After the preparation work done in earlier patches, the
cgroup_lock can be trivially replaced with a memcg-specific lock in all
readers.
The writers, however, used to be naturally called under cgroup_lock, and
now we need to explicitly add the memcg_lock. Those are the callbacks in
attach_task, and parent-dependent value assignment in newly-created
memcgs.
With this, all the calls to cgroup_lock outside cgroup core are gone.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
---
mm/memcontrol.c | 48 ++++++++++++++++++++++++++++++++++--------------
1 file changed, 34 insertions(+), 14 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b6d352f..fd7b5d3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3830,6 +3830,17 @@ static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
} while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0);
}
+static DEFINE_MUTEX(memcg_lock);
+
+/*
+ * must be called with memcg_lock held, unless the cgroup is guaranteed to be
+ * already dead (like in mem_cgroup_force_empty, for instance).
+ */
+static inline bool memcg_has_children(struct mem_cgroup *memcg)
+{
+ return mem_cgroup_count_children(memcg) != 1;
+}
+
/*
* Reclaims as many pages from the given memcg as possible and moves
* the rest to the parent.
@@ -3842,7 +3853,7 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
struct cgroup *cgrp = memcg->css.cgroup;
/* returns EBUSY if there is a task or if we come here twice. */
- if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
+ if (cgroup_task_count(cgrp) || memcg_has_children(memcg))
return -EBUSY;
/* we call try-to-free pages for make this cgroup empty */
@@ -3900,7 +3911,7 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
if (parent)
parent_memcg = mem_cgroup_from_cont(parent);
- cgroup_lock();
+ mutex_lock(&memcg_lock);
if (memcg->use_hierarchy == val)
goto out;
@@ -3915,7 +3926,7 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
*/
if ((!parent_memcg || !parent_memcg->use_hierarchy) &&
(val == 1 || val == 0)) {
- if (list_empty(&cont->children))
+ if (!memcg_has_children(memcg))
memcg->use_hierarchy = val;
else
retval = -EBUSY;
@@ -3923,7 +3934,7 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
retval = -EINVAL;
out:
- cgroup_unlock();
+ mutex_unlock(&memcg_lock);
return retval;
}
@@ -4129,13 +4140,13 @@ static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
* attach(), so we need cgroup lock to prevent this value from being
* inconsistent.
*/
- cgroup_lock();
+ mutex_lock(&memcg_lock);
if (memcg->attach_in_progress)
goto out;
memcg->move_charge_at_immigrate = val;
ret = 0;
out:
- cgroup_unlock();
+ mutex_unlock(&memcg_lock);
return ret;
}
#else
@@ -4314,18 +4325,18 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
parent = mem_cgroup_from_cont(cgrp->parent);
- cgroup_lock();
+ mutex_lock(&memcg_lock);
/* If under hierarchy, only empty-root can set this value */
if ((parent->use_hierarchy) ||
- (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
- cgroup_unlock();
+ (memcg->use_hierarchy && !memcg_has_children(memcg))) {
+ mutex_unlock(&memcg_lock);
return -EINVAL;
}
memcg->swappiness = val;
- cgroup_unlock();
+ mutex_unlock(&memcg_lock);
return 0;
}
@@ -4651,17 +4662,17 @@ static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
parent = mem_cgroup_from_cont(cgrp->parent);
- cgroup_lock();
+ mutex_lock(&memcg_lock);
/* oom-kill-disable is a flag for subhierarchy. */
if ((parent->use_hierarchy) ||
- (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
- cgroup_unlock();
+ (memcg->use_hierarchy && memcg_has_children(memcg))) {
+ mutex_unlock(&memcg_lock);
return -EINVAL;
}
memcg->oom_kill_disable = val;
if (!val)
memcg_oom_recover(memcg);
- cgroup_unlock();
+ mutex_unlock(&memcg_lock);
return 0;
}
@@ -5051,6 +5062,7 @@ mem_cgroup_css_online(struct cgroup *cont)
if (!cont->parent)
return 0;
+ mutex_lock(&memcg_lock);
memcg = mem_cgroup_from_cont(cont);
parent = mem_cgroup_from_cont(cont->parent);
@@ -5082,6 +5094,7 @@ mem_cgroup_css_online(struct cgroup *cont)
memcg->swappiness = mem_cgroup_swappiness(parent);
error = memcg_init_kmem(memcg, &mem_cgroup_subsys);
+ mutex_unlock(&memcg_lock);
if (error) {
/*
* We call put now because our (and parent's) refcnts
@@ -5693,7 +5706,10 @@ static int mem_cgroup_can_attach(struct cgroup *cgroup,
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
+ mutex_lock(&memcg_lock);
memcg->attach_in_progress++;
+ mutex_unlock(&memcg_lock);
+
return __mem_cgroup_can_attach(memcg, tset);
}
@@ -5703,7 +5719,9 @@ static void mem_cgroup_cancel_attach(struct cgroup *cgroup,
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
__mem_cgroup_cancel_attach(memcg, tset);
+ mutex_lock(&memcg_lock);
memcg->attach_in_progress--;
+ mutex_unlock(&memcg_lock);
}
static void mem_cgroup_move_task(struct cgroup *cgroup,
@@ -5712,7 +5730,9 @@ static void mem_cgroup_move_task(struct cgroup *cgroup,
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
__mem_cgroup_move_task(memcg, tset);
+ mutex_lock(&memcg_lock);
memcg->attach_in_progress--;
+ mutex_unlock(&memcg_lock);
}
struct cgroup_subsys mem_cgroup_subsys = {
--
1.7.11.7
--
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