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_IRWXU | 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_alloc_root(inode);
  65         if (!root) {
  66                 pr_debug("%s: could not get root dentry!\n",__func__);
  67                 iput(inode);
  68                 return -ENOMEM;
  69         }
  70         root->d_fsdata = &sysfs_root;
  71         sb->s_root = root;
  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 struct dentry *sysfs_mount(struct file_system_type *fs_type,
  99         int flags, const char *dev_name, void *data)
 100 {
 101         struct sysfs_super_info *info;
 102         enum kobj_ns_type type;
 103         struct super_block *sb;
 104         int error;
 105
 106         info = kzalloc(sizeof(*info), GFP_KERNEL);
 107         if (!info)
 108                 return ERR_PTR(-ENOMEM);
 109
 110         for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
 111                 info->ns[type] = kobj_ns_current(type);
 112
 113         sb = sget(fs_type, sysfs_test_super, sysfs_set_super, info);
 114         if (IS_ERR(sb) || sb->s_fs_info != info)
 115                 kfree(info);
 116         if (IS_ERR(sb))
 117                 return ERR_CAST(sb);
 118         if (!sb->s_root) {
 119                 sb->s_flags = flags;
 120                 error = sysfs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
 121                 if (error) {
 122                         deactivate_locked_super(sb);
 123                         return ERR_PTR(error);
 124                 }
 125                 sb->s_flags |= MS_ACTIVE;
 126         }
 127
 128         return dget(sb->s_root);
 129 }
 130
 131 static void sysfs_kill_sb(struct super_block *sb)
 132 {
 133         struct sysfs_super_info *info = sysfs_info(sb);
 134
 135         /* Remove the superblock from fs_supers/s_instances
 136          * so we can't find it, before freeing sysfs_super_info.
 137          */
 138         kill_anon_super(sb);
 139         kfree(info);
 140 }
 141
 142 static struct file_system_type sysfs_fs_type = {
 143         .name           = "sysfs",
 144         .mount          = sysfs_mount,
 145         .kill_sb        = sysfs_kill_sb,
 146 };
 147
 148 void sysfs_exit_ns(enum kobj_ns_type type, const void *ns)
 149 {
 150         struct super_block *sb;
 151
 152         mutex_lock(&sysfs_mutex);
 153         spin_lock(&sb_lock);
 154         list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
 155                 struct sysfs_super_info *info = sysfs_info(sb);
 156                 /*
 157                  * If we see a superblock on the fs_supers/s_instances
 158                  * list the unmount has not completed and sb->s_fs_info
 159                  * points to a valid struct sysfs_super_info.
 160                  */
 161                 /* Ignore superblocks with the wrong ns */
 162                 if (info->ns[type] != ns)
 163                         continue;
 164                 info->ns[type] = NULL;
 165         }
 166         spin_unlock(&sb_lock);
 167         mutex_unlock(&sysfs_mutex);
 168 }
 169
 170 int __init sysfs_init(void)
 171 {
 172         int err = -ENOMEM;
 173
 174         sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
 175                                               sizeof(struct sysfs_dirent),
 176                                               0, 0, NULL);
 177         if (!sysfs_dir_cachep)
 178                 goto out;
 179
 180         err = sysfs_inode_init();
 181         if (err)
 182                 goto out_err;
 183
 184         err = register_filesystem(&sysfs_fs_type);
 185         if (!err) {
 186                 sysfs_mnt = kern_mount(&sysfs_fs_type);
 187                 if (IS_ERR(sysfs_mnt)) {
 188                         printk(KERN_ERR "sysfs: could not mount!\n");
 189                         err = PTR_ERR(sysfs_mnt);
 190                         sysfs_mnt = NULL;
 191                         unregister_filesystem(&sysfs_fs_type);
 192                         goto out_err;
 193                 }
 194         } else
 195                 goto out_err;
 196 out:
 197         return err;
 198 out_err:
 199         kmem_cache_destroy(sysfs_dir_cachep);
 200         sysfs_dir_cachep = NULL;
 201         goto out;
 202 }
 203
 204 #undef sysfs_get
 205 struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
 206 {
 207         return __sysfs_get(sd);
 208 }
 209 EXPORT_SYMBOL_GPL(sysfs_get);
 210
 211 #undef sysfs_put
 212 void sysfs_put(struct sysfs_dirent *sd)
 213 {
 214         __sysfs_put(sd);
 215 }
 216 EXPORT_SYMBOL_GPL(sysfs_put);