// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2017 Western Digital Corporation or its affiliates.
 *
 * This file is released under the GPL.
 */

#include "dm-zoned.h"

#include <linux/module.h>

#define DM_MSG_PREFIX           "zoned reclaim"

struct dmz_reclaim {
        struct dmz_metadata     *metadata;

        struct delayed_work     work;
        struct workqueue_struct *wq;

        struct dm_kcopyd_client *kc;
        struct dm_kcopyd_throttle kc_throttle;
        int                     kc_err;

        int                     dev_idx;

        unsigned long           flags;

        /* Last target access time */
        unsigned long           atime;
};

/*
 * Reclaim state flags.
 */
enum {
        DMZ_RECLAIM_KCOPY,
};

/*
 * Number of seconds of target BIO inactivity to consider the target idle.
 */
#define DMZ_IDLE_PERIOD                 (10UL * HZ)

/*
 * Percentage of unmapped (free) random zones below which reclaim starts
 * even if the target is busy.
 */
#define DMZ_RECLAIM_LOW_UNMAP_ZONES     30

/*
 * Percentage of unmapped (free) random zones above which reclaim will
 * stop if the target is busy.
 */
#define DMZ_RECLAIM_HIGH_UNMAP_ZONES    50

/*
 * Align a sequential zone write pointer to chunk_block.
 */
static int dmz_reclaim_align_wp(struct dmz_reclaim *zrc, struct dm_zone *zone,
                                sector_t block)
{
        struct dmz_metadata *zmd = zrc->metadata;
        struct dmz_dev *dev = zone->dev;
        sector_t wp_block = zone->wp_block;
        unsigned int nr_blocks;
        int ret;

        if (wp_block == block)
                return 0;

        if (wp_block > block)
                return -EIO;

        /*
         * Zeroout the space between the write
         * pointer and the requested position.
         */
        nr_blocks = block - wp_block;
        ret = blkdev_issue_zeroout(dev->bdev,
                                   dmz_start_sect(zmd, zone) + dmz_blk2sect(wp_block),
                                   dmz_blk2sect(nr_blocks), GFP_NOIO, 0);
        if (ret) {
                dmz_dev_err(dev,
                            "Align zone %u wp %llu to %llu (wp+%u) blocks failed %d",
                            zone->id, (unsigned long long)wp_block,
                            (unsigned long long)block, nr_blocks, ret);
                dmz_check_bdev(dev);
                return ret;
        }

        zone->wp_block = block;

        return 0;
}

/*
 * dm_kcopyd_copy end notification.
 */
static void dmz_reclaim_kcopy_end(int read_err, unsigned long write_err,
                                  void *context)
{
        struct dmz_reclaim *zrc = context;

        if (read_err || write_err)
                zrc->kc_err = -EIO;
        else
                zrc->kc_err = 0;

        clear_bit_unlock(DMZ_RECLAIM_KCOPY, &zrc->flags);
        smp_mb__after_atomic();
        wake_up_bit(&zrc->flags, DMZ_RECLAIM_KCOPY);
}

/*
 * Copy valid blocks of src_zone into dst_zone.
 */
static int dmz_reclaim_copy(struct dmz_reclaim *zrc,
                            struct dm_zone *src_zone, struct dm_zone *dst_zone)
{
        struct dmz_metadata *zmd = zrc->metadata;
        struct dm_io_region src, dst;
        sector_t block = 0, end_block;
        sector_t nr_blocks;
        sector_t src_zone_block;
        sector_t dst_zone_block;
        unsigned long flags = 0;
        int ret;

        if (dmz_is_seq(src_zone))
                end_block = src_zone->wp_block;
        else
                end_block = dmz_zone_nr_blocks(zmd);
        src_zone_block = dmz_start_block(zmd, src_zone);
        dst_zone_block = dmz_start_block(zmd, dst_zone);

        if (dmz_is_seq(dst_zone))
                flags |= BIT(DM_KCOPYD_WRITE_SEQ);

        while (block < end_block) {
                if (src_zone->dev->flags & DMZ_BDEV_DYING)
                        return -EIO;
                if (dst_zone->dev->flags & DMZ_BDEV_DYING)
                        return -EIO;

                if (dmz_reclaim_should_terminate(src_zone))
                        return -EINTR;

