padata: Added sysfs primitives to padata subsystem

Added sysfs primitives to padata subsystem. Now API user may
embedded kobject each padata instance contains into any sysfs
hierarchy. For now padata sysfs interface provides only
two objects:
    serial_cpumask   [RW] - cpumask for serial workers
    parallel_cpumask [RW] - cpumask for parallel workers

Signed-off-by: Dan Kruchinin <dkruchinin@acm.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 146 insertions, 9 deletions

diff --git a/kernel/padata.c b/kernel/padata.c
index 84d0ca9dac9c..526f9ea2fcc8 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -26,6 +26,7 @@
 #include <linux/mutex.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/sysfs.h>
 #include <linux/rcupdate.h>
 
 #define MAX_SEQ_NR (INT_MAX - NR_CPUS)
@@ -924,6 +925,149 @@ static int padata_cpu_callback(struct notifier_block *nfb,
 }
 #endif
 
+static void __padata_free(struct padata_instance *pinst)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+        unregister_hotcpu_notifier(&pinst->cpu_notifier);
+#endif
+
+        padata_stop(pinst);
+        padata_free_pd(pinst->pd);
+        free_cpumask_var(pinst->cpumask.pcpu);
+        free_cpumask_var(pinst->cpumask.cbcpu);
+        kfree(pinst);
+}
+
+#define kobj2pinst(_kobj)                                       \
+        container_of(_kobj, struct padata_instance, kobj)
+#define attr2pentry(_attr)                                      \
+        container_of(_attr, struct padata_sysfs_entry, attr)
+
+static void padata_sysfs_release(struct kobject *kobj)
+{
+        struct padata_instance *pinst = kobj2pinst(kobj);
+        __padata_free(pinst);
+}
+
+struct padata_sysfs_entry {
+        struct attribute attr;
+        ssize_t (*show)(struct padata_instance *, struct attribute *, char *);
+        ssize_t (*store)(struct padata_instance *, struct attribute *,
+                         const char *, size_t);
+};
+
+static ssize_t show_cpumask(struct padata_instance *pinst,
+                            struct attribute *attr,  char *buf)
+{
+        struct cpumask *cpumask;
+        ssize_t len;
+
+        mutex_lock(&pinst->lock);
+        if (!strcmp(attr->name, "serial_cpumask"))
+                cpumask = pinst->cpumask.cbcpu;
+        else
+                cpumask = pinst->cpumask.pcpu;
+
+        len = bitmap_scnprintf(buf, PAGE_SIZE, cpumask_bits(cpumask),
+                               nr_cpu_ids);
+        if (PAGE_SIZE - len < 2)
+                len = -EINVAL;
+        else
+                len += sprintf(buf + len, "\n");
+
+        mutex_unlock(&pinst->lock);
+        return len;
+}
+
+static ssize_t store_cpumask(struct padata_instance *pinst,
+                             struct attribute *attr,
+                             const char *buf, size_t count)
+{
+        cpumask_var_t new_cpumask;
+        ssize_t ret;
+        int mask_type;
+
+        if (!alloc_cpumask_var(&new_cpumask, GFP_KERNEL))
+                return -ENOMEM;
+
+        ret = bitmap_parse(buf, count, cpumask_bits(new_cpumask),
+                           nr_cpumask_bits);
+        if (ret < 0)
+                goto out;
+
+        mask_type = !strcmp(attr->name, "serial_cpumask") ?
+                PADATA_CPU_SERIAL : PADATA_CPU_PARALLEL;
+        ret = padata_set_cpumask(pinst, mask_type, new_cpumask);
+        if (!ret)
+                ret = count;
+
+out:
+        free_cpumask_var(new_cpumask);
+        return ret;
+}
+
+#define PADATA_ATTR_RW(_name, _show_name, _store_name)          \
+        static struct padata_sysfs_entry _name##_attr =         \
+                __ATTR(_name, 0644, _show_name, _store_name)
+#define PADATA_ATTR_RO(_name, _show_name)               \
+        static struct padata_sysfs_entry _name##_attr = \
+                __ATTR(_name, 0400, _show_name, NULL)
+
+PADATA_ATTR_RW(serial_cpumask, show_cpumask, store_cpumask);
+PADATA_ATTR_RW(parallel_cpumask, show_cpumask, store_cpumask);
+
+/*
+ * Padata sysfs provides the following objects:
+ * serial_cpumask   [RW] - cpumask for serial workers
+ * parallel_cpumask [RW] - cpumask for parallel workers
+ */
+static struct attribute *padata_default_attrs[] = {
+        &serial_cpumask_attr.attr,
+        &parallel_cpumask_attr.attr,
+        NULL,
+};
+
+static ssize_t padata_sysfs_show(struct kobject *kobj,
+                                 struct attribute *attr, char *buf)
+{
+        struct padata_instance *pinst;
+        struct padata_sysfs_entry *pentry;
+        ssize_t ret = -EIO;
+
+        pinst = kobj2pinst(kobj);
+        pentry = attr2pentry(attr);
+        if (pentry->show)
+                ret = pentry->show(pinst, attr, buf);
+
+        return ret;
+}
+
+static ssize_t padata_sysfs_store(struct kobject *kobj, struct attribute *attr,
+                                  const char *buf, size_t count)
+{
+        struct padata_instance *pinst;
+        struct padata_sysfs_entry *pentry;
+        ssize_t ret = -EIO;
+
+        pinst = kobj2pinst(kobj);
+        pentry = attr2pentry(attr);
+        if (pentry->show)
+                ret = pentry->store(pinst, attr, buf, count);
+
+        return ret;
+}
+
+static const struct sysfs_ops padata_sysfs_ops = {
+        .show = padata_sysfs_show,
+        .store = padata_sysfs_store,
+};
+
+static struct kobj_type padata_attr_type = {
+        .sysfs_ops = &padata_sysfs_ops,
+        .default_attrs = padata_default_attrs,
+        .release = padata_sysfs_release,
+};
+
 /**
  * padata_alloc - Allocate and initialize padata instance.
  *                Use default cpumask(cpu_possible_mask)
@@ -989,6 +1133,7 @@ struct padata_instance *__padata_alloc(struct workqueue_struct *wq,
         put_online_cpus();
 
         BLOCKING_INIT_NOTIFIER_HEAD(&pinst->cpumask_change_notifier);
+        kobject_init(&pinst->kobj, &padata_attr_type);
         mutex_init(&pinst->lock);
 
         return pinst;
@@ -1011,14 +1156,6 @@ EXPORT_SYMBOL(__padata_alloc);
  */
 void padata_free(struct padata_instance *pinst)
 {
-#ifdef CONFIG_HOTPLUG_CPU
-        unregister_hotcpu_notifier(&pinst->cpu_notifier);
-#endif
-
-        padata_stop(pinst);
-        padata_free_pd(pinst->pd);
-        free_cpumask_var(pinst->cpumask.pcpu);
-        free_cpumask_var(pinst->cpumask.cbcpu);
-        kfree(pinst);
+        kobject_put(&pinst->kobj);
 }
 EXPORT_SYMBOL(padata_free);