1 files changed, 45 insertions, 17 deletions

diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 1438e2322d5c..014cc564d1c4 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -45,6 +45,39 @@ 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(const 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;
+}
+
+#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt)		\
+static int __fops ## _open(struct inode *inode, struct file *file)	\
+{									\
+	__simple_attr_check_format(__fmt, 0ull);			\
+	return simple_attr_open(inode, file, __get, __set, __fmt);	\
+}									\
+static const struct file_operations __fops = {				\
+	.owner	 = THIS_MODULE,						\
+	.open	 = __fops ## _open,					\
+	.release = simple_attr_release,					\
+	.read	 = debugfs_attr_read,					\
+	.write	 = debugfs_attr_write,					\
+	.llseek  = generic_file_llseek,					\
+}
+
 #if defined(CONFIG_DEBUG_FS)
 
 struct dentry *debugfs_create_file(const char *name, umode_t mode,
@@ -82,21 +115,6 @@ ssize_t debugfs_attr_read(struct file *file, char __user *buf,
 ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
 			size_t len, loff_t *ppos);
 
-#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt)		\
-static int __fops ## _open(struct inode *inode, struct file *file)	\
-{									\
-	__simple_attr_check_format(__fmt, 0ull);			\
-	return simple_attr_open(inode, file, __get, __set, __fmt);	\
-}									\
-static const struct file_operations __fops = {				\
-	.owner	 = THIS_MODULE,					\
-	.open	 = __fops ## _open,					\
-	.release = simple_attr_release,				\
-	.read	 = debugfs_attr_read,					\
-	.write	 = debugfs_attr_write,					\
-	.llseek  = generic_file_llseek,				\
-}
-
 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
                 struct dentry *new_dir, const char *new_name);
 
@@ -216,8 +234,18 @@ static inline void debugfs_use_file_finish(int srcu_idx)
 	__releases(&debugfs_srcu)
 { }
 
-#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt)	\
-	static const struct file_operations __fops = { 0 }
+static inline ssize_t debugfs_attr_read(struct file *file, char __user *buf,
+					size_t len, loff_t *ppos)
+{
+	return -ENODEV;
+}
+
+static inline ssize_t debugfs_attr_write(struct file *file,
+					const char __user *buf,
+					size_t len, loff_t *ppos)
+{
+	return -ENODEV;
+}
 
 static inline struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
                 struct dentry *new_dir, char *new_name)