+static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
+ struct bio *bio)
+{
+ const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
+
+ /*
+ * Debug stuff, kill later
+ */
+ if (!rq_mergeable(req)) {
+ blk_dump_rq_flags(req, "back");
+ return false;
+ }
+
+ if (!ll_back_merge_fn(q, req, bio))
+ return false;
+
+ trace_block_bio_backmerge(q, bio);
+
+ if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
+ blk_rq_set_mixed_merge(req);
+
+ req->biotail->bi_next = bio;
+ req->biotail = bio;
+ req->__data_len += bio->bi_size;
+ req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
+
+ drive_stat_acct(req, 0);
+ return true;
+}
+
+static bool bio_attempt_front_merge(struct request_queue *q,
+ struct request *req, struct bio *bio)
+{
+ const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
+ sector_t sector;
+
+ /*
+ * Debug stuff, kill later
+ */
+ if (!rq_mergeable(req)) {
+ blk_dump_rq_flags(req, "front");
+ return false;
+ }
+
+ if (!ll_front_merge_fn(q, req, bio))
+ return false;
+
+ trace_block_bio_frontmerge(q, bio);
+
+ if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
+ blk_rq_set_mixed_merge(req);
+
+ sector = bio->bi_sector;
+
+ bio->bi_next = req->bio;
+ req->bio = bio;
+
+ /*
+ * may not be valid. if the low level driver said
+ * it didn't need a bounce buffer then it better
+ * not touch req->buffer either...
+ */
+ req->buffer = bio_data(bio);
+ req->__sector = bio->bi_sector;
+ req->__data_len += bio->bi_size;
+ req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
+
+ drive_stat_acct(req, 0);
+ return true;
+}
+
+/*
+ * Attempts to merge with the plugged list in the current process. Returns
+ * true if merge was succesful, otherwise false.
+ */
+static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q,
+ struct bio *bio)
+{
+ struct blk_plug *plug;
+ struct request *rq;
+ bool ret = false;
+
+ plug = tsk->plug;
+ if (!plug)
+ goto out;
+
+ list_for_each_entry_reverse(rq, &plug->list, queuelist) {
+ int el_ret;
+
+ if (rq->q != q)
+ continue;
+
+ el_ret = elv_try_merge(rq, bio);
+ if (el_ret == ELEVATOR_BACK_MERGE) {
+ ret = bio_attempt_back_merge(q, rq, bio);
+ if (ret)
+ break;
+ } else if (el_ret == ELEVATOR_FRONT_MERGE) {
+ ret = bio_attempt_front_merge(q, rq, bio);
+ if (ret)
+ break;
+ }
+ }
+out:
+ return ret;
+}
+