Commit ba72cb8c authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

Fix boot problem with iSeries lacking hugepage support 



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: default avatarMel Gorman <mel@csn.ul.ie>
Tested-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ee592a5b

arch/powerpc/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -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

mm/page_alloc.c

+21 −2
Original line number Diff line number Diff line
@@ -3265,6 +3265,16 @@ static void inline setup_usemap(struct pglist_data *pgdat, 
#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)

{
@@ -3280,7 +3290,16 @@ static inline void __init set_pageblock_order(unsigned int order) 
}

#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 */
@@ -3365,7 +3384,7 @@ static void __meminit free_area_init_core(struct pglist_data *pgdat, 
		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);

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