The patch titled
Subject: mm: userfaultfd: move_pages_pte() use pte_offset_map_rw_nolock()
has been added to the -mm mm-unstable branch. Its filename is
mm-userfaultfd-move_pages_pte-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-userfaultfd-move_pages_pte-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
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------------------------------------------------------
From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Subject: mm: userfaultfd: move_pages_pte() use pte_offset_map_rw_nolock()
Date: Thu, 26 Sep 2024 14:46:24 +0800
In move_pages_pte(), we may modify the dst_pte and src_pte after acquiring
the ptl, so convert it to using pte_offset_map_rw_nolock(). But since we
will use pte_same() to detect the change of the pte entry, there is no
need to get pmdval, so just pass a dummy variable to it.
Link: https://lkml.kernel.org/r/1530e8fdbfc72eacf3b095babe139ce3d715600a.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/userfaultfd.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
--- a/mm/userfaultfd.c~mm-userfaultfd-move_pages_pte-use-pte_offset_map_rw_nolock
+++ a/mm/userfaultfd.c
@@ -1135,7 +1135,7 @@ static int move_pages_pte(struct mm_stru
spinlock_t *src_ptl, *dst_ptl;
pte_t *src_pte = NULL;
pte_t *dst_pte = NULL;
-
+ pmd_t dummy_pmdval;
struct folio *src_folio = NULL;
struct anon_vma *src_anon_vma = NULL;
struct mmu_notifier_range range;
@@ -1146,7 +1146,14 @@ static int move_pages_pte(struct mm_stru
src_addr, src_addr + PAGE_SIZE);
mmu_notifier_invalidate_range_start(&range);
retry:
- dst_pte = pte_offset_map_nolock(mm, dst_pmd, dst_addr, &dst_ptl);
+ /*
+ * Use the maywrite version to indicate that dst_pte will be modified,
+ * but since we will use pte_same() to detect the change of the pte
+ * entry, there is no need to get pmdval, so just pass a dummy variable
+ * to it.
+ */
+ dst_pte = pte_offset_map_rw_nolock(mm, dst_pmd, dst_addr, &dummy_pmdval,
+ &dst_ptl);
/* Retry if a huge pmd materialized from under us */
if (unlikely(!dst_pte)) {
@@ -1154,7 +1161,9 @@ retry:
goto out;
}
- src_pte = pte_offset_map_nolock(mm, src_pmd, src_addr, &src_ptl);
+ /* same as dst_pte */
+ src_pte = pte_offset_map_rw_nolock(mm, src_pmd, src_addr, &dummy_pmdval,
+ &src_ptl);
/*
* We held the mmap_lock for reading so MADV_DONTNEED
_
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
