// SPDX-License-Identifier: GPL-2.0

#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/sched/mm.h>
#include "ctree.h"
#include "volumes.h"
#include "zoned.h"
#include "rcu-string.h"
#include "disk-io.h"
#include "block-group.h"
#include "transaction.h"
#include "dev-replace.h"
#include "space-info.h"

/* Maximum number of zones to report per blkdev_report_zones() call */
#define BTRFS_REPORT_NR_ZONES   4096
/* Invalid allocation pointer value for missing devices */
#define WP_MISSING_DEV ((u64)-1)
/* Pseudo write pointer value for conventional zone */
#define WP_CONVENTIONAL ((u64)-2)

/*
 * Location of the first zone of superblock logging zone pairs.
 *
 * - primary superblock:    0B (zone 0)
 * - first copy:          512G (zone starting at that offset)
 * - second copy:           4T (zone starting at that offset)
 */
#define BTRFS_SB_LOG_PRIMARY_OFFSET     (0ULL)
#define BTRFS_SB_LOG_FIRST_OFFSET       (512ULL * SZ_1G)
#define BTRFS_SB_LOG_SECOND_OFFSET      (4096ULL * SZ_1G)

#define BTRFS_SB_LOG_FIRST_SHIFT        const_ilog2(BTRFS_SB_LOG_FIRST_OFFSET)
#define BTRFS_SB_LOG_SECOND_SHIFT       const_ilog2(BTRFS_SB_LOG_SECOND_OFFSET)

/* Number of superblock log zones */
#define BTRFS_NR_SB_LOG_ZONES 2

/*
 * Maximum supported zone size. Currently, SMR disks have a zone size of
 * 256MiB, and we are expecting ZNS drives to be in the 1-4GiB range. We do not
 * expect the zone size to become larger than 8GiB in the near future.
 */
#define BTRFS_MAX_ZONE_SIZE             SZ_8G

static int copy_zone_info_cb(struct blk_zone *zone, unsigned int idx, void *data)
{
        struct blk_zone *zones = data;

        memcpy(&zones[idx], zone, sizeof(*zone));

        return 0;
}

static int sb_write_pointer(struct block_device *bdev, struct blk_zone *zones,
                            u64 *wp_ret)
{
        bool empty[BTRFS_NR_SB_LOG_ZONES];
        bool full[BTRFS_NR_SB_LOG_ZONES];
        sector_t sector;

        ASSERT(zones[0].type != BLK_ZONE_TYPE_CONVENTIONAL &&
               zones[1].type != BLK_ZONE_TYPE_CONVENTIONAL);

        empty[0] = (zones[0].cond == BLK_ZONE_COND_EMPTY);
        empty[1] = (zones[1].cond == BLK_ZONE_COND_EMPTY);
        full[0] = (zones[0].cond == BLK_ZONE_COND_FULL);
        full[1] = (zones[1].cond == BLK_ZONE_COND_FULL);

        /*
         * Possible states of log buffer zones
         *
         *           Empty[0]  In use[0]  Full[0]
         * Empty[1]         *          x        0
         * In use[1]        0          x        0
         * Full[1]          1          1        C
         *
         * Log position:
         *   *: Special case, no superblock is written
         *   0: Use write pointer of zones[0]
         *   1: Use write pointer of zones[1]
         *   C: Compare super blocks from zones[0] and zones[1], use the latest
         *      one determined by generation
         *   x: Invalid state
         */

        if (empty[0] && empty[1]) {
                /* Special case to distinguish no superblock to read */
                *wp_ret = zones[0].start << SECTOR_SHIFT;
                return -ENOENT;
        } else if (full[0] && full[1]) {
                /* Compare two super blocks */
                struct address_space *mapping = bdev->bd_inode->i_mapping;
                struct page *page[BTRFS_NR_SB_LOG_ZONES];
                struct btrfs_super_block *super[BTRFS_NR_SB_LOG_ZONES];
                int i;

                for (i = 0; i < BTRFS_NR_SB_LOG_ZONES; i++) {
                        u64 bytenr;

                        bytenr = ((zones[i].start + zones[i].len)
                                   << SECTOR_SHIFT) - BTRFS_SUPER_INFO_SIZE;

                        page[i] = read_cache_page_gfp(mapping,
                                        bytenr >> PAGE_SHIFT, GFP_NOFS);
                        if (IS_ERR(page[i])) {
                                if (i == 1)
                                        btrfs_release_disk_super(super[0]);
                                return PTR_ERR(page[i]);
                        }
                        super[i] = page_address(page[i]);
                }

                if (super[0]->generation > super[1]->generation)
                        sector = zones[1].start;
                else
                        sector = zones[0].start;

                for (i = 0; i < BTRFS_NR_SB_LOG_ZONES; i++)
                        btrfs_release_disk_super(super[i]);
        } else if (!full[0] && (empty[1] || full[1])) {
                sector = zones[0].wp;
        } else if (full[0]) {
                sector = zones[1].wp;
        } else {
                return -EUCLEAN;
        }
        *wp_ret = sector << SECTOR_SHIFT;
        return 0;
}

/*
 * Get the first zone number of the superblock mirror
 */
static inline u32 sb_zone_number(int shift, int mirror)
{
        u64 zone;

        ASSERT(mirror < BTRFS_SUPER_MIRROR_MAX);
        switch (mirror) {
        case 0: zone = 0; break;
        case 1: zone = 1ULL << (BTRFS_SB_LOG_FIRST_SHIFT - shift); break;
        case 2: zone = 1ULL << (BTRFS_SB_LOG_SECOND_SHIFT - shift); break;
        }

        ASSERT(zone <= U32_MAX);

        return (u32)zone;
}

static inline sector_t zone_start_sector(u32 zone_number,
                                         struct block_device *bdev)
{
        return (sector_t)zone_number << ilog2(bdev_zone_sectors(bdev));
}

static inline u64 zone_start_physical(u32 zone_number,
                                      struct btrfs_zoned_device_info *zone_info)
{
        return (u64)zone_number << zone_info->zone_size_shift;
}

