page++; return nr; The rest of the patch looks good to me. Honza -- Jan Kara SUSE Labs, CR