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| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2016-06-25 00:49:51 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-09-07 09:32:35 +0300 |
| commit | 8ef7c21dd8130e6ce469bbe2747fbc0a5d3e0488 (patch) | |
| tree | 0f0cb72138385f87e8a5da1b9194d094165b43ae /mm | |
| parent | 85184740541c2b80b72ebfa46cfe065ec1d1058f (diff) | |
| download | linux-8ef7c21dd8130e6ce469bbe2747fbc0a5d3e0488.tar.xz | |
hugetlb: fix nr_pmds accounting with shared page tables
commit c17b1f42594eb71b8d3eb5a6dfc907a7eb88a51d upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/hugetlb.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 0c31f184daf8..125c7dd55322 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4213,7 +4213,6 @@ 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; } @@ -4228,9 +4227,9 @@ 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: |