On (15/11/07 02:32), Andrew Morton didst pronounce:
I know the __init is meaningless in this context. It is there as a guide
if someone decides to drop the inline for some reason that it should
remain as __init. I can post a version with just the inline.
It's never used so it could have been anything and still compiled. I admit
this is confusing. I've posted a version below that changes this to a static
inline, returns MAX_ORDER-1 which is a sensible value even if unused and
comments on what is happening.
Understood. Here is an updated version. It is functionally equivilant to
the earlier patch but may be easier on the eye
===
Ordinarily the size of a pageblock is determined at compile-time based on the
hugepage size. On PPC64, the hugepage size is determined at runtime based on
what is supported by the machine. With legacy machines such as iSeries that
do not support hugepages, HPAGE_SHIFT is 0. This results in pageblock_order
being set to -PAGE_SHIFT and a crash results shortly afterwards.
This patch adds a function to select a sensible value for pageblock order by
default when HUGETLB_PAGE_SIZE_VARIABLE is set. It checks that HPAGE_SHIFT
is a sensible value before using the hugepage size; if it is not MAX_ORDER-1
is used.
This is a fix for 2.6.24.
Credit goes to Stephen Rothwell for identifying the bug and testing candidate
patches. Additional credit goes to Andy Whitcroft for spotting a problem
with respects to IA-64 before releasing. Additional credit to David Gibson
for testing with the libhugetlbfs test suite.
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
arch/powerpc/Kconfig | 5 +++++
mm/page_alloc.c | 23 +++++++++++++++++++++--
2 files changed, 26 insertions(+), 2 deletions(-)
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-clean/arch/powerpc/Kconfig linux-2.6.24-rc2-mm1-varpage-fix/arch/powerpc/Kconfig
--- linux-2.6.24-rc2-mm1-clean/arch/powerpc/Kconfig 2007-11-14 11:38:05.000000000 +0000
+++ linux-2.6.24-rc2-mm1-varpage-fix/arch/powerpc/Kconfig 2007-11-15 10:44:38.000000000 +0000
@@ -187,6 +187,11 @@ config FORCE_MAX_ZONEORDER
default "9" if PPC_64K_PAGES
default "13"
+config HUGETLB_PAGE_SIZE_VARIABLE
+ bool
+ depends on HUGETLB_PAGE
+ default y
+
config MATH_EMULATION
bool "Math emulation"
depends on 4xx || 8xx || E200 || PPC_MPC832x || E500
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-clean/mm/page_alloc.c linux-2.6.24-rc2-mm1-varpage-fix/mm/page_alloc.c
--- linux-2.6.24-rc2-mm1-clean/mm/page_alloc.c 2007-11-14 11:38:08.000000000 +0000
+++ linux-2.6.24-rc2-mm1-varpage-fix/mm/page_alloc.c 2007-11-15 11:01:13.000000000 +0000
@@ -3342,6 +3342,16 @@ static void inline setup_usemap(struct p
#endif /* CONFIG_SPARSEMEM */
#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
+
+/* Return a sensible default order for the pageblock size. */
+static inline int pageblock_default_order(void)
+{
+ if (HPAGE_SHIFT > PAGE_SHIFT)
+ return HUGETLB_PAGE_ORDER;
+
+ return MAX_ORDER-1;
+}
+
/* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
static inline void __init set_pageblock_order(unsigned int order)
{
@@ -3357,7 +3367,16 @@ static inline void __init set_pageblock_
}
#else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
-/* Defined this way to avoid accidently referencing HUGETLB_PAGE_ORDER */
+/*
+ * When CONFIG_HUGETLB_PAGE_SIZE_VARIABLE is not set, set_pageblock_order()
+ * and pageblock_default_order() are unused as pageblock_order is set
+ * at compile-time. See include/linux/pageblock-flags.h for the values of
+ * pageblock_order based on the kernel config
+ */
+static inline int pageblock_default_order(unsigned int order)
+{
+ return MAX_ORDER-1;
+}
#define set_pageblock_order(x) do {} while (0)
#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
@@ -3442,7 +3461,7 @@ static void __meminit free_area_init_cor
if (!size)
continue;
- set_pageblock_order(HUGETLB_PAGE_ORDER);
+ set_pageblock_order(pageblock_default_order());
setup_usemap(pgdat, zone, size);
ret = init_currently_empty_zone(zone, zone_start_pfn,
size, MEMMAP_EARLY);
--
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
-
