Merge branch 'for-3.5/core' of git://git.kernel.dk/linux-block

Merge block/IO core bits from Jens Axboe:
 "This is a bit bigger on the core side than usual, but that is purely
  because we decided to hold off on parts of Tejun's submission on 3.4
  to give it a bit more time to simmer.  As a consequence, it's seen a
  long cycle in for-next.

  It contains:

   - Bug fix from Dan, wrong locking type.
   - Relax splice gifting restriction from Eric.
   - A ton of updates from Tejun, primarily for blkcg.  This improves
     the code a lot, making the API nicer and cleaner, and also includes
     fixes for how we handle and tie policies and re-activate on
     switches.  The changes also include generic bug fixes.
   - A simple fix from Vivek, along with a fix for doing proper delayed
     allocation of the blkcg stats."

Fix up annoying conflict just due to different merge resolution in
Documentation/feature-removal-schedule.txt

* 'for-3.5/core' of git://git.kernel.dk/linux-block: (92 commits)
  blkcg: tg_stats_alloc_lock is an irq lock
  vmsplice: relax alignement requirements for SPLICE_F_GIFT
  blkcg: use radix tree to index blkgs from blkcg
  blkcg: fix blkcg->css ref leak in __blkg_lookup_create()
  block: fix elvpriv allocation failure handling
  block: collapse blk_alloc_request() into get_request()
  blkcg: collapse blkcg_policy_ops into blkcg_policy
  blkcg: embed struct blkg_policy_data in policy specific data
  blkcg: mass rename of blkcg API
  blkcg: style cleanups for blk-cgroup.h
  blkcg: remove blkio_group->path[]
  blkcg: blkg_rwstat_read() was missing inline
  blkcg: shoot down blkgs if all policies are deactivated
  blkcg: drop stuff unused after per-queue policy activation update
  blkcg: implement per-queue policy activation
  blkcg: add request_queue->root_blkg
  blkcg: make request_queue bypassing on allocation
  blkcg: make sure blkg_lookup() returns %NULL if @q is bypassing
  blkcg: make blkg_conf_prep() take @pol and return with queue lock held
  blkcg: remove static policy ID enums
  ...

1 files changed, 325 insertions, 372 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f2ddb94626bd..5b0659512047 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -21,6 +21,8 @@ static int throtl_quantum = 32;
 /* Throttling is performed over 100ms slice and after that slice is renewed */
 static unsigned long throtl_slice = HZ/10;      /* 100 ms */
 
+static struct blkcg_policy blkcg_policy_throtl;
+
 /* A workqueue to queue throttle related work */
 static struct workqueue_struct *kthrotld_workqueue;
 static void throtl_schedule_delayed_work(struct throtl_data *td,
@@ -38,9 +40,17 @@ struct throtl_rb_root {
 
 #define rb_entry_tg(node)       rb_entry((node), struct throtl_grp, rb_node)
 
+/* Per-cpu group stats */
+struct tg_stats_cpu {
+        /* total bytes transferred */
+        struct blkg_rwstat              service_bytes;
+        /* total IOs serviced, post merge */
+        struct blkg_rwstat              serviced;
+};
+
 struct throtl_grp {
-        /* List of throtl groups on the request queue*/
-        struct hlist_node tg_node;
+        /* must be the first member */
+        struct blkg_policy_data pd;
 
         /* active throtl group service_tree member */
         struct rb_node rb_node;
@@ -52,8 +62,6 @@ struct throtl_grp {
          */
         unsigned long disptime;
 
-        struct blkio_group blkg;
-        atomic_t ref;
         unsigned int flags;
 
         /* Two lists for READ and WRITE */
@@ -80,18 +88,18 @@ struct throtl_grp {
         /* Some throttle limits got updated for the group */
         int limits_changed;
 
-        struct rcu_head rcu_head;
+        /* Per cpu stats pointer */
+        struct tg_stats_cpu __percpu *stats_cpu;
+
+        /* List of tgs waiting for per cpu stats memory to be allocated */
+        struct list_head stats_alloc_node;
 };
 
 struct throtl_data
 {
-        /* List of throtl groups */
-        struct hlist_head tg_list;
-
         /* service tree for active throtl groups */
         struct throtl_rb_root tg_service_tree;
 
