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

Aneesh Kumar K.V
2022-04-24T06:26:07Z

Jagdish Gediya <jvgediya@linux.ibm.com> writes:

> 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;
> + }

Does this require locking to avoid upating
node_states[N_DEMOTION_TARGETS] while a parallel
set_migratiotn_target_nodes() is running.

> +
> + 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