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[PATCH 02/13] scsi: alua: Create a core ALUA driver

John Garry posted 13 patches 2 weeks, 6 days ago
[PATCH 02/13] scsi: alua: Create a core ALUA driver
Posted by John Garry 2 weeks, 6 days ago 
Add a dedicated ALUA driver which can be used for native SCSI multipath
and also DH-based ALUA support.

The core driver will provide ALUA support for when a scsi_device does not
have a DH attachment.

The core driver will provide functionality to handle RTPG and STPG, but
the scsi DH ALUA driver will be responsible for driving these when DH
attached.

New structure alua_data holds all ALUA-related scsi_device info.

Hannes Reinecke originally authored the kernel ALUA code.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 drivers/scsi/Kconfig                | 10 +++-
 drivers/scsi/Makefile               |  1 +
 drivers/scsi/device_handler/Kconfig |  1 +
 drivers/scsi/scsi.c                 |  7 +++
 drivers/scsi/scsi_alua.c            | 78 +++++++++++++++++++++++++++++
 drivers/scsi/scsi_scan.c            |  4 ++
 drivers/scsi/scsi_sysfs.c           |  3 ++
 include/scsi/scsi_alua.h            | 45 +++++++++++++++++
 include/scsi/scsi_device.h          |  1 +
 9 files changed, 149 insertions(+), 1 deletion(-)
 create mode 100644 drivers/scsi/scsi_alua.c
 create mode 100644 include/scsi/scsi_alua.h

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 19d0884479a24..396cc0fda9fcc 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -76,8 +76,16 @@ config SCSI_LIB_KUNIT_TEST
 
 	  If unsure say N.
 
-comment "SCSI support type (disk, tape, CD-ROM)"
+config SCSI_ALUA
+	tristate "SPC-3 ALUA support"
 	depends on SCSI
+	help
+	  SCSI support for generic SPC-3 Asymmetric Logical Unit
+	  Access (ALUA).
+
+	  If unsure, say Y.
+
+comment "SCSI support type (disk, tape, CD-ROM)"
 
 config BLK_DEV_SD
 	tristate "SCSI disk support"
diff --git a/drivers/scsi/Makefile b/drivers/scsi/Makefile
index 16de3e41f94c4..90c25f36ea3a8 100644
--- a/drivers/scsi/Makefile
+++ b/drivers/scsi/Makefile
@@ -153,6 +153,7 @@ obj-$(CONFIG_SCSI_ENCLOSURE)	+= ses.o
 
 obj-$(CONFIG_SCSI_HISI_SAS) += hisi_sas/
 
+obj-$(CONFIG_SCSI_ALUA) += scsi_alua.o
 # This goes last, so that "real" scsi devices probe earlier
 obj-$(CONFIG_SCSI_DEBUG)	+= scsi_debug.o
 scsi_mod-y			+= scsi.o hosts.o scsi_ioctl.o \
diff --git a/drivers/scsi/device_handler/Kconfig b/drivers/scsi/device_handler/Kconfig
index 368eb94c24562..ff06aea8c272c 100644
--- a/drivers/scsi/device_handler/Kconfig
+++ b/drivers/scsi/device_handler/Kconfig
@@ -35,6 +35,7 @@ config SCSI_DH_EMC
 config SCSI_DH_ALUA
 	tristate "SPC-3 ALUA Device Handler"
 	depends on SCSI_DH && SCSI
+	select SCSI_ALUA
 	help
 	  SCSI Device handler for generic SPC-3 Asymmetric Logical Unit
 	  Access (ALUA).
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 76cdad063f7bc..fc90ee19bb962 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -58,6 +58,7 @@
 #include <linux/unaligned.h>
 
 #include <scsi/scsi.h>
+#include <scsi/scsi_alua.h>
 #include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_dbg.h>
 #include <scsi/scsi_device.h>
@@ -1042,12 +1043,17 @@ static int __init init_scsi(void)
 	error = scsi_sysfs_register();
 	if (error)
 		goto cleanup_sysctl;
+	error = scsi_alua_init();
+	if (error)
+		goto cleanup_sysfs;
 
 	scsi_netlink_init();
 
 	printk(KERN_NOTICE "SCSI subsystem initialized\n");
 	return 0;
 
