procfs: Kill the bkl in ioctl

There are no more users of procfs that implement the ioctl
callback. Drop the bkl from this path and warn on any use
of this callback.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: John Kacur <jkacur@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>

fs/proc/inode.c

@@ -231,9 +231,9 @@ static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigne
 		if (rv == -ENOIOCTLCMD)
 			rv = -EINVAL;
 	} else if (ioctl) {
-		lock_kernel();
+		WARN_ONCE(1, "Procfs ioctl handlers must use unlocked_ioctl, "
+			  "%pf will be called without the Bkl held\n", ioctl);
 		rv = ioctl(file->f_path.dentry->d_inode, file, cmd, arg);
-		unlock_kernel();
 	}
 
 	pde_users_dec(pde);