diff options
Diffstat (limited to 'block/blk-cgroup.c')
| -rw-r--r-- | block/blk-cgroup.c | 1950 |
1 files changed, 1950 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c new file mode 100644 index 000000000..c623632c1 --- /dev/null +++ b/block/blk-cgroup.c @@ -0,0 +1,1950 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Common Block IO controller cgroup interface + * + * Based on ideas and code from CFQ, CFS and BFQ: + * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk> + * + * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it> + * Paolo Valente <paolo.valente@unimore.it> + * + * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com> + * Nauman Rafique <nauman@google.com> + * + * For policy-specific per-blkcg data: + * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it> + * Arianna Avanzini <avanzini.arianna@gmail.com> + */ +#include <linux/ioprio.h> +#include <linux/kdev_t.h> +#include <linux/module.h> +#include <linux/sched/signal.h> +#include <linux/err.h> +#include <linux/blkdev.h> +#include <linux/backing-dev.h> +#include <linux/slab.h> +#include <linux/genhd.h> +#include <linux/delay.h> +#include <linux/atomic.h> +#include <linux/ctype.h> +#include <linux/blk-cgroup.h> +#include <linux/tracehook.h> +#include <linux/psi.h> +#include "blk.h" + +#define MAX_KEY_LEN 100 + +/* + * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation. + * blkcg_pol_register_mutex nests outside of it and synchronizes entire + * policy [un]register operations including cgroup file additions / + * removals. Putting cgroup file registration outside blkcg_pol_mutex + * allows grabbing it from cgroup callbacks. + */ +static DEFINE_MUTEX(blkcg_pol_register_mutex); +static DEFINE_MUTEX(blkcg_pol_mutex); + +struct blkcg blkcg_root; +EXPORT_SYMBOL_GPL(blkcg_root); + +struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css; +EXPORT_SYMBOL_GPL(blkcg_root_css); + +static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS]; + +static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */ + +bool blkcg_debug_stats = false; +static struct workqueue_struct *blkcg_punt_bio_wq; + +static bool blkcg_policy_enabled(struct request_queue *q, + const struct blkcg_policy *pol) +{ + return pol && test_bit(pol->plid, q->blkcg_pols); +} + +/** + * blkg_free - free a blkg + * @blkg: blkg to free + * + * Free @blkg which may be partially allocated. + */ +static void blkg_free(struct blkcg_gq *blkg) +{ + int i; + + if (!blkg) + return; + + for (i = 0; i < BLKCG_MAX_POLS; i++) + if (blkg->pd[i]) + blkcg_policy[i]->pd_free_fn(blkg->pd[i]); + + free_percpu(blkg->iostat_cpu); + percpu_ref_exit(&blkg->refcnt); + kfree(blkg); +} + +static void __blkg_release(struct rcu_head *rcu) +{ + struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head); + + WARN_ON(!bio_list_empty(&blkg->async_bios)); + + /* release the blkcg and parent blkg refs this blkg has been holding */ + css_put(&blkg->blkcg->css); + if (blkg->parent) + blkg_put(blkg->parent); + blkg_free(blkg); +} + +/* + * A group is RCU protected, but having an rcu lock does not mean that one + * can access all the fields of blkg and assume these are valid. For + * example, don't try to follow throtl_data and request queue links. + * + * Having a reference to blkg under an rcu allows accesses to only values + * local to groups like group stats and group rate limits. + */ +static void blkg_release(struct percpu_ref *ref) +{ + struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt); + + call_rcu(&blkg->rcu_head, __blkg_release); +} + +static void blkg_async_bio_workfn(struct work_struct *work) +{ + struct blkcg_gq *blkg = container_of(work, struct blkcg_gq, + async_bio_work); + struct bio_list bios = BIO_EMPTY_LIST; + struct bio *bio; + struct blk_plug plug; + bool need_plug = false; + + /* as long as there are pending bios, @blkg can't go away */ + spin_lock_bh(&blkg->async_bio_lock); + bio_list_merge(&bios, &blkg->async_bios); + bio_list_init(&blkg->async_bios); + spin_unlock_bh(&blkg->async_bio_lock); + + /* start plug only when bio_list contains at least 2 bios */ + if (bios.head && bios.head->bi_next) { + need_plug = true; + blk_start_plug(&plug); + } + while ((bio = bio_list_pop(&bios))) + submit_bio(bio); + if (need_plug) + blk_finish_plug(&plug); +} + +/** + * blkg_alloc - allocate a blkg + * @blkcg: block cgroup the new blkg is associated with + * @q: request_queue the new blkg is associated with + * @gfp_mask: allocation mask to use + * + * Allocate a new blkg assocating @blkcg and @q. + */ +static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, + gfp_t gfp_mask) +{ + struct blkcg_gq *blkg; + int i, cpu; + + /* alloc and init base part */ + blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node); + if (!blkg) + return NULL; + + if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask)) + goto err_free; + + blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask); + if (!blkg->iostat_cpu) + goto err_free; + + blkg->q = q; + INIT_LIST_HEAD(&blkg->q_node); + spin_lock_init(&blkg->async_bio_lock); + bio_list_init(&blkg->async_bios); + INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn); + blkg->blkcg = blkcg; + + u64_stats_init(&blkg->iostat.sync); + for_each_possible_cpu(cpu) + u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync); + + for (i = 0; i < BLKCG_MAX_POLS; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + struct blkg_policy_data *pd; + + if (!blkcg_policy_enabled(q, pol)) + continue; + + /* alloc per-policy data and attach it to blkg */ + pd = pol->pd_alloc_fn(gfp_mask, q, blkcg); + if (!pd) + goto err_free; + + blkg->pd[i] = pd; + pd->blkg = blkg; + pd->plid = i; + } + + return blkg; + +err_free: + blkg_free(blkg); + return NULL; +} + +struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg, + struct request_queue *q, bool update_hint) +{ + struct blkcg_gq *blkg; + + /* + * Hint didn't match. Look up from the radix tree. Note that the + * hint can only be updated under queue_lock as otherwise @blkg + * could have already been removed from blkg_tree. The caller is + * responsible for grabbing queue_lock if @update_hint. + */ + blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id); + if (blkg && blkg->q == q) { + if (update_hint) { + lockdep_assert_held(&q->queue_lock); + rcu_assign_pointer(blkcg->blkg_hint, blkg); + } + return blkg; + } + + return NULL; +} +EXPORT_SYMBOL_GPL(blkg_lookup_slowpath); + +/* + * If @new_blkg is %NULL, this function tries to allocate a new one as + * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return. + */ +static struct