From d75e1842d36fe10414f7069f32e6da9bbbcb0423 Mon Sep 17 00:00:00 2001 From: Hannes Reinecke Date: Thu, 23 Apr 2026 14:17:39 +0200 Subject: [PATCH] ublk: persistent device links Implement a 'uuid' parameter to export a device UUID in a sysfs attribute 'uuid'. The ublk server is required to set the uuid parameter when creating the device. This allows udev to create persistent device links for ublk devices eg with this rule: KERNEL=="ublk*", ATTRS{uuid}=="?*", SYMLINK+="disk/by-id/ublk-$attr{uuid}" Signed-off-by: Hannes Reinecke Reviewed-by: Ming Lei Reviewed-by: Ming Lei --- drivers/block/ublk_drv.c | 55 +++++++++++++++++++++++++++++++++-- include/uapi/linux/ublk_cmd.h | 6 ++++ 2 files changed, 59 insertions(+), 2 deletions(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 603a98a30989f..402058e157eb5 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -100,7 +100,7 @@ (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD | \ UBLK_PARAM_TYPE_DEVT | UBLK_PARAM_TYPE_ZONED | \ UBLK_PARAM_TYPE_DMA_ALIGN | UBLK_PARAM_TYPE_SEGMENT | \ - UBLK_PARAM_TYPE_INTEGRITY) + UBLK_PARAM_TYPE_INTEGRITY | UBLK_PARAM_TYPE_UUID) #define UBLK_BATCH_F_ALL \ (UBLK_BATCH_F_HAS_ZONE_LBA | \ @@ -976,6 +976,14 @@ static int ublk_validate_params(const struct ublk_device *ub) return -EINVAL; } + if (ub->params.types & UBLK_PARAM_TYPE_UUID) { + const struct ublk_param_uuid *p = &ub->params.uuid; + uuid_t uuid; + + import_uuid(&uuid, p->uuid); + if (uuid_is_null(&uuid)) + return -EINVAL; + } return 0; } @@ -4313,6 +4321,49 @@ static int ublk_add_chdev(struct ublk_device *ub) return ret; } +static ssize_t uuid_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct gendisk *disk = dev_to_disk(dev); + struct ublk_device *ub = disk->private_data; + const struct ublk_param_uuid *p = &ub->params.uuid; + uuid_t uuid; + + import_uuid(&uuid, p->uuid); + return sprintf(buf, "%pU\n", &uuid); +} + +static DEVICE_ATTR_RO(uuid); + +static struct attribute *ublk_attrs[] = { + &dev_attr_uuid.attr, + NULL, +}; + +static umode_t ublk_attrs_are_visible(struct kobject *kobj, + struct attribute *a, int n) +{ + struct device *dev = kobj_to_dev(kobj); + struct gendisk *disk = dev_to_disk(dev); + struct ublk_device *ub = disk->private_data; + + if (a == &dev_attr_uuid.attr && + (ub->params.types & UBLK_PARAM_TYPE_UUID)) + return S_IRUGO; + + return a->mode; +} + +static const struct attribute_group ublk_attr_group = { + .attrs = ublk_attrs, + .is_visible = ublk_attrs_are_visible, +}; + +static const struct attribute_group *ublk_attr_groups[] = { + &ublk_attr_group, + NULL, +}; + /* align max io buffer size with PAGE_SIZE */ static void ublk_align_max_io_size(struct ublk_device *ub) { @@ -4508,7 +4559,7 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, goto out_put_cdev; } - ret = add_disk(disk); + ret = device_add_disk(NULL, disk, ublk_attr_groups); if (ret) goto out_put_cdev; diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index 6991370a72ce6..c034b654dc69e 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -770,6 +770,10 @@ struct ublk_param_integrity { __u8 pad[5]; }; +struct ublk_param_uuid { + __u8 uuid[16]; +}; + struct ublk_params { /* * Total length of parameters, userspace has to set 'len' for both @@ -785,6 +789,7 @@ struct ublk_params { #define UBLK_PARAM_TYPE_DMA_ALIGN (1 << 4) #define UBLK_PARAM_TYPE_SEGMENT (1 << 5) #define UBLK_PARAM_TYPE_INTEGRITY (1 << 6) /* requires UBLK_F_INTEGRITY */ +#define UBLK_PARAM_TYPE_UUID (1 << 7) __u32 types; /* types of parameter included */ struct ublk_param_basic basic; @@ -794,6 +799,7 @@ struct ublk_params { struct ublk_param_dma_align dma; struct ublk_param_segment seg; struct ublk_param_integrity integrity; + struct ublk_param_uuid uuid; }; /*