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SubjectRe: [PATCH] Fix boot problem with iSeries lacking hugepage support
On Thu, 15 Nov 2007 10:13:22 +0000 mel@skynet.ie (Mel Gorman) wrote:

> This patch is a fix for 2.6.24.
>
> 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 becomes 0. This results in pageblock_order
> being set to -PAGE_SHIFT and a crash results shortly afterwards.
>
> This patch sets HUGETLB_PAGE_SIZE_VARIABLE for PPC64 and adds a function
> to select a sensible value for pageblock order by default. It checks that
> HPAGE_SHIFT is a sensible value before using the hugepage size; if it is
> not MAX_ORDER-1 is used.
>
> 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.
>

umm.

> +
> +/* Return a sensible default order for the pageblock size. */
> +static inline int __init pageblock_default_order(void)

inline and __init doesn't make sense.

> +{
> + 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 +3367,7 @@ static inline void __init set_pageblock_
> }
> #else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
>
> -/* Defined this way to avoid accidently referencing HUGETLB_PAGE_ORDER */
> +#define pageblock_default_order(x) (0)

that won't compile.

> #define set_pageblock_order(x) do {} while (0)
>
> #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
> @@ -3442,7 +3452,7 @@ 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,


--- a/mm/page_alloc.c~fix-boot-problem-with-iseries-lacking-hugepage-support-fix
+++ a/mm/page_alloc.c
@@ -3268,7 +3268,7 @@ static void inline setup_usemap(struct p
#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE

/* Return a sensible default order for the pageblock size. */
-static inline int __init pageblock_default_order(void)
+static inline int pageblock_default_order(void)
{
if (HPAGE_SHIFT > PAGE_SHIFT)
return HUGETLB_PAGE_ORDER;
@@ -3291,7 +3291,11 @@ static inline void __init set_pageblock_
}
#else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

-#define pageblock_default_order(x) (0)
+static inline int pageblock_default_order(void)
+{
+ return 0;
+}
+
#define set_pageblock_order(x) do {} while (0)

#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
_

please avoid adding macros when C could have been used. C is nicer to look
at and has typechecking and stuff.
-
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