Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

Pull SCSI updates from James Bottomley:
 "This series consists of the usual driver updates (qla2xxx, pm8001,
  libsas, smartpqi, scsi_debug, lpfc, iscsi, mpi3mr) plus minor updates
  and bug fixes.

  The high blast radius core update is the removal of write same, which
  affects block and several non-SCSI devices. The other big change,
  which is more local, is the removal of the SCSI pointer"

* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (281 commits)
  scsi: scsi_ioctl: Drop needless assignment in sg_io()
  scsi: bsg: Drop needless assignment in scsi_bsg_sg_io_fn()
  scsi: lpfc: Copyright updates for 14.2.0.0 patches
  scsi: lpfc: Update lpfc version to 14.2.0.0
  scsi: lpfc: SLI path split: Refactor BSG paths
  scsi: lpfc: SLI path split: Refactor Abort paths
  scsi: lpfc: SLI path split: Refactor SCSI paths
  scsi: lpfc: SLI path split: Refactor CT paths
  scsi: lpfc: SLI path split: Refactor misc ELS paths
  scsi: lpfc: SLI path split: Refactor VMID paths
  scsi: lpfc: SLI path split: Refactor FDISC paths
  scsi: lpfc: SLI path split: Refactor LS_RJT paths
  scsi: lpfc: SLI path split: Refactor LS_ACC paths
  scsi: lpfc: SLI path split: Refactor the RSCN/SCR/RDF/EDC/FARPR paths
  scsi: lpfc: SLI path split: Refactor PLOGI/PRLI/ADISC/LOGO paths
  scsi: lpfc: SLI path split: Refactor base ELS paths and the FLOGI path
  scsi: lpfc: SLI path split: Introduce lpfc_prep_wqe
  scsi: lpfc: SLI path split: Refactor fast and slow paths to native SLI4
  scsi: lpfc: SLI path split: Refactor lpfc_iocbq
  scsi: lpfc: Use kcalloc()
  ...

6 files changed, 204 insertions, 57 deletions

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 2c54c5d8412d..6fe6a6bab3f4 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -702,13 +702,19 @@ static int __init iscsi_target_init_module(void)
 	if (!iscsit_global->ts_bitmap)
 		goto configfs_out;
 
+	if (!zalloc_cpumask_var(&iscsit_global->allowed_cpumask, GFP_KERNEL)) {
+		pr_err("Unable to allocate iscsit_global->allowed_cpumask\n");
+		goto bitmap_out;
+	}
+	cpumask_setall(iscsit_global->allowed_cpumask);
+
 	lio_qr_cache = kmem_cache_create("lio_qr_cache",
 			sizeof(struct iscsi_queue_req),
 			__alignof__(struct iscsi_queue_req), 0, NULL);
 	if (!lio_qr_cache) {
 		pr_err("Unable to kmem_cache_create() for"
 				" lio_qr_cache\n");
-		goto bitmap_out;
+		goto cpumask_out;
 	}
 
 	lio_dr_cache = kmem_cache_create("lio_dr_cache",
@@ -753,6 +759,8 @@ dr_out:
 	kmem_cache_destroy(lio_dr_cache);
 qr_out:
 	kmem_cache_destroy(lio_qr_cache);
+cpumask_out:
+	free_cpumask_var(iscsit_global->allowed_cpumask);
 bitmap_out:
 	vfree(iscsit_global->ts_bitmap);
 configfs_out:
@@ -782,6 +790,7 @@ static void __exit iscsi_target_cleanup_module(void)
 
 	target_unregister_template(&iscsi_ops);
 