/*
 * Emulate blkdev_report_zones() for a non-zoned device. It slices up the block
 * device into static sized chunks and fake a conventional zone on each of
 * them.
 */
static int emulate_report_zones(struct btrfs_device *device, u64 pos,
                                struct blk_zone *zones, unsigned int nr_zones)
{
        const sector_t zone_sectors = device->fs_info->zone_size >> SECTOR_SHIFT;
        sector_t bdev_size = bdev_nr_sectors(device->bdev);
        unsigned int i;

        pos >>= SECTOR_SHIFT;
        for (i = 0; i < nr_zones; i++) {
                zones[i].start = i * zone_sectors + pos;
                zones[i].len = zone_sectors;
                zones[i].capacity = zone_sectors;
                zones[i].wp = zones[i].start + zone_sectors;
                zones[i].type = BLK_ZONE_TYPE_CONVENTIONAL;
                zones[i].cond = BLK_ZONE_COND_NOT_WP;

                if (zones[i].wp >= bdev_size) {
                        i++;
                        break;
                }
        }

        return i;
}

static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
                               struct blk_zone *zones, unsigned int *nr_zones)
{
        int ret;

        if (!*nr_zones)
                return 0;

        if (!bdev_is_zoned(device->bdev)) {
                ret = emulate_report_zones(device, pos, zones, *nr_zones);
                *nr_zones = ret;
                return 0;
        }

        ret = blkdev_report_zones(device->bdev, pos >> SECTOR_SHIFT, *nr_zones,
                                  copy_zone_info_cb, zones);
        if (ret < 0) {
                btrfs_err_in_rcu(device->fs_info,
                                 "zoned: failed to read zone %llu on %s (devid %llu)",
                                 pos, rcu_str_deref(device->name),
                                 device->devid);
                return ret;
        }
        *nr_zones = ret;
        if (!ret)
                return -EIO;

        return 0;
}

/* The emulated zone size is determined from the size of device extent */
static int calculate_emulated_zone_size(struct btrfs_fs_info *fs_info)
{
        struct btrfs_path *path;
        struct btrfs_root *root = fs_info->dev_root;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct btrfs_dev_extent *dext;
        int ret = 0;

        key.objectid = 1;
        key.type = BTRFS_DEV_EXTENT_KEY;
        key.offset = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto out;

        if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
                ret = btrfs_next_leaf(root, path);
                if (ret < 0)
                        goto out;
                /* No dev extents at all? Not good */
                if (ret > 0) {
                        ret = -EUCLEAN;
                        goto out;
                }
        }

        leaf = path->nodes[0];
        dext = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_extent);
        fs_info->zone_size = btrfs_dev_extent_length(leaf, dext);
        ret = 0;

out:
        btrfs_free_path(path);

        return ret;
}

int btrfs_get_dev_zone_info_all_devices(struct btrfs_fs_info *fs_info)
{
        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
        struct btrfs_device *device;
        int ret = 0;

        /* fs_info->zone_size might not set yet. Use the incomapt flag here. */
        if (!btrfs_fs_incompat(fs_info, ZONED))
                return 0;

        mutex_lock(&fs_devices->device_list_mutex);
        list_for_each_entry(device, &fs_devices->devices, dev_list) {
                /* We can skip reading of zone info for missing devices */
                if (!device->bdev)
                        continue;

                ret = btrfs_get_dev_zone_info(device);
                if (ret)
                        break;
        }
        mutex_unlock(&fs_devices->device_list_mutex);

        return ret;
}

int btrfs_get_dev_zone_info(struct btrfs_device *device)
{
        struct btrfs_fs_info *fs_info = device->fs_info;
        struct btrfs_zoned_device_info *zone_info = NULL;
        struct block_device *bdev = device->bdev;
        sector_t nr_sectors;
        sector_t sector = 0;
        struct blk_zone *zones = NULL;
        unsigned int i, nreported = 0, nr_zones;
        sector_t zone_sectors;
        char *model, *emulated;
        int ret;

        /*
         * Cannot use btrfs_is_zoned here, since fs_info::zone_size might not
         * yet be set.
         */
        if (!btrfs_fs_incompat(fs_info, ZONED))
                return 0;

        if (device->zone_info)
                return 0;

        zone_info = kzalloc(sizeof(*zone_info), GFP_KERNEL);
        if (!zone_info)
                return -ENOMEM;

        if (!bdev_is_zoned(bdev)) {
                if (!fs_info->zone_size) {
                        ret = calculate_emulated_zone_size(fs_info);
                        if (ret)
                                goto out;
                }

                ASSERT(fs_info->zone_size);
                zone_sectors = fs_info->zone_size >> SECTOR_SHIFT;
        } else {
                zone_sectors = bdev_zone_sectors(bdev);
        }

        /* Check if it's power of 2 (see is_power_of_2) */
        ASSERT(zone_sectors != 0 && (zone_sectors & (zone_sectors - 1)) == 0);
        zone_info->zone_size = zone_sectors << SECTOR_SHIFT;

        /* We reject devices with a zone size larger than 8GB */
        if (zone_info->zone_size > BTRFS_MAX_ZONE_SIZE) {
                btrfs_err_in_rcu(fs_info,
                "zoned: %s: zone size %llu larger than supported maximum %llu",
                                 rcu_str_deref(device->name),
                                 zone_info->zone_size, BTRFS_MAX_ZONE_SIZE);
                ret = -EINVAL;
                goto out;
        }

        nr_sectors = bdev_nr_sectors(bdev);
        zone_info->zone_size_shift = ilog2(zone_info->zone_size);
        zone_info->nr_zones = nr_sectors >> ilog2(zone_sectors);
        if (!IS_ALIGNED(nr_sectors, zone_sectors))
                zone_info->nr_zones++;

        zone_info->seq_zones = bitmap_zalloc(zone_info->nr_zones, GFP_KERNEL);
        if (!zone_info->seq_zones) {
                ret = -ENOMEM;
                goto out;
        }

        zone_info->empty_zones = bitmap_zalloc(zone_info->nr_zones, GFP_KERNEL);
        if (!zone_info->empty_zones) {
                ret = -ENOMEM;
                goto out;
        }

        zones = kcalloc(BTRFS_REPORT_NR_ZONES, sizeof(struct blk_zone), GFP_KERNEL);
        if (!zones) {
                ret = -ENOMEM;
                goto out;
        }

