x86: fix bad pmd ffff810000207xxx(9090909090909090)

upstream commit: 2884f110d5409714f3a04eeb6d2ecd77da66b242

OGAWA Hirofumi and Fede have reported rare pmd_ERROR messages:
mm/memory.c:127: bad pmd ffff810000207xxx(9090909090909090).

Initialization's cleanup_highmap was leaving alignment filler
behind in the pmd for MODULES_VADDR: when vmalloc's guard page
would occupy a new page table, it's not allocated, and then
module unload's vfree hits the bad 9090 pmd entry left over.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Hugh notes:

 It's actually not a serious problem, but it does look as if it's a
 serious problem, so we should stamp it out.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>

arch/x86/mm/init_64.c

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a02a14f..b2c5231 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -192,7 +192,7 @@
 	pmd_t *last_pmd = pmd + PTRS_PER_PMD;
 
 	for (; pmd < last_pmd; pmd++, vaddr += PMD_SIZE) {
-		if (!pmd_present(*pmd))
+		if (pmd_none(*pmd))
 			continue;
 		if (vaddr < (unsigned long) _text || vaddr > end)
 			set_pmd(pmd, __pmd(0));