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-rw-r--r--block/blk-mq.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index e8d6d7a05a43..40f634ab7026 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -884,10 +884,15 @@ 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();