dm-raid.c

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/*
 * Copyright (C) 2010-2011 Neil Brown
 * Copyright (C) 2010-2011 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include <linux/slab.h>
#include <linux/module.h>

#include "md.h"
#include "raid1.h"
#include "raid5.h"
#include "raid10.h"
#include "bitmap.h"

#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "raid"

/*
 * The following flags are used by dm-raid.c to set up the array state.
 * They must be cleared before md_run is called.
 */
#define FirstUse 10             /* rdev flag */

struct raid_dev {
    /*
     * Two DM devices, one to hold metadata and one to hold the
     * actual data/parity.  The reason for this is to not confuse
     * ti->len and give more flexibility in altering size and
     * characteristics.
     *
     * While it is possible for this device to be associated
     * with a different physical device than the data_dev, it
     * is intended for it to be the same.
     *    |--------- Physical Device ---------|
     *    |- meta_dev -|------ data_dev ------|
     */
    struct dm_dev *meta_dev;
    struct dm_dev *data_dev;
    struct md_rdev rdev;
};

/*
 * Flags for rs->print_flags field.
 */
#define DMPF_SYNC              0x1
#define DMPF_NOSYNC            0x2
#define DMPF_REBUILD           0x4
#define DMPF_DAEMON_SLEEP      0x8
#define DMPF_MIN_RECOVERY_RATE 0x10
#define DMPF_MAX_RECOVERY_RATE 0x20
#define DMPF_MAX_WRITE_BEHIND  0x40
#define DMPF_STRIPE_CACHE      0x80
#define DMPF_REGION_SIZE       0x100
#define DMPF_RAID10_COPIES     0x200
#define DMPF_RAID10_FORMAT     0x400

struct raid_set {
    struct dm_target *ti;

    uint32_t bitmap_loaded;
    uint32_t print_flags;

    struct mddev md;
    struct raid_type *raid_type;
    struct dm_target_callbacks callbacks;

    struct raid_dev dev[0];
};

/* Supported raid types and properties. */
static struct raid_type {
    const char *name;       /* RAID algorithm. */
    const char *descr;      /* Descriptor text for logging. */
    const unsigned parity_devs; /* # of parity devices. */
    const unsigned minimal_devs;    /* minimal # of devices in set. */
    const unsigned level;       /* RAID level. */
    const unsigned algorithm;   /* RAID algorithm. */
} raid_types[] = {
    {"raid1",    "RAID1 (mirroring)",               0, 2, 1, 0 /* NONE */},
    {"raid10",   "RAID10 (striped mirrors)",        0, 2, 10, UINT_MAX /* Varies */},
    {"raid4",    "RAID4 (dedicated parity disk)",   1, 2, 5, ALGORITHM_PARITY_0},
    {"raid5_la", "RAID5 (left asymmetric)",     1, 2, 5, ALGORITHM_LEFT_ASYMMETRIC},
    {"raid5_ra", "RAID5 (right asymmetric)",    1, 2, 5, ALGORITHM_RIGHT_ASYMMETRIC},
    {"raid5_ls", "RAID5 (left symmetric)",      1, 2, 5, ALGORITHM_LEFT_SYMMETRIC},
    {"raid5_rs", "RAID5 (right symmetric)",     1, 2, 5, ALGORITHM_RIGHT_SYMMETRIC},
    {"raid6_zr", "RAID6 (zero restart)",        2, 4, 6, ALGORITHM_ROTATING_ZERO_RESTART},
    {"raid6_nr", "RAID6 (N restart)",       2, 4, 6, ALGORITHM_ROTATING_N_RESTART},
    {"raid6_nc", "RAID6 (N continue)",      2, 4, 6, ALGORITHM_ROTATING_N_CONTINUE}
};

static unsigned raid10_md_layout_to_copies(int layout)
{
    return layout & 0xFF;
}

static int raid10_format_to_md_layout(char *format, unsigned copies)
{
    /* 1 "far" copy, and 'copies' "near" copies */
    return (1 << 8) | (copies & 0xFF);
}

static struct raid_type *get_raid_type(char *name)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(raid_types); i++)
        if (!strcmp(raid_types[i].name, name))
            return &raid_types[i];

    return NULL;
}

static struct raid_set *context_alloc(struct dm_target *ti, struct raid_type *raid_type, unsigned raid_devs)
{
    unsigned i;
    struct raid_set *rs;

    if (raid_devs <= raid_type->parity_devs) {
        ti->error = "Insufficient number of devices";
        return ERR_PTR(-EINVAL);
    }

    rs = kzalloc(sizeof(*rs) + raid_devs * sizeof(rs->dev[0]), GFP_KERNEL);
    if (!rs) {
        ti->error = "Cannot allocate raid context";
        return ERR_PTR(-ENOMEM);
    }

    mddev_init(&rs->md);

    rs->ti = ti;
    rs->raid_type = raid_type;
    rs->md.raid_disks = raid_devs;
    rs->md.level = raid_type->level;
    rs->md.new_level = rs->md.level;
    rs->md.layout = raid_type->algorithm;
    rs->md.new_layout = rs->md.layout;
    rs->md.delta_disks = 0;
    rs->md.recovery_cp = 0;

    for (i = 0; i < raid_devs; i++)
        md_rdev_init(&rs->dev[i].rdev);

    /*
     * Remaining items to be initialized by further RAID params:
     *  rs->md.persistent
     *  rs->md.external
     *  rs->md.chunk_sectors
     *  rs->md.new_chunk_sectors
     *  rs->md.dev_sectors
     */

    return rs;
}

static void context_free(struct raid_set *rs)
{
    int i;

    for (i = 0; i < rs->md.raid_disks; i++) {
        if (rs->dev[i].meta_dev)
            dm_put_device(rs->ti, rs->dev[i].meta_dev);
        md_rdev_clear(&rs->dev[i].rdev);
        if (rs->dev[i].data_dev)
            dm_put_device(rs->ti, rs->dev[i].data_dev);
    }

    kfree(rs);
}

/*
 * For every device we have two words
 *  <meta_dev>: meta device name or '-' if missing
 *  <data_dev>: data device name or '-' if missing
 *
 * The following are permitted:
 *    - -
 *    - <data_dev>
 *    <meta_dev> <data_dev>
 *
 * The following is not allowed:
 *    <meta_dev> -
 *
 * This code parses those words.  If there is a failure,
 * the caller must use context_free to unwind the operations.
 */
static int dev_parms(struct raid_set *rs, char **argv)
{
    int i;
    int rebuild = 0;
    int metadata_available = 0;
    int ret = 0;

    for (i = 0; i < rs->md.raid_disks; i++, argv += 2) {
        rs->dev[i].rdev.raid_disk = i;

        rs->dev[i].meta_dev = NULL;
        rs->dev[i].data_dev = NULL;

        /*
         * There are no offsets, since there is a separate device
         * for data and metadata.
         */
        rs->dev[i].rdev.data_offset = 0;
        rs->dev[i].rdev.mddev = &rs->md;

        if (strcmp(argv[0], "-")) {
            ret = dm_get_device(rs->ti, argv[0],
                        dm_table_get_mode(rs->ti->table),
                        &rs->dev[i].meta_dev);
            rs->ti->error = "RAID metadata device lookup failure";
            if (ret)
                return ret;

            rs->dev[i].rdev.sb_page = alloc_page(GFP_KERNEL);
            if (!rs->dev[i].rdev.sb_page)
                return -ENOMEM;
        }

        if (!strcmp(argv[1], "-")) {
            if (!test_bit(In_sync, &rs->dev[i].rdev.flags) &&
                (!rs->dev[i].rdev.recovery_offset)) {
                rs->ti->error = "Drive designated for rebuild not specified";
                return -EINVAL;
            }

            rs->ti->error = "No data device supplied with metadata device";
            if (rs->dev[i].meta_dev)
                return -EINVAL;

            continue;
        }

        ret = dm_get_device(rs->ti, argv[1],
                    dm_table_get_mode(rs->ti->table),
                    &rs->dev[i].data_dev);
        if (ret) {
            rs->ti->error = "RAID device lookup failure";
            return ret;
        }

        if (rs->dev[i].meta_dev) {
            metadata_available = 1;
            rs->dev[i].rdev.meta_bdev = rs->dev[i].meta_dev->bdev;
        }
        rs->dev[i].rdev.bdev = rs->dev[i].data_dev->bdev;
        list_add(&rs->dev[i].rdev.same_set, &rs->md.disks);
        if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
            rebuild++;
    }

    if (metadata_available) {
        rs->md.external = 0;
        rs->md.persistent = 1;
        rs->md.major_version = 2;
    } else if (rebuild && !rs->md.recovery_cp) {
        /*
         * Without metadata, we will not be able to tell if the array
         * is in-sync or not - we must assume it is not.  Therefore,
         * it is impossible to rebuild a drive.
         *
         * Even if there is metadata, the on-disk information may
         * indicate that the array is not in-sync and it will then
         * fail at that time.
         *
         * User could specify 'nosync' option if desperate.
         */
        DMERR("Unable to rebuild drive while array is not in-sync");
        rs->ti->error = "RAID device lookup failure";
        return -EINVAL;
    }

    return 0;
}

/*
 * validate_region_size
 * @rs
 * @region_size:  region size in sectors.  If 0, pick a size (4MiB default).
 *
 * Set rs->md.bitmap_info.chunksize (which really refers to 'region size').
 * Ensure that (ti->len/region_size < 2^21) - required by MD bitmap.
 *
 * Returns: 0 on success, -EINVAL on failure.
 */
static int validate_region_size(struct raid_set *rs, unsigned long region_size)
{
    unsigned long min_region_size = rs->ti->len / (1 << 21);

    if (!region_size) {
        /*
         * Choose a reasonable default.  All figures in sectors.
         */
        if (min_region_size > (1 << 13)) {
            DMINFO("Choosing default region size of %lu sectors",
                   region_size);
            region_size = min_region_size;
        } else {
            DMINFO("Choosing default region size of 4MiB");
            region_size = 1 << 13; /* sectors */
        }
    } else {
        /*
         * Validate user-supplied value.
         */
        if (region_size > rs->ti->len) {
            rs->ti->error = "Supplied region size is too large";
            return -EINVAL;
        }

        if (region_size < min_region_size) {
            DMERR("Supplied region_size (%lu sectors) below minimum (%lu)",
                  region_size, min_region_size);
            rs->ti->error = "Supplied region size is too small";
            return -EINVAL;
        }

        if (!is_power_of_2(region_size)) {
            rs->ti->error = "Region size is not a power of 2";
            return -EINVAL;
        }

        if (region_size < rs->md.chunk_sectors) {
            rs->ti->error = "Region size is smaller than the chunk size";
            return -EINVAL;
        }
    }

    /*
     * Convert sectors to bytes.
     */
    rs->md.bitmap_info.chunksize = (region_size << 9);

    return 0;
}

/*
 * validate_rebuild_devices
 * @rs
 *
 * Determine if the devices specified for rebuild can result in a valid
 * usable array that is capable of rebuilding the given devices.
 *
 * Returns: 0 on success, -EINVAL on failure.
 */
static int validate_rebuild_devices(struct raid_set *rs)
{
    unsigned i, rebuild_cnt = 0;
    unsigned rebuilds_per_group, copies, d;

    if (!(rs->print_flags & DMPF_REBUILD))
        return 0;

    for (i = 0; i < rs->md.raid_disks; i++)
        if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
            rebuild_cnt++;

    switch (rs->raid_type->level) {
    case 1:
        if (rebuild_cnt >= rs->md.raid_disks)
            goto too_many;
        break;
    case 4:
    case 5:
    case 6:
        if (rebuild_cnt > rs->raid_type->parity_devs)
            goto too_many;
        break;
    case 10:
        copies = raid10_md_layout_to_copies(rs->md.layout);
        if (rebuild_cnt < copies)
            break;

        /*
         * It is possible to have a higher rebuild count for RAID10,
         * as long as the failed devices occur in different mirror
         * groups (i.e. different stripes).
         *
         * Right now, we only allow for "near" copies.  When other
         * formats are added, we will have to check those too.
         *
         * When checking "near" format, make sure no adjacent devices
         * have failed beyond what can be handled.  In addition to the
         * simple case where the number of devices is a multiple of the
         * number of copies, we must also handle cases where the number
         * of devices is not a multiple of the number of copies.
         * E.g.    dev1 dev2 dev3 dev4 dev5
         *          A    A    B    B    C
         *          C    D    D    E    E
         */
        rebuilds_per_group = 0;
        for (i = 0; i < rs->md.raid_disks * copies; i++) {
            d = i % rs->md.raid_disks;
            if (!test_bit(In_sync, &rs->dev[d].rdev.flags) &&
                (++rebuilds_per_group >= copies))
                goto too_many;
            if (!((i + 1) % copies))
                rebuilds_per_group = 0;
        }
        break;
    default:
        DMERR("The rebuild parameter is not supported for %s",
              rs->raid_type->name);
        rs->ti->error = "Rebuild not supported for this RAID type";
        return -EINVAL;
    }

    return 0;

too_many:
    rs->ti->error = "Too many rebuild devices specified";
    return -EINVAL;
}

/*
 * Possible arguments are...
 *  <chunk_size> [optional_args]
 *
 * Argument definitions
 *    <chunk_size>          The number of sectors per disk that
 *                                      will form the "stripe"
 *    [[no]sync]            Force or prevent recovery of the
 *                                      entire array
 *    [rebuild <idx>]           Rebuild the drive indicated by the index
 *    [daemon_sleep <ms>]       Time between bitmap daemon work to
 *                                      clear bits
 *    [min_recovery_rate <kB/sec/disk>] Throttle RAID initialization
 *    [max_recovery_rate <kB/sec/disk>] Throttle RAID initialization
 *    [write_mostly <idx>]      Indicate a write mostly drive via index
 *    [max_write_behind <sectors>]  See '-write-behind=' (man mdadm)
 *    [stripe_cache <sectors>]      Stripe cache size for higher RAIDs
 *    [region_size <sectors>]           Defines granularity of bitmap
 *
 * RAID10-only options:
 *    [raid10_copies <# copies>]        Number of copies.  (Default: 2)
 *    [raid10_format <near>]            Layout algorithm.  (Default: near)
 */
static int parse_raid_params(struct raid_set *rs, char **argv,
                 unsigned num_raid_params)
{
    char *raid10_format = "near";
    unsigned raid10_copies = 2;
    unsigned i;
    unsigned long value, region_size = 0;
    sector_t sectors_per_dev = rs->ti->len;
    sector_t max_io_len;
    char *key;

    /*
     * First, parse the in-order required arguments
     * "chunk_size" is the only argument of this type.
     */
    if ((strict_strtoul(argv[0], 10, &value) < 0)) {
        rs->ti->error = "Bad chunk size";
        return -EINVAL;
    } else if (rs->raid_type->level == 1) {
        if (value)
            DMERR("Ignoring chunk size parameter for RAID 1");
        value = 0;
    } else if (!is_power_of_2(value)) {
        rs->ti->error = "Chunk size must be a power of 2";
        return -EINVAL;
    } else if (value < 8) {
        rs->ti->error = "Chunk size value is too small";
        return -EINVAL;
    }

    rs->md.new_chunk_sectors = rs->md.chunk_sectors = value;
    argv++;
    num_raid_params--;

    /*
     * We set each individual device as In_sync with a completed
     * 'recovery_offset'.  If there has been a device failure or
     * replacement then one of the following cases applies:
     *
     *   1) User specifies 'rebuild'.
     *      - Device is reset when param is read.
     *   2) A new device is supplied.
     *      - No matching superblock found, resets device.
     *   3) Device failure was transient and returns on reload.
     *      - Failure noticed, resets device for bitmap replay.
     *   4) Device hadn't completed recovery after previous failure.
     *      - Superblock is read and overrides recovery_offset.
     *
     * What is found in the superblocks of the devices is always
     * authoritative, unless 'rebuild' or '[no]sync' was specified.
     */
    for (i = 0; i < rs->md.raid_disks; i++) {
        set_bit(In_sync, &rs->dev[i].rdev.flags);
        rs->dev[i].rdev.recovery_offset = MaxSector;
    }

    /*
     * Second, parse the unordered optional arguments
     */
    for (i = 0; i < num_raid_params; i++) {
        if (!strcasecmp(argv[i], "nosync")) {
            rs->md.recovery_cp = MaxSector;
            rs->print_flags |= DMPF_NOSYNC;
            continue;
        }
        if (!strcasecmp(argv[i], "sync")) {
            rs->md.recovery_cp = 0;
            rs->print_flags |= DMPF_SYNC;
            continue;
        }

        /* The rest of the optional arguments come in key/value pairs */
        if ((i + 1) >= num_raid_params) {
            rs->ti->error = "Wrong number of raid parameters given";
            return -EINVAL;
        }

        key = argv[i++];

        /* Parameters that take a string value are checked here. */
        if (!strcasecmp(key, "raid10_format")) {
            if (rs->raid_type->level != 10) {
                rs->ti->error = "'raid10_format' is an invalid parameter for this RAID type";
                return -EINVAL;
            }
            if (strcmp("near", argv[i])) {
                rs->ti->error = "Invalid 'raid10_format' value given";
                return -EINVAL;
            }
            raid10_format = argv[i];
            rs->print_flags |= DMPF_RAID10_FORMAT;
            continue;
        }

        if (strict_strtoul(argv[i], 10, &value) < 0) {
            rs->ti->error = "Bad numerical argument given in raid params";
            return -EINVAL;
        }

