/* * 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" /* 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 */ /* A workqueue to queue throttle related work */ static struct workqueue_struct *kthrotld_workqueue; static void throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay); struct throtl_rb_root { struct rb_root rb; struct rb_node *left; unsigned int count; unsigned long min_disptime; }; #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \ .count = 0, .min_disptime = 0} #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node) struct throtl_grp { /* List of throtl groups on the request queue*/ struct hlist_node tg_node; /* active throtl group service_tree member */ struct rb_node rb_node; /* * 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; struct blkio_group blkg; atomic_t ref; unsigned int flags; /* Two lists for READ and WRITE */ struct bio_list bio_lists[2]; /* Number of queued bios on READ and WRITE lists */ unsigned int nr_queued[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]; /* Some throttle limits got updated for the group */ bool limits_changed; }; 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 */ unsigned int nr_queued[2]; /* * number of total undestroyed groups */ unsigned int nr_undestroyed_grps; /* Work for dispatching throttled bios */ struct delayed_work throtl_work; atomic_t limits_changed; }; enum tg_state_flags { THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */ }; #define THROTL_TG_FNS(name) \ static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \ { \ (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \ } \ static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \ { \ (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \ } \ static inline int throtl_tg_##name(const struct throtl_grp *tg) \ { \ return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \ } 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(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 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_put_tg(struct throtl_grp *tg) { BUG_ON(atomic_read(&tg->ref) <= 0); if (!atomic_dec_and_test(&tg->ref)) return; kfree(tg); } static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td, struct cgroup *cgroup) { struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup); struct throtl_grp *tg = NULL; void *key = td; struct backing_dev_info *bdi = &td->queue->backing_dev_info; unsigned int major, minor; /* * TODO: Speed up blkiocg_lookup_group() by maintaining a radix * tree of blkg (instead of traversing through hash list all * the time. */ /* * 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)); /* Fill in device details for root group */ if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) { sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); tg->blkg.dev = MKDEV(major, minor); goto done; } if (tg) goto done; tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node); if (!tg) goto done; INIT_HLIST_NODE(&tg->tg_node); RB_CLEAR_NODE(&tg->rb_node); bio_list_init(&tg->bio_lists[0]); bio_list_init(&tg->bio_lists[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. */ atomic_set(&tg->ref, 1); /* Add group onto cgroup list */ sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td, MKDEV(major, minor), BLKIO_POLICY_THROTL); 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); hlist_add_head(&tg->tg_node, &td->tg_list); td->nr_undestroyed_grps++; done: return tg; } static struct throtl_grp * throtl_get_tg(struct throtl_data *td) { struct cgroup *cgroup; struct throtl_grp *tg = NULL; rcu_read_lock(); cgroup = task_cgroup(current, blkio_subsys_id); tg = throtl_find_alloc_tg(td, cgroup); if (!tg) tg = &td->root_tg; rcu_read_unlock(); return tg; } static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root) { /* Service tree is empty */ if (!root->count) return NULL; if (!root->left) root->left = rb_first(&root->rb); if (root->left) return rb_entry_tg(root->left); 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_rb_root *root) { if (root->left == n) root->left = NULL; rb_erase_init(n, &root->rb); --root->count; } static void update_min_dispatch_time(struct throtl_rb_root *st) { struct throtl_grp *tg; tg = throtl_rb_first(st); if (!tg) return; st->min_disptime = tg->disptime; } static void tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg) { struct rb_node **node = &st->rb.