[PATCH 08/14] mm: copy_pte_range() use pte_offset_map_maywrite_nolock()

[Qi Zheng]

In copy_pte_range(), we may modify the src_pte entry after holding the
src_ptl, so convert it to using pte_offset_map_maywrite_nolock(). But
since we already hold the write lock of mmap_lock, there is no need to
get pmdval to do pmd_same() check, just pass NULL to pmdvalp parameter.

Signed-off-by: Qi Zheng <zhengqi.arch at bytedance.com>
---
 mm/memory.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index d3378e98faf13..3016b3bf0c3b0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1083,6 +1083,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
 	struct mm_struct *src_mm = src_vma->vm_mm;
 	pte_t *orig_src_pte, *orig_dst_pte;
 	pte_t *src_pte, *dst_pte;
+	pmd_t pmdval;
 	pte_t ptent;
 	spinlock_t *src_ptl, *dst_ptl;
 	int progress, max_nr, ret = 0;
@@ -1108,7 +1109,8 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
 		ret = -ENOMEM;
 		goto out;
 	}
-	src_pte = pte_offset_map_nolock(src_mm, src_pmd, addr, &src_ptl);
+	src_pte = pte_offset_map_maywrite_nolock(src_mm, src_pmd, addr, NULL,
+						 &src_ptl);
 	if (!src_pte) {
 		pte_unmap_unlock(dst_pte, dst_ptl);
 		/* ret == 0 */
-- 
2.20.1