[PATCH v4 05/13] btrfs: zoned: Cache superblock location in btrfs_zoned_device_info

[Pankaj Raghav]

Instead of calculating the superblock location every time, cache the
superblock zone location in btrfs_zoned_device_info struct and use it to
locate the zone index.

The functions such as btrfs_sb_log_location_bdev() and
btrfs_reset_sb_log_zones() which work directly on block_device shall
continue to use the sb_zone_number because btrfs_zoned_device_info
struct might not have been initialized at that point.

This patch will enable non power-of-2 zoned devices to not perform
division to lookup superblock and its mirror location.

Reviewed-by: Luis Chamberlain <mcgrof at kernel.org>
Signed-off-by: Pankaj Raghav <p.raghav at samsung.com>
---
 fs/btrfs/zoned.c | 13 +++++++++----
 fs/btrfs/zoned.h |  1 +
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 06f22c021..e8c7cebb2 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -511,6 +511,11 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device, bool populate_cache)
 			   max_active_zones - nactive);
 	}
 
+	/* Cache the sb zone number */
+	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; ++i) {
+		zone_info->sb_zone_location[i] =
+			sb_zone_number(zone_info->zone_size_shift, i);
+	}
 	/* Validate superblock log */
 	nr_zones = BTRFS_NR_SB_LOG_ZONES;
 	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
@@ -518,7 +523,7 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device, bool populate_cache)
 		u64 sb_wp;
 		int sb_pos = BTRFS_NR_SB_LOG_ZONES * i;
 
-		sb_zone = sb_zone_number(zone_info->zone_size_shift, i);
+		sb_zone = zone_info->sb_zone_location[i];
 		if (sb_zone + 1 >= zone_info->nr_zones)
 			continue;
 
@@ -866,7 +871,7 @@ int btrfs_sb_log_location(struct btrfs_device *device, int mirror, int rw,
 		return 0;
 	}
 
-	zone_num = sb_zone_number(zinfo->zone_size_shift, mirror);
+	zone_num = zinfo->sb_zone_location[mirror];
 	if (zone_num + 1 >= zinfo->nr_zones)
 		return -ENOENT;
 
@@ -883,7 +888,7 @@ static inline bool is_sb_log_zone(struct btrfs_zoned_device_info *zinfo,
 	if (!zinfo)
 		return false;
 
-	zone_num = sb_zone_number(zinfo->zone_size_shift, mirror);
+	zone_num = zinfo->sb_zone_location[mirror];
 	if (zone_num + 1 >= zinfo->nr_zones)
 		return false;
 
@@ -1011,7 +1016,7 @@ u64 btrfs_find_allocatable_zones(struct btrfs_device *device, u64 hole_start,
 			u32 sb_zone;
 			u64 sb_pos;
 
-			sb_zone = sb_zone_number(shift, i);
+			sb_zone = zinfo->sb_zone_location[i];
 			if (!(end <= sb_zone ||
 			      sb_zone + BTRFS_NR_SB_LOG_ZONES <= begin)) {
 				have_sb = true;
diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
index 10f31d1c8..694ab6d1e 100644
--- a/fs/btrfs/zoned.h
+++ b/fs/btrfs/zoned.h
@@ -27,6 +27,7 @@ struct btrfs_zoned_device_info {
 	unsigned long *active_zones;
 	struct blk_zone *zone_cache;
 	struct blk_zone sb_zones[2 * BTRFS_SUPER_MIRROR_MAX];
+	u32 sb_zone_location[BTRFS_SUPER_MIRROR_MAX];
 };
 
 #ifdef CONFIG_BLK_DEV_ZONED
-- 
2.25.1