[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>
diff --git a/arch/i386/mm/hugetlbpage.c b/arch/i386/mm/hugetlbpage.c
index 3b099f3..57c486f 100644
--- a/arch/i386/mm/hugetlbpage.c
+++ b/arch/i386/mm/hugetlbpage.c
@@ -22,12 +22,21 @@
{
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)