diff options
| -rw-r--r-- | mm/memcontrol.c | 98 |
1 files changed, 62 insertions, 36 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 4f9a9c5a02e2..b311f19bbe01 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -162,7 +162,6 @@ struct mem_cgroup { */ bool use_hierarchy; unsigned long last_oom_jiffies; - int obsolete; atomic_t refcnt; unsigned int swappiness; @@ -283,6 +282,31 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p) struct mem_cgroup, css); } +static struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm) +{ + struct mem_cgroup *mem = NULL; + /* + * Because we have no locks, mm->owner's may be being moved to other + * cgroup. We use css_tryget() here even if this looks + * pessimistic (rather than adding locks here). + */ + rcu_read_lock(); + do { + mem = mem_cgroup_from_task(rcu_dereference(mm->owner)); + if (unlikely(!mem)) + break; + } while (!css_tryget(&mem->css)); + rcu_read_unlock(); + return mem; +} + +static bool mem_cgroup_is_obsolete(struct mem_cgroup *mem) +{ + if (!mem) + return true; + return css_is_removed(&mem->css); +} + /* * Following LRU functions are allowed to be used without PCG_LOCK. * Operations are called by routine of global LRU independently from memcg. @@ -622,8 +646,9 @@ mem_cgroup_get_first_node(struct mem_cgroup *root_mem) { struct cgroup *cgroup; struct mem_cgroup *ret; - bool obsolete = (root_mem->last_scanned_child && - root_mem->last_scanned_child->obsolete); + bool obsolete; + + obsolete = mem_cgroup_is_obsolete(root_mem->last_scanned_child); /* * Scan all children under the mem_cgroup mem @@ -636,7 +661,7 @@ mem_cgroup_get_first_node(struct mem_cgroup *root_mem) if (!root_mem->last_scanned_child || obsolete) { - if (obsolete) + if (obsolete && root_mem->last_scanned_child) mem_cgroup_put(root_mem->last_scanned_child); cgroup = list_first_entry(&root_mem->css.cgroup->children, @@ -711,7 +736,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem, next_mem = mem_cgroup_get_first_node(root_mem); while (next_mem != root_mem) { - if (next_mem->obsolete) { + if (mem_cgroup_is_obsolete(next_mem)) { mem_cgroup_put(next_mem); cgroup_lock(); next_mem = mem_cgroup_get_first_node(root_mem); @@ -769,23 +794,17 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, * thread group leader migrates. It's possible that mm is not * set, if so charge the init_mm (happens for pagecache usage). */ - if (likely(!*memcg)) { - rcu_read_lock(); - mem = mem_cgroup_from_task(rcu_dereference(mm->owner)); - if (unlikely(!mem)) { - rcu_read_unlock(); - return 0; - } - /* - * For every charge from the cgroup, increment reference count - */ - css_get(&mem->css); + mem = *memcg; + if (likely(!mem)) { + mem = try_get_mem_cgroup_from_mm(mm); *memcg = mem; - rcu_read_unlock(); } else { - mem = *memcg; css_get(&mem->css); } + if (unlikely(!mem)) + return 0; + + VM_BUG_ON(mem_cgroup_is_obsolete(mem)); while (1) { int ret; @@ -1072,12 +1091,19 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm, MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL); } +/* + * While swap-in, try_charge -> commit or cancel, the page is locked. + * And when try_charge() successfully returns, one refcnt to memcg without + * struct page_cgroup is aquired. This refcnt will be cumsumed by + * "commit()" or removed by "cancel()" + */ int mem_cgroup_try_charge_swapin(struct mm_struct *mm, struct page *page, gfp_t mask, struct mem_cgroup **ptr) { struct mem_cgroup *mem; swp_entry_t ent; + int ret; if (mem_cgroup_disabled()) return 0; @@ -1096,10 +1122,15 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm, ent.val = page_private(page); mem = lookup_swap_cgroup(ent); - if (!mem || mem->obsolete) + if (!mem) + goto charge_cur_mm; + if (!css_tryget(&mem->css)) goto charge_cur_mm; *ptr = mem; - return __mem_cgroup_try_charge(NULL, mask, ptr, true); + ret = __mem_cgroup_try_charge(NULL, mask, ptr, true); + /* drop extra refcnt from tryget */ + css_put(&mem->css); + return ret; charge_cur_mm: if (unlikely(!mm)) mm = &init_mm; @@ -1130,13 +1161,18 @@ int mem_cgroup_cache_charge_swapin(struct page *page, ent.val = page_private(page); if (do_swap_account) { mem = lookup_swap_cgroup(ent); - if (mem && mem->obsolete) - mem = NULL; - if (mem) - mm = NULL; + if (mem) { + if (css_tryget(&mem->css)) + mm = NULL; /* charge to recorded */ + else + mem = NULL; /* charge to current */ + } } ret = mem_cgroup_charge_common(page, mm, mask, MEM_CGROUP_CHARGE_TYPE_SHMEM, mem); + /* drop extra refcnt from tryget */ + if (mem) + css_put(&mem->css); if (!ret && do_swap_account) { /* avoid double counting */ @@ -1178,7 +1214,6 @@ void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) struct mem_cgroup *memcg; memcg = swap_cgroup_record(ent, NULL); if (memcg) { - /* If memcg is obsolete, memcg can be != ptr */ res_counter_uncharge(&memcg->memsw, PAGE_SIZE); mem_cgroup_put(memcg); } @@ -1421,14 +1456,9 @@ int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask) if (!mm) return 0; - rcu_read_lock(); - mem = mem_cgroup_from_task(rcu_dereference(mm->owner)); - if (unlikely(!mem)) { - rcu_read_unlock(); + mem = try_get_mem_cgroup_from_mm(mm); + if (unlikely(!mem)) return 0; - } - css_get(&mem->css); - rcu_read_unlock(); do { progress = mem_cgroup_hierarchical_reclaim(mem, gfp_mask, true); @@ -2086,9 +2116,6 @@ static struct mem_cgroup *mem_cgroup_alloc(void) * the number of reference from swap_cgroup and free mem_cgroup when * it goes down to 0. * - * When mem_cgroup is destroyed, mem->obsolete will be set to 0 and - * entry which points to this memcg will be ignore at swapin. - * * Removal of cgroup itself succeeds regardless of refs from swap. */ @@ -2174,7 +2201,6 @@ static void mem_cgroup_pre_destroy(struct cgroup_subsys *ss, struct cgroup *cont) { struct mem_cgroup *mem = mem_cgroup_from_cont(cont); - mem->obsolete = 1; mem_cgroup_force_empty(mem, false); } |
