linux-kernel - Re: [PROBLEM] 2.6.22-rc2 panics on x86-64 with slub

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Date:	Mon, 21 May 2007 19:44:50 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Christoph Lameter <clameter@....com>
cc:	Srihari Vijayaraghavan <sriharivijayaraghavan@...oo.com.au>,
	Oliver Xymoron <oxymoron@...te.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PROBLEM] 2.6.22-rc2 panics on x86-64 with slub

On Mon, 21 May 2007, Christoph Lameter wrote:
> On Mon, 21 May 2007, Hugh Dickins wrote:
> 
> > Yes, sounded the same to me too: I couldn't reproduce it or see anything
> > wrong in the code back then.  But Srihari's info about CONFIG_DEBUG_SLUB
> > off has helped a lot: I was then able to reproduce it on my x86_64, and
> > after a lot of staring at the code, the problem became obvious...
> 
> Right. The #ifdef CONFIG_SLUB_DEBUG is at the wrong location. The best fix
> is to moving the #ifdef otherwise the size is still wrong for the 
> ctor case.

? My patch did handle the ctor case.

> 
> SLUB Debug: Fix object size calculation
> 
> The object size calculation is wrong if !CONFIG_SLUB_DEBUG because
> the #ifdef CONFIG_SLUB_DEBUG is now switching off the size adjustments
> for DESTROY_BY_RCU and ctor.
> 
> Signed-off-by: Christoph Lameter <clameter@....com>

Yes, I think that should do it too.  The reason behind my repeating
the block was to handle the case where SLAB_POISON is passed to
kmem_cache_create, but CONFIG_SLUB_DEBUG is off.  But apparently
that case would hit the BUG_ON(flags & ~CREATE_MASK), therefore
your patch is simpler and better.  Quite a maze.

Hugh

> 
> ---
>  mm/slub.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: slub/mm/slub.c
> ===================================================================
> --- slub.orig/mm/slub.c	2007-05-21 11:21:36.000000000 -0700
> +++ slub/mm/slub.c	2007-05-21 11:21:49.000000000 -0700
> @@ -1943,7 +1943,6 @@ static int calculate_sizes(struct kmem_c
>  	 */
>  	s->inuse = size;
>  
> -#ifdef CONFIG_SLUB_DEBUG
>  	if (((flags & (SLAB_DESTROY_BY_RCU | SLAB_POISON)) ||
>  		s->ctor)) {
>  		/*
> @@ -1958,6 +1957,7 @@ static int calculate_sizes(struct kmem_c
>  		size += sizeof(void *);
>  	}
>  
> +#ifdef CONFIG_SLUB_DEBUG
>  	if (flags & SLAB_STORE_USER)
>  		/*
>  		 * Need to store information about allocs and frees after
-
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