linux-kernel - Re: [PATCH v3] futex: Remove requirement for lock

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Message-ID: <alpine.DEB.2.11.1601202058520.3575@nanos>
Date:	Wed, 20 Jan 2016 21:01:11 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Davidlohr Bueso <dave@...olabs.net>
cc:	Mel Gorman <mgorman@...hsingularity.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Chris Mason <clm@...com>, Darren Hart <dvhart@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH v3] futex: Remove requirement for lock_page in

On Wed, 20 Jan 2016, Davidlohr Bueso wrote:
> On Tue, 19 Jan 2016, Bueso wrote:
> > +
> > +		/* Should be impossible but lets be paranoid for now */
> > +		BUG_ON(inode->i_mapping != mapping);
> 
> Hmm, do we want to transform this into an if and do rcu unlock and then just
> call BUG()? I't doesn't matter at this point _anyway_, but it would be the
> right
> thing to do, no?

The better solution is to err out gracefully.

    	   if (WARN_ON_ONCE(inode->i_mapping != mapping) {
	      	   err = -EFAULT;
		   rcu_read_unlock();
		   goto out;
    	   }

Hmm?

Thanks,

	tglx