// SPDX-License-Identifier: GPL-2.0-or-later
/*
   md.c : Multiple Devices driver for Linux
     Copyright (C) 1998, 1999, 2000 Ingo Molnar

     completely rewritten, based on the MD driver code from Marc Zyngier

   Changes:

   - RAID-1/RAID-5 extensions by Miguel de Icaza, Gadi Oxman, Ingo Molnar
   - RAID-6 extensions by H. Peter Anvin <hpa@zytor.com>
   - boot support for linear and striped mode by Harald Hoyer <HarryH@Royal.Net>
   - kerneld support by Boris Tobotras <boris@xtalk.msk.su>
   - kmod support by: Cyrus Durgin
   - RAID0 bugfixes: Mark Anthony Lisher <markal@iname.com>
   - Devfs support by Richard Gooch <rgooch@atnf.csiro.au>

   - lots of fixes and improvements to the RAID1/RAID5 and generic
     RAID code (such as request based resynchronization):

     Neil Brown <neilb@cse.unsw.edu.au>.

   - persistent bitmap code
     Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.


   Errors, Warnings, etc.
   Please use:
     pr_crit() for error conditions that risk data loss
     pr_err() for error conditions that are unexpected, like an IO error
         or internal inconsistency
     pr_warn() for error conditions that could have been predicated, like
         adding a device to an array when it has incompatible metadata
     pr_info() for every interesting, very rare events, like an array starting
         or stopping, or resync starting or stopping
     pr_debug() for everything else.

*/

#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
#include <linux/kthread.h>
#include <linux/blkdev.h>
#include <linux/badblocks.h>
#include <linux/sysctl.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/hdreg.h>
#include <linux/proc_fs.h>
#include <linux/random.h>
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/file.h>
#include <linux/compat.h>
#include <linux/delay.h>
#include <linux/raid/md_p.h>
#include <linux/raid/md_u.h>
#include <linux/raid/detect.h>
#include <linux/slab.h>
#include <linux/percpu-refcount.h>
#include <linux/part_stat.h>

#include <trace/events/block.h>
#include "md.h"
#include "md-bitmap.h"
#include "md-cluster.h"

#ifndef MODULE
static void autostart_arrays(int part);
#endif

/* pers_list is a list of registered personalities protected
 * by pers_lock.
 * pers_lock does extra service to protect accesses to
 * mddev->thread when the mutex cannot be held.
 */
static LIST_HEAD(pers_list);
static DEFINE_SPINLOCK(pers_lock);

static struct kobj_type md_ktype;

struct md_cluster_operations *md_cluster_ops;
EXPORT_SYMBOL(md_cluster_ops);
static struct module *md_cluster_mod;

static DECLARE_WAIT_QUEUE_HEAD(resync_wait);
static struct workqueue_struct *md_wq;
static struct workqueue_struct *md_misc_wq;
static struct workqueue_struct *md_rdev_misc_wq;

static int remove_and_add_spares(struct mddev *mddev,
                                 struct md_rdev *this);
static void mddev_detach(struct mddev *mddev);

/*
 * Default number of read corrections we'll attempt on an rdev
 * before ejecting it from the array. We divide the read error
 * count by 2 for every hour elapsed between read errors.
 */
#define MD_DEFAULT_MAX_CORRECTED_READ_ERRORS 20
/*
 * Current RAID-1,4,5 parallel reconstruction 'guaranteed speed limit'
 * is 1000 KB/sec, so the extra system load does not show up that much.
 * Increase it if you want to have more _guaranteed_ speed. Note that
 * the RAID driver will use the maximum available bandwidth if the IO
 * subsystem is idle. There is also an 'absolute maximum' reconstruction
 * speed limit - in case reconstruction slows down your system despite
 * idle IO detection.
 *
 * you can change it via /proc/sys/dev/raid/speed_limit_min and _max.
 * or /sys/block/mdX/md/sync_speed_{min,max}
 */

static int sysctl_speed_limit_min = 1000;
static int sysctl_speed_limit_max = 200000;
static inline int speed_min(struct mddev *mddev)
{
        return mddev->sync_speed_min ?
                mddev->sync_speed_min : sysctl_speed_limit_min;
}

static inline int speed_max(struct mddev *mddev)
{
        return mddev->sync_speed_max ?
                mddev->sync_speed_max : sysctl_speed_limit_max;
}

static void rdev_uninit_serial(struct md_rdev *rdev)
{
        if (!test_and_clear_bit(CollisionCheck, &rdev->flags))
                return;

        kvfree(rdev->serial);
        rdev->serial = NULL;
}

static void rdevs_uninit_serial(struct mddev *mddev)
{
        struct md_rdev *rdev;

        rdev_for_each(rdev, mddev)
                rdev_uninit_serial(rdev);
}

static int rdev_init_serial(struct md_rdev *rdev)
{
        /* serial_nums equals with BARRIER_BUCKETS_NR */
        int i, serial_nums = 1 << ((PAGE_SHIFT - ilog2(sizeof(atomic_t))));
        struct serial_in_rdev *serial = NULL;

        if (test_bit(CollisionCheck, &rdev->flags))
                return 0;

        serial = kvmalloc(sizeof(struct serial_in_rdev) * serial_nums,
                          GFP_KERNEL);
        if (!serial)
                return -ENOMEM;

        for (i = 0; i < serial_nums; i++) {
                struct serial_in_rdev *serial_tmp = &serial[i];

                spin_lock_init(&serial_tmp->serial_lock);
                serial_tmp->serial_rb = RB_ROOT_CACHED;
                init_waitqueue_head(&serial_tmp->serial_io_wait);
        }

        rdev->serial = serial;
        set_bit(CollisionCheck, &rdev->flags);

        return 0;
}

static int rdevs_init_serial(struct mddev *mddev)
{
        struct md_rdev *rdev;
        int ret = 0;

        rdev_for_each(rdev, mddev) {
                ret = rdev_init_serial(rdev);
                if (ret)
                        break;
        }

        /* Free all resources if pool is not existed */
        if (ret && !mddev->serial_info_pool)
                rdevs_uninit_serial(mddev);

        return ret;
}

/*
 * rdev needs to enable serial stuffs if it meets the conditions:
 * 1. it is multi-queue device flaged with writemostly.
 * 2. the write-behind mode is enabled.
 */
static int rdev_need_serial(struct md_rdev *rdev)
{
        return (rdev && rdev->mddev->bitmap_info.max_write_behind > 0 &&
                rdev->bdev->bd_queue->nr_hw_queues != 1 &&
                test_bit(WriteMostly, &rdev->flags));
}

/*
 * Init resource for rdev(s), then create serial_info_pool if:
 * 1. rdev is the first device which return true from rdev_enable_serial.
 * 2. rdev is NULL, means we want to enable serialization for all rdevs.
 */
void mddev_create_serial_pool(struct mddev *mddev, struct md_rdev *rdev,
                              bool is_suspend)
{
        int ret = 0;

        if (rdev && !rdev_need_serial(rdev) &&
            !test_bit(CollisionCheck, &rdev->flags))
                return;

        if (!is_suspend)
                mddev_suspend(mddev);

        if (!rdev)
                ret = rdevs_init_serial(mddev);
        else
                ret = rdev_init_serial(rdev);
        if (ret)
                goto abort;

        if (mddev->serial_info_pool == NULL) {
                /*
                 * already in memalloc noio context by
                 * mddev_suspend()
                 */
                mddev->serial_info_pool =
                        mempool_create_kmalloc_pool(NR_SERIAL_INFOS,
                                                sizeof(struct serial_info));
                if (!mddev->serial_info_pool) {
                        rdevs_uninit_serial(mddev);
                        pr_err("can't alloc memory pool for serialization\n");
                }
        }

abort:
        if (!is_suspend)
                mddev_resume(mddev);
}

/*
 * Free resource from rdev(s), and destroy serial_info_pool under conditions:
 * 1. rdev is the last device flaged with CollisionCheck.
 * 2. when bitmap is destroyed while policy is not enabled.
 * 3. for disable policy, the pool is destroyed only when no rdev needs it.
 */
void mddev_destroy_serial_pool(struct mddev *mddev, struct md_rdev *rdev,
                               bool is_suspend)
{
        if (rdev && !test_bit(CollisionCheck, &rdev->flags))
                return;

        if (mddev->serial_info_pool) {
                struct md_rdev *temp;
                int num = 0; /* used to track if other rdevs need the pool */

                if (!is_suspend)
                        mddev_suspend(mddev);
                rdev_for_each(temp, mddev) {
                        if (!rdev) {
                                if (!mddev->serialize_policy ||
                                    !rdev_need_serial(temp))
                                        rdev_uninit_serial(temp);
                                else
                                        num++;
                        } else if (temp != rdev &&
                                   test_bit(CollisionCheck, &temp->flags))
                                num++;
                }

                if (rdev)
                        rdev_uninit_serial(rdev);

                if (num)
                        pr_info("The mempool could be used by other devices\n");
                else {
                        mempool_destroy(mddev->serial_info_pool);
                        mddev->serial_info_pool = NULL;
                }
                if (!is_suspend)
                        mddev_resume(mddev);
        }
}

static struct ctl_table_header *raid_table_header;

static struct ctl_table raid_table[] = {
        {
                .procname       = "speed_limit_min",
                .data           = &sysctl_speed_limit_min,
                .maxlen         = sizeof(int),
                .mode           = S_IRUGO|S_IWUSR,
                .proc_handler   = proc_dointvec,
        },
        {
                .procname       = "speed_limit_max",
                .data           = &sysctl_speed_limit_max,
                .maxlen         = sizeof(int),
                .mode           = S_IRUGO|S_IWUSR,
                .proc_handler   = proc_dointvec,
        },
        { }
};

static struct ctl_table raid_dir_table[] = {
        {
                .procname       = "raid",
                .maxlen         = 0,
                .mode           = S_IRUGO|S_IXUGO,
                .child          = raid_table,
        },
        { }
};

static struct ctl_table raid_root_table[] = {
        {
                .procname       = "dev",
                .maxlen         = 0,
                .mode           = 0555,
                .child          = raid_dir_table,
        },
        {  }
};

static const struct block_device_operations md_fops;

static int start_readonly;

/*
 * The original mechanism for creating an md device is to create
 * a device node in /dev and to open it.  This causes races with device-close.
 * The preferred method is to write to the "new_array" module parameter.
 * This can avoid races.
 * Setting create_on_open to false disables the original mechanism
 * so all the races disappear.
 */
static bool create_on_open = true;

struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
                            struct mddev *mddev)
{
        if (!mddev || !bioset_initialized(&mddev->bio_set))
                return bio_alloc(gfp_mask, nr_iovecs);

        return bio_alloc_bioset(gfp_mask, nr_iovecs, &mddev->bio_set);
}
EXPORT_SYMBOL_GPL(bio_alloc_mddev);

static struct bio *md_bio_alloc_sync(struct mddev *mddev)
{
        if (!mddev || !bioset_initialized(&mddev->sync_set))
                return bio_alloc(GFP_NOIO, 1);

        return bio_alloc_bioset(GFP_NOIO, 1, &mddev->sync_set);
}

/*
 * We have a system wide 'event count' that is incremented
 * on any 'interesting' event, and readers of /proc/mdstat
 * can use 'poll' or 'select' to find out when the event
 * count increases.
 *
 * Events are:
 *  start array, stop array, error, add device, remove device,
 *  start build, activate spare
 */
static DECLARE_WAIT_QUEUE_HEAD(md_event_waiters);
static atomic_t md_event_count;
void md_new_event(struct mddev *mddev)
{
        atomic_inc(&md_event_count);
        wake_up(&md_event_waiters);
}
EXPORT_SYMBOL_GPL(md_new_event);

/*
 * Enables to iterate over all existing md arrays
 * all_mddevs_lock protects this list.
 */
static LIST_HEAD(all_mddevs);
static DEFINE_SPINLOCK(all_mddevs_lock);

/*
 * iterates through all used mddevs in the system.
 * We take care to grab the all_mddevs_lock whenever navigating
 * the list, and to always hold a refcount when unlocked.
 * Any code which breaks out of this loop while own
 * a reference to the current mddev and must mddev_put it.
 */
#define for_each_mddev(_mddev,_tmp)                                     \
                                                                        \
        for (({ spin_lock(&all_mddevs_lock);                            \
                _tmp = all_mddevs.next;                                 \
                _mddev = NULL;});                                       \
             ({ if (_tmp != &all_mddevs)                                \
                        mddev_get(list_entry(_tmp, struct mddev, all_mddevs));\
                spin_unlock(&all_mddevs_lock);                          \
                if (_mddev) mddev_put(_mddev);                          \
                _mddev = list_entry(_tmp, struct mddev, all_mddevs);    \
                _tmp != &all_mddevs;});                                 \
             ({ spin_lock(&all_mddevs_lock);                            \
                _tmp = _tmp->next;})                                    \
                )

