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