netdev - Re: [RFC PATCH v5 03/27] nvme-tcp-offload: Add device scan implementation

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Message-ID: <e986c505-b81a-36ab-6366-35d5fbc193e1@grimberg.me>
Date:   Fri, 21 May 2021 15:22:00 -0700
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Shai Malin <smalin@...vell.com>, netdev@...r.kernel.org,
        linux-nvme@...ts.infradead.org, davem@...emloft.net,
        kuba@...nel.org, hch@....de, axboe@...com, kbusch@...nel.org
Cc:     aelior@...vell.com, mkalderon@...vell.com, okulkarni@...vell.com,
        pkushwaha@...vell.com, malin1024@...il.com,
        Dean Balandin <dbalandin@...vell.com>
Subject: Re: [RFC PATCH v5 03/27] nvme-tcp-offload: Add device scan
 implementation



On 5/19/21 4:13 AM, Shai Malin wrote:
> From: Dean Balandin <dbalandin@...vell.com>
> 
> As part of create_ctrl(), it scans the registered devices and calls
> the claim_dev op on each of them, to find the first devices that matches
> the connection params. Once the correct devices is found (claim_dev
> returns true), we raise the refcnt of that device and return that device
> as the device to be used for ctrl currently being created.
> 
> Acked-by: Igor Russkikh <irusskikh@...vell.com>
> Signed-off-by: Dean Balandin <dbalandin@...vell.com>
> Signed-off-by: Prabhakar Kushwaha <pkushwaha@...vell.com>
> Signed-off-by: Omkar Kulkarni <okulkarni@...vell.com>
> Signed-off-by: Michal Kalderon <mkalderon@...vell.com>
> Signed-off-by: Ariel Elior <aelior@...vell.com>
> Signed-off-by: Shai Malin <smalin@...vell.com>
> ---
>   drivers/nvme/host/tcp-offload.c | 94 +++++++++++++++++++++++++++++++++
>   1 file changed, 94 insertions(+)
> 
> diff --git a/drivers/nvme/host/tcp-offload.c b/drivers/nvme/host/tcp-offload.c
> index 711232eba339..aa7cc239abf2 100644
> --- a/drivers/nvme/host/tcp-offload.c
> +++ b/drivers/nvme/host/tcp-offload.c
> @@ -13,6 +13,11 @@
>   static LIST_HEAD(nvme_tcp_ofld_devices);
>   static DECLARE_RWSEM(nvme_tcp_ofld_devices_rwsem);
>   
> +static inline struct nvme_tcp_ofld_ctrl *to_tcp_ofld_ctrl(struct nvme_ctrl *nctrl)
> +{
> +	return container_of(nctrl, struct nvme_tcp_ofld_ctrl, nctrl);
> +}
> +
>   /**
>    * nvme_tcp_ofld_register_dev() - NVMeTCP Offload Library registration
>    * function.
> @@ -98,6 +103,94 @@ void nvme_tcp_ofld_req_done(struct nvme_tcp_ofld_req *req,
>   	/* Placeholder - complete request with/without error */
>   }
>   
> +struct nvme_tcp_ofld_dev *
> +nvme_tcp_ofld_lookup_dev(struct nvme_tcp_ofld_ctrl *ctrl)
> +{
> +	struct nvme_tcp_ofld_dev *dev;
> +
> +	down_read(&nvme_tcp_ofld_devices_rwsem);
> +	list_for_each_entry(dev, &nvme_tcp_ofld_devices, entry) {
> +		if (dev->ops->claim_dev(dev, &ctrl->conn_params)) {
> +			/* Increase driver refcnt */
> +			if (!try_module_get(dev->ops->module)) {

This means that every controller will take a long-lived reference on the
module? Why?

> +				pr_err("try_module_get failed\n");
> +				dev = NULL;
> +			}
> +
> +			goto out;
> +		}
> +	}
> +
> +	dev = NULL;
> +out:
> +	up_read(&nvme_tcp_ofld_devices_rwsem);
> +
> +	return dev;
> +}
> +
> +static int nvme_tcp_ofld_setup_ctrl(struct nvme_ctrl *nctrl, bool new)
> +{
> +	/* Placeholder - validates inputs and creates admin and IO queues */
> +
> +	return 0;
> +}
> +
> +static struct nvme_ctrl *
> +nvme_tcp_ofld_create_ctrl(struct device *ndev, struct nvmf_ctrl_options *opts)
> +{
> +	struct nvme_tcp_ofld_ctrl *ctrl;
> +	struct nvme_tcp_ofld_dev *dev;
> +	struct nvme_ctrl *nctrl;
> +	int rc = 0;
> +
> +	ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
> +	if (!ctrl)
> +		return ERR_PTR(-ENOMEM);
> +
> +	nctrl = &ctrl->nctrl;
> +
> +	/* Init nvme_tcp_ofld_ctrl and nvme_ctrl params based on received opts */
> +
> +	/* Find device that can reach the dest addr */
> +	dev = nvme_tcp_ofld_lookup_dev(ctrl);
> +	if (!dev) {
> +		pr_info("no device found for addr %s:%s.\n",
> +			opts->traddr, opts->trsvcid);
> +		rc = -EINVAL;
> +		goto out_free_ctrl;
> +	}
> +
> +	ctrl->dev = dev;
> +
> +	if (ctrl->dev->ops->max_hw_sectors)
> +		nctrl->max_hw_sectors = ctrl->dev->ops->max_hw_sectors;
> +	if (ctrl->dev->ops->max_segments)
> +		nctrl->max_segments = ctrl->dev->ops->max_segments;
> +
> +	/* Init queues */
> +
> +	/* Call nvme_init_ctrl */
> +
> +	rc = ctrl->dev->ops->setup_ctrl(ctrl, true);
> +	if (rc)
> +		goto out_module_put;

goto module_put without an explicit module_get is confusing.

> +
> +	rc = nvme_tcp_ofld_setup_ctrl(nctrl, true);
> +	if (rc)
> +		goto out_uninit_ctrl;

ops->setup_ctrl and then call to nvme_tcp_ofld_setup_ctrl?
Looks weird, why are these separated?

> +
> +	return nctrl;
> +
> +out_uninit_ctrl:
> +	ctrl->dev->ops->release_ctrl(ctrl);
> +out_module_put:
> +	module_put(dev->ops->module);
> +out_free_ctrl:
> +	kfree(ctrl);
> +
> +	return ERR_PTR(rc);
> +}
> +
>   static struct nvmf_transport_ops nvme_tcp_ofld_transport = {
>   	.name		= "tcp_offload",
>   	.module		= THIS_MODULE,
> @@ -107,6 +200,7 @@ static struct nvmf_transport_ops nvme_tcp_ofld_transport = {
>   			  NVMF_OPT_RECONNECT_DELAY | NVMF_OPT_HDR_DIGEST |
>   			  NVMF_OPT_DATA_DIGEST | NVMF_OPT_NR_POLL_QUEUES |
>   			  NVMF_OPT_TOS,
> +	.create_ctrl	= nvme_tcp_ofld_create_ctrl,
>   };
>   
>   static int __init nvme_tcp_ofld_init_module(void)
>