Commit c9afbec2 authored by Nicolai Stange's avatar Nicolai Stange Committed by Greg Kroah-Hartman

debugfs: purge obsolete SRCU based removal protection

Purge the SRCU based file removal race protection in favour of the new,
refcount based debugfs_file_get()/debugfs_file_put() API.

Fixes: 49d200de ("debugfs: prevent access to removed files' private data")
Signed-off-by: default avatarNicolai Stange <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 7cda7b8f
......@@ -22,7 +22,6 @@
#include <linux/slab.h>
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/srcu.h>
#include <asm/poll.h>
#include "internal.h"
......@@ -48,53 +47,6 @@ const struct file_operations debugfs_noop_file_operations = {
.llseek = noop_llseek,
* debugfs_use_file_start - mark the beginning of file data access
* @dentry: the dentry object whose data is being accessed.
* @srcu_idx: a pointer to some memory to store a SRCU index in.
* Up to a matching call to debugfs_use_file_finish(), any
* successive call into the file removing functions debugfs_remove()
* and debugfs_remove_recursive() will block. Since associated private
* file data may only get freed after a successful return of any of
* the removal functions, you may safely access it after a successful
* call to debugfs_use_file_start() without worrying about
* lifetime issues.
* If -%EIO is returned, the file has already been removed and thus,
* it is not safe to access any of its data. If, on the other hand,
* it is allowed to access the file data, zero is returned.
* Regardless of the return code, any call to
* debugfs_use_file_start() must be followed by a matching call
* to debugfs_use_file_finish().
int debugfs_use_file_start(const struct dentry *dentry, int *srcu_idx)
*srcu_idx = srcu_read_lock(&debugfs_srcu);
if (d_unlinked(dentry))
return -EIO;
return 0;
* debugfs_use_file_finish - mark the end of file data access
* @srcu_idx: the SRCU index "created" by a former call to
* debugfs_use_file_start().
* Allow any ongoing concurrent call into debugfs_remove() or
* debugfs_remove_recursive() blocked by a former call to
* debugfs_use_file_start() to proceed and return to its caller.
void debugfs_use_file_finish(int srcu_idx) __releases(&debugfs_srcu)
srcu_read_unlock(&debugfs_srcu, srcu_idx);
#define F_DENTRY(filp) ((filp)->f_path.dentry)
const struct file_operations *debugfs_real_fops(const struct file *filp)
......@@ -27,14 +27,11 @@
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/srcu.h>
#include "internal.h"
static struct vfsmount *debugfs_mount;
static int debugfs_mount_count;
static bool debugfs_registered;
......@@ -693,8 +690,6 @@ void debugfs_remove(struct dentry *dentry)
if (!ret)
simple_release_fs(&debugfs_mount, &debugfs_mount_count);
......@@ -768,8 +763,6 @@ void debugfs_remove_recursive(struct dentry *dentry)
if (!__debugfs_remove(child, parent))
simple_release_fs(&debugfs_mount, &debugfs_mount_count);
......@@ -23,7 +23,6 @@
struct device;
struct file_operations;
struct srcu_struct;
struct debugfs_blob_wrapper {
void *data;
......@@ -43,8 +42,6 @@ struct debugfs_regset32 {
extern struct dentry *arch_debugfs_dir;
extern struct srcu_struct debugfs_srcu;
#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \
static int __fops ## _open(struct inode *inode, struct file *file) \
{ \
......@@ -90,11 +87,6 @@ struct dentry *debugfs_create_automount(const char *name,
void debugfs_remove(struct dentry *dentry);
void debugfs_remove_recursive(struct dentry *dentry);
int debugfs_use_file_start(const struct dentry *dentry, int *srcu_idx)
void debugfs_use_file_finish(int srcu_idx) __releases(&debugfs_srcu);
const struct file_operations *debugfs_real_fops(const struct file *filp);
int debugfs_file_get(struct dentry *dentry);
......@@ -227,17 +219,6 @@ static inline void debugfs_remove(struct dentry *dentry)
static inline void debugfs_remove_recursive(struct dentry *dentry)
{ }
static inline int debugfs_use_file_start(const struct dentry *dentry,
int *srcu_idx)
return 0;
static inline void debugfs_use_file_finish(int srcu_idx)
{ }
static inline int debugfs_file_get(struct dentry *dentry)
return 0;
......@@ -280,7 +280,6 @@ config PAGE_OWNER
config DEBUG_FS
bool "Debug Filesystem"
select SRCU
debugfs is a virtual file system that kernel developers use to put
debugging files into. Enable this option to be able to read and
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