                /* Get a valid region from the source zone */
                ret = dmz_first_valid_block(zmd, src_zone, &block);
                if (ret <= 0)
                        return ret;
                nr_blocks = ret;

                /*
                 * If we are writing in a sequential zone, we must make sure
                 * that writes are sequential. So Zeroout any eventual hole
                 * between writes.
                 */
                if (dmz_is_seq(dst_zone)) {
                        ret = dmz_reclaim_align_wp(zrc, dst_zone, block);
                        if (ret)
                                return ret;
                }

                src.bdev = src_zone->dev->bdev;
                src.sector = dmz_blk2sect(src_zone_block + block);
                src.count = dmz_blk2sect(nr_blocks);

                dst.bdev = dst_zone->dev->bdev;
                dst.sector = dmz_blk2sect(dst_zone_block + block);
                dst.count = src.count;

                /* Copy the valid region */
                set_bit(DMZ_RECLAIM_KCOPY, &zrc->flags);
                dm_kcopyd_copy(zrc->kc, &src, 1, &dst, flags,
                               dmz_reclaim_kcopy_end, zrc);

                /* Wait for copy to complete */
                wait_on_bit_io(&zrc->flags, DMZ_RECLAIM_KCOPY,
                               TASK_UNINTERRUPTIBLE);
                if (zrc->kc_err)
                        return zrc->kc_err;

                block += nr_blocks;
                if (dmz_is_seq(dst_zone))
                        dst_zone->wp_block = block;
        }

        return 0;
}

/*
 * Move valid blocks of dzone buffer zone into dzone (after its write pointer)
 * and free the buffer zone.
 */
static int dmz_reclaim_buf(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
        struct dm_zone *bzone = dzone->bzone;
        sector_t chunk_block = dzone->wp_block;
        struct dmz_metadata *zmd = zrc->metadata;
        int ret;

        DMDEBUG("(%s/%u): Chunk %u, move buf zone %u (weight %u) to data zone %u (weight %u)",
                dmz_metadata_label(zmd), zrc->dev_idx,
                dzone->chunk, bzone->id, dmz_weight(bzone),
                dzone->id, dmz_weight(dzone));

        /* Flush data zone into the buffer zone */
        ret = dmz_reclaim_copy(zrc, bzone, dzone);
        if (ret < 0)
                return ret;

        dmz_lock_flush(zmd);

        /* Validate copied blocks */
        ret = dmz_merge_valid_blocks(zmd, bzone, dzone, chunk_block);
        if (ret == 0) {
                /* Free the buffer zone */
                dmz_invalidate_blocks(zmd, bzone, 0, dmz_zone_nr_blocks(zmd));
                dmz_lock_map(zmd);
                dmz_unmap_zone(zmd, bzone);
                dmz_unlock_zone_reclaim(dzone);
                dmz_free_zone(zmd, bzone);
                dmz_unlock_map(zmd);
        }

        dmz_unlock_flush(zmd);

        return ret;
}

/*
 * Merge valid blocks of dzone into its buffer zone and free dzone.
 */
static int dmz_reclaim_seq_data(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
        unsigned int chunk = dzone->chunk;
        struct dm_zone *bzone = dzone->bzone;
        struct dmz_metadata *zmd = zrc->metadata;
        int ret = 0;

        DMDEBUG("(%s/%u): Chunk %u, move data zone %u (weight %u) to buf zone %u (weight %u)",
                dmz_metadata_label(zmd), zrc->dev_idx,
                chunk, dzone->id, dmz_weight(dzone),
                bzone->id, dmz_weight(bzone));

        /* Flush data zone into the buffer zone */
        ret = dmz_reclaim_copy(zrc, dzone, bzone);
        if (ret < 0)
                return ret;

        dmz_lock_flush(zmd);

