raid1.c

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/*
 * raid1.c : Multiple Devices driver for Linux
 *
 * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
 *
 * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
 *
 * RAID-1 management functions.
 *
 * Better read-balancing code written by Mika Kuoppala <[email protected]>, 2000
 *
 * Fixes to reconstruction by Jakob Østergaard" <[email protected]>
 * Various fixes by Neil Brown <[email protected]>
 *
 * Changes by Peter T. Breuer <[email protected]> 31/1/2003 to support
 * bitmapped intelligence in resync:
 *
 *      - bitmap marked during normal i/o
 *      - bitmap used to skip nondirty blocks during sync
 *
 * Additions to bitmap code, (C) 2003-2004 Paul Clements, SteelEye Technology:
 * - persistent bitmap code
 *
 * 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, or (at your option)
 * any later version.
 *
 * You should have received a copy of the GNU General Public License
 * (for example /usr/src/linux/COPYING); if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/ratelimit.h>
#include "md.h"
#include "raid1.h"
#include "bitmap.h"

/*
 * Number of guaranteed r1bios in case of extreme VM load:
 */
#define NR_RAID1_BIOS 256

/* when we get a read error on a read-only array, we redirect to another
 * device without failing the first device, or trying to over-write to
 * correct the read error.  To keep track of bad blocks on a per-bio
 * level, we store IO_BLOCKED in the appropriate 'bios' pointer
 */
#define IO_BLOCKED ((struct bio *)1)
/* When we successfully write to a known bad-block, we need to remove the
 * bad-block marking which must be done from process context.  So we record
 * the success by setting devs[n].bio to IO_MADE_GOOD
 */
#define IO_MADE_GOOD ((struct bio *)2)

#define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)

/* When there are this many requests queue to be written by
 * the raid1 thread, we become 'congested' to provide back-pressure
 * for writeback.
 */
static int max_queued_requests = 1024;

static void allow_barrier(struct r1conf *conf);
static void lower_barrier(struct r1conf *conf);

static void * r1bio_pool_alloc(gfp_t gfp_flags, void *data)
{
    struct pool_info *pi = data;
    int size = offsetof(struct r1bio, bios[pi->raid_disks]);

    /* allocate a r1bio with room for raid_disks entries in the bios array */
    return kzalloc(size, gfp_flags);
}

static void r1bio_pool_free(void *r1_bio, void *data)
{
    kfree(r1_bio);
}

#define RESYNC_BLOCK_SIZE (64*1024)
//#define RESYNC_BLOCK_SIZE PAGE_SIZE
#define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
#define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
#define RESYNC_WINDOW (2048*1024)

static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
{
    struct pool_info *pi = data;
    struct page *page;
    struct r1bio *r1_bio;
    struct bio *bio;
    int i, j;

    r1_bio = r1bio_pool_alloc(gfp_flags, pi);
    if (!r1_bio)
        return NULL;

    /*
     * Allocate bios : 1 for reading, n-1 for writing
     */
    for (j = pi->raid_disks ; j-- ; ) {
        bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
        if (!bio)
            goto out_free_bio;
        r1_bio->bios[j] = bio;
    }
    /*
     * Allocate RESYNC_PAGES data pages and attach them to
     * the first bio.
     * If this is a user-requested check/repair, allocate
     * RESYNC_PAGES for each bio.
     */
    if (test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery))
        j = pi->raid_disks;
    else
        j = 1;
    while(j--) {
        bio = r1_bio->bios[j];
        for (i = 0; i < RESYNC_PAGES; i++) {
            page = alloc_page(gfp_flags);
            if (unlikely(!page))
                goto out_free_pages;

            bio->bi_io_vec[i].bv_page = page;
            bio->bi_vcnt = i+1;
        }
    }
    /* If not user-requests, copy the page pointers to all bios */
    if (!test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery)) {
        for (i=0; i<RESYNC_PAGES ; i++)
            for (j=1; j<pi->raid_disks; j++)
                r1_bio->bios[j]->bi_io_vec[i].bv_page =
                    r1_bio->bios[0]->bi_io_vec[i].bv_page;
    }

    r1_bio->master_bio = NULL;

    return r1_bio;

out_free_pages:
    for (j=0 ; j < pi->raid_disks; j++)
        for (i=0; i < r1_bio->bios[j]->bi_vcnt ; i++)
            put_page(r1_bio->bios[j]->bi_io_vec[i].bv_page);
    j = -1;
out_free_bio:
    while (++j < pi->raid_disks)
        bio_put(r1_bio->bios[j]);
    r1bio_pool_free(r1_bio, data);
    return NULL;
}

static void r1buf_pool_free(void *__r1_bio, void *data)
{
    struct pool_info *pi = data;
    int i,j;
    struct r1bio *r1bio = __r1_bio;

    for (i = 0; i < RESYNC_PAGES; i++)
        for (j = pi->raid_disks; j-- ;) {
            if (j == 0 ||
                r1bio->bios[j]->bi_io_vec[i].bv_page !=
                r1bio->bios[0]->bi_io_vec[i].bv_page)
                safe_put_page(r1bio->bios[j]->bi_io_vec[i].bv_page);
        }
    for (i=0 ; i < pi->raid_disks; i++)
        bio_put(r1bio->bios[i]);

    r1bio_pool_free(r1bio, data);
}

static void put_all_bios(struct r1conf *conf, struct r1bio *r1_bio)
{
    int i;

    for (i = 0; i < conf->raid_disks * 2; i++) {
        struct bio **bio = r1_bio->bios + i;
        if (!BIO_SPECIAL(*bio))
            bio_put(*bio);
        *bio = NULL;
    }
}

static void free_r1bio(struct r1bio *r1_bio)
{
    struct r1conf *conf = r1_bio->mddev->private;

    put_all_bios(conf, r1_bio);
    mempool_free(r1_bio, conf->r1bio_pool);
}

static void put_buf(struct r1bio *r1_bio)
{
    struct r1conf *conf = r1_bio->mddev->private;
    int i;

    for (i = 0; i < conf->raid_disks * 2; i++) {
        struct bio *bio = r1_bio->bios[i];
        if (bio->bi_end_io)
            rdev_dec_pending(conf->mirrors[i].rdev, r1_bio->mddev);
    }

    mempool_free(r1_bio, conf->r1buf_pool);

    lower_barrier(conf);
}

static void reschedule_retry(struct r1bio *r1_bio)
{
    unsigned long flags;
    struct mddev *mddev = r1_bio->mddev;
    struct r1conf *conf = mddev->private;

    spin_lock_irqsave(&conf->device_lock, flags);
    list_add(&r1_bio->retry_list, &conf->retry_list);
    conf->nr_queued ++;
    spin_unlock_irqrestore(&conf->device_lock, flags);

    wake_up(&conf->wait_barrier);
    md_wakeup_thread(mddev->thread);
}

/*
 * raid_end_bio_io() is called when we have finished servicing a mirrored
 * operation and are ready to return a success/failure code to the buffer
 * cache layer.
 */
static void call_bio_endio(struct r1bio *r1_bio)
{
    struct bio *bio = r1_bio->master_bio;
    int done;
    struct r1conf *conf = r1_bio->mddev->private;

    if (bio->bi_phys_segments) {
        unsigned long flags;
        spin_lock_irqsave(&conf->device_lock, flags);
        bio->bi_phys_segments--;
        done = (bio->bi_phys_segments == 0);
        spin_unlock_irqrestore(&conf->device_lock, flags);
    } else
        done = 1;

    if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
        clear_bit(BIO_UPTODATE, &bio->bi_flags);
    if (done) {
        bio_endio(bio, 0);
        /*
         * Wake up any possible resync thread that waits for the device
         * to go idle.
         */
        allow_barrier(conf);
    }
}

static void raid_end_bio_io(struct r1bio *r1_bio)
{
    struct bio *bio = r1_bio->master_bio;

    /* if nobody has done the final endio yet, do it now */
    if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
        pr_debug("raid1: sync end %s on sectors %llu-%llu\n",
             (bio_data_dir(bio) == WRITE) ? "write" : "read",
             (unsigned long long) bio->bi_sector,
             (unsigned long long) bio->bi_sector +
             (bio->bi_size >> 9) - 1);

        call_bio_endio(r1_bio);
    }
    free_r1bio(r1_bio);
}

/*
 * Update disk head position estimator based on IRQ completion info.
 */
static inline void update_head_pos(int disk, struct r1bio *r1_bio)
{
    struct r1conf *conf = r1_bio->mddev->private;

    conf->mirrors[disk].head_position =
        r1_bio->sector + (r1_bio->sectors);
}

/*
 * Find the disk number which triggered given bio
 */
static int find_bio_disk(struct r1bio *r1_bio, struct bio *bio)
{
    int mirror;
    struct r1conf *conf = r1_bio->mddev->private;
    int raid_disks = conf->raid_disks;

    for (mirror = 0; mirror < raid_disks * 2; mirror++)
        if (r1_bio->bios[mirror] == bio)
            break;

    BUG_ON(mirror == raid_disks * 2);
    update_head_pos(mirror, r1_bio);

    return mirror;
}

static void raid1_end_read_request(struct bio *bio, int error)
{
    int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
    struct r1bio *r1_bio = bio->bi_private;
    int mirror;
    struct r1conf *conf = r1_bio->mddev->private;

    mirror = r1_bio->read_disk;
    /*
     * this branch is our 'one mirror IO has finished' event handler:
     */
    update_head_pos(mirror, r1_bio);

    if (uptodate)
        set_bit(R1BIO_Uptodate, &r1_bio->state);
    else {
        /* If all other devices have failed, we want to return
         * the error upwards rather than fail the last device.
         * Here we redefine "uptodate" to mean "Don't want to retry"
         */
        unsigned long flags;
        spin_lock_irqsave(&conf->device_lock, flags);
        if (r1_bio->mddev->degraded == conf->raid_disks ||
            (r1_bio->mddev->degraded == conf->raid_disks-1 &&
             !test_bit(Faulty, &conf->mirrors[mirror].rdev->flags)))
            uptodate = 1;
        spin_unlock_irqrestore(&conf->device_lock, flags);
    }

    if (uptodate) {
        raid_end_bio_io(r1_bio);
        rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
    } else {
        /*
         * oops, read error:
         */
        char b[BDEVNAME_SIZE];
        printk_ratelimited(
            KERN_ERR "md/raid1:%s: %s: "
            "rescheduling sector %llu\n",
            mdname(conf->mddev),
            bdevname(conf->mirrors[mirror].rdev->bdev,
                 b),
            (unsigned long long)r1_bio->sector);
        set_bit(R1BIO_ReadError, &r1_bio->state);
        reschedule_retry(r1_bio);
        /* don't drop the reference on read_disk yet */
    }
}

static void close_write(struct r1bio *r1_bio)
{
    /* it really is the end of this request */
    if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
        /* free extra copy of the data pages */
        int i = r1_bio->behind_page_count;
        while (i--)
            safe_put_page(r1_bio->behind_bvecs[i].bv_page);
        kfree(r1_bio->behind_bvecs);
        r1_bio->behind_bvecs = NULL;
    }
    /* clear the bitmap if all writes complete successfully */
    bitmap_endwrite(r1_bio->mddev->bitmap, r1_bio->sector,
            r1_bio->sectors,
            !test_bit(R1BIO_Degraded, &r1_bio->state),
            test_bit(R1BIO_BehindIO, &r1_bio->state));
    md_write_end(r1_bio->mddev);
}

static void r1_bio_write_done(struct r1bio *r1_bio)
{
    if (!atomic_dec_and_test(&r1_bio->remaining))
        return;

    if (test_bit(R1BIO_WriteError, &r1_bio->state))
        reschedule_retry(r1_bio);
    else {
        close_write(r1_bio);
        if (test_bit(R1BIO_MadeGood, &r1_bio->state))
            reschedule_retry(r1_bio);
        else
            raid_end_bio_io(r1_bio);
    }
}

static void raid1_end_write_request(struct bio *bio, int error)
{
    int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
    struct r1bio *r1_bio = bio->bi_private;
    int mirror, behind = test_bit(R1BIO_BehindIO, &r1_bio->state);
    struct r1conf *conf = r1_bio->mddev->private;
    struct bio *to_put = NULL;

    mirror = find_bio_disk(r1_bio, bio);