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) st->left = &tg->rb_node; rb_link_node(&tg->rb_node, parent, node); rb_insert_color(&tg->rb_node, &st->rb); } static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) { struct throtl_rb_root *st = &td->tg_service_tree; tg_service_tree_add(st, tg); throtl_mark_tg_on_rr(tg); st->count++; } static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) { if (!throtl_tg_on_rr(tg)) __throtl_enqueue_tg(td, tg); } static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) { throtl_rb_erase(&tg->rb_node, &td->tg_service_tree); throtl_clear_tg_on_rr(tg); } static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) { if (throtl_tg_on_rr(tg)) __throtl_dequeue_tg(td, tg); } static void throtl_schedule_next_dispatch(struct throtl_data *td) { struct throtl_rb_root *st = &td->tg_service_tree; /* * If there are more bios pending, schedule more work. */ if (!total_nr_queued(td)) return; BUG_ON(!st->count); update_min_dispatch_time(st); if (time_before_eq(st->min_disptime, jiffies)) throtl_schedule_delayed_work(td, 0); else throtl_schedule_delayed_work(td, (st->min_disptime - jiffies)); } static inline void throtl_start_new_slice(struct throtl_data *td, 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(td, tg, "[%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_data *td, 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_data *td, struct throtl_grp *tg, bool rw, unsigned long jiffy_end) { tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); throtl_log_tg(td, tg, "[%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_data *td, struct throtl_grp *tg, bool rw) { if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) return 0; return 1; } /* Trim the used slices and adjust slice start accordingly */ static inline void throtl_trim_slice(struct throtl_data *td, 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(td, 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(td, 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(td, tg, "[%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_data *td, 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 1; } /* 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_data *td, 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_size <= bytes_allowed) { if (wait) *wait = 0; return 1; } /* Calc approx time to dispatch */ extra_bytes = tg->bytes_disp[rw] + bio->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_data *td, 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->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw])); /* If tg->bps = -1, then BW is unlimited */ if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { if (wait) *wait = 0; return 1; } /* * 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(td, tg, rw)) throtl_start_new_slice(td, tg, rw); else { if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) throtl_extend_slice(td, tg, rw, jiffies + throtl_slice); } if (tg_with_in_bps_limit(td, tg, bio, &bps_wait) && tg_with_in_iops_limit(td, 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(td, tg, rw, jiffies + max_wait); return 0; } static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) { bool rw = bio_data_dir(bio); bool sync = bio->bi_rw & REQ_SYNC; /* Charge the bio to the group */ tg->bytes_disp[rw] += bio->bi_size; tg->io_disp[rw]++; /* * TODO: This will take blkg->stats_lock. Figure out a way * to avoid this cost. */ blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync); } static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg, struct bio *bio) { bool rw = bio_data_dir(bio); bio_list_add(&tg->bio_lists[rw], bio); /* Take a bio reference on tg */ throtl_ref_get_tg(tg); tg->nr_queued[rw]++; td->nr_queued[rw]++; throtl_enqueue_tg(td, tg); } static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg) { unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; struct bio *bio; if ((bio = bio_list_peek(&tg->bio_lists[READ]))) tg_may_dispatch(td, tg, bio, &read_wait); if ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) tg_may_dispatch(td, tg, bio, &write_wait); min_wait = min(read_wait, write_wait); disptime = jiffies + min_wait; /* Update dispatch time */ throtl_dequeue_tg(td, tg); tg->disptime = disptime; throtl_enqueue_tg(td, tg); } static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg, bool rw, struct bio_list *bl) { struct bio *bio; bio = bio_list_pop(&tg->bio_lists[rw]); tg->nr_queued[rw]--; /* Drop bio reference on tg */ throtl_put_tg(tg); BUG_ON(td->nr_queued[rw] <= 