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Subject[PATCH 04/10] Common hierarchical fair queuing code in elevaotor layer
Date
This patch enables hierarchical fair queuing in common layer. It is
controlled by config option CONFIG_GROUP_IOSCHED.

Signed-off-by: Nauman Rafique <nauman@google.com>
Signed-off-by: Fabio Checconi <fabio@gandalf.sssup.it>
Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-ioc.c | 3 +
block/elevator-fq.c | 991 ++++++++++++++++++++++++++++++++++++++---
block/elevator-fq.h | 113 +++++
block/elevator.c | 2 +
include/linux/blkdev.h | 7 +-
include/linux/cgroup_subsys.h | 7 +
include/linux/iocontext.h | 5 +
init/Kconfig | 8 +
8 files changed, 1064 insertions(+), 72 deletions(-)
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 012f065..8f0f6cf 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -95,6 +95,9 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
spin_lock_init(&ret->lock);
ret->ioprio_changed = 0;
ret->ioprio = 0;
+#ifdef CONFIG_GROUP_IOSCHED
+ ret->cgroup_changed = 0;
+#endif
ret->last_waited = jiffies; /* doesn't matter... */
ret->nr_batch_requests = 0; /* because this is 0 */
ret->aic = NULL;
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index a8addd1..389f68e 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -20,10 +20,82 @@ int elv_slice_idle = HZ / 125;
static struct kmem_cache *elv_ioq_pool;

#define ELV_HW_QUEUE_MIN (5)
+
+#define IO_DEFAULT_GRP_IOPRIO 4
+#define IO_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE
+
#define IO_SERVICE_TREE_INIT ((struct io_service_tree) \
{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })

+void elv_release_ioq(struct elevator_queue *eq, struct io_queue **ioq_ptr);
/* Mainly the BFQ scheduling code Follows */
+#ifdef CONFIG_GROUP_IOSCHED
+#define for_each_entity(entity) \
+ for (; entity != NULL; entity = entity->parent)
+
+#define for_each_entity_safe(entity, parent) \
+ for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
+
+
+struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
+ int extract);
+void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
+ int requeue);
+void elv_activate_ioq(struct io_queue *ioq);
+void elv_deactivate_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
+ int requeue);
+
+static int bfq_update_next_active(struct io_sched_data *sd)
+{
+ struct io_group *iog;
+ struct io_entity *entity, *next_active;
+
+ if (sd->active_entity != NULL)
+ /* will update/requeue at the end of service */
+ return 0;
+
+ /*
+ * NOTE: this can be improved in may ways, such as returning
+ * 1 (and thus propagating upwards the update) only when the
+ * budget changes, or caching the bfqq that will be scheduled
+ * next from this subtree. By now we worry more about
+ * correctness than about performance...
+ */
+ next_active = bfq_lookup_next_entity(sd, 0);
+ sd->next_active = next_active;
+
+ if (next_active != NULL) {
+ iog = container_of(sd, struct io_group, sched_data);
+ entity = iog->my_entity;
+ if (entity != NULL)
+ entity->budget = next_active->budget;
+ }
+
+ return 1;
+}
+
+static inline void bfq_check_next_active(struct io_sched_data *sd,
+ struct io_entity *entity)
+{
+ BUG_ON(sd->next_active != entity);
+}
+#else /* GROUP_IOSCHED */
+#define for_each_entity(entity) \
+ for (; entity != NULL; entity = NULL)
+
+#define for_each_entity_safe(entity, parent) \
+ for (parent = NULL; entity != NULL; entity = parent)
+
+static inline int bfq_update_next_active(struct io_sched_data *sd)
+{
+ return 0;
+}
+
+static inline void bfq_check_next_active(struct io_sched_data *sd,
+ struct io_entity *entity)
+{
+}
+#endif

/*
* Shift for timestamp calculations. This actually limits the maximum
@@ -288,13 +360,6 @@ void bfq_get_entity(struct io_entity *entity)
elv_get_ioq(ioq);
}

-void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
-{
- entity->ioprio = entity->new_ioprio;
- entity->ioprio_class = entity->new_ioprio_class;
- entity->sched_data = &iog->sched_data;
-}
-
/**
* bfq_find_deepest - find the deepest node that an extraction can modify.
* @node: the node being removed.
@@ -520,12 +585,27 @@ static void __bfq_activate_entity(struct io_entity *entity)
}

/**
- * bfq_activate_entity - activate an entity.
+ * bfq_activate_entity - activate an entity and its ancestors if necessary.
* @entity: the entity to activate.
+ *
+ * Activate @entity and all the entities on the path from it to the root.
*/
void bfq_activate_entity(struct io_entity *entity)
{
- __bfq_activate_entity(entity);
+ struct io_sched_data *sd;
+
+ for_each_entity(entity) {
+ __bfq_activate_entity(entity);
+
+ sd = entity->sched_data;
+ if (!bfq_update_next_active(sd))
+ /*
+ * No need to propagate the activation to the
+ * upper entities, as they will be updated when
+ * the active entity is rescheduled.
+ */
+ break;
+ }
}

/**
@@ -561,12 +641,16 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
else if (entity->tree != NULL)
BUG();

+ if (was_active || sd->next_active == entity)
+ ret = bfq_update_next_active(sd);
+
if (!requeue || !bfq_gt(entity->finish, st->vtime))
bfq_forget_entity(st, entity);
else
bfq_idle_insert(st, entity);

