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mm: copy_pte_range() use pte_offset_map_rw_nolock()

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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: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Qi Zheng 2024-09-26 14:46:21 +08:00 committed by Andrew Morton
parent 6dfd0d2cb3
commit 24553a978b
1 changed files with 10 additions and 1 deletions
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11
mm/memory.c
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@ -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 */