    /*
     * 'one mirror IO has finished' event handler:
     */
    if (!uptodate) {
        set_bit(WriteErrorSeen,
            &conf->mirrors[mirror].rdev->flags);
        if (!test_and_set_bit(WantReplacement,
                      &conf->mirrors[mirror].rdev->flags))
            set_bit(MD_RECOVERY_NEEDED, &
                conf->mddev->recovery);

        set_bit(R1BIO_WriteError, &r1_bio->state);
    } else {
        /*
         * Set R1BIO_Uptodate in our master bio, so that we
         * will return a good error code for to the higher
         * levels even if IO on some other mirrored buffer
         * fails.
         *
         * The 'master' represents the composite IO operation
         * to user-side. So if something waits for IO, then it
         * will wait for the 'master' bio.
         */
        sector_t first_bad;
        int bad_sectors;

        r1_bio->bios[mirror] = NULL;
        to_put = bio;
        set_bit(R1BIO_Uptodate, &r1_bio->state);

        /* Maybe we can clear some bad blocks. */
        if (is_badblock(conf->mirrors[mirror].rdev,
                r1_bio->sector, r1_bio->sectors,
                &first_bad, &bad_sectors)) {
            r1_bio->bios[mirror] = IO_MADE_GOOD;
            set_bit(R1BIO_MadeGood, &r1_bio->state);
        }
    }

    if (behind) {
        if (test_bit(WriteMostly, &conf->mirrors[mirror].rdev->flags))
            atomic_dec(&r1_bio->behind_remaining);

        /*
         * In behind mode, we ACK the master bio once the I/O
         * has safely reached all non-writemostly
         * disks. Setting the Returned bit ensures that this
         * gets done only once -- we don't ever want to return
         * -EIO here, instead we'll wait
         */
        if (atomic_read(&r1_bio->behind_remaining) >= (atomic_read(&r1_bio->remaining)-1) &&
            test_bit(R1BIO_Uptodate, &r1_bio->state)) {
            /* Maybe we can return now */
            if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
                struct bio *mbio = r1_bio->master_bio;
                pr_debug("raid1: behind end write sectors"
                     " %llu-%llu\n",
                     (unsigned long long) mbio->bi_sector,
                     (unsigned long long) mbio->bi_sector +
                     (mbio->bi_size >> 9) - 1);
                call_bio_endio(r1_bio);
            }
        }
    }
    if (r1_bio->bios[mirror] == NULL)
        rdev_dec_pending(conf->mirrors[mirror].rdev,
                 conf->mddev);

    /*
     * Let's see if all mirrored write operations have finished
     * already.
     */
    r1_bio_write_done(r1_bio);

    if (to_put)
        bio_put(to_put);
}


/*
 * This routine returns the disk from which the requested read should
 * be done. There is a per-array 'next expected sequential IO' sector
 * number - if this matches on the next IO then we use the last disk.
 * There is also a per-disk 'last know head position' sector that is
 * maintained from IRQ contexts, both the normal and the resync IO
 * completion handlers update this position correctly. If there is no
 * perfect sequential match then we pick the disk whose head is closest.
 *
 * If there are 2 mirrors in the same 2 devices, performance degrades
 * because position is mirror, not device based.
 *
 * The rdev for the device selected will have nr_pending incremented.
 */
static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sectors)
{
    const sector_t this_sector = r1_bio->sector;
    int sectors;
    int best_good_sectors;
    int best_disk, best_dist_disk, best_pending_disk;
    int has_nonrot_disk;
    int disk;
    sector_t best_dist;
    unsigned int min_pending;
    struct md_rdev *rdev;
    int choose_first;
    int choose_next_idle;

    rcu_read_lock();
    /*
     * Check if we can balance. We can balance on the whole
     * device if no resync is going on, or below the resync window.
     * We take the first readable disk when above the resync window.
     */
 retry:
    sectors = r1_bio->sectors;
    best_disk = -1;
    best_dist_disk = -1;
    best_dist = MaxSector;
    best_pending_disk = -1;
    min_pending = UINT_MAX;
    best_good_sectors = 0;
    has_nonrot_disk = 0;
    choose_next_idle = 0;

    if (conf->mddev->recovery_cp < MaxSector &&
        (this_sector + sectors >= conf->next_resync))
        choose_first = 1;
    else
        choose_first = 0;

    for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
        sector_t dist;
        sector_t first_bad;
        int bad_sectors;
        unsigned int pending;
        bool nonrot;

        rdev = rcu_dereference(conf->mirrors[disk].rdev);
        if (r1_bio->bios[disk] == IO_BLOCKED
            || rdev == NULL
            || test_bit(Unmerged, &rdev->flags)
            || test_bit(Faulty, &rdev->flags))
            continue;
        if (!test_bit(In_sync, &rdev->flags) &&
            rdev->recovery_offset < this_sector + sectors)
            continue;
        if (test_bit(WriteMostly, &rdev->flags)) {
            /* Don't balance among write-mostly, just
             * use the first as a last resort */
            if (best_disk < 0) {
                if (is_badblock(rdev, this_sector, sectors,
                        &first_bad, &bad_sectors)) {
                    if (first_bad < this_sector)
                        /* Cannot use this */
                        continue;
                    best_good_sectors = first_bad - this_sector;
                } else
                    best_good_sectors = sectors;
                best_disk = disk;
            }
            continue;
        }
        /* This is a reasonable device to use.  It might
         * even be best.
         */
        if (is_badblock(rdev, this_sector, sectors,
                &first_bad, &bad_sectors)) {
            if (best_dist < MaxSector)
                /* already have a better device */
                continue;
            if (first_bad <= this_sector) {
                /* cannot read here. If this is the 'primary'
                 * device, then we must not read beyond
                 * bad_sectors from another device..
                 */
                bad_sectors -= (this_sector - first_bad);
                if (choose_first && sectors > bad_sectors)
                    sectors = bad_sectors;
                if (best_good_sectors > sectors)
                    best_good_sectors = sectors;

            } else {
                sector_t good_sectors = first_bad - this_sector;
                if (good_sectors > best_good_sectors) {
                    best_good_sectors = good_sectors;
                    best_disk = disk;
                }
                if (choose_first)
                    break;
            }
            continue;
        } else
            best_good_sectors = sectors;

        nonrot = blk_queue_nonrot(bdev_get_queue(rdev->bdev));
        has_nonrot_disk |= nonrot;
        pending = atomic_read(&rdev->nr_pending);
        dist = abs(this_sector - conf->mirrors[disk].head_position);
        if (choose_first) {
            best_disk = disk;
            break;
        }
        /* Don't change to another disk for sequential reads */
        if (conf->mirrors[disk].next_seq_sect == this_sector
            || dist == 0) {
            int opt_iosize = bdev_io_opt(rdev->bdev) >> 9;
            struct raid1_info *mirror = &conf->mirrors[disk];

            best_disk = disk;
            /*
             * If buffered sequential IO size exceeds optimal
             * iosize, check if there is idle disk. If yes, choose
             * the idle disk. read_balance could already choose an
             * idle disk before noticing it's a sequential IO in
             * this disk. This doesn't matter because this disk
             * will idle, next time it will be utilized after the
             * first disk has IO size exceeds optimal iosize. In
             * this way, iosize of the first disk will be optimal
             * iosize at least. iosize of the second disk might be
             * small, but not a big deal since when the second disk
             * starts IO, the first disk is likely still busy.
             */
            if (nonrot && opt_iosize > 0 &&
                mirror->seq_start != MaxSector &&
                mirror->next_seq_sect > opt_iosize &&
                mirror->next_seq_sect - opt_iosize >=
                mirror->seq_start) {
                choose_next_idle = 1;
                continue;
            }
            break;
        }
        /* If device is idle, use it */
        if (pending == 0) {
            best_disk = disk;
            break;
        }

        if (choose_next_idle)
            continue;

        if (min_pending > pending) {
            min_pending = pending;
            best_pending_disk = disk;
        }

        if (dist < best_dist) {
            best_dist = dist;
            best_dist_disk = disk;
        }
    }

    /*
     * If all disks are rotational, choose the closest disk. If any disk is
     * non-rotational, choose the disk with less pending request even the
     * disk is rotational, which might/might not be optimal for raids with
     * mixed ratation/non-rotational disks depending on workload.
     */
    if (best_disk == -1) {
        if (has_nonrot_disk)
            best_disk = best_pending_disk;
        else
            best_disk = best_dist_disk;
    }

    if (best_disk >= 0) {
        rdev = rcu_dereference(conf->mirrors[best_disk].rdev);
        if (!rdev)
            goto retry;
        atomic_inc(&rdev->nr_pending);
        if (test_bit(Faulty, &rdev->flags)) {
            /* cannot risk returning a device that failed
             * before we inc'ed nr_pending
             */
            rdev_dec_pending(rdev, conf->mddev);
            goto retry;
        }
        sectors = best_good_sectors;

        if (conf->mirrors[best_disk].next_seq_sect != this_sector)
            conf->mirrors[best_disk].seq_start = this_sector;

        conf->mirrors[best_disk].next_seq_sect = this_sector + sectors;
    }
    rcu_read_unlock();
    *max_sectors = sectors;

    return best_disk;
}

static int raid1_mergeable_bvec(struct request_queue *q,
                struct bvec_merge_data *bvm,
                struct bio_vec *biovec)
{
    struct mddev *mddev = q->queuedata;
    struct r1conf *conf = mddev->private;
    sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
    int max = biovec->bv_len;

    if (mddev->merge_check_needed) {
        int disk;
        rcu_read_lock();
        for (disk = 0; disk < conf->raid_disks * 2; disk++) {
            struct md_rdev *rdev = rcu_dereference(
                conf->mirrors[disk].rdev);
            if (rdev && !test_bit(Faulty, &rdev->flags)) {
                struct request_queue *q =
                    bdev_get_queue(rdev->bdev);
                if (q->merge_bvec_fn) {
                    bvm->bi_sector = sector +
                        rdev->data_offset;
                    bvm->bi_bdev = rdev->bdev;
                    max = min(max, q->merge_bvec_fn(
                              q, bvm, biovec));
                }
            }
        }
        rcu_read_unlock();
    }
    return max;

}

int md_raid1_congested(struct mddev *mddev, int bits)
{
    struct r1conf *conf = mddev->private;
    int i, ret = 0;

    if ((bits & (1 << BDI_async_congested)) &&
        conf->pending_count >= max_queued_requests)
        return 1;

    rcu_read_lock();
    for (i = 0; i < conf->raid_disks * 2; i++) {
        struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
        if (rdev && !test_bit(Faulty, &rdev->flags)) {
            struct request_queue *q = bdev_get_queue(rdev->bdev);

            BUG_ON(!q);

            /* Note the '|| 1' - when read_balance prefers
             * non-congested targets, it can be removed
             */
            if ((bits & (1<<BDI_async_congested)) || 1)
                ret |= bdi_congested(&q->backing_dev_info, bits);
            else
                ret &= bdi_congested(&q->backing_dev_info, bits);
        }
    }
    rcu_read_unlock();
    return ret;
}
EXPORT_SYMBOL_GPL(md_raid1_congested);

static int raid1_congested(void *data, int bits)
{
    struct mddev *mddev = data;

    return mddev_congested(mddev, bits) ||
        md_raid1_congested(mddev, bits);
}

static void flush_pending_writes(struct r1conf *conf)
{
    /* Any writes that have been queued but are awaiting
     * bitmap updates get flushed here.
     */
    spin_lock_irq(&conf->device_lock);

    if (conf->pending_bio_list.head) {
        struct bio *bio;
        bio = bio_list_get(&conf->pending_bio_list);
        conf->pending_count = 0;
        spin_unlock_irq(&conf->device_lock);
        /* flush any pending bitmap writes to
         * disk before proceeding w/ I/O */
        bitmap_unplug(conf->mddev->bitmap);
        wake_up(&conf->wait_barrier);

        while (bio) { /* submit pending writes */
            struct bio *next = bio->bi_next;
            bio->bi_next = NULL;
            if (unlikely((bio->bi_rw & REQ_DISCARD) &&
                !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
                /* Just ignore it */
                bio_endio(bio, 0);
            else
                generic_make_request(bio);
            bio = next;
        }
    } else
        spin_unlock_irq(&conf->device_lock);
}

/* Barriers....
 * Sometimes we need to suspend IO while we do something else,
 * either some resync/recovery, or reconfigure the array.
 * To do this we raise a 'barrier'.
 * The 'barrier' is a counter that can be raised multiple times
 * to count how many activities are happening which preclude
 * normal IO.
 * We can only raise the barrier if there is no pending IO.
 * i.e. if nr_pending == 0.
 * We choose only to raise the barrier if no-one is waiting for the
 * barrier to go down.  This means that as soon as an IO request
 * is ready, no other operations which require a barrier will start
 * until the IO request has had a chance.
 *
 * So: regular IO calls 'wait_barrier'.  When that returns there
 *    is no backgroup IO happening,  It must arrange to call
 *    allow_barrier when it has finished its IO.
 * backgroup IO calls must call raise_barrier.  Once that returns
 *    there is no normal IO happeing.  It must arrange to call
 *    lower_barrier when the particular background IO completes.
 */
#define RESYNC_DEPTH 32

static void raise_barrier(struct r1conf *conf)
{
    spin_lock_irq(&conf->resync_lock);

