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 <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 8289804..4fba26c 100644
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -514,11 +514,10 @@
 }
 
 static void dm_stat_for_entry(struct dm_stat *s, size_t entry,
-			      unsigned long bi_rw, sector_t len,
+			      int idx, sector_t len,
 			      struct dm_stats_aux *stats_aux, bool end,
 			      unsigned long duration_jiffies)
 {
-	unsigned long idx = bi_rw & REQ_WRITE;
 	struct dm_stat_shared *shared = &s->stat_shared[entry];
 	struct dm_stat_percpu *p;
 
@@ -584,7 +583,7 @@
 #endif
 }
 
-static void __dm_stat_bio(struct dm_stat *s, unsigned long bi_rw,
+static void __dm_stat_bio(struct dm_stat *s, int bi_rw,
 			  sector_t bi_sector, sector_t end_sector,
 			  bool end, unsigned long duration_jiffies,
 			  struct dm_stats_aux *stats_aux)
@@ -645,8 +644,8 @@
 		last = raw_cpu_ptr(stats->last);
 		stats_aux->merged =
 			(bi_sector == (ACCESS_ONCE(last->last_sector) &&
-				       ((bi_rw & (REQ_WRITE | REQ_DISCARD)) ==
-					(ACCESS_ONCE(last->last_rw) & (REQ_WRITE | REQ_DISCARD)))
+				       ((bi_rw == WRITE) ==
+					(ACCESS_ONCE(last->last_rw) == WRITE))
 				       ));
 		ACCESS_ONCE(last->last_sector) = end_sector;
 		ACCESS_ONCE(last->last_rw) = bi_rw;