Re: [PATCH v6 10/10] Disable task moving when using kernel memory accounting

Since this code is still experimental, we are leaving the exact
details of how to move tasks between cgroups when kernel memory
accounting is used as future work.

For now, we simply disallow movement if there are any pending
accounted memory.

Signed-off-by: Glauber Costa <redacted>
CC: Hiroyouki Kamezawa <redacted>
---
 mm/memcontrol.c |   23 ++++++++++++++++++++++-
 1 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2df5d3c..ab7e57b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -5451,10 +5451,19 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 {
 	int ret = 0;
 	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
+	struct mem_cgroup *from = mem_cgroup_from_task(p);
+
+#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_INET)
+	if (from != mem && !mem_cgroup_is_root(from) &&
+	    res_counter_read_u64(&from->tcp_mem.tcp_memory_allocated, RES_USAGE)) {
+		printk(KERN_WARNING "Can't move tasks between cgroups: "
+			"Kernel memory held. task: %s\n", p->comm);
+		return 1;
+	}
+#endif