From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 08E6D2D8375 for ; Fri, 20 Feb 2026 11:35:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771587356; cv=none; b=Z0hUUJyO68i+fYP6Xv9u3Leko4Sw9JMZZdJ0/TwDUaqaq7ZRHAH2pIUxtrG5AK3ZwYbf5OaT/7R7jiYrjgIeCuW8n2OylxyykXdiGAOlWfZTyrU4X7opq073zNdDNF3XAhnpiq1UsMhxJ3fp1/g8NrZeLJ2iAyWjDpvGWGYFL24= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771587356; c=relaxed/simple; bh=2OoGpJ5Mywexi3BTt5E+ogbs4577B+O63xQ7OeKCEwc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Se4Q8cwdqxgTvY4Fy9HauwSN3tZ9nopHJqLc/BrIr7VbY2LnyeJ3K5lWJWfKAmAKLnUrMqz819q4pb+rvUjJa1yxjyNdJOF7lhBrHBeYt8OSobUFriznnAO4pvT/w4bv7OvkvUNl4c32HxwsSD6xP7yWoIb5d/pYb1FlhA2y8GU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=geMVNDIh; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="geMVNDIh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1771587353; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=WBLjTwFOuvMYqr5FtLunJpnAPsrf9ld2OSiOfvJCaJ4=; b=geMVNDIh1I+qYp03+QwbidHmoud4lFvbh8IwPXD/EqaAnuh9/7MADkiI58lrQzsdjO1RmO 9iaI2AFVl/KgpyvRRwrMqu65YkpaVa6G7Cftq9QjIaj2RKVlmtppfA5iYhKHvXTy0LhSnR NmjOEq1w5HlsZMYWjIF96QlTgK0CGTU= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-266-11eGQDexNP-d7MBgxcZyFg-1; Fri, 20 Feb 2026 06:35:49 -0500 X-MC-Unique: 11eGQDexNP-d7MBgxcZyFg-1 X-Mimecast-MFC-AGG-ID: 11eGQDexNP-d7MBgxcZyFg_1771587348 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 168D31956059; Fri, 20 Feb 2026 11:35:48 +0000 (UTC) Received: from fedora (unknown [10.72.116.11]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C22F5180058A; Fri, 20 Feb 2026 11:35:44 +0000 (UTC) Date: Fri, 20 Feb 2026 19:35:39 +0800 From: Ming Lei To: Hannes Reinecke Cc: linux-block@vger.kernel.org, Jens Axboe Subject: Re: [PATCH] ublk: persistent device links Message-ID: References: <20260216122730.144092-1-hare@kernel.org> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260216122730.144092-1-hare@kernel.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On Mon, Feb 16, 2026 at 01:27:30PM +0100, Hannes Reinecke wrote: > Implement a 'uuid' parameter to export a device UUID in a sysfs > attribute 'uuid'. This allows udev to create persistent device > links for ublk devices: > > KERNEL=="ublkb*", ATTRS{uuid}=="?*", SYMLINK+="disk/by-id/ublk-$attr{uuid}" > > Signed-off-by: Hannes Reinecke > --- > drivers/block/ublk_drv.c | 57 +++++++++++++++++++++++++++++++++-- > include/uapi/linux/ublk_cmd.h | 6 ++++ > 2 files changed, 61 insertions(+), 2 deletions(-) > > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c > index aaf94d2fb789..859414065be0 100644 > --- a/drivers/block/ublk_drv.c > +++ b/drivers/block/ublk_drv.c > @@ -89,7 +89,7 @@ > (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) > > struct ublk_uring_cmd_pdu { > /* > @@ -761,6 +761,16 @@ 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)) { > + printk("uuid is NULL\n"); pr_warn() could be better. > + return -EINVAL; > + } > + } > return 0; > } > > @@ -2971,6 +2981,49 @@ 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) > { > @@ -3149,7 +3202,7 @@ 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 90f47da4f435..b30a0de44b85 100644 > --- a/include/uapi/linux/ublk_cmd.h > +++ b/include/uapi/linux/ublk_cmd.h > @@ -630,6 +630,10 @@ 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 > @@ -645,6 +649,7 @@ 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; > @@ -654,6 +659,7 @@ struct ublk_params { > struct ublk_param_dma_align dma; > struct ublk_param_segment seg; > struct ublk_param_integrity integrity; > + struct ublk_param_uuid uuid; Please document ublk server should provide persistent uuid for persistent id or link. Otherwise, this patch looks fine. Thanks, Ming