mm: /proc/pid/smaps_rollup: fix maple tree search

/proc/pid/smaps_rollup showed 0 kB for everything: now find first vma.

Link: https://lkml.kernel.org/r/3011bee7-182-97a2-1083-d5f5b688e54b@google.com
Fixes: c4c84f0 ("fs/proc/task_mmu: stop using linked list and highest_vm_end")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Hugh Dickins

fs/proc/task_mmu.c

@@ -902,7 +902,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
 		goto out_put_mm;
 
 	hold_task_mempolicy(priv);
-	vma = mas_find(&mas, 0);
+	vma = mas_find(&mas, ULONG_MAX);
 
 	if (unlikely(!vma))
 		goto empty_set;