From: Logan Gunthorpe <logang@deltatee.com>
Date: Fri, 24 Jul 2020 11:25:15 -0600
Subject: [PATCH] nvme: introduce nvme_ctrl_get_by_path()
Git-commit: f783f444ceaa7eab043a7a5ae0e34c68743c0358
Patch-mainline: v5.9-rc1
References: jsc#SLE-15608

nvme_ctrl_get_by_path() is analogous 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
and is exported under the NVME_TARGET_PASSTHRU namespace.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/nvme/host/core.c | 23 +++++++++++++++++++++++
 drivers/nvme/host/nvme.h |  1 +
 2 files changed, 24 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 8296c1248f87..c44316c5018f 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4590,6 +4590,29 @@ void nvme_sync_queues(struct nvme_ctrl *ctrl)
 }
 EXPORT_SYMBOL_GPL(nvme_sync_queues);
 
+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_NS_GPL(nvme_ctrl_get_by_path, 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 4e3bc4b66c57..5af59a9bac53 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -793,5 +793,6 @@ static inline void nvme_hwmon_init(struct nvme_ctrl *ctrl) { }
 u32 nvme_command_effects(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 			 u8 opcode);
 void nvme_execute_passthru_rq(struct request *rq);
+struct nvme_ctrl *nvme_ctrl_get_by_path(const char *path);
 
 #endif /* _NVME_H */
-- 
2.16.4