Correctly abort level change when reshape_array fails.

[thirdparty/mdadm.git] / Grow.c

/*
 * mdadm - manage Linux "md" devices aka RAID arrays.
 *
 * Copyright (C) 2001-2009 Neil Brown <neilb@suse.de>
 *
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *    Author: Neil Brown
 *    Email: <neilb@suse.de>
 */
#include        "mdadm.h"
#include        "dlink.h"
#include        <sys/mman.h>

#if ! defined(__BIG_ENDIAN) && ! defined(__LITTLE_ENDIAN)
#error no endian defined
#endif
#include        "md_u.h"
#include        "md_p.h"

#ifndef offsetof
#define offsetof(t,f) ((size_t)&(((t*)0)->f))
#endif

int Grow_Add_device(char *devname, int fd, char *newdev)
{
        /* Add a device to an active array.
         * Currently, just extend a linear array.
         * This requires writing a new superblock on the
         * new device, calling the kernel to add the device,
         * and if that succeeds, update the superblock on
         * all other devices.
         * This means that we need to *find* all other devices.
         */
        struct mdinfo info;

        struct stat stb;
        int nfd, fd2;
        int d, nd;
        struct supertype *st = NULL;
        char *subarray = NULL;

        if (ioctl(fd, GET_ARRAY_INFO, &info.array) < 0) {
                fprintf(stderr, Name ": cannot get array info for %s\n", devname);
                return 1;
        }

        if (info.array.level != -1) {
                fprintf(stderr, Name ": can only add devices to linear arrays\n");
                return 1;
        }

        st = super_by_fd(fd, &subarray);
        if (!st) {
                fprintf(stderr, Name ": cannot handle arrays with superblock version %d\n", info.array.major_version);
                return 1;
        }

        if (subarray) {
                fprintf(stderr, Name ": Cannot grow linear sub-arrays yet\n");
                free(subarray);
                free(st);
        }

        nfd = open(newdev, O_RDWR|O_EXCL|O_DIRECT);
        if (nfd < 0) {
                fprintf(stderr, Name ": cannot open %s\n", newdev);
                free(st);
                return 1;
        }
        fstat(nfd, &stb);
        if ((stb.st_mode & S_IFMT) != S_IFBLK) {
                fprintf(stderr, Name ": %s is not a block device!\n", newdev);
                close(nfd);
                free(st);
                return 1;
        }
        /* now check out all the devices and make sure we can read the superblock */
        for (d=0 ; d < info.array.raid_disks ; d++) {
                mdu_disk_info_t disk;
                char *dv;

                st->ss->free_super(st);

                disk.number = d;
                if (ioctl(fd, GET_DISK_INFO, &disk) < 0) {
                        fprintf(stderr, Name ": cannot get device detail for device %d\n",
                                d);
                        close(nfd);
                        free(st);
                        return 1;
                }
                dv = map_dev(disk.major, disk.minor, 1);
                if (!dv) {
                        fprintf(stderr, Name ": cannot find device file for device %d\n",
                                d);
                        close(nfd);
                        free(st);
                        return 1;
                }
                fd2 = dev_open(dv, O_RDWR);
                if (!fd2) {
                        fprintf(stderr, Name ": cannot open device file %s\n", dv);
                        close(nfd);
                        free(st);
                        return 1;
                }

                if (st->ss->load_super(st, fd2, NULL)) {
                        fprintf(stderr, Name ": cannot find super block on %s\n", dv);
                        close(nfd);
                        close(fd2);
                        free(st);
                        return 1;
                }
                close(fd2);
        }
        /* Ok, looks good. Lets update the superblock and write it out to
         * newdev.
         */

        info.disk.number = d;
        info.disk.major = major(stb.st_rdev);
        info.disk.minor = minor(stb.st_rdev);
        info.disk.raid_disk = d;
        info.disk.state = (1 << MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE);
        st->ss->update_super(st, &info, "linear-grow-new", newdev,
                             0, 0, NULL);

        if (st->ss->store_super(st, nfd)) {
                fprintf(stderr, Name ": Cannot store new superblock on %s\n",
                        newdev);
                close(nfd);
                return 1;
        }
        close(nfd);

        if (ioctl(fd, ADD_NEW_DISK, &info.disk) != 0) {
                fprintf(stderr, Name ": Cannot add new disk to this array\n");
                return 1;
        }
        /* Well, that seems to have worked.
         * Now go through and update all superblocks
         */

        if (ioctl(fd, GET_ARRAY_INFO, &info.array) < 0) {
                fprintf(stderr, Name ": cannot get array info for %s\n", devname);
                return 1;
        }

        nd = d;
        for (d=0 ; d < info.array.raid_disks ; d++) {
                mdu_disk_info_t disk;
                char *dv;

                disk.number = d;
                if (ioctl(fd, GET_DISK_INFO, &disk) < 0) {
                        fprintf(stderr, Name ": cannot get device detail for device %d\n",
                                d);
                        return 1;
                }
                dv = map_dev(disk.major, disk.minor, 1);
                if (!dv) {
                        fprintf(stderr, Name ": cannot find device file for device %d\n",
                                d);
                        return 1;
                }
                fd2 = dev_open(dv, O_RDWR);
                if (fd2 < 0) {
                        fprintf(stderr, Name ": cannot open device file %s\n", dv);
                        return 1;
                }
                if (st->ss->load_super(st, fd2, NULL)) {
                        fprintf(stderr, Name ": cannot find super block on %s\n", dv);
                        close(fd);
                        return 1;
                }
                info.array.raid_disks = nd+1;
                info.array.nr_disks = nd+1;
                info.array.active_disks = nd+1;
                info.array.working_disks = nd+1;

                st->ss->update_super(st, &info, "linear-grow-update", dv,
                                     0, 0, NULL);

                if (st->ss->store_super(st, fd2)) {
                        fprintf(stderr, Name ": Cannot store new superblock on %s\n", dv);
                        close(fd2);
                        return 1;
                }
                close(fd2);
        }

        return 0;
}

int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int write_behind, int force)
{
        /*
         * First check that array doesn't have a bitmap
         * Then create the bitmap
         * Then add it
         *
         * For internal bitmaps, we need to check the version,
         * find all the active devices, and write the bitmap block
         * to all devices
         */
        mdu_bitmap_file_t bmf;
        mdu_array_info_t array;
        struct supertype *st;
        char *subarray = NULL;
        int major = BITMAP_MAJOR_HI;
        int vers = md_get_version(fd);
        unsigned long long bitmapsize, array_size;

        if (vers < 9003) {
                major = BITMAP_MAJOR_HOSTENDIAN;
                fprintf(stderr, Name ": Warning - bitmaps created on this kernel"
                        " are not portable\n"
                        "  between different architectures.  Consider upgrading"
                        " the Linux kernel.\n");
        }

        if (ioctl(fd, GET_BITMAP_FILE, &bmf) != 0) {
                if (errno == ENOMEM)
                        fprintf(stderr, Name ": Memory allocation failure.\n");
                else
                        fprintf(stderr, Name ": bitmaps not supported by this kernel.\n");
                return 1;
        }
        if (bmf.pathname[0]) {
                if (strcmp(file,"none")==0) {
                        if (ioctl(fd, SET_BITMAP_FILE, -1)!= 0) {
                                fprintf(stderr, Name ": failed to remove bitmap %s\n",
                                        bmf.pathname);
                                return 1;
                        }
                        return 0;
                }
                fprintf(stderr, Name ": %s already has a bitmap (%s)\n",
                        devname, bmf.pathname);
                return 1;
        }
        if (ioctl(fd, GET_ARRAY_INFO, &array) != 0) {
                fprintf(stderr, Name ": cannot get array status for %s\n", devname);
                return 1;
        }
        if (array.state & (1<<MD_SB_BITMAP_PRESENT)) {
                if (strcmp(file, "none")==0) {
                        array.state &= ~(1<<MD_SB_BITMAP_PRESENT);
                        if (ioctl(fd, SET_ARRAY_INFO, &array)!= 0) {
                                fprintf(stderr, Name ": failed to remove internal bitmap.\n");
                                return 1;
                        }
                        return 0;
                }
                fprintf(stderr, Name ": Internal bitmap already present on %s\n",
                        devname);
                return 1;
        }

        if (strcmp(file, "none") == 0) {
                fprintf(stderr, Name ": no bitmap found on %s\n", devname);
                return 1;
        }
        if (array.level <= 0) {
                fprintf(stderr, Name ": Bitmaps not meaningful with level %s\n",
                        map_num(pers, array.level)?:"of this array");
                return 1;
        }
        bitmapsize = array.size;
        bitmapsize <<= 1;
        if (get_dev_size(fd, NULL, &array_size) &&
            array_size > (0x7fffffffULL<<9)) {
                /* Array is big enough that we cannot trust array.size
                 * try other approaches
                 */
                bitmapsize = get_component_size(fd);
        }
        if (bitmapsize == 0) {
                fprintf(stderr, Name ": Cannot reliably determine size of array to create bitmap - sorry.\n");
                return 1;
        }

        if (array.level == 10) {
                int ncopies = (array.layout&255)*((array.layout>>8)&255);
                bitmapsize = bitmapsize * array.raid_disks / ncopies;
        }

        st = super_by_fd(fd, &subarray);
        if (!st) {
                fprintf(stderr, Name ": Cannot understand version %d.%d\n",
                        array.major_version, array.minor_version);
                return 1;
        }
        if (subarray) {
                fprintf(stderr, Name ": Cannot add bitmaps to sub-arrays yet\n");
                free(subarray);
                free(st);
                return 1;
        }
        if (strcmp(file, "internal") == 0) {
                int d;
                if (st->ss->add_internal_bitmap == NULL) {
                        fprintf(stderr, Name ": Internal bitmaps not supported "
                                "with %s metadata\n", st->ss->name);
                        return 1;
                }
                for (d=0; d< st->max_devs; d++) {
                        mdu_disk_info_t disk;
                        char *dv;
                        disk.number = d;
                        if (ioctl(fd, GET_DISK_INFO, &disk) < 0)
                                continue;
                        if (disk.major == 0 &&
                            disk.minor == 0)
                                continue;
                        if ((disk.state & (1<<MD_DISK_SYNC))==0)
                                continue;
                        dv = map_dev(disk.major, disk.minor, 1);
                        if (dv) {
                                int fd2 = dev_open(dv, O_RDWR);
                                if (fd2 < 0)
                                        continue;
                                if (st->ss->load_super(st, fd2, NULL)==0) {
                                        if (st->ss->add_internal_bitmap(
                                                    st,
                                                    &chunk, delay, write_behind,
                                                    bitmapsize, 0, major)
                                                )
                                                st->ss->write_bitmap(st, fd2);
                                        else {
                                                fprintf(stderr, Name ": failed to create internal bitmap - chunksize problem.\n");
                                                close(fd2);
                                                return 1;
                                        }
                                }
                                close(fd2);
                        }
                }
                array.state |= (1<<MD_SB_BITMAP_PRESENT);
                if (ioctl(fd, SET_ARRAY_INFO, &array)!= 0) {
                        if (errno == EBUSY)
                                fprintf(stderr, Name
                                        ": Cannot add bitmap while array is"
                                        " resyncing or reshaping etc.\n");
                        fprintf(stderr, Name ": failed to set internal bitmap.\n");
                        return 1;
                }
        } else {
                int uuid[4];
                int bitmap_fd;
                int d;
                int max_devs = st->max_devs;