/* Rather than calling directly into the personality make_request function,
 * IO requests come here first so that we can check if the device is
 * being suspended pending a reconfiguration.
 * We hold a refcount over the call to ->make_request.  By the time that
 * call has finished, the bio has been linked into some internal structure
 * and so is visible to ->quiesce(), so we don't need the refcount any more.
 */
static bool is_suspended(struct mddev *mddev, struct bio *bio)
{
        if (mddev->suspended)
                return true;
        if (bio_data_dir(bio) != WRITE)
                return false;
        if (mddev->suspend_lo >= mddev->suspend_hi)
                return false;
        if (bio->bi_iter.bi_sector >= mddev->suspend_hi)
                return false;
        if (bio_end_sector(bio) < mddev->suspend_lo)
                return false;
        return true;
}

void md_handle_request(struct mddev *mddev, struct bio *bio)
{
check_suspended:
        rcu_read_lock();
        if (is_suspended(mddev, bio)) {
                DEFINE_WAIT(__wait);
                for (;;) {
                        prepare_to_wait(&mddev->sb_wait, &__wait,
                                        TASK_UNINTERRUPTIBLE);
                        if (!is_suspended(mddev, bio))
                                break;
                        rcu_read_unlock();
                        schedule();
                        rcu_read_lock();
                }
                finish_wait(&mddev->sb_wait, &__wait);
        }
        atomic_inc(&mddev->active_io);
        rcu_read_unlock();

        if (!mddev->pers->make_request(mddev, bio)) {
                atomic_dec(&mddev->active_io);
                wake_up(&mddev->sb_wait);
                goto check_suspended;
        }

        if (atomic_dec_and_test(&mddev->active_io) && mddev->suspended)
                wake_up(&mddev->sb_wait);
}
EXPORT_SYMBOL(md_handle_request);

static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio)
{
        const int rw = bio_data_dir(bio);
        const int sgrp = op_stat_group(bio_op(bio));
        struct mddev *mddev = bio->bi_disk->private_data;
        unsigned int sectors;

        if (unlikely(test_bit(MD_BROKEN, &mddev->flags)) && (rw == WRITE)) {
                bio_io_error(bio);
                return BLK_QC_T_NONE;
        }

        blk_queue_split(q, &bio);

        if (mddev == NULL || mddev->pers == NULL) {
                bio_io_error(bio);
                return BLK_QC_T_NONE;
        }
        if (mddev->ro == 1 && unlikely(rw == WRITE)) {
                if (bio_sectors(bio) != 0)
                        bio->bi_status = BLK_STS_IOERR;
                bio_endio(bio);
                return BLK_QC_T_NONE;
        }

        /*
         * save the sectors now since our bio can
         * go away inside make_request
         */
        sectors = bio_sectors(bio);
        /* bio could be mergeable after passing to underlayer */
        bio->bi_opf &= ~REQ_NOMERGE;

        md_handle_request(mddev, bio);

        part_stat_lock();
        part_stat_inc(&mddev->gendisk->part0, ios[sgrp]);
        part_stat_add(&mddev->gendisk->part0, sectors[sgrp], sectors);
        part_stat_unlock();

        return BLK_QC_T_NONE;
}

/* mddev_suspend makes sure no new requests are submitted
 * to the device, and that any requests that have been submitted
 * are completely handled.
 * Once mddev_detach() is called and completes, the module will be
 * completely unused.
 */
void mddev_suspend(struct mddev *mddev)
{
        WARN_ON_ONCE(mddev->thread && current == mddev->thread->tsk);
        lockdep_assert_held(&mddev->reconfig_mutex);
        if (mddev->suspended++)
                return;
        synchronize_rcu();
        wake_up(&mddev->sb_wait);
        set_bit(MD_ALLOW_SB_UPDATE, &mddev->flags);
        smp_mb__after_atomic();
        wait_event(mddev->sb_wait, atomic_read(&mddev->active_io) == 0);
        mddev->pers->quiesce(mddev, 1);
        clear_bit_unlock(MD_ALLOW_SB_UPDATE, &mddev->flags);
        wait_event(mddev->sb_wait, !test_bit(MD_UPDATING_SB, &mddev->flags));

        del_timer_sync(&mddev->safemode_timer);
        /* restrict memory reclaim I/O during raid array is suspend */
        mddev->noio_flag = memalloc_noio_save();
}
EXPORT_SYMBOL_GPL(mddev_suspend);

void mddev_resume(struct mddev *mddev)
{
        /* entred the memalloc scope from mddev_suspend() */
        memalloc_noio_restore(mddev->noio_flag);
        lockdep_assert_held(&mddev->reconfig_mutex);
        if (--mddev->suspended)
                return;
        wake_up(&mddev->sb_wait);
        mddev->pers->quiesce(mddev, 0);

        set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
        md_wakeup_thread(mddev->thread);
        md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
}
EXPORT_SYMBOL_GPL(mddev_resume);

int mddev_congested(struct mddev *mddev, int bits)
{
        struct md_personality *pers = mddev->pers;
        int ret = 0;

        rcu_read_lock();
        if (mddev->suspended)
                ret = 1;
        else if (pers && pers->congested)
                ret = pers->congested(mddev, bits);
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(mddev_congested);
static int md_congested(void *data, int bits)
{
        struct mddev *mddev = data;
        return mddev_congested(mddev, bits);
}

/*
 * Generic flush handling for md
 */

static void md_end_flush(struct bio *bio)
{
        struct md_rdev *rdev = bio->bi_private;
        struct mddev *mddev = rdev->mddev;

        rdev_dec_pending(rdev, mddev);

        if (atomic_dec_and_test(&mddev->flush_pending)) {
                /* The pre-request flush has finished */
                queue_work(md_wq, &mddev->flush_work);
        }
        bio_put(bio);
}

static void md_submit_flush_data(struct work_struct *ws);

static void submit_flushes(struct work_struct *ws)
{
        struct mddev *mddev = container_of(ws, struct mddev, flush_work);
        struct md_rdev *rdev;

        mddev->start_flush = ktime_get_boottime();
        INIT_WORK(&mddev->flush_work, md_submit_flush_data);
        atomic_set(&mddev->flush_pending, 1);
        rcu_read_lock();
        rdev_for_each_rcu(rdev, mddev)
                if (rdev->raid_disk >= 0 &&
                    !test_bit(Faulty, &rdev->flags)) {
                        /* Take two references, one is dropped
                         * when request finishes, one after
                         * we reclaim rcu_read_lock
                         */
                        struct bio *bi;
                        atomic_inc(&rdev->nr_pending);
                        atomic_inc(&rdev->nr_pending);
                        rcu_read_unlock();
                        bi = bio_alloc_mddev(GFP_NOIO, 0, mddev);
                        bi->bi_end_io = md_end_flush;
                        bi->bi_private = rdev;
                        bio_set_dev(bi, rdev->bdev);
                        bi->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
                        atomic_inc(&mddev->flush_pending);
                        submit_bio(bi);
                        rcu_read_lock();
                        rdev_dec_pending(rdev, mddev);
                }
        rcu_read_unlock();
        if (atomic_dec_and_test(&mddev->flush_pending))
                queue_work(md_wq, &mddev->flush_work);
}

static void md_submit_flush_data(struct work_struct *ws)
{
        struct mddev *mddev = container_of(ws, struct mddev, flush_work);
        struct bio *bio = mddev->flush_bio;

        /*
         * must reset flush_bio before calling into md_handle_request to avoid a
         * deadlock, because other bios passed md_handle_request suspend check
         * could wait for this and below md_handle_request could wait for those
         * bios because of suspend check
         */
        mddev->last_flush = mddev->start_flush;
        mddev->flush_bio = NULL;
        wake_up(&mddev->sb_wait);

        if (bio->bi_iter.bi_size == 0) {
                /* an empty barrier - all done */
                bio_endio(bio);
        } else {
                bio->bi_opf &= ~REQ_PREFLUSH;
                md_handle_request(mddev, bio);
        }
}

/*
 * Manages consolidation of flushes and submitting any flushes needed for
 * a bio with REQ_PREFLUSH.  Returns true if the bio is finished or is
 * being finished in another context.  Returns false if the flushing is
 * complete but still needs the I/O portion of the bio to be processed.
 */
bool md_flush_request(struct mddev *mddev, struct bio *bio)
{
        ktime_t start = ktime_get_boottime();
        spin_lock_irq(&mddev->lock);
        wait_event_lock_irq(mddev->sb_wait,
                            !mddev->flush_bio ||
                            ktime_after(mddev->last_flush, start),
                            mddev->lock);
        if (!ktime_after(mddev->last_flush, start)) {
                WARN_ON(mddev->flush_bio);
                mddev->flush_bio = bio;
                bio = NULL;
        }
        spin_unlock_irq(&mddev->lock);

        if (!bio) {
                INIT_WORK(&mddev->flush_work, submit_flushes);
                queue_work(md_wq, &mddev->flush_work);
        } else {
                /* flush was performed for some other bio while we waited. */
                if (bio->bi_iter.bi_size == 0)
                        /* an empty barrier - all done */
                        bio_endio(bio);
                else {
                        bio->bi_opf &= ~REQ_PREFLUSH;
                        return false;
                }
        }
        return true;
}
EXPORT_SYMBOL(md_flush_request);

static inline struct mddev *mddev_get(struct mddev *mddev)
{
        atomic_inc(&mddev->active);
        return mddev;
}

static void mddev_delayed_delete(struct work_struct *ws);

static void mddev_put(struct mddev *mddev)
{
        if (!atomic_dec_and_lock(&mddev->active, &all_mddevs_lock))
                return;
        if (!mddev->raid_disks && list_empty(&mddev->disks) &&
            mddev->ctime == 0 && !mddev->hold_active) {
                /* Array is not configured at all, and not held active,
                 * so destroy it */
                list_del_init(&mddev->all_mddevs);

                /*
                 * Call queue_work inside the spinlock so that
                 * flush_workqueue() after mddev_find will succeed in waiting
                 * for the work to be done.
                 */
                INIT_WORK(&mddev->del_work, mddev_delayed_delete);
                queue_work(md_misc_wq, &mddev->del_work);
        }
        spin_unlock(&all_mddevs_lock);
}

static void md_safemode_timeout(struct timer_list *t);

void mddev_init(struct mddev *mddev)
{
        kobject_init(&mddev->kobj, &md_ktype);
        mutex_init(&mddev->open_mutex);
        mutex_init(&mddev->reconfig_mutex);
        mutex_init(&mddev->bitmap_info.mutex);
        INIT_LIST_HEAD(&mddev->disks);
        INIT_LIST_HEAD(&mddev->all_mddevs);
        timer_setup(&mddev->safemode_timer, md_safemode_timeout, 0);
        atomic_set(&mddev->active, 1);
        atomic_set(&mddev->openers, 0);
        atomic_set(&mddev->active_io, 0);
        spin_lock_init(&mddev->lock);
        atomic_set(&mddev->flush_pending, 0);
        init_waitqueue_head(&mddev->sb_wait);
        init_waitqueue_head(&mddev->recovery_wait);
        mddev->reshape_position = MaxSector;
        mddev->reshape_backwards = 0;
        mddev->last_sync_action = "none";
        mddev->resync_min = 0;
        mddev->resync_max = MaxSector;
        mddev->level = LEVEL_NONE;
}
EXPORT_SYMBOL_GPL(mddev_init);

static struct mddev *mddev_find(dev_t unit)
{
        struct mddev *mddev, *new = NULL;

        if (unit && MAJOR(unit) != MD_MAJOR)
                unit &= ~((1<<MdpMinorShift)-1);

 retry:
        spin_lock(&all_mddevs_lock);

        if (unit) {
                list_for_each_entry(mddev, &all_mddevs, all_mddevs)
                        if (mddev->unit == unit) {
                                mddev_get(mddev);
                                spin_unlock(&all_mddevs_lock);
                                kfree(new);
                                return mddev;
                        }

                if (new) {
                        list_add(&new->all_mddevs, &all_mddevs);
                        spin_unlock(&all_mddevs_lock);
                        new->hold_active = UNTIL_IOCTL;
                        return new;
                }
        } else if (new) {
                /* find an unused unit number */
                static int next_minor = 512;
                int start = next_minor;
                int is_free = 0;
                int dev = 0;
                while (!is_free) {
                        dev = MKDEV(MD_MAJOR, next_minor);
                        next_minor++;
                        if (next_minor > MINORMASK)
                                next_minor = 0;
                        if (next_minor == start) {
                                /* Oh dear, all in use. */
                                spin_unlock(&all_mddevs_lock);
                                kfree(new);
                                return NULL;
                        }

