| Message ID | 20220422195516.10769-4-jvgediya@linux.ibm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: demotion: Introduce new node state N_DEMOTION_TARGETS | expand |
On Fri, Apr 22, 2022 at 12:55 PM Jagdish Gediya <jvgediya@linux.ibm.com> wrote: > > 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> Acked-by: Wei Xu <weixugc@google.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 >
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
On Sat, 2022-04-23 at 01:25 +0530, Jagdish Gediya wrote: > 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> How about discussing the ABI design firstly? I started a discussion in the following thread. I think we can start with the requirements. https://lore.kernel.org/lkml/200e95cf36c1642512d99431014db8943fed715d.camel@intel.com/ Best Regards, Huang, Ying > --- > 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[] = {
On Sun, Apr 24, 2022 at 11:55:45AM +0530, Aneesh Kumar K.V wrote: > 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. I think locking is needed if set_migratiotn_target_nodes() is called form here because currently exclusion is provided by memory hotplug events being single-threaded, but as this path is not hot-plug event, separate lock is needed. > > + > > + 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
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[] = {
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(-)