Re: [PATCH] Fix boot problem in situations where the boot CPU is running on a memoryless node

Pekka J Enberg
2008-01-23T14:49:53Z

Hi,

On Wed, 23 Jan 2008, Pekka J Enberg wrote:
> > I still think Christoph's kmem_getpages() patch is correct (to fix
> > cache_grow() oops) but I overlooked the fact that none the callers of
> > ____cache_alloc_node() deal with bootstrapping (with the exception of
> > __cache_alloc_node() that even has a comment about it).
>
> So something like this (totally untested) patch on top of current git:

Sorry, removed a BUG_ON() from cache_alloc_refill() by mistake, here's a
better one:

[PATCH] slab: fix allocation on memoryless nodes
From: Pekka Enberg <penberg@cs.helsinki.fi>

As memoryless nodes do not have a nodelist, change cache_alloc_refill() to bail
out for those and let ____cache_alloc_node() always deal with that by resorting
to fallback_alloc().

Furthermore, don't let kmem_getpages() call alloc_pages_node() if nodeid passed
to it is -1 as the latter will always translate that to numa_node_id() which
might not have ->nodelist that caused the invocation of fallback_alloc() in the
first place (for example, during bootstrap).

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
---
mm/slab.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

Index: linux-2.6/mm/slab.c
===================================================================
--- linux-2.6.orig/mm/slab.c
+++ linux-2.6/mm/slab.c
@@ -1668,7 +1668,11 @@ static void *kmem_getpages(struct kmem_c
if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
flags |= __GFP_RECLAIMABLE;

- page = alloc_pages_node(nodeid, flags, cachep->gfporder);
+ if (nodeid == -1)
+ page = alloc_pages(flags, cachep->gfporder);
+ else
+ page = alloc_pages_node(nodeid, flags, cachep->gfporder);
+
if (!page)
return NULL;

@@ -2975,9 +2979,11 @@ retry:
*/
batchcount = BATCHREFILL_LIMIT;
}
+ BUG_ON(ac->avail > 0);
l3 = cachep->nodelists[node];
+ if (!l3)
+ return NULL;

- BUG_ON(ac->avail > 0 || !l3);
spin_lock(&l3->list_lock);

/* See if we can refill from the shared array */
@@ -3317,7 +3323,8 @@ static void *____cache_alloc_node(struct
int x;

l3 = cachep->nodelists[nodeid];
- BUG_ON(!l3);
+ if (!l3)
+ return fallback_alloc(cachep, flags);

retry:
check_irq_off();
@@ -3394,12 +3401,6 @@ __cache_alloc_node(struct kmem_cache *ca
if (unlikely(nodeid == -1))
nodeid = numa_node_id();

- if (unlikely(!cachep->nodelists[nodeid])) {
- /* Node not bootstrapped yet */
- ptr = fallback_alloc(cachep, flags);
- goto out;
- }
-
if (nodeid == numa_node_id()) {
/*
* Use the locally cached objects if possible.