Commit 7c8d4698 authored by Nicolai Stange's avatar Nicolai Stange Committed by Greg Kroah-Hartman

debugfs: add support for more elaborate ->d_fsdata

Currently, the user provided fops, "real_fops", are stored directly into

In order to be able to store more per-file state and thus prepare for more
granular file removal protection, wrap the real_fops into a dynamically
allocated container struct, debugfs_fsdata.

A struct debugfs_fsdata gets allocated at file creation and freed from the
newly intoduced ->d_release().

Finally, move the implementation of debugfs_real_fops() out of the public
debugfs header such that struct debugfs_fsdata's declaration can be kept
Signed-off-by: default avatarNicolai Stange <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 2ec16150
......@@ -97,6 +97,18 @@ EXPORT_SYMBOL_GPL(debugfs_use_file_finish);
#define F_DENTRY(filp) ((filp)->f_path.dentry)
const struct file_operations *debugfs_real_fops(const struct file *filp)
struct debugfs_fsdata *fsd = F_DENTRY(filp)->d_fsdata;
* Neither the pointer to the struct file_operations, nor its
* contents ever change -- srcu_dereference() is not needed here.
return fsd->real_fops;
static int open_proxy_open(struct inode *inode, struct file *filp)
const struct dentry *dentry = F_DENTRY(filp);
......@@ -185,6 +185,11 @@ static const struct super_operations debugfs_super_operations = {
.evict_inode = debugfs_evict_inode,
static void debugfs_release_dentry(struct dentry *dentry)
static struct vfsmount *debugfs_automount(struct path *path)
debugfs_automount_t f;
......@@ -194,6 +199,7 @@ static struct vfsmount *debugfs_automount(struct path *path)
static const struct dentry_operations debugfs_dops = {
.d_delete = always_delete_dentry,
.d_release = debugfs_release_dentry,
.d_automount = debugfs_automount,
......@@ -341,24 +347,34 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
struct dentry *dentry;
struct inode *inode;
struct debugfs_fsdata *fsd;
fsd = kmalloc(sizeof(*fsd), GFP_KERNEL);
if (!fsd)
return NULL;
if (!(mode & S_IFMT))
mode |= S_IFREG;
dentry = start_creating(name, parent);
if (IS_ERR(dentry))
if (IS_ERR(dentry)) {
return NULL;
inode = debugfs_get_inode(dentry->d_sb);
if (unlikely(!inode))
if (unlikely(!inode)) {
return failed_creating(dentry);
inode->i_mode = mode;
inode->i_private = data;
inode->i_fop = proxy_fops;
dentry->d_fsdata = (void *)real_fops;
fsd->real_fops = real_fops;
dentry->d_fsdata = fsd;
d_instantiate(dentry, inode);
fsnotify_create(d_inode(dentry->d_parent), dentry);
......@@ -19,4 +19,8 @@ extern const struct file_operations debugfs_noop_file_operations;
extern const struct file_operations debugfs_open_proxy_file_operations;
extern const struct file_operations debugfs_full_proxy_file_operations;
struct debugfs_fsdata {
const struct file_operations *real_fops;
#endif /* _DEBUGFS_INTERNAL_H_ */
......@@ -45,23 +45,6 @@ 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)
* 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) \
{ \
......@@ -112,6 +95,9 @@ 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)
ssize_t debugfs_attr_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos);
ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
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