                /* try to load a superblock */
                for (d=0; d<max_devs; d++) {
                        mdu_disk_info_t disk;
                        char *dv;
                        int fd2;
                        disk.number = d;
                        if (ioctl(fd, GET_DISK_INFO, &disk) < 0)
                                continue;
                        if ((disk.major==0 && disk.minor==0) ||
                            (disk.state & (1<<MD_DISK_REMOVED)))
                                continue;
                        dv = map_dev(disk.major, disk.minor, 1);
                        if (!dv) continue;
                        fd2 = dev_open(dv, O_RDONLY);
                        if (fd2 >= 0 &&
                            st->ss->load_super(st, fd2, NULL) == 0) {
                                close(fd2);
                                st->ss->uuid_from_super(st, uuid);
                                break;
                        }
                        close(fd2);
                }
                if (d == max_devs) {
                        fprintf(stderr, Name ": cannot find UUID for array!\n");
                        return 1;
                }
                if (CreateBitmap(file, force, (char*)uuid, chunk,
                                 delay, write_behind, bitmapsize, major)) {
                        return 1;
                }
                bitmap_fd = open(file, O_RDWR);
                if (bitmap_fd < 0) {
                        fprintf(stderr, Name ": weird: %s cannot be opened\n",
                                file);
                        return 1;
                }
                if (ioctl(fd, SET_BITMAP_FILE, bitmap_fd) < 0) {
                        int err = errno;
                        if (errno == EBUSY)
                                fprintf(stderr, Name
                                        ": Cannot add bitmap while array is"
                                        " resyncing or reshaping etc.\n");
                        fprintf(stderr, Name ": Cannot set bitmap file for %s: %s\n",
                                devname, strerror(err));
                        return 1;
                }
        }

        return 0;
}


/*
 * When reshaping an array we might need to backup some data.
 * This is written to all spares with a 'super_block' describing it.
 * The superblock goes 4K from the end of the used space on the
 * device.
 * It if written after the backup is complete.
 * It has the following structure.
 */

static struct mdp_backup_super {
        char    magic[16];  /* md_backup_data-1 or -2 */
        __u8    set_uuid[16];
        __u64   mtime;
        /* start/sizes in 512byte sectors */
        __u64   devstart;       /* address on backup device/file of data */
        __u64   arraystart;
        __u64   length;
        __u32   sb_csum;        /* csum of preceeding bytes. */
        __u32   pad1;
        __u64   devstart2;      /* offset in to data of second section */
        __u64   arraystart2;
        __u64   length2;
        __u32   sb_csum2;       /* csum of preceeding bytes. */
        __u8 pad[512-68-32];
} __attribute__((aligned(512))) bsb, bsb2;

static __u32 bsb_csum(char *buf, int len)
{
        int i;
        int csum = 0;
        for (i=0; i<len; i++)
                csum = (csum<<3) + buf[0];
        return __cpu_to_le32(csum);
}

static int check_idle(struct supertype *st)
{
        /* Check that all member arrays for this container, or the
         * container of this array, are idle
         */
        int container_dev = (st->container_dev != NoMdDev
                             ? st->container_dev : st->devnum);
        char container[40];
        struct mdstat_ent *ent, *e;
        int is_idle = 1;
        
        fmt_devname(container, container_dev);
        ent = mdstat_read(0, 0);
        for (e = ent ; e; e = e->next) {
                if (!is_container_member(e, container))
                        continue;
                if (e->percent >= 0) {
                        is_idle = 0;
                        break;
                }
        }
        free_mdstat(ent);
        return is_idle;
}

static int freeze_container(struct supertype *st)
{
        int container_dev = (st->container_dev != NoMdDev
                             ? st->container_dev : st->devnum);
        char container[40];

        if (!check_idle(st))
                return -1;
        
        fmt_devname(container, container_dev);

        if (block_monitor(container, 1)) {
                fprintf(stderr, Name ": failed to freeze container\n");
                return -2;
        }

        return 1;
}

static void unfreeze_container(struct supertype *st)
{
        int container_dev = (st->container_dev != NoMdDev
                             ? st->container_dev : st->devnum);
        char container[40];
        
        fmt_devname(container, container_dev);

        unblock_monitor(container, 1);
}

static int freeze(struct supertype *st)
{
        /* Try to freeze resync/rebuild on this array/container.
         * Return -1 if the array is busy,
         * return -2 container cannot be frozen,
         * return 0 if this kernel doesn't support 'frozen'
         * return 1 if it worked.
         */
        if (st->ss->external)
                return freeze_container(st);
        else {
                struct mdinfo *sra = sysfs_read(-1, st->devnum, GET_VERSION);
                int err;

                if (!sra)
                        return -1;
                err = sysfs_freeze_array(sra);
                sysfs_free(sra);
                return err;
        }
}

static void unfreeze(struct supertype *st, int frozen)
{
        /* If 'frozen' is 1, unfreeze the array */
        if (frozen <= 0)
                return;

        if (st->ss->external)
                return unfreeze_container(st);
        else {
                struct mdinfo *sra = sysfs_read(-1, st->devnum, GET_VERSION);

                if (sra)
                        sysfs_set_str(sra, NULL, "sync_action", "idle");
                else
                        fprintf(stderr, Name ": failed to unfreeze array\n");
                sysfs_free(sra);
        }
}

static void wait_reshape(struct mdinfo *sra)
{
        int fd = sysfs_get_fd(sra, NULL, "sync_action");
        char action[20];

        if (fd < 0)
                return;

        while  (sysfs_fd_get_str(fd, action, 20) > 0 &&
                strncmp(action, "reshape", 7) == 0) {
                fd_set rfds;
                FD_ZERO(&rfds);
                FD_SET(fd, &rfds);
                select(fd+1, NULL, NULL, &rfds, NULL);
        }
        close(fd);
}

static int reshape_super(struct supertype *st, long long size, int level,
                         int layout, int chunksize, int raid_disks,
                         char *backup_file, char *dev, int verbose)
{
        /* nothing extra to check in the native case */
        if (!st->ss->external)
                return 0;
        if (!st->ss->reshape_super ||
            !st->ss->manage_reshape) {
                fprintf(stderr, Name ": %s metadata does not support reshape\n",
                        st->ss->name);
                return 1;
        }

        return st->ss->reshape_super(st, size, level, layout, chunksize,
                                     raid_disks, backup_file, dev, verbose);
}

static void sync_metadata(struct supertype *st)
{
        if (st->ss->external) {
                if (st->update_tail) {
                        flush_metadata_updates(st);
                        st->update_tail = &st->updates;
                } else
                        st->ss->sync_metadata(st);
        }
}

static int subarray_set_num(char *container, struct mdinfo *sra, char *name, int n)
{
        /* when dealing with external metadata subarrays we need to be
         * prepared to handle EAGAIN.  The kernel may need to wait for
         * mdmon to mark the array active so the kernel can handle
         * allocations/writeback when preparing the reshape action
         * (md_allow_write()).  We temporarily disable safe_mode_delay
         * to close a race with the array_state going clean before the
         * next write to raid_disks / stripe_cache_size
         */
        char safe[50];
        int rc;

        /* only 'raid_disks' and 'stripe_cache_size' trigger md_allow_write */
        if (!container ||
            (strcmp(name, "raid_disks") != 0 &&
             strcmp(name, "stripe_cache_size") != 0))
                return sysfs_set_num(sra, NULL, name, n);

        rc = sysfs_get_str(sra, NULL, "safe_mode_delay", safe, sizeof(safe));
        if (rc <= 0)
                return -1;
        sysfs_set_num(sra, NULL, "safe_mode_delay", 0);
        rc = sysfs_set_num(sra, NULL, name, n);
        if (rc < 0 && errno == EAGAIN) {
                ping_monitor(container);
                /* if we get EAGAIN here then the monitor is not active
                 * so stop trying
                 */
                rc = sysfs_set_num(sra, NULL, name, n);
        }
        sysfs_set_str(sra, NULL, "safe_mode_delay", safe);
        return rc;
}

int start_reshape(struct mdinfo *sra)
{
        int err;
        sysfs_set_num(sra, NULL, "suspend_lo", 0x7FFFFFFFFFFFFFFFULL);
        err = sysfs_set_num(sra, NULL, "suspend_hi", 0);
        err = err ?: sysfs_set_num(sra, NULL, "suspend_lo", 0);
        err = err ?: sysfs_set_num(sra, NULL, "sync_min", 0);
        err = err ?: sysfs_set_num(sra, NULL, "sync_max", 0);
        err = err ?: sysfs_set_str(sra, NULL, "sync_action", "reshape");

        return err;
}

void abort_reshape(struct mdinfo *sra)
{
        sysfs_set_str(sra, NULL, "sync_action", "idle");
        sysfs_set_num(sra, NULL, "suspend_lo", 0x7FFFFFFFFFFFFFFFULL);
        sysfs_set_num(sra, NULL, "suspend_hi", 0);
        sysfs_set_num(sra, NULL, "suspend_lo", 0);
        sysfs_set_num(sra, NULL, "sync_min", 0);
        sysfs_set_str(sra, NULL, "sync_max", "max");
}

int remove_disks_on_raid10_to_raid0_takeover(struct supertype *st,
                                             struct mdinfo *sra,
                                             int layout)
{
        int nr_of_copies;
        struct mdinfo *remaining;
        int slot;

        nr_of_copies = layout & 0xff;

        remaining = sra->devs;
        sra->devs = NULL;
        /* for each 'copy', select one device and remove from the list. */
        for (slot = 0; slot < sra->array.raid_disks; slot += nr_of_copies) {
                struct mdinfo **diskp;
                int found = 0;

                /* Find a working device to keep */
                for (diskp =  &remaining; *diskp ; diskp = &(*diskp)->next) {
                        struct mdinfo *disk = *diskp;

                        if (disk->disk.raid_disk < slot)
                                continue;
                        if (disk->disk.raid_disk >= slot + nr_of_copies)
                                continue;
                        if (disk->disk.state & (1<<MD_DISK_REMOVED))
                                continue;
                        if (disk->disk.state & (1<<MD_DISK_FAULTY))
                                continue;
                        if (!(disk->disk.state & (1<<MD_DISK_SYNC)))
                                continue;

                        /* We have found a good disk to use! */
                        *diskp = disk->next;
                        disk->next = sra->devs;
                        sra->devs = disk;
                        found = 1;
                        break;
                }
                if (!found)
                        break;
        }

        if (slot < sra->array.raid_disks) {
                /* didn't find all slots */
                struct mdinfo **e;
                e = &remaining;
                while (*e)
                        e = &(*e)->next;
                *e = sra->devs;
                sra->devs = remaining;
                return 1;
        }

        /* Remove all 'remaining' devices from the array */
        while (remaining) {
                struct mdinfo *sd = remaining;
                remaining = sd->next;

                sysfs_set_str(sra, sd, "state", "faulty");
                sysfs_set_str(sra, sd, "slot", "none");
                sysfs_set_str(sra, sd, "state", "remove");
                sd->disk.state |= (1<<MD_DISK_REMOVED);
                sd->disk.state &= ~(1<<MD_DISK_SYNC);
                sd->next = sra->devs;
                sra->devs = sd;
        }
        return 0;
}

void reshape_free_fdlist(int *fdlist,
                         unsigned long long *offsets,
                         int size)
{
        int i;

        for (i = 0; i < size; i++)
                if (fdlist[i] >= 0)
                        close(fdlist[i]);

        free(fdlist);
        free(offsets);
}

int reshape_prepare_fdlist(char *devname,
                           struct mdinfo *sra,
                           int raid_disks,
                           int nrdisks,
                           unsigned long blocks,
                           char *backup_file,
                           int *fdlist,
                           unsigned long long *offsets)
{
        int d = 0;
        struct mdinfo *sd;

        for (d = 0; d <= nrdisks; d++)
                fdlist[d] = -1;
        d = raid_disks;
        for (sd = sra->devs; sd; sd = sd->next) {
                if (sd->disk.state & (1<<MD_DISK_FAULTY))
                        continue;
                if (sd->disk.state & (1<<MD_DISK_SYNC)) {
                        char *dn = map_dev(sd->disk.major,
                                           sd->disk.minor, 1);
                        fdlist[sd->disk.raid_disk]
                                = dev_open(dn, O_RDONLY);
                        offsets[sd->disk.raid_disk] = sd->data_offset*512;
                        if (fdlist[sd->disk.raid_disk] < 0) {
                                fprintf(stderr,
                                        Name ": %s: cannot open component %s\n",
                                        devname, dn ? dn : "-unknown-");
                                d = -1;
                                goto release;
                        }
                } else if (backup_file == NULL) {
                        /* spare */
                        char *dn = map_dev(sd->disk.major,
                                           sd->disk.minor, 1);
                                fdlist[d] = dev_open(dn, O_RDWR);
                                offsets[d] = (sd->data_offset + sra->component_size - blocks - 8)*512;
                                if (fdlist[d] < 0) {
                                        fprintf(stderr, Name ": %s: cannot open component %s\n",
                                                devname, dn ? dn : "-unknown-");
                                        d = -1;
                                        goto release;
                                }
                                d++;
                        }
                }
release:
        return d;
}

int reshape_open_backup_file(char *backup_file,
                             int fd,
                             char *devname,
                             long blocks,
                             int *fdlist,
                             unsigned long long *offsets)
{
        /* Return 1 on success, 0 on any form of failure */
        /* need to check backup file is large enough */
        char buf[512];
        struct stat stb;
        unsigned int dev;
        int i;

