blk_init_queue — prepare a request queue for use with a block device
|request_fn_proc * rfn,|
|spinlock_t * lock|
The function to be called to process requests that have been placed on the queue.
Request queue spin lock
If a block device wishes to use the standard request handling procedures,
which sorts requests and coalesces adjacent requests, then it must
blk_init_queue. The function
rfn will be called when there
are requests on the queue that need to be processed. If the device
supports plugging, then
rfn may not be called immediately when requests
are available on the queue, but may be called at some time later instead.
Plugged queues are generally unplugged when a buffer belonging to one
of the requests on the queue is needed, or due to memory pressure.
rfn is not required, or even expected, to remove all requests off the
queue, but only as many as it can handle at a time. If it does leave
requests on the queue, it is responsible for arranging that the requests
get dealt with eventually.
The queue spin lock must be held while manipulating the requests on the request queue; this lock will be taken also from interrupt context, so irq disabling is needed for it.
Function returns a pointer to the initialized request queue, or
it didn't succeed.