[PATCH v2 0/2] target: Introduce dummy devices

[PATCH v2 0/2] target: Introduce dummy devices

[Konstantin Shelekhin]

This patch series (inspired by SCST) adds support for the dummy devices
via the new DUMMY flag of rd_mcp. The rationale behind the change is to
give a user the ability to create conifgurable devices for LUN 0 with
custom WWN values (like vendor, product or revision) as some tools like
QConvergeGUI use LUN 0 to identify the whole storage.

The advantage over simply creating a NULLIO rd_mcp device is that the
DUMMY device will not be seen as a block device, hence less confusion
for the system administrator.

Konstantin Shelekhin (2):
  target: Add the DUMMY flag to rd_mcp
  target: Make the virtual LUN 0 device dummy

 drivers/target/target_core_device.c |  2 +-
 drivers/target/target_core_rd.c     | 27 +++++++++++++++++++++++----
 drivers/target/target_core_rd.h     |  1 +
 drivers/target/target_core_spc.c    |  6 +-----
 4 files changed, 26 insertions(+), 10 deletions(-)

-- 
2.31.0

[PATCH v2 1/2] target: Add the DUMMY flag to rd_mcp

[Konstantin Shelekhin]

This commit adds the DUMMY flag to the rd_mcp backend that forces a
logical unit to report itself as not connected device of an unknown
type. Essentially this allows users to create devices identical to the
device for the virtual LUN 0, making it possible to explicitly create a
LUN 0 device and configure it's WWNs (e.g. vendor or product name).

Signed-off-by: Konstantin Shelekhin <k.shelekhin@yadro.com>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 drivers/target/target_core_rd.c | 27 +++++++++++++++++++++++----
 drivers/target/target_core_rd.h |  1 +
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
index bf936bbeccfe..6648c1c90e19 100644
--- a/drivers/target/target_core_rd.c
+++ b/drivers/target/target_core_rd.c
@@ -530,12 +530,13 @@ rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 }
 
 enum {
-	Opt_rd_pages, Opt_rd_nullio, Opt_err
+	Opt_rd_pages, Opt_rd_nullio, Opt_rd_dummy, Opt_err
 };
 
 static match_table_t tokens = {
 	{Opt_rd_pages, "rd_pages=%d"},
 	{Opt_rd_nullio, "rd_nullio=%d"},
+	{Opt_rd_dummy, "rd_dummy=%d"},
 	{Opt_err, NULL}
 };
 
@@ -574,6 +575,14 @@ static ssize_t rd_set_configfs_dev_params(struct se_device *dev,
 			pr_debug("RAMDISK: Setting NULLIO flag: %d\n", arg);
 			rd_dev->rd_flags |= RDF_NULLIO;
 			break;
+		case Opt_rd_dummy:
+			match_int(args, &arg);
+			if (arg != 1)
+				break;
+
+			pr_debug("RAMDISK: Setting DUMMY flag: %d\n", arg);
+			rd_dev->rd_flags |= RDF_DUMMY;
+			break;
 		default:
 			break;
 		}
@@ -590,12 +599,22 @@ static ssize_t rd_show_configfs_dev_params(struct se_device *dev, char *b)
 	ssize_t bl = sprintf(b, "TCM RamDisk ID: %u  RamDisk Makeup: rd_mcp\n",
 			rd_dev->rd_dev_id);
 	bl += sprintf(b + bl, "        PAGES/PAGE_SIZE: %u*%lu"
-			"  SG_table_count: %u  nullio: %d\n", rd_dev->rd_page_count,
+			"  SG_table_count: %u  nullio: %d dummy: %d\n",
+			rd_dev->rd_page_count,
 			PAGE_SIZE, rd_dev->sg_table_count,
-			!!(rd_dev->rd_flags & RDF_NULLIO));
+			!!(rd_dev->rd_flags & RDF_NULLIO),
+			!!(rd_dev->rd_flags & RDF_DUMMY));
 	return bl;
 }
 
+static u32 rd_get_device_type(struct se_device *dev)
+{
+	if (RD_DEV(dev)->rd_flags & RDF_DUMMY)
+		return 0x3f; /* Unknown device type, not connected */
+	else
+		return sbc_get_device_type(dev);
+}
+
 static sector_t rd_get_blocks(struct se_device *dev)
 {
 	struct rd_dev *rd_dev = RD_DEV(dev);
@@ -647,7 +666,7 @@ static const struct target_backend_ops rd_mcp_ops = {
 	.parse_cdb		= rd_parse_cdb,
 	.set_configfs_dev_params = rd_set_configfs_dev_params,
 	.show_configfs_dev_params = rd_show_configfs_dev_params,
-	.get_device_type	= sbc_get_device_type,
+	.get_device_type	= rd_get_device_type,
 	.get_blocks		= rd_get_blocks,
 	.init_prot		= rd_init_prot,
 	.free_prot		= rd_free_prot,
diff --git a/drivers/target/target_core_rd.h b/drivers/target/target_core_rd.h
index 8b88f9b14c3f..9ffda5c4b584 100644
--- a/drivers/target/target_core_rd.h
+++ b/drivers/target/target_core_rd.h
@@ -28,6 +28,7 @@ struct rd_dev_sg_table {
 
