diff options
Diffstat (limited to 'block/blk-throttle.c')
| -rw-r--r-- | block/blk-throttle.c | 1911 |
1 files changed, 1911 insertions, 0 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c new file mode 100644 index 000000000..ffc3b7006 --- /dev/null +++ b/block/blk-throttle.c @@ -0,0 +1,1911 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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.h" +#include "blk-cgroup-rwstat.h" +#include "blk-throttle.h" + +/* Max dispatch from a group in 1 round */ +#define THROTL_GRP_QUANTUM 8 + +/* Total max dispatch from all groups in one round */ +#define THROTL_QUANTUM 32 + +/* Throttling is performed over a slice and after that slice is renewed */ +#define DFL_THROTL_SLICE (HZ / 10) + +/* A workqueue to queue throttle related work */ +static struct workqueue_struct *kthrotld_workqueue; + +#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_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]; + + /* Work for dispatching throttled bios */ + struct work_struct dispatch_work; +}; + +static void throtl_pending_timer_fn(struct timer_list *t); + +static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg) +{ + return pd_to_blkg(&tg->pd); +} + +/** + * 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 embedded 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); +} + +static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw) +{ + struct blkcg_gq *blkg = tg_to_blkg(tg); + + if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent) + return U64_MAX; + + return tg->bps[rw]; +} + +static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw) +{ + struct blkcg_gq *blkg = tg_to_blkg(tg); + + if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent) + return UINT_MAX; + + return tg->iops[rw]; +} + +/** + * 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". + */ +#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 (likely(!blk_trace_note_message_enabled(__td->queue))) \ + break; \ + if ((__tg)) { \ + blk_add_cgroup_trace_msg(__td->queue, \ + &tg_to_blkg(__tg)->blkcg->css, "throtl " fmt, ##args);\ + } else { \ + blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \ + } \ +} while (0) + +static inline unsigned int throtl_bio_data_size(struct bio *bio) +{ + /* assume it's one sector */ + if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) + return 512; + return bio->bi_iter.bi_size; +} + +static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg) +{ + INIT_LIST_HEAD(&qn->node); + bio_list_init(&qn->bios_bps); + bio_list_init(&qn->bios_iops); + 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 + * @sq: the service_queue @qn belongs to + * + * Add @bio to @qn and put @qn on @sq->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 throtl_service_queue *sq) +{ + bool rw = bio_data_dir(bio); + + /* + * Split bios have already been throttled by bps, so they are + * directly queued into the iops path. + */ + if (bio_flagged(bio, BIO_TG_BPS_THROTTLED) || + bio_flagged(bio, BIO_BPS_THROTTLED)) { + bio_list_add(&qn->bios_iops, bio); + sq->nr_queued_iops[rw]++; + } else { + bio_list_add(&qn->bios_bps, bio); + sq->nr_queued_bps[rw]++; + } + + if (list_empty(&qn->node)) { + list_add_tail(&qn->node, &sq->queued[rw]); + blkg_get(tg_to_blkg(qn->tg)); + } +} + +/** + * throtl_peek_queued - peek the first bio on a qnode list + * @queued: the qnode list to peek + * + * Always take a bio from the head of the iops queue first. If the queue is + * empty, we then take it from the bps queue to maintain the overall idea of + * fetching bios from the head. + */ +static struct bio *throtl_peek_queued(struct list_head *queued) +{ + struct throtl_qnode *qn; + struct bio *bio; + + if (list_empty(queued)) + return NULL; + + qn = list_first_entry(queued, struct throtl_qnode, node); + bio = bio_list_peek(&qn->bios_iops); + if (!bio) + bio = bio_list_peek(&qn->bios_bps); + WARN_ON_ONCE(!bio); + return bio; +} + +/** + * throtl_pop_queued - pop the first bio form a qnode list + * @sq: the service_queue to pop a bio from + * @tg_to_put: optional out argument for throtl_grp to put + * @rw: read/write + * + * Pop the first bio from the qnode list @sq->queued. Note that we firstly + * focus on the iops list because bios are ultimately dispatched from it. + * After popping, the first qnode is removed from @sq->queued if empty or moved + * to the end of @sq->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 throtl_service_queue *sq, + struct throtl_grp **tg_to_put, bool rw) +{ + struct list_head *queued = &sq->queued[rw]; + struct throtl_qnode *qn; + struct bio *bio; + + if (list_empty(queued)) + return NULL; + + qn = list_first_entry(queued, struct throtl_qnode, node); + bio = bio_list_pop(&qn->bios_iops); + if (bio) { + sq->nr_queued_iops[rw]--; + } else { + bio = bio_list_pop(&qn->bios_bps); + if (bio) + sq->nr_queued_bps[rw]--; + } + WARN_ON_ONCE(!bio); + + if (bio_list_empty(&qn->bios_bps) && bio_list_empty(&qn->bios_iops)) { + 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) +{ + INIT_LIST_HEAD(&sq->queued[READ]); + INIT_LIST_HEAD(&sq->queued[WRITE]); + sq->pending_tree = RB_ROOT_CACHED; + timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0); +} + +static struct blkg_policy_data *throtl_pd_alloc(struct gendisk *disk, + struct blkcg *blkcg, gfp_t gfp) +{ + struct throtl_grp *tg; + int rw; + + tg = kzalloc_node(sizeof(*tg), gfp, disk->node_id); + if (!tg) + return NULL; + + if (blkg_rwstat_init(&tg->stat_bytes, gfp)) + goto err_free_tg; + + if (blkg_rwstat_init(&tg->stat_ios, gfp)) + goto err_exit_stat_bytes; + + throtl_service_queue_init(&tg->service_queue); + + 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->bps[READ] = U64_MAX; + tg->bps[WRITE] = U64_MAX; + tg->iops[READ] = UINT_MAX; + tg->iops[WRITE] = UINT_MAX; + + return &tg->pd; + +err_exit_stat_bytes: + blkg_rwstat_exit(&tg->stat_bytes); +err_free_tg: + kfree(tg); + return NULL; +} + +static void throtl_pd_init(struct blkg_policy_data *pd) +{ + struct throtl_grp *tg = pd_to_tg(pd); + struct blkcg_gq *blkg = tg_to_blkg(tg); + struct throtl_data *td = blkg->q->td; + struct throtl_service_queue *sq = &tg->service_queue; + + /* + * 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 a parent group, summary bps of + * parent group and its subtree groups 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. + */ + sq->parent_sq = &td->service_queue; + if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent) + sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue; + tg->td = td; +} + +/* + * 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_iops[rw] = + (parent_tg && parent_tg->has_rules_iops[rw]) || + tg_iops_limit(tg, rw) != UINT_MAX; + tg->has_rules_bps[rw] = + (parent_tg && parent_tg->has_rules_bps[rw]) || + tg_bps_limit(tg, rw) != U64_MAX; + } +} + +static void throtl_pd_online(struct blkg_policy_data *pd) +{ + struct throtl_grp *tg = pd_to_tg(pd); + /* + * 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(tg); +} + +static void tg_release(struct rcu_head *rcu) +{ + struct blkg_policy_data *pd = + container_of(rcu, struct blkg_policy_data, rcu_head); + struct throtl_grp *tg = pd_to_tg(pd); + + blkg_rwstat_exit(&tg->stat_bytes); + blkg_rwstat_exit(&tg->stat_ios); + kfree(tg); +} + +static void throtl_pd_free(struct blkg_policy_data *pd) +{ + struct throtl_grp *tg = pd_to_tg(pd); + + timer_delete_sync(&tg->service_queue.pending_timer); + call_rcu(&pd->rcu_head, tg_release); +} + +static struct throtl_grp * +throtl_rb_first(struct throtl_service_queue *parent_sq) +{ + struct rb_node *n; + + n = rb_first_cached(&parent_sq->pending_tree); + WARN_ON_ONCE(!n); + if (!n) + return NULL; + return rb_entry_tg(n); +} + +static void throtl_rb_erase(struct rb_node *n, + struct throtl_service_queue *parent_sq) +{ + rb_erase_cached(n, &parent_sq->pending_tree); + RB_CLEAR_NODE(n); +} + +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_root.rb_node; + struct rb_node *parent = NULL; + struct throtl_grp *__tg; + unsigned long key = tg->disptime; + bool leftmost = true; + + 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; + leftmost = false; + } + } + + rb_link_node(&tg->rb_node, parent, node); + rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree, + leftmost); +} + +static void throtl_enqueue_tg(struct throtl_grp *tg) +{ + if (!(tg->flags & THROTL_TG_PENDING)) { + tg_service_queue_add(tg); + tg->flags |= THROTL_TG_PENDING; + tg->service_queue.parent_sq->nr_pending++; + } +} + +static void throtl_dequeue_tg(struct throtl_grp *tg) +{ + if (tg->flags & THROTL_TG_PENDING) { + struct throtl_service_queue *parent_sq = + tg->service_queue.parent_sq; + + throtl_rb_erase(&tg->rb_node, parent_sq); + --parent_sq->nr_pending; + tg->flags &= ~THROTL_TG_PENDING; + } +} + +/* Call with queue lock held */ +static void throtl_schedule_pending_timer(struct throtl_service_queue *sq, + unsigned long expires) +{ + unsigned long max_expire = jiffies + 8 * DFL_THROTL_SLICE; + + /* + * Since we are adjusting the throttle limit dynamically, the sleep + * time calculated according to previous limit might be invalid. It's + * possible the cgroup sleep time is very long and no other cgroups + * have IO running