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Subject: Re: [PATCH v7 07/14] nvmet-passthru: add enable/disable helpers
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>
 <20190801234514.7941-8-logang@deltatee.com>
From:   Max Gurtovoy <maxg@mellanox.com>
Message-ID: <e0323600-c4e8-00e7-d8cc-ff8d31b4ed10@mellanox.com>
Date:   Thu, 15 Aug 2019 15:20:35 +0300
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On 8/2/2019 2:45 AM, Logan Gunthorpe wrote:
> This patch adds helper functions which are used in the NVMeOF configfs
> when the user is configuring the passthru subsystem. Here we ensure
> that only one subsys is assigned to each nvme_ctrl by using an xarray
> on the cntlid.
>
> [chaitanya.kulkarni@wdc.com: this patch is very roughly based
>   on a similar one by Chaitanya]
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> ---
>   drivers/nvme/target/core.c            |  8 +++
>   drivers/nvme/target/io-cmd-passthru.c | 77 +++++++++++++++++++++++++++
>   drivers/nvme/target/nvmet.h           | 10 ++++
>   3 files changed, 95 insertions(+)
>
> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index 50c01b2da568..2e75968af7f4 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -519,6 +519,12 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
>   
>   	mutex_lock(&subsys->lock);
>   	ret = 0;
> +
> +	if (nvmet_passthru_ctrl(subsys)) {
> +		pr_info("cannot enable both passthru and regular namespaces for a single subsystem");
> +		goto out_unlock;
> +	}
> +
>   	if (ns->enabled)
>   		goto out_unlock;
>   
> @@ -1439,6 +1445,8 @@ static void nvmet_subsys_free(struct kref *ref)
>   
>   	WARN_ON_ONCE(!list_empty(&subsys->namespaces));
>   
> +	nvmet_passthru_subsys_free(subsys);
> +
>   	kfree(subsys->subsysnqn);
>   	kfree(subsys);
>   }
> diff --git a/drivers/nvme/target/io-cmd-passthru.c b/drivers/nvme/target/io-cmd-passthru.c
> index 46c58fec5608..b199785500ad 100644
> --- a/drivers/nvme/target/io-cmd-passthru.c
> +++ b/drivers/nvme/target/io-cmd-passthru.c
> @@ -11,6 +11,11 @@
>   #include "../host/nvme.h"
>   #include "nvmet.h"
>   
> +/*
> + * xarray to maintain one passthru subsystem per nvme controller.
> + */
> +static DEFINE_XARRAY(passthru_subsystems);
> +
>   static struct workqueue_struct *passthru_wq;
>   
>   int nvmet_passthru_init(void)
> @@ -27,6 +32,78 @@ void nvmet_passthru_destroy(void)
>   	destroy_workqueue(passthru_wq);
>   }
>   
> +int nvmet_passthru_ctrl_enable(struct nvmet_subsys *subsys)
> +{
> +	struct nvme_ctrl *ctrl;
> +	int ret = -EINVAL;
> +	void *old;
> +
> +	mutex_lock(&subsys->lock);
> +	if (!subsys->passthru_ctrl_path)
> +		goto out_unlock;
> +	if (subsys->passthru_ctrl)
> +		goto out_unlock;
> +
> +	if (subsys->nr_namespaces) {
> +		pr_info("cannot enable both passthru and regular namespaces for a single subsystem");
> +		goto out_unlock;
> +	}
> +
> +	ctrl = nvme_ctrl_get_by_path(subsys->passthru_ctrl_path);
> +	if (IS_ERR(ctrl)) {
> +		ret = PTR_ERR(ctrl);
> +		pr_err("failed to open nvme controller %s\n",
> +		       subsys->passthru_ctrl_path);
> +
> +		goto out_unlock;
> +	}
> +
> +	old = xa_cmpxchg(&passthru_subsystems, ctrl->cntlid, NULL,
> +			 subsys, GFP_KERNEL);
> +	if (xa_is_err(old)) {
> +		ret = xa_err(old);
> +		goto out_put_ctrl;
> +	}
> +
> +	if (old)
> +		goto out_put_ctrl;
> +
> +	subsys->passthru_ctrl = ctrl;
> +	ret = 0;
> +
> +	goto out_unlock;

can we re-arrange the code here ?

it's not so common to see goto in a good flow.

maybe have 1 good flow the goto's will go bellow it as we usually do in 
this subsystem.


> +
> +out_put_ctrl:
> +	nvme_put_ctrl(ctrl);
> +out_unlock:
> +	mutex_unlock(&subsys->lock);
> +	return ret;
> +}
> +
> +static void __nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys)
> +{
> +	if (subsys->passthru_ctrl) {
> +		xa_erase(&passthru_subsystems, subsys->passthru_ctrl->cntlid);
> +		nvme_put_ctrl(subsys->passthru_ctrl);
> +	}
> +	subsys->passthru_ctrl = NULL;
> +}
> +
> +void nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys)
> +{
> +	mutex_lock(&subsys->lock);
> +	__nvmet_passthru_ctrl_disable(subsys);
> +	mutex_unlock(&subsys->lock);
> +}
> +
> +void nvmet_passthru_subsys_free(struct nvmet_subsys *subsys)
> +{
> +	mutex_lock(&subsys->lock);
> +	__nvmet_passthru_ctrl_disable(subsys);
> +	kfree(subsys->passthru_ctrl_path);
> +	mutex_unlock(&subsys->lock);
> +}
> +
>   static void nvmet_passthru_req_complete(struct nvmet_req *req,
>   		struct request *rq, u16 status)
>   {
> diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
> index bd11114ebbb9..aff4db03269d 100644
> --- a/drivers/nvme/target/nvmet.h
> +++ b/drivers/nvme/target/nvmet.h
> @@ -230,6 +230,7 @@ struct nvmet_subsys {
>   
>   #ifdef CONFIG_NVME_TARGET_PASSTHRU
>   	struct nvme_ctrl	*passthru_ctrl;
> +	char			*passthru_ctrl_path;
>   #endif /* CONFIG_NVME_TARGET_PASSTHRU */
>   };
>   
> @@ -509,6 +510,9 @@ static inline u32 nvmet_rw_len(struct nvmet_req *req)
>   
>   int nvmet_passthru_init(void);
>   void nvmet_passthru_destroy(void);
> +void nvmet_passthru_subsys_free(struct nvmet_subsys *subsys);
> +int nvmet_passthru_ctrl_enable(struct nvmet_subsys *subsys);
> +void nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys);
>   u16 nvmet_parse_passthru_cmd(struct nvmet_req *req);
>   
>   static inline
> @@ -526,6 +530,12 @@ static inline int nvmet_passthru_init(void)
>   static inline void nvmet_passthru_destroy(void)
>   {
>   }
> +static inline void nvmet_passthru_subsys_free(struct nvmet_subsys *subsys)
> +{
> +}
> +static inline void nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys)
> +{
> +}
>   static inline u16 nvmet_parse_passthru_cmd(struct nvmet_req *req)
>   {
>   	return 0;