[PATCH v4 08/13] mm: copy_pte_range() use pte_offset_map_rw_nolock()
From: Qi Zheng <hidden>
Date: 2024-09-24 06:11:18
Also in:
linux-arm-kernel, linux-mm, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
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 <redacted> --- 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