Index: stable/12/sys/cam/nvme/nvme_da.c
===================================================================
--- stable/12/sys/cam/nvme/nvme_da.c
+++ stable/12/sys/cam/nvme/nvme_da.c
@@ -787,7 +787,7 @@
 	disk->d_mediasize = (off_t)(disk->d_sectorsize * nsd->nsze);
 	disk->d_delmaxsize = disk->d_mediasize;
 	disk->d_flags = DISKFLAG_DIRECT_COMPLETION;
-//	if (cd->oncs.dsm) // XXX broken?
+	if (nvme_ctrlr_has_dataset_mgmt(cd))
 		disk->d_flags |= DISKFLAG_CANDELETE;
 	vwc_present = (cd->vwc >> NVME_CTRLR_DATA_VWC_PRESENT_SHIFT) &
 		NVME_CTRLR_DATA_VWC_PRESENT_MASK;
Index: stable/12/sys/dev/nvme/nvme.h
===================================================================
--- stable/12/sys/dev/nvme/nvme.h
+++ stable/12/sys/dev/nvme/nvme.h
@@ -1259,6 +1259,13 @@
 device_t	nvme_ctrlr_get_device(struct nvme_controller *ctrlr);
 const struct nvme_controller_data *
 		nvme_ctrlr_get_data(struct nvme_controller *ctrlr);
+static inline bool
+nvme_ctrlr_has_dataset_mgmt(const struct nvme_controller_data *cd)
+{
+	/* Assumes cd was byte swapped by nvme_controller_data_swapbytes() */
+	return ((cd->oncs >> NVME_CTRLR_DATA_ONCS_DSM_SHIFT) &
+		NVME_CTRLR_DATA_ONCS_DSM_MASK);
+}
 
 /* Namespace helper functions */
 uint32_t	nvme_ns_get_max_io_xfer_size(struct nvme_namespace *ns);
Index: stable/12/sys/dev/nvme/nvme_ns.c
===================================================================
--- stable/12/sys/dev/nvme/nvme_ns.c
+++ stable/12/sys/dev/nvme/nvme_ns.c
@@ -498,8 +498,6 @@
 	struct nvme_completion_poll_status	status;
 	int                                     res;
 	int					unit;
-	uint16_t				oncs;
-	uint8_t					dsm;
 	uint8_t					flbas_fmt;
 	uint8_t					vwc_present;
 
@@ -569,9 +567,7 @@
 		return (ENXIO);
 	}
 
-	oncs = ctrlr->cdata.oncs;
-	dsm = (oncs >> NVME_CTRLR_DATA_ONCS_DSM_SHIFT) & NVME_CTRLR_DATA_ONCS_DSM_MASK;
-	if (dsm)
+	if (nvme_ctrlr_has_dataset_mgmt(&ctrlr->cdata))
 		ns->flags |= NVME_NS_DEALLOCATE_SUPPORTED;
 
 	vwc_present = (ctrlr->cdata.vwc >> NVME_CTRLR_DATA_VWC_PRESENT_SHIFT) &