mm/mmap: abstract vma clean up from exit_mmap()

Create the new function tear_down_vmas() to remove a range of vmas. 
exit_mmap() will be removing all the vmas.

This is necessary for future patches.

No functional changes intended.

Link: https://lkml.kernel.org/r/20260121164946.2093480-4-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 24 insertions, 13 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 1f025edf8d7d..9c8adc505d3d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1247,6 +1247,29 @@ limits_failed:
 }
 EXPORT_SYMBOL(vm_brk_flags);
 
+static
+unsigned long tear_down_vmas(struct mm_struct *mm, struct vma_iterator *vmi,
+		struct vm_area_struct *vma, unsigned long end)
+{
+	unsigned long nr_accounted = 0;
+	int count = 0;
+
+	mmap_assert_write_locked(mm);
+	vma_iter_set(vmi, vma->vm_end);
+	do {
+		if (vma->vm_flags & VM_ACCOUNT)
+			nr_accounted += vma_pages(vma);
+		vma_mark_detached(vma);
+		remove_vma(vma);
+		count++;
+		cond_resched();
+		vma = vma_next(vmi);
+	} while (vma && vma->vm_end <= end);
+
+	VM_WARN_ON_ONCE(count != mm->map_count);
+	return nr_accounted;
+}
+
 /* Release all mmaps. */
 void exit_mmap(struct mm_struct *mm)
 {
@@ -1254,7 +1277,6 @@ void exit_mmap(struct mm_struct *mm)
 	struct vm_area_struct *vma;
 	unsigned long nr_accounted = 0;
 	VMA_ITERATOR(vmi, mm, 0);
-	int count = 0;
 
 	/* mm's last user has gone, and its about to be pulled down */
 	mmu_notifier_release(mm);
@@ -1294,18 +1316,7 @@ void exit_mmap(struct mm_struct *mm)
 	 * enabled, without holding any MM locks besides the unreachable
 	 * mmap_write_lock.
 	 */
-	vma_iter_set(&vmi, vma->vm_end);
-	do {
-		if (vma->vm_flags & VM_ACCOUNT)
-			nr_accounted += vma_pages(vma);
-		vma_mark_detached(vma);
-		remove_vma(vma);
-		count++;
-		cond_resched();
-		vma = vma_next(&vmi);
-	} while (vma && likely(!xa_is_zero(vma)));
-
-	BUG_ON(count != mm->map_count);
+	nr_accounted = tear_down_vmas(mm, &vmi, vma, ULONG_MAX);
 
 destroy:
 	__mt_destroy(&mm->mm_mt);