blkcg_gq *blkg_create(struct blkcg *blkcg, + struct request_queue *q, + struct blkcg_gq *new_blkg) +{ + struct blkcg_gq *blkg; + int i, ret; + + WARN_ON_ONCE(!rcu_read_lock_held()); + lockdep_assert_held(&q->queue_lock); + + /* request_queue is dying, do not create/recreate a blkg */ + if (blk_queue_dying(q)) { + ret = -ENODEV; + goto err_free_blkg; + } + + /* blkg holds a reference to blkcg */ + if (!css_tryget_online(&blkcg->css)) { + ret = -ENODEV; + goto err_free_blkg; + } + + /* allocate */ + if (!new_blkg) { + new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT | __GFP_NOWARN); + if (unlikely(!new_blkg)) { + ret = -ENOMEM; + goto err_put_css; + } + } + blkg = new_blkg; + + /* link parent */ + if (blkcg_parent(blkcg)) { + blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false); + if (WARN_ON_ONCE(!blkg->parent)) { + ret = -ENODEV; + goto err_put_css; + } + blkg_get(blkg->parent); + } + + /* invoke per-policy init */ + for (i = 0; i < BLKCG_MAX_POLS; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + + if (blkg->pd[i] && pol->pd_init_fn) + pol->pd_init_fn(blkg->pd[i]); + } + + /* insert */ + spin_lock(&blkcg->lock); + ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg); + if (likely(!ret)) { + hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list); + list_add(&blkg->q_node, &q->blkg_list); + + for (i = 0; i < BLKCG_MAX_POLS; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + + if (blkg->pd[i] && pol->pd_online_fn) + pol->pd_online_fn(blkg->pd[i]); + } + } + blkg->online = true; + spin_unlock(&blkcg->lock); + + if (!ret) + return blkg; + + /* @blkg failed fully initialized, use the usual release path */ + blkg_put(blkg); + return ERR_PTR(ret); + +err_put_css: + css_put(&blkcg->css); +err_free_blkg: + blkg_free(new_blkg); + return ERR_PTR(ret); +} + +/** + * blkg_lookup_create - lookup blkg, try to create one if not there + * @blkcg: blkcg of interest + * @q: request_queue of interest + * + * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to + * create one. blkg creation is performed recursively from blkcg_root such + * that all non-root blkg's have access to the parent blkg. This function + * should be called under RCU read lock and takes @q->queue_lock. + * + * Returns the blkg or the closest blkg if blkg_create() fails as it walks + * down from root. + */ +static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, + struct request_queue *q) +{ + struct blkcg_gq *blkg; + unsigned long flags; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + blkg = blkg_lookup(blkcg, q); + if (blkg) + return blkg; + + spin_lock_irqsave(&q->queue_lock, flags); + blkg = __blkg_lookup(blkcg, q, true); + if (blkg) + goto found; + + /* + * Create blkgs walking down from blkcg_root to @blkcg, so that all + * non-root blkgs have access to their parents. Returns the closest + * blkg to the intended blkg should blkg_create() fail. + */ + while (true) { + struct blkcg *pos = blkcg; + struct blkcg *parent = blkcg_parent(blkcg); + struct blkcg_gq *ret_blkg = q->root_blkg; + + while (parent) { + blkg = __blkg_lookup(parent, q, false); + if (blkg) { + /* remember closest blkg */ + ret_blkg = blkg; + break; + } + pos = parent; + parent = blkcg_parent(parent); + } + + blkg = blkg_create(pos, q, NULL); + if (IS_ERR(blkg)) { + blkg = ret_blkg; + break; + } + if (pos == blkcg) + break; + } + +found: + spin_unlock_irqrestore(&q->queue_lock, flags); + return blkg; +} + +static void blkg_destroy(struct blkcg_gq *blkg) +{ + struct blkcg *blkcg = blkg->blkcg; + int i; + + lockdep_assert_held(&blkg->q->queue_lock); + lockdep_assert_held(&blkcg->lock); + + /* Something wrong if we are trying to remove same group twice */ + WARN_ON_ONCE(list_empty(&blkg->q_node)); + WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node)); + + for (i = 0; i < BLKCG_MAX_POLS; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + + if (blkg->pd[i] && pol->pd_offline_fn) + pol->pd_offline_fn(blkg->pd[i]); + } + + blkg->online = false; + + radix_tree_delete(&blkcg->blkg_tree, blkg->q->id); + list_del_init(&blkg->q_node); + hlist_del_init_rcu(&blkg->blkcg_node); + + /* + * Both setting lookup hint to and clearing it from @blkg are done + * under queue_lock. If it's not pointing to @blkg now, it never + * will. Hint assignment itself can race safely. + */ + if (rcu_access_pointer(blkcg->blkg_hint) == blkg) + rcu_assign_pointer(blkcg->blkg_hint, NULL); + + /* + * Put the reference taken at the time of creation so that when all + * queues are gone, group can be destroyed. + */ + percpu_ref_kill(&blkg->refcnt); +} + +/** + * blkg_destroy_all - destroy all blkgs associated with a request_queue + * @q: request_queue of interest + * + * Destroy all blkgs associated with @q. + */ +static void blkg_destroy_all(struct request_queue *q) +{ + struct blkcg_gq *blkg, *n; + + spin_lock_irq(&q->queue_lock); + list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) { + struct blkcg *blkcg = blkg->blkcg; + + spin_lock(&blkcg->lock); + blkg_destroy(blkg); + spin_unlock(&blkcg->lock); + } + + q->root_blkg = NULL; + spin_unlock_irq(&q->queue_lock); +} + +static int blkcg_reset_stats(struct cgroup_subsys_state *css, + struct cftype *cftype, u64 val) +{ + struct blkcg *blkcg = css_to_blkcg(css); + struct blkcg_gq *blkg; + int i, cpu; + + mutex_lock(&blkcg_pol_mutex); + spin_lock_irq(&blkcg->lock); + + /* + * Note that stat reset is racy - it doesn't synchronize against + * stat updates. This is a debug feature which shouldn't exist + * anyway. If you get hit by a race, retry. + */ + hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) { + for_each_possible_cpu(cpu) { + struct blkg_iostat_set *bis = + per_cpu_ptr(blkg->iostat_cpu, cpu); + memset(bis, 0, sizeof(*bis)); + } + memset(&blkg->iostat, 0, sizeof(blkg->iostat)); + + for (i = 0; i < BLKCG_MAX_POLS; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + + if (blkg->pd[i] && pol->pd_reset_stats_fn) + pol->pd_reset_stats_fn(blkg->pd[i]); + } + } + + spin_unlock_irq(&blkcg->lock); + mutex_unlock(&blkcg_pol_mutex); + return 0; +} + +const char *blkg_dev_name(struct blkcg_gq *blkg) +{ + /* some drivers (floppy) instantiate a queue w/o disk registered */ + if (blkg->q->backing_dev_info->dev) + return bdi_dev_name(blkg->q->backing_dev_info); + return NULL; +} + +/** + * blkcg_print_blkgs - helper for printing per-blkg data + * @sf: seq_file to print to + * @blkcg: blkcg of interest + * @prfill: fill function to print out a blkg + * @pol: policy in question + * @data: data to be passed to @prfill + * @show_total: to print out sum of prfill return