fs/sysfs/inode.c

   1 /*
   2  * fs/sysfs/inode.c - basic sysfs inode and dentry operations
   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 #undef DEBUG
  14
  15 #include <linux/pagemap.h>
  16 #include <linux/namei.h>
  17 #include <linux/backing-dev.h>
  18 #include <linux/capability.h>
  19 #include <linux/errno.h>
  20 #include <linux/sched.h>
  21 #include <linux/slab.h>
  22 #include <linux/xattr.h>
  23 #include <linux/security.h>
  24 #include "sysfs.h"
  25
  26 extern struct super_block * sysfs_sb;
  27
  28 static const struct address_space_operations sysfs_aops = {
  29         .readpage       = simple_readpage,
  30         .write_begin    = simple_write_begin,
  31         .write_end      = simple_write_end,
  32 };
  33
  34 static struct backing_dev_info sysfs_backing_dev_info = {
  35         .name           = "sysfs",
  36         .ra_pages       = 0,    /* No readahead */
  37         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  38 };
  39
  40 static const struct inode_operations sysfs_inode_operations ={
  41         .permission     = sysfs_permission,
  42         .setattr        = sysfs_setattr,
  43         .getattr        = sysfs_getattr,
  44         .setxattr       = sysfs_setxattr,
  45 };
  46
  47 int __init sysfs_inode_init(void)
  48 {
  49         return bdi_init(&sysfs_backing_dev_info);
  50 }
  51
  52 static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)
  53 {
  54         struct sysfs_inode_attrs *attrs;
  55         struct iattr *iattrs;
  56
  57         attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
  58         if (!attrs)
  59                 return NULL;
  60         iattrs = &attrs->ia_iattr;
  61
  62         /* assign default attributes */
  63         iattrs->ia_mode = sd->s_mode;
  64         iattrs->ia_uid = 0;
  65         iattrs->ia_gid = 0;
  66         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  67
  68         return attrs;
  69 }
  70
  71 int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr * iattr)
  72 {
  73         struct sysfs_inode_attrs *sd_attrs;
  74         struct iattr *iattrs;
  75         unsigned int ia_valid = iattr->ia_valid;
  76
  77         sd_attrs = sd->s_iattr;
  78
  79         if (!sd_attrs) {
  80                 /* setting attributes for the first time, allocate now */
  81                 sd_attrs = sysfs_init_inode_attrs(sd);
  82                 if (!sd_attrs)
  83                         return -ENOMEM;
  84                 sd->s_iattr = sd_attrs;
  85         }
  86         /* attributes were changed at least once in past */
  87         iattrs = &sd_attrs->ia_iattr;
  88
  89         if (ia_valid & ATTR_UID)
  90                 iattrs->ia_uid = iattr->ia_uid;
  91         if (ia_valid & ATTR_GID)
  92                 iattrs->ia_gid = iattr->ia_gid;
  93         if (ia_valid & ATTR_ATIME)
  94                 iattrs->ia_atime = iattr->ia_atime;
  95         if (ia_valid & ATTR_MTIME)
  96                 iattrs->ia_mtime = iattr->ia_mtime;
  97         if (ia_valid & ATTR_CTIME)
  98                 iattrs->ia_ctime = iattr->ia_ctime;
  99         if (ia_valid & ATTR_MODE) {
 100                 umode_t mode = iattr->ia_mode;
 101                 iattrs->ia_mode = sd->s_mode = mode;
 102         }
 103         return 0;
 104 }
 105
 106 int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
 107 {
 108         struct inode *inode = dentry->d_inode;
 109         struct sysfs_dirent *sd = dentry->d_fsdata;
 110         int error;
 111
 112         if (!sd)
 113                 return -EINVAL;
 114
 115         mutex_lock(&sysfs_mutex);
 116         error = inode_change_ok(inode, iattr);
 117         if (error)
 118                 goto out;
 119
 120         error = sysfs_sd_setattr(sd, iattr);
 121         if (error)
 122                 goto out;
 123
 124         /* this ignores size changes */
 125         setattr_copy(inode, iattr);
