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 <[email protected]>
> ---
> 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
