linux-kernel - Re: [PATCH] fix BUG_ON(!PageSlab) from fallback

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Message-ID: <Pine.LNX.4.64.0701041840360.23501@blonde.wat.veritas.com>
Date:	Thu, 4 Jan 2007 18:57:56 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Andrew Morton <akpm@...l.org>,
	Christoph Lameter <clameter@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix BUG_ON(!PageSlab) from fallback_alloc

On Thu, 4 Jan 2007, Pekka Enberg wrote:

> Hi Hugh,
> 
> [Sorry, no access to kernel tree right now, so can't send a patch.]
> 
> On 1/4/07, Hugh Dickins <hugh@...itas.com> wrote:
> > @@ -3310,7 +3310,7 @@ retry:
> >                                         */
> >                                         goto retry;
> >                         } else {
> > -                               kmem_freepages(cache, obj);
> > +                               /* cache_grow already freed obj */
> >                                 obj = NULL;
> 
> So, how about we rename the current cache_grow() to __cache_grow() and
> move the kmem_freepages() to a higher level function like this:
> 
> static int cache_grow(struct kmem_cache *cache,
>                                gfp_t flags, int nodeid)
> {
>        void *objp;
>        int ret;
> 
>        if (flags & __GFP_NO_GROW)
>                return 0;
> 
>        objp = kmem_getpages(cachep, flags, nodeid);
>        if (!objp)
>                return 0;
> 
>        ret = __cache_grow(cache, flags, nodeid, objp);
>        if (!ret)
>                kmem_freepages(cachep, objp);
> 
>        return ret;
> }
> 
> And use the non-allocating __cache_grow version() in fallback_alloc() instead?

That does indeed look more tasteful.  But there appears to be a fair
bit more refactoring one would want to do, if aiming for good taste
there: the kmem_flagcheck, the conditional local_irq_dis/enable...
I think I'll leave that to you and Christoph to fight over later!

Hugh
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