block: BFQ: Refactor bfq_exit_icq() to silence sparse warning

Currently building for C=1 generates the following warning:
block/bfq-iosched.c:5498:9: warning: context imbalance in 'bfq_exit_icq' - different lock contexts for basic block

Refactor bfq_exit_icq() into a core part which loops for the actuators,
and only lock calling this routine when necessary.

Signed-off-by: John Garry <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: johnpgarry

block/bfq-iosched.c

@@ -5463,40 +5463,42 @@ static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync,
 	}
 }
 
+static void _bfq_exit_icq(struct bfq_io_cq *bic, unsigned int num_actuators)
+{
+	struct bfq_iocq_bfqq_data *bfqq_data = bic->bfqq_data;
+	unsigned int act_idx;
+
+	for (act_idx = 0; act_idx < num_actuators; act_idx++) {
+		if (bfqq_data[act_idx].stable_merge_bfqq)
+			bfq_put_stable_ref(bfqq_data[act_idx].stable_merge_bfqq);
+
+		bfq_exit_icq_bfqq(bic, true, act_idx);
+		bfq_exit_icq_bfqq(bic, false, act_idx);
+	}
+}
+
 static void bfq_exit_icq(struct io_cq *icq)
 {
 	struct bfq_io_cq *bic = icq_to_bic(icq);
 	struct bfq_data *bfqd = bic_to_bfqd(bic);
 	unsigned long flags;
-	unsigned int act_idx;
+
 	/*
 	 * If bfqd and thus bfqd->num_actuators is not available any
 	 * longer, then cycle over all possible per-actuator bfqqs in
 	 * next loop. We rely on bic being zeroed on creation, and
 	 * therefore on its unused per-actuator fields being NULL.
-	 */
-	unsigned int num_actuators = BFQ_MAX_ACTUATORS;
-	struct bfq_iocq_bfqq_data *bfqq_data = bic->bfqq_data;
-
-	/*
+	 *
 	 * bfqd is NULL if scheduler already exited, and in that case
 	 * this is the last time these queues are accessed.
 	 */
 	if (bfqd) {
 		spin_lock_irqsave(&bfqd->lock, flags);
-		num_actuators = bfqd->num_actuators;
-	}
-
-	for (act_idx = 0; act_idx < num_actuators; act_idx++) {
-		if (bfqq_data[act_idx].stable_merge_bfqq)
-			bfq_put_stable_ref(bfqq_data[act_idx].stable_merge_bfqq);
-
-		bfq_exit_icq_bfqq(bic, true, act_idx);
-		bfq_exit_icq_bfqq(bic, false, act_idx);
-	}
-
-	if (bfqd)
+		_bfq_exit_icq(bic, bfqd->num_actuators);
 		spin_unlock_irqrestore(&bfqd->lock, flags);
+	} else {
+		_bfq_exit_icq(bic, BFQ_MAX_ACTUATORS);
+	}
 }
 
 /*