+cleanup_sysfs:
+	scsi_sysfs_unregister();
 cleanup_sysctl:
 	scsi_exit_sysctl();
 cleanup_hosts:
@@ -1066,6 +1072,7 @@ static int __init init_scsi(void)
 static void __exit exit_scsi(void)
 {
 	scsi_netlink_exit();
+	scsi_exit_alua();
 	scsi_sysfs_unregister();
 	scsi_exit_sysctl();
 	scsi_exit_hosts();
diff --git a/drivers/scsi/scsi_alua.c b/drivers/scsi/scsi_alua.c
new file mode 100644
index 0000000000000..a5a67c6deff17
--- /dev/null
+++ b/drivers/scsi/scsi_alua.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic SCSI-3 ALUA SCSI driver
+ *
+ * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
+ * All rights reserved.
+ */
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_proto.h>
+#include <scsi/scsi_dbg.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_alua.h>
+
+#define DRV_NAME "alua"
+
+static struct workqueue_struct *kalua_wq;
+
+int scsi_alua_sdev_init(struct scsi_device *sdev)
+{
+	int rel_port, ret, tpgs;
+
+	tpgs = scsi_device_tpgs(sdev);
+	if (!tpgs)
+		return 0;
+
+	sdev->alua = kzalloc(sizeof(*sdev->alua), GFP_KERNEL);
+	if (!sdev->alua)
+		return -ENOMEM;
+
+	sdev->alua->group_id = scsi_vpd_tpg_id(sdev, &rel_port);
+	sdev_printk(KERN_INFO, sdev,
+			    "%s: group_id=%d\n",
+			    DRV_NAME, sdev->alua->group_id);
+	if (sdev->alua->group_id < 0) {
+		/*
+		 * Internal error; TPGS supported but required
+		 * VPD identification descriptors not present.
+		 * Disable ALUA support.
+		 */
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: No target port descriptors found\n",
+			    __func__);
+		ret = -EIO;
+		goto out_free_data;
+	}
+
+	sdev->alua->sdev = sdev;
+	sdev->alua->tpgs = tpgs;
+
+	return 0;
+out_free_data:
+	kfree(sdev->alua);
+	sdev->alua = NULL;
+	return ret;
+}
+
+void scsi_alua_sdev_exit(struct scsi_device *sdev)
+{
+	kfree(sdev->alua);
+	sdev->alua = NULL;
+}
+
+int scsi_alua_init(void)
+{
+	kalua_wq = alloc_workqueue("kalua", WQ_MEM_RECLAIM | WQ_PERCPU, 0);
+	if (!kalua_wq)
+		return -ENOMEM;
+	return 0;
+}
+
+void scsi_exit_alua(void)
+{
+	destroy_workqueue(kalua_wq);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("scsi_alua");
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 2cfcf1f5d6a46..3af64d1231445 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -38,6 +38,7 @@
 #include <linux/unaligned.h>
 
 #include <scsi/scsi.h>
+#include <scsi/scsi_alua.h>
 #include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_device.h>
 #include <scsi/scsi_driver.h>
@@ -1123,6 +1124,9 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
 	sdev->max_queue_depth = sdev->queue_depth;
 	WARN_ON_ONCE(sdev->max_queue_depth > sdev->budget_map.depth);
 
+	if (scsi_device_tpgs(sdev))
+		scsi_alua_sdev_init(sdev);
+
 	/*
 	 * Ok, the device is now all set up, we can
 	 * register it and tell the rest of the kernel
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 6b8c5c05f2944..6c4c3c22f6acf 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -16,6 +16,7 @@
 #include <linux/bsg.h>
 
 #include <scsi/scsi.h>
+#include <scsi/scsi_alua.h>
 #include <scsi/scsi_device.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_tcq.h>
@@ -480,6 +481,8 @@ static void scsi_device_dev_release(struct device *dev)
 
 	sbitmap_free(&sdev->budget_map);
 
