// 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>
#include <linux/crc32.h>
#include <linux/sched/mm.h>

#define DM_MSG_PREFIX           "zoned metadata"

/*
 * Metadata version.
 */
#define DMZ_META_VER    2

/*
 * On-disk super block magic.
 */
#define DMZ_MAGIC       ((((unsigned int)('D')) << 24) | \
                         (((unsigned int)('Z')) << 16) | \
                         (((unsigned int)('B')) <<  8) | \
                         ((unsigned int)('D')))

/*
 * On disk super block.
 * This uses only 512 B but uses on disk a full 4KB block. This block is
 * followed on disk by the mapping table of chunks to zones and the bitmap
 * blocks indicating zone block validity.
 * The overall resulting metadata format is:
 *    (1) Super block (1 block)
 *    (2) Chunk mapping table (nr_map_blocks)
 *    (3) Bitmap blocks (nr_bitmap_blocks)
 * All metadata blocks are stored in conventional zones, starting from
 * the first conventional zone found on disk.
 */
struct dmz_super {
        /* Magic number */
        __le32          magic;                  /*   4 */

        /* Metadata version number */
        __le32          version;                /*   8 */

        /* Generation number */
        __le64          gen;                    /*  16 */

        /* This block number */
        __le64          sb_block;               /*  24 */

        /* The number of metadata blocks, including this super block */
        __le32          nr_meta_blocks;         /*  28 */

        /* The number of sequential zones reserved for reclaim */
        __le32          nr_reserved_seq;        /*  32 */

        /* The number of entries in the mapping table */
        __le32          nr_chunks;              /*  36 */

        /* The number of blocks used for the chunk mapping table */
        __le32          nr_map_blocks;          /*  40 */

        /* The number of blocks used for the block bitmaps */
        __le32          nr_bitmap_blocks;       /*  44 */

        /* Checksum */
        __le32          crc;                    /*  48 */

        /* DM-Zoned label */
        u8              dmz_label[32];          /*  80 */

        /* DM-Zoned UUID */
        u8              dmz_uuid[16];           /*  96 */

        /* Device UUID */
        u8              dev_uuid[16];           /* 112 */

        /* Padding to full 512B sector */
        u8              reserved[400];          /* 512 */
};

/*
 * Chunk mapping entry: entries are indexed by chunk number
 * and give the zone ID (dzone_id) mapping the chunk on disk.
 * This zone may be sequential or random. If it is a sequential
 * zone, a second zone (bzone_id) used as a write buffer may
 * also be specified. This second zone will always be a randomly
 * writeable zone.
 */
struct dmz_map {
        __le32                  dzone_id;
        __le32                  bzone_id;
};

/*
 * Chunk mapping table metadata: 512 8-bytes entries per 4KB block.
 */
#define DMZ_MAP_ENTRIES         (DMZ_BLOCK_SIZE / sizeof(struct dmz_map))
#define DMZ_MAP_ENTRIES_SHIFT   (ilog2(DMZ_MAP_ENTRIES))
#define DMZ_MAP_ENTRIES_MASK    (DMZ_MAP_ENTRIES - 1)
#define DMZ_MAP_UNMAPPED        UINT_MAX

/*
 * Meta data block descriptor (for cached metadata blocks).
 */
struct dmz_mblock {
        struct rb_node          node;
        struct list_head        link;
        sector_t                no;
        unsigned int            ref;
        unsigned long           state;
        struct page             *page;
        void                    *data;
};

/*
 * Metadata block state flags.
 */
enum {
        DMZ_META_DIRTY,
        DMZ_META_READING,
        DMZ_META_WRITING,
        DMZ_META_ERROR,
};

/*
 * Super block information (one per metadata set).
 */
struct dmz_sb {
        sector_t                block;
        struct dmz_dev          *dev;
        struct dmz_mblock       *mblk;
        struct dmz_super        *sb;
        struct dm_zone          *zone;
};

/*
 * In-memory metadata.
 */
struct dmz_metadata {
        struct dmz_dev          *dev;
        unsigned int            nr_devs;

        char                    devname[BDEVNAME_SIZE];
        char                    label[BDEVNAME_SIZE];
        uuid_t                  uuid;

        sector_t                zone_bitmap_size;
        unsigned int            zone_nr_bitmap_blocks;
        unsigned int            zone_bits_per_mblk;

        sector_t                zone_nr_blocks;
        sector_t                zone_nr_blocks_shift;

        sector_t                zone_nr_sectors;
        sector_t                zone_nr_sectors_shift;

        unsigned int            nr_bitmap_blocks;
        unsigned int            nr_map_blocks;

        unsigned int            nr_zones;
        unsigned int            nr_useable_zones;
        unsigned int            nr_meta_blocks;
        unsigned int            nr_meta_zones;
        unsigned int            nr_data_zones;
        unsigned int            nr_cache_zones;
        unsigned int            nr_rnd_zones;
        unsigned int            nr_reserved_seq;
        unsigned int            nr_chunks;

        /* Zone information array */
        struct xarray           zones;

        struct dmz_sb           sb[2];
        unsigned int            mblk_primary;
        unsigned int            sb_version;
        u64                     sb_gen;
        unsigned int            min_nr_mblks;
        unsigned int            max_nr_mblks;
        atomic_t                nr_mblks;
        struct rw_semaphore     mblk_sem;
        struct mutex            mblk_flush_lock;
        spinlock_t              mblk_lock;
        struct rb_root          mblk_rbtree;
        struct list_head        mblk_lru_list;
        struct list_head        mblk_dirty_list;
        struct shrinker         mblk_shrinker;

        /* Zone allocation management */
        struct mutex            map_lock;
        struct dmz_mblock       **map_mblk;

        unsigned int            nr_cache;
        atomic_t                unmap_nr_cache;
        struct list_head        unmap_cache_list;
        struct list_head        map_cache_list;

        atomic_t                nr_reserved_seq_zones;
        struct list_head        reserved_seq_zones_list;

        wait_queue_head_t       free_wq;
};

#define dmz_zmd_info(zmd, format, args...)      \
        DMINFO("(%s): " format, (zmd)->label, ## args)

#define dmz_zmd_err(zmd, format, args...)       \
        DMERR("(%s): " format, (zmd)->label, ## args)

#define dmz_zmd_warn(zmd, format, args...)      \
        DMWARN("(%s): " format, (zmd)->label, ## args)

#define dmz_zmd_debug(zmd, format, args...)     \
        DMDEBUG("(%s): " format, (zmd)->label, ## args)
/*
 * Various accessors
 */
static unsigned int dmz_dev_zone_id(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        if (WARN_ON(!zone))
                return 0;

        return zone->id - zone->dev->zone_offset;
}

sector_t dmz_start_sect(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        unsigned int zone_id = dmz_dev_zone_id(zmd, zone);

        return (sector_t)zone_id << zmd->zone_nr_sectors_shift;
}

sector_t dmz_start_block(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        unsigned int zone_id = dmz_dev_zone_id(zmd, zone);

        return (sector_t)zone_id << zmd->zone_nr_blocks_shift;
}

unsigned int dmz_zone_nr_blocks(struct dmz_metadata *zmd)
{
        return zmd->zone_nr_blocks;
}

unsigned int dmz_zone_nr_blocks_shift(struct dmz_metadata *zmd)
{
        return zmd->zone_nr_blocks_shift;
}

unsigned int dmz_zone_nr_sectors(struct dmz_metadata *zmd)
{
        return zmd->zone_nr_sectors;
}

unsigned int dmz_zone_nr_sectors_shift(struct dmz_metadata *zmd)
{
        return zmd->zone_nr_sectors_shift;
}

unsigned int dmz_nr_zones(struct dmz_metadata *zmd)
{
        return zmd->nr_zones;
}

unsigned int dmz_nr_chunks(struct dmz_metadata *zmd)
{
        return zmd->nr_chunks;
}

unsigned int dmz_nr_rnd_zones(struct dmz_metadata *zmd, int idx)
{
        return zmd->dev[idx].nr_rnd;
}

unsigned int dmz_nr_unmap_rnd_zones(struct dmz_metadata *zmd, int idx)
{
        return atomic_read(&zmd->dev[idx].unmap_nr_rnd);
}

unsigned int dmz_nr_cache_zones(struct dmz_metadata *zmd)
{
        return zmd->nr_cache;
}

unsigned int dmz_nr_unmap_cache_zones(struct dmz_metadata *zmd)
{
        return atomic_read(&zmd->unmap_nr_cache);
}

unsigned int dmz_nr_seq_zones(struct dmz_metadata *zmd, int idx)
{
        return zmd->dev[idx].nr_seq;
}

unsigned int dmz_nr_unmap_seq_zones(struct dmz_metadata *zmd, int idx)
{
        return atomic_read(&zmd->dev[idx].unmap_nr_seq);
}

static struct dm_zone *dmz_get(struct dmz_metadata *zmd, unsigned int zone_id)
{
        return xa_load(&zmd->zones, zone_id);
}

static struct dm_zone *dmz_insert(struct dmz_metadata *zmd,
                                  unsigned int zone_id, struct dmz_dev *dev)
{
        struct dm_zone *zone = kzalloc(sizeof(struct dm_zone), GFP_KERNEL);

        if (!zone)
                return ERR_PTR(-ENOMEM);

        if (xa_insert(&zmd->zones, zone_id, zone, GFP_KERNEL)) {
                kfree(zone);
                return ERR_PTR(-EBUSY);
        }

        INIT_LIST_HEAD(&zone->link);
        atomic_set(&zone->refcount, 0);
        zone->id = zone_id;
        zone->chunk = DMZ_MAP_UNMAPPED;
        zone->dev = dev;

        return zone;
}

const char *dmz_metadata_label(struct dmz_metadata *zmd)
{
        return (const char *)zmd->label;
}

bool dmz_check_dev(struct dmz_metadata *zmd)
{
        unsigned int i;

        for (i = 0; i < zmd->nr_devs; i++) {
                if (!dmz_check_bdev(&zmd->dev[i]))
                        return false;
        }
        return true;
}

bool dmz_dev_is_dying(struct dmz_metadata *zmd)
{
        unsigned int i;

        for (i = 0; i < zmd->nr_devs; i++) {
                if (dmz_bdev_is_dying(&zmd->dev[i]))
                        return true;
        }
        return false;
}

/*
 * Lock/unlock mapping table.
 * The map lock also protects all the zone lists.
 */
void dmz_lock_map(struct dmz_metadata *zmd)
{
        mutex_lock(&zmd->map_lock);
}

void dmz_unlock_map(struct dmz_metadata *zmd)
{
        mutex_unlock(&zmd->map_lock);
}

/*
 * Lock/unlock metadata access. This is a "read" lock on a semaphore
 * that prevents metadata flush from running while metadata are being
 * modified. The actual metadata write mutual exclusion is achieved with
 * the map lock and zone state management (active and reclaim state are
 * mutually exclusive).
 */
void dmz_lock_metadata(struct dmz_metadata *zmd)
{
        down_read(&zmd->mblk_sem);
}

void dmz_unlock_metadata(struct dmz_metadata *zmd)
{
        up_read(&zmd->mblk_sem);
}

/*
 * Lock/unlock flush: prevent concurrent executions
 * of dmz_flush_metadata as well as metadata modification in reclaim
 * while flush is being executed.
 */
void dmz_lock_flush(struct dmz_metadata *zmd)
{
        mutex_lock(&zmd->mblk_flush_lock);
}

void dmz_unlock_flush(struct dmz_metadata *zmd)
{
        mutex_unlock(&zmd->mblk_flush_lock);
}

/*
 * Allocate a metadata block.
 */
static struct dmz_mblock *dmz_alloc_mblock(struct dmz_metadata *zmd,
                                           sector_t mblk_no)
{
        struct dmz_mblock *mblk = NULL;

        /* See if we can reuse cached blocks */
        if (zmd->max_nr_mblks && atomic_read(&zmd->nr_mblks) > zmd->max_nr_mblks) {
                spin_lock(&zmd->mblk_lock);
                mblk = list_first_entry_or_null(&zmd->mblk_lru_list,
                                                struct dmz_mblock, link);
                if (mblk) {
                        list_del_init(&mblk->link);
                        rb_erase(&mblk->node, &zmd->mblk_rbtree);
                        mblk->no = mblk_no;
                }
                spin_unlock(&zmd->mblk_lock);
                if (mblk)
                        return mblk;
        }

