patch "debugfs: introduce a public file_operations accessor" added to driver-core-next

patch "debugfs: introduce a public file_operations accessor" added to driver-core-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    debugfs: introduce a public file_operations accessor

to my driver-core git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
in the driver-core-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From 86f0e06767dda7863d6d2a8f0b3b857e6ea876a0 Mon Sep 17 00:00:00 2001
From: Christian Lamparter <chunkeey@googlemail.com>
Date: Sat, 17 Sep 2016 21:43:01 +0200
Subject: debugfs: introduce a public file_operations accessor

This patch introduces an accessor which can be used
by the users of debugfs (drivers, fs, ...) to get the
original file_operations struct. It also removes the
REAL_FOPS_DEREF macro in file.c and converts the code
to use the public version.

Previously, REAL_FOPS_DEREF was only available within
the file.c of debugfs. But having a public getter
available for debugfs users is important as some
drivers (carl9170 and b43) use the pointer of the
original file_operations in conjunction with container_of()
within their debugfs implementations.

Reviewed-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Cc: stable <stable@vger.kernel.org> # 4.7+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/file.c       | 13 +++++--------
 include/linux/debugfs.h | 17 +++++++++++++++++
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 592059f88e04..309f4e9b2419 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -97,9 +97,6 @@ EXPORT_SYMBOL_GPL(debugfs_use_file_finish);
 
 #define F_DENTRY(filp) ((filp)->f_path.dentry)
 
-#define REAL_FOPS_DEREF(dentry)					\
-	((const struct file_operations *)(dentry)->d_fsdata)
-
 static int open_proxy_open(struct inode *inode, struct file *filp)
 {
 	const struct dentry *dentry = F_DENTRY(filp);
@@ -112,7 +109,7 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
 		goto out;
 	}
 
-	real_fops = REAL_FOPS_DEREF(dentry);
+	real_fops = debugfs_real_fops(filp);
 	real_fops = fops_get(real_fops);
 	if (!real_fops) {
 		/* Huh? Module did not clean up after itself at exit? */
@@ -143,7 +140,7 @@ static ret_type full_proxy_ ## name(proto)				\
 {									\
 	const struct dentry *dentry = F_DENTRY(filp);			\
 	const struct file_operations *real_fops =			\
-		REAL_FOPS_DEREF(dentry);				\
+		debugfs_real_fops(filp);				\
 	int srcu_idx;							\
 	ret_type r;							\
 									\
@@ -176,7 +173,7 @@ static unsigned int full_proxy_poll(struct file *filp,
 				struct poll_table_struct *wait)
 {
 	const struct dentry *dentry = F_DENTRY(filp);
-	const struct file_operations *real_fops = REAL_FOPS_DEREF(dentry);
+	const struct file_operations *real_fops = debugfs_real_fops(filp);
 	int srcu_idx;
 	unsigned int r = 0;
 
@@ -193,7 +190,7 @@ static unsigned int full_proxy_poll(struct file *filp,
 static int full_proxy_release(struct inode *inode, struct file *filp)
 {
 	const struct dentry *dentry = F_DENTRY(filp);
-	const struct file_operations *real_fops = REAL_FOPS_DEREF(dentry);
+	const struct file_operations *real_fops = debugfs_real_fops(filp);
 	const struct file_operations *proxy_fops = filp->f_op;
 	int r = 0;
 
@@ -241,7 +238,7 @@ static int full_proxy_open(struct inode *inode, struct file *filp)
 		goto out;
 	}
 
-	real_fops = REAL_FOPS_DEREF(dentry);
+	real_fops = debugfs_real_fops(filp);
 	real_fops = fops_get(real_fops);
 	if (!real_fops) {
 		/* Huh? Module did not cleanup after itself at exit? */
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 1438e2322d5c..4d3f0d1aec73 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -45,6 +45,23 @@ extern struct dentry *arch_debugfs_dir;
 
 extern struct srcu_struct debugfs_srcu;
 
+/**
+ * debugfs_real_fops - getter for the real file operation
+ * @filp: a pointer to a struct file
+ *
+ * Must only be called under the protection established by
+ * debugfs_use_file_start().
+ */
+static inline const struct file_operations *debugfs_real_fops(struct file *filp)
+	__must_hold(&debugfs_srcu)
+{
+	/*
+	 * Neither the pointer to the struct file_operations, nor its
+	 * contents ever change -- srcu_dereference() is not needed here.
+	 */
+	return filp->f_path.dentry->d_fsdata;
+}
+
 #if defined(CONFIG_DEBUG_FS)
 
 struct dentry *debugfs_create_file(const char *name, umode_t mode,
-- 
2.10.0