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hugetlbfs: handle pages higher order than MAX_ORDER

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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: Andy 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andy Whitcroft 2008-11-06 12:53:26 -08:00 committed by Linus Torvalds
parent 22bece00dc
commit 69d177c2fc
2 changed files with 64 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

37
mm/hugetlb.c
View file

@ -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 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
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]);
}

28
mm/internal.h
View file

@ -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