In move_ptes(), we may modify the new_pte after acquiring the new_ptl, so
convert it to using pte_offset_map_maywrite_nolock(). But since we already
hold the exclusive 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@xxxxxxxxxxxxx>
---
mm/mremap.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/mremap.c b/mm/mremap.c
index e7ae140fc6409..33a0ccf79c32d 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -175,7 +175,12 @@ static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
err = -EAGAIN;
goto out;
}
- new_pte = pte_offset_map_nolock(mm, new_pmd, new_addr, &new_ptl);
+ /*
+ * Use the maywrite version to indicate that new_pte will be modified,
+ * but since we hold the exclusive mmap_lock, there is no need to
+ * recheck pmd_same() after acquiring the new_ptl.
+ */
+ new_pte = pte_offset_map_maywrite_nolock(mm, new_pmd, new_addr, NULL, &new_ptl);
if (!new_pte) {
pte_unmap_unlock(old_pte, old_ptl);
err = -EAGAIN;
--
2.20.1
