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Commit bdcbb659 authored by Qiang Huang's avatar Qiang Huang Committed by Linus Torvalds
Browse files

memcg: fold mem_cgroup_stolen 



It is only used in __mem_cgroup_begin_update_page_stat(), the name is
confusing and 2 routines for one thing also confuse people, so fold this
function seems more clear.

[akpm@linux-foundation.org: fix typo, per Michal]
Signed-off-by: default avatarQiang Huang <h.huangqiang@huawei.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
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 3fb1c8dc

mm/memcontrol.c

+7 −18
Original line number Original line Diff line number Diff line
@@ -1594,23 +1594,12 @@ static void mem_cgroup_end_move(struct mem_cgroup *memcg) 
}

}





/*

/*

 * 2 routines for checking "mem" is under move_account() or not.

 * A routine for checking "mem" is under move_account() or not.

 *

 *

 * mem_cgroup_stolen() -  checking whether a cgroup is mc.from or not. This

 * Checking a cgroup is mc.from or mc.to or under hierarchy of

 *			  is used for avoiding races in accounting.  If true,

 * moving cgroups. This is for waiting at high-memory pressure

 *			  pc->mem_cgroup may be overwritten.

 * caused by "move".

 *

 * mem_cgroup_under_move() - checking a cgroup is mc.from or mc.to or

 *			  under hierarchy of moving cgroups. This is for

 *			  waiting at hith-memory prressure caused by "move".

 */

 */



static bool mem_cgroup_stolen(struct mem_cgroup *memcg)

{

	VM_BUG_ON(!rcu_read_lock_held());

	return atomic_read(&memcg->moving_account) > 0;

}



static bool mem_cgroup_under_move(struct mem_cgroup *memcg)

static bool mem_cgroup_under_move(struct mem_cgroup *memcg)

{

{

	struct mem_cgroup *from;

	struct mem_cgroup *from;
@@ -1653,7 +1642,6 @@ static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg) 
 * Take this lock when

 * Take this lock when

 * - a code tries to modify page's memcg while it's USED.

 * - a code tries to modify page's memcg while it's USED.

 * - a code tries to modify page state accounting in a memcg.

 * - a code tries to modify page state accounting in a memcg.

 * see mem_cgroup_stolen(), too.

 */

 */

static void move_lock_mem_cgroup(struct mem_cgroup *memcg,

static void move_lock_mem_cgroup(struct mem_cgroup *memcg,

				  unsigned long *flags)

				  unsigned long *flags)
@@ -2326,9 +2314,10 @@ void __mem_cgroup_begin_update_page_stat(struct page *page, 
	 * If this memory cgroup is not under account moving, we don't

	 * If this memory cgroup is not under account moving, we don't

	 * need to take move_lock_mem_cgroup(). Because we already hold

	 * need to take move_lock_mem_cgroup(). Because we already hold

	 * rcu_read_lock(), any calls to move_account will be delayed until

	 * rcu_read_lock(), any calls to move_account will be delayed until

	 * rcu_read_unlock() if mem_cgroup_stolen() == true.

	 * rcu_read_unlock().

	 */

	 */

	if (!mem_cgroup_stolen(memcg))

	VM_BUG_ON(!rcu_read_lock_held());

	if (atomic_read(&memcg->moving_account) <= 0)

		return;

		return;





	move_lock_mem_cgroup(memcg, flags);

	move_lock_mem_cgroup(memcg, flags);