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    Subject[PATCH 17/19] io-controller: Support per cgroup per device weights and io class
    Date
    This patch enables per-cgroup per-device weight and ioprio_class handling.
    A new cgroup interface "policy" is introduced. You can make use of this
    file to configure weight and ioprio_class for each device in a given cgroup.
    The original "weight" and "ioprio_class" files are still available. If you
    don't do special configuration for a particular device, "weight" and
    "ioprio_class" are used as default values in this device.

    You can use the following format to play with the new interface.
    #echo DEV:weight:ioprio_class > /patch/to/cgroup/policy
    weight=0 means removing the policy for DEV.

    Examples:
    Configure weight=300 ioprio_class=2 on /dev/hdb in this cgroup
    # echo /dev/hdb:300:2 > io.policy
    # cat io.policy
    dev weight class
    /dev/hdb 300 2

    Configure weight=500 ioprio_class=1 on /dev/hda in this cgroup
    # echo /dev/hda:500:1 > io.policy
    # cat io.policy
    dev weight class
    /dev/hda 500 1
    /dev/hdb 300 2

    Remove the policy for /dev/hda in this cgroup
    # echo /dev/hda:0:1 > io.policy
    # cat io.policy
    dev weight class
    /dev/hdb 300 2

    Changelog (v1 -> v2)
    - Rename some structures
    - Use spin_lock_irqsave() and spin_lock_irqrestore() version to prevent
    from enabling the interrupts unconditionally.
    - Fix policy setup bug when switching to another io scheduler.
    - If a policy is available for a specific device, don't update weight and
    io class when writing "weight" and "iprio_class".
    - Fix a bug when parsing policy string.

    Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
    Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
    ---
    block/elevator-fq.c | 246 +++++++++++++++++++++++++++++++++++++++++++++++++--
    block/elevator-fq.h | 11 +++
    2 files changed, 251 insertions(+), 6 deletions(-)

    diff --git a/block/elevator-fq.c b/block/elevator-fq.c
    index 68aaaa7..207664d 100644
    --- a/block/elevator-fq.c
    +++ b/block/elevator-fq.c
    @@ -15,6 +15,7 @@
    #include <linux/blktrace_api.h>
    #include <linux/seq_file.h>
    #include <linux/biotrack.h>
    +#include <linux/genhd.h>

    /* Values taken from cfq */
    const int elv_slice_sync = HZ / 10;
    @@ -1041,12 +1042,31 @@ struct io_group *io_cgroup_lookup_group(struct io_cgroup *iocg, void *key)
    return NULL;
    }

    -void io_group_init_entity(struct io_cgroup *iocg, struct io_group *iog)
    +static struct io_policy_node *policy_search_node(const struct io_cgroup *iocg,
    + dev_t dev);
    +
    +void io_group_init_entity(struct io_cgroup *iocg, struct io_group *iog,
    + dev_t dev)
    {
    struct io_entity *entity = &iog->entity;
    + struct io_policy_node *pn;
    + unsigned long flags;
    +
    + spin_lock_irqsave(&iocg->lock, flags);
    + pn = policy_search_node(iocg, dev);
    + if (pn) {
    + entity->weight = pn->weight;
    + entity->new_weight = pn->weight;
    + entity->ioprio_class = pn->ioprio_class;
    + entity->new_ioprio_class = pn->ioprio_class;
    + } else {
    + entity->weight = iocg->weight;
    + entity->new_weight = iocg->weight;
    + entity->ioprio_class = iocg->ioprio_class;
    + entity->new_ioprio_class = iocg->ioprio_class;
    + }
    + spin_unlock_irqrestore(&iocg->lock, flags);

    - entity->weight = entity->new_weight = iocg->weight;
    - entity->ioprio_class = entity->new_ioprio_class = iocg->ioprio_class;
    entity->ioprio_changed = 1;
    entity->my_sched_data = &iog->sched_data;
    }
    @@ -1098,6 +1118,7 @@ static int io_cgroup_##__VAR##_write(struct cgroup *cgroup, \
    struct io_cgroup *iocg; \
    struct io_group *iog; \
    struct hlist_node *n; \
    + struct io_policy_node *pn; \
    \
    if (val < (__MIN) || val > (__MAX)) \
    return -EINVAL; \
    @@ -1110,6 +1131,9 @@ static int io_cgroup_##__VAR##_write(struct cgroup *cgroup, \
    spin_lock_irq(&iocg->lock); \
    iocg->__VAR = (unsigned long)val; \
    hlist_for_each_entry(iog, n, &iocg->group_data, group_node) { \
    + pn = policy_search_node(iocg, iog->dev); \
    + if (pn) \
    + continue; \
    iog->entity.new_##__VAR = (unsigned long)val; \
    smp_wmb(); \
    iog->entity.ioprio_changed = 1; \
    @@ -1218,9 +1242,6 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
    if (!iog)
    goto cleanup;

