diff options
Diffstat (limited to 'block/blk-throttle.c')
| -rw-r--r-- | block/blk-throttle.c | 1699 |
1 files changed, 1699 insertions, 0 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c new file mode 100644 index 000000000..5b9c6d5c3 --- /dev/null +++ b/block/blk-throttle.c @@ -0,0 +1,1699 @@ +/* + * Interface for controlling IO bandwidth on a request queue + * + * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com> + */ + +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/blkdev.h> +#include <linux/bio.h> +#include <linux/blktrace_api.h> +#include "blk-cgroup.h" +#include "blk.h" + +/* Max dispatch from a group in 1 round */ +static int throtl_grp_quantum = 8; + +/* Total max dispatch from all groups in one round */ +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; + +/* + * To implement hierarchical throttling, throtl_grps form a tree and bios + * are dispatched upwards level by level until they reach the top and get + * issued. When dispatching bios from the children and local group at each + * level, if the bios are dispatched into a single bio_list, there's a risk + * of a local or child group which can queue many bios at once filling up + * the list starving others. + * + * To avoid such starvation, dispatched bios are queued separately + * according to where they came from. When they are again dispatched to + * the parent, they're popped in round-robin order so that no single source + * hogs the dispatch window. + * + * throtl_qnode is used to keep the queued bios separated by their sources. + * Bios are queued to throtl_qnode which in turn is queued to + * throtl_service_queue and then dispatched in round-robin order. + * + * It's also used to track the reference counts on blkg's. A qnode always + * belongs to a throtl_grp and gets queued on itself or the parent, so + * incrementing the reference of the associated throtl_grp when a qnode is + * queued and decrementing when dequeued is enough to keep the whole blkg + * tree pinned while bios are in flight. + */ +struct throtl_qnode { + struct list_head node; /* service_queue->queued[] */ + struct bio_list bios; /* queued bios */ + struct throtl_grp *tg; /* tg this qnode belongs to */ +}; + +struct throtl_service_queue { + struct throtl_service_queue *parent_sq; /* the parent service_queue */ + + /* + * Bios queued directly to this service_queue or dispatched from + * children throtl_grp's. + */ + struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */ + unsigned int nr_queued[2]; /* number of queued bios */ + + /* + * RB tree of active children throtl_grp's, which are sorted by + * their ->disptime. + */ + struct rb_root pending_tree; /* RB tree of active tgs */ + struct rb_node *first_pending; /* first node in the tree */ + unsigned int nr_pending; /* # queued in the tree */ + unsigned long first_pending_disptime; /* disptime of the first tg */ + struct timer_list pending_timer; /* fires on first_pending_disptime */ +}; + +enum tg_state_flags { + THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */ + THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */ +}; + +#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 { + /* must be the first member */ + struct blkg_policy_data pd; + + /* active throtl group service_queue member */ + struct rb_node rb_node; + + /* throtl_data this group belongs to */ + struct throtl_data *td; + + /* this group's service queue */ + struct throtl_service_queue service_queue; + + /* + * qnode_on_self is used when bios are directly queued to this + * throtl_grp so that local bios compete fairly with bios + * dispatched from children. qnode_on_parent is used when bios are + * dispatched from this throtl_grp into its parent and will compete + * with the sibling qnode_on_parents and the parent's + * qnode_on_self. + */ + struct throtl_qnode qnode_on_self[2]; + struct throtl_qnode qnode_on_parent[2]; + + /* + * Dispatch time in jiffies. This is the estimated time when group + * will unthrottle and is ready to dispatch more bio. It is used as + * key to sort active groups in service tree. + */ + unsigned long disptime; + + unsigned int flags; + + /* are there any throtl rules between this group and td? */ + bool has_rules[2]; + + /* bytes per second rate limits */ + uint64_t bps[2]; + + /* IOPS limits */ + unsigned int iops[2]; + + /* Number of bytes disptached in current slice */ + uint64_t bytes_disp[2]; + /* Number of bio's dispatched in current slice */ + unsigned int io_disp[2]; + + /* When did we start a new slice */ + unsigned long slice_start[2]; + unsigned long slice_end[2]; + + /* 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 +{ + /* service tree for active throtl groups */ + struct throtl_service_queue service_queue; + + struct request_queue *queue; + + /* Total Number of queued bios on READ and WRITE lists */ + unsigned int nr_queued[2]; + + /* + * number of total undestroyed groups + */ + unsigned int nr_undestroyed_grps; + + /* Work for dispatching throttled bios */ + struct work_struct dispatch_work; +}; + +/* 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 void throtl_pending_timer_fn(unsigned long arg); + +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); +} + +/** + * sq_to_tg - return the throl_grp the specified service queue belongs to + * @sq: the throtl_service_queue of interest + * + * Return the throtl_grp @sq belongs to. If @sq is the top-level one + * embedded in throtl_data, %NULL is returned. + */ +static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq) +{ + if (sq && sq->parent_sq) + return container_of(sq, struct throtl_grp, service_queue); + else + return NULL; +} + +/** + * sq_to_td - return throtl_data the specified service queue belongs to + * @sq: the throtl_service_queue of interest + * + * A service_queue can be embeded in either a throtl_grp or throtl_data. + * Determine the associated throtl_data accordingly and return it. + */ +static struct throtl_data *sq_to_td(struct throtl_service_queue *sq) +{ + struct throtl_grp *tg = sq_to_tg(sq); + + if (tg) + return tg->td; + else + return container_of(sq, struct throtl_data, service_queue); +} + +/** + * throtl_log - log debug message via blktrace + * @sq: the service_queue being reported + * @fmt: printf format string + * @args: printf args + * + * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a + * throtl_grp; otherwise, just "throtl". + * + * TODO: this should be made a function and name formatting should happen + * after testing whether blktrace is enabled. + */ +#define throtl_log(sq, fmt, args...) do { \ + struct throtl_grp *__tg = sq_to_tg((sq)); \ + struct throtl_data *__td = sq_to_td((sq)); \ + \ + (void)__td; \ + if ((__tg)) { \ + char __pbuf[128]; \ + \ + blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \ + blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \ + } else { \ + blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \ + } \ +} while (0) + +static void tg_stats_init(struct tg_stats_cpu *tg_stats) +{ + blkg_rwstat_init(&tg_stats->service_bytes); + blkg_rwstat_init(&tg_stats->serviced); +} + +/* + * Worker for allocating per cpu stat for tgs. This is scheduled on the + * system_wq once there are some groups on the alloc_list waiting for + * allocation. + */ +static void tg_stats_alloc_fn(struct work_struct *work) +{ + 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) { + int cpu; + + stats_cpu = alloc_percpu(struct tg_stats_cpu); + if (!stats_cpu) { + /* allocation failed, try again after some time */ + schedule_delayed_work(dwork, msecs_to_jiffies(10)); + return; + } + for_each_possible_cpu(cpu) + tg_stats_init(per_cpu_ptr(stats_cpu, cpu)); + } + + spin_lock_irq(&tg_stats_alloc_lock); + + 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); + } + + empty = list_empty(&tg_stats_alloc_list); + spin_unlock_irq(&tg_stats_alloc_lock); + if (!empty) + goto alloc_stats; +} + +static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg) +{ + INIT_LIST_HEAD(&qn->node); + bio_list_init(&qn->bios); + qn->tg = tg; +} + +/** + * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it + * @bio: bio being added + * @qn: qnode to add bio to + * @queued: the service_queue->queued[] list @qn belongs to + * + * Add @bio to @qn and put @qn on @queued if it's not already on. + * @qn->tg's reference count is bumped when @qn is activated. See the + * comment on top of throtl_qnode definition for details. + */ +static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn, + struct list_head *queued) +{ + bio_list_add(&qn->bios, bio); + if (list_empty(&qn->node)) { + list_add_tail(&qn->node, queued); + blkg_get(tg_to_blkg(qn->tg)); + } +} + +/** + * throtl_peek_queued - peek the first bio on a qnode list + * @queued: the qnode list to peek + */ +static struct bio *throtl_peek_queued(struct list_head *queued) +{ + struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); + struct bio *bio; + + if (list_empty(queued)) + return NULL; + + bio = bio_list_peek(&qn->bios); + WARN_ON_ONCE(!bio); + return bio; +} + +/** + * throtl_pop_queued - pop the first bio form a qnode list + * @queued: the qnode list to pop a bio from + * @tg_to_put: optional out argument for throtl_grp to put + * + * Pop the first bio from the qnode list @queued. After popping, the first + * qnode is removed from @queued if empty or moved to the end of @queued so + * that the popping order is round-robin. + * + * When the first qnode is removed, its associated throtl_grp should be put + * too. If @tg_to_put is NULL, this function automatically puts it; + * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is + * responsible for putting it. + */ +static struct bio *throtl_pop_queued(struct list_head *queued, + struct throtl_grp **tg_to_put) +{ + struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); + struct bio *bio; + + if (list_empty(queued)) + return NULL; + + bio = bio_list_pop(&qn->bios); + WARN_ON_ONCE(!bio); + + if (bio_list_empty(&qn->bios)) { + list_del_init(&qn->node); + if (tg_to_put) + *tg_to_put = qn->tg; + else + blkg_put(tg_to_blkg(qn->tg)); + } else { + list_move_tail(&qn->node, queued); + } + + return bio; +} + +/* init a service_queue, assumes the caller zeroed it */ +static void throtl_service_queue_init(struct throtl_service_queue *sq, + struct throtl_service_queue *parent_sq) +{ + INIT_LIST_HEAD(&sq->queued[0]); + INIT_LIST_HEAD(&sq->queued[1]); + sq->pending_tree = RB_ROOT; + sq->parent_sq = parent_sq; + setup_timer(&sq->pending_timer, throtl_pending_timer_fn, + (unsigned long)sq); +} + +static void throtl_service_queue_exit(struct throtl_service_queue *sq) +{ + del_timer_sync(&sq->pending_timer); +} + +static void throtl_pd_init(struct blkcg_gq *blkg) +{ + struct throtl_grp *tg = blkg_to_tg(blkg); + struct throtl_data *td = blkg->q->td; + struct throtl_service_queue *parent_sq; + unsigned long flags; + int rw; + + /* + * If on the default hierarchy, we switch to properly hierarchical + * behavior where limits on a given throtl_grp are applied to the + * whole subtree rather than just the group