        /* Parameters that take a numeric value are checked here */
        if (!strcasecmp(key, "rebuild")) {
            if (value >= rs->md.raid_disks) {
                rs->ti->error = "Invalid rebuild index given";
                return -EINVAL;
            }
            clear_bit(In_sync, &rs->dev[value].rdev.flags);
            rs->dev[value].rdev.recovery_offset = 0;
            rs->print_flags |= DMPF_REBUILD;
        } else if (!strcasecmp(key, "write_mostly")) {
            if (rs->raid_type->level != 1) {
                rs->ti->error = "write_mostly option is only valid for RAID1";
                return -EINVAL;
            }
            if (value >= rs->md.raid_disks) {
                rs->ti->error = "Invalid write_mostly drive index given";
                return -EINVAL;
            }
            set_bit(WriteMostly, &rs->dev[value].rdev.flags);
        } else if (!strcasecmp(key, "max_write_behind")) {
            if (rs->raid_type->level != 1) {
                rs->ti->error = "max_write_behind option is only valid for RAID1";
                return -EINVAL;
            }
            rs->print_flags |= DMPF_MAX_WRITE_BEHIND;

            /*
             * In device-mapper, we specify things in sectors, but
             * MD records this value in kB
             */
            value /= 2;
            if (value > COUNTER_MAX) {
                rs->ti->error = "Max write-behind limit out of range";
                return -EINVAL;
            }
            rs->md.bitmap_info.max_write_behind = value;
        } else if (!strcasecmp(key, "daemon_sleep")) {
            rs->print_flags |= DMPF_DAEMON_SLEEP;
            if (!value || (value > MAX_SCHEDULE_TIMEOUT)) {
                rs->ti->error = "daemon sleep period out of range";
                return -EINVAL;
            }
            rs->md.bitmap_info.daemon_sleep = value;
        } else if (!strcasecmp(key, "stripe_cache")) {
            rs->print_flags |= DMPF_STRIPE_CACHE;

            /*
             * In device-mapper, we specify things in sectors, but
             * MD records this value in kB
             */
            value /= 2;

            if ((rs->raid_type->level != 5) &&
                (rs->raid_type->level != 6)) {
                rs->ti->error = "Inappropriate argument: stripe_cache";
                return -EINVAL;
            }
            if (raid5_set_cache_size(&rs->md, (int)value)) {
                rs->ti->error = "Bad stripe_cache size";
                return -EINVAL;
            }
        } else if (!strcasecmp(key, "min_recovery_rate")) {
            rs->print_flags |= DMPF_MIN_RECOVERY_RATE;
            if (value > INT_MAX) {
                rs->ti->error = "min_recovery_rate out of range";
                return -EINVAL;
            }
            rs->md.sync_speed_min = (int)value;
        } else if (!strcasecmp(key, "max_recovery_rate")) {
            rs->print_flags |= DMPF_MAX_RECOVERY_RATE;
            if (value > INT_MAX) {
                rs->ti->error = "max_recovery_rate out of range";
                return -EINVAL;
            }
            rs->md.sync_speed_max = (int)value;
        } else if (!strcasecmp(key, "region_size")) {
            rs->print_flags |= DMPF_REGION_SIZE;
            region_size = value;
        } else if (!strcasecmp(key, "raid10_copies") &&
               (rs->raid_type->level == 10)) {
            if ((value < 2) || (value > 0xFF)) {
                rs->ti->error = "Bad value for 'raid10_copies'";
                return -EINVAL;
            }
            rs->print_flags |= DMPF_RAID10_COPIES;
            raid10_copies = value;
        } else {
            DMERR("Unable to parse RAID parameter: %s", key);
            rs->ti->error = "Unable to parse RAID parameters";
            return -EINVAL;
        }
    }

    if (validate_region_size(rs, region_size))
        return -EINVAL;

    if (rs->md.chunk_sectors)
        max_io_len = rs->md.chunk_sectors;
    else
        max_io_len = region_size;

    if (dm_set_target_max_io_len(rs->ti, max_io_len))
        return -EINVAL;

    if (rs->raid_type->level == 10) {
        if (raid10_copies > rs->md.raid_disks) {
            rs->ti->error = "Not enough devices to satisfy specification";
            return -EINVAL;
        }

        /* (Len * #mirrors) / #devices */
        sectors_per_dev = rs->ti->len * raid10_copies;
        sector_div(sectors_per_dev, rs->md.raid_disks);

        rs->md.layout = raid10_format_to_md_layout(raid10_format,
                               raid10_copies);
        rs->md.new_layout = rs->md.layout;
    } else if ((rs->raid_type->level > 1) &&
           sector_div(sectors_per_dev,
                  (rs->md.raid_disks - rs->raid_type->parity_devs))) {
        rs->ti->error = "Target length not divisible by number of data devices";
        return -EINVAL;
    }
    rs->md.dev_sectors = sectors_per_dev;

    if (validate_rebuild_devices(rs))
        return -EINVAL;

    /* Assume there are no metadata devices until the drives are parsed */
    rs->md.persistent = 0;
    rs->md.external = 1;

    return 0;
}

static void do_table_event(struct work_struct *ws)
{
    struct raid_set *rs = container_of(ws, struct raid_set, md.event_work);

    dm_table_event(rs->ti->table);
}

static int raid_is_congested(struct dm_target_callbacks *cb, int bits)
{
    struct raid_set *rs = container_of(cb, struct raid_set, callbacks);

    if (rs->raid_type->level == 1)
        return md_raid1_congested(&rs->md, bits);

    if (rs->raid_type->level == 10)
        return md_raid10_congested(&rs->md, bits);

    return md_raid5_congested(&rs->md, bits);
}

/*
 * This structure is never routinely used by userspace, unlike md superblocks.
 * Devices with this superblock should only ever be accessed via device-mapper.
 */
#define DM_RAID_MAGIC 0x64526D44
struct dm_raid_superblock {
    __le32 magic;       /* "DmRd" */
    __le32 features;    /* Used to indicate possible future changes */

