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Commit 9da61aef authored by David Gibson's avatar David Gibson Committed by Linus Torvalds
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[PATCH] hugepage: Fix hugepage logic in free_pgtables() 



free_pgtables() has special logic to call hugetlb_free_pgd_range() instead
of the normal free_pgd_range() on hugepage VMAs.  However, the test it uses
to do so is incorrect: it calls is_hugepage_only_range on a hugepage sized
range at the start of the vma.  is_hugepage_only_range() will return true
if the given range has any intersection with a hugepage address region, and
in this case the given region need not be hugepage aligned.  So, for
example, this test can return true if called on, say, a 4k VMA immediately
preceding a (nicely aligned) hugepage VMA.

At present we get away with this because the powerpc version of
hugetlb_free_pgd_range() is just a call to free_pgd_range().  On ia64 (the
only other arch with a non-trivial is_hugepage_only_range()) we get away
with it for a different reason; the hugepage area is not contiguous with
the rest of the user address space, and VMAs are not permitted in between,
so the test can't return a false positive there.

Nonetheless this should be fixed.  We do that in the patch below by
replacing the is_hugepage_only_range() test with an explicit test of the
VMA using is_vm_hugetlb_page().

This in turn changes behaviour for platforms where is_hugepage_only_range()
returns false always (everything except powerpc and ia64).  We address this
by ensuring that hugetlb_free_pgd_range() is defined to be identical to
free_pgd_range() (instead of a no-op) on everything except ia64.  Even so,
it will prevent some otherwise possible coalescing of calls down to
free_pgd_range().  Since this only happens for hugepage VMAs, removing this
small optimization seems unlikely to cause any trouble.

This patch causes no regressions on the libhugetlbfs testsuite - ppc64
POWER5 (8-way), ppc64 G5 (2-way) and i386 Pentium M (UP).

Signed-off-by: default avatarDavid Gibson <dwg@au1.ibm.com>
Cc: William Lee Irwin III <wli@holomorphy.com>
Acked-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 27a85ef1

include/asm-ia64/page.h

+1 −0
Original line number Diff line number Diff line
@@ -57,6 +57,7 @@ 


# define HAVE_ARCH_HUGETLB_UNMAPPED_AREA

# define ARCH_HAS_HUGEPAGE_ONLY_RANGE

# define ARCH_HAS_HUGETLB_FREE_PGD_RANGE

#endif /* CONFIG_HUGETLB_PAGE */



#ifdef __ASSEMBLY__

include/asm-powerpc/pgtable.h

+0 −5
Original line number Diff line number Diff line
@@ -468,11 +468,6 @@ extern pgd_t swapper_pg_dir[]; 


extern void paging_init(void);



#ifdef CONFIG_HUGETLB_PAGE

#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) \

	free_pgd_range(tlb, addr, end, floor, ceiling)

#endif



/*

 * This gets called at the end of handling a page fault, when

 * the kernel has put a new PTE into the page table for the process.

include/linux/hugetlb.h

+5 −4
Original line number Diff line number Diff line
@@ -43,8 +43,10 @@ void hugetlb_change_protection(struct vm_area_struct *vma, 


#ifndef ARCH_HAS_HUGEPAGE_ONLY_RANGE

#define is_hugepage_only_range(mm, addr, len)	0

#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) \

						do { } while (0)

#endif



#ifndef ARCH_HAS_HUGETLB_FREE_PGD_RANGE

#define hugetlb_free_pgd_range	free_pgd_range

#endif



#ifndef ARCH_HAS_PREPARE_HUGEPAGE_RANGE
@@ -93,8 +95,7 @@ static inline unsigned long hugetlb_total_pages(void) 
#define prepare_hugepage_range(addr, len)	(-EINVAL)

#define pmd_huge(x)	0

#define is_hugepage_only_range(mm, addr, len)	0

#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) \

						do { } while (0)

#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) ({BUG(); 0; })

#define hugetlb_fault(mm, vma, addr, write)	({ BUG(); 0; })



#define hugetlb_change_protection(vma, address, end, newprot)

mm/memory.c

+2 −3
Original line number Diff line number Diff line
@@ -277,7 +277,7 @@ void free_pgtables(struct mmu_gather **tlb, struct vm_area_struct *vma, 
		anon_vma_unlink(vma);

		unlink_file_vma(vma);



		if (is_hugepage_only_range(vma->vm_mm, addr, HPAGE_SIZE)) {

		if (is_vm_hugetlb_page(vma)) {

			hugetlb_free_pgd_range(tlb, addr, vma->vm_end,

				floor, next? next->vm_start: ceiling);

		} else {
@@ -285,8 +285,7 @@ void free_pgtables(struct mmu_gather **tlb, struct vm_area_struct *vma, 
			 * Optimization: gather nearby vmas into one call down

			 */

			while (next && next->vm_start <= vma->vm_end + PMD_SIZE

			  && !is_hugepage_only_range(vma->vm_mm, next->vm_start,

							HPAGE_SIZE)) {

			       && !is_vm_hugetlb_page(vma)) {

				vma = next;

				next = vma->vm_next;

				anon_vma_unlink(vma);