[PATCH v7 08/28] block: Fake max open zones limit when there is no limit

Damien Le Moal
2024-04-08T01:41:46Z

For a zoned block device that has no limit on the number of open zones
and no limit on the number of active zones, the zone write plug mempool
is created with a size of 128 zone write plugs. For such case, set the
device max_open_zones queue limit to this value to indicate to the user
the potential performance penalty that may happen when writing
simultaneously to more zones than the mempool size.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Tested-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
---
block/blk-zoned.c | 41 +++++++++++++++++++++++++++++++++++------
1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index fefcebd70445..4b21a1ec00d4 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1503,6 +1503,38 @@ struct blk_revalidate_zone_args {
sector_t sector;
};

+/*
+ * Update the disk zone resources information and device queue limits.
+ * The disk queue is frozen when this is executed.
+ */
+static int disk_update_zone_resources(struct gendisk *disk,
+ struct blk_revalidate_zone_args *args)
+{
+ struct request_queue *q = disk->queue;
+ struct queue_limits lim;
+
+ disk->nr_zones = args->nr_zones;
+ disk->zone_capacity = args->zone_capacity;
+ swap(disk->seq_zones_wlock, args->seq_zones_wlock);
+ swap(disk->conv_zones_bitmap, args->conv_zones_bitmap);
+
+ /*
+ * If the device has no limit on the maximum number of open and active
+ * zones, set its max open zone limit to the mempool size to indicate
+ * to the user that there is a potential performance impact due to
+ * dynamic zone write plug allocation when simultaneously writing to
+ * more zones than the size of the mempool.
+ */
+ if (disk->zone_wplugs_pool) {
+ lim = queue_limits_start_update(q);
+ if (!lim.max_open_zones && !lim.max_active_zones)
+ lim.max_open_zones = disk->zone_wplugs_pool->min_nr;
+ return queue_limits_commit_update(q, &lim);
+ }
+
+ return 0;
+}
+
/*
* Helper function to check the validity of zones of a zoned block device.
*/
@@ -1703,17 +1735,14 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
*/
blk_mq_freeze_queue(q);
if (ret > 0) {
- disk->nr_zones = args.nr_zones;
- disk->zone_capacity = args.zone_capacity;
- swap(disk->seq_zones_wlock, args.seq_zones_wlock);
- swap(disk->conv_zones_bitmap, args.conv_zones_bitmap);
+ ret = disk_update_zone_resources(disk, &args);
if (update_driver_data)
update_driver_data(disk);
- ret = 0;
} else {
pr_warn("%s: failed to revalidate zones\n", disk->disk_name);
- disk_free_zone_resources(disk);
}
+ if (ret)
+ disk_free_zone_resources(disk);
blk_mq_unfreeze_queue(q);

kfree(args.seq_zones_wlock);
--
2.44.0