From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Date: Mon, 18 Sep 2017 16:10:35 +0200
Subject: [PATCH] s390/mm: make pmdp_invalidate() do invalidation only
Git-commit: 91c575b335766effa6103eba42a82aea560c365f
Patch-Mainline: v4.14-rc2
References: bsc#1079840

Commit 227be799c39a ("s390/mm: uninline pmdp_xxx functions from pgtable.h")
inadvertently changed the behavior of pmdp_invalidate(), so that it now
clears the pmd instead of just marking it as invalid. Fix this by restoring
the original behavior.

A possible impact of the misbehaving pmdp_invalidate() would be the
MADV_DONTNEED races (see commits ced10803 and 58ceeb6b), although we
should not have any negative impact on the related dirty/young flags,
since those flags are not set by the hardware on s390.

Fixes: 227be799c39a ("s390/mm: uninline pmdp_xxx functions from pgtable.h")
Cc: <stable@vger.kernel.org> # v4.6+
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 arch/s390/include/asm/pgtable.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 8755d2eb1e23..f73e3bf19d3c 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1441,7 +1441,9 @@ static inline pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
 static inline void pmdp_invalidate(struct vm_area_struct *vma,
 				   unsigned long addr, pmd_t *pmdp)
 {
-	pmdp_xchg_direct(vma->vm_mm, addr, pmdp, __pmd(_SEGMENT_ENTRY_EMPTY));
+	pmd_t pmd = __pmd(pmd_val(*pmdp) | _SEGMENT_ENTRY_INVALID);
+
+	pmdp_xchg_direct(vma->vm_mm, addr, pmdp, pmd);
 }
 
 #define __HAVE_ARCH_PMDP_SET_WRPROTECT
-- 
2.12.3