/* * Common Block IO controller cgroup interface * * Based on ideas and code from CFQ, CFS and BFQ: * Copyright (C) 2003 Jens Axboe * * Copyright (C) 2008 Fabio Checconi * Paolo Valente * * Copyright (C) 2009 Vivek Goyal * Nauman Rafique * * For policy-specific per-blkcg data: * Copyright (C) 2015 Paolo Valente * Arianna Avanzini */ #include #include #include #include #include #include #include #include #include #include #include #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_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->rl); 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; 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; } /* * 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 = -EINVAL; goto err_free_blkg; } wb_congested = wb_congested_get_create(&q->backing_dev_info, blkcg->css.id, GFP_NOWAIT); if (!wb_congested) { ret = -ENOMEM; goto err_put_css; } /* allocate */ if (!new_blkg) { new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT); 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 = -EINVAL; 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) ? -EINVAL : -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; } } EXPORT_SYMBOL_GPL(blkg_lookup_create); 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. */ 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); } } /* * 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) { 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; } static 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 dev_name(blkg->q->backing_dev_info.dev); 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); /** * __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", }; 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)rwstat->cnt[i]); v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE]; 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); /** * blkg_stat_recursive_sum - collect hierarchical blkg_stat * @pd: policy private data of interest * @off: offset to the blkg_stat in @pd * * Collect the blkg_stat specified by @off from @pd and all its online * descendants and return the sum. The caller must be holding the queue * lock for online tests. */ u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off) { struct blkcg_policy *pol = blkcg_policy[pd->plid]; struct blkcg_gq *pos_blkg; struct cgroup_subsys_state *pos_css; u64 sum = 0; lockdep_assert_held(pd->blkg->q->queue_lock); rcu_read_lock(); blkg_for_each_descendant_pre(pos_blkg, pos_css, pd_to_blkg(pd)) { struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol); struct blkg_stat *stat = (void *)pos_pd + off; if (pos_blkg->online) sum += blkg_stat_read(stat); } rcu_read_unlock(); return sum; } EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum); /** * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat * @pd: policy private data of interest * @off: offset to the blkg_stat in @pd * * Collect the blkg_rwstat specified by @off from @pd and all its online * descendants and return the sum. The caller must be holding the queue * lock for online tests. */ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd, int off) { struct blkcg_policy *pol = blkcg_policy[pd->plid]; struct blkcg_gq *pos_blkg; struct cgroup_subsys_state *pos_css; struct blkg_rwstat sum = { }; int i; lockdep_assert_held(pd->blkg->q->queue_lock); rcu_read_lock(); blkg_for_each_descendant_pre(pos_blkg, pos_css, pd_to_blkg(pd)) { struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol); struct blkg_rwstat *rwstat = (void *)pos_pd + off; struct blkg_rwstat tmp; if (!pos_blkg->online) continue; tmp = blkg_rwstat_read(rwstat); for (i = 0; i < BLKG_RWSTAT_NR; i++) sum.cnt[i] += tmp.cnt[i]; } rcu_read_unlock(); return sum; } EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum); /** * 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->v the new * value. 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, const char *input, struct blkg_conf_ctx *ctx) __acquires(rcu) __acquires(disk->queue->queue_lock) { struct gendisk *disk; struct blkcg_gq *blkg; unsigned int major, minor; unsigned long long v; int part, ret; if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3) return -EINVAL; disk = get_gendisk(MKDEV(major, minor), &part); if (!disk) return -EINVAL; if (part) { put_disk(disk); return -EINVAL; } rcu_read_lock(); spin_lock_irq(disk->queue->queue_lock); if (blkcg_policy_enabled(disk->queue, pol)) blkg = blkg_lookup_create(blkcg, disk->queue); else blkg = ERR_PTR(-EINVAL); if (IS_ERR(blkg)) { ret = PTR_ERR(blkg); rcu_read_unlock(); spin_unlock_irq(disk->queue->queue_lock); put_disk(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; } ctx->disk = disk; ctx->blkg = blkg; ctx->v = v; return 0; } 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(ctx->disk); } EXPORT_SYMBOL_GPL(blkg_conf_finish); struct cftype blkcg_files[] = { { .name = "reset_stats", .write_u64 = blkcg_reset_stats, }, { } /* terminate */ }; /** * blkcg_css_offline - cgroup css_offline callback * @css: css of interest * * This function is called when @css is about to go away and responsible * for shooting down all blkgs associated with @css. 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. * * This is the blkcg counterpart of ioc_release_fn(). */ static void blkcg_css_offline(struct cgroup_subsys_state *css) { struct blkcg *blkcg = css_to_blkcg(css); 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); wb_blkcg_offline(blkcg); } 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 free_blkcg; } } 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); 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]); free_blkcg: kfree(blkcg); 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 and count the existing blkgs. As * @q is bypassing at this point, blkg_lookup_create() can't be * used. Open code insertion. */ rcu_read_lock(); spin_lock_irq(q->queue_lock); blkg = blkg_create(&blkcg_root, q, new_blkg); spin_unlock_irq(q->queue_lock); rcu_read_unlock(); if (preloaded) radix_tree_preload_end(); if (IS_ERR(blkg)) { blkg_free(new_blkg); return PTR_ERR(blkg); } q->root_blkg = blkg; q->root_rl.blkg = blkg; 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; } /** * 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_subsys_state *css, struct cgroup_taskset *tset) { struct task_struct *task; struct io_context *ioc; int ret = 0; /* task_lock() is needed to avoid races with exit_io_context() */ cgroup_taskset_for_each(task, 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; } struct cgroup_subsys blkio_cgrp_subsys = { .css_alloc = blkcg_css_alloc, .css_offline = blkcg_css_offline, .css_free = blkcg_css_free, .can_attach = blkcg_can_attach, .legacy_cftypes = blkcg_files, #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(blkio_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; 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, 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: 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; 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) { /* grab blkcg lock too while removing @pd from @blkg */ spin_lock(&blkg->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(&blkg->blkcg->lock); } spin_unlock_irq(q->queue_lock); 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) 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) { mutex_unlock(&blkcg_pol_mutex); 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->cftypes) WARN_ON(cgroup_add_legacy_cftypes(&blkio_cgrp_subsys, pol->cftypes)); mutex_unlock(&blkcg_pol_register_mutex); return 0; err_free_cpds: if (pol->cpd_alloc_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->cftypes) cgroup_rm_cftypes(pol->cftypes); /* remove cpds and unregister */ mutex_lock(&blkcg_pol_mutex); if (pol->cpd_alloc_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);