+	scsi_alua_sdev_exit(sdev);
+
 	mutex_lock(&sdev->inquiry_mutex);
 	vpd_pg0 = rcu_replace_pointer(sdev->vpd_pg0, vpd_pg0,
 				       lockdep_is_held(&sdev->inquiry_mutex));
diff --git a/include/scsi/scsi_alua.h b/include/scsi/scsi_alua.h
new file mode 100644
index 0000000000000..07cdcb4f5b518
--- /dev/null
+++ b/include/scsi/scsi_alua.h
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic SCSI-3 ALUA SCSI Device Handler
+ *
+ * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
+ * All rights reserved.
+ */
+#ifndef _SCSI_ALUA_H
+#define _SCSI_ALUA_H
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_device.h>
+
+#if IS_ENABLED(CONFIG_SCSI_ALUA)
+
+struct alua_data {
+	int			group_id;
+	int			tpgs;
+	struct scsi_device	*sdev;
+};
+
+int scsi_alua_sdev_init(struct scsi_device *sdev);
+void scsi_alua_sdev_exit(struct scsi_device *sdev);
+
+int scsi_alua_init(void);
+void scsi_exit_alua(void);
+#else //CONFIG_SCSI_ALUA
+
+static inline int scsi_alua_sdev_init(struct scsi_device *sdev)
+{
+	return 0;
+}
+static inline void scsi_alua_sdev_exit(struct scsi_device *sdev)
+{
+
+}
+static inline int scsi_alua_init(void)
+{
+	return 0;
+}
+static inline void scsi_exit_alua(void)
+{
+}
+#endif // CONFIG_SCSI_ALUA
+#endif // _SCSI_ALUA_H
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index d32f5841f4f85..c439e837dcaa6 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -295,6 +295,7 @@ struct scsi_device {
 	struct mutex		state_mutex;
 	enum scsi_device_state sdev_state;
 	struct task_struct	*quiesced_by;
+	struct alua_data	*alua;
 	unsigned long		sdev_data[];
 } __attribute__((aligned(sizeof(unsigned long))));
 
-- 
2.43.5
Re: [PATCH 02/13] scsi: alua: Create a core ALUA driver
Posted by kernel test robot 2 weeks, 5 days ago 
Hi John,

kernel test robot noticed the following build errors:

[auto build test ERROR on mkp-scsi/for-next]
[also build test ERROR on jejb-scsi/for-next linus/master v7.0-rc4 next-20260318]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/John-Garry/scsi-scsi_dh_alua-Delete-alua_port_group/20260318-105207
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git for-next
patch link:    https://lore.kernel.org/r/20260317120703.3702387-3-john.g.garry%40oracle.com
patch subject: [PATCH 02/13] scsi: alua: Create a core ALUA driver
config: um-randconfig-001-20260319 (https://download.01.org/0day-ci/archive/20260319/202603190613.weiFq4ac-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260319/202603190613.weiFq4ac-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603190613.weiFq4ac-lkp@intel.com/

All errors (new ones prefixed by >>):

   /usr/bin/ld: drivers/scsi/scsi.o: in function `exit_scsi':
>> scsi.c:(.exit.text+0x1b): undefined reference to `scsi_exit_alua'
   /usr/bin/ld: drivers/scsi/scsi.o: in function `init_scsi':
>> scsi.c:(.init.text+0x8c): undefined reference to `scsi_alua_init'
   /usr/bin/ld: drivers/scsi/scsi_scan.o: in function `scsi_add_lun':
>> scsi_scan.c:(.text+0x1797): undefined reference to `scsi_alua_sdev_init'
   /usr/bin/ld: drivers/scsi/scsi_sysfs.o: in function `scsi_device_dev_release':
>> scsi_sysfs.c:(.text+0x1e8a): undefined reference to `scsi_alua_sdev_exit'
   collect2: error: ld returned 1 exit status

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH 02/13] scsi: alua: Create a core ALUA driver
Posted by kernel test robot 2 weeks, 5 days ago 
Hi John,

kernel test robot noticed the following build errors:

[auto build test ERROR on mkp-scsi/for-next]
[also build test ERROR on jejb-scsi/for-next linus/master v7.0-rc4 next-20260317]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/John-Garry/scsi-scsi_dh_alua-Delete-alua_port_group/20260318-105207
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git for-next
patch link:    https://lore.kernel.org/r/20260317120703.3702387-3-john.g.garry%40oracle.com
patch subject: [PATCH 02/13] scsi: alua: Create a core ALUA driver
config: s390-randconfig-001-20260318 (https://download.01.org/0day-ci/archive/20260319/202603190113.JzA11dmp-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260319/202603190113.JzA11dmp-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603190113.JzA11dmp-lkp@intel.com/

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "scsi_exit_alua" [drivers/scsi/scsi_mod.ko] undefined!
>> ERROR: modpost: "scsi_alua_init" [drivers/scsi/scsi_mod.ko] undefined!
>> ERROR: modpost: "scsi_alua_sdev_exit" [drivers/scsi/scsi_mod.ko] undefined!
>> ERROR: modpost: "scsi_alua_sdev_init" [drivers/scsi/scsi_mod.ko] undefined!

