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    Subject[PATCH v7 08/14] nvmet-core: allow one host per passthru-ctrl
    This patch rejects any new connection to the passthru-ctrl if this
    controller is already connected to a different host. At the time of
    allocating the controller we check if the subsys associated with
    the passthru ctrl is already connected to a host and reject it
    if the hostnqn differs.

    Connections from the same host (by hostnqn) are supported to allow
    for multipath.

    [chaitanya.kulkarni@wdc.com: based conceptually on a similar patch but
    different implementation]
    Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
    Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
    ---
    drivers/nvme/target/core.c | 4 ++++
    drivers/nvme/target/io-cmd-passthru.c | 31 +++++++++++++++++++++++++++
    drivers/nvme/target/nvmet.h | 7 ++++++
    3 files changed, 42 insertions(+)

    diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
    index 2e75968af7f4..c655f26db3da 100644
    --- a/drivers/nvme/target/core.c
    +++ b/drivers/nvme/target/core.c
    @@ -1278,6 +1278,10 @@ u16 nvmet_alloc_ctrl(const char *subsysnqn, const char *hostnqn,
    if (!ctrl->sqs)
    goto out_free_cqs;

    + ret = nvmet_passthru_alloc_ctrl(subsys, hostnqn);
    + if (ret)
    + goto out_free_sqs;
    +
    ret = ida_simple_get(&cntlid_ida,
    NVME_CNTLID_MIN, NVME_CNTLID_MAX,
    GFP_KERNEL);
    diff --git a/drivers/nvme/target/io-cmd-passthru.c b/drivers/nvme/target/io-cmd-passthru.c
    index b199785500ad..06a919283cc5 100644
    --- a/drivers/nvme/target/io-cmd-passthru.c
    +++ b/drivers/nvme/target/io-cmd-passthru.c
    @@ -104,6 +104,37 @@ void nvmet_passthru_subsys_free(struct nvmet_subsys *subsys)
    mutex_unlock(&subsys->lock);
    }

    +int nvmet_passthru_alloc_ctrl(struct nvmet_subsys *subsys,
    + const char *hostnqn)
    +{
    + struct nvmet_ctrl *ctrl;
    +
    + /*
    + * Check here if this subsystem is already connected to the passthru
    + * ctrl. We allow only one host to connect to a given passthru
    + * subsystem.
    + */
    + int rc = 0;
    +
    + mutex_lock(&subsys->lock);
    +
    + if (!subsys->passthru_ctrl)
    + goto out;
    +
    + if (list_empty(&subsys->ctrls))
    + goto out;
    +
    + ctrl = list_first_entry(&subsys->ctrls, struct nvmet_ctrl,
    + subsys_entry);
    +
    + if (strcmp(hostnqn, ctrl->hostnqn))
    + rc = -ENODEV;
    +
    +out:
    + mutex_unlock(&subsys->lock);
    + return rc;
    +}
    +
    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 aff4db03269d..6436cb990905 100644
    --- a/drivers/nvme/target/nvmet.h
    +++ b/drivers/nvme/target/nvmet.h
    @@ -513,6 +513,8 @@ 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);
    +int nvmet_passthru_alloc_ctrl(struct nvmet_subsys *subsys,
    + const char *hostnqn);
    u16 nvmet_parse_passthru_cmd(struct nvmet_req *req);

    static inline
    @@ -536,6 +538,11 @@ static inline void nvmet_passthru_subsys_free(struct nvmet_subsys *subsys)
    static inline void nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys)
    {
    }
    +static inline int nvmet_passthru_alloc_ctrl(struct nvmet_subsys *subsys,
    + const char *hostnqn)
    +{
    + return 0;
    +}
    static inline u16 nvmet_parse_passthru_cmd(struct nvmet_req *req)
    {
    return 0;
    --
    2.20.1
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