        /* Get zones type */
        while (sector < nr_sectors) {
                nr_zones = BTRFS_REPORT_NR_ZONES;
                ret = btrfs_get_dev_zones(device, sector << SECTOR_SHIFT, zones,
                                          &nr_zones);
                if (ret)
                        goto out;

                for (i = 0; i < nr_zones; i++) {
                        if (zones[i].type == BLK_ZONE_TYPE_SEQWRITE_REQ)
                                __set_bit(nreported, zone_info->seq_zones);
                        if (zones[i].cond == BLK_ZONE_COND_EMPTY)
                                __set_bit(nreported, zone_info->empty_zones);
                        nreported++;
                }
                sector = zones[nr_zones - 1].start + zones[nr_zones - 1].len;
        }

        if (nreported != zone_info->nr_zones) {
                btrfs_err_in_rcu(device->fs_info,
                                 "inconsistent number of zones on %s (%u/%u)",
                                 rcu_str_deref(device->name), nreported,
                                 zone_info->nr_zones);
                ret = -EIO;
                goto out;
        }

        /* Validate superblock log */
        nr_zones = BTRFS_NR_SB_LOG_ZONES;
        for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
                u32 sb_zone;
                u64 sb_wp;
                int sb_pos = BTRFS_NR_SB_LOG_ZONES * i;

                sb_zone = sb_zone_number(zone_info->zone_size_shift, i);
                if (sb_zone + 1 >= zone_info->nr_zones)
                        continue;

                ret = btrfs_get_dev_zones(device,
                                          zone_start_physical(sb_zone, zone_info),
                                          &zone_info->sb_zones[sb_pos],
                                          &nr_zones);
                if (ret)
                        goto out;

                if (nr_zones != BTRFS_NR_SB_LOG_ZONES) {
                        btrfs_err_in_rcu(device->fs_info,
        "zoned: failed to read super block log zone info at devid %llu zone %u",
                                         device->devid, sb_zone);
                        ret = -EUCLEAN;
                        goto out;
                }

                /*
                 * If zones[0] is conventional, always use the beginning of the
                 * zone to record superblock. No need to validate in that case.
                 */
                if (zone_info->sb_zones[BTRFS_NR_SB_LOG_ZONES * i].type ==
                    BLK_ZONE_TYPE_CONVENTIONAL)
                        continue;

                ret = sb_write_pointer(device->bdev,
                                       &zone_info->sb_zones[sb_pos], &sb_wp);
                if (ret != -ENOENT && ret) {
                        btrfs_err_in_rcu(device->fs_info,
                        "zoned: super block log zone corrupted devid %llu zone %u",
                                         device->devid, sb_zone);
                        ret = -EUCLEAN;
                        goto out;
                }
        }


        kfree(zones);

        device->zone_info = zone_info;

        switch (bdev_zoned_model(bdev)) {
        case BLK_ZONED_HM:
                model = "host-managed zoned";
                emulated = "";
                break;
        case BLK_ZONED_HA:
                model = "host-aware zoned";
                emulated = "";
                break;
        case BLK_ZONED_NONE:
                model = "regular";
                emulated = "emulated ";
                break;
        default:
                /* Just in case */
                btrfs_err_in_rcu(fs_info, "zoned: unsupported model %d on %s",
                                 bdev_zoned_model(bdev),
                                 rcu_str_deref(device->name));
                ret = -EOPNOTSUPP;
                goto out_free_zone_info;
        }

        btrfs_info_in_rcu(fs_info,
                "%s block device %s, %u %szones of %llu bytes",
                model, rcu_str_deref(device->name), zone_info->nr_zones,
                emulated, zone_info->zone_size);

        return 0;

out:
        kfree(zones);
out_free_zone_info:
        bitmap_free(zone_info->empty_zones);
        bitmap_free(zone_info->seq_zones);
        kfree(zone_info);
        device->zone_info = NULL;

        return ret;
}

void btrfs_destroy_dev_zone_info(struct btrfs_device *device)
{
        struct btrfs_zoned_device_info *zone_info = device->zone_info;

        if (!zone_info)
                return;

        bitmap_free(zone_info->seq_zones);
        bitmap_free(zone_info->empty_zones);
        kfree(zone_info);
        device->zone_info = NULL;
}

int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
                       struct blk_zone *zone)
{
        unsigned int nr_zones = 1;
        int ret;

        ret = btrfs_get_dev_zones(device, pos, zone, &nr_zones);
        if (ret != 0 || !nr_zones)
                return ret ? ret : -EIO;

        return 0;
}

int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info)
{
        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
        struct btrfs_device *device;
        u64 zoned_devices = 0;
        u64 nr_devices = 0;
        u64 zone_size = 0;
        const bool incompat_zoned = btrfs_fs_incompat(fs_info, ZONED);
        int ret = 0;

        /* Count zoned devices */
        list_for_each_entry(device, &fs_devices->devices, dev_list) {
                enum blk_zoned_model model;

                if (!device->bdev)
                        continue;

                model = bdev_zoned_model(device->bdev);
                /*
                 * A Host-Managed zoned device must be used as a zoned device.
                 * A Host-Aware zoned device and a non-zoned devices can be
                 * treated as a zoned device, if ZONED flag is enabled in the
                 * superblock.
                 */
                if (model == BLK_ZONED_HM ||
                    (model == BLK_ZONED_HA && incompat_zoned) ||
                    (model == BLK_ZONED_NONE && incompat_zoned)) {
                        struct btrfs_zoned_device_info *zone_info =
                                device->zone_info;

                        zone_info = device->zone_info;
                        zoned_devices++;
                        if (!zone_size) {
                                zone_size = zone_info->zone_size;
                        } else if (zone_info->zone_size != zone_size) {
                                btrfs_err(fs_info,
                "zoned: unequal block device zone sizes: have %llu found %llu",
                                          device->zone_info->zone_size,
                                          zone_size);
                                ret = -EINVAL;
                                goto out;
                        }
                }
                nr_devices++;
        }

        if (!zoned_devices && !incompat_zoned)
                goto out;

        if (!zoned_devices && incompat_zoned) {
                /* No zoned block device found on ZONED filesystem */
                btrfs_err(fs_info,
                          "zoned: no zoned devices found on a zoned filesystem");
                ret = -EINVAL;
                goto out;
        }

        if (zoned_devices && !incompat_zoned) {
                btrfs_err(fs_info,
                          "zoned: mode not enabled but zoned device found");
                ret = -EINVAL;
                goto out;
        }

        if (zoned_devices != nr_devices) {
                btrfs_err(fs_info,
                          "zoned: cannot mix zoned and regular devices");
                ret = -EINVAL;
                goto out;
        }

        /*
         * stripe_size is always aligned to BTRFS_STRIPE_LEN in
         * __btrfs_alloc_chunk(). Since we want stripe_len == zone_size,
         * check the alignment here.
         */
        if (!IS_ALIGNED(zone_size, BTRFS_STRIPE_LEN)) {
                btrfs_err(fs_info,
                          "zoned: zone size %llu not aligned to stripe %u",
                          zone_size, BTRFS_STRIPE_LEN);
                ret = -EINVAL;
                goto out;
        }

        if (btrfs_fs_incompat(fs_info, MIXED_GROUPS)) {
                btrfs_err(fs_info, "zoned: mixed block groups not supported");
                ret = -EINVAL;
                goto out;
        }

        fs_info->zone_size = zone_size;
        fs_info->fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_ZONED;

        /*
         * Check mount options here, because we might change fs_info->zoned
         * from fs_info->zone_size.
         */
        ret = btrfs_check_mountopts_zoned(fs_info);
        if (ret)
                goto out;

        btrfs_info(fs_info, "zoned mode enabled with zone size %llu", zone_size);
out:
        return ret;
}

int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
{
        if (!btrfs_is_zoned(info))
                return 0;

        /*
         * Space cache writing is not COWed. Disable that to avoid write errors
         * in sequential zones.
         */
        if (btrfs_test_opt(info, SPACE_CACHE)) {
                btrfs_err(info, "zoned: space cache v1 is not supported");
                return -EINVAL;
        }

        if (btrfs_test_opt(info, NODATACOW)) {
                btrfs_err(info, "zoned: NODATACOW not supported");
                return -EINVAL;
        }

        return 0;
}

static int sb_log_location(struct block_device *bdev, struct blk_zone *zones,
                           int rw, u64 *bytenr_ret)
{
        u64 wp;
        int ret;

        if (zones[0].type == BLK_ZONE_TYPE_CONVENTIONAL) {
                *bytenr_ret = zones[0].start << SECTOR_SHIFT;
                return 0;
        }

        ret = sb_write_pointer(bdev, zones, &wp);
        if (ret != -ENOENT && ret < 0)
                return ret;

        if (rw == WRITE) {
                struct blk_zone *reset = NULL;

                if (wp == zones[0].start << SECTOR_SHIFT)
                        reset = &zones[0];
                else if (wp == zones[1].start << SECTOR_SHIFT)
                        reset = &zones[1];

                if (reset && reset->cond != BLK_ZONE_COND_EMPTY) {
                        ASSERT(reset->cond == BLK_ZONE_COND_FULL);

                        ret = blkdev_zone_mgmt(bdev, REQ_OP_ZONE_RESET,
                                               reset->start, reset->len,
                                               GFP_NOFS);
                        if (ret)
                                return ret;

                        reset->cond = BLK_ZONE_COND_EMPTY;
                        reset->wp = reset->start;
                }
        } else if (ret != -ENOENT) {
                /* For READ, we want the precious one */
                if (wp == zones[0].start << SECTOR_SHIFT)
                        wp = (zones[1].start + zones[1].len) << SECTOR_SHIFT;
                wp -= BTRFS_SUPER_INFO_SIZE;
        }

        *bytenr_ret = wp;
        return 0;

}

int btrfs_sb_log_location_bdev(struct block_device *bdev, int mirror, int rw,
                               u64 *bytenr_ret)
{
        struct blk_zone zones[BTRFS_NR_SB_LOG_ZONES];
        sector_t zone_sectors;
        u32 sb_zone;
        int ret;
        u8 zone_sectors_shift;
        sector_t nr_sectors;
        u32 nr_zones;

        if (!bdev_is_zoned(bdev)) {
                *bytenr_ret = btrfs_sb_offset(mirror);
                return 0;
        }

        ASSERT(rw == READ || rw == WRITE);

        zone_sectors = bdev_zone_sectors(bdev);
        if (!is_power_of_2(zone_sectors))
                return -EINVAL;
        zone_sectors_shift = ilog2(zone_sectors);
        nr_sectors = bdev_nr_sectors(bdev);
        nr_zones = nr_sectors >> zone_sectors_shift;

        sb_zone = sb_zone_number(zone_sectors_shift + SECTOR_SHIFT, mirror);
        if (sb_zone + 1 >= nr_zones)
                return -ENOENT;

        ret = blkdev_report_zones(bdev, zone_start_sector(sb_zone, bdev),
                                  BTRFS_NR_SB_LOG_ZONES, copy_zone_info_cb,
                                  zones);
        if (ret < 0)
                return ret;
        if (ret != BTRFS_NR_SB_LOG_ZONES)
                return -EIO;

        return sb_log_location(bdev, zones, rw, bytenr_ret);
}

int btrfs_sb_log_location(struct btrfs_device *device, int mirror, int rw,
                          u64 *bytenr_ret)
{
        struct btrfs_zoned_device_info *zinfo = device->zone_info;
        u32 zone_num;

        /*
         * For a zoned filesystem on a non-zoned block device, use the same
         * super block locations as regular filesystem. Doing so, the super
         * block can always be retrieved and the zoned flag of the volume
         * detected from the super block information.
         */
        if (!bdev_is_zoned(device->bdev)) {
                *bytenr_ret = btrfs_sb_offset(mirror);
                return 0;
        }

        zone_num = sb_zone_number(zinfo->zone_size_shift, mirror);
        if (zone_num + 1 >= zinfo->nr_zones)
                return -ENOENT;

        return sb_log_location(device->bdev,
                               &zinfo->sb_zones[BTRFS_NR_SB_LOG_ZONES * mirror],
                               rw, bytenr_ret);
}

static inline bool is_sb_log_zone(struct btrfs_zoned_device_info *zinfo,
                                  int mirror)
{
        u32 zone_num;

        if (!zinfo)
                return false;

        zone_num = sb_zone_number(zinfo->zone_size_shift, mirror);
        if (zone_num + 1 >= zinfo->nr_zones)
                return false;

        if (!test_bit(zone_num, zinfo->seq_zones))
                return false;

        return true;
}

void btrfs_advance_sb_log(struct btrfs_device *device, int mirror)
{
        struct btrfs_zoned_device_info *zinfo = device->zone_info;
        struct blk_zone *zone;

        if (!is_sb_log_zone(zinfo, mirror))
                return;

        zone = &zinfo->sb_zones[BTRFS_NR_SB_LOG_ZONES * mirror];
        if (zone->cond != BLK_ZONE_COND_FULL) {
                if (zone->cond == BLK_ZONE_COND_EMPTY)
                        zone->cond = BLK_ZONE_COND_IMP_OPEN;

                zone->wp += (BTRFS_SUPER_INFO_SIZE >> SECTOR_SHIFT);

                if (zone->wp == zone->start + zone->len)
                        zone->cond = BLK_ZONE_COND_FULL;

                return;
        }

        zone++;
        ASSERT(zone->cond != BLK_ZONE_COND_FULL);
        if (zone->cond == BLK_ZONE_COND_EMPTY)
                zone->cond = BLK_ZONE_COND_IMP_OPEN;

        zone->wp += (BTRFS_SUPER_INFO_SIZE >> SECTOR_SHIFT);

        if (zone->wp == zone->start + zone->len)
                zone->cond = BLK_ZONE_COND_FULL;
}

int btrfs_reset_sb_log_zones(struct block_device *bdev, int mirror)
{
        sector_t zone_sectors;
        sector_t nr_sectors;
        u8 zone_sectors_shift;
        u32 sb_zone;
        u32 nr_zones;

        zone_sectors = bdev_zone_sectors(bdev);
        zone_sectors_shift = ilog2(zone_sectors);
        nr_sectors = bdev_nr_sectors(bdev);
        nr_zones = nr_sectors >> zone_sectors_shift;

        sb_zone = sb_zone_number(zone_sectors_shift + SECTOR_SHIFT, mirror);
        if (sb_zone + 1 >= nr_zones)
                return -ENOENT;

        return blkdev_zone_mgmt(bdev, REQ_OP_ZONE_RESET,
                                zone_start_sector(sb_zone, bdev),
                                zone_sectors * BTRFS_NR_SB_LOG_ZONES, GFP_NOFS);
}

/**
 * btrfs_find_allocatable_zones - find allocatable zones within a given region
 *
 * @device:     the device to allocate a region on
 * @hole_start: the position of the hole to allocate the region
 * @num_bytes:  size of wanted region
 * @hole_end:   the end of the hole
 * @return:     position of allocatable zones
 *
 * Allocatable region should not contain any superblock locations.
 */
u64 btrfs_find_allocatable_zones(struct btrfs_device *device, u64 hole_start,
                                 u64 hole_end, u64 num_bytes)
{
        struct btrfs_zoned_device_info *zinfo = device->zone_info;
        const u8 shift = zinfo->zone_size_shift;
        u64 nzones = num_bytes >> shift;
        u64 pos = hole_start;
        u64 begin, end;
        bool have_sb;
        int i;

        ASSERT(IS_ALIGNED(hole_start, zinfo->zone_size));
        ASSERT(IS_ALIGNED(num_bytes, zinfo->zone_size));

        while (pos < hole_end) {
                begin = pos >> shift;
                end = begin + nzones;

                if (end > zinfo->nr_zones)
                        return hole_end;

                /* Check if zones in the region are all empty */
                if (btrfs_dev_is_sequential(device, pos) &&
                    find_next_zero_bit(zinfo->empty_zones, end, begin) != end) {
                        pos += zinfo->zone_size;
                        continue;
                }

                have_sb = false;
                for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
                        u32 sb_zone;
                        u64 sb_pos;

                        sb_zone = sb_zone_number(shift, i);
                        if (!(end <= sb_zone ||
                              sb_zone + BTRFS_NR_SB_LOG_ZONES <= begin)) {
                                have_sb = true;
                                pos = zone_start_physical(
                                        sb_zone + BTRFS_NR_SB_LOG_ZONES, zinfo);
                                break;
                        }

                        /* We also need to exclude regular superblock positions */
                        sb_pos = btrfs_sb_offset(i);
                        if (!(pos + num_bytes <= sb_pos ||
                              sb_pos + BTRFS_SUPER_INFO_SIZE <= pos)) {
                                have_sb = true;
                                pos = ALIGN(sb_pos + BTRFS_SUPER_INFO_SIZE,
                                            zinfo->zone_size);
                                break;
                        }
                }
                if (!have_sb)
                        break;
        }

        return pos;
}

int btrfs_reset_device_zone(struct btrfs_device *device, u64 physical,
                            u64 length, u64 *bytes)
{
        int ret;

        *bytes = 0;
        ret = blkdev_zone_mgmt(device->bdev, REQ_OP_ZONE_RESET,
                               physical >> SECTOR_SHIFT, length >> SECTOR_SHIFT,
                               GFP_NOFS);
        if (ret)
                return ret;

        *bytes = length;
        while (length) {
                btrfs_dev_set_zone_empty(device, physical);
                physical += device->zone_info->zone_size;
                length -= device->zone_info->zone_size;
        }

        return 0;
}

int btrfs_ensure_empty_zones(struct btrfs_device *device, u64 start, u64 size)
{
        struct btrfs_zoned_device_info *zinfo = device->zone_info;
        const u8 shift = zinfo->zone_size_shift;
        unsigned long begin = start >> shift;
        unsigned long end = (start + size) >> shift;
        u64 pos;
        int ret;

        ASSERT(IS_ALIGNED(start, zinfo->zone_size));
        ASSERT(IS_ALIGNED(size, zinfo->zone_size));

        if (end > zinfo->nr_zones)
                return -ERANGE;

        /* All the zones are conventional */
        if (find_next_bit(zinfo->seq_zones, begin, end) == end)
                return 0;

        /* All the zones are sequential and empty */
        if (find_next_zero_bit(zinfo->seq_zones, begin, end) == end &&
            find_next_zero_bit(zinfo->empty_zones, begin, end) == end)
                return 0;

        for (pos = start; pos < start + size; pos += zinfo->zone_size) {
                u64 reset_bytes;

                if (!btrfs_dev_is_sequential(device, pos) ||
                    btrfs_dev_is_empty_zone(device, pos))
                        continue;

                /* Free regions should be empty */
                btrfs_warn_in_rcu(
                        device->fs_info,
                "zoned: resetting device %s (devid %llu) zone %llu for allocation",
                        rcu_str_deref(device->name), device->devid, pos >> shift);
                WARN_ON_ONCE(1);

                ret = btrfs_reset_device_zone(device, pos, zinfo->zone_size,
                                              &reset_bytes);
                if (ret)
                        return ret;
        }

        return 0;
}

/*
 * Calculate an allocation pointer from the extent allocation information
 * for a block group consist of conventional zones. It is pointed to the
 * end of the highest addressed extent in the block group as an allocation
 * offset.
 */
static int calculate_alloc_pointer(struct btrfs_block_group *cache,
                                   u64 *offset_ret)
{
        struct btrfs_fs_info *fs_info = cache->fs_info;
        struct btrfs_root *root = fs_info->extent_root;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct btrfs_key found_key;
        int ret;
        u64 length;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        key.objectid = cache->start + cache->length;
        key.type = 0;
        key.offset = 0;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        /* We should not find the exact match */
        if (!ret)
                ret = -EUCLEAN;
        if (ret < 0)
                goto out;

        ret = btrfs_previous_extent_item(root, path, cache->start);
        if (ret) {

                if (ret == 1) {
                        ret = 0;
                        *offset_ret = 0;
                }
                goto out;
        }

        btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);

        if (found_key.type == BTRFS_EXTENT_ITEM_KEY)
                length = found_key.offset;
        else
                length = fs_info->nodesize;

        if (!(found_key.objectid >= cache->start &&
               found_key.objectid + length <= cache->start + cache->length)) {
                ret = -EUCLEAN;
                goto out;
        }
        *offset_ret = found_key.objectid + length - cache->start;
        ret = 0;

out:
        btrfs_free_path(path);
        return ret;
}

int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache, bool new)
{
        struct btrfs_fs_info *fs_info = cache->fs_info;
        struct extent_map_tree *em_tree = &fs_info->mapping_tree;
        struct extent_map *em;
        struct map_lookup *map;
        struct btrfs_device *device;
        u64 logical = cache->start;
        u64 length = cache->length;
        u64 physical = 0;
        int ret;
        int i;
        unsigned int nofs_flag;
        u64 *alloc_offsets = NULL;
        u64 last_alloc = 0;
        u32 num_sequential = 0, num_conventional = 0;

        if (!btrfs_is_zoned(fs_info))
                return 0;

        /* Sanity check */
        if (!IS_ALIGNED(length, fs_info->zone_size)) {
                btrfs_err(fs_info,
                "zoned: block group %llu len %llu unaligned to zone size %llu",
                          logical, length, fs_info->zone_size);
                return -EIO;
        }

        /* Get the chunk mapping */
        read_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, logical, length);
        read_unlock(&em_tree->lock);

        if (!em)
                return -EINVAL;

        map = em->map_lookup;

        alloc_offsets = kcalloc(map->num_stripes, sizeof(*alloc_offsets), GFP_NOFS);
        if (!alloc_offsets) {
                free_extent_map(em);
                return -ENOMEM;
        }

        for (i = 0; i < map->num_stripes; i++) {
                bool is_sequential;
                struct blk_zone zone;
                struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
                int dev_replace_is_ongoing = 0;

                device = map->stripes[i].dev;
                physical = map->stripes[i].physical;

                if (device->bdev == NULL) {
                        alloc_offsets[i] = WP_MISSING_DEV;
                        continue;
                }

                is_sequential = btrfs_dev_is_sequential(device, physical);
                if (is_sequential)
                        num_sequential++;
                else
                        num_conventional++;

                if (!is_sequential) {
                        alloc_offsets[i] = WP_CONVENTIONAL;
                        continue;
                }

                /*
                 * This zone will be used for allocation, so mark this zone
                 * non-empty.
                 */
                btrfs_dev_clear_zone_empty(device, physical);

                down_read(&dev_replace->rwsem);
                dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace);
                if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL)
                        btrfs_dev_clear_zone_empty(dev_replace->tgtdev, physical);
                up_read(&dev_replace->rwsem);

                /*
                 * The group is mapped to a sequential zone. Get the zone write
                 * pointer to determine the allocation offset within the zone.
                 */
                WARN_ON(!IS_ALIGNED(physical, fs_info->zone_size));
                nofs_flag = memalloc_nofs_save();
                ret = btrfs_get_dev_zone(device, physical, &zone);
                memalloc_nofs_restore(nofs_flag);
                if (ret == -EIO || ret == -EOPNOTSUPP) {
                        ret = 0;
                        alloc_offsets[i] = WP_MISSING_DEV;
                        continue;
                } else if (ret) {
                        goto out;
                }

                if (zone.type == BLK_ZONE_TYPE_CONVENTIONAL) {
                        btrfs_err_in_rcu(fs_info,
        "zoned: unexpected conventional zone %llu on device %s (devid %llu)",
                                zone.start << SECTOR_SHIFT,
                                rcu_str_deref(device->name), device->devid);
                        ret = -EIO;
                        goto out;
                }

                switch (zone.cond) {
                case BLK_ZONE_COND_OFFLINE:
                case BLK_ZONE_COND_READONLY:
                        btrfs_err(fs_info,
                "zoned: offline/readonly zone %llu on device %s (devid %llu)",
                                  physical >> device->zone_info->zone_size_shift,
                                  rcu_str_deref(device->name), device->devid);
                        alloc_offsets[i] = WP_MISSING_DEV;
                        break;
                case BLK_ZONE_COND_EMPTY:
                        alloc_offsets[i] = 0;
                        break;
                case BLK_ZONE_COND_FULL:
                        alloc_offsets[i] = fs_info->zone_size;
                        break;
                default:
                        /* Partially used zone */
                        alloc_offsets[i] =
                                        ((zone.wp - zone.start) << SECTOR_SHIFT);
                        break;
                }
        }

        if (num_sequential > 0)
                cache->seq_zone = true;

        if (num_conventional > 0) {
                /*
                 * Avoid calling calculate_alloc_pointer() for new BG. It
                 * is no use for new BG. It must be always 0.
                 *
                 * Also, we have a lock chain of extent buffer lock ->
                 * chunk mutex.  For new BG, this function is called from
                 * btrfs_make_block_group() which is already taking the
                 * chunk mutex. Thus, we cannot call
                 * calculate_alloc_pointer() which takes extent buffer
                 * locks to avoid deadlock.
                 */
                if (new) {
                        cache->alloc_offset = 0;
                        goto out;
                }
                ret = calculate_alloc_pointer(cache, &last_alloc);
                if (ret || map->num_stripes == num_conventional) {
                        if (!ret)
                                cache->alloc_offset = last_alloc;
                        else
                                btrfs_err(fs_info,
                        "zoned: failed to determine allocation offset of bg %llu",
                                          cache->start);
                        goto out;
                }
        }

        switch (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
        case 0: /* single */
                if (alloc_offsets[0] == WP_MISSING_DEV) {
                        btrfs_err(fs_info,
                        "zoned: cannot recover write pointer for zone %llu",
                                physical);
                        ret = -EIO;
                        goto out;
                }
                cache->alloc_offset = alloc_offsets[0];
                break;
        case BTRFS_BLOCK_GROUP_DUP:
        case BTRFS_BLOCK_GROUP_RAID1:
        case BTRFS_BLOCK_GROUP_RAID0:
        case BTRFS_BLOCK_GROUP_RAID10:
        case BTRFS_BLOCK_GROUP_RAID5:
        case BTRFS_BLOCK_GROUP_RAID6:
                /* non-single profiles are not supported yet */
        default:
                btrfs_err(fs_info, "zoned: profile %s not yet supported",
                          btrfs_bg_type_to_raid_name(map->type));
                ret = -EINVAL;
                goto out;
        }

out:
        if (cache->alloc_offset > fs_info->zone_size) {
                btrfs_err(fs_info,
                        "zoned: invalid write pointer %llu in block group %llu",
                        cache->alloc_offset, cache->start);
                ret = -EIO;
        }

        /* An extent is allocated after the write pointer */
        if (!ret && num_conventional && last_alloc > cache->alloc_offset) {
                btrfs_err(fs_info,
                          "zoned: got wrong write pointer in BG %llu: %llu > %llu",
                          logical, last_alloc, cache->alloc_offset);
                ret = -EIO;
        }

        if (!ret)
                cache->meta_write_pointer = cache->alloc_offset + cache->start;

        kfree(alloc_offsets);
        free_extent_map(em);

        return ret;
}

void btrfs_calc_zone_unusable(struct btrfs_block_group *cache)
{
        u64 unusable, free;

        if (!btrfs_is_zoned(cache->fs_info))
                return;

        WARN_ON(cache->bytes_super != 0);
        unusable = cache->alloc_offset - cache->used;
        free = cache->length - cache->alloc_offset;

        /* We only need ->free_space in ALLOC_SEQ block groups */
        cache->last_byte_to_unpin = (u64)-1;
        cache->cached = BTRFS_CACHE_FINISHED;
        cache->free_space_ctl->free_space = free;
        cache->zone_unusable = unusable;

        /* Should not have any excluded extents. Just in case, though */
        btrfs_free_excluded_extents(cache);
}

void btrfs_redirty_list_add(struct btrfs_transaction *trans,
                            struct extent_buffer *eb)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;

        if (!btrfs_is_zoned(fs_info) ||
            btrfs_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN) ||
            !list_empty(&eb->release_list))
                return;

        set_extent_buffer_dirty(eb);
        set_extent_bits_nowait(&trans->dirty_pages, eb->start,
                               eb->start + eb->len - 1, EXTENT_DIRTY);
        memzero_extent_buffer(eb, 0, eb->len);
        set_bit(EXTENT_BUFFER_NO_CHECK, &eb->bflags);

        spin_lock(&trans->releasing_ebs_lock);
        list_add_tail(&eb->release_list, &trans->releasing_ebs);
        spin_unlock(&trans->releasing_ebs_lock);
        atomic_inc(&eb->refs);
}

void btrfs_free_redirty_list(struct btrfs_transaction *trans)
{
        spin_lock(&trans->releasing_ebs_lock);
        while (!list_empty(&trans->releasing_ebs)) {
                struct extent_buffer *eb;

                eb = list_first_entry(&trans->releasing_ebs,
                                      struct extent_buffer, release_list);
                list_del_init(&eb->release_list);
                free_extent_buffer(eb);
        }
        spin_unlock(&trans->releasing_ebs_lock);
}

bool btrfs_use_zone_append(struct btrfs_inode *inode, u64 start)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct btrfs_block_group *cache;
        bool ret = false;

        if (!btrfs_is_zoned(fs_info))
                return false;

        if (!is_data_inode(&inode->vfs_inode))
                return false;

        cache = btrfs_lookup_block_group(fs_info, start);
        ASSERT(cache);
        if (!cache)
                return false;

        ret = cache->seq_zone;
        btrfs_put_block_group(cache);

        return ret;
}

void btrfs_record_physical_zoned(struct inode *inode, u64 file_offset,
                                 struct bio *bio)
{
        struct btrfs_ordered_extent *ordered;
        const u64 physical = bio->bi_iter.bi_sector << SECTOR_SHIFT;

        if (bio_op(bio) != REQ_OP_ZONE_APPEND)
                return;

        ordered = btrfs_lookup_ordered_extent(BTRFS_I(inode), file_offset);
        if (WARN_ON(!ordered))
                return;

        ordered->physical = physical;
        ordered->bdev = bio->bi_bdev;

        btrfs_put_ordered_extent(ordered);
}

void btrfs_rewrite_logical_zoned(struct btrfs_ordered_extent *ordered)
{
        struct btrfs_inode *inode = BTRFS_I(ordered->inode);
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct extent_map_tree *em_tree;
        struct extent_map *em;
        struct btrfs_ordered_sum *sum;
        u64 orig_logical = ordered->disk_bytenr;
        u64 *logical = NULL;
        int nr, stripe_len;