BUG_ON(sd->active_entity == entity);
+ BUG_ON(sd->next_active == entity);

return ret;
}
@@ -578,7 +662,46 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
*/
void bfq_deactivate_entity(struct io_entity *entity, int requeue)
{
- __bfq_deactivate_entity(entity, requeue);
+ struct io_sched_data *sd;
+ struct io_entity *parent;
+
+ for_each_entity_safe(entity, parent) {
+ sd = entity->sched_data;
+
+ if (!__bfq_deactivate_entity(entity, requeue))
+ /*
+ * The parent entity is still backlogged, and
+ * we don't need to update it as it is still
+ * under service.
+ */
+ break;
+
+ if (sd->next_active != NULL)
+ /*
+ * The parent entity is still backlogged and
+ * the budgets on the path towards the root
+ * need to be updated.
+ */
+ goto update;
+
+ /*
+ * If we reach there the parent is no more backlogged and
+ * we want to propagate the dequeue upwards.
+ */
+ requeue = 1;
+ }
+
+ return;
+
+update:
+ entity = parent;
+ for_each_entity(entity) {
+ __bfq_activate_entity(entity);
+
+ sd = entity->sched_data;
+ if (!bfq_update_next_active(sd))
+ break;
+ }
}

/**
@@ -695,8 +818,10 @@ struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
entity = __bfq_lookup_next_entity(st);
if (entity != NULL) {
if (extract) {
+ bfq_check_next_active(sd, entity);
bfq_active_extract(st, entity);
sd->active_entity = entity;
+ sd->next_active = NULL;
}
break;
}
@@ -709,14 +834,756 @@ void entity_served(struct io_entity *entity, bfq_service_t served)
{
struct io_service_tree *st;

- st = io_entity_service_tree(entity);
- entity->service += served;
- WARN_ON_ONCE(entity->service > entity->budget);
- BUG_ON(st->wsum == 0);
- st->vtime += bfq_delta(served, st->wsum);
- bfq_forget_idle(st);
+ for_each_entity(entity) {
+ st = io_entity_service_tree(entity);
+ entity->service += served;
+ WARN_ON_ONCE(entity->service > entity->budget);
+ BUG_ON(st->wsum == 0);
+ st->vtime += bfq_delta(served, st->wsum);
+ bfq_forget_idle(st);
+ }
+}
+
+/*
+ * Release all the io group references to its async queues.
+ */
+void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
+{
+ int i, j;
+
+ for (i = 0; i < 2; i++)
+ for (j = 0; j < IOPRIO_BE_NR; j++)
+ elv_release_ioq(e, &iog->async_queue[i][j]);
+
+ /* Free up async idle queue */
+ elv_release_ioq(e, &iog->async_idle_queue);
+}
+
+
+/* Mainly hierarchical grouping code */
+#ifdef CONFIG_GROUP_IOSCHED
+
+struct io_cgroup io_root_cgroup = {
+ .ioprio = IO_DEFAULT_GRP_IOPRIO,
+ .ioprio_class = IO_DEFAULT_GRP_CLASS,
+};
+
+void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
+{
+ entity->ioprio = entity->new_ioprio;
+ entity->ioprio_class = entity->new_ioprio_class;
+ entity->parent = iog->my_entity;
+ entity->sched_data = &iog->sched_data;
+}
+
+struct io_cgroup *cgroup_to_io_cgroup(struct cgroup *cgroup)
+{
+ return container_of(cgroup_subsys_state(cgroup, io_subsys_id),
+ struct io_cgroup, css);
+}
+
+/*
+ * Search the bfq_group for bfqd into the hash table (by now only a list)
+ * of bgrp. Must be called under rcu_read_lock().
+ */
+struct io_group *io_cgroup_lookup_group(struct io_cgroup *iocg, void *key)
+{
+ struct io_group *iog;
+ struct hlist_node *n;
+ void *__key;
+
+ hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+ __key = rcu_dereference(iog->key);
+ if (__key == key)
+ return iog;
+ }
+
+ return NULL;
+}
+
+struct io_group *io_lookup_io_group_current(struct request_queue *q)
+{
+ struct io_group *iog;
+ struct io_cgroup *iocg;
+ struct cgroup *cgroup;
+ struct elv_fq_data *efqd = &q->elevator->efqd;
+
+ cgroup = task_cgroup(current, io_subsys_id);
+ iocg = cgroup_to_io_cgroup(cgroup);
+ iog = io_cgroup_lookup_group(iocg, efqd);
+ return iog;
+}
+EXPORT_SYMBOL(io_lookup_io_group_current);
+
