block: introduce bdev_zone_start()

Introduce the function bdev_zone_start() as a more explicit (and clear)
replacement for ALIGN_DOWN() to get the start sector of a zone
containing a particular sector of a zoned block device.

Use this new helper in blkdev_get_zone_info() and
blkdev_report_zones_cached().

Signed-off-by: Damien Le Moal <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: damien-lemoal

block/blk-zoned.c

@@ -950,7 +950,7 @@ int blkdev_get_zone_info(struct block_device *bdev, sector_t sector,
 		return -EINVAL;
 
 	memset(zone, 0, sizeof(*zone));
-	sector = ALIGN_DOWN(sector, zone_sectors);
+	sector = bdev_zone_start(bdev, sector);
 
 	if (!blkdev_has_cached_report_zones(bdev))
 		return blkdev_report_zone_fallback(bdev, sector, zone);
@@ -1068,7 +1068,7 @@ int blkdev_report_zones_cached(struct block_device *bdev, sector_t sector,
 		return blkdev_do_report_zones(bdev, sector, nr_zones, &args);
 	}
 
-	for (sector = ALIGN_DOWN(sector, zone_sectors);
+	for (sector = bdev_zone_start(bdev, sector);
 	     sector < capacity && idx < nr_zones;
 	     sector += zone_sectors, idx++) {
 		ret = blkdev_get_zone_info(bdev, sector, &zone);

include/linux/blkdev.h

@@ -1522,6 +1522,12 @@ static inline sector_t bdev_zone_sectors(struct block_device *bdev)
 	return q->limits.chunk_sectors;
 }
 
+static inline sector_t bdev_zone_start(struct block_device *bdev,
+				       sector_t sector)
+{
+	return sector & ~(bdev_zone_sectors(bdev) - 1);
+}
+
 static inline sector_t bdev_offset_from_zone_start(struct block_device *bdev,
 						   sector_t sector)
 {