itself. e.g. If 16M + * read_bps limit is set on the root group, the whole system can't + * exceed 16M for the device. + * + * If not on the default hierarchy, the broken flat hierarchy + * behavior is retained where all throtl_grps are treated as if + * they're all separate root groups right below throtl_data. + * Limits of a group don't interact with limits of other groups + * regardless of the position of the group in the hierarchy. + */ + parent_sq = &td->service_queue; + + if (cgroup_on_dfl(blkg->blkcg->css.cgroup) && blkg->parent) + parent_sq = &blkg_to_tg(blkg->parent)->service_queue; + + throtl_service_queue_init(&tg->service_queue, parent_sq); + + for (rw = READ; rw <= WRITE; rw++) { + throtl_qnode_init(&tg->qnode_on_self[rw], tg); + throtl_qnode_init(&tg->qnode_on_parent[rw], tg); + } + + RB_CLEAR_NODE(&tg->rb_node); + tg->td = td; + + tg->bps[READ] = -1; + tg->bps[WRITE] = -1; + tg->iops[READ] = -1; + tg->iops[WRITE] = -1; + + /* + * 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. + */ + spin_lock_irqsave(&tg_stats_alloc_lock, flags); + list_add(&tg->stats_alloc_node, &tg_stats_alloc_list); + schedule_delayed_work(&tg_stats_alloc_work, 0); + spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); +} + +/* + * Set has_rules[] if @tg or any of its parents have limits configured. + * This doesn't require walking up to the top of the hierarchy as the + * parent's has_rules[] is guaranteed to be correct. + */ +static void tg_update_has_rules(struct throtl_grp *tg) +{ + struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq); + int rw; + + for (rw = READ; rw <= WRITE; rw++) + tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) || + (tg->bps[rw] != -1 || tg->iops[rw] != -1); +} + +static void throtl_pd_online(struct blkcg_gq *blkg) +{ + /* + * We don't want new groups to escape the limits of its ancestors. + * Update has_rules[] after a new group is brought online. + */ + tg_update_has_rules(blkg_to_tg(blkg)); +} + +static void throtl_pd_exit(struct blkcg_gq *blkg) +{ + struct throtl_grp *tg = blkg_to_tg(blkg); + unsigned long flags; + + spin_lock_irqsave(&tg_stats_alloc_lock, flags); + list_del_init(&tg->stats_alloc_node); + spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); + + free_percpu(tg->stats_cpu); + + throtl_service_queue_exit(&tg->service_queue); +} + +static void throtl_pd_reset_stats(struct blkcg_gq *blkg) +{ + struct throtl_grp *tg = blkg_to_tg(blkg); + int cpu; + + if (tg->stats_cpu == NULL) + return; + + for_each_possible_cpu(cpu) { + struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); + + blkg_rwstat_reset(&sc->service_bytes); + blkg_rwstat_reset(&sc->serviced); + } +} + +static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td, + struct blkcg *blkcg) +{ + /* + * This is the common case when there are no blkcgs. Avoid lookup + * in this case + */ + if (blkcg == &blkcg_root) + return td_root_tg(td); + + return blkg_to_tg(blkg_lookup(blkcg, td->queue)); +} + +static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td, + struct blkcg *blkcg) +{ + struct request_queue *q = td->queue; + struct throtl_grp *tg = NULL; + + /* + * This is the common case when there are no blkcgs. Avoid lookup + * in this case + */ + 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_dying(q)) + tg = td_root_tg(td); + } + + return tg; +} + +static struct throtl_grp * +throtl_rb_first(struct throtl_service_queue *parent_sq) +{ + /* Service tree is empty */ + if (!parent_sq->nr_pending) + return NULL; + + if (!parent_sq->first_pending) + parent_sq->first_pending = rb_first(&parent_sq->pending_tree); + + if (parent_sq->first_pending) + return rb_entry_tg(parent_sq->first_pending); + + return NULL; +} + +static void rb_erase_init(struct rb_node *n, struct rb_root *root) +{ + rb_erase(n, root); + RB_CLEAR_NODE(n); +} + +static void throtl_rb_erase(struct rb_node *n, + struct throtl_service_queue *parent_sq) +{ + if (parent_sq->first_pending == n) + parent_sq->first_pending = NULL; + rb_erase_init(n, &parent_sq->pending_tree); + --parent_sq->nr_pending; +} + +static void update_min_dispatch_time(struct throtl_service_queue *parent_sq) +{ + struct throtl_grp *tg; + + tg = throtl_rb_first(parent_sq); + if (!tg) + return; + + parent_sq->first_pending_disptime = tg->disptime; +} + +static void tg_service_queue_add(struct throtl_grp *tg) +{ + struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq; + struct rb_node **node = &parent_sq->pending_tree.rb_node; + struct rb_node *parent = NULL; + struct throtl_grp *__tg; + unsigned long key = tg->disptime; + int left = 1; + + while (*node != NULL) { + parent = *node; + __tg = rb_entry_tg(parent); + + if (time_before(key, __tg->disptime)) + node = &parent->rb_left; + else { + node = &parent->rb_right; + left = 0; + } + } + + if (left) + parent_sq->first_pending = &tg->rb_node; + + rb_link_node(&tg->rb_node, parent, node); + rb_insert_color(&tg->rb_node, &parent_sq->pending_tree); +} + +static void __throtl_enqueue_tg(struct throtl_grp *tg) +{ + tg_service_queue_add(tg); + tg->flags |= THROTL_TG_PENDING; + tg->service_queue.parent_sq->nr_pending++; +} + +static void throtl_enqueue_tg(struct throtl_grp *tg) +{ + if (!