+void io_group_init_entity(struct io_cgroup *iocg, struct io_group *iog)
+{
+ struct io_entity *entity = &iog->entity;
+
+ entity->ioprio = entity->new_ioprio = iocg->ioprio;
+ entity->ioprio_class = entity->new_ioprio_class = iocg->ioprio_class;
+ entity->ioprio_changed = 1;
+ entity->my_sched_data = &iog->sched_data;
+}
+
+void io_group_set_parent(struct io_group *iog, struct io_group *parent)
+{
+ struct io_entity *entity;
+
+ BUG_ON(parent == NULL);
+ BUG_ON(iog == NULL);
+
+ entity = &iog->entity;
+ entity->parent = parent->my_entity;
+ entity->sched_data = &parent->sched_data;
+}
+
+/**
+ * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
+ * @st: the service tree being flushed.
+ */
+void io_flush_idle_tree(struct io_service_tree *st)
+{
+ struct io_entity *entity = st->first_idle;
+
+ for (; entity != NULL; entity = st->first_idle)
+ __bfq_deactivate_entity(entity, 0);
+}
+
+#define SHOW_FUNCTION(__VAR) \
+static u64 io_cgroup_##__VAR##_read(struct cgroup *cgroup, \
+ struct cftype *cftype) \
+{ \
+ struct io_cgroup *iocg; \
+ u64 ret; \
+ \
+ if (!cgroup_lock_live_group(cgroup)) \
+ return -ENODEV; \
+ \
+ iocg = cgroup_to_io_cgroup(cgroup); \
+ spin_lock_irq(&iocg->lock); \
+ ret = iocg->__VAR; \
+ spin_unlock_irq(&iocg->lock); \
+ \
+ cgroup_unlock(); \
+ \
+ return ret; \
+}
+
+SHOW_FUNCTION(ioprio);
+SHOW_FUNCTION(ioprio_class);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__VAR, __MIN, __MAX) \
+static int io_cgroup_##__VAR##_write(struct cgroup *cgroup, \
+ struct cftype *cftype, \
+ u64 val) \
+{ \
+ struct io_cgroup *iocg; \
+ struct io_group *iog; \
+ struct hlist_node *n; \
+ \
+ if (val < (__MIN) || val > (__MAX)) \
+ return -EINVAL; \
+ \
+ if (!cgroup_lock_live_group(cgroup)) \
+ return -ENODEV; \
+ \
+ iocg = cgroup_to_io_cgroup(cgroup); \
+ \
+ spin_lock_irq(&iocg->lock); \
+ iocg->__VAR = (unsigned char)val; \
+ hlist_for_each_entry(iog, n, &iocg->group_data, group_node) { \
+ iog->entity.new_##__VAR = (unsigned char)val; \
+ smp_wmb(); \
+ iog->entity.ioprio_changed = 1; \
+ } \
+ spin_unlock_irq(&iocg->lock); \
+ \
+ cgroup_unlock(); \
+ \
+ return 0; \
+}
+
+STORE_FUNCTION(ioprio, 0, IOPRIO_BE_NR - 1);
+STORE_FUNCTION(ioprio_class, IOPRIO_CLASS_RT, IOPRIO_CLASS_IDLE);
+#undef STORE_FUNCTION
+
+/**
+ * bfq_group_chain_alloc - allocate a chain of groups.
+ * @bfqd: queue descriptor.
+ * @cgroup: the leaf cgroup this chain starts from.
+ *
+ * Allocate a chain of groups starting from the one belonging to
+ * @cgroup up to the root cgroup. Stop if a cgroup on the chain
+ * to the root has already an allocated group on @bfqd.
+ */
+struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
+ struct cgroup *cgroup)
+{
+ struct io_cgroup *iocg;
+ struct io_group *iog, *leaf = NULL, *prev = NULL;
+ gfp_t flags = GFP_ATOMIC | __GFP_ZERO;
+
+ for (; cgroup != NULL; cgroup = cgroup->parent) {
+ iocg = cgroup_to_io_cgroup(cgroup);
+
+ iog = io_cgroup_lookup_group(iocg, key);
+ if (iog != NULL) {
+ /*
+ * All the cgroups in the path from there to the
+ * root must have a bfq_group for bfqd, so we don't
+ * need any more allocations.
+ */
+ break;
+ }
+
+ iog = kzalloc_node(sizeof(*iog), flags, q->node);
+ if (!iog)
+ goto cleanup;
+
+ io_group_init_entity(iocg, iog);
+ iog->my_entity = &iog->entity;
+
+ if (leaf == NULL) {
+ leaf = iog;
+ prev = leaf;
+ } else {
+ io_group_set_parent(prev, iog);
+ /*
+ * Build a list of allocated nodes using the bfqd
+ * filed, that is still unused and will be initialized
+ * only after the node will be connected.
+ */
+ prev->key = iog;
+ prev = iog;
+ }
+ }
+
+ return leaf;
+
+cleanup:
+ while (leaf != NULL) {
+ prev = leaf;
+ leaf = leaf->key;
+ kfree(iog);
+ }
+
+ return NULL;
}

