[PATCH 1/2] null_blk: remove hardcoded alloc_cmd() parameter

[Chaitanya Kulkarni <kch@nvidia.com>]

Only caller of alloc_cmd() is null_submit_bio() unconditionally sets
second parameter to true & that is statically hard-coded in null_blk.
There is no point in having statically hardcoded function parameter.

Remove the unnecessary parameter can_wait and adjust the code so it
can retain existing behavior of waiting when we don't get valid
nullb_cmd from __alloc_cmd() in alloc_cmd().

The restructured code avoids multiple return statements, multiple
calls to __alloc_cmd() and resulting a fast path call to
prepare_to_wait() due to removal of first alloc_cmd() call.

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
---
 drivers/block/null_blk/main.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 13004beb48ca..d78fc3edb22e 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -719,26 +719,23 @@ static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
 	return NULL;
 }
 
-static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)
+static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq)
 {
 	struct nullb_cmd *cmd;
 	DEFINE_WAIT(wait);
 
-	cmd = __alloc_cmd(nq);
-	if (cmd || !can_wait)
-		return cmd;
-
 	do {
-		prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);
+		/*
+		 * This avoids multiple return statements, multiple calls to
+		 * __alloc_cmd() and a fast path call to prepare_to_wait().
+		 */
 		cmd = __alloc_cmd(nq);
 		if (cmd)
-			break;
-
+			return cmd;
+		prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);
 		io_schedule();
+		finish_wait(&nq->wait, &wait);
 	} while (1);
-
-	finish_wait(&nq->wait, &wait);
-	return cmd;
 }
 
 static void end_cmd(struct nullb_cmd *cmd)
@@ -1478,7 +1475,7 @@ static void null_submit_bio(struct bio *bio)
 	struct nullb_queue *nq = nullb_to_queue(nullb);
 	struct nullb_cmd *cmd;
 
-	cmd = alloc_cmd(nq, 1);
+	cmd = alloc_cmd(nq);
 	cmd->bio = bio;
 
 	null_handle_cmd(cmd, sector, nr_sectors, bio_op(bio));
-- 
2.29.0