block: Add nr_bios to block_rq_remap tracepoint

Adding the number of bios in a remapped request to 'block_rq_remap'
tracepoint.

Request remapper clones bios in a request to track the completion
status of each bio. So the number of bios can be useful information
for investigation.

Related discussions:
  http://www.redhat.com/archives/dm-devel/2013-August/msg00084.html
  http://www.redhat.com/archives/dm-devel/2013-September/msg00024.html

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2fdb4a451b49..0e6f765aa1f5 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -862,6 +862,17 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq)
         return blk_queue_get_max_sectors(q, rq->cmd_flags);
 }
 
+static inline unsigned int blk_rq_count_bios(struct request *rq)
+{
+        unsigned int nr_bios = 0;
+        struct bio *bio;
+
+        __rq_for_each_bio(bio, rq)
+                nr_bios++;
+
+        return nr_bios;
+}
+
 /*
  * Request issue related functions.
  */