(tg->flags & THROTL_TG_PENDING)) + __throtl_enqueue_tg(tg); +} + +static void __throtl_dequeue_tg(struct throtl_grp *tg) +{ + throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq); + tg->flags &= ~THROTL_TG_PENDING; +} + +static void throtl_dequeue_tg(struct throtl_grp *tg) +{ + if (tg->flags & THROTL_TG_PENDING) + __throtl_dequeue_tg(tg); +} + +/* Call with queue lock held */ +static void throtl_schedule_pending_timer(struct throtl_service_queue *sq, + unsigned long expires) +{ + mod_timer(&sq->pending_timer, expires); + throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu", + expires - jiffies, jiffies); +} + +/** + * throtl_schedule_next_dispatch - schedule the next dispatch cycle + * @sq: the service_queue to schedule dispatch for + * @force: force scheduling + * + * Arm @sq->pending_timer so that the next dispatch cycle starts on the + * dispatch time of the first pending child. Returns %true if either timer + * is armed or there's no pending child left. %false if the current + * dispatch window is still open and the caller should continue + * dispatching. + * + * If @force is %true, the dispatch timer is always scheduled and this + * function is guaranteed to return %true. This is to be used when the + * caller can't dispatch itself and needs to invoke pending_timer + * unconditionally. Note that forced scheduling is likely to induce short + * delay before dispatch starts even if @sq->first_pending_disptime is not + * in the future and thus shouldn't be used in hot paths. + */ +static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq, + bool force) +{ + /* any pending children left? */ + if (!sq->nr_pending) + return true; + + update_min_dispatch_time(sq); + + /* is the next dispatch time in the future? */ + if (force || time_after(sq->first_pending_disptime, jiffies)) { + throtl_schedule_pending_timer(sq, sq->first_pending_disptime); + return true; + } + + /* tell the caller to continue dispatching */ + return false; +} + +static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg, + bool rw, unsigned long start) +{ + tg->bytes_disp[rw] = 0; + tg->io_disp[rw] = 0; + + /* + * Previous slice has expired. We must have trimmed it after last + * bio dispatch. That means since start of last slice, we never used + * that bandwidth. Do try to make use of that bandwidth while giving + * credit. + */ + if (time_after_eq(start, tg->slice_start[rw])) + tg->slice_start[rw] = start; + + tg->slice_end[rw] = jiffies + throtl_slice; + throtl_log(&tg->service_queue, + "[%c] new slice with credit start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', tg->slice_start[rw], + tg->slice_end[rw], jiffies); +} + +static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw) +{ + tg->bytes_disp[rw] = 0; + tg->io_disp[rw] = 0; + tg->slice_start[rw] = jiffies; + tg->slice_end[rw] = jiffies + throtl_slice; + throtl_log(&tg->service_queue, + "[%c] new slice start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', tg->slice_start[rw], + tg->slice_end[rw], jiffies); +} + +static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw, + unsigned long jiffy_end) +{ + tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); +} + +static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw, + unsigned long jiffy_end) +{ + tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); + throtl_log(&tg->service_queue, + "[%c] extend slice start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', tg->slice_start[rw], + tg->slice_end[rw], jiffies); +} + +/* Determine if previously allocated or extended slice is complete or not */ +static bool throtl_slice_used(struct throtl_grp *tg, bool rw) +{ + if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) + return false; + + return 1; +} + +/* Trim the used slices and adjust slice start accordingly */ +static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw) +{ + unsigned long nr_slices, time_elapsed, io_trim; + u64 bytes_trim, tmp; + + BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])); + + /* + * If bps are unlimited (-1), then time slice don't get + * renewed. Don't try to trim the slice if slice is used. A new + * slice will start when appropriate. + */ + if (throtl_slice_used(tg, rw)) + return; + + /* + * A bio has been dispatched. Also adjust slice_end. It might happen + * that initially cgroup limit was very low resulting in high + * slice_end, but later limit was bumped up and bio was dispached + * sooner, then we need to reduce slice_end. A high bogus slice_end + * is bad because it does not allow new slice to start. + */ + + throtl_set_slice_end(tg, rw, jiffies + throtl_slice); + + time_elapsed = jiffies - tg->slice_start[rw]; + + nr_slices = time_elapsed / throtl_slice; + + if (!nr_slices) + return; + tmp = tg->bps[rw] * throtl_slice * nr_slices; + do_div(tmp, HZ); + bytes_trim = tmp; + + io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ; + + if (!bytes_trim && !io_trim) + return; + + if (tg->bytes_disp[rw] >= bytes_trim) + tg->bytes_disp[rw] -= bytes_trim; + else + tg->bytes_disp[rw] = 0; + + if (tg->io_disp[rw] >= io_trim) + tg->io_disp[rw] -= io_trim; + else + tg->io_disp[rw] = 0; + + tg->slice_start[rw] += nr_slices * throtl_slice; + + throtl_log(&tg->service_queue, + "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, + tg->slice_start[rw], tg->slice_end[rw], jiffies); +} + +static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio, + unsigned long *wait) +{ + bool rw = bio_data_dir(bio); + unsigned int io_allowed; + unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; + u64 tmp; + + jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; + + /* Slice has just started. Consider one slice interval */ + if (!jiffy_elapsed) + jiffy_elapsed_rnd = throtl_slice; + + jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); + + /* + * jiffy_elapsed_rnd should not be a big value