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-rw-r--r--arch/arm/Kconfig6
-rw-r--r--include/linux/mmzone.h26
-rw-r--r--mm/mmzone.c15
-rw-r--r--mm/vmstat.c19
4 files changed, 48 insertions, 18 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e60ec54df33..9d02cdb15b2 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -273,6 +273,7 @@ config ARCH_EP93XX
select HAVE_CLK
select COMMON_CLKDEV
select ARCH_REQUIRE_GPIOLIB
+ select ARCH_HAS_HOLES_MEMORYMODEL
help
This enables support for the Cirrus EP93xx series of CPUs.
@@ -976,10 +977,9 @@ config OABI_COMPAT
UNPREDICTABLE (in fact it can be predicted that it won't work
at all). If in doubt say Y.
-config ARCH_FLATMEM_HAS_HOLES
+config ARCH_HAS_HOLES_MEMORYMODEL
bool
- default y
- depends on FLATMEM
+ default n
# Discontigmem is deprecated
config ARCH_DISCONTIGMEM_ENABLE
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 186ec6ab334..a47c879e130 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1097,6 +1097,32 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
#define pfn_valid_within(pfn) (1)
#endif
+#ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
+/*
+ * pfn_valid() is meant to be able to tell if a given PFN has valid memmap
+ * associated with it or not. In FLATMEM, it is expected that holes always
+ * have valid memmap as long as there is valid PFNs either side of the hole.
+ * In SPARSEMEM, it is assumed that a valid section has a memmap for the
+ * entire section.
+ *
+ * However, an ARM, and maybe other embedded architectures in the future
+ * free memmap backing holes to save memory on the assumption the memmap is
+ * never used. The page_zone linkages are then broken even though pfn_valid()
+ * returns true. A walker of the full memmap must then do this additional
+ * check to ensure the memmap they are looking at is sane by making sure
+ * the zone and PFN linkages are still valid. This is expensive, but walkers
+ * of the full memmap are extremely rare.
+ */
+int memmap_valid_within(unsigned long pfn,
+ struct page *page, struct zone *zone);
+#else
+static inline int memmap_valid_within(unsigned long pfn,
+ struct page *page, struct zone *zone)
+{
+ return 1;
+}
+#endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */
+
#endif /* !__GENERATING_BOUNDS.H */
#endif /* !__ASSEMBLY__ */
#endif /* _LINUX_MMZONE_H */
diff --git a/mm/mmzone.c b/mm/mmzone.c
index 16ce8b955dc..f5b7d176021 100644
--- a/mm/mmzone.c
+++ b/mm/mmzone.c
@@ -6,6 +6,7 @@
#include <linux/stddef.h>
+#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/module.h>
@@ -72,3 +73,17 @@ struct zoneref *next_zones_zonelist(struct zoneref *z,
*zone = zonelist_zone(z);
return z;
}
+
+#ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
+int memmap_valid_within(unsigned long pfn,
+ struct page *page, struct zone *zone)
+{
+ if (page_to_pfn(page) != pfn)
+ return 0;
+
+ if (page_zone(page) != zone)
+ return 0;
+
+ return 1;
+}
+#endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 66f6130976c..74d66dba0cb 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -509,22 +509,11 @@ static void pagetypeinfo_showblockcount_print(struct seq_file *m,
continue;
page = pfn_to_page(pfn);
-#ifdef CONFIG_ARCH_FLATMEM_HAS_HOLES
- /*
- * Ordinarily, memory holes in flatmem still have a valid
- * memmap for the PFN range. However, an architecture for
- * embedded systems (e.g. ARM) can free up the memmap backing
- * holes to save memory on the assumption the memmap is
- * never used. The page_zone linkages are then broken even
- * though pfn_valid() returns true. Skip the page if the
- * linkages are broken. Even if this test passed, the impact
- * is that the counters for the movable type are off but
- * fragmentation monitoring is likely meaningless on small
- * systems.
- */
- if (page_zone(page) != zone)
+
+ /* Watch for unexpected holes punched in the memmap */
+ if (!memmap_valid_within(pfn, page, zone))
continue;
-#endif
+
mtype = get_pageblock_migratetype(page);
if (mtype < MIGRATE_TYPES)