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH 02/13] scsi: alua: Create a core ALUA driver
Posted by Hannes Reinecke 2 weeks, 5 days ago 
On 3/17/26 13:06, John Garry wrote:
> Add a dedicated ALUA driver which can be used for native SCSI multipath
> and also DH-based ALUA support.
> 
Is this really a 'driver'? It's more additional functionality for a SCSI
device, and not really a driver.
At least I _think_ it is ...

> The core driver will provide ALUA support for when a scsi_device does not
> have a DH attachment.
> 
> The core driver will provide functionality to handle RTPG and STPG, but
> the scsi DH ALUA driver will be responsible for driving these when DH
> attached.
> 
> New structure alua_data holds all ALUA-related scsi_device info.
> 
> Hannes Reinecke originally authored the kernel ALUA code.
> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
>   drivers/scsi/Kconfig                | 10 +++-
>   drivers/scsi/Makefile               |  1 +
>   drivers/scsi/device_handler/Kconfig |  1 +
>   drivers/scsi/scsi.c                 |  7 +++
>   drivers/scsi/scsi_alua.c            | 78 +++++++++++++++++++++++++++++
>   drivers/scsi/scsi_scan.c            |  4 ++
>   drivers/scsi/scsi_sysfs.c           |  3 ++
>   include/scsi/scsi_alua.h            | 45 +++++++++++++++++
>   include/scsi/scsi_device.h          |  1 +
>   9 files changed, 149 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/scsi/scsi_alua.c
>   create mode 100644 include/scsi/scsi_alua.h
> 
> diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
> index 19d0884479a24..396cc0fda9fcc 100644
> --- a/drivers/scsi/Kconfig
> +++ b/drivers/scsi/Kconfig
> @@ -76,8 +76,16 @@ config SCSI_LIB_KUNIT_TEST
>   
>   	  If unsure say N.
>   
> -comment "SCSI support type (disk, tape, CD-ROM)"
> +config SCSI_ALUA
> +	tristate "SPC-3 ALUA support"
>   	depends on SCSI
> +	help
> +	  SCSI support for generic SPC-3 Asymmetric Logical Unit
> +	  Access (ALUA).
> +
> +	  If unsure, say Y.
> +
> +comment "SCSI support type (disk, tape, CD-ROM)"
>   
>   config BLK_DEV_SD
>   	tristate "SCSI disk support"
> diff --git a/drivers/scsi/Makefile b/drivers/scsi/Makefile
> index 16de3e41f94c4..90c25f36ea3a8 100644
> --- a/drivers/scsi/Makefile
> +++ b/drivers/scsi/Makefile
> @@ -153,6 +153,7 @@ obj-$(CONFIG_SCSI_ENCLOSURE)	+= ses.o
>   
>   obj-$(CONFIG_SCSI_HISI_SAS) += hisi_sas/
>   
> +obj-$(CONFIG_SCSI_ALUA) += scsi_alua.o
>   # This goes last, so that "real" scsi devices probe earlier
>   obj-$(CONFIG_SCSI_DEBUG)	+= scsi_debug.o
>   scsi_mod-y			+= scsi.o hosts.o scsi_ioctl.o \
> diff --git a/drivers/scsi/device_handler/Kconfig b/drivers/scsi/device_handler/Kconfig
> index 368eb94c24562..ff06aea8c272c 100644
> --- a/drivers/scsi/device_handler/Kconfig
> +++ b/drivers/scsi/device_handler/Kconfig
> @@ -35,6 +35,7 @@ config SCSI_DH_EMC
>   config SCSI_DH_ALUA
>   	tristate "SPC-3 ALUA Device Handler"
>   	depends on SCSI_DH && SCSI
> +	select SCSI_ALUA
>   	help
>   	  SCSI Device handler for generic SPC-3 Asymmetric Logical Unit
>   	  Access (ALUA).
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 76cdad063f7bc..fc90ee19bb962 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -58,6 +58,7 @@
>   #include <linux/unaligned.h>
>   
>   #include <scsi/scsi.h>
> +#include <scsi/scsi_alua.h>
>   #include <scsi/scsi_cmnd.h>
>   #include <scsi/scsi_dbg.h>
>   #include <scsi/scsi_device.h>
> @@ -1042,12 +1043,17 @@ static int __init init_scsi(void)
>   	error = scsi_sysfs_register();
>   	if (error)
>   		goto cleanup_sysctl;
> +	error = scsi_alua_init();
> +	if (error)
> +		goto cleanup_sysfs;
>   
>   	scsi_netlink_init();
>   
>   	printk(KERN_NOTICE "SCSI subsystem initialized\n");
>   	return 0;
>   
> +cleanup_sysfs:
> +	scsi_sysfs_unregister();
>   cleanup_sysctl:
>   	scsi_exit_sysctl();
>   cleanup_hosts:
> @@ -1066,6 +1072,7 @@ static int __init init_scsi(void)
>   static void __exit exit_scsi(void)
>   {
>   	scsi_netlink_exit();
> +	scsi_exit_alua();
>   	scsi_sysfs_unregister();
>   	scsi_exit_sysctl();
>   	scsi_exit_hosts();
> diff --git a/drivers/scsi/scsi_alua.c b/drivers/scsi/scsi_alua.c
> new file mode 100644
> index 0000000000000..a5a67c6deff17
> --- /dev/null
> +++ b/drivers/scsi/scsi_alua.c
> @@ -0,0 +1,78 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Generic SCSI-3 ALUA SCSI driver
> + *
> + * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
> + * All rights reserved.
> + */
> +
> +#include <scsi/scsi.h>
> +#include <scsi/scsi_proto.h>
> +#include <scsi/scsi_dbg.h>
> +#include <scsi/scsi_eh.h>
> +#include <scsi/scsi_alua.h>
> +
> +#define DRV_NAME "alua"
> +
> +static struct workqueue_struct *kalua_wq;
> +
> +int scsi_alua_sdev_init(struct scsi_device *sdev)
> +{
> +	int rel_port, ret, tpgs;
> +
> +	tpgs = scsi_device_tpgs(sdev);
> +	if (!tpgs)
> +		return 0;
> +
> +	sdev->alua = kzalloc(sizeof(*sdev->alua), GFP_KERNEL);
> +	if (!sdev->alua)
> +		return -ENOMEM;
> +

