The patch titled
mm: skip memory holes in FLATMEM when reading /proc/pagetypeinfo
has been removed from the -mm tree. Its filename was
mm-skip-memory-holes-in-flatmem-when-reading-proc-pagetypeinfo.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: mm: skip memory holes in FLATMEM when reading /proc/pagetypeinfo
From: Mel Gorman <mel@xxxxxxxxx>
Fixes an oops on arm.
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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
Tested-by: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx> [2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm/Kconfig | 5 +++++
mm/vmstat.c | 19 ++++++++++++++++++-
2 files changed, 23 insertions(+), 1 deletion(-)
diff -puN arch/arm/Kconfig~mm-skip-memory-holes-in-flatmem-when-reading-proc-pagetypeinfo arch/arm/Kconfig
--- a/arch/arm/Kconfig~mm-skip-memory-holes-in-flatmem-when-reading-proc-pagetypeinfo
+++ a/arch/arm/Kconfig
@@ -810,6 +810,11 @@ 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
+ bool
+ default y
+ depends on FLATMEM
+
config ARCH_DISCONTIGMEM_ENABLE
bool
default (ARCH_LH7A40X && !LH7A40X_CONTIGMEM)
diff -puN mm/vmstat.c~mm-skip-memory-holes-in-flatmem-when-reading-proc-pagetypeinfo mm/vmstat.c
--- a/mm/vmstat.c~mm-skip-memory-holes-in-flatmem-when-reading-proc-pagetypeinfo
+++ a/mm/vmstat.c
@@ -516,9 +516,26 @@ static void pagetypeinfo_showblockcount_
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)
+ continue;
+#endif
mtype = get_pageblock_migratetype(page);
- count[mtype]++;
+ if (mtype < MIGRATE_TYPES)
+ count[mtype]++;
}
/* Print counts */
_
Patches currently in -mm which might be from mel@xxxxxxxxx are
mm-make-setup_zone_migrate_reserve-aware-of-overlapping-nodes.patch
linux-next.patch
mm-page_allocc-free_area_init_nodes-fix-inappropriate-use-of-enum.patch
page-owner-tracking-leak-detector.patch
add-debugging-aid-for-memory-initialisation-problems.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
