mm/madvise: use vma_lookup() instead of find_vma()

Using vma_lookup() verifies the start address is contained in the found
vma.  This results in easier to read the code.

Link: https://lkml.kernel.org/r/20220311082731.63513-1-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/madvise.c

@@ -849,8 +849,8 @@ static long madvise_populate(struct vm_area_struct *vma,
 		 * our VMA might have been split.
 		 */
 		if (!vma || start >= vma->vm_end) {
-			vma = find_vma(mm, start);
-			if (!vma || start < vma->vm_start)
+			vma = vma_lookup(mm, start);
+			if (!vma)
 				return -ENOMEM;
 		}