block: Clean up special command handling logic

Remove special-casing of non-rw fs style requests (discard). The nomerge
flags are consolidated in blk_types.h, and rq_mergeable() and
bio_mergeable() have been modified to use them.

bio_is_rw() is used in place of bio_has_data() a few places. This is
done to to distinguish true reads and writes from other fs type requests
that carry a payload (e.g. write same).

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 11 insertions, 35 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 2d739ca..5cc2929 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1657,8 +1657,8 @@ generic_make_request_checks(struct bio *bio)
 		goto end_io;
 	}
 
-	if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
-		     nr_sectors > queue_max_hw_sectors(q))) {
+	if (likely(bio_is_rw(bio) &&
+		   nr_sectors > queue_max_hw_sectors(q))) {
 		printk(KERN_ERR "bio too big device %s (%u > %u)\n",
 		       bdevname(bio->bi_bdev, b),
 		       bio_sectors(bio),
@@ -1699,8 +1699,7 @@ generic_make_request_checks(struct bio *bio)
 
 	if ((bio->bi_rw & REQ_DISCARD) &&
 	    (!blk_queue_discard(q) ||
-	     ((bio->bi_rw & REQ_SECURE) &&
-	      !blk_queue_secdiscard(q)))) {
+	     ((bio->bi_rw & REQ_SECURE) && !blk_queue_secdiscard(q)))) {
 		err = -EOPNOTSUPP;
 		goto end_io;
 	}
@@ -1818,7 +1817,7 @@ void submit_bio(int rw, struct bio *bio)
 	 * If it's a regular read/write or a barrier with data attached,
 	 * go through the normal accounting stuff before submission.
 	 */
-	if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
+	if (bio_has_data(bio)) {
 		if (rw & WRITE) {
 			count_vm_events(PGPGOUT, count);
 		} else {
@@ -1864,7 +1863,7 @@ EXPORT_SYMBOL(submit_bio);
  */
 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
 {
-	if (rq->cmd_flags & REQ_DISCARD)
+	if (!rq_mergeable(rq))
 		return 0;
 
 	if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
@@ -2338,7 +2337,7 @@ bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
 	req->buffer = bio_data(req->bio);
 
 	/* update sector only for requests with clear definition of sector */
-	if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
+	if (req->cmd_type == REQ_TYPE_FS)
 		req->__sector += total_bytes >> 9;
 
 	/* mixed attributes always follow the first bio */
diff --git a/block/blk-merge.c b/block/blk-merge.c
index e76279e..86710ca 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -418,18 +418,6 @@ static int attempt_merge(struct request_queue *q, struct request *req,
 		return 0;
 
 	/*
-	 * Don't merge file system requests and discard requests
-	 */
-	if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
-		return 0;
-
-	/*
-	 * Don't merge discard requests and secure discard requests
-	 */
-	if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
-		return 0;
-
-	/*
 	 * not contiguous
 	 */
 	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
@@ -521,15 +509,7 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 
 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 {
-	if (!rq_mergeable(rq))
-		return false;
-
-	/* don't merge file system requests and discard requests */
-	if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))
-		return false;
-
-	/* don't merge discard requests and secure discard requests */
-	if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))
+	if (!rq_mergeable(rq) || !bio_mergeable(bio))
 		return false;
 
 	/* different data direction or already started, don't merge */
diff --git a/block/blk.h b/block/blk.h
index 2a0ea32..ca51543 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -171,14 +171,13 @@ static inline int queue_congestion_off_threshold(struct request_queue *q)
  *
  *	a) it's attached to a gendisk, and
  *	b) the queue had IO stats enabled when this request was started, and
- *	c) it's a file system request or a discard request
+ *	c) it's a file system request
  */
 static inline int blk_do_io_stat(struct request *rq)
 {
 	return rq->rq_disk &&
 	       (rq->cmd_flags & REQ_IO_STAT) &&
-	       (rq->cmd_type == REQ_TYPE_FS ||
-	        (rq->cmd_flags & REQ_DISCARD));
+		(rq->cmd_type == REQ_TYPE_FS);
 }
 
 /*
diff --git a/block/elevator.c b/block/elevator.c
index 6a55d41..9b1d42b 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -562,8 +562,7 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where)
 
 	if (rq->cmd_flags & REQ_SOFTBARRIER) {
 		/* barriers are scheduling boundary, update end_sector */
-		if (rq->cmd_type == REQ_TYPE_FS ||
-		    (rq->cmd_flags & REQ_DISCARD)) {
+		if (rq->cmd_type == REQ_TYPE_FS) {
 			q->end_sector = rq_end_sector(rq);
 			q->boundary_rq = rq;
 		}
@@ -605,8 +604,7 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where)
 		if (elv_attempt_insert_merge(q, rq))
 			break;
 	case ELEVATOR_INSERT_SORT:
-		BUG_ON(rq->cmd_type != REQ_TYPE_FS &&
-		       !(rq->cmd_flags & REQ_DISCARD));
+		BUG_ON(rq->cmd_type != REQ_TYPE_FS);
 		rq->cmd_flags |= REQ_SORTED;
 		q->nr_sorted++;
 		if (rq_mergeable(rq)) {