    /* Wait until no block IO is waiting */
    wait_event_lock_irq(conf->wait_barrier, !conf->nr_waiting,
                conf->resync_lock, );

    /* block any new IO from starting */
    conf->barrier++;

    /* Now wait for all pending IO to complete */
    wait_event_lock_irq(conf->wait_barrier,
                !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
                conf->resync_lock, );

    spin_unlock_irq(&conf->resync_lock);
}

static void lower_barrier(struct r1conf *conf)
{
    unsigned long flags;
    BUG_ON(conf->barrier <= 0);
    spin_lock_irqsave(&conf->resync_lock, flags);
    conf->barrier--;
    spin_unlock_irqrestore(&conf->resync_lock, flags);
    wake_up(&conf->wait_barrier);
}

static void wait_barrier(struct r1conf *conf)
{
    spin_lock_irq(&conf->resync_lock);
    if (conf->barrier) {
        conf->nr_waiting++;
        /* Wait for the barrier to drop.
         * However if there are already pending
         * requests (preventing the barrier from
         * rising completely), and the
         * pre-process bio queue isn't empty,
         * then don't wait, as we need to empty
         * that queue to get the nr_pending
         * count down.
         */
        wait_event_lock_irq(conf->wait_barrier,
                    !conf->barrier ||
                    (conf->nr_pending &&
                     current->bio_list &&
                     !bio_list_empty(current->bio_list)),
                    conf->resync_lock,
            );
        conf->nr_waiting--;
    }
    conf->nr_pending++;
    spin_unlock_irq(&conf->resync_lock);
}

static void allow_barrier(struct r1conf *conf)
{
    unsigned long flags;
    spin_lock_irqsave(&conf->resync_lock, flags);
    conf->nr_pending--;
    spin_unlock_irqrestore(&conf->resync_lock, flags);
    wake_up(&conf->wait_barrier);
}

static void freeze_array(struct r1conf *conf)
{
    /* stop syncio and normal IO and wait for everything to
     * go quite.
     * We increment barrier and nr_waiting, and then
     * wait until nr_pending match nr_queued+1
     * This is called in the context of one normal IO request
     * that has failed. Thus any sync request that might be pending
     * will be blocked by nr_pending, and we need to wait for
     * pending IO requests to complete or be queued for re-try.
     * Thus the number queued (nr_queued) plus this request (1)
     * must match the number of pending IOs (nr_pending) before
     * we continue.
     */
    spin_lock_irq(&conf->resync_lock);
    conf->barrier++;
    conf->nr_waiting++;
    wait_event_lock_irq(conf->wait_barrier,
                conf->nr_pending == conf->nr_queued+1,
                conf->resync_lock,
                flush_pending_writes(conf));
    spin_unlock_irq(&conf->resync_lock);
}
static void unfreeze_array(struct r1conf *conf)
{
    /* reverse the effect of the freeze */
    spin_lock_irq(&conf->resync_lock);
    conf->barrier--;
    conf->nr_waiting--;
    wake_up(&conf->wait_barrier);
    spin_unlock_irq(&conf->resync_lock);
}


/* duplicate the data pages for behind I/O 
 */
static void alloc_behind_pages(struct bio *bio, struct r1bio *r1_bio)
{
    int i;
    struct bio_vec *bvec;
    struct bio_vec *bvecs = kzalloc(bio->bi_vcnt * sizeof(struct bio_vec),
                    GFP_NOIO);
    if (unlikely(!bvecs))
        return;

    bio_for_each_segment(bvec, bio, i) {
        bvecs[i] = *bvec;
        bvecs[i].bv_page = alloc_page(GFP_NOIO);
        if (unlikely(!bvecs[i].bv_page))
            goto do_sync_io;
        memcpy(kmap(bvecs[i].bv_page) + bvec->bv_offset,
               kmap(bvec->bv_page) + bvec->bv_offset, bvec->bv_len);
        kunmap(bvecs[i].bv_page);
        kunmap(bvec->bv_page);
    }
    r1_bio->behind_bvecs = bvecs;
    r1_bio->behind_page_count = bio->bi_vcnt;
    set_bit(R1BIO_BehindIO, &r1_bio->state);
    return;

do_sync_io:
    for (i = 0; i < bio->bi_vcnt; i++)
        if (bvecs[i].bv_page)
            put_page(bvecs[i].bv_page);
    kfree(bvecs);
    pr_debug("%dB behind alloc failed, doing sync I/O\n", bio->bi_size);
}

struct raid1_plug_cb {
    struct blk_plug_cb  cb;
    struct bio_list     pending;
    int         pending_cnt;
};

static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule)
{
    struct raid1_plug_cb *plug = container_of(cb, struct raid1_plug_cb,
                          cb);
    struct mddev *mddev = plug->cb.data;
    struct r1conf *conf = mddev->private;
    struct bio *bio;

    if (from_schedule || current->bio_list) {
        spin_lock_irq(&conf->device_lock);
        bio_list_merge(&conf->pending_bio_list, &plug->pending);
        conf->pending_count += plug->pending_cnt;
        spin_unlock_irq(&conf->device_lock);
        md_wakeup_thread(mddev->thread);
        kfree(plug);
        return;
    }

    /* we aren't scheduling, so we can do the write-out directly. */
    bio = bio_list_get(&plug->pending);
    bitmap_unplug(mddev->bitmap);
    wake_up(&conf->wait_barrier);

    while (bio) { /* submit pending writes */
        struct bio *next = bio->bi_next;
        bio->bi_next = NULL;
        generic_make_request(bio);
        bio = next;
    }
    kfree(plug);
}

static void make_request(struct mddev *mddev, struct bio * bio)
{
    struct r1conf *conf = mddev->private;
    struct raid1_info *mirror;
    struct r1bio *r1_bio;
    struct bio *read_bio;
    int i, disks;
    struct bitmap *bitmap;
    unsigned long flags;
    const int rw = bio_data_dir(bio);
    const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
    const unsigned long do_flush_fua = (bio->bi_rw & (REQ_FLUSH | REQ_FUA));
    const unsigned long do_discard = (bio->bi_rw
                      & (REQ_DISCARD | REQ_SECURE));
    struct md_rdev *blocked_rdev;
    struct blk_plug_cb *cb;
    struct raid1_plug_cb *plug = NULL;
    int first_clone;
    int sectors_handled;
    int max_sectors;

    /*
     * Register the new request and wait if the reconstruction
     * thread has put up a bar for new requests.
     * Continue immediately if no resync is active currently.
     */

    md_write_start(mddev, bio); /* wait on superblock update early */

    if (bio_data_dir(bio) == WRITE &&
        bio->bi_sector + bio->bi_size/512 > mddev->suspend_lo &&
        bio->bi_sector < mddev->suspend_hi) {
        /* As the suspend_* range is controlled by
         * userspace, we want an interruptible
         * wait.
         */
        DEFINE_WAIT(w);
        for (;;) {
            flush_signals(current);
            prepare_to_wait(&conf->wait_barrier,
                    &w, TASK_INTERRUPTIBLE);
            if (bio->bi_sector + bio->bi_size/512 <= mddev->suspend_lo ||
                bio->bi_sector >= mddev->suspend_hi)
                break;
            schedule();
        }
        finish_wait(&conf->wait_barrier, &w);
    }

    wait_barrier(conf);

    bitmap = mddev->bitmap;

    /*
     * make_request() can abort the operation when READA is being
     * used and no empty request is available.
     *
     */
    r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);

    r1_bio->master_bio = bio;
    r1_bio->sectors = bio->bi_size >> 9;
    r1_bio->state = 0;
    r1_bio->mddev = mddev;
    r1_bio->sector = bio->bi_sector;

    /* We might need to issue multiple reads to different
     * devices if there are bad blocks around, so we keep
     * track of the number of reads in bio->bi_phys_segments.
     * If this is 0, there is only one r1_bio and no locking
     * will be needed when requests complete.  If it is
     * non-zero, then it is the number of not-completed requests.
     */
    bio->bi_phys_segments = 0;
    clear_bit(BIO_SEG_VALID, &bio->bi_flags);

    if (rw == READ) {
        /*
         * read balancing logic:
         */
        int rdisk;

read_again:
        rdisk = read_balance(conf, r1_bio, &max_sectors);

        if (rdisk < 0) {
            /* couldn't find anywhere to read from */
            raid_end_bio_io(r1_bio);
            return;
        }
        mirror = conf->mirrors + rdisk;

        if (test_bit(WriteMostly, &mirror->rdev->flags) &&
            bitmap) {
            /* Reading from a write-mostly device must
             * take care not to over-take any writes
             * that are 'behind'
             */
            wait_event(bitmap->behind_wait,
                   atomic_read(&bitmap->behind_writes) == 0);
        }
        r1_bio->read_disk = rdisk;

        read_bio = bio_clone_mddev(bio, GFP_NOIO, mddev);
        md_trim_bio(read_bio, r1_bio->sector - bio->bi_sector,
                max_sectors);

        r1_bio->bios[rdisk] = read_bio;

        read_bio->bi_sector = r1_bio->sector + mirror->rdev->data_offset;
        read_bio->bi_bdev = mirror->rdev->bdev;
        read_bio->bi_end_io = raid1_end_read_request;
        read_bio->bi_rw = READ | do_sync;
        read_bio->bi_private = r1_bio;

        if (max_sectors < r1_bio->sectors) {
            /* could not read all from this device, so we will
             * need another r1_bio.
             */

            sectors_handled = (r1_bio->sector + max_sectors
                       - bio->bi_sector);
            r1_bio->sectors = max_sectors;
            spin_lock_irq(&conf->device_lock);
            if (bio->bi_phys_segments == 0)
                bio->bi_phys_segments = 2;
            else
                bio->bi_phys_segments++;
            spin_unlock_irq(&conf->device_lock);
            /* Cannot call generic_make_request directly
             * as that will be queued in __make_request
             * and subsequent mempool_alloc might block waiting
             * for it.  So hand bio over to raid1d.
             */
            reschedule_retry(r1_bio);

            r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);

            r1_bio->master_bio = bio;
            r1_bio->sectors = (bio->bi_size >> 9) - sectors_handled;
            r1_bio->state = 0;
            r1_bio->mddev = mddev;
            r1_bio->sector = bio->bi_sector + sectors_handled;
            goto read_again;
        } else
            generic_make_request(read_bio);
        return;
    }