        /* Allocate a new block */
        mblk = kmalloc(sizeof(struct dmz_mblock), GFP_NOIO);
        if (!mblk)
                return NULL;

        mblk->page = alloc_page(GFP_NOIO);
        if (!mblk->page) {
                kfree(mblk);
                return NULL;
        }

        RB_CLEAR_NODE(&mblk->node);
        INIT_LIST_HEAD(&mblk->link);
        mblk->ref = 0;
        mblk->state = 0;
        mblk->no = mblk_no;
        mblk->data = page_address(mblk->page);

        atomic_inc(&zmd->nr_mblks);

        return mblk;
}

/*
 * Free a metadata block.
 */
static void dmz_free_mblock(struct dmz_metadata *zmd, struct dmz_mblock *mblk)
{
        __free_pages(mblk->page, 0);
        kfree(mblk);

        atomic_dec(&zmd->nr_mblks);
}

/*
 * Insert a metadata block in the rbtree.
 */
static void dmz_insert_mblock(struct dmz_metadata *zmd, struct dmz_mblock *mblk)
{
        struct rb_root *root = &zmd->mblk_rbtree;
        struct rb_node **new = &(root->rb_node), *parent = NULL;
        struct dmz_mblock *b;

        /* Figure out where to put the new node */
        while (*new) {
                b = container_of(*new, struct dmz_mblock, node);
                parent = *new;
                new = (b->no < mblk->no) ? &((*new)->rb_left) : &((*new)->rb_right);
        }

        /* Add new node and rebalance tree */
        rb_link_node(&mblk->node, parent, new);
        rb_insert_color(&mblk->node, root);
}

/*
 * Lookup a metadata block in the rbtree. If the block is found, increment
 * its reference count.
 */
static struct dmz_mblock *dmz_get_mblock_fast(struct dmz_metadata *zmd,
                                              sector_t mblk_no)
{
        struct rb_root *root = &zmd->mblk_rbtree;
        struct rb_node *node = root->rb_node;
        struct dmz_mblock *mblk;

        while (node) {
                mblk = container_of(node, struct dmz_mblock, node);
                if (mblk->no == mblk_no) {
                        /*
                         * If this is the first reference to the block,
                         * remove it from the LRU list.
                         */
                        mblk->ref++;
                        if (mblk->ref == 1 &&
                            !test_bit(DMZ_META_DIRTY, &mblk->state))
                                list_del_init(&mblk->link);
                        return mblk;
                }
                node = (mblk->no < mblk_no) ? node->rb_left : node->rb_right;
        }

        return NULL;
}

/*
 * Metadata block BIO end callback.
 */
static void dmz_mblock_bio_end_io(struct bio *bio)
{
        struct dmz_mblock *mblk = bio->bi_private;
        int flag;

        if (bio->bi_status)
                set_bit(DMZ_META_ERROR, &mblk->state);

        if (bio_op(bio) == REQ_OP_WRITE)
                flag = DMZ_META_WRITING;
        else
                flag = DMZ_META_READING;

        clear_bit_unlock(flag, &mblk->state);
        smp_mb__after_atomic();
        wake_up_bit(&mblk->state, flag);

        bio_put(bio);
}

/*
 * Read an uncached metadata block from disk and add it to the cache.
 */
static struct dmz_mblock *dmz_get_mblock_slow(struct dmz_metadata *zmd,
                                              sector_t mblk_no)
{
        struct dmz_mblock *mblk, *m;
        sector_t block = zmd->sb[zmd->mblk_primary].block + mblk_no;
        struct dmz_dev *dev = zmd->sb[zmd->mblk_primary].dev;
        struct bio *bio;

        if (dmz_bdev_is_dying(dev))
                return ERR_PTR(-EIO);

        /* Get a new block and a BIO to read it */
        mblk = dmz_alloc_mblock(zmd, mblk_no);
        if (!mblk)
                return ERR_PTR(-ENOMEM);

        bio = bio_alloc(GFP_NOIO, 1);
        if (!bio) {
                dmz_free_mblock(zmd, mblk);
                return ERR_PTR(-ENOMEM);
        }

        spin_lock(&zmd->mblk_lock);

        /*
         * Make sure that another context did not start reading
         * the block already.
         */
        m = dmz_get_mblock_fast(zmd, mblk_no);
        if (m) {
                spin_unlock(&zmd->mblk_lock);
                dmz_free_mblock(zmd, mblk);
                bio_put(bio);
                return m;
        }

        mblk->ref++;
        set_bit(DMZ_META_READING, &mblk->state);
        dmz_insert_mblock(zmd, mblk);

        spin_unlock(&zmd->mblk_lock);

        /* Submit read BIO */
        bio->bi_iter.bi_sector = dmz_blk2sect(block);
        bio_set_dev(bio, dev->bdev);
        bio->bi_private = mblk;
        bio->bi_end_io = dmz_mblock_bio_end_io;
        bio_set_op_attrs(bio, REQ_OP_READ, REQ_META | REQ_PRIO);
        bio_add_page(bio, mblk->page, DMZ_BLOCK_SIZE, 0);
        submit_bio(bio);

        return mblk;
}

/*
 * Free metadata blocks.
 */
static unsigned long dmz_shrink_mblock_cache(struct dmz_metadata *zmd,
                                             unsigned long limit)
{
        struct dmz_mblock *mblk;
        unsigned long count = 0;

        if (!zmd->max_nr_mblks)
                return 0;

        while (!list_empty(&zmd->mblk_lru_list) &&
               atomic_read(&zmd->nr_mblks) > zmd->min_nr_mblks &&
               count < limit) {
                mblk = list_first_entry(&zmd->mblk_lru_list,
                                        struct dmz_mblock, link);
                list_del_init(&mblk->link);
                rb_erase(&mblk->node, &zmd->mblk_rbtree);
                dmz_free_mblock(zmd, mblk);
                count++;
        }

        return count;
}

/*
 * For mblock shrinker: get the number of unused metadata blocks in the cache.
 */
static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink,
                                               struct shrink_control *sc)
{
        struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker);

        return atomic_read(&zmd->nr_mblks);
}

/*
 * For mblock shrinker: scan unused metadata blocks and shrink the cache.
 */
static unsigned long dmz_mblock_shrinker_scan(struct shrinker *shrink,
                                              struct shrink_control *sc)
{
        struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker);
        unsigned long count;

        spin_lock(&zmd->mblk_lock);
        count = dmz_shrink_mblock_cache(zmd, sc->nr_to_scan);
        spin_unlock(&zmd->mblk_lock);

        return count ? count : SHRINK_STOP;
}

/*
 * Release a metadata block.
 */
static void dmz_release_mblock(struct dmz_metadata *zmd,
                               struct dmz_mblock *mblk)
{

        if (!mblk)
                return;

        spin_lock(&zmd->mblk_lock);

        mblk->ref--;
        if (mblk->ref == 0) {
                if (test_bit(DMZ_META_ERROR, &mblk->state)) {
                        rb_erase(&mblk->node, &zmd->mblk_rbtree);
                        dmz_free_mblock(zmd, mblk);
                } else if (!test_bit(DMZ_META_DIRTY, &mblk->state)) {
                        list_add_tail(&mblk->link, &zmd->mblk_lru_list);
                        dmz_shrink_mblock_cache(zmd, 1);
                }
        }

        spin_unlock(&zmd->mblk_lock);
}

/*
 * Get a metadata block from the rbtree. If the block
 * is not present, read it from disk.
 */
static struct dmz_mblock *dmz_get_mblock(struct dmz_metadata *zmd,
                                         sector_t mblk_no)
{
        struct dmz_mblock *mblk;
        struct dmz_dev *dev = zmd->sb[zmd->mblk_primary].dev;

        /* Check rbtree */
        spin_lock(&zmd->mblk_lock);
        mblk = dmz_get_mblock_fast(zmd, mblk_no);
        spin_unlock(&zmd->mblk_lock);

        if (!mblk) {
                /* Cache miss: read the block from disk */
                mblk = dmz_get_mblock_slow(zmd, mblk_no);
                if (IS_ERR(mblk))
                        return mblk;
        }

        /* Wait for on-going read I/O and check for error */
        wait_on_bit_io(&mblk->state, DMZ_META_READING,
                       TASK_UNINTERRUPTIBLE);
        if (test_bit(DMZ_META_ERROR, &mblk->state)) {
                dmz_release_mblock(zmd, mblk);
                dmz_check_bdev(dev);
                return ERR_PTR(-EIO);
        }

        return mblk;
}

/*
 * Mark a metadata block dirty.
 */
static void dmz_dirty_mblock(struct dmz_metadata *zmd, struct dmz_mblock *mblk)
{
        spin_lock(&zmd->mblk_lock);
        if (!test_and_set_bit(DMZ_META_DIRTY, &mblk->state))
                list_add_tail(&mblk->link, &zmd->mblk_dirty_list);
        spin_unlock(&zmd->mblk_lock);
}

/*
 * Issue a metadata block write BIO.
 */
static int dmz_write_mblock(struct dmz_metadata *zmd, struct dmz_mblock *mblk,
                            unsigned int set)
{
        struct dmz_dev *dev = zmd->sb[set].dev;
        sector_t block = zmd->sb[set].block + mblk->no;
        struct bio *bio;

        if (dmz_bdev_is_dying(dev))
                return -EIO;

        bio = bio_alloc(GFP_NOIO, 1);
        if (!bio) {
                set_bit(DMZ_META_ERROR, &mblk->state);
                return -ENOMEM;
        }

        set_bit(DMZ_META_WRITING, &mblk->state);

        bio->bi_iter.bi_sector = dmz_blk2sect(block);
        bio_set_dev(bio, dev->bdev);
        bio->bi_private = mblk;
        bio->bi_end_io = dmz_mblock_bio_end_io;
        bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_META | REQ_PRIO);
        bio_add_page(bio, mblk->page, DMZ_BLOCK_SIZE, 0);
        submit_bio(bio);

        return 0;
}

/*
 * Read/write a metadata block.
 */
static int dmz_rdwr_block(struct dmz_dev *dev, int op,
                          sector_t block, struct page *page)
{
        struct bio *bio;
        int ret;

        if (WARN_ON(!dev))
                return -EIO;

        if (dmz_bdev_is_dying(dev))
                return -EIO;

        bio = bio_alloc(GFP_NOIO, 1);
        if (!bio)
                return -ENOMEM;

        bio->bi_iter.bi_sector = dmz_blk2sect(block);
        bio_set_dev(bio, dev->bdev);
        bio_set_op_attrs(bio, op, REQ_SYNC | REQ_META | REQ_PRIO);
        bio_add_page(bio, page, DMZ_BLOCK_SIZE, 0);
        ret = submit_bio_wait(bio);
        bio_put(bio);

        if (ret)
                dmz_check_bdev(dev);
        return ret;
}

/*
 * Write super block of the specified metadata set.
 */
static int dmz_write_sb(struct dmz_metadata *zmd, unsigned int set)
{
        struct dmz_mblock *mblk = zmd->sb[set].mblk;
        struct dmz_super *sb = zmd->sb[set].sb;
        struct dmz_dev *dev = zmd->sb[set].dev;
        sector_t sb_block;
        u64 sb_gen = zmd->sb_gen + 1;
        int ret;

        sb->magic = cpu_to_le32(DMZ_MAGIC);

        sb->version = cpu_to_le32(zmd->sb_version);
        if (zmd->sb_version > 1) {
                BUILD_BUG_ON(UUID_SIZE != 16);
                export_uuid(sb->dmz_uuid, &zmd->uuid);
                memcpy(sb->dmz_label, zmd->label, BDEVNAME_SIZE);
                export_uuid(sb->dev_uuid, &dev->uuid);
        }

        sb->gen = cpu_to_le64(sb_gen);