Why do you allocate a separate structure?
Is this structure shared with something?
Wouldn't it be better to just add some field to the scsi_device?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
Re: [PATCH 02/13] scsi: alua: Create a core ALUA driver
Posted by John Garry 2 weeks ago 
On 18/03/2026 07:47, Hannes Reinecke wrote:
> On 3/17/26 13:06, John Garry wrote:
>> Add a dedicated ALUA driver which can be used for native SCSI multipath
>> and also DH-based ALUA support.
>>
> Is this really a 'driver'? It's more additional functionality for a SCSI
> device, and not really a driver.
> At least I _think_ it is ...

Actually it's more of a library than anything :)

>> +
>> +static struct workqueue_struct *kalua_wq;
>> +
>> +int scsi_alua_sdev_init(struct scsi_device *sdev)
>> +{
>> +    int rel_port, ret, tpgs;
>> +
>> +    tpgs = scsi_device_tpgs(sdev);
>> +    if (!tpgs)
>> +        return 0;
>> +
>> +    sdev->alua = kzalloc(sizeof(*sdev->alua), GFP_KERNEL);
>> +    if (!sdev->alua)
>> +        return -ENOMEM;
>> +
> 
> Why do you allocate a separate structure?
> Is this structure shared with something?
> Wouldn't it be better to just add some field to the scsi_device?
>

I could embed the structure in scsi_device, but it's just convenient to 
ever check sdev->alua to see if alua is supported and also know that the 
members are initialized and hold valid values.

Thanks,
John

Patchew 2.1-devel-ea86937

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