values or not + * + * This function invokes @prfill on each blkg of @blkcg if pd for the + * policy specified by @pol exists. @prfill is invoked with @sf, the + * policy data and @data and the matching queue lock held. If @show_total + * is %true, the sum of the return values from @prfill is printed with + * "Total" label at the end. + * + * This is to be used to construct print functions for + * cftype->read_seq_string method. + */ +void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg, + u64 (*prfill)(struct seq_file *, + struct blkg_policy_data *, int), + const struct blkcg_policy *pol, int data, + bool show_total) +{ + struct blkcg_gq *blkg; + u64 total = 0; + + rcu_read_lock(); + hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) { + spin_lock_irq(&blkg->q->queue_lock); + if (blkcg_policy_enabled(blkg->q, pol)) + total += prfill(sf, blkg->pd[pol->plid], data); + spin_unlock_irq(&blkg->q->queue_lock); + } + rcu_read_unlock(); + + if (show_total) + seq_printf(sf, "Total %llu\n", (unsigned long long)total); +} +EXPORT_SYMBOL_GPL(blkcg_print_blkgs); + +/** + * __blkg_prfill_u64 - prfill helper for a single u64 value + * @sf: seq_file to print to + * @pd: policy private data of interest + * @v: value to print + * + * Print @v to @sf for the device assocaited with @pd. + */ +u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v) +{ + const char *dname = blkg_dev_name(pd->blkg); + + if (!dname) + return 0; + + seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v); + return v; +} +EXPORT_SYMBOL_GPL(__blkg_prfill_u64); + +/* Performs queue bypass and policy enabled checks then looks up blkg. */ +static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg, + const struct blkcg_policy *pol, + struct request_queue *q) +{ + WARN_ON_ONCE(!rcu_read_lock_held()); + lockdep_assert_held(&q->queue_lock); + + if (!blkcg_policy_enabled(q, pol)) + return ERR_PTR(-EOPNOTSUPP); + return __blkg_lookup(blkcg, q, true /* update_hint */); +} + +/** + * blkg_conf_prep - parse and prepare for per-blkg config update + * @inputp: input string pointer + * + * Parse the device node prefix part, MAJ:MIN, of per-blkg config update + * from @input and get and return the matching gendisk. *@inputp is + * updated to point past the device node prefix. Returns an ERR_PTR() + * value on error. + * + * Use this function iff blkg_conf_prep() can't be used for some reason. + */ +struct gendisk *blkcg_conf_get_disk(char **inputp) +{ + char *input = *inputp; + unsigned int major, minor; + struct gendisk *disk; + int key_len, part; + + if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2) + return ERR_PTR(-EINVAL); + + input += key_len; + if (!isspace(*input)) + return ERR_PTR(-EINVAL); + input = skip_spaces(input); + + disk = get_gendisk(MKDEV(major, minor), &part); + if (!disk) + return ERR_PTR(-ENODEV); + if (part) { + put_disk_and_module(disk); + return ERR_PTR(-ENODEV); + } + + *inputp = input; + return disk; +} + +/** + * blkg_conf_prep - parse and prepare for per-blkg config update + * @blkcg: target block cgroup + * @pol: target policy + * @input: input string + * @ctx: blkg_conf_ctx to be filled + * + * Parse per-blkg config update from @input and initialize @ctx with the + * result. @ctx->blkg points to the blkg to be updated and @ctx->body the + * part of @input following MAJ:MIN. This function returns with RCU read + * lock and queue lock held and must be paired with blkg_conf_finish(). + */ +int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, + char *input, struct blkg_conf_ctx *ctx) + __acquires(rcu) __acquires(&disk->queue->queue_lock) +{ + struct gendisk *disk; + struct request_queue *q; + struct blkcg_gq *blkg; + int ret; + + disk = blkcg_conf_get_disk(&input); + if (IS_ERR(disk)) + return PTR_ERR(disk); + + q = disk->queue; + + rcu_read_lock(); + spin_lock_irq(&q->queue_lock); + + blkg = blkg_lookup_check(blkcg, pol, q); + if (IS_ERR(blkg)) { + ret = PTR_ERR(blkg); + goto fail_unlock; + } + + if (blkg) + goto success; + + /* + * Create blkgs walking down from blkcg_root to @blkcg, so that all + * non-root blkgs have access to their parents. + */ + while (true) { + struct blkcg *pos = blkcg; + struct blkcg *parent; + struct blkcg_gq *new_blkg; + + parent = blkcg_parent(blkcg); + while (parent && !__blkg_lookup(parent, q, false)) { + pos = parent; + parent = blkcg_parent(parent); + } + + /* Drop locks to do new blkg allocation with GFP_KERNEL. */ + spin_unlock_irq(&q->queue_lock); + rcu_read_unlock(); + + new_blkg = blkg_alloc(pos, q, GFP_KERNEL); + if (unlikely(!new_blkg)) { + ret = -ENOMEM; + goto fail; + } + + if (radix_tree_preload(GFP_KERNEL)) { + blkg_free(new_blkg); + ret = -ENOMEM; + goto fail; + } + + rcu_read_lock(); + spin_lock_irq(&q->queue_lock); + + blkg = blkg_lookup_check(pos, pol, q); + if (IS_ERR(blkg)) { + ret = PTR_ERR(blkg); + blkg_free(new_blkg); + goto fail_preloaded; + } + + if (blkg) { + blkg_free(new_blkg); + } else { + blkg = blkg_create(pos, q, new_blkg); + if (IS_ERR(blkg)) { + ret = PTR_ERR(blkg); + goto fail_preloaded; + } + } + + radix_tree_preload_end(); + + if (pos == blkcg) + goto success; + } +success: + ctx->disk = disk; + ctx->blkg = blkg; + ctx->body = input; + return 0; + +fail_preloaded: + radix_tree_preload_end(); +fail_unlock: + spin_unlock_irq(&q->queue_lock); + rcu_read_unlock(); +fail: + put_disk_and_module(disk); + /* + * If queue was bypassing, we should retry. Do so after a + * short msleep(). It isn't strictly necessary but queue + * can be bypassing for some time and it's always nice to + * avoid busy looping. + */ + if (ret == -EBUSY) { + msleep(10); + ret = restart_syscall(); + } + return ret; +} +EXPORT_SYMBOL_GPL(blkg_conf_prep); + +/** + * blkg_conf_finish - finish up per-blkg config update + * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep() + * + * Finish up after per-blkg config update. This function must be paired + * with blkg_conf_prep(). + */ +void blkg_conf_finish(struct blkg_conf_ctx *ctx) + __releases(&ctx->disk->queue->queue_lock) __releases(rcu) +{ + spin_unlock_irq(&ctx->disk->queue->queue_lock); + rcu_read_unlock(); + put_disk_and_module(ctx->disk); +} +EXPORT_SYMBOL_GPL(blkg_conf_finish); + +static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src) +{ + int i; + + for (i = 0; i < BLKG_IOSTAT_NR; i++) { + dst->bytes[i] = src->bytes[i]; + dst->ios[i] = src->ios[i]; + } +} + +static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src) +{ + int i; + + for (i = 0; i < BLKG_IOSTAT_NR; i++) { + dst->bytes[i] += src->bytes[i]; + dst->ios[i] += src->ios[i]; + } +} + +static