        /*
         * The metadata always references the absolute block address,
         * ie relative to the entire block range, not the per-device
         * block address.
         */
        sb_block = zmd->sb[set].zone->id << zmd->zone_nr_blocks_shift;
        sb->sb_block = cpu_to_le64(sb_block);
        sb->nr_meta_blocks = cpu_to_le32(zmd->nr_meta_blocks);
        sb->nr_reserved_seq = cpu_to_le32(zmd->nr_reserved_seq);
        sb->nr_chunks = cpu_to_le32(zmd->nr_chunks);

        sb->nr_map_blocks = cpu_to_le32(zmd->nr_map_blocks);
        sb->nr_bitmap_blocks = cpu_to_le32(zmd->nr_bitmap_blocks);

        sb->crc = 0;
        sb->crc = cpu_to_le32(crc32_le(sb_gen, (unsigned char *)sb, DMZ_BLOCK_SIZE));

        ret = dmz_rdwr_block(dev, REQ_OP_WRITE, zmd->sb[set].block,
                             mblk->page);
        if (ret == 0)
                ret = blkdev_issue_flush(dev->bdev);

        return ret;
}

/*
 * Write dirty metadata blocks to the specified set.
 */
static int dmz_write_dirty_mblocks(struct dmz_metadata *zmd,
                                   struct list_head *write_list,
                                   unsigned int set)
{
        struct dmz_mblock *mblk;
        struct dmz_dev *dev = zmd->sb[set].dev;
        struct blk_plug plug;
        int ret = 0, nr_mblks_submitted = 0;

        /* Issue writes */
        blk_start_plug(&plug);
        list_for_each_entry(mblk, write_list, link) {
                ret = dmz_write_mblock(zmd, mblk, set);
                if (ret)
                        break;
                nr_mblks_submitted++;
        }
        blk_finish_plug(&plug);

        /* Wait for completion */
        list_for_each_entry(mblk, write_list, link) {
                if (!nr_mblks_submitted)
                        break;
                wait_on_bit_io(&mblk->state, DMZ_META_WRITING,
                               TASK_UNINTERRUPTIBLE);
                if (test_bit(DMZ_META_ERROR, &mblk->state)) {
                        clear_bit(DMZ_META_ERROR, &mblk->state);
                        dmz_check_bdev(dev);
                        ret = -EIO;
                }
                nr_mblks_submitted--;
        }

        /* Flush drive cache (this will also sync data) */
        if (ret == 0)
                ret = blkdev_issue_flush(dev->bdev);

        return ret;
}

/*
 * Log dirty metadata blocks.
 */
static int dmz_log_dirty_mblocks(struct dmz_metadata *zmd,
                                 struct list_head *write_list)
{
        unsigned int log_set = zmd->mblk_primary ^ 0x1;
        int ret;

        /* Write dirty blocks to the log */
        ret = dmz_write_dirty_mblocks(zmd, write_list, log_set);
        if (ret)
                return ret;

        /*
         * No error so far: now validate the log by updating the
         * log index super block generation.
         */
        ret = dmz_write_sb(zmd, log_set);
        if (ret)
                return ret;

        return 0;
}

/*
 * Flush dirty metadata blocks.
 */
int dmz_flush_metadata(struct dmz_metadata *zmd)
{
        struct dmz_mblock *mblk;
        struct list_head write_list;
        struct dmz_dev *dev;
        int ret;

        if (WARN_ON(!zmd))
                return 0;

        INIT_LIST_HEAD(&write_list);

        /*
         * Make sure that metadata blocks are stable before logging: take
         * the write lock on the metadata semaphore to prevent target BIOs
         * from modifying metadata.
         */
        down_write(&zmd->mblk_sem);
        dev = zmd->sb[zmd->mblk_primary].dev;

        /*
         * This is called from the target flush work and reclaim work.
         * Concurrent execution is not allowed.
         */
        dmz_lock_flush(zmd);

        if (dmz_bdev_is_dying(dev)) {
                ret = -EIO;
                goto out;
        }

        /* Get dirty blocks */
        spin_lock(&zmd->mblk_lock);
        list_splice_init(&zmd->mblk_dirty_list, &write_list);
        spin_unlock(&zmd->mblk_lock);

        /* If there are no dirty metadata blocks, just flush the device cache */
        if (list_empty(&write_list)) {
                ret = blkdev_issue_flush(dev->bdev);
                goto err;
        }

        /*
         * The primary metadata set is still clean. Keep it this way until
         * all updates are successful in the secondary set. That is, use
         * the secondary set as a log.
         */
        ret = dmz_log_dirty_mblocks(zmd, &write_list);
        if (ret)
                goto err;

        /*
         * The log is on disk. It is now safe to update in place
         * in the primary metadata set.
         */
        ret = dmz_write_dirty_mblocks(zmd, &write_list, zmd->mblk_primary);
        if (ret)
                goto err;

        ret = dmz_write_sb(zmd, zmd->mblk_primary);
        if (ret)
                goto err;

        while (!list_empty(&write_list)) {
                mblk = list_first_entry(&write_list, struct dmz_mblock, link);
                list_del_init(&mblk->link);

                spin_lock(&zmd->mblk_lock);
                clear_bit(DMZ_META_DIRTY, &mblk->state);
                if (mblk->ref == 0)
                        list_add_tail(&mblk->link, &zmd->mblk_lru_list);
                spin_unlock(&zmd->mblk_lock);
        }

        zmd->sb_gen++;
out:
        dmz_unlock_flush(zmd);
        up_write(&zmd->mblk_sem);

        return ret;

err:
        if (!list_empty(&write_list)) {
                spin_lock(&zmd->mblk_lock);
                list_splice(&write_list, &zmd->mblk_dirty_list);
                spin_unlock(&zmd->mblk_lock);
        }
        if (!dmz_check_bdev(dev))
                ret = -EIO;
        goto out;
}

/*
 * Check super block.
 */
static int dmz_check_sb(struct dmz_metadata *zmd, struct dmz_sb *dsb,
                        bool tertiary)
{
        struct dmz_super *sb = dsb->sb;
        struct dmz_dev *dev = dsb->dev;
        unsigned int nr_meta_zones, nr_data_zones;
        u32 crc, stored_crc;
        u64 gen, sb_block;

        if (le32_to_cpu(sb->magic) != DMZ_MAGIC) {
                dmz_dev_err(dev, "Invalid meta magic (needed 0x%08x, got 0x%08x)",
                            DMZ_MAGIC, le32_to_cpu(sb->magic));
                return -ENXIO;
        }

        zmd->sb_version = le32_to_cpu(sb->version);
        if (zmd->sb_version > DMZ_META_VER) {
                dmz_dev_err(dev, "Invalid meta version (needed %d, got %d)",
                            DMZ_META_VER, zmd->sb_version);
                return -EINVAL;
        }
        if (zmd->sb_version < 2 && tertiary) {
                dmz_dev_err(dev, "Tertiary superblocks are not supported");
                return -EINVAL;
        }

        gen = le64_to_cpu(sb->gen);
        stored_crc = le32_to_cpu(sb->crc);
        sb->crc = 0;
        crc = crc32_le(gen, (unsigned char *)sb, DMZ_BLOCK_SIZE);
        if (crc != stored_crc) {
                dmz_dev_err(dev, "Invalid checksum (needed 0x%08x, got 0x%08x)",
                            crc, stored_crc);
                return -ENXIO;
        }

        sb_block = le64_to_cpu(sb->sb_block);
        if (sb_block != (u64)dsb->zone->id << zmd->zone_nr_blocks_shift ) {
                dmz_dev_err(dev, "Invalid superblock position "
                            "(is %llu expected %llu)",
                            sb_block,
                            (u64)dsb->zone->id << zmd->zone_nr_blocks_shift);
                return -EINVAL;
        }
        if (zmd->sb_version > 1) {
                uuid_t sb_uuid;

                import_uuid(&sb_uuid, sb->dmz_uuid);
                if (uuid_is_null(&sb_uuid)) {
                        dmz_dev_err(dev, "NULL DM-Zoned uuid");
                        return -ENXIO;
                } else if (uuid_is_null(&zmd->uuid)) {
                        uuid_copy(&zmd->uuid, &sb_uuid);
                } else if (!uuid_equal(&zmd->uuid, &sb_uuid)) {
                        dmz_dev_err(dev, "mismatching DM-Zoned uuid, "
                                    "is %pUl expected %pUl",
                                    &sb_uuid, &zmd->uuid);
                        return -ENXIO;
                }
                if (!strlen(zmd->label))
                        memcpy(zmd->label, sb->dmz_label, BDEVNAME_SIZE);
                else if (memcmp(zmd->label, sb->dmz_label, BDEVNAME_SIZE)) {
                        dmz_dev_err(dev, "mismatching DM-Zoned label, "
                                    "is %s expected %s",
                                    sb->dmz_label, zmd->label);
                        return -ENXIO;
                }
                import_uuid(&dev->uuid, sb->dev_uuid);
                if (uuid_is_null(&dev->uuid)) {
                        dmz_dev_err(dev, "NULL device uuid");
                        return -ENXIO;
                }

                if (tertiary) {
                        /*
                         * Generation number should be 0, but it doesn't
                         * really matter if it isn't.
                         */
                        if (gen != 0)
                                dmz_dev_warn(dev, "Invalid generation %llu",
                                            gen);
                        return 0;
                }
        }

        nr_meta_zones = (le32_to_cpu(sb->nr_meta_blocks) + zmd->zone_nr_blocks - 1)
                >> zmd->zone_nr_blocks_shift;
        if (!nr_meta_zones ||
            (zmd->nr_devs <= 1 && nr_meta_zones >= zmd->nr_rnd_zones) ||
            (zmd->nr_devs > 1 && nr_meta_zones >= zmd->nr_cache_zones)) {
                dmz_dev_err(dev, "Invalid number of metadata blocks");
                return -ENXIO;
        }

        if (!le32_to_cpu(sb->nr_reserved_seq) ||
            le32_to_cpu(sb->nr_reserved_seq) >= (zmd->nr_useable_zones - nr_meta_zones)) {
                dmz_dev_err(dev, "Invalid number of reserved sequential zones");
                return -ENXIO;
        }

        nr_data_zones = zmd->nr_useable_zones -
                (nr_meta_zones * 2 + le32_to_cpu(sb->nr_reserved_seq));
        if (le32_to_cpu(sb->nr_chunks) > nr_data_zones) {
                dmz_dev_err(dev, "Invalid number of chunks %u / %u",
                            le32_to_cpu(sb->nr_chunks), nr_data_zones);
                return -ENXIO;
        }

        /* OK */
        zmd->nr_meta_blocks = le32_to_cpu(sb->nr_meta_blocks);
        zmd->nr_reserved_seq = le32_to_cpu(sb->nr_reserved_seq);
        zmd->nr_chunks = le32_to_cpu(sb->nr_chunks);
        zmd->nr_map_blocks = le32_to_cpu(sb->nr_map_blocks);
        zmd->nr_bitmap_blocks = le32_to_cpu(sb->nr_bitmap_blocks);
        zmd->nr_meta_zones = nr_meta_zones;
        zmd->nr_data_zones = nr_data_zones;

        return 0;
}

/*
 * Read the first or second super block from disk.
 */
static int dmz_read_sb(struct dmz_metadata *zmd, struct dmz_sb *sb, int set)
{
        dmz_zmd_debug(zmd, "read superblock set %d dev %s block %llu",
                      set, sb->dev->name, sb->block);

        return dmz_rdwr_block(sb->dev, REQ_OP_READ,
                              sb->block, sb->mblk->page);
}

/*
 * Determine the position of the secondary super blocks on disk.
 * This is used only if a corruption of the primary super block
 * is detected.
 */
static int dmz_lookup_secondary_sb(struct dmz_metadata *zmd)
{
        unsigned int zone_nr_blocks = zmd->zone_nr_blocks;
        struct dmz_mblock *mblk;
        unsigned int zone_id = zmd->sb[0].zone->id;
        int i;

        /* Allocate a block */
        mblk = dmz_alloc_mblock(zmd, 0);
        if (!mblk)
                return -ENOMEM;

        zmd->sb[1].mblk = mblk;
        zmd->sb[1].sb = mblk->data;

        /* Bad first super block: search for the second one */
        zmd->sb[1].block = zmd->sb[0].block + zone_nr_blocks;
        zmd->sb[1].zone = dmz_get(zmd, zone_id + 1);
        zmd->sb[1].dev = zmd->sb[0].dev;
        for (i = 1; i < zmd->nr_rnd_zones; i++) {
                if (dmz_read_sb(zmd, &zmd->sb[1], 1) != 0)
                        break;
                if (le32_to_cpu(zmd->sb[1].sb->magic) == DMZ_MAGIC)
                        return 0;
                zmd->sb[1].block += zone_nr_blocks;
                zmd->sb[1].zone = dmz_get(zmd, zone_id + i);
        }

        dmz_free_mblock(zmd, mblk);
        zmd->sb[1].mblk = NULL;
        zmd->sb[1].zone = NULL;
        zmd->sb[1].dev = NULL;

        return -EIO;
}

/*
 * Read a super block from disk.
 */
static int dmz_get_sb(struct dmz_metadata *zmd, struct dmz_sb *sb, int set)
{
        struct dmz_mblock *mblk;
        int ret;