+	free_cpumask_var(iscsit_global->allowed_cpumask);
 	vfree(iscsit_global->ts_bitmap);
 	kfree(iscsit_global);
 }
@@ -3587,6 +3596,11 @@ static int iscsit_send_reject(
 void iscsit_thread_get_cpumask(struct iscsi_conn *conn)
 {
 	int ord, cpu;
+	cpumask_t conn_allowed_cpumask;
+
+	cpumask_and(&conn_allowed_cpumask, iscsit_global->allowed_cpumask,
+		    cpu_online_mask);
+
 	/*
 	 * bitmap_id is assigned from iscsit_global->ts_bitmap from
 	 * within iscsit_start_kthreads()
@@ -3595,8 +3609,9 @@ void iscsit_thread_get_cpumask(struct iscsi_conn *conn)
 	 * iSCSI connection's RX/TX threads will be scheduled to
 	 * execute upon.
 	 */
-	ord = conn->bitmap_id % cpumask_weight(cpu_online_mask);
-	for_each_online_cpu(cpu) {
+	cpumask_clear(conn->conn_cpumask);
+	ord = conn->bitmap_id % cpumask_weight(&conn_allowed_cpumask);
+	for_each_cpu(cpu, &conn_allowed_cpumask) {
 		if (ord-- == 0) {
 			cpumask_set_cpu(cpu, conn->conn_cpumask);
 			return;
@@ -3609,6 +3624,62 @@ void iscsit_thread_get_cpumask(struct iscsi_conn *conn)
 	cpumask_setall(conn->conn_cpumask);
 }
 
+static void iscsit_thread_reschedule(struct iscsi_conn *conn)
+{
+	/*
+	 * If iscsit_global->allowed_cpumask modified, reschedule iSCSI
+	 * connection's RX/TX threads update conn->allowed_cpumask.
+	 */
+	if (!cpumask_equal(iscsit_global->allowed_cpumask,
+			   conn->allowed_cpumask)) {
+		iscsit_thread_get_cpumask(conn);
+		conn->conn_tx_reset_cpumask = 1;
+		conn->conn_rx_reset_cpumask = 1;
+		cpumask_copy(conn->allowed_cpumask,
+			     iscsit_global->allowed_cpumask);
+	}
+}
+
+void iscsit_thread_check_cpumask(
+	struct iscsi_conn *conn,
+	struct task_struct *p,
+	int mode)
+{
+	/*
+	 * The TX and RX threads maybe call iscsit_thread_check_cpumask()
+	 * at the same time. The RX thread might be faster and return from
+	 * iscsit_thread_reschedule() with conn_rx_reset_cpumask set to 0.
+	 * Then the TX thread sets it back to 1.
+	 * The next time the RX thread loops, it sees conn_rx_reset_cpumask
+	 * set to 1 and calls set_cpus_allowed_ptr() again and set it to 0.
+	 */
+	iscsit_thread_reschedule(conn);
+
+	/*
+	 * mode == 1 signals iscsi_target_tx_thread() usage.
+	 * mode == 0 signals iscsi_target_rx_thread() usage.
+	 */
+	if (mode == 1) {
+		if (!conn->conn_tx_reset_cpumask)
+			return;
+	} else {
+		if (!conn->conn_rx_reset_cpumask)
+			return;
+	}
+
+	/*
+	 * Update the CPU mask for this single kthread so that
+	 * both TX and RX kthreads are scheduled to run on the
+	 * same CPU.
+	 */
+	set_cpus_allowed_ptr(p, conn->conn_cpumask);
+	if (mode == 1)
+		conn->conn_tx_reset_cpumask = 0;
+	else
+		conn->conn_rx_reset_cpumask = 0;
+}
+EXPORT_SYMBOL(iscsit_thread_check_cpumask);
+
 int
 iscsit_immediate_queue(struct iscsi_conn *conn, struct iscsi_cmd *cmd, int state)
 {
diff --git a/drivers/target/iscsi/iscsi_target_configfs.c b/drivers/target/iscsi/iscsi_target_configfs.c
index 2a9de24a8bbe..0cedcfe207b5 100644
--- a/drivers/target/iscsi/iscsi_target_configfs.c
+++ b/drivers/target/iscsi/iscsi_target_configfs.c
@@ -1127,8 +1127,40 @@ static ssize_t lio_target_wwn_lio_version_show(struct config_item *item,
 
 CONFIGFS_ATTR_RO(lio_target_wwn_, lio_version);
 
