Re: [memcg BUG] unable to handle kernel NULL pointer derefence at00000000

[亀澤 寛之 <kamezawa.hiroyu@jp.fujitsu.com>]

> KAMEZAWA Hiroyuki wrote:
>> On Tue, 21 Oct 2008 17:44:40 +0530
>> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>>>> I got an idea and maybe can send a patch soon. I'm now finding x86-32
>>>> box..
>>> Please send it to me, I am able to reproduce the problem with my kvm
>>> setup on my
>>> 32 bit system. I can do a quick test/verification for you.
>>>
>> Thanks. how about this ? test on x86-64 is done.
>> -Kame
>> ==
>>
>>
>>
>> page_cgroup_init() is called from mem_cgroup_init(). But at this
>> point, we cannot call alloc_bootmem().
>> (and this caused panic at boot.)
>>
>> This patch moves page_cgroup_init() to init/main.c.
>>
>> Time table is following:
>> ==
>>   parse_args(). # we can trust mem_cgroup_subsys.disabled bit after
>> this.
>>   ....
>>   cgroup_init_early()  # "early" init of cgroup.
>>   ....
>>   setup_arch()         # memmap is allocated.
>>   ...
>>   page_cgroup_init();
>>   mem_init();   # we cannot call alloc_bootmem after this.
>>   ....
>>   cgroup_init() # mem_cgroup is initialized.
>> ==
>>
>> Before page_cgroup_init(), mem_map must be initialized. So,
>> I added page_cgroup_init() to init/main.c directly.
>>
>> (*) maybe this is not very clean but cgroup_init_early() is too early
>>     and we have to use vmalloc instead of alloc_bootmem() in
>> cgroup_init().
>>     usage of vmalloc area in x86-32 is important and we should avoid
>>     vmalloc() in x86-32. So, we want to use alloc_bootmem() from
>>     sutaible place.
>>
>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>>
>>  include/linux/page_cgroup.h |    1 +
>>  init/main.c                 |    2 ++
>>  mm/memcontrol.c             |    1 -
>>  mm/page_cgroup.c            |   35 ++++++++++++++++++++++++++++-------
>>  4 files changed, 31 insertions(+), 8 deletions(-)
>>
>> Index: linux-2.6/init/main.c
>> ===================================================================
>> --- linux-2.6.orig/init/main.c
>> +++ linux-2.6/init/main.c
>> @@ -62,6 +62,7 @@
>>  #include <linux/signal.h>
>>  #include <linux/idr.h>
>>  #include <linux/ftrace.h>
>> +#include <linux/page_cgroup.h>
>>
>>  #include <asm/io.h>
>>  #include <asm/bugs.h>
>> @@ -647,6 +648,7 @@ asmlinkage void __init start_kernel(void
>>  	vmalloc_init();
>>  	vfs_caches_init_early();
>>  	cpuset_init_early();
>> +	page_cgroup_init();
>>  	mem_init();
>>  	enable_debug_pagealloc();
>>  	cpu_hotplug_init();
>> Index: linux-2.6/mm/memcontrol.c
>> ===================================================================
>> --- linux-2.6.orig/mm/memcontrol.c
>> +++ linux-2.6/mm/memcontrol.c
>> @@ -1088,7 +1088,6 @@ mem_cgroup_create(struct cgroup_subsys *
>>  	int node;
>>
>>  	if (unlikely((cont->parent) == NULL)) {
>> -		page_cgroup_init();
>>  		mem = &init_mem_cgroup;
>>  	} else {
>>  		mem = mem_cgroup_alloc();
>> Index: linux-2.6/include/linux/page_cgroup.h
>> ===================================================================
>> --- linux-2.6.orig/include/linux/page_cgroup.h
>> +++ linux-2.6/include/linux/page_cgroup.h
>> @@ -3,6 +3,7 @@
>>
>>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR
>>  #include <linux/bit_spinlock.h>
>> +
>>  /*
>>   * Page Cgroup can be considered as an extended mem_map.
>>   * A page_cgroup page is associated with every page descriptor. The
>> Index: linux-2.6/mm/page_cgroup.c
>> ===================================================================
>> --- linux-2.6.orig/mm/page_cgroup.c
>> +++ linux-2.6/mm/page_cgroup.c
>> @@ -4,7 +4,12 @@
>>  #include <linux/bit_spinlock.h>
>>  #include <linux/page_cgroup.h>
>>  #include <linux/hash.h>
>> +#include <linux/slab.h>
>>  #include <linux/memory.h>
>> +#include <linux/cgroup.h>
>> +
>> +extern struct cgroup_subsys	mem_cgroup_subsys;
>> +
>>
>>  static void __meminit
>>  __init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
>> @@ -66,6 +71,9 @@ void __init page_cgroup_init(void)
>>
>>  	int nid, fail;
>>
>> +	if (mem_cgroup_subsys.disabled)
>> +		return;
>> +
>>  	for_each_online_node(nid)  {
>>  		fail = alloc_node_page_cgroup(nid);
>>  		if (fail)
>> @@ -106,9 +114,14 @@ int __meminit init_section_page_cgroup(u
>>  	nid = page_to_nid(pfn_to_page(pfn));
>>
>>  	table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
>> -	base = kmalloc_node(table_size, GFP_KERNEL, nid);
>> -	if (!base)
>> -		base = vmalloc_node(table_size, nid);
>> +	if (slab_is_available()) {
>> +		base = kmalloc_node(table_size, GFP_KERNEL, nid);
>> +		if (!base)
>> +			base = vmalloc_node(table_size, nid);
>> +	} else {
>> +		base = __alloc_bootmem_node_nopanic(NODE_DATA(nid), table_size,
>> +				PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
>> +	}
>>
>>  	if (!base) {
>>  		printk(KERN_ERR "page cgroup allocation failure\n");
>> @@ -135,11 +148,16 @@ void __free_page_cgroup(unsigned long pf
>>  	if (!ms || !ms->page_cgroup)
>>  		return;
>>  	base = ms->page_cgroup + pfn;
>> -	ms->page_cgroup = NULL;
>> -	if (is_vmalloc_addr(base))
>> +	if (is_vmalloc_addr(base)) {
>>  		vfree(base);
>> -	else
>> -		kfree(base);
>> +		ms->page_cgroup = NULL;
>> +	} else {
>> +		struct page *page = virt_to_page(base);
>> +		if (!PageReserved(page)) { /* Is bootmem ? */
>> +			kfree(base);
>> +			ms->page_cgroup = NULL;
>> +		}
>> +	}
>>  }
>>
>>  int online_page_cgroup(unsigned long start_pfn,
>> @@ -213,6 +231,9 @@ void __init page_cgroup_init(void)
>>  	unsigned long pfn;
>>  	int fail = 0;
>>
>> +	if (mem_cgroup_subsys.disabled)
>> +		return;
>> +
>>  	for (pfn = 0; !fail && pfn < max_pfn; pfn += PAGES_PER_SECTION) {
>>  		if (!pfn_present(pfn))
>>  			continue;
>
> Booted on x86_32 for me
>
> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> Tested-by: Balbir Singh <balbir@linux.vnet.ibm.com>
>

Thank you ! (I'll resend later if necessary.)

-Kame

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