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Subject: Re: [PATCH v7 01/14] nvme-core: introduce nvme_ctrl_get_by_path()
To:     Logan Gunthorpe <logang@deltatee.com>,
        <linux-kernel@vger.kernel.org>, <linux-nvme@lists.infradead.org>,
        <linux-block@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>
CC:     Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
        "Keith Busch" <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
        Stephen Bates <sbates@raithlin.com>
References: <20190801234514.7941-1-logang@deltatee.com>
 <20190801234514.7941-2-logang@deltatee.com>
From:   Max Gurtovoy <maxg@mellanox.com>
Message-ID: <563baec2-61f6-5705-d751-1eee75370e66@mellanox.com>
Date:   Thu, 15 Aug 2019 14:46:35 +0300
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On 8/2/2019 2:45 AM, Logan Gunthorpe wrote:
> nvme_ctrl_get_by_path() is analagous to blkdev_get_by_path() except it
> gets a struct nvme_ctrl from the path to its char dev (/dev/nvme0).
> It makes use of filp_open() to open the file and uses the private
> data to obtain a pointer to the struct nvme_ctrl. If the fops of the
> file do not match, -EINVAL is returned.
>
> The purpose of this function is to support NVMe-OF target passthru.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> ---
>   drivers/nvme/host/core.c | 24 ++++++++++++++++++++++++
>   drivers/nvme/host/nvme.h |  2 ++
>   2 files changed, 26 insertions(+)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index e6ee6f2a3da6..f72334f34a30 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2817,6 +2817,30 @@ static const struct file_operations nvme_dev_fops = {
>   	.compat_ioctl	= nvme_dev_ioctl,
>   };
>   
> +struct nvme_ctrl *nvme_ctrl_get_by_path(const char *path)
> +{
> +	struct nvme_ctrl *ctrl;
> +	struct file *f;
> +
> +	f = filp_open(path, O_RDWR, 0);
> +	if (IS_ERR(f))
> +		return ERR_CAST(f);
> +
> +	if (f->f_op != &nvme_dev_fops) {
> +		ctrl = ERR_PTR(-EINVAL);
> +		goto out_close;
> +	}

Logan,

this means that the PT is for nvme-pci and also nvme-fabrics as well.

Is this the intention ? or we want to restrict it to pci only.


> +
> +	ctrl = f->private_data;
> +	nvme_get_ctrl(ctrl);
> +
> +out_close:
> +	filp_close(f, NULL);
> +
> +	return ctrl;
> +}
> +EXPORT_SYMBOL_GPL(nvme_ctrl_get_by_path);
> +
>   static ssize_t nvme_sysfs_reset(struct device *dev,
>   				struct device_attribute *attr, const char *buf,
>   				size_t count)
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index ecbd90c31d0d..7e827c9e892c 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -484,6 +484,8 @@ int nvme_get_log(struct nvme_ctrl *ctrl, u32 nsid, u8 log_page, u8 lsp,
>   extern const struct attribute_group *nvme_ns_id_attr_groups[];
>   extern const struct block_device_operations nvme_ns_head_ops;
>   
> +struct nvme_ctrl *nvme_ctrl_get_by_path(const char *path);
> +
>   #ifdef CONFIG_NVME_MULTIPATH
>   static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
>   {