The patch titled
Subject: mm: copy_pte_range() use pte_offset_map_rw_nolock()
has been added to the -mm mm-unstable branch. Its filename is
mm-copy_pte_range-use-pte_offset_map_rw_nolock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-copy_pte_range-use-pte_offset_map_rw_nolock.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Subject: mm: copy_pte_range() use pte_offset_map_rw_nolock()
Date: Thu, 26 Sep 2024 14:46:21 +0800
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@xxxxxxxxxxxxx
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/mm/memory.c~mm-copy_pte_range-use-pte_offset_map_rw_nolock
+++ a/mm/memory.c
@@ -1084,6 +1084,7 @@ copy_pte_range(struct vm_area_struct *ds
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 @@ again:
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 */
_
Patches currently in -mm which might be from zhengqi.arch@xxxxxxxxxxxxx are
mm-pgtable-introduce-pte_offset_map_rorw_nolock.patch
powerpc-assert_pte_locked-use-pte_offset_map_ro_nolock.patch
mm-filemap-filemap_fault_recheck_pte_none-use-pte_offset_map_ro_nolock.patch
mm-khugepaged-__collapse_huge_page_swapin-use-pte_offset_map_ro_nolock.patch
arm-adjust_pte-use-pte_offset_map_rw_nolock.patch
mm-handle_pte_fault-use-pte_offset_map_rw_nolock.patch
mm-khugepaged-collapse_pte_mapped_thp-use-pte_offset_map_rw_nolock.patch
mm-copy_pte_range-use-pte_offset_map_rw_nolock.patch
mm-mremap-move_ptes-use-pte_offset_map_rw_nolock.patch
mm-page_vma_mapped_walk-map_pte-use-pte_offset_map_rw_nolock.patch
mm-userfaultfd-move_pages_pte-use-pte_offset_map_rw_nolock.patch
mm-multi-gen-lru-walk_pte_range-use-pte_offset_map_rw_nolock.patch
mm-pgtable-remove-pte_offset_map_nolock.patch
