fs/sysfs/mount.c

   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
  26 static struct vfsmount *sysfs_mnt;
  27 struct kmem_cache *sysfs_dir_cachep;
  28
  29 static const struct super_operations sysfs_ops = {
  30         .statfs         = simple_statfs,
  31         .drop_inode     = generic_delete_inode,
  32         .evict_inode    = sysfs_evict_inode,
  33 };
  34
  35 struct 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
  43 static 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
  75 static 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
  89 static 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
  98 static 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
 106 static 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
 138 static 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
 148 static struct file_system_type sysfs_fs_type = {
 149         .name           = "sysfs",
 150         .mount          = sysfs_mount,
 151         .kill_sb        = sysfs_kill_sb,
 152         .fs_flags       = FS_USERNS_MOUNT,
 153 };
 154
 155 int __init sysfs_init(void)
 156 {
 157         int err = -ENOMEM;
 158
 159         sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
 160                                               sizeof(struct sysfs_dirent),
 161                                               0, 0, NULL);
 162         if (!sysfs_dir_cachep)
 163                 goto out;
 164
 165         err = sysfs_inode_init();
 166         if (err)
 167                 goto out_err;
 168
 169         err = register_filesystem(&sysfs_fs_type);
 170         if (!err) {
 171                 sysfs_mnt = kern_mount(&sysfs_fs_type);
 172                 if (IS_ERR(sysfs_mnt)) {
 173                         printk(KERN_ERR "sysfs: could not mount!\n");
 174                         err = PTR_ERR(sysfs_mnt);
 175                         sysfs_mnt = NULL;
 176                         unregister_filesystem(&sysfs_fs_type);
 177                         goto out_err;
 178                 }
 179         } else
 180                 goto out_err;
 181 out:
 182         return err;
 183 out_err:
 184         kmem_cache_destroy(sysfs_dir_cachep);
 185         sysfs_dir_cachep = NULL;
 186         goto out;
 187 }
 188
 189 #undef sysfs_get
 190 struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
 191 {
 192         return __sysfs_get(sd);
 193 }
 194 EXPORT_SYMBOL_GPL(sysfs_get);
 195
 196 #undef sysfs_put
 197 void sysfs_put(struct sysfs_dirent *sd)
 198 {
 199         __sysfs_put(sd);
 200 }
 201 EXPORT_SYMBOL_GPL(sysfs_put);