Merge tag 'md/3.20' of git://neil.brown.name/md

Pull md updates from Neil Brown:

 - assorted locking changes so that access to /proc/mdstat
   and much of /sys/block/mdXX/md/* is protected by a spinlock
   rather than a mutex and will never block indefinitely.

 - Make an 'if' condition in RAID5 - which has been implicated
   in recent bugs - more readable.

 - misc minor fixes

* tag 'md/3.20' of git://neil.brown.name/md: (28 commits)
  md/raid10: fix conversion from RAID0 to RAID10
  md: wakeup thread upon rdev_dec_pending()
  md: make reconfig_mutex optional for writes to md sysfs files.
  md: move mddev_lock and related to md.h
  md: use mddev->lock to protect updates to resync_{min,max}.
  md: minor cleanup in safe_delay_store.
  md: move GET_BITMAP_FILE ioctl out from mddev_lock.
  md: tidy up set_bitmap_file
  md: remove unnecessary 'buf' from get_bitmap_file.
  md: remove mddev_lock from rdev_attr_show()
  md: remove mddev_lock() from md_attr_show()
  md/raid5: use ->lock to protect accessing raid5 sysfs attributes.
  md: remove need for mddev_lock() in md_seq_show()
  md/bitmap: protect clearing of ->bitmap by mddev->lock
  md: protect ->pers changes with mddev->lock
  md: level_store: group all important changes into one place.
  md: rename ->stop to ->free
  md: split detach operation out from ->stop.
  md/linear: remove rcu protections in favour of suspend/resume
  md: make merge_bvec_fn more robust in face of personality changes.
  ...

14 files changed, 858 insertions, 606 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 1695ee5f3ffc..3a5767968ba0 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1619,7 +1619,9 @@ void bitmap_destroy(struct mddev *mddev)
 		return;
 
 	mutex_lock(&mddev->bitmap_info.mutex);
+	spin_lock(&mddev->lock);
 	mddev->bitmap = NULL; /* disconnect from the md device */
+	spin_unlock(&mddev->lock);
 	mutex_unlock(&mddev->bitmap_info.mutex);
 	if (mddev->thread)
 		mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
@@ -2209,11 +2211,13 @@ __ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store);
 static ssize_t can_clear_show(struct mddev *mddev, char *page)
 {
 	int len;
+	spin_lock(&mddev->lock);
 	if (mddev->bitmap)
 		len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ?
 					     "false" : "true"));
 	else
 		len = sprintf(page, "\n");
+	spin_unlock(&mddev->lock);
 	return len;
 }
 
@@ -2238,10 +2242,15 @@ __ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store);
 static ssize_t
 behind_writes_used_show(struct mddev *mddev, char *page)
 {
+	ssize_t ret;
+	spin_lock(&mddev->lock);
 	if (mddev->bitmap == NULL)
-		return sprintf(page, "0\n");
-	return sprintf(page, "%lu\n",
-		       mddev->bitmap->behind_writes_used);
+		ret = sprintf(page, "0\n");
+	else
+		ret = sprintf(page, "%lu\n",
+			      mddev->bitmap->behind_writes_used);
+	spin_unlock(&mddev->lock);
+	return ret;
 }
 
 static ssize_t
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 07c0fa0fa284..777d9ba2acad 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -746,13 +746,7 @@ static int raid_is_congested(struct dm_target_callbacks *cb, int bits)
 {
 	struct raid_set *rs = container_of(cb, struct raid_set, callbacks);
 
-	if (rs->raid_type->level == 1)
-		return md_raid1_congested(&rs->md, bits);
-
-	if (rs->raid_type->level == 10)
-		return md_raid10_congested(&rs->md, bits);
-
-	return md_raid5_congested(&rs->md, bits);
+	return mddev_congested(&rs->md, bits);
 }
 
 /*
diff --git a/drivers/md/faulty.c b/drivers/md/faulty.c
index e8b4574956c7..1277eb26b58a 100644
--- a/drivers/md/faulty.c
+++ b/drivers/md/faulty.c
@@ -332,13 +332,11 @@ static int run(struct mddev *mddev)
 	return 0;
 }
 
-static int stop(struct mddev *mddev)
+static void faulty_free(struct mddev *mddev, void *priv)
 {
-	struct faulty_conf *conf = mddev->private;
+	struct faulty_conf *conf = priv;
 
 	kfree(conf);
-	mddev->private = NULL;
-	return 0;
 }
 
 static struct md_personality faulty_personality =
@@ -348,7 +346,7 @@ static struct md_personality faulty_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= faulty_free,
 	.status		= status,
 	.check_reshape	= reshape,
 	.size		= faulty_size,
diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index 64713b77df1c..fa7d577f3d12 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -34,7 +34,7 @@ static inline struct dev_info *which_dev(struct mddev *mddev, sector_t sector)
 
 	lo = 0;
 	hi = mddev->raid_disks - 1;
-	conf = rcu_dereference(mddev->private);
+	conf = mddev->private;
 
 	/*
 	 * Binary Search
@@ -60,18 +60,16 @@ static inline struct dev_info *which_dev(struct mddev *mddev, sector_t sector)
  *
  *	Return amount of bytes we can take at this offset
  */
-static int linear_mergeable_bvec(struct request_queue *q,
+static int linear_mergeable_bvec(struct mddev *mddev,
 				 struct bvec_merge_data *bvm,
 				 struct bio_vec *biovec)
 {
-	struct mddev *mddev = q->queuedata;
 	struct dev_info *dev0;
 	unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
 	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
 	int maxbytes = biovec->bv_len;
 	struct request_queue *subq;
 
-	rcu_read_lock();
 	dev0 = which_dev(mddev, sector);
 	maxsectors = dev0->end_sector - sector;
 	subq = bdev_get_queue(dev0->rdev->bdev);
@@ -81,7 +79,6 @@ static int linear_mergeable_bvec(struct request_queue *q,
 		maxbytes = min(maxbytes, subq->merge_bvec_fn(subq, bvm,
 							     biovec));
 	}
-	rcu_read_unlock();
 
 	if (maxsectors < bio_sectors)
 		maxsectors = 0;
@@ -97,24 +94,18 @@ static int linear_mergeable_bvec(struct request_queue *q,
 		return maxsectors << 9;
 }
 
-static int linear_congested(void *data, int bits)
+static int linear_congested(struct mddev *mddev, int bits)
 {
-	struct mddev *mddev = data;
 	struct linear_conf *conf;
 	int i, ret = 0;
 
-	if (mddev_congested(mddev, bits))
-		return 1;
-
-	rcu_read_lock();
-	conf = rcu_dereference(mddev->private);
+	conf = mddev->private;
 
 	for (i = 0; i < mddev->raid_disks && !ret ; i++) {
 		struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
 		ret |= bdi_congested(&q->backing_dev_info, bits);
 	}
 
-	rcu_read_unlock();
 	return ret;
 }
 
@@ -123,12 +114,10 @@ static sector_t linear_size(struct mddev *mddev, sector_t sectors, int raid_disk
 	struct linear_conf *conf;
 	sector_t array_sectors;
 
-	rcu_read_lock();
-	conf = rcu_dereference(mddev->private);
+	conf = mddev->private;
 	WARN_ONCE(sectors || raid_disks,
 		  "%s does not support generic reshape\n", __func__);
 	array_sectors = conf->array_sectors;
-	rcu_read_unlock();
 
 	return array_sectors;
 }
@@ -217,10 +206,6 @@ static int linear_run (struct mddev *mddev)
 	mddev->private = conf;
 	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 
-	blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
-	mddev->queue->backing_dev_info.congested_fn = linear_congested;
-	mddev->queue->backing_dev_info.congested_data = mddev;
-
 	ret =  md_integrity_register(mddev);
 	if (ret) {
 		kfree(conf);
@@ -252,38 +237,23 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
 	if (!newconf)
 		return -ENOMEM;
 
-	oldconf = rcu_dereference_protected(mddev->private,
-					    lockdep_is_held(
-						    &mddev->reconfig_mutex));
+	mddev_suspend(mddev);
+	oldconf = mddev->private;
 	mddev->raid_disks++;
-	rcu_assign_pointer(mddev->private, newconf);
+	mddev->private = newconf;
 	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 	set_capacity(mddev->gendisk, mddev->array_sectors);
+	mddev_resume(mddev);
 	revalidate_disk(mddev->gendisk);
-	kfree_rcu(oldconf, rcu);
+	kfree(oldconf);
 	return 0;
 }
 
-static int linear_stop (struct mddev *mddev)
+static void linear_free(struct mddev *mddev, void *priv)
 {
-	struct linear_conf *conf =
-		rcu_dereference_protected(mddev->private,
-					  lockdep_is_held(
-						  &mddev->reconfig_mutex));
+	struct linear_conf *conf = priv;
 
-	/*
-	 * We do not require rcu protection here since
-	 * we hold reconfig_mutex for both linear_add and
-	 * linear_stop, so they cannot race.
-	 * We should make sure any old 'conf's are properly
-	 * freed though.
-	 */
-	rcu_barrier();
-	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 	kfree(conf);
-	mddev->private = NULL;
-
-	return 0;
 }
 
 static void linear_make_request(struct mddev *mddev, struct bio *bio)
@@ -299,16 +269,12 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio)
 	}
 
 	do {
-		rcu_read_lock();
-
 		tmp_dev = which_dev(mddev, bio->bi_iter.bi_sector);
 		start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
 		end_sector = tmp_dev->end_sector;
 		data_offset = tmp_dev->rdev->data_offset;
 		bio->bi_bdev = tmp_dev->rdev->bdev;
 
-		rcu_read_unlock();
-
 		if (unlikely(bio->bi_iter.bi_sector >= end_sector ||
 			     bio->bi_iter.bi_sector < start_sector))
 			goto out_of_bounds;
@@ -355,6 +321,10 @@ static void linear_status (struct seq_file *seq, struct mddev *mddev)
 	seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
 }
 
+static void linear_quiesce(struct mddev *mddev, int state)
+{
+}
+
 static struct md_personality linear_personality =
 {
 	.name		= "linear",
@@ -362,10 +332,13 @@ static struct md_personality linear_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= linear_make_request,
 	.run		= linear_run,
-	.stop		= linear_stop,
+	.free		= linear_free,
 	.status		= linear_status,
 	.hot_add_disk	= linear_add,
 	.size		= linear_size,
+	.quiesce	= linear_quiesce,
+	.congested	= linear_congested,
+	.mergeable_bvec	= linear_mergeable_bvec,
 };
 
 static int __init linear_init (void)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 709755fb6d7b..c8d2bac4e28b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -72,6 +72,7 @@ static struct workqueue_struct *md_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
@@ -292,8 +293,8 @@ static void md_make_request(struct request_queue *q, struct bio *bio)
 /* mddev_suspend makes sure no new requests are submitted
  * to the device, and that any requests that have been submitted
  * are completely handled.
- * Once ->stop is called and completes, the module will be completely
- * unused.
+ * Once mddev_detach() is called and completes, the module will be
+ * completely unused.
  */
 void mddev_suspend(struct mddev *mddev)
 {
@@ -321,10 +322,47 @@ EXPORT_SYMBOL_GPL(mddev_resume);
 
 int mddev_congested(struct mddev *mddev, int bits)
 {
-	return mddev->suspended;
+	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);
 }
-EXPORT_SYMBOL(mddev_congested);
 
+static int md_mergeable_bvec(struct request_queue *q,
+			     struct bvec_merge_data *bvm,
+			     struct bio_vec *biovec)
+{
+	struct mddev *mddev = q->queuedata;
+	int ret;
+	rcu_read_lock();
+	if (mddev->suspended) {
+		/* Must always allow one vec */
+		if (bvm->bi_size == 0)
+			ret = biovec->bv_len;
+		else
+			ret = 0;
+	} else {
+		struct md_personality *pers = mddev->pers;
+		if (pers && pers->mergeable_bvec)
+			ret = pers->mergeable_bvec(mddev, bvm, biovec);
+		else
+			ret = biovec->bv_len;
+	}
+	rcu_read_unlock();
+	return ret;
+}
 /*
  * Generic flush handling for md
  */
@@ -397,12 +435,12 @@ static void md_submit_flush_data(struct work_struct *ws)
 
 void md_flush_request(struct mddev *mddev, struct bio *bio)
 {
-	spin_lock_irq(&mddev->write_lock);
+	spin_lock_irq(&mddev->lock);
 	wait_event_lock_irq(mddev->sb_wait,
 			    !mddev->flush_bio,
-			    mddev->write_lock);
+			    mddev->lock);
 	mddev->flush_bio = bio;
-	spin_unlock_irq(&mddev->write_lock);
+	spin_unlock_irq(&mddev->lock);
 
