dm zoned: ignore last smaller runt zone

The SCSI layer allows ZBC drives to have a smaller last runt zone. For
such a device, specifying the entire capacity for a dm-zoned target
table entry fails because the specified capacity is not aligned on a
device zone size indicated in the request queue structure of the
device.

Fix this problem by ignoring the last runt zone in the entry length
when seting up the dm-zoned target (ctr method) and when iterating table
entries of the target (iterate_devices method). This allows dm-zoned
users to still easily setup a target using the entire device capacity
(as mandated by dm-zoned) or the aligned capacity excluding the last
runt zone.

While at it, replace direct references to the device queue chunk_sectors
limit with calls to the accessor blk_queue_zone_sectors().

Reported-by: Peter Desnoyers <pjd@ccs.neu.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-zoned-target.c

@@ -660,6 +660,7 @@ static int dmz_get_zoned_device(struct dm_target *ti, char *path)
 	struct dmz_target *dmz = ti->private;
 	struct request_queue *q;
 	struct dmz_dev *dev;
+	sector_t aligned_capacity;
 	int ret;
 
 	/* Get the target device */
@@ -685,15 +686,17 @@ static int dmz_get_zoned_device(struct dm_target *ti, char *path)
 		goto err;
 	}
 
+	q = bdev_get_queue(dev->bdev);
 	dev->capacity = i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
-	if (ti->begin || (ti->len != dev->capacity)) {
+	aligned_capacity = dev->capacity & ~(blk_queue_zone_sectors(q) - 1);
+	if (ti->begin ||
+	    ((ti->len != dev->capacity) && (ti->len != aligned_capacity))) {
 		ti->error = "Partial mapping not supported";
 		ret = -EINVAL;
 		goto err;
 	}
 
-	q = bdev_get_queue(dev->bdev);
-	dev->zone_nr_sectors = q->limits.chunk_sectors;
+	dev->zone_nr_sectors = blk_queue_zone_sectors(q);
 	dev->zone_nr_sectors_shift = ilog2(dev->zone_nr_sectors);
 
 	dev->zone_nr_blocks = dmz_sect2blk(dev->zone_nr_sectors);
@@ -929,8 +932,10 @@ static int dmz_iterate_devices(struct dm_target *ti,
 			       iterate_devices_callout_fn fn, void *data)
 {
 	struct dmz_target *dmz = ti->private;
+	struct dmz_dev *dev = dmz->dev;
+	sector_t capacity = dev->capacity & ~(dev->zone_nr_sectors - 1);
 
-	return fn(ti, dmz->ddev, 0, dmz->dev->capacity, data);
+	return fn(ti, dmz->ddev, 0, capacity, data);
 }
 
 static struct target_type dmz_type = {