[merged mm-stable] mm-userfaultfd-move_pages_pte-use-pte_offset_map_rw_nolock.patch removed from -mm tree

[merged mm-stable] mm-userfaultfd-move_pages_pte-use-pte_offset_map_rw_nolock.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: userfaultfd: move_pages_pte() use pte_offset_map_rw_nolock()
has been removed from the -mm tree.  Its filename was
     mm-userfaultfd-move_pages_pte-use-pte_offset_map_rw_nolock.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Qi Zheng <zhengqi.arch@bytedance.com>
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@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>
---

 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@bytedance.com are