 	INIT_WORK(&mddev->flush_work, submit_flushes);
 	queue_work(md_wq, &mddev->flush_work);
@@ -465,7 +503,7 @@ void mddev_init(struct mddev *mddev)
 	atomic_set(&mddev->active, 1);
 	atomic_set(&mddev->openers, 0);
 	atomic_set(&mddev->active_io, 0);
-	spin_lock_init(&mddev->write_lock);
+	spin_lock_init(&mddev->lock);
 	atomic_set(&mddev->flush_pending, 0);
 	init_waitqueue_head(&mddev->sb_wait);
 	init_waitqueue_head(&mddev->recovery_wait);
@@ -552,32 +590,9 @@ static struct mddev *mddev_find(dev_t unit)
 	goto retry;
 }
 
-static inline int __must_check mddev_lock(struct mddev *mddev)
-{
-	return mutex_lock_interruptible(&mddev->reconfig_mutex);
-}
-
-/* Sometimes we need to take the lock in a situation where
- * failure due to interrupts is not acceptable.
- */
-static inline void mddev_lock_nointr(struct mddev *mddev)
-{
-	mutex_lock(&mddev->reconfig_mutex);
-}
-
-static inline int mddev_is_locked(struct mddev *mddev)
-{
-	return mutex_is_locked(&mddev->reconfig_mutex);
-}
-
-static inline int mddev_trylock(struct mddev *mddev)
-{
-	return mutex_trylock(&mddev->reconfig_mutex);
-}
-
 static struct attribute_group md_redundancy_group;
 
-static void mddev_unlock(struct mddev *mddev)
+void mddev_unlock(struct mddev *mddev)
 {
 	if (mddev->to_remove) {
 		/* These cannot be removed under reconfig_mutex as
@@ -619,6 +634,7 @@ static void mddev_unlock(struct mddev *mddev)
 	md_wakeup_thread(mddev->thread);
 	spin_unlock(&pers_lock);
 }
+EXPORT_SYMBOL_GPL(mddev_unlock);
 
 static struct md_rdev *find_rdev_nr_rcu(struct mddev *mddev, int nr)
 {
@@ -2230,7 +2246,7 @@ repeat:
 		return;
 	}
 
-	spin_lock_irq(&mddev->write_lock);
+	spin_lock(&mddev->lock);
 
 	mddev->utime = get_seconds();
 
@@ -2287,7 +2303,7 @@ repeat:
 	}
 
 	sync_sbs(mddev, nospares);
-	spin_unlock_irq(&mddev->write_lock);
+	spin_unlock(&mddev->lock);
 
 	pr_debug("md: updating %s RAID superblock on device (in sync %d)\n",
 		 mdname(mddev), mddev->in_sync);
@@ -2326,15 +2342,15 @@ repeat:
 	md_super_wait(mddev);
 	/* if there was a failure, MD_CHANGE_DEVS was set, and we re-write super */
 
-	spin_lock_irq(&mddev->write_lock);
+	spin_lock(&mddev->lock);
 	if (mddev->in_sync != sync_req ||
 	    test_bit(MD_CHANGE_DEVS, &mddev->flags)) {
 		/* have to write it out again */
-		spin_unlock_irq(&mddev->write_lock);
+		spin_unlock(&mddev->lock);
 		goto repeat;
 	}
 	clear_bit(MD_CHANGE_PENDING, &mddev->flags);
-	spin_unlock_irq(&mddev->write_lock);
+	spin_unlock(&mddev->lock);
 	wake_up(&mddev->sb_wait);
 	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
 		sysfs_notify(&mddev->kobj, NULL, "sync_completed");
@@ -2381,40 +2397,41 @@ state_show(struct md_rdev *rdev, char *page)
 {
 	char *sep = "";
 	size_t len = 0;
+	unsigned long flags = ACCESS_ONCE(rdev->flags);
 
-	if (test_bit(Faulty, &rdev->flags) ||
+	if (test_bit(Faulty, &flags) ||
 	    rdev->badblocks.unacked_exist) {
 		len+= sprintf(page+len, "%sfaulty",sep);
 		sep = ",";
 	}
-	if (test_bit(In_sync, &rdev->flags)) {
+	if (test_bit(In_sync, &flags)) {
 		len += sprintf(page+len, "%sin_sync",sep);
 		sep = ",";
 	}
-	if (test_bit(WriteMostly, &rdev->flags)) {
+	if (test_bit(WriteMostly, &flags)) {
 		len += sprintf(page+len, "%swrite_mostly",sep);
 		sep = ",";
 	}
-	if (test_bit(Blocked, &rdev->flags) ||
+	if (test_bit(Blocked, &flags) ||
 	    (rdev->badblocks.unacked_exist
-	     && !test_bit(Faulty, &rdev->flags))) {
+	     && !test_bit(Faulty, &flags))) {
 		len += sprintf(page+len, "%sblocked", sep);
 		sep = ",";
 	}
-	if (!test_bit(Faulty, &rdev->flags) &&
-	    !test_bit(In_sync, &rdev->flags)) {
+	if (!test_bit(Faulty, &flags) &&
+	    !test_bit(In_sync, &flags)) {
 		len += sprintf(page+len, "%sspare", sep);
 		sep = ",";
 	}
-	if (test_bit(WriteErrorSeen, &rdev->flags)) {
+	if (test_bit(WriteErrorSeen, &flags)) {
 		len += sprintf(page+len, "%swrite_error", sep);
 		sep = ",";
 	}
-	if (test_bit(WantReplacement, &rdev->flags)) {
+	if (test_bit(WantReplacement, &flags)) {
 		len += sprintf(page+len, "%swant_replacement", sep);
 		sep = ",";
 	}
-	if (test_bit(Replacement, &rdev->flags)) {
+	if (test_bit(Replacement, &flags)) {
 		len += sprintf(page+len, "%sreplacement", sep);
 		sep = ",";
 	}
@@ -2927,21 +2944,12 @@ rdev_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 {
 	struct rdev_sysfs_entry *entry = container_of(attr, struct rdev_sysfs_entry, attr);
 	struct md_rdev *rdev = container_of(kobj, struct md_rdev, kobj);
-	struct mddev *mddev = rdev->mddev;
-	ssize_t rv;
 
 	if (!entry->show)
 		return -EIO;
-
-	rv = mddev ? mddev_lock(mddev) : -EBUSY;
-	if (!rv) {
-		if (rdev->mddev == NULL)
-			rv = -EBUSY;
-		else
-			rv = entry->show(rdev, page);
-		mddev_unlock(mddev);
-	}
-	return rv;
+	if (!rdev->mddev)
+		return -EBUSY;
+	return entry->show(rdev, page);
 }
 
 static ssize_t
@@ -3212,11 +3220,13 @@ safe_delay_store(struct mddev *mddev, const char *cbuf, size_t len)
 		mddev->safemode_delay = 0;
 	else {
 		unsigned long old_delay = mddev->safemode_delay;
-		mddev->safemode_delay = (msec*HZ)/1000;
-		if (mddev->safemode_delay == 0)
-			mddev->safemode_delay = 1;
-		if (mddev->safemode_delay < old_delay || old_delay == 0)
-			md_safemode_timeout((unsigned long)mddev);
+		unsigned long new_delay = (msec*HZ)/1000;
+
+		if (new_delay == 0)
+			new_delay = 1;
+		mddev->safemode_delay = new_delay;
+		if (new_delay < old_delay || old_delay == 0)
+			mod_timer(&mddev->safemode_timer, jiffies+1);
 	}
 	return len;
 }
@@ -3226,41 +3236,52 @@ __ATTR(safe_mode_delay, S_IRUGO|S_IWUSR,safe_delay_show, safe_delay_store);
 static ssize_t
 level_show(struct mddev *mddev, char *page)
 {
-	struct md_personality *p = mddev->pers;
+	struct md_personality *p;
+	int ret;
+	spin_lock(&mddev->lock);
+	p = mddev->pers;
 	if (p)
-		return sprintf(page, "%s\n", p->name);
+		ret = sprintf(page, "%s\n", p->name);
 	else if (mddev->clevel[0])
-		return sprintf(page, "%s\n", mddev->clevel);
+		ret = sprintf(page, "%s\n", mddev->clevel);
 	else if (mddev->level != LEVEL_NONE)
-		return sprintf(page, "%d\n", mddev->level);
+		ret = sprintf(page, "%d\n", mddev->level);
 	else
-		return 0;
+		ret = 0;
+	spin_unlock(&mddev->lock);
+	return ret;
 }
 
 static ssize_t
 level_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	char clevel[16];
-	ssize_t rv = len;
-	struct md_personality *pers;
+	ssize_t rv;
+	size_t slen = len;
+	struct md_personality *pers, *oldpers;
 	long level;
-	void *priv;
+	void *priv, *oldpriv;
 	struct md_rdev *rdev;
 
+	if (slen == 0 || slen >= sizeof(clevel))
+		return -EINVAL;
+
+	rv = mddev_lock(mddev);
+	if (rv)
+		return rv;
+
 	if (mddev->pers == NULL) {
-		if (len == 0)
-			return 0;
-		if (len >= sizeof(mddev->clevel))
-			return -ENOSPC;
-		strncpy(mddev->clevel, buf, len);
-		if (mddev->clevel[len-1] == '\n')
-			len--;
-		mddev->clevel[len] = 0;
+		strncpy(mddev->clevel, buf, slen);
+		if (mddev->clevel[slen-1] == '\n')
+			slen--;
+		mddev->clevel[slen] = 0;
 		mddev->level = LEVEL_NONE;
-		return rv;
+		rv = len;
+		goto out_unlock;
 	}
+	rv = -EROFS;
 	if (mddev->ro)
-		return  -EROFS;
+		goto out_unlock;
 
 	/* request to change the personality.  Need to ensure:
 	 *  - array is not engaged in resync/recovery/reshape
@@ -3268,25 +3289,25 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 	 *  - new personality will access other array.
 	 */
 
+	rv = -EBUSY;
 	if (mddev->sync_thread ||
 	    test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
 	    mddev->reshape_position != MaxSector ||
 	    mddev->sysfs_active)
-		return -EBUSY;
+		goto out_unlock;
 
+	rv = -EINVAL;
 	if (!mddev->pers->quiesce) {
 		printk(KERN_WARNING "md: %s: %s does not support online personality change\n",
 		       mdname(mddev), mddev->pers->name);
-		return -EINVAL;
+		goto out_unlock;
 	}
 
 	/* Now find the new personality */
-	if (len == 0 || len >= sizeof(clevel))
-		return -EINVAL;
-	strncpy(clevel, buf, len);
-	if (clevel[len-1] == '\n')
-		len--;
-	clevel[len] = 0;
+	strncpy(clevel, buf, slen);
+	if (clevel[slen-1] == '\n')
+		slen--;
+	clevel[slen] = 0;
 	if (kstrtol(clevel, 10, &level))
 		level = LEVEL_NONE;
 
@@ -3297,20 +3318,23 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 	if (!pers || !try_module_get(pers->owner)) {
 		spin_unlock(&pers_lock);
 		printk(KERN_WARNING "md: personality %s not loaded\n", clevel);
-		return -EINVAL;
+		rv = -EINVAL;
+		goto out_unlock;
 	}
 	spin_unlock(&pers_lock);
 
 	if (pers == mddev->pers) {
 		/* Nothing to do! */
 		module_put(pers->owner);
-		return rv;
+		rv = len;
+		goto out_unlock;
 	}
 	if (!pers->takeover) {
 		module_put(pers->owner);
 		printk(KERN_WARNING "md: %s: %s does not support personality takeover\n",
 		       mdname(mddev), clevel);
-		return -EINVAL;
+		rv = -EINVAL;
+		goto out_unlock;
 	}
 
 	rdev_for_each(rdev, mddev)
@@ -3330,30 +3354,29 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		module_put(pers->owner);
 		printk(KERN_WARNING "md: %s: %s would not accept array\n",
 		       mdname(mddev), clevel);
-		return PTR_ERR(priv);
+		rv = PTR_ERR(priv);
+		goto out_unlock;
 	}
 
 	/* Looks like we have a winner */
 	mddev_suspend(mddev);
-	mddev->pers->stop(mddev);
+	mddev_detach(mddev);
 
-	if (mddev->pers->sync_request == NULL &&
-	    pers->sync_request != NULL) {
-		/* need to add the md_redundancy_group */
-		if (sysfs_create_group(&mddev->kobj, &md_redundancy_group))
-			printk(KERN_WARNING
-			       "md: cannot register extra attributes for %s\n",
-			       mdname(mddev));
-		mddev->sysfs_action = sysfs_get_dirent(mddev->kobj.sd, "sync_action");
-	}
-	if (mddev->pers->sync_request != NULL &&
-	    pers->sync_request == NULL) {
-		/* need to remove the md_redundancy_group */
-		if (mddev->to_remove == NULL)
-			mddev->to_remove = &md_redundancy_group;
-	}
+	spin_lock(&mddev->lock);
+	oldpers = mddev->pers;
+	oldpriv = mddev->private;
+	mddev->pers = pers;
+	mddev->private = priv;
+	strlcpy(mddev->clevel, pers->name, sizeof(mddev->clevel));
+	mddev->level = mddev->new_level;
+	mddev->layout = mddev->new_layout;
+	mddev->chunk_sectors = mddev->new_chunk_sectors;
+	mddev->delta_disks = 0;
+	mddev->reshape_backwards = 0;
+	mddev->degraded = 0;
+	spin_unlock(&mddev->lock);
 
