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memory hotplug: make kmem_cache_node for SLUB on memory online avoid panic 

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.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: locking fix]
[akpm@linux-foundation.org: build fix]
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yasunori Goto 2007-10-21 16:41:37 -07:00 committed by Linus Torvalds
parent 7b78d335ac
commit b9049e2344
2 changed files with 122 additions and 0 deletions
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4
include/linux/memory.h
View File

@ -83,10 +83,14 @@ extern int memory_notify(unsigned long val, void *v);
#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
#ifdef CONFIG_MEMORY_HOTPLUG
#define hotplug_memory_notifier(fn, pri) { \
static struct notifier_block fn##_mem_nb = \
{ .notifier_call = fn, .priority = pri }; \
register_memory_notifier(&fn##_mem_nb); \
}
#else
#define hotplug_memory_notifier(fn, pri) do { } while (0)
#endif
#endif /* _LINUX_MEMORY_H_ */

118
mm/slub.c
View File

@ -20,6 +20,7 @@
#include <linux/mempolicy.h>
#include <linux/ctype.h>
#include <linux/kallsyms.h>
#include <linux/memory.h>
/*
* Lock order:
@ -2694,6 +2695,121 @@ int kmem_cache_shrink(struct kmem_cache *s)
}
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;
int ret = 0;
/*
* 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) {
ret = -ENOMEM;
goto out;
}
init_kmem_cache_node(n);
s->node[nid] = n;
}
out:
up_read(&slub_lock);
return ret;
}
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 +2831,8 @@ 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 */