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Commit 4050377b authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds
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memcg: use css_get/put for swap memcg 



Use css_get/put instead of mem_cgroup_get/put.  A simple replacement
will do.

The historical reason that memcg has its own refcnt instead of always
using css_get/put, is that cgroup couldn't be removed if there're still
css refs, so css refs can't be used as long-lived reference.  The
situation has changed so that rmdir a cgroup will succeed regardless css
refs, but won't be freed until css refs goes down to 0.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 10d5ebf4

mm/memcontrol.c

+16 −10
Original line number Diff line number Diff line
@@ -4231,12 +4231,12 @@ __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
@@ -4348,7 +4348,7 @@ 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));
@@ -4379,7 +4379,7 @@ 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();

}
@@ -4413,11 +4413,14 @@ 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;
@@ -6718,6 +6721,7 @@ 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) {
@@ -6738,7 +6742,9 @@ 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)) {

			/*
@@ -6748,7 +6754,7 @@ 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);