mm/vmalloc: revert "mm/vmalloc.c: check VM_UNINITIALIZED flag in s_show instead of show_numa_info"

The VM_UNINITIALIZED/VM_UNLIST flag introduced by f5252e009d5b ("mm:
avoid null pointer access in vm_struct via /proc/vmallocinfo") is used
to avoid accessing the pages field with unallocated page when
show_numa_info() is called.

This patch moves the check just before show_numa_info in order that some
messages still can be dumped via /proc/vmallocinfo.  This patch reverts
commit d157a55815ff ("mm/vmalloc.c: check VM_UNINITIALIZED flag in
s_show instead of show_numa_info");

Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmalloc.c

@@ -2562,6 +2562,11 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v)
 		if (!counters)
 			return;
 
+		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
+		smp_rmb();
+		if (v->flags & VM_UNINITIALIZED)
+			return;
+
 		memset(counters, 0, nr_node_ids * sizeof(unsigned int));
 
 		for (nr = 0; nr < v->nr_pages; nr++)
@@ -2587,11 +2592,6 @@ static int s_show(struct seq_file *m, void *p)
 
 	v = va->vm;
 
-	/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
-	smp_rmb();
-	if (v->flags & VM_UNINITIALIZED)
-		return 0;
-
 	seq_printf(m, "0x%pK-0x%pK %7ld",
 		v->addr, v->addr + v->size, v->size);