block: Consolidate command flag and queue limit checks for merges

 - blk_check_merge_flags() verifies that cmd_flags / bi_rw are
   compatible. This function is called for both req-req and req-bio
   merging.

 - blk_rq_get_max_sectors() and blk_queue_get_max_sectors() can be used
   to query the maximum sector count for a given request or queue. The
   calls will return the right value from the queue limits given the
   type of command (RW, discard, write same, etc.)

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>

1 files changed, 31 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3a6fea7460f..90f7abe8f18 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -605,6 +605,18 @@ static inline bool rq_mergeable(struct request *rq)
         return true;
 }
 
+static inline bool blk_check_merge_flags(unsigned int flags1,
+                                         unsigned int flags2)
+{
+        if ((flags1 & REQ_DISCARD) != (flags2 & REQ_DISCARD))
+                return false;
+
+        if ((flags1 & REQ_SECURE) != (flags2 & REQ_SECURE))
+                return false;
+
+        return true;
+}
+
 /*
  * q->prep_rq_fn return values
  */
@@ -800,6 +812,25 @@ static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
         return blk_rq_cur_bytes(rq) >> 9;
 }
 
+static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
+                                                     unsigned int cmd_flags)
+{
+        if (unlikely(cmd_flags & REQ_DISCARD))
+                return q->limits.max_discard_sectors;
+
+        return q->limits.max_sectors;
+}
+
+static inline unsigned int blk_rq_get_max_sectors(struct request *rq)
+{
+        struct request_queue *q = rq->q;
+
+        if (unlikely(rq->cmd_type == REQ_TYPE_BLOCK_PC))
+                return q->limits.max_hw_sectors;
+
+        return blk_queue_get_max_sectors(q, rq->cmd_flags);
+}
+
 /*
  * Request issue related functions.
  */