    __le32 num_devices; /* Number of devices in this array. (Max 64) */
    __le32 array_position;  /* The position of this drive in the array */

    __le64 events;      /* Incremented by md when superblock updated */
    __le64 failed_devices;  /* Bit field of devices to indicate failures */

    /*
     * This offset tracks the progress of the repair or replacement of
     * an individual drive.
     */
    __le64 disk_recovery_offset;

    /*
     * This offset tracks the progress of the initial array
     * synchronisation/parity calculation.
     */
    __le64 array_resync_offset;

    /*
     * RAID characteristics
     */
    __le32 level;
    __le32 layout;
    __le32 stripe_sectors;

    __u8 pad[452];      /* Round struct to 512 bytes. */
                /* Always set to 0 when writing. */
} __packed;

static int read_disk_sb(struct md_rdev *rdev, int size)
{
    BUG_ON(!rdev->sb_page);

    if (rdev->sb_loaded)
        return 0;

    if (!sync_page_io(rdev, 0, size, rdev->sb_page, READ, 1)) {
        DMERR("Failed to read superblock of device at position %d",
              rdev->raid_disk);
        md_error(rdev->mddev, rdev);
        return -EINVAL;
    }

    rdev->sb_loaded = 1;

    return 0;
}

static void super_sync(struct mddev *mddev, struct md_rdev *rdev)
{
    int i;
    uint64_t failed_devices;
    struct dm_raid_superblock *sb;
    struct raid_set *rs = container_of(mddev, struct raid_set, md);

    sb = page_address(rdev->sb_page);
    failed_devices = le64_to_cpu(sb->failed_devices);

    for (i = 0; i < mddev->raid_disks; i++)
        if (!rs->dev[i].data_dev ||
            test_bit(Faulty, &(rs->dev[i].rdev.flags)))
            failed_devices |= (1ULL << i);

    memset(sb, 0, sizeof(*sb));

    sb->magic = cpu_to_le32(DM_RAID_MAGIC);
    sb->features = cpu_to_le32(0);  /* No features yet */

    sb->num_devices = cpu_to_le32(mddev->raid_disks);
    sb->array_position = cpu_to_le32(rdev->raid_disk);

    sb->events = cpu_to_le64(mddev->events);
    sb->failed_devices = cpu_to_le64(failed_devices);

    sb->disk_recovery_offset = cpu_to_le64(rdev->recovery_offset);
    sb->array_resync_offset = cpu_to_le64(mddev->recovery_cp);

    sb->level = cpu_to_le32(mddev->level);
    sb->layout = cpu_to_le32(mddev->layout);
    sb->stripe_sectors = cpu_to_le32(mddev->chunk_sectors);
}

/*
 * super_load
 *
 * This function creates a superblock if one is not found on the device
 * and will decide which superblock to use if there's a choice.
 *
 * Return: 1 if use rdev, 0 if use refdev, -Exxx otherwise
 */
static int super_load(struct md_rdev *rdev, struct md_rdev *refdev)
{
    int ret;
    struct dm_raid_superblock *sb;
    struct dm_raid_superblock *refsb;
    uint64_t events_sb, events_refsb;

    rdev->sb_start = 0;
    rdev->sb_size = sizeof(*sb);

    ret = read_disk_sb(rdev, rdev->sb_size);
    if (ret)
        return ret;

    sb = page_address(rdev->sb_page);

    /*
     * Two cases that we want to write new superblocks and rebuild:
     * 1) New device (no matching magic number)
     * 2) Device specified for rebuild (!In_sync w/ offset == 0)
     */
    if ((sb->magic != cpu_to_le32(DM_RAID_MAGIC)) ||
        (!test_bit(In_sync, &rdev->flags) && !rdev->recovery_offset)) {
        super_sync(rdev->mddev, rdev);

        set_bit(FirstUse, &rdev->flags);

        /* Force writing of superblocks to disk */
        set_bit(MD_CHANGE_DEVS, &rdev->mddev->flags);

        /* Any superblock is better than none, choose that if given */
        return refdev ? 0 : 1;
    }

    if (!refdev)
        return 1;

    events_sb = le64_to_cpu(sb->events);

    refsb = page_address(refdev->sb_page);
    events_refsb = le64_to_cpu(refsb->events);

    return (events_sb > events_refsb) ? 1 : 0;
}

static int super_init_validation(struct mddev *mddev, struct md_rdev *rdev)
{
    int role;
    struct raid_set *rs = container_of(mddev, struct raid_set, md);
    uint64_t events_sb;
    uint64_t failed_devices;
    struct dm_raid_superblock *sb;
    uint32_t new_devs = 0;
    uint32_t rebuilds = 0;
    struct md_rdev *r;
    struct dm_raid_superblock *sb2;

    sb = page_address(rdev->sb_page);
    events_sb = le64_to_cpu(sb->events);
    failed_devices = le64_to_cpu(sb->failed_devices);

    /*
     * Initialise to 1 if this is a new superblock.
     */
    mddev->events = events_sb ? : 1;

    /*
     * Reshaping is not currently allowed
     */
    if ((le32_to_cpu(sb->level) != mddev->level) ||
        (le32_to_cpu(sb->layout) != mddev->layout) ||
        (le32_to_cpu(sb->stripe_sectors) != mddev->chunk_sectors)) {
        DMERR("Reshaping arrays not yet supported.");
        return -EINVAL;
    }

    /* We can only change the number of devices in RAID1 right now */
    if ((rs->raid_type->level != 1) &&
        (le32_to_cpu(sb->num_devices) != mddev->raid_disks)) {
        DMERR("Reshaping arrays not yet supported.");
        return -EINVAL;
    }

    if (!(rs->print_flags & (DMPF_SYNC | DMPF_NOSYNC)))
        mddev->recovery_cp = le64_to_cpu(sb->array_resync_offset);

