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 "sysfs.h"
  22
  23 extern struct super_block * sysfs_sb;
  24
  25 static const struct address_space_operations sysfs_aops = {
  26         .readpage       = simple_readpage,
  27         .write_begin    = simple_write_begin,
  28         .write_end      = simple_write_end,
  29 };
  30
  31 static struct backing_dev_info sysfs_backing_dev_info = {
  32         .ra_pages       = 0,    /* No readahead */
  33         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  34 };
  35
  36 static const struct inode_operations sysfs_inode_operations ={
  37         .setattr        = sysfs_setattr,
  38 };
  39
  40 int __init sysfs_inode_init(void)
  41 {
  42         return bdi_init(&sysfs_backing_dev_info);
  43 }
  44
  45 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  46 {
  47         struct inode * inode = dentry->d_inode;
  48         struct sysfs_dirent * sd = dentry->d_fsdata;
  49         struct iattr * sd_iattr;
  50         unsigned int ia_valid = iattr->ia_valid;
  51         int error;
  52
  53         if (!sd)
  54                 return -EINVAL;
  55
  56         sd_iattr = sd->s_iattr;
  57
  58         error = inode_change_ok(inode, iattr);
  59         if (error)
  60                 return error;
  61
  62         iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
  63
  64         error = inode_setattr(inode, iattr);
  65         if (error)
  66                 return error;
  67
  68         if (!sd_iattr) {
  69                 /* setting attributes for the first time, allocate now */
  70                 sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
  71                 if (!sd_iattr)
  72                         return -ENOMEM;
  73                 /* assign default attributes */
  74                 sd_iattr->ia_mode = sd->s_mode;
  75                 sd_iattr->ia_uid = 0;
  76                 sd_iattr->ia_gid = 0;
  77                 sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
  78                 sd->s_iattr = sd_iattr;
  79         }
  80
  81         /* attributes were changed atleast once in past */
  82
  83         if (ia_valid & ATTR_UID)
  84                 sd_iattr->ia_uid = iattr->ia_uid;
  85         if (ia_valid & ATTR_GID)
  86                 sd_iattr->ia_gid = iattr->ia_gid;
  87         if (ia_valid & ATTR_ATIME)
  88                 sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
  89                                                 inode->i_sb->s_time_gran);
  90         if (ia_valid & ATTR_MTIME)
  91                 sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
  92                                                 inode->i_sb->s_time_gran);
  93         if (ia_valid & ATTR_CTIME)
  94                 sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
  95                                                 inode->i_sb->s_time_gran);
  96         if (ia_valid & ATTR_MODE) {
  97                 umode_t mode = iattr->ia_mode;
  98
  99                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
 100                         mode &= ~S_ISGID;
 101                 sd_iattr->ia_mode = sd->s_mode = mode;
 102         }
 103
 104         return error;
 105 }
 106
 107 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
 108 {
 109         inode->i_mode = mode;
 110         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 111 }
 112
 113 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 114 {
 115         inode->i_mode = iattr->ia_mode;
 116         inode->i_uid = iattr->ia_uid;
 117         inode->i_gid = iattr->ia_gid;
 118         inode->i_atime = iattr->ia_atime;
 119         inode->i_mtime = iattr->ia_mtime;
 120         inode->i_ctime = iattr->ia_ctime;
 121 }
 122
 123
 124 /*
 125  * sysfs has a different i_mutex lock order behavior for i_mutex than other
 126  * filesystems; sysfs i_mutex is called in many places with subsystem locks
 127  * held. At the same time, many of the VFS locking rules do not apply to
 128  * sysfs at all (cross directory rename for example). To untangle this mess
 129  * (which gives false positives in lockdep), we're giving sysfs inodes their
 130  * own class for i_mutex.
