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/* SPDX-License-Identifier: GPL-2.0 / #ifndef _BLK_CGROUP_H #define _BLK_CGROUP_H / * 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> / #include <linux/cgroup.h> #include <linux/percpu_counter.h> #include <linux/seq_file.h> #include <linux/radix-tree.h> #include <linux/blkdev.h> #include <linux/atomic.h> #include <linux/kthread.h> #include <linux/fs.h> #include <linux/blkdev.h> / percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter / #define BLKG_STAT_CPU_BATCH (INT_MAX / 2) / Max limits for throttle policy / #define THROTL_IOPS_MAX UINT_MAX #ifdef CONFIG_BLK_CGROUP enum blkg_rwstat_type { BLKG_RWSTAT_READ, BLKG_RWSTAT_WRITE, BLKG_RWSTAT_SYNC, BLKG_RWSTAT_ASYNC, BLKG_RWSTAT_DISCARD, BLKG_RWSTAT_NR, BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR, }; struct blkcg_gq; struct blkcg { struct cgroup_subsys_state css; spinlock_t lock; struct radix_tree_root blkg_tree; struct blkcg_gq __rcu blkg_hint; struct hlist_head blkg_list; struct blkcg_policy_data cpd[BLKCG_MAX_POLS]; struct list_head all_blkcgs_node; #ifdef CONFIG_CGROUP_WRITEBACK struct list_head cgwb_list; refcount_t cgwb_refcnt; #endif }; / * blkg_[rw]stat->aux_cnt is excluded for local stats but included for * recursive. Used to carry stats of dead children. / struct blkg_rwstat { struct percpu_counter cpu_cnt[BLKG_RWSTAT_NR]; atomic64_t aux_cnt[BLKG_RWSTAT_NR]; }; struct blkg_rwstat_sample { u64 cnt[BLKG_RWSTAT_NR]; }; / * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a * request_queue (q). This is used by blkcg policies which need to track * information per blkcg - q pair. * * There can be multiple active blkcg policies and each blkg:policy pair is * represented by a blkg_policy_data which is allocated and freed by each * policy's pd_alloc/free_fn() methods. A policy can allocate private data * area by allocating larger data structure which embeds blkg_policy_data * at the beginning. / struct blkg_policy_data { / the blkg and policy id this per-policy data belongs to / struct blkcg_gq blkg; int plid; }; /* * Policies that need to keep per-blkcg data which is independent from any * request_queue associated to it should implement cpd_alloc/free_fn() * methods. A policy can allocate private data area by allocating larger * data structure which embeds blkcg_policy_data at the beginning. * cpd_init() is invoked to let each policy handle per-blkcg data. / struct blkcg_policy_data { / the blkcg and policy id this per-policy data belongs to / struct blkcg blkcg; int plid; }; /* association between a blk cgroup and a request queue / struct blkcg_gq { / Pointer to the associated request_queue / struct request_queue q; struct list_head q_node; struct hlist_node blkcg_node; struct blkcg blkcg; / * Each blkg gets congested separately and the congestion state is * propagated to the matching bdi_writeback_congested. / struct bdi_writeback_congested wb_congested; /* all non-root blkcg_gq's are guaranteed to have access to parent / struct blkcg_gq parent; /* reference count / struct percpu_ref refcnt; / is this blkg online? protected by both blkcg and q locks / bool online; struct blkg_rwstat stat_bytes; struct blkg_rwstat stat_ios; struct blkg_policy_data pd[BLKCG_MAX_POLS]; spinlock_t async_bio_lock; struct bio_list async_bios; struct work_struct async_bio_work; atomic_t use_delay; atomic64_t delay_nsec; atomic64_t delay_start; u64 last_delay; int last_use; struct rcu_head rcu_head; }; typedef struct blkcg_policy_data (blkcg_pol_alloc_cpd_fn)(gfp_t gfp); typedef void (blkcg_pol_init_cpd_fn)(struct blkcg_policy_data cpd); typedef void (blkcg_pol_free_cpd_fn)(struct blkcg_policy_data cpd); typedef void (blkcg_pol_bind_cpd_fn)(struct blkcg_policy_data cpd); typedef struct blkg_policy_data (blkcg_pol_alloc_pd_fn)(gfp_t gfp, struct request_queue q, struct blkcg blkcg); typedef void (blkcg_pol_init_pd_fn)(struct blkg_policy_data pd); typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data pd); typedef void (blkcg_pol_offline_pd_fn)(struct blkg_policy_data