linux-kernel - [RFC V2 06/12] mm: Exclude CDM nodes from task->mems

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Date:   Mon, 30 Jan 2017 09:05:47 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     mhocko@...e.com, vbabka@...e.cz, mgorman@...e.de,
        minchan@...nel.org, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, srikar@...ux.vnet.ibm.com,
        haren@...ux.vnet.ibm.com, jglisse@...hat.com,
        dave.hansen@...el.com, dan.j.williams@...el.com
Subject: [RFC V2 06/12] mm: Exclude CDM nodes from task->mems_allowed and root cpuset

Task struct's mems_allowed element decides the final nodemask from which
memory can be allocated in the task context irrespective any applicable
memory policy. CDM nodes should not be used for user allocations, its one
of the overall requirements of it's isolation. So they should not be part
of any task's mems_allowed nodemask. System RAM nodemask is used instead
of node_states[N_MEMORY] nodemask during mems_allowed initialization and
it's update during memory hotlugs.

Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
---
 kernel/cpuset.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index be75f3f..4e1df26 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -364,9 +364,11 @@ static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
  */
 static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
 {
-	while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
+	nodemask_t ram_nodes = ram_nodemask();
+
+	while (!nodes_intersects(cs->effective_mems, ram_nodes))
 		cs = parent_cs(cs);
-	nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
+	nodes_and(*pmask, cs->effective_mems, ram_nodes);
 }
 
 /*
@@ -2303,7 +2305,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
 
 	/* fetch the available cpus/mems and find out which changed how */
 	cpumask_copy(&new_cpus, cpu_active_mask);
-	new_mems = node_states[N_MEMORY];
+	new_mems = ram_nodemask();
 
 	cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus);
 	mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
@@ -2395,11 +2397,11 @@ static struct notifier_block cpuset_track_online_nodes_nb = {
 void __init cpuset_init_smp(void)
 {
 	cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
-	top_cpuset.mems_allowed = node_states[N_MEMORY];
+	top_cpuset.mems_allowed = ram_nodemask();
 	top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;
 
 	cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
-	top_cpuset.effective_mems = node_states[N_MEMORY];
+	top_cpuset.effective_mems = ram_nodemask();
 
 	register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
 
-- 
2.9.3