+/**
+ * bfq_group_chain_link - link an allocatd group chain to a cgroup hierarchy.
+ * @bfqd: the queue descriptor.
+ * @cgroup: the leaf cgroup to start from.
+ * @leaf: the leaf group (to be associated to @cgroup).
+ *
+ * Try to link a chain of groups to a cgroup hierarchy, connecting the
+ * nodes bottom-up, so we can be sure that when we find a cgroup in the
+ * hierarchy that already as a group associated to @bfqd all the nodes
+ * in the path to the root cgroup have one too.
+ *
+ * On locking: the queue lock protects the hierarchy (there is a hierarchy
+ * per device) while the bfqio_cgroup lock protects the list of groups
+ * belonging to the same cgroup.
+ */
+void io_group_chain_link(struct request_queue *q, void *key,
+ struct cgroup *cgroup,
+ struct io_group *leaf,
+ struct elv_fq_data *efqd)
+{
+ struct io_cgroup *iocg;
+ struct io_group *iog, *next, *prev = NULL;
+ unsigned long flags;
+
+ assert_spin_locked(q->queue_lock);
+
+ for (; cgroup != NULL && leaf != NULL; cgroup = cgroup->parent) {
+ iocg = cgroup_to_io_cgroup(cgroup);
+ next = leaf->key;
+
+ iog = io_cgroup_lookup_group(iocg, key);
+ BUG_ON(iog != NULL);
+
+ spin_lock_irqsave(&iocg->lock, flags);
+
+ rcu_assign_pointer(leaf->key, key);
+ hlist_add_head_rcu(&leaf->group_node, &iocg->group_data);
+ hlist_add_head(&leaf->elv_data_node, &efqd->group_list);
+
+ spin_unlock_irqrestore(&iocg->lock, flags);
+
+ prev = leaf;
+ leaf = next;
+ }
+
+ BUG_ON(cgroup == NULL && leaf != NULL);
+
+ if (cgroup != NULL && prev != NULL) {
+ iocg = cgroup_to_io_cgroup(cgroup);
+ iog = io_cgroup_lookup_group(iocg, key);
+ io_group_set_parent(prev, iog);
+ }
+}
+
+/**
+ * bfq_find_alloc_group - return the group associated to @bfqd in @cgroup.
+ * @bfqd: queue descriptor.
+ * @cgroup: cgroup being searched for.
+ *
+ * Return a group associated to @bfqd in @cgroup, allocating one if
+ * necessary. When a group is returned all the cgroups in the path
+ * to the root have a group associated to @bfqd.
+ *
+ * If the allocation fails, return the root group: this breaks guarantees
+ * but is a safe fallbak. If this loss becames a problem it can be
+ * mitigated using the equivalent weight (given by the product of the
+ * weights of the groups in the path from @group to the root) in the
+ * root scheduler.
+ *
+ * We allocate all the missing nodes in the path from the leaf cgroup
+ * to the root and we connect the nodes only after all the allocations
+ * have been successful.
+ */
+struct io_group *io_find_alloc_group(struct request_queue *q,
+ struct cgroup *cgroup, struct elv_fq_data *efqd)
+{
+ struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
+ struct io_group *iog;
+ /* Note: Use efqd as key */
+ void *key = efqd;
+
+ iog = io_cgroup_lookup_group(iocg, key);
+ if (iog != NULL)
+ return iog;
+
+ iog = io_group_chain_alloc(q, key, cgroup);
+ if (iog != NULL)
+ io_group_chain_link(q, key, cgroup, iog, efqd);
+
+ return iog;
+}
+
+/*
+ * Generic function to make sure cgroup hierarchy is all setup once a request
+ * from a cgroup is received by the io scheduler.
+ */
+struct io_group *io_get_io_group(struct request_queue *q)
+{
+ struct cgroup *cgroup;
+ struct io_group *iog;
+ struct elv_fq_data *efqd = &q->elevator->efqd;
+
+ rcu_read_lock();
+ cgroup = task_cgroup(current, io_subsys_id);
+ iog = io_find_alloc_group(q, cgroup, efqd);
+ if (iog == NULL)
+ iog = efqd->root_group;
+ rcu_read_unlock();
+
+ return iog;
+}
+
+void io_free_root_group(struct elevator_queue *e)
+{
+ struct io_cgroup *iocg = &io_root_cgroup;
+ struct elv_fq_data *efqd = &e->efqd;
+ struct io_group *iog = efqd->root_group;
+
+ BUG_ON(!iog);
+ spin_lock_irq(&iocg->lock);
+ hlist_del_rcu(&iog->group_node);
+ spin_unlock_irq(&iocg->lock);
+ io_put_io_group_queues(e, iog);
+ kfree(iog);
+}
+
+struct io_group *io_alloc_root_group(struct request_queue *q,
+ struct elevator_queue *e, void *key)
+{
+ struct io_group *iog;
+ struct io_cgroup *iocg;
+ int i;
+
+ iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
+ if (iog == NULL)
+ return NULL;
+
+ iog->entity.parent = NULL;
+ for (i = 0; i < IO_IOPRIO_CLASSES; i++)
+ iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
+
+ iocg = &io_root_cgroup;
+ spin_lock_irq(&iocg->lock);
+ rcu_assign_pointer(iog->key, key);
+ hlist_add_head_rcu(&iog->group_node, &iocg->group_data);
+ spin_unlock_irq(&iocg->lock);
+
+ return iog;
+}
+
+struct cftype bfqio_files[] = {
+ {
+ .name = "ioprio",
+ .read_u64 = io_cgroup_ioprio_read,
+ .write_u64 = io_cgroup_ioprio_write,
+ },
+ {
+ .name = "ioprio_class",
+ .read_u64 = io_cgroup_ioprio_class_read,
+ .write_u64 = io_cgroup_ioprio_class_write,
+ },
+};
+
+int iocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
+{
+ return cgroup_add_files(cgroup, subsys, bfqio_files,
+ ARRAY_SIZE(bfqio_files));
+}
+
+struct cgroup_subsys_state *iocg_create(struct cgroup_subsys *subsys,
+ struct cgroup *cgroup)