    - io_group_init_entity(iocg, iog);
    - iog->my_entity = &iog->entity;
    -
    atomic_set(&iog->ref, 0);
    iog->deleting = 0;

    @@ -1233,6 +1254,8 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
    elv_get_iog(iog);

    iog->iocg_id = css_id(&iocg->css);
    + io_group_init_entity(iocg, iog, iog->dev);
    + iog->my_entity = &iog->entity;

    if (bio) {
    struct gendisk *disk = bio->bi_bdev->bd_disk;
    @@ -1520,8 +1543,212 @@ struct io_group *io_alloc_root_group(struct request_queue *q,
    return iog;
    }

    +static int io_cgroup_policy_read(struct cgroup *cgrp, struct cftype *cft,
    + struct seq_file *m)
    +{
    + struct io_cgroup *iocg;
    + struct io_policy_node *pn;
    +
    + iocg = cgroup_to_io_cgroup(cgrp);
    +
    + if (list_empty(&iocg->policy_list))
    + goto out;
    +
    + seq_printf(m, "dev weight class\n");
    +
    + spin_lock_irq(&iocg->lock);
    + list_for_each_entry(pn, &iocg->policy_list, node) {
    + seq_printf(m, "%s %lu %lu\n", pn->dev_name,
    + pn->weight, pn->ioprio_class);
    + }
    + spin_unlock_irq(&iocg->lock);
    +out:
    + return 0;
    +}
    +
    +static inline void policy_insert_node(struct io_cgroup *iocg,
    + struct io_policy_node *pn)
    +{
    + list_add(&pn->node, &iocg->policy_list);
    +}
    +
    +/* Must be called with iocg->lock held */
    +static inline void policy_delete_node(struct io_policy_node *pn)
    +{
    + list_del(&pn->node);
    +}
    +
    +/* Must be called with iocg->lock held */
    +static struct io_policy_node *policy_search_node(const struct io_cgroup *iocg,
    + dev_t dev)
    +{
    + struct io_policy_node *pn;
    +
    + if (list_empty(&iocg->policy_list))
    + return NULL;
    +
    + list_for_each_entry(pn, &iocg->policy_list, node) {
    + if (pn->dev == dev)
    + return pn;
    + }
    +
    + return NULL;
    +}
    +
    +static int devname_to_devnum(const char *buf, dev_t *dev)
    +{
    + struct block_device *bdev;
    + struct gendisk *disk;
    + int part;
    +
    + bdev = lookup_bdev(buf);
    + if (IS_ERR(bdev))
    + return -ENODEV;
    +
    + disk = get_gendisk(bdev->bd_dev, &part);
    + if (part)
    + return -EINVAL;
    +
    + *dev = MKDEV(disk->major, disk->first_minor);
    + bdput(bdev);
    +
    + return 0;
    +}
    +
    +static int policy_parse_and_set(char *buf, struct io_policy_node *newpn)
    +{
    + char *s[3], *p;
    + int ret;
    + int i = 0;
    +
    + memset(s, 0, sizeof(s));
    + while ((p = strsep(&buf, ":")) != NULL) {
    + if (!*p)
    + continue;
    + s[i++] = p;
    + }
    +
    + ret = devname_to_devnum(s[0], &newpn->dev);
    + if (ret)
    + return ret;
    +
    + strcpy(newpn->dev_name, s[0]);
    +
    + if (s[1] == NULL)
    + return -EINVAL;
    +
    + ret = strict_strtoul(s[1], 10, &newpn->weight);
    + if (ret || newpn->weight > WEIGHT_MAX)
    + return -EINVAL;
    +
    + if (s[2] == NULL)
    + return -EINVAL;
    +
    + ret = strict_strtoul(s[2], 10, &newpn->ioprio_class);
    + if (ret || newpn->ioprio_class < IOPRIO_CLASS_RT ||
    + newpn->ioprio_class > IOPRIO_CLASS_IDLE)
    + return -EINVAL;
    +
    + return 0;
    +}
    +
    +static int io_cgroup_policy_write(struct cgroup *cgrp, struct cftype *cft,
    + const char *buffer)
    +{
    + struct io_cgroup *iocg;
    + struct io_policy_node *newpn, *pn;
    + char *buf;
    + int ret = 0;
    + int keep_newpn = 0;
    + struct hlist_node *n;
    + struct io_group *iog;
    +
    + buf = kstrdup(buffer, GFP_KERNEL);
    + if (!buf)
    + return -ENOMEM;
    +
    + newpn = kzalloc(sizeof(*newpn), GFP_KERNEL);
    + if (!newpn) {
    + ret = -ENOMEM;
    + goto free_buf;
    + }
    +
    + ret = policy_parse_and_set(buf, newpn);
    + if (ret)
    + goto free_newpn;
    +
    + if (!cgroup_lock_live_group(cgrp)) {
    + ret = -ENODEV;
    + goto free_newpn;
    + }
    +
    + iocg = cgroup_to_io_cgroup(cgrp);
    + spin_lock_irq(&iocg->lock);
    +
    + pn = policy_search_node(iocg, newpn->dev);
    + if (!pn) {
    + if (newpn->weight != 0) {
    + policy_insert_node(iocg, newpn);
    + keep_newpn = 1;
    + }
    + goto update_io_group;
    + }
    +
    + if (newpn->weight == 0) {
    + /* weight == 0 means deleteing a policy */
    + policy_delete_node(pn);
    + goto update_io_group;
    + }
    +
    + pn->weight = newpn->weight;
    + pn->ioprio_class = newpn->ioprio_class;
    +
    +update_io_group:
    + hlist_for_each_entry(iog, n, &iocg->group_data, group_node) {
    + if (iog->dev == newpn->dev) {
    + if (newpn->weight) {
    + iog->entity.new_weight = newpn->weight;
    + iog->entity.new_ioprio_class =
    + newpn->ioprio_class;
    + /*
    + * iog weight and ioprio_class updating
    + * actually happens if ioprio_changed is set.
    + * So ensure ioprio_changed is not set until
    + * new weight and new ioprio_class are updated.
    + */
    + smp_wmb();
    + iog->entity.ioprio_changed = 1;
    + } else {
    + iog->entity.new_weight = iocg->weight;
    + iog->entity.new_ioprio_class =
    + iocg->ioprio_class;
    +
    + /* The same as above */
    + smp_wmb();
    + iog->entity.ioprio_changed = 1;
    + }
    + }
    + }
    + spin_unlock_irq(&iocg->lock);
    +
    + cgroup_unlock();
    +
    +free_newpn:
    + if (!keep_newpn)
    + kfree(newpn);
    +free_buf:
    + kfree(buf);
    + return ret;
    +}
    +
    struct cftype bfqio_files[] = {
    {
    + .name = "policy",
    + .read_seq_string = io_cgroup_policy_read,
    + .write_string = io_cgroup_policy_write,
    + .max_write_len = 256,
    + },
    + {
    .name = "weight",
    .read_u64 = io_cgroup_weight_read,
    .write_u64 = io_cgroup_weight_write,
    @@ -1563,6 +1790,7 @@ struct cgroup_subsys_state *iocg_create(struct cgroup_subsys *subsys,
    INIT_HLIST_HEAD(&iocg->group_data);
    iocg->weight = IO_DEFAULT_GRP_WEIGHT;
    iocg->ioprio_class = IO_DEFAULT_GRP_CLASS;
    + INIT_LIST_HEAD(&iocg->policy_list);

