diff mbox series

[09/14] mm: mremap: move_ptes() use pte_offset_map_maywrite_nolock()

Message ID 89bd1d48db1986ec83dcae228defa748f38238ff.1724226076.git.zhengqi.arch@bytedance.com (mailing list archive)
State Handled Elsewhere
Headers show
Series introduce pte_offset_map_{readonly|maywrite}_nolock() | expand

Commit Message

Qi Zheng Aug. 21, 2024, 8:18 a.m. UTC 
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@bytedance.com>
---
 mm/mremap.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
diff mbox series

Patch

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;