In copy_pte_range(), we may modify the src_pte entry after holding the
src_ptl, so convert it to using pte_offset_map_rw_nolock(). Since we
already hold the exclusive mmap_lock, and the copy_pte_range() and
retract_page_tables() are using vma->anon_vma to be exclusive, so the PTE
page is stable, there is no need to get pmdval and do pmd_same() check.
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
---
mm/memory.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index 6432b636d1ba7..c19cf14e1c565 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1086,6 +1086,7 @@ 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 dummy_pmdval;
pte_t ptent;
spinlock_t *src_ptl, *dst_ptl;
int progress, max_nr, ret = 0;
@@ -1111,7 +1112,15 @@ 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);
+
+ /*
+ * We already hold the exclusive mmap_lock, the copy_pte_range() and
+ * retract_page_tables() are using vma->anon_vma to be exclusive, so
+ * the PTE page is stable, and there is no need to get pmdval and do
+ * pmd_same() check.
+ */
+ src_pte = pte_offset_map_rw_nolock(src_mm, src_pmd, addr, &dummy_pmdval,
+ &src_ptl);
if (!src_pte) {
pte_unmap_unlock(dst_pte, dst_ptl);
/* ret == 0 */
--
2.20.1
