[PATCH v4 2/2] md: suspend the array instead of freezing the queue for limits updates

[Jack Wang]

Provide ->suspend() and ->resume() for md_fops using mddev_suspend() and
mddev_resume(), so sysfs limits updates no longer freeze the queue.

mddev_suspend() only waits for active_io, but md_submit_bio() reads the
limits in bio_split_to_limits() before taking it. A bio already there may
see a mix of old and new limits, as with mddev_update_io_opt().

Fixes: c99f66e4084a ("block: fix queue freeze vs limits lock order in sysfs store methods")
Suggested-by: Yu Kuai <yukuai@xxxxxxx>
Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxx>
---
 drivers/md/md.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 03e35386a802..c9fa4e99569a 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8669,6 +8669,16 @@ static unsigned int md_check_events(struct gendisk *disk, unsigned int clearing)
 	return ret;
 }
 
+static int md_suspend_disk(struct gendisk *disk)
+{
+	return mddev_suspend(disk->private_data, true);
+}
+
+static void md_resume_disk(struct gendisk *disk)
+{
+	mddev_resume(disk->private_data);
+}
+
 static void md_free_disk(struct gendisk *disk)
 {
 	struct mddev *mddev = disk->private_data;
@@ -8689,6 +8699,8 @@ const struct block_device_operations md_fops =
 	.getgeo		= md_getgeo,
 	.check_events	= md_check_events,
 	.set_read_only	= md_set_read_only,
+	.suspend	= md_suspend_disk,
+	.resume		= md_resume_disk,
 	.free_disk	= md_free_disk,
 };
 
-- 
2.43.0