The patch titled
memory hotplug: make kmem_cache_node for SLUB on memory online avoid panic
has been added to the -mm tree. Its filename is
memory-hotplug-make-kmem_cache_node-for-slub-on-memory-online-avoid-panic.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: memory hotplug: make kmem_cache_node for SLUB on memory online avoid panic
From: Yasunori Goto <y-goto@xxxxxxxxxxxxxx>
Fix a 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.
Signed-off-by: Yasunori Goto <y-goto@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 115 insertions(+)
diff -puN mm/slub.c~memory-hotplug-make-kmem_cache_node-for-slub-on-memory-online-avoid-panic mm/slub.c
--- a/mm/slub.c~memory-hotplug-make-kmem_cache_node-for-slub-on-memory-online-avoid-panic
+++ a/mm/slub.c
@@ -20,6 +20,7 @@
#include <linux/mempolicy.h>
#include <linux/ctype.h>
#include <linux/kallsyms.h>
+#include <linux/memory.h>
/*
* Lock order:
@@ -2694,6 +2695,118 @@ 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
*******************************************************************/
@@ -2715,6 +2828,8 @@ 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 */
_
Patches currently in -mm which might be from y-goto@xxxxxxxxxxxxxx are
origin.patch
memory-hotplug-make-description-of-memory-hotplug-notifier-in-document.patch
memory-hotplug-rearrange-patch-for-notifier-of-memory-hotplug.patch
memory-hotplug-make-kmem_cache_node-for-slub-on-memory-online-avoid-panic.patch
memory-hotplug-make-kmem_cache_node-for-slub-on-memory-online-avoid-panic-fix.patch
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