[PATCH 03/11] mm: mmzone: introduce zone_pfn_same_memmap()
From: m.szyprowski@samsung.com (Marek Szyprowski)
Date: 2011-11-18 16:43:26
Also in:
linux-media, linux-mm, lkml
Subsystem:
memory management, memory management - core, memory management - mglru (multi-gen lru), memory management - page allocator, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Vlastimil Babka, Linus Torvalds
From: Michal Nazarewicz <redacted> This commit introduces zone_pfn_same_memmap() function which checkes whether two PFNs within the same zone have struct pages within the same memmap. This check is needed because in general pointer arithmetic on struct pages may lead to invalid pointers. On memory models that are not affected, zone_pfn_same_memmap() is defined as always returning true so the call should be optimised at compile time. Signed-off-by: Michal Nazarewicz <redacted> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- include/linux/mmzone.h | 16 ++++++++++++++++ mm/compaction.c | 5 ++++- 2 files changed, 20 insertions(+), 1 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 188cb2f..84e07d0 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h@@ -1166,6 +1166,22 @@ static inline int memmap_valid_within(unsigned long pfn, } #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */ +#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) +/* + * Both PFNs must be from the same zone! If this function returns + * true, pfn_to_page(pfn1) + (pfn2 - pfn1) == pfn_to_page(pfn2). + */ +static inline bool zone_pfn_same_memmap(unsigned long pfn1, unsigned long pfn2) +{ + return pfn_to_section_nr(pfn1) == pfn_to_section_nr(pfn2); +} + +#else + +#define zone_pfn_same_memmap(pfn1, pfn2) (true) + +#endif + #endif /* !__GENERATING_BOUNDS.H */ #endif /* !__ASSEMBLY__ */ #endif /* _LINUX_MMZONE_H */
diff --git a/mm/compaction.c b/mm/compaction.c
index 6afae0e..09c9702 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c@@ -111,7 +111,10 @@ skip: next: pfn += isolated; - page += isolated; + if (zone_pfn_same_memmap(pfn - isolated, pfn)) + page += isolated; + else + page = pfn_to_page(pfn); } trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
--
1.7.1.569.g6f426