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

#define CUTOFF_WRITEBACK        40
#define CUTOFF_WRITEBACK_SYNC   70

#define CUTOFF_WRITEBACK_MAX            70
#define CUTOFF_WRITEBACK_SYNC_MAX       90

#define MAX_WRITEBACKS_IN_PASS  5
#define MAX_WRITESIZE_IN_PASS   5000    /* *512b */

#define WRITEBACK_RATE_UPDATE_SECS_MAX          60
#define WRITEBACK_RATE_UPDATE_SECS_DEFAULT      5

#define BCH_AUTO_GC_DIRTY_THRESHOLD     50

#define BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW 50
#define BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID 57
#define BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH 64

#define BCH_DIRTY_INIT_THRD_MAX 12
/*
 * 14 (16384ths) is chosen here as something that each backing device
 * should be a reasonable fraction of the share, and not to blow up
 * until individual backing devices are a petabyte.
 */
#define WRITEBACK_SHARE_SHIFT   14

struct bch_dirty_init_state;
struct dirty_init_thrd_info {
        struct bch_dirty_init_state     *state;
        struct task_struct              *thread;
};

struct bch_dirty_init_state {
        struct cache_set                *c;
        struct bcache_device            *d;
        int                             total_threads;
        int                             key_idx;
        spinlock_t                      idx_lock;
        atomic_t                        started;
        atomic_t                        enough;
        wait_queue_head_t               wait;
        struct dirty_init_thrd_info     infos[BCH_DIRTY_INIT_THRD_MAX];
};

static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d)
{
        uint64_t i, ret = 0;

        for (i = 0; i < d->nr_stripes; i++)
                ret += atomic_read(d->stripe_sectors_dirty + i);

        return ret;
}

static inline int offset_to_stripe(struct bcache_device *d,
                                        uint64_t offset)
{
        do_div(offset, d->stripe_size);

        /* d->nr_stripes is in range [1, INT_MAX] */
        if (unlikely(offset >= d->nr_stripes)) {
                pr_err("Invalid stripe %llu (>= nr_stripes %d).\n",
                        offset, d->nr_stripes);
                return -EINVAL;
        }

        /*
         * Here offset is definitly smaller than INT_MAX,
         * return it as int will never overflow.
         */
        return offset;
}

static inline bool bcache_dev_stripe_dirty(struct cached_dev *dc,
                                           uint64_t offset,
                                           unsigned int nr_sectors)
{
        int stripe = offset_to_stripe(&dc->disk, offset);

        if (stripe < 0)
                return false;

        while (1) {
                if (atomic_read(dc->disk.stripe_sectors_dirty + stripe))
                        return true;

                if (nr_sectors <= dc->disk.stripe_size)
                        return false;

                nr_sectors -= dc->disk.stripe_size;
                stripe++;
        }
}

extern unsigned int bch_cutoff_writeback;
extern unsigned int bch_cutoff_writeback_sync;

static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
                                    unsigned int cache_mode, bool would_skip)
{
        unsigned int in_use = dc->disk.c->gc_stats.in_use;

        if (cache_mode != CACHE_MODE_WRITEBACK ||
            test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
            in_use > bch_cutoff_writeback_sync)
                return false;

        if (bio_op(bio) == REQ_OP_DISCARD)
                return false;

        if (dc->partial_stripes_expensive &&
            bcache_dev_stripe_dirty(dc, bio->bi_iter.bi_sector,
                                    bio_sectors(bio)))
                return true;

        if (would_skip)
                return false;

        return (op_is_sync(bio->bi_opf) ||
                bio->bi_opf & (REQ_META|REQ_PRIO) ||
                in_use <= bch_cutoff_writeback);
}

static inline void bch_writeback_queue(struct cached_dev *dc)
{
        if (!IS_ERR_OR_NULL(dc->writeback_thread))
                wake_up_process(dc->writeback_thread);
}

static inline void bch_writeback_add(struct cached_dev *dc)
{
        if (!atomic_read(&dc->has_dirty) &&
            !atomic_xchg(&dc->has_dirty, 1)) {
                if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
                        SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
                        /* XXX: should do this synchronously */
                        bch_write_bdev_super(dc, NULL);
                }

                bch_writeback_queue(dc);
        }
}

void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,
                                  uint64_t offset, int nr_sectors);

void bch_sectors_dirty_init(struct bcache_device *d);
void bch_cached_dev_writeback_init(struct cached_dev *dc);
int bch_cached_dev_writeback_start(struct cached_dev *dc);

#endif