-        struct throtl_grp *root_tg;
         struct request_queue *queue;
 
         /* Total Number of queued bios on READ and WRITE lists */
@@ -108,6 +116,33 @@ struct throtl_data
         int limits_changed;
 };
 
+/* list and work item to allocate percpu group stats */
+static DEFINE_SPINLOCK(tg_stats_alloc_lock);
+static LIST_HEAD(tg_stats_alloc_list);
+
+static void tg_stats_alloc_fn(struct work_struct *);
+static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
+
+static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
+{
+        return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
+}
+
+static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
+{
+        return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
+}
+
+static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
+{
+        return pd_to_blkg(&tg->pd);
+}
+
+static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
+{
+        return blkg_to_tg(td->queue->root_blkg);
+}
+
 enum tg_state_flags {
         THROTL_TG_FLAG_on_rr = 0,       /* on round-robin busy list */
 };
@@ -128,244 +163,150 @@ static inline int throtl_tg_##name(const struct throtl_grp *tg)		\
 
 THROTL_TG_FNS(on_rr);
 
-#define throtl_log_tg(td, tg, fmt, args...)                             \
-        blk_add_trace_msg((td)->queue, "throtl %s " fmt,                \
-                                blkg_path(&(tg)->blkg), ##args);        \
+#define throtl_log_tg(td, tg, fmt, args...)     do {                    \
+        char __pbuf[128];                                               \
+                                                                        \
+        blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf));              \
+        blk_add_trace_msg((td)->queue, "throtl %s " fmt, __pbuf, ##args); \
+} while (0)
 
 #define throtl_log(td, fmt, args...)    \
         blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
 
-static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg)
-{
-        if (blkg)
-                return container_of(blkg, struct throtl_grp, blkg);
-
-        return NULL;
-}
-
 static inline unsigned int total_nr_queued(struct throtl_data *td)
 {
         return td->nr_queued[0] + td->nr_queued[1];
 }
 
-static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
-{
-        atomic_inc(&tg->ref);
-        return tg;
-}
-
-static void throtl_free_tg(struct rcu_head *head)
+/*
+ * Worker for allocating per cpu stat for tgs. This is scheduled on the
+ * system_nrt_wq once there are some groups on the alloc_list waiting for
+ * allocation.
+ */
+static void tg_stats_alloc_fn(struct work_struct *work)
 {
-        struct throtl_grp *tg;
+        static struct tg_stats_cpu *stats_cpu;  /* this fn is non-reentrant */
+        struct delayed_work *dwork = to_delayed_work(work);
+        bool empty = false;
+
+alloc_stats:
+        if (!stats_cpu) {
+                stats_cpu = alloc_percpu(struct tg_stats_cpu);
+                if (!stats_cpu) {
+                        /* allocation failed, try again after some time */
+                        queue_delayed_work(system_nrt_wq, dwork,
+                                           msecs_to_jiffies(10));
+                        return;
+                }
+        }
 
-        tg = container_of(head, struct throtl_grp, rcu_head);
-        free_percpu(tg->blkg.stats_cpu);
-        kfree(tg);
-}
+        spin_lock_irq(&tg_stats_alloc_lock);
 
-static void throtl_put_tg(struct throtl_grp *tg)
-{
-        BUG_ON(atomic_read(&tg->ref) <= 0);
-        if (!atomic_dec_and_test(&tg->ref))
-                return;
+        if (!list_empty(&tg_stats_alloc_list)) {
+                struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list,
+                                                         struct throtl_grp,
+                                                         stats_alloc_node);
+                swap(tg->stats_cpu, stats_cpu);
+                list_del_init(&tg->stats_alloc_node);
+        }
 
-        /*
-         * A group is freed in rcu manner. But having an rcu lock does not
-         * mean that one can access all the fields of blkg and assume these
-         * are valid. For example, don't try to follow throtl_data and
-         * request queue links.
-         *
-         * Having a reference to blkg under an rcu allows acess to only
-         * values local to groups like group stats and group rate limits
-         */
-        call_rcu(&tg->rcu_head, throtl_free_tg);
+        empty = list_empty(&tg_stats_alloc_list);
+        spin_unlock_irq(&tg_stats_alloc_lock);
+        if (!empty)
+                goto alloc_stats;
 }
 
