ipc/util.c: use __seq_open_private() instead of seq_open()

Using __seq_open_private() removes boilerplate code from
sysvipc_proc_open().

The resultant code is shorter and easier to follow.

However, please note that __seq_open_private() call kzalloc() rather than
kmalloc() which may affect timing due to the memory initialisation
overhead.

Signed-off-by: Rob Jones <rob.jones@codethink.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ipc/util.c

@@ -892,28 +892,16 @@ static const struct seq_operations sysvipc_proc_seqops = {
 
 static int sysvipc_proc_open(struct inode *inode, struct file *file)
 {
-	int ret;
-	struct seq_file *seq;
 	struct ipc_proc_iter *iter;
 
-	ret = -ENOMEM;
-	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
+	iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
 	if (!iter)
-		goto out;
-
-	ret = seq_open(file, &sysvipc_proc_seqops);
-	if (ret) {
-		kfree(iter);
-		goto out;
-	}
-
-	seq = file->private_data;
-	seq->private = iter;
+		return -ENOMEM;
 
 	iter->iface = PDE_DATA(inode);
 	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
-out:
-	return ret;
+
+	return 0;
 }
 
 static int sysvipc_proc_release(struct inode *inode, struct file *file)