On Wed 24-08-16 12:23:00, Arnd Bergmann wrote:
> A bugfix in v4.8-rc2 introduced a harmless warning when CONFIG_MEMCG_SWAP
> is disabled but CONFIG_MEMCG is enabled:
>
> mm/memcontrol.c:4085:27: error: 'mem_cgroup_id_get_online' defined but not used [-Werror=unused-function]
> static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
>
> This moves the function inside of the #ifdef block that hides the
> calling function, to avoid the warning.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Fixes: 1f47b61fb407 ("mm: memcontrol: fix swap counter leak on swapout from offline cgroup")
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Acked-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Thanks a lot for respinning this Arnd!
> ---
> mm/memcontrol.c | 36 ++++++++++++++++++------------------
> 1 file changed, 18 insertions(+), 18 deletions(-)
>
> This is the alternative to the original patch, as suggested by Michal Hocko.
> Andrew, please pick whichever version you like better.
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2ff0289ad061..9a6a51a7c416 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4082,24 +4082,6 @@ static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
> atomic_add(n, &memcg->id.ref);
> }
>
> -static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
> -{
> - while (!atomic_inc_not_zero(&memcg->id.ref)) {
> - /*
> - * The root cgroup cannot be destroyed, so it's refcount must
> - * always be >= 1.
> - */
> - if (WARN_ON_ONCE(memcg == root_mem_cgroup)) {
> - VM_BUG_ON(1);
> - break;
> - }
> - memcg = parent_mem_cgroup(memcg);
> - if (!memcg)
> - memcg = root_mem_cgroup;
> - }
> - return memcg;
> -}
> -
> static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
> {
> if (atomic_sub_and_test(n, &memcg->id.ref)) {
> @@ -5821,6 +5803,24 @@ static int __init mem_cgroup_init(void)
> subsys_initcall(mem_cgroup_init);
>
> #ifdef CONFIG_MEMCG_SWAP
> +static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
> +{
> + while (!atomic_inc_not_zero(&memcg->id.ref)) {
> + /*
> + * The root cgroup cannot be destroyed, so it's refcount must
> + * always be >= 1.
> + */
> + if (WARN_ON_ONCE(memcg == root_mem_cgroup)) {
> + VM_BUG_ON(1);
> + break;
> + }
> + memcg = parent_mem_cgroup(memcg);
> + if (!memcg)
> + memcg = root_mem_cgroup;
> + }
> + return memcg;
> +}
> +
> /**
> * mem_cgroup_swapout - transfer a memsw charge to swap
> * @page: page whose memsw charge to transfer
> --
> 2.9.0
--
Michal Hocko
SUSE Labs
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