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@xxxxxxxxx>
Signed-off-by: Christian Lamparter <chunkeey@xxxxxxxxx>
---
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 592059f..309f4e9 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 1438e23..4d3f0d1 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,
--
2.9.3