+{
+ struct io_cgroup *iocg;
+
+ if (cgroup->parent != NULL) {
+ iocg = kzalloc(sizeof(*iocg), GFP_KERNEL);
+ if (iocg == NULL)
+ return ERR_PTR(-ENOMEM);
+ } else
+ iocg = &io_root_cgroup;
+
+ spin_lock_init(&iocg->lock);
+ INIT_HLIST_HEAD(&iocg->group_data);
+ iocg->ioprio = IO_DEFAULT_GRP_IOPRIO;
+ iocg->ioprio_class = IO_DEFAULT_GRP_CLASS;
+
+ return &iocg->css;
+}
+
+/*
+ * We cannot support shared io contexts, as we have no mean to support
+ * two tasks with the same ioc in two different groups without major rework
+ * of the main cic/bfqq data structures. By now we allow a task to change
+ * its cgroup only if it's the only owner of its ioc; the drawback of this
+ * behavior is that a group containing a task that forked using CLONE_IO
+ * will not be destroyed until the tasks sharing the ioc die.
+ */
+int iocg_can_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
+ struct task_struct *tsk)
+{
+ struct io_context *ioc;
+ int ret = 0;
+
+ /* task_lock() is needed to avoid races with exit_io_context() */
+ task_lock(tsk);
+ ioc = tsk->io_context;
+ if (ioc != NULL && atomic_read(&ioc->nr_tasks) > 1)
+ /*
+ * ioc == NULL means that the task is either too young or
+ * exiting: if it has still no ioc the ioc can't be shared,
+ * if the task is exiting the attach will fail anyway, no
+ * matter what we return here.
+ */
+ ret = -EINVAL;
+ task_unlock(tsk);
+
+ return ret;
+}
+
+void iocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
+ struct cgroup *prev, struct task_struct *tsk)
+{
+ struct io_context *ioc;
+
+ task_lock(tsk);
+ ioc = tsk->io_context;
+ if (ioc != NULL)
+ ioc->cgroup_changed = 1;
+ task_unlock(tsk);
+}
+
+/*
+ * Move the queue to the root group if it is active. This is needed when
+ * a cgroup is being deleted and all the IO is not done yet. This is not
+ * very good scheme as a user might get unfair share. This needs to be
+ * fixed.
+ */
+void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
+ struct io_group *iog)
+{
+ int busy, resume;
+ struct io_entity *entity = &ioq->entity;
+ struct elv_fq_data *efqd = &e->efqd;
+ struct io_service_tree *st = io_entity_service_tree(entity);
+
+ busy = elv_ioq_busy(ioq);
+ resume = !!ioq->nr_queued;
+
+ BUG_ON(resume && !entity->on_st);
+ BUG_ON(busy && !resume && entity->on_st && ioq != efqd->active_queue);
+
+ /*
+ * We could be moving an queue which is on idle tree of previous group
+ * What to do? I guess anyway this queue does not have any requests.
+ * just forget the entity and free up from idle tree.
+ *
+ * This needs cleanup. Hackish.
+ */
+ if (entity->tree == &st->idle) {
+ BUG_ON(atomic_read(&ioq->ref) < 2);
+ bfq_put_idle_entity(st, entity);
+ }
+
+ if (busy) {
+ BUG_ON(atomic_read(&ioq->ref) < 2);
+
+ if (!resume)
+ elv_del_ioq_busy(e, ioq, 0);
+ else
+ elv_deactivate_ioq(efqd, ioq, 0);
+ }
+
+ /*
+ * Here we use a reference to bfqg. We don't need a refcounter
+ * as the cgroup reference will not be dropped, so that its
+ * destroy() callback will not be invoked.
+ */
+ entity->parent = iog->my_entity;
+ entity->sched_data = &iog->sched_data;
+
+ if (busy && resume)
+ elv_activate_ioq(ioq);
+}
+EXPORT_SYMBOL(io_ioq_move);
+
+static void __io_destroy_group(struct elv_fq_data *efqd, struct io_group *iog)
+{
+ struct elevator_queue *eq;
+ struct io_entity *entity = iog->my_entity;
+ struct io_service_tree *st;
+ int i;
+
+ eq = container_of(efqd, struct elevator_queue, efqd);
+ hlist_del(&iog->elv_data_node);
+ __bfq_deactivate_entity(entity, 0);
+ io_put_io_group_queues(eq, iog);
+
+ for (i = 0; i < IO_IOPRIO_CLASSES; i++) {
+ st = iog->sched_data.service_tree + i;
+
+ /*
+ * The idle tree may still contain bfq_queues belonging
+ * to exited task because they never migrated to a different
+ * cgroup from the one being destroyed now. Noone else
+ * can access them so it's safe to act without any lock.
+ */
+ io_flush_idle_tree(st);
+
+ BUG_ON(!RB_EMPTY_ROOT(&st->active));
+ BUG_ON(!RB_EMPTY_ROOT(&st->idle));
+ }
+
+ BUG_ON(iog->sched_data.next_active != NULL);
+ BUG_ON(iog->sched_data.active_entity != NULL);
+ BUG_ON(entity->tree != NULL);
+}
+
+/**
+ * bfq_destroy_group - destroy @bfqg.
+ * @bgrp: the bfqio_cgroup containing @bfqg.
+ * @bfqg: the group being destroyed.
+ *
+ * Destroy @bfqg, making sure that it is not referenced from its parent.
+ */
+static void io_destroy_group(struct io_cgroup *iocg, struct io_group *iog)
+{
+ struct elv_fq_data *efqd = NULL;
+ unsigned long uninitialized_var(flags);
+
+ /* Remove io group from cgroup list */
+ hlist_del(&iog->group_node);
+
+ /*
+ * io groups are linked in two lists. One list is maintained
+ * in elevator (efqd->group_list) and other is maintained
+ * per cgroup structure (iocg->group_data).
+ *
+ * While a cgroup is being deleted, elevator also might be
+ * exiting and both might try to cleanup the same io group
+ * so need to be little careful.
+ *