        /* Validate copied blocks */
        ret = dmz_merge_valid_blocks(zmd, dzone, bzone, 0);
        if (ret == 0) {
                /*
                 * Free the data zone and remap the chunk to
                 * the buffer zone.
                 */
                dmz_invalidate_blocks(zmd, dzone, 0, dmz_zone_nr_blocks(zmd));
                dmz_lock_map(zmd);
                dmz_unmap_zone(zmd, bzone);
                dmz_unmap_zone(zmd, dzone);
                dmz_unlock_zone_reclaim(dzone);
                dmz_free_zone(zmd, dzone);
                dmz_map_zone(zmd, bzone, chunk);
                dmz_unlock_map(zmd);
        }

        dmz_unlock_flush(zmd);

        return ret;
}

/*
 * Move valid blocks of the random data zone dzone into a free sequential zone.
 * Once blocks are moved, remap the zone chunk to the sequential zone.
 */
static int dmz_reclaim_rnd_data(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
        unsigned int chunk = dzone->chunk;
        struct dm_zone *szone = NULL;
        struct dmz_metadata *zmd = zrc->metadata;
        int ret;
        int alloc_flags = DMZ_ALLOC_SEQ;

        /* Get a free random or sequential zone */
        dmz_lock_map(zmd);
again:
        szone = dmz_alloc_zone(zmd, zrc->dev_idx,
                               alloc_flags | DMZ_ALLOC_RECLAIM);
        if (!szone && alloc_flags == DMZ_ALLOC_SEQ && dmz_nr_cache_zones(zmd)) {
                alloc_flags = DMZ_ALLOC_RND;
                goto again;
        }
        dmz_unlock_map(zmd);
        if (!szone)
                return -ENOSPC;

        DMDEBUG("(%s/%u): Chunk %u, move %s zone %u (weight %u) to %s zone %u",
                dmz_metadata_label(zmd), zrc->dev_idx, chunk,
                dmz_is_cache(dzone) ? "cache" : "rnd",
                dzone->id, dmz_weight(dzone),
                dmz_is_rnd(szone) ? "rnd" : "seq", szone->id);

        /* Flush the random data zone into the sequential zone */
        ret = dmz_reclaim_copy(zrc, dzone, szone);

        dmz_lock_flush(zmd);

        if (ret == 0) {
                /* Validate copied blocks */
                ret = dmz_copy_valid_blocks(zmd, dzone, szone);
        }
        if (ret) {
                /* Free the sequential zone */
                dmz_lock_map(zmd);
                dmz_free_zone(zmd, szone);
                dmz_unlock_map(zmd);
        } else {
                /* Free the data zone and remap the chunk */
                dmz_invalidate_blocks(zmd, dzone, 0, dmz_zone_nr_blocks(zmd));
                dmz_lock_map(zmd);
                dmz_unmap_zone(zmd, dzone);
                dmz_unlock_zone_reclaim(dzone);
                dmz_free_zone(zmd, dzone);
                dmz_map_zone(zmd, szone, chunk);
                dmz_unlock_map(zmd);
        }

        dmz_unlock_flush(zmd);

        return ret;
}

/*
 * Reclaim an empty zone.
 */
static void dmz_reclaim_empty(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
        struct dmz_metadata *zmd = zrc->metadata;

        dmz_lock_flush(zmd);
        dmz_lock_map(zmd);
        dmz_unmap_zone(zmd, dzone);
        dmz_unlock_zone_reclaim(dzone);
        dmz_free_zone(zmd, dzone);
        dmz_unlock_map(zmd);
        dmz_unlock_flush(zmd);
}

/*
 * Test if the target device is idle.
 */
static inline int dmz_target_idle(struct dmz_reclaim *zrc)
{
        return time_is_before_jiffies(zrc->atime + DMZ_IDLE_PERIOD);
}

/*
 * Find a candidate zone for reclaim and process it.
 */
static int dmz_do_reclaim(struct dmz_reclaim *zrc)
{
        struct dmz_metadata *zmd = zrc->metadata;
        struct dm_zone *dzone;
        struct dm_zone *rzone;
        unsigned long start;
        int ret;

        /* Get a data zone */
        dzone = dmz_get_zone_for_reclaim(zmd, zrc->dev_idx,
                                         dmz_target_idle(zrc));
        if (!dzone) {
                DMDEBUG("(%s/%u): No zone found to reclaim",
                        dmz_metadata_label(zmd), zrc->dev_idx);
                return -EBUSY;
        }
        rzone = dzone;

        start = jiffies;
        if (dmz_is_cache(dzone) || dmz_is_rnd(dzone)) {
                if (!dmz_weight(dzone)) {
                        /* Empty zone */
                        dmz_reclaim_empty(zrc, dzone);
                        ret = 0;
                } else {
                        /*
                         * Reclaim the random data zone by moving its
                         * valid data blocks to a free sequential zone.
                         */
                        ret = dmz_reclaim_rnd_data(zrc, dzone);
                }
        } else {
                struct dm_zone *bzone = dzone->bzone;
                sector_t chunk_block = 0;

                ret = dmz_first_valid_block(zmd, bzone, &chunk_block);
                if (ret < 0)
                        goto out;

                if (ret == 0 || chunk_block >= dzone->wp_block) {
                        /*
                         * The buffer zone is empty or its valid blocks are
                         * after the data zone write pointer.
                         */
                        ret = dmz_reclaim_buf(zrc, dzone);
                        rzone = bzone;
                } else {
                        /*
                         * Reclaim the data zone by merging it into the
                         * buffer zone so that the buffer zone itself can
                         * be later reclaimed.
                         */
                        ret = dmz_reclaim_seq_data(zrc, dzone);
                }
        }
out:
        if (ret) {
                if (ret == -EINTR)
                        DMDEBUG("(%s/%u): reclaim zone %u interrupted",
                                dmz_metadata_label(zmd), zrc->dev_idx,
                                rzone->id);
                else
                        DMDEBUG("(%s/%u): Failed to reclaim zone %u, err %d",
                                dmz_metadata_label(zmd), zrc->dev_idx,
                                rzone->id, ret);
                dmz_unlock_zone_reclaim(dzone);
                return ret;
        }

        ret = dmz_flush_metadata(zrc->metadata);
        if (ret) {
                DMDEBUG("(%s/%u): Metadata flush for zone %u failed, err %d",
                        dmz_metadata_label(zmd), zrc->dev_idx, rzone->id, ret);
                return ret;
        }

        DMDEBUG("(%s/%u): Reclaimed zone %u in %u ms",
                dmz_metadata_label(zmd), zrc->dev_idx,
                rzone->id, jiffies_to_msecs(jiffies - start));
        return 0;
}

static unsigned int dmz_reclaim_percentage(struct dmz_reclaim *zrc)
{
        struct dmz_metadata *zmd = zrc->metadata;
        unsigned int nr_cache = dmz_nr_cache_zones(zmd);
        unsigned int nr_unmap, nr_zones;

        if (nr_cache) {
                nr_zones = nr_cache;
                nr_unmap = dmz_nr_unmap_cache_zones(zmd);
        } else {
                nr_zones = dmz_nr_rnd_zones(zmd, zrc->dev_idx);
                nr_unmap = dmz_nr_unmap_rnd_zones(zmd, zrc->dev_idx);
        }
        if (nr_unmap <= 1)
                return 0;
        return nr_unmap * 100 / nr_zones;
}

/*
 * Test if reclaim is necessary.
 */
static bool dmz_should_reclaim(struct dmz_reclaim *zrc, unsigned int p_unmap)
{
        unsigned int nr_reclaim;

        nr_reclaim = dmz_nr_rnd_zones(zrc->metadata, zrc->dev_idx);

        if (dmz_nr_cache_zones(zrc->metadata)) {
                /*
                 * The first device in a multi-device
                 * setup only contains cache zones, so
                 * never start reclaim there.
                 */
                if (zrc->dev_idx == 0)
                        return false;
                nr_reclaim += dmz_nr_cache_zones(zrc->metadata);
        }

        /* Reclaim when idle */
        if (dmz_target_idle(zrc) && nr_reclaim)
                return true;

        /* If there are still plenty of cache zones, do not reclaim */
        if (p_unmap >= DMZ_RECLAIM_HIGH_UNMAP_ZONES)
                return false;

        /*
         * If the percentage of unmapped cache zones is low,
         * reclaim even if the target is busy.
         */
        return p_unmap <= DMZ_RECLAIM_LOW_UNMAP_ZONES;
}

/*
 * Reclaim work function.
 */
static void dmz_reclaim_work(struct work_struct *work)
{
        struct dmz_reclaim *zrc = container_of(work, struct dmz_reclaim, work.work);
        struct dmz_metadata *zmd = zrc->metadata;
        unsigned int p_unmap;
        int ret;

        if (dmz_dev_is_dying(zmd))
                return;

        p_unmap = dmz_reclaim_percentage(zrc);
        if (!dmz_should_reclaim(zrc, p_unmap)) {
                mod_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
                return;
        }

