[PATCH v15 5/9] nvme-core: Introduce nvme_ctrl_get_by_path()

[Logan Gunthorpe]

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 at deltatee.com>
Reviewed-by: Max Gurtovoy <maxg at mellanox.com>
Reviewed-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/host/core.c | 31 +++++++++++++++++++++++++++++++
 drivers/nvme/host/nvme.h |  6 ++++++
 2 files changed, 37 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 817ab76d2838..6e7d5cb43a06 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4572,6 +4572,37 @@ void nvme_sync_queues(struct nvme_ctrl *ctrl)
 }
 EXPORT_SYMBOL_GPL(nvme_sync_queues);
 
+#ifdef CONFIG_NVME_TARGET_PASSTHRU
+/*
+ * The exports that follow within this ifdef are only for
+ * use by the nvmet-passthru and should not be used for
+ * other things.
+ */
+
+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;
+	}
+
+	ctrl = f->private_data;
+	nvme_get_ctrl(ctrl);
+
+out_close:
+	filp_close(f, NULL);
+	return ctrl;
+}
+EXPORT_SYMBOL_GPL(nvme_ctrl_get_by_path);
+#endif /* CONFIG_NVME_TARGET_PASSTHRU */
+
 /*
  * Check we didn't inadvertently grow the command structure sizes:
  */
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 13ca90bcd352..485492a98ef5 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -763,4 +763,10 @@ void nvme_hwmon_init(struct nvme_ctrl *ctrl);
 static inline void nvme_hwmon_init(struct nvme_ctrl *ctrl) { }
 #endif
 
+/*
+ * These functions are only for use by nvmet-passthru and are only exported
+ * if CONFIG_NVME_TARGET_PASSTHRU is set.
+ */
+struct nvme_ctrl *nvme_ctrl_get_by_path(const char *path);
+
 #endif /* _NVME_H */
-- 
2.20.1