Re: [PATCH V2 2/2] nvme: decouple nvme_get_ctrl() from file open

[Christoph Hellwig <hch@lst.de>]

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This needs to be split into a fix and a cleanup.

Attached is how I'd do it.


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From 497f52797e6d068712ecd794bd54d59fd7af3036 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Wed, 16 Sep 2020 08:47:50 +0200
Subject: nvmet: ensure the passthrough controller has a reference to the
 transport

Grab a reference to the transport driver to ensure it can't be unloaded
while a passthrough controller is active.

Fixes: c1fef73f793b ("nvmet: add passthru code to process commands")
Reported-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/nvme/target/passthru.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
index 8bd7f656e240b2..dacfa7435d0b2f 100644
--- a/drivers/nvme/target/passthru.c
+++ b/drivers/nvme/target/passthru.c
@@ -517,6 +517,7 @@ int nvmet_passthru_ctrl_enable(struct nvmet_subsys *subsys)
 		subsys->ver = NVME_VS(1, 2, 1);
 	}
 
+	__module_get(subsys->passthru_ctrl->ops->module);
 	mutex_unlock(&subsys->lock);
 	return 0;
 
@@ -531,6 +532,7 @@ static void __nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys)
 {
 	if (subsys->passthru_ctrl) {
 		xa_erase(&passthru_subsystems, subsys->passthru_ctrl->cntlid);
+		module_put(subsys->passthru_ctrl->ops->module);
 		nvme_put_ctrl(subsys->passthru_ctrl);
 	}
 	subsys->passthru_ctrl = NULL;
-- 
2.28.0


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From e912746df46bed02b695c9869544a111f0f7487f Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Wed, 16 Sep 2020 08:48:21 +0200
Subject: nvme: decouple nvme_get_ctrl() from file open

Lift opening the file from nvme_ctrl_get_by_path into the caller, just
keeping a simple nvme_ctrl_from_file helper.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
[hch: refactored a bit, split the bug fixes into a separate prep patch]
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/nvme/host/core.c       | 25 +++++--------------------
 drivers/nvme/host/nvme.h       |  2 +-
 drivers/nvme/target/passthru.c | 27 ++++++++++++++++-----------
 3 files changed, 22 insertions(+), 32 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c5f9d64b2bec02..f51ccb43002231 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4649,28 +4649,13 @@ 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 *nvme_ctrl_from_file(struct file *file)
 {
-	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;
+	if (file->f_op != &nvme_dev_fops)
+		return NULL;
+	return file->private_data;
 }
-EXPORT_SYMBOL_NS_GPL(nvme_ctrl_get_by_path, NVME_TARGET_PASSTHRU);
+EXPORT_SYMBOL_NS_GPL(nvme_ctrl_from_file, 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 9fd45ff656da81..1e6aaa7102627a 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -835,7 +835,7 @@ 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);
+struct nvme_ctrl *nvme_ctrl_from_file(struct file *file);
 struct nvme_ns *nvme_find_get_ns(struct nvme_ctrl *ctrl, unsigned nsid);
 void nvme_put_ns(struct nvme_ns *ns);
 
diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
index dacfa7435d0b2f..c0fd20d8097ee8 100644
--- a/drivers/nvme/target/passthru.c
+++ b/drivers/nvme/target/passthru.c
@@ -474,6 +474,7 @@ u16 nvmet_parse_passthru_admin_cmd(struct nvmet_req *req)
 int nvmet_passthru_ctrl_enable(struct nvmet_subsys *subsys)
 {
 	struct nvme_ctrl *ctrl;
+	struct file *file;
 	int ret = -EINVAL;
 	void *old;
 
@@ -488,24 +489,28 @@ int nvmet_passthru_ctrl_enable(struct nvmet_subsys *subsys)
 		goto out_unlock;
 	}
 
-	ctrl = nvme_ctrl_get_by_path(subsys->passthru_ctrl_path);
-	if (IS_ERR(ctrl)) {
-		ret = PTR_ERR(ctrl);
+	file = filp_open(subsys->passthru_ctrl_path, O_RDWR, 0);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto out_unlock;
+	}
+
+	ctrl = nvme_ctrl_from_file(file);
+	if (!ctrl) {
 		pr_err("failed to open nvme controller %s\n",
 		       subsys->passthru_ctrl_path);
-
-		goto out_unlock;
+		goto out_put_file;
 	}
 
 	old = xa_cmpxchg(&passthru_subsystems, ctrl->cntlid, NULL,
 			 subsys, GFP_KERNEL);
 	if (xa_is_err(old)) {
 		ret = xa_err(old);
-		goto out_put_ctrl;
+		goto out_put_file;
 	}
 
 	if (old)
-		goto out_put_ctrl;
+		goto out_put_file;
 
 	subsys->passthru_ctrl = ctrl;
 	subsys->ver = ctrl->vs;
@@ -517,12 +522,12 @@ int nvmet_passthru_ctrl_enable(struct nvmet_subsys *subsys)
 		subsys->ver = NVME_VS(1, 2, 1);
 	}
 
+	nvme_get_ctrl(ctrl);
 	__module_get(subsys->passthru_ctrl->ops->module);
-	mutex_unlock(&subsys->lock);
-	return 0;
+	ret = 0;
 
-out_put_ctrl:
-	nvme_put_ctrl(ctrl);
+out_put_file:
+	filp_close(file, NULL);
 out_unlock:
 	mutex_unlock(&subsys->lock);
 	return ret;
-- 
2.28.0


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