[PATCH net-next 0/2] net: wwan: debugfs dev reference not dropped

[PATCH net-next 0/2] net: wwan: debugfs dev reference not dropped

[M Chetan Kumar]

This patch series contains WWAN subsystem & IOSM Driver changes to
drop dev reference obtained as part of wwan debugfs dir entry retrieval.

PATCH1: A new debugfs interface is introduced in wwan subsystem so
that wwan driver can drop the obtained dev reference post debugfs use.

PATCH2: IOSM Driver uses new debugfs interface to drop dev reference.

Please refer to commit messages for details.

M Chetan Kumar (2):
  net: wwan: debugfs obtained dev reference not dropped
  net: wwan: iosm: drop debugfs dev reference

 drivers/net/wwan/iosm/iosm_ipc_debugfs.c |  5 ++--
 drivers/net/wwan/iosm/iosm_ipc_imem.h    |  2 ++
 drivers/net/wwan/wwan_core.c             | 35 ++++++++++++++++++++++++
 include/linux/wwan.h                     |  2 ++
 4 files changed, 42 insertions(+), 2 deletions(-)

-- 
2.25.1

[PATCH net-next 1/2] net: wwan: debugfs obtained dev reference not dropped

[M Chetan Kumar]

WWAN driver call's wwan_get_debugfs_dir() to obtain
WWAN debugfs dir entry. As part of this procedure it
returns a reference to a found device.

Since there is no debugfs interface available at WWAN
subsystem, it is not possible to drop dev reference post
debugfs use. This leads to side effects like post wwan
driver load and reload the wwan instance gets increment
from wwanX to wwanX+1.

A new debugfs interface is added in wwan subsystem so that
wwan driver can drop the obtained dev reference post debugfs
use.

void wwan_put_debugfs_dir(struct dentry *dir)

Signed-off-by: M Chetan Kumar <m.chetan.kumar@linux.intel.com>
---
 drivers/net/wwan/wwan_core.c | 35 +++++++++++++++++++++++++++++++++++
 include/linux/wwan.h         |  2 ++
 2 files changed, 37 insertions(+)

diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index 1508dc2a497b..147b88464cbd 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -160,6 +160,42 @@ struct dentry *wwan_get_debugfs_dir(struct device *parent)
 	return wwandev->debugfs_dir;
 }
 EXPORT_SYMBOL_GPL(wwan_get_debugfs_dir);
+
+static int wwan_dev_debugfs_match(struct device *dev, const void *dir)
+{
+	struct wwan_device *wwandev;
+
+	if (dev->type != &wwan_dev_type)
+		return 0;
+
+	wwandev = to_wwan_dev(dev);
+
+	return wwandev->debugfs_dir == dir;
+}
+
+static struct wwan_device *wwan_dev_get_by_debugfs(struct dentry *dir)
+{
+	struct device *dev;
+
+	dev = class_find_device(wwan_class, NULL, dir, wwan_dev_debugfs_match);
+	if (!dev)
+		return ERR_PTR(-ENODEV);
+
+	return to_wwan_dev(dev);
+}
+
+void wwan_put_debugfs_dir(struct dentry *dir)
+{
+	struct wwan_device *wwandev = wwan_dev_get_by_debugfs(dir);
+
+	if (WARN_ON(IS_ERR(wwandev)))
+		return;
+
+	/* wwan_dev_get_by_debugfs() also got a reference */
+	put_device(&wwandev->dev);
+	put_device(&wwandev->dev);
+}
+EXPORT_SYMBOL_GPL(wwan_put_debugfs_dir);
 #endif
 
 /* This function allocates and registers a new WWAN device OR if a WWAN device
diff --git a/include/linux/wwan.h b/include/linux/wwan.h
index afb3334ec8c5..5ce2acf444fb 100644
--- a/include/linux/wwan.h
+++ b/include/linux/wwan.h
@@ -174,11 +174,13 @@ void wwan_unregister_ops(struct device *parent);
 
 #ifdef CONFIG_WWAN_DEBUGFS
 struct dentry *wwan_get_debugfs_dir(struct device *parent);
+void wwan_put_debugfs_dir(struct dentry *dir);
 #else
 static inline struct dentry *wwan_get_debugfs_dir(struct device *parent)
 {
 	return ERR_PTR(-ENODEV);
 }
+static inline void wwan_put_debugfs_dir(struct dentry *dir) {}
 #endif
 
 #endif /* __WWAN_H */
-- 
2.25.1

[PATCH net-next 2/2] net: wwan: iosm: drop debugfs dev reference

[M Chetan Kumar]

Post debugfs use call wwan_put_debugfs_dir()to drop
debugfs dev reference.

