From: Michal Hocko <mhocko@xxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit cc81717ed3bc6d4f3738d13a1e097437caada0e9 upstream.
Commit 11c731e81bb0 ("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@xxxxxxx>
Reviewed-by: Bob Liu <bob.liu@xxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
mm/mempolicy.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 41a42902ef21..3650036bb910 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1200,10 +1200,8 @@ static struct page *new_page(struct page *page, unsigned long start, int **x)
}
if (PageHuge(page)) {
- if (vma)
- return alloc_huge_page_noerr(vma, address, 1);
- else
- return NULL;
+ BUG_ON(!vma);
+ return alloc_huge_page_noerr(vma, address, 1);
}
/*
* if !vma, alloc_page_vma() will use task or system default policy
--
2.1.1
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