The new zswap writeback scheme requires an online-only memcg hierarchy traversal. Add this functionality via the new mem_cgroup_iter_online() function - the old mem_cgroup_iter() is a special case of this new function.
Suggested-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Nhat Pham nphamcs@gmail.com --- include/linux/memcontrol.h | 13 +++++++++++++ mm/memcontrol.c | 29 +++++++++++++++++++++++++---- 2 files changed, 38 insertions(+), 4 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 7bdcf3020d7a..5bfe41840e80 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -833,6 +833,10 @@ static inline void mem_cgroup_put(struct mem_cgroup *memcg) struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *, struct mem_cgroup *, struct mem_cgroup_reclaim_cookie *); +struct mem_cgroup *mem_cgroup_iter_online(struct mem_cgroup *root, + struct mem_cgroup *prev, + struct mem_cgroup_reclaim_cookie *reclaim, + bool online); void mem_cgroup_iter_break(struct mem_cgroup *, struct mem_cgroup *); void mem_cgroup_scan_tasks(struct mem_cgroup *memcg, int (*)(struct task_struct *, void *), void *arg); @@ -1386,6 +1390,15 @@ mem_cgroup_iter(struct mem_cgroup *root, return NULL; }
+static inline struct mem_cgroup * +mem_cgroup_iter_online(struct mem_cgroup *root, + struct mem_cgroup *prev, + struct mem_cgroup_reclaim_cookie *reclaim, + bool online) +{ + return NULL; +} + static inline void mem_cgroup_iter_break(struct mem_cgroup *root, struct mem_cgroup *prev) { diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 470821d1ba1a..b1fb96233fa1 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1111,10 +1111,11 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) }
/** - * mem_cgroup_iter - iterate over memory cgroup hierarchy + * mem_cgroup_iter_online - iterate over memory cgroup hierarchy * @root: hierarchy root * @prev: previously returned memcg, NULL on first invocation * @reclaim: cookie for shared reclaim walks, NULL for full walks + * @online: whether to skip offline memcgs * * Returns references to children of the hierarchy below @root, or * @root itself, or %NULL after a full round-trip. @@ -1123,13 +1124,16 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) * invocations for reference counting, or use mem_cgroup_iter_break() * to cancel a hierarchy walk before the round-trip is complete. * + * Caller can skip offline memcgs by passing true for @online. + * * Reclaimers can specify a node in @reclaim to divide up the memcgs * in the hierarchy among all concurrent reclaimers operating on the * same node. */ -struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, +struct mem_cgroup *mem_cgroup_iter_online(struct mem_cgroup *root, struct mem_cgroup *prev, - struct mem_cgroup_reclaim_cookie *reclaim) + struct mem_cgroup_reclaim_cookie *reclaim, + bool online) { struct mem_cgroup_reclaim_iter *iter; struct cgroup_subsys_state *css = NULL; @@ -1199,7 +1203,8 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, * is provided by the caller, so we know it's alive * and kicking, and don't take an extra reference. */ - if (css == &root->css || css_tryget(css)) { + if (css == &root->css || (!online && css_tryget(css)) || + css_tryget_online(css)) { memcg = mem_cgroup_from_css(css); break; } @@ -1228,6 +1233,22 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, return memcg; }
+/** + * mem_cgroup_iter - iterate over memory cgroup hierarchy + * @root: hierarchy root + * @prev: previously returned memcg, NULL on first invocation + * @reclaim: cookie for shared reclaim walks, NULL for full walks + * + * Perform an iteration on the memory cgroup hierarchy without skipping + * offline memcgs. + */ +struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, + struct mem_cgroup *prev, + struct mem_cgroup_reclaim_cookie *reclaim) +{ + return mem_cgroup_iter_online(root, prev, reclaim, false); +} + /** * mem_cgroup_iter_break - abort a hierarchy walk prematurely * @root: hierarchy root