void blkg_iostat_sub(struct blkg_iostat *dst, struct blkg_iostat *src) +{ + int i; + + for (i = 0; i < BLKG_IOSTAT_NR; i++) { + dst->bytes[i] -= src->bytes[i]; + dst->ios[i] -= src->ios[i]; + } +} + +static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu) +{ + struct blkcg *blkcg = css_to_blkcg(css); + struct blkcg_gq *blkg; + + rcu_read_lock(); + + hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) { + struct blkcg_gq *parent = blkg->parent; + struct blkg_iostat_set *bisc = per_cpu_ptr(blkg->iostat_cpu, cpu); + struct blkg_iostat cur, delta; + unsigned int seq; + + /* fetch the current per-cpu values */ + do { + seq = u64_stats_fetch_begin(&bisc->sync); + blkg_iostat_set(&cur, &bisc->cur); + } while (u64_stats_fetch_retry(&bisc->sync, seq)); + + /* propagate percpu delta to global */ + u64_stats_update_begin(&blkg->iostat.sync); + blkg_iostat_set(&delta, &cur); + blkg_iostat_sub(&delta, &bisc->last); + blkg_iostat_add(&blkg->iostat.cur, &delta); + blkg_iostat_add(&bisc->last, &delta); + u64_stats_update_end(&blkg->iostat.sync); + + /* propagate global delta to parent */ + if (parent) { + u64_stats_update_begin(&parent->iostat.sync); + blkg_iostat_set(&delta, &blkg->iostat.cur); + blkg_iostat_sub(&delta, &blkg->iostat.last); + blkg_iostat_add(&parent->iostat.cur, &delta); + blkg_iostat_add(&blkg->iostat.last, &delta); + u64_stats_update_end(&parent->iostat.sync); + } + } + + rcu_read_unlock(); +} + +/* + * The rstat algorithms intentionally don't handle the root cgroup to avoid + * incurring overhead when no cgroups are defined. For that reason, + * cgroup_rstat_flush in blkcg_print_stat does not actually fill out the + * iostat in the root cgroup's blkcg_gq. + * + * However, we would like to re-use the printing code between the root and + * non-root cgroups to the extent possible. For that reason, we simulate + * flushing the root cgroup's stats by explicitly filling in the iostat + * with disk level statistics. + */ +static void blkcg_fill_root_iostats(void) +{ + struct class_dev_iter iter; + struct device *dev; + + class_dev_iter_init(&iter, &block_class, NULL, &disk_type); + while ((dev = class_dev_iter_next(&iter))) { + struct gendisk *disk = dev_to_disk(dev); + struct hd_struct *part = disk_get_part(disk, 0); + struct blkcg_gq *blkg = blk_queue_root_blkg(disk->queue); + struct blkg_iostat tmp; + int cpu; + + memset(&tmp, 0, sizeof(tmp)); + for_each_possible_cpu(cpu) { + struct disk_stats *cpu_dkstats; + + cpu_dkstats = per_cpu_ptr(part->dkstats, cpu); + tmp.ios[BLKG_IOSTAT_READ] += + cpu_dkstats->ios[STAT_READ]; + tmp.ios[BLKG_IOSTAT_WRITE] += + cpu_dkstats->ios[STAT_WRITE]; + tmp.ios[BLKG_IOSTAT_DISCARD] += + cpu_dkstats->ios[STAT_DISCARD]; + // convert sectors to bytes + tmp.bytes[BLKG_IOSTAT_READ] += + cpu_dkstats->sectors[STAT_READ] << 9; + tmp.bytes[BLKG_IOSTAT_WRITE] += + cpu_dkstats->sectors[STAT_WRITE] << 9; + tmp.bytes[BLKG_IOSTAT_DISCARD] += + cpu_dkstats->sectors[STAT_DISCARD] << 9; + + u64_stats_update_begin(&blkg->iostat.sync); + blkg_iostat_set(&blkg->iostat.cur, &tmp); + u64_stats_update_end(&blkg->iostat.sync); + } + disk_put_part(part); + } +} + +static int blkcg_print_stat(struct seq_file *sf, void *v) +{ + struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); + struct blkcg_gq *blkg; + + if (!seq_css(sf)->parent) + blkcg_fill_root_iostats(); + else + cgroup_rstat_flush(blkcg->css.cgroup); + + rcu_read_lock(); + + hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) { + struct blkg_iostat_set *bis = &blkg->iostat; + const char *dname; + char *buf; + u64 rbytes, wbytes, rios, wios, dbytes, dios; + size_t size = seq_get_buf(sf, &buf), off = 0; + int i; + bool has_stats = false; + unsigned seq; + + spin_lock_irq(&blkg->q->queue_lock); + + if (!blkg->online) + goto skip; + + dname = blkg_dev_name(blkg); + if (!dname) + goto skip; + + /* + * Hooray string manipulation, count is the size written NOT + * INCLUDING THE \0, so size is now count+1 less than what we + * had before, but we want to start writing the next bit from + * the \0 so we only add count to buf. + */ + off += scnprintf(buf+off, size-off, "%s ", dname); + + do { + seq = u64_stats_fetch_begin(&bis->sync); + + rbytes = bis->cur.bytes[BLKG_IOSTAT_READ]; + wbytes = bis->cur.bytes[BLKG_IOSTAT_WRITE]; + dbytes = bis->cur.bytes[BLKG_IOSTAT_DISCARD]; + rios = bis->cur.ios[BLKG_IOSTAT_READ]; + wios = bis->cur.ios[BLKG_IOSTAT_WRITE]; + dios = bis->cur.ios[BLKG_IOSTAT_DISCARD]; + } while (u64_stats_fetch_retry(&bis->sync, seq)); + + if (rbytes || wbytes || rios || wios) { + has_stats = true; + off += scnprintf(buf+off, size-off, + "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu", + rbytes, wbytes, rios, wios, + dbytes, dios); + } + + if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) { + has_stats = true; + off += scnprintf(buf+off, size-off, + " use_delay=%d delay_nsec=%llu", + atomic_read(&blkg->use_delay), + (unsigned long long)atomic64_read(&blkg->delay_nsec)); + } + + for (i = 0; i < BLKCG_MAX_POLS; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + size_t written; + + if (!blkg->pd[i] || !pol->pd_stat_fn) + continue; + + written = pol->pd_stat_fn(blkg->pd[i], buf+off, size-off); + if (written) + has_stats = true; + off += written; + } + + if (has_stats) { + if (off < size - 1) { + off += scnprintf(buf+off, size-off, "\n"); + seq_commit(sf, off); + } else { + seq_commit(sf, -1); + } + } + skip: + spin_unlock_irq(&blkg->q->queue_lock); + } + + rcu_read_unlock(); + return 0; +} + +static struct cftype blkcg_files[] = { + { + .name = "stat", + .seq_show = blkcg_print_stat, + }, + { } /* terminate */ +}; + +static struct cftype blkcg_legacy_files[] = { + { + .name = "reset_stats", + .write_u64 = blkcg_reset_stats, + }, + { } /* terminate */ +}; + +/* + * blkcg destruction is a three-stage process. + * + * 1. Destruction starts. The blkcg_css_offline() callback is invoked + * which offlines writeback. Here we tie the next stage of blkg destruction + * to the completion of writeback associated with the blkcg. This lets us + * avoid punting potentially large amounts of outstanding writeback to root + * while maintaining any ongoing policies. The next stage is triggered when + * the nr_cgwbs count goes to zero. + * + * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called + * and handles the destruction of blkgs. Here the css reference held by + * the blkg is put back eventually allowing blkcg_css_free() to be called. + * This work may occur in cgwb_release_workfn() on the cgwb_release + * workqueue. Any submitted ios that fail to get the blkg