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>

7 files changed, 46 insertions, 49 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 2d739ca10923..5cc29299f6ac 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 e76279e41162..86710ca408b8 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 2a0ea32d249f..ca51543b248c 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 6a55d418896f..9b1d42b62f20 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)) {
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 52b9cbc3e4da..e54305cacc98 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -386,9 +386,28 @@ static inline char *__bio_kmap_irq(struct bio *bio, unsigned short idx,
 /*
  * Check whether this bio carries any data or not. A NULL bio is allowed.
  */
-static inline int bio_has_data(struct bio *bio)
+static inline bool bio_has_data(struct bio *bio)
 {
-        return bio && bio->bi_io_vec != NULL;
+        if (bio && bio->bi_vcnt)
+                return true;
+
+        return false;
+}
+
+static inline bool bio_is_rw(struct bio *bio)
+{
+        if (!bio_has_data(bio))
+                return false;
+
+        return true;
+}
+
+static inline bool bio_mergeable(struct bio *bio)
+{
+        if (bio->bi_rw & REQ_NOMERGE_FLAGS)
+                return false;
+
+        return true;
 }
 
 /*
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 3eefbb291192..1b229664f573 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -194,6 +194,10 @@ enum rq_flag_bits {
          REQ_DISCARD | REQ_NOIDLE | REQ_FLUSH | REQ_FUA | REQ_SECURE)
 #define REQ_CLONE_MASK          REQ_COMMON_MASK
 
+/* This mask is used for both bio and request merge checking */
+#define REQ_NOMERGE_FLAGS \
+        (REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA)
+
 #define REQ_RAHEAD              (1 << __REQ_RAHEAD)
 #define REQ_THROTTLED           (1 << __REQ_THROTTLED)
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4a2ab7c85393..3a6fea7460f1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -540,8 +540,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
 
 #define blk_account_rq(rq) \
         (((rq)->cmd_flags & REQ_STARTED) && \
-         ((rq)->cmd_type == REQ_TYPE_FS || \
-          ((rq)->cmd_flags & REQ_DISCARD)))
+         ((rq)->cmd_type == REQ_TYPE_FS))
 
 #define blk_pm_request(rq)      \
         ((rq)->cmd_type == REQ_TYPE_PM_SUSPEND || \
@@ -595,17 +594,16 @@ static inline void blk_clear_rl_full(struct request_list *rl, bool sync)
         rl->flags &= ~flag;
 }
 
+static inline bool rq_mergeable(struct request *rq)
+{
+        if (rq->cmd_type != REQ_TYPE_FS)
+                return false;
 
-/*
- * mergeable request must not have _NOMERGE or _BARRIER bit set, nor may
- * it already be started by driver.
- */
-#define RQ_NOMERGE_FLAGS        \
-        (REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA | REQ_DISCARD)
-#define rq_mergeable(rq)        \
-        (!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
-         (((rq)->cmd_flags & REQ_DISCARD) || \
-          (rq)->cmd_type == REQ_TYPE_FS))
+        if (rq->cmd_flags & REQ_NOMERGE_FLAGS)
+                return false;
+
+        return true;
+}
 
 /*
  * q->prep_rq_fn return values