-static void throtl_init_group(struct throtl_grp *tg)
+static void throtl_pd_init(struct blkcg_gq *blkg)
 {
-        INIT_HLIST_NODE(&tg->tg_node);
+        struct throtl_grp *tg = blkg_to_tg(blkg);
+        unsigned long flags;
+
         RB_CLEAR_NODE(&tg->rb_node);
         bio_list_init(&tg->bio_lists[0]);
         bio_list_init(&tg->bio_lists[1]);
         tg->limits_changed = false;
 
-        /* Practically unlimited BW */
-        tg->bps[0] = tg->bps[1] = -1;
-        tg->iops[0] = tg->iops[1] = -1;
+        tg->bps[READ] = -1;
+        tg->bps[WRITE] = -1;
+        tg->iops[READ] = -1;
+        tg->iops[WRITE] = -1;
 
         /*
-         * Take the initial reference that will be released on destroy
-         * This can be thought of a joint reference by cgroup and
-         * request queue which will be dropped by either request queue
-         * exit or cgroup deletion path depending on who is exiting first.
+         * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
+         * but percpu allocator can't be called from IO path.  Queue tg on
+         * tg_stats_alloc_list and allocate from work item.
          */
-        atomic_set(&tg->ref, 1);
+        spin_lock_irqsave(&tg_stats_alloc_lock, flags);
+        list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
+        queue_delayed_work(system_nrt_wq, &tg_stats_alloc_work, 0);
+        spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
 }
 
-/* Should be called with rcu read lock held (needed for blkcg) */
-static void
-throtl_add_group_to_td_list(struct throtl_data *td, struct throtl_grp *tg)
+static void throtl_pd_exit(struct blkcg_gq *blkg)
 {
-        hlist_add_head(&tg->tg_node, &td->tg_list);
-        td->nr_undestroyed_grps++;
-}
-
-static void
-__throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg)
-{
-        struct backing_dev_info *bdi = &td->queue->backing_dev_info;
-        unsigned int major, minor;
-
-        if (!tg || tg->blkg.dev)
-                return;
-
-        /*
-         * Fill in device details for a group which might not have been
-         * filled at group creation time as queue was being instantiated
-         * and driver had not attached a device yet
-         */
-        if (bdi->dev && dev_name(bdi->dev)) {
-                sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
-                tg->blkg.dev = MKDEV(major, minor);
-        }
-}
-
-/*
- * Should be called with without queue lock held. Here queue lock will be
- * taken rarely. It will be taken only once during life time of a group
- * if need be
- */
-static void
-throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg)
-{
-        if (!tg || tg->blkg.dev)
-                return;
-
-        spin_lock_irq(td->queue->queue_lock);
-        __throtl_tg_fill_dev_details(td, tg);
-        spin_unlock_irq(td->queue->queue_lock);
-}
-
-static void throtl_init_add_tg_lists(struct throtl_data *td,
-                        struct throtl_grp *tg, struct blkio_cgroup *blkcg)
-{
-        __throtl_tg_fill_dev_details(td, tg);
-
-        /* Add group onto cgroup list */
-        blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td,
-                                tg->blkg.dev, BLKIO_POLICY_THROTL);
+        struct throtl_grp *tg = blkg_to_tg(blkg);
+        unsigned long flags;
 
-        tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
-        tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
-        tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev);
-        tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev);
+        spin_lock_irqsave(&tg_stats_alloc_lock, flags);
+        list_del_init(&tg->stats_alloc_node);
+        spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
 
-        throtl_add_group_to_td_list(td, tg);
+        free_percpu(tg->stats_cpu);
 }
 
-/* Should be called without queue lock and outside of rcu period */
-static struct throtl_grp *throtl_alloc_tg(struct throtl_data *td)
+static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
 {
-        struct throtl_grp *tg = NULL;
-        int ret;
+        struct throtl_grp *tg = blkg_to_tg(blkg);
+        int cpu;
 
-        tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node);
-        if (!tg)
-                return NULL;
+        if (tg->stats_cpu == NULL)
+                return;
 
-        ret = blkio_alloc_blkg_stats(&tg->blkg);
+        for_each_possible_cpu(cpu) {
+                struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
 
