diff options
Diffstat (limited to '')
| -rw-r--r-- | block/blk-cgroup.c | 1834 |
1 files changed, 1834 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c new file mode 100644 index 000000000..ddde117eb --- /dev/null +++ b/block/blk-cgroup.c @@ -0,0 +1,1834 @@ +/* + * 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 "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; + +static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS]; + +static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */ + +static bool blkcg_debug_stats = false; + +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]); + + if (blkg->blkcg != &blkcg_root) + blk_exit_rl(blkg->q, &blkg->rl); + + blkg_rwstat_exit(&blkg->stat_ios); + blkg_rwstat_exit(&blkg->stat_bytes); + kfree(blkg); +} + +/** + * 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; + + /* alloc and init base part */ + blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node); + if (!blkg) + return NULL; + + if (blkg_rwstat_init(&blkg->stat_bytes, gfp_mask) || + blkg_rwstat_init(&blkg->stat_ios, gfp_mask)) + goto err_free; + + blkg->q = q; + INIT_LIST_HEAD(&blkg->q_node); + blkg->blkcg = blkcg; + atomic_set(&blkg->refcnt, 1); + + /* root blkg uses @q->root_rl, init rl only for !root blkgs */ + if (blkcg != &blkcg_root) { + if (blk_init_rl(&blkg->rl, q, gfp_mask)) + goto err_free; + blkg->rl.blkg = blkg; + } + + 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->node); + 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; + struct bdi_writeback_congested *wb_congested; + int i, ret; + + WARN_ON_ONCE(!rcu_read_lock_held()); + lockdep_assert_held(q->queue_lock); + + /* blkg holds a reference to blkcg */ + if (!css_tryget_online(&blkcg->css)) { + ret = -ENODEV; + goto err_free_blkg; + } + + wb_congested = wb_congested_get_create(q->backing_dev_info, + blkcg->css.id, + GFP_NOWAIT | __GFP_NOWARN); + if (!wb_congested) { + ret = -ENOMEM; + goto err_put_css; + } + + /* allocate */ + if (!new_blkg) { + new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT | __GFP_NOWARN); + if (unlikely(!new_blkg)) { + ret = -ENOMEM; + goto err_put_congested; + } + } + blkg = new_blkg; + blkg->wb_congested = wb_congested; + + /* 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_congested; + } + 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_congested: + wb_congested_put(wb_congested); +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 @q->queue_lock. + * + * Returns pointer to the looked up or created blkg on success, ERR_PTR() + * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not + * dead and bypassing, returns ERR_PTR(-EBUSY). + */ +struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, + struct request_queue *q) +{ + struct blkcg_gq *blkg; + + WARN_ON_ONCE(!rcu_read_lock_held()); + lockdep_assert_held(q->queue_lock); + + /* + * This could be the first entry point of blkcg implementation and + * we shouldn't allow anything to go through for a bypassing queue. + */ + if (unlikely(blk_queue_bypass(q))) + return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY); + + blkg = __blkg_lookup(blkcg, q, true); + if (blkg) + return blkg; + + /* + * 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 = blkcg_parent(blkcg); + + while (parent && !__blkg_lookup(parent, q, false)) { + pos = parent; + parent = blkcg_parent(parent); + } + + blkg = blkg_create(pos, q, NULL); + if (pos == blkcg || IS_ERR(blkg)) + return blkg; + } +} + +static void blkg_destroy(struct blkcg_gq *blkg) +{ + struct blkcg *blkcg = blkg->blkcg; + struct blkcg_gq *parent = blkg->parent; + 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]); + } + + if (parent) { + blkg_rwstat_add_aux(&parent->stat_bytes, &blkg->stat_bytes); + blkg_rwstat_add_aux(&parent->stat_ios, &blkg->stat_ios); + } + + 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. + */ + blkg_put(blkg); +} + +/** + * 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; + + lockdep_assert_held(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; + q->root_rl.blkg = NULL; +} + +/* + * 