Commit c6468808 authored by Nicolai Stange's avatar Nicolai Stange Committed by Greg Kroah-Hartman
Browse files

debugfs: add support for self-protecting attribute file fops



In order to protect them against file removal issues, debugfs_create_file()
creates a lifetime managing proxy around each struct file_operations
handed in.

In cases where this struct file_operations is able to manage file lifetime
by itself already, the proxy created by debugfs is a waste of resources.

The most common class of struct file_operations given to debugfs are those
defined by means of the DEFINE_SIMPLE_ATTRIBUTE() macro.

Introduce a DEFINE_DEBUGFS_ATTRIBUTE() macro to allow any
struct file_operations of this class to be easily made file lifetime aware
and thus, to be operated unproxied.

Specifically, introduce debugfs_attr_read() and debugfs_attr_write()
which wrap simple_attr_read() and simple_attr_write() under the protection
of a debugfs_use_file_start()/debugfs_use_file_finish() pair.

Make DEFINE_DEBUGFS_ATTRIBUTE() set the defined struct file_operations'
->read() and ->write() members to these wrappers.

Export debugfs_create_file_unsafe() in order to allow debugfs users to
create their files in non-proxying operation mode.
Signed-off-by: default avatarNicolai Stange <nicstange@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 49d200de
......@@ -284,6 +284,34 @@ const struct file_operations debugfs_full_proxy_file_operations = {
.open = full_proxy_open,
};
ssize_t debugfs_attr_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
ssize_t ret;
int srcu_idx;
ret = debugfs_use_file_start(F_DENTRY(file), &srcu_idx);
if (likely(!ret))
ret = simple_attr_read(file, buf, len, ppos);
debugfs_use_file_finish(srcu_idx);
return ret;
}
EXPORT_SYMBOL_GPL(debugfs_attr_read);
ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos)
{
ssize_t ret;
int srcu_idx;
ret = debugfs_use_file_start(F_DENTRY(file), &srcu_idx);
if (likely(!ret))
ret = simple_attr_write(file, buf, len, ppos);
debugfs_use_file_finish(srcu_idx);
return ret;
}
EXPORT_SYMBOL_GPL(debugfs_attr_write);
static struct dentry *debugfs_create_mode(const char *name, umode_t mode,
struct dentry *parent, void *value,
const struct file_operations *fops,
......
......@@ -369,6 +369,33 @@ struct dentry *debugfs_create_file(const char *name, umode_t mode,
}
EXPORT_SYMBOL_GPL(debugfs_create_file);
/**
* debugfs_create_file_unsafe - create a file in the debugfs filesystem
* @name: a pointer to a string containing the name of the file to create.
* @mode: the permission that the file should have.
* @parent: a pointer to the parent dentry for this file. This should be a
* directory dentry if set. If this parameter is NULL, then the
* file will be created in the root of the debugfs filesystem.
* @data: a pointer to something that the caller will want to get to later
* on. The inode.i_private pointer will point to this value on
* the open() call.
* @fops: a pointer to a struct file_operations that should be used for
* this file.
*
* debugfs_create_file_unsafe() is completely analogous to
* debugfs_create_file(), the only difference being that the fops
* handed it will not get protected against file removals by the
* debugfs core.
*
* It is your responsibility to protect your struct file_operation
* methods against file removals by means of debugfs_use_file_start()
* and debugfs_use_file_finish(). ->open() is still protected by
* debugfs though.
*
* Any struct file_operations defined by means of
* DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
* thus, may be used here.
*/
struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)
......@@ -379,6 +406,7 @@ struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
&debugfs_noop_file_operations,
fops);
}
EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
/**
* debugfs_create_file_size - create a file in the debugfs filesystem
......
......@@ -50,6 +50,9 @@ extern struct srcu_struct debugfs_srcu;
struct dentry *debugfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);
struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);
struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
struct dentry *parent, void *data,
......@@ -74,6 +77,26 @@ int debugfs_use_file_start(const struct dentry *dentry, int *srcu_idx)
void debugfs_use_file_finish(int srcu_idx) __releases(&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,
size_t len, loff_t *ppos);
#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \
static int __fops ## _open(struct inode *inode, struct file *file) \
{ \
__simple_attr_check_format(__fmt, 0ull); \
return simple_attr_open(inode, file, __get, __set, __fmt); \
} \
static const struct file_operations __fops = { \
.owner = THIS_MODULE, \
.open = __fops ## _open, \
.release = simple_attr_release, \
.read = debugfs_attr_read, \
.write = debugfs_attr_write, \
.llseek = generic_file_llseek, \
}
struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
struct dentry *new_dir, const char *new_name);
......@@ -193,6 +216,9 @@ static inline void debugfs_use_file_finish(int srcu_idx)
__releases(&debugfs_srcu)
{ }
#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \
static const struct file_operations __fops = { 0 }
static inline struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
struct dentry *new_dir, char *new_name)
{
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment