dm: pass dm stats data dir instead of bi_rw

It looks like dm stats cares about the data direction
(READ vs WRITE) and does not need the bio/request flags.
Commands like REQ_FLUSH, REQ_DISCARD and REQ_WRITE_SAME
are currently always set with REQ_WRITE, so the extra check for
REQ_DISCARD in dm_stats_account_io is not needed.

This patch has it use the bio and request data_dir helpers
instead of accessing the bi_rw/cmd_flags directly. This makes
the next patches that remove the operation from the cmd_flags
and bi_rw easier, because we will no longer have the REQ_WRITE
bit set for operations like discards.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1b2f962..f5ac0a32 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -723,8 +723,9 @@
 		atomic_inc_return(&md->pending[rw]));
 
 	if (unlikely(dm_stats_used(&md->stats)))
-		dm_stats_account_io(&md->stats, bio->bi_rw, bio->bi_iter.bi_sector,
-				    bio_sectors(bio), false, 0, &io->stats_aux);
+		dm_stats_account_io(&md->stats, bio_data_dir(bio),
+				    bio->bi_iter.bi_sector, bio_sectors(bio),
+				    false, 0, &io->stats_aux);
 }
 
 static void end_io_acct(struct dm_io *io)
@@ -738,8 +739,9 @@
 	generic_end_io_acct(rw, &dm_disk(md)->part0, io->start_time);
 
 	if (unlikely(dm_stats_used(&md->stats)))
-		dm_stats_account_io(&md->stats, bio->bi_rw, bio->bi_iter.bi_sector,
-				    bio_sectors(bio), true, duration, &io->stats_aux);
+		dm_stats_account_io(&md->stats, bio_data_dir(bio),
+				    bio->bi_iter.bi_sector, bio_sectors(bio),
+				    true, duration, &io->stats_aux);
 
 	/*
 	 * After this is decremented the bio must not be touched if it is
@@ -1121,9 +1123,9 @@
 	if (unlikely(dm_stats_used(&md->stats))) {
 		struct dm_rq_target_io *tio = tio_from_request(orig);
 		tio->duration_jiffies = jiffies - tio->duration_jiffies;
-		dm_stats_account_io(&md->stats, orig->cmd_flags, blk_rq_pos(orig),
-				    tio->n_sectors, true, tio->duration_jiffies,
-				    &tio->stats_aux);
+		dm_stats_account_io(&md->stats, rq_data_dir(orig),
+				    blk_rq_pos(orig), tio->n_sectors, true,
+				    tio->duration_jiffies, &tio->stats_aux);
 	}
 }
 
@@ -2082,8 +2084,9 @@
 		struct dm_rq_target_io *tio = tio_from_request(orig);
 		tio->duration_jiffies = jiffies;
 		tio->n_sectors = blk_rq_sectors(orig);
-		dm_stats_account_io(&md->stats, orig->cmd_flags, blk_rq_pos(orig),
-				    tio->n_sectors, false, 0, &tio->stats_aux);
+		dm_stats_account_io(&md->stats, rq_data_dir(orig),
+				    blk_rq_pos(orig), tio->n_sectors, false, 0,
+				    &tio->stats_aux);
 	}
 
 	/*