+ * Following code first accesses efqd under RCU to make sure
+ * iog->key is pointing to valid efqd and then takes the
+ * associated queue lock. After gettting the queue lock it
+ * again checks whether elevator exit path had alreday got
+ * hold of io group (iog->key == NULL). If yes, it does not
+ * try to free up async queues again or flush the idle tree.
+ */
+
+ rcu_read_lock();
+ efqd = rcu_dereference(iog->key);
+ if (efqd != NULL) {
+ spin_lock_irqsave(efqd->queue->queue_lock, flags);
+ if (iog->key == efqd)
+ __io_destroy_group(efqd, iog);
+ spin_unlock_irqrestore(efqd->queue->queue_lock, flags);
+ }
+ rcu_read_unlock();
+
+ /*
+ * No need to defer the kfree() to the end of the RCU grace
+ * period: we are called from the destroy() callback of our
+ * cgroup, so we can be sure that noone is a) still using
+ * this cgroup or b) doing lookups in it.
+ */
+ kfree(iog);
+}
+
+void iocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
+{
+ struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
+ struct hlist_node *n, *tmp;
+ struct io_group *iog;
+
+ /*
+ * Since we are destroying the cgroup, there are no more tasks
+ * referencing it, and all the RCU grace periods that may have
+ * referenced it are ended (as the destruction of the parent
+ * cgroup is RCU-safe); bgrp->group_data will not be accessed by
+ * anything else and we don't need any synchronization.
+ */
+ hlist_for_each_entry_safe(iog, n, tmp, &iocg->group_data, group_node)
+ io_destroy_group(iocg, iog);
+
+ BUG_ON(!hlist_empty(&iocg->group_data));
+
+ kfree(iocg);
+}
+
+void io_disconnect_groups(struct elevator_queue *e)
+{
+ struct hlist_node *pos, *n;
+ struct io_group *iog;
+ struct elv_fq_data *efqd = &e->efqd;
+
+ hlist_for_each_entry_safe(iog, pos, n, &efqd->group_list,
+ elv_data_node) {
+ hlist_del(&iog->elv_data_node);
+
+ __bfq_deactivate_entity(iog->my_entity, 0);
+
+ /*
+ * Don't remove from the group hash, just set an
+ * invalid key. No lookups can race with the
+ * assignment as bfqd is being destroyed; this
+ * implies also that new elements cannot be added
+ * to the list.
+ */
+ rcu_assign_pointer(iog->key, NULL);
+ io_put_io_group_queues(e, iog);
+ }
+}
+
+struct cgroup_subsys io_subsys = {
+ .name = "io",
+ .create = iocg_create,
+ .can_attach = iocg_can_attach,
+ .attach = iocg_attach,
+ .destroy = iocg_destroy,
+ .populate = iocg_populate,
+ .subsys_id = io_subsys_id,
+};
+
+/* if bio sumbmitting task and rq don't belong to same io_group, it can't
+ * be merged */
+int io_group_allow_merge(struct request *rq, struct bio *bio)
+{
+ struct request_queue *q = rq->q;
+ struct io_queue *ioq = rq->ioq;
+ struct io_group *iog, *__iog;
+
+ if (!elv_iosched_fair_queuing_enabled(q->elevator))
+ return 1;
+
+ /* Determine the io group of the bio submitting task */
+ iog = io_lookup_io_group_current(q);
+ if (!iog) {
+ /* May be task belongs to a differet cgroup for which io
+ * group has not been setup yet. */
+ return 0;
+ }
+
+ /* Determine the io group of the ioq, rq belongs to*/
+ __iog = ioq_to_io_group(ioq);
+
+ return (iog == __iog);
+}
+
+/* find/create the io group request belongs to and put that info in rq */
+void elv_fq_set_request_io_group(struct request_queue *q,
+ struct request *rq)
+{
+ struct io_group *iog;
+ unsigned long flags;
+
+ /* Make sure io group hierarchy has been setup and also set the
+ * io group to which rq belongs. Later we should make use of
+ * bio cgroup patches to determine the io group */
+ spin_lock_irqsave(q->queue_lock, flags);
+ iog = io_get_io_group(q);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+ BUG_ON(!iog);
+
+ /* Store iog in rq. TODO: take care of referencing */
+ rq->iog = iog;
+}
+
+#else /* GROUP_IOSCHED */
+void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
+{
+ entity->ioprio = entity->new_ioprio;
+ entity->ioprio_class = entity->new_ioprio_class;
+ entity->sched_data = &iog->sched_data;
+}
+
+struct io_group *io_alloc_root_group(struct request_queue *q,
+ struct elevator_queue *e, void *key)
+{
+ struct io_group *iog;
+ int i;
+
+ iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
+ if (iog == NULL)
+ return NULL;
+
+ for (i = 0; i < IO_IOPRIO_CLASSES; i++)
+ iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
+
+ return iog;
+}
+
+struct io_group *io_lookup_io_group_current(struct request_queue *q)
+{
+ struct elv_fq_data *efqd = &q->elevator->efqd;
+
+ return efqd->root_group;
+}
+EXPORT_SYMBOL(io_lookup_io_group_current);
+
+void io_free_root_group(struct elevator_queue *e)
+{
+ struct io_group *iog = e->efqd.root_group;
+ io_put_io_group_queues(e, iog);
+ kfree(iog);
+}
+
+struct io_group *io_get_io_group(struct request_queue *q)
+{
+ return q->elevator->efqd.root_group;
+}
+
+#endif /* CONFIG_GROUP_IOSCHED*/
+
/* Elevator fair queuing function */
struct io_queue *rq_ioq(struct request *rq)
{
@@ -995,9 +1862,11 @@ EXPORT_SYMBOL(elv_put_ioq);