    /*
     * WRITE:
     */
    if (conf->pending_count >= max_queued_requests) {
        md_wakeup_thread(mddev->thread);
        wait_event(conf->wait_barrier,
               conf->pending_count < max_queued_requests);
    }
    /* first select target devices under rcu_lock and
     * inc refcount on their rdev.  Record them by setting
     * bios[x] to bio
     * If there are known/acknowledged bad blocks on any device on
     * which we have seen a write error, we want to avoid writing those
     * blocks.
     * This potentially requires several writes to write around
     * the bad blocks.  Each set of writes gets it's own r1bio
     * with a set of bios attached.
     */

    disks = conf->raid_disks * 2;
 retry_write:
    blocked_rdev = NULL;
    rcu_read_lock();
    max_sectors = r1_bio->sectors;
    for (i = 0;  i < disks; i++) {
        struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
        if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
            atomic_inc(&rdev->nr_pending);
            blocked_rdev = rdev;
            break;
        }
        r1_bio->bios[i] = NULL;
        if (!rdev || test_bit(Faulty, &rdev->flags)
            || test_bit(Unmerged, &rdev->flags)) {
            if (i < conf->raid_disks)
                set_bit(R1BIO_Degraded, &r1_bio->state);
            continue;
        }

        atomic_inc(&rdev->nr_pending);
        if (test_bit(WriteErrorSeen, &rdev->flags)) {
            sector_t first_bad;
            int bad_sectors;
            int is_bad;

            is_bad = is_badblock(rdev, r1_bio->sector,
                         max_sectors,
                         &first_bad, &bad_sectors);
            if (is_bad < 0) {
                /* mustn't write here until the bad block is
                 * acknowledged*/
                set_bit(BlockedBadBlocks, &rdev->flags);
                blocked_rdev = rdev;
                break;
            }
            if (is_bad && first_bad <= r1_bio->sector) {
                /* Cannot write here at all */
                bad_sectors -= (r1_bio->sector - first_bad);
                if (bad_sectors < max_sectors)
                    /* mustn't write more than bad_sectors
                     * to other devices yet
                     */
                    max_sectors = bad_sectors;
                rdev_dec_pending(rdev, mddev);
                /* We don't set R1BIO_Degraded as that
                 * only applies if the disk is
                 * missing, so it might be re-added,
                 * and we want to know to recover this
                 * chunk.
                 * In this case the device is here,
                 * and the fact that this chunk is not
                 * in-sync is recorded in the bad
                 * block log
                 */
                continue;
            }
            if (is_bad) {
                int good_sectors = first_bad - r1_bio->sector;
                if (good_sectors < max_sectors)
                    max_sectors = good_sectors;
            }
        }
        r1_bio->bios[i] = bio;
    }
    rcu_read_unlock();

    if (unlikely(blocked_rdev)) {
        /* Wait for this device to become unblocked */
        int j;

        for (j = 0; j < i; j++)
            if (r1_bio->bios[j])
                rdev_dec_pending(conf->mirrors[j].rdev, mddev);
        r1_bio->state = 0;
        allow_barrier(conf);
        md_wait_for_blocked_rdev(blocked_rdev, mddev);
        wait_barrier(conf);
        goto retry_write;
    }

    if (max_sectors < r1_bio->sectors) {
        /* We are splitting this write into multiple parts, so
         * we need to prepare for allocating another r1_bio.
         */
        r1_bio->sectors = max_sectors;
        spin_lock_irq(&conf->device_lock);
        if (bio->bi_phys_segments == 0)
            bio->bi_phys_segments = 2;
        else
            bio->bi_phys_segments++;
        spin_unlock_irq(&conf->device_lock);
    }
    sectors_handled = r1_bio->sector + max_sectors - bio->bi_sector;

    atomic_set(&r1_bio->remaining, 1);
    atomic_set(&r1_bio->behind_remaining, 0);

    first_clone = 1;
    for (i = 0; i < disks; i++) {
        struct bio *mbio;
        if (!r1_bio->bios[i])
            continue;

        mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
        md_trim_bio(mbio, r1_bio->sector - bio->bi_sector, max_sectors);

        if (first_clone) {
            /* do behind I/O ?
             * Not if there are too many, or cannot
             * allocate memory, or a reader on WriteMostly
             * is waiting for behind writes to flush */
            if (bitmap &&
                (atomic_read(&bitmap->behind_writes)
                 < mddev->bitmap_info.max_write_behind) &&
                !waitqueue_active(&bitmap->behind_wait))
                alloc_behind_pages(mbio, r1_bio);

            bitmap_startwrite(bitmap, r1_bio->sector,
                      r1_bio->sectors,
                      test_bit(R1BIO_BehindIO,
                           &r1_bio->state));
            first_clone = 0;
        }
        if (r1_bio->behind_bvecs) {
            struct bio_vec *bvec;
            int j;

            /* Yes, I really want the '__' version so that
             * we clear any unused pointer in the io_vec, rather
             * than leave them unchanged.  This is important
             * because when we come to free the pages, we won't
             * know the original bi_idx, so we just free
             * them all
             */
            __bio_for_each_segment(bvec, mbio, j, 0)
                bvec->bv_page = r1_bio->behind_bvecs[j].bv_page;
            if (test_bit(WriteMostly, &conf->mirrors[i].rdev->flags))
                atomic_inc(&r1_bio->behind_remaining);
        }

        r1_bio->bios[i] = mbio;

        mbio->bi_sector = (r1_bio->sector +
                   conf->mirrors[i].rdev->data_offset);
        mbio->bi_bdev = conf->mirrors[i].rdev->bdev;
        mbio->bi_end_io = raid1_end_write_request;
        mbio->bi_rw = WRITE | do_flush_fua | do_sync | do_discard;
        mbio->bi_private = r1_bio;

        atomic_inc(&r1_bio->remaining);

        cb = blk_check_plugged(raid1_unplug, mddev, sizeof(*plug));
        if (cb)
            plug = container_of(cb, struct raid1_plug_cb, cb);
        else
            plug = NULL;
        spin_lock_irqsave(&conf->device_lock, flags);
        if (plug) {
            bio_list_add(&plug->pending, mbio);
            plug->pending_cnt++;
        } else {
            bio_list_add(&conf->pending_bio_list, mbio);
            conf->pending_count++;
        }
        spin_unlock_irqrestore(&conf->device_lock, flags);
        if (!plug)
            md_wakeup_thread(mddev->thread);
    }
    /* Mustn't call r1_bio_write_done before this next test,
     * as it could result in the bio being freed.
     */
    if (sectors_handled < (bio->bi_size >> 9)) {
        r1_bio_write_done(r1_bio);
        /* We need another r1_bio.  It has already been counted
         * in bio->bi_phys_segments
         */
        r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);
        r1_bio->master_bio = bio;
        r1_bio->sectors = (bio->bi_size >> 9) - sectors_handled;
        r1_bio->state = 0;
        r1_bio->mddev = mddev;
        r1_bio->sector = bio->bi_sector + sectors_handled;
        goto retry_write;
    }

    r1_bio_write_done(r1_bio);

    /* In case raid1d snuck in to freeze_array */
    wake_up(&conf->wait_barrier);
}

static void status(struct seq_file *seq, struct mddev *mddev)
{
    struct r1conf *conf = mddev->private;
    int i;

    seq_printf(seq, " [%d/%d] [", conf->raid_disks,
           conf->raid_disks - mddev->degraded);
    rcu_read_lock();
    for (i = 0; i < conf->raid_disks; i++) {
        struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
        seq_printf(seq, "%s",
               rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
    }
    rcu_read_unlock();
    seq_printf(seq, "]");
}


static void error(struct mddev *mddev, struct md_rdev *rdev)
{
    char b[BDEVNAME_SIZE];
    struct r1conf *conf = mddev->private;

    /*
     * If it is not operational, then we have already marked it as dead
     * else if it is the last working disks, ignore the error, let the
     * next level up know.
     * else mark the drive as failed
     */
    if (test_bit(In_sync, &rdev->flags)
        && (conf->raid_disks - mddev->degraded) == 1) {
        /*
         * Don't fail the drive, act as though we were just a
         * normal single drive.
         * However don't try a recovery from this drive as
         * it is very likely to fail.
         */
        conf->recovery_disabled = mddev->recovery_disabled;
        return;
    }
    set_bit(Blocked, &rdev->flags);
    if (test_and_clear_bit(In_sync, &rdev->flags)) {
        unsigned long flags;
        spin_lock_irqsave(&conf->device_lock, flags);
        mddev->degraded++;
        set_bit(Faulty, &rdev->flags);
        spin_unlock_irqrestore(&conf->device_lock, flags);
        /*
         * if recovery is running, make sure it aborts.
         */
        set_bit(MD_RECOVERY_INTR, &mddev->recovery);
    } else
        set_bit(Faulty, &rdev->flags);
    set_bit(MD_CHANGE_DEVS, &mddev->flags);
    printk(KERN_ALERT
           "md/raid1:%s: Disk failure on %s, disabling device.\n"
           "md/raid1:%s: Operation continuing on %d devices.\n",
           mdname(mddev), bdevname(rdev->bdev, b),
           mdname(mddev), conf->raid_disks - mddev->degraded);
}

static void print_conf(struct r1conf *conf)
{
    int i;

    printk(KERN_DEBUG "RAID1 conf printout:\n");
    if (!conf) {
        printk(KERN_DEBUG "(!conf)\n");
        return;
    }
    printk(KERN_DEBUG " --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
        conf->raid_disks);

    rcu_read_lock();
    for (i = 0; i < conf->raid_disks; i++) {
        char b[BDEVNAME_SIZE];
        struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
        if (rdev)
            printk(KERN_DEBUG " disk %d, wo:%d, o:%d, dev:%s\n",
                   i, !test_bit(In_sync, &rdev->flags),
                   !test_bit(Faulty, &rdev->flags),
                   bdevname(rdev->bdev,b));
    }
    rcu_read_unlock();
}

static void close_sync(struct r1conf *conf)
{
    wait_barrier(conf);
    allow_barrier(conf);

    mempool_destroy(conf->r1buf_pool);
    conf->r1buf_pool = NULL;
}

static int raid1_spare_active(struct mddev *mddev)
{
    int i;
    struct r1conf *conf = mddev->private;
    int count = 0;
    unsigned long flags;

    /*
     * Find all failed disks within the RAID1 configuration 
     * and mark them readable.
     * Called under mddev lock, so rcu protection not needed.
     */
    for (i = 0; i < conf->raid_disks; i++) {
        struct md_rdev *rdev = conf->mirrors[i].rdev;
        struct md_rdev *repl = conf->mirrors[conf->raid_disks + i].rdev;
        if (repl
            && repl->recovery_offset == MaxSector
            && !test_bit(Faulty, &repl->flags)
            && !test_and_set_bit(In_sync, &repl->flags)) {
            /* replacement has just become active */
            if (!rdev ||
                !test_and_clear_bit(In_sync, &rdev->flags))
                count++;
            if (rdev) {
                /* Replaced device not technically
                 * faulty, but we need to be sure
                 * it gets removed and never re-added
                 */
                set_bit(Faulty, &rdev->flags);
                sysfs_notify_dirent_safe(
                    rdev->sysfs_state);
            }
        }
        if (rdev
            && !test_bit(Faulty, &rdev->flags)
            && !test_and_set_bit(In_sync, &rdev->flags)) {
            count++;
            sysfs_notify_dirent_safe(rdev->sysfs_state);
        }
    }
    spin_lock_irqsave(&conf->device_lock, flags);
    mddev->degraded -= count;
    spin_unlock_irqrestore(&conf->device_lock, flags);

    print_conf(conf);
    return count;
}


static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
{
    struct r1conf *conf = mddev->private;
    int err = -EEXIST;
    int mirror = 0;
    struct raid1_info *p;
    int first = 0;
    int last = conf->raid_disks - 1;
    struct request_queue *q = bdev_get_queue(rdev->bdev);

    if (mddev->recovery_disabled == conf->recovery_disabled)
        return -EBUSY;

    if (rdev->raid_disk >= 0)
        first = last = rdev->raid_disk;

    if (q->merge_bvec_fn) {
        set_bit(Unmerged, &rdev->flags);
        mddev->merge_check_needed = 1;
    }

    for (mirror = first; mirror <= last; mirror++) {
        p = conf->mirrors+mirror;
        if (!p->rdev) {

            disk_stack_limits(mddev->gendisk, rdev->bdev,
                      rdev->data_offset << 9);

            p->head_position = 0;
            rdev->raid_disk = mirror;
            err = 0;
            /* As all devices are equivalent, we don't need a full recovery
             * if this was recently any drive of the array
             */
            if (rdev->saved_raid_disk < 0)
                conf->fullsync = 1;
            rcu_assign_pointer(p->rdev, rdev);
            break;
        }
        if (test_bit(WantReplacement, &p->rdev->flags) &&
            p[conf->raid_disks].rdev == NULL) {
            /* Add this device as a replacement */
            clear_bit(In_sync, &rdev->flags);
            set_bit(Replacement, &rdev->flags);
            rdev->raid_disk = mirror;
            err = 0;
            conf->fullsync = 1;
            rcu_assign_pointer(p[conf->raid_disks].rdev, rdev);
            break;
        }
    }
    if (err == 0 && test_bit(Unmerged, &rdev->flags)) {
        /* Some requests might not have seen this new
         * merge_bvec_fn.  We must wait for them to complete
         * before merging the device fully.
         * First we make sure any code which has tested
         * our function has submitted the request, then
         * we wait for all outstanding requests to complete.
         */
        synchronize_sched();
        raise_barrier(conf);
        lower_barrier(conf);
        clear_bit(Unmerged, &rdev->flags);
    }
    md_integrity_add_rdev(rdev, mddev);
    if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
    print_conf(conf);
    return err;
}

static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
{
    struct r1conf *conf = mddev->private;
    int err = 0;
    int number = rdev->raid_disk;
    struct raid1_info *p = conf->mirrors + number;

    if (rdev != p->rdev)
        p = conf->mirrors + conf->raid_disks + number;

    print_conf(conf);
    if (rdev == p->rdev) {
        if (test_bit(In_sync, &rdev->flags) ||
            atomic_read(&rdev->nr_pending)) {
            err = -EBUSY;
            goto abort;
        }
        /* Only remove non-faulty devices if recovery
         * is not possible.
         */
        if (!test_bit(Faulty, &rdev->flags) &&
            mddev->recovery_disabled != conf->recovery_disabled &&
            mddev->degraded < conf->raid_disks) {
            err = -EBUSY;
            goto abort;
        }
        p->rdev = NULL;
        synchronize_rcu();
        if (atomic_read(&rdev->nr_pending)) {
            /* lost the race, try later */
            err = -EBUSY;
            p->rdev = rdev;
            goto abort;
        } else if (conf->mirrors[conf->raid_disks + number].rdev) {
            /* We just removed a device that is being replaced.
             * Move down the replacement.  We drain all IO before
             * doing this to avoid confusion.
             */
            struct md_rdev *repl =
                conf->mirrors[conf->raid_disks + number].rdev;
            raise_barrier(conf);
            clear_bit(Replacement, &repl->flags);
            p->rdev = repl;
            conf->mirrors[conf->raid_disks + number].rdev = NULL;
            lower_barrier(conf);
            clear_bit(WantReplacement, &rdev->flags);
        } else
            clear_bit(WantReplacement, &rdev->flags);
        err = md_integrity_register(mddev);
    }
abort:

    print_conf(conf);
    return err;
}


static void end_sync_read(struct bio *bio, int error)
{
    struct r1bio *r1_bio = bio->bi_private;

    update_head_pos(r1_bio->read_disk, r1_bio);