so notify the limit changes. Make sure the cgroup + * doesn't sleep too long to avoid the missed notification. + */ + if (time_after(expires, max_expire)) + expires = max_expire; + 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(start, tg->slice_start[rw])) + tg->slice_start[rw] = start; + + tg->slice_end[rw] = jiffies + DFL_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, + bool clear) +{ + if (clear) { + tg->bytes_disp[rw] = 0; + tg->io_disp[rw] = 0; + } + tg->slice_start[rw] = jiffies; + tg->slice_end[rw] = jiffies + DFL_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, DFL_THROTL_SLICE); +} + +static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw, + unsigned long jiffy_end) +{ + if (!time_before(tg->slice_end[rw], jiffy_end)) + return; + + throtl_set_slice_end(tg, rw, jiffy_end); + 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 true; +} + +static unsigned int sq_queued(struct throtl_service_queue *sq, int type) +{ + return sq->nr_queued_bps[type] + sq->nr_queued_iops[type]; +} + +static unsigned int calculate_io_allowed(u32 iops_limit, + unsigned long jiffy_elapsed) +{ + unsigned int io_allowed; + u64 tmp; + + /* + * jiffy_elapsed 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)iops_limit * jiffy_elapsed; + do_div(tmp, HZ); + + if (tmp > UINT_MAX) + io_allowed = UINT_MAX; + else + io_allowed = tmp; + + return io_allowed; +} + +static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed) +{ + /* + * Can result be wider than 64 bits? + * We check against 62, not 64, due to ilog2 truncation. + */ + if (ilog2(bps_limit) + ilog2(jiffy_elapsed) - ilog2(HZ) > 62) + return U64_MAX; + return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ); +} + +static long long throtl_trim_bps(struct throtl_grp *tg, bool rw, + unsigned long time_elapsed) +{ + u64 bps_limit = tg_bps_limit(tg, rw); + long long bytes_trim; + + if (bps_limit == U64_MAX) + return 0; + + /* Need to consider the case of bytes_allowed overflow. */ + bytes_trim = calculate_bytes_allowed(bps_limit, time_elapsed); + if (bytes_trim <= 0 || tg->bytes_disp[rw] < bytes_trim) { + bytes_trim = tg->bytes_disp[rw]; + tg->bytes_disp[rw] = 0; + } else { + tg->bytes_disp[rw] -= bytes_trim; + } + + return bytes_trim; +} + +static int throtl_trim_iops(struct throtl_grp *tg, bool rw, + unsigned long time_elapsed) +{ + u32 iops_limit = tg_iops_limit(tg, rw); + int io_trim; + + if (iops_limit == UINT_MAX) + return 0; + + /* Need to consider the case of io_allowed overflow. */ + io_trim = calculate_io_allowed(iops_limit, time_elapsed); + if (io_trim <= 0 || tg->io_disp[rw] < io_trim) { + io_trim = tg->io_disp[rw]; + tg->io_disp[rw] = 0; + } else { + tg->io_disp[rw] -= io_trim; + } + + return io_trim; +} + +/* Trim the used slices and adjust slice start accordingly */ +static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw) +{ + unsigned long time_elapsed; + long long bytes_trim; + int io_trim; + + 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 dispatched + * 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 + DFL_THROTL_SLICE); + + time_elapsed = rounddown(jiffies - tg->slice_start[rw], + DFL_THROTL_SLICE); + /* Don't trim slice until at least 2 slices are used */ + if (time_elapsed < DFL_THROTL_SLICE * 2) + return; + + /* + * The bio submission time may be a few jiffies more than the expected + * waiting time, due to 'extra_bytes' can't be divided in + * tg_within_bps_limit(), and also due to timer wakeup delay. In this + * case, adjust slice_start will discard the extra wait time, causing + * lower rate than expected. Therefore, other than the above rounddown, + * one extra slice is preserved for deviation. + */ + time_elapsed -= DFL_THROTL_SLICE; + bytes_trim = throtl_trim_bps(tg, rw, time_elapsed); + io_trim = throtl_trim_iops(tg, rw, time_elapsed); + if (!bytes_trim && !io_trim) + return; + + tg->slice_start[rw] += time_elapsed; + + throtl_log(&tg->service_queue, + "[%c] trim slice nr=%lu bytes=%lld io=%d start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', time_elapsed / DFL_THROTL_SLICE, + bytes_trim, io_trim, tg->slice_start[rw], tg->slice_end[rw], + jiffies); +} + +static void __tg_update_carryover(struct throtl_grp *tg, bool rw, + long long *bytes, int *ios) +{ + unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw]; + u64 bps_limit = tg_bps_limit(tg, rw); + u32 iops_limit = tg_iops_limit(tg, rw); + long long bytes_allowed; + int io_allowed; + + /* + * If the queue is empty, carryover handling is not needed. In such cases, + * tg->[bytes/io]_disp should be reset to 0 to avoid impacting the