ref will be + * punted to the root_blkg. + * + * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called. + * This finally frees the blkcg. + */ + +/** + * blkcg_css_offline - cgroup css_offline callback + * @css: css of interest + * + * This function is called when @css is about to go away. Here the cgwbs are + * offlined first and only once writeback associated with the blkcg has + * finished do we start step 2 (see above). + */ +static void blkcg_css_offline(struct cgroup_subsys_state *css) +{ + struct blkcg *blkcg = css_to_blkcg(css); + + /* this prevents anyone from attaching or migrating to this blkcg */ + wb_blkcg_offline(blkcg); + + /* put the base online pin allowing step 2 to be triggered */ + blkcg_unpin_online(blkcg); +} + +/** + * blkcg_destroy_blkgs - responsible for shooting down blkgs + * @blkcg: blkcg of interest + * + * blkgs should be removed while holding both q and blkcg locks. As blkcg lock + * is nested inside q lock, this function performs reverse double lock dancing. + * Destroying the blkgs releases the reference held on the blkcg's css allowing + * blkcg_css_free to eventually be called. + * + * This is the blkcg counterpart of ioc_release_fn(). + */ +void blkcg_destroy_blkgs(struct blkcg *blkcg) +{ + might_sleep(); + + spin_lock_irq(&blkcg->lock); + + while (!hlist_empty(&blkcg->blkg_list)) { + struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first, + struct blkcg_gq, blkcg_node); + struct request_queue *q = blkg->q; + + if (need_resched() || !spin_trylock(&q->queue_lock)) { + /* + * Given that the system can accumulate a huge number + * of blkgs in pathological cases, check to see if we + * need to rescheduling to avoid softlockup. + */ + spin_unlock_irq(&blkcg->lock); + cond_resched(); + spin_lock_irq(&blkcg->lock); + continue; + } + + blkg_destroy(blkg); + spin_unlock(&q->queue_lock); + } + + spin_unlock_irq(&blkcg->lock); +} + +static void blkcg_css_free(struct cgroup_subsys_state *css) +{ + struct blkcg *blkcg = css_to_blkcg(css); + int i; + + mutex_lock(&blkcg_pol_mutex); + + list_del(&blkcg->all_blkcgs_node); + + for (i = 0; i < BLKCG_MAX_POLS; i++) + if (blkcg->cpd[i]) + blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]); + + mutex_unlock(&blkcg_pol_mutex); + + kfree(blkcg); +} + +static struct cgroup_subsys_state * +blkcg_css_alloc(struct cgroup_subsys_state *parent_css) +{ + struct blkcg *blkcg; + struct cgroup_subsys_state *ret; + int i; + + mutex_lock(&blkcg_pol_mutex); + + if (!parent_css) { + blkcg = &blkcg_root; + } else { + blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL); + if (!blkcg) { + ret = ERR_PTR(-ENOMEM); + goto unlock; + } + } + + for (i = 0; i < BLKCG_MAX_POLS ; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + struct blkcg_policy_data *cpd; + + /* + * If the policy hasn't been attached yet, wait for it + * to be attached before doing anything else. Otherwise, + * check if the policy requires any specific per-cgroup + * data: if it does, allocate and initialize it. + */ + if (!pol || !pol->cpd_alloc_fn) + continue; + + cpd = pol->cpd_alloc_fn(GFP_KERNEL); + if (!cpd) { + ret = ERR_PTR(-ENOMEM); + goto free_pd_blkcg; + } + blkcg->cpd[i] = cpd; + cpd->blkcg = blkcg; + cpd->plid = i; + if (pol->cpd_init_fn) + pol->cpd_init_fn(cpd); + } + + spin_lock_init(&blkcg->lock); + refcount_set(&blkcg->online_pin, 1); + INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN); + INIT_HLIST_HEAD(&blkcg->blkg_list); +#ifdef CONFIG_CGROUP_WRITEBACK + INIT_LIST_HEAD(&blkcg->cgwb_list); +#endif + list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs); + + mutex_unlock(&blkcg_pol_mutex); + return &blkcg->css; + +free_pd_blkcg: + for (i--; i >= 0; i--) + if (blkcg->cpd[i]) + blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]); + + if (blkcg != &blkcg_root) + kfree(blkcg); +unlock: + mutex_unlock(&blkcg_pol_mutex); + return ret; +} + +static int blkcg_css_online(struct cgroup_subsys_state *css) +{ + struct blkcg *blkcg = css_to_blkcg(css); + struct blkcg *parent = blkcg_parent(blkcg); + + /* + * blkcg_pin_online() is used to delay blkcg offline so that blkgs + * don't go offline while cgwbs are still active on them. Pin the + * parent so that offline always happens towards the root. + */ + if (parent) + blkcg_pin_online(parent); + return 0; +} + +/** + * blkcg_init_queue - initialize blkcg part of request queue + * @q: request_queue to initialize + * + * Called from blk_alloc_queue(). Responsible for initializing blkcg + * part of new request_queue @q. + * + * RETURNS: + * 0 on success, -errno on failure. + */ +int blkcg_init_queue(struct request_queue *q) +{ + struct blkcg_gq *new_blkg, *blkg; + bool preloaded; + int ret; + + new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL); + if (!new_blkg) + return -ENOMEM; + + preloaded = !radix_tree_preload(GFP_KERNEL); + + /* Make sure the root blkg exists. */ + rcu_read_lock(); + spin_lock_irq(&q->queue_lock); + blkg = blkg_create(&blkcg_root, q, new_blkg); + if (IS_ERR(blkg)) + goto err_unlock; + q->root_blkg = blkg; + spin_unlock_irq(&q->queue_lock); + rcu_read_unlock(); + + if (preloaded) + radix_tree_preload_end(); + + ret = blk_throtl_init(q); + if (ret) + goto err_destroy_all; + + ret = blk_iolatency_init(q); + if (ret) { + blk_throtl_exit(q); + goto err_destroy_all; + } + return 0; + +err_destroy_all: + blkg_destroy_all(q); + return ret; +err_unlock: + spin_unlock_irq(&q->queue_lock); + rcu_read_unlock(); + if (preloaded) + radix_tree_preload_end(); + return PTR_ERR(blkg); +} + +/** + * blkcg_exit_queue - exit and release blkcg part of request_queue + * @q: request_queue being released + * + * Called from blk_exit_queue(). Responsible for exiting blkcg part. + */ +void blkcg_exit_queue(struct request_queue *q) +{ + blkg_destroy_all(q); + blk_throtl_exit(q); +} + +/* + * We cannot support shared io contexts, as we have no mean to support + * two tasks with the same ioc in two different groups without major rework + * of the main cic data structures. For now we allow a task to change + * its cgroup only if it's the only owner of its ioc. + */ +static int blkcg_can_attach(struct cgroup_taskset *tset) +{ + struct task_struct *task; + struct cgroup_subsys_state *dst_css; + struct io_context *ioc; + int ret = 0; + + /* task_lock() is needed to avoid races with exit_io_context() */ + cgroup_taskset_for_each(task, dst_css, tset) { + task_lock(task); + ioc = task->io_context; + if (ioc && atomic_read(&ioc->nr_tasks) > 1) + ret = -EINVAL; + task_unlock(task); + if (ret) + break; + } + return ret; +} + +static void blkcg_bind(struct