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 B27E1C432C3 for ; Tue, 19 Nov 2019 10:19:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9504622304 for ; Tue, 19 Nov 2019 10:19:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727646AbfKSKTS (ORCPT ); Tue, 19 Nov 2019 05:19:18 -0500 Received: from mx2.suse.de ([195.135.220.15]:49868 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726555AbfKSKTS (ORCPT ); Tue, 19 Nov 2019 05:19:18 -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 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 Content-Transfer-Encoding: 8bit In-Reply-To: <20191119081643.1866232-3-jhubbard@nvidia.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org 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. > > 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 Looks good to me now! You can add: Reviewed-by: Jan Kara Honza > --- > mm/gup.c | 91 ++++++++++++++++++++++---------------------------------- > 1 file changed, 36 insertions(+), 55 deletions(-) > > 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 > > +static int __record_subpages(struct page *page, unsigned long addr, > + unsigned long end, struct page **pages) > +{ > + int nr; > + > + for (nr = 0; addr != end; addr += PAGE_SIZE) > + pages[nr++] = page++; > + > + return nr; > +} > + > +static void put_compound_head(struct page *page, int refs) > +{ > + /* Do a get_page() first, in case refs == 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 long end, > unsigned long sz) > @@ -1998,32 +2017,20 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, > /* hugepages are never "special" */ > VM_BUG_ON(!pfn_valid(pte_pfn(pte))); > > - refs = 0; > head = pte_page(pte); > - > page = head + ((addr & (sz-1)) >> PAGE_SHIFT); > - do { > - VM_BUG_ON(compound_head(page) != head); > - pages[*nr] = page; > - (*nr)++; > - page++; > - refs++; > - } while (addr += PAGE_SIZE, addr != end); > + refs = __record_subpages(page, addr, end, pages + *nr); > > head = try_get_compound_head(head, refs); > - if (!head) { > - *nr -= refs; > + if (!head) > return 0; > - } > > if (unlikely(pte_val(pte) != pte_val(*ptep))) { > - /* Could be optimized better */ > - *nr -= refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > > + *nr += 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); > } > > - refs = 0; > page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > - do { > - pages[*nr] = page; > - (*nr)++; > - page++; > - refs++; > - } while (addr += PAGE_SIZE, addr != end); > + refs = __record_subpages(page, addr, end, pages + *nr); > > head = try_get_compound_head(pmd_page(orig), refs); > - if (!head) { > - *nr -= refs; > + if (!head) > return 0; > - } > > if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { > - *nr -= refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > > + *nr += 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); > } > > - refs = 0; > page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > - do { > - pages[*nr] = page; > - (*nr)++; > - page++; > - refs++; > - } while (addr += PAGE_SIZE, addr != end); > + refs = __record_subpages(page, addr, end, pages + *nr); > > head = try_get_compound_head(pud_page(orig), refs); > - if (!head) { > - *nr -= refs; > + if (!head) > return 0; > - } > > if (unlikely(pud_val(orig) != pud_val(*pudp))) { > - *nr -= refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > > + *nr += 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; > > BUILD_BUG_ON(pgd_devmap(orig)); > - refs = 0; > + > page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); > - do { > - pages[*nr] = page; > - (*nr)++; > - page++; > - refs++; > - } while (addr += PAGE_SIZE, addr != end); > + refs = __record_subpages(page, addr, end, pages + *nr); > > head = try_get_compound_head(pgd_page(orig), refs); > - if (!head) { > - *nr -= refs; > + if (!head) > return 0; > - } > > if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { > - *nr -= refs; > - while (refs--) > - put_page(head); > + put_compound_head(head, refs); > return 0; > } > > + *nr += refs; > SetPageReferenced(head); > return 1; > } > -- > 2.24.0 > -- Jan Kara SUSE Labs, CR