mount.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * mount.c - operations for initializing and mounting 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/fs.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/slab.h>

#include <linux/configfs.h>
#include "configfs_internal.h"

/* Random magic number */
#define CONFIGFS_MAGIC 0x62656570

static struct vfsmount *configfs_mount = NULL;
struct kmem_cache *configfs_dir_cachep;
static int configfs_mnt_count = 0;

static const struct super_operations configfs_ops = {
    .statfs     = simple_statfs,
    .drop_inode = generic_delete_inode,
};

static struct config_group configfs_root_group = {
    .cg_item = {
        .ci_namebuf = "root",
        .ci_name    = configfs_root_group.cg_item.ci_namebuf,
    },
};

int configfs_is_root(struct config_item *item)
{
    return item == &configfs_root_group.cg_item;
}

static struct configfs_dirent configfs_root = {
    .s_sibling  = LIST_HEAD_INIT(configfs_root.s_sibling),
    .s_children = LIST_HEAD_INIT(configfs_root.s_children),
    .s_element  = &configfs_root_group.cg_item,
    .s_type     = CONFIGFS_ROOT,
    .s_iattr    = NULL,
};

static int configfs_fill_super(struct super_block *sb, void *data, int silent)
{
    struct inode *inode;
    struct dentry *root;

    sb->s_blocksize = PAGE_CACHE_SIZE;
    sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
    sb->s_magic = CONFIGFS_MAGIC;
    sb->s_op = &configfs_ops;
    sb->s_time_gran = 1;

    inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
                   &configfs_root, sb);
    if (inode) {
        inode->i_op = &configfs_root_inode_operations;
        inode->i_fop = &configfs_dir_operations;
        /* directory inodes start off with i_nlink == 2 (for "." entry) */
        inc_nlink(inode);
    } else {
        pr_debug("configfs: could not get root inode\n");
        return -ENOMEM;
    }

    root = d_make_root(inode);
    if (!root) {
        pr_debug("%s: could not get root dentry!\n",__func__);
        return -ENOMEM;
    }
    config_group_init(&configfs_root_group);
    configfs_root_group.cg_item.ci_dentry = root;
    root->d_fsdata = &configfs_root;
    sb->s_root = root;
    sb->s_d_op = &configfs_dentry_ops; /* the rest get that */
    return 0;
}

static struct dentry *configfs_do_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *data)
{
    return mount_single(fs_type, flags, data, configfs_fill_super);
}

static struct file_system_type configfs_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "configfs",
    .mount      = configfs_do_mount,
    .kill_sb    = kill_litter_super,
};

struct dentry *configfs_pin_fs(void)
{
    int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
                 &configfs_mnt_count);
    return err ? ERR_PTR(err) : configfs_mount->mnt_root;
}

void configfs_release_fs(void)
{
    simple_release_fs(&configfs_mount, &configfs_mnt_count);
}


static struct kobject *config_kobj;

static int __init configfs_init(void)
{
    int err = -ENOMEM;

    configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
                        sizeof(struct configfs_dirent),
                        0, 0, NULL);
    if (!configfs_dir_cachep)
        goto out;

    config_kobj = kobject_create_and_add("config", kernel_kobj);
    if (!config_kobj)
        goto out2;

    err = configfs_inode_init();
    if (err)
        goto out3;

    err = register_filesystem(&configfs_fs_type);
    if (err)
        goto out4;

    return 0;
out4:
    printk(KERN_ERR "configfs: Unable to register filesystem!\n");
    configfs_inode_exit();
out3:
    kobject_put(config_kobj);
out2:
    kmem_cache_destroy(configfs_dir_cachep);
    configfs_dir_cachep = NULL;
out:
    return err;
}

static void __exit configfs_exit(void)
{
    unregister_filesystem(&configfs_fs_type);
    kobject_put(config_kobj);
    kmem_cache_destroy(configfs_dir_cachep);
    configfs_dir_cachep = NULL;
    configfs_inode_exit();
}

MODULE_AUTHOR("Oracle");
MODULE_LICENSE("GPL");
MODULE_VERSION("0.0.2");
MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");

module_init(configfs_init);
module_exit(configfs_exit);