Hi Hugh,
On Mon, Jan 10, 2011 at 04:55:53PM -0800, Hugh Dickins wrote:
> If you configure THP in addition to HUGETLB_PAGE on x86_32 without PAE,
> the p?d-folding works out that munlock_vma_pages_range() can crash to
> follow_page()'s pud_huge() BUG_ON(flags & FOLL_GET): it needs the same
> VM_HUGETLB check already there on the pmd_huge() line. Conveniently,
> openSUSE provides a "blogd" which tests this out at startup!
>
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
> ---
> This massive rework belongs just after thp-transparent-hugepage-core.patch
>
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- mmotm.orig/mm/memory.c 2011-01-10 16:31:29.000000000 -0800
> +++ mmotm/mm/memory.c 2011-01-10 16:33:16.000000000 -0800
> @@ -1288,7 +1288,7 @@ struct page *follow_page(struct vm_area_
> pud = pud_offset(pgd, address);
> if (pud_none(*pud))
> goto no_page_table;
> - if (pud_huge(*pud)) {
> + if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
> BUG_ON(flags & FOLL_GET);
> page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
> goto out;
How is THP related to this? pud_trans_huge doesn't exist, if pud_huge
is true, vma is already guaranteed to belong to hugetlbfs without
requiring the additional check.
I added the check to pmd_huge already, there it is needed, but for
pud_huge it isn't as far as I can tell.
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