Commit 7063fbf2 authored by Joel Becker's avatar Joel Becker

[PATCH] configfs: User-driven configuration filesystem

Configfs, a file system for userspace-driven kernel object configuration.
The OCFS2 stack makes extensive use of this for propagation of cluster
configuration information into kernel.
Signed-off-by: default avatarJoel Becker <joel.becker@oracle.com>
parent 88026842
......@@ -12,6 +12,8 @@ cifs.txt
- description of the CIFS filesystem
coda.txt
- description of the CODA filesystem.
configfs/
- directory containing configfs documentation and example code.
cramfs.txt
- info on the cram filesystem for small storage (ROMs etc)
devfs/
......
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......@@ -554,6 +554,11 @@ W: http://us1.samba.org/samba/Linux_CIFS_client.html
T: git kernel.org:/pub/scm/linux/kernel/git/sfrench/cifs-2.6.git
S: Supported
CONFIGFS
P: Joel Becker
M: Joel Becker <joel.becker@oracle.com>
S: Supported
CIRRUS LOGIC GENERIC FBDEV DRIVER
P: Jeff Garzik
M: jgarzik@pobox.com
......
......@@ -841,6 +841,20 @@ config RELAYFS_FS
If unsure, say N.
config CONFIGFS_FS
tristate "Userspace-driven configuration filesystem (EXPERIMENTAL)"
depends on EXPERIMENTAL
help
configfs is a ram-based filesystem that provides the converse
of sysfs's functionality. Where sysfs is a filesystem-based
view of kernel objects, configfs is a filesystem-based manager
of kernel objects, or config_items.
Both sysfs and configfs can and should exist together on the
same system. One is not a replacement for the other.
If unsure, say N.
endmenu
menu "Miscellaneous filesystems"
......
......@@ -101,3 +101,4 @@ obj-$(CONFIG_BEFS_FS) += befs/
obj-$(CONFIG_HOSTFS) += hostfs/
obj-$(CONFIG_HPPFS) += hppfs/
obj-$(CONFIG_DEBUG_FS) += debugfs/
obj-$(CONFIG_CONFIGFS_FS) += configfs/
#
# Makefile for the configfs virtual filesystem
#
obj-$(CONFIG_CONFIGFS_FS) += configfs.o
configfs-objs := inode.o file.o dir.o symlink.o mount.o item.o
/* -*- mode: c; c-basic-offset:8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* configfs_internal.h - Internal stuff for configfs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*
* Based on sysfs:
* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
*
* configfs Copyright (C) 2005 Oracle. All rights reserved.
*/
#include <linux/slab.h>
#include <linux/list.h>
struct configfs_dirent {
atomic_t s_count;
struct list_head s_sibling;
struct list_head s_children;
struct list_head s_links;
void * s_element;
int s_type;
umode_t s_mode;
struct dentry * s_dentry;
};
#define CONFIGFS_ROOT 0x0001
#define CONFIGFS_DIR 0x0002
#define CONFIGFS_ITEM_ATTR 0x0004
#define CONFIGFS_ITEM_LINK 0x0020
#define CONFIGFS_USET_DIR 0x0040
#define CONFIGFS_USET_DEFAULT 0x0080
#define CONFIGFS_USET_DROPPING 0x0100
#define CONFIGFS_NOT_PINNED (CONFIGFS_ITEM_ATTR)
extern struct vfsmount * configfs_mount;
extern int configfs_is_root(struct config_item *item);
extern struct inode * configfs_new_inode(mode_t mode);
extern int configfs_create(struct dentry *, int mode, int (*init)(struct inode *));
extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
extern int configfs_make_dirent(struct configfs_dirent *,
struct dentry *, void *, umode_t, int);
extern int configfs_add_file(struct dentry *, const struct configfs_attribute *, int);
extern void configfs_hash_and_remove(struct dentry * dir, const char * name);
extern const unsigned char * configfs_get_name(struct configfs_dirent *sd);
extern void configfs_drop_dentry(struct configfs_dirent *sd, struct dentry *parent);
extern int configfs_pin_fs(void);
extern void configfs_release_fs(void);
extern struct rw_semaphore configfs_rename_sem;
extern struct super_block * configfs_sb;
extern struct file_operations configfs_dir_operations;
extern struct file_operations configfs_file_operations;
extern struct file_operations bin_fops;
extern struct inode_operations configfs_dir_inode_operations;
extern struct inode_operations configfs_symlink_inode_operations;
extern int configfs_symlink(struct inode *dir, struct dentry *dentry,
const char *symname);
extern int configfs_unlink(struct inode *dir, struct dentry *dentry);
struct configfs_symlink {
struct list_head sl_list;
struct config_item *sl_target;