        /* Allocate a block */
        mblk = dmz_alloc_mblock(zmd, 0);
        if (!mblk)
                return -ENOMEM;

        sb->mblk = mblk;
        sb->sb = mblk->data;

        /* Read super block */
        ret = dmz_read_sb(zmd, sb, set);
        if (ret) {
                dmz_free_mblock(zmd, mblk);
                sb->mblk = NULL;
                return ret;
        }

        return 0;
}

/*
 * Recover a metadata set.
 */
static int dmz_recover_mblocks(struct dmz_metadata *zmd, unsigned int dst_set)
{
        unsigned int src_set = dst_set ^ 0x1;
        struct page *page;
        int i, ret;

        dmz_dev_warn(zmd->sb[dst_set].dev,
                     "Metadata set %u invalid: recovering", dst_set);

        if (dst_set == 0)
                zmd->sb[0].block = dmz_start_block(zmd, zmd->sb[0].zone);
        else
                zmd->sb[1].block = dmz_start_block(zmd, zmd->sb[1].zone);

        page = alloc_page(GFP_NOIO);
        if (!page)
                return -ENOMEM;

        /* Copy metadata blocks */
        for (i = 1; i < zmd->nr_meta_blocks; i++) {
                ret = dmz_rdwr_block(zmd->sb[src_set].dev, REQ_OP_READ,
                                     zmd->sb[src_set].block + i, page);
                if (ret)
                        goto out;
                ret = dmz_rdwr_block(zmd->sb[dst_set].dev, REQ_OP_WRITE,
                                     zmd->sb[dst_set].block + i, page);
                if (ret)
                        goto out;
        }

        /* Finalize with the super block */
        if (!zmd->sb[dst_set].mblk) {
                zmd->sb[dst_set].mblk = dmz_alloc_mblock(zmd, 0);
                if (!zmd->sb[dst_set].mblk) {
                        ret = -ENOMEM;
                        goto out;
                }
                zmd->sb[dst_set].sb = zmd->sb[dst_set].mblk->data;
        }

        ret = dmz_write_sb(zmd, dst_set);
out:
        __free_pages(page, 0);

        return ret;
}

/*
 * Get super block from disk.
 */
static int dmz_load_sb(struct dmz_metadata *zmd)
{
        bool sb_good[2] = {false, false};
        u64 sb_gen[2] = {0, 0};
        int ret;

        if (!zmd->sb[0].zone) {
                dmz_zmd_err(zmd, "Primary super block zone not set");
                return -ENXIO;
        }

        /* Read and check the primary super block */
        zmd->sb[0].block = dmz_start_block(zmd, zmd->sb[0].zone);
        zmd->sb[0].dev = zmd->sb[0].zone->dev;
        ret = dmz_get_sb(zmd, &zmd->sb[0], 0);
        if (ret) {
                dmz_dev_err(zmd->sb[0].dev, "Read primary super block failed");
                return ret;
        }

        ret = dmz_check_sb(zmd, &zmd->sb[0], false);

        /* Read and check secondary super block */
        if (ret == 0) {
                sb_good[0] = true;
                if (!zmd->sb[1].zone) {
                        unsigned int zone_id =
                                zmd->sb[0].zone->id + zmd->nr_meta_zones;

                        zmd->sb[1].zone = dmz_get(zmd, zone_id);
                }
                zmd->sb[1].block = dmz_start_block(zmd, zmd->sb[1].zone);
                zmd->sb[1].dev = zmd->sb[0].dev;
                ret = dmz_get_sb(zmd, &zmd->sb[1], 1);
        } else
                ret = dmz_lookup_secondary_sb(zmd);

        if (ret) {
                dmz_dev_err(zmd->sb[1].dev, "Read secondary super block failed");
                return ret;
        }

        ret = dmz_check_sb(zmd, &zmd->sb[1], false);
        if (ret == 0)
                sb_good[1] = true;

        /* Use highest generation sb first */
        if (!sb_good[0] && !sb_good[1]) {
                dmz_zmd_err(zmd, "No valid super block found");
                return -EIO;
        }

        if (sb_good[0])
                sb_gen[0] = le64_to_cpu(zmd->sb[0].sb->gen);
        else {
                ret = dmz_recover_mblocks(zmd, 0);
                if (ret) {
                        dmz_dev_err(zmd->sb[0].dev,
                                    "Recovery of superblock 0 failed");
                        return -EIO;
                }
        }

        if (sb_good[1])
                sb_gen[1] = le64_to_cpu(zmd->sb[1].sb->gen);
        else {
                ret = dmz_recover_mblocks(zmd, 1);

                if (ret) {
                        dmz_dev_err(zmd->sb[1].dev,
                                    "Recovery of superblock 1 failed");
                        return -EIO;
                }
        }

        if (sb_gen[0] >= sb_gen[1]) {
                zmd->sb_gen = sb_gen[0];
                zmd->mblk_primary = 0;
        } else {
                zmd->sb_gen = sb_gen[1];
                zmd->mblk_primary = 1;
        }

        dmz_dev_debug(zmd->sb[zmd->mblk_primary].dev,
                      "Using super block %u (gen %llu)",
                      zmd->mblk_primary, zmd->sb_gen);

        if (zmd->sb_version > 1) {
                int i;
                struct dmz_sb *sb;

                sb = kzalloc(sizeof(struct dmz_sb), GFP_KERNEL);
                if (!sb)
                        return -ENOMEM;
                for (i = 1; i < zmd->nr_devs; i++) {
                        sb->block = 0;
                        sb->zone = dmz_get(zmd, zmd->dev[i].zone_offset);
                        sb->dev = &zmd->dev[i];
                        if (!dmz_is_meta(sb->zone)) {
                                dmz_dev_err(sb->dev,
                                            "Tertiary super block zone %u not marked as metadata zone",
                                            sb->zone->id);
                                ret = -EINVAL;
                                goto out_kfree;
                        }
                        ret = dmz_get_sb(zmd, sb, i + 1);
                        if (ret) {
                                dmz_dev_err(sb->dev,
                                            "Read tertiary super block failed");
                                dmz_free_mblock(zmd, sb->mblk);
                                goto out_kfree;
                        }
                        ret = dmz_check_sb(zmd, sb, true);
                        dmz_free_mblock(zmd, sb->mblk);
                        if (ret == -EINVAL)
                                goto out_kfree;
                }
        out_kfree:
                kfree(sb);
        }
        return ret;
}

/*
 * Initialize a zone descriptor.
 */
static int dmz_init_zone(struct blk_zone *blkz, unsigned int num, void *data)
{
        struct dmz_dev *dev = data;
        struct dmz_metadata *zmd = dev->metadata;
        int idx = num + dev->zone_offset;
        struct dm_zone *zone;

        zone = dmz_insert(zmd, idx, dev);
        if (IS_ERR(zone))
                return PTR_ERR(zone);

        if (blkz->len != zmd->zone_nr_sectors) {
                if (zmd->sb_version > 1) {
                        /* Ignore the eventual runt (smaller) zone */
                        set_bit(DMZ_OFFLINE, &zone->flags);
                        return 0;
                } else if (blkz->start + blkz->len == dev->capacity)
                        return 0;
                return -ENXIO;
        }

        /*
         * Devices that have zones with a capacity smaller than the zone size
         * (e.g. NVMe zoned namespaces) are not supported.
         */
        if (blkz->capacity != blkz->len)
                return -ENXIO;

        switch (blkz->type) {
        case BLK_ZONE_TYPE_CONVENTIONAL:
                set_bit(DMZ_RND, &zone->flags);
                break;
        case BLK_ZONE_TYPE_SEQWRITE_REQ:
        case BLK_ZONE_TYPE_SEQWRITE_PREF:
                set_bit(DMZ_SEQ, &zone->flags);
                break;
        default:
                return -ENXIO;
        }

        if (dmz_is_rnd(zone))
                zone->wp_block = 0;
        else
                zone->wp_block = dmz_sect2blk(blkz->wp - blkz->start);

        if (blkz->cond == BLK_ZONE_COND_OFFLINE)
                set_bit(DMZ_OFFLINE, &zone->flags);
        else if (blkz->cond == BLK_ZONE_COND_READONLY)
                set_bit(DMZ_READ_ONLY, &zone->flags);
        else {
                zmd->nr_useable_zones++;
                if (dmz_is_rnd(zone)) {
                        zmd->nr_rnd_zones++;
                        if (zmd->nr_devs == 1 && !zmd->sb[0].zone) {
                                /* Primary super block zone */
                                zmd->sb[0].zone = zone;
                        }
                }
                if (zmd->nr_devs > 1 && num == 0) {
                        /*
                         * Tertiary superblock zones are always at the
                         * start of the zoned devices, so mark them
                         * as metadata zone.
                         */
                        set_bit(DMZ_META, &zone->flags);
                }
        }
        return 0;
}

static int dmz_emulate_zones(struct dmz_metadata *zmd, struct dmz_dev *dev)
{
        int idx;
        sector_t zone_offset = 0;

        for(idx = 0; idx < dev->nr_zones; idx++) {
                struct dm_zone *zone;

                zone = dmz_insert(zmd, idx, dev);
                if (IS_ERR(zone))
                        return PTR_ERR(zone);
                set_bit(DMZ_CACHE, &zone->flags);
                zone->wp_block = 0;
                zmd->nr_cache_zones++;
                zmd->nr_useable_zones++;
                if (dev->capacity - zone_offset < zmd->zone_nr_sectors) {
                        /* Disable runt zone */
                        set_bit(DMZ_OFFLINE, &zone->flags);
                        break;
                }
                zone_offset += zmd->zone_nr_sectors;
        }
        return 0;
}

/*
 * Free zones descriptors.
 */
static void dmz_drop_zones(struct dmz_metadata *zmd)
{
        int idx;

        for(idx = 0; idx < zmd->nr_zones; idx++) {
                struct dm_zone *zone = xa_load(&zmd->zones, idx);

                kfree(zone);
                xa_erase(&zmd->zones, idx);
        }
        xa_destroy(&zmd->zones);
}

/*
 * Allocate and initialize zone descriptors using the zone
 * information from disk.
 */
static int dmz_init_zones(struct dmz_metadata *zmd)
{
        int i, ret;
        struct dmz_dev *zoned_dev = &zmd->dev[0];

        /* Init */
        zmd->zone_nr_sectors = zmd->dev[0].zone_nr_sectors;
        zmd->zone_nr_sectors_shift = ilog2(zmd->zone_nr_sectors);
        zmd->zone_nr_blocks = dmz_sect2blk(zmd->zone_nr_sectors);
        zmd->zone_nr_blocks_shift = ilog2(zmd->zone_nr_blocks);
        zmd->zone_bitmap_size = zmd->zone_nr_blocks >> 3;
        zmd->zone_nr_bitmap_blocks =
                max_t(sector_t, 1, zmd->zone_bitmap_size >> DMZ_BLOCK_SHIFT);
        zmd->zone_bits_per_mblk = min_t(sector_t, zmd->zone_nr_blocks,
                                        DMZ_BLOCK_SIZE_BITS);

        /* Allocate zone array */
        zmd->nr_zones = 0;
        for (i = 0; i < zmd->nr_devs; i++) {
                struct dmz_dev *dev = &zmd->dev[i];

                dev->metadata = zmd;
                zmd->nr_zones += dev->nr_zones;

                atomic_set(&dev->unmap_nr_rnd, 0);
                INIT_LIST_HEAD(&dev->unmap_rnd_list);
                INIT_LIST_HEAD(&dev->map_rnd_list);

                atomic_set(&dev->unmap_nr_seq, 0);
                INIT_LIST_HEAD(&dev->unmap_seq_list);
                INIT_LIST_HEAD(&dev->map_seq_list);
        }

        if (!zmd->nr_zones) {
                DMERR("(%s): No zones found", zmd->devname);
                return -ENXIO;
        }
        xa_init(&zmd->zones);

        DMDEBUG("(%s): Using %zu B for zone information",
                zmd->devname, sizeof(struct dm_zone) * zmd->nr_zones);

        if (zmd->nr_devs > 1) {
                ret = dmz_emulate_zones(zmd, &zmd->dev[0]);
                if (ret < 0) {
                        DMDEBUG("(%s): Failed to emulate zones, error %d",
                                zmd->devname, ret);
                        dmz_drop_zones(zmd);
                        return ret;
                }

                /*
                 * Primary superblock zone is always at zone 0 when multiple
                 * drives are present.
                 */
                zmd->sb[0].zone = dmz_get(zmd, 0);

                for (i = 1; i < zmd->nr_devs; i++) {
                        zoned_dev = &zmd->dev[i];

                        ret = blkdev_report_zones(zoned_dev->bdev, 0,
                                                  BLK_ALL_ZONES,
                                                  dmz_init_zone, zoned_dev);
                        if (ret < 0) {
                                DMDEBUG("(%s): Failed to report zones, error %d",
                                        zmd->devname, ret);
                                dmz_drop_zones(zmd);
                                return ret;
                        }
                }
                return 0;
        }

        /*
         * Get zone information and initialize zone descriptors.  At the same
         * time, determine where the super block should be: first block of the
         * first randomly writable zone.
         */
        ret = blkdev_report_zones(zoned_dev->bdev, 0, BLK_ALL_ZONES,
                                  dmz_init_zone, zoned_dev);
        if (ret < 0) {
                DMDEBUG("(%s): Failed to report zones, error %d",
                        zmd->devname, ret);
                dmz_drop_zones(zmd);
                return ret;
        }

        return 0;
}

static int dmz_update_zone_cb(struct blk_zone *blkz, unsigned int idx,
                              void *data)
{
        struct dm_zone *zone = data;

        clear_bit(DMZ_OFFLINE, &zone->flags);
        clear_bit(DMZ_READ_ONLY, &zone->flags);
        if (blkz->cond == BLK_ZONE_COND_OFFLINE)
                set_bit(DMZ_OFFLINE, &zone->flags);
        else if (blkz->cond == BLK_ZONE_COND_READONLY)
                set_bit(DMZ_READ_ONLY, &zone->flags);

        if (dmz_is_seq(zone))
                zone->wp_block = dmz_sect2blk(blkz->wp - blkz->start);
        else
                zone->wp_block = 0;
        return 0;
}

/*
 * Update a zone information.
 */
static int dmz_update_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        struct dmz_dev *dev = zone->dev;
        unsigned int noio_flag;
        int ret;

        if (dev->flags & DMZ_BDEV_REGULAR)
                return 0;

        /*
         * Get zone information from disk. Since blkdev_report_zones() uses
         * GFP_KERNEL by default for memory allocations, set the per-task
         * PF_MEMALLOC_NOIO flag so that all allocations are done as if
         * GFP_NOIO was specified.
         */
        noio_flag = memalloc_noio_save();
        ret = blkdev_report_zones(dev->bdev, dmz_start_sect(zmd, zone), 1,
                                  dmz_update_zone_cb, zone);
        memalloc_noio_restore(noio_flag);

        if (ret == 0)
                ret = -EIO;
        if (ret < 0) {
                dmz_dev_err(dev, "Get zone %u report failed",
                            zone->id);
                dmz_check_bdev(dev);
                return ret;
        }

        return 0;
}

/*
 * Check a zone write pointer position when the zone is marked
 * with the sequential write error flag.
 */
static int dmz_handle_seq_write_err(struct dmz_metadata *zmd,
                                    struct dm_zone *zone)
{
        struct dmz_dev *dev = zone->dev;
        unsigned int wp = 0;
        int ret;

        wp = zone->wp_block;
        ret = dmz_update_zone(zmd, zone);
        if (ret)
                return ret;

        dmz_dev_warn(dev, "Processing zone %u write error (zone wp %u/%u)",
                     zone->id, zone->wp_block, wp);

        if (zone->wp_block < wp) {
                dmz_invalidate_blocks(zmd, zone, zone->wp_block,
                                      wp - zone->wp_block);
        }

        return 0;
}

/*
 * Reset a zone write pointer.
 */
static int dmz_reset_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        int ret;

        /*
         * Ignore offline zones, read only zones,
         * and conventional zones.
         */
        if (dmz_is_offline(zone) ||
            dmz_is_readonly(zone) ||
            dmz_is_rnd(zone))
                return 0;

        if (!dmz_is_empty(zone) || dmz_seq_write_err(zone)) {
                struct dmz_dev *dev = zone->dev;

                ret = blkdev_zone_mgmt(dev->bdev, REQ_OP_ZONE_RESET,
                                       dmz_start_sect(zmd, zone),
                                       zmd->zone_nr_sectors, GFP_NOIO);
                if (ret) {
                        dmz_dev_err(dev, "Reset zone %u failed %d",
                                    zone->id, ret);
                        return ret;
                }
        }

        /* Clear write error bit and rewind write pointer position */
        clear_bit(DMZ_SEQ_WRITE_ERR, &zone->flags);
        zone->wp_block = 0;

        return 0;
}

static void dmz_get_zone_weight(struct dmz_metadata *zmd, struct dm_zone *zone);

/*
 * Initialize chunk mapping.
 */
static int dmz_load_mapping(struct dmz_metadata *zmd)
{
        struct dm_zone *dzone, *bzone;
        struct dmz_mblock *dmap_mblk = NULL;
        struct dmz_map *dmap;
        unsigned int i = 0, e = 0, chunk = 0;
        unsigned int dzone_id;
        unsigned int bzone_id;

        /* Metadata block array for the chunk mapping table */
        zmd->map_mblk = kcalloc(zmd->nr_map_blocks,
                                sizeof(struct dmz_mblk *), GFP_KERNEL);
        if (!zmd->map_mblk)
                return -ENOMEM;

        /* Get chunk mapping table blocks and initialize zone mapping */
        while (chunk < zmd->nr_chunks) {
                if (!dmap_mblk) {
                        /* Get mapping block */
                        dmap_mblk = dmz_get_mblock(zmd, i + 1);
                        if (IS_ERR(dmap_mblk))
                                return PTR_ERR(dmap_mblk);
                        zmd->map_mblk[i] = dmap_mblk;
                        dmap = (struct dmz_map *) dmap_mblk->data;
                        i++;
                        e = 0;
                }

                /* Check data zone */
                dzone_id = le32_to_cpu(dmap[e].dzone_id);
                if (dzone_id == DMZ_MAP_UNMAPPED)
                        goto next;

                if (dzone_id >= zmd->nr_zones) {
                        dmz_zmd_err(zmd, "Chunk %u mapping: invalid data zone ID %u",
                                    chunk, dzone_id);
                        return -EIO;
                }

                dzone = dmz_get(zmd, dzone_id);
                if (!dzone) {
                        dmz_zmd_err(zmd, "Chunk %u mapping: data zone %u not present",
                                    chunk, dzone_id);
                        return -EIO;
                }
                set_bit(DMZ_DATA, &dzone->flags);
                dzone->chunk = chunk;
                dmz_get_zone_weight(zmd, dzone);

                if (dmz_is_cache(dzone))
                        list_add_tail(&dzone->link, &zmd->map_cache_list);
                else if (dmz_is_rnd(dzone))
                        list_add_tail(&dzone->link, &dzone->dev->map_rnd_list);
                else
                        list_add_tail(&dzone->link, &dzone->dev->map_seq_list);

                /* Check buffer zone */
                bzone_id = le32_to_cpu(dmap[e].bzone_id);
                if (bzone_id == DMZ_MAP_UNMAPPED)
                        goto next;

                if (bzone_id >= zmd->nr_zones) {
                        dmz_zmd_err(zmd, "Chunk %u mapping: invalid buffer zone ID %u",
                                    chunk, bzone_id);
                        return -EIO;
                }

                bzone = dmz_get(zmd, bzone_id);
                if (!bzone) {
                        dmz_zmd_err(zmd, "Chunk %u mapping: buffer zone %u not present",
                                    chunk, bzone_id);
                        return -EIO;
                }
                if (!dmz_is_rnd(bzone) && !dmz_is_cache(bzone)) {
                        dmz_zmd_err(zmd, "Chunk %u mapping: invalid buffer zone %u",
                                    chunk, bzone_id);
                        return -EIO;
                }

                set_bit(DMZ_DATA, &bzone->flags);
                set_bit(DMZ_BUF, &bzone->flags);
                bzone->chunk = chunk;
                bzone->bzone = dzone;
                dzone->bzone = bzone;
                dmz_get_zone_weight(zmd, bzone);
                if (dmz_is_cache(bzone))
                        list_add_tail(&bzone->link, &zmd->map_cache_list);
                else
                        list_add_tail(&bzone->link, &bzone->dev->map_rnd_list);
next:
                chunk++;
                e++;
                if (e >= DMZ_MAP_ENTRIES)
                        dmap_mblk = NULL;
        }

        /*
         * At this point, only meta zones and mapped data zones were
         * fully initialized. All remaining zones are unmapped data
         * zones. Finish initializing those here.
         */
        for (i = 0; i < zmd->nr_zones; i++) {
                dzone = dmz_get(zmd, i);
                if (!dzone)
                        continue;
                if (dmz_is_meta(dzone))
                        continue;
                if (dmz_is_offline(dzone))
                        continue;

                if (dmz_is_cache(dzone))
                        zmd->nr_cache++;
                else if (dmz_is_rnd(dzone))
                        dzone->dev->nr_rnd++;
                else
                        dzone->dev->nr_seq++;

                if (dmz_is_data(dzone)) {
                        /* Already initialized */
                        continue;
                }

                /* Unmapped data zone */
                set_bit(DMZ_DATA, &dzone->flags);
                dzone->chunk = DMZ_MAP_UNMAPPED;
                if (dmz_is_cache(dzone)) {
                        list_add_tail(&dzone->link, &zmd->unmap_cache_list);
                        atomic_inc(&zmd->unmap_nr_cache);
                } else if (dmz_is_rnd(dzone)) {
                        list_add_tail(&dzone->link,
                                      &dzone->dev->unmap_rnd_list);
                        atomic_inc(&dzone->dev->unmap_nr_rnd);
                } else if (atomic_read(&zmd->nr_reserved_seq_zones) < zmd->nr_reserved_seq) {
                        list_add_tail(&dzone->link, &zmd->reserved_seq_zones_list);
                        set_bit(DMZ_RESERVED, &dzone->flags);
                        atomic_inc(&zmd->nr_reserved_seq_zones);
                        dzone->dev->nr_seq--;
                } else {
                        list_add_tail(&dzone->link,
                                      &dzone->dev->unmap_seq_list);
                        atomic_inc(&dzone->dev->unmap_nr_seq);
                }
        }

        return 0;
}

/*
 * Set a data chunk mapping.
 */
static void dmz_set_chunk_mapping(struct dmz_metadata *zmd, unsigned int chunk,
                                  unsigned int dzone_id, unsigned int bzone_id)
{
        struct dmz_mblock *dmap_mblk = zmd->map_mblk[chunk >> DMZ_MAP_ENTRIES_SHIFT];
        struct dmz_map *dmap = (struct dmz_map *) dmap_mblk->data;
        int map_idx = chunk & DMZ_MAP_ENTRIES_MASK;

        dmap[map_idx].dzone_id = cpu_to_le32(dzone_id);
        dmap[map_idx].bzone_id = cpu_to_le32(bzone_id);
        dmz_dirty_mblock(zmd, dmap_mblk);
}

/*
 * The list of mapped zones is maintained in LRU order.
 * This rotates a zone at the end of its map list.
 */
static void __dmz_lru_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        if (list_empty(&zone->link))
                return;

        list_del_init(&zone->link);
        if (dmz_is_seq(zone)) {
                /* LRU rotate sequential zone */
                list_add_tail(&zone->link, &zone->dev->map_seq_list);
        } else if (dmz_is_cache(zone)) {
                /* LRU rotate cache zone */
                list_add_tail(&zone->link, &zmd->map_cache_list);
        } else {
                /* LRU rotate random zone */
                list_add_tail(&zone->link, &zone->dev->map_rnd_list);
        }
}

/*
 * The list of mapped random zones is maintained
 * in LRU order. This rotates a zone at the end of the list.
 */
static void dmz_lru_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        __dmz_lru_zone(zmd, zone);
        if (zone->bzone)
                __dmz_lru_zone(zmd, zone->bzone);
}

/*
 * Wait for any zone to be freed.
 */
static void dmz_wait_for_free_zones(struct dmz_metadata *zmd)
{
        DEFINE_WAIT(wait);

        prepare_to_wait(&zmd->free_wq, &wait, TASK_UNINTERRUPTIBLE);
        dmz_unlock_map(zmd);
        dmz_unlock_metadata(zmd);

        io_schedule_timeout(HZ);

        dmz_lock_metadata(zmd);
        dmz_lock_map(zmd);
        finish_wait(&zmd->free_wq, &wait);
}

