Introduce a new class for multipathed devices, scsi_mpath_device_class.
The purpose of this class is for managing the scsi_mpath_head.dev member.
The naming for the scsi_device structure is in form H:C:I:L,
where H is host, C is channel, I is ID, and L is lun.
However, for a multipathed scsi_device, all the naming members may be
different between member scsi_device's. As such, just use a simple
single-number naming index for each scsi_mpath_head.
The sysfs device folder will have links to the scsi_device's so, it will
be possible to lookup the member scsi_device's.
An example sysfs entry is as follows:
# ls -l /sys/class/scsi_mpath_device/0/
total 0
drwxr-xr-x 2 root root 0 Feb 24 11:56 power
lrwxrwxrwx 1 root root 0 Feb 24 11:56 subsystem -> ../../../../class/scsi_mpath_device
-rw-r--r-- 1 root root 4096 Feb 24 11:55 uevent
-r--r--r-- 1 root root 4096 Feb 24 11:56 wwid
# cat /sys/class/scsi_mpath_device/0/wwid
naa.600140505200a986f0043c9afa1fd077
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
drivers/scsi/scsi_multipath.c | 67 ++++++++++++++++++++++++++++++++++-
1 file changed, 66 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
index 49316269fad8e..05af178921cb4 100644
--- a/drivers/scsi/scsi_multipath.c
+++ b/drivers/scsi/scsi_multipath.c
@@ -85,6 +85,69 @@ static int scsi_mpath_unique_lun_id(struct scsi_device *sdev)
return 0;
}
+static void scsi_mpath_delete_head(struct scsi_mpath_head *scsi_mpath_head)
+{
+ mutex_lock(&scsi_mpath_heads_lock);
+ list_del_init(&scsi_mpath_head->entry);
+ mutex_unlock(&scsi_mpath_heads_lock);
+}
+
+static void scsi_mpath_head_release(struct device *dev)
+{
+ struct scsi_mpath_head *scsi_mpath_head =
+ container_of(dev, struct scsi_mpath_head, dev);
+ struct mpath_head *mpath_head = scsi_mpath_head->mpath_head;
+
+ scsi_mpath_delete_head(scsi_mpath_head);
+ ida_free(&scsi_multipath_dev_ida, scsi_mpath_head->index);
+ mpath_put_head(mpath_head);
+ kfree(scsi_mpath_head);
+}
+
+static ssize_t scsi_mpath_device_wwid_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct scsi_mpath_head *scsi_mpath_head =
+ container_of(dev, struct scsi_mpath_head, dev);
+
+ return sysfs_emit(buf, "%s\n", scsi_mpath_head->wwid);
+}
+
+static DEVICE_ATTR(wwid, S_IRUGO, scsi_mpath_device_wwid_show, NULL);
+
+static struct attribute *scsi_mpath_device_attrs[] = {
+ &dev_attr_wwid.attr,
+ NULL
+};
+
+static const struct attribute_group scsi_mpath_device_attrs_group = {
+ .attrs = scsi_mpath_device_attrs,
+};
+
+static bool scsi_multipath_sysfs_group_visible(struct kobject *kobj)
+{
+ return true;
+}
+
+static bool scsi_multipath_sysfs_attr_visible(struct kobject *kobj,
+ struct attribute *attr, int n)
+{
+ return false;
+}
+DEFINE_SYSFS_GROUP_VISIBLE(scsi_multipath_sysfs)
+
+const struct attribute_group *scsi_mpath_device_groups[] = {
+ &scsi_mpath_device_attrs_group,
+ NULL
+};
+
+static const struct class scsi_mpath_device_class = {
+ .name = "scsi_mpath_device",
+ .dev_groups = scsi_mpath_device_groups,
+ .dev_release = scsi_mpath_head_release,
+};
+
static int scsi_multipath_sdev_init(struct scsi_device *sdev)
{
struct Scsi_Host *shost = sdev->host;
@@ -129,6 +192,7 @@ static struct scsi_mpath_head *scsi_mpath_alloc_head(void)
goto out_put_head;
device_initialize(&scsi_mpath_head->dev);
+ scsi_mpath_head->dev.class = &scsi_mpath_device_class;
ret = dev_set_name(&scsi_mpath_head->dev, "%d", scsi_mpath_head->index);
if (ret) {
put_device(&scsi_mpath_head->dev);
@@ -294,11 +358,12 @@ EXPORT_SYMBOL_GPL(scsi_mpath_put_head);
int __init scsi_multipath_init(void)
{
- return 0;
+ return class_register(&scsi_mpath_device_class);
}
void __exit scsi_multipath_exit(void)
{
+ class_unregister(&scsi_mpath_device_class);
}
MODULE_LICENSE("GPL");
--