-        if (ret) {
-                kfree(tg);
-                return NULL;
+                blkg_rwstat_reset(&sc->service_bytes);
+                blkg_rwstat_reset(&sc->serviced);
         }
-
-        throtl_init_group(tg);
-        return tg;
 }
 
-static struct
-throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
+static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td,
+                                           struct blkcg *blkcg)
 {
-        struct throtl_grp *tg = NULL;
-        void *key = td;
-
         /*
-         * This is the common case when there are no blkio cgroups.
-         * Avoid lookup in this case
-         */
-        if (blkcg == &blkio_root_cgroup)
-                tg = td->root_tg;
-        else
-                tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
+         * This is the common case when there are no blkcgs.  Avoid lookup
+         * in this case
+         */
+        if (blkcg == &blkcg_root)
+                return td_root_tg(td);
 
-        __throtl_tg_fill_dev_details(td, tg);
-        return tg;
+        return blkg_to_tg(blkg_lookup(blkcg, td->queue));
 }
 
-static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
+static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
+                                                  struct blkcg *blkcg)
 {
-        struct throtl_grp *tg = NULL, *__tg = NULL;
-        struct blkio_cgroup *blkcg;
         struct request_queue *q = td->queue;
-
-        /* no throttling for dead queue */
-        if (unlikely(blk_queue_dead(q)))
-                return NULL;
-
-        rcu_read_lock();
-        blkcg = task_blkio_cgroup(current);
-        tg = throtl_find_tg(td, blkcg);
-        if (tg) {
-                rcu_read_unlock();
-                return tg;
-        }
-
-        /*
-         * Need to allocate a group. Allocation of group also needs allocation
-         * of per cpu stats which in-turn takes a mutex() and can block. Hence
-         * we need to drop rcu lock and queue_lock before we call alloc.
-         */
-        rcu_read_unlock();
-        spin_unlock_irq(q->queue_lock);
-
-        tg = throtl_alloc_tg(td);
-
-        /* Group allocated and queue is still alive. take the lock */
-        spin_lock_irq(q->queue_lock);
-
-        /* Make sure @q is still alive */
-        if (unlikely(blk_queue_dead(q))) {
-                kfree(tg);
-                return NULL;
-        }
-
-        /*
-         * Initialize the new group. After sleeping, read the blkcg again.
-         */
-        rcu_read_lock();
-        blkcg = task_blkio_cgroup(current);
+        struct throtl_grp *tg = NULL;
 
         /*
-         * If some other thread already allocated the group while we were
-         * not holding queue lock, free up the group
+         * This is the common case when there are no blkcgs.  Avoid lookup
+         * in this case
          */
-        __tg = throtl_find_tg(td, blkcg);
-
-        if (__tg) {
-                kfree(tg);
-                rcu_read_unlock();
-                return __tg;
-        }
-
-        /* Group allocation failed. Account the IO to root group */
-        if (!tg) {
-                tg = td->root_tg;
-                return tg;
+        if (blkcg == &blkcg_root) {
+                tg = td_root_tg(td);
+        } else {
+                struct blkcg_gq *blkg;
+
+                blkg = blkg_lookup_create(blkcg, q);
+
+                /* if %NULL and @q is alive, fall back to root_tg */
+                if (!IS_ERR(blkg))
+                        tg = blkg_to_tg(blkg);
+                else if (!blk_queue_dead(q))
+                        tg = td_root_tg(td);
         }
 
-        throtl_init_add_tg_lists(td, tg, blkcg);
-        rcu_read_unlock();
         return tg;
 }
 
@@ -734,16 +675,41 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
         return 0;
 }
 
+static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
+                                         int rw)
+{
+        struct throtl_grp *tg = blkg_to_tg(blkg);
+        struct tg_stats_cpu *stats_cpu;
+        unsigned long flags;
+
+        /* If per cpu stats are not allocated yet, don't do any accounting. */
+        if (tg->stats_cpu == NULL)
+                return;
+
+        /*
+         * Disabling interrupts to provide mutual exclusion between two
+         * writes on same cpu. It probably is not needed for 64bit. Not
+         * optimizing that case yet.
+         */
+        local_irq_save(flags);
+
+        stats_cpu = this_cpu_ptr(tg->stats_cpu);
+
+        blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
+        blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
+
+        local_irq_restore(flags);
+}
+
 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
 {
         bool rw = bio_data_dir(bio);
-        bool sync = rw_is_sync(bio->bi_rw);
 
