Currently, we rely on the cgroup_lock() to prevent changes to
move_charge_at_immigrate during task migration. We can do something
similar to what cpuset is doing, and flip a flag to tell us if task
movement is taking place.
In theory, we could busy loop waiting for that value to return to 0 - it
will eventually. But I am judging that returning EAGAIN is not too much
of a problem, since file writers already should be checking for error
codes anyway.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
---
mm/memcontrol.c | 64 +++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 51 insertions(+), 13 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index feba87d..d80b6b5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -311,7 +311,13 @@ struct mem_cgroup {
* Should we move charges of a task when a task is moved into this
* mem_cgroup ? And what type of charges should we move ?
*/
- unsigned long move_charge_at_immigrate;
+ unsigned long move_charge_at_immigrate;
+ /*
+ * Tasks are being attached to this memcg. Used mostly to prevent
+ * changes to move_charge_at_immigrate
+ */
+ int attach_in_progress;
+
/*
* set > 0 if pages under this cgroup are moving to other cgroup.
*/
@@ -4114,6 +4120,7 @@ static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
struct cftype *cft, u64 val)
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+ int ret = -EAGAIN;
if (val >= (1 << NR_MOVE_TYPE))
return -EINVAL;
@@ -4123,10 +4130,13 @@ static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
* inconsistent.
*/
cgroup_lock();
+ if (memcg->attach_in_progress)
+ goto out;
memcg->move_charge_at_immigrate = val;
+ ret = 0;
+out:
cgroup_unlock();
-
- return 0;
+ return ret;
}
#else
static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
@@ -5443,12 +5453,12 @@ static void mem_cgroup_clear_mc(void)
mem_cgroup_end_move(from);
}
-static int mem_cgroup_can_attach(struct cgroup *cgroup,
- struct cgroup_taskset *tset)
+
+static int __mem_cgroup_can_attach(struct mem_cgroup *memcg,
+ struct cgroup_taskset *tset)
{
struct task_struct *p = cgroup_taskset_first(tset);
int ret = 0;
- struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
if (memcg->move_charge_at_immigrate) {
struct mm_struct *mm;
@@ -5482,8 +5492,8 @@ static int mem_cgroup_can_attach(struct cgroup *cgroup,
return ret;
}
-static void mem_cgroup_cancel_attach(struct cgroup *cgroup,
- struct cgroup_taskset *tset)
+static void __mem_cgroup_cancel_attach(struct mem_cgroup *memcg,
+ struct cgroup_taskset *tset)
{
mem_cgroup_clear_mc();
}
@@ -5630,8 +5640,8 @@ retry:
up_read(&mm->mmap_sem);
}
-static void mem_cgroup_move_task(struct cgroup *cont,
- struct cgroup_taskset *tset)
+static void __mem_cgroup_move_task(struct mem_cgroup *memcg,
+ struct cgroup_taskset *tset)
{
struct task_struct *p = cgroup_taskset_first(tset);
struct mm_struct *mm = get_task_mm(p);
@@ -5645,20 +5655,48 @@ static void mem_cgroup_move_task(struct cgroup *cont,
mem_cgroup_clear_mc();
}
#else /* !CONFIG_MMU */
+static int __mem_cgroup_can_attach(struct mem_cgroup *memcg,
+ struct cgroup_taskset *tset)
+{
+ return 0;
+}
+
+static void __mem_cgroup_cancel_attach(struct mem_cgroup *memcg,
+ struct cgroup_taskset *tset)
+{
+}
+
+static void __mem_cgroup_move_task(struct mem_cgroup *memcg,
+ struct cgroup_taskset *tset)
+{
+}
+#endif
static int mem_cgroup_can_attach(struct cgroup *cgroup,
struct cgroup_taskset *tset)
{
- return 0;
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
+
+ memcg->attach_in_progress++;
+ return __mem_cgroup_can_attach(memcg, tset);
}
+
static void mem_cgroup_cancel_attach(struct cgroup *cgroup,
struct cgroup_taskset *tset)
{
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
+
+ __mem_cgroup_cancel_attach(memcg, tset);
+ memcg->attach_in_progress--;
}
-static void mem_cgroup_move_task(struct cgroup *cont,
+
+static void mem_cgroup_move_task(struct cgroup *cgroup,
struct cgroup_taskset *tset)
{
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
+
+ __mem_cgroup_move_task(memcg, tset);
+ memcg->attach_in_progress--;
}
-#endif
struct cgroup_subsys mem_cgroup_subsys = {
.name = "memory",
--
1.7.11.7
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