        /* Zoned devices should not have partitions. So, we can assume it is 0 */
        ASSERT(!bdev_is_partition(ordered->bdev));
        if (WARN_ON(!ordered->bdev))
                return;

        if (WARN_ON(btrfs_rmap_block(fs_info, orig_logical, ordered->bdev,
                                     ordered->physical, &logical, &nr,
                                     &stripe_len)))
                goto out;

        WARN_ON(nr != 1);

        if (orig_logical == *logical)
                goto out;

        ordered->disk_bytenr = *logical;

        em_tree = &inode->extent_tree;
        write_lock(&em_tree->lock);
        em = search_extent_mapping(em_tree, ordered->file_offset,
                                   ordered->num_bytes);
        em->block_start = *logical;
        free_extent_map(em);
        write_unlock(&em_tree->lock);

        list_for_each_entry(sum, &ordered->list, list) {
                if (*logical < orig_logical)
                        sum->bytenr -= orig_logical - *logical;
                else
                        sum->bytenr += *logical - orig_logical;
        }

out:
        kfree(logical);
}

bool btrfs_check_meta_write_pointer(struct btrfs_fs_info *fs_info,
                                    struct extent_buffer *eb,
                                    struct btrfs_block_group **cache_ret)
{
        struct btrfs_block_group *cache;
        bool ret = true;

        if (!btrfs_is_zoned(fs_info))
                return true;

        cache = *cache_ret;

        if (cache && (eb->start < cache->start ||
                      cache->start + cache->length <= eb->start)) {
                btrfs_put_block_group(cache);
                cache = NULL;
                *cache_ret = NULL;
        }

        if (!cache)
                cache = btrfs_lookup_block_group(fs_info, eb->start);

        if (cache) {
                if (cache->meta_write_pointer != eb->start) {
                        btrfs_put_block_group(cache);
                        cache = NULL;
                        ret = false;
                } else {
                        cache->meta_write_pointer = eb->start + eb->len;
                }

                *cache_ret = cache;
        }

        return ret;
}

void btrfs_revert_meta_write_pointer(struct btrfs_block_group *cache,
                                     struct extent_buffer *eb)
{
        if (!btrfs_is_zoned(eb->fs_info) || !cache)
                return;

        ASSERT(cache->meta_write_pointer == eb->start + eb->len);
        cache->meta_write_pointer = eb->start;
}

int btrfs_zoned_issue_zeroout(struct btrfs_device *device, u64 physical, u64 length)
{
        if (!btrfs_dev_is_sequential(device, physical))
                return -EOPNOTSUPP;

        return blkdev_issue_zeroout(device->bdev, physical >> SECTOR_SHIFT,
                                    length >> SECTOR_SHIFT, GFP_NOFS, 0);
}

static int read_zone_info(struct btrfs_fs_info *fs_info, u64 logical,
                          struct blk_zone *zone)
{
        struct btrfs_bio *bbio = NULL;
        u64 mapped_length = PAGE_SIZE;
        unsigned int nofs_flag;
        int nmirrors;
        int i, ret;

        ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS, logical,
                               &mapped_length, &bbio);
        if (ret || !bbio || mapped_length < PAGE_SIZE) {
                btrfs_put_bbio(bbio);
                return -EIO;
        }

        if (bbio->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK)
                return -EINVAL;

        nofs_flag = memalloc_nofs_save();
        nmirrors = (int)bbio->num_stripes;
        for (i = 0; i < nmirrors; i++) {
                u64 physical = bbio->stripes[i].physical;
                struct btrfs_device *dev = bbio->stripes[i].dev;

                /* Missing device */
                if (!dev->bdev)
                        continue;

                ret = btrfs_get_dev_zone(dev, physical, zone);
                /* Failing device */
                if (ret == -EIO || ret == -EOPNOTSUPP)
                        continue;
                break;
        }
        memalloc_nofs_restore(nofs_flag);

        return ret;
}

/*
 * Synchronize write pointer in a zone at @physical_start on @tgt_dev, by
 * filling zeros between @physical_pos to a write pointer of dev-replace
 * source device.
 */
int btrfs_sync_zone_write_pointer(struct btrfs_device *tgt_dev, u64 logical,
                                    u64 physical_start, u64 physical_pos)
{
        struct btrfs_fs_info *fs_info = tgt_dev->fs_info;
        struct blk_zone zone;
        u64 length;
        u64 wp;
        int ret;

        if (!btrfs_dev_is_sequential(tgt_dev, physical_pos))
                return 0;

        ret = read_zone_info(fs_info, logical, &zone);
        if (ret)
                return ret;

        wp = physical_start + ((zone.wp - zone.start) << SECTOR_SHIFT);

        if (physical_pos == wp)
                return 0;

        if (physical_pos > wp)
                return -EUCLEAN;

        length = wp - physical_pos;
        return btrfs_zoned_issue_zeroout(tgt_dev, physical_pos, length);
}

struct btrfs_device *btrfs_zoned_get_device(struct btrfs_fs_info *fs_info,
                                            u64 logical, u64 length)
{
        struct btrfs_device *device;
        struct extent_map *em;
        struct map_lookup *map;

        em = btrfs_get_chunk_map(fs_info, logical, length);
        if (IS_ERR(em))
                return ERR_CAST(em);

        map = em->map_lookup;
        /* We only support single profile for now */
        ASSERT(map->num_stripes == 1);
        device = map->stripes[0].dev;

        free_extent_map(em);

        return device;
}