-	if (mddev->pers->sync_request == NULL &&
+	if (oldpers->sync_request == NULL &&
 	    mddev->external) {
 		/* We are converting from a no-redundancy array
 		 * to a redundancy array and metadata is managed
@@ -3367,6 +3390,24 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->safemode = 0;
 	}
 
+	oldpers->free(mddev, oldpriv);
+
+	if (oldpers->sync_request == NULL &&
+	    pers->sync_request != NULL) {
+		/* need to add the md_redundancy_group */
+		if (sysfs_create_group(&mddev->kobj, &md_redundancy_group))
+			printk(KERN_WARNING
+			       "md: cannot register extra attributes for %s\n",
+			       mdname(mddev));
+		mddev->sysfs_action = sysfs_get_dirent(mddev->kobj.sd, "sync_action");
+	}
+	if (oldpers->sync_request != NULL &&
+	    pers->sync_request == NULL) {
+		/* need to remove the md_redundancy_group */
+		if (mddev->to_remove == NULL)
+			mddev->to_remove = &md_redundancy_group;
+	}
+
 	rdev_for_each(rdev, mddev) {
 		if (rdev->raid_disk < 0)
 			continue;
@@ -3392,17 +3433,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		}
 	}
 
-	module_put(mddev->pers->owner);
-	mddev->pers = pers;
-	mddev->private = priv;
-	strlcpy(mddev->clevel, pers->name, sizeof(mddev->clevel));
-	mddev->level = mddev->new_level;
-	mddev->layout = mddev->new_layout;
-	mddev->chunk_sectors = mddev->new_chunk_sectors;
-	mddev->delta_disks = 0;
-	mddev->reshape_backwards = 0;
-	mddev->degraded = 0;
-	if (mddev->pers->sync_request == NULL) {
+	if (pers->sync_request == NULL) {
 		/* this is now an array without redundancy, so
 		 * it must always be in_sync
 		 */
@@ -3417,6 +3448,9 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		md_update_sb(mddev, 1);
 	sysfs_notify(&mddev->kobj, NULL, "level");
 	md_new_event(mddev);
+	rv = len;
+out_unlock:
+	mddev_unlock(mddev);
 	return rv;
 }
 
@@ -3439,28 +3473,32 @@ layout_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	char *e;
 	unsigned long n = simple_strtoul(buf, &e, 10);
+	int err;
 
 	if (!*buf || (*e && *e != '\n'))
 		return -EINVAL;
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 
 	if (mddev->pers) {
-		int err;
 		if (mddev->pers->check_reshape == NULL)
-			return -EBUSY;
-		if (mddev->ro)
-			return -EROFS;
-		mddev->new_layout = n;
-		err = mddev->pers->check_reshape(mddev);
-		if (err) {
-			mddev->new_layout = mddev->layout;
-			return err;
+			err = -EBUSY;
+		else if (mddev->ro)
+			err = -EROFS;
+		else {
+			mddev->new_layout = n;
+			err = mddev->pers->check_reshape(mddev);
+			if (err)
+				mddev->new_layout = mddev->layout;
 		}
 	} else {
 		mddev->new_layout = n;
 		if (mddev->reshape_position == MaxSector)
 			mddev->layout = n;
 	}
-	return len;
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 static struct md_sysfs_entry md_layout =
 __ATTR(layout, S_IRUGO|S_IWUSR, layout_show, layout_store);
@@ -3483,32 +3521,39 @@ static ssize_t
 raid_disks_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	char *e;
-	int rv = 0;
+	int err;
 	unsigned long n = simple_strtoul(buf, &e, 10);
 
 	if (!*buf || (*e && *e != '\n'))
 		return -EINVAL;
 
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 	if (mddev->pers)
-		rv = update_raid_disks(mddev, n);
+		err = update_raid_disks(mddev, n);
 	else if (mddev->reshape_position != MaxSector) {
 		struct md_rdev *rdev;
 		int olddisks = mddev->raid_disks - mddev->delta_disks;
 
+		err = -EINVAL;
 		rdev_for_each(rdev, mddev) {
 			if (olddisks < n &&
 			    rdev->data_offset < rdev->new_data_offset)
-				return -EINVAL;
+				goto out_unlock;
 			if (olddisks > n &&
 			    rdev->data_offset > rdev->new_data_offset)
-				return -EINVAL;
+				goto out_unlock;
 		}
+		err = 0;
 		mddev->delta_disks = n - olddisks;
 		mddev->raid_disks = n;
 		mddev->reshape_backwards = (mddev->delta_disks < 0);
 	} else
 		mddev->raid_disks = n;
-	return rv ? rv : len;
+out_unlock:
+	mddev_unlock(mddev);
+	return err ? err : len;
 }
 static struct md_sysfs_entry md_raid_disks =
 __ATTR(raid_disks, S_IRUGO|S_IWUSR, raid_disks_show, raid_disks_store);
@@ -3527,30 +3572,34 @@ chunk_size_show(struct mddev *mddev, char *page)
 static ssize_t
 chunk_size_store(struct mddev *mddev, const char *buf, size_t len)
 {
+	int err;
 	char *e;
 	unsigned long n = simple_strtoul(buf, &e, 10);
 
 	if (!*buf || (*e && *e != '\n'))
 		return -EINVAL;
 
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 	if (mddev->pers) {
-		int err;
 		if (mddev->pers->check_reshape == NULL)
-			return -EBUSY;
-		if (mddev->ro)
-			return -EROFS;
-		mddev->new_chunk_sectors = n >> 9;
-		err = mddev->pers->check_reshape(mddev);
-		if (err) {
-			mddev->new_chunk_sectors = mddev->chunk_sectors;
-			return err;
+			err = -EBUSY;
+		else if (mddev->ro)
+			err = -EROFS;
+		else {
+			mddev->new_chunk_sectors = n >> 9;
+			err = mddev->pers->check_reshape(mddev);
+			if (err)
+				mddev->new_chunk_sectors = mddev->chunk_sectors;
 		}
 	} else {
 		mddev->new_chunk_sectors = n >> 9;
 		if (mddev->reshape_position == MaxSector)
 			mddev->chunk_sectors = n >> 9;
 	}
-	return len;
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 static struct md_sysfs_entry md_chunk_size =
 __ATTR(chunk_size, S_IRUGO|S_IWUSR, chunk_size_show, chunk_size_store);
@@ -3566,20 +3615,27 @@ resync_start_show(struct mddev *mddev, char *page)
 static ssize_t
 resync_start_store(struct mddev *mddev, const char *buf, size_t len)
 {
+	int err;
 	char *e;
 	unsigned long long n = simple_strtoull(buf, &e, 10);
 
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 	if (mddev->pers && !test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
-		return -EBUSY;
-	if (cmd_match(buf, "none"))
+		err = -EBUSY;
+	else if (cmd_match(buf, "none"))
 		n = MaxSector;
 	else if (!*buf || (*e && *e != '\n'))
-		return -EINVAL;
+		err = -EINVAL;
 
-	mddev->recovery_cp = n;
-	if (mddev->pers)
-		set_bit(MD_CHANGE_CLEAN, &mddev->flags);
-	return len;
+	if (!err) {
+		mddev->recovery_cp = n;
+		if (mddev->pers)
+			set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+	}
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 static struct md_sysfs_entry md_resync_start =
 __ATTR(resync_start, S_IRUGO|S_IWUSR, resync_start_show, resync_start_store);
@@ -3677,8 +3733,39 @@ static int restart_array(struct mddev *mddev);
 static ssize_t
 array_state_store(struct mddev *mddev, const char *buf, size_t len)
 {
-	int err = -EINVAL;
+	int err;
 	enum array_state st = match_word(buf, array_states);
+
+	if (mddev->pers && (st == active || st == clean) && mddev->ro != 1) {
+		/* don't take reconfig_mutex when toggling between
+		 * clean and active
+		 */
+		spin_lock(&mddev->lock);
+		if (st == active) {
+			restart_array(mddev);
+			clear_bit(MD_CHANGE_PENDING, &mddev->flags);
+			wake_up(&mddev->sb_wait);
+			err = 0;
+		} else /* st == clean */ {
+			restart_array(mddev);
+			if (atomic_read(&mddev->writes_pending) == 0) {
+				if (mddev->in_sync == 0) {
+					mddev->in_sync = 1;
+					if (mddev->safemode == 1)
+						mddev->safemode = 0;
+					set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+				}
+				err = 0;
+			} else
+				err = -EBUSY;
+		}
+		spin_unlock(&mddev->lock);
+		return err;
+	}
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	err = -EINVAL;
 	switch(st) {
 	case bad_word:
 		break;
@@ -3722,7 +3809,7 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
 	case clean:
 		if (mddev->pers) {
 			restart_array(mddev);
-			spin_lock_irq(&mddev->write_lock);
+			spin_lock(&mddev->lock);
 			if (atomic_read(&mddev->writes_pending) == 0) {
 				if (mddev->in_sync == 0) {
 					mddev->in_sync = 1;
@@ -3733,7 +3820,7 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
 				err = 0;
 			} else
 				err = -EBUSY;
-			spin_unlock_irq(&mddev->write_lock);
+			spin_unlock(&mddev->lock);
 		} else
 			err = -EINVAL;
 		break;
@@ -3754,14 +3841,14 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
 		/* these cannot be set */
 		break;
 	}
-	if (err)
-		return err;
-	else {
+
+	if (!err) {
 		if (mddev->hold_active == UNTIL_IOCTL)
 			mddev->hold_active = 0;
 		sysfs_notify_dirent_safe(mddev->sysfs_state);
-		return len;
 	}
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 static struct md_sysfs_entry md_array_state =
 __ATTR(array_state, S_IRUGO|S_IWUSR, array_state_show, array_state_store);
@@ -3822,6 +3909,11 @@ new_dev_store(struct mddev *mddev, const char *buf, size_t len)
 	    minor != MINOR(dev))
 		return -EOVERFLOW;
 
+	flush_workqueue(md_misc_wq);
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 	if (mddev->persistent) {
 		rdev = md_import_device(dev, mddev->major_version,
 					mddev->minor_version);
@@ -3845,6 +3937,7 @@ new_dev_store(struct mddev *mddev, const char *buf, size_t len)
  out:
 	if (err)
 		export_rdev(rdev);
+	mddev_unlock(mddev);
 	return err ? err : len;
 }
 
@@ -3856,7 +3949,11 @@ bitmap_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	char *end;
 	unsigned long chunk, end_chunk;
+	int err;
 
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 	if (!mddev->bitmap)
 		goto out;
 	/* buf should be <chunk> <chunk> ... or <chunk>-<chunk> ... (range) */
@@ -3874,6 +3971,7 @@ bitmap_store(struct mddev *mddev, const char *buf, size_t len)
 	}
 	bitmap_unplug(mddev->bitmap); /* flush the bits to disk */
 out:
+	mddev_unlock(mddev);
 	return len;
 }
 
@@ -3901,6 +3999,9 @@ size_store(struct mddev *mddev, const char *buf, size_t len)
 
 	if (err < 0)
 		return err;
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 	if (mddev->pers) {
 		err = update_size(mddev, sectors);
 		md_update_sb(mddev, 1);
@@ -3911,6 +4012,7 @@ size_store(struct mddev *mddev, const char *buf, size_t len)
 		else
 			err = -ENOSPC;
 	}
+	mddev_unlock(mddev);
 	return err ? err : len;
 }
 
@@ -3940,21 +4042,28 @@ metadata_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	int major, minor;
 	char *e;
+	int err;
 	/* Changing the details of 'external' metadata is
 	 * always permitted.  Otherwise there must be
 	 * no devices attached to the array.
 	 */
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	err = -EBUSY;
 	if (mddev->external && strncmp(buf, "external:", 9) == 0)
 		;
 	else if (!list_empty(&mddev->disks))
-		return -EBUSY;
+		goto out_unlock;
 
