Commit cc81717e authored Jan 23, 2014 by Michal Hocko Committed by Linus Torvalds Jan 23, 2014

mm: new_vma_page() cannot see NULL vma for hugetlb pages



Commit 11c731e8 ("mm/mempolicy: fix !vma in new_vma_page()") has
removed BUG_ON(!vma) from new_vma_page which is partially correct
because page_address_in_vma will return EFAULT for non-linear mappings
and at least shared shmem might be mapped this way.

The patch also tried to prevent NULL ptr for hugetlb pages which is not
correct AFAICS because hugetlb pages cannot be mapped as VM_NONLINEAR
and other conditions in page_address_in_vma seem to be legit and catch
real bugs.

This patch restores BUG_ON for PageHuge to catch potential issues when
the to-be-migrated page is not setup properly.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 54b9dd14

mm/mempolicy.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -1199,10 +1199,8 @@ static struct page new_vma_page(struct page page, unsigned long private, int *
		}

		if (PageHuge(page)) {
		if (vma)
		BUG_ON(!vma);
		return alloc_huge_page_noerr(vma, address, 1);
		else
		return NULL;
		}
		/*
		* if !vma, alloc_page_vma() will use task or system default policy

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