pd); typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data pd); typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkg_policy_data pd); typedef size_t (blkcg_pol_stat_pd_fn)(struct blkg_policy_data pd, char buf, size_t size); struct blkcg_policy { int plid; /* cgroup files for the policy / struct cftype dfl_cftypes; struct cftype legacy_cftypes; / operations / blkcg_pol_alloc_cpd_fn cpd_alloc_fn; blkcg_pol_init_cpd_fn cpd_init_fn; blkcg_pol_free_cpd_fn cpd_free_fn; blkcg_pol_bind_cpd_fn cpd_bind_fn; blkcg_pol_alloc_pd_fn pd_alloc_fn; blkcg_pol_init_pd_fn pd_init_fn; blkcg_pol_online_pd_fn pd_online_fn; blkcg_pol_offline_pd_fn pd_offline_fn; blkcg_pol_free_pd_fn pd_free_fn; blkcg_pol_reset_pd_stats_fn pd_reset_stats_fn; blkcg_pol_stat_pd_fn pd_stat_fn; }; extern struct blkcg blkcg_root; extern struct cgroup_subsys_state * const blkcg_root_css; extern bool blkcg_debug_stats; struct blkcg_gq blkg_lookup_slowpath(struct blkcg blkcg, struct request_queue q, bool update_hint); struct blkcg_gq __blkg_lookup_create(struct blkcg blkcg, struct request_queue q); struct blkcg_gq blkg_lookup_create(struct blkcg blkcg, struct request_queue q); int blkcg_init_queue(struct request_queue q); void blkcg_drain_queue(struct request_queue q); void blkcg_exit_queue(struct request_queue q); /* Blkio controller policy registration / int blkcg_policy_register(struct blkcg_policy pol); void blkcg_policy_unregister(struct blkcg_policy pol); int blkcg_activate_policy(struct request_queue q, const struct blkcg_policy pol); void blkcg_deactivate_policy(struct request_queue q, const struct blkcg_policy pol); static inline u64 blkg_rwstat_read_counter(struct blkg_rwstat rwstat, unsigned int idx) { return atomic64_read(&rwstat->aux_cnt[idx]) + percpu_counter_sum_positive(&rwstat->cpu_cnt[idx]); } const char blkg_dev_name(struct blkcg_gq blkg); 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); u64 __blkg_prfill_u64(struct seq_file sf, struct blkg_policy_data pd, u64 v); u64 __blkg_prfill_rwstat(struct seq_file sf, struct blkg_policy_data pd, const struct blkg_rwstat_sample rwstat); u64 blkg_prfill_rwstat(struct seq_file sf, struct blkg_policy_data pd, int off); int blkg_print_stat_bytes(struct seq_file sf, void v); int blkg_print_stat_ios(struct seq_file sf, void v); int blkg_print_stat_bytes_recursive(struct seq_file sf, void v); int blkg_print_stat_ios_recursive(struct seq_file sf, void v); void blkg_rwstat_recursive_sum(struct blkcg_gq blkg, struct blkcg_policy pol, int off, struct blkg_rwstat_sample sum); struct blkg_conf_ctx { struct gendisk disk; struct blkcg_gq blkg; char body; }; struct gendisk blkcg_conf_get_disk(char *inputp); int blkg_conf_prep(struct blkcg blkcg, const struct blkcg_policy pol, char input, struct blkg_conf_ctx ctx); void blkg_conf_finish(struct blkg_conf_ctx ctx); /** * blkcg_css - find the current css * * Find the css associated with either the kthread or the current task. * This may return a dying css, so it is up to the caller to use tryget logic * to confirm it is alive and well. / static inline struct cgroup_subsys_state blkcg_css(void) { struct cgroup_subsys_state css; css = kthread_blkcg(); if (css) return css; return task_css(current, io_cgrp_id); } static inline struct blkcg css_to_blkcg(struct cgroup_subsys_state css) { return css ? container_of(css, struct blkcg, css) : NULL; } /* * __bio_blkcg - internal, inconsistent version to get blkcg * * DO NOT USE. * This function is inconsistent and consequently is dangerous to use. The * first part of the function returns a blkcg where a reference is owned by the * bio. This means it does not need to be rcu protected as it cannot go away * with the bio owning a reference to it. However, the latter potentially gets * it from task_css(). This can race against task migration and the cgroup * dying. It is also semantically different as it must be called rcu protected * and is susceptible to failure when trying to get a reference to it. * Therefore, it is not ok to assume that _get() will always succeed on the blkcg returned here. / static inline struct blkcg __bio_blkcg(struct