cgroup_subsys_state *root_css) +{ + int i; + + mutex_lock(&blkcg_pol_mutex); + + for (i = 0; i < BLKCG_MAX_POLS; i++) { + struct blkcg_policy *pol = blkcg_policy[i]; + struct blkcg *blkcg; + + if (!pol || !pol->cpd_bind_fn) + continue; + + list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) + if (blkcg->cpd[pol->plid]) + pol->cpd_bind_fn(blkcg->cpd[pol->plid]); + } + mutex_unlock(&blkcg_pol_mutex); +} + +static void blkcg_exit(struct task_struct *tsk) +{ + if (tsk->throttle_queue) + blk_put_queue(tsk->throttle_queue); + tsk->throttle_queue = NULL; +} + +struct cgroup_subsys io_cgrp_subsys = { + .css_alloc = blkcg_css_alloc, + .css_online = blkcg_css_online, + .css_offline = blkcg_css_offline, + .css_free = blkcg_css_free, + .can_attach = blkcg_can_attach, + .css_rstat_flush = blkcg_rstat_flush, + .bind = blkcg_bind, + .dfl_cftypes = blkcg_files, + .legacy_cftypes = blkcg_legacy_files, + .legacy_name = "blkio", + .exit = blkcg_exit, +#ifdef CONFIG_MEMCG + /* + * This ensures that, if available, memcg is automatically enabled + * together on the default hierarchy so that the owner cgroup can + * be retrieved from writeback pages. + */ + .depends_on = 1 << memory_cgrp_id, +#endif +}; +EXPORT_SYMBOL_GPL(io_cgrp_subsys); + +/** + * blkcg_activate_policy - activate a blkcg policy on a request_queue + * @q: request_queue of interest + * @pol: blkcg policy to activate + * + * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through + * bypass mode to populate its blkgs with policy_data for @pol. + * + * Activation happens with @q bypassed, so nobody would be accessing blkgs + * from IO path. Update of each blkg is protected by both queue and blkcg + * locks so that holding either lock and testing blkcg_policy_enabled() is + * always enough for dereferencing policy data. + * + * The caller is responsible for synchronizing [de]activations and policy + * [un]registerations. Returns 0 on success, -errno on failure. + */ +int blkcg_activate_policy(struct request_queue *q, + const struct blkcg_policy *pol) +{ + struct blkg_policy_data *pd_prealloc = NULL; + struct blkcg_gq *blkg, *pinned_blkg = NULL; + int ret; + + if (blkcg_policy_enabled(q, pol)) + return 0; + + if (queue_is_mq(q)) + blk_mq_freeze_queue(q); +retry: + spin_lock_irq(&q->queue_lock); + + /* blkg_list is pushed at the head, reverse walk to allocate parents first */ + list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) { + struct blkg_policy_data *pd; + + if (blkg->pd[pol->plid]) + continue; + + /* If prealloc matches, use it; otherwise try GFP_NOWAIT */ + if (blkg == pinned_blkg) { + pd = pd_prealloc; + pd_prealloc = NULL; + } else { + pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q, + blkg->blkcg); + } + + if (!pd) { + /* + * GFP_NOWAIT failed. Free the existing one and + * prealloc for @blkg w/ GFP_KERNEL. + */ + if (pinned_blkg) + blkg_put(pinned_blkg); + blkg_get(blkg); + pinned_blkg = blkg; + + spin_unlock_irq(&q->queue_lock); + + if (pd_prealloc) + pol->pd_free_fn(pd_prealloc); + pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q, + blkg->blkcg); + if (pd_prealloc) + goto retry; + else + goto enomem; + } + + blkg->pd[pol->plid] = pd; + pd->blkg = blkg; + pd->plid = pol->plid; + } + + /* all allocated, init in the same order */ + if (pol->pd_init_fn) + list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) + pol->pd_init_fn(blkg->pd[pol->plid]); + + if (pol->pd_online_fn) + list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) + pol->pd_online_fn(blkg->pd[pol->plid]); + + __set_bit(pol->plid, q->blkcg_pols); + ret = 0; + + spin_unlock_irq(&q->queue_lock); +out: + if (queue_is_mq(q)) + blk_mq_unfreeze_queue(q); + if (pinned_blkg) + blkg_put(pinned_blkg); + if (pd_prealloc) + pol->pd_free_fn(pd_prealloc); + return ret; + +enomem: + /* alloc failed, nothing's initialized yet, free everything */ + spin_lock_irq(&q->queue_lock); + list_for_each_entry(blkg, &q->blkg_list, q_node) { + struct blkcg *blkcg = blkg->blkcg; + + spin_lock(&blkcg->lock); + if (blkg->pd[pol->plid]) { + pol->pd_free_fn(blkg->pd[pol->plid]); + blkg->pd[pol->plid] = NULL; + } + spin_unlock(&blkcg->lock); + } + spin_unlock_irq(&q->queue_lock); + ret = -ENOMEM; + goto out; +} +EXPORT_SYMBOL_GPL(blkcg_activate_policy); + +/** + * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue + * @q: request_queue of interest + * @pol: blkcg policy to deactivate + * + * Deactivate @pol on @q. Follows the same synchronization rules as + * blkcg_activate_policy(). + */ +void blkcg_deactivate_policy(struct request_queue *q, + const struct blkcg_policy *pol) +{ + struct blkcg_gq *blkg; + + if (!blkcg_policy_enabled(q, pol)) + return; + + if (queue_is_mq(q)) + blk_mq_freeze_queue(q); + + spin_lock_irq(&q->queue_lock); + + __clear_bit(pol->plid, q->blkcg_pols); + + list_for_each_entry(blkg, &q->blkg_list, q_node) { + struct blkcg *blkcg = blkg->blkcg; + + spin_lock(&blkcg->lock); + if (blkg->pd[pol->plid]) { + if (pol->pd_offline_fn) + pol->pd_offline_fn(blkg->pd[pol->plid]); + pol->pd_free_fn(blkg->pd[pol->plid]); + blkg->pd[pol->plid] = NULL; + } + spin_unlock(&blkcg->lock); + } + + spin_unlock_irq(&q->queue_lock); + + if (queue_is_mq(q)) + blk_mq_unfreeze_queue(q); +} +EXPORT_SYMBOL_GPL(blkcg_deactivate_policy); + +/** + * blkcg_policy_register - register a blkcg policy + * @pol: blkcg policy to register + * + * Register @pol with blkcg core. Might sleep and @pol may be modified on + * successful registration. Returns 0 on success and -errno on failure. + */ +int blkcg_policy_register(struct blkcg_policy *pol) +{ + struct blkcg *blkcg; + int i, ret; + + mutex_lock(&blkcg_pol_register_mutex); + mutex_lock(&blkcg_pol_mutex); + + /* find an empty slot */ + ret = -ENOSPC; + for (i = 0; i < BLKCG_MAX_POLS; i++) + if (!blkcg_policy[i]) + break; + if (i >= BLKCG_MAX_POLS) { + pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n"); + goto err_unlock; + } + + /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */ + if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) || + (!pol->pd_alloc_fn ^ !pol->pd_free_fn)) + goto err_unlock; + + /* register @pol */ + pol->plid = i; + blkcg_policy[pol->plid] = pol; + + /* allocate and install cpd's */ + if (pol->cpd_alloc_fn) { + list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) { + struct blkcg_policy_data *cpd; + + cpd = pol->cpd_alloc_fn(GFP_KERNEL); + if (!cpd) + goto err_free_cpds; + + blkcg->cpd[pol->plid] = cpd; + cpd->blkcg = blkcg; + cpd->plid = pol->plid; + if (pol->cpd_init_fn) + pol->cpd_init_fn(cpd); + } + } + + mutex_unlock(&blkcg_pol_mutex); + + /* everything