+static ssize_t lio_target_wwn_cpus_allowed_list_show(
+		struct config_item *item, char *page)
+{
+	return sprintf(page, "%*pbl\n",
+		       cpumask_pr_args(iscsit_global->allowed_cpumask));
+}
+
+static ssize_t lio_target_wwn_cpus_allowed_list_store(
+		struct config_item *item, const char *page, size_t count)
+{
+	int ret;
+	char *orig;
+	cpumask_t new_allowed_cpumask;
+
+	orig = kstrdup(page, GFP_KERNEL);
+	if (!orig)
+		return -ENOMEM;
+
+	cpumask_clear(&new_allowed_cpumask);
+	ret = cpulist_parse(orig, &new_allowed_cpumask);
+
+	kfree(orig);
+	if (ret != 0)
+		return ret;
+
+	cpumask_copy(iscsit_global->allowed_cpumask, &new_allowed_cpumask);
+	return count;
+}
+
+CONFIGFS_ATTR(lio_target_wwn_, cpus_allowed_list);
+
 static struct configfs_attribute *lio_target_wwn_attrs[] = {
 	&lio_target_wwn_attr_lio_version,
+	&lio_target_wwn_attr_cpus_allowed_list,
 	NULL,
 };
 
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index 1a9c50401bdb..9c01fb864585 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -1129,8 +1129,15 @@ static struct iscsi_conn *iscsit_alloc_conn(struct iscsi_np *np)
 		goto free_conn_ops;
 	}
 
+	if (!zalloc_cpumask_var(&conn->allowed_cpumask, GFP_KERNEL)) {
+		pr_err("Unable to allocate conn->allowed_cpumask\n");
+		goto free_conn_cpumask;
+	}
+
 	return conn;
 
+free_conn_cpumask:
+	free_cpumask_var(conn->conn_cpumask);
 free_conn_ops:
 	kfree(conn->conn_ops);
 put_transport:
@@ -1142,6 +1149,7 @@ free_conn:
 
 void iscsit_free_conn(struct iscsi_conn *conn)
 {
+	free_cpumask_var(conn->allowed_cpumask);
 	free_cpumask_var(conn->conn_cpumask);
 	kfree(conn->conn_ops);
 	iscsit_put_transport(conn->conn_transport);
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 0fae71ac5cc8..ff292b75e23f 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -592,16 +592,14 @@ static void pscsi_complete_cmd(struct se_cmd *cmd, u8 scsi_status,
 {
 	struct pscsi_dev_virt *pdv = PSCSI_DEV(cmd->se_dev);
 	struct scsi_device *sd = pdv->pdv_sd;
-	struct pscsi_plugin_task *pt = cmd->priv;
-	unsigned char *cdb;
+	unsigned char *cdb = cmd->priv;
+
 	/*
-	 * Special case for REPORT_LUNs handling where pscsi_plugin_task has
-	 * not been allocated because TCM is handling the emulation directly.
+	 * Special case for REPORT_LUNs which is emulated and not passed on.
 	 */
-	if (!pt)
+	if (!cdb)
 		return;
 
-	cdb = &pt->pscsi_cdb[0];
 	/*
 	 * Hack to make sure that Write-Protect modepage is set if R/O mode is
 	 * forced.
@@ -962,30 +960,15 @@ pscsi_execute_cmd(struct se_cmd *cmd)
 	struct scatterlist *sgl = cmd->t_data_sg;
 	u32 sgl_nents = cmd->t_data_nents;
 	struct pscsi_dev_virt *pdv = PSCSI_DEV(cmd->se_dev);
-	struct pscsi_plugin_task *pt;
+	struct scsi_cmnd *scmd;
 	struct request *req;
 	sense_reason_t ret;
 
-	/*
-	 * Dynamically alloc cdb space, since it may be larger than
-	 * TCM_MAX_COMMAND_SIZE
-	 */
-	pt = kzalloc(sizeof(*pt) + scsi_command_size(cmd->t_task_cdb), GFP_KERNEL);
-	if (!pt) {
-		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
-	}
-	cmd->priv = pt;
-
-	memcpy(pt->pscsi_cdb, cmd->t_task_cdb,
-		scsi_command_size(cmd->t_task_cdb));
-
 	req = scsi_alloc_request(pdv->pdv_sd->request_queue,
 			cmd->data_direction == DMA_TO_DEVICE ?
 			REQ_OP_DRV_OUT : REQ_OP_DRV_IN, 0);
-	if (IS_ERR(req)) {
-		ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
-		goto fail;
-	}
+	if (IS_ERR(req))
+		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 
 	if (sgl) {
 		ret = pscsi_map_sg(cmd, sgl, sgl_nents, req);
@@ -995,14 +978,23 @@ pscsi_execute_cmd(struct se_cmd *cmd)
 