};
extern int configfs_create_link(struct configfs_symlink *sl,
struct dentry *parent,
struct dentry *dentry);
static inline struct config_item * to_item(struct dentry * dentry)
{
struct configfs_dirent * sd = dentry->d_fsdata;
return ((struct config_item *) sd->s_element);
}
static inline struct configfs_attribute * to_attr(struct dentry * dentry)
{
struct configfs_dirent * sd = dentry->d_fsdata;
return ((struct configfs_attribute *) sd->s_element);
}
static inline struct config_item *configfs_get_config_item(struct dentry *dentry)
{
struct config_item * item = NULL;
spin_lock(&dcache_lock);
if (!d_unhashed(dentry)) {
struct configfs_dirent * sd = dentry->d_fsdata;
if (sd->s_type & CONFIGFS_ITEM_LINK) {
struct configfs_symlink * sl = sd->s_element;
item = config_item_get(sl->sl_target);
} else
item = config_item_get(sd->s_element);
}
spin_unlock(&dcache_lock);
return item;
}
static inline void release_configfs_dirent(struct configfs_dirent * sd)
{
if (!(sd->s_type & CONFIGFS_ROOT))
kfree(sd);
}
static inline struct configfs_dirent * configfs_get(struct configfs_dirent * sd)
{
if (sd) {
WARN_ON(!atomic_read(&sd->s_count));
atomic_inc(&sd->s_count);
}
return sd;
}
static inline void configfs_put(struct configfs_dirent * sd)
{
WARN_ON(!atomic_read(&sd->s_count));
if (atomic_dec_and_test(&sd->s_count))
release_configfs_dirent(sd);
}
This diff is collapsed.
/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* file.c - operations for regular (text) files.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*
* Based on sysfs:
* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
*
* configfs Copyright (C) 2005 Oracle. All rights reserved.
*/
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/dnotify.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/semaphore.h>
#include <linux/configfs.h>
#include "configfs_internal.h"
struct configfs_buffer {
size_t count;
loff_t pos;
char * page;
struct configfs_item_operations * ops;
struct semaphore sem;
int needs_read_fill;
};
/**
* fill_read_buffer - allocate and fill buffer from item.
* @dentry: dentry pointer.
* @buffer: data buffer for file.
*
* Allocate @buffer->page, if it hasn't been already, then call the
* config_item's show() method to fill the buffer with this attribute's
* data.
* This is called only once, on the file's first read.
*/
static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
{
struct configfs_attribute * attr = to_attr(dentry);
struct config_item * item = to_item(dentry->d_parent);
struct configfs_item_operations * ops = buffer->ops;
int ret = 0;
ssize_t count;
if (!buffer->page)
buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
if (!buffer->page)
return -ENOMEM;
count = ops->show_attribute(item,attr,buffer->page);
buffer->needs_read_fill = 0;
BUG_ON(count > (ssize_t)PAGE_SIZE);
if (count >= 0)
buffer->count = count;
else
ret = count;
return ret;
}
/**
* flush_read_buffer - push buffer to userspace.
* @buffer: data buffer for file.
* @userbuf: user-passed buffer.
* @count: number of bytes requested.
* @ppos: file position.
*
* Copy the buffer we filled in fill_read_buffer() to userspace.
* This is done at the reader's leisure, copying and advancing
* the amount they specify each time.
* This may be called continuously until the buffer is empty.
*/
static int flush_read_buffer(struct configfs_buffer * buffer, char __user * buf,
size_t count, loff_t * ppos)
{
int error;
if (*ppos > buffer->count)
return 0;
if (count > (buffer->count - *ppos))
count = buffer->count - *ppos;
error = copy_to_user(buf,buffer->page + *ppos,count);
if (!error)
*ppos += count;
return error ? -EFAULT : count;
}
/**
* configfs_read_file - read an attribute.
* @file: file pointer.
* @buf: buffer to fill.
* @count: number of bytes to read.
* @ppos: starting offset in file.
*
* Userspace wants to read an attribute file. The attribute descriptor
* is in the file's ->d_fsdata. The target item is in the directory's
* ->d_fsdata.
*
* We call fill_read_buffer() to allocate and fill the buffer from the
* item's show() method exactly once (if the read is happening from
* the beginning of the file). That should fill the entire buffer with
* all the data the item has to offer for that attribute.