as minimum iops can be + * 1 then at max jiffy elapsed should be equivalent of 1 second as we + * will allow dispatch after 1 second and after that slice should + * have been trimmed. + */ + + tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; + do_div(tmp, HZ); + + if (tmp > UINT_MAX) + io_allowed = UINT_MAX; + else + io_allowed = tmp; + + if (tg->io_disp[rw] + 1 <= io_allowed) { + if (wait) + *wait = 0; + return true; + } + + /* Calc approx time to dispatch */ + jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1; + + if (jiffy_wait > jiffy_elapsed) + jiffy_wait = jiffy_wait - jiffy_elapsed; + else + jiffy_wait = 1; + + if (wait) + *wait = jiffy_wait; + return 0; +} + +static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, + unsigned long *wait) +{ + bool rw = bio_data_dir(bio); + u64 bytes_allowed, extra_bytes, tmp; + unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; + + jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; + + /* Slice has just started. Consider one slice interval */ + if (!jiffy_elapsed) + jiffy_elapsed_rnd = throtl_slice; + + jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); + + tmp = tg->bps[rw] * jiffy_elapsed_rnd; + do_div(tmp, HZ); + bytes_allowed = tmp; + + if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) { + if (wait) + *wait = 0; + return true; + } + + /* Calc approx time to dispatch */ + extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed; + jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]); + + if (!jiffy_wait) + jiffy_wait = 1; + + /* + * This wait time is without taking into consideration the rounding + * up we did. Add that time also. + */ + jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); + if (wait) + *wait = jiffy_wait; + return 0; +} + +/* + * Returns whether one can dispatch a bio or not. Also returns approx number + * of jiffies to wait before this bio is with-in IO rate and can be dispatched + */ +static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio, + unsigned long *wait) +{ + bool rw = bio_data_dir(bio); + unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; + + /* + * Currently whole state machine of group depends on first bio + * queued in the group bio list. So one should not be calling + * this function with a different bio if there are other bios + * queued. + */ + BUG_ON(tg->service_queue.nr_queued[rw] && + bio != throtl_peek_queued(&tg->service_queue.queued[rw])); + + /* If tg->bps = -1, then BW is unlimited */ + if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { + if (wait) + *wait = 0; + return true; + } + + /* + * If previous slice expired, start a new one otherwise renew/extend + * existing slice to make sure it is at least throtl_slice interval + * long since now. + */ + if (throtl_slice_used(tg, rw)) + throtl_start_new_slice(tg, rw); + else { + if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) + throtl_extend_slice(tg, rw, jiffies + throtl_slice); + } + + if (tg_with_in_bps_limit(tg, bio, &bps_wait) && + tg_with_in_iops_limit(tg, bio, &iops_wait)) { + if (wait) + *wait = 0; + return 1; + } + + max_wait = max(bps_wait, iops_wait); + + if (wait) + *wait = max_wait; + + if (time_before(tg->slice_end[rw], jiffies + max_wait)) + throtl_extend_slice(tg, rw, jiffies + max_wait); + + 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); + + /* Charge the bio to the group */ + tg->bytes_disp[rw] += bio->bi_iter.bi_size; + tg->io_disp[rw]++; + + /* + * REQ_THROTTLED is used to prevent the same bio to be throttled + * more than once as a throttled bio will go through blk-throtl the + * second time when it eventually gets issued. Set it when a bio + * is being charged to a tg. + * + * Dispatch stats aren't recursive and each @bio should only be + * accounted by the @tg it was originally associated with. Let's + * update the stats when setting REQ_THROTTLED for the first time + * which is guaranteed to be for the @bio's original tg. + */ + if (!(bio->bi_rw & REQ_THROTTLED)) { + bio->bi_rw |= REQ_THROTTLED; + throtl_update_dispatch_stats(tg_to_blkg(tg), + bio->bi_iter.bi_size, bio->bi_rw); + } +} + +/** + * throtl_add_bio_tg - add a bio to the specified throtl_grp + * @bio: bio to add + * @qn: qnode to use + * @tg: the target throtl_grp + * + * Add @bio to @tg's service_queue using @qn. If @qn is not specified, + * tg->qnode_on_self[] is used. + */ +static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn, + struct throtl_grp *tg) +{ + struct throtl_service_queue *sq = &tg->service_queue; + bool rw = bio_data_dir(bio); + + if (!qn) + qn = &tg->qnode_on_self[rw]; + + /* + * If @tg doesn't currently have any bios queued in the same + * direction, queueing @bio can change when @tg should be + * dispatched. Mark that @tg was empty. This is automatically + * cleaered on the next tg_update_disptime(). + */ + if (!sq->nr_queued[rw]) + tg->flags |= THROTL_TG_WAS_EMPTY; + + throtl_qnode_add_bio(bio, qn, &sq->queued[rw]); + + sq->nr_queued[rw]++; + throtl_enqueue_tg(tg); +} + +static void tg_update_disptime(struct throtl_grp *tg) +{ + struct throtl_service_queue *sq = &tg->service_queue; + unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; + struct bio *bio; + + if ((bio = throtl_peek_queued(&sq->queued[READ]))) + tg_may_dispatch(tg, bio, &read_wait); + + if ((bio = throtl_peek_queued(&sq->queued[WRITE]))) + tg_may_dispatch(tg, bio, &write_wait); + + min_wait = min(read_wait, write_wait); + disptime = jiffies + min_wait; + + /* Update dispatch time */ + throtl_dequeue_tg(tg); + tg->disptime = disptime; + throtl_enqueue_tg(tg); + + /* see throtl_add_bio_tg() */ + tg->flags &= ~THROTL_TG_WAS_EMPTY; +} + +static void start_parent_slice_with_credit(struct throtl_grp *child_tg, + struct throtl_grp *parent_tg, bool rw) +{ + if (throtl_slice_used(parent_tg, rw)) { + throtl_start_new_slice_with_credit(parent_tg, rw, + child_tg->slice_start[rw]); + } + +} + +static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw) +{ + struct throtl_service_queue *sq = &tg->service_queue; + struct throtl_service_queue *parent_sq = sq->parent_sq; + struct throtl_grp *parent_tg = sq_to_tg(parent_sq); + struct throtl_grp *tg_to_put = NULL; + struct bio *bio; + + /* + * @bio is being transferred from @tg to @parent_sq. Popping a bio + * from @tg may put its reference and @parent_sq might end up + * getting released prematurely. Remember the tg to put and put it + * after @bio is transferred to @parent_sq. + */ + bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put); + sq->nr_queued[rw]--; + + throtl_charge_bio(tg, bio); + + /* + * If our parent is another tg, we just need to transfer @bio to + * the parent using throtl_add_bio_tg(). If our parent is + * @td->service_queue, @bio is ready to be issued. Put it on its + * bio_lists[] and decrease total number queued. The caller is + * responsible for issuing these bios. + */ + if (parent_tg) { + throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg); + start_parent_slice_with_credit(tg, parent_tg, rw); + } else { + throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw], + &parent_sq->queued[rw]); + BUG_ON(tg->td->nr_queued[rw] <= 0); + tg->td->nr_queued[rw]--; + } + + throtl_trim_slice(tg, rw); + + if (tg_to_put) + blkg_put(tg_to_blkg(tg_to_put)); +} + +static int throtl_dispatch_tg(struct throtl_grp *tg) +{ + struct throtl_service_queue *sq = &tg->service_queue; + unsigned int nr_reads = 0, nr_writes = 0; + unsigned int max_nr_reads = throtl_grp_quantum*3/4; + unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; + struct bio *bio; + + /* Try to dispatch 75% READS and 25% WRITES */ + + while ((bio = throtl_peek_queued(&sq->queued[READ])) && + tg_may_dispatch(tg, bio, NULL)) { + + tg_dispatch_one_bio(tg, bio_data_dir(bio)); + nr_reads++; + + if (nr_reads >= max_nr_reads) + break; + } + + while ((bio = throtl_peek_queued(&sq->queued[WRITE])) && + tg_may_dispatch(tg, bio, NULL)) { + + tg_dispatch_one_bio(tg, bio_data_dir(bio)); + nr_writes++; + + if (nr_writes >= max_nr_writes) + break; + } + + return nr_reads + nr_writes; +} + +static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) +{ + unsigned int nr_disp = 0; + + while (1) { + struct throtl_grp *tg = throtl_rb_first(parent_sq); + struct throtl_service_queue *sq = &tg->service_queue; + + if (!tg) + break; + + if (time_before(jiffies, tg->disptime)) + break; + + throtl_dequeue_tg(tg); + + nr_disp += throtl_dispatch_tg(tg); + + if (sq->nr_queued[0] || sq->nr_queued[1]) + tg_update_disptime(tg); + + if (nr_disp >= throtl_quantum) + break; + } + + return nr_disp; +} + +/** + * throtl_pending_timer_fn - timer function for service_queue->pending_timer + * @arg: the throtl_service_queue being serviced + * + * This timer is armed when a child throtl_grp with active bio's become + * pending and queued on the service_queue's pending_tree and expires when + * the first child throtl_grp should be dispatched. This function + * dispatches bio's from the children throtl_grps to the parent + * service_queue. + * + * If the parent's parent is another throtl_grp, dispatching is propagated + * by either arming its pending_timer or repeating dispatch directly. If + * the top-level service_tree is reached, throtl_data->dispatch_work is + * kicked so that the ready bio's are issued. + */ +static void throtl_pending_timer_fn(unsigned long arg) +{ + struct throtl_service_queue *sq = (void *)arg; + struct throtl_grp *tg = sq_to_tg(sq); + struct throtl_data *td = sq_to_td(sq); + struct request_queue *q = td->queue; + struct throtl_service_queue *parent_sq; + bool dispatched; + int ret; + + spin_lock_irq(q->queue_lock); +again: + parent_sq = sq->parent_sq; + dispatched = false; + + while (true) { + throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u", + sq->nr_queued[READ] + sq->nr_queued[WRITE], + sq->nr_queued[READ], sq->nr_queued[WRITE]); + + ret = throtl_select_dispatch(sq); + if (ret) { + throtl_log(sq, "bios disp=%u", ret); + dispatched = true; + } + + if (throtl_schedule_next_dispatch(sq, false)) + break; + + /* this dispatch windows is still open, relax and repeat */ + spin_unlock_irq(q->queue_lock); + cpu_relax(); + spin_lock_irq(q->queue_lock); + } + + if (!dispatched) + goto out_unlock; + + if (parent_sq) { + /* @parent_sq is another throl_grp, propagate dispatch */ + if (tg->flags & THROTL_TG_WAS_EMPTY) { + tg_update_disptime(tg); + if (!throtl_schedule_next_dispatch(parent_sq, false)) { + /* window is already open, repeat dispatching */ + sq = parent_sq; + tg = sq_to_tg(sq); + goto again; + } + } + } else { + /* reached the top-level, queue issueing */ + queue_work(kthrotld_workqueue, &td->dispatch_work); + } +out_unlock: + spin_unlock_irq(q->queue_lock); +} + +/** + * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work + * @work: work item being executed + * + * This function is queued for execution when bio's reach the bio_lists[] + * of throtl_data->service_queue. Those bio's are ready and issued by this + * function. + */ +static void blk_throtl_dispatch_work_fn(struct work_struct *work) +{ + struct throtl_data *td = container_of(work, struct throtl_data, + dispatch_work); + struct throtl_service_queue *td_sq = &td->service_queue; + struct request_queue *q = td->queue; + struct bio_list bio_list_on_stack; + struct bio *bio; + struct blk_plug plug; + int rw; + + bio_list_init(&bio_list_on_stack); + + spin_lock_irq(q->queue_lock); + for (rw = READ; rw <= WRITE; rw++) + while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL))) + bio_list_add(&bio_list_on_stack, bio); + spin_unlock_irq(q->queue_lock); + + if (!bio_list_empty(&bio_list_on_stack)) { + blk_start_plug(&plug); + while((bio = bio_list_pop(&bio_list_on_stack))) + generic_make_request(bio); + blk_finish_plug(&plug); + } +} + +static u64 tg_prfill_cpu_rwstat(struct seq_file *sf, + struct blkg_policy_data *pd, int off) +{ + struct throtl_grp *tg = pd_to_tg(pd); + struct blkg_rwstat rwstat = { }, tmp; + int i, cpu; + + if (tg->stats_cpu == NULL) + return 0; + + for_each_possible_cpu(cpu) { + struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); + + 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 int tg_print_cpu_rwstat(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_cpu_rwstat, + &blkcg_policy_throtl, seq_cft(sf)->private, true); + return 0; +} + +static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd, + int off) +{ + struct throtl_grp *tg = pd_to_tg(pd); + u64 v = *(u64 *)((void *)tg + off); + + if (v == -1) + return 0; + return __blkg_prfill_u64(sf, pd, v); +} + +static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd, + int off) +{ + 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); +} + +static int tg_print_conf_u64(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64, + &blkcg_policy_throtl, seq_cft(sf)->private, false); + return 0; +} + +static int tg_print_conf_uint(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint, + &blkcg_policy_throtl, seq_cft(sf)->private, false); + return 0; +} + +static ssize_t tg_set_conf(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off, bool is_u64) +{ + struct blkcg *blkcg = css_to_blkcg(of_css(of)); + struct blkg_conf_ctx ctx; + struct throtl_grp *tg; + struct throtl_service_queue *sq; + struct blkcg_gq *blkg; + struct cgroup_subsys_state *pos_css; + int ret; + + ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx); + if (ret) + return ret; + + tg = blkg_to_tg(ctx.blkg); + sq = &tg->service_queue; + + if (!ctx.v) + ctx.v = -1; + + if (is_u64) + *(u64 *)((void *)tg + of_cft(of)->private) = ctx.v; + else + *(unsigned int *)((void *)tg + of_cft(of)->private) = ctx.v; + + throtl_log(&tg->service_queue, + "limit change rbps=%llu wbps=%llu riops=%u wiops=%u", + tg->bps[READ], tg->bps[WRITE], + tg->iops[READ], tg->iops[WRITE]); + + /* + * Update has_rules[] flags for the updated tg's subtree. A tg is + * considered to have rules if either the tg itself or any of its + * ancestors has rules. This identifies groups without any + * restrictions in the whole hierarchy and allows them to bypass + * blk-throttle. + */ + blkg_for_each_descendant_pre(blkg, pos_css, ctx.blkg) + tg_update_has_rules(blkg_to_tg(blkg)); + + /* + * We're already holding queue_lock and know @tg is valid. Let's + * apply the new config directly. + * + * Restart the slices for both READ and WRITES. It might happen + * that a group's limit are dropped suddenly and we don't want to + * account recently dispatched IO with new low rate. + */ + throtl_start_new_slice(tg, 0); + throtl_start_new_slice(tg, 1); + + if (tg->flags & THROTL_TG_PENDING) { + tg_update_disptime(tg); + throtl_schedule_next_dispatch(sq->parent_sq, true); + } + + blkg_conf_finish(&ctx); + return nbytes; +} + +static ssize_t tg_set_conf_u64(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) +{ + return tg_set_conf(of, buf, nbytes, off, true); +} + +static ssize_t tg_set_conf_uint(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) +{ + return tg_set_conf(of, buf, nbytes, off, false); +} + +static struct cftype throtl_files[] = { + { + .name = "throttle.read_bps_device", + .private = offsetof(struct throtl_grp, bps[READ]), + .seq_show = tg_print_conf_u64, + .write = tg_set_conf_u64, + }, + { + .name = "throttle.write_bps_device", + .private = offsetof(struct throtl_grp, bps[WRITE]), + .seq_show = tg_print_conf_u64, + .write = tg_set_conf_u64, + }, + { + .name = "throttle.read_iops_device", + .private = offsetof(struct throtl_grp, iops[READ]), + .seq_show = tg_print_conf_uint, + .write = tg_set_conf_uint, + }, + { + .name = "throttle.write_iops_device", + .private = offsetof(struct throtl_grp, iops[WRITE]), + .seq_show = tg_print_conf_uint, + .write = tg_set_conf_uint, + }, + { + .name = "throttle.io_service_bytes", + .private = offsetof(struct tg_stats_cpu, service_bytes), + .seq_show = tg_print_cpu_rwstat, + }, + { + .name = "throttle.io_serviced", + .private = offsetof(struct tg_stats_cpu, serviced), + .seq_show = tg_print_cpu_rwstat, + }, + { } /* terminate */ +}; + +static void throtl_shutdown_wq(struct request_queue *q) +{ + struct throtl_data *td = q->td; + + cancel_work_sync(&td->dispatch_work); +} + +static struct blkcg_policy blkcg_policy_throtl = { + .pd_size = sizeof(struct throtl_grp), + .cftypes = throtl_files, + + .pd_init_fn = throtl_pd_init, + .pd_online_fn = throtl_pd_online, + .