[RFC 8/8] mm: Add N_COHERENT_DEVICE node type into node_states[]

[Anshuman Khandual]

Add a new member N_COHERENT_DEVICE into node_states[] nodemask array to
enlist all those nodes which contain only coherent device memory. Also
creates a new sysfs interface /sys/devices/system/node/is_coherent_device
to list down all those nodes which has coherent device memory.

Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
---
 Documentation/ABI/stable/sysfs-devices-node |  7 +++++++
 drivers/base/node.c                         |  6 ++++++
 include/linux/nodemask.h                    |  3 +++
 mm/memory_hotplug.c                         | 10 ++++++++++
 4 files changed, 26 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-devices-node 
b/Documentation/ABI/stable/sysfs-devices-node
index 5b2d0f0..5538791 100644
--- a/Documentation/ABI/stable/sysfs-devices-node
+++ b/Documentation/ABI/stable/sysfs-devices-node
@@ -29,6 +29,13 @@ Description:
                Nodes that have regular or high memory.
                Depends on CONFIG_HIGHMEM.
 
+What:          /sys/devices/system/node/is_coherent_device
+Date:          October 2016
+Contact:       Linux Memory Management list <linux...@kvack.org>
+Description:
+               Lists the nodemask of nodes that have coherent memory.
+               Depends on CONFIG_COHERENT_DEVICE.
+
 What:          /sys/devices/system/node/nodeX
 Date:          October 2002
 Contact:       Linux Memory Management list <linux...@kvack.org>
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 5548f96..5b5dd89 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -661,6 +661,9 @@ static struct node_attr node_state_attr[] = {
        [N_MEMORY] = _NODE_ATTR(has_memory, N_MEMORY),
 #endif
        [N_CPU] = _NODE_ATTR(has_cpu, N_CPU),
+#ifdef CONFIG_COHERENT_DEVICE
+       [N_COHERENT_DEVICE] = _NODE_ATTR(is_coherent_device, N_COHERENT_DEVICE),
+#endif
 };
 
 static struct attribute *node_state_attrs[] = {
@@ -674,6 +677,9 @@ static struct attribute *node_state_attrs[] = {
        &node_state_attr[N_MEMORY].attr.attr,
 #endif
        &node_state_attr[N_CPU].attr.attr,
+#ifdef CONFIG_COHERENT_DEVICE
+       &node_state_attr[N_COHERENT_DEVICE].attr.attr,
+#endif
        NULL
 };
 
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index f746e44..605cb0d 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -393,6 +393,9 @@ enum node_states {
        N_MEMORY = N_HIGH_MEMORY,
 #endif
        N_CPU,          /* The node has one or more cpus */
+#ifdef CONFIG_COHERENT_DEVICE
+       N_COHERENT_DEVICE,      /* The node has coherent device memory */
+#endif
        NR_NODE_STATES
 };
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9629273..8f03962 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1044,6 +1044,11 @@ static void node_states_set_node(int node, struct 
memory_notify *arg)
        if (arg->status_change_nid_high >= 0)
                node_set_state(node, N_HIGH_MEMORY);
 
+#ifdef CONFIG_COHERENT_DEVICE
+       if (isolated_cdm_node(node))
+               node_set_state(node, N_COHERENT_DEVICE);
+#endif
+
        node_set_state(node, N_MEMORY);
 }
 
@@ -1858,6 +1863,11 @@ static void node_states_clear_node(int node, struct 
memory_notify *arg)
        if ((N_MEMORY != N_HIGH_MEMORY) &&
            (arg->status_change_nid >= 0))
                node_clear_state(node, N_MEMORY);
+
+#ifdef CONFIG_COHERENT_DEVICE
+       if (isolated_cdm_node(node))
+               node_clear_state(node, N_COHERENT_DEVICE);
+#endif
 }
 
 static int __ref __offline_pages(unsigned long start_pfn,
-- 
2.1.0