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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-06-24 14:49:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-06-24 17:23:52 -0700
commitc17b1f42594eb71b8d3eb5a6dfc907a7eb88a51d (patch)
treeb24f8fa0aaa1537ea9965e22ca6b9c9a030d2be5
parent06d8fbc7cfd655d202cfac9870bd79c18c2db698 (diff)
downloadlinux-c17b1f42594eb71b8d3eb5a6dfc907a7eb88a51d.tar.gz
hugetlb: fix nr_pmds accounting with shared page tables
We account HugeTLB's shared page table to all processes who share it. The accounting happens during huge_pmd_share(). If somebody populates pud entry under us, we should decrease pagetable's refcount and decrease nr_pmds of the process. By mistake, I increase nr_pmds again in this case. :-/ It will lead to "BUG: non-zero nr_pmds on freeing mm: 2" on process' exit. Let's fix this by increasing nr_pmds only when we're sure that the page table will be used. Link: http://lkml.kernel.org/r/20160617122506.GC6534@node.shutemov.name Fixes: dc6c9a35b66b ("mm: account pmd page tables to the process") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: zhongjiang <zhongjiang@huawei.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/hugetlb.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 388c2bb9b55c..ee0302169959 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4228,7 +4228,6 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
if (saddr) {
spte = huge_pte_offset(svma->vm_mm, saddr);
if (spte) {
- mm_inc_nr_pmds(mm);
get_page(virt_to_page(spte));
break;
}
@@ -4243,9 +4242,9 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
if (pud_none(*pud)) {
pud_populate(mm, pud,
(pmd_t *)((unsigned long)spte & PAGE_MASK));
+ mm_inc_nr_pmds(mm);
} else {
put_page(virt_to_page(spte));
- mm_inc_nr_pmds(mm);
}
spin_unlock(ptl);
out: