[PATCH 01/14] blk-mq: do not include passthrough requests in I/O accounting

[Christoph Hellwig <hch@lst.de>]

I/O accounting buckets I/O into the read/write/discard categories into
which passthrough I/O does not fit at all.  It also accounts to the
block_device, which may not even exist for passthrough I/O.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
---
 block/blk-mq.c | 11 ++++++++---
 block/blk.h    |  2 +-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a05ce77250316..ab4b646551334 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -883,10 +883,15 @@ static inline void blk_account_io_done(struct request *req, u64 now)
 
 static void __blk_account_io_start(struct request *rq)
 {
-	/* passthrough requests can hold bios that do not have ->bi_bdev set */
-	if (rq->bio && rq->bio->bi_bdev)
+	/*
+	 * All non-passthrough requests are created from a bio with one
+	 * exception: when a flush command that is part of a flush sequence
+	 * generated by the state machine in blk-flush.c is cloned onto the
+	 * lower device by dm-multipath we can get here without a bio.
+	 */
+	if (rq->bio)
 		rq->part = rq->bio->bi_bdev;
-	else if (rq->q->disk)
+	else
 		rq->part = rq->q->disk->part0;
 
 	part_stat_lock();
diff --git a/block/blk.h b/block/blk.h
index ebaa59ca46ca6..6f21859c7f0ff 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -325,7 +325,7 @@ int blk_dev_init(void);
  */
 static inline bool blk_do_io_stat(struct request *rq)
 {
-	return (rq->rq_flags & RQF_IO_STAT) && rq->q->disk;
+	return (rq->rq_flags & RQF_IO_STAT) && !blk_rq_is_passthrough(rq);
 }
 
 void update_io_ticks(struct block_device *part, unsigned long now, bool end);
-- 
2.30.2