linux/fs/sysfs/mount.c
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   1/*
   2 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
   3 *
   4 * Copyright (c) 2001-3 Patrick Mochel
   5 * Copyright (c) 2007 SUSE Linux Products GmbH
   6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   7 *
   8 * This file is released under the GPLv2.
   9 *
  10 * Please see Documentation/filesystems/sysfs.txt for more information.
  11 */
  12
  13#define DEBUG 
  14
  15#include <linux/fs.h>
  16#include <linux/mount.h>
  17#include <linux/pagemap.h>
  18#include <linux/init.h>
  19#include <linux/module.h>
  20#include <linux/magic.h>
  21#include <linux/slab.h>
  22
  23#include "sysfs.h"
  24
  25
  26static struct vfsmount *sysfs_mnt;
  27struct kmem_cache *sysfs_dir_cachep;
  28
  29static const struct super_operations sysfs_ops = {
  30        .statfs         = simple_statfs,
  31        .drop_inode     = generic_delete_inode,
  32        .evict_inode    = sysfs_evict_inode,
  33};
  34
  35struct sysfs_dirent sysfs_root = {
  36        .s_name         = "",
  37        .s_count        = ATOMIC_INIT(1),
  38        .s_flags        = SYSFS_DIR | (KOBJ_NS_TYPE_NONE << SYSFS_NS_TYPE_SHIFT),
  39        .s_mode         = S_IFDIR | S_IRUGO | S_IXUGO,
  40        .s_ino          = 1,
  41};
  42
  43static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
  44{
  45        struct inode *inode;
  46        struct dentry *root;
  47
  48        sb->s_blocksize = PAGE_CACHE_SIZE;
  49        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
  50        sb->s_magic = SYSFS_MAGIC;
  51        sb->s_op = &sysfs_ops;
  52        sb->s_time_gran = 1;
  53
  54        /* get root inode, initialize and unlock it */
  55        mutex_lock(&sysfs_mutex);
  56        inode = sysfs_get_inode(sb, &sysfs_root);
  57        mutex_unlock(&sysfs_mutex);
  58        if (!inode) {
  59                pr_debug("sysfs: could not get root inode\n");
  60                return -ENOMEM;
  61        }
  62
  63        /* instantiate and link root dentry */
  64        root = d_make_root(inode);
  65        if (!root) {
  66                pr_debug("%s: could not get root dentry!\n",__func__);
  67                return -ENOMEM;
  68        }
  69        root->d_fsdata = &sysfs_root;
  70        sb->s_root = root;
  71        sb->s_d_op = &sysfs_dentry_ops;
  72        return 0;
  73}
  74
  75static int sysfs_test_super(struct super_block *sb, void *data)
  76{
  77        struct sysfs_super_info *sb_info = sysfs_info(sb);
  78        struct sysfs_super_info *info = data;
  79        enum kobj_ns_type type;
  80        int found = 1;
  81
  82        for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
  83                if (sb_info->ns[type] != info->ns[type])
  84                        found = 0;
  85        }
  86        return found;
  87}
  88
  89static int sysfs_set_super(struct super_block *sb, void *data)
  90{
  91        int error;
  92        error = set_anon_super(sb, data);
  93        if (!error)
  94                sb->s_fs_info = data;
  95        return error;
  96}
  97
  98static void free_sysfs_super_info(struct sysfs_super_info *info)
  99{
 100        int type;
 101        for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
 102                kobj_ns_drop(type, info->ns[type]);
 103        kfree(info);
 104}
 105
 106static struct dentry *sysfs_mount(struct file_system_type *fs_type,
 107        int flags, const char *dev_name, void *data)
 108{
 109        struct sysfs_super_info *info;
 110        enum kobj_ns_type type;
 111        struct super_block *sb;
 112        int error;
 113
 114        info = kzalloc(sizeof(*info), GFP_KERNEL);
 115        if (!info)
 116                return ERR_PTR(-ENOMEM);
 117
 118        for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
 119                info->ns[type] = kobj_ns_grab_current(type);
 120
 121        sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
 122        if (IS_ERR(sb) || sb->s_fs_info != info)
 123                free_sysfs_super_info(info);
 124        if (IS_ERR(sb))
 125                return ERR_CAST(sb);
 126        if (!sb->s_root) {
 127                error = sysfs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
 128                if (error) {
 129                        deactivate_locked_super(sb);
 130                        return ERR_PTR(error);
 131                }
 132                sb->s_flags |= MS_ACTIVE;
 133        }
 134
 135        return dget(sb->s_root);
 136}
 137
 138static void sysfs_kill_sb(struct super_block *sb)
 139{
 140        struct sysfs_super_info *info = sysfs_info(sb);
 141        /* Remove the superblock from fs_supers/s_instances
 142         * so we can't find it, before freeing sysfs_super_info.
 143         */
 144        kill_anon_super(sb);
 145        free_sysfs_super_info(info);
 146}
 147
 148static struct file_system_type sysfs_fs_type = {
 149        .name           = "sysfs",
 150        .mount          = sysfs_mount,
 151        .kill_sb        = sysfs_kill_sb,
 152};
 153
 154int __init sysfs_init(void)
 155{
 156        int err = -ENOMEM;
 157
 158        sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
 159                                              sizeof(struct sysfs_dirent),
 160                                              0, 0, NULL);
 161        if (!sysfs_dir_cachep)
 162                goto out;
 163
 164        err = sysfs_inode_init();
 165        if (err)
 166                goto out_err;
 167
 168        err = register_filesystem(&sysfs_fs_type);
 169        if (!err) {
 170                sysfs_mnt = kern_mount(&sysfs_fs_type);
 171                if (IS_ERR(sysfs_mnt)) {
 172                        printk(KERN_ERR "sysfs: could not mount!\n");
 173                        err = PTR_ERR(sysfs_mnt);
 174                        sysfs_mnt = NULL;
 175                        unregister_filesystem(&sysfs_fs_type);
 176                        goto out_err;
 177                }
 178        } else
 179                goto out_err;
 180out:
 181        return err;
 182out_err:
 183        kmem_cache_destroy(sysfs_dir_cachep);
 184        sysfs_dir_cachep = NULL;
 185        goto out;
 186}
 187
 188#undef sysfs_get
 189struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
 190{
 191        return __sysfs_get(sd);
 192}
 193EXPORT_SYMBOL_GPL(sysfs_get);
 194
 195#undef sysfs_put
 196void sysfs_put(struct sysfs_dirent *sd)
 197{
 198        __sysfs_put(sd);
 199}
 200EXPORT_SYMBOL_GPL(sysfs_put);
 201
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