[PATCH v4 03/29] scsi: core: Make the budget map optional

[Bart Van Assche <bvanassche@acm.org>]

Prepare for not allocating a budget map for pseudo SCSI devices by
checking whether a budget map has been allocated before using a budget
map.

Cc: Hannes Reinecke <hare@suse.de>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi.c     |  2 ++
 drivers/scsi/scsi_lib.c | 14 ++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 9a0f467264b3..ff6b0973d3b4 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -216,6 +216,8 @@ int scsi_device_max_queue_depth(struct scsi_device *sdev)
  */
 int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
 {
+	WARN_ON_ONCE(!sdev->budget_map.map);
+
 	depth = min_t(int, depth, scsi_device_max_queue_depth(sdev));
 
 	if (depth > 0) {
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9c67e04265ce..91a0c7f843c1 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -396,7 +396,8 @@ void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd)
 	if (starget->can_queue > 0)
 		atomic_dec(&starget->target_busy);
 
-	sbitmap_put(&sdev->budget_map, cmd->budget_token);
+	if (sdev->budget_map.map)
+		sbitmap_put(&sdev->budget_map, cmd->budget_token);
 	cmd->budget_token = -1;
 }
 
@@ -1360,6 +1361,14 @@ static inline int scsi_dev_queue_ready(struct request_queue *q,
 {
 	int token;
 
+	/*
+	 * Do not allocate a budget token for reserved SCSI commands. Budget
+	 * tokens are used to enforce the cmd_per_lun limit. That limit does not
+	 * apply to reserved commands.
+	 */
+	if (!sdev->budget_map.map)
+		return INT_MAX;
+
 	token = sbitmap_get(&sdev->budget_map);
 	if (token < 0)
 		return -1;
@@ -1749,7 +1758,8 @@ static void scsi_mq_put_budget(struct request_queue *q, int budget_token)
 {
 	struct scsi_device *sdev = q->queuedata;
 
-	sbitmap_put(&sdev->budget_map, budget_token);
+	if (sdev->budget_map.map)
+		sbitmap_put(&sdev->budget_map, budget_token);
 }
 
 /*