[PATCH v2 11/18] scsi-multipath: block PR commands

[John Garry <john.g.garry@oracle.com>]

As described by Benjamin in the following link, PR support for SCSI is
quite complicated:
https://lore.kernel.org/linux-scsi/aaHecneNg9Q8EtiS@redhat.com/

For initial scsi-multipath support, just don't support PRs. This means that
we need to intercept PR SCSI commands for passthrough and reject them.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 drivers/scsi/scsi_lib.c       |  6 ++++++
 drivers/scsi/scsi_multipath.c | 11 +++++++++++
 include/scsi/scsi_multipath.h |  5 +++++
 3 files changed, 22 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 46ed669c41dc9..c3c6831af97dc 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1296,6 +1296,12 @@ static blk_status_t scsi_setup_scsi_cmnd(struct scsi_device *sdev,
 {
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
 
+	if (sdev->scsi_mpath_dev) {
+		blk_status_t ret = scsi_mpath_setup_scsi_cmnd(cmd);
+		if (ret)
+			return ret;
+	}
+
 	/*
 	 * Passthrough requests may transfer data, in which case they must
 	 * a bio attached to them.  Or they might contain a SCSI command
diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
index a2a21793db895..e0670d353e59f 100644
--- a/drivers/scsi/scsi_multipath.c
+++ b/drivers/scsi/scsi_multipath.c
@@ -242,6 +242,17 @@ static int scsi_multipath_sdev_init(struct scsi_device *sdev)
 	return 0;
 }
 
+blk_status_t scsi_mpath_setup_scsi_cmnd(struct scsi_cmnd *scmd)
+{
+	switch (scmd->cmnd[0]) {
+	/* Special handling required which is not yet supported */
+	case PERSISTENT_RESERVE_IN:
+	case PERSISTENT_RESERVE_OUT:
+		return BLK_STS_NOTSUPP;
+	}
+	return BLK_STS_OK;
+}
+
 static inline void bio_list_add_clone(struct bio_list *bl,
 				struct bio *clone)
 {
diff --git a/include/scsi/scsi_multipath.h b/include/scsi/scsi_multipath.h
index fdbdb0e5d02e0..52c80b0658d61 100644
--- a/include/scsi/scsi_multipath.h
+++ b/include/scsi/scsi_multipath.h
@@ -43,6 +43,7 @@ struct scsi_mpath_device {
 #define to_scsi_mpath_device(d) \
 	container_of(d, struct scsi_mpath_device, mpath_device)
 
+blk_status_t scsi_mpath_setup_scsi_cmnd(struct scsi_cmnd *);
 int scsi_mpath_dev_alloc(struct scsi_device *sdev);
 void scsi_mpath_dev_release(struct scsi_device *sdev);
 int scsi_multipath_init(void);
@@ -63,6 +64,10 @@ struct scsi_mpath_head {
 struct scsi_mpath_device {
 };
 
+static inline blk_status_t scsi_mpath_setup_scsi_cmnd(struct scsi_cmnd *)
+{
+	return BLK_STS_OK;
+}
 static inline int scsi_mpath_dev_alloc(struct scsi_device *sdev)
 {
 	return 0;
-- 
2.43.5