bio bio) { if (bio && bio->bi_blkg) return bio->bi_blkg->blkcg; return css_to_blkcg(blkcg_css()); } /* * bio_blkcg - grab the blkcg associated with a bio * @bio: target bio * * This returns the blkcg associated with a bio, %NULL if not associated. * Callers are expected to either handle %NULL or know association has been * done prior to calling this. / static inline struct blkcg bio_blkcg(struct bio bio) { if (bio && bio->bi_blkg) return bio->bi_blkg->blkcg; return NULL; } static inline bool blk_cgroup_congested(void) { struct cgroup_subsys_state css; bool ret = false; rcu_read_lock(); css = kthread_blkcg(); if (!css) css = task_css(current, io_cgrp_id); while (css) { if (atomic_read(&css->cgroup->congestion_count)) { ret = true; break; } css = css->parent; } rcu_read_unlock(); return ret; } /** * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg * @return: true if this bio needs to be submitted with the root blkg context. * * In order to avoid priority inversions we sometimes need to issue a bio as if * it were attached to the root blkg, and then backcharge to the actual owning * blkg. The idea is we do bio_blkcg() to look up the actual context for the * bio and attach the appropriate blkg to the bio. Then we call this helper and * if it is true run with the root blkg for that queue and then do any * backcharging to the originating cgroup once the io is complete. / static inline bool bio_issue_as_root_blkg(struct bio bio) { return (bio->bi_opf & (REQ_META \| REQ_SWAP)) != 0; } /** * blkcg_parent - get the parent of a blkcg * @blkcg: blkcg of interest * * Return the parent blkcg of @blkcg. Can be called anytime. / static inline struct blkcg blkcg_parent(struct blkcg blkcg) { return css_to_blkcg(blkcg->css.parent); } /* * __blkg_lookup - internal version of blkg_lookup() * @blkcg: blkcg of interest * @q: request_queue of interest * @update_hint: whether to update lookup hint with the result or not * * This is internal version and shouldn't be used by policy * implementations. Looks up blkgs for the @blkcg - @q pair regardless of * @q's bypass state. If @update_hint is %true, the caller should be * holding @q->queue_lock and lookup hint is updated on success. / static inline struct blkcg_gq __blkg_lookup(struct blkcg blkcg, struct request_queue q, bool update_hint) { struct blkcg_gq blkg; if (blkcg == &blkcg_root) return q->root_blkg; blkg = rcu_dereference(blkcg->blkg_hint); if (blkg && blkg->q == q) return blkg; return blkg_lookup_slowpath(blkcg, q, update_hint); } /* * blkg_lookup - lookup blkg for the specified blkcg - q pair * @blkcg: blkcg of interest * @q: request_queue of interest * * Lookup blkg for the @blkcg - @q pair. This function should be called * under RCU read lock. / static inline struct blkcg_gq blkg_lookup(struct blkcg blkcg, struct request_queue q) { WARN_ON_ONCE(!rcu_read_lock_held()); return __blkg_lookup(blkcg, q, false); } /** * blk_queue_root_blkg - return blkg for the (blkcg_root, @q) pair * @q: request_queue of interest * * Lookup blkg for @q at the root level. See also blkg_lookup(). / static inline struct blkcg_gq blk_queue_root_blkg(struct request_queue q) { return q->root_blkg; } /* * blkg_to_pdata - get policy private data * @blkg: blkg of interest * @pol: policy of interest * * Return pointer to private data associated with the @blkg-@pol pair. / static inline struct blkg_policy_data blkg_to_pd(struct blkcg_gq blkg, struct blkcg_policy pol) { return blkg ? blkg->pd[pol->plid] : NULL; } static inline struct blkcg_policy_data blkcg_to_cpd(struct blkcg blkcg, struct blkcg_policy pol) { return blkcg ? blkcg->cpd[pol->plid] : NULL; } /* * pdata_to_blkg - get blkg associated with policy private data * @pd: policy private data of interest * * @pd is policy private data. Determine the blkg it's associated with. / static inline struct blkcg_gq pd_to_blkg(struct blkg_policy_data pd) { return pd ? pd->blkg : NULL; } static inline struct blkcg cpd_to_blkcg(struct blkcg_policy_data cpd) { return cpd ? cpd->blkcg : NULL; } extern void blkcg_destroy_blkgs(struct blkcg blkcg); #ifdef