[PATCH v3 3/7] drivers/base/node: Add support to write node_states[] via sysfs

Jagdish Gediya
2022-04-22T22:07:05Z

Current /sys/devices/system/node/* interface doesn't support
to write node_states[], however write support is needed in case
users want to set them manually e.g. when user want to override
default N_DEMOTION_TARGETS found by the kernel.

Rename existing _NODE_ATTR to _NODE_ATTR_RO and introduce new
_NODE_ATTR_RW which can be used for node_states[] which can
be written from sysfs.

It may be necessary to validate written values and take action
based on them in a state specific way so a callback 'write' is
introduced in 'struct node_attr'.

A new function demotion_targets_write() is added to validate
the input nodes for N_DEMOTION_TARGETS which should be subset
of N_MEMORY and to build new demotion list based on new nodes.

Signed-off-by: Jagdish Gediya <jvgediya@linux.ibm.com>
---
drivers/base/node.c | 62 +++++++++++++++++++++++++++++++++++----------
1 file changed, 49 insertions(+), 13 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 6eef22e6413e..e03eedbc421b 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -20,6 +20,7 @@
#include <linux/pm_runtime.h>
#include <linux/swap.h>
#include <linux/slab.h>
+#include <linux/migrate.h>

static struct bus_type node_subsys = {
.name = "node",
@@ -1013,6 +1014,7 @@ void unregister_one_node(int nid)
struct node_attr {
struct device_attribute attr;
enum node_states state;
+ int (*write)(nodemask_t nodes);
};

static ssize_t show_node_state(struct device *dev,
@@ -1024,23 +1026,57 @@ static ssize_t show_node_state(struct device *dev,
nodemask_pr_args(&node_states[na->state]));
}

-#define _NODE_ATTR(name, state) \
- { __ATTR(name, 0444, show_node_state, NULL), state }
+static ssize_t store_node_state(struct device *s,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ nodemask_t nodes;
+ struct node_attr *na = container_of(attr, struct node_attr, attr);
+
+ if (nodelist_parse(buf, nodes))
+ return -EINVAL;
+
+ if (na->write) {
+ if (na->write(nodes))
+ return -EINVAL;
+ } else {
+ node_states[na->state] = nodes;
+ }
+
+ return count;
+}
+
+static int demotion_targets_write(nodemask_t nodes)
+{
+ if (nodes_subset(nodes, node_states[N_MEMORY])) {
+ node_states[N_DEMOTION_TARGETS] = nodes;
+ set_migration_target_nodes();
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+#define _NODE_ATTR_RO(name, state) \
+ { __ATTR(name, 0444, show_node_state, NULL), state, NULL }
+
+#define _NODE_ATTR_RW(name, state, write_fn) \
+ { __ATTR(name, 0644, show_node_state, store_node_state), state, write_fn }

static struct node_attr node_state_attr[] = {
- [N_POSSIBLE] = _NODE_ATTR(possible, N_POSSIBLE),
- [N_ONLINE] = _NODE_ATTR(online, N_ONLINE),
- [N_NORMAL_MEMORY] = _NODE_ATTR(has_normal_memory, N_NORMAL_MEMORY),
+ [N_POSSIBLE] = _NODE_ATTR_RO(possible, N_POSSIBLE),
+ [N_ONLINE] = _NODE_ATTR_RO(online, N_ONLINE),
+ [N_NORMAL_MEMORY] = _NODE_ATTR_RO(has_normal_memory, N_NORMAL_MEMORY),
#ifdef CONFIG_HIGHMEM
- [N_HIGH_MEMORY] = _NODE_ATTR(has_high_memory, N_HIGH_MEMORY),
+ [N_HIGH_MEMORY] = _NODE_ATTR_RO(has_high_memory, N_HIGH_MEMORY),
#endif
- [N_MEMORY] = _NODE_ATTR(has_memory, N_MEMORY),
- [N_CPU] = _NODE_ATTR(has_cpu, N_CPU),
- [N_GENERIC_INITIATOR] = _NODE_ATTR(has_generic_initiator,
- N_GENERIC_INITIATOR),
- [N_DEMOTION_TARGETS] = _NODE_ATTR(demotion_targets,
- N_DEMOTION_TARGETS),
-
+ [N_MEMORY] = _NODE_ATTR_RO(has_memory, N_MEMORY),
+ [N_CPU] = _NODE_ATTR_RO(has_cpu, N_CPU),
+ [N_GENERIC_INITIATOR] = _NODE_ATTR_RO(has_generic_initiator,
+ N_GENERIC_INITIATOR),
+ [N_DEMOTION_TARGETS] = _NODE_ATTR_RW(demotion_targets,
+ N_DEMOTION_TARGETS,
+ demotion_targets_write),
};

static struct attribute *node_state_attrs[] = {
--
2.35.1