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Subject: Re: [RFC][PATCH] slub: Check for page NULL before doing the
 node_match check
From: Steven Rostedt <rostedt@goodmis.org>
Date: Thu, 17 Jan 2013 16:44:21 -0500
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To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Christoph Lameter <cl@linux.com>, LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, Andrew Morton <akpm@linux-foundation.org>, Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>, Thomas Gleixner <tglx@linutronix.de>, RT <linux-rt-users@vger.kernel.org>, Clark Williams <clark@redhat.com>, John Kacur <jkacur@gmail.com>, "Luis Claudio
 R. Goncalves" <lgoncalv@redhat.com>

On Thu, 2013-01-17 at 13:36 -0800, Eric Dumazet wrote:

> > Index: linux/mm/slub.c
> > ===================================================================
> > --- linux.orig/mm/slub.c	2013-01-15 10:42:08.490183607 -0600
> > +++ linux/mm/slub.c	2013-01-17 15:27:48.973051155 -0600
> > @@ -1993,8 +1993,8 @@ static inline void flush_slab(struct kme
> >  	deactivate_slab(s, c->page, c->freelist);
> > 
> >  	c->tid = next_tid(c->tid);
> > -	c->page = NULL;
> >  	c->freelist = NULL;
> > +	c->page = NULL;
> >  }
> > 
> >  /*
> > @@ -2227,8 +2227,8 @@ redo:
> >  	if (unlikely(!node_match(page, node))) {
> >  		stat(s, ALLOC_NODE_MISMATCH);
> >  		deactivate_slab(s, page, c->freelist);
> > -		c->page = NULL;
> >  		c->freelist = NULL;
> > +		c->page = NULL;
> >  		goto new_slab;
> >  	}
> > 
> > @@ -2239,8 +2239,8 @@ redo:
> >  	 */
> >  	if (unlikely(!pfmemalloc_match(page, gfpflags))) {
> >  		deactivate_slab(s, page, c->freelist);
> > -		c->page = NULL;
> >  		c->freelist = NULL;
> > +		c->page = NULL;
> >  		goto new_slab;
> >  	}
> > 
> 
> Without appropriate barriers, this change is a shoot in the dark.

Totally agree.

-- Steve


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