    return &iocg->css;
    }
    @@ -1752,6 +1980,7 @@ void iocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
    struct io_group *iog;
    struct elv_fq_data *efqd;
    unsigned long uninitialized_var(flags);
    + struct io_policy_node *pn, *pntmp;

    /*
    * io groups are linked in two lists. One list is maintained
    @@ -1790,6 +2019,11 @@ remove_entry:
    goto remove_entry;

    done:
    + list_for_each_entry_safe(pn, pntmp, &iocg->policy_list, node) {
    + policy_delete_node(pn);
    + kfree(pn);
    + }
    +
    free_css_id(&io_subsys, &iocg->css);
    rcu_read_unlock();
    BUG_ON(!hlist_empty(&iocg->group_data));
    diff --git a/block/elevator-fq.h b/block/elevator-fq.h
    index 2655611..ff409ec 100644
    --- a/block/elevator-fq.h
    +++ b/block/elevator-fq.h
    @@ -253,6 +253,14 @@ struct io_group {
    struct request_list rl;
    };

    +struct io_policy_node {
    + struct list_head node;
    + char dev_name[32];
    + dev_t dev;
    + unsigned long weight;
    + unsigned long ioprio_class;
    +};
    +
    /**
    * struct bfqio_cgroup - bfq cgroup data structure.
    * @css: subsystem state for bfq in the containing cgroup.
    @@ -269,6 +277,9 @@ struct io_cgroup {

    unsigned long weight, ioprio_class;

    + /* list of io_policy_node */
    + struct list_head policy_list;
    +
    spinlock_t lock;
    struct hlist_head group_data;
    };
    --
    1.6.0.6


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