Input: remove BKL, fix input_open_file() locking

Holding the BKL in input_open_file seems pointless because it does not
protect against updates of input_table, and all open functions from the
underlying drivers have proper mutex locking.

This makes input_open_file take the input_mutex when accessing
the table and no lock when calling into the lower function.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/input.c

@@ -1879,35 +1879,37 @@ static int input_open_file(struct inode *inode, struct file *file)
 	const struct file_operations *old_fops, *new_fops = NULL;
 	int err;
 
-	lock_kernel();
+	err = mutex_lock_interruptible(&input_mutex);
+	if (err)
+		return err;
+
 	/* No load-on-demand here? */
 	handler = input_table[iminor(inode) >> 5];
-	if (!handler || !(new_fops = fops_get(handler->fops))) {
-		err = -ENODEV;
-		goto out;
-	}
+	if (handler)
+		new_fops = fops_get(handler->fops);
+
+	mutex_unlock(&input_mutex);
 
 	/*
 	 * That's _really_ odd. Usually NULL ->open means "nothing special",
 	 * not "no device". Oh, well...
 	 */
-	if (!new_fops->open) {
+	if (!new_fops || !new_fops->open) {
 		fops_put(new_fops);
 		err = -ENODEV;
 		goto out;
 	}
+
 	old_fops = file->f_op;
 	file->f_op = new_fops;
 
 	err = new_fops->open(inode, file);
-
 	if (err) {
 		fops_put(file->f_op);
 		file->f_op = fops_get(old_fops);
 	}
 	fops_put(old_fops);
 out:
-	unlock_kernel();
 	return err;
 }