On Thu, 20 Dec 2007 14:31:52 +0530
Balbir Singh <[email protected]> wrote:
>
>
> Hugh Dickins noticed that we were using rcu_dereference() without
> rcu_read_lock() in the cache charging routine. The patch below fixes
> this problem
>
> Signed-off-by: Balbir Singh <[email protected]>
> ---
>
> mm/memcontrol.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff -puN mm/memcontrol.c~memory-controller-use-rcu-lead-lock mm/memcontrol.c
> --- linux-2.6.24-rc5/mm/memcontrol.c~memory-controller-use-rcu-lead-lock 2007-12-19 11:52:44.000000000 +0530
> +++ linux-2.6.24-rc5-balbir/mm/memcontrol.c 2007-12-20 14:01:45.000000000 +0530
> @@ -717,16 +717,20 @@ int mem_cgroup_charge(struct page *page,
> int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> gfp_t gfp_mask)
> {
> + int ret = 0;
> struct mem_cgroup *mem;
> if (!mm)
> mm = &init_mm;
>
> + rcu_read_lock();
> mem = rcu_dereference(mm->mem_cgroup);
> + css_get(&mem->css);
> + rcu_read_unlock();
> if (mem->control_type == MEM_CGROUP_TYPE_ALL)
> - return mem_cgroup_charge_common(page, mm, gfp_mask,
> + ret = mem_cgroup_charge_common(page, mm, gfp_mask,
> MEM_CGROUP_CHARGE_TYPE_CACHE);
> - else
> - return 0;
> + css_put(&mem->css);
> + return ret;
> }
>
> /*
> _
Seems reasonable to me.
Acked-by: KAMEZAWA Hiroyuki <[email protected]>
Thanks,
-Kame
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