/*
 * Lock a zone for reclaim (set the zone RECLAIM bit).
 * Returns false if the zone cannot be locked or if it is already locked
 * and 1 otherwise.
 */
int dmz_lock_zone_reclaim(struct dm_zone *zone)
{
        /* Active zones cannot be reclaimed */
        if (dmz_is_active(zone))
                return 0;

        return !test_and_set_bit(DMZ_RECLAIM, &zone->flags);
}

/*
 * Clear a zone reclaim flag.
 */
void dmz_unlock_zone_reclaim(struct dm_zone *zone)
{
        WARN_ON(dmz_is_active(zone));
        WARN_ON(!dmz_in_reclaim(zone));

        clear_bit_unlock(DMZ_RECLAIM, &zone->flags);
        smp_mb__after_atomic();
        wake_up_bit(&zone->flags, DMZ_RECLAIM);
}

/*
 * Wait for a zone reclaim to complete.
 */
static void dmz_wait_for_reclaim(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        dmz_unlock_map(zmd);
        dmz_unlock_metadata(zmd);
        set_bit(DMZ_RECLAIM_TERMINATE, &zone->flags);
        wait_on_bit_timeout(&zone->flags, DMZ_RECLAIM, TASK_UNINTERRUPTIBLE, HZ);
        clear_bit(DMZ_RECLAIM_TERMINATE, &zone->flags);
        dmz_lock_metadata(zmd);
        dmz_lock_map(zmd);
}

/*
 * Select a cache or random write zone for reclaim.
 */
static struct dm_zone *dmz_get_rnd_zone_for_reclaim(struct dmz_metadata *zmd,
                                                    unsigned int idx, bool idle)
{
        struct dm_zone *dzone = NULL;
        struct dm_zone *zone, *maxw_z = NULL;
        struct list_head *zone_list;

        /* If we have cache zones select from the cache zone list */
        if (zmd->nr_cache) {
                zone_list = &zmd->map_cache_list;
                /* Try to relaim random zones, too, when idle */
                if (idle && list_empty(zone_list))
                        zone_list = &zmd->dev[idx].map_rnd_list;
        } else
                zone_list = &zmd->dev[idx].map_rnd_list;

        /*
         * Find the buffer zone with the heaviest weight or the first (oldest)
         * data zone that can be reclaimed.
         */
        list_for_each_entry(zone, zone_list, link) {
                if (dmz_is_buf(zone)) {
                        dzone = zone->bzone;
                        if (dmz_is_rnd(dzone) && dzone->dev->dev_idx != idx)
                                continue;
                        if (!maxw_z || maxw_z->weight < dzone->weight)
                                maxw_z = dzone;
                } else {
                        dzone = zone;
                        if (dmz_lock_zone_reclaim(dzone))
                                return dzone;
                }
        }

        if (maxw_z && dmz_lock_zone_reclaim(maxw_z))
                return maxw_z;

        /*
         * If we come here, none of the zones inspected could be locked for
         * reclaim. Try again, being more aggressive, that is, find the
         * first zone that can be reclaimed regardless of its weitght.
         */
        list_for_each_entry(zone, zone_list, link) {
                if (dmz_is_buf(zone)) {
                        dzone = zone->bzone;

                        if (dmz_is_rnd(dzone) && dzone->dev->dev_idx != idx)
                                continue;
                } else
                        dzone = zone;
                if (dmz_lock_zone_reclaim(dzone))
                        return dzone;
        }

        return NULL;
}

/*
 * Select a buffered sequential zone for reclaim.
 */
static struct dm_zone *dmz_get_seq_zone_for_reclaim(struct dmz_metadata *zmd,
                                                    unsigned int idx)
{
        struct dm_zone *zone;

        list_for_each_entry(zone, &zmd->dev[idx].map_seq_list, link) {
                if (!zone->bzone)
                        continue;
                if (dmz_lock_zone_reclaim(zone))
                        return zone;
        }

        return NULL;
}

/*
 * Select a zone for reclaim.
 */
struct dm_zone *dmz_get_zone_for_reclaim(struct dmz_metadata *zmd,
                                         unsigned int dev_idx, bool idle)
{
        struct dm_zone *zone = NULL;

        /*
         * Search for a zone candidate to reclaim: 2 cases are possible.
         * (1) There is no free sequential zones. Then a random data zone
         *     cannot be reclaimed. So choose a sequential zone to reclaim so
         *     that afterward a random zone can be reclaimed.
         * (2) At least one free sequential zone is available, then choose
         *     the oldest random zone (data or buffer) that can be locked.
         */
        dmz_lock_map(zmd);
        if (list_empty(&zmd->reserved_seq_zones_list))
                zone = dmz_get_seq_zone_for_reclaim(zmd, dev_idx);
        if (!zone)
                zone = dmz_get_rnd_zone_for_reclaim(zmd, dev_idx, idle);
        dmz_unlock_map(zmd);

        return zone;
}

/*
 * Get the zone mapping a chunk, if the chunk is mapped already.
 * If no mapping exist and the operation is WRITE, a zone is
 * allocated and used to map the chunk.
 * The zone returned will be set to the active state.
 */
struct dm_zone *dmz_get_chunk_mapping(struct dmz_metadata *zmd, unsigned int chunk, int op)
{
        struct dmz_mblock *dmap_mblk = zmd->map_mblk[chunk >> DMZ_MAP_ENTRIES_SHIFT];
        struct dmz_map *dmap = (struct dmz_map *) dmap_mblk->data;
        int dmap_idx = chunk & DMZ_MAP_ENTRIES_MASK;
        unsigned int dzone_id;
        struct dm_zone *dzone = NULL;
        int ret = 0;
        int alloc_flags = zmd->nr_cache ? DMZ_ALLOC_CACHE : DMZ_ALLOC_RND;

        dmz_lock_map(zmd);
again:
        /* Get the chunk mapping */
        dzone_id = le32_to_cpu(dmap[dmap_idx].dzone_id);
        if (dzone_id == DMZ_MAP_UNMAPPED) {
                /*
                 * Read or discard in unmapped chunks are fine. But for
                 * writes, we need a mapping, so get one.
                 */
                if (op != REQ_OP_WRITE)
                        goto out;

                /* Allocate a random zone */
                dzone = dmz_alloc_zone(zmd, 0, alloc_flags);
                if (!dzone) {
                        if (dmz_dev_is_dying(zmd)) {
                                dzone = ERR_PTR(-EIO);
                                goto out;
                        }
                        dmz_wait_for_free_zones(zmd);
                        goto again;
                }

                dmz_map_zone(zmd, dzone, chunk);

        } else {
                /* The chunk is already mapped: get the mapping zone */
                dzone = dmz_get(zmd, dzone_id);
                if (!dzone) {
                        dzone = ERR_PTR(-EIO);
                        goto out;
                }
                if (dzone->chunk != chunk) {
                        dzone = ERR_PTR(-EIO);
                        goto out;
                }

                /* Repair write pointer if the sequential dzone has error */
                if (dmz_seq_write_err(dzone)) {
                        ret = dmz_handle_seq_write_err(zmd, dzone);
                        if (ret) {
                                dzone = ERR_PTR(-EIO);
                                goto out;
                        }
                        clear_bit(DMZ_SEQ_WRITE_ERR, &dzone->flags);
                }
        }

        /*
         * If the zone is being reclaimed, the chunk mapping may change
         * to a different zone. So wait for reclaim and retry. Otherwise,
         * activate the zone (this will prevent reclaim from touching it).
         */
        if (dmz_in_reclaim(dzone)) {
                dmz_wait_for_reclaim(zmd, dzone);
                goto again;
        }
        dmz_activate_zone(dzone);
        dmz_lru_zone(zmd, dzone);
out:
        dmz_unlock_map(zmd);

        return dzone;
}

/*
 * Write and discard change the block validity of data zones and their buffer
 * zones. Check here that valid blocks are still present. If all blocks are
 * invalid, the zones can be unmapped on the fly without waiting for reclaim
 * to do it.
 */
void dmz_put_chunk_mapping(struct dmz_metadata *zmd, struct dm_zone *dzone)
{
        struct dm_zone *bzone;

        dmz_lock_map(zmd);

        bzone = dzone->bzone;
        if (bzone) {
                if (dmz_weight(bzone))
                        dmz_lru_zone(zmd, bzone);
                else {
                        /* Empty buffer zone: reclaim it */
                        dmz_unmap_zone(zmd, bzone);
                        dmz_free_zone(zmd, bzone);
                        bzone = NULL;
                }
        }

        /* Deactivate the data zone */
        dmz_deactivate_zone(dzone);
        if (dmz_is_active(dzone) || bzone || dmz_weight(dzone))
                dmz_lru_zone(zmd, dzone);
        else {
                /* Unbuffered inactive empty data zone: reclaim it */
                dmz_unmap_zone(zmd, dzone);
                dmz_free_zone(zmd, dzone);
        }

        dmz_unlock_map(zmd);
}

/*
 * Allocate and map a random zone to buffer a chunk
 * already mapped to a sequential zone.
 */
struct dm_zone *dmz_get_chunk_buffer(struct dmz_metadata *zmd,
                                     struct dm_zone *dzone)
{
        struct dm_zone *bzone;
        int alloc_flags = zmd->nr_cache ? DMZ_ALLOC_CACHE : DMZ_ALLOC_RND;

        dmz_lock_map(zmd);
again:
        bzone = dzone->bzone;
        if (bzone)
                goto out;

        /* Allocate a random zone */
        bzone = dmz_alloc_zone(zmd, 0, alloc_flags);
        if (!bzone) {
                if (dmz_dev_is_dying(zmd)) {
                        bzone = ERR_PTR(-EIO);
                        goto out;
                }
                dmz_wait_for_free_zones(zmd);
                goto again;
        }

        /* Update the chunk mapping */
        dmz_set_chunk_mapping(zmd, dzone->chunk, dzone->id, bzone->id);

        set_bit(DMZ_BUF, &bzone->flags);
        bzone->chunk = dzone->chunk;
        bzone->bzone = dzone;
        dzone->bzone = bzone;
        if (dmz_is_cache(bzone))
                list_add_tail(&bzone->link, &zmd->map_cache_list);
        else
                list_add_tail(&bzone->link, &bzone->dev->map_rnd_list);
out:
        dmz_unlock_map(zmd);

        return bzone;
}

/*
 * Get an unmapped (free) zone.
 * This must be called with the mapping lock held.
 */
struct dm_zone *dmz_alloc_zone(struct dmz_metadata *zmd, unsigned int dev_idx,
                               unsigned long flags)
{
        struct list_head *list;
        struct dm_zone *zone;
        int i;

        /* Schedule reclaim to ensure free zones are available */
        if (!(flags & DMZ_ALLOC_RECLAIM)) {
                for (i = 0; i < zmd->nr_devs; i++)
                        dmz_schedule_reclaim(zmd->dev[i].reclaim);
        }

        i = 0;
again:
        if (flags & DMZ_ALLOC_CACHE)
                list = &zmd->unmap_cache_list;
        else if (flags & DMZ_ALLOC_RND)
                list = &zmd->dev[dev_idx].unmap_rnd_list;
        else
                list = &zmd->dev[dev_idx].unmap_seq_list;

        if (list_empty(list)) {
                /*
                 * No free zone: return NULL if this is for not reclaim.
                 */
                if (!(flags & DMZ_ALLOC_RECLAIM))
                        return NULL;
                /*
                 * Try to allocate from other devices
                 */
                if (i < zmd->nr_devs) {
                        dev_idx = (dev_idx + 1) % zmd->nr_devs;
                        i++;
                        goto again;
                }

                /*
                 * Fallback to the reserved sequential zones
                 */
                zone = list_first_entry_or_null(&zmd->reserved_seq_zones_list,
                                                struct dm_zone, link);
                if (zone) {
                        list_del_init(&zone->link);
                        atomic_dec(&zmd->nr_reserved_seq_zones);
                }
                return zone;
        }

        zone = list_first_entry(list, struct dm_zone, link);
        list_del_init(&zone->link);

        if (dmz_is_cache(zone))
                atomic_dec(&zmd->unmap_nr_cache);
        else if (dmz_is_rnd(zone))
                atomic_dec(&zone->dev->unmap_nr_rnd);
        else
                atomic_dec(&zone->dev->unmap_nr_seq);

        if (dmz_is_offline(zone)) {
                dmz_zmd_warn(zmd, "Zone %u is offline", zone->id);
                zone = NULL;
                goto again;
        }
        if (dmz_is_meta(zone)) {
                dmz_zmd_warn(zmd, "Zone %u has metadata", zone->id);
                zone = NULL;
                goto again;
        }
        return zone;
}

