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=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 DFD89C432C0 for ; Tue, 19 Nov 2019 10:19:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9D7C722303 for ; Tue, 19 Nov 2019 10:19:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D7C722303 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 49CCC6B000A; Tue, 19 Nov 2019 05:19:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 44D8E6B026A; Tue, 19 Nov 2019 05:19:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 315486B026F; Tue, 19 Nov 2019 05:19:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0117.hostedemail.com [216.40.44.117]) by kanga.kvack.org (Postfix) with ESMTP id 1AB3E6B000A for ; Tue, 19 Nov 2019 05:19:17 -0500 (EST) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id C2D8E181AC9CC for ; Tue, 19 Nov 2019 10:19:16 +0000 (UTC) X-FDA: 76172629512.05.face50_6e07024f09d15 X-HE-Tag: face50_6e07024f09d15 X-Filterd-Recvd-Size: 8068 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Tue, 19 Nov 2019 10:19:15 +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 737CFAE87; Tue, 19 Nov 2019 10:19:13 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id D586A1E47E5; Tue, 19 Nov 2019 11:19:10 +0100 (CET) Date: Tue, 19 Nov 2019 11:19:10 +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 v6 02/24] mm/gup: factor out duplicate code from four routines Message-ID: <20191119101910.GC25605@quack2.suse.cz> References: <20191119081643.1866232-1-jhubbard@nvidia.com> <20191119081643.1866232-3-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20191119081643.1866232-3-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 19-11-19 00:16:21, 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: Jan Kara > Cc: Ira Weiny > Cc: Christoph Hellwig > Cc: Aneesh Kumar K.V > Signed-off-by: John Hubbard Looks good to me now! You can add: Reviewed-by: Jan Kara Honza > --- > mm/gup.c | 91 ++++++++++++++++++++++---------------------------------- > 1 file changed, 36 insertions(+), 55 deletions(-) >=20 > diff --git a/mm/gup.c b/mm/gup.c > index 85caf76b3012..f3c7d6625817 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1969,6 +1969,25 @@ 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; > + > + for (nr =3D 0; addr !=3D end; addr +=3D PAGE_SIZE) > + pages[nr++] =3D page++; > + > + return 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); > +} > + > #ifdef CONFIG_ARCH_HAS_HUGEPD > static unsigned long hugepte_addr_end(unsigned long addr, unsigned lon= g end, > unsigned long sz) > @@ -1998,32 +2017,20 @@ static int gup_hugepte(pte_t *ptep, unsigned lo= ng sz, unsigned long addr, > /* hugepages are never "special" */ > VM_BUG_ON(!pfn_valid(pte_pfn(pte))); > =20 > - refs =3D 0; > head =3D pte_page(pte); > - > page =3D head + ((addr & (sz-1)) >> PAGE_SHIFT); > - do { > - VM_BUG_ON(compound_head(page) !=3D head); > - pages[*nr] =3D page; > - (*nr)++; > - page++; > - refs++; > - } while (addr +=3D PAGE_SIZE, addr !=3D end); > + refs =3D __record_subpages(page, addr, end, pages + *nr); > =20 > head =3D try_get_compound_head(head, refs); > - if (!head) { > - *nr -=3D refs; > + if (!head) > return 0; > - } > =20 > if (unlikely(pte_val(pte) !=3D pte_val(*ptep))) { > - /* Could be optimized better */ > - *nr -=3D refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > =20 > + *nr +=3D refs; > SetPageReferenced(head); > return 1; > } > @@ -2071,28 +2078,19 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp= , unsigned long addr, > pages, nr); > } > =20 > - refs =3D 0; > page =3D pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > - do { > - pages[*nr] =3D page; > - (*nr)++; > - page++; > - refs++; > - } while (addr +=3D PAGE_SIZE, addr !=3D end); > + refs =3D __record_subpages(page, addr, end, pages + *nr); > =20 > head =3D try_get_compound_head(pmd_page(orig), refs); > - if (!head) { > - *nr -=3D refs; > + if (!head) > return 0; > - } > =20 > if (unlikely(pmd_val(orig) !=3D pmd_val(*pmdp))) { > - *nr -=3D refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > =20 > + *nr +=3D refs; > SetPageReferenced(head); > return 1; > } > @@ -2114,28 +2112,19 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp= , unsigned long addr, > pages, nr); > } > =20 > - refs =3D 0; > page =3D pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > - do { > - pages[*nr] =3D page; > - (*nr)++; > - page++; > - refs++; > - } while (addr +=3D PAGE_SIZE, addr !=3D end); > + refs =3D __record_subpages(page, addr, end, pages + *nr); > =20 > head =3D try_get_compound_head(pud_page(orig), refs); > - if (!head) { > - *nr -=3D refs; > + if (!head) > return 0; > - } > =20 > if (unlikely(pud_val(orig) !=3D pud_val(*pudp))) { > - *nr -=3D refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > =20 > + *nr +=3D refs; > SetPageReferenced(head); > return 1; > } > @@ -2151,28 +2140,20 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp= , unsigned long addr, > return 0; > =20 > BUILD_BUG_ON(pgd_devmap(orig)); > - refs =3D 0; > + > page =3D pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); > - do { > - pages[*nr] =3D page; > - (*nr)++; > - page++; > - refs++; > - } while (addr +=3D PAGE_SIZE, addr !=3D end); > + refs =3D __record_subpages(page, addr, end, pages + *nr); > =20 > head =3D try_get_compound_head(pgd_page(orig), refs); > - if (!head) { > - *nr -=3D refs; > + if (!head) > return 0; > - } > =20 > if (unlikely(pgd_val(orig) !=3D pgd_val(*pgdp))) { > - *nr -=3D refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > =20 > + *nr +=3D refs; > SetPageReferenced(head); > return 1; > } > --=20 > 2.24.0 >=20 --=20 Jan Kara SUSE Labs, CR