void elv_release_ioq(struct elevator_queue *e, struct io_queue **ioq_ptr)
{
+ struct io_group *root_group = e->efqd.root_group;
struct io_queue *ioq = *ioq_ptr;

if (ioq != NULL) {
+ io_ioq_move(e, ioq, root_group);
/* Drop the reference taken by the io group */
elv_put_ioq(ioq);
*ioq_ptr = NULL;
@@ -1022,14 +1891,27 @@ struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
return NULL;

sd = &efqd->root_group->sched_data;
- if (extract)
- entity = bfq_lookup_next_entity(sd, 1);
- else
- entity = bfq_lookup_next_entity(sd, 0);
+ for (; sd != NULL; sd = entity->my_sched_data) {
+ if (extract)
+ entity = bfq_lookup_next_entity(sd, 1);
+ else
+ entity = bfq_lookup_next_entity(sd, 0);
+
+ /*
+ * entity can be null despite the fact that there are busy
+ * queues. if all the busy queues are under a group which is
+ * currently under service.
+ * So if we are just looking for next ioq while something is
+ * being served, null entity is not an error.
+ */
+ BUG_ON(!entity && extract);

- BUG_ON(!entity);
- if (extract)
- entity->service = 0;
+ if (extract)
+ entity->service = 0;
+
+ if (!entity)
+ return NULL;
+ }
ioq = io_entity_to_ioq(entity);

return ioq;
@@ -1262,6 +2144,7 @@ int elv_should_preempt(struct request_queue *q, struct io_queue *new_ioq,
{
struct io_queue *ioq;
struct elevator_queue *eq = q->elevator;
+ struct io_group *iog = NULL, *new_iog = NULL;

ioq = elv_active_ioq(eq);

@@ -1283,10 +2166,17 @@ int elv_should_preempt(struct request_queue *q, struct io_queue *new_ioq,
if (elv_ioq_class_rt(new_ioq) && !elv_ioq_class_rt(ioq))
return 1;

+ iog = ioq_to_io_group(ioq);
+ new_iog = ioq_to_io_group(new_ioq);
+
/*
- * Check with io scheduler if it has additional criterion based on
- * which it wants to preempt existing queue.
+ * If both the queues belong to same group, check with io scheduler
+ * if it has additional criterion based on which it wants to
+ * preempt existing queue.
*/
+ if (iog != new_iog)
+ return 0;
+
if (eq->ops->elevator_should_preempt_fn)
return eq->ops->elevator_should_preempt_fn(q, new_ioq, rq);

@@ -1663,14 +2553,6 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
elv_schedule_dispatch(q);
}

-struct io_group *io_lookup_io_group_current(struct request_queue *q)
-{
- struct elv_fq_data *efqd = &q->elevator->efqd;
-
- return efqd->root_group;
-}
-EXPORT_SYMBOL(io_lookup_io_group_current);
-
void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
int ioprio)
{
@@ -1721,44 +2603,6 @@ void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
}
EXPORT_SYMBOL(io_group_set_async_queue);

-/*
- * Release all the io group references to its async queues.
- */
-void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
-{
- int i, j;
-
- for (i = 0; i < 2; i++)
- for (j = 0; j < IOPRIO_BE_NR; j++)
- elv_release_ioq(e, &iog->async_queue[i][j]);
-
- /* Free up async idle queue */
- elv_release_ioq(e, &iog->async_idle_queue);
-}
-
-struct io_group *io_alloc_root_group(struct request_queue *q,
- struct elevator_queue *e, void *key)
-{
- struct io_group *iog;
- int i;
-
- iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
- if (iog == NULL)
- return NULL;
-
- for (i = 0; i < IO_IOPRIO_CLASSES; i++)
- iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
-
- return iog;
-}
-
-void io_free_root_group(struct elevator_queue *e)
-{
- struct io_group *iog = e->efqd.root_group;
- io_put_io_group_queues(e, iog);
- kfree(iog);
-}
-
static void elv_slab_kill(void)
{
/*
@@ -1804,6 +2648,7 @@ int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e)
INIT_WORK(&efqd->unplug_work, elv_kick_queue);

INIT_LIST_HEAD(&efqd->idle_list);
+ INIT_HLIST_HEAD(&efqd->group_list);

efqd->elv_slice[0] = elv_slice_async;
efqd->elv_slice[1] = elv_slice_sync;
@@ -1833,10 +2678,14 @@ void elv_exit_fq_data(struct elevator_queue *e)
spin_lock_irq(q->queue_lock);
/* This should drop all the idle tree references of ioq */
elv_free_idle_ioq_list(e);
+ /* This should drop all the io group references of async queues */
+ io_disconnect_groups(e);
spin_unlock_irq(q->queue_lock);

elv_shutdown_timer_wq(e);

+ /* Wait for iog->key accessors to exit their grace periods. */
+ synchronize_rcu();
BUG_ON(timer_pending(&efqd->idle_slice_timer));
io_free_root_group(e);
}
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index b5a0d08..3fab8f8 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -9,6 +9,7 @@
*/

#include <linux/blkdev.h>
+#include <linux/cgroup.h>

#ifndef _BFQ_SCHED_H
#define _BFQ_SCHED_H
@@ -69,6 +70,7 @@ struct io_service_tree {
*/
struct io_sched_data {
struct io_entity *active_entity;
+ struct io_entity *next_active;
struct io_service_tree service_tree[IO_IOPRIO_CLASSES];
};

@@ -183,17 +185,90 @@ struct io_queue {
unsigned long total_service;
};

+#ifdef CONFIG_GROUP_IOSCHED
+/**
+ * struct bfq_group - per (device, cgroup) data structure.
+ * @entity: schedulable entity to insert into the parent group sched_data.
+ * @sched_data: own sched_data, to contain child entities (they may be
+ * both bfq_queues and bfq_groups).
+ * @group_node: node to be inserted into the bfqio_cgroup->group_data
+ * list of the containing cgroup's bfqio_cgroup.
+ * @bfqd_node: node to be inserted into the @bfqd->group_list list
+ * of the groups active on the same device; used for cleanup.
+ * @bfqd: the bfq_data for the device this group acts upon.
+ * @async_bfqq: array of async queues for all the tasks belonging to
+ * the group, one queue per ioprio value per ioprio_class,
+ * except for the idle class that has only one queue.
+ * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
+ * @my_entity: pointer to @entity, %NULL for the toplevel group; used
+ * to avoid too many special cases during group creation/migration.
+ *
+ * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
+ * there is a set of bfq_groups, each one collecting the lower-level
+ * entities belonging to the group that are acting on the same device.
+ *
+ * Locking works as follows:
+ * o @group_node is protected by the bfqio_cgroup lock, and is accessed
+ * via RCU from its readers.
+ * o @bfqd is protected by the queue lock, RCU is used to access it
+ * from the readers.
+ * o All the other fields are protected by the @bfqd queue lock.
+ */
struct io_group {
+ struct io_entity entity;
+ struct hlist_node elv_data_node;
+ struct hlist_node group_node;
struct io_sched_data sched_data;

