/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_BACKING_DEV_DEFS_H
#define __LINUX_BACKING_DEV_DEFS_H

#include <linux/list.h>
#include <linux/radix-tree.h>
#include <linux/rbtree.h>
#include <linux/spinlock.h>
#include <linux/percpu_counter.h>
#include <linux/percpu-refcount.h>
#include <linux/flex_proportions.h>
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/kref.h>
#include <linux/refcount.h>

struct page;
struct device;
struct dentry;

/*
 * Bits in bdi_writeback.state
 */
enum wb_state {
        WB_registered,          /* bdi_register() was done */
        WB_writeback_running,   /* Writeback is in progress */
        WB_has_dirty_io,        /* Dirty inodes on ->b_{dirty|io|more_io} */
        WB_start_all,           /* nr_pages == 0 (all) work pending */
};

enum wb_congested_state {
        WB_async_congested,     /* The async (write) queue is getting full */
        WB_sync_congested,      /* The sync queue is getting full */
};

typedef int (congested_fn)(void *, int);

enum wb_stat_item {
        WB_RECLAIMABLE,
        WB_WRITEBACK,
        WB_DIRTIED,
        WB_WRITTEN,
        NR_WB_STAT_ITEMS
};

#define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))

/*
 * why some writeback work was initiated
 */
enum wb_reason {
        WB_REASON_BACKGROUND,
        WB_REASON_VMSCAN,
        WB_REASON_SYNC,
        WB_REASON_PERIODIC,
        WB_REASON_LAPTOP_TIMER,
        WB_REASON_FREE_MORE_MEM,
        WB_REASON_FS_FREE_SPACE,
        /*
         * There is no bdi forker thread any more and works are done
         * by emergency worker, however, this is TPs userland visible
         * and we'll be exposing exactly the same information,
         * so it has a mismatch name.
         */
        WB_REASON_FORKER_THREAD,

        WB_REASON_MAX,
};

/*
 * For cgroup writeback, multiple wb's may map to the same blkcg.  Those
 * wb's can operate mostly independently but should share the congested
 * state.  To facilitate such sharing, the congested state is tracked using
 * the following struct which is created on demand, indexed by blkcg ID on
 * its bdi, and refcounted.
 */
struct bdi_writeback_congested {
        unsigned long state;            /* WB_[a]sync_congested flags */
        refcount_t refcnt;              /* nr of attached wb's and blkg */

#ifdef CONFIG_CGROUP_WRITEBACK
        struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
                                         * on bdi unregistration. For memcg-wb
                                         * internal use only! */
        int blkcg_id;                   /* ID of the associated blkcg */
        struct rb_node rb_node;         /* on bdi->cgwb_congestion_tree */
#endif
};

/*
 * Each wb (bdi_writeback) can perform writeback operations, is measured
 * and throttled, independently.  Without cgroup writeback, each bdi
 * (bdi_writeback) is served by its embedded bdi->wb.
 *
 * On the default hierarchy, blkcg implicitly enables memcg.  This allows
 * using memcg's page ownership for attributing writeback IOs, and every
 * memcg - blkcg combination can be served by its own wb by assigning a
 * dedicated wb to each memcg, which enables isolation across different
 * cgroups and propagation of IO back pressure down from the IO layer upto
 * the tasks which are generating the dirty pages to be written back.
 *
 * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
 * refcounted with the number of inodes attached to it, and pins the memcg
 * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
 * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
 * is tested for blkcg after lookup and removed from index on mismatch so
 * that a new wb for the combination can be created.
 */
struct bdi_writeback {
        struct backing_dev_info *bdi;   /* our parent bdi */

        unsigned long state;            /* Always use atomic bitops on this */
        unsigned long last_old_flush;   /* last old data flush */

        struct list_head b_dirty;       /* dirty inodes */
        struct list_head b_io;          /* parked for writeback */
        struct list_head b_more_io;     /* parked for more writeback */
        struct list_head b_dirty_time;  /* time stamps are dirty */
        spinlock_t list_lock;           /* protects the b_* lists */

        struct percpu_counter stat[NR_WB_STAT_ITEMS];

        struct bdi_writeback_congested *congested;

        unsigned long bw_time_stamp;    /* last time write bw is updated */
        unsigned long dirtied_stamp;
        unsigned long written_stamp;    /* pages written at bw_time_stamp */
        unsigned long write_bandwidth;  /* the estimated write bandwidth */
        unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */

        /*
         * The base dirty throttle rate, re-calculated on every 200ms.
         * All the bdi tasks' dirty rate will be curbed under it.
         * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
         * in small steps and is much more smooth/stable than the latter.
         */
        unsigned long dirty_ratelimit;
        unsigned long balanced_dirty_ratelimit;

        struct fprop_local_percpu completions;
        int dirty_exceeded;
        enum wb_reason start_all_reason;

        spinlock_t work_lock;           /* protects work_list & dwork scheduling */
        struct list_head work_list;
        struct delayed_work dwork;      /* work item used for writeback */

        unsigned long dirty_sleep;      /* last wait */

        struct list_head bdi_node;      /* anchored at bdi->wb_list */

#ifdef CONFIG_CGROUP_WRITEBACK
        struct percpu_ref refcnt;       /* used only for !root wb's */
        struct fprop_local_percpu memcg_completions;
        struct cgroup_subsys_state *memcg_css; /* the associated memcg */
        struct cgroup_subsys_state *blkcg_css; /* and blkcg */
        struct list_head memcg_node;    /* anchored at memcg->cgwb_list */
        struct list_head blkcg_node;    /* anchored at blkcg->cgwb_list */

        union {
                struct work_struct release_work;
                struct rcu_head rcu;
        };
#endif
};

struct backing_dev_info {
        struct list_head bdi_list;
        unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
        unsigned long io_pages; /* max allowed IO size */
        congested_fn *congested_fn; /* Function pointer if device is md/dm */
        void *congested_data;   /* Pointer to aux data for congested func */

        const char *name;

        struct kref refcnt;     /* Reference counter for the structure */
        unsigned int capabilities; /* Device capabilities */
        unsigned int min_ratio;
        unsigned int max_ratio, max_prop_frac;

        /*
         * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
         * any dirty wbs, which is depended upon by bdi_has_dirty().
         */
        atomic_long_t tot_write_bandwidth;

        struct bdi_writeback wb;  /* the root writeback info for this bdi */
        struct list_head wb_list; /* list of all wbs */
#ifdef CONFIG_CGROUP_WRITEBACK
        struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
        struct rb_root cgwb_congested_tree; /* their congested states */
        struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
        struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
#else
        struct bdi_writeback_congested *wb_congested;
#endif
        wait_queue_head_t wb_waitq;

        struct device *dev;
        struct device *owner;

        struct timer_list laptop_mode_wb_timer;

#ifdef CONFIG_DEBUG_FS
        struct dentry *debug_dir;
#endif
};

enum {
        BLK_RW_ASYNC    = 0,
        BLK_RW_SYNC     = 1,
};

void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
void set_wb_congested(struct bdi_writeback_congested *congested, int sync);

static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
{
        clear_wb_congested(bdi->wb.congested, sync);
}

static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
{
        set_wb_congested(bdi->wb.congested, sync);
}

struct wb_lock_cookie {
        bool locked;
        unsigned long flags;
};

#ifdef CONFIG_CGROUP_WRITEBACK

/**
 * wb_tryget - try to increment a wb's refcount
 * @wb: bdi_writeback to get
 */
static inline bool wb_tryget(struct bdi_writeback *wb)
{
        if (wb != &wb->bdi->wb)
                return percpu_ref_tryget(&wb->refcnt);
        return true;
}

/**
 * wb_get - increment a wb's refcount
 * @wb: bdi_writeback to get
 */
static inline void wb_get(struct bdi_writeback *wb)
{
        if (wb != &wb->bdi->wb)
                percpu_ref_get(&wb->refcnt);
}

/**
 * wb_put - decrement a wb's refcount
 * @wb: bdi_writeback to put
 */
static inline void wb_put(struct bdi_writeback *wb)
{
        if (WARN_ON_ONCE(!wb->bdi)) {
                /*
                 * A driver bug might cause a file to be removed before bdi was
                 * initialized.
                 */
                return;
        }

        if (wb != &wb->bdi->wb)
                percpu_ref_put(&wb->refcnt);
}

/**
 * wb_dying - is a wb dying?
 * @wb: bdi_writeback of interest
 *
 * Returns whether @wb is unlinked and being drained.
 */
static inline bool wb_dying(struct bdi_writeback *wb)
{
        return percpu_ref_is_dying(&wb->refcnt);
}

#else   /* CONFIG_CGROUP_WRITEBACK */

static inline bool wb_tryget(struct bdi_writeback *wb)
{
        return true;
}

static inline void wb_get(struct bdi_writeback *wb)
{
}

static inline void wb_put(struct bdi_writeback *wb)
{
}

static inline bool wb_dying(struct bdi_writeback *wb)
{
        return false;
}

#endif  /* CONFIG_CGROUP_WRITEBACK */

#endif  /* __LINUX_BACKING_DEV_DEFS_H */