    /*
     * we have read a block, now it needs to be re-written,
     * or re-read if the read failed.
     * We don't do much here, just schedule handling by raid1d
     */
    if (test_bit(BIO_UPTODATE, &bio->bi_flags))
        set_bit(R1BIO_Uptodate, &r1_bio->state);

    if (atomic_dec_and_test(&r1_bio->remaining))
        reschedule_retry(r1_bio);
}

static void end_sync_write(struct bio *bio, int error)
{
    int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
    struct r1bio *r1_bio = bio->bi_private;
    struct mddev *mddev = r1_bio->mddev;
    struct r1conf *conf = mddev->private;
    int mirror=0;
    sector_t first_bad;
    int bad_sectors;

    mirror = find_bio_disk(r1_bio, bio);

    if (!uptodate) {
        sector_t sync_blocks = 0;
        sector_t s = r1_bio->sector;
        long sectors_to_go = r1_bio->sectors;
        /* make sure these bits doesn't get cleared. */
        do {
            bitmap_end_sync(mddev->bitmap, s,
                    &sync_blocks, 1);
            s += sync_blocks;
            sectors_to_go -= sync_blocks;
        } while (sectors_to_go > 0);
        set_bit(WriteErrorSeen,
            &conf->mirrors[mirror].rdev->flags);
        if (!test_and_set_bit(WantReplacement,
                      &conf->mirrors[mirror].rdev->flags))
            set_bit(MD_RECOVERY_NEEDED, &
                mddev->recovery);
        set_bit(R1BIO_WriteError, &r1_bio->state);
    } else if (is_badblock(conf->mirrors[mirror].rdev,
                   r1_bio->sector,
                   r1_bio->sectors,
                   &first_bad, &bad_sectors) &&
           !is_badblock(conf->mirrors[r1_bio->read_disk].rdev,
                r1_bio->sector,
                r1_bio->sectors,
                &first_bad, &bad_sectors)
        )
        set_bit(R1BIO_MadeGood, &r1_bio->state);

    if (atomic_dec_and_test(&r1_bio->remaining)) {
        int s = r1_bio->sectors;
        if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
            test_bit(R1BIO_WriteError, &r1_bio->state))
            reschedule_retry(r1_bio);
        else {
            put_buf(r1_bio);
            md_done_sync(mddev, s, uptodate);
        }
    }
}

static int r1_sync_page_io(struct md_rdev *rdev, sector_t sector,
                int sectors, struct page *page, int rw)
{
    if (sync_page_io(rdev, sector, sectors << 9, page, rw, false))
        /* success */
        return 1;
    if (rw == WRITE) {
        set_bit(WriteErrorSeen, &rdev->flags);
        if (!test_and_set_bit(WantReplacement,
                      &rdev->flags))
            set_bit(MD_RECOVERY_NEEDED, &
                rdev->mddev->recovery);
    }
    /* need to record an error - either for the block or the device */
    if (!rdev_set_badblocks(rdev, sector, sectors, 0))
        md_error(rdev->mddev, rdev);
    return 0;
}

static int fix_sync_read_error(struct r1bio *r1_bio)
{
    /* Try some synchronous reads of other devices to get
     * good data, much like with normal read errors.  Only
     * read into the pages we already have so we don't
     * need to re-issue the read request.
     * We don't need to freeze the array, because being in an
     * active sync request, there is no normal IO, and
     * no overlapping syncs.
     * We don't need to check is_badblock() again as we
     * made sure that anything with a bad block in range
     * will have bi_end_io clear.
     */
    struct mddev *mddev = r1_bio->mddev;
    struct r1conf *conf = mddev->private;
    struct bio *bio = r1_bio->bios[r1_bio->read_disk];
    sector_t sect = r1_bio->sector;
    int sectors = r1_bio->sectors;
    int idx = 0;

    while(sectors) {
        int s = sectors;
        int d = r1_bio->read_disk;
        int success = 0;
        struct md_rdev *rdev;
        int start;

        if (s > (PAGE_SIZE>>9))
            s = PAGE_SIZE >> 9;
        do {
            if (r1_bio->bios[d]->bi_end_io == end_sync_read) {
                /* No rcu protection needed here devices
                 * can only be removed when no resync is
                 * active, and resync is currently active
                 */
                rdev = conf->mirrors[d].rdev;
                if (sync_page_io(rdev, sect, s<<9,
                         bio->bi_io_vec[idx].bv_page,
                         READ, false)) {
                    success = 1;
                    break;
                }
            }
            d++;
            if (d == conf->raid_disks * 2)
                d = 0;
        } while (!success && d != r1_bio->read_disk);

        if (!success) {
            char b[BDEVNAME_SIZE];
            int abort = 0;
            /* Cannot read from anywhere, this block is lost.
             * Record a bad block on each device.  If that doesn't
             * work just disable and interrupt the recovery.
             * Don't fail devices as that won't really help.
             */
            printk(KERN_ALERT "md/raid1:%s: %s: unrecoverable I/O read error"
                   " for block %llu\n",
                   mdname(mddev),
                   bdevname(bio->bi_bdev, b),
                   (unsigned long long)r1_bio->sector);
            for (d = 0; d < conf->raid_disks * 2; d++) {
                rdev = conf->mirrors[d].rdev;
                if (!rdev || test_bit(Faulty, &rdev->flags))
                    continue;
                if (!rdev_set_badblocks(rdev, sect, s, 0))
                    abort = 1;
            }
            if (abort) {
                conf->recovery_disabled =
                    mddev->recovery_disabled;
                set_bit(MD_RECOVERY_INTR, &mddev->recovery);
                md_done_sync(mddev, r1_bio->sectors, 0);
                put_buf(r1_bio);
                return 0;
            }
            /* Try next page */
            sectors -= s;
            sect += s;
            idx++;
            continue;
        }

        start = d;
        /* write it back and re-read */
        while (d != r1_bio->read_disk) {
            if (d == 0)
                d = conf->raid_disks * 2;
            d--;
            if (r1_bio->bios[d]->bi_end_io != end_sync_read)
                continue;
            rdev = conf->mirrors[d].rdev;
            if (r1_sync_page_io(rdev, sect, s,
                        bio->bi_io_vec[idx].bv_page,
                        WRITE) == 0) {
                r1_bio->bios[d]->bi_end_io = NULL;
                rdev_dec_pending(rdev, mddev);
            }
        }
        d = start;
        while (d != r1_bio->read_disk) {
            if (d == 0)
                d = conf->raid_disks * 2;
            d--;
            if (r1_bio->bios[d]->bi_end_io != end_sync_read)
                continue;
            rdev = conf->mirrors[d].rdev;
            if (r1_sync_page_io(rdev, sect, s,
                        bio->bi_io_vec[idx].bv_page,
                        READ) != 0)
                atomic_add(s, &rdev->corrected_errors);
        }
        sectors -= s;
        sect += s;
        idx ++;
    }
    set_bit(R1BIO_Uptodate, &r1_bio->state);
    set_bit(BIO_UPTODATE, &bio->bi_flags);
    return 1;
}

static int process_checks(struct r1bio *r1_bio)
{
    /* We have read all readable devices.  If we haven't
     * got the block, then there is no hope left.
     * If we have, then we want to do a comparison
     * and skip the write if everything is the same.
     * If any blocks failed to read, then we need to
     * attempt an over-write
     */
    struct mddev *mddev = r1_bio->mddev;
    struct r1conf *conf = mddev->private;
    int primary;
    int i;
    int vcnt;

    for (primary = 0; primary < conf->raid_disks * 2; primary++)
        if (r1_bio->bios[primary]->bi_end_io == end_sync_read &&
            test_bit(BIO_UPTODATE, &r1_bio->bios[primary]->bi_flags)) {
            r1_bio->bios[primary]->bi_end_io = NULL;
            rdev_dec_pending(conf->mirrors[primary].rdev, mddev);
            break;
        }
    r1_bio->read_disk = primary;
    vcnt = (r1_bio->sectors + PAGE_SIZE / 512 - 1) >> (PAGE_SHIFT - 9);
    for (i = 0; i < conf->raid_disks * 2; i++) {
        int j;
        struct bio *pbio = r1_bio->bios[primary];
        struct bio *sbio = r1_bio->bios[i];
        int size;

        if (r1_bio->bios[i]->bi_end_io != end_sync_read)
            continue;

        if (test_bit(BIO_UPTODATE, &sbio->bi_flags)) {
            for (j = vcnt; j-- ; ) {
                struct page *p, *s;
                p = pbio->bi_io_vec[j].bv_page;
                s = sbio->bi_io_vec[j].bv_page;
                if (memcmp(page_address(p),
                       page_address(s),
                       sbio->bi_io_vec[j].bv_len))
                    break;
            }
        } else
            j = 0;
        if (j >= 0)
            atomic64_add(r1_bio->sectors, &mddev->resync_mismatches);
        if (j < 0 || (test_bit(MD_RECOVERY_CHECK, &mddev->recovery)
                  && test_bit(BIO_UPTODATE, &sbio->bi_flags))) {
            /* No need to write to this device. */
            sbio->bi_end_io = NULL;
            rdev_dec_pending(conf->mirrors[i].rdev, mddev);
            continue;
        }
        /* fixup the bio for reuse */
        sbio->bi_vcnt = vcnt;
        sbio->bi_size = r1_bio->sectors << 9;
        sbio->bi_idx = 0;
        sbio->bi_phys_segments = 0;
        sbio->bi_flags &= ~(BIO_POOL_MASK - 1);
        sbio->bi_flags |= 1 << BIO_UPTODATE;
        sbio->bi_next = NULL;
        sbio->bi_sector = r1_bio->sector +
            conf->mirrors[i].rdev->data_offset;
        sbio->bi_bdev = conf->mirrors[i].rdev->bdev;
        size = sbio->bi_size;
        for (j = 0; j < vcnt ; j++) {
            struct bio_vec *bi;
            bi = &sbio->bi_io_vec[j];
            bi->bv_offset = 0;
            if (size > PAGE_SIZE)
                bi->bv_len = PAGE_SIZE;
            else
                bi->bv_len = size;
            size -= PAGE_SIZE;
            memcpy(page_address(bi->bv_page),
                   page_address(pbio->bi_io_vec[j].bv_page),
                   PAGE_SIZE);
        }
    }
    return 0;
}

static void sync_request_write(struct mddev *mddev, struct r1bio *r1_bio)
{
    struct r1conf *conf = mddev->private;
    int i;
    int disks = conf->raid_disks * 2;
    struct bio *bio, *wbio;

    bio = r1_bio->bios[r1_bio->read_disk];

    if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
        /* ouch - failed to read all of that. */
        if (!fix_sync_read_error(r1_bio))
            return;

    if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
        if (process_checks(r1_bio) < 0)
            return;
    /*
     * schedule writes
     */
    atomic_set(&r1_bio->remaining, 1);
    for (i = 0; i < disks ; i++) {
        wbio = r1_bio->bios[i];
        if (wbio->bi_end_io == NULL ||
            (wbio->bi_end_io == end_sync_read &&
             (i == r1_bio->read_disk ||
              !test_bit(MD_RECOVERY_SYNC, &mddev->recovery))))
            continue;

        wbio->bi_rw = WRITE;
        wbio->bi_end_io = end_sync_write;
        atomic_inc(&r1_bio->remaining);
        md_sync_acct(conf->mirrors[i].rdev->bdev, wbio->bi_size >> 9);

        generic_make_request(wbio);
    }

    if (atomic_dec_and_test(&r1_bio->remaining)) {
        /* if we're here, all write(s) have completed, so clean up */
        int s = r1_bio->sectors;
        if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
            test_bit(R1BIO_WriteError, &r1_bio->state))
            reschedule_retry(r1_bio);
        else {
            put_buf(r1_bio);
            md_done_sync(mddev, s, 1);
        }
    }
}