0); td->nr_queued[rw]--; throtl_charge_bio(tg, bio); bio_list_add(bl, bio); bio->bi_rw |= REQ_THROTTLED; throtl_trim_slice(td, tg, rw); } static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, struct bio_list *bl) { 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 = bio_list_peek(&tg->bio_lists[READ])) && tg_may_dispatch(td, tg, bio, NULL)) { tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); nr_reads++; if (nr_reads >= max_nr_reads) break; } while ((bio = bio_list_peek(&tg->bio_lists[WRITE])) && tg_may_dispatch(td, tg, bio, NULL)) { tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); nr_writes++; if (nr_writes >= max_nr_writes) break; } return nr_reads + nr_writes; } static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) { unsigned int nr_disp = 0; struct throtl_grp *tg; struct throtl_rb_root *st = &td->tg_service_tree; while (1) { tg = throtl_rb_first(st); if (!tg) break; if (time_before(jiffies, tg->disptime)) break; throtl_dequeue_tg(td, tg); nr_disp += throtl_dispatch_tg(td, tg, bl); if (tg->nr_queued[0] || tg->nr_queued[1]) { tg_update_disptime(td, tg); throtl_enqueue_tg(td, tg); } if (nr_disp >= throtl_quantum) break; } return nr_disp; } static void throtl_process_limit_change(struct throtl_data *td) { struct throtl_grp *tg; struct hlist_node *pos, *n; if (!atomic_read(&td->limits_changed)) return; throtl_log(td, "limit changed =%d", atomic_read(&td->limits_changed)); /* * Make sure updates from throtl_update_blkio_group_read_bps() group * of functions to tg->limits_changed are visible. We do not * want update td->limits_changed to be visible but update to * tg->limits_changed not being visible yet on this cpu. Hence * the read barrier. */ smp_rmb(); hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) { if (throtl_tg_on_rr(tg) && tg->limits_changed) { throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu" " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE], tg->iops[READ], tg->iops[WRITE]); tg_update_disptime(td, tg); tg->limits_changed = false; } } smp_mb__before_atomic_dec(); atomic_dec(&td->limits_changed); smp_mb__after_atomic_dec(); } /* Dispatch throttled bios. Should be called without queue lock held. */ static int throtl_dispatch(struct request_queue *q) { struct throtl_data *td = q->td; unsigned int nr_disp = 0; struct bio_list bio_list_on_stack; struct bio *bio; spin_lock_irq(q->queue_lock); throtl_process_limit_change(td); if (!total_nr_queued(td)) goto out; bio_list_init(&bio_list_on_stack); throtl_log(td, "dispatch nr_queued=%lu read=%u write=%u", total_nr_queued(td), td->nr_queued[READ], td->nr_queued[WRITE]); nr_disp = throtl_select_dispatch(td, &bio_list_on_stack); if (nr_disp) throtl_log(td, "bios disp=%u", nr_disp); throtl_schedule_next_dispatch(td); out: spin_unlock_irq(q->queue_lock); /* * If we dispatched some requests, unplug the queue to make sure * immediate dispatch */ if (nr_disp) { while((bio = bio_list_pop(&bio_list_on_stack))) generic_make_request(bio); blk_unplug(q); } return nr_disp; } void blk_throtl_work(struct work_struct *work) { struct throtl_data *td = container_of(work, struct throtl_data, throtl_work.work); struct request_queue *q = td->queue; throtl_dispatch(q); } /* Call with queue lock held */ static void throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay) { struct delayed_work *dwork = &td->throtl_work; if (total_nr_queued(td) > 0) { /* * We might have a work scheduled to be executed in future. * Cancel that and schedule a new one. */ __cancel_delayed_work(dwork); queue_delayed_work(kthrotld_workqueue, dwork, delay); throtl_log(td, "schedule work. delay=%lu jiffies=%lu", delay, jiffies); } } static void throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg) { /* Something wrong if we are trying to remove same group twice */ BUG_ON(hlist_unhashed(&tg->tg_node)); hlist_del_init(&tg->tg_node); /* * 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--; } static void throtl_release_tgs(struct throtl_data *td) { struct hlist_node *pos, *n; struct throtl_grp *tg; 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); } } static void throtl_td_free(struct throtl_data *td) { kfree(td); } /* * 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) { unsigned long flags; struct throtl_data *td = key; spin_lock_irqsave(td->queue->queue_lock, flags); throtl_destroy_tg(td, tg_of_blkg(blkg)); spin_unlock_irqrestore(td->queue->queue_lock, flags); } /* * 