io-controller: Add a new interface "weight_device" for IO-Controller

Currently, IO Controller makes use of blkio.weight to assign weight for
all devices. Here a new user interface "blkio.weight_device" is introduced to
assign different weights for different devices. blkio.weight becomes the
default value for devices which are not configured by "blkio.weight_device"

You can use the following format to assigned specific weight for a given
device:
#echo "major:minor weight" > blkio.weight_device

major:minor represents device number.

And you can remove weight for a given device as following:
#echo "major:minor 0" > blkio.weight_device

V1->V2 changes:
- use user interface "weight_device" instead of "policy" suggested by Vivek
- rename some struct suggested by Vivek
- rebase to 2.6-block "for-linus" branch
- remove an useless list_empty check pointed out by Li Zefan
- some trivial typo fix

V2->V3 changes:
- Move policy_*_node() functions up to get rid of forward declarations
- rename related functions by adding prefix "blkio_"

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

3 files changed, 247 insertions, 1 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1ecff7a39f2c..649b05d7f291 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -17,6 +17,7 @@
 #include <linux/err.h>
 #include <linux/blkdev.h>
 #include "blk-cgroup.h"
+#include <linux/genhd.h>
 
 #define MAX_KEY_LEN 100
 
@@ -51,6 +52,32 @@ struct cgroup_subsys blkio_subsys = {
 };
 EXPORT_SYMBOL_GPL(blkio_subsys);
 
+static inline void blkio_policy_insert_node(struct blkio_cgroup *blkcg,
+                                            struct blkio_policy_node *pn)
+{
+        list_add(&pn->node, &blkcg->policy_list);
+}
+
+/* Must be called with blkcg->lock held */
+static inline void blkio_policy_delete_node(struct blkio_policy_node *pn)
+{
+        list_del(&pn->node);
+}
+
+/* Must be called with blkcg->lock held */
+static struct blkio_policy_node *
+blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev)
+{
+        struct blkio_policy_node *pn;
+
+        list_for_each_entry(pn, &blkcg->policy_list, node) {
+                if (pn->dev == dev)
+                        return pn;
+        }
+
+        return NULL;
+}
+
 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 {
         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
@@ -398,6 +425,7 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
         struct blkio_group *blkg;
         struct hlist_node *n;
         struct blkio_policy_type *blkiop;
+        struct blkio_policy_node *pn;
 
         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
                 return -EINVAL;
@@ -406,7 +434,13 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
         spin_lock(&blkio_list_lock);
         spin_lock_irq(&blkcg->lock);
         blkcg->weight = (unsigned int)val;
+
         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
+                pn = blkio_policy_search_node(blkcg, blkg->dev);
+
+                if (pn)
+                        continue;
+
                 list_for_each_entry(blkiop, &blkio_list, list)
                         blkiop->ops.blkio_update_group_weight_fn(blkg,
                                         blkcg->weight);
@@ -611,8 +645,203 @@ void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
 EXPORT_SYMBOL_GPL(blkiocg_update_dequeue_stats);
 #endif
 