    /*
     * During load, we set FirstUse if a new superblock was written.
     * There are two reasons we might not have a superblock:
     * 1) The array is brand new - in which case, all of the
     *    devices must have their In_sync bit set.  Also,
     *    recovery_cp must be 0, unless forced.
     * 2) This is a new device being added to an old array
     *    and the new device needs to be rebuilt - in which
     *    case the In_sync bit will /not/ be set and
     *    recovery_cp must be MaxSector.
     */
    rdev_for_each(r, mddev) {
        if (!test_bit(In_sync, &r->flags)) {
            DMINFO("Device %d specified for rebuild: "
                   "Clearing superblock", r->raid_disk);
            rebuilds++;
        } else if (test_bit(FirstUse, &r->flags))
            new_devs++;
    }

    if (!rebuilds) {
        if (new_devs == mddev->raid_disks) {
            DMINFO("Superblocks created for new array");
            set_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
        } else if (new_devs) {
            DMERR("New device injected "
                  "into existing array without 'rebuild' "
                  "parameter specified");
            return -EINVAL;
        }
    } else if (new_devs) {
        DMERR("'rebuild' devices cannot be "
              "injected into an array with other first-time devices");
        return -EINVAL;
    } else if (mddev->recovery_cp != MaxSector) {
        DMERR("'rebuild' specified while array is not in-sync");
        return -EINVAL;
    }

    /*
     * Now we set the Faulty bit for those devices that are
     * recorded in the superblock as failed.
     */
    rdev_for_each(r, mddev) {
        if (!r->sb_page)
            continue;
        sb2 = page_address(r->sb_page);
        sb2->failed_devices = 0;

        /*
         * Check for any device re-ordering.
         */
        if (!test_bit(FirstUse, &r->flags) && (r->raid_disk >= 0)) {
            role = le32_to_cpu(sb2->array_position);
            if (role != r->raid_disk) {
                if (rs->raid_type->level != 1) {
                    rs->ti->error = "Cannot change device "
                        "positions in RAID array";
                    return -EINVAL;
                }
                DMINFO("RAID1 device #%d now at position #%d",
                       role, r->raid_disk);
            }

            /*
             * Partial recovery is performed on
             * returning failed devices.
             */
            if (failed_devices & (1 << role))
                set_bit(Faulty, &r->flags);
        }
    }

    return 0;
}

static int super_validate(struct mddev *mddev, struct md_rdev *rdev)
{
    struct dm_raid_superblock *sb = page_address(rdev->sb_page);

    /*
     * If mddev->events is not set, we know we have not yet initialized
     * the array.
     */
    if (!mddev->events && super_init_validation(mddev, rdev))
        return -EINVAL;

    mddev->bitmap_info.offset = 4096 >> 9; /* Enable bitmap creation */
    rdev->mddev->bitmap_info.default_offset = 4096 >> 9;
    if (!test_bit(FirstUse, &rdev->flags)) {
        rdev->recovery_offset = le64_to_cpu(sb->disk_recovery_offset);
        if (rdev->recovery_offset != MaxSector)
            clear_bit(In_sync, &rdev->flags);
    }

    /*
     * If a device comes back, set it as not In_sync and no longer faulty.
     */
    if (test_bit(Faulty, &rdev->flags)) {
        clear_bit(Faulty, &rdev->flags);
        clear_bit(In_sync, &rdev->flags);
        rdev->saved_raid_disk = rdev->raid_disk;
        rdev->recovery_offset = 0;
    }

    clear_bit(FirstUse, &rdev->flags);

    return 0;
}

/*
 * Analyse superblocks and select the freshest.
 */
static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
{
    int ret;
    unsigned redundancy = 0;
    struct raid_dev *dev;
    struct md_rdev *rdev, *tmp, *freshest;
    struct mddev *mddev = &rs->md;

    switch (rs->raid_type->level) {
    case 1:
        redundancy = rs->md.raid_disks - 1;
        break;
    case 4:
    case 5:
    case 6:
        redundancy = rs->raid_type->parity_devs;
        break;
    case 10:
        redundancy = raid10_md_layout_to_copies(mddev->layout) - 1;
        break;
    default:
        ti->error = "Unknown RAID type";
        return -EINVAL;
    }

    freshest = NULL;
    rdev_for_each_safe(rdev, tmp, mddev) {
        /*
         * Skipping super_load due to DMPF_SYNC will cause
         * the array to undergo initialization again as
         * though it were new.  This is the intended effect
         * of the "sync" directive.
         *
         * When reshaping capability is added, we must ensure
         * that the "sync" directive is disallowed during the
         * reshape.
         */
        if (rs->print_flags & DMPF_SYNC)
            continue;

        if (!rdev->meta_bdev)
            continue;

        ret = super_load(rdev, freshest);

        switch (ret) {
        case 1:
            freshest = rdev;
            break;
        case 0:
            break;
        default:
            dev = container_of(rdev, struct raid_dev, rdev);
            if (redundancy--) {
                if (dev->meta_dev)
                    dm_put_device(ti, dev->meta_dev);

                dev->meta_dev = NULL;
                rdev->meta_bdev = NULL;

                if (rdev->sb_page)
                    put_page(rdev->sb_page);

                rdev->sb_page = NULL;

                rdev->sb_loaded = 0;

                /*
                 * We might be able to salvage the data device
                 * even though the meta device has failed.  For
                 * now, we behave as though '- -' had been
                 * set for this device in the table.
                 */
                if (dev->data_dev)
                    dm_put_device(ti, dev->data_dev);

                dev->data_dev = NULL;
                rdev->bdev = NULL;

                list_del(&rdev->same_set);

                continue;
            }
            ti->error = "Failed to load superblock";
            return ret;
        }
    }

    if (!freshest)
        return 0;

