centos man page for blk_attempt_plug_merge

BLK_ATTEMPT_PLUG_MER(9) 					   Block Devices					   BLK_ATTEMPT_PLUG_MER(9)

NAME
       blk_attempt_plug_merge - try to merge with current's plugged list

SYNOPSIS
       bool blk_attempt_plug_merge(struct request_queue * q, struct bio * bio, unsigned int * request_count);

ARGUMENTS
       q
	   request_queue new bio is being queued at

       bio
	   new bio being queued

       request_count
	   out parameter for number of traversed plugged requests

DESCRIPTION
       Determine whether bio being queued on q can be merged with a request on current's plugged list. Returns true if merge was successful,
       otherwise false.

       Plugging coalesces IOs from the same issuer for the same purpose without going through q->queue_lock. As such it's more of an issuing
       mechanism than scheduling, and the request, while may have elvpriv data, is not added on the elevator at this point. In addition, we don't
       have reliable access to the elevator outside queue lock. Only check basic merging parameters without querying the elevator.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						   BLK_ATTEMPT_PLUG_MER(9)