linux-kernel - [PATCH] thp, dax: do not try to withdraw pgtable from non-anon VMA

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Date:	Thu, 11 Feb 2016 05:40:45 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Matthew Wilcox <willy@...ux.intel.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH] thp, dax: do not try to withdraw pgtable from non-anon VMA

DAX doesn't deposit pgtables when it maps huge pages: nothing to
withdraw. It can lead to crash.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/huge_memory.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5404f7534366..ca7f21516c3a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1706,7 +1706,8 @@ bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
 		pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
 		VM_BUG_ON(!pmd_none(*new_pmd));
 
-		if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
+		if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
+				vma_is_anonymous(vma)) {
 			pgtable_t pgtable;
 			pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
 			pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
-- 
2.7.0