 	req->end_io = pscsi_req_done;
 	req->end_io_data = cmd;
-	scsi_req(req)->cmd_len = scsi_command_size(pt->pscsi_cdb);
-	scsi_req(req)->cmd = &pt->pscsi_cdb[0];
+
+	scmd = blk_mq_rq_to_pdu(req);
+	scmd->cmd_len = scsi_command_size(cmd->t_task_cdb);
+	if (scmd->cmd_len > sizeof(scmd->cmnd)) {
+		ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+		goto fail_put_request;
+	}
+	memcpy(scmd->cmnd, cmd->t_task_cdb, scmd->cmd_len);
+
 	if (pdv->pdv_sd->type == TYPE_DISK ||
 	    pdv->pdv_sd->type == TYPE_ZBC)
 		req->timeout = PS_TIMEOUT_DISK;
 	else
 		req->timeout = PS_TIMEOUT_OTHER;
-	scsi_req(req)->retries = PS_RETRY;
+	scmd->allowed = PS_RETRY;
+
+	cmd->priv = scmd->cmnd;
 
 	blk_execute_rq_nowait(req, cmd->sam_task_attr == TCM_HEAD_TAG,
 			pscsi_req_done);
@@ -1011,8 +1003,6 @@ pscsi_execute_cmd(struct se_cmd *cmd)
 
 fail_put_request:
 	blk_mq_free_request(req);
-fail:
-	kfree(pt);
 	return ret;
 }
 
@@ -1040,33 +1030,30 @@ static sector_t pscsi_get_blocks(struct se_device *dev)
 static void pscsi_req_done(struct request *req, blk_status_t status)
 {
 	struct se_cmd *cmd = req->end_io_data;
-	struct pscsi_plugin_task *pt = cmd->priv;
-	int result = scsi_req(req)->result;
-	enum sam_status scsi_status = result & 0xff;
+	struct scsi_cmnd *scmd = blk_mq_rq_to_pdu(req);
+	enum sam_status scsi_status = scmd->result & 0xff;
+	u8 *cdb = cmd->priv;
 
 	if (scsi_status != SAM_STAT_GOOD) {
 		pr_debug("PSCSI Status Byte exception at cmd: %p CDB:"
-			" 0x%02x Result: 0x%08x\n", cmd, pt->pscsi_cdb[0],
-			result);
+			" 0x%02x Result: 0x%08x\n", cmd, cdb[0], scmd->result);
 	}
 
-	pscsi_complete_cmd(cmd, scsi_status, scsi_req(req)->sense);
+	pscsi_complete_cmd(cmd, scsi_status, scmd->sense_buffer);
 
-	switch (host_byte(result)) {
+	switch (host_byte(scmd->result)) {
 	case DID_OK:
 		target_complete_cmd_with_length(cmd, scsi_status,
-			cmd->data_length - scsi_req(req)->resid_len);
+			cmd->data_length - scmd->resid_len);
 		break;
 	default:
 		pr_debug("PSCSI Host Byte exception at cmd: %p CDB:"
-			" 0x%02x Result: 0x%08x\n", cmd, pt->pscsi_cdb[0],
-			result);
+			" 0x%02x Result: 0x%08x\n", cmd, cdb[0], scmd->result);
 		target_complete_cmd(cmd, SAM_STAT_CHECK_CONDITION);
 		break;
 	}
 
 	blk_mq_free_request(req);
-	kfree(pt);
 }
 
 static const struct target_backend_ops pscsi_ops = {
diff --git a/drivers/target/target_core_pscsi.h b/drivers/target/target_core_pscsi.h
index e8458b5e85c9..23d9a6e340d4 100644
--- a/drivers/target/target_core_pscsi.h
+++ b/drivers/target/target_core_pscsi.h
@@ -23,10 +23,6 @@ struct block_device;
 struct scsi_device;
 struct Scsi_Host;
 
