Linux Virtualization - Oct 2008 - [PATCH][cfq-cgroups] Introduce cgroups structure with ioprio entry.

This patch introcude cfq_cgroup structure which is type for
  group control within expanded CFQ scheduler.
  In addition, the cfq_cgroup structure has "ioprio" entry which 
  is preference of group for I/O.


    Signed-off-by: Satoshi UCHIDA <s-uchida at ap.jp.nec.com>

---
 block/cfq-cgroup.c            |  148 +++++++++++++++++++++++++++++++++++++++++
 include/linux/cgroup_subsys.h |    6 ++
 2 files changed, 154 insertions(+), 0 deletions(-)

diff --git a/block/cfq-cgroup.c b/block/cfq-cgroup.c
index aaa00ef..733980d 100644
--- a/block/cfq-cgroup.c
+++ b/block/cfq-cgroup.c
@@ -15,6 +15,154 @@
 #include <linux/cgroup.h>
 #include <linux/cfq-iosched.h>
 
+#define CFQ_CGROUP_MAX_IOPRIO		(7)
+
+
+struct cfq_cgroup {
+	struct cgroup_subsys_state css;
+	unsigned int ioprio;
+};
+
+static inline struct cfq_cgroup *cgroup_to_cfq_cgroup(struct cgroup *cont)
+{
+	return container_of(cgroup_subsys_state(cont, cfq_subsys_id),
+			    struct cfq_cgroup, css);
+}
+
+static inline struct cfq_cgroup *task_to_cfq_cgroup(struct task_struct *tsk)
+{
+	return container_of(task_subsys_state(tsk, cfq_subsys_id),
+			    struct cfq_cgroup, css);
+}
+
+
+static struct cgroup_subsys_state *
+cfq_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+	struct cfq_cgroup *cfqc;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return ERR_PTR(-EPERM);
+
+	if (!cgroup_is_descendant(cont))
+		return ERR_PTR(-EPERM);
+
+	cfqc = kzalloc(sizeof(struct cfq_cgroup), GFP_KERNEL);
+	if (unlikely(!cfqc))
+		return ERR_PTR(-ENOMEM);
+
+	cfqc->ioprio = 3;
+
+	return &cfqc->css;
+}
+
+static void cfq_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+	kfree(cgroup_to_cfq_cgroup(cont));
+}
+
+static ssize_t cfq_cgroup_read(struct cgroup *cont, struct cftype *cft,
+			       struct file *file, char __user *userbuf,
+			       size_t nbytes, loff_t *ppos)
+{
+	struct cfq_cgroup *cfqc;
+	char *page;
+	ssize_t ret;
+
+	page = (char *)__get_free_page(GFP_TEMPORARY);
+	if (!page)
+		return -ENOMEM;
+
+	cgroup_lock();
+	if (cgroup_is_removed(cont)) {
+		cgroup_unlock();
+		ret = -ENODEV;
+		goto out;
+	}
+
+	cfqc = cgroup_to_cfq_cgroup(cont);
+
+	cgroup_unlock();
+
+	/* print priority */
+	ret = snprintf(page, PAGE_SIZE, "%d \n", cfqc->ioprio);
+
+	ret = simple_read_from_buffer(userbuf, nbytes, ppos, page, ret);
+
+out:
+	free_page((unsigned long)page);
+	return ret;
+}
+
+static ssize_t cfq_cgroup_write(struct cgroup *cont, struct cftype *cft,
+				struct file *file, const char __user *userbuf,
+				size_t nbytes, loff_t *ppos)
+{
+	struct cfq_cgroup *cfqc;
+	ssize_t ret;
+	long new_prio;
+	int err;
+	char *buffer = NULL;
+
+	cgroup_lock();
+	if (cgroup_is_removed(cont)) {
+		cgroup_unlock();
+		ret = -ENODEV;
+		goto out;
+	}
+
+	cfqc = cgroup_to_cfq_cgroup(cont);
+	cgroup_unlock();
+
+	/* set priority */
+	buffer = kmalloc(nbytes + 1, GFP_KERNEL);
+	if (buffer == NULL)
+		return -ENOMEM;
+
+	if (copy_from_user(buffer, userbuf, nbytes)) {
+		ret = -EFAULT;
+		goto out;
+	}
+	buffer[nbytes] = 0;
+
+	err = strict_strtoul(buffer, 10, &new_prio);
+	if ((err) || ((new_prio < 0) || (new_prio > CFQ_CGROUP_MAX_IOPRIO))) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	cfqc->ioprio = new_prio;
+
+	ret = nbytes;
+
+out:
+	kfree(buffer);
+
+	return ret;
+}
+
+static struct cftype files[] = {
+	{
+		.name = "ioprio",
+		.read = cfq_cgroup_read,
+		.write = cfq_cgroup_write,
+	},
+};
+
+static int cfq_cgroup_populate(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+	return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
+}
+
+struct cgroup_subsys cfq_subsys = {
+	.name = "cfq",
+	.create = cfq_cgroup_create,
+	.destroy = cfq_cgroup_destroy,
+	.populate = cfq_cgroup_populate,
+	.subsys_id = cfq_subsys_id,
+};
+
+
 /*
  * sysfs parts below -->
  */
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 9c22396..a9482aa 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -54,3 +54,9 @@ SUBSYS(freezer)
 #endif
 
 /* */
+
+#ifdef CONFIG_IOSCHED_CFQ_CGROUP
+SUBSYS(cfq)
+#endif
+
+/* */
-- 
1.5.6.5