Question about request queues in I/O scheduling

[Max Kanushin]

Hello,

I was searching for a way to find out the length of a request_queue 
(that is defined as a structure in linux/include/linux/blkdev.h). 
However I am new to the kernel development and can't figure out where is 
the actual list of requests to be processed by an elevator.
Is there a way to iterate requests in a queue or at least find a number 
of them?

Please make a personal CC for me. I will really appreciate your help.
Best regards

  Max Kanushin.