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;
--
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