Get a free request
struct request * get_request(struct request_queue * q, int rw_flags, struct bio * bio, gfp_t gfp_mask);
q
request_queue to allocate request from
rw_flags
RW and SYNC flags
bio
bio to allocate request for (can be NULL)
gfp_mask
allocation mask
Get a free request from q. If __GFP_WAIT is set in gfp_mask, this function keeps retrying under memory pressure and fails iff q is dead.
Must be callled with q->queue_lock held and, Returns NULL on failure, with q->queue_lock held. Returns !NULL on success, with q->queue_lock *not held*.