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authorMike Rapoport <rppt@linux.ibm.com>2021-07-01 04:51:13 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-07-01 06:47:29 +0300
commit51c656aef629bae94f2b07fcee7eabe280b905ea (patch)
treeea21617e8fb1f9938495cbb169f121e51aa30fee /include/linux/mmzone.h
parent269fbe72cded0afce0090103e90d2ae8ef8ac5b5 (diff)
downloadlinux-51c656aef629bae94f2b07fcee7eabe280b905ea.tar.xz
include/linux/mmzone.h: add documentation for pfn_valid()
Patch series "arm64: drop pfn_valid_within() and simplify pfn_valid()", v4. These patches aim to remove CONFIG_HOLES_IN_ZONE and essentially hardwire pfn_valid_within() to 1. The idea is to mark NOMAP pages as reserved in the memory map and restore the intended semantics of pfn_valid() to designate availability of struct page for a pfn. With this the core mm will be able to cope with the fact that it cannot use NOMAP pages and the holes created by NOMAP ranges within MAX_ORDER blocks will be treated correctly even without the need for pfn_valid_within. This patch (of 4): 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(). Link: https://lkml.kernel.org/r/20210511100550.28178-1-rppt@kernel.org Link: https://lkml.kernel.org/r/20210511100550.28178-2-rppt@kernel.org Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Suggested-by: Anshuman Khandual <anshuman.khandual@arm.com> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mike Rapoport <rppt@linux.ibm.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mmzone.h')
-rw-r--r--include/linux/mmzone.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 265a32e1ff74..7da43337ad23 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1445,6 +1445,17 @@ 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;