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,
                                   struct request ** same_queue_rq);

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

       same_queue_rq
           pointer to struct request that gets filled in when another request associated with q
           is found on the plug list (optional, may be NULL)

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.

       Caller must ensure !blk_queue_nomerges(q) beforehand.

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