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, USER_AGENT_SANE_1 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 3A994C17442 for ; Wed, 13 Nov 2019 11:15:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 01DB8222D0 for ; Wed, 13 Nov 2019 11:15:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01DB8222D0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8DA006B0005; Wed, 13 Nov 2019 06:15:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 88BB56B0006; Wed, 13 Nov 2019 06:15:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7523E6B0007; Wed, 13 Nov 2019 06:15:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0210.hostedemail.com [216.40.44.210]) by kanga.kvack.org (Postfix) with ESMTP id 602286B0005 for ; Wed, 13 Nov 2019 06:15:26 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 08E9D180AD82F for ; Wed, 13 Nov 2019 11:15:26 +0000 (UTC) X-FDA: 76150998252.28.coat81_6992e58914820 X-HE-Tag: coat81_6992e58914820 X-Filterd-Recvd-Size: 4738 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Wed, 13 Nov 2019 11:15:25 +0000 (UTC) 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 69351B4F8; Wed, 13 Nov 2019 11:15:23 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id D45001E1498; Wed, 13 Nov 2019 12:15:21 +0100 (CET) Date: Wed, 13 Nov 2019 12:15:21 +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 v4 02/23] mm/gup: factor out duplicate code from four routines Message-ID: <20191113111521.GI6367@quack2.suse.cz> References: <20191113042710.3997854-1-jhubbard@nvidia.com> <20191113042710.3997854-3-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20191113042710.3997854-3-jhubbard@nvidia.com> User-Agent: Mutt/1.10.1 (2018-07-13) Content-Transfer-Encoding: quoted-printable 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 Tue 12-11-19 20:26:49, 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. >=20 > Factor out the common code into static functions, thus reducing the > overall line count and the code's complexity. >=20 > 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(). >=20 > Also, further simplify (slightly), by waiting until the the successful > end of each routine, to increment *nr. >=20 > Reviewed-by: J=E9r=F4me Glisse > Cc: Ira Weiny > Cc: Christoph Hellwig > Cc: Aneesh Kumar K.V > Signed-off-by: John Hubbard > diff --git a/mm/gup.c b/mm/gup.c > index 85caf76b3012..199da99e8ffc 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1969,6 +1969,34 @@ static int __gup_device_huge_pud(pud_t pud, pud_= t *pudp, unsigned long addr, > } > #endif > =20 > +static int __record_subpages(struct page *page, unsigned long addr, > + unsigned long end, struct page **pages, int nr) > +{ > + int nr_recorded_pages =3D 0; > + > + do { > + pages[nr] =3D page; > + nr++; > + page++; > + nr_recorded_pages++; > + } while (addr +=3D PAGE_SIZE, addr !=3D end); > + return nr_recorded_pages; > +} Why don't you pass in already pages + nr? > + > +static void put_compound_head(struct page *page, int refs) > +{ > + /* Do a get_page() first, in case refs =3D=3D page->_refcount */ > + get_page(page); > + page_ref_sub(page, refs); > + put_page(page); > +} > + > +static void __huge_pt_done(struct page *head, int nr_recorded_pages, i= nt *nr) > +{ > + *nr +=3D nr_recorded_pages; > + SetPageReferenced(head); > +} I don't find this last helper very useful. It seems to muddy water more than necessary... Other than that the cleanup looks nice to me. Honza --=20 Jan Kara SUSE Labs, CR