Commit 69d177c2 authored by Andy Whitcroft's avatar Andy Whitcroft Committed by Linus Torvalds
Browse files

hugetlbfs: handle pages higher order than MAX_ORDER 



When working with hugepages, hugetlbfs assumes that those hugepages are
smaller than MAX_ORDER.  Specifically it assumes that the mem_map is
contigious and uses that to optimise access to the elements of the mem_map
that represent the hugepage.  Gigantic pages (such as 16GB pages on
powerpc) by definition are of greater order than MAX_ORDER (larger than
MAX_ORDER_NR_PAGES in size).  This means that we can no longer make use of
the buddy alloctor guarentees for the contiguity of the mem_map, which
ensures that the mem_map is at least contigious for maximmally aligned
areas of MAX_ORDER_NR_PAGES pages.

This patch adds new mem_map accessors and iterator helpers which handle
any discontiguity at MAX_ORDER_NR_PAGES boundaries.  It then uses these to
implement gigantic page versions of copy_huge_page and clear_huge_page,
and to allow follow_hugetlb_page handle gigantic pages.

Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
Cc: Jon Tollefson <kniht@linux.vnet.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: <stable@kernel.org>		[2.6.27.x]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 22bece00

mm/hugetlb.c

+36 −1
Original line number Diff line number Diff line
@@ -354,11 +354,26 @@ static int vma_has_reserves(struct vm_area_struct *vma) 
	return 0;

}



static void clear_gigantic_page(struct page *page,

			unsigned long addr, unsigned long sz)

{

	int i;

	struct page *p = page;



	might_sleep();

	for (i = 0; i < sz/PAGE_SIZE; i++, p = mem_map_next(p, page, i)) {

		cond_resched();

		clear_user_highpage(p, addr + i * PAGE_SIZE);

	}

}

static void clear_huge_page(struct page *page,

			unsigned long addr, unsigned long sz)

{

	int i;



	if (unlikely(sz > MAX_ORDER_NR_PAGES))

		return clear_gigantic_page(page, addr, sz);



	might_sleep();

	for (i = 0; i < sz/PAGE_SIZE; i++) {

		cond_resched();
@@ -366,12 +381,32 @@ static void clear_huge_page(struct page *page, 
	}

}



static void copy_gigantic_page(struct page *dst, struct page *src,

			   unsigned long addr, struct vm_area_struct *vma)

{

	int i;

	struct hstate *h = hstate_vma(vma);

	struct page *dst_base = dst;

	struct page *src_base = src;

	might_sleep();

	for (i = 0; i < pages_per_huge_page(h); ) {

		cond_resched();

		copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);



		i++;

		dst = mem_map_next(dst, dst_base, i);

		src = mem_map_next(src, src_base, i);

	}

}

static void copy_huge_page(struct page *dst, struct page *src,

			   unsigned long addr, struct vm_area_struct *vma)

{

	int i;

	struct hstate *h = hstate_vma(vma);



	if (unlikely(pages_per_huge_page(h) > MAX_ORDER_NR_PAGES))

		return copy_gigantic_page(dst, src, addr, vma);



	might_sleep();

	for (i = 0; i < pages_per_huge_page(h); i++) {

		cond_resched();
@@ -2130,7 +2165,7 @@ same_page: 
			if (zeropage_ok)

				pages[i] = ZERO_PAGE(0);

			else

				pages[i] = page + pfn_offset;

				pages[i] = mem_map_offset(page, pfn_offset);

			get_page(pages[i]);

		}

mm/internal.h

+28 −0
Original line number Diff line number Diff line
@@ -175,6 +175,34 @@ static inline void free_page_mlock(struct page *page) { } 


#endif /* CONFIG_UNEVICTABLE_LRU */



/*

 * Return the mem_map entry representing the 'offset' subpage within

 * the maximally aligned gigantic page 'base'.  Handle any discontiguity

 * in the mem_map at MAX_ORDER_NR_PAGES boundaries.

 */

static inline struct page *mem_map_offset(struct page *base, int offset)

{

	if (unlikely(offset >= MAX_ORDER_NR_PAGES))

		return pfn_to_page(page_to_pfn(base) + offset);

	return base + offset;

}



/*

 * Iterator over all subpages withing the maximally aligned gigantic

 * page 'base'.  Handle any discontiguity in the mem_map.

 */

static inline struct page *mem_map_next(struct page *iter,

						struct page *base, int offset)

{

	if (unlikely((offset & (MAX_ORDER_NR_PAGES - 1)) == 0)) {

		unsigned long pfn = page_to_pfn(base) + offset;

		if (!pfn_valid(pfn))

			return NULL;

		return pfn_to_page(pfn);

	}

	return iter + 1;

}



/*

 * FLATMEM and DISCONTIGMEM configurations use alloc_bootmem_node,

 * so all functions starting at paging_init should be marked __init

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