loop: fold loop_update_rotational into loop_reconfigure_limits

This prepares for moving the rotational flag into the queue_limits and
also fixes it for the case where the loop device is backed by a block
device.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240617060532.127975-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -916,24 +916,6 @@ static void loop_free_idle_workers_timer(struct timer_list *timer)
 	return loop_free_idle_workers(lo, false);
 }
 
-static void loop_update_rotational(struct loop_device *lo)
-{
-	struct file *file = lo->lo_backing_file;
-	struct inode *file_inode = file->f_mapping->host;
-	struct block_device *file_bdev = file_inode->i_sb->s_bdev;
-	struct request_queue *q = lo->lo_queue;
-	bool nonrot = true;
-
-	/* not all filesystems (e.g. tmpfs) have a sb->s_bdev */
-	if (file_bdev)
-		nonrot = bdev_nonrot(file_bdev);
-
-	if (nonrot)
-		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
-	else
-		blk_queue_flag_clear(QUEUE_FLAG_NONROT, q);
-}
-
 /**
  * loop_set_status_from_info - configure device from loop_info
  * @lo: struct loop_device to configure
@@ -1003,6 +985,10 @@ static int loop_reconfigure_limits(struct loop_device *lo, unsigned short bsize)
 	lim.logical_block_size = bsize;
 	lim.physical_block_size = bsize;
 	lim.io_min = bsize;
+	if (!backing_bdev || bdev_nonrot(backing_bdev))
+		blk_queue_flag_set(QUEUE_FLAG_NONROT, lo->lo_queue);
+	else
+		blk_queue_flag_clear(QUEUE_FLAG_NONROT, lo->lo_queue);
 	loop_config_discard(lo, &lim);
 	return queue_limits_commit_update(lo->lo_queue, &lim);
 }
@@ -1099,7 +1085,6 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 	if (WARN_ON_ONCE(error))
 		goto out_unlock;
 
-	loop_update_rotational(lo);
 	loop_update_dio(lo);
 	loop_sysfs_init(lo);