dispatch + * of subsequent bios. The same handling applies when the previous BPS/IOPS + * limit was set to max. + */ + if (sq_queued(&tg->service_queue, rw) == 0) { + tg->bytes_disp[rw] = 0; + tg->io_disp[rw] = 0; + return; + } + + /* + * If config is updated while bios are still throttled, calculate and + * accumulate how many bytes/ios are waited across changes. And use the + * calculated carryover (@bytes/@ios) to update [bytes/io]_disp, which + * will be used to calculate new wait time under new configuration. + * And we need to consider the case of bytes/io_allowed overflow. + */ + if (bps_limit != U64_MAX) { + bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed); + if (bytes_allowed > 0) + *bytes = bytes_allowed - tg->bytes_disp[rw]; + } + if (iops_limit != UINT_MAX) { + io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed); + if (io_allowed > 0) + *ios = io_allowed - tg->io_disp[rw]; + } + + tg->bytes_disp[rw] = -*bytes; + tg->io_disp[rw] = -*ios; +} + +static void tg_update_carryover(struct throtl_grp *tg) +{ + long long bytes[2] = {0}; + int ios[2] = {0}; + + __tg_update_carryover(tg, READ, &bytes[READ], &ios[READ]); + __tg_update_carryover(tg, WRITE, &bytes[WRITE], &ios[WRITE]); + + /* see comments in struct throtl_grp for meaning of carryover. */ + throtl_log(&tg->service_queue, "%s: %lld %lld %d %d\n", __func__, + bytes[READ], bytes[WRITE], ios[READ], ios[WRITE]); +} + +static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio, + u32 iops_limit) +{ + bool rw = bio_data_dir(bio); + int io_allowed; + unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; + + jiffy_elapsed = jiffies - tg->slice_start[rw]; + + /* Round up to the next throttle slice, wait time must be nonzero */ + jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, DFL_THROTL_SLICE); + io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd); + if (io_allowed > 0 && tg->io_disp[rw] + 1 <= io_allowed) + return 0; + + /* Calc approx time to dispatch */ + jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed; + + /* make sure at least one io can be dispatched after waiting */ + jiffy_wait = max(jiffy_wait, HZ / iops_limit + 1); + return jiffy_wait; +} + +static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio, + u64 bps_limit) +{ + bool rw = bio_data_dir(bio); + long long bytes_allowed; + u64 extra_bytes; + unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; + unsigned int bio_size = throtl_bio_data_size(bio); + + jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; + + /* Slice has just started. Consider one slice interval */ + if (!jiffy_elapsed) + jiffy_elapsed_rnd = DFL_THROTL_SLICE; + + jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, DFL_THROTL_SLICE); + bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd); + /* Need to consider the case of bytes_allowed overflow. */ + if ((bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed) + || bytes_allowed < 0) + return 0; + + /* Calc approx time to dispatch */ + extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed; + jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit); + + 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); + return jiffy_wait; +} + +static void throtl_charge_bps_bio(struct throtl_grp *tg, struct bio *bio) +{ + unsigned int bio_size = throtl_bio_data_size(bio); + + /* Charge the bio to the group */ + if (!bio_flagged(bio, BIO_BPS_THROTTLED) && + !bio_flagged(bio, BIO_TG_BPS_THROTTLED)) { + bio_set_flag(bio, BIO_TG_BPS_THROTTLED); + tg->bytes_disp[bio_data_dir(bio)] += bio_size; + } +} + +static void throtl_charge_iops_bio(struct throtl_grp *tg, struct bio *bio) +{ + bio_clear_flag(bio, BIO_TG_BPS_THROTTLED); + tg->io_disp[bio_data_dir(bio)]++; +} + +/* + * 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. New + * slice is started only for empty throttle group. If there is queued bio, that + * means there should be an active slice and it should be extended instead. + */ +static void tg_update_slice(struct throtl_grp *tg, bool rw) +{ + if (throtl_slice_used(tg, rw) && + sq_queued(&tg->service_queue, rw) == 0) + throtl_start_new_slice(tg, rw, true); + else + throtl_extend_slice(tg, rw, jiffies + DFL_THROTL_SLICE); +} + +static unsigned long tg_dispatch_bps_time(struct throtl_grp *tg, struct bio *bio) +{ + bool rw = bio_data_dir(bio); + u64 bps_limit = tg_bps_limit(tg, rw); + unsigned long bps_wait; + + /* no need to throttle if this bio's bytes have been accounted */ + if (bps_limit == U64_MAX || tg->flags & THROTL_TG_CANCELING || + bio_flagged(bio, BIO_BPS_THROTTLED) || + bio_flagged(bio, BIO_TG_BPS_THROTTLED)) + return 