is in place, add intf files for the new policy */ + if (pol->dfl_cftypes) + WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys, + pol->dfl_cftypes)); + if (pol->legacy_cftypes) + WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys, + pol->legacy_cftypes)); + mutex_unlock(&blkcg_pol_register_mutex); + return 0; + +err_free_cpds: + if (pol->cpd_free_fn) { + list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) { + if (blkcg->cpd[pol->plid]) { + pol->cpd_free_fn(blkcg->cpd[pol->plid]); + blkcg->cpd[pol->plid] = NULL; + } + } + } + blkcg_policy[pol->plid] = NULL; +err_unlock: + mutex_unlock(&blkcg_pol_mutex); + mutex_unlock(&blkcg_pol_register_mutex); + return ret; +} +EXPORT_SYMBOL_GPL(blkcg_policy_register); + +/** + * blkcg_policy_unregister - unregister a blkcg policy + * @pol: blkcg policy to unregister + * + * Undo blkcg_policy_register(@pol). Might sleep. + */ +void blkcg_policy_unregister(struct blkcg_policy *pol) +{ + struct blkcg *blkcg; + + mutex_lock(&blkcg_pol_register_mutex); + + if (WARN_ON(blkcg_policy[pol->plid] != pol)) + goto out_unlock; + + /* kill the intf files first */ + if (pol->dfl_cftypes) + cgroup_rm_cftypes(pol->dfl_cftypes); + if (pol->legacy_cftypes) + cgroup_rm_cftypes(pol->legacy_cftypes); + + /* remove cpds and unregister */ + mutex_lock(&blkcg_pol_mutex); + + if (pol->cpd_free_fn) { + list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) { + if (blkcg->cpd[pol->plid]) { + pol->cpd_free_fn(blkcg->cpd[pol->plid]); + blkcg->cpd[pol->plid] = NULL; + } + } + } + blkcg_policy[pol->plid] = NULL; + + mutex_unlock(&blkcg_pol_mutex); +out_unlock: + mutex_unlock(&blkcg_pol_register_mutex); +} +EXPORT_SYMBOL_GPL(blkcg_policy_unregister); + +bool __blkcg_punt_bio_submit(struct bio *bio) +{ + struct blkcg_gq *blkg = bio->bi_blkg; + + /* consume the flag first */ + bio->bi_opf &= ~REQ_CGROUP_PUNT; + + /* never bounce for the root cgroup */ + if (!blkg->parent) + return false; + + spin_lock_bh(&blkg->async_bio_lock); + bio_list_add(&blkg->async_bios, bio); + spin_unlock_bh(&blkg->async_bio_lock); + + queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work); + return true; +} + +/* + * Scale the accumulated delay based on how long it has been since we updated + * the delay. We only call this when we are adding delay, in case it's been a + * while since we added delay, and when we are checking to see if we need to + * delay a task, to account for any delays that may have occurred. + */ +static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now) +{ + u64 old = atomic64_read(&blkg->delay_start); + + /* negative use_delay means no scaling, see blkcg_set_delay() */ + if (atomic_read(&blkg->use_delay) < 0) + return; + + /* + * We only want to scale down every second. The idea here is that we + * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain + * time window. We only want to throttle tasks for recent delay that + * has occurred, in 1 second time windows since that's the maximum + * things can be throttled. We save the current delay window in + * blkg->last_delay so we know what amount is still left to be charged + * to the blkg from this point onward. blkg->last_use keeps track of + * the use_delay counter. The idea is if we're unthrottling the blkg we + * are ok with whatever is happening now, and we can take away more of + * the accumulated delay as we've already throttled enough that + * everybody is happy with their IO latencies. + */ + if (time_before64(old + NSEC_PER_SEC, now) && + atomic64_cmpxchg(&blkg->delay_start, old, now) == old) { + u64 cur = atomic64_read(&blkg->delay_nsec); + u64 sub = min_t(u64, blkg->last_delay, now - old); + int cur_use = atomic_read(&blkg->use_delay); + + /* + * We've been unthrottled, subtract a larger chunk of our + * accumulated delay. + */ + if (cur_use < blkg->last_use) + sub = max_t(u64, sub, blkg->last_delay >> 1); + + /* + * This shouldn't happen, but handle it anyway. Our delay_nsec + * should only ever be growing except here where we subtract out + * min(last_delay, 1 second), but lord knows bugs happen and I'd + * rather not end up with negative numbers. + */ + if (unlikely(cur < sub)) { + atomic64_set(&blkg->delay_nsec, 0); + blkg->last_delay = 0; + } else { + atomic64_sub(sub, &blkg->delay_nsec); + blkg->last_delay = cur - sub; + } + blkg->last_use = cur_use; + } +} + +/* + * This is called when we want to actually walk up the hierarchy and check to + * see if we need to throttle, and then actually throttle if there is some + * accumulated delay. This should only be called upon return to user space so + * we're not holding some lock that would induce a priority inversion. + */ +static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay) +{ + unsigned long pflags; + bool clamp; + u64 now = ktime_to_ns(ktime_get()); + u64 exp; + u64 delay_nsec = 0; + int tok; + + while (blkg->parent) { + int use_delay = atomic_read(&blkg->use_delay); + + if (use_delay) { + u64 this_delay; + + blkcg_scale_delay(blkg, now); + this_delay = atomic64_read(&blkg->delay_nsec); + if (this_delay > delay_nsec) { + delay_nsec = this_delay; + clamp = use_delay > 0; + } + } + blkg = blkg->parent; + } + + if (!delay_nsec) + return; + + /* + * Let's not sleep for all eternity if we've amassed a huge delay. + * Swapping or metadata IO can accumulate 10's of seconds worth of + * delay, and we want userspace to be able to do _something_ so cap the + * delays at 0.25s. If there's 10's of seconds worth of delay then the + * tasks will be delayed for 0.25 second for every syscall. If + * blkcg_set_delay() was used as indicated by negative use_delay, the + * caller is responsible for regulating the range. + */ + if (clamp) + delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC); + + if (use_memdelay) + psi_memstall_enter(&pflags); + + exp = ktime_add_ns(now, delay_nsec); + tok = io_schedule_prepare(); + do { + __set_current_state(TASK_KILLABLE); + if (!schedule_hrtimeout(&exp, HRTIMER_MODE_ABS)) + break; + } while (!fatal_signal_pending(current)); + io_schedule_finish(tok); + + if (use_memdelay) + psi_memstall_leave(&pflags); +} + +/** + * blkcg_maybe_throttle_current - throttle the current task if it has been marked + * + * This is only called if we've been marked with set_notify_resume(). Obviously + * we can be set_notify_resume() for reasons other than blkcg throttling, so we + * check to see if current->throttle_queue is set and if not this doesn't do + * anything. This should only ever be called by the resume code, it's not meant + * to be called by people willy-nilly as it