[PATCH 01/13] block: freeze queue when updating zone resources

[Damien Le Moal]

Modify disk_update_zone_resources() to freeze the device queue before
updating the number of zones, zone capacity and other zone related
resources. The locking order resulting from the call to
queue_limits_commit_update_frozen() is preserved, that is, the queue
limits lock is first taken by calling queue_limits_start_update() before
freezing the queue, and the queue is unfrozen after executing
queue_limits_commit_update(), which replaces the call to
queue_limits_commit_update_frozen().

This change ensures that there are no in-flights I/Os when the zone
resources are updated due to a zone revalidation.

Fixes: 0b83c86b444a ("block: Prevent potential deadlock in blk_revalidate_disk_zones()")
Cc: stable at vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal at kernel.org>
---
 block/blk-zoned.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 5e2a5788dc3b..f3b371056df4 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1516,8 +1516,13 @@ static int disk_update_zone_resources(struct gendisk *disk,
 {
 	struct request_queue *q = disk->queue;
 	unsigned int nr_seq_zones, nr_conv_zones;
-	unsigned int pool_size;
+	unsigned int pool_size, memflags;
 	struct queue_limits lim;
+	int ret;
+
+	lim = queue_limits_start_update(q);
+
+	memflags = blk_mq_freeze_queue(q);
 
 	disk->nr_zones = args->nr_zones;
 	disk->zone_capacity = args->zone_capacity;
@@ -1527,11 +1532,10 @@ static int disk_update_zone_resources(struct gendisk *disk,
 	if (nr_conv_zones >= disk->nr_zones) {
 		pr_warn("%s: Invalid number of conventional zones %u / %u\n",
 			disk->disk_name, nr_conv_zones, disk->nr_zones);
-		return -ENODEV;
+		ret = -ENODEV;
+		goto unfreeze;
 	}
 
-	lim = queue_limits_start_update(q);
-
 	/*
 	 * Some devices can advertize zone resource limits that are larger than
 	 * the number of sequential zones of the zoned block device, e.g. a
@@ -1568,7 +1572,12 @@ static int disk_update_zone_resources(struct gendisk *disk,
 	}
 
 commit:
-	return queue_limits_commit_update_frozen(q, &lim);
+	ret = queue_limits_commit_update(q, &lim);
+
+unfreeze:
+	blk_mq_unfreeze_queue(q, memflags);
+
+	return ret;
 }
 
 static int blk_revalidate_conv_zone(struct blk_zone *zone, unsigned int idx,
-- 
2.51.0