/*
 * This is a kernel thread which:
 *
 *  1.  Retries failed read operations on working mirrors.
 *  2.  Updates the raid superblock when problems encounter.
 *  3.  Performs writes following reads for array synchronising.
 */

static void fix_read_error(struct r1conf *conf, int read_disk,
               sector_t sect, int sectors)
{
    struct mddev *mddev = conf->mddev;
    while(sectors) {
        int s = sectors;
        int d = read_disk;
        int success = 0;
        int start;
        struct md_rdev *rdev;

        if (s > (PAGE_SIZE>>9))
            s = PAGE_SIZE >> 9;

        do {
            /* Note: no rcu protection needed here
             * as this is synchronous in the raid1d thread
             * which is the thread that might remove
             * a device.  If raid1d ever becomes multi-threaded....
             */
            sector_t first_bad;
            int bad_sectors;

            rdev = conf->mirrors[d].rdev;
            if (rdev &&
                (test_bit(In_sync, &rdev->flags) ||
                 (!test_bit(Faulty, &rdev->flags) &&
                  rdev->recovery_offset >= sect + s)) &&
                is_badblock(rdev, sect, s,
                    &first_bad, &bad_sectors) == 0 &&
                sync_page_io(rdev, sect, s<<9,
                     conf->tmppage, READ, false))
                success = 1;
            else {
                d++;
                if (d == conf->raid_disks * 2)
                    d = 0;
            }
        } while (!success && d != read_disk);

        if (!success) {
            /* Cannot read from anywhere - mark it bad */
            struct md_rdev *rdev = conf->mirrors[read_disk].rdev;
            if (!rdev_set_badblocks(rdev, sect, s, 0))
                md_error(mddev, rdev);
            break;
        }
        /* write it back and re-read */
        start = d;
        while (d != read_disk) {
            if (d==0)
                d = conf->raid_disks * 2;
            d--;
            rdev = conf->mirrors[d].rdev;
            if (rdev &&
                test_bit(In_sync, &rdev->flags))
                r1_sync_page_io(rdev, sect, s,
                        conf->tmppage, WRITE);
        }
        d = start;
        while (d != read_disk) {
            char b[BDEVNAME_SIZE];
            if (d==0)
                d = conf->raid_disks * 2;
            d--;
            rdev = conf->mirrors[d].rdev;
            if (rdev &&
                test_bit(In_sync, &rdev->flags)) {
                if (r1_sync_page_io(rdev, sect, s,
                            conf->tmppage, READ)) {
                    atomic_add(s, &rdev->corrected_errors);
                    printk(KERN_INFO
                           "md/raid1:%s: read error corrected "
                           "(%d sectors at %llu on %s)\n",
                           mdname(mddev), s,
                           (unsigned long long)(sect +
                               rdev->data_offset),
                           bdevname(rdev->bdev, b));
                }
            }
        }
        sectors -= s;
        sect += s;
    }
}

static void bi_complete(struct bio *bio, int error)
{
    complete((struct completion *)bio->bi_private);
}

static int submit_bio_wait(int rw, struct bio *bio)
{
    struct completion event;
    rw |= REQ_SYNC;

    init_completion(&event);
    bio->bi_private = &event;
    bio->bi_end_io = bi_complete;
    submit_bio(rw, bio);
    wait_for_completion(&event);

    return test_bit(BIO_UPTODATE, &bio->bi_flags);
}

static int narrow_write_error(struct r1bio *r1_bio, int i)
{
    struct mddev *mddev = r1_bio->mddev;
    struct r1conf *conf = mddev->private;
    struct md_rdev *rdev = conf->mirrors[i].rdev;
    int vcnt, idx;
    struct bio_vec *vec;

    /* bio has the data to be written to device 'i' where
     * we just recently had a write error.
     * We repeatedly clone the bio and trim down to one block,
     * then try the write.  Where the write fails we record
     * a bad block.
     * It is conceivable that the bio doesn't exactly align with
     * blocks.  We must handle this somehow.
     *
     * We currently own a reference on the rdev.
     */

    int block_sectors;
    sector_t sector;
    int sectors;
    int sect_to_write = r1_bio->sectors;
    int ok = 1;

    if (rdev->badblocks.shift < 0)
        return 0;

    block_sectors = 1 << rdev->badblocks.shift;
    sector = r1_bio->sector;
    sectors = ((sector + block_sectors)
           & ~(sector_t)(block_sectors - 1))
        - sector;

    if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
        vcnt = r1_bio->behind_page_count;
        vec = r1_bio->behind_bvecs;
        idx = 0;
        while (vec[idx].bv_page == NULL)
            idx++;
    } else {
        vcnt = r1_bio->master_bio->bi_vcnt;
        vec = r1_bio->master_bio->bi_io_vec;
        idx = r1_bio->master_bio->bi_idx;
    }
    while (sect_to_write) {
        struct bio *wbio;
        if (sectors > sect_to_write)
            sectors = sect_to_write;
        /* Write at 'sector' for 'sectors'*/

        wbio = bio_alloc_mddev(GFP_NOIO, vcnt, mddev);
        memcpy(wbio->bi_io_vec, vec, vcnt * sizeof(struct bio_vec));
        wbio->bi_sector = r1_bio->sector;
        wbio->bi_rw = WRITE;
        wbio->bi_vcnt = vcnt;
        wbio->bi_size = r1_bio->sectors << 9;
        wbio->bi_idx = idx;

        md_trim_bio(wbio, sector - r1_bio->sector, sectors);
        wbio->bi_sector += rdev->data_offset;
        wbio->bi_bdev = rdev->bdev;
        if (submit_bio_wait(WRITE, wbio) == 0)
            /* failure! */
            ok = rdev_set_badblocks(rdev, sector,
                        sectors, 0)
                && ok;

        bio_put(wbio);
        sect_to_write -= sectors;
        sector += sectors;
        sectors = block_sectors;
    }
    return ok;
}

static void handle_sync_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
{
    int m;
    int s = r1_bio->sectors;
    for (m = 0; m < conf->raid_disks * 2 ; m++) {
        struct md_rdev *rdev = conf->mirrors[m].rdev;
        struct bio *bio = r1_bio->bios[m];
        if (bio->bi_end_io == NULL)
            continue;
        if (test_bit(BIO_UPTODATE, &bio->bi_flags) &&
            test_bit(R1BIO_MadeGood, &r1_bio->state)) {
            rdev_clear_badblocks(rdev, r1_bio->sector, s, 0);
        }
        if (!test_bit(BIO_UPTODATE, &bio->bi_flags) &&
            test_bit(R1BIO_WriteError, &r1_bio->state)) {
            if (!rdev_set_badblocks(rdev, r1_bio->sector, s, 0))
                md_error(conf->mddev, rdev);
        }
    }
    put_buf(r1_bio);
    md_done_sync(conf->mddev, s, 1);
}

static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
{
    int m;
    for (m = 0; m < conf->raid_disks * 2 ; m++)
        if (r1_bio->bios[m] == IO_MADE_GOOD) {
            struct md_rdev *rdev = conf->mirrors[m].rdev;
            rdev_clear_badblocks(rdev,
                         r1_bio->sector,
                         r1_bio->sectors, 0);
            rdev_dec_pending(rdev, conf->mddev);
        } else if (r1_bio->bios[m] != NULL) {
            /* This drive got a write error.  We need to
             * narrow down and record precise write
             * errors.
             */
            if (!narrow_write_error(r1_bio, m)) {
                md_error(conf->mddev,
                     conf->mirrors[m].rdev);
                /* an I/O failed, we can't clear the bitmap */
                set_bit(R1BIO_Degraded, &r1_bio->state);
            }
            rdev_dec_pending(conf->mirrors[m].rdev,
                     conf->mddev);
        }
    if (test_bit(R1BIO_WriteError, &r1_bio->state))
        close_write(r1_bio);
    raid_end_bio_io(r1_bio);
}

static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
{
    int disk;
    int max_sectors;
    struct mddev *mddev = conf->mddev;
    struct bio *bio;
    char b[BDEVNAME_SIZE];
    struct md_rdev *rdev;

    clear_bit(R1BIO_ReadError, &r1_bio->state);
    /* we got a read error. Maybe the drive is bad.  Maybe just
     * the block and we can fix it.
     * We freeze all other IO, and try reading the block from
     * other devices.  When we find one, we re-write
     * and check it that fixes the read error.
     * This is all done synchronously while the array is
     * frozen
     */
    if (mddev->ro == 0) {
        freeze_array(conf);
        fix_read_error(conf, r1_bio->read_disk,
                   r1_bio->sector, r1_bio->sectors);
        unfreeze_array(conf);
    } else
        md_error(mddev, conf->mirrors[r1_bio->read_disk].rdev);
    rdev_dec_pending(conf->mirrors[r1_bio->read_disk].rdev, conf->mddev);

    bio = r1_bio->bios[r1_bio->read_disk];
    bdevname(bio->bi_bdev, b);
read_more:
    disk = read_balance(conf, r1_bio, &max_sectors);
    if (disk == -1) {
        printk(KERN_ALERT "md/raid1:%s: %s: unrecoverable I/O"
               " read error for block %llu\n",
               mdname(mddev), b, (unsigned long long)r1_bio->sector);
        raid_end_bio_io(r1_bio);
    } else {
        const unsigned long do_sync
            = r1_bio->master_bio->bi_rw & REQ_SYNC;
        if (bio) {
            r1_bio->bios[r1_bio->read_disk] =
                mddev->ro ? IO_BLOCKED : NULL;
            bio_put(bio);
        }
        r1_bio->read_disk = disk;
        bio = bio_clone_mddev(r1_bio->master_bio, GFP_NOIO, mddev);
        md_trim_bio(bio, r1_bio->sector - bio->bi_sector, max_sectors);
        r1_bio->bios[r1_bio->read_disk] = bio;
        rdev = conf->mirrors[disk].rdev;
        printk_ratelimited(KERN_ERR
                   "md/raid1:%s: redirecting sector %llu"
                   " to other mirror: %s\n",
                   mdname(mddev),
                   (unsigned long long)r1_bio->sector,
                   bdevname(rdev->bdev, b));
        bio->bi_sector = r1_bio->sector + rdev->data_offset;
        bio->bi_bdev = rdev->bdev;
        bio->bi_end_io = raid1_end_read_request;
        bio->bi_rw = READ | do_sync;
        bio->bi_private = r1_bio;
        if (max_sectors < r1_bio->sectors) {
            /* Drat - have to split this up more */
            struct bio *mbio = r1_bio->master_bio;
            int sectors_handled = (r1_bio->sector + max_sectors
                           - mbio->bi_sector);
            r1_bio->sectors = max_sectors;
            spin_lock_irq(&conf->device_lock);
            if (mbio->bi_phys_segments == 0)
                mbio->bi_phys_segments = 2;
            else
                mbio->bi_phys_segments++;
            spin_unlock_irq(&conf->device_lock);
            generic_make_request(bio);
            bio = NULL;

            r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);

            r1_bio->master_bio = mbio;
            r1_bio->sectors = (mbio->bi_size >> 9)
                      - sectors_handled;
            r1_bio->state = 0;
            set_bit(R1BIO_ReadError, &r1_bio->state);
            r1_bio->mddev = mddev;
            r1_bio->sector = mbio->bi_sector + sectors_handled;

            goto read_more;
        } else
            generic_make_request(bio);
    }
}

static void raid1d(struct md_thread *thread)
{
    struct mddev *mddev = thread->mddev;
    struct r1bio *r1_bio;
    unsigned long flags;
    struct r1conf *conf = mddev->private;
    struct list_head *head = &conf->retry_list;
    struct blk_plug plug;

    md_check_recovery(mddev);

    blk_start_plug(&plug);
    for (;;) {

        flush_pending_writes(conf);

        spin_lock_irqsave(&conf->device_lock, flags);
        if (list_empty(head)) {
            spin_unlock_irqrestore(&conf->device_lock, flags);
            break;
        }
        r1_bio = list_entry(head->prev, struct r1bio, retry_list);
        list_del(head->prev);
        conf->nr_queued--;
        spin_unlock_irqrestore(&conf->device_lock, flags);

        mddev = r1_bio->mddev;
        conf = mddev->private;
        if (test_bit(R1BIO_IsSync, &r1_bio->state)) {
            if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
                test_bit(R1BIO_WriteError, &r1_bio->state))
                handle_sync_write_finished(conf, r1_bio);
            else
                sync_request_write(mddev, r1_bio);
        } else if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
               test_bit(R1BIO_WriteError, &r1_bio->state))
            handle_write_finished(conf, r1_bio);
        else if (test_bit(R1BIO_ReadError, &r1_bio->state))
            handle_read_error(conf, r1_bio);
        else
            /* just a partial read to be scheduled from separate
             * context
             */
            generic_make_request(r1_bio->bios[r1_bio->read_disk]);

        cond_resched();
        if (mddev->flags & ~(1<<MD_CHANGE_PENDING))
            md_check_recovery(mddev);
    }
    blk_finish_plug(&plug);
}


static int init_resync(struct r1conf *conf)
{
    int buffs;

    buffs = RESYNC_WINDOW / RESYNC_BLOCK_SIZE;
    BUG_ON(conf->r1buf_pool);
    conf->r1buf_pool = mempool_create(buffs, r1buf_pool_alloc, r1buf_pool_free,
                      conf->poolinfo);
    if (!conf->r1buf_pool)
        return -ENOMEM;
    conf->next_resync = 0;
    return 0;
}