2.43.5On 2/25/26 16:36, John Garry wrote: > Introduce a new class for multipathed devices, scsi_mpath_device_class. > > The purpose of this class is for managing the scsi_mpath_head.dev member. > > The naming for the scsi_device structure is in form H:C:I:L, > where H is host, C is channel, I is ID, and L is lun. > > However, for a multipathed scsi_device, all the naming members may be > different between member scsi_device's. As such, just use a simple > single-number naming index for each scsi_mpath_head. > > The sysfs device folder will have links to the scsi_device's so, it will > be possible to lookup the member scsi_device's. > > An example sysfs entry is as follows: > # ls -l /sys/class/scsi_mpath_device/0/ > total 0 > drwxr-xr-x 2 root root 0 Feb 24 11:56 power > lrwxrwxrwx 1 root root 0 Feb 24 11:56 subsystem -> ../../../../class/scsi_mpath_device > -rw-r--r-- 1 root root 4096 Feb 24 11:55 uevent > -r--r--r-- 1 root root 4096 Feb 24 11:56 wwid > # cat /sys/class/scsi_mpath_device/0/wwid > naa.600140505200a986f0043c9afa1fd077 > Ah, here it is. So you can ignore my comments from the previous patch. (and you might think of merging this and the previous patch). But device naming is still dodgy. A plain number has so many ways of being misinterpreted. Wouldn't it be better to name it 'mpathX' ? And, of course: how can we get the topology? Do we get a list of the underlying scsi devices from sysfs? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.com +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
On 03/03/2026 07:16, Hannes Reinecke wrote: > On 2/25/26 16:36, John Garry wrote: >> Introduce a new class for multipathed devices, scsi_mpath_device_class. >> >> The purpose of this class is for managing the scsi_mpath_head.dev member. >> >> The naming for the scsi_device structure is in form H:C:I:L, >> where H is host, C is channel, I is ID, and L is lun. >> >> However, for a multipathed scsi_device, all the naming members may be >> different between member scsi_device's. As such, just use a simple >> single-number naming index for each scsi_mpath_head. >> >> The sysfs device folder will have links to the scsi_device's so, it will >> be possible to lookup the member scsi_device's. >> >> An example sysfs entry is as follows: >> # ls -l /sys/class/scsi_mpath_device/0/ >> total 0 >> drwxr-xr-x 2 root root 0 Feb 24 11:56 power >> lrwxrwxrwx 1 root root 0 Feb 24 11:56 subsystem - >> > ../../../../class/scsi_mpath_device >> -rw-r--r-- 1 root root 4096 Feb 24 11:55 uevent >> -r--r--r-- 1 root root 4096 Feb 24 11:56 wwid >> # cat /sys/class/scsi_mpath_device/0/wwid >> naa.600140505200a986f0043c9afa1fd077 >> > Ah, here it is. > So you can ignore my comments from the previous patch. > (and you might think of merging this and the previous patch). ok, I can reorder and/or merge. > > But device naming is still dodgy. A plain number has so many ways of > being misinterpreted. > Wouldn't it be better to name it 'mpathX' ? > sure, maybe that is better. Any other naming suggestions? Originally I had smpdX (but dropped it), where that is "Scsi MultiPath Device" and X is a number index. Cheers
On Wed, Feb 25, 2026 at 03:36:07PM +0000, John Garry wrote:
> Introduce a new class for multipathed devices, scsi_mpath_device_class.
>
> The purpose of this class is for managing the scsi_mpath_head.dev member.
>
> The naming for the scsi_device structure is in form H:C:I:L,
> where H is host, C is channel, I is ID, and L is lun.
>
> However, for a multipathed scsi_device, all the naming members may be
> different between member scsi_device's. As such, just use a simple
> single-number naming index for each scsi_mpath_head.
>
> The sysfs device folder will have links to the scsi_device's so, it will
> be possible to lookup the member scsi_device's.