        *fdlist = open(backup_file, O_RDWR|O_CREAT|O_EXCL,
                       S_IRUSR | S_IWUSR);
        *offsets = 8 * 512;
        if (*fdlist < 0) {
                fprintf(stderr, Name ": %s: cannot create backup file %s: %s\n",
                        devname, backup_file, strerror(errno));
                return 0;
        }
        /* Guard against backup file being on array device.
         * If array is partitioned or if LVM etc is in the
         * way this will not notice, but it is better than
         * nothing.
         */
        fstat(*fdlist, &stb);
        dev = stb.st_dev;
        fstat(fd, &stb);
        if (stb.st_rdev == dev) {
                fprintf(stderr, Name ": backup file must NOT be"
                        " on the array being reshaped.\n");
                close(*fdlist);
                return 0;
        }

        memset(buf, 0, 512);
        for (i=0; i < blocks + 1 ; i++) {
                if (write(*fdlist, buf, 512) != 512) {
                        fprintf(stderr, Name ": %s: cannot create"
                                " backup file %s: %s\n",
                                devname, backup_file, strerror(errno));
                        return 0;
                }
        }
        if (fsync(*fdlist) != 0) {
                fprintf(stderr, Name ": %s: cannot create backup file %s: %s\n",
                        devname, backup_file, strerror(errno));
                return 0;
        }

        return 1;
}

unsigned long compute_backup_blocks(int nchunk, int ochunk,
                                    unsigned int ndata, unsigned int odata)
{
        unsigned long a, b, blocks;
        /* So how much do we need to backup.
         * We need an amount of data which is both a whole number of
         * old stripes and a whole number of new stripes.
         * So LCM for (chunksize*datadisks).
         */
        a = (ochunk/512) * odata;
        b = (nchunk/512) * ndata;
        /* Find GCD */
        while (a != b) {
                if (a < b)
                        b -= a;
                if (b < a)
                        a -= b;
        }
        /* LCM == product / GCD */
        blocks = (ochunk/512) * (nchunk/512) * odata * ndata / a;

        return blocks;
}

/* 'struct reshape' records the intermediate states
 * a general reshape.
 * The starting geometry is converted to the 'before' geometry
 * by at most an atomic level change. They could be the same.
 * Similarly the 'after' geometry is converted to the final
 * geometry by at most a level change.
 * Note that 'before' and 'after' must have the same level.
 * 'blocks' is the minimum number of sectors for a reshape unit.
 * This will be a multiple of the stripe size in each of the
 * 'before' and 'after' geometries.
 * If 'blocks' is 0, no restriping is necessary.
 */
struct reshape {
        int level;
        int parity; /* number of parity blocks/devices */
        struct {
                int layout;
                int data_disks;
        } before, after;
        unsigned long long blocks;
        unsigned long long stripes; /* number of old stripes that comprise 'blocks'*/
        unsigned long long new_size; /* New size of array in sectors */
};

char *analyse_change(struct mdinfo *info, struct reshape *re)
{
        /* Based on the current array state in info->array and
         * the changes in info->new_* etc, determine:
         *  - whether the change is possible
         *  - Intermediate level/raid_disks/layout
         *  - whether a restriping reshape is needed
         *  - number of sectors in minimum change unit.  This
         *    will cover a whole number of stripes in 'before' and
         *    'after'.
         *
         * Return message if the change should be rejected
         *        NULL if the change can be achieved
         *
         * This can be called as part of starting a reshape, or
         * when assembling an array that is undergoing reshape.
         */
        int new_disks;

        /* If a new level not explicitly given, we assume no-change */
        if (info->new_level == UnSet)
                info->new_level = info->array.level;

        if (info->new_chunk)
                switch (info->new_level) {
                case 0:
                case 4:
                case 5:
                case 6:
                case 10:
                        /* chunk size is meaningful, must divide component_size
                         * evenly
                         */
                        if (info->component_size % (info->new_chunk/512))
                                return "New chunk size does not"
                                        " divide component size";
                        break;
                default:
                        return "chunk size not meaningful for this level";
                }
        else
                info->new_chunk = info->array.chunk_size;

        switch (info->array.level) {
        case 1:
                /* RAID1 can convert to RAID1 with different disks, or
                 * raid5 with 2 disks
                 */
                if (info->new_level == 1) {
                        if (info->delta_disks == UnSet)
                                /* Don't know what to do */
                                return "no change requested for Growing RAID1";
                        re->level = 1;
                        re->before.data_disks = (info->array.raid_disks +
                                                 info->delta_disks);
                        re->before.layout = 0;
                        re->blocks = 0;
                        re->parity = 0;
                        return NULL;
                }
                if (info->array.raid_disks == 2 &&
                    info->array.raid_disks == 5) {
                        /* simple in-place conversion */
                        re->level = 5;
                        re->parity = 1;
                        re->before.data_disks = 1;
                        re->before.layout = ALGORITHM_LEFT_SYMMETRIC;
                        re->blocks = 0;
                        return NULL;
                }
                /* Could do some multi-stage conversions, but leave that to
                 * later.
                 */
                return "Impossibly level change request for RAID1";

        case 10:
                /* RAID10 can only be converted from near mode to
                 * RAID0 by removing some devices
                 */
                if ((info->array.layout & ~0xff) != 0x100)
                        return "Cannot Grow RAID10 with far/offset layout";
                /* number of devices must be multiple of number of copies */
                if (info->array.raid_disks % (info->array.layout & 0xff))
                        return "RAID10 layout too complex for Grow operation";

                if (info->new_level != 0)
                        return "RAID10 can only be changed to RAID0";
                new_disks = (info->array.raid_disks
                             / (info->array.layout & 0xff));
                if (info->delta_disks != UnSet) {
                        info->delta_disks = (new_disks
                                             - info->array.raid_disks);
                }
                if (info->delta_disks != new_disks - info->array.raid_disks)
                        return "New number of raid-devices impossible for RAID10";
                if (info->new_chunk &&
                    info->new_chunk != info->array.chunk_size)
                        return "Cannot change chunk-size with RAID10 Grow";

                /* looks good */
                re->level = 0;
                re->parity = 0;
                re->before.data_disks = new_disks;
                re->before.layout = 0;
                re->blocks = 0;
                return NULL;

        case 0:
                /* RAID0 can be converted to RAID10, or to RAID456 */
                if (info->new_level == 10) {
                        if (info->new_layout == UnSet && info->delta_disks == UnSet) {
                                /* Assume near=2 layout */
                                info->new_layout = 0x102;
                                info->delta_disks = info->array.raid_disks;
                        }
                        if (info->new_layout == UnSet) {
                                int copies = 1 + (info->delta_disks
                                                  / info->array.raid_disks);
                                if (info->array.raid_disks * (copies-1)
                                    != info->delta_disks)
                                        return "Impossible number of devices"
                                                " for RAID0->RAID10";
                                info->new_layout = 0x100 + copies;
                        }
                        if (info->delta_disks == UnSet) {
                                int copies = info->new_layout & 0xff;
                                if (info->new_layout != 0x100 + copies)
                                        return "New layout impossible"
                                                " for RAID0->RAID10";;
                                info->delta_disks = (copies - 1) *
                                        info->array.raid_disks;
                        }
                        if (info->new_chunk &&
                            info->new_chunk != info->array.chunk_size)
                                return "Cannot change chunk-size with RAID0->RAID10";
                        /* looks good */
                        re->level = 10;
                        re->parity = 0;
                        re->before.data_disks = (info->array.raid_disks +
                                                 info->delta_disks);
                        re->before.layout = info->new_layout;
                        re->blocks = 0;
                        return NULL;
                }

                /* RAID0 can also covert to RAID0/4/5/6 by first converting to
                 * a raid4 style layout of the final level.
                 */
                switch (info->new_level) {
                case 0:
                case 4:
                        re->level = 4;
                        re->before.layout = 0;
                        break;
                case 5:
                        re->level = 5;
                        re->before.layout = ALGORITHM_PARITY_N;
                        break;
                case 6:
                        re->level = 6;
                        re->before.layout = ALGORITHM_PARITY_N;
                        break;
                default:
                        return "Impossible level change requested";
                }
                re->before.data_disks = info->array.raid_disks;
                /* determining 'after' layout happens outside this 'switch' */
                break;

        case 4:
                info->array.layout = ALGORITHM_PARITY_N;
        case 5:
                switch (info->new_level) {
                case 4:
                        re->level = info->array.level;
                        re->before.data_disks = info->array.raid_disks - 1;
                        re->before.layout = info->array.layout;
                        break;
                case 5:
                        re->level = 5;
                        re->before.data_disks = info->array.raid_disks - 1;
                        re->before.layout = info->array.layout;
                        break;
                case 6:
                        re->level = 6;
                        re->before.data_disks = info->array.raid_disks - 1;
                        switch (info->array.layout) {
                        case ALGORITHM_LEFT_ASYMMETRIC:
                                re->before.layout = ALGORITHM_LEFT_ASYMMETRIC_6;
                                break;
                        case ALGORITHM_RIGHT_ASYMMETRIC:
                                re->before.layout = ALGORITHM_RIGHT_ASYMMETRIC_6;
                                break;
                        case ALGORITHM_LEFT_SYMMETRIC:
                                re->before.layout = ALGORITHM_LEFT_SYMMETRIC_6;
                                break;
                        case ALGORITHM_RIGHT_SYMMETRIC:
                                re->before.layout = ALGORITHM_RIGHT_SYMMETRIC_6;
                                break;
                        case ALGORITHM_PARITY_0:
                                re->before.layout = ALGORITHM_PARITY_0_6;
                                break;
                        case ALGORITHM_PARITY_N:
                                re->before.layout = ALGORITHM_PARITY_N_6;
                                break;
                        default:
                                return "Cannot convert an array with this layout";
                        }
                        break;
                case 1:
                        if (info->array.raid_disks != 2)
                                return "Can only convert a 2-device array to RAID1";
                        re->level = 1;
                        re->before.data_disks = 2;
                        re->before.layout = 0;
                        break;
                default:
                        return "Impossible level change requested";
                }
                break;
        case 6:
                switch (info->new_level) {
                case 4:
                case 5:
                case 6:
                        re->level = 6;
                        re->before.data_disks = info->array.raid_disks - 2;
                        re->before.layout = info->array.layout;
                        break;
                default:
                        return "Impossible level change requested";
                }
                break;
        }

        /* If we reached here then it looks like a re-stripe is
         * happening.  We have determined the intermediate level
         * and initial raid_disks/layout and stored these in 're'.
         *
         * We need to deduce the final layout that can be atomically
         * converted to the end state.
         */
        switch (info->new_level) {
        case 0:
                /* We can only get to RAID0 from RAID4 or RAID5
                 * with appropriate layout and one extra device
                 */
                if (re->level != 4 && re->level != 5)
                        return "Cannot covert to RAID0 from this level";
                if (info->delta_disks == UnSet)
                        re->after.data_disks = re->before.data_disks;
                else
                        re->after.data_disks =
                                info->array.raid_disks + info->delta_disks;
                switch (re->level) {
                case 4:
                        re->after.layout = 0 ; break;
                case 5:
                        re->after.layout = ALGORITHM_PARITY_N; break;
                }
                break;

        case 4:
                /* We can only get to RAID4 from RAID5 */
                if (re->level != 4 && re->level != 5)
                        return "Cannot convert to RAID4 from this level";
                if (info->delta_disks == UnSet)
                        re->after.data_disks = re->before.data_disks;
                else
                        re->after.data_disks =
                                re->before.data_disks + info->delta_disks;
                switch (re->level) {
                case 4:
                        re->after.layout = 0 ; break;
                case 5:
                        re->after.layout = ALGORITHM_PARITY_N; break;
                }
                break;

        case 5:
                /* We get to RAID5 for RAID5 or RAID6 */
                if (re->level != 5 && re->level != 6)
                        return "Cannot convert to RAID5 from this level";
                if (info->delta_disks == UnSet)
                        re->after.data_disks = re->before.data_disks;
                else if (re->level == 5)
                        re->after.data_disks =
                                re->before.data_disks + info->delta_disks;
                else
                        re->after.data_disks =
                                info->array.raid_disks + info->delta_disks - 1;
                switch (re->level) {
                case 5:
                        if (info->new_layout == UnSet)
                                re->after.layout = re->before.layout;
                        else
                                re->after.layout = info->new_layout;
                        break;
                case 6:
                        if (info->new_layout == UnSet)
                                info->new_layout = re->before.layout;

                        /* after.layout needs to be raid6 version of new_layout */
                        if (info->new_layout == ALGORITHM_PARITY_N)
                                re->after.layout = ALGORITHM_PARITY_N;
                        else {
                                char layout[40];
                                char *ls = map_num(r5layout, info->new_layout);
                                int l;
                                strcat(strcpy(layout, ls), "-6");
                                l = map_name(r6layout, layout);
                                if (l == UnSet)
                                        return "Cannot find RAID6 layout"
                                                " to convert to";
                                re->after.layout = l;
                        }
                }
                break;

        case 6:
                /* We must already be at level 6 */
                if (re->level != 6)
                        return "Impossible level change";
                if (info->delta_disks == UnSet)
                        re->after.data_disks = re->before.data_disks;
                else
                        re->after.data_disks = (info->array.raid_disks +
                                                info->delta_disks) - 2;
                if (info->new_layout == UnSet)
                        re->after.layout = info->array.layout;
                else
                        re->after.layout = info->new_layout;
                break;
        default:
                return "Impossible level change requested";
        }
        switch (re->level) {
        case 6: re->parity = 2; break;
        case 4:
        case 5: re->parity = 1; break;
        default: re->parity = 0; break;
        }
        /* So we have a restripe operation, we need to calculate the number
         * of blocks per reshape operation.
         */
        if (info->new_chunk == 0)
                info->new_chunk = info->array.chunk_size;
        if (re->after.data_disks == re->before.data_disks &&
            re->after.layout == re->before.layout &&
            info->new_chunk == info->array.chunk_size) {
                /* Nothing to change */
                re->blocks = 0;
                return NULL;
        }
        if (re->after.data_disks == 1 && re->before.data_disks == 1) {
                /* chunks can layout changes make no difference */
                re->blocks = 0;
                return NULL;
        }

        if (re->after.data_disks == re->before.data_disks &&
            get_linux_version() < 2006032)
                return "in-place reshape is not safe before 2.6.32 - sorry.";

        if (re->after.data_disks < re->before.data_disks &&
            get_linux_version() < 2006030)
                return "reshape to fewer devices is not supported before 2.6.32 - sorry.";

        re->blocks = compute_backup_blocks(
                info->new_chunk, info->array.chunk_size,
                re->after.data_disks,
                re->before.data_disks);

        re->new_size = info->component_size * re->after.data_disks;
        return NULL;
}

static int reshape_array(char *container, int fd, char *devname,
                         struct supertype *st, struct mdinfo *info,
                         int force, char *backup_file, int quiet, int forked);
static int reshape_container(char *container, int cfd, char *devname,
                             struct supertype *st, 
                             struct mdinfo *info,
                             int force,
                             char *backup_file,
                             int quiet);
static int child_monitor(int afd, struct mdinfo *sra, struct reshape *reshape,
                         unsigned long stripes,
                         int *fds, unsigned long long *offsets,
                         int dests, int *destfd, unsigned long long *destoffsets);


int Grow_reshape(char *devname, int fd, int quiet, char *backup_file,
                 long long size,
                 int level, char *layout_str, int chunksize, int raid_disks,
                 int force)
{
        /* Make some changes in the shape of an array.
         * The kernel must support the change.
         *
         * There are three different changes.  Each can trigger
         * a resync or recovery so we freeze that until we have
         * requested everything (if kernel supports freezing - 2.6.30).
         * The steps are:
         *  - change size (i.e. component_size)
         *  - change level
         *  - change layout/chunksize/ndisks
         *
         * The last can require a reshape.  It is different on different
         * levels so we need to check the level before actioning it.
         * Some times the level change needs to be requested after the
         * reshape (e.g. raid6->raid5, raid5->raid0)
         *
         */
        struct mdu_array_info_s array;
        int rv = 0;
        struct supertype *st;
        char *subarray = NULL;

        int frozen;
        int changed = 0;
        char *container = NULL;
        char container_buf[20];
        int cfd = -1;

        struct mdinfo info;
        struct mdinfo *sra;

        if (ioctl(fd, GET_ARRAY_INFO, &array) < 0) {
                fprintf(stderr, Name ": %s is not an active md array - aborting\n",
                        devname);
                return 1;
        }

        if (size >= 0 &&
            (chunksize || level!= UnSet || layout_str || raid_disks)) {
                fprintf(stderr, Name ": cannot change component size at the same time "
                        "as other changes.\n"
                        "   Change size first, then check data is intact before "
                        "making other changes.\n");
                return 1;
        }

        if (raid_disks && raid_disks < array.raid_disks && array.level > 1 &&
            get_linux_version() < 2006032 &&
            !check_env("MDADM_FORCE_FEWER")) {
                fprintf(stderr, Name ": reducing the number of devices is not safe before Linux 2.6.32\n"
                        "       Please use a newer kernel\n");
                return 1;
        }

        st = super_by_fd(fd, &subarray);
        if (!st) {
                fprintf(stderr, Name ": Unable to determine metadata format for %s\n", devname);
                return 1;
        }
        if (raid_disks > st->max_devs) {
                fprintf(stderr, Name ": Cannot increase raid-disks on this array"
                        " beyond %d\n", st->max_devs);
                return 1;
        }

        /* in the external case we need to check that the requested reshape is
         * supported, and perform an initial check that the container holds the
         * pre-requisite spare devices (mdmon owns final validation)
         */
        if (st->ss->external) {
                int container_dev;
                int rv;

                if (subarray) {
                        container_dev = st->container_dev;
                        cfd = open_dev_excl(st->container_dev);
                } else {
                        container_dev = st->devnum;
                        close(fd);
                        cfd = open_dev_excl(st->devnum);
                        fd = cfd;
                }
                if (cfd < 0) {
                        fprintf(stderr, Name ": Unable to open container for %s\n",
                                devname);
                        free(subarray);
                        return 1;
                }

                fmt_devname(container_buf, container_dev);
                container = container_buf;

                if (subarray)
                        rv = st->ss->load_container(st, cfd, NULL);
                else
                        rv = st->ss->load_super(st, cfd, NULL);
                if (rv) {
                        fprintf(stderr, Name ": Cannot read superblock for %s\n",
                                devname);
                        free(subarray);
                        return 1;
                }

                if (mdmon_running(container_dev))
                        st->update_tail = &st->updates;
        } 

        if (raid_disks > array.raid_disks &&
            array.spare_disks < (raid_disks - array.raid_disks) &&
            !force) {
                fprintf(stderr,
                        Name ": Need %d spare%s to avoid degraded array,"
                        " and only have %d.\n"
                        "       Use --force to over-ride this check.\n",
                        raid_disks - array.raid_disks, 
                        raid_disks - array.raid_disks == 1 ? "" : "s", 
                        array.spare_disks);
                return 1;
        }

        sra = sysfs_read(fd, 0, GET_LEVEL | GET_DISKS | GET_DEVS | GET_STATE);
        if (sra) {
                if (st->ss->external && subarray == NULL) {
                        array.level = LEVEL_CONTAINER;
                        sra->array.level = LEVEL_CONTAINER;
                }
        } else {
                fprintf(stderr, Name ": failed to read sysfs parameters for %s\n",
                        devname);
                return 1;
        }
        frozen = freeze(st);
        if (frozen < -1) {
                /* freeze() already spewed the reason */
                return 1;
        } else if (frozen < 0) {
                fprintf(stderr, Name ": %s is performing resync/recovery and cannot"
                        " be reshaped\n", devname);
                return 1;
        }

        /* ========= set size =============== */
        if (size >= 0 && (size == 0 || size != array.size)) {
                long long orig_size = array.size;

                if (reshape_super(st, size, UnSet, UnSet, 0, 0, NULL, devname, !quiet)) {
                        rv = 1;
                        goto release;
                }
                sync_metadata(st);
                array.size = size;
                if (array.size != size) {
                        /* got truncated to 32bit, write to
                         * component_size instead
                         */
                        if (sra)
                                rv = sysfs_set_num(sra, NULL,
                                                   "component_size", size);
                        else
                                rv = -1;
                } else
                        rv = ioctl(fd, SET_ARRAY_INFO, &array);
                if (rv != 0) {
                        int err = errno;

                        /* restore metadata */
                        if (reshape_super(st, orig_size, UnSet, UnSet, 0, 0,
                                          NULL, devname, !quiet) == 0)
                                sync_metadata(st);
                        fprintf(stderr, Name ": Cannot set device size for %s: %s\n",
                                devname, strerror(err));
                        if (err == EBUSY && 
                            (array.state & (1<<MD_SB_BITMAP_PRESENT)))
                                fprintf(stderr, "       Bitmap must be removed before size can be changed\n");
                        rv = 1;
                        goto release;
                }
                ioctl(fd, GET_ARRAY_INFO, &array);
                size = get_component_size(fd)/2;
                if (size == 0)
                        size = array.size;
                if (!quiet)
                        fprintf(stderr, Name ": component size of %s has been set to %lluK\n",
                                devname, size);
                changed = 1;
        } else if (array.level != LEVEL_CONTAINER) {
                size = get_component_size(fd)/2;
                if (size == 0)
                        size = array.size;
        }

        /* ========= check for Raid10 -> Raid0 conversion ===============
         * current implementation assumes that following conditions must be met:
         * - far_copies == 1
         * - near_copies == 2
         */
        if (level == 0 && array.level == 10 && sra &&
            array.layout == ((1 << 8) + 2) && !(array.raid_disks & 1)) {
                int err;
                err = remove_disks_on_raid10_to_raid0_takeover(st, sra, array.layout);
                if (err) {
                        dprintf(Name": Array cannot be reshaped\n");
                        if (cfd > -1)
                                close(cfd);
                        rv = 1;
                        goto release;
                }
        }

        info.array = array;
        sysfs_init(&info, fd, NoMdDev);
        info.component_size = size*2;
        info.new_level = level;
        info.new_chunk = chunksize * 1024;
        if (raid_disks)
                info.delta_disks = raid_disks - info.array.raid_disks;
        else
                info.delta_disks = UnSet;
        if (layout_str == NULL) {
                info.new_layout = UnSet;
                if (info.array.level == 6 &&
                    (info.new_level == 6 || info.new_level == UnSet) &&
                    info.array.layout >= 16) {
                        fprintf(stderr, Name
                                ": %s has a non-standard layout.  If you"
                                " wish to preserve this\n"
                                "      during the reshape, please specify"
                                " --layout=preserve\n"
                                "      If you want to change it, specify a"
                                " layout or use --layout=normalise\n",
                                devname);
                        rv = 1;
                        goto release;
                }
        } else if (strcmp(layout_str, "normalise") == 0 ||
                 strcmp(layout_str, "normalize") == 0) {
                /* If we have a -6 RAID6 layout, remove the '-6'. */
                info.new_layout = UnSet;
                if (info.array.level == 6 && info.new_level == UnSet) {
                        char l[40], *h;
                        strcpy(l, map_num(r6layout, info.array.layout));
                        h = strrchr(l, '-');
                        if (h && strcmp(h, "-6") == 0) {
                                *h = 0;
                                info.new_layout = map_name(r6layout, l);
                        }
                }
        } else if (strcmp(layout_str, "preserve") == 0) {
                info.new_layout = UnSet;
        } else {
                int l = info.new_level;
                if (l == UnSet)
                        l = info.array.level;
                switch (l) {
                case 5:
                        info.new_layout = map_name(r5layout, layout_str);
                        break;
                case 6:
                        info.new_layout = map_name(r6layout, layout_str);
                        break;
                case 10:
                        info.new_layout = parse_layout_10(layout_str);
                        break;
                case LEVEL_FAULTY:
                        info.new_layout = parse_layout_faulty(layout_str);
                        break;
                default:
                        fprintf(stderr, Name ": layout not meaningful"
                                " with this level\n");
                        rv = 1;
                        goto release;
                }
                if (info.new_layout == UnSet) {
                        fprintf(stderr, Name ": layout %s not understood"
                                " for this level\n",
                                layout_str);
                        rv = 1;
                        goto release;
                }
        }

        if (array.level == LEVEL_CONTAINER) {
                /* This change is to be applied to every array in the
                 * container.  This is only needed when the metadata imposes
                 * restraints of the various arrays in the container.
                 * Currently we only know that IMSM requires all arrays
                 * to have the same number of devices so changing the
                 * number of devices (On-Line Capacity Expansion) must be
                 * performed at the level of the container
                 */
                rv = reshape_container(container, fd, devname, st, &info,
                                       force, backup_file, quiet);
        } else {
                /* Impose these changes on a single array.  First
                 * check that the metadata is OK with the change. */

                if (reshape_super(st, info.component_size, info.new_level,
                                  info.new_layout, info.new_chunk,
                                  info.array.raid_disks + info.delta_disks,
                                  backup_file, devname, quiet)) {
                        rv = 1;
                        goto release;
                }
                sync_metadata(st);
                rv = reshape_array(container, fd, devname, st, &info, force,
                                   backup_file, quiet, 0);
        }
        /* reshape_* released the array */
        return rv;
release:
        unfreeze(st, frozen);
        return rv;
}

static int reshape_array(char *container, int fd, char *devname,
                         struct supertype *st, struct mdinfo *info,
                         int force,
                         char *backup_file, int quiet, int forked)
{
        struct reshape reshape;
        int spares_needed;
        char *msg;
        int orig_level = UnSet;
        int disks, odisks;

        struct mdu_array_info_s array;
        char *c;
        int rv = 0;

        int *fdlist;
        unsigned long long *offsets;
        int d;
        int nrdisks;
        int err;
        int frozen;
        unsigned long blocks, stripes;
        unsigned long cache;
        unsigned long long array_size;
        int done;
        struct mdinfo *sra, *sd;

        msg = analyse_change(info, &reshape);
        if (msg) {
                fprintf(stderr, Name ": %s\n", msg);
                return 1;
        }
        if (ioctl(fd, GET_ARRAY_INFO, &array) != 0) {
                dprintf("Canot get array information.\n");
                return 1;
        }
        spares_needed = max(reshape.before.data_disks,
                            reshape.after.data_disks)
                + reshape.parity - array.raid_disks;

        if (!force && spares_needed > info->array.spare_disks) {
                fprintf(stderr,
                        Name ": Need %d spare%s to avoid degraded array,"
                        " and only have %d.\n"
                        "       Use --force to over-ride this check.\n",
                        spares_needed,
                        spares_needed == 1 ? "" : "s", 
                        info->array.spare_disks);
                return 1;
        }

        if (reshape.level != info->array.level) {
                char *c = map_num(pers, reshape.level);
                int err;
                if (c == NULL)
                        return 1; /* This should not be possible */

                err = sysfs_set_str(info, NULL, "level", c);
                if (err) {
                        err = errno;
                        fprintf(stderr, Name ": %s: could not set level to %s\n",
                                devname, c);
                        if (err == EBUSY && 
                            (info->array.state & (1<<MD_SB_BITMAP_PRESENT)))
                                fprintf(stderr, "       Bitmap must be removed"
                                        " before level can be changed\n");
                        return 1;
                }
                if (!quiet)
                        fprintf(stderr, Name ": level of %s changed to %s\n",
                                devname, c);    
                orig_level = info->array.level;
        }

        if (reshape.level > 0 && st->ss->external &&
            !mdmon_running(st->container_dev)) {
                start_mdmon(st->container_dev);
                ping_monitor(container);
        }

