dm: simplify dm_start_io_acct

Pull common DM_IO_ACCOUNTED check out to beginning of dm_start_io_acct.
Also, use dm_tio_is_normal (and move it to dm-core.h).
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

drivers/md/dm-core.h

@@ -237,6 +237,12 @@ static inline void dm_tio_set_flag(struct dm_target_io *tio, unsigned int bit)
 	tio->flags |= (1U << bit);
 }
 
+static inline bool dm_tio_is_normal(struct dm_target_io *tio)
+{
+	return (dm_tio_flagged(tio, DM_TIO_INSIDE_DM_IO) &&
+		!dm_tio_flagged(tio, DM_TIO_IS_DUPLICATE_BIO));
+}
+
 /*
  * One of these is allocated per original bio.
  * It contains the first clone used for that original.

drivers/md/dm.c

@@ -538,17 +538,15 @@ static void dm_start_io_acct(struct dm_io *io, struct bio *clone)
 
 	/*
 	 * Ensure IO accounting is only ever started once.
-	 * Expect no possibility for race unless DM_TIO_IS_DUPLICATE_BIO.
 	 */
-	if (!clone ||
-	    likely(!dm_tio_flagged(clone_to_tio(clone), DM_TIO_IS_DUPLICATE_BIO))) {
-		if (WARN_ON_ONCE(dm_io_flagged(io, DM_IO_ACCOUNTED)))
-			return;
+	if (dm_io_flagged(io, DM_IO_ACCOUNTED))
+		return;
+
+	/* Expect no possibility for race unless DM_TIO_IS_DUPLICATE_BIO. */
+	if (!clone || likely(dm_tio_is_normal(clone_to_tio(clone)))) {
 		dm_io_set_flag(io, DM_IO_ACCOUNTED);
 	} else {
 		unsigned long flags;
-		if (dm_io_flagged(io, DM_IO_ACCOUNTED))
-			return;
 		/* Can afford locking given DM_TIO_IS_DUPLICATE_BIO */
 		spin_lock_irqsave(&io->lock, flags);
 		dm_io_set_flag(io, DM_IO_ACCOUNTED);
@@ -923,12 +921,6 @@ static void dm_io_complete(struct dm_io *io)
 	}
 }
 
-static inline bool dm_tio_is_normal(struct dm_target_io *tio)
-{
-	return (dm_tio_flagged(tio, DM_TIO_INSIDE_DM_IO) &&
-		!dm_tio_flagged(tio, DM_TIO_IS_DUPLICATE_BIO));
-}
-
 /*
  * Decrements the number of outstanding ios that a bio has been
  * cloned into, completing the original io if necc.