         /* Charge the bio to the group */
         tg->bytes_disp[rw] += bio->bi_size;
         tg->io_disp[rw]++;
 
-        blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
+        throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw);
 }
 
 static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
@@ -753,7 +719,7 @@ static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
 
         bio_list_add(&tg->bio_lists[rw], bio);
         /* Take a bio reference on tg */
-        throtl_ref_get_tg(tg);
+        blkg_get(tg_to_blkg(tg));
         tg->nr_queued[rw]++;
         td->nr_queued[rw]++;
         throtl_enqueue_tg(td, tg);
@@ -786,8 +752,8 @@ static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
 
         bio = bio_list_pop(&tg->bio_lists[rw]);
         tg->nr_queued[rw]--;
-        /* Drop bio reference on tg */
-        throtl_put_tg(tg);
+        /* Drop bio reference on blkg */
+        blkg_put(tg_to_blkg(tg));
 
         BUG_ON(td->nr_queued[rw] <= 0);
         td->nr_queued[rw]--;
@@ -865,8 +831,8 @@ static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
 
 static void throtl_process_limit_change(struct throtl_data *td)
 {
-        struct throtl_grp *tg;
-        struct hlist_node *pos, *n;
+        struct request_queue *q = td->queue;
+        struct blkcg_gq *blkg, *n;
 
         if (!td->limits_changed)
                 return;
@@ -875,7 +841,9 @@ static void throtl_process_limit_change(struct throtl_data *td)
 
         throtl_log(td, "limits changed");
 
-        hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
+        list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
+                struct throtl_grp *tg = blkg_to_tg(blkg);
+
                 if (!tg->limits_changed)
                         continue;
 
@@ -973,120 +941,159 @@ throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
         }
 }
 
-static void
-throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
+static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
+                                struct blkg_policy_data *pd, int off)
 {
-        /* Something wrong if we are trying to remove same group twice */
-        BUG_ON(hlist_unhashed(&tg->tg_node));
+        struct throtl_grp *tg = pd_to_tg(pd);
+        struct blkg_rwstat rwstat = { }, tmp;
+        int i, cpu;
 
-        hlist_del_init(&tg->tg_node);
+        for_each_possible_cpu(cpu) {
+                struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
 
-        /*
-         * Put the reference taken at the time of creation so that when all
-         * queues are gone, group can be destroyed.
-         */
-        throtl_put_tg(tg);
-        td->nr_undestroyed_grps--;
+                tmp = blkg_rwstat_read((void *)sc + off);
+                for (i = 0; i < BLKG_RWSTAT_NR; i++)
+                        rwstat.cnt[i] += tmp.cnt[i];
+        }
+
+        return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 
-static void throtl_release_tgs(struct throtl_data *td)
+static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
+                               struct seq_file *sf)
 {
-        struct hlist_node *pos, *n;
-        struct throtl_grp *tg;
+        struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
 
-        hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
-                /*
-                 * If cgroup removal path got to blk_group first and removed
-                 * it from cgroup list, then it will take care of destroying
-                 * cfqg also.
-                 */
-                if (!blkiocg_del_blkio_group(&tg->blkg))
-                        throtl_destroy_tg(td, tg);
-        }
+        blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat, &blkcg_policy_throtl,
+                          cft->private, true);
+        return 0;
 }
 
-/*
- * Blk cgroup controller notification saying that blkio_group object is being
- * delinked as associated cgroup object is going away. That also means that
- * no new IO will come in this group. So get rid of this group as soon as
- * any pending IO in the group is finished.
- *
- * This function is called under rcu_read_lock(). key is the rcu protected
- * pointer. That means "key" is a valid throtl_data pointer as long as we are
- * rcu read lock.
- *
- * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
- * it should not be NULL as even if queue was going away, cgroup deltion
- * path got to it first.
- */
-void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg)
+static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
+                              int off)
 {
-        unsigned long flags;
-        struct throtl_data *td = key;
+        struct throtl_grp *tg = pd_to_tg(pd);
+        u64 v = *(u64 *)((void *)tg + off);
 
-        spin_lock_irqsave(td->queue->queue_lock, flags);
-        throtl_destroy_tg(td, tg_of_blkg(blkg));
-        spin_unlock_irqrestore(td->queue->queue_lock, flags);
+        if (v == -1)
+                return 0;
+        return __blkg_prfill_u64(sf, pd, v);
 }
 
-static void throtl_update_blkio_group_common(struct throtl_data *td,
-                                struct throtl_grp *tg)
+static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
+                               int off)
 {
-        xchg(&tg->limits_changed, true);
-        xchg(&td->limits_changed, true);
-        /* Schedule a work now to process the limit change */
-        throtl_schedule_delayed_work(td, 0);
+        struct throtl_grp *tg = pd_to_tg(pd);
+        unsigned int v = *(unsigned int *)((void *)tg + off);
+
+        if (v == -1)
+                return 0;
+        return __blkg_prfill_u64(sf, pd, v);
 }
 
-/*
- * For all update functions, key should be a valid pointer because these
- * update functions are called under blkcg_lock, that means, blkg is
- * valid and in turn key is valid. queue exit path can not race because
- * of blkcg_lock
- *
- * Can not take queue lock in update functions as queue lock under blkcg_lock
- * is not allowed. Under other paths we take blkcg_lock under queue_lock.
- */
-static void throtl_update_blkio_group_read_bps(void *key,
-                                struct blkio_group *blkg, u64 read_bps)
+static int tg_print_conf_u64(struct cgroup *cgrp, struct cftype *cft,
+                             struct seq_file *sf)
 {
-        struct throtl_data *td = key;
-        struct throtl_grp *tg = tg_of_blkg(blkg);
-
-        tg->bps[READ] = read_bps;
-        throtl_update_blkio_group_common(td, tg);
+        blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_u64,
+                          &blkcg_policy_throtl, cft->private, false);
+        return 0;
 }
 
-static void throtl_update_blkio_group_write_bps(void *key,
-                                struct blkio_group *blkg, u64 write_bps)
+static int tg_print_conf_uint(struct cgroup *cgrp, struct cftype *cft,
+                              struct seq_file *sf)
 {
-        struct throtl_data *td = key;
-        struct throtl_grp *tg = tg_of_blkg(blkg);
-
-        tg->bps[WRITE] = write_bps;
-        throtl_update_blkio_group_common(td, tg);
+        blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_uint,
+                          &blkcg_policy_throtl, cft->private, false);
+        return 0;
 }
 
-static void throtl_update_blkio_group_read_iops(void *key,
-                        struct blkio_group *blkg, unsigned int read_iops)
+static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf,
+                       bool is_u64)
 {
-        struct throtl_data *td = key;
-        struct throtl_grp *tg = tg_of_blkg(blkg);
+        struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+        struct blkg_conf_ctx ctx;
+        struct throtl_grp *tg;
+        struct throtl_data *td;
+        int ret;
+
+        ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
+        if (ret)
+                return ret;
+
+        tg = blkg_to_tg(ctx.blkg);
+        td = ctx.blkg->q->td;
+
+        if (!ctx.v)
+                ctx.v = -1;
+
+        if (is_u64)
+                *(u64 *)((void *)tg + cft->private) = ctx.v;
+        else
+                *(unsigned int *)((void *)tg + cft->private) = ctx.v;
+
+        /* XXX: we don't need the following deferred processing */
+        xchg(&tg->limits_changed, true);
+        xchg(&td->limits_changed, true);
+        throtl_schedule_delayed_work(td, 0);
 
-        tg->iops[READ] = read_iops;
-        throtl_update_blkio_group_common(td, tg);
+        blkg_conf_finish(&ctx);
+        return 0;
 }
 
-static void throtl_update_blkio_group_write_iops(void *key,
-                        struct blkio_group *blkg, unsigned int write_iops)
+static int tg_set_conf_u64(struct cgroup *cgrp, struct cftype *cft,
+                           const char *buf)
 {
-        struct throtl_data *td = key;
-        struct throtl_grp *tg = tg_of_blkg(blkg);
+        return tg_set_conf(cgrp, cft, buf, true);
+}
 