 126
 127 out:
 128         mutex_unlock(&sysfs_mutex);
 129         return error;
 130 }
 131
 132 static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata, u32 *secdata_len)
 133 {
 134         struct sysfs_inode_attrs *iattrs;
 135         void *old_secdata;
 136         size_t old_secdata_len;
 137
 138         iattrs = sd->s_iattr;
 139         if (!iattrs)
 140                 iattrs = sysfs_init_inode_attrs(sd);
 141         if (!iattrs)
 142                 return -ENOMEM;
 143
 144         old_secdata = iattrs->ia_secdata;
 145         old_secdata_len = iattrs->ia_secdata_len;
 146
 147         iattrs->ia_secdata = *secdata;
 148         iattrs->ia_secdata_len = *secdata_len;
 149
 150         *secdata = old_secdata;
 151         *secdata_len = old_secdata_len;
 152         return 0;
 153 }
 154
 155 int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 156                 size_t size, int flags)
 157 {
 158         struct sysfs_dirent *sd = dentry->d_fsdata;
 159         void *secdata;
 160         int error;
 161         u32 secdata_len = 0;
 162
 163         if (!sd)
 164                 return -EINVAL;
 165
 166         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
 167                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 168                 error = security_inode_setsecurity(dentry->d_inode, suffix,
 169                                                 value, size, flags);
 170                 if (error)
 171                         goto out;
 172                 error = security_inode_getsecctx(dentry->d_inode,
 173                                                 &secdata, &secdata_len);
 174                 if (error)
 175                         goto out;
 176
 177                 mutex_lock(&sysfs_mutex);
 178                 error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
 179                 mutex_unlock(&sysfs_mutex);
 180
 181                 if (secdata)
 182                         security_release_secctx(secdata, secdata_len);
 183         } else
 184                 return -EINVAL;
 185 out:
 186         return error;
 187 }
 188
 189 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
 190 {
 191         inode->i_mode = mode;
 192         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 193 }
 194
 195 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 196 {
 197         inode->i_uid = iattr->ia_uid;
 198         inode->i_gid = iattr->ia_gid;
 199         inode->i_atime = iattr->ia_atime;
 200         inode->i_mtime = iattr->ia_mtime;
 201         inode->i_ctime = iattr->ia_ctime;
 202 }
 203
 204 static int sysfs_count_nlink(struct sysfs_dirent *sd)
 205 {
 206         struct sysfs_dirent *child;
 207         int nr = 0;
 208
 209         for (child = sd->s_dir.children; child; child = child->s_sibling)
 210                 if (sysfs_type(child) == SYSFS_DIR)
 211                         nr++;
 212
 213         return nr + 2;
 214 }
 215
 216 static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
 217 {
 218         struct sysfs_inode_attrs *iattrs = sd->s_iattr;
 219
 220         inode->i_mode = sd->s_mode;
 221         if (iattrs) {
 222                 /* sysfs_dirent has non-default attributes
 223                  * get them from persistent copy in sysfs_dirent
 224                  */
 225                 set_inode_attr(inode, &iattrs->ia_iattr);
 226                 security_inode_notifysecctx(inode,
 227                                             iattrs->ia_secdata,
 228                                             iattrs->ia_secdata_len);
 229         }
 230
 231         if (sysfs_type(sd) == SYSFS_DIR)
 232                 inode->i_nlink = sysfs_count_nlink(sd);
 233 }
 234
 235 int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 236 {
 237         struct sysfs_dirent *sd = dentry->d_fsdata;
 238         struct inode *inode = dentry->d_inode;
 239
