[PATCH 3/6] mm: replace mmap with vma write lock assertions when operating on a vma

[Suren Baghdasaryan <surenb@xxxxxxxxxx>]

Vma write lock assertion always includes mmap write lock assertion and
additional vma lock checks when per-VMA locks are enabled. Replace
weaker mmap_assert_write_locked() assertions with stronger
vma_assert_write_locked() ones when we are operating on a vma which
is expected to be locked.

Suggested-by: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
---
 mm/hugetlb.c    | 2 +-
 mm/khugepaged.c | 5 +++--
 mm/memory.c     | 2 +-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 64a3239b6407..1d871a1167d8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5028,7 +5028,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 					src_vma->vm_start,
 					src_vma->vm_end);
 		mmu_notifier_invalidate_range_start(&range);
-		mmap_assert_write_locked(src);
+		vma_assert_write_locked(src_vma);
 		raw_write_seqcount_begin(&src->write_protect_seq);
 	} else {
 		/*
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 78c8d5d8b628..1e43a56fba31 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1495,7 +1495,7 @@ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
 	};
 
 	VM_BUG_ON(!PageTransHuge(hpage));
-	mmap_assert_write_locked(vma->vm_mm);
+	vma_assert_write_locked(vma);
 
 	if (do_set_pmd(&vmf, hpage))
 		return SCAN_FAIL;
@@ -1525,7 +1525,7 @@ static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *v
 	pmd_t pmd;
 	struct mmu_notifier_range range;
 
-	mmap_assert_write_locked(mm);
+	vma_assert_write_locked(vma);
 	if (vma->vm_file)
 		lockdep_assert_held_write(&vma->vm_file->f_mapping->i_mmap_rwsem);
 	/*
@@ -1570,6 +1570,7 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
 	int count = 0, result = SCAN_FAIL;
 	int i;
 
+	/* Ensure vma can't change, it will be locked below after checks */
 	mmap_assert_write_locked(mm);
 
 	/* Fast check before locking page if already PMD-mapped */
diff --git a/mm/memory.c b/mm/memory.c
index 603b2f419948..652d99b9858a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1312,7 +1312,7 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
 		 * Use the raw variant of the seqcount_t write API to avoid
 		 * lockdep complaining about preemptibility.
 		 */
-		mmap_assert_write_locked(src_mm);
+		vma_assert_write_locked(src_vma);
 		raw_write_seqcount_begin(&src_mm->write_protect_seq);
 	}
 
-- 
2.41.0.487.g6d72f3e995-goog