-        tg->iops[WRITE] = write_iops;
-        throtl_update_blkio_group_common(td, tg);
+static int tg_set_conf_uint(struct cgroup *cgrp, struct cftype *cft,
+                            const char *buf)
+{
+        return tg_set_conf(cgrp, cft, buf, false);
 }
 
+static struct cftype throtl_files[] = {
+        {
+                .name = "throttle.read_bps_device",
+                .private = offsetof(struct throtl_grp, bps[READ]),
+                .read_seq_string = tg_print_conf_u64,
+                .write_string = tg_set_conf_u64,
+                .max_write_len = 256,
+        },
+        {
+                .name = "throttle.write_bps_device",
+                .private = offsetof(struct throtl_grp, bps[WRITE]),
+                .read_seq_string = tg_print_conf_u64,
+                .write_string = tg_set_conf_u64,
+                .max_write_len = 256,
+        },
+        {
+                .name = "throttle.read_iops_device",
+                .private = offsetof(struct throtl_grp, iops[READ]),
+                .read_seq_string = tg_print_conf_uint,
+                .write_string = tg_set_conf_uint,
+                .max_write_len = 256,
+        },
+        {
+                .name = "throttle.write_iops_device",
+                .private = offsetof(struct throtl_grp, iops[WRITE]),
+                .read_seq_string = tg_print_conf_uint,
+                .write_string = tg_set_conf_uint,
+                .max_write_len = 256,
+        },
+        {
+                .name = "throttle.io_service_bytes",
+                .private = offsetof(struct tg_stats_cpu, service_bytes),
+                .read_seq_string = tg_print_cpu_rwstat,
+        },
+        {
+                .name = "throttle.io_serviced",
+                .private = offsetof(struct tg_stats_cpu, serviced),
+                .read_seq_string = tg_print_cpu_rwstat,
+        },
+        { }     /* terminate */
+};
+
 static void throtl_shutdown_wq(struct request_queue *q)
 {
         struct throtl_data *td = q->td;
@@ -1094,19 +1101,13 @@ static void throtl_shutdown_wq(struct request_queue *q)
         cancel_delayed_work_sync(&td->throtl_work);
 }
 
-static struct blkio_policy_type blkio_policy_throtl = {
-        .ops = {
-                .blkio_unlink_group_fn = throtl_unlink_blkio_group,
-                .blkio_update_group_read_bps_fn =
-                                        throtl_update_blkio_group_read_bps,
-                .blkio_update_group_write_bps_fn =
-                                        throtl_update_blkio_group_write_bps,
-                .blkio_update_group_read_iops_fn =
-                                        throtl_update_blkio_group_read_iops,
-                .blkio_update_group_write_iops_fn =
-                                        throtl_update_blkio_group_write_iops,
-        },
-        .plid = BLKIO_POLICY_THROTL,
+static struct blkcg_policy blkcg_policy_throtl = {
+        .pd_size                = sizeof(struct throtl_grp),
+        .cftypes                = throtl_files,
+
+        .pd_init_fn             = throtl_pd_init,
+        .pd_exit_fn             = throtl_pd_exit,
+        .pd_reset_stats_fn      = throtl_pd_reset_stats,
 };
 
 bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
@@ -1114,7 +1115,7 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
         struct throtl_data *td = q->td;
         struct throtl_grp *tg;
         bool rw = bio_data_dir(bio), update_disptime = true;
-        struct blkio_cgroup *blkcg;
+        struct blkcg *blkcg;
         bool throttled = false;
 
         if (bio->bi_rw & REQ_THROTTLED) {
@@ -1122,33 +1123,31 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
                 goto out;
         }
 
+        /* bio_associate_current() needs ioc, try creating */
+        create_io_context(GFP_ATOMIC, q->node);
+
         /*
          * A throtl_grp pointer retrieved under rcu can be used to access
          * basic fields like stats and io rates. If a group has no rules,
          * just update the dispatch stats in lockless manner and return.
          */
-
         rcu_read_lock();
-        blkcg = task_blkio_cgroup(current);
-        tg = throtl_find_tg(td, blkcg);
+        blkcg = bio_blkcg(bio);
+        tg = throtl_lookup_tg(td, blkcg);
         if (tg) {
-                throtl_tg_fill_dev_details(td, tg);
-
                 if (tg_no_rule_group(tg, rw)) {
-                        blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size,
-                                        rw, rw_is_sync(bio->bi_rw));
-                        rcu_read_unlock();
-                        goto out;
+                        throtl_update_dispatch_stats(tg_to_blkg(tg),
+                                                     bio->bi_size, bio->bi_rw);
+                        goto out_unlock_rcu;
                 }
         }
-        rcu_read_unlock();
 
