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         .setattr        = sysfs_setattr,
  41         .setxattr       = sysfs_setxattr,
  42 };
  43
  44 int __init sysfs_inode_init(void)
  45 {
  46         return bdi_init(&sysfs_backing_dev_info);
  47 }
  48
  49 struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)
  50 {
  51         struct sysfs_inode_attrs *attrs;
  52         struct iattr *iattrs;
  53
  54         attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
  55         if (!attrs)
  56                 return NULL;
  57         iattrs = &attrs->ia_iattr;
  58
  59         /* assign default attributes */
  60         iattrs->ia_mode = sd->s_mode;
  61         iattrs->ia_uid = 0;
  62         iattrs->ia_gid = 0;
  63         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  64
  65         return attrs;
  66 }
  67 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  68 {
  69         struct inode * inode = dentry->d_inode;
  70         struct sysfs_dirent * sd = dentry->d_fsdata;
  71         struct sysfs_inode_attrs *sd_attrs;
  72         struct iattr *iattrs;
  73         unsigned int ia_valid = iattr->ia_valid;
  74         int error;
  75
  76         if (!sd)
  77                 return -EINVAL;
  78
  79         sd_attrs = sd->s_iattr;
  80
  81         error = inode_change_ok(inode, iattr);
  82         if (error)
  83                 return error;
  84
  85         iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
  86
  87         error = inode_setattr(inode, iattr);
  88         if (error)
  89                 return error;
  90
  91         if (!sd_attrs) {
  92                 /* setting attributes for the first time, allocate now */
  93                 sd_attrs = sysfs_init_inode_attrs(sd);
  94                 if (!sd_attrs)
  95                         return -ENOMEM;
  96                 sd->s_iattr = sd_attrs;
  97         } else {
  98                 /* attributes were changed at least once in past */
  99                 iattrs = &sd_attrs->ia_iattr;
 100
 101                 if (ia_valid & ATTR_UID)
 102                         iattrs->ia_uid = iattr->ia_uid;
 103                 if (ia_valid & ATTR_GID)
 104                         iattrs->ia_gid = iattr->ia_gid;
 105                 if (ia_valid & ATTR_ATIME)
 106                         iattrs->ia_atime = timespec_trunc(iattr->ia_atime,
 107                                         inode->i_sb->s_time_gran);
 108                 if (ia_valid & ATTR_MTIME)
 109                         iattrs->ia_mtime = timespec_trunc(iattr->ia_mtime,
 110                                         inode->i_sb->s_time_gran);
 111                 if (ia_valid & ATTR_CTIME)
 112                         iattrs->ia_ctime = timespec_trunc(iattr->ia_ctime,
 113                                         inode->i_sb->s_time_gran);
 114                 if (ia_valid & ATTR_MODE) {
 115                         umode_t mode = iattr->ia_mode;
 116
 117                         if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
 118                                 mode &= ~S_ISGID;
 119                         iattrs->ia_mode = sd->s_mode = mode;
 120                 }
 121         }
 122         return error;
 123 }
 124
 125 int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 126                 size_t size, int flags)
 127 {
 128         struct sysfs_dirent *sd = dentry->d_fsdata;
 129         struct sysfs_inode_attrs *iattrs;
 130         void *secdata;
 131         int error;
 132         u32 secdata_len = 0;
 133
 134         if (!sd)
 135                 return -EINVAL;
 136         if (!sd->s_iattr)
 137                 sd->s_iattr = sysfs_init_inode_attrs(sd);
 138         if (!sd->s_iattr)
 139                 return -ENOMEM;
 140
 141         iattrs = sd->s_iattr;
 142
 143         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
 144                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 145                 error = security_inode_setsecurity(dentry->d_inode, suffix,
 146                                                 value, size, flags);
 147                 if (error)
 148                         goto out;
 149                 error = security_inode_getsecctx(dentry->d_inode,
 150                                                 &secdata, &secdata_len);
 151                 if (error)
 152                         goto out;
 153                 if (iattrs->ia_secdata)
 154                         security_release_secctx(iattrs->ia_secdata,
 155                                                 iattrs->ia_secdata_len);
 156                 iattrs->ia_secdata = secdata;
 157                 iattrs->ia_secdata_len = secdata_len;
 158
 159         } else
 160                 return -EINVAL;
 161 out:
 162         return error;
 163 }
 164
 165 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
 166 {
 167         inode->i_mode = mode;
 168         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 169 }
 170
 171 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 172 {
 173         inode->i_mode = iattr->ia_mode;
 174         inode->i_uid = iattr->ia_uid;
 175         inode->i_gid = iattr->ia_gid;
 176         inode->i_atime = iattr->ia_atime;
 177         inode->i_mtime = iattr->ia_mtime;
 178         inode->i_ctime = iattr->ia_ctime;
 179 }
 180
 181
 182 /*
 183  * sysfs has a different i_mutex lock order behavior for i_mutex than other
 184  * filesystems; sysfs i_mutex is called in many places with subsystem locks
 185  * held. At the same time, many of the VFS locking rules do not apply to
 186  * sysfs at all (cross directory rename for example). To untangle this mess
 187  * (which gives false positives in lockdep), we're giving sysfs inodes their
 188  * own class for i_mutex.
