linux-kernel - Re: [RFC][PATCH] slub: Check for page NULL before doing the node

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

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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