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. + */ +void __blkg_release_rcu(struct rcu_head *rcu_head) +{ + struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head); + + /* release the blkcg and parent blkg refs this blkg has been holding */ + css_put(&blkg->blkcg->css); + if (blkg->parent) + blkg_put(blkg->parent); + + wb_congested_put(blkg->wb_congested); + + blkg_free(blkg); +} +EXPORT_SYMBOL_GPL(__blkg_release_rcu); + +/* + * The next function used by blk_queue_for_each_rl(). It's a bit tricky + * because the root blkg uses @q->root_rl instead of its own rl. + */ +struct request_list *__blk_queue_next_rl(struct request_list *rl, + struct request_queue *q) +{ + struct list_head *ent; + struct blkcg_gq *blkg; + + /* + * Determine the current blkg list_head. The first entry is + * root_rl which is off @q->blkg_list and mapped to the head. + */ + if (rl == &q->root_rl) { + ent = &q->blkg_list; + /* There are no more block groups, hence no request lists */ + if (list_empty(ent)) + return NULL; + } else { + blkg = container_of(rl, struct blkcg_gq, rl); + ent = &blkg->q_node; + } + + /* walk to the next list_head, skip root blkcg */ + ent = ent->next; + if (ent == &q->root_blkg->q_node) + ent = ent->next; + if (ent == &q->blkg_list) + return NULL; + + blkg = container_of(ent, struct blkcg_gq, q_node); + return &blkg->rl; +} + +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; + + 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) { + blkg_rwstat_reset(&blkg->stat_bytes); + blkg_rwstat_reset(&blkg->stat_ios); + + 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; +} +EXPORT_SYMBOL_GPL(blkg_dev_name); + +/** + * 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); + +/** + * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat + * @sf: seq_file to print to + * @pd: policy private data of interest + * @rwstat: rwstat to print + * + * Print @rwstat to @sf for the device assocaited with @pd. + */ +u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd, + const struct blkg_rwstat *rwstat) +{ + static const char *rwstr[] = { + [BLKG_RWSTAT_READ] = "Read", + [BLKG_RWSTAT_WRITE] = "Write", + [BLKG_RWSTAT_SYNC] = "Sync", + [BLKG_RWSTAT_ASYNC] = "Async", + [BLKG_RWSTAT_DISCARD] = "Discard", + }; + const char *dname = blkg_dev_name(pd->blkg); + u64 v; + int i; + + if (!dname) + return 0; + + for (i = 0; i < BLKG_RWSTAT_NR; i++) + seq_printf(sf, "%s %s %llu\n", dname, rwstr[i], + (unsigned long long)atomic64_read(&rwstat->aux_cnt[i])); + + v = atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_READ]) + + atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]) + + atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_DISCARD]); + seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v); + return v; +} +EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat); + +/** + * blkg_prfill_stat - prfill callback for blkg_stat + * @sf: seq_file to print to + * @pd: policy private data of interest + * @off: offset to the blkg_stat in @pd + * + * prfill callback for printing a blkg_stat. + */ +u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off) +{ + return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off)); +} +EXPORT_SYMBOL_GPL(blkg_prfill_stat); + +/** + * blkg_prfill_rwstat - prfill callback for blkg_rwstat + * @sf: seq_file to print to + * @pd: policy private data of interest + * @off: offset to the blkg_rwstat in @pd + * + * prfill callback for printing a blkg_rwstat. + */ +u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd, + int off) +{ + struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off); + + return __blkg_prfill_rwstat(sf, pd, &rwstat); +} +EXPORT_SYMBOL_GPL(blkg_prfill_rwstat); + +static u64 blkg_prfill_rwstat_field(struct seq_file *sf, + struct blkg_policy_data *pd, int off) +{ + struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->blkg + off); + + return __blkg_prfill_rwstat(sf, pd, &rwstat); +} + +/** + * blkg_print_stat_bytes - seq_show callback for blkg->stat_bytes + * @sf: seq_file to print to + * @v: unused + * + * To be used as cftype->seq_show to print