[PATCH 6.3 231/286] block: fix revalidate performance regression

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From: Damien Le Moal <dlemoal@xxxxxxxxxx>

commit 47fe1c3064c6bc1bfa3c032ff78e603e5dd6e5bc upstream.

The scsi driver function sd_read_block_characteristics() always calls
disk_set_zoned() to 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 disk_clear_zone_settings() done from
disk_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
disk_clear_zone_settings() in disk_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@xxxxxxxxxxxxxxx>

Fixes: 508aebb80527 ("block: introduce blk_queue_clear_zone_settings()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230529073237.1339862-1-dlemoal@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 block/blk-settings.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -915,6 +915,7 @@ static bool disk_has_partitions(struct g
 void disk_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:
@@ -952,7 +953,7 @@ void disk_set_zoned(struct gendisk *disk
 		 */
 		blk_queue_zone_write_granularity(q,
 						queue_logical_block_size(q));
-	} else {
+	} else if (old_model != BLK_ZONED_NONE) {
 		disk_clear_zone_settings(disk);
 	}
 }





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