Re: [memcg BUG] unable to handle kernel NULL pointer derefence at 00000000

Balbir Singh
2008-10-21T13:34:07Z

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>

--
Balbir