blkg->stat_bytes. + * cftype->private must be set to the blkcg_policy. + */ +int blkg_print_stat_bytes(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), + blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private, + offsetof(struct blkcg_gq, stat_bytes), true); + return 0; +} +EXPORT_SYMBOL_GPL(blkg_print_stat_bytes); + +/** + * blkg_print_stat_bytes - seq_show callback for blkg->stat_ios + * @sf: seq_file to print to + * @v: unused + * + * To be used as cftype->seq_show to print blkg->stat_ios. cftype->private + * must be set to the blkcg_policy. + */ +int blkg_print_stat_ios(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), + blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private, + offsetof(struct blkcg_gq, stat_ios), true); + return 0; +} +EXPORT_SYMBOL_GPL(blkg_print_stat_ios); + +static u64 blkg_prfill_rwstat_field_recursive(struct seq_file *sf, + struct blkg_policy_data *pd, + int off) +{ + struct blkg_rwstat rwstat = blkg_rwstat_recursive_sum(pd->blkg, + NULL, off); + return __blkg_prfill_rwstat(sf, pd, &rwstat); +} + +/** + * blkg_print_stat_bytes_recursive - recursive version of blkg_print_stat_bytes + * @sf: seq_file to print to + * @v: unused + */ +int blkg_print_stat_bytes_recursive(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), + blkg_prfill_rwstat_field_recursive, + (void *)seq_cft(sf)->private, + offsetof(struct blkcg_gq, stat_bytes), true); + return 0; +} +EXPORT_SYMBOL_GPL(blkg_print_stat_bytes_recursive); + +/** + * blkg_print_stat_ios_recursive - recursive version of blkg_print_stat_ios + * @sf: seq_file to print to + * @v: unused + */ +int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v) +{ + blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), + blkg_prfill_rwstat_field_recursive, + (void *)seq_cft(sf)->private, + offsetof(struct blkcg_gq, stat_ios), true); + return 0; +} +EXPORT_SYMBOL_GPL(blkg_print_stat_ios_recursive); + +/** + * blkg_stat_recursive_sum - collect hierarchical blkg_stat + * @blkg: blkg of interest + * @pol: blkcg_policy which contains the blkg_stat + * @off: offset to the blkg_stat in blkg_policy_data or @blkg + * + * Collect the blkg_stat specified by @blkg, @pol and @off and all its + * online descendants and their aux counts. The caller must be holding the + * queue lock for online tests. + * + * If @pol is NULL, blkg_stat is at @off bytes into @blkg; otherwise, it is + * at @off bytes into @blkg's blkg_policy_data of the policy. + */ +u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg, + struct blkcg_policy *pol, int off) +{ + struct blkcg_gq *pos_blkg; + struct cgroup_subsys_state *pos_css; + u64 sum = 0; + + lockdep_assert_held(blkg->q->queue_lock); + + rcu_read_lock(); + blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) { + struct blkg_stat *stat; + + if (!pos_blkg->online) + continue; + + if (pol) + stat = (void *)blkg_to_pd(pos_blkg, pol) + off; + else + stat = (void *)blkg + off; + + sum += blkg_stat_read(stat) + atomic64_read(&stat->aux_cnt); + } + rcu_read_unlock(); + + return sum; +} +EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum); + +/** + * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat + * @blkg: blkg of interest + * @pol: blkcg_policy which contains the blkg_rwstat + * @off: offset to the blkg_rwstat in blkg_policy_data or @blkg + * + * Collect the blkg_rwstat specified by @blkg, @pol and @off and all its + * online descendants and their aux counts. The caller must be holding the + * queue lock for online tests. + * + * If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it + * is at @off bytes into @blkg's blkg_policy_data of the policy. + */ +struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg, + struct blkcg_policy *pol, int off) +{ + struct blkcg_gq *pos_blkg; + struct cgroup_subsys_state *pos_css; + struct blkg_rwstat sum = { }; + int i; + + lockdep_assert_held(blkg->q->queue_lock); + + rcu_read_lock(); + blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) { + struct blkg_rwstat *rwstat; + + if (!pos_blkg->online) + continue; + + if (pol) + rwstat = (void *)blkg_to_pd(pos_blkg, pol) + off; + else + rwstat = (void *)pos_blkg + off; + + for (i = 0; i < BLKG_RWSTAT_NR; i++) + atomic64_add(atomic64_read(&rwstat->aux_cnt[i]) + + percpu_counter_sum_positive(&rwstat->cpu_cnt[i]), + &sum.aux_cnt[i]); + } + rcu_read_unlock(); + + return sum; +} +EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum); + +/* 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); + + /* + * This could be the first entry point of blkcg implementation and + * we shouldn't allow anything to go through for a bypassing queue. + */ + if (unlikely(blk_queue_bypass(q))) + return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY); + + return __blkg_lookup(blkcg, q, true /* update_hint */); +} + +/** + * 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; + unsigned int major, minor; + int key_len, part, ret; + char *body; + + if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2) + return -EINVAL; + + body = input + key_len; + if (!isspace(*body)) + return -EINVAL; + body = skip_spaces(body); + + disk = get_gendisk(MKDEV(major, minor), &part); + if (!disk) + return -ENODEV; + if (part) { + ret = -ENODEV; + goto fail; + } + + 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 (unlikely(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 = body; + 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 int blkcg_print_stat(struct seq_file *sf, void *v) +{ + struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); + struct blkcg_gq *blkg; + + rcu_read_lock(); + + hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) { + const char *dname; + char *buf; + struct blkg_rwstat rwstat; + u64 rbytes, wbytes, rios, wios, dbytes, dios; + size_t size = seq_get_buf(sf, &buf), off = 0; + int i; + bool has_stats = false; + + 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); + + rwstat = blkg_rwstat_recursive_sum(blkg, NULL, + offsetof(struct blkcg_gq, stat_bytes)); + rbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]); + wbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]); + dbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_DISCARD]); + + rwstat = blkg_rwstat_recursive_sum(blkg, NULL, + offsetof(struct blkcg_gq, stat_ios)); + rios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]); + wios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]); + dios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_DISCARD]); + + 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) + goto next; + + if (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; + } +next: + 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", + .flags = CFTYPE_NOT_ON_ROOT, + .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 cgwb reference allowing step 2 to be triggered */ + blkcg_cgwb_put(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) +{ + 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 (spin_trylock(q->queue_lock)) { + blkg_destroy(blkg); + spin_unlock(q->queue_lock); + } else { + spin_unlock_irq(&blkcg->lock); + cpu_relax(); + spin_lock_irq(&blkcg->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); + 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); + refcount_set(&blkcg->cgwb_refcnt, 1); +#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; +} + +/** + * blkcg_init_queue - initialize blkcg part of request queue + * @q: request_queue to initialize + * + * Called from blk_alloc_queue_node(). 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; + q->root_rl.blkg = blkg; + spin_unlock_irq(q->queue_lock); + rcu_read_unlock(); + + if (preloaded) + radix_tree_preload_end(); + + ret = blk_iolatency_init(q); + if (ret) { + spin_lock_irq(q->queue_lock); + blkg_destroy_all(q); + spin_unlock_irq(q->queue_lock); + return ret; + } + + ret = blk_throtl_init(q); + if (ret) { + spin_lock_irq(q->queue_lock); + blkg_destroy_all(q); + spin_unlock_irq(q->queue_lock); + } + return ret; + +err_unlock: + spin_unlock_irq(q->queue_lock); + rcu_read_unlock(); + if (preloaded) + radix_tree_preload_end(); + return PTR_ERR(blkg); +} + +/** + * blkcg_drain_queue - drain blkcg part of request_queue + * @q: request_queue to drain + * + * Called from blk_drain_queue(). Responsible for draining blkcg part. + */ +void blkcg_drain_queue(struct request_queue *q) +{ + lockdep_assert_held(q->queue_lock); + + /* + * @q could be exiting and already have destroyed all blkgs as + * indicated by NULL root_blkg. If so, don't confuse policies. + */ + if (!q->root_blkg) + return; + + blk_throtl_drain(q); +} + +/** + * blkcg_exit_queue - exit and release blkcg part of request_queue + * @q: request_queue being released + * + * Called from blk_release_queue(). Responsible for exiting blkcg part. + */ +void blkcg_exit_queue(struct request_queue *q) +{ + spin_lock_irq(q->queue_lock); + blkg_destroy_all(q); + spin_unlock_irq(q->queue_lock); + + 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_offline = blkcg_css_offline, + .css_free = blkcg_css_free, + .can_attach = blkcg_can_attach, + .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; + int ret; + + if (blkcg_policy_enabled(q, pol)) + return 0; + + if (q->mq_ops) + blk_mq_freeze_queue(q); + else + blk_queue_bypass_start(q); +pd_prealloc: + if (!pd_prealloc) { + pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q->node); + if (!pd_prealloc) { + ret = -ENOMEM; + goto out_bypass_end; + } + } + + spin_lock_irq(q->queue_lock); + + list_for_each_entry(blkg, &q->blkg_list, q_node) { + struct blkg_policy_data *pd; + + if (blkg->pd[pol->plid]) + continue; + + pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q->node); + if (!pd) + swap(pd, pd_prealloc); + if (!pd) { + spin_unlock_irq(q->queue_lock); + goto pd_prealloc; + } + + blkg->pd[pol->plid] = pd; + pd->blkg = blkg; + pd->plid = pol->plid; + if (pol->pd_init_fn) + pol->pd_init_fn(pd); + } + + __set_bit(pol->plid, q->blkcg_pols); + ret = 0; + + spin_unlock_irq(q->queue_lock); +out_bypass_end: + if (q->mq_ops) + blk_mq_unfreeze_queue(q); + else + blk_queue_bypass_end(q); + if (pd_prealloc) + pol->pd_free_fn(pd_prealloc); + return ret; +} +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 (q->mq_ops) + blk_mq_freeze_queue(q); + else + blk_queue_bypass_start(q); + + spin_lock_irq(q->queue_lock); + + __clear_bit(pol->plid, q->blkcg_pols); + + list_for_each_entry(blkg, &q->blkg_list, q_node) { + 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_irq(q->queue_lock); + + if (q->mq_ops) + blk_mq_unfreeze_queue(q); + else + blk_queue_bypass_end(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; + 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); + +/* + * 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); + + /* + * 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) +{ + u64 now = ktime_to_ns(ktime_get()); + u64 exp; + u64 delay_nsec = 0; + int tok; + + while (blkg->parent) { + if (atomic_read(&blkg->use_delay)) { + blkcg_scale_delay(blkg, now); + delay_nsec = max_t(u64, delay_nsec, + atomic64_read(&blkg->delay_nsec)); + } + 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 1 second. If there's 10's of seconds worth of delay then + * the tasks will be delayed for 1 second for every syscall. + */ + delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC); + + /* + * TODO: the use_memdelay flag is going to be for the upcoming psi stuff + * that hasn't landed upstream yet. Once that stuff is in place we need + * to do a psi_memstall_enter/leave if memdelay is set. + */ + + 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); +} + +/** + * 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; + blkg = blkg_try_get(blkg); + if (!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); +} +EXPORT_SYMBOL_GPL(blkcg_maybe_throttle_current); + +/** + * 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); +} +EXPORT_SYMBOL_GPL(blkcg_schedule_throttle); + +/** + * blkcg_add_delay - add delay to this blkg + * @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) +{ + blkcg_scale_delay(blkg, now); + atomic64_add(delta, &blkg->delay_nsec); +} +EXPORT_SYMBOL_GPL(blkcg_add_delay); + +module_param(blkcg_debug_stats, bool, 0644); +MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not"); |