target: Don't allow setting WC emulation if device doesn't support

Just like for pSCSI, if the transport sets get_write_cache, then it is
not valid to enable write cache emulation for it. Return an error.

see https://bugzilla.redhat.com/show_bug.cgi?id=1082675

Reviewed-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Andy Grover <agrover@redhat.com>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 382b66b..26416c1 100644 (file)
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -798,10 +798,10 @@ int se_dev_set_emulate_write_cache(struct se_device *dev, int flag)
                pr_err("emulate_write_cache not supported for pSCSI\n");
                return -EINVAL;
        }
-       if (dev->transport->get_write_cache) {
-               pr_warn("emulate_write_cache cannot be changed when underlying"
-                       " HW reports WriteCacheEnabled, ignoring request\n");
-               return 0;
+       if (flag &&
+           dev->transport->get_write_cache) {
+               pr_err("emulate_write_cache not supported for this device\n");
+               return -EINVAL;
        }
 
        dev->dev_attrib.emulate_write_cache = flag;