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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _BLK_CGROUP_PRIVATE_H
 #define _BLK_CGROUP_PRIVATE_H
 /*
  * block cgroup private header
  *
  * 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/blk-cgroup.h>
 #include <linux/cgroup.h>
 #include <linux/kthread.h>
 #include <linux/blk-mq.h>
 
 struct blkcg_gq;
 struct blkg_policy_data;
 
 
 /* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
 #define BLKG_STAT_CPU_BATCH (INT_MAX / 2)
 
 #ifdef CONFIG_BLK_CGROUP
 
 enum blkg_iostat_type {
     BLKG_IOSTAT_READ,
     BLKG_IOSTAT_WRITE,
     BLKG_IOSTAT_DISCARD,
 
     BLKG_IOSTAT_NR,
 };
 
 struct blkg_iostat {
     u64             bytes[BLKG_IOSTAT_NR];
     u64             ios[BLKG_IOSTAT_NR];
 };
 
 struct blkg_iostat_set {
     struct u64_stats_sync       sync;
     struct blkg_iostat      cur;
     struct blkg_iostat      last;
 };
 
 /* 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;
 
     /* 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_iostat_set __percpu *iostat_cpu;
     struct blkg_iostat_set      iostat;
 
     struct blkg_policy_data     *pd[BLKCG_MAX_POLS];
 
     spinlock_t          async_bio_lock;
     struct bio_list         async_bios;
     union {
         struct work_struct  async_bio_work;
         struct work_struct  free_work;
     };
 
     atomic_t            use_delay;
     atomic64_t          delay_nsec;
     atomic64_t          delay_start;
     u64             last_delay;
     int             last_use;
 
     struct rcu_head         rcu_head;
 };
 
 struct blkcg {
     struct cgroup_subsys_state  css;
     spinlock_t          lock;
     refcount_t          online_pin;
 
     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_BLK_CGROUP_FC_APPID
     char                            fc_app_id[FC_APPID_LEN];
 #endif
 #ifdef CONFIG_CGROUP_WRITEBACK
     struct list_head        cgwb_list;
 #endif
 };
 
 static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 {
     return css ? container_of(css, struct blkcg, css) : NULL;
 }
 
 /*
  * 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;
 };
 
 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 void (blkcg_pol_stat_pd_fn)(struct blkg_policy_data *pd,
                 struct seq_file *s);
 
 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 bool blkcg_debug_stats;
 
 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
                       struct request_queue *q, bool update_hint);
 int blkcg_init_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);
 
 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);
 
 struct blkg_conf_ctx {
     struct block_device     *bdev;
     struct blkcg_gq         *blkg;
     char                *body;
 };
 
 struct block_device *blkcg_conf_open_bdev(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);
 
 /**
  * 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_css() 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;
 }
 
 /**
  * __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;
 }
 
 /**
  * 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_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)))
 
 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 void blkcg_use_delay(struct blkcg_gq *blkg)
 {
     if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
         return;
     if (atomic_add_return(1, &blkg->use_delay) == 1)
         atomic_inc(&blkg->blkcg->css.cgroup->congestion_count);
 }
 
 static inline int blkcg_unuse_delay(struct blkcg_gq *blkg)
 {
     int old = atomic_read(&blkg->use_delay);
 
     if (WARN_ON_ONCE(old < 0))
         return 0;
     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 && !atomic_try_cmpxchg(&blkg->use_delay, &old, old - 1))
         ;
 
     if (old == 0)
         return 0;
     if (old == 1)
         atomic_dec(&blkg->blkcg->css.cgroup->congestion_count);
     return 1;
 }
 
 /**
  * blkcg_set_delay - Enable allocator delay mechanism with the specified delay amount
  * @blkg: target blkg
  * @delay: delay duration in nsecs
  *
  * When enabled with this function, the delay is not decayed and must be
  * explicitly cleared with blkcg_clear_delay(). Must not be mixed with
  * blkcg_[un]use_delay() and blkcg_add_delay() usages.
  */
 static inline void blkcg_set_delay(struct blkcg_gq *blkg, u64 delay)
 {
     int old = atomic_read(&blkg->use_delay);
 
     /* We only want 1 person setting the congestion count for this blkg. */
     if (!old && atomic_try_cmpxchg(&blkg->use_delay, &old, -1))
         atomic_inc(&blkg->blkcg->css.cgroup->congestion_count);
 
     atomic64_set(&blkg->delay_nsec, delay);
 }
 
 /**
  * blkcg_clear_delay - Disable allocator delay mechanism
  * @blkg: target blkg
  *
  * Disable use_delay mechanism. See blkcg_set_delay().
  */
 static inline void blkcg_clear_delay(struct blkcg_gq *blkg)
 {
     int old = atomic_read(&blkg->use_delay);
 
     /* We only want 1 person clearing the congestion count for this blkg. */
     if (old && atomic_try_cmpxchg(&blkg->use_delay, &old, 0))
         atomic_dec(&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);
 }
 
 void blk_cgroup_bio_start(struct bio *bio);
 void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta);
 #else   /* CONFIG_BLK_CGROUP */
 
 struct blkg_policy_data {
 };
 
 struct blkcg_policy_data {
 };
 
 struct blkcg_policy {
 };
 
 struct blkcg {
 };
 
 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_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 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 void blk_cgroup_bio_start(struct bio *bio) { }
 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_BLK_CGROUP */
 
 #endif /* _BLK_CGROUP_PRIVATE_H */

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