Signed-off-by: M Chetan Kumar <m.chetan.kumar@linux.intel.com>
---
 drivers/net/wwan/iosm/iosm_ipc_debugfs.c | 5 +++--
 drivers/net/wwan/iosm/iosm_ipc_imem.h    | 2 ++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wwan/iosm/iosm_ipc_debugfs.c b/drivers/net/wwan/iosm/iosm_ipc_debugfs.c
index f2f57751a7d2..e916139b8cd4 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_debugfs.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_debugfs.c
@@ -12,10 +12,10 @@
 
 void ipc_debugfs_init(struct iosm_imem *ipc_imem)
 {
-	struct dentry *debugfs_pdev = wwan_get_debugfs_dir(ipc_imem->dev);
+	ipc_imem->debugfs_wwan_dir = wwan_get_debugfs_dir(ipc_imem->dev);
 
 	ipc_imem->debugfs_dir = debugfs_create_dir(KBUILD_MODNAME,
-						   debugfs_pdev);
+						   ipc_imem->debugfs_wwan_dir);
 
 	ipc_imem->trace = ipc_trace_init(ipc_imem);
 	if (!ipc_imem->trace)
@@ -26,4 +26,5 @@ void ipc_debugfs_deinit(struct iosm_imem *ipc_imem)
 {
 	ipc_trace_deinit(ipc_imem->trace);
 	debugfs_remove_recursive(ipc_imem->debugfs_dir);
+	wwan_put_debugfs_dir(ipc_imem->debugfs_wwan_dir);
 }
diff --git a/drivers/net/wwan/iosm/iosm_ipc_imem.h b/drivers/net/wwan/iosm/iosm_ipc_imem.h
index 5682e8d6be7b..e700dc8bfe0a 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_imem.h
+++ b/drivers/net/wwan/iosm/iosm_ipc_imem.h
@@ -341,6 +341,7 @@ enum ipc_phase {
  * @ev_mux_net_transmit_pending:0 means inform the IPC tasklet to pass
  * @reset_det_n:		Reset detect flag
  * @pcie_wake_n:		Pcie wake flag
+ * @debugfs_wwan_dir:		WWAN Debug FS directory entry
  * @debugfs_dir:		Debug FS directory for driver-specific entries
  */
 struct iosm_imem {
@@ -384,6 +385,7 @@ struct iosm_imem {
 	   reset_det_n:1,
 	   pcie_wake_n:1;
 #ifdef CONFIG_WWAN_DEBUGFS
+	struct dentry *debugfs_wwan_dir;
 	struct dentry *debugfs_dir;
 #endif
 };
-- 
2.25.1

Re: [PATCH net-next 0/2] net: wwan: debugfs dev reference not dropped

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (master)
by David S. Miller <davem@davemloft.net>:

On Mon, 14 Feb 2022 12:46:51 +0530 you wrote:
> This patch series contains WWAN subsystem & IOSM Driver changes to
> drop dev reference obtained as part of wwan debugfs dir entry retrieval.
> 
> PATCH1: A new debugfs interface is introduced in wwan subsystem so
> that wwan driver can drop the obtained dev reference post debugfs use.
> 
> PATCH2: IOSM Driver uses new debugfs interface to drop dev reference.
> 
> [...]

Here is the summary with links:
  - [net-next,1/2] net: wwan: debugfs obtained dev reference not dropped
    https://git.kernel.org/netdev/net-next/c/76f05d88623e
  - [net-next,2/2] net: wwan: iosm: drop debugfs dev reference
    https://git.kernel.org/netdev/net-next/c/163f69ae22e5

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html