    /*
     * Validation of the freshest device provides the source of
     * validation for the remaining devices.
     */
    ti->error = "Unable to assemble array: Invalid superblocks";
    if (super_validate(mddev, freshest))
        return -EINVAL;

    rdev_for_each(rdev, mddev)
        if ((rdev != freshest) && super_validate(mddev, rdev))
            return -EINVAL;

    return 0;
}

/*
 * Construct a RAID4/5/6 mapping:
 * Args:
 *  <raid_type> <#raid_params> <raid_params>        \
 *  <#raid_devs> { <meta_dev1> <dev1> .. <meta_devN> <devN> }
 *
 * <raid_params> varies by <raid_type>.  See 'parse_raid_params' for
 * details on possible <raid_params>.
 */
static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
{
    int ret;
    struct raid_type *rt;
    unsigned long num_raid_params, num_raid_devs;
    struct raid_set *rs = NULL;

    /* Must have at least <raid_type> <#raid_params> */
    if (argc < 2) {
        ti->error = "Too few arguments";
        return -EINVAL;
    }

    /* raid type */
    rt = get_raid_type(argv[0]);
    if (!rt) {
        ti->error = "Unrecognised raid_type";
        return -EINVAL;
    }
    argc--;
    argv++;

    /* number of RAID parameters */
    if (strict_strtoul(argv[0], 10, &num_raid_params) < 0) {
        ti->error = "Cannot understand number of RAID parameters";
        return -EINVAL;
    }
    argc--;
    argv++;

    /* Skip over RAID params for now and find out # of devices */
    if (num_raid_params + 1 > argc) {
        ti->error = "Arguments do not agree with counts given";
        return -EINVAL;
    }

    if ((strict_strtoul(argv[num_raid_params], 10, &num_raid_devs) < 0) ||
        (num_raid_devs >= INT_MAX)) {
        ti->error = "Cannot understand number of raid devices";
        return -EINVAL;
    }

    rs = context_alloc(ti, rt, (unsigned)num_raid_devs);
    if (IS_ERR(rs))
        return PTR_ERR(rs);

    ret = parse_raid_params(rs, argv, (unsigned)num_raid_params);
    if (ret)
        goto bad;

    ret = -EINVAL;

    argc -= num_raid_params + 1; /* +1: we already have num_raid_devs */
    argv += num_raid_params + 1;

    if (argc != (num_raid_devs * 2)) {
        ti->error = "Supplied RAID devices does not match the count given";
        goto bad;
    }

    ret = dev_parms(rs, argv);
    if (ret)
        goto bad;

    rs->md.sync_super = super_sync;
    ret = analyse_superblocks(ti, rs);
    if (ret)
        goto bad;

    INIT_WORK(&rs->md.event_work, do_table_event);
    ti->private = rs;
    ti->num_flush_requests = 1;

    mutex_lock(&rs->md.reconfig_mutex);
    ret = md_run(&rs->md);
    rs->md.in_sync = 0; /* Assume already marked dirty */
    mutex_unlock(&rs->md.reconfig_mutex);

    if (ret) {
        ti->error = "Fail to run raid array";
        goto bad;
    }

    if (ti->len != rs->md.array_sectors) {
        ti->error = "Array size does not match requested target length";
        ret = -EINVAL;
        goto size_mismatch;
    }
    rs->callbacks.congested_fn = raid_is_congested;
    dm_table_add_target_callbacks(ti->table, &rs->callbacks);

    mddev_suspend(&rs->md);
    return 0;

size_mismatch:
    md_stop(&rs->md);
bad:
    context_free(rs);

    return ret;
}

static void raid_dtr(struct dm_target *ti)
{
    struct raid_set *rs = ti->private;

    list_del_init(&rs->callbacks.list);
    md_stop(&rs->md);
    context_free(rs);
}

static int raid_map(struct dm_target *ti, struct bio *bio, union map_info *map_context)
{
    struct raid_set *rs = ti->private;
    struct mddev *mddev = &rs->md;

    mddev->pers->make_request(mddev, bio);

    return DM_MAPIO_SUBMITTED;
}

static int raid_status(struct dm_target *ti, status_type_t type,
               unsigned status_flags, char *result, unsigned maxlen)
{
    struct raid_set *rs = ti->private;
    unsigned raid_param_cnt = 1; /* at least 1 for chunksize */
    unsigned sz = 0;
    int i, array_in_sync = 0;
    sector_t sync;

    switch (type) {
    case STATUSTYPE_INFO:
        DMEMIT("%s %d ", rs->raid_type->name, rs->md.raid_disks);

        if (test_bit(MD_RECOVERY_RUNNING, &rs->md.recovery))
            sync = rs->md.curr_resync_completed;
        else
            sync = rs->md.recovery_cp;

        if (sync >= rs->md.resync_max_sectors) {
            array_in_sync = 1;
            sync = rs->md.resync_max_sectors;
        } else {
            /*
             * The array may be doing an initial sync, or it may
             * be rebuilding individual components.  If all the
             * devices are In_sync, then it is the array that is
             * being initialized.
             */
            for (i = 0; i < rs->md.raid_disks; i++)
                if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
                    array_in_sync = 1;
        }
        /*
         * Status characters:
         *  'D' = Dead/Failed device
         *  'a' = Alive but not in-sync
         *  'A' = Alive and in-sync
         */
        for (i = 0; i < rs->md.raid_disks; i++) {
            if (test_bit(Faulty, &rs->dev[i].rdev.flags))
                DMEMIT("D");
            else if (!array_in_sync ||
                 !test_bit(In_sync, &rs->dev[i].rdev.flags))
                DMEMIT("a");
            else
                DMEMIT("A");
        }