+static int blkio_check_dev_num(dev_t dev)
+{
+        int part = 0;
+        struct gendisk *disk;
+
+        disk = get_gendisk(dev, &part);
+        if (!disk || part)
+                return -ENODEV;
+
+        return 0;
+}
+
+static int blkio_policy_parse_and_set(char *buf,
+                                      struct blkio_policy_node *newpn)
+{
+        char *s[4], *p, *major_s = NULL, *minor_s = NULL;
+        int ret;
+        unsigned long major, minor, temp;
+        int i = 0;
+        dev_t dev;
+
+        memset(s, 0, sizeof(s));
+
+        while ((p = strsep(&buf, " ")) != NULL) {
+                if (!*p)
+                        continue;
+
+                s[i++] = p;
+
+                /* Prevent from inputing too many things */
+                if (i == 3)
+                        break;
+        }
+
+        if (i != 2)
+                return -EINVAL;
+
+        p = strsep(&s[0], ":");
+        if (p != NULL)
+                major_s = p;
+        else
+                return -EINVAL;
+
+        minor_s = s[0];
+        if (!minor_s)
+                return -EINVAL;
+
+        ret = strict_strtoul(major_s, 10, &major);
+        if (ret)
+                return -EINVAL;
+
+        ret = strict_strtoul(minor_s, 10, &minor);
+        if (ret)
+                return -EINVAL;
+
+        dev = MKDEV(major, minor);
+
+        ret = blkio_check_dev_num(dev);
+        if (ret)
+                return ret;
+
+        newpn->dev = dev;
+
+        if (s[1] == NULL)
+                return -EINVAL;
+
+        ret = strict_strtoul(s[1], 10, &temp);
+        if (ret || (temp < BLKIO_WEIGHT_MIN && temp > 0) ||
+            temp > BLKIO_WEIGHT_MAX)
+                return -EINVAL;
+
+        newpn->weight =  temp;
+
+        return 0;
+}
+
+unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,
+                              dev_t dev)
+{
+        struct blkio_policy_node *pn;
+
+        pn = blkio_policy_search_node(blkcg, dev);
+        if (pn)
+                return pn->weight;
+        else
+                return blkcg->weight;
+}
+EXPORT_SYMBOL_GPL(blkcg_get_weight);
+
+
+static int blkiocg_weight_device_write(struct cgroup *cgrp, struct cftype *cft,
+                                       const char *buffer)
+{
+        int ret = 0;
+        char *buf;
+        struct blkio_policy_node *newpn, *pn;
+        struct blkio_cgroup *blkcg;
+        struct blkio_group *blkg;
+        int keep_newpn = 0;
+        struct hlist_node *n;
+        struct blkio_policy_type *blkiop;
+
+        buf = kstrdup(buffer, GFP_KERNEL);
+        if (!buf)
+                return -ENOMEM;
+
+        newpn = kzalloc(sizeof(*newpn), GFP_KERNEL);
+        if (!newpn) {
+                ret = -ENOMEM;
+                goto free_buf;
+        }
+
+        ret = blkio_policy_parse_and_set(buf, newpn);
+        if (ret)
+                goto free_newpn;
+
+        blkcg = cgroup_to_blkio_cgroup(cgrp);
+
+        spin_lock_irq(&blkcg->lock);
+
+        pn = blkio_policy_search_node(blkcg, newpn->dev);
+        if (!pn) {
+                if (newpn->weight != 0) {
+                        blkio_policy_insert_node(blkcg, newpn);
+                        keep_newpn = 1;
+                }
+                spin_unlock_irq(&blkcg->lock);
+                goto update_io_group;
+        }
+
+        if (newpn->weight == 0) {
+                /* weight == 0 means deleteing a specific weight */
+                blkio_policy_delete_node(pn);
+                spin_unlock_irq(&blkcg->lock);
+                goto update_io_group;
+        }
+        spin_unlock_irq(&blkcg->lock);
+
+        pn->weight = newpn->weight;
+
+update_io_group:
+        /* update weight for each cfqg */
+        spin_lock(&blkio_list_lock);
+        spin_lock_irq(&blkcg->lock);
+
+        hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
+                if (newpn->dev == blkg->dev) {
+                        list_for_each_entry(blkiop, &blkio_list, list)
+                                blkiop->ops.blkio_update_group_weight_fn(blkg,
+                                                         newpn->weight ?
+                                                         newpn->weight :
+                                                         blkcg->weight);
+                }
+        }
+
+        spin_unlock_irq(&blkcg->lock);
+        spin_unlock(&blkio_list_lock);
+
+free_newpn:
+        if (!keep_newpn)
+                kfree(newpn);
+free_buf:
+        kfree(buf);
+        return ret;
+}
+
+static int blkiocg_weight_device_read(struct cgroup *cgrp, struct cftype *cft,
+                                      struct seq_file *m)
+{
+        struct blkio_cgroup *blkcg;
+        struct blkio_policy_node *pn;
+
+        seq_printf(m, "dev\tweight\n");
+
+        blkcg = cgroup_to_blkio_cgroup(cgrp);
+        if (list_empty(&blkcg->policy_list))
+                goto out;
+
+        spin_lock_irq(&blkcg->lock);
+        list_for_each_entry(pn, &blkcg->policy_list, node) {
+                seq_printf(m, "%u:%u\t%u\n", MAJOR(pn->dev),
+                           MINOR(pn->dev), pn->weight);
+        }
+        spin_unlock_irq(&blkcg->lock);
+
+out:
+        return 0;
+}
+
 struct cftype blkio_files[] = {
         {
+                .name = "weight_device",
+                .read_seq_string = blkiocg_weight_device_read,
+                .write_string = blkiocg_weight_device_write,
+                .max_write_len = 256,
+        },
+        {
                 .name = "weight",
                 .read_u64 = blkiocg_weight_read,
                 .write_u64 = blkiocg_weight_write,
@@ -690,6 +919,7 @@ static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
         struct blkio_group *blkg;
         void *key;
         struct blkio_policy_type *blkiop;
+        struct blkio_policy_node *pn, *pntmp;
 
         rcu_read_lock();
 remove_entry:
@@ -720,7 +950,12 @@ remove_entry:
                 blkiop->ops.blkio_unlink_group_fn(key, blkg);
         spin_unlock(&blkio_list_lock);
         goto remove_entry;
+
 done:
+        list_for_each_entry_safe(pn, pntmp, &blkcg->policy_list, node) {
+                blkio_policy_delete_node(pn);
+                kfree(pn);
+        }
         free_css_id(&blkio_subsys, &blkcg->css);
         rcu_read_unlock();
         if (blkcg != &blkio_root_cgroup)
@@ -751,6 +986,7 @@ done:
         spin_lock_init(&blkcg->lock);
         INIT_HLIST_HEAD(&blkcg->blkg_list);
 
+        INIT_LIST_HEAD(&blkcg->policy_list);
         return &blkcg->css;
 }
 
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index bfce085b1962..3c27bdfc97b9 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -70,6 +70,7 @@ struct blkio_cgroup {
         unsigned int weight;
         spinlock_t lock;
         struct hlist_head blkg_list;
+        struct list_head policy_list; /* list of blkio_policy_node */
 };
 
 struct blkio_group_stats {
@@ -119,6 +120,15 @@ struct blkio_group {
         struct blkio_group_stats stats;
 };
 
+struct blkio_policy_node {
+        struct list_head node;
+        dev_t dev;
+        unsigned int weight;
+};
+
+extern unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,
+                                     dev_t dev);
+
 typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg);
 typedef void (blkio_update_group_weight_fn) (struct blkio_group *blkg,
                                                 unsigned int weight);
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b6e095c7ef5e..91af2f2e59ce 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -952,7 +952,6 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
         if (!cfqg)
                 goto done;
 
-        cfqg->weight = blkcg->weight;
         for_each_cfqg_st(cfqg, i, j, st)
                 *st = CFQ_RB_ROOT;
         RB_CLEAR_NODE(&cfqg->rb_node);
@@ -970,6 +969,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
         sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
         blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
                                         MKDEV(major, minor));
+        cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
 
         /* Add group on cfqd list */
         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);