+	err = 0;
 	if (cmd_match(buf, "none")) {
 		mddev->persistent = 0;
 		mddev->external = 0;
 		mddev->major_version = 0;
 		mddev->minor_version = 90;
-		return len;
+		goto out_unlock;
 	}
 	if (strncmp(buf, "external:", 9) == 0) {
 		size_t namelen = len-9;
@@ -3968,22 +4077,27 @@ metadata_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->external = 1;
 		mddev->major_version = 0;
 		mddev->minor_version = 90;
-		return len;
+		goto out_unlock;
 	}
 	major = simple_strtoul(buf, &e, 10);
+	err = -EINVAL;
 	if (e==buf || *e != '.')
-		return -EINVAL;
+		goto out_unlock;
 	buf = e+1;
 	minor = simple_strtoul(buf, &e, 10);
 	if (e==buf || (*e && *e != '\n') )
-		return -EINVAL;
+		goto out_unlock;
+	err = -ENOENT;
 	if (major >= ARRAY_SIZE(super_types) || super_types[major].name == NULL)
-		return -ENOENT;
+		goto out_unlock;
 	mddev->major_version = major;
 	mddev->minor_version = minor;
 	mddev->persistent = 1;
 	mddev->external = 0;
-	return len;
+	err = 0;
+out_unlock:
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry md_metadata =
@@ -3993,20 +4107,21 @@ static ssize_t
 action_show(struct mddev *mddev, char *page)
 {
 	char *type = "idle";
-	if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
+	unsigned long recovery = mddev->recovery;
+	if (test_bit(MD_RECOVERY_FROZEN, &recovery))
 		type = "frozen";
-	else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
-	    (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) {
-		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+	else if (test_bit(MD_RECOVERY_RUNNING, &recovery) ||
+	    (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &recovery))) {
+		if (test_bit(MD_RECOVERY_RESHAPE, &recovery))
 			type = "reshape";
-		else if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
-			if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+		else if (test_bit(MD_RECOVERY_SYNC, &recovery)) {
+			if (!test_bit(MD_RECOVERY_REQUESTED, &recovery))
 				type = "resync";
-			else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
+			else if (test_bit(MD_RECOVERY_CHECK, &recovery))
 				type = "check";
 			else
 				type = "repair";
-		} else if (test_bit(MD_RECOVERY_RECOVER, &mddev->recovery))
+		} else if (test_bit(MD_RECOVERY_RECOVER, &recovery))
 			type = "recover";
 	}
 	return sprintf(page, "%s\n", type);
@@ -4027,7 +4142,10 @@ action_store(struct mddev *mddev, const char *page, size_t len)
 		flush_workqueue(md_misc_wq);
 		if (mddev->sync_thread) {
 			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
-			md_reap_sync_thread(mddev);
+			if (mddev_lock(mddev) == 0) {
+				md_reap_sync_thread(mddev);
+				mddev_unlock(mddev);
+			}
 		}
 	} else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
 		   test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
@@ -4041,7 +4159,11 @@ action_store(struct mddev *mddev, const char *page, size_t len)
 		int err;
 		if (mddev->pers->start_reshape == NULL)
 			return -EINVAL;
-		err = mddev->pers->start_reshape(mddev);
+		err = mddev_lock(mddev);
+		if (!err) {
+			err = mddev->pers->start_reshape(mddev);
+			mddev_unlock(mddev);
+		}
 		if (err)
 			return err;
 		sysfs_notify(&mddev->kobj, NULL, "degraded");
@@ -4225,22 +4347,36 @@ static ssize_t
 min_sync_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	unsigned long long min;
+	int err;
+	int chunk;
+
 	if (kstrtoull(buf, 10, &min))
 		return -EINVAL;
+
+	spin_lock(&mddev->lock);
+	err = -EINVAL;
 	if (min > mddev->resync_max)
-		return -EINVAL;
+		goto out_unlock;
+
+	err = -EBUSY;
 	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
-		return -EBUSY;
+		goto out_unlock;
 
 	/* Must be a multiple of chunk_size */
-	if (mddev->chunk_sectors) {
+	chunk = mddev->chunk_sectors;
+	if (chunk) {
 		sector_t temp = min;
-		if (sector_div(temp, mddev->chunk_sectors))
-			return -EINVAL;
+
+		err = -EINVAL;
+		if (sector_div(temp, chunk))
+			goto out_unlock;
 	}
 	mddev->resync_min = min;
+	err = 0;
 
-	return len;
+out_unlock:
+	spin_unlock(&mddev->lock);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry md_min_sync =
@@ -4258,29 +4394,42 @@ max_sync_show(struct mddev *mddev, char *page)
 static ssize_t
 max_sync_store(struct mddev *mddev, const char *buf, size_t len)
 {
+	int err;
+	spin_lock(&mddev->lock);
 	if (strncmp(buf, "max", 3) == 0)
 		mddev->resync_max = MaxSector;
 	else {
 		unsigned long long max;
+		int chunk;
+
+		err = -EINVAL;
 		if (kstrtoull(buf, 10, &max))
-			return -EINVAL;
+			goto out_unlock;
 		if (max < mddev->resync_min)
-			return -EINVAL;
+			goto out_unlock;
+
+		err = -EBUSY;
 		if (max < mddev->resync_max &&
 		    mddev->ro == 0 &&
 		    test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
-			return -EBUSY;
+			goto out_unlock;
 
 		/* Must be a multiple of chunk_size */
-		if (mddev->chunk_sectors) {
+		chunk = mddev->chunk_sectors;
+		if (chunk) {
 			sector_t temp = max;
-			if (sector_div(temp, mddev->chunk_sectors))
-				return -EINVAL;
+
+			err = -EINVAL;
+			if (sector_div(temp, chunk))
+				goto out_unlock;
 		}
 		mddev->resync_max = max;
 	}
 	wake_up(&mddev->recovery_wait);
-	return len;
+	err = 0;
+out_unlock:
+	spin_unlock(&mddev->lock);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry md_max_sync =
@@ -4297,14 +4446,20 @@ suspend_lo_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	char *e;
 	unsigned long long new = simple_strtoull(buf, &e, 10);
-	unsigned long long old = mddev->suspend_lo;
+	unsigned long long old;
+	int err;
 
-	if (mddev->pers == NULL ||
-	    mddev->pers->quiesce == NULL)
-		return -EINVAL;
 	if (buf == e || (*e && *e != '\n'))
 		return -EINVAL;
 
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	err = -EINVAL;
+	if (mddev->pers == NULL ||
+	    mddev->pers->quiesce == NULL)
+		goto unlock;
+	old = mddev->suspend_lo;
 	mddev->suspend_lo = new;
 	if (new >= old)
 		/* Shrinking suspended region */
@@ -4314,7 +4469,10 @@ suspend_lo_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->pers->quiesce(mddev, 1);
 		mddev->pers->quiesce(mddev, 0);
 	}
-	return len;
+	err = 0;
+unlock:
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 static struct md_sysfs_entry md_suspend_lo =
 __ATTR(suspend_lo, S_IRUGO|S_IWUSR, suspend_lo_show, suspend_lo_store);
@@ -4330,14 +4488,20 @@ suspend_hi_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	char *e;
 	unsigned long long new = simple_strtoull(buf, &e, 10);
-	unsigned long long old = mddev->suspend_hi;
+	unsigned long long old;
+	int err;
 
-	if (mddev->pers == NULL ||
-	    mddev->pers->quiesce == NULL)
-		return -EINVAL;
 	if (buf == e || (*e && *e != '\n'))
 		return -EINVAL;
 
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	err = -EINVAL;
+	if (mddev->pers == NULL ||
+	    mddev->pers->quiesce == NULL)
+		goto unlock;
+	old = mddev->suspend_hi;
 	mddev->suspend_hi = new;
 	if (new <= old)
 		/* Shrinking suspended region */
@@ -4347,7 +4511,10 @@ suspend_hi_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->pers->quiesce(mddev, 1);
 		mddev->pers->quiesce(mddev, 0);
 	}
-	return len;
+	err = 0;
+unlock:
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 static struct md_sysfs_entry md_suspend_hi =
 __ATTR(suspend_hi, S_IRUGO|S_IWUSR, suspend_hi_show, suspend_hi_store);
@@ -4367,11 +4534,17 @@ reshape_position_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	struct md_rdev *rdev;
 	char *e;
+	int err;
 	unsigned long long new = simple_strtoull(buf, &e, 10);
-	if (mddev->pers)
-		return -EBUSY;
+
 	if (buf == e || (*e && *e != '\n'))
 		return -EINVAL;
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	err = -EBUSY;
+	if (mddev->pers)
+		goto unlock;
 	mddev->reshape_position = new;
 	mddev->delta_disks = 0;
 	mddev->reshape_backwards = 0;
@@ -4380,7 +4553,10 @@ reshape_position_store(struct mddev *mddev, const char *buf, size_t len)
 	mddev->new_chunk_sectors = mddev->chunk_sectors;
 	rdev_for_each(rdev, mddev)
 		rdev->new_data_offset = rdev->data_offset;
-	return len;
+	err = 0;
+unlock:
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry md_reshape_position =
@@ -4398,6 +4574,8 @@ static ssize_t
 reshape_direction_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	int backwards = 0;
+	int err;
+
 	if (cmd_match(buf, "forwards"))
 		backwards = 0;
 	else if (cmd_match(buf, "backwards"))
@@ -4407,16 +4585,19 @@ reshape_direction_store(struct mddev *mddev, const char *buf, size_t len)
 	if (mddev->reshape_backwards == backwards)
 		return len;
 
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 	/* check if we are allowed to change */
 	if (mddev->delta_disks)
-		return -EBUSY;
-
-	if (mddev->persistent &&
+		err = -EBUSY;
+	else if (mddev->persistent &&
 	    mddev->major_version == 0)
-		return -EINVAL;
-
-	mddev->reshape_backwards = backwards;
-	return len;
+		err =  -EINVAL;
+	else
+		mddev->reshape_backwards = backwards;
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry md_reshape_direction =
@@ -4437,6 +4618,11 @@ static ssize_t
 array_size_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	sector_t sectors;
+	int err;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
 
 	if (strncmp(buf, "default", 7) == 0) {
 		if (mddev->pers)
@@ -4447,19 +4633,22 @@ array_size_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->external_size = 0;
 	} else {
 		if (strict_blocks_to_sectors(buf, &sectors) < 0)
-			return -EINVAL;
-		if (mddev->pers && mddev->pers->size(mddev, 0, 0) < sectors)
-			return -E2BIG;
-
-		mddev->external_size = 1;
+			err = -EINVAL;
+		else if (mddev->pers && mddev->pers->size(mddev, 0, 0) < sectors)
+			err = -E2BIG;
+		else
+			mddev->external_size = 1;
 	}
 
-	mddev->array_sectors = sectors;
-	if (mddev->pers) {
-		set_capacity(mddev->gendisk, mddev->array_sectors);
-		revalidate_disk(mddev->gendisk);
+	if (!err) {
+		mddev->array_sectors = sectors;
+		if (mddev->pers) {
+			set_capacity(mddev->gendisk, mddev->array_sectors);
+			revalidate_disk(mddev->gendisk);
+		}
 	}
-	return len;
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry md_array_size =
@@ -4523,11 +4712,7 @@ md_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 	mddev_get(mddev);
 	spin_unlock(&all_mddevs_lock);
 
-	rv = mddev_lock(mddev);
-	if (!rv) {
-		rv = entry->show(mddev, page);
-		mddev_unlock(mddev);
-	}
+	rv = entry->show(mddev, page);
 	mddev_put(mddev);
 	return rv;
 }
@@ -4551,13 +4736,7 @@ md_attr_store(struct kobject *kobj, struct attribute *attr,
 	}
 	mddev_get(mddev);
 	spin_unlock(&all_mddevs_lock);
-	if (entry->store == new_dev_store)
-		flush_workqueue(md_misc_wq);
-	rv = mddev_lock(mddev);
-	if (!rv) {
-		rv = entry->store(mddev, page, length);
-		mddev_unlock(mddev);
-	}
+	rv = entry->store(mddev, page, length);
 	mddev_put(mddev);
 	return rv;
 }
@@ -4825,7 +5004,6 @@ int md_run(struct mddev *mddev)
 			       mddev->clevel);
 		return -EINVAL;
 	}
-	mddev->pers = pers;
 	spin_unlock(&pers_lock);
 	if (mddev->level != pers->level) {
 		mddev->level = pers->level;
@@ -4836,7 +5014,6 @@ int md_run(struct mddev *mddev)
 	if (mddev->reshape_position != MaxSector &&
 	    pers->start_reshape == NULL) {
 		/* This personality cannot handle reshaping... */
-		mddev->pers = NULL;
 		module_put(pers->owner);
 		return -EINVAL;
 	}
@@ -4880,35 +5057,38 @@ int md_run(struct mddev *mddev)
 	if (start_readonly && mddev->ro == 0)
 		mddev->ro = 2; /* read-only, but switch on first write */
 