         /*
          * Either group has not been allocated yet or it is not an unlimited
          * IO group
          */
         spin_lock_irq(q->queue_lock);
-        tg = throtl_get_tg(td);
+        tg = throtl_lookup_create_tg(td, blkcg);
         if (unlikely(!tg))
                 goto out_unlock;
 
@@ -1189,6 +1188,7 @@ queue_bio:
                         tg->io_disp[rw], tg->iops[rw],
                         tg->nr_queued[READ], tg->nr_queued[WRITE]);
 
+        bio_associate_current(bio);
         throtl_add_bio_tg(q->td, tg, bio);
         throttled = true;
 
@@ -1199,6 +1199,8 @@ queue_bio:
 
 out_unlock:
         spin_unlock_irq(q->queue_lock);
+out_unlock_rcu:
+        rcu_read_unlock();
 out:
         return throttled;
 }
@@ -1241,79 +1243,31 @@ void blk_throtl_drain(struct request_queue *q)
 int blk_throtl_init(struct request_queue *q)
 {
         struct throtl_data *td;
-        struct throtl_grp *tg;
+        int ret;
 
         td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
         if (!td)
                 return -ENOMEM;
 
-        INIT_HLIST_HEAD(&td->tg_list);
         td->tg_service_tree = THROTL_RB_ROOT;
         td->limits_changed = false;
         INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
 
-        /* alloc and Init root group. */
+        q->td = td;
         td->queue = q;
-        tg = throtl_alloc_tg(td);
 
-        if (!tg) {
+        /* activate policy */
+        ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
+        if (ret)
                 kfree(td);
-                return -ENOMEM;
-        }
-
-        td->root_tg = tg;
-
-        rcu_read_lock();
-        throtl_init_add_tg_lists(td, tg, &blkio_root_cgroup);
-        rcu_read_unlock();
-
-        /* Attach throtl data to request queue */
-        q->td = td;
-        return 0;
+        return ret;
 }
 
 void blk_throtl_exit(struct request_queue *q)
 {
-        struct throtl_data *td = q->td;
-        bool wait = false;
-
-        BUG_ON(!td);
-
-        throtl_shutdown_wq(q);
-
-        spin_lock_irq(q->queue_lock);
-        throtl_release_tgs(td);
-
-        /* If there are other groups */
-        if (td->nr_undestroyed_grps > 0)
-                wait = true;
-
-        spin_unlock_irq(q->queue_lock);
-
-        /*
-         * Wait for tg->blkg->key accessors to exit their grace periods.
-         * Do this wait only if there are other undestroyed groups out
-         * there (other than root group). This can happen if cgroup deletion
-         * path claimed the responsibility of cleaning up a group before
-         * queue cleanup code get to the group.
-         *
-         * Do not call synchronize_rcu() unconditionally as there are drivers
-         * which create/delete request queue hundreds of times during scan/boot
-         * and synchronize_rcu() can take significant time and slow down boot.
-         */
-        if (wait)
-                synchronize_rcu();
-
-        /*
-         * Just being safe to make sure after previous flush if some body did
-         * update limits through cgroup and another work got queued, cancel
-         * it.
-         */
+        BUG_ON(!q->td);
         throtl_shutdown_wq(q);
-}
-
-void blk_throtl_release(struct request_queue *q)
-{
+        blkcg_deactivate_policy(q, &blkcg_policy_throtl);
         kfree(q->td);
 }
 
@@ -1323,8 +1277,7 @@ static int __init throtl_init(void)
         if (!kthrotld_workqueue)
                 panic("Failed to create kthrotld\n");
 
-        blkio_policy_register(&blkio_policy_throtl);
-        return 0;
+        return blkcg_policy_register(&blkcg_policy_throtl);
 }
 
 module_init(throtl_init);