Re: [PATCH v4 1/4] include/linux/mmzone.h: add documentation for pfn_valid()
From: Ard Biesheuvel <ardb@kernel.org>
Date: 2021-05-11 10:22:58
Also in:
kvmarm, linux-mm, lkml
On Tue, 11 May 2021 at 12:06, Mike Rapoport [off-list ref] wrote:
From: Mike Rapoport <redacted> 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 <redacted> Signed-off-by: Mike Rapoport <redacted> Reviewed-by: Anshuman Khandual <redacted>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
quoted hunk ↗ jump to hunk
--- 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; --2.28.0
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