-struct pscsi_plugin_task {
-	unsigned char pscsi_cdb[0];
-} ____cacheline_aligned;
-
 #define PDF_HAS_CHANNEL_ID	0x01
 #define PDF_HAS_TARGET_ID	0x02
 #define PDF_HAS_LUN_ID		0x04
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 7b2a89a67cdb..95d4ca50a605 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -61,10 +61,10 @@
 #define TCMU_TIME_OUT (30 * MSEC_PER_SEC)
 
 /* For mailbox plus cmd ring, the size is fixed 8MB */
-#define MB_CMDR_SIZE (8 * 1024 * 1024)
+#define MB_CMDR_SIZE_DEF (8 * 1024 * 1024)
 /* Offset of cmd ring is size of mailbox */
-#define CMDR_OFF sizeof(struct tcmu_mailbox)
-#define CMDR_SIZE (MB_CMDR_SIZE - CMDR_OFF)
+#define CMDR_OFF ((__u32)sizeof(struct tcmu_mailbox))
+#define CMDR_SIZE_DEF (MB_CMDR_SIZE_DEF - CMDR_OFF)
 
 /*
  * For data area, the default block size is PAGE_SIZE and
@@ -1617,6 +1617,7 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 
 	udev->data_pages_per_blk = DATA_PAGES_PER_BLK_DEF;
 	udev->max_blocks = DATA_AREA_PAGES_DEF / udev->data_pages_per_blk;
+	udev->cmdr_size = CMDR_SIZE_DEF;
 	udev->data_area_mb = TCMU_PAGES_TO_MBS(DATA_AREA_PAGES_DEF);
 
 	mutex_init(&udev->cmdr_lock);
@@ -2189,7 +2190,7 @@ static int tcmu_configure_device(struct se_device *dev)
 		goto err_bitmap_alloc;
 	}
 
-	mb = vzalloc(MB_CMDR_SIZE);
+	mb = vzalloc(udev->cmdr_size + CMDR_OFF);
 	if (!mb) {
 		ret = -ENOMEM;
 		goto err_vzalloc;
@@ -2198,10 +2199,9 @@ static int tcmu_configure_device(struct se_device *dev)
 	/* mailbox fits in first part of CMDR space */
 	udev->mb_addr = mb;
 	udev->cmdr = (void *)mb + CMDR_OFF;
-	udev->cmdr_size = CMDR_SIZE;
-	udev->data_off = MB_CMDR_SIZE;
+	udev->data_off = udev->cmdr_size + CMDR_OFF;
 	data_size = TCMU_MBS_TO_PAGES(udev->data_area_mb) << PAGE_SHIFT;
-	udev->mmap_pages = (data_size + MB_CMDR_SIZE) >> PAGE_SHIFT;
+	udev->mmap_pages = (data_size + udev->cmdr_size + CMDR_OFF) >> PAGE_SHIFT;
 	udev->data_blk_size = udev->data_pages_per_blk * PAGE_SIZE;
 	udev->dbi_thresh = 0; /* Default in Idle state */
 
@@ -2221,7 +2221,7 @@ static int tcmu_configure_device(struct se_device *dev)
 
 	info->mem[0].name = "tcm-user command & data buffer";
 	info->mem[0].addr = (phys_addr_t)(uintptr_t)udev->mb_addr;
-	info->mem[0].size = data_size + MB_CMDR_SIZE;
+	info->mem[0].size = data_size + udev->cmdr_size + CMDR_OFF;
 	info->mem[0].memtype = UIO_MEM_NONE;
 
 	info->irqcontrol = tcmu_irqcontrol;
@@ -2401,7 +2401,7 @@ static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)
 enum {
 	Opt_dev_config, Opt_dev_size, Opt_hw_block_size, Opt_hw_max_sectors,
 	Opt_nl_reply_supported, Opt_max_data_area_mb, Opt_data_pages_per_blk,
-	Opt_err,
+	Opt_cmd_ring_size_mb, Opt_err,
 };
 
 static match_table_t tokens = {
@@ -2412,6 +2412,7 @@ static match_table_t tokens = {
 	{Opt_nl_reply_supported, "nl_reply_supported=%d"},
 	{Opt_max_data_area_mb, "max_data_area_mb=%d"},
 	{Opt_data_pages_per_blk, "data_pages_per_blk=%d"},
+	{Opt_cmd_ring_size_mb, "cmd_ring_size_mb=%d"},
 	{Opt_err, NULL}
 };
 
