Re: [git pull] m68k SLUB fix for 2.6.39

James Bottomley
2011-05-04T15:02:35Z

On Thu, 2011-04-28 at 14:41 -0700, David Rientjes wrote:
> On Thu, 28 Apr 2011, James Bottomley wrote:
>
> > > Since 4a5fa3590f09 ([PARISC] slub: fix panic with DISCONTIGMEM) from
> > > 2.6.39-rc4, you can't actually select slub on m68k without CONFIG_ADVANCED
> > > and CONFIG_SINGLE_MEMORY_CHUNK because it otherwises defaults to
> > > discontigmem.
> > >
> > > James tested hppa64 with my N_NORMAL_MEMORY fix and found that it turned
> > > an SMP box into UP. If you've tested slub on m68k without regressions,
> > > then perhaps you'd like to add a "|| M68K" to CONFIG_SLUB?
> >
> > To be honest, I really don't see that fixing it. As soon as you
> > allocate memory beyond range zero, you move onto a non-zero node as far
> > as slub is concerned, and that will oops.
> >
>
> Possible nodes are represented in slub with N_NORMAL_MEMORY, so the
> kmem_cache_node structures are allocated and initialized based on this
> nodemask. As long as the memory ranges map to nodes set in the nodemask,
> this should be fine.
>
> > I think what the N_NORMAL_MEMORY patch did is just make it take a whiile
> > before you start allocating from that range. Try executing a memory
> > balloon on the platform; that was how we first demonstrated the problem
> > on parisc.
> >
>
> With parisc, you encountered an oops in add_partial() because the
> kmem_cache_node structure for the memory range returned by page_to_nid()
> was not allocated. init_kmem_cache_nodes() takes care of this for all
> memory ranges set in N_NORMAL_MEMORY.

Yes, but I also encountered it after I applied you patch, which is why I
still pushed the Kconfig patch. It's possible, since there were a huge
number of patches flying around that the kernel base was contaminated,
so I'll strip down to just linus HEAD + parisc coherence patches,
reverting the Kconfig one and try again.

James