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