[PATCH 3.11 075/138] x86, mm, hugetlb: Add missing TLB page invalidation for hugetlb_cow()

[Luis Henriques]

3.11.10.11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Anthony Iliopoulos <anthony.iliopoulos at huawei.com>

commit 9844f5462392b53824e8b86726e7c33b5ecbb676 upstream.

The invalidation is required in order to maintain proper semantics
under CoW conditions. In scenarios where a process clones several
threads, a thread operating on a core whose DTLB entry for a
particular hugepage has not been invalidated, will be reading from
the hugepage that belongs to the forked child process, even after
hugetlb_cow().

The thread will not see the updated page as long as the stale DTLB
entry remains cached, the thread attempts to write into the page,
the child process exits, or the thread gets migrated to a different
processor.

Signed-off-by: Anthony Iliopoulos <anthony.iliopoulos at huawei.com>
Link: http://lkml.kernel.org/r/20140514092948.GA17391@server-36.huawei.corp
Suggested-by: Shay Goikhman <shay.goikhman at huawei.com>
Acked-by: Dave Hansen <dave.hansen at intel.com>
Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/include/asm/hugetlb.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/hugetlb.h b/arch/x86/include/asm/hugetlb.h
index a8091216963b..68c05398bba9 100644
--- a/arch/x86/include/asm/hugetlb.h
+++ b/arch/x86/include/asm/hugetlb.h
@@ -52,6 +52,7 @@ static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
 					 unsigned long addr, pte_t *ptep)
 {
+	ptep_clear_flush(vma, addr, ptep);
 }
 
 static inline int huge_pte_none(pte_t pte)
-- 
1.9.1