 189  */
 190 static struct lock_class_key sysfs_inode_imutex_key;
 191
 192 static int sysfs_count_nlink(struct sysfs_dirent *sd)
 193 {
 194         struct sysfs_dirent *child;
 195         int nr = 0;
 196
 197         for (child = sd->s_dir.children; child; child = child->s_sibling)
 198                 if (sysfs_type(child) == SYSFS_DIR)
 199                         nr++;
 200
 201         return nr + 2;
 202 }
 203
 204 static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 205 {
 206         struct bin_attribute *bin_attr;
 207         struct sysfs_inode_attrs *iattrs;
 208
 209         inode->i_private = sysfs_get(sd);
 210         inode->i_mapping->a_ops = &sysfs_aops;
 211         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 212         inode->i_op = &sysfs_inode_operations;
 213         inode->i_ino = sd->s_ino;
 214         lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 215
 216         iattrs = sd->s_iattr;
 217         if (iattrs) {
 218                 /* sysfs_dirent has non-default attributes
 219                  * get them for the new inode from persistent copy
 220                  * in sysfs_dirent
 221                  */
 222                 set_inode_attr(inode, &iattrs->ia_iattr);
 223                 if (iattrs->ia_secdata)
 224                         security_inode_notifysecctx(inode,
 225                                                 iattrs->ia_secdata,
 226                                                 iattrs->ia_secdata_len);
 227         } else
 228                 set_default_inode_attr(inode, sd->s_mode);
 229
 230         /* initialize inode according to type */
 231         switch (sysfs_type(sd)) {
 232         case SYSFS_DIR:
 233                 inode->i_op = &sysfs_dir_inode_operations;
 234                 inode->i_fop = &sysfs_dir_operations;
 235                 inode->i_nlink = sysfs_count_nlink(sd);
 236                 break;
 237         case SYSFS_KOBJ_ATTR:
 238                 inode->i_size = PAGE_SIZE;
 239                 inode->i_fop = &sysfs_file_operations;
 240                 break;
 241         case SYSFS_KOBJ_BIN_ATTR:
 242                 bin_attr = sd->s_bin_attr.bin_attr;
 243                 inode->i_size = bin_attr->size;
 244                 inode->i_fop = &bin_fops;
 245                 break;
 246         case SYSFS_KOBJ_LINK:
 247                 inode->i_op = &sysfs_symlink_inode_operations;
 248                 break;
 249         default:
 250                 BUG();
 251         }
 252
 253         unlock_new_inode(inode);
 254 }
 255
 256 /**
 257  *      sysfs_get_inode - get inode for sysfs_dirent
 258  *      @sd: sysfs_dirent to allocate inode for
 259  *
 260  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 261  *      is allocated and basics are initialized.  New inode is
 262  *      returned locked.
 263  *
 264  *      LOCKING:
 265  *      Kernel thread context (may sleep).
 266  *
 267  *      RETURNS:
 268  *      Pointer to allocated inode on success, NULL on failure.
 269  */
 270 struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 271 {
 272         struct inode *inode;
 273
 274         inode = iget_locked(sysfs_sb, sd->s_ino);
 275         if (inode && (inode->i_state & I_NEW))
 276                 sysfs_init_inode(sd, inode);
 277
 278         return inode;
 279 }
 280
 281 /*
 282  * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
 283  * To prevent the sysfs inode numbers from being freed prematurely we take a
 284  * reference to sysfs_dirent from the sysfs inode.  A
 285  * super_operations.delete_inode() implementation is needed to drop that
 286  * reference upon inode destruction.
 287  */
 288 void sysfs_delete_inode(struct inode *inode)
 289 {
 290         struct sysfs_dirent *sd  = inode->i_private;
 291
 292         truncate_inode_pages(&inode->i_data, 0);
 293         clear_inode(inode);
 294         sysfs_put(sd);
 295 }
 296
 297 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
 298 {
 299         struct sysfs_addrm_cxt acxt;
 300         struct sysfs_dirent *sd;
 301
 302         if (!dir_sd)
 303                 return -ENOENT;
 304
 305         sysfs_addrm_start(&acxt, dir_sd);
 306
 307         sd = sysfs_find_dirent(dir_sd, name);
 308         if (sd)
 309                 sysfs_remove_one(&acxt, sd);
 310
 311         sysfs_addrm_finish(&acxt);
 312
 313         if (sd)
 314                 return 0;
 315         else
 316                 return -ENOENT;
 317 }