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

KAMEZAWA Hiroyuki
2008-10-21T13:09:54Z

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;