        /*
         * In-sync ratio:
         *  The in-sync ratio shows the progress of:
         *   - Initializing the array
         *   - Rebuilding a subset of devices of the array
         *  The user can distinguish between the two by referring
         *  to the status characters.
         */
        DMEMIT(" %llu/%llu",
               (unsigned long long) sync,
               (unsigned long long) rs->md.resync_max_sectors);

        break;
    case STATUSTYPE_TABLE:
        /* The string you would use to construct this array */
        for (i = 0; i < rs->md.raid_disks; i++) {
            if ((rs->print_flags & DMPF_REBUILD) &&
                rs->dev[i].data_dev &&
                !test_bit(In_sync, &rs->dev[i].rdev.flags))
                raid_param_cnt += 2; /* for rebuilds */
            if (rs->dev[i].data_dev &&
                test_bit(WriteMostly, &rs->dev[i].rdev.flags))
                raid_param_cnt += 2;
        }

        raid_param_cnt += (hweight32(rs->print_flags & ~DMPF_REBUILD) * 2);
        if (rs->print_flags & (DMPF_SYNC | DMPF_NOSYNC))
            raid_param_cnt--;

        DMEMIT("%s %u %u", rs->raid_type->name,
               raid_param_cnt, rs->md.chunk_sectors);

        if ((rs->print_flags & DMPF_SYNC) &&
            (rs->md.recovery_cp == MaxSector))
            DMEMIT(" sync");
        if (rs->print_flags & DMPF_NOSYNC)
            DMEMIT(" nosync");

        for (i = 0; i < rs->md.raid_disks; i++)
            if ((rs->print_flags & DMPF_REBUILD) &&
                rs->dev[i].data_dev &&
                !test_bit(In_sync, &rs->dev[i].rdev.flags))
                DMEMIT(" rebuild %u", i);

        if (rs->print_flags & DMPF_DAEMON_SLEEP)
            DMEMIT(" daemon_sleep %lu",
                   rs->md.bitmap_info.daemon_sleep);

        if (rs->print_flags & DMPF_MIN_RECOVERY_RATE)
            DMEMIT(" min_recovery_rate %d", rs->md.sync_speed_min);

        if (rs->print_flags & DMPF_MAX_RECOVERY_RATE)
            DMEMIT(" max_recovery_rate %d", rs->md.sync_speed_max);

        for (i = 0; i < rs->md.raid_disks; i++)
            if (rs->dev[i].data_dev &&
                test_bit(WriteMostly, &rs->dev[i].rdev.flags))
                DMEMIT(" write_mostly %u", i);

        if (rs->print_flags & DMPF_MAX_WRITE_BEHIND)
            DMEMIT(" max_write_behind %lu",
                   rs->md.bitmap_info.max_write_behind);

        if (rs->print_flags & DMPF_STRIPE_CACHE) {
            struct r5conf *conf = rs->md.private;

            /* convert from kiB to sectors */
            DMEMIT(" stripe_cache %d",
                   conf ? conf->max_nr_stripes * 2 : 0);
        }

        if (rs->print_flags & DMPF_REGION_SIZE)
            DMEMIT(" region_size %lu",
                   rs->md.bitmap_info.chunksize >> 9);

        if (rs->print_flags & DMPF_RAID10_COPIES)
            DMEMIT(" raid10_copies %u",
                   raid10_md_layout_to_copies(rs->md.layout));

        if (rs->print_flags & DMPF_RAID10_FORMAT)
            DMEMIT(" raid10_format near");

        DMEMIT(" %d", rs->md.raid_disks);
        for (i = 0; i < rs->md.raid_disks; i++) {
            if (rs->dev[i].meta_dev)
                DMEMIT(" %s", rs->dev[i].meta_dev->name);
            else
                DMEMIT(" -");

            if (rs->dev[i].data_dev)
                DMEMIT(" %s", rs->dev[i].data_dev->name);
            else
                DMEMIT(" -");
        }
    }

    return 0;
}

static int raid_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
{
    struct raid_set *rs = ti->private;
    unsigned i;
    int ret = 0;

    for (i = 0; !ret && i < rs->md.raid_disks; i++)
        if (rs->dev[i].data_dev)
            ret = fn(ti,
                 rs->dev[i].data_dev,
                 0, /* No offset on data devs */
                 rs->md.dev_sectors,
                 data);

    return ret;
}

static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
    struct raid_set *rs = ti->private;
    unsigned chunk_size = rs->md.chunk_sectors << 9;
    struct r5conf *conf = rs->md.private;

    blk_limits_io_min(limits, chunk_size);
    blk_limits_io_opt(limits, chunk_size * (conf->raid_disks - conf->max_degraded));
}

static void raid_presuspend(struct dm_target *ti)
{
    struct raid_set *rs = ti->private;

    md_stop_writes(&rs->md);
}

static void raid_postsuspend(struct dm_target *ti)
{
    struct raid_set *rs = ti->private;

    mddev_suspend(&rs->md);
}

static void raid_resume(struct dm_target *ti)
{
    struct raid_set *rs = ti->private;

    set_bit(MD_CHANGE_DEVS, &rs->md.flags);
    if (!rs->bitmap_loaded) {
        bitmap_load(&rs->md);
        rs->bitmap_loaded = 1;
    }

    clear_bit(MD_RECOVERY_FROZEN, &rs->md.recovery);
    mddev_resume(&rs->md);
}

static struct target_type raid_target = {
    .name = "raid",
    .version = {1, 3, 1},
    .module = THIS_MODULE,
    .ctr = raid_ctr,
    .dtr = raid_dtr,
    .map = raid_map,
    .status = raid_status,
    .iterate_devices = raid_iterate_devices,
    .io_hints = raid_io_hints,
    .presuspend = raid_presuspend,
    .postsuspend = raid_postsuspend,
    .resume = raid_resume,
};

static int __init dm_raid_init(void)
{
    return dm_register_target(&raid_target);
}

static void __exit dm_raid_exit(void)
{
    dm_unregister_target(&raid_target);
}

module_init(dm_raid_init);
module_exit(dm_raid_exit);

MODULE_DESCRIPTION(DM_NAME " raid4/5/6 target");
MODULE_ALIAS("dm-raid1");
MODULE_ALIAS("dm-raid10");
MODULE_ALIAS("dm-raid4");
MODULE_ALIAS("dm-raid5");
MODULE_ALIAS("dm-raid6");
MODULE_AUTHOR("Neil Brown <[email protected]>");
MODULE_LICENSE("GPL");