 240         mutex_lock(&sysfs_mutex);
 241         sysfs_refresh_inode(sd, inode);
 242         mutex_unlock(&sysfs_mutex);
 243
 244         generic_fillattr(inode, stat);
 245         return 0;
 246 }
 247
 248 static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 249 {
 250         struct bin_attribute *bin_attr;
 251
 252         inode->i_private = sysfs_get(sd);
 253         inode->i_mapping->a_ops = &sysfs_aops;
 254         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 255         inode->i_op = &sysfs_inode_operations;
 256
 257         set_default_inode_attr(inode, sd->s_mode);
 258         sysfs_refresh_inode(sd, inode);
 259
 260         /* initialize inode according to type */
 261         switch (sysfs_type(sd)) {
 262         case SYSFS_DIR:
 263                 inode->i_op = &sysfs_dir_inode_operations;
 264                 inode->i_fop = &sysfs_dir_operations;
 265                 break;
 266         case SYSFS_KOBJ_ATTR:
 267                 inode->i_size = PAGE_SIZE;
 268                 inode->i_fop = &sysfs_file_operations;
 269                 break;
 270         case SYSFS_KOBJ_BIN_ATTR:
 271                 bin_attr = sd->s_bin_attr.bin_attr;
 272                 inode->i_size = bin_attr->size;
 273                 inode->i_fop = &bin_fops;
 274                 break;
 275         case SYSFS_KOBJ_LINK:
 276                 inode->i_op = &sysfs_symlink_inode_operations;
 277                 break;
 278         default:
 279                 BUG();
 280         }
 281
 282         unlock_new_inode(inode);
 283 }
 284
 285 /**
 286  *      sysfs_get_inode - get inode for sysfs_dirent
 287  *      @sb: super block
 288  *      @sd: sysfs_dirent to allocate inode for
 289  *
 290  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 291  *      is allocated and basics are initialized.  New inode is
 292  *      returned locked.
 293  *
 294  *      LOCKING:
 295  *      Kernel thread context (may sleep).
 296  *
 297  *      RETURNS:
 298  *      Pointer to allocated inode on success, NULL on failure.
 299  */
 300 struct inode * sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd)
 301 {
 302         struct inode *inode;
 303
 304         inode = iget_locked(sb, sd->s_ino);
 305         if (inode && (inode->i_state & I_NEW))
 306                 sysfs_init_inode(sd, inode);
 307
 308         return inode;
 309 }
 310
 311 /*
 312  * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
 313  * To prevent the sysfs inode numbers from being freed prematurely we take a
 314  * reference to sysfs_dirent from the sysfs inode.  A
 315  * super_operations.evict_inode() implementation is needed to drop that
 316  * reference upon inode destruction.
 317  */
 318 void sysfs_evict_inode(struct inode *inode)
 319 {
 320         struct sysfs_dirent *sd  = inode->i_private;
 321
 322         truncate_inode_pages(&inode->i_data, 0);
 323         end_writeback(inode);
 324         sysfs_put(sd);
 325 }
 326
 327 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const char *name)
 328 {
 329         struct sysfs_addrm_cxt acxt;
 330         struct sysfs_dirent *sd;
 331
 332         if (!dir_sd)
 333                 return -ENOENT;
 334
 335         sysfs_addrm_start(&acxt, dir_sd);
 336
 337         sd = sysfs_find_dirent(dir_sd, ns, name);
 338         if (sd && (sd->s_ns != ns))
 339                 sd = NULL;
 340         if (sd)
 341                 sysfs_remove_one(&acxt, sd);
 342
 343         sysfs_addrm_finish(&acxt);
 344
 345         if (sd)
 346                 return 0;
 347         else
 348                 return -ENOENT;
 349 }
 350
 351 int sysfs_permission(struct inode *inode, int mask)
 352 {
 353         struct sysfs_dirent *sd = inode->i_private;
 354
 355         mutex_lock(&sysfs_mutex);
 356         sysfs_refresh_inode(sd, inode);
 357         mutex_unlock(&sysfs_mutex);
 358
 359         return generic_permission(inode, mask, NULL);
 360 }