X-Git-Url: http://git.cascardo.info/?a=blobdiff_plain;f=mm%2Fmemcontrol.c;h=d12ca6f3c2934bc83bd83c467ed672c7f352d172;hb=365279167c1ee54c8f4c7cf77752433a3e41b30b;hp=6b73d8657d64ae45bfd0085e6d4111fa417f3337;hpb=fa460c2d37870e0a6f94c70e8b76d05ca11b6db0;p=cascardo%2Flinux.git diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 6b73d8657d64..d12ca6f3c293 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -263,28 +263,10 @@ struct mem_cgroup { /* vmpressure notifications */ struct vmpressure vmpressure; - union { - /* - * the counter to account for mem+swap usage. - */ - struct res_counter memsw; - - /* - * rcu_freeing is used only when freeing struct mem_cgroup, - * so put it into a union to avoid wasting more memory. - * It must be disjoint from the css field. It could be - * in a union with the res field, but res plays a much - * larger part in mem_cgroup life than memsw, and might - * be of interest, even at time of free, when debugging. - * So share rcu_head with the less interesting memsw. - */ - struct rcu_head rcu_freeing; - /* - * We also need some space for a worker in deferred freeing. - * By the time we call it, rcu_freeing is no longer in use. - */ - struct work_struct work_freeing; - }; + /* + * the counter to account for mem+swap usage. + */ + struct res_counter memsw; /* * the counter to account for kernel memory usage. @@ -299,8 +281,6 @@ struct mem_cgroup { bool oom_lock; atomic_t under_oom; - atomic_t refcnt; - int swappiness; /* OOM-Killer disable */ int oom_kill_disable; @@ -406,6 +386,11 @@ static void memcg_kmem_clear_activated(struct mem_cgroup *memcg) static void memcg_kmem_mark_dead(struct mem_cgroup *memcg) { + /* + * Our caller must use css_get() first, because memcg_uncharge_kmem() + * will call css_put() if it sees the memcg is dead. + */ + smp_wmb(); if (test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags)) set_bit(KMEM_ACCOUNTED_DEAD, &memcg->kmem_account_flags); } @@ -498,9 +483,6 @@ enum res_type { */ static DEFINE_MUTEX(memcg_create_mutex); -static void mem_cgroup_get(struct mem_cgroup *memcg); -static void mem_cgroup_put(struct mem_cgroup *memcg); - static inline struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s) { @@ -551,15 +533,15 @@ void sock_update_memcg(struct sock *sk) */ if (sk->sk_cgrp) { BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg)); - mem_cgroup_get(sk->sk_cgrp->memcg); + css_get(&sk->sk_cgrp->memcg->css); return; } rcu_read_lock(); memcg = mem_cgroup_from_task(current); cg_proto = sk->sk_prot->proto_cgroup(memcg); - if (!mem_cgroup_is_root(memcg) && memcg_proto_active(cg_proto)) { - mem_cgroup_get(memcg); + if (!mem_cgroup_is_root(memcg) && + memcg_proto_active(cg_proto) && css_tryget(&memcg->css)) { sk->sk_cgrp = cg_proto; } rcu_read_unlock(); @@ -573,7 +555,7 @@ void sock_release_memcg(struct sock *sk) struct mem_cgroup *memcg; WARN_ON(!sk->sk_cgrp->memcg); memcg = sk->sk_cgrp->memcg; - mem_cgroup_put(memcg); + css_put(&sk->sk_cgrp->memcg->css); } } @@ -3050,8 +3032,16 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg, u64 size) if (res_counter_uncharge(&memcg->kmem, size)) return; + /* + * Releases a reference taken in kmem_cgroup_css_offline in case + * this last uncharge is racing with the offlining code or it is + * outliving the memcg existence. + * + * The memory barrier imposed by test&clear is paired with the + * explicit one in memcg_kmem_mark_dead(). + */ if (memcg_kmem_test_and_clear_dead(memcg)) - mem_cgroup_put(memcg); + css_put(&memcg->css); } void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep) @@ -3242,7 +3232,7 @@ void memcg_release_cache(struct kmem_cache *s) list_del(&s->memcg_params->list); mutex_unlock(&memcg->slab_caches_mutex); - mem_cgroup_put(memcg); + css_put(&memcg->css); out: kfree(s->memcg_params); } @@ -3402,16 +3392,18 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg, mutex_lock(&memcg_cache_mutex); new_cachep = cachep->memcg_params->memcg_caches[idx]; - if (new_cachep) + if (new_cachep) { + css_put(&memcg->css); goto out; + } new_cachep = kmem_cache_dup(memcg, cachep); if (new_cachep == NULL) { new_cachep = cachep; + css_put(&memcg->css); goto out; } - mem_cgroup_get(memcg); atomic_set(&new_cachep->memcg_params->nr_pages , 0); cachep->memcg_params->memcg_caches[idx] = new_cachep; @@ -3499,8 +3491,6 @@ static void memcg_create_cache_work_func(struct work_struct *w) cw = container_of(w, struct create_work, work); memcg_create_kmem_cache(cw->memcg, cw->cachep); - /* Drop the reference gotten when we