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

debugfs: add support for more elaborate ->d_fsdata 



Currently, the user provided fops, "real_fops", are stored directly into
->d_fsdata.

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
private.

Signed-off-by: default avatarNicolai Stange <nicstange@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2ec16150

fs/debugfs/file.c

+12 −0
Original line number Diff line number Diff line
@@ -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)

	__must_hold(&debugfs_srcu)

{

	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;

}

EXPORT_SYMBOL_GPL(debugfs_real_fops);



static int open_proxy_open(struct inode *inode, struct file *filp)

{

	const struct dentry *dentry = F_DENTRY(filp);

fs/debugfs/inode.c

+19 −3
Original line number Diff line number Diff line
@@ -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)

{

	kfree(dentry->d_fsdata);

}



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;

	BUG_ON(!S_ISREG(mode));

	dentry = start_creating(name, parent);



	if (IS_ERR(dentry))

	if (IS_ERR(dentry)) {

		kfree(fsd);

		return NULL;

	}



	inode = debugfs_get_inode(dentry->d_sb);

	if (unlikely(!inode))

	if (unlikely(!inode)) {

		kfree(fsd);

		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);

fs/debugfs/internal.h

+4 −0
Original line number Diff line number Diff line
@@ -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_ */

include/linux/debugfs.h

+3 −17
Original line number Diff line number Diff line
@@ -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)

	__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)	\

{									\
@@ -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)

	__must_hold(&debugfs_srcu);



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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