 131  */
 132 static struct lock_class_key sysfs_inode_imutex_key;
 133
 134 static int sysfs_count_nlink(struct sysfs_dirent *sd)
 135 {
 136         struct sysfs_dirent *child;
 137         int nr = 0;
 138
 139         for (child = sd->s_dir.children; child; child = child->s_sibling)
 140                 if (sysfs_type(child) == SYSFS_DIR)
 141                         nr++;
 142
 143         return nr + 2;
 144 }
 145
 146 static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 147 {
 148         struct bin_attribute *bin_attr;
 149
 150         inode->i_private = sysfs_get(sd);
 151         inode->i_mapping->a_ops = &sysfs_aops;
 152         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 153         inode->i_op = &sysfs_inode_operations;
 154         inode->i_ino = sd->s_ino;
 155         lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 156
 157         if (sd->s_iattr) {
 158                 /* sysfs_dirent has non-default attributes
 159                  * get them for the new inode from persistent copy
 160                  * in sysfs_dirent
 161                  */
 162                 set_inode_attr(inode, sd->s_iattr);
 163         } else
 164                 set_default_inode_attr(inode, sd->s_mode);
 165
 166
 167         /* initialize inode according to type */
 168         switch (sysfs_type(sd)) {
 169         case SYSFS_DIR:
 170                 inode->i_op = &sysfs_dir_inode_operations;
 171                 inode->i_fop = &sysfs_dir_operations;
 172                 inode->i_nlink = sysfs_count_nlink(sd);
 173                 break;
 174         case SYSFS_KOBJ_ATTR:
 175                 inode->i_size = PAGE_SIZE;
 176                 inode->i_fop = &sysfs_file_operations;
 177                 break;
 178         case SYSFS_KOBJ_BIN_ATTR:
 179                 bin_attr = sd->s_bin_attr.bin_attr;
 180                 inode->i_size = bin_attr->size;
 181                 inode->i_fop = &bin_fops;
 182                 break;
 183         case SYSFS_KOBJ_LINK:
 184                 inode->i_op = &sysfs_symlink_inode_operations;
 185                 break;
 186         default:
 187                 BUG();
 188         }
 189
 190         unlock_new_inode(inode);
 191 }
 192
 193 /**
 194  *      sysfs_get_inode - get inode for sysfs_dirent
 195  *      @sd: sysfs_dirent to allocate inode for
 196  *
 197  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 198  *      is allocated and basics are initialized.  New inode is
 199  *      returned locked.
 200  *
 201  *      LOCKING:
 202  *      Kernel thread context (may sleep).
 203  *
 204  *      RETURNS:
 205  *      Pointer to allocated inode on success, NULL on failure.
 206  */
 207 struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 208 {
 209         struct inode *inode;
 210
 211         inode = iget_locked(sysfs_sb, sd->s_ino);
 212         if (inode && (inode->i_state & I_NEW))
 213                 sysfs_init_inode(sd, inode);
 214
 215         return inode;
 216 }
 217
 218 /*
 219  * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
 220  * To prevent the sysfs inode numbers from being freed prematurely we take a
 221  * reference to sysfs_dirent from the sysfs inode.  A
 222  * super_operations.delete_inode() implementation is needed to drop that
 223  * reference upon inode destruction.
 224  */
 225 void sysfs_delete_inode(struct inode *inode)
 226 {
 227         struct sysfs_dirent *sd  = inode->i_private;
 228
 229         truncate_inode_pages(&inode->i_data, 0);
 230         clear_inode(inode);
 231         sysfs_put(sd);
 232 }
 233
 234 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
 235 {
 236         struct sysfs_addrm_cxt acxt;
 237         struct sysfs_dirent *sd;
 238
 239         if (!dir_sd)
 240                 return -ENOENT;
 241
 242         sysfs_addrm_start(&acxt, dir_sd);
 243
 244         sd = sysfs_find_dirent(dir_sd, name);
 245         if (sd)
 246                 sysfs_remove_one(&acxt, sd);
 247
 248         sysfs_addrm_finish(&acxt);
 249
 250         if (sd)
 251                 return 0;
 252         else
 253                 return -ENOENT;
 254 }