[PATCH RFC v3 03/41] scsi: Implement scsi_cmd_is_reserved()

[Hannes Reinecke <hare@suse.de>]

Add function to check if a SCSI command originates from the reserved
tag pool and update scsi_put_reserved_cmd() to only free commands if
they originate from the reserved tag pool.

Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-mq.c           | 15 +++++++++++++++
 drivers/scsi/scsi_lib.c  |  7 +++++--
 include/linux/blk-mq.h   |  1 +
 include/scsi/scsi_cmnd.h | 13 +++++++++++++
 4 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8e56884fd2e9..44482aaed11e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -604,6 +604,21 @@ static void __blk_mq_complete_request(struct request *rq)
 	put_cpu();
 }
 
+/**
+ * blk_mq_rq_is_reserved - Check for reserved request
+ *
+ * @rq: Request to check
+ *
+ * Returns true if the request originates from the reserved tag pool.
+ */
+bool blk_mq_rq_is_reserved(struct request *rq)
+{
+	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+
+	return blk_mq_tag_is_reserved(hctx->tags, rq->tag);
+}
+EXPORT_SYMBOL_GPL(blk_mq_rq_is_reserved);
+
 static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
 	__releases(hctx->srcu)
 {
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d0972744ea7f..30f9ca9fce22 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1930,9 +1930,12 @@ EXPORT_SYMBOL_GPL(scsi_get_reserved_cmd);
  */
 void scsi_put_reserved_cmd(struct scsi_cmnd *scmd)
 {
-	struct request *rq = blk_mq_rq_from_pdu(scmd);
+	struct request *rq;
 
-	blk_mq_free_request(rq);
+	if (scmd && scsi_cmd_is_reserved(scmd)) {
+		rq = blk_mq_rq_from_pdu(scmd);
+		blk_mq_free_request(rq);
+	}
 }
 EXPORT_SYMBOL_GPL(scsi_put_reserved_cmd);
 
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index f389d7c724bd..c186dc25fc1c 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -494,6 +494,7 @@ void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list);
 void blk_mq_kick_requeue_list(struct request_queue *q);
 void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
 bool blk_mq_complete_request(struct request *rq);
+bool blk_mq_rq_is_reserved(struct request *rq);
 bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
 			   struct bio *bio, unsigned int nr_segs);
 bool blk_mq_queue_stopped(struct request_queue *q);
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 80ac89e47b47..2cd894fbdcfa 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -159,6 +159,19 @@ static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
 	return *(struct scsi_driver **)cmd->request->rq_disk->private_data;
 }
 
+/**
+ * scsi_cmd_is_reserved - check for reserved scsi command
+ * @scmd: command to check
+ *
+ * Returns true if @scmd originates from the reserved tag pool.
+ */
+static inline bool scsi_cmd_is_reserved(struct scsi_cmnd *scmd)
+{
+	struct request *rq = blk_mq_rq_from_pdu(scmd);
+
+	return blk_mq_rq_is_reserved(rq);
+}
+
 extern void scsi_finish_command(struct scsi_cmnd *cmd);
 
 extern void *scsi_kmap_atomic_sg(struct scatterlist *sg, int sg_count,
-- 
2.16.4