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From:   Pankaj Raghav <p.raghav@samsung.com>
To:     axboe@kernel.dk, damien.lemoal@opensource.wdc.com,
        pankydev8@gmail.com, dsterba@suse.com, hch@lst.de
Cc:     linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org,
        linux-btrfs@vger.kernel.org, jiangbo.365@bytedance.com,
        linux-block@vger.kernel.org, gost.dev@samsung.com,
        p.raghav@samsung.com, linux-kernel@vger.kernel.org,
        dm-devel@redhat.com, Damien Le Moal <damien.lemoal@wdc.com>
Subject: [PATCH v4 12/13] null_blk: use zone_size_sects_shift for power of 2
 zoned devices
Date:   Mon, 16 May 2022 18:54:15 +0200
Message-Id: <20220516165416.171196-13-p.raghav@samsung.com>
In-Reply-To: <20220516165416.171196-1-p.raghav@samsung.com>
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References: <20220516165416.171196-1-p.raghav@samsung.com>
        <CGME20220516165435eucas1p1dff8d9d039a76278ef1c09dba4b4e1fe@eucas1p1.samsung.com>
Precedence: bulk

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@wdc.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 drivers/block/null_blk/null_blk.h |  6 ++++++
 drivers/block/null_blk/zoned.c    | 10 ++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index 4525a65e1..3bbae8be4 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -76,6 +76,12 @@ 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 00c34e65e..806bef98a 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);
 }
@@ -82,6 +82,12 @@ 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 =
 		div64_u64(roundup(dev_capacity_sects, dev->zone_size_sects),
 			  dev->zone_size_sects);
-- 
2.25.1