/*
 * perform a "sync" on one "block"
 *
 * We need to make sure that no normal I/O request - particularly write
 * requests - conflict with active sync requests.
 *
 * This is achieved by tracking pending requests and a 'barrier' concept
 * that can be installed to exclude normal IO requests.
 */

static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipped, int go_faster)
{
    struct r1conf *conf = mddev->private;
    struct r1bio *r1_bio;
    struct bio *bio;
    sector_t max_sector, nr_sectors;
    int disk = -1;
    int i;
    int wonly = -1;
    int write_targets = 0, read_targets = 0;
    sector_t sync_blocks;
    int still_degraded = 0;
    int good_sectors = RESYNC_SECTORS;
    int min_bad = 0; /* number of sectors that are bad in all devices */

    if (!conf->r1buf_pool)
        if (init_resync(conf))
            return 0;

    max_sector = mddev->dev_sectors;
    if (sector_nr >= max_sector) {
        /* If we aborted, we need to abort the
         * sync on the 'current' bitmap chunk (there will
         * only be one in raid1 resync.
         * We can find the current addess in mddev->curr_resync
         */
        if (mddev->curr_resync < max_sector) /* aborted */
            bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
                        &sync_blocks, 1);
        else /* completed sync */
            conf->fullsync = 0;

        bitmap_close_sync(mddev->bitmap);
        close_sync(conf);
        return 0;
    }

    if (mddev->bitmap == NULL &&
        mddev->recovery_cp == MaxSector &&
        !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
        conf->fullsync == 0) {
        *skipped = 1;
        return max_sector - sector_nr;
    }
    /* before building a request, check if we can skip these blocks..
     * This call the bitmap_start_sync doesn't actually record anything
     */
    if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
        !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
        /* We can skip this block, and probably several more */
        *skipped = 1;
        return sync_blocks;
    }
    /*
     * If there is non-resync activity waiting for a turn,
     * and resync is going fast enough,
     * then let it though before starting on this new sync request.
     */
    if (!go_faster && conf->nr_waiting)
        msleep_interruptible(1000);

    bitmap_cond_end_sync(mddev->bitmap, sector_nr);
    r1_bio = mempool_alloc(conf->r1buf_pool, GFP_NOIO);
    raise_barrier(conf);

    conf->next_resync = sector_nr;

    rcu_read_lock();
    /*
     * If we get a correctably read error during resync or recovery,
     * we might want to read from a different device.  So we
     * flag all drives that could conceivably be read from for READ,
     * and any others (which will be non-In_sync devices) for WRITE.
     * If a read fails, we try reading from something else for which READ
     * is OK.
     */

    r1_bio->mddev = mddev;
    r1_bio->sector = sector_nr;
    r1_bio->state = 0;
    set_bit(R1BIO_IsSync, &r1_bio->state);

    for (i = 0; i < conf->raid_disks * 2; i++) {
        struct md_rdev *rdev;
        bio = r1_bio->bios[i];

        /* take from bio_init */
        bio->bi_next = NULL;
        bio->bi_flags &= ~(BIO_POOL_MASK-1);
        bio->bi_flags |= 1 << BIO_UPTODATE;
        bio->bi_rw = READ;
        bio->bi_vcnt = 0;
        bio->bi_idx = 0;
        bio->bi_phys_segments = 0;
        bio->bi_size = 0;
        bio->bi_end_io = NULL;
        bio->bi_private = NULL;

        rdev = rcu_dereference(conf->mirrors[i].rdev);
        if (rdev == NULL ||
            test_bit(Faulty, &rdev->flags)) {
            if (i < conf->raid_disks)
                still_degraded = 1;
        } else if (!test_bit(In_sync, &rdev->flags)) {
            bio->bi_rw = WRITE;
            bio->bi_end_io = end_sync_write;
            write_targets ++;
        } else {
            /* may need to read from here */
            sector_t first_bad = MaxSector;
            int bad_sectors;

            if (is_badblock(rdev, sector_nr, good_sectors,
                    &first_bad, &bad_sectors)) {
                if (first_bad > sector_nr)
                    good_sectors = first_bad - sector_nr;
                else {
                    bad_sectors -= (sector_nr - first_bad);
                    if (min_bad == 0 ||
                        min_bad > bad_sectors)
                        min_bad = bad_sectors;
                }
            }
            if (sector_nr < first_bad) {
                if (test_bit(WriteMostly, &rdev->flags)) {
                    if (wonly < 0)
                        wonly = i;
                } else {
                    if (disk < 0)
                        disk = i;
                }
                bio->bi_rw = READ;
                bio->bi_end_io = end_sync_read;
                read_targets++;
            } else if (!test_bit(WriteErrorSeen, &rdev->flags) &&
                test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
                !test_bit(MD_RECOVERY_CHECK, &mddev->recovery)) {
                /*
                 * The device is suitable for reading (InSync),
                 * but has bad block(s) here. Let's try to correct them,
                 * if we are doing resync or repair. Otherwise, leave
                 * this device alone for this sync request.
                 */
                bio->bi_rw = WRITE;
                bio->bi_end_io = end_sync_write;
                write_targets++;
            }
        }
        if (bio->bi_end_io) {
            atomic_inc(&rdev->nr_pending);
            bio->bi_sector = sector_nr + rdev->data_offset;
            bio->bi_bdev = rdev->bdev;
            bio->bi_private = r1_bio;
        }
    }
    rcu_read_unlock();
    if (disk < 0)
        disk = wonly;
    r1_bio->read_disk = disk;

    if (read_targets == 0 && min_bad > 0) {
        /* These sectors are bad on all InSync devices, so we
         * need to mark them bad on all write targets
         */
        int ok = 1;
        for (i = 0 ; i < conf->raid_disks * 2 ; i++)
            if (r1_bio->bios[i]->bi_end_io == end_sync_write) {
                struct md_rdev *rdev = conf->mirrors[i].rdev;
                ok = rdev_set_badblocks(rdev, sector_nr,
                            min_bad, 0
                    ) && ok;
            }
        set_bit(MD_CHANGE_DEVS, &mddev->flags);
        *skipped = 1;
        put_buf(r1_bio);

        if (!ok) {
            /* Cannot record the badblocks, so need to
             * abort the resync.
             * If there are multiple read targets, could just
             * fail the really bad ones ???
             */
            conf->recovery_disabled = mddev->recovery_disabled;
            set_bit(MD_RECOVERY_INTR, &mddev->recovery);
            return 0;
        } else
            return min_bad;

    }
    if (min_bad > 0 && min_bad < good_sectors) {
        /* only resync enough to reach the next bad->good
         * transition */
        good_sectors = min_bad;
    }

    if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) && read_targets > 0)
        /* extra read targets are also write targets */
        write_targets += read_targets-1;

    if (write_targets == 0 || read_targets == 0) {
        /* There is nowhere to write, so all non-sync
         * drives must be failed - so we are finished
         */
        sector_t rv;
        if (min_bad > 0)
            max_sector = sector_nr + min_bad;
        rv = max_sector - sector_nr;
        *skipped = 1;
        put_buf(r1_bio);
        return rv;
    }

    if (max_sector > mddev->resync_max)
        max_sector = mddev->resync_max; /* Don't do IO beyond here */
    if (max_sector > sector_nr + good_sectors)
        max_sector = sector_nr + good_sectors;
    nr_sectors = 0;
    sync_blocks = 0;
    do {
        struct page *page;
        int len = PAGE_SIZE;
        if (sector_nr + (len>>9) > max_sector)
            len = (max_sector - sector_nr) << 9;
        if (len == 0)
            break;
        if (sync_blocks == 0) {
            if (!bitmap_start_sync(mddev->bitmap, sector_nr,
                           &sync_blocks, still_degraded) &&
                !conf->fullsync &&
                !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
                break;
            BUG_ON(sync_blocks < (PAGE_SIZE>>9));
            if ((len >> 9) > sync_blocks)
                len = sync_blocks<<9;
        }

        for (i = 0 ; i < conf->raid_disks * 2; i++) {
            bio = r1_bio->bios[i];
            if (bio->bi_end_io) {
                page = bio->bi_io_vec[bio->bi_vcnt].bv_page;
                if (bio_add_page(bio, page, len, 0) == 0) {
                    /* stop here */
                    bio->bi_io_vec[bio->bi_vcnt].bv_page = page;
                    while (i > 0) {
                        i--;
                        bio = r1_bio->bios[i];
                        if (bio->bi_end_io==NULL)
                            continue;
                        /* remove last page from this bio */
                        bio->bi_vcnt--;
                        bio->bi_size -= len;
                        bio->bi_flags &= ~(1<< BIO_SEG_VALID);
                    }
                    goto bio_full;
                }
            }
        }
        nr_sectors += len>>9;
        sector_nr += len>>9;
        sync_blocks -= (len>>9);
    } while (r1_bio->bios[disk]->bi_vcnt < RESYNC_PAGES);
 bio_full:
    r1_bio->sectors = nr_sectors;

    /* For a user-requested sync, we read all readable devices and do a
     * compare
     */
    if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
        atomic_set(&r1_bio->remaining, read_targets);
        for (i = 0; i < conf->raid_disks * 2 && read_targets; i++) {
            bio = r1_bio->bios[i];
            if (bio->bi_end_io == end_sync_read) {
                read_targets--;
                md_sync_acct(bio->bi_bdev, nr_sectors);
                generic_make_request(bio);
            }
        }
    } else {
        atomic_set(&r1_bio->remaining, 1);
        bio = r1_bio->bios[r1_bio->read_disk];
        md_sync_acct(bio->bi_bdev, nr_sectors);
        generic_make_request(bio);

