[PATCH 3.16.y-ckt 173/183] target: Allow Write Exclusive non-reservation holders to READ

[Luis Henriques]

3.16.7-ckt8 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lee Duncan <lduncan at suse.com>

commit 1ecc7586922662e3ca2f3f0c3f17fec8749fc621 upstream.

For PGR reservation of type Write Exclusive Access, allow all non
reservation holding I_T nexuses with active registrations to READ
from the device.

This addresses a bug where active registrations that attempted
to READ would result in an reservation conflict.

Signed-off-by: Lee Duncan <lduncan at suse.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/target/target_core_pr.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/target/target_core_pr.c b/drivers/target/target_core_pr.c
index fde735eeea57..ec155de017f4 100644
--- a/drivers/target/target_core_pr.c
+++ b/drivers/target/target_core_pr.c
@@ -528,6 +528,18 @@ static int core_scsi3_pr_seq_non_holder(
 
 			return 0;
 		}
+       } else if (we && registered_nexus) {
+               /*
+                * Reads are allowed for Write Exclusive locks
+                * from all registrants.
+                */
+               if (cmd->data_direction == DMA_FROM_DEVICE) {
+                       pr_debug("Allowing READ CDB: 0x%02x for %s"
+                               " reservation\n", cdb[0],
+                               core_scsi3_pr_dump_type(pr_reg_type));
+
+                       return 0;
+               }
 	}
 	pr_debug("%s Conflict for %sregistered nexus %s CDB: 0x%2x"
 		" for %s reservation\n", transport_dump_cmd_direction(cmd),