-	err = mddev->pers->run(mddev);
+	err = pers->run(mddev);
 	if (err)
 		printk(KERN_ERR "md: pers->run() failed ...\n");
-	else if (mddev->pers->size(mddev, 0, 0) < mddev->array_sectors) {
+	else if (pers->size(mddev, 0, 0) < mddev->array_sectors) {
 		WARN_ONCE(!mddev->external_size, "%s: default size too small,"
 			  " but 'external_size' not in effect?\n", __func__);
 		printk(KERN_ERR
 		       "md: invalid array_size %llu > default size %llu\n",
 		       (unsigned long long)mddev->array_sectors / 2,
-		       (unsigned long long)mddev->pers->size(mddev, 0, 0) / 2);
+		       (unsigned long long)pers->size(mddev, 0, 0) / 2);
 		err = -EINVAL;
-		mddev->pers->stop(mddev);
 	}
-	if (err == 0 && mddev->pers->sync_request &&
+	if (err == 0 && pers->sync_request &&
 	    (mddev->bitmap_info.file || mddev->bitmap_info.offset)) {
 		err = bitmap_create(mddev);
-		if (err) {
+		if (err)
 			printk(KERN_ERR "%s: failed to create bitmap (%d)\n",
 			       mdname(mddev), err);
-			mddev->pers->stop(mddev);
-		}
 	}
 	if (err) {
-		module_put(mddev->pers->owner);
-		mddev->pers = NULL;
+		mddev_detach(mddev);
+		pers->free(mddev, mddev->private);
+		module_put(pers->owner);
 		bitmap_destroy(mddev);
 		return err;
 	}
-	if (mddev->pers->sync_request) {
+	if (mddev->queue) {
+		mddev->queue->backing_dev_info.congested_data = mddev;
+		mddev->queue->backing_dev_info.congested_fn = md_congested;
+		blk_queue_merge_bvec(mddev->queue, md_mergeable_bvec);
+	}
+	if (pers->sync_request) {
 		if (mddev->kobj.sd &&
 		    sysfs_create_group(&mddev->kobj, &md_redundancy_group))
 			printk(KERN_WARNING
@@ -4927,7 +5107,10 @@ int md_run(struct mddev *mddev)
 	mddev->safemode_delay = (200 * HZ)/1000 +1; /* 200 msec delay */
 	mddev->in_sync = 1;
 	smp_wmb();
+	spin_lock(&mddev->lock);
+	mddev->pers = pers;
 	mddev->ready = 1;
+	spin_unlock(&mddev->lock);
 	rdev_for_each(rdev, mddev)
 		if (rdev->raid_disk >= 0)
 			if (sysfs_link_rdev(mddev, rdev))
@@ -5070,14 +5253,38 @@ void md_stop_writes(struct mddev *mddev)
 }
 EXPORT_SYMBOL_GPL(md_stop_writes);
 
+static void mddev_detach(struct mddev *mddev)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+	/* wait for behind writes to complete */
+	if (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
+		printk(KERN_INFO "md:%s: behind writes in progress - waiting to stop.\n",
+		       mdname(mddev));
+		/* need to kick something here to make sure I/O goes? */
+		wait_event(bitmap->behind_wait,
+			   atomic_read(&bitmap->behind_writes) == 0);
+	}
+	if (mddev->pers && mddev->pers->quiesce) {
+		mddev->pers->quiesce(mddev, 1);
+		mddev->pers->quiesce(mddev, 0);
+	}
+	md_unregister_thread(&mddev->thread);
+	if (mddev->queue)
+		blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
+}
+
 static void __md_stop(struct mddev *mddev)
 {
+	struct md_personality *pers = mddev->pers;
+	mddev_detach(mddev);
+	spin_lock(&mddev->lock);
 	mddev->ready = 0;
-	mddev->pers->stop(mddev);
-	if (mddev->pers->sync_request && mddev->to_remove == NULL)
-		mddev->to_remove = &md_redundancy_group;
-	module_put(mddev->pers->owner);
 	mddev->pers = NULL;
+	spin_unlock(&mddev->lock);
+	pers->free(mddev, mddev->private);
+	if (pers->sync_request && mddev->to_remove == NULL)
+		mddev->to_remove = &md_redundancy_group;
+	module_put(pers->owner);
 	clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 }
 
@@ -5226,8 +5433,11 @@ static int do_md_stop(struct mddev *mddev, int mode,
 
 		bitmap_destroy(mddev);
 		if (mddev->bitmap_info.file) {
-			fput(mddev->bitmap_info.file);
+			struct file *f = mddev->bitmap_info.file;
+			spin_lock(&mddev->lock);
 			mddev->bitmap_info.file = NULL;
+			spin_unlock(&mddev->lock);
+			fput(f);
 		}
 		mddev->bitmap_info.offset = 0;
 
@@ -5436,37 +5646,31 @@ static int get_array_info(struct mddev *mddev, void __user *arg)
 static int get_bitmap_file(struct mddev *mddev, void __user * arg)
 {
 	mdu_bitmap_file_t *file = NULL; /* too big for stack allocation */
-	char *ptr, *buf = NULL;
-	int err = -ENOMEM;
+	char *ptr;
+	int err;
 
 	file = kmalloc(sizeof(*file), GFP_NOIO);
-
 	if (!file)
-		goto out;
+		return -ENOMEM;
 
+	err = 0;
+	spin_lock(&mddev->lock);
 	/* bitmap disabled, zero the first byte and copy out */
-	if (!mddev->bitmap || !mddev->bitmap->storage.file) {
+	if (!mddev->bitmap_info.file)
 		file->pathname[0] = '\0';
-		goto copy_out;
-	}
-
-	buf = kmalloc(sizeof(file->pathname), GFP_KERNEL);
-	if (!buf)
-		goto out;
-
-	ptr = d_path(&mddev->bitmap->storage.file->f_path,
-		     buf, sizeof(file->pathname));
-	if (IS_ERR(ptr))
-		goto out;
-
-	strcpy(file->pathname, ptr);
+	else if ((ptr = d_path(&mddev->bitmap_info.file->f_path,
+			       file->pathname, sizeof(file->pathname))),
+		 IS_ERR(ptr))
+		err = PTR_ERR(ptr);
+	else
+		memmove(file->pathname, ptr,
+			sizeof(file->pathname)-(ptr-file->pathname));
+	spin_unlock(&mddev->lock);
 
-copy_out:
-	err = 0;
-	if (copy_to_user(arg, file, sizeof(*file)))
+	if (err == 0 &&
+	    copy_to_user(arg, file, sizeof(*file)))
 		err = -EFAULT;
-out:
-	kfree(buf);
+
 	kfree(file);
 	return err;
 }
@@ -5789,22 +5993,24 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
 
 	if (fd >= 0) {
 		struct inode *inode;
-		if (mddev->bitmap)
+		struct file *f;
+
+		if (mddev->bitmap || mddev->bitmap_info.file)
 			return -EEXIST; /* cannot add when bitmap is present */
-		mddev->bitmap_info.file = fget(fd);
+		f = fget(fd);
 
-		if (mddev->bitmap_info.file == NULL) {
+		if (f == NULL) {
 			printk(KERN_ERR "%s: error: failed to get bitmap file\n",
 			       mdname(mddev));
 			return -EBADF;
 		}
 
-		inode = mddev->bitmap_info.file->f_mapping->host;
+		inode = f->f_mapping->host;
 		if (!S_ISREG(inode->i_mode)) {
 			printk(KERN_ERR "%s: error: bitmap file must be a regular file\n",
 			       mdname(mddev));
 			err = -EBADF;
-		} else if (!(mddev->bitmap_info.file->f_mode & FMODE_WRITE)) {
+		} else if (!(f->f_mode & FMODE_WRITE)) {
 			printk(KERN_ERR "%s: error: bitmap file must open for write\n",
 			       mdname(mddev));
 			err = -EBADF;
@@ -5814,10 +6020,10 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
 			err = -EBUSY;
 		}
 		if (err) {
-			fput(mddev->bitmap_info.file);
-			mddev->bitmap_info.file = NULL;
+			fput(f);
 			return err;
 		}
+		mddev->bitmap_info.file = f;
 		mddev->bitmap_info.offset = 0; /* file overrides offset */
 	} else if (mddev->bitmap == NULL)
 		return -ENOENT; /* cannot remove what isn't there */
@@ -5836,9 +6042,13 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
 		mddev->pers->quiesce(mddev, 0);
 	}
 	if (fd < 0) {
-		if (mddev->bitmap_info.file)
-			fput(mddev->bitmap_info.file);
-		mddev->bitmap_info.file = NULL;
+		struct file *f = mddev->bitmap_info.file;
+		if (f) {
+			spin_lock(&mddev->lock);
+			mddev->bitmap_info.file = NULL;
+			spin_unlock(&mddev->lock);
+			fput(f);
+		}
 	}
 
 	return err;
@@ -6251,6 +6461,11 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 	case SET_DISK_FAULTY:
 		err = set_disk_faulty(mddev, new_decode_dev(arg));
 		goto out;
+
+	case GET_BITMAP_FILE:
+		err = get_bitmap_file(mddev, argp);
+		goto out;
+
 	}
 
 	if (cmd == ADD_NEW_DISK)
@@ -6342,10 +6557,6 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 	 * Commands even a read-only array can execute:
 	 */
 	switch (cmd) {
-	case GET_BITMAP_FILE:
-		err = get_bitmap_file(mddev, argp);
-		goto unlock;
-
 	case RESTART_ARRAY_RW:
 		err = restart_array(mddev);
 		goto unlock;
@@ -6873,9 +7084,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
 		return 0;
 	}
 
-	if (mddev_lock(mddev) < 0)
-		return -EINTR;
-
+	spin_lock(&mddev->lock);
 	if (mddev->pers || mddev->raid_disks || !list_empty(&mddev->disks)) {
 		seq_printf(seq, "%s : %sactive", mdname(mddev),
 						mddev->pers ? "" : "in");
@@ -6888,7 +7097,8 @@ static int md_seq_show(struct seq_file *seq, void *v)
 		}
 
 		sectors = 0;
-		rdev_for_each(rdev, mddev) {
+		rcu_read_lock();
+		rdev_for_each_rcu(rdev, mddev) {
 			char b[BDEVNAME_SIZE];
 			seq_printf(seq, " %s[%d]",
 				bdevname(rdev->bdev,b), rdev->desc_nr);
@@ -6904,6 +7114,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
 				seq_printf(seq, "(R)");
 			sectors += rdev->sectors;
 		}
+		rcu_read_unlock();
 
 		if (!list_empty(&mddev->disks)) {
 			if (mddev->pers)
@@ -6946,7 +7157,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
 
 		seq_printf(seq, "\n");
 	}
-	mddev_unlock(mddev);
+	spin_unlock(&mddev->lock);
 
 	return 0;
 }
@@ -7102,7 +7313,7 @@ void md_write_start(struct mddev *mddev, struct bio *bi)
 	if (mddev->safemode == 1)
 		mddev->safemode = 0;
 	if (mddev->in_sync) {
-		spin_lock_irq(&mddev->write_lock);
+		spin_lock(&mddev->lock);
 		if (mddev->in_sync) {
 			mddev->in_sync = 0;
 			set_bit(MD_CHANGE_CLEAN, &mddev->flags);
@@ -7110,7 +7321,7 @@ void md_write_start(struct mddev *mddev, struct bio *bi)
 			md_wakeup_thread(mddev->thread);
 			did_change = 1;
 		}
-		spin_unlock_irq(&mddev->write_lock);
+		spin_unlock(&mddev->lock);
 	}
 	if (did_change)
 		sysfs_notify_dirent_safe(mddev->sysfs_state);
@@ -7148,7 +7359,7 @@ int md_allow_write(struct mddev *mddev)
 	if (!mddev->pers->sync_request)
 		return 0;
 
-	spin_lock_irq(&mddev->write_lock);
+	spin_lock(&mddev->lock);
 	if (mddev->in_sync) {
 		mddev->in_sync = 0;
 		set_bit(MD_CHANGE_CLEAN, &mddev->flags);
@@ -7156,11 +7367,11 @@ int md_allow_write(struct mddev *mddev)
 		if (mddev->safemode_delay &&
 		    mddev->safemode == 0)
 			mddev->safemode = 1;
-		spin_unlock_irq(&mddev->write_lock);
+		spin_unlock(&mddev->lock);
 		md_update_sb(mddev, 0);
 		sysfs_notify_dirent_safe(mddev->sysfs_state);
 	} else
-		spin_unlock_irq(&mddev->write_lock);
+		spin_unlock(&mddev->lock);
 
 	if (test_bit(MD_CHANGE_PENDING, &mddev->flags))
 		return -EAGAIN;
@@ -7513,6 +7724,7 @@ void md_do_sync(struct md_thread *thread)
  skip:
 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
 
+	spin_lock(&mddev->lock);
 	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
 		/* We completed so min/max setting can be forgotten if used. */
 		if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
@@ -7521,6 +7733,8 @@ void md_do_sync(struct md_thread *thread)
 	} else if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
 		mddev->resync_min = mddev->curr_resync_completed;
 	mddev->curr_resync = 0;
+	spin_unlock(&mddev->lock);
+
 	wake_up(&resync_wait);
 	set_bit(MD_RECOVERY_DONE, &mddev->recovery);
 	md_wakeup_thread(mddev->thread);
@@ -7688,7 +7902,7 @@ void md_check_recovery(struct mddev *mddev)
 
 		if (!mddev->external) {
 			int did_change = 0;
-			spin_lock_irq(&mddev->write_lock);
+			spin_lock(&mddev->lock);
 			if (mddev->safemode &&
 			    !atomic_read(&mddev->writes_pending) &&
 			    !mddev->in_sync &&
@@ -7699,7 +7913,7 @@ void md_check_recovery(struct mddev *mddev)
 			}
 			if (mddev->safemode == 1)
 				mddev->safemode = 0;
-			spin_unlock_irq(&mddev->write_lock);
+			spin_unlock(&mddev->lock);
 			if (did_change)
 				sysfs_notify_dirent_safe(mddev->sysfs_state);
 		}
@@ -7721,7 +7935,9 @@ void md_check_recovery(struct mddev *mddev)
 		 * any transients in the value of "sync_action".
 		 */
 		mddev->curr_resync_completed = 0;
+		spin_lock(&mddev->lock);
 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
+		spin_unlock(&mddev->lock);
 		/* Clear some bits that don't mean anything, but
 		 * might be left set
 		 */
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 03cec5bdcaae..318ca8fd430f 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -386,7 +386,18 @@ struct mddev {
 
 	struct work_struct del_work;	/* used for delayed sysfs removal */
 
-	spinlock_t			write_lock;
+	/* "lock" protects:
+	 *   flush_bio transition from NULL to !NULL
+	 *   rdev superblocks, events
+	 *   clearing MD_CHANGE_*
+	 *   in_sync - and related safemode and MD_CHANGE changes
+	 *   pers (also protected by reconfig_mutex and pending IO).
+	 *   clearing ->bitmap
+	 *   clearing ->bitmap_info.file
+	 *   changing ->resync_{min,max}
+	 *   setting MD_RECOVERY_RUNNING (which interacts with resync_{min,max})
+	 */
+	spinlock_t			lock;
 	wait_queue_head_t		sb_wait;	/* for waiting on superblock updates */
 	atomic_t			pending_writes;	/* number of active superblock writes */
 
@@ -439,13 +450,30 @@ struct mddev {
 	void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);
 };
 
-static inline void rdev_dec_pending(struct md_rdev *rdev, struct mddev *mddev)
+static inline int __must_check mddev_lock(struct mddev *mddev)
 {
-	int faulty = test_bit(Faulty, &rdev->flags);
-	if (atomic_dec_and_test(&rdev->nr_pending) && faulty)
-		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	return mutex_lock_interruptible(&mddev->reconfig_mutex);
+}
+
+/* Sometimes we need to take the lock in a situation where
+ * failure due to interrupts is not acceptable.
+ */
+static inline void mddev_lock_nointr(struct mddev *mddev)
+{
+	mutex_lock(&mddev->reconfig_mutex);
+}
+
+static inline int mddev_is_locked(struct mddev *mddev)
+{
+	return mutex_is_locked(&mddev->reconfig_mutex);
 }
 
+static inline int mddev_trylock(struct mddev *mddev)
+{
+	return mutex_trylock(&mddev->reconfig_mutex);
+}
+extern void mddev_unlock(struct mddev *mddev);
+
 static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
 {
 	atomic_add(nr_sectors, &bdev->bd_contains->bd_disk->sync_io);
@@ -459,7 +487,7 @@ struct md_personality
 	struct module *owner;
 	void (*make_request)(struct mddev *mddev, struct bio *bio);
 	int (*run)(struct mddev *mddev);
-	int (*stop)(struct mddev *mddev);
+	void (*free)(struct mddev *mddev, void *priv);
 	void (*status)(struct seq_file *seq, struct mddev *mddev);
 	/* error_handler must set ->faulty and clear ->in_sync
 	 * if appropriate, and should abort recovery if needed
@@ -490,6 +518,13 @@ struct md_personality
 	 * array.
 	 */
 	void *(*takeover) (struct mddev *mddev);
+	/* congested implements bdi.congested_fn().
+	 * Will not be called while array is 'suspended' */
+	int (*congested)(struct mddev *mddev, int bits);
+	/* mergeable_bvec is use to implement ->merge_bvec_fn */
+	int (*mergeable_bvec)(struct mddev *mddev,
+			      struct bvec_merge_data *bvm,
+			      struct bio_vec *biovec);
 };
 
 struct md_sysfs_entry {
@@ -624,4 +659,14 @@ static inline int mddev_check_plugged(struct mddev *mddev)
 	return !!blk_check_plugged(md_unplug, mddev,
 				   sizeof(struct blk_plug_cb));
 }
+
+static inline void rdev_dec_pending(struct md_rdev *rdev, struct mddev *mddev)
+{
+	int faulty = test_bit(Faulty, &rdev->flags);
+	if (atomic_dec_and_test(&rdev->nr_pending) && faulty) {
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+		md_wakeup_thread(mddev->thread);
+	}
+}
+
 #endif /* _MD_MD_H */
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 399272f9c042..ac3ede2bd00e 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -153,15 +153,11 @@ static void multipath_status (struct seq_file *seq, struct mddev *mddev)
 	seq_printf (seq, "]");
 }
 
-static int multipath_congested(void *data, int bits)
+static int multipath_congested(struct mddev *mddev, int bits)
 {
-	struct mddev *mddev = data;
 	struct mpconf *conf = mddev->private;
 	int i, ret = 0;
 
-	if (mddev_congested(mddev, bits))
-		return 1;
-
 	rcu_read_lock();
 	for (i = 0; i < mddev->raid_disks ; i++) {
 		struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
@@ -403,7 +399,7 @@ static int multipath_run (struct mddev *mddev)
 	/*
 	 * copy the already verified devices into our private MULTIPATH
 	 * bookkeeping area. [whatever we allocate in multipath_run(),
-	 * should be freed in multipath_stop()]
+	 * should be freed in multipath_free()]
 	 */
 
 	conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
@@ -489,9 +485,6 @@ static int multipath_run (struct mddev *mddev)
 	 */
 	md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
 
-	mddev->queue->backing_dev_info.congested_fn = multipath_congested;
-	mddev->queue->backing_dev_info.congested_data = mddev;
-
 	if (md_integrity_register(mddev))
 		goto out_free_conf;
 
@@ -507,17 +500,13 @@ out:
 	return -EIO;
 }
 
-static int multipath_stop (struct mddev *mddev)
+static void multipath_free(struct mddev *mddev, void *priv)
 {
-	struct mpconf *conf = mddev->private;
+	struct mpconf *conf = priv;
 
-	md_unregister_thread(&mddev->thread);
-	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 	mempool_destroy(conf->pool);
 	kfree(conf->multipaths);
 	kfree(conf);
-	mddev->private = NULL;
-	return 0;
 }
 
 static struct md_personality multipath_personality =
@@ -527,12 +516,13 @@ static struct md_personality multipath_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= multipath_make_request,
 	.run		= multipath_run,
-	.stop		= multipath_stop,
+	.free		= multipath_free,
 	.status		= multipath_status,
 	.error_handler	= multipath_error,
 	.hot_add_disk	= multipath_add_disk,
 	.hot_remove_disk= multipath_remove_disk,
 	.size		= multipath_size,
+	.congested	= multipath_congested,
 };
 
 static int __init multipath_init (void)
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index ba6b85de96d2..a13f738a7b39 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -25,17 +25,13 @@
 #include "raid0.h"
 #include "raid5.h"
 
-static int raid0_congested(void *data, int bits)
+static int raid0_congested(struct mddev *mddev, int bits)
 {
-	struct mddev *mddev = data;
 	struct r0conf *conf = mddev->private;
 	struct md_rdev **devlist = conf->devlist;
 	int raid_disks = conf->strip_zone[0].nb_dev;
 	int i, ret = 0;
 
-	if (mddev_congested(mddev, bits))
-		return 1;
-
 	for (i = 0; i < raid_disks && !ret ; i++) {
 		struct request_queue *q = bdev_get_queue(devlist[i]->bdev);
 
@@ -263,8 +259,6 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
 			 mdname(mddev),
 			 (unsigned long long)smallest->sectors);
 	}
-	mddev->queue->backing_dev_info.congested_fn = raid0_congested;
-	mddev->queue->backing_dev_info.congested_data = mddev;
 
 	/*
 	 * now since we have the hard sector sizes, we can make sure
@@ -356,17 +350,16 @@ static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,
 
 /**
  *	raid0_mergeable_bvec -- tell bio layer if two requests can be merged
- *	@q: request queue
+ *	@mddev: the md device
  *	@bvm: properties of new bio
  *	@biovec: the request that could be merged to it.
  *
  *	Return amount of bytes we can accept at this offset
  */
-static int raid0_mergeable_bvec(struct request_queue *q,
+static int raid0_mergeable_bvec(struct mddev *mddev,
 				struct bvec_merge_data *bvm,
 				struct bio_vec *biovec)
 {
-	struct mddev *mddev = q->queuedata;
 	struct r0conf *conf = mddev->private;
 	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
 	sector_t sector_offset = sector;
@@ -422,7 +415,7 @@ static sector_t raid0_size(struct mddev *mddev, sector_t sectors, int raid_disks
 	return array_sectors;
 }
 
-static int raid0_stop(struct mddev *mddev);
+static void raid0_free(struct mddev *mddev, void *priv);
 
 static int raid0_run(struct mddev *mddev)
 {
@@ -471,26 +464,22 @@ static int raid0_run(struct mddev *mddev)
 			mddev->queue->backing_dev_info.ra_pages = 2* stripe;
 	}
 
-	blk_queue_merge_bvec(mddev->queue, raid0_mergeable_bvec);
 	dump_zones(mddev);
 
 	ret = md_integrity_register(mddev);
 	if (ret)
-		raid0_stop(mddev);
+		raid0_free(mddev, conf);
 
 	return ret;
 }
 
-static int raid0_stop(struct mddev *mddev)
+static void raid0_free(struct mddev *mddev, void *priv)
 {
-	struct r0conf *conf = mddev->private;
+	struct r0conf *conf = priv;
 
-	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 	kfree(conf->strip_zone);
 	kfree(conf->devlist);
 	kfree(conf);
-	mddev->private = NULL;
-	return 0;
 }
 
 /*
@@ -724,11 +713,13 @@ static struct md_personality raid0_personality=
 	.owner		= THIS_MODULE,
 	.make_request	= raid0_make_request,
 	.run		= raid0_run,
-	.stop		= raid0_stop,
+	.free		= raid0_free,
 	.status		= raid0_status,
 	.size		= raid0_size,
 	.takeover	= raid0_takeover,
 	.quiesce	= raid0_quiesce,
+	.congested	= raid0_congested,
+	.mergeable_bvec	= raid0_mergeable_bvec,
 };
 
 static int __init raid0_init (void)
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 40b35be34f8d..5dd0c2e59ab9 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -701,11 +701,10 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 	return best_disk;
 }
 
-static int raid1_mergeable_bvec(struct request_queue *q,
+static int raid1_mergeable_bvec(struct mddev *mddev,
 				struct bvec_merge_data *bvm,
 				struct bio_vec *biovec)
 {
-	struct mddev *mddev = q->queuedata;
 	struct r1conf *conf = mddev->private;
 	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
 	int max = biovec->bv_len;
@@ -734,7 +733,7 @@ static int raid1_mergeable_bvec(struct request_queue *q,
 
 }
 
-int md_raid1_congested(struct mddev *mddev, int bits)
+static int raid1_congested(struct mddev *mddev, int bits)
 {
 	struct r1conf *conf = mddev->private;
 	int i, ret = 0;
@@ -763,15 +762,6 @@ int md_raid1_congested(struct mddev *mddev, int bits)
 	rcu_read_unlock();
 	return ret;
 }
-EXPORT_SYMBOL_GPL(md_raid1_congested);
-
-static int raid1_congested(void *data, int bits)
-{
-	struct mddev *mddev = data;
-
-	return mddev_congested(mddev, bits) ||
-		md_raid1_congested(mddev, bits);
-}
 
 static void flush_pending_writes(struct r1conf *conf)
 {
@@ -2882,7 +2872,7 @@ static struct r1conf *setup_conf(struct mddev *mddev)
 	return ERR_PTR(err);
 }
 
-static int stop(struct mddev *mddev);
+static void raid1_free(struct mddev *mddev, void *priv);
 static int run(struct mddev *mddev)
 {
 	struct r1conf *conf;
@@ -2904,7 +2894,7 @@ static int run(struct mddev *mddev)
 	/*
 	 * copy the already verified devices into our private RAID1
 	 * bookkeeping area. [whatever we allocate in run(),
-	 * should be freed in stop()]
+	 * should be freed in raid1_free()]
 	 */
 	if (mddev->private == NULL)
 		conf = setup_conf(mddev);
@@ -2955,10 +2945,6 @@ static int run(struct mddev *mddev)
 	md_set_array_sectors(mddev, raid1_size(mddev, 0, 0));
 
 	if (mddev->queue) {
-		mddev->queue->backing_dev_info.congested_fn = raid1_congested;
-		mddev->queue->backing_dev_info.congested_data = mddev;
-		blk_queue_merge_bvec(mddev->queue, raid1_mergeable_bvec);
-
 		if (discard_supported)
 			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
 						mddev->queue);
@@ -2968,37 +2954,23 @@ static int run(struct mddev *mddev)
 	}
 
 	ret =  md_integrity_register(mddev);
-	if (ret)
-		stop(mddev);
+	if (ret) {
+		md_unregister_thread(&mddev->thread);
+		raid1_free(mddev, conf);
+	}
 	return ret;
 }
 
-static int stop(struct mddev *mddev)
+static void raid1_free(struct mddev *mddev, void *priv)
 {
-	struct r1conf *conf = mddev->private;
-	struct bitmap *bitmap = mddev->bitmap;
+	struct r1conf *conf = priv;
 
-	/* wait for behind writes to complete */
-	if (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
-		printk(KERN_INFO "md/raid1:%s: behind writes in progress - waiting to stop.\n",
-		       mdname(mddev));
-		/* need to kick something here to make sure I/O goes? */
-		wait_event(bitmap->behind_wait,
-			   atomic_read(&bitmap->behind_writes) == 0);
-	}
-
-	freeze_array(conf, 0);
-	unfreeze_array(conf);
-
-	md_unregister_thread(&mddev->thread);
 	if (conf->r1bio_pool)
 		mempool_destroy(conf->r1bio_pool);
 	kfree(conf->mirrors);
 	safe_put_page(conf->tmppage);
 	kfree(conf->poolinfo);
 	kfree(conf);
-	mddev->private = NULL;
-	return 0;
 }
 
 static int raid1_resize(struct mddev *mddev, sector_t sectors)
@@ -3181,7 +3153,7 @@ static struct md_personality raid1_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid1_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid1_add_disk,
@@ -3193,6 +3165,8 @@ static struct md_personality raid1_personality =
 	.check_reshape	= raid1_reshape,
 	.quiesce	= raid1_quiesce,
 	.takeover	= raid1_takeover,
+	.congested	= raid1_congested,
+	.mergeable_bvec	= raid1_mergeable_bvec,
 };
 
 static int __init raid_init(void)
diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
index 33bda55ef9f7..14ebb288c1ef 100644
--- a/drivers/md/raid1.h
+++ b/drivers/md/raid1.h
@@ -170,7 +170,4 @@ struct r1bio {
  */
 #define	R1BIO_MadeGood 7
 #define	R1BIO_WriteError 8
-
-extern int md_raid1_congested(struct mddev *mddev, int bits);
-
 #endif
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 32e282f4c83c..b8d76b1fba64 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -674,7 +674,7 @@ static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
 
 /**
  *	raid10_mergeable_bvec -- tell bio layer if a two requests can be merged
- *	@q: request queue
+ *	@mddev: the md device
  *	@bvm: properties of new bio
  *	@biovec: the request that could be merged to it.
  *
@@ -682,11 +682,10 @@ static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
  *	This requires checking for end-of-chunk if near_copies != raid_disks,
  *	and for subordinate merge_bvec_fns if merge_check_needed.
  */
-static int raid10_mergeable_bvec(struct request_queue *q,
+static int raid10_mergeable_bvec(struct mddev *mddev,
 				 struct bvec_merge_data *bvm,
 				 struct bio_vec *biovec)
 {
-	struct mddev *mddev = q->queuedata;
 	struct r10conf *conf = mddev->private;
 	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
 	int max;
@@ -910,7 +909,7 @@ retry:
 	return rdev;
 }
 
-int md_raid10_congested(struct mddev *mddev, int bits)
+static int raid10_congested(struct mddev *mddev, int bits)
 {
 	struct r10conf *conf = mddev->private;
 	int i, ret = 0;
@@ -934,15 +933,6 @@ int md_raid10_congested(struct mddev *mddev, int bits)
 	rcu_read_unlock();
 	return ret;
 }
-EXPORT_SYMBOL_GPL(md_raid10_congested);
-
-static int raid10_congested(void *data, int bits)
-{
-	struct mddev *mddev = data;
-
-	return mddev_congested(mddev, bits) ||
-		md_raid10_congested(mddev, bits);
-}
 
 static void flush_pending_writes(struct r10conf *conf)
 {
@@ -3757,8 +3747,6 @@ static int run(struct mddev *mddev)
 	if (mddev->queue) {
 		int stripe = conf->geo.raid_disks *
 			((mddev->chunk_sectors << 9) / PAGE_SIZE);
-		mddev->queue->backing_dev_info.congested_fn = raid10_congested;
-		mddev->queue->backing_dev_info.congested_data = mddev;
 
 		/* Calculate max read-ahead size.
 		 * We need to readahead at least twice a whole stripe....
@@ -3767,7 +3755,6 @@ static int run(struct mddev *mddev)
 		stripe /= conf->geo.near_copies;
 		if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
 			mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
-		blk_queue_merge_bvec(mddev->queue, raid10_mergeable_bvec);
 	}
 
 	if (md_integrity_register(mddev))
@@ -3811,17 +3798,9 @@ out:
 	return -EIO;
 }
 
-static int stop(struct mddev *mddev)
+static void raid10_free(struct mddev *mddev, void *priv)
 {
-	struct r10conf *conf = mddev->private;
-
-	raise_barrier(conf, 0);
-	lower_barrier(conf);
-
-	md_unregister_thread(&mddev->thread);
-	if (mddev->queue)
-		/* the unplug fn references 'conf'*/
-		blk_sync_queue(mddev->queue);
+	struct r10conf *conf = priv;
 
 	if (conf->r10bio_pool)
 		mempool_destroy(conf->r10bio_pool);
@@ -3830,8 +3809,6 @@ static int stop(struct mddev *mddev)
 	kfree(conf->mirrors_old);
 	kfree(conf->mirrors_new);
 	kfree(conf);
-	mddev->private = NULL;
-	return 0;
 }
 
 static void raid10_quiesce(struct mddev *mddev, int state)
@@ -3895,7 +3872,7 @@ static int raid10_resize(struct mddev *mddev, sector_t sectors)
 	return 0;
 }
 
-static void *raid10_takeover_raid0(struct mddev *mddev)
+static void *raid10_takeover_raid0(struct mddev *mddev, sector_t size, int devs)
 {
 	struct md_rdev *rdev;
 	struct r10conf *conf;
@@ -3905,6 +3882,7 @@ static void *raid10_takeover_raid0(struct mddev *mddev)
 		       mdname(mddev));
 		return ERR_PTR(-EINVAL);
 	}
+	sector_div(size, devs);
 
 	/* Set new parameters */
 	mddev->new_level = 10;
@@ -3915,12 +3893,15 @@ static void *raid10_takeover_raid0(struct mddev *mddev)
 	mddev->raid_disks *= 2;
 	/* make sure it will be not marked as dirty */
 	mddev->recovery_cp = MaxSector;
+	mddev->dev_sectors = size;
 
 	conf = setup_conf(mddev);
 	if (!IS_ERR(conf)) {
 		rdev_for_each(rdev, mddev)
-			if (rdev->raid_disk >= 0)
+			if (rdev->raid_disk >= 0) {
 				rdev->new_raid_disk = rdev->raid_disk * 2;
+				rdev->sectors = size;
+			}
 		conf->barrier = 1;
 	}
 
@@ -3943,7 +3924,9 @@ static void *raid10_takeover(struct mddev *mddev)
 			       mdname(mddev));
 			return ERR_PTR(-EINVAL);
 		}
-		return raid10_takeover_raid0(mddev);
+		return raid10_takeover_raid0(mddev,
+			raid0_conf->strip_zone->zone_end,
+			raid0_conf->strip_zone->nb_dev);
 	}
 	return ERR_PTR(-EINVAL);
 }
@@ -4713,7 +4696,7 @@ static struct md_personality raid10_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid10_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid10_add_disk,
@@ -4727,6 +4710,8 @@ static struct md_personality raid10_personality =
 	.check_reshape	= raid10_check_reshape,
 	.start_reshape	= raid10_start_reshape,
 	.finish_reshape	= raid10_finish_reshape,
+	.congested	= raid10_congested,
+	.mergeable_bvec	= raid10_mergeable_bvec,
 };
 
 static int __init raid_init(void)
diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index 157d69e83ff4..5ee6473ddc2c 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -150,7 +150,4 @@ enum r10bio_state {
  */
 	R10BIO_Previous,
 };
-
-extern int md_raid10_congested(struct mddev *mddev, int bits);
-
 #endif
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b98765f6f77f..aa76865b804b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -296,12 +296,9 @@ static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
 	BUG_ON(atomic_read(&conf->active_stripes)==0);
 	if (test_bit(STRIPE_HANDLE, &sh->state)) {
 		if (test_bit(STRIPE_DELAYED, &sh->state) &&
-		    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+		    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
 			list_add_tail(&sh->lru, &conf->delayed_list);
-			if (atomic_read(&conf->preread_active_stripes)
-			    < IO_THRESHOLD)
-				md_wakeup_thread(conf->mddev->thread);
-		} else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
+		else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
 			   sh->bm_seq - conf->seq_write > 0)
 			list_add_tail(&sh->lru, &conf->bitmap_list);
 		else {
@@ -2898,31 +2895,102 @@ static int want_replace(struct stripe_head *sh, int disk_idx)
  * Returns 1 when no more member devices need to be checked, otherwise returns
  * 0 to tell the loop in handle_stripe_fill to continue
  */
-static int fetch_block(struct stripe_head *sh, struct stripe_head_state *s,
-		       int disk_idx, int disks)
+
+static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
+			   int disk_idx, int disks)
 {
 	struct r5dev *dev = &sh->dev[disk_idx];
 	struct r5dev *fdev[2] = { &sh->dev[s->failed_num[0]],
 				  &sh->dev[s->failed_num[1]] };
+	int i;
+
+
+	if (test_bit(R5_LOCKED, &dev->flags) ||
+	    test_bit(R5_UPTODATE, &dev->flags))
+		/* No point reading this as we already have it or have
+		 * decided to get it.
+		 */
+		return 0;
+
+	if (dev->toread ||
+	    (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)))
+		/* We need this block to directly satisfy a request */
+		return 1;
+
+	if (s->syncing || s->expanding ||
+	    (s->replacing && want_replace(sh, disk_idx)))
+		/* When syncing, or expanding we read everything.
+		 * When replacing, we need the replaced block.
+		 */
+		return 1;
+
+	if ((s->failed >= 1 && fdev[0]->toread) ||
+	    (s->failed >= 2 && fdev[1]->toread))
+		/* If we want to read from a failed device, then
+		 * we need to actually read every other device.
+		 */
+		return 1;
+
+	/* Sometimes neither read-modify-write nor reconstruct-write
+	 * cycles can work.  In those cases we read every block we
+	 * can.  Then the parity-update is certain to have enough to
+	 * work with.
+	 * This can only be a problem when we need to write something,
+	 * and some device has failed.  If either of those tests
+	 * fail we need look no further.
+	 */
+	if (!s->failed || !s->to_write)
+		return 0;
+
+	if (test_bit(R5_Insync, &dev->flags) &&
+	    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		/* Pre-reads at not permitted until after short delay
+		 * to gather multiple requests.  However if this
+		 * device is no Insync, the block could only be be computed
+		 * and there is no need to delay that.
+		 */
+		return 0;
+
+	for (i = 0; i < s->failed; i++) {
+		if (fdev[i]->towrite &&
+		    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&
+		    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
+			/* If we have a partial write to a failed
+			 * device, then we will need to reconstruct
+			 * the content of that device, so all other
+			 * devices must be read.
+			 */
+			return 1;
+	}
+
+	/* If we are forced to do a reconstruct-write, either because
+	 * the current RAID6 implementation only supports that, or
+	 * or because parity cannot be trusted and we are currently
+	 * recovering it, there is extra need to be careful.
+	 * If one of the devices that we would need to read, because
+	 * it is not being overwritten (and maybe not written at all)
+	 * is missing/faulty, then we need to read everything we can.
+	 */
+	if (sh->raid_conf->level != 6 &&
+	    sh->sector < sh->raid_conf->mddev->recovery_cp)
+		/* reconstruct-write isn't being forced */
+		return 0;
+	for (i = 0; i < s->failed; i++) {
+		if (!test_bit(R5_UPTODATE, &fdev[i]->flags) &&
+		    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
+			return 1;
+	}
+
+	return 0;
+}
+
+static int fetch_block(struct stripe_head *sh, struct stripe_head_state *s,
+		       int disk_idx, int disks)
+{
+	struct r5dev *dev = &sh->dev[disk_idx];
 
 	/* is the data in this block needed, and can we get it? */
-	if (!test_bit(R5_LOCKED, &dev->flags) &&
-	    !test_bit(R5_UPTODATE, &dev->flags) &&
-	    (dev->toread ||
-	     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
-	     s->syncing || s->expanding ||
-	     (s->replacing && want_replace(sh, disk_idx)) ||
-	     (s->failed >= 1 && fdev[0]->toread) ||
-	     (s->failed >= 2 && fdev[1]->toread) ||
-	     (sh->raid_conf->level <= 5 && s->failed && fdev[0]->towrite &&
-	      (!test_bit(R5_Insync, &dev->flags) || test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) &&
-	      !test_bit(R5_OVERWRITE, &fdev[0]->flags)) ||
-	     ((sh->raid_conf->level == 6 ||
-	       sh->sector >= sh->raid_conf->mddev->recovery_cp)
-	      && s->failed && s->to_write &&
-	      (s->to_write - s->non_overwrite <
-	       sh->raid_conf->raid_disks - sh->raid_conf->max_degraded) &&
-	      (!test_bit(R5_Insync, &dev->flags) || test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))))) {
+	if (need_this_block(sh, s, disk_idx, disks)) {
 		/* we would like to get this block, possibly by computing it,
 		 * otherwise read it if the backing disk is insync
 		 */
@@ -4081,7 +4149,7 @@ static void activate_bit_delay(struct r5conf *conf,
 	}
 }
 
-int md_raid5_congested(struct mddev *mddev, int bits)
+static int raid5_congested(struct mddev *mddev, int bits)
 {
 	struct r5conf *conf = mddev->private;
 
@@ -4098,24 +4166,14 @@ int md_raid5_congested(struct mddev *mddev, int bits)
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(md_raid5_congested);
-
-static int raid5_congested(void *data, int bits)
-{
-	struct mddev *mddev = data;
-
-	return mddev_congested(mddev, bits) ||
-		md_raid5_congested(mddev, bits);
-}
 
 /* We want read requests to align with chunks where possible,
  * but write requests don't need to.
  */
-static int raid5_mergeable_bvec(struct request_queue *q,
+static int raid5_mergeable_bvec(struct mddev *mddev,
 				struct bvec_merge_data *bvm,
 				struct bio_vec *biovec)
 {
-	struct mddev *mddev = q->queuedata;
 	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
 	int max;
 	unsigned int chunk_sectors = mddev->chunk_sectors;
@@ -5296,11 +5354,14 @@ static void raid5d(struct md_thread *thread)
 static ssize_t
 raid5_show_stripe_cache_size(struct mddev *mddev, char *page)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
 	if (conf)
-		return sprintf(page, "%d\n", conf->max_nr_stripes);
-	else
-		return 0;
+		ret = sprintf(page, "%d\n", conf->max_nr_stripes);
+	spin_unlock(&mddev->lock);
+	return ret;
 }
 
 int
@@ -5339,21 +5400,25 @@ EXPORT_SYMBOL(raid5_set_cache_size);
 static ssize_t
 raid5_store_stripe_cache_size(struct mddev *mddev, const char *page, size_t len)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
 	unsigned long new;
 	int err;
 
 	if (len >= PAGE_SIZE)
 		return -EINVAL;
-	if (!conf)
-		return -ENODEV;
-
 	if (kstrtoul(page, 10, &new))
 		return -EINVAL;
-	err = raid5_set_cache_size(mddev, new);
+	err = mddev_lock(mddev);
 	if (err)
 		return err;
-	return len;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else
+		err = raid5_set_cache_size(mddev, new);
+	mddev_unlock(mddev);
+
+	return err ?: len;
 }
 
 static struct md_sysfs_entry
@@ -5364,29 +5429,40 @@ raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
 static ssize_t
 raid5_show_preread_threshold(struct mddev *mddev, char *page)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
 	if (conf)
-		return sprintf(page, "%d\n", conf->bypass_threshold);
-	else
-		return 0;
+		ret = sprintf(page, "%d\n", conf->bypass_threshold);
+	spin_unlock(&mddev->lock);
+	return ret;
 }
 
 static ssize_t
 raid5_store_preread_threshold(struct mddev *mddev, const char *page, size_t len)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
 	unsigned long new;
+	int err;
+
 	if (len >= PAGE_SIZE)
 		return -EINVAL;
-	if (!conf)
-		return -ENODEV;
-
 	if (kstrtoul(page, 10, &new))
 		return -EINVAL;
-	if (new > conf->max_nr_stripes)
-		return -EINVAL;
-	conf->bypass_threshold = new;
-	return len;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else if (new > conf->max_nr_stripes)
+		err = -EINVAL;
+	else
+		conf->bypass_threshold = new;
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry
@@ -5398,39 +5474,48 @@ raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold,
 static ssize_t
 raid5_show_skip_copy(struct mddev *mddev, char *page)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
 	if (conf)
-		return sprintf(page, "%d\n", conf->skip_copy);
-	else
-		return 0;
+		ret = sprintf(page, "%d\n", conf->skip_copy);
+	spin_unlock(&mddev->lock);
+	return ret;
 }
 
 static ssize_t
 raid5_store_skip_copy(struct mddev *mddev, const char *page, size_t len)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
 	unsigned long new;
+	int err;
+
 	if (len >= PAGE_SIZE)
 		return -EINVAL;
-	if (!conf)
-		return -ENODEV;
-
 	if (kstrtoul(page, 10, &new))
 		return -EINVAL;
 	new = !!new;
-	if (new == conf->skip_copy)
-		return len;
 
-	mddev_suspend(mddev);
-	conf->skip_copy = new;
-	if (new)
-		mddev->queue->backing_dev_info.capabilities |=
-						BDI_CAP_STABLE_WRITES;
-	else
-		mddev->queue->backing_dev_info.capabilities &=
-						~BDI_CAP_STABLE_WRITES;
-	mddev_resume(mddev);
-	return len;
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else if (new != conf->skip_copy) {
+		mddev_suspend(mddev);
+		conf->skip_copy = new;
+		if (new)
+			mddev->queue->backing_dev_info.capabilities |=
+				BDI_CAP_STABLE_WRITES;
+		else
+			mddev->queue->backing_dev_info.capabilities &=
+				~BDI_CAP_STABLE_WRITES;
+		mddev_resume(mddev);
+	}
+	mddev_unlock(mddev);
+	return err ?: len;
 }
 
 static struct md_sysfs_entry
@@ -5454,11 +5539,14 @@ raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
 static ssize_t
 raid5_show_group_thread_cnt(struct mddev *mddev, char *page)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
 	if (conf)
-		return sprintf(page, "%d\n", conf->worker_cnt_per_group);
-	else
-		return 0;
+		ret = sprintf(page, "%d\n", conf->worker_cnt_per_group);
+	spin_unlock(&mddev->lock);
+	return ret;
 }
 
 static int alloc_thread_groups(struct r5conf *conf, int cnt,
@@ -5468,7 +5556,7 @@ static int alloc_thread_groups(struct r5conf *conf, int cnt,
 static ssize_t
 raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf;
 	unsigned long new;
 	int err;
 	struct r5worker_group *new_groups, *old_groups;
@@ -5476,41 +5564,41 @@ raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
 
 	if (len >= PAGE_SIZE)
 		return -EINVAL;
-	if (!conf)
-		return -ENODEV;
-
 	if (kstrtoul(page, 10, &new))
 		return -EINVAL;
 
-	if (new == conf->worker_cnt_per_group)
-		return len;
-
-	mddev_suspend(mddev);
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else if (new != conf->worker_cnt_per_group) {
+		mddev_suspend(mddev);
 
-	old_groups = conf->worker_groups;
-	if (old_groups)
-		flush_workqueue(raid5_wq);
+		old_groups = conf->worker_groups;
+		if (old_groups)
+			flush_workqueue(raid5_wq);
 
-	err = alloc_thread_groups(conf, new,
-				  &group_cnt, &worker_cnt_per_group,
-				  &new_groups);
-	if (!err) {
-		spin_lock_irq(&conf->device_lock);
-		conf->group_cnt = group_cnt;
-		conf->worker_cnt_per_group = worker_cnt_per_group;
-		conf->worker_groups = new_groups;
-		spin_unlock_irq(&conf->device_lock);
+		err = alloc_thread_groups(conf, new,
+					  &group_cnt, &worker_cnt_per_group,
+					  &new_groups);
+		if (!err) {
+			spin_lock_irq(&conf->device_lock);
+			conf->group_cnt = group_cnt;
+			conf->worker_cnt_per_group = worker_cnt_per_group;
+			conf->worker_groups = new_groups;
+			spin_unlock_irq(&conf->device_lock);
 
-		if (old_groups)
-			kfree(old_groups[0].workers);
-		kfree(old_groups);
+			if (old_groups)
+				kfree(old_groups[0].workers);
+			kfree(old_groups);
+		}
+		mddev_resume(mddev);
 	}
+	mddev_unlock(mddev);
 
-	mddev_resume(mddev);
-
-	if (err)
-		return err;
-	return len;
+	return err ?: len;
 }
 
 static struct md_sysfs_entry
@@ -6178,11 +6266,6 @@ static int run(struct mddev *mddev)
 		if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
 			mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
 
-		blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
-
-		mddev->queue->backing_dev_info.congested_data = mddev;
-		mddev->queue->backing_dev_info.congested_fn = raid5_congested;
-
 		chunk_size = mddev->chunk_sectors << 9;
 		blk_queue_io_min(mddev->queue, chunk_size);
 		blk_queue_io_opt(mddev->queue, chunk_size *
@@ -6260,17 +6343,12 @@ abort:
 	return -EIO;
 }
 
-static int stop(struct mddev *mddev)
+static void raid5_free(struct mddev *mddev, void *priv)
 {
-	struct r5conf *conf = mddev->private;
+	struct r5conf *conf = priv;
 
-	md_unregister_thread(&mddev->thread);
-	if (mddev->queue)
-		mddev->queue->backing_dev_info.congested_fn = NULL;
 	free_conf(conf);
-	mddev->private = NULL;
 	mddev->to_remove = &raid5_attrs_group;
-	return 0;
 }
 
 static void status(struct seq_file *seq, struct mddev *mddev)
@@ -7044,7 +7122,7 @@ static struct md_personality raid6_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid5_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid5_add_disk,
@@ -7058,6 +7136,8 @@ static struct md_personality raid6_personality =
 	.finish_reshape = raid5_finish_reshape,
 	.quiesce	= raid5_quiesce,
 	.takeover	= raid6_takeover,
+	.congested	= raid5_congested,
+	.mergeable_bvec	= raid5_mergeable_bvec,
 };
 static struct md_personality raid5_personality =
 {
@@ -7066,7 +7146,7 @@ static struct md_personality raid5_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid5_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid5_add_disk,
@@ -7080,6 +7160,8 @@ static struct md_personality raid5_personality =
 	.finish_reshape = raid5_finish_reshape,
 	.quiesce	= raid5_quiesce,
 	.takeover	= raid5_takeover,
+	.congested	= raid5_congested,
+	.mergeable_bvec	= raid5_mergeable_bvec,
 };
 
 static struct md_personality raid4_personality =
@@ -7089,7 +7171,7 @@ static struct md_personality raid4_personality =
 	.owner		= THIS_MODULE,
 	.make_request	= make_request,
 	.run		= run,
-	.stop		= stop,
+	.free		= raid5_free,
 	.status		= status,
 	.error_handler	= error,
 	.hot_add_disk	= raid5_add_disk,
@@ -7103,6 +7185,8 @@ static struct md_personality raid4_personality =
 	.finish_reshape = raid5_finish_reshape,
 	.quiesce	= raid5_quiesce,
 	.takeover	= raid4_takeover,
+	.congested	= raid5_congested,
+	.mergeable_bvec	= raid5_mergeable_bvec,
 };
 
 static int __init raid5_init(void)
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index d59f5ca743cd..983e18a83db1 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -558,7 +558,6 @@ static inline int algorithm_is_DDF(int layout)
 	return layout >= 8 && layout <= 10;
 }
 
-extern int md_raid5_congested(struct mddev *mddev, int bits);
 extern void md_raid5_kick_device(struct r5conf *conf);
 extern int raid5_set_cache_size(struct mddev *mddev, int size);
 #endif