0; + + tg_update_slice(tg, rw); + bps_wait = tg_within_bps_limit(tg, bio, bps_limit); + throtl_extend_slice(tg, rw, jiffies + bps_wait); + + return bps_wait; +} + +static unsigned long tg_dispatch_iops_time(struct throtl_grp *tg, struct bio *bio) +{ + bool rw = bio_data_dir(bio); + u32 iops_limit = tg_iops_limit(tg, rw); + unsigned long iops_wait; + + if (iops_limit == UINT_MAX || tg->flags & THROTL_TG_CANCELING) + return 0; + + tg_update_slice(tg, rw); + iops_wait = tg_within_iops_limit(tg, bio, iops_limit); + throtl_extend_slice(tg, rw, jiffies + iops_wait); + + return iops_wait; +} + +/* + * Returns approx number of jiffies to wait before this bio is with-in IO rate + * and can be moved to other queue or dispatched. + */ +static unsigned long tg_dispatch_time(struct throtl_grp *tg, struct bio *bio) +{ + bool rw = bio_data_dir(bio); + unsigned long wait; + + /* + * 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(sq_queued(&tg->service_queue, rw) && + bio != throtl_peek_queued(&tg->service_queue.queued[rw])); + + wait = tg_dispatch_bps_time(tg, bio); + if (wait != 0) + return wait; + + /* + * Charge bps here because @bio will be directly placed into the + * iops queue afterward. + */ + throtl_charge_bps_bio(tg, bio); + + return tg_dispatch_iops_time(tg, bio); +} + +/** + * 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 + * cleared on the next tg_update_disptime(). + */ + if (sq_queued(sq, rw) == 0) + tg->flags |= THROTL_TG_WAS_EMPTY; + + throtl_qnode_add_bio(bio, qn, sq); + + /* + * Since we have split the queues, when the iops queue is + * previously empty and a new @bio is added into the first @qn, + * we also need to update the @tg->disptime. + */ + if (bio_flagged(bio, BIO_BPS_THROTTLED) && + bio == throtl_peek_queued(&sq->queued[rw])) + tg->flags |= THROTL_TG_IOPS_WAS_EMPTY; + + 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, disptime; + struct bio *bio; + + bio = throtl_peek_queued(&sq->queued[READ]); + if (bio) + read_wait = tg_dispatch_time(tg, bio); + + bio = throtl_peek_queued(&sq->queued[WRITE]); + if (bio) + write_wait = tg_dispatch_time(tg, bio); + + min_wait = min(read_wait, write_wait); + disptime = jiffies + min_wait; + + /* Update dispatch time */ + throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq); + tg->disptime = disptime; + tg_service_queue_add(tg); + + /* see throtl_add_bio_tg() */ + tg->flags &= ~THROTL_TG_WAS_EMPTY; + tg->flags &= ~THROTL_TG_IOPS_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, &tg_to_put, rw); + + throtl_charge_iops_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 { + bio_set_flag(bio, BIO_BPS_THROTTLED); + throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw], + parent_sq); + 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_dispatch_time(tg, bio) == 0) { + + tg_dispatch_one_bio(tg, READ); + nr_reads++; + + if (nr_reads >= max_nr_reads) + break; + } + + while ((bio = throtl_peek_queued(&sq->queued[WRITE])) && + tg_dispatch_time(tg, bio) == 0) { + + tg_dispatch_one_bio(tg, WRITE); + 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; + struct throtl_service_queue *sq; + + if (!parent_sq->nr_pending) + break; + + tg = throtl_rb_first(parent_sq); + if (!tg) + break; + + if (time_before(jiffies, tg->disptime)) + break; + + nr_disp += throtl_dispatch_tg(tg); + + sq = &tg->service_queue; + if (sq_queued(sq, READ) || sq_queued(sq, WRITE)) + tg_update_disptime(tg); + else + throtl_dequeue_tg(tg); + + if (nr_disp >= THROTL_QUANTUM) + break; + } + + return nr_disp; +} + +/** + * throtl_pending_timer_fn - timer function for service_queue->pending_timer + * @t: the pending_timer member of 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(struct timer_list *t) +{ + struct throtl_service_queue *sq = timer_container_of(sq, t, + pending_timer); + struct throtl_grp *tg = sq_to_tg(sq); + struct throtl_data *td = sq_to_td(sq); + struct throtl_service_queue *parent_sq; + struct request_queue *q; + bool dispatched; + int ret; + + /* throtl_data may be gone, so figure out request queue by blkg */ + if (tg) + q = tg->pd.blkg->q; + else + q = td->queue; + + spin_lock_irq(&q->queue_lock); + + if (!q->root_blkg) + goto out_unlock; + +again: + parent_sq = sq->parent_sq; + dispatched = false; + + while (true) { + unsigned int __maybe_unused bio_cnt_r = sq_queued(sq, READ); + unsigned int __maybe_unused bio_cnt_w = sq_queued(sq, WRITE); + + throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u", + bio_cnt_r + bio_cnt_w, bio_cnt_r, bio_cnt_w); + + 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->flags & THROTL_TG_IOPS_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 issuing */ + 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 bios reach the bio_lists[] + * of throtl_data->service_queue. Those bios 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, NULL, rw))) + 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))) + submit_bio_noacct_nocheck(bio, false); + blk_finish_plug(&plug); + } +} + +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 == U64_MAX) + 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 == UINT_MAX) + 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 void tg_conf_updated(struct throtl_grp *tg, bool global) +{ + struct throtl_service_queue *sq = &tg->service_queue; + struct cgroup_subsys_state *pos_css; + struct blkcg_gq *blkg; + + throtl_log(&tg->service_queue, + "limit change rbps=%llu wbps=%llu riops=%u wiops=%u", + tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE), + tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE)); + + rcu_read_lock(); + /* + * 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, + global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) { + struct throtl_grp *this_tg = blkg_to_tg(blkg); + + tg_update_has_rules(this_tg); + /* ignore root/second level */ + if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent || + !blkg->parent->parent) + continue; + } + rcu_read_unlock(); + + /* + * 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, READ, false); + throtl_start_new_slice(tg, WRITE, false); + + if (tg->flags & THROTL_TG_PENDING) { + tg_update_disptime(tg); + throtl_schedule_next_dispatch(sq->parent_sq, true); + } +} + +static int blk_throtl_init(struct gendisk *disk) +{ + struct request_queue *q = disk->queue; + struct throtl_data *td; + unsigned int memflags; + 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); + + memflags = blk_mq_freeze_queue(disk->queue); + blk_mq_quiesce_queue(disk->queue); + + q->td = td; + td->queue = q; + + /* activate policy, blk_throtl_activated() will return true */ + ret = blkcg_activate_policy(disk, &blkcg_policy_throtl); + if (ret) { + q->td = NULL; + kfree(td); + } + + blk_mq_unquiesce_queue(disk->queue); + blk_mq_unfreeze_queue(disk->queue, memflags); + + return ret; +} + + +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; + int ret; + u64 v; + + blkg_conf_init(&ctx, buf); + + ret = blkg_conf_open_bdev(&ctx); + if (ret) + return ret; + + if (!blk_throtl_activated(ctx.bdev->bd_queue)) { + ret = blk_throtl_init(ctx.bdev->bd_disk); + if (ret) + goto close_bdev; + } + + ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx); + if (ret) + goto close_bdev; + + ret = -EINVAL; + if (sscanf(ctx.body, "%llu", &v) != 1) + goto unprep; + if (!v) + v = U64_MAX; + + tg = blkg_to_tg(ctx.blkg); + tg_update_carryover(tg); + + if (is_u64) + *(u64 *)((void *)tg + of_cft(of)->private) = v; + else + *(unsigned int *)((void *)tg + of_cft(of)->private) = v; + + tg_conf_updated(tg, false); + ret = 0; + +unprep: + blkg_conf_unprep(&ctx); + +close_bdev: + blkg_conf_close_bdev(&ctx); + return ret ?: 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 int tg_print_rwstat(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), + blkg_prfill_rwstat, &blkcg_policy_throtl, + seq_cft(sf)->private, true); + return 0; +} + +static u64 tg_prfill_rwstat_recursive(struct seq_file *sf, + struct blkg_policy_data *pd, int off) +{ + struct blkg_rwstat_sample sum; + + blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_throtl, off, + &sum); + return __blkg_prfill_rwstat(sf, pd, &sum); +} + +static int tg_print_rwstat_recursive(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), + tg_prfill_rwstat_recursive, &blkcg_policy_throtl, + seq_cft(sf)->private, true); + return 0; +} + +static struct cftype throtl_legacy_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 throtl_grp, stat_bytes), + .seq_show = tg_print_rwstat, + }, + { + .name = "throttle.io_service_bytes_recursive", + .private = offsetof(struct throtl_grp, stat_bytes), + .seq_show = tg_print_rwstat_recursive, + }, + { + .name = "throttle.io_serviced", + .private = offsetof(struct throtl_grp, stat_ios), + .seq_show = tg_print_rwstat, + }, + { + .name = "throttle.io_serviced_recursive", + .private = offsetof(struct throtl_grp, stat_ios), + .seq_show = tg_print_rwstat_recursive, + }, + { } /* terminate */ +}; + +static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd, + int off) +{ + struct throtl_grp *tg = pd_to_tg(pd); + const char *dname = blkg_dev_name(pd->blkg); + u64 bps_dft; + unsigned int iops_dft; + + if (!dname) + return 0; + + bps_dft = U64_MAX; + iops_dft = UINT_MAX; + + if (tg->bps[READ] == bps_dft && + tg->bps[WRITE] == bps_dft && + tg->iops[READ] == iops_dft && + tg->iops[WRITE] == iops_dft) + return 0; + + seq_printf(sf, "%s", dname); + if (tg->bps[READ] == U64_MAX) + seq_printf(sf, " rbps=max"); + else + seq_printf(sf, " rbps=%llu", tg->bps[READ]); + + if (tg->bps[WRITE] == U64_MAX) + seq_printf(sf, " wbps=max"); + else + seq_printf(sf, " wbps=%llu", tg->bps[WRITE]); + + if (tg->iops[READ] == UINT_MAX) + seq_printf(sf, " riops=max"); + else + seq_printf(sf, " riops=%u", tg->iops[READ]); + + if (tg->iops[WRITE] == UINT_MAX) + seq_printf(sf, " wiops=max"); + else + seq_printf(sf, " wiops=%u", tg->iops[WRITE]); + + seq_printf(sf, "\n"); + return 0; +} + +static int tg_print_limit(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit, + &blkcg_policy_throtl, seq_cft(sf)->private, false); + return 0; +} + +static ssize_t tg_set_limit(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) +{ + struct blkcg *blkcg = css_to_blkcg(of_css(of)); + struct blkg_conf_ctx ctx; + struct throtl_grp *tg; + u64 v[4]; + int ret; + + blkg_conf_init(&ctx, buf); + + ret = blkg_conf_open_bdev(&ctx); + if (ret) + return ret; + + if (!blk_throtl_activated(ctx.bdev->bd_queue)) { + ret = blk_throtl_init(ctx.bdev->bd_disk); + if (ret) + goto close_bdev; + } + + ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx); + if (ret) + goto close_bdev; + + tg = blkg_to_tg(ctx.blkg); + tg_update_carryover(tg); + + v[0] = tg->bps[READ]; + v[1] = tg->bps[WRITE]; + v[2] = tg->iops[READ]; + v[3] = tg->iops[WRITE]; + + while (true) { + char tok[27]; /* wiops=18446744073709551616 */ + char *p; + u64 val = U64_MAX; + int len; + + if (sscanf(ctx.body, "%26s%n", tok, &len) != 1) + break; + if (tok[0] == '\0') + break; + ctx.body += len; + + ret = -EINVAL; + p = tok; + strsep(&p, "="); + if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max"))) + goto unprep; + + ret = -ERANGE; + if (!val) + goto unprep; + + ret = -EINVAL; + if (!strcmp(tok, "rbps")) + v[0] = val; + else if (!strcmp(tok, "wbps")) + v[1] = val; + else if (!strcmp(tok, "riops")) + v[2] = min_t(u64, val, UINT_MAX); + else if (!strcmp(tok, "wiops")) + v[3] = min_t(u64, val, UINT_MAX); + else + goto unprep; + } + + tg->bps[READ] = v[0]; + tg->bps[WRITE] = v[1]; + tg->iops[READ] = v[2]; + tg->iops[WRITE] = v[3]; + + tg_conf_updated(tg, false); + ret = 0; +unprep: + blkg_conf_unprep(&ctx); +close_bdev: + blkg_conf_close_bdev(&ctx); + return ret ?: nbytes; +} + +static struct cftype throtl_files[] = { + { + .name = "max", + .flags = CFTYPE_NOT_ON_ROOT, + .seq_show = tg_print_limit, + .write = tg_set_limit, + }, + { } /* terminate */ +}; + +static void throtl_shutdown_wq(struct request_queue *q) +{ + struct throtl_data *td = q->td; + + cancel_work_sync(&td->dispatch_work); +} + +static void tg_flush_bios(struct throtl_grp *tg) +{ + struct throtl_service_queue *sq = &tg->service_queue; + + if (tg->flags & THROTL_TG_CANCELING) + return; + /* + * Set the flag to make sure throtl_pending_timer_fn() won't + * stop until all throttled bios are dispatched. + */ + tg->flags |= THROTL_TG_CANCELING; + + /* + * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup + * will be inserted to service queue without THROTL_TG_PENDING + * set in tg_update_disptime below. Then IO dispatched from + * child in tg_dispatch_one_bio will trigger double insertion + * and corrupt the tree. + */ + if (!(tg->flags & THROTL_TG_PENDING)) + return; + + /* + * Update disptime after setting the above flag to make sure + * throtl_select_dispatch() won't exit without dispatching. + */ + tg_update_disptime(tg); + + throtl_schedule_next_dispatch(sq->parent_sq, true); +} + +static void throtl_pd_offline(struct blkg_policy_data *pd) +{ + tg_flush_bios(pd_to_tg(pd)); +} + +struct blkcg_policy blkcg_policy_throtl = { + .dfl_cftypes = throtl_files, + .legacy_cftypes = throtl_legacy_files, + + .pd_alloc_fn = throtl_pd_alloc, + .pd_init_fn = throtl_pd_init, + .pd_online_fn = throtl_pd_online, + .pd_offline_fn = throtl_pd_offline, + .pd_free_fn = throtl_pd_free, +}; + +static void tg_cancel_writeback_bios(struct throtl_grp *tg, + struct bio_list *cancel_bios) +{ + struct throtl_service_queue *sq = &tg->service_queue; + struct throtl_data *td = sq_to_td(sq); + int rw; + + if (tg->flags & THROTL_TG_CANCELING) + return; + tg->flags |= THROTL_TG_CANCELING; + + for (rw = READ; rw <= WRITE; rw++) { + struct throtl_qnode *qn, *tmp; + unsigned int nr_bios = 0; + + list_for_each_entry_safe(qn, tmp, &sq->queued[rw], node) { + struct bio *bio; + + while ((bio = bio_list_pop(&qn->bios_iops))) { + sq->nr_queued_iops[rw]--; + bio_list_add(&cancel_bios[rw], bio); + nr_bios++; + } + while ((bio = bio_list_pop(&qn->bios_bps))) { + sq->nr_queued_bps[rw]--; + bio_list_add(&cancel_bios[rw], bio); + nr_bios++; + } + + list_del_init(&qn->node); + blkg_put(tg_to_blkg(qn->tg)); + } + + td->nr_queued[rw] -= nr_bios; + } + + throtl_dequeue_tg(tg); +} + +void blk_throtl_cancel_bios(struct gendisk *disk) +{ + struct request_queue *q = disk->queue; + struct cgroup_subsys_state *pos_css; + struct blkcg_gq *blkg; + struct bio_list cancel_bios[2] = { }; + int rw; + + if (!blk_throtl_activated(q)) + return; + + spin_lock_irq(&q->queue_lock); + /* + * queue_lock is held, rcu lock is not needed here technically. + * However, rcu lock is still held to emphasize that following + * path need RCU protection and to prevent warning from lockdep. + */ + rcu_read_lock(); + blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) { + /* + * disk_release will call pd_offline_fn to cancel bios. + * However, disk_release can't be called if someone get + * the refcount of device and issued bios which are + * inflight after del_gendisk. + * Cancel bios here to ensure no bios are inflight after + * del_gendisk. + */ + tg_cancel_writeback_bios(blkg_to_tg(blkg), cancel_bios); + } + rcu_read_unlock(); + spin_unlock_irq(&q->queue_lock); + + for (rw = READ; rw <= WRITE; rw++) { + struct bio *bio; + while ((bio = bio_list_pop(&cancel_bios[rw]))) + bio_io_error(bio); + } +} + +static bool tg_within_limit(struct throtl_grp *tg, struct bio *bio, bool rw) +{ + struct throtl_service_queue *sq = &tg->service_queue; + + /* + * For a split bio, we need to specifically distinguish whether the + * iops queue is empty. + */ + if (bio_flagged(bio, BIO_BPS_THROTTLED)) + return sq->nr_queued_iops[rw] == 0 && + tg_dispatch_iops_time(tg, bio) == 0; + + /* + * Throtl is FIFO - if bios are already queued, should queue. + * If the bps queue is empty and @bio is within the bps limit, charge + * bps here for direct placement into the iops queue. + */ + if (sq_queued(&tg->service_queue, rw)) { + if (sq->nr_queued_bps[rw] == 0 && + tg_dispatch_bps_time(tg, bio) == 0) + throtl_charge_bps_bio(tg, bio); + + return false; + } + + return tg_dispatch_time(tg, bio) == 0; +} + +bool __blk_throtl_bio(struct bio *bio) +{ + struct request_queue *q = bdev_get_queue(bio->bi_bdev); + struct blkcg_gq *blkg = bio->bi_blkg; + struct throtl_qnode *qn = NULL; + struct throtl_grp *tg = blkg_to_tg(blkg); + struct throtl_service_queue *sq; + bool rw = bio_data_dir(bio); + bool throttled = false; + struct throtl_data *td = tg->td; + + rcu_read_lock(); + spin_lock_irq(&q->queue_lock); + sq = &tg->service_queue; + + while (true) { + if (tg_within_limit(tg, bio, rw)) { + /* within limits, let's charge and dispatch directly */ + throtl_charge_iops_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); + } else if (bio_issue_as_root_blkg(bio)) { + /* + * IOs which may cause priority inversions are + * dispatched directly, even if they're over limit. + * + * Charge and dispatch directly, and our throttle + * control algorithm is adaptive, and extra IO bytes + * will be throttled for paying the debt + */ + throtl_charge_bps_bio(tg, bio); + throtl_charge_iops_bio(tg, bio); + } else { + /* if above limits, break to queue */ + break; + } + + /* + * @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) { + bio_set_flag(bio, BIO_BPS_THROTTLED); + 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_limit(tg, rw), + tg->io_disp[rw], tg_iops_limit(tg, rw), + sq_queued(sq, READ), sq_queued(sq, WRITE)); + + 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, or the iops queue is empty and @bio will + * add to. 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->flags & THROTL_TG_IOPS_WAS_EMPTY) { + tg_update_disptime(tg); + throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true); + } + +out_unlock: + spin_unlock_irq(&q->queue_lock); + + rcu_read_unlock(); + return throttled; +} + +void blk_throtl_exit(struct gendisk *disk) +{ + struct request_queue *q = disk->queue; + + /* + * blkg_destroy_all() already deactivate throtl policy, just check and + * free throtl data. + */ + if (!q->td) + return; + + timer_delete_sync(&q->td->service_queue.pending_timer); + throtl_shutdown_wq(q); + kfree(q->td); +} + +static int __init throtl_init(void) +{ + kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM | WQ_PERCPU, 0); + if (!kthrotld_workqueue) + panic("Failed to create kthrotld\n"); + + return blkcg_policy_register(&blkcg_policy_throtl); +} + +module_init(throtl_init); |