[merged mm-stable] mm-khugepaged-collapse_pte_mapped_thp-use-pte_offset_map_rw_nolock.patch removed from -mm tree

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The quilt patch titled
     Subject: mm: khugepaged: collapse_pte_mapped_thp() use pte_offset_map_rw_nolock()
has been removed from the -mm tree.  Its filename was
     mm-khugepaged-collapse_pte_mapped_thp-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@xxxxxxxxxxxxx>
Subject: mm: khugepaged: collapse_pte_mapped_thp() use pte_offset_map_rw_nolock()
Date: Thu, 26 Sep 2024 14:46:20 +0800

In collapse_pte_mapped_thp(), we may modify the pte and pmd entry after
acquiring the ptl, so convert it to using pte_offset_map_rw_nolock().  At
this time, the pte_same() check is not performed after the PTL held.  So
we should get pgt_pmd and do pmd_same() check after the ptl held.

Link: https://lkml.kernel.org/r/055e42db68da00ac8ecab94bd2633c7cd965eb1c.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/khugepaged.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

--- a/mm/khugepaged.c~mm-khugepaged-collapse_pte_mapped_thp-use-pte_offset_map_rw_nolock
+++ a/mm/khugepaged.c
@@ -1608,7 +1608,7 @@ int collapse_pte_mapped_thp(struct mm_st
 	if (userfaultfd_armed(vma) && !(vma->vm_flags & VM_SHARED))
 		pml = pmd_lock(mm, pmd);
 
-	start_pte = pte_offset_map_nolock(mm, pmd, haddr, &ptl);
+	start_pte = pte_offset_map_rw_nolock(mm, pmd, haddr, &pgt_pmd, &ptl);
 	if (!start_pte)		/* mmap_lock + page lock should prevent this */
 		goto abort;
 	if (!pml)
@@ -1616,6 +1616,9 @@ int collapse_pte_mapped_thp(struct mm_st
 	else if (ptl != pml)
 		spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
 
+	if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd))))
+		goto abort;
+
 	/* step 2: clear page table and adjust rmap */
 	for (i = 0, addr = haddr, pte = start_pte;
 	     i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
@@ -1648,7 +1651,6 @@ int collapse_pte_mapped_thp(struct mm_st
 		nr_ptes++;
 	}
 
-	pte_unmap(start_pte);
 	if (!pml)
 		spin_unlock(ptl);
 
@@ -1661,14 +1663,19 @@ int collapse_pte_mapped_thp(struct mm_st
 	/* step 4: remove empty page table */
 	if (!pml) {
 		pml = pmd_lock(mm, pmd);
-		if (ptl != pml)
+		if (ptl != pml) {
 			spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
+			if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) {
+				flush_tlb_mm(mm);
+				goto unlock;
+			}
+		}
 	}
 	pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd);
 	pmdp_get_lockless_sync();
+	pte_unmap_unlock(start_pte, ptl);
 	if (ptl != pml)
-		spin_unlock(ptl);
-	spin_unlock(pml);
+		spin_unlock(pml);
 
 	mmu_notifier_invalidate_range_end(&range);
 
@@ -1688,6 +1695,7 @@ abort:
 		folio_ref_sub(folio, nr_ptes);
 		add_mm_counter(mm, mm_counter_file(folio), -nr_ptes);
 	}
+unlock:
 	if (start_pte)
 		pte_unmap_unlock(start_pte, ptl);
 	if (pml && pml != ptl)
_

Patches currently in -mm which might be from zhengqi.arch@xxxxxxxxxxxxx are






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