linux-kernel - Re: slub: Fix per cpu partial statistics

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Message-ID: <alpine.DEB.2.00.1112141858380.27595@chino.kir.corp.google.com>
Date:	Wed, 14 Dec 2011 19:05:21 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Pekka Enberg <penberg@...nel.org>
cc:	Christoph Lameter <cl@...ux.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: slub: Fix per cpu partial statistics

On Mon, 12 Dec 2011, Pekka Enberg wrote:

> > Subject: slub: Fix per cpu partial statistics
> > 
> > Support for SO_OBJECTS was not properly added to show_slab_objects().
> > 
> > If SO_OBJECTS is not set then the number of slab pages needs to be
> > returned and not the number of objects in the partial slabs as now.
> > 
> > We do not have that number so just return 1 until we find a better
> > way to determine that.
> > 
> > Signed-off-by: Christoph Lameter <cl@...ux.com>
> > 
> > ---
> > mm/slub.c |   10 +++++++---
> > 1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > Index: linux-2.6/mm/slub.c
> > ===================================================================
> > --- linux-2.6.orig/mm/slub.c	2011-11-22 13:42:23.000000000 -0600
> > +++ linux-2.6/mm/slub.c	2011-11-22 13:47:52.000000000 -0600
> > @@ -4451,8 +4451,8 @@ static ssize_t show_slab_objects(struct
> > 				continue;
> > 
> > 			if (c->page) {
> > -					if (flags & SO_TOTAL)
> > -						x = c->page->objects;
> > +				if (flags & SO_TOTAL)
> > +					x = c->page->objects;
> > 				else if (flags & SO_OBJECTS)
> > 					x = c->page->inuse;
> > 				else

This was already fixed up by "slub: avoid potential NULL dereference or 
corruption" in slab/next, so I suggest dropping this hunk.

> > @@ -4464,7 +4464,11 @@ static ssize_t show_slab_objects(struct
> > 			page = c->partial;
> > 
> > 			if (page) {
> > -				x = page->pobjects;
> > +				if (flags & SO_OBJECTS)
> > +					x = page->pobjects;
> > +				else
> > +					/* Assume one */
> > +					x = 1;
> >                                 total += x;
> >                                 nodes[c->node] += x;
> > 			}
> > 
> 
> Looks OK to me. David, Eric?
> 

I thought page->pages would be better?
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