CONFIG_CGROUP_WRITEBACK /** * blkcg_cgwb_get - get a reference for blkcg->cgwb_list * @blkcg: blkcg of interest * * This is used to track the number of active wb's related to a blkcg. / static inline void blkcg_cgwb_get(struct blkcg blkcg) { refcount_inc(&blkcg->cgwb_refcnt); } /** * blkcg_cgwb_put - put a reference for @blkcg->cgwb_list * @blkcg: blkcg of interest * * This is used to track the number of active wb's related to a blkcg. * When this count goes to zero, all active wb has finished so the * blkcg can continue destruction by calling blkcg_destroy_blkgs(). * This work may occur in cgwb_release_workfn() on the cgwb_release * workqueue. / static inline void blkcg_cgwb_put(struct blkcg blkcg) { if (refcount_dec_and_test(&blkcg->cgwb_refcnt)) blkcg_destroy_blkgs(blkcg); } #else static inline void blkcg_cgwb_get(struct blkcg blkcg) { } static inline void blkcg_cgwb_put(struct blkcg blkcg) { /* wb isn't being accounted, so trigger destruction right away / blkcg_destroy_blkgs(blkcg); } #endif /* * blkg_path - format cgroup path of blkg * @blkg: blkg of interest * @buf: target buffer * @buflen: target buffer length * * Format the path of the cgroup of @blkg into @buf. / static inline int blkg_path(struct blkcg_gq blkg, char buf, int buflen) { return cgroup_path(blkg->blkcg->css.cgroup, buf, buflen); } /* * blkg_get - get a blkg reference * @blkg: blkg to get * * The caller should be holding an existing reference. / static inline void blkg_get(struct blkcg_gq blkg) { percpu_ref_get(&blkg->refcnt); } /** * blkg_tryget - try and get a blkg reference * @blkg: blkg to get * * This is for use when doing an RCU lookup of the blkg. We may be in the midst * of freeing this blkg, so we can only use it if the refcnt is not zero. / static inline bool blkg_tryget(struct blkcg_gq blkg) { return blkg && percpu_ref_tryget(&blkg->refcnt); } /** * blkg_tryget_closest - try and get a blkg ref on the closet blkg * @blkg: blkg to get * * This needs to be called rcu protected. 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 blkcg_gq blkg) { struct blkcg_gq ret_blkg = NULL; WARN_ON_ONCE(!rcu_read_lock_held()); while (blkg) { if (blkg_tryget(blkg)) { ret_blkg = blkg; break; } blkg = blkg->parent; } return ret_blkg; } /** * blkg_put - put a blkg reference * @blkg: blkg to put / static inline void blkg_put(struct blkcg_gq blkg) { percpu_ref_put(&blkg->refcnt); } /** * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants * @d_blkg: loop cursor pointing to the current descendant * @pos_css: used for iteration * @p_blkg: target blkg to walk descendants of * * Walk @c_blkg through the descendants of @p_blkg. Must be used with RCU * read locked. If called under either blkcg or queue lock, the iteration * is guaranteed to include all and only online blkgs. The caller may * update @pos_css by calling css_rightmost_descendant() to skip subtree. * @p_blkg is included in the iteration and the first node to be visited. / #define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg) \ css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css) \ if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css), \ (p_blkg)->q, false))) /* * blkg_for_each_descendant_post - post-order walk of a blkg's descendants * @d_blkg: loop cursor pointing to the current descendant * @pos_css: used for iteration * @p_blkg: target blkg to walk descendants of * * Similar to blkg_for_each_descendant_pre() but performs post-order * traversal instead. Synchronization rules are the same. @p_blkg is * included in the iteration and the last node to be visited. / #define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg) \ css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css) \ if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css), \ (p_blkg)->q, false))) static inline int blkg_rwstat_init(struct blkg_rwstat rwstat, gfp_t gfp) { int i, ret; for (i = 0; i < BLKG_RWSTAT_NR; i++) { ret = percpu_counter_init(&rwstat->cpu_cnt[i], 0, gfp); if (ret) { while (--i >= 0) percpu_counter_destroy(&rwstat->cpu_cnt[i]); return ret; } atomic64_set(&rwstat->aux_cnt[i], 