>
> An example sysfs entry is as follows:
> # ls -l /sys/class/scsi_mpath_device/0/
> total 0
> drwxr-xr-x 2 root root 0 Feb 24 11:56 power
> lrwxrwxrwx 1 root root 0 Feb 24 11:56 subsystem -> ../../../../class/scsi_mpath_device
> -rw-r--r-- 1 root root 4096 Feb 24 11:55 uevent
> -r--r--r-- 1 root root 4096 Feb 24 11:56 wwid
> # cat /sys/class/scsi_mpath_device/0/wwid
> naa.600140505200a986f0043c9afa1fd077
>
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
> drivers/scsi/scsi_multipath.c | 67 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 66 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
> index 49316269fad8e..05af178921cb4 100644
> --- a/drivers/scsi/scsi_multipath.c
> +++ b/drivers/scsi/scsi_multipath.c
> @@ -85,6 +85,69 @@ static int scsi_mpath_unique_lun_id(struct scsi_device *sdev)
> return 0;
> }
>
> +static void scsi_mpath_delete_head(struct scsi_mpath_head *scsi_mpath_head)
> +{
> + mutex_lock(&scsi_mpath_heads_lock);
> + list_del_init(&scsi_mpath_head->entry);
> + mutex_unlock(&scsi_mpath_heads_lock);
> +}
> +
> +static void scsi_mpath_head_release(struct device *dev)
> +{
> + struct scsi_mpath_head *scsi_mpath_head =
> + container_of(dev, struct scsi_mpath_head, dev);
> + struct mpath_head *mpath_head = scsi_mpath_head->mpath_head;
> +
> + scsi_mpath_delete_head(scsi_mpath_head);
> + ida_free(&scsi_multipath_dev_ida, scsi_mpath_head->index);
> + mpath_put_head(mpath_head);
> + kfree(scsi_mpath_head);
> +}
> +
> +static ssize_t scsi_mpath_device_wwid_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct scsi_mpath_head *scsi_mpath_head =
> + container_of(dev, struct scsi_mpath_head, dev);
> +
> + return sysfs_emit(buf, "%s\n", scsi_mpath_head->wwid);
> +}
> +
> +static DEVICE_ATTR(wwid, S_IRUGO, scsi_mpath_device_wwid_show, NULL);
> +
> +static struct attribute *scsi_mpath_device_attrs[] = {
> + &dev_attr_wwid.attr,
> + NULL
> +};
> +
> +static const struct attribute_group scsi_mpath_device_attrs_group = {
> + .attrs = scsi_mpath_device_attrs,
> +};
> +
> +static bool scsi_multipath_sysfs_group_visible(struct kobject *kobj)
> +{
> + return true;
> +}
> +
> +static bool scsi_multipath_sysfs_attr_visible(struct kobject *kobj,
> + struct attribute *attr, int n)
The return for this is actually a umode_t.
> +{
> + return false;
> +}
> +DEFINE_SYSFS_GROUP_VISIBLE(scsi_multipath_sysfs)
Nitpick again: This could just use DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE()
Also, this code would make more sense in the next patch.
-Ben
> +
> +const struct attribute_group *scsi_mpath_device_groups[] = {
> + &scsi_mpath_device_attrs_group,
> + NULL
> +};
> +
> +static const struct class scsi_mpath_device_class = {
> + .name = "scsi_mpath_device",
> + .dev_groups = scsi_mpath_device_groups,
> + .dev_release = scsi_mpath_head_release,
> +};
> +
> static int scsi_multipath_sdev_init(struct scsi_device *sdev)
> {
> struct Scsi_Host *shost = sdev->host;
> @@ -129,6 +192,7 @@ static struct scsi_mpath_head *scsi_mpath_alloc_head(void)
> goto out_put_head;
>
> device_initialize(&scsi_mpath_head->dev);
> + scsi_mpath_head->dev.class = &scsi_mpath_device_class;
> ret = dev_set_name(&scsi_mpath_head->dev, "%d", scsi_mpath_head->index);
> if (ret) {
> put_device(&scsi_mpath_head->dev);
> @@ -294,11 +358,12 @@ EXPORT_SYMBOL_GPL(scsi_mpath_put_head);
>
> int __init scsi_multipath_init(void)
> {
> - return 0;
> + return class_register(&scsi_mpath_device_class);
> }
>
> void __exit scsi_multipath_exit(void)
> {
> + class_unregister(&scsi_mpath_device_class);
> }
>
> MODULE_LICENSE("GPL");
> --
> 2.43.5
On 02/03/2026 02:54, Benjamin Marzinski wrote:
>> static bool scsi_multipath_sysfs_attr_visible(struct kobject *kobj,
>> + struct attribute *attr, int n)
> The return for this is actually a umode_t.
>
>> +{
>> + return false;
>> +}
>> +DEFINE_SYSFS_GROUP_VISIBLE(scsi_multipath_sysfs)
> Nitpick again: This could just use DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE()
> Also, this code would make more sense in the next patch.
ok, can change, thanks!
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