Commit 24553a97 authored by Qi Zheng's avatar Qi Zheng Committed by Andrew Morton
Browse files

mm: copy_pte_range() use pte_offset_map_rw_nolock() 

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.

Link: https://lkml.kernel.org/r/9166f6fad806efbca72e318ab6f0f8af458056a9.1727332572.git.zhengqi.arch@bytedance.com


Signed-off-by: default avatarQi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: default avatarMuchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 6dfd0d2c

mm/memory.c

+10 −1
Original line number Diff line number Diff line
@@ -1084,6 +1084,7 @@ 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;
@@ -1109,7 +1110,15 @@ 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 */