/*
 * Free a zone.
 * This must be called with the mapping lock held.
 */
void dmz_free_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        /* If this is a sequential zone, reset it */
        if (dmz_is_seq(zone))
                dmz_reset_zone(zmd, zone);

        /* Return the zone to its type unmap list */
        if (dmz_is_cache(zone)) {
                list_add_tail(&zone->link, &zmd->unmap_cache_list);
                atomic_inc(&zmd->unmap_nr_cache);
        } else if (dmz_is_rnd(zone)) {
                list_add_tail(&zone->link, &zone->dev->unmap_rnd_list);
                atomic_inc(&zone->dev->unmap_nr_rnd);
        } else if (dmz_is_reserved(zone)) {
                list_add_tail(&zone->link, &zmd->reserved_seq_zones_list);
                atomic_inc(&zmd->nr_reserved_seq_zones);
        } else {
                list_add_tail(&zone->link, &zone->dev->unmap_seq_list);
                atomic_inc(&zone->dev->unmap_nr_seq);
        }

        wake_up_all(&zmd->free_wq);
}

/*
 * Map a chunk to a zone.
 * This must be called with the mapping lock held.
 */
void dmz_map_zone(struct dmz_metadata *zmd, struct dm_zone *dzone,
                  unsigned int chunk)
{
        /* Set the chunk mapping */
        dmz_set_chunk_mapping(zmd, chunk, dzone->id,
                              DMZ_MAP_UNMAPPED);
        dzone->chunk = chunk;
        if (dmz_is_cache(dzone))
                list_add_tail(&dzone->link, &zmd->map_cache_list);
        else if (dmz_is_rnd(dzone))
                list_add_tail(&dzone->link, &dzone->dev->map_rnd_list);
        else
                list_add_tail(&dzone->link, &dzone->dev->map_seq_list);
}

/*
 * Unmap a zone.
 * This must be called with the mapping lock held.
 */
void dmz_unmap_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        unsigned int chunk = zone->chunk;
        unsigned int dzone_id;

        if (chunk == DMZ_MAP_UNMAPPED) {
                /* Already unmapped */
                return;
        }

        if (test_and_clear_bit(DMZ_BUF, &zone->flags)) {
                /*
                 * Unmapping the chunk buffer zone: clear only
                 * the chunk buffer mapping
                 */
                dzone_id = zone->bzone->id;
                zone->bzone->bzone = NULL;
                zone->bzone = NULL;

        } else {
                /*
                 * Unmapping the chunk data zone: the zone must
                 * not be buffered.
                 */
                if (WARN_ON(zone->bzone)) {
                        zone->bzone->bzone = NULL;
                        zone->bzone = NULL;
                }
                dzone_id = DMZ_MAP_UNMAPPED;
        }

        dmz_set_chunk_mapping(zmd, chunk, dzone_id, DMZ_MAP_UNMAPPED);

        zone->chunk = DMZ_MAP_UNMAPPED;
        list_del_init(&zone->link);
}

/*
 * Set @nr_bits bits in @bitmap starting from @bit.
 * Return the number of bits changed from 0 to 1.
 */
static unsigned int dmz_set_bits(unsigned long *bitmap,
                                 unsigned int bit, unsigned int nr_bits)
{
        unsigned long *addr;
        unsigned int end = bit + nr_bits;
        unsigned int n = 0;

        while (bit < end) {
                if (((bit & (BITS_PER_LONG - 1)) == 0) &&
                    ((end - bit) >= BITS_PER_LONG)) {
                        /* Try to set the whole word at once */
                        addr = bitmap + BIT_WORD(bit);
                        if (*addr == 0) {
                                *addr = ULONG_MAX;
                                n += BITS_PER_LONG;
                                bit += BITS_PER_LONG;
                                continue;
                        }
                }

                if (!test_and_set_bit(bit, bitmap))
                        n++;
                bit++;
        }

        return n;
}

/*
 * Get the bitmap block storing the bit for chunk_block in zone.
 */
static struct dmz_mblock *dmz_get_bitmap(struct dmz_metadata *zmd,
                                         struct dm_zone *zone,
                                         sector_t chunk_block)
{
        sector_t bitmap_block = 1 + zmd->nr_map_blocks +
                (sector_t)(zone->id * zmd->zone_nr_bitmap_blocks) +
                (chunk_block >> DMZ_BLOCK_SHIFT_BITS);

        return dmz_get_mblock(zmd, bitmap_block);
}

/*
 * Copy the valid blocks bitmap of from_zone to the bitmap of to_zone.
 */
int dmz_copy_valid_blocks(struct dmz_metadata *zmd, struct dm_zone *from_zone,
                          struct dm_zone *to_zone)
{
        struct dmz_mblock *from_mblk, *to_mblk;
        sector_t chunk_block = 0;

        /* Get the zones bitmap blocks */
        while (chunk_block < zmd->zone_nr_blocks) {
                from_mblk = dmz_get_bitmap(zmd, from_zone, chunk_block);
                if (IS_ERR(from_mblk))
                        return PTR_ERR(from_mblk);
                to_mblk = dmz_get_bitmap(zmd, to_zone, chunk_block);
                if (IS_ERR(to_mblk)) {
                        dmz_release_mblock(zmd, from_mblk);
                        return PTR_ERR(to_mblk);
                }

                memcpy(to_mblk->data, from_mblk->data, DMZ_BLOCK_SIZE);
                dmz_dirty_mblock(zmd, to_mblk);

                dmz_release_mblock(zmd, to_mblk);
                dmz_release_mblock(zmd, from_mblk);

                chunk_block += zmd->zone_bits_per_mblk;
        }

        to_zone->weight = from_zone->weight;

        return 0;
}

/*
 * Merge the valid blocks bitmap of from_zone into the bitmap of to_zone,
 * starting from chunk_block.
 */
int dmz_merge_valid_blocks(struct dmz_metadata *zmd, struct dm_zone *from_zone,
                           struct dm_zone *to_zone, sector_t chunk_block)
{
        unsigned int nr_blocks;
        int ret;

        /* Get the zones bitmap blocks */
        while (chunk_block < zmd->zone_nr_blocks) {
                /* Get a valid region from the source zone */
                ret = dmz_first_valid_block(zmd, from_zone, &chunk_block);
                if (ret <= 0)
                        return ret;

                nr_blocks = ret;
                ret = dmz_validate_blocks(zmd, to_zone, chunk_block, nr_blocks);
                if (ret)
                        return ret;

                chunk_block += nr_blocks;
        }

        return 0;
}

/*
 * Validate all the blocks in the range [block..block+nr_blocks-1].
 */
int dmz_validate_blocks(struct dmz_metadata *zmd, struct dm_zone *zone,
                        sector_t chunk_block, unsigned int nr_blocks)
{
        unsigned int count, bit, nr_bits;
        unsigned int zone_nr_blocks = zmd->zone_nr_blocks;
        struct dmz_mblock *mblk;
        unsigned int n = 0;

        dmz_zmd_debug(zmd, "=> VALIDATE zone %u, block %llu, %u blocks",
                      zone->id, (unsigned long long)chunk_block,
                      nr_blocks);

        WARN_ON(chunk_block + nr_blocks > zone_nr_blocks);

        while (nr_blocks) {
                /* Get bitmap block */
                mblk = dmz_get_bitmap(zmd, zone, chunk_block);
                if (IS_ERR(mblk))
                        return PTR_ERR(mblk);

                /* Set bits */
                bit = chunk_block & DMZ_BLOCK_MASK_BITS;
                nr_bits = min(nr_blocks, zmd->zone_bits_per_mblk - bit);

                count = dmz_set_bits((unsigned long *)mblk->data, bit, nr_bits);
                if (count) {
                        dmz_dirty_mblock(zmd, mblk);
                        n += count;
                }
                dmz_release_mblock(zmd, mblk);

                nr_blocks -= nr_bits;
                chunk_block += nr_bits;
        }

        if (likely(zone->weight + n <= zone_nr_blocks))
                zone->weight += n;
        else {
                dmz_zmd_warn(zmd, "Zone %u: weight %u should be <= %u",
                             zone->id, zone->weight,
                             zone_nr_blocks - n);
                zone->weight = zone_nr_blocks;
        }

        return 0;
}

/*
 * Clear nr_bits bits in bitmap starting from bit.
 * Return the number of bits cleared.
 */
static int dmz_clear_bits(unsigned long *bitmap, int bit, int nr_bits)
{
        unsigned long *addr;
        int end = bit + nr_bits;
        int n = 0;

        while (bit < end) {
                if (((bit & (BITS_PER_LONG - 1)) == 0) &&
                    ((end - bit) >= BITS_PER_LONG)) {
                        /* Try to clear whole word at once */
                        addr = bitmap + BIT_WORD(bit);
                        if (*addr == ULONG_MAX) {
                                *addr = 0;
                                n += BITS_PER_LONG;
                                bit += BITS_PER_LONG;
                                continue;
                        }
                }

                if (test_and_clear_bit(bit, bitmap))
                        n++;
                bit++;
        }

        return n;
}

/*
 * Invalidate all the blocks in the range [block..block+nr_blocks-1].
 */
int dmz_invalidate_blocks(struct dmz_metadata *zmd, struct dm_zone *zone,
                          sector_t chunk_block, unsigned int nr_blocks)
{
        unsigned int count, bit, nr_bits;
        struct dmz_mblock *mblk;
        unsigned int n = 0;

        dmz_zmd_debug(zmd, "=> INVALIDATE zone %u, block %llu, %u blocks",
                      zone->id, (u64)chunk_block, nr_blocks);

        WARN_ON(chunk_block + nr_blocks > zmd->zone_nr_blocks);

        while (nr_blocks) {
                /* Get bitmap block */
                mblk = dmz_get_bitmap(zmd, zone, chunk_block);
                if (IS_ERR(mblk))
                        return PTR_ERR(mblk);

                /* Clear bits */
                bit = chunk_block & DMZ_BLOCK_MASK_BITS;
                nr_bits = min(nr_blocks, zmd->zone_bits_per_mblk - bit);

                count = dmz_clear_bits((unsigned long *)mblk->data,
                                       bit, nr_bits);
                if (count) {
                        dmz_dirty_mblock(zmd, mblk);
                        n += count;
                }
                dmz_release_mblock(zmd, mblk);

                nr_blocks -= nr_bits;
                chunk_block += nr_bits;
        }

        if (zone->weight >= n)
                zone->weight -= n;
        else {
                dmz_zmd_warn(zmd, "Zone %u: weight %u should be >= %u",
                             zone->id, zone->weight, n);
                zone->weight = 0;
        }

        return 0;
}

/*
 * Get a block bit value.
 */
static int dmz_test_block(struct dmz_metadata *zmd, struct dm_zone *zone,
                          sector_t chunk_block)
{
        struct dmz_mblock *mblk;
        int ret;

        WARN_ON(chunk_block >= zmd->zone_nr_blocks);

        /* Get bitmap block */
        mblk = dmz_get_bitmap(zmd, zone, chunk_block);
        if (IS_ERR(mblk))
                return PTR_ERR(mblk);

        /* Get offset */
        ret = test_bit(chunk_block & DMZ_BLOCK_MASK_BITS,
                       (unsigned long *) mblk->data) != 0;

        dmz_release_mblock(zmd, mblk);

        return ret;
}

/*
 * Return the number of blocks from chunk_block to the first block with a bit
 * value specified by set. Search at most nr_blocks blocks from chunk_block.
 */
static int dmz_to_next_set_block(struct dmz_metadata *zmd, struct dm_zone *zone,
                                 sector_t chunk_block, unsigned int nr_blocks,
                                 int set)
{
        struct dmz_mblock *mblk;
        unsigned int bit, set_bit, nr_bits;
        unsigned int zone_bits = zmd->zone_bits_per_mblk;
        unsigned long *bitmap;
        int n = 0;

