BLK_QUEUE_MAKE_REQUE(9)                   Block Devices                   BLK_QUEUE_MAKE_REQUE(9)



NAME
       blk_queue_make_request - define an alternate make_request function for a device

SYNOPSIS
       void blk_queue_make_request(struct request_queue * q, make_request_fn * mfn);

ARGUMENTS
       q
           the request queue for the device to be affected

       mfn
           the alternate make_request function

DESCRIPTION
       The normal way for struct bios to be passed to a device driver is for them to be collected
       into requests on a request queue, and then to allow the device driver to select requests
       off that queue when it is ready. This works well for many block devices. However some
       block devices (typically virtual devices such as md or lvm) do not benefit from the
       processing on the request queue, and are served best by having the requests passed
       directly to them. This can be achieved by providing a function to blk_queue_make_request.

       Caveat: The driver that does this *must* be able to deal appropriately with buffers in
       “highmemory”. This can be accomplished by either calling __bio_kmap_atomic to get a
       temporary kernel mapping, or by calling blk_queue_bounce to create a buffer in normal
       memory.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                   BLK_QUEUE_MAKE_REQUE(9)