loop: Factor out configuring loop from status

Factor out this code into a separate function, so it can be reused by
other code more easily.
Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1251,75 +1251,43 @@ static int loop_clr_fd(struct loop_device *lo)
 	return __loop_clr_fd(lo, false);
 }
 
+/**
+ * loop_set_status_from_info - configure device from loop_info
+ * @lo: struct loop_device to configure
+ * @info: struct loop_info64 to configure the device with
+ *
+ * Configures the loop device parameters according to the passed
+ * in loop_info64 configuration.
+ */
 static int
-loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
+loop_set_status_from_info(struct loop_device *lo,
+			  const struct loop_info64 *info)
 {
 	int err;
 	struct loop_func_table *xfer;
 	kuid_t uid = current_uid();
-	struct block_device *bdev;
-	bool partscan = false;
-	bool size_changed = false;
-
-	err = mutex_lock_killable(&loop_ctl_mutex);
-	if (err)
-		return err;
-	if (lo->lo_encrypt_key_size &&
-	    !uid_eq(lo->lo_key_owner, uid) &&
-	    !capable(CAP_SYS_ADMIN)) {
-		err = -EPERM;
-		goto out_unlock;
-	}
-	if (lo->lo_state != Lo_bound) {
-		err = -ENXIO;
-		goto out_unlock;
-	}
-	if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE) {
-		err = -EINVAL;
-		goto out_unlock;
-	}
-
-	if (lo->lo_offset != info->lo_offset ||
-	    lo->lo_sizelimit != info->lo_sizelimit) {
-		size_changed = true;
-		sync_blockdev(lo->lo_device);
-		kill_bdev(lo->lo_device);
-	}
 
-	/* I/O need to be drained during transfer transition */
-	blk_mq_freeze_queue(lo->lo_queue);
-
-	if (size_changed && lo->lo_device->bd_inode->i_mapping->nrpages) {
-		/* If any pages were dirtied after kill_bdev(), try again */
-		err = -EAGAIN;
-		pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
-			__func__, lo->lo_number, lo->lo_file_name,
-			lo->lo_device->bd_inode->i_mapping->nrpages);
-		goto out_unfreeze;
-	}
+	if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
+		return -EINVAL;
 
 	err = loop_release_xfer(lo);
 	if (err)
-		goto out_unfreeze;
+		return err;
 
 	if (info->lo_encrypt_type) {
 		unsigned int type = info->lo_encrypt_type;
 
-		if (type >= MAX_LO_CRYPT) {
-			err = -EINVAL;
-			goto out_unfreeze;
-		}
+		if (type >= MAX_LO_CRYPT)
+			return -EINVAL;
 		xfer = xfer_funcs[type];
-		if (xfer == NULL) {
-			err = -EINVAL;
-			goto out_unfreeze;
-		}
+		if (xfer == NULL)
+			return -EINVAL;
 	} else
 		xfer = NULL;
 
 	err = loop_init_xfer(lo, xfer, info);
 	if (err)
-		goto out_unfreeze;
+		return err;
 
 	lo->lo_offset = info->lo_offset;
 	lo->lo_sizelimit = info->lo_sizelimit;
@@ -1346,6 +1314,55 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 		lo->lo_key_owner = uid;
 	}
 
+	return 0;
+}
+
+static int
+loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
+{
+	int err;
+	struct block_device *bdev;
+	kuid_t uid = current_uid();
+	bool partscan = false;
+	bool size_changed = false;
+
+	err = mutex_lock_killable(&loop_ctl_mutex);
+	if (err)
+		return err;
+	if (lo->lo_encrypt_key_size &&
+	    !uid_eq(lo->lo_key_owner, uid) &&
+	    !capable(CAP_SYS_ADMIN)) {
+		err = -EPERM;
+		goto out_unlock;
+	}
+	if (lo->lo_state != Lo_bound) {
+		err = -ENXIO;
+		goto out_unlock;
+	}
+
+	if (lo->lo_offset != info->lo_offset ||
+	    lo->lo_sizelimit != info->lo_sizelimit) {
+		size_changed = true;
+		sync_blockdev(lo->lo_device);
+		kill_bdev(lo->lo_device);
+	}
+
+	/* I/O need to be drained during transfer transition */
+	blk_mq_freeze_queue(lo->lo_queue);
+
+	if (size_changed && lo->lo_device->bd_inode->i_mapping->nrpages) {
+		/* If any pages were dirtied after kill_bdev(), try again */
+		err = -EAGAIN;
+		pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
+			__func__, lo->lo_number, lo->lo_file_name,
+			lo->lo_device->bd_inode->i_mapping->nrpages);
+		goto out_unfreeze;
+	}
+
+	err = loop_set_status_from_info(lo, info);
+	if (err)
+		goto out_unfreeze;
+
 	if (size_changed) {
 		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
 					   lo->lo_backing_file);