This patch fixes panic due to access NULL pointer of kmem_cache_node at discard_slab() after memory online.
When memory online is called, kmem_cache_nodes are created for all SLUBs for new node whose memory are available. slab_mem_going_online_callback() is called to make kmem_cache_node() in callback of memory online event. If it (or other callbacks) fails, then slab_mem_offline_callback() is called for rollback. In memory offline, slab_mem_going_offline_callback() is called to shrink all slub cache, then slab_mem_offline_callback() is called later. This patch is tested on my ia64 box. Please apply. Signed-off-by: Yasunori Goto <[EMAIL PROTECTED]> --- mm/slub.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) Index: current/mm/slub.c =================================================================== --- current.orig/mm/slub.c 2007-10-17 21:17:53.000000000 +0900 +++ current/mm/slub.c 2007-10-17 22:23:08.000000000 +0900 @@ -20,6 +20,7 @@ #include <linux/mempolicy.h> #include <linux/ctype.h> #include <linux/kallsyms.h> +#include <linux/memory.h> /* * Lock order: @@ -2688,6 +2689,118 @@ int kmem_cache_shrink(struct kmem_cache } EXPORT_SYMBOL(kmem_cache_shrink); +#if defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG) +static int slab_mem_going_offline_callback(void *arg) +{ + struct kmem_cache *s; + + down_read(&slub_lock); + list_for_each_entry(s, &slab_caches, list) + kmem_cache_shrink(s); + up_read(&slub_lock); + + return 0; +} + +static void slab_mem_offline_callback(void *arg) +{ + struct kmem_cache_node *n; + struct kmem_cache *s; + struct memory_notify *marg = arg; + int offline_node; + + offline_node = marg->status_change_nid; + + /* + * If the node still has available memory. we need kmem_cache_node + * for it yet. + */ + if (offline_node < 0) + return; + + down_read(&slub_lock); + list_for_each_entry(s, &slab_caches, list) { + n = get_node(s, offline_node); + if (n) { + /* + * if n->nr_slabs > 0, slabs still exist on the node + * that is going down. We were unable to free them, + * and offline_pages() function shoudn't call this + * callback. So, we must fail. + */ + BUG_ON(atomic_read(&n->nr_slabs)); + + s->node[offline_node] = NULL; + kmem_cache_free(kmalloc_caches, n); + } + } + up_read(&slub_lock); +} + +static int slab_mem_going_online_callback(void *arg) +{ + struct kmem_cache_node *n; + struct kmem_cache *s; + struct memory_notify *marg = arg; + int nid = marg->status_change_nid; + + /* + * If the node's memory is already available, then kmem_cache_node is + * already created. Nothing to do. + */ + if (nid < 0) + return 0; + + /* + * We are bringing a node online. No memory is availabe yet. We must + * allocate a kmem_cache_node structure in order to bring the node + * online. + */ + down_read(&slub_lock); + list_for_each_entry(s, &slab_caches, list) { + /* + * XXX: kmem_cache_alloc_node will fallback to other nodes + * since memory is not yet available from the node that + * is brought up. + */ + n = kmem_cache_alloc(kmalloc_caches, GFP_KERNEL); + if (!n) + return -ENOMEM; + init_kmem_cache_node(n); + s->node[nid] = n; + } + up_read(&slub_lock); + + return 0; +} + +static int slab_memory_callback(struct notifier_block *self, + unsigned long action, void *arg) +{ + int ret = 0; + + switch (action) { + case MEM_GOING_ONLINE: + ret = slab_mem_going_online_callback(arg); + break; + case MEM_GOING_OFFLINE: + ret = slab_mem_going_offline_callback(arg); + break; + case MEM_OFFLINE: + case MEM_CANCEL_ONLINE: + slab_mem_offline_callback(arg); + break; + case MEM_ONLINE: + case MEM_CANCEL_OFFLINE: + break; + } + + ret = notifier_from_errno(ret); + return ret; +} + +#endif /* CONFIG_MEMORY_HOTPLUG */ + /******************************************************************** * Basic setup of slabs *******************************************************************/ @@ -2709,6 +2822,8 @@ void __init kmem_cache_init(void) sizeof(struct kmem_cache_node), GFP_KERNEL); kmalloc_caches[0].refcount = -1; caches++; + + hotplug_memory_notifier(slab_memory_callback, 1); #endif /* Able to allocate the per node structures */ -- Yasunori Goto - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/