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) +{ + struct throtl_data *td = q->td; + struct throtl_qnode *qn = NULL; + struct throtl_grp *tg; + struct throtl_service_queue *sq; + bool rw = bio_data_dir(bio); + struct blkcg *blkcg; + bool throttled = false; + + /* see throtl_charge_bio() */ + if (bio->bi_rw & REQ_THROTTLED) + goto out; + + /* + * 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 = bio_blkcg(bio); + tg = throtl_lookup_tg(td, blkcg); + if (tg) { + if (!tg->has_rules[rw]) { + throtl_update_dispatch_stats(tg_to_blkg(tg), + bio->bi_iter.bi_size, bio->bi_rw); + goto out_unlock_rcu; + } + } + + /* + * Either group has not been allocated yet or it is not an unlimited + * IO group + */ + spin_lock_irq(q->queue_lock); + tg = throtl_lookup_create_tg(td, blkcg); + if (unlikely(!tg)) + goto out_unlock; + + sq = &tg->service_queue; + + while (true) { + /* throtl is FIFO - if bios are already queued, should queue */ + if (sq->nr_queued[rw]) + break; + + /* if above limits, break to queue */ + if (!tg_may_dispatch(tg, bio, NULL)) + break; + + /* within limits, let's charge and dispatch directly */ + throtl_charge_bio(tg, bio); + + /* + * We need to trim slice even when bios are not being queued + * otherwise it might happen that a bio is not queued for + * a long time and slice keeps on extending and trim is not + * called for a long time. Now if limits are reduced suddenly + * we take into account all the IO dispatched so far at new + * low rate and * newly queued IO gets a really long dispatch + * time. + * + * So keep on trimming slice even if bio is not queued. + */ + throtl_trim_slice(tg, rw); + + /* + * @bio passed through this layer without being throttled. + * Climb up the ladder. If we''re already at the top, it + * can be executed directly. + */ + qn = &tg->qnode_on_parent[rw]; + sq = sq->parent_sq; + tg = sq_to_tg(sq); + if (!tg) + goto out_unlock; + } + + /* out-of-limit, queue to @tg */ + throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d", + rw == READ ? 'R' : 'W', + tg->bytes_disp[rw], bio->bi_iter.bi_size, tg->bps[rw], + tg->io_disp[rw], tg->iops[rw], + sq->nr_queued[READ], sq->nr_queued[WRITE]); + + bio_associate_current(bio); + tg->td->nr_queued[rw]++; + throtl_add_bio_tg(bio, qn, tg); + throttled = true; + + /* + * Update @tg's dispatch time and force schedule dispatch if @tg + * was empty before @bio. The forced scheduling isn't likely to + * cause undue delay as @bio is likely to be dispatched directly if + * its @tg's disptime is not in the future. + */ + if (tg->flags & THROTL_TG_WAS_EMPTY) { + tg_update_disptime(tg); + throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true); + } + +out_unlock: + spin_unlock_irq(q->queue_lock); +out_unlock_rcu: + rcu_read_unlock(); +out: + /* + * As multiple blk-throtls may stack in the same issue path, we + * don't want bios to leave with the flag set. Clear the flag if + * being issued. + */ + if (!throttled) + bio->bi_rw &= ~REQ_THROTTLED; + return throttled; +} + +/* + * Dispatch all bios from all children tg's queued on @parent_sq. On + * return, @parent_sq is guaranteed to not have any active children tg's + * and all bios from previously active tg's are on @parent_sq->bio_lists[]. + */ +static void tg_drain_bios(struct throtl_service_queue *parent_sq) +{ + struct throtl_grp *tg; + + while ((tg = throtl_rb_first(parent_sq))) { + struct throtl_service_queue *sq = &tg->service_queue; + struct bio *bio; + + throtl_dequeue_tg(tg); + + while ((bio = throtl_peek_queued(&sq->queued[READ]))) + tg_dispatch_one_bio(tg, bio_data_dir(bio)); + while ((bio = throtl_peek_queued(&sq->queued[WRITE]))) + tg_dispatch_one_bio(tg, bio_data_dir(bio)); + } +} + +/** + * blk_throtl_drain - drain throttled bios + * @q: request_queue to drain throttled bios for + * + * Dispatch all currently throttled bios on @q through ->make_request_fn(). + */ +void blk_throtl_drain(struct request_queue *q) + __releases(q->queue_lock) __acquires(q->queue_lock) +{ + struct throtl_data *td = q->td; + struct blkcg_gq *blkg; + struct cgroup_subsys_state *pos_css; + struct bio *bio; + int rw; + + queue_lockdep_assert_held(q); + rcu_read_lock(); + + /* + * Drain each tg while doing post-order walk on the blkg tree, so + * that all bios are propagated to td->service_queue. It'd be + * better to walk service_queue tree directly but blkg walk is + * easier. + */ + blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) + tg_drain_bios(&blkg_to_tg(blkg)->service_queue); + + /* finally, transfer bios from top-level tg's into the td */ + tg_drain_bios(&td->service_queue); + + rcu_read_unlock(); + spin_unlock_irq(q->queue_lock); + + /* all bios now should be in td->service_queue, issue them */ + for (rw = READ; rw <= WRITE; rw++) + while ((bio = throtl_pop_queued(&td->service_queue.queued[rw], + NULL))) + generic_make_request(bio); + + spin_lock_irq(q->queue_lock); +} + +int blk_throtl_init(struct request_queue *q) +{ + struct throtl_data *td; + int ret; + + td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node); + if (!td) + return -ENOMEM; + + INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn); + throtl_service_queue_init(&td->service_queue, NULL); + + q->td = td; + td->queue = q; + + /* activate policy */ + ret = blkcg_activate_policy(q, &blkcg_policy_throtl); + if (ret) + kfree(td); + return ret; +} + +void blk_throtl_exit(struct request_queue *q) +{ + BUG_ON(!q->td); + throtl_shutdown_wq(q); + blkcg_deactivate_policy(q, &blkcg_policy_throtl); + kfree(q->td); +} + +static int __init throtl_init(void) +{ + kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0); + if (!kthrotld_workqueue) + panic("Failed to create kthrotld\n"); + + return blkcg_policy_register(&blkcg_policy_throtl); +} + +module_init(throtl_init); |