0); } return 0; } static inline void blkg_rwstat_exit(struct blkg_rwstat rwstat) { int i; for (i = 0; i < BLKG_RWSTAT_NR; i++) percpu_counter_destroy(&rwstat->cpu_cnt[i]); } /* * blkg_rwstat_add - add a value to a blkg_rwstat * @rwstat: target blkg_rwstat * @op: REQ_OP and flags * @val: value to add * * Add @val to @rwstat. The counters are chosen according to @rw. The * caller is responsible for synchronizing calls to this function. / static inline void blkg_rwstat_add(struct blkg_rwstat rwstat, unsigned int op, uint64_t val) { struct percpu_counter cnt; if (op_is_discard(op)) cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_DISCARD]; else if (op_is_write(op)) cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_WRITE]; else cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_READ]; percpu_counter_add_batch(cnt, val, BLKG_STAT_CPU_BATCH); if (op_is_sync(op)) cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_SYNC]; else cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_ASYNC]; percpu_counter_add_batch(cnt, val, BLKG_STAT_CPU_BATCH); } /* * blkg_rwstat_read - read the current values of a blkg_rwstat * @rwstat: blkg_rwstat to read * * Read the current snapshot of @rwstat and return it in the aux counts. / static inline void blkg_rwstat_read(struct blkg_rwstat rwstat, struct blkg_rwstat_sample result) { int i; for (i = 0; i < BLKG_RWSTAT_NR; i++) result->cnt[i] = percpu_counter_sum_positive(&rwstat->cpu_cnt[i]); } /* * blkg_rwstat_total - read the total count of a blkg_rwstat * @rwstat: blkg_rwstat to read * * Return the total count of @rwstat regardless of the IO direction. This * function can be called without synchronization and takes care of u64 * atomicity. / static inline uint64_t blkg_rwstat_total(struct blkg_rwstat rwstat) { struct blkg_rwstat_sample tmp = { }; blkg_rwstat_read(rwstat, &tmp); return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE]; } /** * blkg_rwstat_reset - reset a blkg_rwstat * @rwstat: blkg_rwstat to reset / static inline void blkg_rwstat_reset(struct blkg_rwstat rwstat) { int i; for (i = 0; i < BLKG_RWSTAT_NR; i++) { percpu_counter_set(&rwstat->cpu_cnt[i], 0); atomic64_set(&rwstat->aux_cnt[i], 0); } } /** * blkg_rwstat_add_aux - add a blkg_rwstat into another's aux count * @to: the destination blkg_rwstat * @from: the source * * Add @from's count including the aux one to @to's aux count. / static inline void blkg_rwstat_add_aux(struct blkg_rwstat to, struct blkg_rwstat from) { u64 sum[BLKG_RWSTAT_NR]; int i; for (i = 0; i < BLKG_RWSTAT_NR; i++) sum[i] = percpu_counter_sum_positive(&from->cpu_cnt[i]); for (i = 0; i < BLKG_RWSTAT_NR; i++) atomic64_add(sum[i] + atomic64_read(&from->aux_cnt[i]), &to->aux_cnt[i]); } #ifdef CONFIG_BLK_DEV_THROTTLING extern bool blk_throtl_bio(struct request_queue q, struct blkcg_gq blkg, struct bio bio); #else static inline bool blk_throtl_bio(struct request_queue q, struct blkcg_gq blkg, struct bio bio) { return false; } #endif bool __blkcg_punt_bio_submit(struct bio bio); static inline bool blkcg_punt_bio_submit(struct bio bio) { if (bio->bi_opf & REQ_CGROUP_PUNT) return __blkcg_punt_bio_submit(bio); else return false; } static inline void blkcg_bio_issue_init(struct bio bio) { bio_issue_init(&bio->bi_issue, bio_sectors(bio)); } static inline bool blkcg_bio_issue_check(struct request_queue q, struct bio bio) { struct blkcg_gq blkg; bool throtl = false; rcu_read_lock(); if (!bio->bi_blkg) { char b[BDEVNAME_SIZE]; WARN_ONCE(1, "no blkg associated for bio on block-device: %s\n", bio_devname(bio, b)); bio_associate_blkg(bio); } blkg = bio->bi_blkg; throtl = blk_throtl_bio(q, blkg, bio); if (!throtl) { / * If the bio is flagged with BIO_QUEUE_ENTERED it means this * is a split bio and we would have already accounted for the * size of the bio. / if (!bio_flagged(bio, BIO_QUEUE_ENTERED)) blkg_rwstat_add(&blkg->stat_bytes, bio->bi_opf, bio->bi_iter.bi_size); blkg_rwstat_add(&blkg->stat_ios, bio->bi_opf, 1); } blkcg_bio_issue_init(bio); rcu_read_unlock(); return !throtl; } static inline void blkcg_use_delay(struct blkcg_gq