Merge tag 'nfs-for-3.6-1' of git://git.linux-nfs.org/projects/trondmy/linux-nfs

[deliverable/linux.git] / drivers / md / dm-raid.c

/*
 * 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 "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
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 */},
        {"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 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;
}

/*
 * 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
 */
static int parse_raid_params(struct raid_set *rs, char **argv,
                             unsigned num_raid_params)
{
        unsigned i, rebuild_cnt = 0;
        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++];
                if (strict_strtoul(argv[i], 10, &value) < 0) {
                        rs->ti->error = "Bad numerical argument given in raid params";
                        return -EINVAL;
                }

                if (!strcasecmp(key, "rebuild")) {
                        rebuild_cnt++;

                        switch (rs->raid_type->level) {
                        case 1:
                                if (rebuild_cnt >= rs->md.raid_disks) {
                                        rs->ti->error = "Too many rebuild devices specified";
                                        return -EINVAL;
                                }
                                break;
                        case 4:
                        case 5:
                        case 6:
                                if (rebuild_cnt > rs->raid_type->parity_devs) {
                                        rs->ti->error = "Too many rebuild devices specified for given RAID type";
                                        return -EINVAL;
                                }
                                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;
                        }

                        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->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 {
                        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 > 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;

        /* 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);

        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;
        default:
                ti->error = "Unknown RAID type";
                return -EINVAL;
        }

        freshest = NULL;
        rdev_for_each_safe(rdev, tmp, mddev) {
                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;
        }

        rs->callbacks.congested_fn = raid_is_congested;
        dm_table_add_target_callbacks(ti->table, &rs->callbacks);

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

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);

                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, 2, 0},
        .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-raid4");
MODULE_ALIAS("dm-raid5");
MODULE_ALIAS("dm-raid6");
MODULE_AUTHOR("Neil Brown <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");