[PATCH 5.15.y] block: fix revalidate performance regression

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

commit 47fe1c3064c6bc1bfa3c032ff78e603e5dd6e5bc upstream.

The scsi driver function sd_read_block_characteristics() always calls
blk_queue_set_zoned() to set a disk zoned model correctly, in case the
device model changed. This is done even for regular disks to set the
zoned model to BLK_ZONED_NONE and free any zone related resources if the
drive previously was zoned.

This behavior significantly impact the time it takes to revalidate disks
on a large system as the call to blk_queue_clear_zone_settings() done
from blk_queue_set_zoned() for the BLK_ZONED_NONE case results in the
device request queued to be frozen, even if there are no zone resources
to free.

Avoid this overhead for non-zoned devices by not calling
blk_queue_clear_zone_settings() in blk_queue_set_zoned() if the device
model was already set to BLK_ZONED_NONE, which is always the case for
regular devices.

Reported by: Brian Bunker <brian@purestorage.com>
Fixes: 508aebb80527 ("block: introduce blk_queue_clear_zone_settings()")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230529073237.1339862-1-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/blk-settings.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index b880c70e22e4..73a80895e3ae 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -875,6 +875,7 @@ static bool disk_has_partitions(struct gendisk *disk)
 void blk_queue_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
 {
 	struct request_queue *q = disk->queue;
+	unsigned int old_model = q->limits.zoned;
 
 	switch (model) {
 	case BLK_ZONED_HM:
@@ -912,7 +913,7 @@ void blk_queue_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
 		 */
 		blk_queue_zone_write_granularity(q,
 						queue_logical_block_size(q));
-	} else {
+	} else if (old_model != BLK_ZONED_NONE) {
 		blk_queue_clear_zone_settings(q);
 	}
 }
-- 
2.40.1