blkg) { if (atomic_add_return(1, &blkg->use_delay) == 1) atomic_inc(&blkg->blkcg->css.cgroup->congestion_count); } /** * blk_cgroup_mergeable - Determine whether to allow or disallow merges * @rq: request to merge into * @bio: bio to merge * * @bio and @rq should belong to the same cgroup and their issue_as_root should * match. The latter is necessary as we don't want to throttle e.g. a metadata * update because it happens to be next to a regular IO. / static inline bool blk_cgroup_mergeable(struct request rq, struct bio bio) { return rq->bio->bi_blkg == bio->bi_blkg && bio_issue_as_root_blkg(rq->bio) == bio_issue_as_root_blkg(bio); } static inline int blkcg_unuse_delay(struct blkcg_gq blkg) { int old = atomic_read(&blkg->use_delay); if (old == 0) return 0; /* * We do this song and dance because we can race with somebody else * adding or removing delay. If we just did an atomic_dec we'd end up * negative and we'd already be in trouble. We need to subtract 1 and * then check to see if we were the last delay so we can drop the * congestion count on the cgroup. / while (old) { int cur = atomic_cmpxchg(&blkg->use_delay, old, old - 1); if (cur == old) break; old = cur; } if (old == 0) return 0; if (old == 1) atomic_dec(&blkg->blkcg->css.cgroup->congestion_count); return 1; } static inline void blkcg_clear_delay(struct blkcg_gq blkg) { int old = atomic_read(&blkg->use_delay); if (!old) return; /* We only want 1 person clearing the congestion count for this blkg. / while (old) { int cur = atomic_cmpxchg(&blkg->use_delay, old, 0); if (cur == old) { atomic_dec(&blkg->blkcg->css.cgroup->congestion_count); break; } old = cur; } } void blkcg_add_delay(struct blkcg_gq blkg, u64 now, u64 delta); void blkcg_schedule_throttle(struct request_queue q, bool use_memdelay); void blkcg_maybe_throttle_current(void); #else / CONFIG_BLK_CGROUP / struct blkcg { }; struct blkg_policy_data { }; struct blkcg_policy_data { }; struct blkcg_gq { }; struct blkcg_policy { }; #define blkcg_root_css ((struct cgroup_subsys_state )ERR_PTR(-EINVAL)) static inline void blkcg_maybe_throttle_current(void) { } static inline bool blk_cgroup_congested(void) { return false; } #ifdef CONFIG_BLOCK static inline void blkcg_schedule_throttle(struct request_queue q, bool use_memdelay) { } static inline struct blkcg_gq blkg_lookup(struct blkcg blkcg, void key) { return NULL; } static inline struct blkcg_gq blk_queue_root_blkg(struct request_queue q) { return NULL; } static inline int blkcg_init_queue(struct request_queue q) { return 0; } static inline void blkcg_drain_queue(struct request_queue q) { } static inline void blkcg_exit_queue(struct request_queue q) { } static inline int blkcg_policy_register(struct blkcg_policy pol) { return 0; } static inline void blkcg_policy_unregister(struct blkcg_policy pol) { } static inline int blkcg_activate_policy(struct request_queue q, const struct blkcg_policy pol) { return 0; } static inline void blkcg_deactivate_policy(struct request_queue q, const struct blkcg_policy pol) { } static inline struct blkcg __bio_blkcg(struct bio bio) { return NULL; } static inline struct blkcg bio_blkcg(struct bio bio) { return NULL; } static inline struct blkg_policy_data blkg_to_pd(struct blkcg_gq blkg, struct blkcg_policy pol) { return NULL; } static inline struct blkcg_gq pd_to_blkg(struct blkg_policy_data pd) { return NULL; } static inline char blkg_path(struct blkcg_gq blkg) { return NULL; } static inline void blkg_get(struct blkcg_gq blkg) { } static inline void blkg_put(struct blkcg_gq blkg) { } static inline bool blkcg_punt_bio_submit(struct bio bio) { return false; } static inline void blkcg_bio_issue_init(struct bio bio) { } static inline bool blkcg_bio_issue_check(struct request_queue q, struct bio bio) { return true; } static inline bool blk_cgroup_mergeable(struct request rq, struct bio bio) { return true; } #define blk_queue_for_each_rl(rl, q) \ for ((rl) = &(q)->root_rl; (rl); (rl) = NULL) #endif /* CONFIG_BLOCK / #endif / CONFIG_BLK_CGROUP / #endif / _BLK_CGROUP_H */

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