[PATCH 6/9] scsi: add scsi_host_busy_iter()

[Hannes Reinecke <hare@suse.de>]

Add an iterator scsi_host_busy_iter() to traverse all busy commands.
If locking against concurrent command completions is required it
has to be provided by the caller.

Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/hosts.c     | 33 +++++++++++++++++++++++++++++++++
 include/scsi/scsi_host.h |  5 +++++
 2 files changed, 38 insertions(+)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index da1df48ef27c..a0a660b50929 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -674,3 +674,36 @@ void scsi_host_flush_commands(struct Scsi_Host *shost, int status)
 	blk_mq_tagset_busy_iter(&shost->tag_set, flush_cmds_iter, &status);
 }
 EXPORT_SYMBOL_GPL(scsi_host_flush_commands);
+
+struct scsi_host_busy_iter_data {
+	scsi_host_busy_iter_fn *fn;
+	void *priv;
+};
+
+static bool __scsi_host_busy_iter_fn(struct request *req, void *priv,
+				   bool reserved)
+{
+	struct scsi_host_busy_iter_data *iter_data = priv;
+	struct scsi_cmnd *sc = blk_mq_rq_to_pdu(req);
+
+	return iter_data->fn(sc, iter_data->priv, reserved);
+}
+
+/**
+ * scsi_host_busy_iter - Iterate over all busy commands
+ * @shost:	Pointer to Scsi_Host.
+ * @fn:		Function to call on each busy command
+ * @priv:	Data pointer passed to @fn
+ **/
+void scsi_host_busy_iter(struct Scsi_Host *shost,
+			 scsi_host_busy_iter_fn *fn, void *priv)
+{
+	struct scsi_host_busy_iter_data iter_data = {
+		.fn = fn,
+		.priv = priv,
+	};
+
+	blk_mq_tagset_busy_iter(&shost->tag_set, __scsi_host_busy_iter_fn,
+				&iter_data);
+}
+EXPORT_SYMBOL_GPL(scsi_host_busy_iter);
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index cb9a6fe9ad5b..1293d9686115 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -761,6 +761,11 @@ static inline int scsi_host_scan_allowed(struct Scsi_Host *shost)
 extern void scsi_unblock_requests(struct Scsi_Host *);
 extern void scsi_block_requests(struct Scsi_Host *);
 
+typedef bool (scsi_host_busy_iter_fn)(struct scsi_cmnd *, void *, bool);
+
+void scsi_host_busy_iter(struct Scsi_Host *,
+			 scsi_host_busy_iter_fn *fn, void *priv);
+
 struct class_container;
 
 /*
-- 
2.16.4