+ struct io_entity *my_entity;
+
+ /*
+ * A cgroup has multiple io_groups, one for each request queue.
+ * to find io group belonging to a particular queue, elv_fq_data
+ * pointer is stored as a key.
+ */
+ void *key;
+
/* async_queue and idle_queue are used only for cfq */
struct io_queue *async_queue[2][IOPRIO_BE_NR];
struct io_queue *async_idle_queue;
};

+/**
+ * struct bfqio_cgroup - bfq cgroup data structure.
+ * @css: subsystem state for bfq in the containing cgroup.
+ * @ioprio: cgroup ioprio.
+ * @ioprio_class: cgroup ioprio_class.
+ * @lock: spinlock that protects @ioprio, @ioprio_class and @group_data.
+ * @group_data: list containing the bfq_group belonging to this cgroup.
+ *
+ * @group_data is accessed using RCU, with @lock protecting the updates,
+ * @ioprio and @ioprio_class are protected by @lock.
+ */
+struct io_cgroup {
+ struct cgroup_subsys_state css;
+
+ unsigned short ioprio, ioprio_class;
+
+ spinlock_t lock;
+ struct hlist_head group_data;
+};
+#else
+struct io_group {
+ struct io_sched_data sched_data;
+
+ /* async_queue and idle_queue are used only for cfq */
+ struct io_queue *async_queue[2][IOPRIO_BE_NR];
+ struct io_queue *async_idle_queue;
+};
+#endif
+
struct elv_fq_data {
struct io_group *root_group;

+ /* List of io groups hanging on this elevator */
+ struct hlist_head group_list;
+
/* List of io queues on idle tree. */
struct list_head idle_list;

@@ -380,6 +455,39 @@ static inline struct io_group *ioq_to_io_group(struct io_queue *ioq)
sched_data);
}

+#ifdef CONFIG_GROUP_IOSCHED
+extern int io_group_allow_merge(struct request *rq, struct bio *bio);
+extern void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
+ struct io_group *iog);
+extern void elv_fq_set_request_io_group(struct request_queue *q,
+ struct request *rq);
+#else /* !GROUP_IOSCHED */
+/*
+ * No ioq movement is needed in case of flat setup. root io group gets cleaned
+ * up upon elevator exit and before that it has been made sure that both
+ * active and idle tree are empty.
+ */
+static inline void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
+ struct io_group *iog)
+{
+}
+
+static inline int io_group_allow_merge(struct request *rq, struct bio *bio)
+{
+ return 1;
+}
+/*
+ * Currently root group is not part of elevator group list and freed
+ * separately. Hence in case of non-hierarchical setup, nothing todo.
+ */
+static inline void io_disconnect_groups(struct elevator_queue *e) {}
+static inline void elv_fq_set_request_io_group(struct request_queue *q,
+ struct request *rq)
+{
+}
+
+#endif /* GROUP_IOSCHED */
+
/* Functions used by blksysfs.c */
extern ssize_t elv_slice_idle_show(struct request_queue *q, char *name);
extern ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
@@ -475,5 +583,10 @@ static inline void *elv_fq_select_ioq(struct request_queue *q, int force)
{
return NULL;
}
+
+static inline void elv_fq_set_request_io_group(struct request_queue *q,
+ struct request *rq)
+{
+}
#endif /* CONFIG_ELV_FAIR_QUEUING */
#endif /* _BFQ_SCHED_H */
diff --git a/block/elevator.c b/block/elevator.c
index 7a3a7e9..27889bc 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -888,6 +888,8 @@ int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
{
struct elevator_queue *e = q->elevator;

+ elv_fq_set_request_io_group(q, rq);
+
if (e->ops->elevator_set_req_fn)
return e->ops->elevator_set_req_fn(q, rq, gfp_mask);

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index cf02216..0baeb8e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -238,7 +238,12 @@ struct request {
#ifdef CONFIG_ELV_FAIR_QUEUING
/* io queue request belongs to */
struct io_queue *ioq;
-#endif
+
+#ifdef CONFIG_GROUP_IOSCHED
+ /* io group request belongs to */
+ struct io_group *iog;
+#endif /* GROUP_IOSCHED */
+#endif /* ELV_FAIR_QUEUING */
};

static inline unsigned short req_get_ioprio(struct request *req)
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 9c8d31b..68ea6bd 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -60,3 +60,10 @@ SUBSYS(net_cls)
#endif

/* */
+
+#ifdef CONFIG_GROUP_IOSCHED
+SUBSYS(io)
+#endif
+
+/* */
+
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 08b987b..51664bb 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -73,6 +73,11 @@ struct io_context {
unsigned short ioprio;
unsigned short ioprio_changed;

+#ifdef CONFIG_GROUP_IOSCHED
+ /* If task changes the cgroup, elevator processes it asynchronously */
+ unsigned short cgroup_changed;
+#endif
+
/*
* For request batching
*/
diff --git a/init/Kconfig b/init/Kconfig
index 6a5c5fe..66c2310 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -538,6 +538,14 @@ config CGROUP_MEM_RES_CTLR_SWAP
there will be no overhead from this. Even when you set this config=y,
if boot option "noswapaccount" is set, swap will not be accounted.

+config GROUP_IOSCHED
+ bool "Group IO Scheduler"
+ depends on CGROUPS && ELV_FAIR_QUEUING
+ default n
+ ---help---
+ This feature lets IO scheduler recognize task groups and control
+ disk bandwidth allocation to such task groups.
+
endif # CGROUPS

config MM_OWNER
--
1.6.0.1


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