linux-kernel - Re: [PATCH v7 11/14] nvmet-configfs: introduce passthru configfs interface

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Date:   Thu, 15 Aug 2019 15:46:16 +0300
From:   Max Gurtovoy <maxg@...lanox.com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        <linux-kernel@...r.kernel.org>, <linux-nvme@...ts.infradead.org>,
        <linux-block@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
CC:     Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
        "Keith Busch" <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        Stephen Bates <sbates@...thlin.com>
Subject: Re: [PATCH v7 11/14] nvmet-configfs: introduce passthru configfs
 interface


On 8/2/2019 2:45 AM, Logan Gunthorpe wrote:
> When CONFIG_NVME_TARGET_PASSTHRU as 'passthru' directory will
> be added to each subsystem. The directory is similar to a namespace
> and has two attributes: device_path and enable. The user must set the
> path to the nvme controller's char device and write '1' to enable the
> subsystem to use passthru.
>
> Any given subsystem is prevented from enabling both a regular namespace
> and the passthru device. If one is enabled, enabling the other will
> produce an error.
>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> ---
>   drivers/nvme/target/configfs.c | 99 ++++++++++++++++++++++++++++++++++
>   drivers/nvme/target/nvmet.h    |  1 +
>   2 files changed, 100 insertions(+)
>
> diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
> index 98613a45bd3b..b15d64c19f58 100644
> --- a/drivers/nvme/target/configfs.c
> +++ b/drivers/nvme/target/configfs.c
> @@ -615,6 +615,103 @@ static const struct config_item_type nvmet_namespaces_type = {
>   	.ct_owner		= THIS_MODULE,
>   };
>   
> +#ifdef CONFIG_NVME_TARGET_PASSTHRU
> +
> +static ssize_t nvmet_passthru_device_path_show(struct config_item *item,
> +		char *page)
> +{
> +	struct nvmet_subsys *subsys = to_subsys(item->ci_parent);
> +
> +	return snprintf(page, PAGE_SIZE, "%s\n", subsys->passthru_ctrl_path);
> +}
> +
> +static ssize_t nvmet_passthru_device_path_store(struct config_item *item,
> +		const char *page, size_t count)
> +{
> +	struct nvmet_subsys *subsys = to_subsys(item->ci_parent);
> +	int ret = -ENOMEM;

seems like a redundant initialization.

> +	size_t len;
> +
> +	mutex_lock(&subsys->lock);
> +
> +	ret = -EBUSY;
> +	if (subsys->passthru_ctrl)
> +		goto out_unlock;
> +
> +	ret = -EINVAL;
> +	len = strcspn(page, "\n");
> +	if (!len)
> +		goto out_unlock;
> +
> +	kfree(subsys->passthru_ctrl_path);
> +	ret = -ENOMEM;
> +	subsys->passthru_ctrl_path = kstrndup(page, len, GFP_KERNEL);
> +	if (!subsys->passthru_ctrl_path)
> +		goto out_unlock;
> +
> +	mutex_unlock(&subsys->lock);
> +
> +	return count;
> +out_unlock:
> +	mutex_unlock(&subsys->lock);
> +	return ret;
> +}
> +CONFIGFS_ATTR(nvmet_passthru_, device_path);
> +
> +static ssize_t nvmet_passthru_enable_show(struct config_item *item,
> +		char *page)
> +{
> +	struct nvmet_subsys *subsys = to_subsys(item->ci_parent);
> +
> +	return sprintf(page, "%d\n", subsys->passthru_ctrl ? 1 : 0);
> +}
> +
> +static ssize_t nvmet_passthru_enable_store(struct config_item *item,
> +		const char *page, size_t count)
> +{
> +	struct nvmet_subsys *subsys = to_subsys(item->ci_parent);
> +	bool enable;
> +	int ret = 0;
> +
> +	if (strtobool(page, &enable))
> +		return -EINVAL;
> +
> +	if (enable)
> +		ret = nvmet_passthru_ctrl_enable(subsys);
> +	else
> +		nvmet_passthru_ctrl_disable(subsys);
> +
> +	return ret ? ret : count;
> +}
> +CONFIGFS_ATTR(nvmet_passthru_, enable);
> +
> +static struct configfs_attribute *nvmet_passthru_attrs[] = {
> +	&nvmet_passthru_attr_device_path,
> +	&nvmet_passthru_attr_enable,
> +	NULL,
> +};
> +
> +static const struct config_item_type nvmet_passthru_type = {
> +	.ct_attrs		= nvmet_passthru_attrs,
> +	.ct_owner		= THIS_MODULE,
> +};
> +
> +static void nvmet_add_passthru_group(struct nvmet_subsys *subsys)
> +{
> +	config_group_init_type_name(&subsys->passthru_group,
> +				    "passthru", &nvmet_passthru_type);
> +	configfs_add_default_group(&subsys->passthru_group,
> +				   &subsys->group);
> +}
> +
> +#else /* CONFIG_NVME_TARGET_PASSTHRU */
> +
> +static void nvmet_add_passthru_group(struct nvmet_subsys *subsys)
> +{
> +}
> +
> +#endif /* CONFIG_NVME_TARGET_PASSTHRU */
> +
>   static int nvmet_port_subsys_allow_link(struct config_item *parent,
>   		struct config_item *target)
>   {
> @@ -915,6 +1012,8 @@ static struct config_group *nvmet_subsys_make(struct config_group *group,
>   	configfs_add_default_group(&subsys->allowed_hosts_group,
>   			&subsys->group);
>   
> +	nvmet_add_passthru_group(subsys);
> +
>   	return &subsys->group;
>   }
>   
> diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
> index 6436cb990905..f9c593f1305d 100644
> --- a/drivers/nvme/target/nvmet.h
> +++ b/drivers/nvme/target/nvmet.h
> @@ -231,6 +231,7 @@ struct nvmet_subsys {
>   #ifdef CONFIG_NVME_TARGET_PASSTHRU
>   	struct nvme_ctrl	*passthru_ctrl;
>   	char			*passthru_ctrl_path;
> +	struct config_group	passthru_group;
>   #endif /* CONFIG_NVME_TARGET_PASSTHRU */
>   };
>