nvmet-passthru: clear EUID/NGUID/UUID while using loop target

When nvme passthru is configured using loop target, the clear_ids
attribute is, by default, set to true. This attribute would ensure that
EUID/NGUID/UUID is cleared for the loop passthru target.

The newer NVMe disk supporting the NVMe spec 1.3 or higher, typically,
implements the support for "Namespace Identification Descriptor list"
command. This command when issued from host returns EUID/NGUID/UUID
assigned to the inquired namespace. Not clearing these values, while
using nvme passthru using loop target, would result in NVMe host driver
rejecting the namespace. This check was implemented in the commit
2079f41e ("nvme: check that EUI/GUID/UUID are globally unique").

The fix implemented in this commit ensure that when host issues ns-id
descriptor list command, the EUID/NGUID/UUID are cleared by passthru
target. In fact, the function nvmet_passthru_override_id_descs() which
clears those unique ids already exits, so we just need to ensure that
ns-id descriptor list command falls through the corretc code path. And
while we're at it, we also combines the three passthru admin command
cases together which shares the same code.
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/target/passthru.c

@@ -535,10 +535,6 @@ u16 nvmet_parse_passthru_admin_cmd(struct nvmet_req *req)
 		break;
 	case nvme_admin_identify:
 		switch (req->cmd->identify.cns) {
-		case NVME_ID_CNS_CTRL:
-			req->execute = nvmet_passthru_execute_cmd;
-			req->p.use_workqueue = true;
-			return NVME_SC_SUCCESS;
 		case NVME_ID_CNS_CS_CTRL:
 			switch (req->cmd->identify.csi) {
 			case NVME_CSI_ZNS:
@@ -547,7 +543,9 @@ u16 nvmet_parse_passthru_admin_cmd(struct nvmet_req *req)
 				return NVME_SC_SUCCESS;
 			}
 			return NVME_SC_INVALID_OPCODE | NVME_STATUS_DNR;
+		case NVME_ID_CNS_CTRL:
 		case NVME_ID_CNS_NS:
+		case NVME_ID_CNS_NS_DESC_LIST:
 			req->execute = nvmet_passthru_execute_cmd;
 			req->p.use_workqueue = true;
 			return NVME_SC_SUCCESS;