                        is_free = 1;
                        list_for_each_entry(mddev, &all_mddevs, all_mddevs)
                                if (mddev->unit == dev) {
                                        is_free = 0;
                                        break;
                                }
                }
                new->unit = dev;
                new->md_minor = MINOR(dev);
                new->hold_active = UNTIL_STOP;
                list_add(&new->all_mddevs, &all_mddevs);
                spin_unlock(&all_mddevs_lock);
                return new;
        }
        spin_unlock(&all_mddevs_lock);

        new = kzalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                return NULL;

        new->unit = unit;
        if (MAJOR(unit) == MD_MAJOR)
                new->md_minor = MINOR(unit);
        else
                new->md_minor = MINOR(unit) >> MdpMinorShift;

        mddev_init(new);

        goto retry;
}

static struct attribute_group md_redundancy_group;

void mddev_unlock(struct mddev *mddev)
{
        if (mddev->to_remove) {
                /* These cannot be removed under reconfig_mutex as
                 * an access to the files will try to take reconfig_mutex
                 * while holding the file unremovable, which leads to
                 * a deadlock.
                 * So hold set sysfs_active while the remove in happeing,
                 * and anything else which might set ->to_remove or my
                 * otherwise change the sysfs namespace will fail with
                 * -EBUSY if sysfs_active is still set.
                 * We set sysfs_active under reconfig_mutex and elsewhere
                 * test it under the same mutex to ensure its correct value
                 * is seen.
                 */
                struct attribute_group *to_remove = mddev->to_remove;
                mddev->to_remove = NULL;
                mddev->sysfs_active = 1;
                mutex_unlock(&mddev->reconfig_mutex);

                if (mddev->kobj.sd) {
                        if (to_remove != &md_redundancy_group)
                                sysfs_remove_group(&mddev->kobj, to_remove);
                        if (mddev->pers == NULL ||
                            mddev->pers->sync_request == NULL) {
                                sysfs_remove_group(&mddev->kobj, &md_redundancy_group);
                                if (mddev->sysfs_action)
                                        sysfs_put(mddev->sysfs_action);
                                mddev->sysfs_action = NULL;
                        }
                }
                mddev->sysfs_active = 0;
        } else
                mutex_unlock(&mddev->reconfig_mutex);

        /* As we've dropped the mutex we need a spinlock to
         * make sure the thread doesn't disappear
         */
        spin_lock(&pers_lock);
        md_wakeup_thread(mddev->thread);
        wake_up(&mddev->sb_wait);
        spin_unlock(&pers_lock);
}
EXPORT_SYMBOL_GPL(mddev_unlock);

struct md_rdev *md_find_rdev_nr_rcu(struct mddev *mddev, int nr)
{
        struct md_rdev *rdev;

        rdev_for_each_rcu(rdev, mddev)
                if (rdev->desc_nr == nr)
                        return rdev;

        return NULL;
}
EXPORT_SYMBOL_GPL(md_find_rdev_nr_rcu);

static struct md_rdev *find_rdev(struct mddev *mddev, dev_t dev)
{
        struct md_rdev *rdev;

        rdev_for_each(rdev, mddev)
                if (rdev->bdev->bd_dev == dev)
                        return rdev;

        return NULL;
}

struct md_rdev *md_find_rdev_rcu(struct mddev *mddev, dev_t dev)
{
        struct md_rdev *rdev;

        rdev_for_each_rcu(rdev, mddev)
                if (rdev->bdev->bd_dev == dev)
                        return rdev;

        return NULL;
}
EXPORT_SYMBOL_GPL(md_find_rdev_rcu);

static struct md_personality *find_pers(int level, char *clevel)
{
        struct md_personality *pers;
        list_for_each_entry(pers, &pers_list, list) {
                if (level != LEVEL_NONE && pers->level == level)
                        return pers;
                if (strcmp(pers->name, clevel)==0)
                        return pers;
        }
        return NULL;
}

/* return the offset of the super block in 512byte sectors */
static inline sector_t calc_dev_sboffset(struct md_rdev *rdev)
{
        sector_t num_sectors = i_size_read(rdev->bdev->bd_inode) / 512;
        return MD_NEW_SIZE_SECTORS(num_sectors);
}

static int alloc_disk_sb(struct md_rdev *rdev)
{
        rdev->sb_page = alloc_page(GFP_KERNEL);
        if (!rdev->sb_page)
                return -ENOMEM;
        return 0;
}

void md_rdev_clear(struct md_rdev *rdev)
{
        if (rdev->sb_page) {
                put_page(rdev->sb_page);
                rdev->sb_loaded = 0;
                rdev->sb_page = NULL;
                rdev->sb_start = 0;
                rdev->sectors = 0;
        }
        if (rdev->bb_page) {
                put_page(rdev->bb_page);
                rdev->bb_page = NULL;
        }
        badblocks_exit(&rdev->badblocks);
}
EXPORT_SYMBOL_GPL(md_rdev_clear);

static void super_written(struct bio *bio)
{
        struct md_rdev *rdev = bio->bi_private;
        struct mddev *mddev = rdev->mddev;

        if (bio->bi_status) {
                pr_err("md: super_written gets error=%d\n", bio->bi_status);
                md_error(mddev, rdev);
                if (!test_bit(Faulty, &rdev->flags)
                    && (bio->bi_opf & MD_FAILFAST)) {
                        set_bit(MD_SB_NEED_REWRITE, &mddev->sb_flags);
                        set_bit(LastDev, &rdev->flags);
                }
        } else
                clear_bit(LastDev, &rdev->flags);

        if (atomic_dec_and_test(&mddev->pending_writes))
                wake_up(&mddev->sb_wait);
        rdev_dec_pending(rdev, mddev);
        bio_put(bio);
}

void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
                   sector_t sector, int size, struct page *page)
{
        /* write first size bytes of page to sector of rdev
         * Increment mddev->pending_writes before returning
         * and decrement it on completion, waking up sb_wait
         * if zero is reached.
         * If an error occurred, call md_error
         */
        struct bio *bio;
        int ff = 0;

        if (!page)
                return;

        if (test_bit(Faulty, &rdev->flags))
                return;

        bio = md_bio_alloc_sync(mddev);

        atomic_inc(&rdev->nr_pending);

        bio_set_dev(bio, rdev->meta_bdev ? rdev->meta_bdev : rdev->bdev);
        bio->bi_iter.bi_sector = sector;
        bio_add_page(bio, page, size, 0);
        bio->bi_private = rdev;
        bio->bi_end_io = super_written;

        if (test_bit(MD_FAILFAST_SUPPORTED, &mddev->flags) &&
            test_bit(FailFast, &rdev->flags) &&
            !test_bit(LastDev, &rdev->flags))
                ff = MD_FAILFAST;
        bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH | REQ_FUA | ff;

        atomic_inc(&mddev->pending_writes);
        submit_bio(bio);
}

int md_super_wait(struct mddev *mddev)
{
        /* wait for all superblock writes that were scheduled to complete */
        wait_event(mddev->sb_wait, atomic_read(&mddev->pending_writes)==0);
        if (test_and_clear_bit(MD_SB_NEED_REWRITE, &mddev->sb_flags))
                return -EAGAIN;
        return 0;
}

int sync_page_io(struct md_rdev *rdev, sector_t sector, int size,
                 struct page *page, int op, int op_flags, bool metadata_op)
{
        struct bio *bio = md_bio_alloc_sync(rdev->mddev);
        int ret;

        if (metadata_op && rdev->meta_bdev)
                bio_set_dev(bio, rdev->meta_bdev);
        else
                bio_set_dev(bio, rdev->bdev);
        bio_set_op_attrs(bio, op, op_flags);
        if (metadata_op)
                bio->bi_iter.bi_sector = sector + rdev->sb_start;
        else if (rdev->mddev->reshape_position != MaxSector &&
                 (rdev->mddev->reshape_backwards ==
                  (sector >= rdev->mddev->reshape_position)))
                bio->bi_iter.bi_sector = sector + rdev->new_data_offset;
        else
                bio->bi_iter.bi_sector = sector + rdev->data_offset;
        bio_add_page(bio, page, size, 0);

        submit_bio_wait(bio);

        ret = !bio->bi_status;
        bio_put(bio);
        return ret;
}
EXPORT_SYMBOL_GPL(sync_page_io);

static int read_disk_sb(struct md_rdev *rdev, int size)
{
        char b[BDEVNAME_SIZE];

        if (rdev->sb_loaded)
                return 0;

        if (!sync_page_io(rdev, 0, size, rdev->sb_page, REQ_OP_READ, 0, true))
                goto fail;
        rdev->sb_loaded = 1;
        return 0;

fail:
        pr_err("md: disabled device %s, could not read superblock.\n",
               bdevname(rdev->bdev,b));
        return -EINVAL;
}

static int md_uuid_equal(mdp_super_t *sb1, mdp_super_t *sb2)
{
        return  sb1->set_uuid0 == sb2->set_uuid0 &&
                sb1->set_uuid1 == sb2->set_uuid1 &&
                sb1->set_uuid2 == sb2->set_uuid2 &&
                sb1->set_uuid3 == sb2->set_uuid3;
}

static int md_sb_equal(mdp_super_t *sb1, mdp_super_t *sb2)
{
        int ret;
        mdp_super_t *tmp1, *tmp2;

        tmp1 = kmalloc(sizeof(*tmp1),GFP_KERNEL);
        tmp2 = kmalloc(sizeof(*tmp2),GFP_KERNEL);

        if (!tmp1 || !tmp2) {
                ret = 0;
                goto abort;
        }

        *tmp1 = *sb1;
        *tmp2 = *sb2;

        /*
         * nr_disks is not constant
         */
        tmp1->nr_disks = 0;
        tmp2->nr_disks = 0;

        ret = (memcmp(tmp1, tmp2, MD_SB_GENERIC_CONSTANT_WORDS * 4) == 0);
abort:
        kfree(tmp1);
        kfree(tmp2);
        return ret;
}

static u32 md_csum_fold(u32 csum)
{
        csum = (csum & 0xffff) + (csum >> 16);
        return (csum & 0xffff) + (csum >> 16);
}

static unsigned int calc_sb_csum(mdp_super_t *sb)
{
        u64 newcsum = 0;
        u32 *sb32 = (u32*)sb;
        int i;
        unsigned int disk_csum, csum;

        disk_csum = sb->sb_csum;
        sb->sb_csum = 0;

        for (i = 0; i < MD_SB_BYTES/4 ; i++)
                newcsum += sb32[i];
        csum = (newcsum & 0xffffffff) + (newcsum>>32);

#ifdef CONFIG_ALPHA
        /* This used to use csum_partial, which was wrong for several
         * reasons including that different results are returned on
         * different architectures.  It isn't critical that we get exactly
         * the same return value as before (we always csum_fold before
         * testing, and that removes any differences).  However as we
         * know that csum_partial always returned a 16bit value on
         * alphas, do a fold to maximise conformity to previous behaviour.
         */
        sb->sb_csum = md_csum_fold(disk_csum);
#else
        sb->sb_csum = disk_csum;
#endif
        return csum;
}

/*
 * Handle superblock details.
 * We want to be able to handle multiple superblock formats
 * so we have a common interface to them all, and an array of
 * different handlers.
 * We rely on user-space to write the initial superblock, and support
 * reading and updating of superblocks.
 * Interface methods are:
 *   int load_super(struct md_rdev *dev, struct md_rdev *refdev, int minor_version)
 *      loads and validates a superblock on dev.
 *      if refdev != NULL, compare superblocks on both devices
 *    Return:
 *      0 - dev has a superblock that is compatible with refdev
 *      1 - dev has a superblock that is compatible and newer than refdev
 *          so dev should be used as the refdev in future
 *     -EINVAL superblock incompatible or invalid
 *     -othererror e.g. -EIO
 *
 *   int validate_super(struct mddev *mddev, struct md_rdev *dev)
 *      Verify that dev is acceptable into mddev.
 *       The first time, mddev->raid_disks will be 0, and data from
 *       dev should be merged in.  Subsequent calls check that dev
 *       is new enough.  Return 0 or -EINVAL
 *
 *   void sync_super(struct mddev *mddev, struct md_rdev *dev)
 *     Update the superblock for rdev with data in mddev
 *     This does not write to disc.
 *
 */

struct super_type  {
        char                *name;
        struct module       *owner;
        int                 (*load_super)(struct md_rdev *rdev,
                                          struct md_rdev *refdev,
                                          int minor_version);
        int                 (*validate_super)(struct mddev *mddev,
                                              struct md_rdev *rdev);
        void                (*sync_super)(struct mddev *mddev,
                                          struct md_rdev *rdev);
        unsigned long long  (*rdev_size_change)(struct md_rdev *rdev,
                                                sector_t num_sectors);
        int                 (*allow_new_offset)(struct md_rdev *rdev,
                                                unsigned long long new_offset);
};

/*
 * Check that the given mddev has no bitmap.
 *
 * This function is called from the run method of all personalities that do not
 * support bitmaps. It prints an error message and returns non-zero if mddev
 * has a bitmap. Otherwise, it returns 0.
 *
 */
int md_check_no_bitmap(struct mddev *mddev)
{
        if (!mddev->bitmap_info.file && !mddev->bitmap_info.offset)
                return 0;
        pr_warn("%s: bitmaps are not supported for %s\n",
                mdname(mddev), mddev->pers->name);
        return 1;
}
EXPORT_SYMBOL(md_check_no_bitmap);

/*
 * load_super for 0.90.0
 */
static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_version)
{
        char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
        mdp_super_t *sb;
        int ret;
        bool spare_disk = true;

