mm: memcontrol: take a css reference for each charged page
Charges currently pin the css indirectly by playing tricks during css_offline(): user pages stall the offlining process until all of them have been reparented, whereas kmemcg acquires a keep-alive reference if outstanding kernel pages are detected at that point. In preparation for removing all this complexity, make the pinning explicit and acquire a css references for every charged page. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Vladimir Davydov <vdavydov@parallels.com> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -112,6 +112,19 @@ static inline void css_get(struct cgroup_subsys_state *css)
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percpu_ref_get(&css->refcnt);
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}
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/**
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* css_get_many - obtain references on the specified css
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* @css: target css
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* @n: number of references to get
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*
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* The caller must already have a reference.
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*/
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static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n)
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{
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if (!(css->flags & CSS_NO_REF))
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percpu_ref_get_many(&css->refcnt, n);
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}
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/**
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* css_tryget - try to obtain a reference on the specified css
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* @css: target css
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@ -159,6 +172,19 @@ static inline void css_put(struct cgroup_subsys_state *css)
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percpu_ref_put(&css->refcnt);
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}
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/**
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* css_put_many - put css references
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* @css: target css
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* @n: number of references to put
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*
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* Put references obtained via css_get() and css_tryget_online().
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*/
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static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
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{
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if (!(css->flags & CSS_NO_REF))
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percpu_ref_put_many(&css->refcnt, n);
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}
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/* bits in struct cgroup flags field */
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enum {
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/* Control Group requires release notifications to userspace */
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@ -146,6 +146,29 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref,
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return true;
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}
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/**
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* percpu_ref_get_many - increment a percpu refcount
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* @ref: percpu_ref to get
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* @nr: number of references to get
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*
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* Analogous to atomic_long_add().
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*
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* This function is safe to call as long as @ref is between init and exit.
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*/
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static inline void percpu_ref_get_many(struct percpu_ref *ref, unsigned long nr)
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{
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unsigned long __percpu *percpu_count;
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rcu_read_lock_sched();
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if (__ref_is_percpu(ref, &percpu_count))
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this_cpu_add(*percpu_count, nr);
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else
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atomic_long_add(nr, &ref->count);
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rcu_read_unlock_sched();
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}
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/**
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* percpu_ref_get - increment a percpu refcount
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* @ref: percpu_ref to get
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@ -156,16 +179,7 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref,
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*/
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static inline void percpu_ref_get(struct percpu_ref *ref)
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{
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unsigned long __percpu *percpu_count;
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rcu_read_lock_sched();
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if (__ref_is_percpu(ref, &percpu_count))
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this_cpu_inc(*percpu_count);
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else
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atomic_long_inc(&ref->count);
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rcu_read_unlock_sched();
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percpu_ref_get_many(ref, 1);
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}
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/**
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@ -230,6 +244,30 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
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return ret;
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}
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/**
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* percpu_ref_put_many - decrement a percpu refcount
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* @ref: percpu_ref to put
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* @nr: number of references to put
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*
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* Decrement the refcount, and if 0, call the release function (which was passed
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* to percpu_ref_init())
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*
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* This function is safe to call as long as @ref is between init and exit.
