[PATCH 24/30] blk_end_request: add callback feature (take 4)

This patch adds a variant of the interface, blk_end_request_callback(), which has driver callback feature. Drivers may need to do special works between end_that_request_first() and end_that_request_last(). For such drivers, blk_end_request_callback() allows it to pass a callback function which is

[PATCH 24/30] blk_end_request: add callback feature (take 4)

This patch adds a variant of the interface, blk_end_request_callback(), which has driver callback feature. Drivers may need to do special works between end_that_request_first() and end_that_request_last(). For such drivers, blk_end_request_callback() allows it to pass a callback function which is