        /*
         * Calculate the position of the superblock (512byte sectors),
         * it's at the end of the disk.
         *
         * It also happens to be a multiple of 4Kb.
         */
        rdev->sb_start = calc_dev_sboffset(rdev);

        ret = read_disk_sb(rdev, MD_SB_BYTES);
        if (ret)
                return ret;

        ret = -EINVAL;

        bdevname(rdev->bdev, b);
        sb = page_address(rdev->sb_page);

        if (sb->md_magic != MD_SB_MAGIC) {
                pr_warn("md: invalid raid superblock magic on %s\n", b);
                goto abort;
        }

        if (sb->major_version != 0 ||
            sb->minor_version < 90 ||
            sb->minor_version > 91) {
                pr_warn("Bad version number %d.%d on %s\n",
                        sb->major_version, sb->minor_version, b);
                goto abort;
        }

        if (sb->raid_disks <= 0)
                goto abort;

        if (md_csum_fold(calc_sb_csum(sb)) != md_csum_fold(sb->sb_csum)) {
                pr_warn("md: invalid superblock checksum on %s\n", b);
                goto abort;
        }

        rdev->preferred_minor = sb->md_minor;
        rdev->data_offset = 0;
        rdev->new_data_offset = 0;
        rdev->sb_size = MD_SB_BYTES;
        rdev->badblocks.shift = -1;

        if (sb->level == LEVEL_MULTIPATH)
                rdev->desc_nr = -1;
        else
                rdev->desc_nr = sb->this_disk.number;

        /* not spare disk, or LEVEL_MULTIPATH */
        if (sb->level == LEVEL_MULTIPATH ||
                (rdev->desc_nr >= 0 &&
                 rdev->desc_nr < MD_SB_DISKS &&
                 sb->disks[rdev->desc_nr].state &
                 ((1<<MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE))))
                spare_disk = false;

        if (!refdev) {
                if (!spare_disk)
                        ret = 1;
                else
                        ret = 0;
        } else {
                __u64 ev1, ev2;
                mdp_super_t *refsb = page_address(refdev->sb_page);
                if (!md_uuid_equal(refsb, sb)) {
                        pr_warn("md: %s has different UUID to %s\n",
                                b, bdevname(refdev->bdev,b2));
                        goto abort;
                }
                if (!md_sb_equal(refsb, sb)) {
                        pr_warn("md: %s has same UUID but different superblock to %s\n",
                                b, bdevname(refdev->bdev, b2));
                        goto abort;
                }
                ev1 = md_event(sb);
                ev2 = md_event(refsb);

                if (!spare_disk && ev1 > ev2)
                        ret = 1;
                else
                        ret = 0;
        }
        rdev->sectors = rdev->sb_start;
        /* Limit to 4TB as metadata cannot record more than that.
         * (not needed for Linear and RAID0 as metadata doesn't
         * record this size)
         */
        if ((u64)rdev->sectors >= (2ULL << 32) && sb->level >= 1)
                rdev->sectors = (sector_t)(2ULL << 32) - 2;

        if (rdev->sectors < ((sector_t)sb->size) * 2 && sb->level >= 1)
                /* "this cannot possibly happen" ... */
                ret = -EINVAL;

 abort:
        return ret;
}

/*
 * validate_super for 0.90.0
 */
static int super_90_validate(struct mddev *mddev, struct md_rdev *rdev)
{
        mdp_disk_t *desc;
        mdp_super_t *sb = page_address(rdev->sb_page);
        __u64 ev1 = md_event(sb);

        rdev->raid_disk = -1;
        clear_bit(Faulty, &rdev->flags);
        clear_bit(In_sync, &rdev->flags);
        clear_bit(Bitmap_sync, &rdev->flags);
        clear_bit(WriteMostly, &rdev->flags);

        if (mddev->raid_disks == 0) {
                mddev->major_version = 0;
                mddev->minor_version = sb->minor_version;
                mddev->patch_version = sb->patch_version;
                mddev->external = 0;
                mddev->chunk_sectors = sb->chunk_size >> 9;
                mddev->ctime = sb->ctime;
                mddev->utime = sb->utime;
                mddev->level = sb->level;
                mddev->clevel[0] = 0;
                mddev->layout = sb->layout;
                mddev->raid_disks = sb->raid_disks;
                mddev->dev_sectors = ((sector_t)sb->size) * 2;
                mddev->events = ev1;
                mddev->bitmap_info.offset = 0;
                mddev->bitmap_info.space = 0;
                /* bitmap can use 60 K after the 4K superblocks */
                mddev->bitmap_info.default_offset = MD_SB_BYTES >> 9;
                mddev->bitmap_info.default_space = 64*2 - (MD_SB_BYTES >> 9);
                mddev->reshape_backwards = 0;

                if (mddev->minor_version >= 91) {
                        mddev->reshape_position = sb->reshape_position;
                        mddev->delta_disks = sb->delta_disks;
                        mddev->new_level = sb->new_level;
                        mddev->new_layout = sb->new_layout;
                        mddev->new_chunk_sectors = sb->new_chunk >> 9;
                        if (mddev->delta_disks < 0)
                                mddev->reshape_backwards = 1;
                } else {
                        mddev->reshape_position = MaxSector;
                        mddev->delta_disks = 0;
                        mddev->new_level = mddev->level;
                        mddev->new_layout = mddev->layout;
                        mddev->new_chunk_sectors = mddev->chunk_sectors;
                }
                if (mddev->level == 0)
                        mddev->layout = -1;

                if (sb->state & (1<<MD_SB_CLEAN))
                        mddev->recovery_cp = MaxSector;
                else {
                        if (sb->events_hi == sb->cp_events_hi &&
                                sb->events_lo == sb->cp_events_lo) {
                                mddev->recovery_cp = sb->recovery_cp;
                        } else
                                mddev->recovery_cp = 0;
                }

                memcpy(mddev->uuid+0, &sb->set_uuid0, 4);
                memcpy(mddev->uuid+4, &sb->set_uuid1, 4);
                memcpy(mddev->uuid+8, &sb->set_uuid2, 4);
                memcpy(mddev->uuid+12,&sb->set_uuid3, 4);

                mddev->max_disks = MD_SB_DISKS;

                if (sb->state & (1<<MD_SB_BITMAP_PRESENT) &&
                    mddev->bitmap_info.file == NULL) {
                        mddev->bitmap_info.offset =
                                mddev->bitmap_info.default_offset;
                        mddev->bitmap_info.space =
                                mddev->bitmap_info.default_space;
                }

        } else if (mddev->pers == NULL) {
                /* Insist on good event counter while assembling, except
                 * for spares (which don't need an event count) */
                ++ev1;
                if (sb->disks[rdev->desc_nr].state & (
                            (1<<MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE)))
                        if (ev1 < mddev->events)
                                return -EINVAL;
        } else if (mddev->bitmap) {
                /* if adding to array with a bitmap, then we can accept an
                 * older device ... but not too old.
                 */
                if (ev1 < mddev->bitmap->events_cleared)
                        return 0;
                if (ev1 < mddev->events)
                        set_bit(Bitmap_sync, &rdev->flags);
        } else {
                if (ev1 < mddev->events)
                        /* just a hot-add of a new device, leave raid_disk at -1 */
                        return 0;
        }

        if (mddev->level != LEVEL_MULTIPATH) {
                desc = sb->disks + rdev->desc_nr;

                if (desc->state & (1<<MD_DISK_FAULTY))
                        set_bit(Faulty, &rdev->flags);
                else if (desc->state & (1<<MD_DISK_SYNC) /* &&
                            desc->raid_disk < mddev->raid_disks */) {
                        set_bit(In_sync, &rdev->flags);
                        rdev->raid_disk = desc->raid_disk;
                        rdev->saved_raid_disk = desc->raid_disk;
                } else if (desc->state & (1<<MD_DISK_ACTIVE)) {
                        /* active but not in sync implies recovery up to
                         * reshape position.  We don't know exactly where
                         * that is, so set to zero for now */
                        if (mddev->minor_version >= 91) {
                                rdev->recovery_offset = 0;
                                rdev->raid_disk = desc->raid_disk;
                        }
                }
                if (desc->state & (1<<MD_DISK_WRITEMOSTLY))
                        set_bit(WriteMostly, &rdev->flags);
                if (desc->state & (1<<MD_DISK_FAILFAST))
                        set_bit(FailFast, &rdev->flags);
        } else /* MULTIPATH are always insync */
                set_bit(In_sync, &rdev->flags);
        return 0;
}

/*
 * sync_super for 0.90.0
 */
static void super_90_sync(struct mddev *mddev, struct md_rdev *rdev)
{
        mdp_super_t *sb;
        struct md_rdev *rdev2;
        int next_spare = mddev->raid_disks;

        /* make rdev->sb match mddev data..
         *
         * 1/ zero out disks
         * 2/ Add info for each disk, keeping track of highest desc_nr (next_spare);
         * 3/ any empty disks < next_spare become removed
         *
         * disks[0] gets initialised to REMOVED because
         * we cannot be sure from other fields if it has
         * been initialised or not.
         */
        int i;
        int active=0, working=0,failed=0,spare=0,nr_disks=0;

        rdev->sb_size = MD_SB_BYTES;

        sb = page_address(rdev->sb_page);

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

        sb->md_magic = MD_SB_MAGIC;
        sb->major_version = mddev->major_version;
        sb->patch_version = mddev->patch_version;
        sb->gvalid_words  = 0; /* ignored */
        memcpy(&sb->set_uuid0, mddev->uuid+0, 4);
        memcpy(&sb->set_uuid1, mddev->uuid+4, 4);
        memcpy(&sb->set_uuid2, mddev->uuid+8, 4);
        memcpy(&sb->set_uuid3, mddev->uuid+12,4);

        sb->ctime = clamp_t(time64_t, mddev->ctime, 0, U32_MAX);
        sb->level = mddev->level;
        sb->size = mddev->dev_sectors / 2;
        sb->raid_disks = mddev->raid_disks;
        sb->md_minor = mddev->md_minor;
        sb->not_persistent = 0;
        sb->utime = clamp_t(time64_t, mddev->utime, 0, U32_MAX);
        sb->state = 0;
        sb->events_hi = (mddev->events>>32);
        sb->events_lo = (u32)mddev->events;

        if (mddev->reshape_position == MaxSector)
                sb->minor_version = 90;
        else {
                sb->minor_version = 91;
                sb->reshape_position = mddev->reshape_position;
                sb->new_level = mddev->new_level;
                sb->delta_disks = mddev->delta_disks;
                sb->new_layout = mddev->new_layout;
                sb->new_chunk = mddev->new_chunk_sectors << 9;
        }
        mddev->minor_version = sb->minor_version;
        if (mddev->in_sync)
        {
                sb->recovery_cp = mddev->recovery_cp;
                sb->cp_events_hi = (mddev->events>>32);
                sb->cp_events_lo = (u32)mddev->events;
                if (mddev->recovery_cp == MaxSector)
                        sb->state = (1<< MD_SB_CLEAN);
        } else
                sb->recovery_cp = 0;

        sb->layout = mddev->layout;
        sb->chunk_size = mddev->chunk_sectors << 9;

        if (mddev->bitmap && mddev->bitmap_info.file == NULL)
                sb->state |= (1<<MD_SB_BITMAP_PRESENT);

        sb->disks[0].state = (1<<MD_DISK_REMOVED);
        rdev_for_each(rdev2, mddev) {
                mdp_disk_t *d;
                int desc_nr;
                int is_active = test_bit(In_sync, &rdev2->flags);

                if (rdev2->raid_disk >= 0 &&
                    sb->minor_version >= 91)
                        /* we have nowhere to store the recovery_offset,
                         * but if it is not below the reshape_position,
                         * we can piggy-back on that.
                         */
                        is_active = 1;
                if (rdev2->raid_disk < 0 ||
                    test_bit(Faulty, &rdev2->flags))
                        is_active = 0;
                if (is_active)
                        desc_nr = rdev2->raid_disk;
                else
                        desc_nr = next_spare++;
                rdev2->desc_nr = desc_nr;
                d = &sb->disks[rdev2->desc_nr];
                nr_disks++;
                d->number = rdev2->desc_nr;
                d->major = MAJOR(rdev2->bdev->bd_dev);
                d->minor = MINOR(rdev2->bdev->bd_dev);
                if (is_active)
                        d->raid_disk = rdev2->raid_disk;
                else
                        d->raid_disk = rdev2->desc_nr; /* compatibility */
                if (test_bit(Faulty, &rdev2->flags))
                        d->state = (1<<MD_DISK_FAULTY);
                else if (is_active) {
                        d->state = (1<<MD_DISK_ACTIVE);
                        if (test_bit(In_sync, &rdev2->flags))
                                d->state |= (1<<MD_DISK_SYNC);
                        active++;
                        working++;
                } else {
                        d->state = 0;
                        spare++;
                        working++;
                }
                if (test_bit(WriteMostly, &rdev2->flags))
                        d->state |= (1<<MD_DISK_WRITEMOSTLY);
                if (test_bit(FailFast, &rdev2->flags))
                        d->state |= (1<<MD_DISK_FAILFAST);
        }
        /* now set the "removed" and "faulty" bits on any missing devices */
        for (i=0 ; i < mddev->raid_disks ; i++) {
                mdp_disk_t *d = &sb->disks[i];
                if (d->state == 0 && d->number == 0) {
                        d->number = i;
                        d->raid_disk = i;
                        d->state = (1<<MD_DISK_REMOVED);
                        d->state |= (1<<MD_DISK_FAULTY);
                        failed++;
                }
        }
        sb->nr_disks = nr_disks;
        sb->active_disks = active;
        sb->working_disks = working;
        sb->failed_disks = failed;
        sb->spare_disks = spare;

        sb->this_disk = sb->disks[rdev->desc_nr];
        sb->sb_csum = calc_sb_csum(sb);
}

