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debugfs: introduce a public file_operations accessor

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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>
This commit is contained in:
Christian Lamparter 2016-09-17 21:43:01 +02:00 committed by Greg Kroah-Hartman
parent 2f5bb02ff2
commit 86f0e06767
2 changed files with 22 additions and 8 deletions
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13
fs/debugfs/file.c
View File

@ -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? */

17
include/linux/debugfs.h
View File

@ -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,