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 becuase * 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) { struct throtl_data *td = key; tg_of_blkg(blkg)->bps[READ] = read_bps; /* Make sure read_bps is updated before setting limits_changed */ smp_wmb(); tg_of_blkg(blkg)->limits_changed = true; /* Make sure tg->limits_changed is updated before td->limits_changed */ smp_mb__before_atomic_inc(); atomic_inc(&td->limits_changed); smp_mb__after_atomic_inc(); /* Schedule a work now to process the limit change */ throtl_schedule_delayed_work(td, 0); } static void throtl_update_blkio_group_write_bps(void *key, struct blkio_group *blkg, u64 write_bps) { struct throtl_data *td = key; tg_of_blkg(blkg)->bps[WRITE] = write_bps; smp_wmb(); tg_of_blkg(blkg)->limits_changed = true; smp_mb__before_atomic_inc(); atomic_inc(&td->limits_changed); smp_mb__after_atomic_inc(); throtl_schedule_delayed_work(td, 0); } static void throtl_update_blkio_group_read_iops(void *key, struct blkio_group *blkg, unsigned int read_iops) { struct throtl_data *td = key; tg_of_blkg(blkg)->iops[READ] = read_iops; smp_wmb(); tg_of_blkg(blkg)->limits_changed = true; smp_mb__before_atomic_inc(); atomic_inc(&td->limits_changed); smp_mb__after_atomic_inc(); throtl_schedule_delayed_work(td, 0); } static void throtl_update_blkio_group_write_iops(void *key, struct blkio_group *blkg, unsigned int write_iops) { struct throtl_data *td = key; tg_of_blkg(blkg)->iops[WRITE] = write_iops; smp_wmb(); tg_of_blkg(blkg)->limits_changed = true; smp_mb__before_atomic_inc(); atomic_inc(&td->limits_changed); smp_mb__after_atomic_inc(); throtl_schedule_delayed_work(td, 0); } void throtl_shutdown_timer_wq(struct request_queue *q) { struct throtl_data *td = q->td; 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, }; int blk_throtl_bio(struct request_queue *q, struct bio **biop) { struct throtl_data *td = q->td; struct throtl_grp *tg; struct bio *bio = *biop; bool rw = bio_data_dir(bio), update_disptime = true; if (bio->bi_rw & REQ_THROTTLED) { bio->bi_rw &= ~REQ_THROTTLED; return 0; } spin_lock_irq(q->queue_lock); tg = throtl_get_tg(td); if (tg->nr_queued[rw]) { /* * There is already another bio queued in same dir. No * need to update dispatch time. * Still update the disptime if rate limits on this group * were changed. */ if (!tg->limits_changed) update_disptime = false; else tg->limits_changed = false; goto queue_bio; } /* Bio is with-in rate limit of group */ if (tg_may_dispatch(td, tg, bio, NULL)) { throtl_charge_bio(tg, bio); goto out; } queue_bio: throtl_log_tg(td, tg, "[%c] bio. bdisp=%u sz=%u bps=%llu" " iodisp=%u iops=%u queued=%d/%d", rw == READ ? 'R' : 'W', tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], tg->io_disp[rw], tg->iops[rw], tg->nr_queued[READ], tg->nr_queued[WRITE]); throtl_add_bio_tg(q->td, tg, bio); *biop = NULL; if (update_disptime) { tg_update_disptime(td, tg); throtl_schedule_next_dispatch(td); } out: spin_unlock_irq(q->queue_lock); return 0; } int blk_throtl_init(struct request_queue *q) { struct throtl_data *td; struct throtl_grp *tg; 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; atomic_set(&td->limits_changed, 0); /* Init root group */ tg = &td->root_tg; INIT_HLIST_NODE(&tg->tg_node); RB_CLEAR_NODE(&tg->rb_node); bio_list_init(&tg->bio_lists[0]); bio_list_init(&tg->bio_lists[1]); /* Practically unlimited BW */ tg->bps[0] = tg->bps[1] = -1; tg->iops[0] = tg->iops[1] = -1; /* * Set root group reference to 2. One reference will be dropped when * all groups on tg_list are being deleted during queue exit. Other * reference will remain there as we don't want to delete this group * as it is statically allocated and gets destroyed when throtl_data * goes away. */ atomic_set(&tg->ref, 2); hlist_add_head(&tg->tg_node, &td->tg_list); td->nr_undestroyed_grps++; INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work); rcu_read_lock(); blkiocg_add_blkio_group(&blkio_root_cgroup, &tg->blkg, (void *)td, 0, BLKIO_POLICY_THROTL); rcu_read_unlock(); /* Attach throtl data to request queue */ td->queue = q; q->td = td; return 0; } void blk_throtl_exit(struct request_queue *q) { struct throtl_data *td = q->td; bool wait = false; BUG_ON(!td); throtl_shutdown_timer_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. */ throtl_shutdown_timer_wq(q); throtl_td_free(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"); blkio_policy_register(&blkio_policy_throtl); return 0; } module_init(throtl_init);