This patch implements a helper function that try to get a reference to an memcg's css, as well as checking if it is online. This new function is almost exactly the same as the existing mem_cgroup_tryget(), except for the onlineness check. In the !CONFIG_MEMCG case, it always returns true, analogous to mem_cgroup_tryget(). This is useful for e.g to the new zswap writeback scheme, where we need to select the next online memcg as a candidate for the global limit reclaim.
Signed-off-by: Nhat Pham <[email protected]> --- include/linux/memcontrol.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 7bdcf3020d7a..2bd7d14ace78 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -821,6 +821,11 @@ static inline bool mem_cgroup_tryget(struct mem_cgroup *memcg) return !memcg || css_tryget(&memcg->css); } +static inline bool mem_cgroup_tryget_online(struct mem_cgroup *memcg) +{ + return !memcg || css_tryget_online(&memcg->css); +} + static inline void mem_cgroup_put(struct mem_cgroup *memcg) { if (memcg) @@ -1349,6 +1354,11 @@ static inline bool mem_cgroup_tryget(struct mem_cgroup *memcg) return true; } +static inline bool mem_cgroup_tryget_online(struct mem_cgroup *memcg) +{ + return true; +} + static inline void mem_cgroup_put(struct mem_cgroup *memcg) { } -- 2.34.1
