slub: use irqsafe_cpu_cmpxchg for put_cpu_partial

The cmpxchg must be irq safe. The fallback for this_cpu_cmpxchg only
disables preemption which results in per cpu partial page operation
potentially failing on non x86 platforms.

This patch fixes the following problem reported by Christian Kujau:

  I seem to hit it with heavy disk & cpu IO is in progress on this
  PowerBook
  G4. Full dmesg & .config: http://nerdbynature.de/bits/3.2.0-rc1/oops/

  I've enabled some debug options and now it really points to slub.c:2166

    http://nerdbynature.de/bits/3.2.0-rc1/oops/oops4m.jpg

  With debug options enabled I'm currently in the xmon debugger, not sure
  what to make of it yet, I'll try to get something useful out of it :)

Reported-by: Christian Kujau <lists@nerdbynature.de>
Tested-by: Christian Kujau <lists@nerdbynature.de>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

mm/slub.c

@@ -1978,7 +1978,7 @@ int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
 		page->pobjects = pobjects;
 		page->next = oldpage;
 
-	} while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
+	} while (irqsafe_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
 	stat(s, CPU_PARTIAL_FREE);
 	return pobjects;
 }