[PATCH v6 10/16] nvmet-passthru: add enable/disable helpers

[Logan Gunthorpe <logang@xxxxxxxxxxxx>]

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@xxxxxxx: this patch is very roughly based
 on a similar one by Chaitanya]
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
 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 920b102ec13b..9ddcdb8415fc 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;
+
+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;
-- 
2.20.1