will actually do the work to + * throttle the task if it is setup for throttling. + */ +void blkcg_maybe_throttle_current(void) +{ + struct request_queue *q = current->throttle_queue; + struct cgroup_subsys_state *css; + struct blkcg *blkcg; + struct blkcg_gq *blkg; + bool use_memdelay = current->use_memdelay; + + if (!q) + return; + + current->throttle_queue = NULL; + current->use_memdelay = false; + + rcu_read_lock(); + css = kthread_blkcg(); + if (css) + blkcg = css_to_blkcg(css); + else + blkcg = css_to_blkcg(task_css(current, io_cgrp_id)); + + if (!blkcg) + goto out; + blkg = blkg_lookup(blkcg, q); + if (!blkg) + goto out; + if (!blkg_tryget(blkg)) + goto out; + rcu_read_unlock(); + + blkcg_maybe_throttle_blkg(blkg, use_memdelay); + blkg_put(blkg); + blk_put_queue(q); + return; +out: + rcu_read_unlock(); + blk_put_queue(q); +} + +/** + * blkcg_schedule_throttle - this task needs to check for throttling + * @q: the request queue IO was submitted on + * @use_memdelay: do we charge this to memory delay for PSI + * + * This is called by the IO controller when we know there's delay accumulated + * for the blkg for this task. We do not pass the blkg because there are places + * we call this that may not have that information, the swapping code for + * instance will only have a request_queue at that point. This set's the + * notify_resume for the task to check and see if it requires throttling before + * returning to user space. + * + * We will only schedule once per syscall. You can call this over and over + * again and it will only do the check once upon return to user space, and only + * throttle once. If the task needs to be throttled again it'll need to be + * re-set at the next time we see the task. + */ +void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay) +{ + if (unlikely(current->flags & PF_KTHREAD)) + return; + + if (!blk_get_queue(q)) + return; + + if (current->throttle_queue) + blk_put_queue(current->throttle_queue); + current->throttle_queue = q; + if (use_memdelay) + current->use_memdelay = use_memdelay; + set_notify_resume(current); +} + +/** + * blkcg_add_delay - add delay to this blkg + * @blkg: blkg of interest + * @now: the current time in nanoseconds + * @delta: how many nanoseconds of delay to add + * + * Charge @delta to the blkg's current delay accumulation. This is used to + * throttle tasks if an IO controller thinks we need more throttling. + */ +void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta) +{ + if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0)) + return; + blkcg_scale_delay(blkg, now); + atomic64_add(delta, &blkg->delay_nsec); +} + +/** + * blkg_tryget_closest - try and get a blkg ref on the closet blkg + * @bio: target bio + * @css: target css + * + * As the failure mode here is to walk up the blkg tree, this ensure that the + * blkg->parent pointers are always valid. This returns the blkg that it ended + * up taking a reference on or %NULL if no reference was taken. + */ +static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, + struct cgroup_subsys_state *css) +{ + struct blkcg_gq *blkg, *ret_blkg = NULL; + + rcu_read_lock(); + blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_disk->queue); + while (blkg) { + if (blkg_tryget(blkg)) { + ret_blkg = blkg; + break; + } + blkg = blkg->parent; + } + rcu_read_unlock(); + + return ret_blkg; +} + +/** + * bio_associate_blkg_from_css - associate a bio with a specified css + * @bio: target bio + * @css: target css + * + * Associate @bio with the blkg found by combining the css's blkg and the + * request_queue of the @bio. An association failure is handled by walking up + * the blkg tree. Therefore, the blkg associated can be anything between @blkg + * and q->root_blkg. This situation only happens when a cgroup is dying and + * then the remaining bios will spill to the closest alive blkg. + * + * A reference will be taken on the blkg and will be released when @bio is + * freed. + */ +void bio_associate_blkg_from_css(struct bio *bio, + struct cgroup_subsys_state *css) +{ + if (bio->bi_blkg) + blkg_put(bio->bi_blkg); + + if (css && css->parent) { + bio->bi_blkg = blkg_tryget_closest(bio, css); + } else { + blkg_get(bio->bi_disk->queue->root_blkg); + bio->bi_blkg = bio->bi_disk->queue->root_blkg; + } +} +EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); + +/** + * bio_associate_blkg - associate a bio with a blkg + * @bio: target bio + * + * Associate @bio with the blkg found from the bio's css and request_queue. + * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is + * already associated, the css is reused and association redone as the + * request_queue may have changed. + */ +void bio_associate_blkg(struct bio *bio) +{ + struct cgroup_subsys_state *css; + + rcu_read_lock(); + + if (bio->bi_blkg) + css = &bio_blkcg(bio)->css; + else + css = blkcg_css(); + + bio_associate_blkg_from_css(bio, css); + + rcu_read_unlock(); +} +EXPORT_SYMBOL_GPL(bio_associate_blkg); + +/** + * bio_clone_blkg_association - clone blkg association from src to dst bio + * @dst: destination bio + * @src: source bio + */ +void bio_clone_blkg_association(struct bio *dst, struct bio *src) +{ + if (src->bi_blkg) + bio_associate_blkg_from_css(dst, &bio_blkcg(src)->css); +} +EXPORT_SYMBOL_GPL(bio_clone_blkg_association); + +static int blk_cgroup_io_type(struct bio *bio) +{ + if (op_is_discard(bio->bi_opf)) + return BLKG_IOSTAT_DISCARD; + if (op_is_write(bio->bi_opf)) + return BLKG_IOSTAT_WRITE; + return BLKG_IOSTAT_READ; +} + +void blk_cgroup_bio_start(struct bio *bio) +{ + int rwd = blk_cgroup_io_type(bio), cpu; + struct blkg_iostat_set *bis; + + cpu = get_cpu(); + bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu); + u64_stats_update_begin(&bis->sync); + + /* + * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split + * bio and we would have already accounted for the size of the bio. + */ + if (!bio_flagged(bio, BIO_CGROUP_ACCT)) { + bio_set_flag(bio, BIO_CGROUP_ACCT); + bis->cur.bytes[rwd] += bio->bi_iter.bi_size; + } + bis->cur.ios[rwd]++; + + u64_stats_update_end(&bis->sync); + if (cgroup_subsys_on_dfl(io_cgrp_subsys)) + cgroup_rstat_updated(bio->bi_blkg->blkcg->css.cgroup, cpu); + put_cpu(); +} + +static int __init blkcg_init(void) +{ + blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio", + WQ_MEM_RECLAIM | WQ_FREEZABLE | + WQ_UNBOUND | WQ_SYSFS, 0); + if (!blkcg_punt_bio_wq) + return -ENOMEM; + return 0; +} +subsys_initcall(blkcg_init); + +module_param(blkcg_debug_stats, bool, 0644); +MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not"); |