        /* ->reshape_super might have chosen some spares from the
         * container that it wants to be part of the new array.
         * We can collect them with ->container_content and give
         * them to the kernel.
         */
        if (st->ss->reshape_super && st->ss->container_content) {
                char *subarray = strchr(info->text_version+1, '/')+1;
                struct mdinfo *info2 =
                        st->ss->container_content(st, subarray);
                struct mdinfo *d;

                if (info2)
                        for (d = info2->devs; d; d = d->next) {
                                if (d->disk.state == 0 &&
                                    d->disk.raid_disk >= 0) {
                                        /* This is a spare that wants to
                                         * be part of the array.
                                         */
                                        add_disk(fd, st, info2, d);
                                }
                        }
                sysfs_free(info2);
        }

        if (reshape.blocks == 0) {
                /* No restriping needed, but we might need to impose
                 * some more changes: layout, raid_disks, chunk_size
                 */
                if (info->new_layout != UnSet &&
                    info->new_layout != info->array.layout) {
                        info->array.layout = info->new_layout;
                        if (ioctl(fd, SET_ARRAY_INFO, &info->array) != 0) {
                                fprintf(stderr, Name ": failed to set new layout\n");
                                rv = 1;
                        } else if (!quiet)
                                printf("layout for %s set to %d\n",
                                       devname, info->array.layout);
                }
                if (info->delta_disks != UnSet &&
                    info->delta_disks != 0) {
                        info->array.raid_disks += info->delta_disks;
                        if (ioctl(fd, SET_ARRAY_INFO, &info->array) != 0) {
                                fprintf(stderr, Name ": failed to set raid disks\n");
                                rv = 1;
                        } else if (!quiet)
                                printf("raid_disks for %s set to %d\n",
                                       devname, info->array.raid_disks);
                }
                if (info->new_chunk != 0 &&
                    info->new_chunk != info->array.chunk_size) {
                        if (sysfs_set_num(info, NULL,
                                          "chunk_size", info->new_chunk) != 0) {
                                fprintf(stderr, Name ": failed to set chunk size\n");
                                rv = 1;
                        } else if (!quiet)
                                printf("chunk size for %s set to %d\n",
                                       devname, info->array.chunk_size);
                }

                return rv;
        }

        /*
         * There are three possibilities.
         * 1/ The array will shrink.
         *    We need to ensure the reshape will pause before reaching
         *    the 'critical section'.  We also need to fork and wait for
         *    that to happen.  When it does we 
         *       suspend/backup/complete/unfreeze
         *
         * 2/ The array will not change size.
         *    This requires that we keep a backup of a sliding window
         *    so that we can restore data after a crash.  So we need
         *    to fork and monitor progress.
         *    In future we will allow the data_offset to change, so
         *    a sliding backup becomes unnecessary.
         *
         * 3/ The array will grow. This is relatively easy.
         *    However the kernel's restripe routines will cheerfully
         *    overwrite some early data before it is safe.  So we
         *    need to make a backup of the early parts of the array
         *    and be ready to restore it if rebuild aborts very early.
         *    For externally managed metadata, we still need a forked
         *    child to monitor the reshape and suspend IO over the region
         *    that is being reshaped.
         *
         *    We backup data by writing it to one spare, or to a
         *    file which was given on command line.
         *
         * In each case, we first make sure that storage is available
         * for the required backup.
         * Then we:
         *   -  request the shape change.
         *   -  fork to handle backup etc.
         */

        /* Check that we can hold all the data */
        get_dev_size(fd, NULL, &array_size);
        if (reshape.new_size < (array_size/512)) {
                fprintf(stderr,
                        Name ": this change will reduce the size of the array.\n"
                        "       use --grow --array-size first to truncate array.\n"
                        "       e.g. mdadm --grow %s --array-size %llu\n",
                        devname, reshape.new_size/2);
                rv = 1;
                goto release;
        }

        sra = sysfs_read(fd, 0,
                         GET_COMPONENT|GET_DEVS|GET_OFFSET|GET_STATE|GET_CHUNK|
                         GET_CACHE);

        if (!sra) {
                fprintf(stderr, Name ": %s: Cannot get array details from sysfs\n",
                        devname);
                rv = 1;
                goto release;
        }

        /* Decide how many blocks (sectors) for a reshape
         * unit.  The number we have so far is just a minimum
         */
        blocks = reshape.blocks;
        if (reshape.before.data_disks == 
            reshape.after.data_disks) {
                /* Make 'blocks' bigger for better throughput, but
                 * not so big that we reject it below.
                 * Try for 16 megabytes
                 */
                while (blocks * 32 < sra->component_size &&
                       blocks < 16*1024*2)
                        blocks *= 2;
        } else
                fprintf(stderr, Name ": Need to backup %luK of critical "
                        "section..\n", blocks/2);

        if (blocks >= sra->component_size/2) {
                fprintf(stderr, Name ": %s: Something wrong"
                        " - reshape aborted\n",
                        devname);
                rv = 1;
                goto release;
        }

        /* Now we need to open all these devices so we can read/write.
         */
        nrdisks = array.raid_disks + sra->array.spare_disks;
        fdlist = malloc((1+nrdisks) * sizeof(int));
        offsets = malloc((1+nrdisks) * sizeof(offsets[0]));
        if (!fdlist || !offsets) {
                fprintf(stderr, Name ": malloc failed: grow aborted\n");
                rv = 1;
                goto release;
        }

        d = reshape_prepare_fdlist(devname, sra, array.raid_disks,
                                   nrdisks, blocks, backup_file,
                                   fdlist, offsets);
        if (d < 0) {
                rv = 1;
                goto release;
        }
        if (backup_file == NULL) {
                if (reshape.after.data_disks <= reshape.before.data_disks) {
                        fprintf(stderr,
                                Name ": %s: Cannot grow - need backup-file\n", 
                                devname);
                        rv = 1;
                        goto release;
                } else if (sra->array.spare_disks == 0) {
                        fprintf(stderr, Name ": %s: Cannot grow - need a spare or "
                                "backup-file to backup critical section\n",
                                devname);
                        rv = 1;
                        goto release;
                }
        } else {
                if (!reshape_open_backup_file(backup_file, fd, devname,
                                              (signed)blocks,
                                              fdlist+d, offsets+d)) {
                        rv = 1;
                        goto release;
                }
                d++;
        }

        /* lastly, check that the internal stripe cache is
         * large enough, or it won't work.
         * It must hold at least 4 stripes of the larger
         * chunk size
         */
        cache = max(info->array.chunk_size, info->new_chunk);
        cache *= 4; /* 4 stripes minimum */
        cache /= 512; /* convert to sectors */
        disks = min(reshape.before.data_disks, reshape.after.data_disks);
        /* make sure there is room for 'blocks' with a bit to spare */
        if (cache < 16 + blocks / disks)
                cache = 16 + blocks / disks;
        cache /= (4096/512); /* Covert from sectors to pages */

        if (sra->cache_size < cache)
                subarray_set_num(container, sra, "stripe_cache_size",
                                 cache+1);

        /* Right, everything seems fine. Let's kick things off.
         * If only changing raid_disks, use ioctl, else use
         * sysfs.
         */
        sync_metadata(st);

        if (info->array.chunk_size == info->new_chunk &&
            reshape.before.layout == reshape.after.layout &&
            st->ss->external == 0) {
                array.raid_disks = reshape.after.data_disks + reshape.parity;
                if (ioctl(fd, SET_ARRAY_INFO, &array) != 0) {
                        int err = errno;
                        rv = 1;
                        fprintf(stderr,
                                Name ": Cannot set device shape for %s: %s\n",
                                devname, strerror(errno));

                        if (err == EBUSY && 
                            (array.state & (1<<MD_SB_BITMAP_PRESENT)))
                                fprintf(stderr,
                                        "       Bitmap must be removed before"
                                        " shape can be changed\n");

                        goto release;
                }
        } else {
                /* set them all just in case some old 'new_*' value
                 * persists from some earlier problem
                 */
                int err = err; /* only used if rv==1, and always set if
                                * rv==1, so initialisation not needed,
                                * despite gcc warning
                                */
                if (sysfs_set_num(sra, NULL, "chunk_size", info->new_chunk) < 0)
                        rv = 1, err = errno;
                if (!rv && sysfs_set_num(sra, NULL, "layout", 
                                         reshape.after.layout) < 0)
                        rv = 1, err = errno;
                if (!rv && subarray_set_num(container, sra, "raid_disks",
                                            reshape.after.data_disks +
                                            reshape.parity) < 0)
                        rv = 1, err = errno;
                if (rv) {
                        fprintf(stderr, Name ": Cannot set device shape for %s\n",
                                devname);

                        if (err == EBUSY && 
                            (array.state & (1<<MD_SB_BITMAP_PRESENT)))
                                fprintf(stderr,
                                        "       Bitmap must be removed before"
                                        " shape can be changed\n");
                        goto release;
                }
        }

        start_reshape(sra);
        if (st->ss->external) {
                /* metadata handler takes it from here */
                ping_manager(container);
                st->ss->manage_reshape(st, backup_file);
                frozen = 0;
                goto release;
        }

        /* set up the backup-super-block.  This requires the
         * uuid from the array.
         */
        /* Find a superblock */
        for (sd = sra->devs; sd; sd = sd->next) {
                char *dn;
                int devfd;
                int ok;
                if (sd->disk.state & (1<<MD_DISK_FAULTY))
                        continue;
                dn = map_dev(sd->disk.major, sd->disk.minor, 1);
                devfd = dev_open(dn, O_RDONLY);
                if (devfd < 0)
                        continue;
                ok = st->ss->load_super(st, devfd, NULL);
                close(devfd);
                if (ok >= 0)
                        break;
        }
        if (!sd) {
                fprintf(stderr, Name ": %s: Cannot find a superblock\n",
                        devname);
                rv = 1;
                abort_reshape(sra);
                goto release;
        }

        memset(&bsb, 0, 512);
        memcpy(bsb.magic, "md_backup_data-1", 16);
        st->ss->uuid_from_super(st, (int*)&bsb.set_uuid);
        bsb.mtime = __cpu_to_le64(time(0));
        bsb.devstart2 = blocks;

        stripes = reshape.blocks / (info->array.chunk_size/512) /
                reshape.before.data_disks;

        /* Now we just need to kick off the reshape and watch, while
         * handling backups of the data...
         * This is all done by a forked background process.
         */
        switch(forked ? 0 : fork()) {
        case 0:
                close(fd);
                if (check_env("MDADM_GROW_VERIFY"))
                        fd = open(devname, O_RDONLY | O_DIRECT);
                else
                        fd = -1;
                mlockall(MCL_FUTURE);

                odisks = reshape.before.data_disks + reshape.parity;

                done = child_monitor(fd, sra, &reshape, stripes,
                                     fdlist, offsets,
                                     d - odisks, fdlist+odisks, offsets+odisks);

                if (backup_file && done)
                        unlink(backup_file);
                if (!done) {
                        abort_reshape(sra);
                        goto out;
                }
                /* set new array size if required customer_array_size is used
                 * by this metadata.
                 */
                if (reshape.before.data_disks !=
                    reshape.after.data_disks &&
                    info->custom_array_size) {
                        struct mdinfo *info2;
                        char *subarray = strchr(info->text_version+1, '/')+1;

                        wait_reshape(sra);
                        ping_monitor(container);

                        info2 = st->ss->container_content(st, subarray);
                        if (info2) {
                                unsigned long long current_size = 0;
                                unsigned long long new_size =
                                        info2->custom_array_size/2;