        /*
         * We need to start reclaiming random zones: set up zone copy
         * throttling to either go fast if we are very low on random zones
         * and slower if there are still some free random zones to avoid
         * as much as possible to negatively impact the user workload.
         */
        if (dmz_target_idle(zrc) || p_unmap < DMZ_RECLAIM_LOW_UNMAP_ZONES / 2) {
                /* Idle or very low percentage: go fast */
                zrc->kc_throttle.throttle = 100;
        } else {
                /* Busy but we still have some random zone: throttle */
                zrc->kc_throttle.throttle = min(75U, 100U - p_unmap / 2);
        }

        DMDEBUG("(%s/%u): Reclaim (%u): %s, %u%% free zones (%u/%u cache %u/%u random)",
                dmz_metadata_label(zmd), zrc->dev_idx,
                zrc->kc_throttle.throttle,
                (dmz_target_idle(zrc) ? "Idle" : "Busy"),
                p_unmap, dmz_nr_unmap_cache_zones(zmd),
                dmz_nr_cache_zones(zmd),
                dmz_nr_unmap_rnd_zones(zmd, zrc->dev_idx),
                dmz_nr_rnd_zones(zmd, zrc->dev_idx));

        ret = dmz_do_reclaim(zrc);
        if (ret && ret != -EINTR) {
                if (!dmz_check_dev(zmd))
                        return;
        }

        dmz_schedule_reclaim(zrc);
}

/*
 * Initialize reclaim.
 */
int dmz_ctr_reclaim(struct dmz_metadata *zmd,
                    struct dmz_reclaim **reclaim, int idx)
{
        struct dmz_reclaim *zrc;
        int ret;

        zrc = kzalloc(sizeof(struct dmz_reclaim), GFP_KERNEL);
        if (!zrc)
                return -ENOMEM;

        zrc->metadata = zmd;
        zrc->atime = jiffies;
        zrc->dev_idx = idx;

        /* Reclaim kcopyd client */
        zrc->kc = dm_kcopyd_client_create(&zrc->kc_throttle);
        if (IS_ERR(zrc->kc)) {
                ret = PTR_ERR(zrc->kc);
                zrc->kc = NULL;
                goto err;
        }

        /* Reclaim work */
        INIT_DELAYED_WORK(&zrc->work, dmz_reclaim_work);
        zrc->wq = alloc_ordered_workqueue("dmz_rwq_%s_%d", WQ_MEM_RECLAIM,
                                          dmz_metadata_label(zmd), idx);
        if (!zrc->wq) {
                ret = -ENOMEM;
                goto err;
        }

        *reclaim = zrc;
        queue_delayed_work(zrc->wq, &zrc->work, 0);

        return 0;
err:
        if (zrc->kc)
                dm_kcopyd_client_destroy(zrc->kc);
        kfree(zrc);

        return ret;
}

/*
 * Terminate reclaim.
 */
void dmz_dtr_reclaim(struct dmz_reclaim *zrc)
{
        cancel_delayed_work_sync(&zrc->work);
        destroy_workqueue(zrc->wq);
        dm_kcopyd_client_destroy(zrc->kc);
        kfree(zrc);
}

/*
 * Suspend reclaim.
 */
void dmz_suspend_reclaim(struct dmz_reclaim *zrc)
{
        cancel_delayed_work_sync(&zrc->work);
}

/*
 * Resume reclaim.
 */
void dmz_resume_reclaim(struct dmz_reclaim *zrc)
{
        queue_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
}

/*
 * BIO accounting.
 */
void dmz_reclaim_bio_acc(struct dmz_reclaim *zrc)
{
        zrc->atime = jiffies;
}

/*
 * Start reclaim if necessary.
 */
void dmz_schedule_reclaim(struct dmz_reclaim *zrc)
{
        unsigned int p_unmap = dmz_reclaim_percentage(zrc);

        if (dmz_should_reclaim(zrc, p_unmap))
                mod_delayed_work(zrc->wq, &zrc->work, 0);
}