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*/
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static inline void percpu_ref_put_many(struct percpu_ref *ref, unsigned long nr)
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{
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unsigned long __percpu *percpu_count;
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rcu_read_lock_sched();
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if (__ref_is_percpu(ref, &percpu_count))
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this_cpu_sub(*percpu_count, nr);
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else if (unlikely(atomic_long_sub_and_test(nr, &ref->count)))
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ref->release(ref);
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rcu_read_unlock_sched();
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}
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/**
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* percpu_ref_put - decrement a percpu refcount
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* @ref: percpu_ref to put
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@ -241,16 +279,7 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
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*/
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static inline void percpu_ref_put(struct percpu_ref *ref)
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{
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unsigned long __percpu *percpu_count;
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rcu_read_lock_sched();
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if (__ref_is_percpu(ref, &percpu_count))
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this_cpu_dec(*percpu_count);
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else if (unlikely(atomic_long_dec_and_test(&ref->count)))
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ref->release(ref);
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rcu_read_unlock_sched();
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percpu_ref_put_many(ref, 1);
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}
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/**
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@ -2273,6 +2273,7 @@ static void drain_stock(struct memcg_stock_pcp *stock)
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page_counter_uncharge(&old->memory, stock->nr_pages);
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if (do_swap_account)
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page_counter_uncharge(&old->memsw, stock->nr_pages);
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css_put_many(&old->css, stock->nr_pages);
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stock->nr_pages = 0;
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}
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stock->cached = NULL;
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@ -2530,6 +2531,7 @@ bypass:
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return -EINTR;
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done_restock:
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css_get_many(&memcg->css, batch);
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if (batch > nr_pages)
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refill_stock(memcg, batch - nr_pages);
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done:
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@ -2544,6 +2546,8 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
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page_counter_uncharge(&memcg->memory, nr_pages);
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if (do_swap_account)
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page_counter_uncharge(&memcg->memsw, nr_pages);
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css_put_many(&memcg->css, nr_pages);
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}
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/*
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@ -2739,6 +2743,7 @@ static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp,
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page_counter_charge(&memcg->memory, nr_pages);
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if (do_swap_account)
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page_counter_charge(&memcg->memsw, nr_pages);
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css_get_many(&memcg->css, nr_pages);
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ret = 0;
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} else if (ret)
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page_counter_uncharge(&memcg->kmem, nr_pages);
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@ -2754,8 +2759,10 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg,
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page_counter_uncharge(&memcg->memsw, nr_pages);
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/* Not down to 0 */
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if (page_counter_uncharge(&memcg->kmem, nr_pages))
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if (page_counter_uncharge(&memcg->kmem, nr_pages)) {
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css_put_many(&memcg->css, nr_pages);
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return;
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}
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/*
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* Releases a reference taken in kmem_cgroup_css_offline in case
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@ -2767,6 +2774,8 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg,
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*/
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if (memcg_kmem_test_and_clear_dead(memcg))
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css_put(&memcg->css);
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css_put_many(&memcg->css, nr_pages);
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}
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/*
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@ -3394,10 +3403,13 @@ static int mem_cgroup_move_parent(struct page *page,
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ret = mem_cgroup_move_account(page, nr_pages,
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pc, child, parent);
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if (!ret) {
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if (!mem_cgroup_is_root(parent))
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css_get_many(&parent->css, nr_pages);
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/* Take charge off the local counters */
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page_counter_cancel(&child->memory, nr_pages);
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if (do_swap_account)
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page_counter_cancel(&child->memsw, nr_pages);
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css_put_many(&child->css, nr_pages);
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}
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if (nr_pages > 1)
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@ -5767,7 +5779,6 @@ static void __mem_cgroup_clear_mc(void)
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{
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struct mem_cgroup *from = mc.from;
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struct mem_cgroup *to = mc.to;
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int i;
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/* we must uncharge all the leftover precharges from mc.to */
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if (mc.precharge) {
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@ -5795,8 +5806,7 @@ static void __mem_cgroup_clear_mc(void)
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if (!mem_cgroup_is_root(mc.to))
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page_counter_uncharge(&mc.to->memory, mc.moved_swap);
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for (i = 0; i < mc.moved_swap; i++)
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css_put(&mc.from->css);
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css_put_many(&mc.from->css, mc.moved_swap);
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/* we've already done css_get(mc.to) */
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mc.moved_swap = 0;
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__this_cpu_add(memcg->stat->nr_page_events, nr_anon + nr_file);
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memcg_check_events(memcg, dummy_page);
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local_irq_restore(flags);
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if (!mem_cgroup_is_root(memcg))
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css_put_many(&memcg->css, max(nr_mem, nr_memsw));
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}
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static void uncharge_list(struct list_head *page_list)
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