mm/vmalloc: explicitly identify vm_map_ram area when shown in /proc/vmcoreinfo

Now, by marking VMAP_RAM in vmap_area->flags for vm_map_ram area, we can
clearly differentiate it with other vmalloc areas.  So identify
vm_map_area area by checking VMAP_RAM of vmap_area->flags when shown in
/proc/vmcoreinfo.

Meanwhile, the code comment above vm_map_ram area checking in s_show() is
not needed any more, remove it here.

Link: https://lkml.kernel.org/r/20230206084020.174506-5-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmalloc.c

@@ -4152,14 +4152,11 @@ static int s_show(struct seq_file *m, void *p)
 
 	va = list_entry(p, struct vmap_area, list);
 
-	/*
-	 * s_show can encounter race with remove_vm_area, !vm on behalf
-	 * of vmap area is being tear down or vm_map_ram allocation.
-	 */
 	if (!va->vm) {
-		seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
+		if (va->flags & VMAP_RAM)
-			(void *)va->va_start, (void *)va->va_end,
+			seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
-			va->va_end - va->va_start);
+				(void *)va->va_start, (void *)va->va_end,
+				va->va_end - va->va_start);
 
 		goto final;
 	}