/*
 * rdev_size_change for 0.90.0
 */
static unsigned long long
super_90_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
{
        if (num_sectors && num_sectors < rdev->mddev->dev_sectors)
                return 0; /* component must fit device */
        if (rdev->mddev->bitmap_info.offset)
                return 0; /* can't move bitmap */
        rdev->sb_start = calc_dev_sboffset(rdev);
        if (!num_sectors || num_sectors > rdev->sb_start)
                num_sectors = rdev->sb_start;
        /* Limit to 4TB as metadata cannot record more than that.
         * 4TB == 2^32 KB, or 2*2^32 sectors.
         */
        if ((u64)num_sectors >= (2ULL << 32) && rdev->mddev->level >= 1)
                num_sectors = (sector_t)(2ULL << 32) - 2;
        do {
                md_super_write(rdev->mddev, rdev, rdev->sb_start, rdev->sb_size,
                       rdev->sb_page);
        } while (md_super_wait(rdev->mddev) < 0);
        return num_sectors;
}

static int
super_90_allow_new_offset(struct md_rdev *rdev, unsigned long long new_offset)
{
        /* non-zero offset changes not possible with v0.90 */
        return new_offset == 0;
}

/*
 * version 1 superblock
 */

static __le32 calc_sb_1_csum(struct mdp_superblock_1 *sb)
{
        __le32 disk_csum;
        u32 csum;
        unsigned long long newcsum;
        int size = 256 + le32_to_cpu(sb->max_dev)*2;
        __le32 *isuper = (__le32*)sb;

        disk_csum = sb->sb_csum;
        sb->sb_csum = 0;
        newcsum = 0;
        for (; size >= 4; size -= 4)
                newcsum += le32_to_cpu(*isuper++);

        if (size == 2)
                newcsum += le16_to_cpu(*(__le16*) isuper);

        csum = (newcsum & 0xffffffff) + (newcsum >> 32);
        sb->sb_csum = disk_csum;
        return cpu_to_le32(csum);
}

static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_version)
{
        struct mdp_superblock_1 *sb;
        int ret;
        sector_t sb_start;
        sector_t sectors;
        char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
        int bmask;
        bool spare_disk = true;

        /*
         * Calculate the position of the superblock in 512byte sectors.
         * It is always aligned to a 4K boundary and
         * depeding on minor_version, it can be:
         * 0: At least 8K, but less than 12K, from end of device
         * 1: At start of device
         * 2: 4K from start of device.
         */
        switch(minor_version) {
        case 0:
                sb_start = i_size_read(rdev->bdev->bd_inode) >> 9;
                sb_start -= 8*2;
                sb_start &= ~(sector_t)(4*2-1);
                break;
        case 1:
                sb_start = 0;
                break;
        case 2:
                sb_start = 8;
                break;
        default:
                return -EINVAL;
        }
        rdev->sb_start = sb_start;

        /* superblock is rarely larger than 1K, but it can be larger,
         * and it is safe to read 4k, so we do that
         */
        ret = read_disk_sb(rdev, 4096);
        if (ret) return ret;

        sb = page_address(rdev->sb_page);

        if (sb->magic != cpu_to_le32(MD_SB_MAGIC) ||
            sb->major_version != cpu_to_le32(1) ||
            le32_to_cpu(sb->max_dev) > (4096-256)/2 ||
            le64_to_cpu(sb->super_offset) != rdev->sb_start ||
            (le32_to_cpu(sb->feature_map) & ~MD_FEATURE_ALL) != 0)
                return -EINVAL;

        if (calc_sb_1_csum(sb) != sb->sb_csum) {
                pr_warn("md: invalid superblock checksum on %s\n",
                        bdevname(rdev->bdev,b));
                return -EINVAL;
        }
        if (le64_to_cpu(sb->data_size) < 10) {
                pr_warn("md: data_size too small on %s\n",
                        bdevname(rdev->bdev,b));
                return -EINVAL;
        }
        if (sb->pad0 ||
            sb->pad3[0] ||
            memcmp(sb->pad3, sb->pad3+1, sizeof(sb->pad3) - sizeof(sb->pad3[1])))
                /* Some padding is non-zero, might be a new feature */
                return -EINVAL;

        rdev->preferred_minor = 0xffff;
        rdev->data_offset = le64_to_cpu(sb->data_offset);
        rdev->new_data_offset = rdev->data_offset;
        if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_RESHAPE_ACTIVE) &&
            (le32_to_cpu(sb->feature_map) & MD_FEATURE_NEW_OFFSET))
                rdev->new_data_offset += (s32)le32_to_cpu(sb->new_offset);
        atomic_set(&rdev->corrected_errors, le32_to_cpu(sb->cnt_corrected_read));

        rdev->sb_size = le32_to_cpu(sb->max_dev) * 2 + 256;
        bmask = queue_logical_block_size(rdev->bdev->bd_disk->queue)-1;
        if (rdev->sb_size & bmask)
                rdev->sb_size = (rdev->sb_size | bmask) + 1;

        if (minor_version
            && rdev->data_offset < sb_start + (rdev->sb_size/512))
                return -EINVAL;
        if (minor_version
            && rdev->new_data_offset < sb_start + (rdev->sb_size/512))
                return -EINVAL;

        if (sb->level == cpu_to_le32(LEVEL_MULTIPATH))
                rdev->desc_nr = -1;
        else
                rdev->desc_nr = le32_to_cpu(sb->dev_number);

        if (!rdev->bb_page) {
                rdev->bb_page = alloc_page(GFP_KERNEL);
                if (!rdev->bb_page)
                        return -ENOMEM;
        }
        if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BAD_BLOCKS) &&
            rdev->badblocks.count == 0) {
                /* need to load the bad block list.
                 * Currently we limit it to one page.
                 */
                s32 offset;
                sector_t bb_sector;
                __le64 *bbp;
                int i;
                int sectors = le16_to_cpu(sb->bblog_size);
                if (sectors > (PAGE_SIZE / 512))
                        return -EINVAL;
                offset = le32_to_cpu(sb->bblog_offset);
                if (offset == 0)
                        return -EINVAL;
                bb_sector = (long long)offset;
                if (!sync_page_io(rdev, bb_sector, sectors << 9,
                                  rdev->bb_page, REQ_OP_READ, 0, true))
                        return -EIO;
                bbp = (__le64 *)page_address(rdev->bb_page);
                rdev->badblocks.shift = sb->bblog_shift;
                for (i = 0 ; i < (sectors << (9-3)) ; i++, bbp++) {
                        u64 bb = le64_to_cpu(*bbp);
                        int count = bb & (0x3ff);
                        u64 sector = bb >> 10;
                        sector <<= sb->bblog_shift;
                        count <<= sb->bblog_shift;
                        if (bb + 1 == 0)
                                break;
                        if (badblocks_set(&rdev->badblocks, sector, count, 1))
                                return -EINVAL;
                }
        } else if (sb->bblog_offset != 0)
                rdev->badblocks.shift = 0;

        if ((le32_to_cpu(sb->feature_map) &
            (MD_FEATURE_PPL | MD_FEATURE_MULTIPLE_PPLS))) {
                rdev->ppl.offset = (__s16)le16_to_cpu(sb->ppl.offset);
                rdev->ppl.size = le16_to_cpu(sb->ppl.size);
                rdev->ppl.sector = rdev->sb_start + rdev->ppl.offset;
        }

        if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_RAID0_LAYOUT) &&
            sb->level != 0)
                return -EINVAL;

        /* not spare disk, or LEVEL_MULTIPATH */
        if (sb->level == cpu_to_le32(LEVEL_MULTIPATH) ||
                (rdev->desc_nr >= 0 &&
                rdev->desc_nr < le32_to_cpu(sb->max_dev) &&
                (le16_to_cpu(sb->dev_roles[rdev->desc_nr]) < MD_DISK_ROLE_MAX ||
                 le16_to_cpu(sb->dev_roles[rdev->desc_nr]) == MD_DISK_ROLE_JOURNAL)))
                spare_disk = false;

        if (!refdev) {
                if (!spare_disk)
                        ret = 1;
                else
                        ret = 0;
        } else {
                __u64 ev1, ev2;
                struct mdp_superblock_1 *refsb = page_address(refdev->sb_page);

                if (memcmp(sb->set_uuid, refsb->set_uuid, 16) != 0 ||
                    sb->level != refsb->level ||
                    sb->layout != refsb->layout ||
                    sb->chunksize != refsb->chunksize) {
                        pr_warn("md: %s has strangely different superblock to %s\n",
                                bdevname(rdev->bdev,b),
                                bdevname(refdev->bdev,b2));
                        return -EINVAL;
                }
                ev1 = le64_to_cpu(sb->events);
                ev2 = le64_to_cpu(refsb->events);

                if (!spare_disk && ev1 > ev2)
                        ret = 1;
                else
                        ret = 0;
        }
        if (minor_version) {
                sectors = (i_size_read(rdev->bdev->bd_inode) >> 9);
                sectors -= rdev->data_offset;
        } else
                sectors = rdev->sb_start;
        if (sectors < le64_to_cpu(sb->data_size))
                return -EINVAL;
        rdev->sectors = le64_to_cpu(sb->data_size);
        return ret;
}

static int super_1_validate(struct mddev *mddev, struct md_rdev *rdev)
{
        struct mdp_superblock_1 *sb = page_address(rdev->sb_page);
        __u64 ev1 = le64_to_cpu(sb->events);

        rdev->raid_disk = -1;
        clear_bit(Faulty, &rdev->flags);
        clear_bit(In_sync, &rdev->flags);
        clear_bit(Bitmap_sync, &rdev->flags);
        clear_bit(WriteMostly, &rdev->flags);

        if (mddev->raid_disks == 0) {
                mddev->major_version = 1;
                mddev->patch_version = 0;
                mddev->external = 0;
                mddev->chunk_sectors = le32_to_cpu(sb->chunksize);
                mddev->ctime = le64_to_cpu(sb->ctime);
                mddev->utime = le64_to_cpu(sb->utime);
                mddev->level = le32_to_cpu(sb->level);
                mddev->clevel[0] = 0;
                mddev->layout = le32_to_cpu(sb->layout);
                mddev->raid_disks = le32_to_cpu(sb->raid_disks);
                mddev->dev_sectors = le64_to_cpu(sb->size);
                mddev->events = ev1;
                mddev->bitmap_info.offset = 0;
                mddev->bitmap_info.space = 0;
                /* Default location for bitmap is 1K after superblock
                 * using 3K - total of 4K
                 */
                mddev->bitmap_info.default_offset = 1024 >> 9;
                mddev->bitmap_info.default_space = (4096-1024) >> 9;
                mddev->reshape_backwards = 0;

                mddev->recovery_cp = le64_to_cpu(sb->resync_offset);
                memcpy(mddev->uuid, sb->set_uuid, 16);

                mddev->max_disks =  (4096-256)/2;

                if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
                    mddev->bitmap_info.file == NULL) {
                        mddev->bitmap_info.offset =
                                (__s32)le32_to_cpu(sb->bitmap_offset);
                        /* Metadata doesn't record how much space is available.
                         * For 1.0, we assume we can use up to the superblock
                         * if before, else to 4K beyond superblock.
                         * For others, assume no change is possible.
                         */
                        if (mddev->minor_version > 0)
                                mddev->bitmap_info.space = 0;
                        else if (mddev->bitmap_info.offset > 0)
                                mddev->bitmap_info.space =
                                        8 - mddev->bitmap_info.offset;
                        else
                                mddev->bitmap_info.space =
                                        -mddev->bitmap_info.offset;
                }

                if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_RESHAPE_ACTIVE)) {
                        mddev->reshape_position = le64_to_cpu(sb->reshape_position);
                        mddev->delta_disks = le32_to_cpu(sb->delta_disks);
                        mddev->new_level = le32_to_cpu(sb->new_level);
                        mddev->new_layout = le32_to_cpu(sb->new_layout);
                        mddev->new_chunk_sectors = le32_to_cpu(sb->new_chunk);
                        if (mddev->delta_disks < 0 ||
                            (mddev->delta_disks == 0 &&
                             (le32_to_cpu(sb->feature_map)
                              & MD_FEATURE_RESHAPE_BACKWARDS)))
                                mddev->reshape_backwards = 1;
                } else {
                        mddev->reshape_position = MaxSector;
                        mddev->delta_disks = 0;
                        mddev->new_level = mddev->level;
                        mddev->new_layout = mddev->layout;
                        mddev->new_chunk_sectors = mddev->chunk_sectors;
                }

                if (mddev->level == 0 &&
                    !(le32_to_cpu(sb->feature_map) & MD_FEATURE_RAID0_LAYOUT))
                        mddev->layout = -1;

                if (le32_to_cpu(sb->feature_map) & MD_FEATURE_JOURNAL)
                        set_bit(MD_HAS_JOURNAL, &mddev->flags);

                if (le32_to_cpu(sb->feature_map) &
                    (MD_FEATURE_PPL | MD_FEATURE_MULTIPLE_PPLS)) {
                        if (le32_to_cpu(sb->feature_map) &
                            (MD_FEATURE_BITMAP_OFFSET | MD_FEATURE_JOURNAL))
                                return -EINVAL;
                        if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_PPL) &&
                            (le32_to_cpu(sb->feature_map) &
                                            MD_FEATURE_MULTIPLE_PPLS))
                                return -EINVAL;
                        set_bit(MD_HAS_PPL, &mddev->flags);
                }
        } else if (mddev->pers == NULL) {
                /* Insist of good event counter while assembling, except for
                 * spares (which don't need an event count) */
                ++ev1;
                if (rdev->desc_nr >= 0 &&
                    rdev->desc_nr < le32_to_cpu(sb->max_dev) &&
                    (le16_to_cpu(sb->dev_roles[rdev->desc_nr]) < MD_DISK_ROLE_MAX ||
                     le16_to_cpu(sb->dev_roles[rdev->desc_nr]) == MD_DISK_ROLE_JOURNAL))
                        if (ev1 < mddev->events)
                                return -EINVAL;
        } else if (mddev->bitmap) {
                /* If adding to array with a bitmap, then we can accept an
                 * older device, but not too old.
                 */
                if (ev1 < mddev->bitmap->events_cleared)
                        return 0;
                if (ev1 < mddev->events)
                        set_bit(Bitmap_sync, &rdev->flags);
        } else {
                if (ev1 < mddev->events)
                        /* just a hot-add of a new device, leave raid_disk at -1 */
                        return 0;
        }
        if (mddev->level != LEVEL_MULTIPATH) {
                int role;
                if (rdev->desc_nr < 0 ||
                    rdev->desc_nr >= le32_to_cpu(sb->max_dev)) {
                        role = MD_DISK_ROLE_SPARE;
                        rdev->desc_nr = -1;
                } else
                        role = le16_to_cpu(sb->dev_roles[rdev->desc_nr]);
                switch(role) {
                case MD_DISK_ROLE_SPARE: /* spare */
                        break;
                case MD_DISK_ROLE_FAULTY: /* faulty */
                        set_bit(Faulty, &rdev->flags);
                        break;
                case MD_DISK_ROLE_JOURNAL: /* journal device */
                        if (!(le32_to_cpu(sb->feature_map) & MD_FEATURE_JOURNAL)) {
                                /* journal device without journal feature */
                                pr_warn("md: journal device provided without journal feature, ignoring the device\n");
                                return -EINVAL;
                        }
                        set_bit(Journal, &rdev->flags);
                        rdev->journal_tail = le64_to_cpu(sb->journal_tail);
                        rdev->raid_disk = 0;
                        break;
                default:
                        rdev->saved_raid_disk = role;
                        if ((le32_to_cpu(sb->feature_map) &
                             MD_FEATURE_RECOVERY_OFFSET)) {
                                rdev->recovery_offset = le64_to_cpu(sb->recovery_offset);
                                if (!(le32_to_cpu(sb->feature_map) &
                                      MD_FEATURE_RECOVERY_BITMAP))
                                        rdev->saved_raid_disk = -1;
                        } else {
                                /*
                                 * If the array is FROZEN, then the device can't
                                 * be in_sync with rest of array.
                                 */
                                if (!test_bit(MD_RECOVERY_FROZEN,
                                              &mddev->recovery))
                                        set_bit(In_sync, &rdev->flags);
                        }
                        rdev->raid_disk = role;
                        break;
                }
                if (sb->devflags & WriteMostly1)
                        set_bit(WriteMostly, &rdev->flags);
                if (sb->devflags & FailFast1)
                        set_bit(FailFast, &rdev->flags);
                if (le32_to_cpu(sb->feature_map) & MD_FEATURE_REPLACEMENT)
                        set_bit(Replacement, &rdev->flags);
        } else /* MULTIPATH are always insync */
                set_bit(In_sync, &rdev->flags);

        return 0;
}

static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
{
        struct mdp_superblock_1 *sb;

        struct md_rdev *rdev2;
        int max_dev, i;
        /* make rdev->sb match mddev and rdev data. */

        sb = page_address(rdev->sb_page);

        sb->feature_map = 0;
        sb->pad0 = 0;
        sb->recovery_offset = cpu_to_le64(0);
        memset(sb->pad3, 0, sizeof(sb->pad3));

        sb->utime = cpu_to_le64((__u64)mddev->utime);
        sb->events = cpu_to_le64(mddev->events);
        if (mddev->in_sync)
                sb->resync_offset = cpu_to_le64(mddev->recovery_cp);
        else if (test_bit(MD_JOURNAL_CLEAN, &mddev->flags))
                sb->resync_offset = cpu_to_le64(MaxSector);
        else
                sb->resync_offset = cpu_to_le64(0);

        sb->cnt_corrected_read = cpu_to_le32(atomic_read(&rdev->corrected_errors));

        sb->raid_disks = cpu_to_le32(mddev->raid_disks);
        sb->size = cpu_to_le64(mddev->dev_sectors);
        sb->chunksize = cpu_to_le32(mddev->chunk_sectors);
        sb->level = cpu_to_le32(mddev->level);
        sb->layout = cpu_to_le32(mddev->layout);
        if (test_bit(FailFast, &rdev->flags))
                sb->devflags |= FailFast1;
        else
                sb->devflags &= ~FailFast1;

        if (test_bit(WriteMostly, &rdev->flags))
                sb->devflags |= WriteMostly1;
        else
                sb->devflags &= ~WriteMostly1;
        sb->data_offset = cpu_to_le64(rdev->data_offset);
        sb->data_size = cpu_to_le64(rdev->sectors);

        if (mddev->bitmap && mddev->bitmap_info.file == NULL) {
                sb->bitmap_offset = cpu_to_le32((__u32)mddev->bitmap_info.offset);
                sb->feature_map = cpu_to_le32(MD_FEATURE_BITMAP_OFFSET);
        }

        if (rdev->raid_disk >= 0 && !test_bit(Journal, &rdev->flags) &&
            !test_bit(In_sync, &rdev->flags)) {
                sb->feature_map |=
                        cpu_to_le32(MD_FEATURE_RECOVERY_OFFSET);
                sb->recovery_offset =
                        cpu_to_le64(rdev->recovery_offset);
                if (rdev->saved_raid_disk >= 0 && mddev->bitmap)
                        sb->feature_map |=
                                cpu_to_le32(MD_FEATURE_RECOVERY_BITMAP);
        }
        /* Note: recovery_offset and journal_tail share space  */
        if (test_bit(Journal, &rdev->flags))
                sb->journal_tail = cpu_to_le64(rdev->journal_tail);
        if (test_bit(Replacement, &rdev->flags))
                sb->feature_map |=
                        cpu_to_le32(MD_FEATURE_REPLACEMENT);

        if (mddev->reshape_position != MaxSector) {
                sb->feature_map |= cpu_to_le32(MD_FEATURE_RESHAPE_ACTIVE);
                sb->reshape_position = cpu_to_le64(mddev->reshape_position);
                sb->new_layout = cpu_to_le32(mddev->new_layout);
                sb->delta_disks = cpu_to_le32(mddev->delta_disks);
                sb->new_level = cpu_to_le32(mddev->new_level);
                sb->new_chunk = cpu_to_le32(mddev->new_chunk_sectors);
                if (mddev->delta_disks == 0 &&
                    mddev->reshape_backwards)
                        sb->feature_map
                                |= cpu_to_le32(MD_FEATURE_RESHAPE_BACKWARDS);
                if (rdev->new_data_offset != rdev->data_offset) {
                        sb->feature_map
                                |= cpu_to_le32(MD_FEATURE_NEW_OFFSET);
                        sb->new_offset = cpu_to_le32((__u32)(rdev->new_data_offset
                                                             - rdev->data_offset));
                }
        }

        if (mddev_is_clustered(mddev))
                sb->feature_map |= cpu_to_le32(MD_FEATURE_CLUSTERED);

        if (rdev->badblocks.count == 0)
                /* Nothing to do for bad blocks*/ ;
        else if (sb->bblog_offset == 0)
                /* Cannot record bad blocks on this device */
                md_error(mddev, rdev);
        else {
                struct badblocks *bb = &rdev->badblocks;
                __le64 *bbp = (__le64 *)page_address(rdev->bb_page);
                u64 *p = bb->page;
                sb->feature_map |= cpu_to_le32(MD_FEATURE_BAD_BLOCKS);
                if (bb->changed) {
                        unsigned seq;

retry:
                        seq = read_seqbegin(&bb->lock);

                        memset(bbp, 0xff, PAGE_SIZE);

                        for (i = 0 ; i < bb->count ; i++) {
                                u64 internal_bb = p[i];
                                u64 store_bb = ((BB_OFFSET(internal_bb) << 10)
                                                | BB_LEN(internal_bb));
                                bbp[i] = cpu_to_le64(store_bb);
                        }
                        bb->changed = 0;
                        if (read_seqretry(&bb->lock, seq))
                                goto retry;

                        bb->sector = (rdev->sb_start +
                                      (int)le32_to_cpu(sb->bblog_offset));
                        bb->size = le16_to_cpu(sb->bblog_size);
                }
        }

        max_dev = 0;
        rdev_for_each(rdev2, mddev)
                if (rdev2->desc_nr+1 > max_dev)
                        max_dev = rdev2->desc_nr+1;

        if (max_dev > le32_to_cpu(sb->max_dev)) {
                int bmask;
                sb->max_dev = cpu_to_le32(max_dev);
                rdev->sb_size = max_dev * 2 + 256;
                bmask = queue_logical_block_size(rdev->bdev->bd_disk->queue)-1;
                if (rdev->sb_size & bmask)
                        rdev->sb_size = (rdev->sb_size | bmask) + 1;
        } else
                max_dev = le32_to_cpu(sb->max_dev);

        for (i=0; i<max_dev;i++)
                sb->dev_roles[i] = cpu_to_le16(MD_DISK_ROLE_SPARE);

        if (test_bit(MD_HAS_JOURNAL, &mddev->flags))
                sb->feature_map |= cpu_to_le32(MD_FEATURE_JOURNAL);

        if (test_bit(MD_HAS_PPL, &mddev->flags)) {
                if (test_bit(MD_HAS_MULTIPLE_PPLS, &mddev->flags))
                        sb->feature_map |=
                            cpu_to_le32(MD_FEATURE_MULTIPLE_PPLS);
                else
                        sb->feature_map |= cpu_to_le32(MD_FEATURE_PPL);
                sb->ppl.offset = cpu_to_le16(rdev->ppl.offset);
                sb->ppl.size = cpu_to_le16(rdev->ppl.size);
        }

        rdev_for_each(rdev2, mddev) {
                i = rdev2->desc_nr;
                if (test_bit(Faulty, &rdev2->flags))
                        sb->dev_roles[i] = cpu_to_le16(MD_DISK_ROLE_FAULTY);
                else if (test_bit(In_sync, &rdev2->flags))
                        sb->dev_roles[i] = cpu_to_le16(rdev2->raid_disk);
                else if (test_bit(Journal, &rdev2->flags))
                        sb->dev_roles[i] = cpu_to_le16(MD_DISK_ROLE_JOURNAL);
                else if (rdev2->raid_disk >= 0)
                        sb->dev_roles[i] = cpu_to_le16(rdev2->raid_disk);
                else
                        sb->dev_roles[i] = cpu_to_le16(MD_DISK_ROLE_SPARE);
        }

        sb->sb_csum = calc_sb_1_csum(sb);
}

static unsigned long long
super_1_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
{
        struct mdp_superblock_1 *sb;
        sector_t max_sectors;
        if (num_sectors && num_sectors < rdev->mddev->dev_sectors)
                return 0; /* component must fit device */
        if (rdev->data_offset != rdev->new_data_offset)
                return 0; /* too confusing */
        if (rdev->sb_start < rdev->data_offset) {
                /* minor versions 1 and 2; superblock before data */
                max_sectors = i_size_read(rdev->bdev->bd_inode) >> 9;
                max_sectors -= rdev->data_offset;
                if (!num_sectors || num_sectors > max_sectors)
                        num_sectors = max_sectors;
        } else if (rdev->mddev->bitmap_info.offset) {
                /* minor version 0 with bitmap we can't move */
                return 0;
        } else {
                /* minor version 0; superblock after data */
                sector_t sb_start;
                sb_start = (i_size_read(rdev->bdev->bd_inode) >> 9) - 8*2;
                sb_start &= ~(sector_t)(4*2 - 1);
                max_sectors = rdev->sectors + sb_start - rdev->sb_start;
                if (!num_sectors || num_sectors > max_sectors)
                        num_sectors = max_sectors;
                rdev->sb_start = sb_start;
        }
        sb = page_address(rdev->sb_page);
        sb->data_size = cpu_to_le64(num_sectors);
        sb->super_offset = cpu_to_le64(rdev->sb_start);
        sb->sb_csum = calc_sb_1_csum(sb);
        do {
                md_super_write(rdev->mddev, rdev, rdev->sb_start, rdev->sb_size,
                               rdev->sb_page);
        } while (md_super_wait(rdev->mddev) < 0);
        return num_sectors;

}

static int
super_1_allow_new_offset(struct md_rdev *rdev,
                         unsigned long long new_offset)
{
        /* All necessary checks on new >= old have been done */
        struct bitmap *bitmap;
        if (new_offset >= rdev->data_offset)
                return 1;

        /* with 1.0 metadata, there is no metadata to tread on
         * so we can always move back */
        if (rdev->mddev->minor_version == 0)
                return 1;

        /* otherwise we must be sure not to step on
         * any metadata, so stay:
         * 36K beyond start of superblock
         * beyond end of badblocks
         * beyond write-intent bitmap
         */
        if (rdev->sb_start + (32+4)*2 > new_offset)
                return 0;
        bitmap = rdev->mddev->bitmap;
        if (bitmap && !rdev->mddev->bitmap_info.file &&
            rdev->sb_start + rdev->mddev->bitmap_info.offset +
            bitmap->storage.file_pages * (PAGE_SIZE>>9) > new_offset)
                return 0;
        if (rdev->badblocks.sector + rdev->badblocks.size > new_offset)
                return 0;

        return 1;
}

static struct super_type super_types[] = {
        [0] = {
                .name   = "0.90.0",
                .owner  = THIS_MODULE,
                .load_super         = super_90_load,
                .validate_super     = super_90_validate,
                .sync_super         = super_90_sync,
                .rdev_size_change   = super_90_rdev_size_change,
                .allow_new_offset   = super_90_allow_new_offset,
        },
        [1] = {
                .name   = "md-1",
                .owner  = THIS_MODULE,
                .load_super         = super_1_load,
                .validate_super     = super_1_validate,
                .sync_super         = super_1_sync,
                .rdev_size_change   = super_1_rdev_size_change,
                .allow_new_offset   = super_1_allow_new_offset,
        },
};

static void sync_super(struct mddev *mddev, struct md_rdev *rdev)
{
        if (mddev->sync_super) {
                mddev->sync_super(mddev, rdev);
                return;
        }

        BUG_ON(mddev->major_version >= ARRAY_SIZE(super_types));

        super_types[mddev->major_version].sync_super(mddev, rdev);
}

static int match_mddev_units(struct mddev *mddev1, struct mddev *mddev2)
{
        struct md_rdev *rdev, *rdev2;

        rcu_read_lock();
        rdev_for_each_rcu(rdev, mddev1) {
                if (test_bit(Faulty, &rdev->flags) ||
                    test_bit(Journal, &rdev->flags) ||
                    rdev->raid_disk == -1)
                        continue;
                rdev_for_each_rcu(rdev2, mddev2) {
                        if (test_bit(Faulty, &rdev2->flags) ||
                            test_bit(Journal, &rdev2->flags) ||
                            rdev2->raid_disk == -1)
                                continue;
                        if (rdev->bdev->bd_contains ==
                            rdev2->bdev->bd_contains) {
                                rcu_read_unlock();
                                return 1;
                        }
                }
        }
        rcu_read_unlock();
        return 0;
}

static LIST_HEAD(pending_raid_disks);

/*
 * Try to register data integrity profile for an mddev
 *
 * This is called when an array is started and after a disk has been kicked
 * from the array. It only succeeds if all working and active component devices
 * are integrity capable with matching profiles.
 */
int md_integrity_register(struct mddev *mddev)
{
        struct md_rdev *rdev, *reference = NULL;

        if (list_empty(&mddev->disks))
                return 0; /* nothing to do */
        if (!mddev->gendisk || blk_get_integrity(mddev->gendisk))
                return 0; /* shouldn't register, or already is */
        rdev_for_each(rdev, mddev) {
                /* skip spares and non-functional disks */
                if (test_bit(Faulty, &rdev->flags))
                        continue;
                if (rdev->raid_disk < 0)
                        continue;
                if (!reference) {
                        /* Use the first rdev as the reference */
                        reference = rdev;
                        continue;
                }
                /* does this rdev's profile match the reference profile? */
                if (blk_integrity_compare(reference->bdev->bd_disk,
                                rdev->bdev->bd_disk) < 0)
                        return -EINVAL;
        }
        if (!reference || !bdev_get_integrity(reference->bdev))
                return 0;
        /*
         * All component devices are integrity capable and have matching
         * profiles, register the common profile for the md device.
         */
        blk_integrity_register(mddev->gendisk,
                               bdev_get_integrity(reference->bdev));

        pr_debug("md: data integrity enabled on %s\n", mdname(mddev));
        if (bioset_integrity_create(&mddev->bio_set, BIO_POOL_SIZE)) {
                pr_err("md: failed to create integrity pool for %s\n",
                       mdname(mddev));
                return -EINVAL;
        }
        return 0;
}
EXPORT_SYMBOL(md_integrity_register);

/*
 * Attempt to add an rdev, but only if it is consistent with the current
 * integrity profile
 */
int md_integrity_add_rdev(struct md_rdev *rdev, struct mddev *mddev)
{
        struct blk_integrity *bi_mddev;
        char name[BDEVNAME_SIZE];

        if (!mddev->gendisk)
                return 0;

        bi_mddev = blk_get_integrity(mddev->gendisk);

        if (!bi_mddev) /* nothing to do */
                return 0;

        if (blk_integrity_compare(mddev->gendisk, rdev->bdev->bd_disk) != 0) {
                pr_err("%s: incompatible integrity profile for %s\n",
                       mdname(mddev), bdevname(rdev->bdev, name));
                return -ENXIO;
        }

        return 0;
}
EXPORT_SYMBOL(md_integrity_add_rdev);

static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
{
        char b[BDEVNAME_SIZE];
        struct kobject *ko;
        int err;

        /* prevent duplicates */
        if (find_rdev(mddev, rdev->bdev->bd_dev))
                return -EEXIST;

        if ((bdev_read_only(rdev->bdev) || bdev_read_only(rdev->meta_bdev)) &&
            mddev->pers)
                return -EROFS;

        /* make sure rdev->sectors exceeds mddev->dev_sectors */
        if (!test_bit(Journal, &rdev->flags) &&
            rdev->sectors &&
            (mddev->dev_sectors == 0 || rdev->sectors < mddev->dev_sectors)) {
                if (mddev->pers) {
                        /* Cannot change size, so fail
                         * If mddev->level <= 0, then we don't care
                         * about aligning sizes (e.g. linear)
                         */
                        if (mddev->level > 0)
                                return -ENOSPC;
                } else
                        mddev->dev_sectors = rdev->sectors;
        }

        /* Verify rdev->desc_nr is unique.
         * If it is -1, assign a free number, else
         * check number is not in use
         */
        rcu_read_lock();
        if (rdev->desc_nr < 0) {
                int choice = 0;
                if (mddev->pers)
                        choice = mddev->raid_disks;
                while (md_find_rdev_nr_rcu(mddev, choice))
                        choice++;
                rdev->desc_nr = choice;
        } else {
                if (md_find_rdev_nr_rcu(mddev, rdev->desc_nr)) {
                        rcu_read_unlock();
                        return -EBUSY;
                }
        }
        rcu_read_unlock();
        if (!test_bit(Journal, &rdev->flags) &&
            mddev->max_disks && rdev->desc_nr >= mddev->max_disks) {
                pr_warn("md: %s: array is limited to %d devices\n",
                        mdname(mddev), mddev->max_disks);
                return -EBUSY;
        }
        bdevname(rdev->bdev,b);
        strreplace(b, '/', '!');

        rdev->mddev = mddev;
        pr_debug("md: bind<%s>\n", b);

        if (mddev->raid_disks)
                mddev_create_serial_pool(mddev, rdev, false);

        if ((err = kobject_add(&rdev->kobj, &mddev->kobj, "dev-%s", b)))
                goto fail;

        ko = &part_to_dev(rdev->bdev->bd_part)->kobj;
        if (sysfs_create_link(&rdev->kobj, ko, "block"))
                /* failure here is OK */;
        rdev->sysfs_state = sysfs_get_dirent_safe(rdev->kobj.sd, "state");

        list_add_rcu(&rdev->same_set, &mddev->disks);
        bd_link_disk_holder(rdev->bdev, mddev->gendisk);

        /* May as well allow recovery to be retried once */
        mddev->recovery_disabled++;

        return 0;

 fail:
        pr_warn("md: failed to register dev-%s for %s\n",
                b, mdname(mddev));
        return err;
}

static void rdev_delayed_delete(struct work_struct *ws)
{
        struct md_rdev *rdev = container_of(ws, struct md_rdev, del_work);
        kobject_del(&rdev->kobj);
        kobject_put(&rdev->kobj);
}

static void unbind_rdev_from_array(struct md_rdev *rdev)
{
        char b[BDEVNAME_SIZE];

        bd_unlink_disk_holder(rdev->bdev, rdev->mddev->gendisk);
        list_del_rcu(&rdev->same_set);
        pr_debug("md: unbind<%s>\n", bdevname(rdev->bdev,b));
        mddev_destroy_serial_pool(rdev->mddev, rdev, false);
        rdev->mddev = NULL;
        sysfs_remove_link(&rdev->kobj, "block");
        sysfs_put(rdev->sysfs_state);
        rdev->sysfs_state = NULL;
        rdev->badblocks.count = 0;
        /* We need to delay this, otherwise we can deadlock when
         * writing to 'remove' to "dev/state".  We also need
         * to delay it due to rcu usage.
         */
        synchronize_rcu();
        INIT_WORK(&rdev->del_work, rdev_delayed_delete);
        kobject_get(&rdev->kobj);
        queue_work(md_rdev_misc_wq, &rdev->del_work);
}

/*
 * prevent the device from being mounted, repartitioned or
 * otherwise reused by a RAID array (or any other kernel
 * subsystem), by bd_claiming the device.
 */
static int lock_rdev(struct md_rdev *rdev, dev_t dev, int shared)
{
        int err = 0;
        struct block_device *bdev;

        bdev = blkdev_get_by_dev(dev, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
                                 shared ? (struct md_rdev *)lock_rdev : rdev);
        if (IS_ERR(bdev)) {
                pr_warn("md: could not open device unknown-block(%u,%u).\n",
                        MAJOR(dev), MINOR(dev));
                return PTR_ERR(bdev);
        }
        rdev->bdev = bdev;
        return err;
}

static void unlock_rdev(struct md_rdev *rdev)
{
        struct block_device *bdev = rdev->bdev;
        rdev->bdev = NULL;
        blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
}

void md_autodetect_dev(dev_t dev);

static void export_rdev(struct md_rdev *rdev)
{
        char b[BDEVNAME_SIZE];

        pr_debug("md: export_rdev(%s)\n", bdevname(rdev->bdev,b));
        md_rdev_clear(rdev);
#ifndef MODULE
        if (test_bit(AutoDetected, &rdev->flags))
                md_autodetect_dev(rdev->bdev->bd_dev);
#endif
        unlock_rdev(rdev);
        kobject_put(&rdev->kobj);
}

void md_kick_rdev_from_array(struct md_rdev *rdev)
{
        unbind_rdev_from_array(rdev);
        export_rdev(rdev);
}
EXPORT_SYMBOL_GPL(md_kick_rdev_from_array);

static void export_array(struct mddev *mddev)
{
        struct md_rdev *rdev;

        while (!list_empty(&mddev->disks)) {
                rdev = list_first_entry(&mddev->disks, struct md_rdev,
                                        same_set);
                md_kick_rdev_from_array(rdev);
        }
        mddev->raid_disks = 0;
        mddev->major_version = 0;
}

static bool set_in_sync(struct mddev *mddev)
{
        lockdep_assert_held(&mddev->lock);
        if (!mddev->in_sync) {
                mddev->sync_checkers++;
                spin_unlock(&mddev->lock);
                percpu_ref_switch_to_atomic_sync(&mddev->writes_pending);
                spin_lock(&mddev->lock);
                if (!mddev->in_sync &&
                    percpu_ref_is_zero(&mddev->writes_pending)) {
                        mddev->in_sync = 1;
                        /*
                         * Ensure ->in_sync is visible before we clear
                         * ->sync_checkers.
                         */
                        smp_mb();
                        set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags);
                        sysfs_notify_dirent_safe(mddev->sysfs_state);
                }
                if (--mddev->sync_checkers == 0)
                        percpu_ref_switch_to_percpu(&mddev->writes_pending);
        }
        if (mddev->safemode == 1)
                mddev->safemode = 0;
        return mddev->in_sync;
}

static void sync_sbs(struct mddev *mddev, int nospares)
{
        /* Update each superblock (in-memory image), but
         * if we are allowed to, skip spares which already
         * have the right event counter, or have one earlier
         * (which would mean they aren't being marked as dirty
         * with the rest of the array)
         */
        struct md_rdev *rdev;
        rdev_for_each(rdev, mddev) {
                if (rdev->sb_events == mddev->events ||
                    (nospares &&
                     rdev->raid_disk < 0 &&
                     rdev->sb_events+1 == mddev->events)) {
                        /* Don't update this superblock */
                        rdev->sb_loaded = 2;
                } else {
                        sync_super(mddev, rdev);
                        rdev->sb_loaded = 1;
                }
        }
}

static bool does_sb_need_changing(struct mddev *mddev)
{
        struct md_rdev *rdev;
        struct mdp_superblock_1 *sb;
        int role;

        /* Find a good rdev */
        rdev_for_each(rdev, mddev)
                if ((rdev->raid_disk >= 0) && !test_bit(Faulty, &rdev->flags))
                        break;

        /* No good device found. */
        if (!rdev)
                return false;

        sb = page_address(rdev->sb_page);
        /* Check if a device has become faulty or a spare become active */
        rdev_for_each(rdev, mddev) {
                role = le16_to_cpu(sb->dev_roles[rdev->desc_nr]);
                /* Device activated? */
                if (role == 0xffff && rdev->raid_disk >=0 &&
                    !test_bit(Faulty, &rdev->flags))
                        return true;
                /* Device turned faulty? */
                if (test_bit(Faulty, &rdev->flags) && (role < 0xfffd))
                        return true;
        }

        /* Check if any mddev parameters have changed */
        if ((mddev->dev_sectors != le64_to_cpu(sb->size)) ||
            (mddev->reshape_position != le64_to_cpu(sb->reshape_position)) ||
            (mddev->layout != le32_to_cpu(sb->layout)) ||
            (mddev->raid_disks != le32_to_cpu(sb->raid_disks)) ||
            (mddev->chunk_sectors != le32_to_cpu(sb->chunksize)))
                return true;

        return false;
}

void md_update_sb(struct mddev *mddev, int force_change)
{
        struct md_rdev *rdev;
        int sync_req;
        int nospares = 0;
        int any_badblocks_changed = 0;
        int ret = -1;

        if (mddev->ro) {
                if (force_change)
                        set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
                return;
        }

repeat:
        if (mddev_is_clustered(mddev)) {
                if (test_and_clear_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags))
                        force_change = 1;
                if (test_and_clear_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags))
                        nospares = 1;
                ret = md_cluster_ops->metadata_update_start(mddev);
                /* Has someone else has updated the sb */
                if (!does_sb_need_changing(mddev)) {
                        if (ret == 0)
                                md_cluster_ops->metadata_update_cancel(mddev);
                        bit_clear_unless(&mddev->sb_flags, BIT(MD_SB_CHANGE_PENDING),
                                                         BIT(MD_SB_CHANGE_DEVS) |
                                                         BIT(MD_SB_CHANGE_CLEAN));
                        return;
                }
        }

        /*
         * First make sure individual recovery_offsets are correct
         * curr_resync_completed can only be used during recovery.
         * During reshape/resync it might use array-addresses rather
         * that device addresses.
         */
        rdev_for_each(rdev, mddev) {
                if (rdev->raid_disk >= 0 &&
                    mddev->delta_disks >= 0 &&
                    test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) &&
                    test_bit(MD_RECOVERY_RECOVER, &mddev->recovery) &&
                    !test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
                    !test_bit(Journal, &rdev->flags) &&
                    !test_bit(In_sync, &rdev->flags) &&
                    mddev->curr_resync_completed > rdev->recovery_offset)
                                rdev->recovery_offset = mddev->curr_resync_completed;

        }
        if (!mddev->persistent) {
                clear_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags);
                clear_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
                if (!mddev->external) {
                        clear_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags);
                        rdev_for_each(rdev, mddev) {
                                if (rdev->badblocks.changed) {
                                        rdev->badblocks.changed = 0;
                                        ack_all_badblocks(&rdev->badblocks);
                                        md_error(mddev, rdev);
                                }
                                clear_bit(Blocked, &rdev->flags);
                                clear_bit(BlockedBadBlocks, &rdev->flags);
                                wake_up(&rdev->blocked_wait);
                        }
                }
                wake_up(&mddev->sb_wait);
                return;
        }

        spin_lock(&mddev->lock);

        mddev->utime = ktime_get_real_seconds();

        if (test_and_clear_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags))
                force_change = 1;
        if (test_and_clear_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags))
                /* just a clean<-> dirty transition, possibly leave spares alone,
                 * though if events isn't the right even/odd, we will have to do
                 * spares after all
                 */
                nospares = 1;
        if (force_change)
                nospares = 0;
        if (mddev->degraded)
                /* If the array is degraded, then skipping spares is both
                 * dangerous and fairly pointless.
                 * Dangerous because a device that was removed from the array
                 * might have a event_count that still looks up-to-date,
                 * so it can be re-added without a resync.
                 * Pointless because if there are any spares to skip,
                 * then a recovery will happen and soon that array won't
                 * be degraded any more and the spare can go back to sleep then.
                 */
                nospares = 0;

        sync_req = mddev->in_sync;

        /* If this is just a dirty<->clean transition, and the array is clean
         * and 'events' is odd, we can roll back to the previous clean state */
        if (nospares
            && (mddev->in_sync && mddev->recovery_cp == MaxSector)
            && mddev->can_decrease_events
            && mddev->events != 1) {
                mddev->events--;
                mddev->can_decrease_events = 0;
        } else {
                /* otherwise we have to go forward and ... */
                mddev->events ++;
                mddev->can_decrease_events = nospares;
        }

        /*
         * This 64-bit counter should never wrap.
         * Either we are in around ~1 trillion A.C., assuming
         * 1 reboot per second, or we have a bug...
         */
        WARN_ON(mddev->events == 0);

        rdev_for_each(rdev, mddev) {
                if (rdev->badblocks.changed)
                        any_badblocks_changed++;
                if (test_bit(Faulty, &rdev->flags))
                        set_bit(FaultRecorded, &rdev->flags);
        }

        sync_sbs(mddev, nospares);
        spin_unlock(&mddev->lock);

        pr_debug("md: updating %s RAID superblock on device (in sync %d)\n",
                 mdname(mddev), mddev->in_sync);

        if (mddev->queue)
                blk_add_trace_msg(mddev->queue, "md md_update_sb");
rewrite:
        md_bitmap_update_sb(mddev->bitmap);
        rdev_for_each(rdev, mddev) {
                char b[BDEVNAME_SIZE];

                if (rdev->sb_loaded != 1)
                        continue; /* no noise on spare devices */

                if (!test_bit(Faulty, &rdev->flags)) {
                        md_super_write(mddev,rdev,
                                       rdev->sb_start, rdev->sb_size,
                                       rdev->sb_page);
                        pr_debug("md: (write) %s's sb offset: %llu\n",
                                 bdevname(rdev->bdev, b),
                                 (unsigned long long)rdev->sb_start);
                        rdev->sb_events = mddev->events;
                        if (rdev->badblocks.size) {
                                md_super_write(mddev, rdev,
                                               rdev->badblocks.sector,
                                               rdev->badblocks.size << 9,
                                               rdev->bb_page);
                                rdev->badblocks.size = 0;
                        }

                } else
                        pr_debug("md: %s (skipping faulty)\n",
                                 bdevname(rdev->bdev, b));

                if (mddev->level == LEVEL_MULTIPATH)
                        /* only need to write one superblock... */
                        break;
        }
        if (md_super_wait(mddev) < 0)
                goto rewrite;
        /* if there was a failure, MD_SB_CHANGE_DEVS was set, and we re-write super */

        if (mddev_is_clustered(mddev) && ret == 0)
                md_cluster_ops->metadata_update_finish(mddev);

        if (mddev->in_sync != sync_req ||
            !bit_clear_unless(&mddev->sb_flags, BIT(MD_SB_CHANGE_PENDING),
                               BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_CLEAN)))
                /* have to write it out again */
                goto repeat;
        wake_up(&mddev->sb_wait);
        if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
                sysfs_notify(&mddev->kobj, NULL, "sync_completed");

        rdev_for_each(rdev, mddev) {
                if (test_and_clear_bit(FaultRecorded, &rdev->flags))
                        clear_bit(Blocked, &rdev->flags);

                if (any_badblocks_changed)
                        ack_all_badblocks(&rdev->badblocks);
                clear_bit(BlockedBadBlocks, &rdev->flags);
                wake_up(&rdev->blocked_wait);
        }
}
EXPORT_SYMBOL(md_update_sb);

static int add_bound_rdev(struct md_rdev *rdev)
{
        struct mddev *mddev = rdev->mddev;
        int err = 0;
        bool add_journal = test_bit(Journal, &rdev->flags);

        if (!mddev->pers->hot_remove_disk || add_journal) {
                /* If there is hot_add_disk but no hot_remove_disk
                 * then added disks for geometry changes,
                 * and should be added immediately.
                 */
                super_types[mddev->major_version].
                        validate_super(mddev, rdev);
                if (add_journal)
                        mddev_suspend(mddev);
                err = mddev->pers->hot_add_disk(mddev, rdev);
                if (add_journal)
                        mddev_resume(mddev);
                if (err) {
                        md_kick_rdev_from_array(rdev);
                        return err;
                }
        }
        sysfs_notify_dirent_safe(rdev->sysfs_state);

        set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
        if (mddev->degraded)
                set_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
        set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
        md_new_event(mddev);
        md_wakeup_thread(mddev->thread);
        return 0;
}

/* words written to sysfs files may, or may not, be \n terminated.
 * We want to accept with case. For this we use cmd_match.
 */
static int cmd_match(const char *cmd, const char *str)
{
        /* See if cmd, written into a sysfs file, matches
         * str.  They must either be the same, or cmd can
         * have a trailing newline
         */
        while (*cmd && *str && *cmd == *str) {
                cmd++;
                str++;
        }
        if (*cmd == '\n')
                cmd++;
        if (*str || *cmd)
                return 0;
        return 1;
}

struct rdev_sysfs_entry {
        struct attribute attr;
        ssize_t (*show)(struct md_rdev *, char *);
        ssize_t (*store)(struct md_rdev *, const char *, size_t);
};

static ssize_t
state_show(struct md_rdev *rdev, char *page)
{
        char *sep = ",";
        size_t len = 0;
        unsigned long flags = READ_ONCE(rdev->flags);

        if (test_bit(Faulty, &flags) ||
            (!test_bit(ExternalBbl, &flags) &&
            rdev->badblocks.unacked_exist))
                len += sprintf(page+len, "faulty%s", sep);
        if (test_bit(In_sync, &flags))
                len += sprintf(page+len, "in_sync%s", sep);
        if (test_bit(Journal, &flags))
                len += sprintf(page+len, "journal%s", sep);
        if (test_bit(WriteMostly, &flags))
                len += sprintf(page+len, "write_mostly%s", sep);
        if (test_bit(Blocked, &flags) ||
            (rdev->badblocks.unacked_exist
             && !test_bit(Faulty, &flags)))
                len += sprintf(page+len, "blocked%s", sep);
        if (!test_bit(Faulty, &flags) &&
            !test_bit(Journal, &flags) &&
            !test_bit(In_sync, &flags))
                len += sprintf(page+len, "spare%s", sep);
        if (test_bit(WriteErrorSeen, &flags))
                len += sprintf(page+len, "write_error%s", sep);
        if (test_bit(WantReplacement, &flags))
                len += sprintf(page+len, "want_replacement%s", sep);
        if (test_bit(Replacement, &flags))
                len += sprintf(page+len, "replacement%s", sep);
        if (test_bit(ExternalBbl, &flags))
                len += sprintf(page+len, "external_bbl%s", sep);
        if (test_bit(FailFast, &flags))
                len += sprintf(page+len, "failfast%s", sep);

        if (len)
                len -= strlen(sep);

        return len+sprintf(page+len, "\n");
}

static ssize_t
state_store(struct md_rdev *rdev, const char *buf, size_t len)
{
        /* can write
         *  faulty  - simulates an error
         *  remove  - disconnects the device
         *  writemostly - sets write_mostly
         *  -writemostly - clears write_mostly
         *  blocked - sets the Blocked flags
         *  -blocked - clears the Blocked and possibly simulates an error
         *  insync - sets Insync providing device isn't active
         *  -insync - clear Insync for a device with a slot assigned,
         *            so that it gets rebuilt based on bitmap
         *  write_error - sets WriteErrorSeen
         *  -write_error - clears WriteErrorSeen
         *  {,-}failfast - set/clear FailFast
         */
        int err = -EINVAL;
        if (cmd_match(buf, "faulty") && rdev->mddev->pers) {
                md_error(rdev->mddev, rdev);
                if (test_bit(Faulty, &rdev->flags))
                        err = 0;
                else
                        err = -EBUSY;
        } else if (cmd_match(buf, "remove")) {
                if (rdev->mddev->pers) {
                        clear_bit(Blocked, &rdev->flags);
                        remove_and_add_spares(rdev->mddev, rdev);
                }
                if (rdev->raid_disk >= 0)
                        err = -EBUSY;
                else {
                        struct mddev *mddev = rdev->mddev;
                        err = 0;
                        if (mddev_is_clustered(mddev))
                                err = md_cluster_ops->remove_disk(mddev, rdev);

                        if (err == 0) {
                                md_kick_rdev_from_array(rdev);
                                if (mddev->pers) {
                                        set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
                                        md_wakeup_thread(mddev->thread);
                                }
                                md_new_event(mddev);
                        }
                }
        } else if (cmd_match(buf, "writemostly")) {
                set_bit(WriteMostly, &rdev->flags);
                mddev_create_serial_pool(rdev->mddev, rdev, false);
                err = 0;
        } else if (cmd_match(buf, "-writemostly")) {
                mddev_destroy_serial_pool(rdev->mddev, rdev, false);
                clear_bit(WriteMostly, &rdev->flags);
                err = 0;
        } else if (cmd_match(buf, "blocked")) {
                set_bit(Blocked, &rdev->flags);
                err = 0;
        } else if (cmd_match(buf, "-blocked")) {
                if (!test_bit(Faulty, &rdev->flags) &&
                    !test_bit(ExternalBbl, &rdev->flags) &&