[PATCH v6 6/8] null_blk: use zone_size_sects_shift for power of 2 zoned devices

[Pankaj Raghav]

Instead of doing is_power_of_2 and ilog2 operation for every IO, cache
the zone_size_sects_shift variable and use it for power of 2 zoned
devices.

This variable will be set to zero for non power of 2 zoned devices.

Suggested-by: Damien Le Moal <damien.lemoal at wdc.com>
Reviewed-by: Hannes Reinecke <hare at suse.de>
Reviewed-by: Luis Chamberlain <mcgrof at kernel.org>
Signed-off-by: Pankaj Raghav <p.raghav at samsung.com>
---
 drivers/block/null_blk/null_blk.h |  6 ++++++
 drivers/block/null_blk/zoned.c    | 11 ++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index 78eb56b0ca55..3d6e41a9491f 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -74,6 +74,12 @@ struct nullb_device {
 	unsigned int imp_close_zone_no;
 	struct nullb_zone *zones;
 	sector_t zone_size_sects;
+	/*
+	 * zone_size_sects_shift is only useful when the zone size is
+	 * power of 2. This variable is set to zero when zone size is non
+	 * power of 2.
+	 */
+	unsigned int zone_size_sects_shift;
 	bool need_zone_res_mgmt;
 	spinlock_t zone_res_lock;
 
diff --git a/drivers/block/null_blk/zoned.c b/drivers/block/null_blk/zoned.c
index b79091b5e4b1..a8be1011def5 100644
--- a/drivers/block/null_blk/zoned.c
+++ b/drivers/block/null_blk/zoned.c
@@ -13,8 +13,8 @@ static inline sector_t mb_to_sects(unsigned long mb)
 
 static inline unsigned int null_zone_no(struct nullb_device *dev, sector_t sect)
 {
-	if (is_power_of_2(dev->zone_size_sects))
-		return sect >> ilog2(dev->zone_size_sects);
+	if (dev->zone_size_sects_shift)
+		return sect >> dev->zone_size_sects_shift;
 
 	return div64_u64(sect, dev->zone_size_sects);
 }
@@ -82,9 +82,14 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
 	zone_capacity_sects = mb_to_sects(dev->zone_capacity);
 	dev_capacity_sects = mb_to_sects(dev->size);
 	dev->zone_size_sects = mb_to_sects(dev->zone_size);
+
+	if (is_power_of_2(dev->zone_size_sects))
+		dev->zone_size_sects_shift = ilog2(dev->zone_size_sects);
+	else
+		dev->zone_size_sects_shift = 0;
+
 	dev->nr_zones =	DIV_ROUND_UP_SECTOR_T(dev_capacity_sects,
 					      dev->zone_size_sects);
-
 	dev->zones = kvmalloc_array(dev->nr_zones, sizeof(struct nullb_zone),
 				    GFP_KERNEL | __GFP_ZERO);
 	if (!dev->zones)
-- 
2.25.1