                                if (sysfs_get_ll(sra,
                                                 NULL,
                                                 "array_size",
                                                 &current_size) == 0 &&
                                    new_size > current_size) {
                                        if (sysfs_set_num(sra, NULL,
                                                          "array_size", new_size)
                                            < 0)
                                                dprintf("Error: Cannot"
                                                        " set array size");
                                        else
                                                dprintf("Array size "
                                                        "changed");
                                        dprintf(" from %llu to %llu.\n",
                                                current_size, new_size);
                                }
                                sysfs_free(info2);
                        }
                }

                if (info->new_level != reshape.level) {
                        /* We need to wait for the reshape to finish
                         * (which will have happened unless
                         * odata < ndata) and then set the level
                         */

                        if (reshape.before.data_disks <
                            reshape.after.data_disks)
                                wait_reshape(sra);

                        c = map_num(pers, info->new_level);
                        if (c == NULL)
                                goto out;/* not possible */

                        err = sysfs_set_str(sra, NULL, "level", c);
                        if (err)
                                fprintf(stderr, Name\
                                        ": %s: could not set level "
                                        "to %s\n", devname, c);
                }
        out:
                if (forked)
                        return 0;
                exit(0);
        case -1:
                fprintf(stderr, Name ": Cannot run child to monitor reshape: %s\n",
                        strerror(errno));
                rv = 1;
                abort_reshape(sra);
                break;
        default:
                /* The child will take care of unfreezing the array */
                frozen = 0;
                break;
        }


 release:
        if (!rv) {
                if (container)
                        ping_monitor(container);
                if (st->ss->external) {
                        /* Re-load the metadata as much could have changed */
                        int cfd = open_dev(st->container_dev);
                        if (cfd >= 0) {
                                st->ss->free_super(st);
                                st->ss->load_container(st, cfd, container);
                                close(cfd);
                        }
                }
        }
        if (rv && orig_level != UnSet && sra) {
                c = map_num(pers, orig_level);
                if (c && sysfs_set_str(sra, NULL, "level", c) == 0)
                        fprintf(stderr, Name ": aborting level change\n");
        }
        unfreeze(st, frozen);
        return rv;
}

int reshape_container(char *container, int cfd, char *devname,
                      struct supertype *st, 
                      struct mdinfo *info,
                      int force,
                      char *backup_file,
                      int quiet)
{
        struct mdinfo *cc = NULL;

        if (reshape_super(st, info->component_size, info->new_level,
                          info->new_layout, info->new_chunk,
                          info->array.raid_disks + info->delta_disks,
                          backup_file, devname, quiet))
                return 1;

        sync_metadata(st);

        /* ping monitor to be sure that update is on disk
         */
        ping_monitor(container);

        switch (fork()) {
        case -1: /* error */
                perror("Cannot fork to complete reshape\n");
                return 1;
        default: /* parent */
                printf(Name ": multi-array reshape continues in background\n");
                return 0;
        case 0: /* child */
                break;
        }

        while(1) {
                /* For each member array with reshape_active,
                 * we need to perform the reshape.
                 * We pick the first array that needs reshaping and
                 * reshape it.  reshape_array() will re-read the metadata
                 * so the next time through a different array should be
                 * ready for reshape.
                 */
                struct mdinfo *content;
                int rv;
                int fd;
                struct mdstat_ent *mdstat;
                char *adev;

                sysfs_free(cc);

                cc = st->ss->container_content(st, NULL);

                for (content = cc; content ; content = content->next) {
                        char *subarray;
                        if (!content->reshape_active)
                                continue;

                        subarray = strchr(content->text_version+1, '/')+1;
                        mdstat = mdstat_by_subdev(subarray,
                                                  devname2devnum(container));
                        if (!mdstat)
                                continue;
                        break;
                }
                if (!content)
                        break;

                fd = open_dev_excl(mdstat->devnum);
                if (fd < 0)
                        break;
                adev = map_dev(dev2major(mdstat->devnum),
                               dev2minor(mdstat->devnum),
                               0);
                if (!adev)
                        adev = content->text_version;

                sysfs_init(content, fd, mdstat->devnum);

                rv = reshape_array(container, fd, adev, st,
                                   content, force,
                                   backup_file, quiet, 1);
                close(fd);
                if (rv)
                        break;
        }
        sysfs_free(cc);
        exit(0);
}

/*
 * We run a child process in the background which performs the following
 * steps:
 *   - wait for resync to reach a certain point
 *   - suspend io to the following section
 *   - backup that section
 *   - allow resync to proceed further
 *   - resume io
 *   - discard the backup.
 *
 * When are combined in slightly different ways in the three cases.
 * Grow:
 *   - suspend/backup/allow/wait/resume/discard
 * Shrink:
 *   - allow/wait/suspend/backup/allow/wait/resume/discard
 * same-size:
 *   - wait/resume/discard/suspend/backup/allow
 *
 * suspend/backup/allow always come together
 * wait/resume/discard do too.
 * For the same-size case we have two backups to improve flow.
 * 
 */

int progress_reshape(struct mdinfo *info, struct reshape *reshape,
                     unsigned long long backup_point,
                     unsigned long long wait_point,
                     unsigned long long *suspend_point,
                     unsigned long long *reshape_completed)
{
        /* This function is called repeatedly by the reshape manager.
         * It determines how much progress can safely be made and allows
         * that progress.
         * - 'info' identifies the array and particularly records in
         *    ->reshape_progress the metadata's knowledge of progress
         *      This is a sector offset from the start of the array
         *      of the next array block to be relocated.  This number
         *      may increase from 0 or decrease from array_size, depending
         *      on the type of reshape that is happening.
         *    Note that in contrast, 'sync_completed' is a block count of the
         *    reshape so far.  It gives the distance between the start point
         *    (head or tail of device) and the next place that data will be
         *    written.  It always increases.
         * - 'reshape' is the structure created by analyse_change
         * - 'backup_point' shows how much the metadata manager has backed-up
         *   data.  For reshapes with increasing progress, it is the next address
         *   to be backed up, previous addresses have been backed-up.  For
         *   decreasing progress, it is the earliest address that has been
         *   backed up - later address are also backed up.
         *   So addresses between reshape_progress and backup_point are
         *   backed up providing those are in the 'correct' order.
         * - 'wait_point' is an array address.  When reshape_completed
         *   passes this point, progress_reshape should return.  It might
         *   return earlier if it determines that ->reshape_progress needs
         *   to be updated or further backup is needed.
         * - suspend_point is maintained by progress_reshape and the caller
         *   should not touch it except to initialise to zero.
         *   It is an array address and it only increases in 2.6.37 and earlier.
         *   This makes it difficult to handle reducing reshapes with
         *   external metadata.
         *   However:  it is similar to backup_point in that it records the
         *     other end of a suspended region from  reshape_progress.
         *     it is moved to extend the region that is safe to backup and/or
         *     reshape
         * - reshape_completed is read from sysfs and returned.  The caller
         *   should copy this into ->reshape_progress when it has reason to
         *   believe that the metadata knows this, and any backup outside this
         *   has been erased.
         *
         * Return value is:
         *   1 if more data from backup_point - but only as far as suspend_point,
         *     should be backed up
         *   0 if things are progressing smoothly
         *  -1 if the reshape is finished, either because it is all done,
         *     or due to an error.
         */

        int advancing = (reshape->after.data_disks
                         >= reshape->before.data_disks);
        int need_backup = (reshape->after.data_disks
                           == reshape->before.data_disks);
        unsigned long long read_offset, write_offset;
        unsigned long long read_range, write_range;
        unsigned long long max_progress, target, completed;
        int fd;

        /* First, we unsuspend any region that is now known to be safe.
         * If suspend_point is on the 'wrong' side of reshape_progress, then
         * we don't have or need suspension at the moment.  This is true for
         * native metadata when we don't need to back-up.
         */
        if (advancing) {
                if (info->reshape_progress < *suspend_point)
                        sysfs_set_num(info, NULL, "suspend_lo",
                                      info->reshape_progress);
        } else {
                /* Note: this won't work in 2.6.37 and before.
                 * Something somewhere should make sure we don't need it!
                 */
                if (info->reshape_progress > *suspend_point)
                        sysfs_set_num(info, NULL, "suspend_hi",
                                      info->reshape_progress);
        }

        /* Now work out how far it is safe to progress.
         * If the read_offset for ->reshape_progress is less than
         * 'blocks' beyond the write_offset, we can only progress as far
         * as a backup.
         * Otherwise we can progress until the write_offset for the new location
         * reaches (within 'blocks' of) the read_offset at the current location.
         * However that region must be suspended unless we are using native
         * metadata.
         * If we need to suspend more, we limit it to 128M per device, which is
         * rather arbitrary and should be some time-based calculation.
         */
        write_offset = info->reshape_progress / reshape->before.data_disks;
        read_offset = info->reshape_progress / reshape->after.data_disks;
        write_range = reshape->blocks / reshape->before.data_disks;
        read_range = reshape->blocks / reshape->after.data_disks;
        if (advancing) {
                if (read_offset < write_offset + write_range) {
                        max_progress = backup_point;
                        if (max_progress <= info->reshape_progress)
                                need_backup = 1;
                } else {
                        max_progress =
                                (read_offset - write_range) *
                                reshape->before.data_disks;
                }
        } else {
                if (read_offset > write_offset - write_range) {
                        max_progress = backup_point;
                        if (max_progress >= info->reshape_progress)
                                need_backup = 1;
                } else {
                        max_progress =
                                (read_offset + write_range) *
                                reshape->before.data_disks;
                        /* If we are using internal metadata, then we can
                         * progress all the way to the suspend_point without
                         * worrying about backing-up/suspending along the
                         * way.
                         */
                        if (max_progress < *suspend_point &&
                                info->array.major_version >= 0)
                                max_progress = *suspend_point;
                }
        }

        /* We know it is safe to progress to 'max_progress' providing
         * it is suspended or we are using native metadata.
         * Consider extending suspend_point 128M per device if it
         * is less than 64M per device beyond reshape_progress.
         * But always do a multiple of 'blocks'
         */
        target = 64*1024*2 * min(reshape->before.data_disks,
                                  reshape->after.data_disks);
        target /= reshape->blocks;
        if (target < 2)
                target = 2;
        target *= reshape->blocks;

        /* For externally managed metadata we always need to suspend IO to
         * the area being reshaped so we regularly push suspend_point forward.
         * For native metadata we only need the suspend if we are going to do
         * a backup.
         */
        if (advancing) {
                if ((need_backup || info->array.major_version < 0) &&
                    *suspend_point < info->reshape_progress + target) {
                        if (max_progress < *suspend_point + 2 * target)
                                *suspend_point = max_progress;
                        else
                                *suspend_point += 2 * target;
                        sysfs_set_num(info, NULL, "suspend_hi", *suspend_point);
                        max_progress = *suspend_point;
                }
        } else {
                if ((need_backup || info->array.major_version < 0) &&
                    *suspend_point > info->reshape_progress - target) {
                        if (max_progress > *suspend_point - 2 * target)
                                *suspend_point = max_progress;
                        else
                                *suspend_point -= 2 * target;
                        sysfs_set_num(info, NULL, "suspend_lo", *suspend_point);
                        max_progress = *suspend_point;
                }
        }

        /* now set sync_max to allow that progress. sync_max, like
         * sync_completed is a count of sectors written per device, so
         * we find the difference between max_progress and the start point,
         * and divide that by after.data_disks to get a sync_max
         * number.
         * At the same time we convert wait_point to a similar number
         * for comparing against sync_completed.
         */
        if (!advancing) {
                max_progress = info->component_size * reshape->after.data_disks
                        - max_progress;
                wait_point = info->component_size * reshape->after.data_disks
                        - wait_point;
        }
        max_progress /= reshape->after.data_disks;
        wait_point /= reshape->after.data_disks;

        sysfs_set_num(info, NULL, "sync_max", max_progress);

        /* Now wait.  If we have already reached the point that we were
         * asked to wait to, don't wait at all, else wait for any change.
         * We need to select on 'sync_completed' as that is the place that
         * notifications happen, but we are really interested in
         * 'reshape_position'
         */
        fd = sysfs_get_fd(info, NULL, "sync_completed");
        if (fd < 0)
                return -1;

        if (sysfs_fd_get_ll(fd, &completed) < 0) {
                close(fd);
                return -1;
        }
        while (completed < max_progress && completed < wait_point) {
                /* Check that sync_action is still 'reshape' to avoid
                 * waiting forever on a dead array
                 */
                char action[20];
                fd_set rfds;
                if (sysfs_get_str(info, NULL, "sync_action",
                                  action, 20) <= 0 ||
                    strncmp(action, "reshape", 7) != 0)
                        break;
                FD_ZERO(&rfds);
                FD_SET(fd, &rfds);
                select(fd+1, NULL, NULL, &rfds, NULL);
                if (sysfs_fd_get_ll(fd, &completed) < 0) {
                        close(fd);
                        return -1;
                }
        }
        /* Convert 'completed' back in to a 'progress' number */
        completed *= reshape->after.data_disks;
        if (!advancing) {
                completed = info->component_size * reshape->after.data_disks
                        - completed;
        }
        *reshape_completed = completed;
        
        close(fd);

        /* We return the need_backup flag.  Caller will decide
         * how much (a multiple of ->blocks) and will adjust
         * suspend_{lo,hi} and suspend_point.
         */
        return need_backup;
}


/* FIXME return status is never checked */
static int grow_backup(struct mdinfo *sra,
                unsigned long long offset, /* per device */
                unsigned long stripes, /* per device, in old chunks */
                int *sources, unsigned long long *offsets,
                int disks, int chunk, int level, int layout,
                int dests, int *destfd, unsigned long long *destoffsets,
                int part, int *degraded,
                char *buf)
{
        /* Backup 'blocks' sectors at 'offset' on each device of the array,
         * to storage 'destfd' (offset 'destoffsets'), after first
         * suspending IO.  Then allow resync to continue
         * over the suspended section.
         * Use part 'part' of the backup-super-block.
         */
        int odata = disks;
        int rv = 0;
        int i;
        unsigned long long ll;
        int new_degraded;
        //printf("offset %llu\n", offset);
        if (level >= 4)
                odata--;
        if (level == 6)
                odata--;

        /* Check that array hasn't become degraded, else we might backup the wrong data */
        sysfs_get_ll(sra, NULL, "degraded", &ll);
        new_degraded = (int)ll;
        if (new_degraded != *degraded) {
                /* check each device to ensure it is still working */
                struct mdinfo *sd;
                for (sd = sra->devs ; sd ; sd = sd->next) {
                        if (sd->disk.state & (1<<MD_DISK_FAULTY))
                                continue;
                        if (sd->disk.state & (1<<MD_DISK_SYNC)) {
                                char sbuf[20];
                                if (sysfs_get_str(sra, sd, "state", sbuf, 20) < 0 ||
                                    strstr(sbuf, "faulty") ||
                                    strstr(sbuf, "in_sync") == NULL) {
                                        /* this device is dead */
                                        sd->disk.state = (1<<MD_DISK_FAULTY);
                                        if (sd->disk.raid_disk >= 0 &&
                                            sources[sd->disk.raid_disk] >= 0) {
                                                close(sources[sd->disk.raid_disk]);
                                                sources[sd->disk.raid_disk] = -1;
                                        }
                                }
                        }
                }
                *degraded = new_degraded;
        }
        if (part) {
                bsb.arraystart2 = __cpu_to_le64(offset * odata);
                bsb.length2 = __cpu_to_le64(stripes * (chunk/512) * odata);
        } else {
                bsb.arraystart = __cpu_to_le64(offset * odata);
                bsb.length = __cpu_to_le64(stripes * (chunk/512) * odata);
        }
        if (part)
                bsb.magic[15] = '2';
        for (i = 0; i < dests; i++)
                if (part)
                        lseek64(destfd[i], destoffsets[i] + __le64_to_cpu(bsb.devstart2)*512, 0);
                else
                        lseek64(destfd[i], destoffsets[i], 0);

        rv = save_stripes(sources, offsets, 
                          disks, chunk, level, layout,
                          dests, destfd,
                          offset*512*odata, stripes * chunk * odata,
                          buf);

        if (rv)
                return rv;
        bsb.mtime = __cpu_to_le64(time(0));
        for (i = 0; i < dests; i++) {
                bsb.devstart = __cpu_to_le64(destoffsets[i]/512);

                bsb.sb_csum = bsb_csum((char*)&bsb, ((char*)&bsb.sb_csum)-((char*)&bsb));
                if (memcmp(bsb.magic, "md_backup_data-2", 16) == 0)
                        bsb.sb_csum2 = bsb_csum((char*)&bsb,
                                                ((char*)&bsb.sb_csum2)-((char*)&bsb));

                rv = -1;
                if ((unsigned long long)lseek64(destfd[i], destoffsets[i] - 4096, 0)
                    != destoffsets[i] - 4096)
                        break;
                if (write(destfd[i], &bsb, 512) != 512)
                        break;
                if (destoffsets[i] > 4096) {
                        if ((unsigned long long)lseek64(destfd[i], destoffsets[i]+stripes*chunk*odata, 0) !=
                            destoffsets[i]+stripes*chunk*odata)
                                break;
                        if (write(destfd[i], &bsb, 512) != 512)
                                break;
                }
                fsync(destfd[i]);
                rv = 0;
        }

        return rv;
}

/* in 2.6.30, the value reported by sync_completed can be
 * less that it should be by one stripe.
 * This only happens when reshape hits sync_max and pauses.
 * So allow wait_backup to either extent sync_max further
 * than strictly necessary, or return before the
 * sync has got quite as far as we would really like.
 * This is what 'blocks2' is for.
 * The various caller give appropriate values so that
 * every works.
 */
/* FIXME return value is often ignored */
static int forget_backup(
                int dests, int *destfd, unsigned long long *destoffsets,
                int part)
{
        /* 
         * Erase backup 'part' (which is 0 or 1)
         */
        int i;
        int rv;

        if (part) {
                bsb.arraystart2 = __cpu_to_le64(0);
                bsb.length2 = __cpu_to_le64(0);
        } else {
                bsb.arraystart = __cpu_to_le64(0);
                bsb.length = __cpu_to_le64(0);
        }
        bsb.mtime = __cpu_to_le64(time(0));
        rv = 0;
        for (i = 0; i < dests; i++) {
                bsb.devstart = __cpu_to_le64(destoffsets[i]/512);
                bsb.sb_csum = bsb_csum((char*)&bsb, ((char*)&bsb.sb_csum)-((char*)&bsb));
                if (memcmp(bsb.magic, "md_backup_data-2", 16) == 0)
                        bsb.sb_csum2 = bsb_csum((char*)&bsb,
                                                ((char*)&bsb.sb_csum2)-((char*)&bsb));
                if ((unsigned long long)lseek64(destfd[i], destoffsets[i]-4096, 0) !=
                    destoffsets[i]-4096)
                        rv = -1;
                if (rv == 0 && 
                    write(destfd[i], &bsb, 512) != 512)
                        rv = -1;
                fsync(destfd[i]);
        }
        return rv;
}

static void fail(char *msg)
{
        int rv;
        rv = (write(2, msg, strlen(msg)) != (int)strlen(msg));
        rv |= (write(2, "\n", 1) != 1);
        exit(rv ? 1 : 2);
}

static char *abuf, *bbuf;
static unsigned long long abuflen;
static void validate(int afd, int bfd, unsigned long long offset)
{
        /* check that the data in the backup against the array.
         * This is only used for regression testing and should not
         * be used while the array is active
         */
        if (afd < 0)
                return;
        lseek64(bfd, offset - 4096, 0);
        if (read(bfd, &bsb2, 512) != 512)
                fail("cannot read bsb");
        if (bsb2.sb_csum != bsb_csum((char*)&bsb2,
                                     ((char*)&bsb2.sb_csum)-((char*)&bsb2)))
                fail("first csum bad");
        if (memcmp(bsb2.magic, "md_backup_data", 14) != 0)
                fail("magic is bad");
        if (memcmp(bsb2.magic, "md_backup_data-2", 16) == 0 &&
            bsb2.sb_csum2 != bsb_csum((char*)&bsb2,
                                     ((char*)&bsb2.sb_csum2)-((char*)&bsb2)))
                fail("second csum bad");

        if (__le64_to_cpu(bsb2.devstart)*512 != offset)
                fail("devstart is wrong");

        if (bsb2.length) {
                unsigned long long len = __le64_to_cpu(bsb2.length)*512;

                if (abuflen < len) {
                        free(abuf);
                        free(bbuf);
                        abuflen = len;
                        if (posix_memalign((void**)&abuf, 4096, abuflen) ||
                            posix_memalign((void**)&bbuf, 4096, abuflen)) {
                                abuflen = 0;
                                /* just stop validating on mem-alloc failure */
                                return;
                        }
                }

                lseek64(bfd, offset, 0);
                if ((unsigned long long)read(bfd, bbuf, len) != len) {
                        //printf("len %llu\n", len);
                        fail("read first backup failed");
                }
                lseek64(afd, __le64_to_cpu(bsb2.arraystart)*512, 0);
                if ((unsigned long long)read(afd, abuf, len) != len)
                        fail("read first from array failed");
                if (memcmp(bbuf, abuf, len) != 0) {
                        #if 0
                        int i;
                        printf("offset=%llu len=%llu\n",
                               (unsigned long long)__le64_to_cpu(bsb2.arraystart)*512, len);
                        for (i=0; i<len; i++)
                                if (bbuf[i] != abuf[i]) {
                                        printf("first diff byte %d\n", i);
                                        break;
                                }
                        #endif
                        fail("data1 compare failed");
                }
        }
        if (bsb2.length2) {
                unsigned long long len = __le64_to_cpu(bsb2.length2)*512;

                if (abuflen < len) {
                        free(abuf);
                        free(bbuf);
                        abuflen = len;
                        abuf = malloc(abuflen);
                        bbuf = malloc(abuflen);
                }

                lseek64(bfd, offset+__le64_to_cpu(bsb2.devstart2)*512, 0);
                if ((unsigned long long)read(bfd, bbuf, len) != len)
                        fail("read second backup failed");
                lseek64(afd, __le64_to_cpu(bsb2.arraystart2)*512, 0);
                if ((unsigned long long)read(afd, abuf, len) != len)
                        fail("read second from array failed");
                if (memcmp(bbuf, abuf, len) != 0)
                        fail("data2 compare failed");
        }
}

static int child_monitor(int afd, struct mdinfo *sra, struct reshape *reshape,
                         unsigned long stripes,
                         int *fds, unsigned long long *offsets,
                         int dests, int *destfd, unsigned long long *destoffsets)
{
        /* Monitor a reshape where backup is being performed using
         * 'native' mechanism - either to a backup file, or
         * to some space in a spare.
         */
        char *buf;
        int degraded = -1;
        unsigned long long speed;
        unsigned long long suspend_point, array_size;
        unsigned long long backup_point, wait_point;
        unsigned long long reshape_completed;
        int done = 0;
        int increasing = reshape->after.data_disks >= reshape->before.data_disks;
        int part = 0; /* The next part of the backup area to fill.  It may already
                       * be full, so we need to check */
        int level = reshape->level;
        int layout = reshape->before.layout;
        int data = reshape->before.data_disks;
        int disks = reshape->before.data_disks + reshape->parity;
        int chunk = sra->array.chunk_size;

        if (posix_memalign((void**)&buf, 4096, disks * chunk))
                /* Don't start the 'reshape' */
                return 0;
        if (reshape->before.data_disks == reshape->after.data_disks) {
                sysfs_get_ll(sra, NULL, "sync_speed_min", &speed);
                sysfs_set_num(sra, NULL, "sync_speed_min", 200000);
        }

        array_size = sra->component_size * data;
        if (increasing) {
                backup_point = sra->reshape_progress;
                suspend_point = 0;
        } else {
                backup_point = array_size;
                suspend_point = array_size;
        }

        while (!done) {
                int rv;

                /* Want to return as soon the oldest backup slot can
                 * be released as that allows us to start backing up
                 * some more, providing suspend_point has been
                 * advanced, which it should have.
                 */
                if (increasing) {
                        wait_point = array_size;
                        if (part == 0 && __le64_to_cpu(bsb.length) > 0)
                                wait_point = (__le64_to_cpu(bsb.arraystart) +
                                              __le64_to_cpu(bsb.length));
                        if (part == 1 && __le64_to_cpu(bsb.length2) > 0)
                                wait_point = (__le64_to_cpu(bsb.arraystart2) +
                                              __le64_to_cpu(bsb.length2));
                } else {
                        wait_point = 0;
                        if (part == 0 && __le64_to_cpu(bsb.length) > 0)
                                wait_point = __le64_to_cpu(bsb.arraystart);
                        if (part == 1 && __le64_to_cpu(bsb.length2) > 0)
                                wait_point = __le64_to_cpu(bsb.arraystart2);
                }

                rv = progress_reshape(sra, reshape,
                                      backup_point, wait_point,
                                      &suspend_point, &reshape_completed);
                if (rv < 0) {
                        done = 1;
                        break;
                }

                /* external metadata would need to ping_monitor here */
                sra->reshape_progress = reshape_completed;