enqueued. */ - css_put(&cw->memcg->css); kfree(cw); } @@ -4218,12 +4208,12 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype, unlock_page_cgroup(pc); /* * even after unlock, we have memcg->res.usage here and this memcg - * will never be freed. + * will never be freed, so it's safe to call css_get(). */ memcg_check_events(memcg, page); if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) { mem_cgroup_swap_statistics(memcg, true); - mem_cgroup_get(memcg); + css_get(&memcg->css); } /* * Migration does not charge the res_counter for the @@ -4335,7 +4325,7 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout) /* * record memcg information, if swapout && memcg != NULL, - * mem_cgroup_get() was called in uncharge(). + * css_get() was called in uncharge(). */ if (do_swap_account && swapout && memcg) swap_cgroup_record(ent, css_id(&memcg->css)); @@ -4366,7 +4356,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent) if (!mem_cgroup_is_root(memcg)) res_counter_uncharge(&memcg->memsw, PAGE_SIZE); mem_cgroup_swap_statistics(memcg, false); - mem_cgroup_put(memcg); + css_put(&memcg->css); } rcu_read_unlock(); } @@ -4400,11 +4390,14 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry, * This function is only called from task migration context now. * It postpones res_counter and refcount handling till the end * of task migration(mem_cgroup_clear_mc()) for performance - * improvement. But we cannot postpone mem_cgroup_get(to) - * because if the process that has been moved to @to does - * swap-in, the refcount of @to might be decreased to 0. + * improvement. But we cannot postpone css_get(to) because if + * the process that has been moved to @to does swap-in, the + * refcount of @to might be decreased to 0. + * + * We are in attach() phase, so the cgroup is guaranteed to be + * alive, so we can just call css_get(). */ - mem_cgroup_get(to); + css_get(&to->css); return 0; } return -EINVAL; @@ -5183,14 +5176,6 @@ static int memcg_update_kmem_limit(struct cgroup *cont, u64 val) * starts accounting before all call sites are patched */ memcg_kmem_set_active(memcg); - - /* - * kmem charges can outlive the cgroup. In the case of slab - * pages, for instance, a page contain objects from various - * processes, so it is unfeasible to migrate them away. We - * need to reference count the memcg because of that. - */ - mem_cgroup_get(memcg); } else ret = res_counter_set_limit(&memcg->kmem, val); out: @@ -5223,12 +5208,10 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg) goto out; /* - * destroy(), called if we fail, will issue static_key_slow_inc() and - * mem_cgroup_put() if kmem is enabled. We have to either call them - * unconditionally, or clear the KMEM_ACTIVE flag. I personally find - * this more consistent, since it always leads to the same destroy path + * __mem_cgroup_free() will issue static_key_slow_dec() because this + * memcg is active already. If the later initialization fails then the + * cgroup core triggers the cleanup so we do not have to do it here. */ - mem_cgroup_get(memcg); static_key_slow_inc(&memcg_kmem_enabled_key); mutex_lock(&set_limit_mutex); @@ -5913,23 +5896,43 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss) return mem_cgroup_sockets_init(memcg, ss); } -static void kmem_cgroup_destroy(struct mem_cgroup *memcg) +static void memcg_destroy_kmem(struct mem_cgroup *memcg) { mem_cgroup_sockets_destroy(memcg); +} + +static void kmem_cgroup_css_offline(struct mem_cgroup *memcg) +{ + if (!memcg_kmem_is_active(memcg)) + return; + + /* + * kmem charges can outlive the cgroup. In the case of slab + * pages, for instance, a page contain objects from various + * processes. As we prevent from taking a reference for every + * such allocation we have to be careful when doing uncharge + * (see memcg_uncharge_kmem) and here during offlining. + * + * The idea is that that only the _last_ uncharge which sees + * the dead memcg will drop the last reference. An additional + * reference is taken here before the group is marked dead + * which is then paired with css_put during uncharge resp. here. + * + * Although this might sound strange as this path is called from + * css_offline() when the referencemight have dropped down to 0 + * and shouldn't be incremented anymore (css_tryget would fail) + * we do not have other options because of the kmem allocations + * lifetime. + */ + css_get(&memcg->css); memcg_kmem_mark_dead(memcg); if (res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0) return; - /* - * Charges already down to 0, undo mem_cgroup_get() done in the charge - * path here, being careful not to race with memcg_uncharge_kmem: it is - * possible that the charges went down to 0 between mark_dead and the - * res_counter read, so in that case, we don't need the put - */ if (memcg_kmem_test_and_clear_dead(memcg)) - mem_cgroup_put(memcg); + css_put(&memcg->css); } #else static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss) @@ -5937,7 +5940,11 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss) return 0; } -static void kmem_cgroup_destroy(struct mem_cgroup *memcg) +static void memcg_destroy_kmem(struct mem_cgroup *memcg) +{ +} + +static void kmem_cgroup_css_offline(struct mem_cgroup *memcg) { } #endif @@ -6186,49 +6193,6 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg) vfree(memcg); } - -/* - * Helpers for freeing a kmalloc()ed/vzalloc()ed mem_cgroup by RCU, - * but in process context. The work_freeing structure is overlaid - * on the rcu_freeing structure, which itself is overlaid on memsw. - */ -static void free_work(struct work_struct *work) -{ - struct mem_cgroup *memcg; - - memcg = container_of(work, struct mem_cgroup, work_freeing); - __mem_cgroup_free(memcg); -} - -static void free_rcu(struct rcu_head *rcu_head) -{ - struct mem_cgroup *memcg; - - memcg = container_of(rcu_head, struct mem_cgroup, rcu_freeing); - INIT_WORK(&memcg->work_freeing, free_work); - schedule_work(&memcg->work_freeing); -} - -static void mem_cgroup_get(struct mem_cgroup *memcg) -{ - atomic_inc(&memcg->refcnt); -} - -static void __mem_cgroup_put(struct mem_cgroup *memcg, int count) -{ - if (atomic_sub_and_test(count, &memcg->refcnt)) { - struct mem_cgroup *parent = parent_mem_cgroup(memcg); - call_rcu(&memcg->rcu_freeing, free_rcu); - if (parent) - mem_cgroup_put(parent); - } -} - -static void mem_cgroup_put(struct mem_cgroup *memcg) -{ - __mem_cgroup_put(memcg, 1); -} - /* * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled. */ @@ -6288,7 +6252,6 @@ mem_cgroup_css_alloc(struct cgroup *cont) memcg->last_scanned_node = MAX_NUMNODES; INIT_LIST_HEAD(&memcg->oom_notify); - atomic_set(&memcg->refcnt, 1); memcg->move_charge_at_immigrate = 0; mutex_init(&memcg->thresholds_lock); spin_lock_init(&memcg->move_lock); @@ -6324,12 +6287,9 @@ mem_cgroup_css_online(struct cgroup *cont) res_counter_init(&memcg->kmem, &parent->kmem); /* - * We increment refcnt of the parent to ensure that we can - * safely access it on res_counter_charge/uncharge. - * This refcnt will be decremented when freeing this - * mem_cgroup(see mem_cgroup_put). + * No need to take a reference to the parent because cgroup + * core guarantees its existence. */ - mem_cgroup_get(parent); } else { res_counter_init(&memcg->res, NULL); res_counter_init(&memcg->memsw, NULL); @@ -6345,14 +6305,6 @@ mem_cgroup_css_online(struct cgroup *cont) error = memcg_init_kmem(memcg, &mem_cgroup_subsys); mutex_unlock(&memcg_create_mutex); - if (error) { - /* - * We call put now because our (and parent's) refcnts - * are already in place. mem_cgroup_put() will internally - * call __mem_cgroup_free, so return directly - */ - mem_cgroup_put(memcg); - } return error; } @@ -6378,6 +6330,8 @@ static void mem_cgroup_css_offline(struct cgroup *cont) { struct mem_cgroup *memcg = mem_cgroup_from_cont(cont); + kmem_cgroup_css_offline(memcg); + mem_cgroup_invalidate_reclaim_iterators(memcg); mem_cgroup_reparent_charges(memcg); mem_cgroup_destroy_all_caches(memcg); @@ -6387,9 +6341,8 @@ static void mem_cgroup_css_free(struct cgroup *cont) { struct mem_cgroup *memcg = mem_cgroup_from_cont(cont); - kmem_cgroup_destroy(memcg); - - mem_cgroup_put(memcg); + memcg_destroy_kmem(memcg); + __mem_cgroup_free(memcg); } #ifdef CONFIG_MMU @@ -6698,6 +6651,7 @@ static void __mem_cgroup_clear_mc(void) { struct mem_cgroup *from = mc.from; struct mem_cgroup *to = mc.to; + int i; /* we must uncharge all the leftover precharges from mc.to */ if (mc.precharge) { @@ -6718,7 +6672,9 @@ static void __mem_cgroup_clear_mc(void) if (!mem_cgroup_is_root(mc.from)) res_counter_uncharge(&mc.from->memsw, PAGE_SIZE * mc.moved_swap); - __mem_cgroup_put(mc.from, mc.moved_swap); + + for (i = 0; i < mc.moved_swap; i++) + css_put(&mc.from->css); if (!mem_cgroup_is_root(mc.to)) { /* @@ -6728,7 +6684,7 @@ static void __mem_cgroup_clear_mc(void) res_counter_uncharge(&mc.to->res, PAGE_SIZE * mc.moved_swap); } - /* we've already done mem_cgroup_get(mc.to) */ + /* we've already done css_get(mc.to) */ mc.moved_swap = 0; } memcg_oom_recover(from);