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Thu, 19 Mar 2020 21:51:28 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 19 Mar 2020 14:49:48 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 19 Mar 2020 14:51:27 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 19 Mar 2020 14:51:27 -0700 Received: from [10.2.57.192] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 19 Mar 2020 21:51:26 +0000 Subject: Re: [PATCHv6 1/3] mm/gup: rename nr as nr_pinned in get_user_pages_fast() To: Pingfan Liu , CC: Ira Weiny , Andrew Morton , Mike Rapoport , Dan Williams , Matthew Wilcox , Aneesh Kumar K.V , Christoph Hellwig , Shuah Khan , References: <1584333244-10480-1-git-send-email-kernelfans@gmail.com> <1584333244-10480-2-git-send-email-kernelfans@gmail.com> From: John Hubbard X-Nvconfidentiality: public Message-ID: Date: Thu, 19 Mar 2020 14:51:26 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <1584333244-10480-2-git-send-email-kernelfans@gmail.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1584654589; bh=aNwT0rnAdur+Xm0ZOCaKajCmnsKnwTUwOTyCXrOJe5k=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=eQxQss1cnwvTesj1+v6b1PsHcJsauNOq0+bfVM6SFlpXbIgd01zqkJBuk6ednkT3Q IuabKgEbo6CIewJx/f7N98ACzzv3HSEEj5rNXXB/nVC8XSnH+r/4334Tf0Xv7C9udq iG9/yAI66fUtwzQGx3gkyJDi4a2sJxrIYY5UnEIo9TjPhL3tR+IVO3PcAUTjdVMCUb ee2p3ViBFfD+n79uvS+RstNrJt4ErNWqF2hXa0sh0sY3Qo1Gkvl5jajw1FRKDMThIy nNDHlfTDHuEVwGGhZhIx7J+k0VS5fwkEFw13enVwjImjdoRHz/4tx+iLVub232kdky luCRG16D1NRWQ== 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 3/15/20 9:34 PM, Pingfan Liu wrote: > To better reflect the held state of pages and make code > self-explaining, rename nr as nr_pinned. > > Signed-off-by: Pingfan Liu Cc: Ira Weiny > Cc: Andrew Morton > Cc: Mike Rapoport Cc: Dan Williams > Cc: Matthew Wilcox > Cc: John Hubbard Cc: "Aneesh Kumar K.V" > Cc: Christoph Hellwig > Cc: Shuah Khan To: > linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- mm/gup.c | 20 > ++++++++++---------- 1 file changed, 10 insertions(+), 10 > deletions(-) > Hi Pingfan, This is correct as far as it goes, but it doesn't go quite far enough. This should at least should cover the other caller of gup_pgd_range(). Background: There are two internal-to-gup.c entry points to gup fast: internal_get_user_pages_fast(), and __get_user_pages_fast(). Quite commonly when submitting fixes to one of these functions, the other is overlooked, as happened here. Here's a diff on top of your patch, that I think should be squashed into your patch: diff --git a/mm/gup.c b/mm/gup.c index d0c0d084e792..56052b73abc3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2676,7 +2676,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, { unsigned long len, end; unsigned long flags; - int nr = 0; + int nr_pinned = 0; /* * Internally (within mm/gup.c), gup fast variants must set FOLL_GET, * because gup fast is always a "pin with a +1 page refcount" request. @@ -2710,11 +2710,11 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) { local_irq_save(flags); - gup_pgd_range(start, end, gup_flags, pages, &nr); + gup_pgd_range(start, end, gup_flags, pages, &nr_pinned); local_irq_restore(flags); } - return nr; + return nr_pinned; } EXPORT_SYMBOL_GPL(__get_user_pages_fast); With that applied, you can add: Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > diff --git a/mm/gup.c b/mm/gup.c index e8aaa40..9df77b1 100644 --- > a/mm/gup.c +++ b/mm/gup.c @@ -2735,7 +2735,7 @@ static int > internal_get_user_pages_fast(unsigned long start, int nr_pages, > struct page **pages) { unsigned long addr, len, end; - int nr = 0, > ret = 0; + int nr_pinned = 0, ret = 0; > > if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | > FOLL_FORCE | FOLL_PIN | FOLL_GET))) @@ -2754,25 +2754,25 @@ static > int internal_get_user_pages_fast(unsigned long start, int nr_pages, > if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, > end)) { local_irq_disable(); - gup_pgd_range(addr, end, gup_flags, > pages, &nr); + gup_pgd_range(addr, end, gup_flags, pages, > &nr_pinned); local_irq_enable(); - ret = nr; + ret = nr_pinned; } > > - if (nr < nr_pages) { + if (nr_pinned < nr_pages) { /* Try to get > the remaining pages with get_user_pages */ - start += nr << > PAGE_SHIFT; - pages += nr; + start += nr_pinned << PAGE_SHIFT; + > pages += nr_pinned; > > - ret = __gup_longterm_unlocked(start, nr_pages - nr, + ret = > __gup_longterm_unlocked(start, nr_pages - nr_pinned, gup_flags, > pages); > > /* Have to be a bit careful with return values */ - if (nr > 0) { + > if (nr_pinned > 0) { if (ret < 0) - ret = nr; + ret = > nr_pinned; else - ret += nr; + ret += nr_pinned; } } > > -- 2.7.5 >