                /* Clear any backup region that is before 'here' */
                if (increasing) {
                        if (reshape_completed >= (__le64_to_cpu(bsb.arraystart) +
                                                  __le64_to_cpu(bsb.length)))
                                forget_backup(dests, destfd,
                                              destoffsets, 0);
                        if (reshape_completed >= (__le64_to_cpu(bsb.arraystart2) +
                                                  __le64_to_cpu(bsb.length2)))
                                forget_backup(dests, destfd,
                                              destoffsets, 1);
                } else {
                        if (reshape_completed <= (__le64_to_cpu(bsb.arraystart)))
                                forget_backup(dests, destfd,
                                              destoffsets, 0);
                        if (reshape_completed <= (__le64_to_cpu(bsb.arraystart2)))
                                forget_backup(dests, destfd,
                                              destoffsets, 1);
                }

                if (rv) {
                        unsigned long long offset;
                        /* need to backup some space... */
                        /* Check that 'part' is unused */
                        if (part == 0 && __le64_to_cpu(bsb.length) != 0)
                                abort(); /* BUG here */
                        if (part == 1 && __le64_to_cpu(bsb.length2) != 0)
                                abort();

                        offset = backup_point / data;
                        if (!increasing)
                                offset -= stripes * (chunk/512);
                        grow_backup(sra, offset, stripes,
                                    fds, offsets,
                                    disks, chunk, level, layout,
                                    dests, destfd, destoffsets,
                                    part, &degraded, buf);
                        validate(afd, destfd[0], destoffsets[0]);
                        /* record where 'part' is up to */
                        part = !part;
                        if (increasing)
                                backup_point += stripes * (chunk/512) * data;
                        else
                                backup_point -= stripes * (chunk/512) * data;
                }
        }

        if (reshape->before.data_disks == reshape->after.data_disks)
                sysfs_set_num(sra, NULL, "sync_speed_min", speed);
        free(buf);
        return 1; /* FIXME what does this mean? */
}

/*
 * If any spare contains md_back_data-1 which is recent wrt mtime,
 * write that data into the array and update the super blocks with
 * the new reshape_progress
 */
int Grow_restart(struct supertype *st, struct mdinfo *info, int *fdlist, int cnt,
                 char *backup_file, int verbose)
{
        int i, j;
        int old_disks;
        unsigned long long *offsets;
        unsigned long long  nstripe, ostripe;
        int ndata, odata;

        if (info->new_level != info->array.level)
                return 1; /* Cannot handle level changes (they are instantaneous) */

        odata = info->array.raid_disks - info->delta_disks - 1;
        if (info->array.level == 6) odata--; /* number of data disks */
        ndata = info->array.raid_disks - 1;
        if (info->new_level == 6) ndata--;

        old_disks = info->array.raid_disks - info->delta_disks;

        if (info->delta_disks <= 0)
                /* Didn't grow, so the backup file must have
                 * been used
                 */
                old_disks = cnt;
        for (i=old_disks-(backup_file?1:0); i<cnt; i++) {
                struct mdinfo dinfo;
                int fd;
                int bsbsize;
                char *devname, namebuf[20];

                /* This was a spare and may have some saved data on it.
                 * Load the superblock, find and load the
                 * backup_super_block.
                 * If either fail, go on to next device.
                 * If the backup contains no new info, just return
                 * else restore data and update all superblocks
                 */
                if (i == old_disks-1) {
                        fd = open(backup_file, O_RDONLY);
                        if (fd<0) {
                                fprintf(stderr, Name ": backup file %s inaccessible: %s\n",
                                        backup_file, strerror(errno));
                                continue;
                        }
                        devname = backup_file;
                } else {
                        fd = fdlist[i];
                        if (fd < 0)
                                continue;
                        if (st->ss->load_super(st, fd, NULL))
                                continue;

                        st->ss->getinfo_super(st, &dinfo, NULL);
                        st->ss->free_super(st);

                        if (lseek64(fd,
                                    (dinfo.data_offset + dinfo.component_size - 8) <<9,
                                    0) < 0) {
                                fprintf(stderr, Name ": Cannot seek on device %d\n", i);
                                continue; /* Cannot seek */
                        }
                        sprintf(namebuf, "device-%d", i);
                        devname = namebuf;
                }
                if (read(fd, &bsb, sizeof(bsb)) != sizeof(bsb)) {
                        if (verbose)
                                fprintf(stderr, Name ": Cannot read from %s\n", devname);
                        continue; /* Cannot read */
                }
                if (memcmp(bsb.magic, "md_backup_data-1", 16) != 0 &&
                    memcmp(bsb.magic, "md_backup_data-2", 16) != 0) {
                        if (verbose)
                                fprintf(stderr, Name ": No backup metadata on %s\n", devname);
                        continue;
                }
                if (bsb.sb_csum != bsb_csum((char*)&bsb, ((char*)&bsb.sb_csum)-((char*)&bsb))) {
                        if (verbose)
                                fprintf(stderr, Name ": Bad backup-metadata checksum on %s\n", devname);
                        continue; /* bad checksum */
                }
                if (memcmp(bsb.magic, "md_backup_data-2", 16) == 0 &&
                    bsb.sb_csum2 != bsb_csum((char*)&bsb, ((char*)&bsb.sb_csum2)-((char*)&bsb))) {
                        if (verbose)
                                fprintf(stderr, Name ": Bad backup-metadata checksum2 on %s\n", devname);
                        continue; /* Bad second checksum */
                }
                if (memcmp(bsb.set_uuid,info->uuid, 16) != 0) {
                        if (verbose)
                                fprintf(stderr, Name ": Wrong uuid on backup-metadata on %s\n", devname);
                        continue; /* Wrong uuid */
                }

                /* array utime and backup-mtime should be updated at much the same time, but it seems that
                 * sometimes they aren't... So allow considerable flexability in matching, and allow
                 * this test to be overridden by an environment variable.
                 */
                if (info->array.utime > (int)__le64_to_cpu(bsb.mtime) + 2*60*60 ||
                    info->array.utime < (int)__le64_to_cpu(bsb.mtime) - 10*60) {
                        if (check_env("MDADM_GROW_ALLOW_OLD")) {
                                fprintf(stderr, Name ": accepting backup with timestamp %lu "
                                        "for array with timestamp %lu\n",
                                        (unsigned long)__le64_to_cpu(bsb.mtime),
                                        (unsigned long)info->array.utime);
                        } else {
                                if (verbose)
                                        fprintf(stderr, Name ": too-old timestamp on "
                                                "backup-metadata on %s\n", devname);
                                continue; /* time stamp is too bad */
                        }
                }

                if (bsb.magic[15] == '1') {
                if (info->delta_disks >= 0) {
                        /* reshape_progress is increasing */
                        if (__le64_to_cpu(bsb.arraystart) + __le64_to_cpu(bsb.length) <
                            info->reshape_progress) {
                        nonew:
                                if (verbose)
                                        fprintf(stderr, Name ": backup-metadata found on %s but is not needed\n", devname);
                                continue; /* No new data here */
                        }
                } else {
                        /* reshape_progress is decreasing */
                        if (__le64_to_cpu(bsb.arraystart) >=
                            info->reshape_progress)
                                goto nonew; /* No new data here */
                }
                } else {
                if (info->delta_disks >= 0) {
                        /* reshape_progress is increasing */
                        if (__le64_to_cpu(bsb.arraystart) + __le64_to_cpu(bsb.length) <
                            info->reshape_progress &&
                            __le64_to_cpu(bsb.arraystart2) + __le64_to_cpu(bsb.length2) <
                            info->reshape_progress)
                                goto nonew; /* No new data here */
                } else {
                        /* reshape_progress is decreasing */
                        if (__le64_to_cpu(bsb.arraystart) >=
                            info->reshape_progress &&
                            __le64_to_cpu(bsb.arraystart2) >=
                            info->reshape_progress)
                                goto nonew; /* No new data here */
                }
                }
                if (lseek64(fd, __le64_to_cpu(bsb.devstart)*512, 0)< 0) {
                second_fail:
                        if (verbose)
                                fprintf(stderr, Name ": Failed to verify secondary backup-metadata block on %s\n",
                                        devname);
                        continue; /* Cannot seek */
                }
                /* There should be a duplicate backup superblock 4k before here */
                if (lseek64(fd, -4096, 1) < 0 ||
                    read(fd, &bsb2, sizeof(bsb2)) != sizeof(bsb2))
                        goto second_fail; /* Cannot find leading superblock */
                if (bsb.magic[15] == '1')
                        bsbsize = offsetof(struct mdp_backup_super, pad1);
                else
                        bsbsize = offsetof(struct mdp_backup_super, pad);
                if (memcmp(&bsb2, &bsb, bsbsize) != 0)
                        goto second_fail; /* Cannot find leading superblock */

                /* Now need the data offsets for all devices. */
                offsets = malloc(sizeof(*offsets)*info->array.raid_disks);
                for(j=0; j<info->array.raid_disks; j++) {
                        if (fdlist[j] < 0)
                                continue;
                        if (st->ss->load_super(st, fdlist[j], NULL))
                                /* FIXME should be this be an error */
                                continue;
                        st->ss->getinfo_super(st, &dinfo, NULL);
                        st->ss->free_super(st);
                        offsets[j] = dinfo.data_offset * 512;
                }
                printf(Name ": restoring critical section\n");

                if (restore_stripes(fdlist, offsets,
                                    info->array.raid_disks,
                                    info->new_chunk,
                                    info->new_level,
                                    info->new_layout,
                                    fd, __le64_to_cpu(bsb.devstart)*512,
                                    __le64_to_cpu(bsb.arraystart)*512,
                                    __le64_to_cpu(bsb.length)*512)) {
                        /* didn't succeed, so giveup */
                        if (verbose)
                                fprintf(stderr, Name ": Error restoring backup from %s\n",
                                        devname);
                        return 1;
                }
                
                if (bsb.magic[15] == '2' &&
                    restore_stripes(fdlist, offsets,
                                    info->array.raid_disks,
                                    info->new_chunk,
                                    info->new_level,
                                    info->new_layout,
                                    fd, __le64_to_cpu(bsb.devstart)*512 +
                                    __le64_to_cpu(bsb.devstart2)*512,
                                    __le64_to_cpu(bsb.arraystart2)*512,
                                    __le64_to_cpu(bsb.length2)*512)) {
                        /* didn't succeed, so giveup */
                        if (verbose)
                                fprintf(stderr, Name ": Error restoring second backup from %s\n",
                                        devname);
                        return 1;
                }


                /* Ok, so the data is restored. Let's update those superblocks. */

                if (info->delta_disks >= 0) {
                        info->reshape_progress = __le64_to_cpu(bsb.arraystart) +
                                __le64_to_cpu(bsb.length);
                        if (bsb.magic[15] == '2') {
                                unsigned long long p2 = __le64_to_cpu(bsb.arraystart2) +
                                        __le64_to_cpu(bsb.length2);
                                if (p2 > info->reshape_progress)
                                        info->reshape_progress = p2;
                        }
                } else {
                        info->reshape_progress = __le64_to_cpu(bsb.arraystart);
                        if (bsb.magic[15] == '2') {
                                unsigned long long p2 = __le64_to_cpu(bsb.arraystart2);
                                if (p2 < info->reshape_progress)
                                        info->reshape_progress = p2;
                        }
                }
                for (j=0; j<info->array.raid_disks; j++) {
                        if (fdlist[j] < 0) continue;
                        if (st->ss->load_super(st, fdlist[j], NULL))
                                continue;
                        st->ss->getinfo_super(st, &dinfo, NULL);
                        dinfo.reshape_progress = info->reshape_progress;
                        st->ss->update_super(st, &dinfo,
                                             "_reshape_progress",
                                             NULL,0, 0, NULL);
                        st->ss->store_super(st, fdlist[j]);
                        st->ss->free_super(st);
                }
                return 0;
        }
        /* Didn't find any backup data, try to see if any
         * was needed.
         */
        if (info->delta_disks < 0) {
                /* When shrinking, the critical section is at the end.
                 * So see if we are before the critical section.
                 */
                unsigned long long first_block;
                nstripe = ostripe = 0;
                first_block = 0;
                while (ostripe >= nstripe) {
                        ostripe += info->array.chunk_size / 512;
                        first_block = ostripe * odata;
                        nstripe = first_block / ndata / (info->new_chunk/512) *
                                (info->new_chunk/512);
                }

                if (info->reshape_progress >= first_block)
                        return 0;
        }
        if (info->delta_disks > 0) {
                /* See if we are beyond the critical section. */
                unsigned long long last_block;
                nstripe = ostripe = 0;
                last_block = 0;
                while (nstripe >= ostripe) {
                        nstripe += info->new_chunk / 512;
                        last_block = nstripe * ndata;
                        ostripe = last_block / odata / (info->array.chunk_size/512) *
                                (info->array.chunk_size/512);
                }

                if (info->reshape_progress >= last_block)
                        return 0;
        }
        /* needed to recover critical section! */
        if (verbose)
                fprintf(stderr, Name ": Failed to find backup of critical section\n");
        return 1;
}

int Grow_continue(int mdfd, struct supertype *st, struct mdinfo *info,
                  char *backup_file)
{
        int err = sysfs_set_str(info, NULL, "array_state", "readonly");
        if (err)
                return err;
        return reshape_array(NULL, mdfd, "array", st, info, 1, backup_file, 0, 0);
}