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authorMel Gorman <mel@csn.ul.ie>2008-08-14 06:10:14 -0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2008-08-27 15:09:28 -0400
commite80d6a248298721e0ec2cac150c539d8378577d8 (patch)
tree0ad2112037cc28e3faab41baf2b6ea1851748019 /arch
parentf1bcf7e3e734ea8713e08fbc3409f8bf26ec418f (diff)
[ARM] Skip memory holes in FLATMEM when reading /proc/pagetypeinfo
Ordinarily, memory holes in flatmem still have a valid memmap and is safe to use. However, an architecture (ARM) frees up the memmap backing memory holes on the assumption it is never used. /proc/pagetypeinfo reads the whole range of pages in a zone believing that the memmap is valid and that pfn_valid will return false if it is not. On ARM, freeing the memmap breaks the page->zone linkages even though pfn_valid() returns true and the kernel can oops shortly afterwards due to accessing a bogus struct zone *. This patch lets architectures say when FLATMEM can have holes in the memmap. Rather than an expensive check for valid memory, /proc/pagetypeinfo will confirm that the page linkages are still valid by checking page->zone is still the expected zone. The lookup of page_zone is safe as there is a limited range of memory that is accessed when calling page_zone. Even if page_zone happens to return the correct zone, the impact is that the counters in /proc/pagetypeinfo are slightly off but fragmentation monitoring is unlikely to be relevant on an embedded system. Reported-by: H Hartley Sweeten <hsweeten@visionengravers.com> Signed-off-by: Mel Gorman <mel@csn.ul.ie> Tested-by: H Hartley Sweeten <hsweeten@visionengravers.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/Kconfig5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4b8acd2851f4..70dba1668907 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -810,6 +810,11 @@ config OABI_COMPAT
810 UNPREDICTABLE (in fact it can be predicted that it won't work 810 UNPREDICTABLE (in fact it can be predicted that it won't work
811 at all). If in doubt say Y. 811 at all). If in doubt say Y.
812 812
813config ARCH_FLATMEM_HAS_HOLES
814 bool
815 default y
816 depends on FLATMEM
817
813config ARCH_DISCONTIGMEM_ENABLE 818config ARCH_DISCONTIGMEM_ENABLE
814 bool 819 bool
815 default (ARCH_LH7A40X && !LH7A40X_CONTIGMEM) 820 default (ARCH_LH7A40X && !LH7A40X_CONTIGMEM)