    }
    return nr_sectors;
}

static sector_t raid1_size(struct mddev *mddev, sector_t sectors, int raid_disks)
{
    if (sectors)
        return sectors;

    return mddev->dev_sectors;
}

static struct r1conf *setup_conf(struct mddev *mddev)
{
    struct r1conf *conf;
    int i;
    struct raid1_info *disk;
    struct md_rdev *rdev;
    int err = -ENOMEM;

    conf = kzalloc(sizeof(struct r1conf), GFP_KERNEL);
    if (!conf)
        goto abort;

    conf->mirrors = kzalloc(sizeof(struct raid1_info)
                * mddev->raid_disks * 2,
                 GFP_KERNEL);
    if (!conf->mirrors)
        goto abort;

    conf->tmppage = alloc_page(GFP_KERNEL);
    if (!conf->tmppage)
        goto abort;

    conf->poolinfo = kzalloc(sizeof(*conf->poolinfo), GFP_KERNEL);
    if (!conf->poolinfo)
        goto abort;
    conf->poolinfo->raid_disks = mddev->raid_disks * 2;
    conf->r1bio_pool = mempool_create(NR_RAID1_BIOS, r1bio_pool_alloc,
                      r1bio_pool_free,
                      conf->poolinfo);
    if (!conf->r1bio_pool)
        goto abort;

    conf->poolinfo->mddev = mddev;

    err = -EINVAL;
    spin_lock_init(&conf->device_lock);
    rdev_for_each(rdev, mddev) {
        struct request_queue *q;
        int disk_idx = rdev->raid_disk;
        if (disk_idx >= mddev->raid_disks
            || disk_idx < 0)
            continue;
        if (test_bit(Replacement, &rdev->flags))
            disk = conf->mirrors + mddev->raid_disks + disk_idx;
        else
            disk = conf->mirrors + disk_idx;

        if (disk->rdev)
            goto abort;
        disk->rdev = rdev;
        q = bdev_get_queue(rdev->bdev);
        if (q->merge_bvec_fn)
            mddev->merge_check_needed = 1;

        disk->head_position = 0;
        disk->seq_start = MaxSector;
    }
    conf->raid_disks = mddev->raid_disks;
    conf->mddev = mddev;
    INIT_LIST_HEAD(&conf->retry_list);

    spin_lock_init(&conf->resync_lock);
    init_waitqueue_head(&conf->wait_barrier);

    bio_list_init(&conf->pending_bio_list);
    conf->pending_count = 0;
    conf->recovery_disabled = mddev->recovery_disabled - 1;

    err = -EIO;
    for (i = 0; i < conf->raid_disks * 2; i++) {

        disk = conf->mirrors + i;

        if (i < conf->raid_disks &&
            disk[conf->raid_disks].rdev) {
            /* This slot has a replacement. */
            if (!disk->rdev) {
                /* No original, just make the replacement
                 * a recovering spare
                 */
                disk->rdev =
                    disk[conf->raid_disks].rdev;
                disk[conf->raid_disks].rdev = NULL;
            } else if (!test_bit(In_sync, &disk->rdev->flags))
                /* Original is not in_sync - bad */
                goto abort;
        }

        if (!disk->rdev ||
            !test_bit(In_sync, &disk->rdev->flags)) {
            disk->head_position = 0;
            if (disk->rdev &&
                (disk->rdev->saved_raid_disk < 0))
                conf->fullsync = 1;
        }
    }

    err = -ENOMEM;
    conf->thread = md_register_thread(raid1d, mddev, "raid1");
    if (!conf->thread) {
        printk(KERN_ERR
               "md/raid1:%s: couldn't allocate thread\n",
               mdname(mddev));
        goto abort;
    }

    return conf;

 abort:
    if (conf) {
        if (conf->r1bio_pool)
            mempool_destroy(conf->r1bio_pool);
        kfree(conf->mirrors);
        safe_put_page(conf->tmppage);
        kfree(conf->poolinfo);
        kfree(conf);
    }
    return ERR_PTR(err);
}

static int stop(struct mddev *mddev);
static int run(struct mddev *mddev)
{
    struct r1conf *conf;
    int i;
    struct md_rdev *rdev;
    int ret;
    bool discard_supported = false;

    if (mddev->level != 1) {
        printk(KERN_ERR "md/raid1:%s: raid level not set to mirroring (%d)\n",
               mdname(mddev), mddev->level);
        return -EIO;
    }
    if (mddev->reshape_position != MaxSector) {
        printk(KERN_ERR "md/raid1:%s: reshape_position set but not supported\n",
               mdname(mddev));
        return -EIO;
    }
    /*
     * copy the already verified devices into our private RAID1
     * bookkeeping area. [whatever we allocate in run(),
     * should be freed in stop()]
     */
    if (mddev->private == NULL)
        conf = setup_conf(mddev);
    else
        conf = mddev->private;

    if (IS_ERR(conf))
        return PTR_ERR(conf);

    rdev_for_each(rdev, mddev) {
        if (!mddev->gendisk)
            continue;
        disk_stack_limits(mddev->gendisk, rdev->bdev,
                  rdev->data_offset << 9);
        if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
            discard_supported = true;
    }

    mddev->degraded = 0;
    for (i=0; i < conf->raid_disks; i++)
        if (conf->mirrors[i].rdev == NULL ||
            !test_bit(In_sync, &conf->mirrors[i].rdev->flags) ||
            test_bit(Faulty, &conf->mirrors[i].rdev->flags))
            mddev->degraded++;

    if (conf->raid_disks - mddev->degraded == 1)
        mddev->recovery_cp = MaxSector;

    if (mddev->recovery_cp != MaxSector)
        printk(KERN_NOTICE "md/raid1:%s: not clean"
               " -- starting background reconstruction\n",
               mdname(mddev));
    printk(KERN_INFO 
        "md/raid1:%s: active with %d out of %d mirrors\n",
        mdname(mddev), mddev->raid_disks - mddev->degraded, 
        mddev->raid_disks);

    /*
     * Ok, everything is just fine now
     */
    mddev->thread = conf->thread;
    conf->thread = NULL;
    mddev->private = conf;

    md_set_array_sectors(mddev, raid1_size(mddev, 0, 0));

    if (mddev->queue) {
        mddev->queue->backing_dev_info.congested_fn = raid1_congested;
        mddev->queue->backing_dev_info.congested_data = mddev;
        blk_queue_merge_bvec(mddev->queue, raid1_mergeable_bvec);

        if (discard_supported)
            queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
                        mddev->queue);
        else
            queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD,
                          mddev->queue);
    }

    ret =  md_integrity_register(mddev);
    if (ret)
        stop(mddev);
    return ret;
}

static int stop(struct mddev *mddev)
{
    struct r1conf *conf = mddev->private;
    struct bitmap *bitmap = mddev->bitmap;

    /* wait for behind writes to complete */
    if (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
        printk(KERN_INFO "md/raid1:%s: behind writes in progress - waiting to stop.\n",
               mdname(mddev));
        /* need to kick something here to make sure I/O goes? */
        wait_event(bitmap->behind_wait,
               atomic_read(&bitmap->behind_writes) == 0);
    }

    raise_barrier(conf);
    lower_barrier(conf);

    md_unregister_thread(&mddev->thread);
    if (conf->r1bio_pool)
        mempool_destroy(conf->r1bio_pool);
    kfree(conf->mirrors);
    kfree(conf->poolinfo);
    kfree(conf);
    mddev->private = NULL;
    return 0;
}

static int raid1_resize(struct mddev *mddev, sector_t sectors)
{
    /* no resync is happening, and there is enough space
     * on all devices, so we can resize.
     * We need to make sure resync covers any new space.
     * If the array is shrinking we should possibly wait until
     * any io in the removed space completes, but it hardly seems
     * worth it.
     */
    sector_t newsize = raid1_size(mddev, sectors, 0);
    if (mddev->external_size &&
        mddev->array_sectors > newsize)
        return -EINVAL;
    if (mddev->bitmap) {
        int ret = bitmap_resize(mddev->bitmap, newsize, 0, 0);
        if (ret)
            return ret;
    }
    md_set_array_sectors(mddev, newsize);
    set_capacity(mddev->gendisk, mddev->array_sectors);
    revalidate_disk(mddev->gendisk);
    if (sectors > mddev->dev_sectors &&
        mddev->recovery_cp > mddev->dev_sectors) {
        mddev->recovery_cp = mddev->dev_sectors;
        set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
    }
    mddev->dev_sectors = sectors;
    mddev->resync_max_sectors = sectors;
    return 0;
}

static int raid1_reshape(struct mddev *mddev)
{
    /* We need to:
     * 1/ resize the r1bio_pool
     * 2/ resize conf->mirrors
     *
     * We allocate a new r1bio_pool if we can.
     * Then raise a device barrier and wait until all IO stops.
     * Then resize conf->mirrors and swap in the new r1bio pool.
     *
     * At the same time, we "pack" the devices so that all the missing
     * devices have the higher raid_disk numbers.
     */
    mempool_t *newpool, *oldpool;
    struct pool_info *newpoolinfo;
    struct raid1_info *newmirrors;
    struct r1conf *conf = mddev->private;
    int cnt, raid_disks;
    unsigned long flags;
    int d, d2, err;

    /* Cannot change chunk_size, layout, or level */
    if (mddev->chunk_sectors != mddev->new_chunk_sectors ||
        mddev->layout != mddev->new_layout ||
        mddev->level != mddev->new_level) {
        mddev->new_chunk_sectors = mddev->chunk_sectors;
        mddev->new_layout = mddev->layout;
        mddev->new_level = mddev->level;
        return -EINVAL;
    }

    err = md_allow_write(mddev);
    if (err)
        return err;

    raid_disks = mddev->raid_disks + mddev->delta_disks;

    if (raid_disks < conf->raid_disks) {
        cnt=0;
        for (d= 0; d < conf->raid_disks; d++)
            if (conf->mirrors[d].rdev)
                cnt++;
        if (cnt > raid_disks)
            return -EBUSY;
    }

    newpoolinfo = kmalloc(sizeof(*newpoolinfo), GFP_KERNEL);
    if (!newpoolinfo)
        return -ENOMEM;
    newpoolinfo->mddev = mddev;
    newpoolinfo->raid_disks = raid_disks * 2;

    newpool = mempool_create(NR_RAID1_BIOS, r1bio_pool_alloc,
                 r1bio_pool_free, newpoolinfo);
    if (!newpool) {
        kfree(newpoolinfo);
        return -ENOMEM;
    }
    newmirrors = kzalloc(sizeof(struct raid1_info) * raid_disks * 2,
                 GFP_KERNEL);
    if (!newmirrors) {
        kfree(newpoolinfo);
        mempool_destroy(newpool);
        return -ENOMEM;
    }

    raise_barrier(conf);

    /* ok, everything is stopped */
    oldpool = conf->r1bio_pool;
    conf->r1bio_pool = newpool;

    for (d = d2 = 0; d < conf->raid_disks; d++) {
        struct md_rdev *rdev = conf->mirrors[d].rdev;
        if (rdev && rdev->raid_disk != d2) {
            sysfs_unlink_rdev(mddev, rdev);
            rdev->raid_disk = d2;
            sysfs_unlink_rdev(mddev, rdev);
            if (sysfs_link_rdev(mddev, rdev))
                printk(KERN_WARNING
                       "md/raid1:%s: cannot register rd%d\n",
                       mdname(mddev), rdev->raid_disk);
        }
        if (rdev)
            newmirrors[d2++].rdev = rdev;
    }
    kfree(conf->mirrors);
    conf->mirrors = newmirrors;
    kfree(conf->poolinfo);
    conf->poolinfo = newpoolinfo;

    spin_lock_irqsave(&conf->device_lock, flags);
    mddev->degraded += (raid_disks - conf->raid_disks);
    spin_unlock_irqrestore(&conf->device_lock, flags);
    conf->raid_disks = mddev->raid_disks = raid_disks;
    mddev->delta_disks = 0;

    lower_barrier(conf);

    set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
    md_wakeup_thread(mddev->thread);

    mempool_destroy(oldpool);
    return 0;
}

static void raid1_quiesce(struct mddev *mddev, int state)
{
    struct r1conf *conf = mddev->private;

    switch(state) {
    case 2: /* wake for suspend */
        wake_up(&conf->wait_barrier);
        break;
    case 1:
        raise_barrier(conf);
        break;
    case 0:
        lower_barrier(conf);
        break;
    }
}

static void *raid1_takeover(struct mddev *mddev)
{
    /* raid1 can take over:
     *  raid5 with 2 devices, any layout or chunk size
     */
    if (mddev->level == 5 && mddev->raid_disks == 2) {
        struct r1conf *conf;
        mddev->new_level = 1;
        mddev->new_layout = 0;
        mddev->new_chunk_sectors = 0;
        conf = setup_conf(mddev);
        if (!IS_ERR(conf))
            conf->barrier = 1;
        return conf;
    }
    return ERR_PTR(-EINVAL);
}

static struct md_personality raid1_personality =
{
    .name       = "raid1",
    .level      = 1,
    .owner      = THIS_MODULE,
    .make_request   = make_request,
    .run        = run,
    .stop       = stop,
    .status     = status,
    .error_handler  = error,
    .hot_add_disk   = raid1_add_disk,
    .hot_remove_disk= raid1_remove_disk,
    .spare_active   = raid1_spare_active,
    .sync_request   = sync_request,
    .resize     = raid1_resize,
    .size       = raid1_size,
    .check_reshape  = raid1_reshape,
    .quiesce    = raid1_quiesce,
    .takeover   = raid1_takeover,
};

static int __init raid_init(void)
{
    return register_md_personality(&raid1_personality);
}

static void raid_exit(void)
{
    unregister_md_personality(&raid1_personality);
}

module_init(raid_init);
module_exit(raid_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("RAID1 (mirroring) personality for MD");
MODULE_ALIAS("md-personality-3"); /* RAID1 */
MODULE_ALIAS("md-raid1");
MODULE_ALIAS("md-level-1");

module_param(max_queued_requests, int, S_IRUGO|S_IWUSR);