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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 3D29CC433B4 for ; Wed, 21 Apr 2021 10:48:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0304A61447 for ; Wed, 21 Apr 2021 10:48:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235178AbhDUKtI (ORCPT ); Wed, 21 Apr 2021 06:49:08 -0400 Received: from foss.arm.com ([217.140.110.172]:59128 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230259AbhDUKtH (ORCPT ); Wed, 21 Apr 2021 06:49:07 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1C4FA113E; Wed, 21 Apr 2021 03:48:34 -0700 (PDT) Received: from [10.163.74.228] (unknown [10.163.74.228]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A00AE3F73B; Wed, 21 Apr 2021 03:48:29 -0700 (PDT) From: Anshuman Khandual Subject: Re: [PATCH v2 1/4] include/linux/mmzone.h: add documentation for pfn_valid() To: Mike Rapoport , linux-arm-kernel@lists.infradead.org Cc: Andrew Morton , Ard Biesheuvel , Catalin Marinas , David Hildenbrand , Marc Zyngier , Mark Rutland , Mike Rapoport , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210421065108.1987-1-rppt@kernel.org> <20210421065108.1987-2-rppt@kernel.org> Message-ID: Date: Wed, 21 Apr 2021 16:19:15 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210421065108.1987-2-rppt@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/21/21 12:21 PM, Mike Rapoport wrote: > From: Mike Rapoport > > Add comment describing the semantics of pfn_valid() that clarifies that > pfn_valid() only checks for availability of a memory map entry (i.e. struct > page) for a PFN rather than availability of usable memory backing that PFN. > > The most "generic" version of pfn_valid() used by the configurations with > SPARSEMEM enabled resides in include/linux/mmzone.h so this is the most > suitable place for documentation about semantics of pfn_valid(). > > Suggested-by: Anshuman Khandual > Signed-off-by: Mike Rapoport Reviewed-by: Anshuman Khandual > --- > include/linux/mmzone.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 47946cec7584..961f0eeefb62 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1410,6 +1410,17 @@ static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn) > #endif > > #ifndef CONFIG_HAVE_ARCH_PFN_VALID > +/** > + * pfn_valid - check if there is a valid memory map entry for a PFN > + * @pfn: the page frame number to check > + * > + * Check if there is a valid memory map entry aka struct page for the @pfn. > + * Note, that availability of the memory map entry does not imply that > + * there is actual usable memory at that @pfn. The struct page may > + * represent a hole or an unusable page frame. > + * > + * Return: 1 for PFNs that have memory map entries and 0 otherwise > + */ > static inline int pfn_valid(unsigned long pfn) > { > struct mem_section *ms; >