 #define RDF_HAS_PAGE_COUNT	0x01
 #define RDF_NULLIO		0x02
+#define RDF_DUMMY		0x04
 
 struct rd_dev {
 	struct se_device dev;
-- 
2.31.0

[PATCH v2 2/2] target: Make the virtual LUN 0 device dummy

[Konstantin Shelekhin]

Create the device for the virtual LUN 0 using the DUMMY flag. This
change makes it possible to remove some special-casing in the
INQUIRY code.

Signed-off-by: Konstantin Shelekhin <k.shelekhin@yadro.com>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 drivers/target/target_core_device.c | 2 +-
 drivers/target/target_core_spc.c    | 6 +-----
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 7787c527aad3..2d50da7840fc 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -1029,7 +1029,7 @@ int core_dev_setup_virtual_lun0(void)
 {
 	struct se_hba *hba;
 	struct se_device *dev;
-	char buf[] = "rd_pages=8,rd_nullio=1";
+	char buf[] = "rd_pages=8,rd_nullio=1,rd_dummy=1";
 	int ret;
 
 	hba = core_alloc_hba("rd_mcp", 0, HBA_FLAGS_INTERNAL_USE);
diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
index ca5579ebc81d..70a661801cb9 100644
--- a/drivers/target/target_core_spc.c
+++ b/drivers/target/target_core_spc.c
@@ -701,7 +701,6 @@ static sense_reason_t
 spc_emulate_inquiry(struct se_cmd *cmd)
 {
 	struct se_device *dev = cmd->se_dev;
-	struct se_portal_group *tpg = cmd->se_lun->lun_tpg;
 	unsigned char *rbuf;
 	unsigned char *cdb = cmd->t_task_cdb;
 	unsigned char *buf;
@@ -715,10 +714,7 @@ spc_emulate_inquiry(struct se_cmd *cmd)
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 	}
 
-	if (dev == rcu_access_pointer(tpg->tpg_virt_lun0->lun_se_dev))
-		buf[0] = 0x3f; /* Not connected */
-	else
-		buf[0] = dev->transport->get_device_type(dev);
+	buf[0] = dev->transport->get_device_type(dev);
 
 	if (!(cdb[1] & 0x1)) {
 		if (cdb[2]) {
-- 
2.31.0

Re: [PATCH v2 0/2] target: Introduce dummy devices

[michael.christie]

On 3/22/21 3:09 PM, Konstantin Shelekhin wrote:
> This patch series (inspired by SCST) adds support for the dummy devices
> via the new DUMMY flag of rd_mcp. The rationale behind the change is to
> give a user the ability to create conifgurable devices for LUN 0 with
> custom WWN values (like vendor, product or revision) as some tools like
> QConvergeGUI use LUN 0 to identify the whole storage.
> 
> The advantage over simply creating a NULLIO rd_mcp device is that the
> DUMMY device will not be seen as a block device, hence less confusion
> for the system administrator.
> 
> Konstantin Shelekhin (2):
>   target: Add the DUMMY flag to rd_mcp
>   target: Make the virtual LUN 0 device dummy
> 
>  drivers/target/target_core_device.c |  2 +-
>  drivers/target/target_core_rd.c     | 27 +++++++++++++++++++++++----
>  drivers/target/target_core_rd.h     |  1 +
>  drivers/target/target_core_spc.c    |  6 +-----
>  4 files changed, 26 insertions(+), 10 deletions(-)
> 

Patches look ok and tested ok for me.

Reviewed-by: Mike Christie <michael.christie@oracle.com>

Re: [PATCH v2 0/2] target: Introduce dummy devices

[Martin K. Petersen]

On Mon, 22 Mar 2021 23:09:36 +0300, Konstantin Shelekhin wrote:

> This patch series (inspired by SCST) adds support for the dummy devices
> via the new DUMMY flag of rd_mcp. The rationale behind the change is to
> give a user the ability to create conifgurable devices for LUN 0 with
> custom WWN values (like vendor, product or revision) as some tools like
> QConvergeGUI use LUN 0 to identify the whole storage.
> 
> The advantage over simply creating a NULLIO rd_mcp device is that the
> DUMMY device will not be seen as a block device, hence less confusion
> for the system administrator.
> 
> [...]

Applied to 5.13/scsi-queue, thanks!

[1/2] target: Add the DUMMY flag to rd_mcp
      https://git.kernel.org/mkp/scsi/c/0aecfa662e43
[2/2] target: Make the virtual LUN 0 device dummy
      https://git.kernel.org/mkp/scsi/c/1b5ad814af5e

-- 
Martin K. Petersen	Oracle Linux Engineering