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[PATCH] hugetlb: move stale pte check into huge_pte_alloc() 

Initial Post (Wed, 17 Aug 2005)

This patch moves the
	if (! pte_none(*pte))
		hugetlb_clean_stale_pgtable(pte);
logic into huge_pte_alloc() so all of its callers can be immune to the bug
described by Kenneth Chen at http://lkml.org/lkml/2004/6/16/246

> It turns out there is a bug in hugetlb_prefault(): with 3 level page table,
> huge_pte_alloc() might return a pmd that points to a PTE page. It happens
> if the virtual address for hugetlb mmap is recycled from previously used
> normal page mmap. free_pgtables() might not scrub the pmd entry on
> munmap and hugetlb_prefault skips on any pmd presence regardless what type
> it is.

Unless I am missing something, it seems more correct to place the check inside
huge_pte_alloc() to prevent a the same bug wherever a huge pte is allocated.
It also allows checking for this condition when lazily faulting huge pages
later in the series.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Adam Litke 2005-09-03 15:55:00 -07:00 committed by Linus Torvalds
parent 32e51a8c97
commit 7bf07f3d4b
2 changed files with 11 additions and 4 deletions
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13
arch/i386/mm/hugetlbpage.c
View File

@ -22,12 +22,21 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd = NULL;
pmd_t *pmd;
pte_t *pte = NULL;
pgd = pgd_offset(mm, addr);
pud = pud_alloc(mm, pgd, addr);
pmd = pmd_alloc(mm, pud, addr);
return (pte_t *) pmd;
if (!pmd)
goto out;
pte = (pte_t *) pmd;
if (!pte_none(*pte) && !pte_huge(*pte))
hugetlb_clean_stale_pgtable(pte);
out:
return pte;
}
pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)

2
mm/hugetlb.c
View File

@ -360,8 +360,6 @@ int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
ret = -ENOMEM;
goto out;
}
if (! pte_none(*pte))
hugetlb_clean_stale_pgtable(pte);
idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));