[PATCH v3 24/35] block: null_blk: replace get_tag() with a generic find_and_set_bit_lock()

[Yury Norov <yury.norov@xxxxxxxxx>]

get_tag() opencodes find_and_set_bit(). Simplify the code by getting
rid of it.

Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
Reviewed-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
 drivers/block/null_blk/main.c | 41 +++++++++++------------------------
 1 file changed, 13 insertions(+), 28 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 3021d58ca51c..671dbb9ab928 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -760,19 +760,6 @@ static void put_tag(struct nullb_queue *nq, unsigned int tag)
 		wake_up(&nq->wait);
 }
 
-static unsigned int get_tag(struct nullb_queue *nq)
-{
-	unsigned int tag;
-
-	do {
-		tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
-		if (tag >= nq->queue_depth)
-			return -1U;
-	} while (test_and_set_bit_lock(tag, nq->tag_map));
-
-	return tag;
-}
-
 static void free_cmd(struct nullb_cmd *cmd)
 {
 	put_tag(cmd->nq, cmd->tag);
@@ -782,24 +769,22 @@ static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer);
 
 static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
 {
+	unsigned int tag = find_and_set_bit_lock(nq->tag_map, nq->queue_depth);
 	struct nullb_cmd *cmd;
-	unsigned int tag;
-
-	tag = get_tag(nq);
-	if (tag != -1U) {
-		cmd = &nq->cmds[tag];
-		cmd->tag = tag;
-		cmd->error = BLK_STS_OK;
-		cmd->nq = nq;
-		if (nq->dev->irqmode == NULL_IRQ_TIMER) {
-			hrtimer_init(&cmd->timer, CLOCK_MONOTONIC,
-				     HRTIMER_MODE_REL);
-			cmd->timer.function = null_cmd_timer_expired;
-		}
-		return cmd;
+
+	if (tag >= nq->queue_depth)
+		return NULL;
+
+	cmd = &nq->cmds[tag];
+	cmd->tag = tag;
+	cmd->error = BLK_STS_OK;
+	cmd->nq = nq;
+	if (nq->dev->irqmode == NULL_IRQ_TIMER) {
+		hrtimer_init(&cmd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+		cmd->timer.function = null_cmd_timer_expired;
 	}
 
-	return NULL;
+	return cmd;
 }
 
 static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, struct bio *bio)
-- 
2.40.1