@@ -2509,6 +2510,41 @@ unlock:
 	return ret;
 }
 
+static int tcmu_set_cmd_ring_size(struct tcmu_dev *udev, substring_t *arg)
+{
+	int val, ret;
+
+	ret = match_int(arg, &val);
+	if (ret < 0) {
+		pr_err("match_int() failed for cmd_ring_size_mb=. Error %d.\n",
+		       ret);
+		return ret;
+	}
+
+	if (val <= 0) {
+		pr_err("Invalid cmd_ring_size_mb %d.\n", val);
+		return -EINVAL;
+	}
+
+	mutex_lock(&udev->cmdr_lock);
+	if (udev->data_bitmap) {
+		pr_err("Cannot set cmd_ring_size_mb after it has been enabled.\n");
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	udev->cmdr_size = (val << 20) - CMDR_OFF;
+	if (val > (MB_CMDR_SIZE_DEF >> 20)) {
+		pr_err("%d is too large. Adjusting cmd_ring_size_mb to global limit of %u\n",
+		       val, (MB_CMDR_SIZE_DEF >> 20));
+		udev->cmdr_size = CMDR_SIZE_DEF;
+	}
+
+unlock:
+	mutex_unlock(&udev->cmdr_lock);
+	return ret;
+}
+
 static ssize_t tcmu_set_configfs_dev_params(struct se_device *dev,
 		const char *page, ssize_t count)
 {
@@ -2563,6 +2599,9 @@ static ssize_t tcmu_set_configfs_dev_params(struct se_device *dev,
 		case Opt_data_pages_per_blk:
 			ret = tcmu_set_data_pages_per_blk(udev, &args[0]);
 			break;
+		case Opt_cmd_ring_size_mb:
+			ret = tcmu_set_cmd_ring_size(udev, &args[0]);
+			break;
 		default:
 			break;
 		}
@@ -2584,7 +2623,9 @@ static ssize_t tcmu_show_configfs_dev_params(struct se_device *dev, char *b)
 		     udev->dev_config[0] ? udev->dev_config : "NULL");
 	bl += sprintf(b + bl, "Size: %llu ", udev->dev_size);
 	bl += sprintf(b + bl, "MaxDataAreaMB: %u ", udev->data_area_mb);
-	bl += sprintf(b + bl, "DataPagesPerBlk: %u\n", udev->data_pages_per_blk);
+	bl += sprintf(b + bl, "DataPagesPerBlk: %u ", udev->data_pages_per_blk);
+	bl += sprintf(b + bl, "CmdRingSizeMB: %u\n",
+		      (udev->cmdr_size + CMDR_OFF) >> 20);
 
 	return bl;
 }
@@ -2693,6 +2734,17 @@ static ssize_t tcmu_data_pages_per_blk_show(struct config_item *item,
 }
 CONFIGFS_ATTR_RO(tcmu_, data_pages_per_blk);
 
+static ssize_t tcmu_cmd_ring_size_mb_show(struct config_item *item, char *page)
+{
+	struct se_dev_attrib *da = container_of(to_config_group(item),
+						struct se_dev_attrib, da_group);
+	struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
+
+	return snprintf(page, PAGE_SIZE, "%u\n",
+			(udev->cmdr_size + CMDR_OFF) >> 20);
+}
+CONFIGFS_ATTR_RO(tcmu_, cmd_ring_size_mb);
+
 static ssize_t tcmu_dev_config_show(struct config_item *item, char *page)
 {
 	struct se_dev_attrib *da = container_of(to_config_group(item),
@@ -3064,6 +3116,7 @@ static struct configfs_attribute *tcmu_attrib_attrs[] = {
 	&tcmu_attr_qfull_time_out,
 	&tcmu_attr_max_data_area_mb,
 	&tcmu_attr_data_pages_per_blk,
+	&tcmu_attr_cmd_ring_size_mb,
 	&tcmu_attr_dev_config,
 	&tcmu_attr_dev_size,
 	&tcmu_attr_emulate_write_cache,