linux-kernel - Re: [PATCH 6/6] procfs: Kill the bkl in ioctl

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Date:	Tue, 30 Mar 2010 09:07:34 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Kacur <jkacur@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 6/6] procfs: Kill the bkl in ioctl

On Tue, Mar 30, 2010 at 09:38:11AM +0300, Alexey Dobriyan wrote:
> On Tue, Mar 30, 2010 at 9:20 AM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> > --- a/fs/proc/inode.c
> > +++ b/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();
> 
> Then delete the branch.
> Or go through formal feature-removal procedure.


I thought about it. I even started to write something in this
feature-removal file but realized that I can't remove the
.ioctl() callback from file operations. We still need to check
the user hasn't made the mistake of implementing it.

What I can plan as a feature removal, though, is to keep the warning
but don't actually call the ioctl.

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