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Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lgPH9-009SUD-E2 for linux-arm-kernel@lists.infradead.org; Tue, 11 May 2021 10:06:04 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6326C61925; Tue, 11 May 2021 10:05:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1620727563; bh=LE00JXn6JpyvcSFw6kRi1i0Orit+XbdWVHE/yEogFnA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DyQ3OZvSpvBGY8GWhx+paJ4GHTInjnncZyvBdLrzCeKw+tVJD/bre4JHwued/V+XH TrQwMGnvKv4QIh1VTrIT2Tui+R1GRR1oW0XGi5NylsraCRFzTSID4lWjqzWgaUKmIb pgnutv8LqAga8qZgOwP5UgZPNwT4TkuUMdV2/vsZNoX9x7qzae9FZVULOHeSq4MVJh Md+dGyBByx6uf+FfwitOYmGNcjWr//k6PF79Wkn3PglNUW0td2CnHm3N4gnEy0o3DY 0zLd/vZ+ezusbAInkkIU3sYTQSvObfmfWj+9N9MzhUVstJoyabmNpnl+dPMXOOD43M oYcU4Kocv97RA== From: Mike Rapoport To: Andrew Morton Cc: Anshuman Khandual , Ard Biesheuvel , Catalin Marinas , David Hildenbrand , Marc Zyngier , Mark Rutland , Mike Rapoport , Mike Rapoport , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 1/4] include/linux/mmzone.h: add documentation for pfn_valid() Date: Tue, 11 May 2021 13:05:47 +0300 Message-Id: <20210511100550.28178-2-rppt@kernel.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20210511100550.28178-1-rppt@kernel.org> References: <20210511100550.28178-1-rppt@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210511_030603_523991_1FA2967E X-CRM114-Status: GOOD ( 12.47 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 Acked-by: Ard Biesheuvel --- include/linux/mmzone.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 0d53eba1c383..e5945ca24df7 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1427,6 +1427,17 @@ 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;