[PATCH v7 66/70] nommu: Remove uses of VMA linked list

[Liam Howlett <liam.howlett@oracle.com>]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Use the maple tree or VMA iterator instead.  This is faster and will
allow us to shrink the VMA.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/nommu.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 26a9056e508f..645d11d3a8ab 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1381,6 +1381,7 @@ static int shrink_vma(struct mm_struct *mm,
  */
 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
 {
+	MA_STATE(mas, &mm->mm_mt, start, start);
 	struct vm_area_struct *vma;
 	unsigned long end;
 	int ret;
@@ -1392,7 +1393,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list
 	end = start + len;
 
 	/* find the first potentially overlapping VMA */
-	vma = find_vma(mm, start);
+	vma = mas_find(&mas, end - 1);
 	if (!vma) {
 		static int limit;
 		if (limit < 5) {
@@ -1411,7 +1412,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list
 				return -EINVAL;
 			if (end == vma->vm_end)
 				goto erase_whole_vma;
-			vma = vma->vm_next;
+			vma = mas_next(&mas, end - 1);
 		} while (vma);
 		return -EINVAL;
 	} else {
@@ -1460,6 +1461,7 @@ SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
  */
 void exit_mmap(struct mm_struct *mm)
 {
+	VMA_ITERATOR(vmi, mm, 0);
 	struct vm_area_struct *vma;
 
 	if (!mm)
@@ -1467,12 +1469,17 @@ void exit_mmap(struct mm_struct *mm)
 
 	mm->total_vm = 0;
 
-	while ((vma = mm->mmap)) {
-		mm->mmap = vma->vm_next;
+	/*
+	 * Lock the mm to avoid assert complaining even though this is the only
+	 * user of the mm
+	 */
+	mmap_write_lock(mm);
+	for_each_vma(vmi, vma) {
 		delete_vma_from_mm(vma);
 		delete_vma(mm, vma);
 		cond_resched();
 	}
+	mmap_write_unlock(mm);
 	__mt_destroy(&mm->mm_mt);
 }
 
-- 
2.34.1