[PATCH v2 02/15] block: freeze queue when updating zone resources

[Damien Le Moal <dlemoal@kernel.org>]

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. In case of error when
the limits are applied, directly call disk_free_zone_resources() from
disk_update_zone_resources() while the disk queue is still frozen to
avoid needing to freeze & unfreeze the queue again in
blk_revalidate_disk_zones(), thus simplifying that function code a
little.

Fixes: 0b83c86b444a ("block: Prevent potential deadlock in blk_revalidate_disk_zones()")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
---
 block/blk-zoned.c | 42 ++++++++++++++++++++++++------------------
 1 file changed, 24 insertions(+), 18 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 1621e8f78338..39381f2b2e94 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1557,8 +1557,13 @@ 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 = 0;
+
+	lim = queue_limits_start_update(q);
+
+	memflags = blk_mq_freeze_queue(q);
 
 	disk->nr_zones = args->nr_zones;
 	disk->zone_capacity = args->zone_capacity;
@@ -1568,11 +1573,10 @@ 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
@@ -1609,7 +1613,15 @@ 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:
+	if (ret)
+		disk_free_zone_resources(disk);
+
+	blk_mq_unfreeze_queue(q, memflags);
+
+	return ret;
 }
 
 static int blk_revalidate_conv_zone(struct blk_zone *zone, unsigned int idx,
@@ -1774,7 +1786,7 @@ int blk_revalidate_disk_zones(struct gendisk *disk)
 	sector_t zone_sectors = q->limits.chunk_sectors;
 	sector_t capacity = get_capacity(disk);
 	struct blk_revalidate_zone_args args = { };
-	unsigned int noio_flag;
+	unsigned int memflags, noio_flag;
 	int ret = -ENOMEM;
 
 	if (WARN_ON_ONCE(!blk_queue_is_zoned(q)))
@@ -1824,20 +1836,14 @@ int blk_revalidate_disk_zones(struct gendisk *disk)
 		ret = -ENODEV;
 	}
 
-	/*
-	 * Set the new disk zone parameters only once the queue is frozen and
-	 * all I/Os are completed.
-	 */
 	if (ret > 0)
-		ret = disk_update_zone_resources(disk, &args);
-	else
-		pr_warn("%s: failed to revalidate zones\n", disk->disk_name);
-	if (ret) {
-		unsigned int memflags = blk_mq_freeze_queue(q);
+		return disk_update_zone_resources(disk, &args);
 
-		disk_free_zone_resources(disk);
-		blk_mq_unfreeze_queue(q, memflags);
-	}
+	pr_warn("%s: failed to revalidate zones\n", disk->disk_name);
+
+	memflags = blk_mq_freeze_queue(q);
+	disk_free_zone_resources(disk);
+	blk_mq_unfreeze_queue(q, memflags);
 
 	return ret;
 }
-- 
2.51.0