diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2016-06-24 14:49:51 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-06-24 17:23:52 -0700 |
| commit | c17b1f42594eb71b8d3eb5a6dfc907a7eb88a51d (patch) | |
| tree | b24f8fa0aaa1537ea9965e22ca6b9c9a030d2be5 /mm/hugetlb.c | |
| parent | 06d8fbc7cfd655d202cfac9870bd79c18c2db698 (diff) | |
| download | lwn-c17b1f42594eb71b8d3eb5a6dfc907a7eb88a51d.tar.gz lwn-c17b1f42594eb71b8d3eb5a6dfc907a7eb88a51d.zip | |
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>
Diffstat (limited to 'mm/hugetlb.c')
| -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 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: |