IB/srp: Avoid duplicate devices from LUN scan

commit fd1b6c4a693c9cac59375ffb36ffe5d7c079037c upstream.

SCSI scanning of a channel:id:lun triplet in Linux works as follows
(function scsi_scan_target() in drivers/scsi/scsi_scan.c):

- If lun == SCAN_WILD_CARD, send a REPORT LUNS command to the target
  and process the result.

- If lun != SCAN_WILD_CARD, send an INQUIRY command to the LUN
  corresponding to the specified channel:id:lun triplet to verify
  whether the LUN exists.

So a SCSI driver must either take the channel and target id values in
account in its quecommand() function or it should declare that it only
supports one channel and one target id.

Currently the ib_srp driver does neither.  As a result scanning the
SCSI bus via e.g. rescan-scsi-bus.sh causes many duplicate SCSI
devices to be created. For each 0:0:L device, several duplicates are
created with the same LUN number and with (C:I) != (0:0). Fix this by
declaring that the ib_srp driver only supports one channel and one
target id.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Change-Id: Ic3a3d7ca60895d7890ed1f275db2f2fc49f75aac
Reviewed-on: http://gerrit.lud.stericsson.com/gerrit/35610
Tested-by: Per VAHLNE <per.xx.vahlne@stericsson.com>
Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index ee165fdcb59..7d5109bbd1a 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -2127,6 +2127,8 @@ static ssize_t srp_create_target(struct device *dev,
 		return -ENOMEM;
 
 	target_host->transportt  = ib_srp_transport_template;
+	target_host->max_channel = 0;
+	target_host->max_id      = 1;
 	target_host->max_lun     = SRP_MAX_LUN;
 	target_host->max_cmd_len = sizeof ((struct srp_cmd *) (void *) 0L)->cdb;