+/**
+ * blk_check_logical_block_size - check if logical block size is supported
+ * by the kernel
+ * @size:  the logical block size, in bytes
+ *
+ * Description:
+ *   This function checks if the block layers supports given block size
+ **/
+bool blk_is_valid_logical_block_size(unsigned int size)
+{
+	return size >= SECTOR_SIZE && size <= PAGE_SIZE && !is_power_of_2(size);

Shouldn't this be a ... && is_power_of_2(size)?

 	if (q->limits.io_min < q->limits.physical_block_size)
 		q->limits.io_min = q->limits.physical_block_size;
+
 }

This adds a pointless empty line.

+extern bool blk_is_valid_logical_block_size(unsigned int size);

No need for externs on function declarations.