Since we unable to handle error returned by cftype.unregister_event() properly, let's make the callback void-returning.
mem_cgroup_unregister_event() has been rewritten to be "never fail" function. On mem_cgroup_usage_register_event() we save old buffer for thresholds array and reuse it in mem_cgroup_usage_unregister_event() to avoid allocation. Signed-off-by: Kirill A. Shutemov <[email protected]> --- include/linux/cgroup.h | 2 +- kernel/cgroup.c | 1 - mm/memcontrol.c | 64 ++++++++++++++++++++++++++++++------------------ 3 files changed, 41 insertions(+), 26 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 8f78073..0c62160 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -397,7 +397,7 @@ struct cftype { * This callback must be implemented, if you want provide * notification functionality. */ - int (*unregister_event)(struct cgroup *cgrp, struct cftype *cft, + void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft, struct eventfd_ctx *eventfd); }; diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 06dbf97..6675e8c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2988,7 +2988,6 @@ static void cgroup_event_remove(struct work_struct *work) remove); struct cgroup *cgrp = event->cgrp; - /* TODO: check return code */ event->cft->unregister_event(cgrp, event->cft, event->eventfd); eventfd_ctx_put(event->eventfd); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8cb2722..0a37b5d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -226,9 +226,19 @@ struct mem_cgroup { /* thresholds for memory usage. RCU-protected */ struct mem_cgroup_threshold_ary *thresholds; + /* + * Preallocated buffer to be used in mem_cgroup_unregister_event() + * to make it "never fail". + * It must be able to store at least thresholds->size - 1 entries. + */ + struct mem_cgroup_threshold_ary *__thresholds; + /* thresholds for mem+swap usage. RCU-protected */ struct mem_cgroup_threshold_ary *memsw_thresholds; + /* the same as __thresholds, but for memsw_thresholds */ + struct mem_cgroup_threshold_ary *__memsw_thresholds; + /* For oom notifier event fd */ struct list_head oom_notify; @@ -3575,17 +3585,27 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp, else rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new); - /* To be sure that nobody uses thresholds before freeing it */ + /* To be sure that nobody uses thresholds */ synchronize_rcu(); - kfree(thresholds); + /* + * Free old preallocated buffer and use thresholds as new + * preallocated buffer. + */ + if (type == _MEM) { + kfree(memcg->__thresholds); + memcg->__thresholds = thresholds; + } else { + kfree(memcg->__memsw_thresholds); + memcg->__memsw_thresholds = thresholds; + } unlock: mutex_unlock(&memcg->thresholds_lock); return ret; } -static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, +static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp, struct cftype *cft, struct eventfd_ctx *eventfd) { struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp); @@ -3593,7 +3613,7 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, int type = MEMFILE_TYPE(cft->private); u64 usage; int size = 0; - int i, j, ret = 0; + int i, j; mutex_lock(&memcg->thresholds_lock); if (type == _MEM) @@ -3623,17 +3643,15 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, /* Set thresholds array to NULL if we don't have thresholds */ if (!size) { thresholds_new = NULL; - goto assign; + goto swap_buffers; } - /* Allocate memory for new array of thresholds */ - thresholds_new = kmalloc(sizeof(*thresholds_new) + - size * sizeof(struct mem_cgroup_threshold), - GFP_KERNEL); - if (!thresholds_new) { - ret = -ENOMEM; - goto unlock; - } + /* Use preallocated buffer for new array of thresholds */ + if (type == _MEM) + thresholds_new = memcg->__thresholds; + else + thresholds_new = memcg->__memsw_thresholds; + thresholds_new->size = size; /* Copy thresholds and find current threshold */ @@ -3654,20 +3672,20 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, j++; } -assign: - if (type == _MEM) +swap_buffers: + /* Swap thresholds array and preallocated buffer */ + if (type == _MEM) { + memcg->__thresholds = thresholds; rcu_assign_pointer(memcg->thresholds, thresholds_new); - else + } else { + memcg->__memsw_thresholds = thresholds; rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new); + } - /* To be sure that nobody uses thresholds before freeing it */ + /* To be sure that nobody uses thresholds */ synchronize_rcu(); - kfree(thresholds); -unlock: mutex_unlock(&memcg->thresholds_lock); - - return ret; } static int mem_cgroup_oom_register_event(struct cgroup *cgrp, @@ -3695,7 +3713,7 @@ static int mem_cgroup_oom_register_event(struct cgroup *cgrp, return 0; } -static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp, +static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp, struct cftype *cft, struct eventfd_ctx *eventfd) { struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp); @@ -3714,8 +3732,6 @@ static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp, } mutex_unlock(&memcg_oom_mutex); - - return 0; } static int mem_cgroup_oom_control_read(struct cgroup *cgrp, -- 1.7.0.4 _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