* We then call flush_read_buffer() to copy the buffer to userspace
* in the increments specified.
*/
static ssize_t
configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct configfs_buffer * buffer = file->private_data;
ssize_t retval = 0;
down(&buffer->sem);
if (buffer->needs_read_fill) {
if ((retval = fill_read_buffer(file->f_dentry,buffer)))
goto out;
}
pr_debug("%s: count = %d, ppos = %lld, buf = %s\n",
__FUNCTION__,count,*ppos,buffer->page);
retval = flush_read_buffer(buffer,buf,count,ppos);
out:
up(&buffer->sem);
return retval;
}
/**
* fill_write_buffer - copy buffer from userspace.
* @buffer: data buffer for file.
* @userbuf: data from user.
* @count: number of bytes in @userbuf.
*
* Allocate @buffer->page if it hasn't been already, then
* copy the user-supplied buffer into it.
*/
static int
fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
{
int error;
if (!buffer->page)
buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
if (!buffer->page)
return -ENOMEM;
if (count > PAGE_SIZE)
count = PAGE_SIZE;
error = copy_from_user(buffer->page,buf,count);
buffer->needs_read_fill = 1;
return error ? -EFAULT : count;
}
/**
* flush_write_buffer - push buffer to config_item.
* @file: file pointer.
* @buffer: data buffer for file.
*
* Get the correct pointers for the config_item and the attribute we're
* dealing with, then call the store() method for the attribute,
* passing the buffer that we acquired in fill_write_buffer().
*/
static int
flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
{
struct configfs_attribute * attr = to_attr(dentry);
struct config_item * item = to_item(dentry->d_parent);
struct configfs_item_operations * ops = buffer->ops;
return ops->store_attribute(item,attr,buffer->page,count);
}
/**
* configfs_write_file - write an attribute.
* @file: file pointer
* @buf: data to write
* @count: number of bytes
* @ppos: starting offset
*
* Similar to configfs_read_file(), though working in the opposite direction.
* We allocate and fill the data from the user in fill_write_buffer(),
* then push it to the config_item in flush_write_buffer().
* There is no easy way for us to know if userspace is only doing a partial
* write, so we don't support them. We expect the entire buffer to come
* on the first write.
* Hint: if you're writing a value, first read the file, modify only the
* the value you're changing, then write entire buffer back.
*/
static ssize_t
configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
struct configfs_buffer * buffer = file->private_data;
down(&buffer->sem);
count = fill_write_buffer(buffer,buf,count);
if (count > 0)
count = flush_write_buffer(file->f_dentry,buffer,count);
if (count > 0)
*ppos += count;
up(&buffer->sem);
return count;
}
static int check_perm(struct inode * inode, struct file * file)
{
struct config_item *item = configfs_get_config_item(file->f_dentry->d_parent);
struct configfs_attribute * attr = to_attr(file->f_dentry);
struct configfs_buffer * buffer;
struct configfs_item_operations * ops = NULL;
int error = 0;
if (!item || !attr)
goto Einval;
/* Grab the module reference for this attribute if we have one */
if (!try_module_get(attr->ca_owner)) {
error = -ENODEV;
goto Done;
}
if (item->ci_type)
ops = item->ci_type->ct_item_ops;
else
goto Eaccess;
/* File needs write support.
* The inode's perms must say it's ok,
* and we must have a store method.
*/
if (file->f_mode & FMODE_WRITE) {
if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute)
goto Eaccess;
}
/* File needs read support.
* The inode's perms must say it's ok, and we there
* must be a show method for it.
*/
if (file->f_mode & FMODE_READ) {
if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute)
goto Eaccess;
}
/* No error? Great, allocate a buffer for the file, and store it
* it in file->private_data for easy access.
*/
buffer = kmalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
if (buffer) {
memset(buffer,0,sizeof(struct configfs_buffer));
init_MUTEX(&buffer->sem);
buffer->needs_read_fill = 1;
buffer->ops = ops;
file->private_data = buffer;
} else
error = -ENOMEM;
goto Done;
Einval:
error = -EINVAL;
goto Done;
Eaccess:
error = -EACCES;
module_put(attr->ca_owner);
Done:
if (error && item)
config_item_put(item);
return error;
}
static int configfs_open_file(struct inode * inode, struct file * filp)
{
return check_perm(inode,filp);
}
static int configfs_release(struct inode * inode, struct file * filp)
{
struct config_item * item = to_item(filp->f_dentry->d_parent);
struct configfs_attribute * attr = to_attr(filp->f_dentry);
struct module * owner = attr->ca_owner;
struct configfs_buffer * buffer = filp->private_data;
if (item)
config_item_put(item);
/* After this point, attr should not be accessed. */
module_put(owner);
if (buffer) {
if (buffer->page)
free_page((unsigned long)buffer->page);
kfree(buffer);
}
return 0;
}
struct file_operations configfs_file_operations = {
.read = configfs_read_file,
.write = configfs_write_file,
.llseek = generic_file_llseek,
.open = configfs_open_file,
.release = configfs_release,
};
int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type)
{
struct configfs_dirent * parent_sd = dir->d_fsdata;
umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
int error = 0;
down(&dir->d_inode->i_sem);
error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type);
up(&dir->d_inode->i_sem);
return error;
}
/**
* configfs_create_file - create an attribute file for an item.
* @item: item we're creating for.
* @attr: atrribute descriptor.
*/
int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
{
BUG_ON(!item || !item->ci_dentry || !attr);
return configfs_add_file(item->ci_dentry, attr,
CONFIGFS_ITEM_ATTR);
}
/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* inode.c - basic inode and dentry operations.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*
* Based on sysfs:
* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
*
* configfs Copyright (C) 2005 Oracle. All rights reserved.
*
* Please see Documentation/filesystems/configfs.txt for more information.
*/
#undef DEBUG
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/configfs.h>
#include "configfs_internal.h"
extern struct super_block * configfs_sb;
static struct address_space_operations configfs_aops = {
.readpage = simple_readpage,
.prepare_write = simple_prepare_write,
.commit_write = simple_commit_write
};
static struct backing_dev_info configfs_backing_dev_info = {
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};
struct inode * configfs_new_inode(mode_t mode)
{
struct inode * inode = new_inode(configfs_sb);
if (inode) {
inode->i_mode = mode;
inode->i_uid = 0;
inode->i_gid = 0;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_mapping->a_ops = &configfs_aops;
inode->i_mapping->backing_dev_info = &configfs_backing_dev_info;
}
return inode;
}
int configfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
{
int error = 0;
struct inode * inode = NULL;
if (dentry) {
if (!dentry->d_inode) {
if ((inode = configfs_new_inode(mode))) {
if (dentry->d_parent && dentry->d_parent->d_inode) {
struct inode *p_inode = dentry->d_parent->d_inode;
p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
}
goto Proceed;
}
else
error = -ENOMEM;
} else
error = -EEXIST;
} else
error = -ENOENT;
goto Done;
Proceed:
if (init)
error = init(inode);
if (!error) {
d_instantiate(dentry, inode);
if (S_ISDIR(mode) || S_ISLNK(mode))
dget(dentry); /* pin link and directory dentries in core */
} else
iput(inode);
Done:
return error;
}
/*
* Get the name for corresponding element represented by the given configfs_dirent
*/
const unsigned char * configfs_get_name(struct configfs_dirent *sd)
{
struct attribute * attr;
if (!sd || !sd->s_element)
BUG();
/* These always have a dentry, so use that */
if (sd->s_type & (CONFIGFS_DIR | CONFIGFS_ITEM_LINK))
return sd->s_dentry->d_name.name;
if (sd->s_type & CONFIGFS_ITEM_ATTR) {
attr = sd->s_element;
return attr->name;
}
return NULL;
}
/*
* Unhashes the dentry corresponding to given configfs_dirent
* Called with parent inode's i_sem held.
*/
void configfs_drop_dentry(struct configfs_dirent * sd, struct dentry * parent)
{
struct dentry * dentry = sd->s_dentry;
if (dentry) {
spin_lock(&dcache_lock);
if (!(d_unhashed(dentry) && dentry->d_inode)) {
dget_locked(dentry);
__d_drop(dentry);
spin_unlock(&dcache_lock);
simple_unlink(parent->d_inode, dentry);
} else
spin_unlock(&dcache_lock);
}
}
void configfs_hash_and_remove(struct dentry * dir, const char * name)
{
struct configfs_dirent * sd;
struct configfs_dirent * parent_sd = dir->d_fsdata;
down(&dir->d_inode->i_sem);
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if (!sd->s_element)
continue;
if (!strcmp(configfs_get_name(sd), name)) {
list_del_init(&sd->s_sibling);
configfs_drop_dentry(sd, dir);
configfs_put(sd);
break;
}
}
up(&dir->d_inode->i_sem);
}
/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* item.c - library routines for handling generic config items
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*