        WARN_ON(chunk_block + nr_blocks > zmd->zone_nr_blocks);

        while (nr_blocks) {
                /* Get bitmap block */
                mblk = dmz_get_bitmap(zmd, zone, chunk_block);
                if (IS_ERR(mblk))
                        return PTR_ERR(mblk);

                /* Get offset */
                bitmap = (unsigned long *) mblk->data;
                bit = chunk_block & DMZ_BLOCK_MASK_BITS;
                nr_bits = min(nr_blocks, zone_bits - bit);
                if (set)
                        set_bit = find_next_bit(bitmap, zone_bits, bit);
                else
                        set_bit = find_next_zero_bit(bitmap, zone_bits, bit);
                dmz_release_mblock(zmd, mblk);

                n += set_bit - bit;
                if (set_bit < zone_bits)
                        break;

                nr_blocks -= nr_bits;
                chunk_block += nr_bits;
        }

        return n;
}

/*
 * Test if chunk_block is valid. If it is, the number of consecutive
 * valid blocks from chunk_block will be returned.
 */
int dmz_block_valid(struct dmz_metadata *zmd, struct dm_zone *zone,
                    sector_t chunk_block)
{
        int valid;

        valid = dmz_test_block(zmd, zone, chunk_block);
        if (valid <= 0)
                return valid;

        /* The block is valid: get the number of valid blocks from block */
        return dmz_to_next_set_block(zmd, zone, chunk_block,
                                     zmd->zone_nr_blocks - chunk_block, 0);
}

/*
 * Find the first valid block from @chunk_block in @zone.
 * If such a block is found, its number is returned using
 * @chunk_block and the total number of valid blocks from @chunk_block
 * is returned.
 */
int dmz_first_valid_block(struct dmz_metadata *zmd, struct dm_zone *zone,
                          sector_t *chunk_block)
{
        sector_t start_block = *chunk_block;
        int ret;

        ret = dmz_to_next_set_block(zmd, zone, start_block,
                                    zmd->zone_nr_blocks - start_block, 1);
        if (ret < 0)
                return ret;

        start_block += ret;
        *chunk_block = start_block;

        return dmz_to_next_set_block(zmd, zone, start_block,
                                     zmd->zone_nr_blocks - start_block, 0);
}

/*
 * Count the number of bits set starting from bit up to bit + nr_bits - 1.
 */
static int dmz_count_bits(void *bitmap, int bit, int nr_bits)
{
        unsigned long *addr;
        int end = bit + nr_bits;
        int n = 0;

        while (bit < end) {
                if (((bit & (BITS_PER_LONG - 1)) == 0) &&
                    ((end - bit) >= BITS_PER_LONG)) {
                        addr = (unsigned long *)bitmap + BIT_WORD(bit);
                        if (*addr == ULONG_MAX) {
                                n += BITS_PER_LONG;
                                bit += BITS_PER_LONG;
                                continue;
                        }
                }

                if (test_bit(bit, bitmap))
                        n++;
                bit++;
        }

        return n;
}

/*
 * Get a zone weight.
 */
static void dmz_get_zone_weight(struct dmz_metadata *zmd, struct dm_zone *zone)
{
        struct dmz_mblock *mblk;
        sector_t chunk_block = 0;
        unsigned int bit, nr_bits;
        unsigned int nr_blocks = zmd->zone_nr_blocks;
        void *bitmap;
        int n = 0;

        while (nr_blocks) {
                /* Get bitmap block */
                mblk = dmz_get_bitmap(zmd, zone, chunk_block);
                if (IS_ERR(mblk)) {
                        n = 0;
                        break;
                }

                /* Count bits in this block */
                bitmap = mblk->data;
                bit = chunk_block & DMZ_BLOCK_MASK_BITS;
                nr_bits = min(nr_blocks, zmd->zone_bits_per_mblk - bit);
                n += dmz_count_bits(bitmap, bit, nr_bits);

                dmz_release_mblock(zmd, mblk);

                nr_blocks -= nr_bits;
                chunk_block += nr_bits;
        }

        zone->weight = n;
}

/*
 * Cleanup the zoned metadata resources.
 */
static void dmz_cleanup_metadata(struct dmz_metadata *zmd)
{
        struct rb_root *root;
        struct dmz_mblock *mblk, *next;
        int i;

        /* Release zone mapping resources */
        if (zmd->map_mblk) {
                for (i = 0; i < zmd->nr_map_blocks; i++)
                        dmz_release_mblock(zmd, zmd->map_mblk[i]);
                kfree(zmd->map_mblk);
                zmd->map_mblk = NULL;
        }

        /* Release super blocks */
        for (i = 0; i < 2; i++) {
                if (zmd->sb[i].mblk) {
                        dmz_free_mblock(zmd, zmd->sb[i].mblk);
                        zmd->sb[i].mblk = NULL;
                }
        }

        /* Free cached blocks */
        while (!list_empty(&zmd->mblk_dirty_list)) {
                mblk = list_first_entry(&zmd->mblk_dirty_list,
                                        struct dmz_mblock, link);
                dmz_zmd_warn(zmd, "mblock %llu still in dirty list (ref %u)",
                             (u64)mblk->no, mblk->ref);
                list_del_init(&mblk->link);
                rb_erase(&mblk->node, &zmd->mblk_rbtree);
                dmz_free_mblock(zmd, mblk);
        }

        while (!list_empty(&zmd->mblk_lru_list)) {
                mblk = list_first_entry(&zmd->mblk_lru_list,
                                        struct dmz_mblock, link);
                list_del_init(&mblk->link);
                rb_erase(&mblk->node, &zmd->mblk_rbtree);
                dmz_free_mblock(zmd, mblk);
        }

        /* Sanity checks: the mblock rbtree should now be empty */
        root = &zmd->mblk_rbtree;
        rbtree_postorder_for_each_entry_safe(mblk, next, root, node) {
                dmz_zmd_warn(zmd, "mblock %llu ref %u still in rbtree",
                             (u64)mblk->no, mblk->ref);
                mblk->ref = 0;
                dmz_free_mblock(zmd, mblk);
        }

        /* Free the zone descriptors */
        dmz_drop_zones(zmd);

        mutex_destroy(&zmd->mblk_flush_lock);
        mutex_destroy(&zmd->map_lock);
}

static void dmz_print_dev(struct dmz_metadata *zmd, int num)
{
        struct dmz_dev *dev = &zmd->dev[num];

        if (bdev_zoned_model(dev->bdev) == BLK_ZONED_NONE)
                dmz_dev_info(dev, "Regular block device");
        else
                dmz_dev_info(dev, "Host-%s zoned block device",
                             bdev_zoned_model(dev->bdev) == BLK_ZONED_HA ?
                             "aware" : "managed");
        if (zmd->sb_version > 1) {
                sector_t sector_offset =
                        dev->zone_offset << zmd->zone_nr_sectors_shift;

                dmz_dev_info(dev, "  %llu 512-byte logical sectors (offset %llu)",
                             (u64)dev->capacity, (u64)sector_offset);
                dmz_dev_info(dev, "  %u zones of %llu 512-byte logical sectors (offset %llu)",
                             dev->nr_zones, (u64)zmd->zone_nr_sectors,
                             (u64)dev->zone_offset);
        } else {
                dmz_dev_info(dev, "  %llu 512-byte logical sectors",
                             (u64)dev->capacity);
                dmz_dev_info(dev, "  %u zones of %llu 512-byte logical sectors",
                             dev->nr_zones, (u64)zmd->zone_nr_sectors);
        }
}

/*
 * Initialize the zoned metadata.
 */
int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
                     struct dmz_metadata **metadata,
                     const char *devname)
{
        struct dmz_metadata *zmd;
        unsigned int i;
        struct dm_zone *zone;
        int ret;

        zmd = kzalloc(sizeof(struct dmz_metadata), GFP_KERNEL);
        if (!zmd)
                return -ENOMEM;

        strcpy(zmd->devname, devname);
        zmd->dev = dev;
        zmd->nr_devs = num_dev;
        zmd->mblk_rbtree = RB_ROOT;
        init_rwsem(&zmd->mblk_sem);
        mutex_init(&zmd->mblk_flush_lock);
        spin_lock_init(&zmd->mblk_lock);
        INIT_LIST_HEAD(&zmd->mblk_lru_list);
        INIT_LIST_HEAD(&zmd->mblk_dirty_list);

        mutex_init(&zmd->map_lock);

        atomic_set(&zmd->unmap_nr_cache, 0);
        INIT_LIST_HEAD(&zmd->unmap_cache_list);
        INIT_LIST_HEAD(&zmd->map_cache_list);

        atomic_set(&zmd->nr_reserved_seq_zones, 0);
        INIT_LIST_HEAD(&zmd->reserved_seq_zones_list);

        init_waitqueue_head(&zmd->free_wq);

        /* Initialize zone descriptors */
        ret = dmz_init_zones(zmd);
        if (ret)
                goto err;

        /* Get super block */
        ret = dmz_load_sb(zmd);
        if (ret)
                goto err;

        /* Set metadata zones starting from sb_zone */
        for (i = 0; i < zmd->nr_meta_zones << 1; i++) {
                zone = dmz_get(zmd, zmd->sb[0].zone->id + i);
                if (!zone) {
                        dmz_zmd_err(zmd,
                                    "metadata zone %u not present", i);
                        ret = -ENXIO;
                        goto err;
                }
                if (!dmz_is_rnd(zone) && !dmz_is_cache(zone)) {
                        dmz_zmd_err(zmd,
                                    "metadata zone %d is not random", i);
                        ret = -ENXIO;
                        goto err;
                }
                set_bit(DMZ_META, &zone->flags);
        }
        /* Load mapping table */
        ret = dmz_load_mapping(zmd);
        if (ret)
                goto err;

        /*
         * Cache size boundaries: allow at least 2 super blocks, the chunk map
         * blocks and enough blocks to be able to cache the bitmap blocks of
         * up to 16 zones when idle (min_nr_mblks). Otherwise, if busy, allow
         * the cache to add 512 more metadata blocks.
         */
        zmd->min_nr_mblks = 2 + zmd->nr_map_blocks + zmd->zone_nr_bitmap_blocks * 16;
        zmd->max_nr_mblks = zmd->min_nr_mblks + 512;
        zmd->mblk_shrinker.count_objects = dmz_mblock_shrinker_count;
        zmd->mblk_shrinker.scan_objects = dmz_mblock_shrinker_scan;
        zmd->mblk_shrinker.seeks = DEFAULT_SEEKS;

        /* Metadata cache shrinker */
        ret = register_shrinker(&zmd->mblk_shrinker);
        if (ret) {
                dmz_zmd_err(zmd, "Register metadata cache shrinker failed");
                goto err;
        }

        dmz_zmd_info(zmd, "DM-Zoned metadata version %d", zmd->sb_version);
        for (i = 0; i < zmd->nr_devs; i++)
                dmz_print_dev(zmd, i);

        dmz_zmd_info(zmd, "  %u zones of %llu 512-byte logical sectors",
                     zmd->nr_zones, (u64)zmd->zone_nr_sectors);
        dmz_zmd_debug(zmd, "  %u metadata zones",
                      zmd->nr_meta_zones * 2);
        dmz_zmd_debug(zmd, "  %u data zones for %u chunks",
                      zmd->nr_data_zones, zmd->nr_chunks);
        dmz_zmd_debug(zmd, "    %u cache zones (%u unmapped)",
                      zmd->nr_cache, atomic_read(&zmd->unmap_nr_cache));
        for (i = 0; i < zmd->nr_devs; i++) {
                dmz_zmd_debug(zmd, "    %u random zones (%u unmapped)",
                              dmz_nr_rnd_zones(zmd, i),
                              dmz_nr_unmap_rnd_zones(zmd, i));
                dmz_zmd_debug(zmd, "    %u sequential zones (%u unmapped)",
                              dmz_nr_seq_zones(zmd, i),
                              dmz_nr_unmap_seq_zones(zmd, i));
        }
        dmz_zmd_debug(zmd, "  %u reserved sequential data zones",
                      zmd->nr_reserved_seq);
        dmz_zmd_debug(zmd, "Format:");
        dmz_zmd_debug(zmd, "%u metadata blocks per set (%u max cache)",
                      zmd->nr_meta_blocks, zmd->max_nr_mblks);
        dmz_zmd_debug(zmd, "  %u data zone mapping blocks",
                      zmd->nr_map_blocks);
        dmz_zmd_debug(zmd, "  %u bitmap blocks",
                      zmd->nr_bitmap_blocks);

        *metadata = zmd;

        return 0;
err: