The '2' argument means "wake up anything that is waiting".
This is an inelegant part of the design and was added
to help support management of suspend_lo/suspend_hi setting.
Now that suspend_lo/hi is managed in mddev_suspend/resume,
that need is gone.
These is still a couple of places where we call 'quiesce'
with an argument of '2', but they can safely be changed to
call ->quiesce(.., 1); ->quiesce(.., 0) which
achieve the same result at the small cost of pausing IO
briefly.

This removes a small "optimization" from suspend_{hi,lo}_store,
but it isn't clear that optimization served a useful purpose.
The code now is a lot clearer.

Suggested-by: Shaohua Li <shli@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.com>
---

As suggested, this remove the special meaning of '2'.

Thanks,
NeilBrown

 drivers/md/md-cluster.c  |  6 +++---
 drivers/md/md.c          | 34 ++++++++++------------------------
 drivers/md/md.h          |  9 ++++-----
 drivers/md/raid0.c       |  2 +-
 drivers/md/raid1.c       | 13 +++----------
 drivers/md/raid10.c      | 10 +++-------
 drivers/md/raid5-cache.c | 12 ++++++------
 drivers/md/raid5-log.h   |  2 +-
 drivers/md/raid5.c       | 18 ++++++------------
 9 files changed, 37 insertions(+), 69 deletions(-)

diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 03082e17c65c..72ce0bccc865 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -442,10 +442,11 @@ static void __remove_suspend_info(struct md_cluster_info *cinfo, int slot)
 static void remove_suspend_info(struct mddev *mddev, int slot)
 {
 	struct md_cluster_info *cinfo = mddev->cluster_info;
+	mddev->pers->quiesce(mddev, 1);
 	spin_lock_irq(&cinfo->suspend_lock);
 	__remove_suspend_info(cinfo, slot);
 	spin_unlock_irq(&cinfo->suspend_lock);
-	mddev->pers->quiesce(mddev, 2);
+	mddev->pers->quiesce(mddev, 0);
 }
 
 
@@ -492,13 +493,12 @@ static void process_suspend_info(struct mddev *mddev,
 	s->lo = lo;
 	s->hi = hi;
 	mddev->pers->quiesce(mddev, 1);
-	mddev->pers->quiesce(mddev, 0);
 	spin_lock_irq(&cinfo->suspend_lock);
 	/* Remove existing entry (if exists) before adding */
 	__remove_suspend_info(cinfo, slot);
 	list_add(&s->list, &cinfo->suspend_list);
 	spin_unlock_irq(&cinfo->suspend_lock);
-	mddev->pers->quiesce(mddev, 2);
+	mddev->pers->quiesce(mddev, 0);
 }
 
 static void process_add_new_disk(struct mddev *mddev, struct cluster_msg *cmsg)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4be3140adfe8..e1e7e8dc6878 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4857,7 +4857,7 @@ suspend_lo_show(struct mddev *mddev, char *page)
 static ssize_t
 suspend_lo_store(struct mddev *mddev, const char *buf, size_t len)
 {
-	unsigned long long old, new;
+	unsigned long long new;
 	int err;
 
 	err = kstrtoull(buf, 10, &new);
@@ -4873,17 +4873,10 @@ suspend_lo_store(struct mddev *mddev, const char *buf, size_t len)
 	if (mddev->pers == NULL ||
 	    mddev->pers->quiesce == NULL)
 		goto unlock;
-	old = mddev->suspend_lo;
+	mddev_suspend(mddev);
 	mddev->suspend_lo = new;
-	if (new >= old) {
-		/* Shrinking suspended region */
-		wake_up(&mddev->sb_wait);
-		mddev->pers->quiesce(mddev, 2);
-	} else {
-		/* Expanding suspended region - need to wait */
-		mddev_suspend(mddev);
-		mddev_resume(mddev);
-	}
+	mddev_resume(mddev);
+
 	err = 0;
 unlock:
 	mddev_unlock(mddev);
@@ -4901,7 +4894,7 @@ suspend_hi_show(struct mddev *mddev, char *page)
 static ssize_t
 suspend_hi_store(struct mddev *mddev, const char *buf, size_t len)
 {
-	unsigned long long old, new;
+	unsigned long long new;
 	int err;
 
 	err = kstrtoull(buf, 10, &new);
@@ -4914,20 +4907,13 @@ suspend_hi_store(struct mddev *mddev, const char *buf, size_t len)
 	if (err)
 		return err;
 	err = -EINVAL;
-	if (mddev->pers == NULL ||
-	    mddev->pers->quiesce == NULL)
+	if (mddev->pers == NULL)
 		goto unlock;
-	old = mddev->suspend_hi;
+
+	mddev_suspend(mddev);
 	mddev->suspend_hi = new;
-	if (new <= old) {
-		/* Shrinking suspended region */
-		wake_up(&mddev->sb_wait);
-		mddev->pers->quiesce(mddev, 2);
-	} else {
-		/* Expanding suspended region - need to wait */
-		mddev_suspend(mddev);
-		mddev_resume(mddev);
-	}
+	mddev_resume(mddev);
+
 	err = 0;
 unlock:
 	mddev_unlock(mddev);
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 8c2158f3bd59..5dcdba84932f 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -545,12 +545,11 @@ struct md_personality
 	int (*check_reshape) (struct mddev *mddev);
 	int (*start_reshape) (struct mddev *mddev);
 	void (*finish_reshape) (struct mddev *mddev);
-	/* quiesce moves between quiescence states
-	 * 0 - fully active
-	 * 1 - no new requests allowed
-	 * others - reserved
+	/* quiesce suspends or resumes internal processing.
+	 * 1 - stop new actions and wait for action io to complete
+	 * 0 - return to normal behaviour
 	 */
-	void (*quiesce) (struct mddev *mddev, int state);
+	void (*quiesce) (struct mddev *mddev, int quiesce);
 	/* takeover is used to transition an array from one
 	 * personality to another.  The new personality must be able
 	 * to handle the data in the current layout.
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 5a00fc118470..5ecba9eef441 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -768,7 +768,7 @@ static void *raid0_takeover(struct mddev *mddev)
 	return ERR_PTR(-EINVAL);
 }
 
-static void raid0_quiesce(struct mddev *mddev, int state)
+static void raid0_quiesce(struct mddev *mddev, int quiesce)
 {
 }
 
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 277a145b3ff5..5f21cb9ac778 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -3273,21 +3273,14 @@ static int raid1_reshape(struct mddev *mddev)
 	return 0;
 }
 
-static void raid1_quiesce(struct mddev *mddev, int state)
+static void raid1_quiesce(struct mddev *mddev, int quiesce)
 {
 	struct r1conf *conf = mddev->private;
 
-	switch(state) {
-	case 2: /* wake for suspend */
-		wake_up(&conf->wait_barrier);
-		break;
-	case 1:
+	if (quiesce)
 		freeze_array(conf, 0);
-		break;
-	case 0:
+	else
 		unfreeze_array(conf);
-		break;
-	}
 }
 
 static void *raid1_takeover(struct mddev *mddev)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 374df5796649..76f042bf9a57 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3832,18 +3832,14 @@ static void raid10_free(struct mddev *mddev, void *priv)
 	kfree(conf);
 }
 
-static void raid10_quiesce(struct mddev *mddev, int state)
+static void raid10_quiesce(struct mddev *mddev, int quiesce)
 {
 	struct r10conf *conf = mddev->private;
 
-	switch(state) {
-	case 1:
+	if (quiesce)
 		raise_barrier(conf, 0);
-		break;
-	case 0:
+	else
 		lower_barrier(conf);
-		break;
-	}
 }
 
 static int raid10_resize(struct mddev *mddev, sector_t sectors)
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 6a631dd21f0b..fce290878eb5 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1589,21 +1589,21 @@ void r5l_wake_reclaim(struct r5l_log *log, sector_t space)
 	md_wakeup_thread(log->reclaim_thread);
 }
 
-void r5l_quiesce(struct r5l_log *log, int state)
+void r5l_quiesce(struct r5l_log *log, int quiesce)
 {
 	struct mddev *mddev;
-	if (!log || state == 2)
+	if (!log)
 		return;
-	if (state == 0)
-		kthread_unpark(log->reclaim_thread->tsk);
-	else if (state == 1) {
+
+	if (quiesce) {
 		/* make sure r5l_write_super_and_discard_space exits */
 		mddev = log->rdev->mddev;
 		wake_up(&mddev->sb_wait);
 		kthread_park(log->reclaim_thread->tsk);
 		r5l_wake_reclaim(log, MaxSector);
 		r5l_do_reclaim(log);
-	}
+	} else
+		kthread_unpark(log->reclaim_thread->tsk);
 }
 
 bool r5l_log_disk_error(struct r5conf *conf)
diff --git a/drivers/md/raid5-log.h b/drivers/md/raid5-log.h
index 328d67aedda4..c3596a27a5a8 100644
--- a/drivers/md/raid5-log.h
+++ b/drivers/md/raid5-log.h
@@ -8,7 +8,7 @@ extern void r5l_write_stripe_run(struct r5l_log *log);
 extern void r5l_flush_stripe_to_raid(struct r5l_log *log);
 extern void r5l_stripe_write_finished(struct stripe_head *sh);
 extern int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio);
-extern void r5l_quiesce(struct r5l_log *log, int state);
+extern void r5l_quiesce(struct r5l_log *log, int quiesce);
 extern bool r5l_log_disk_error(struct r5conf *conf);
 extern bool r5c_is_writeback(struct r5l_log *log);
 extern int
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 89ad79614309..13db3d31e983 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -8026,16 +8026,12 @@ static void raid5_finish_reshape(struct mddev *mddev)
 	}
 }
 
-static void raid5_quiesce(struct mddev *mddev, int state)
+static void raid5_quiesce(struct mddev *mddev, int quiesce)
 {
 	struct r5conf *conf = mddev->private;
 
-	switch(state) {
-	case 2: /* resume for a suspend */
-		wake_up(&conf->wait_for_overlap);
-		break;
-
-	case 1: /* stop all writes */
+	if (quiesce) {
+		/* stop all writes */
 		lock_all_device_hash_locks_irq(conf);
 		/* '2' tells resync/reshape to pause so that all
 		 * active stripes can drain
@@ -8051,17 +8047,15 @@ static void raid5_quiesce(struct mddev *mddev, int state)
 		unlock_all_device_hash_locks_irq(conf);
 		/* allow reshape to continue */
 		wake_up(&conf->wait_for_overlap);
-		break;
-
-	case 0: /* re-enable writes */
+	} else {
+		/* re-enable writes */
 		lock_all_device_hash_locks_irq(conf);
 		conf->quiesce = 0;
 		wake_up(&conf->wait_for_quiescent);
 		wake_up(&conf->wait_for_overlap);
 		unlock_all_device_hash_locks_irq(conf);
-		break;
 	}
-	r5l_quiesce(conf->log, state);
+	r5l_quiesce(conf->log, quiesce);
 }
 
 static void *raid45_takeover_raid0(struct mddev *mddev, int level)
-- 
2.14.0.rc0.dirty