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         .name           = "sysfs",
  33         .ra_pages       = 0,    /* No readahead */
  34         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  35 };
  36
  37 static const struct inode_operations sysfs_inode_operations ={
  38         .setattr        = sysfs_setattr,
  39 };
  40
  41 int __init sysfs_inode_init(void)
  42 {
  43         return bdi_init(&sysfs_backing_dev_info);
  44 }
  45
  46 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  47 {
  48         struct inode * inode = dentry->d_inode;
  49         struct sysfs_dirent * sd = dentry->d_fsdata;
  50         struct iattr * sd_iattr;
  51         unsigned int ia_valid = iattr->ia_valid;
  52         int error;
  53
  54         if (!sd)
  55                 return -EINVAL;
  56
  57         sd_iattr = sd->s_iattr;
  58
  59         error = inode_change_ok(inode, iattr);
  60         if (error)
  61                 return error;
  62
  63         iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
  64
  65         error = inode_setattr(inode, iattr);
  66         if (error)
  67                 return error;
  68
  69         if (!sd_iattr) {
  70                 /* setting attributes for the first time, allocate now */
  71                 sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
  72                 if (!sd_iattr)
  73                         return -ENOMEM;
  74                 /* assign default attributes */
  75                 sd_iattr->ia_mode = sd->s_mode;
  76                 sd_iattr->ia_uid = 0;
  77                 sd_iattr->ia_gid = 0;
  78                 sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
  79                 sd->s_iattr = sd_iattr;
  80         }
  81
  82         /* attributes were changed atleast once in past */
  83
  84         if (ia_valid & ATTR_UID)
  85                 sd_iattr->ia_uid = iattr->ia_uid;
  86         if (ia_valid & ATTR_GID)
  87                 sd_iattr->ia_gid = iattr->ia_gid;
  88         if (ia_valid & ATTR_ATIME)
  89                 sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
  90                                                 inode->i_sb->s_time_gran);
  91         if (ia_valid & ATTR_MTIME)
  92                 sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
  93                                                 inode->i_sb->s_time_gran);
  94         if (ia_valid & ATTR_CTIME)
  95                 sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
  96                                                 inode->i_sb->s_time_gran);
  97         if (ia_valid & ATTR_MODE) {
  98                 umode_t mode = iattr->ia_mode;
  99
 100                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
 101                         mode &= ~S_ISGID;
 102                 sd_iattr->ia_mode = sd->s_mode = mode;
 103         }
 104
 105         return error;
 106 }
 107
 108 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
 109 {
 110         inode->i_mode = mode;
 111         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 112 }
 113
 114 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 115 {
 116         inode->i_mode = iattr->ia_mode;
 117         inode->i_uid = iattr->ia_uid;
 118         inode->i_gid = iattr->ia_gid;
 119         inode->i_atime = iattr->ia_atime;
 120         inode->i_mtime = iattr->ia_mtime;
 121         inode->i_ctime = iattr->ia_ctime;
 122 }
 123
 124
 125 /*
 126  * sysfs has a different i_mutex lock order behavior for i_mutex than other
 127  * filesystems; sysfs i_mutex is called in many places with subsystem locks
 128  * held. At the same time, many of the VFS locking rules do not apply to
 129  * sysfs at all (cross directory rename for example). To untangle this mess
 130  * (which gives false positives in lockdep), we're giving sysfs inodes their
 131  * own class for i_mutex.
 132  */
 133 static struct lock_class_key sysfs_inode_imutex_key;
 134
 135 static int sysfs_count_nlink(struct sysfs_dirent *sd)
 136 {
 137         struct sysfs_dirent *child;
 138         int nr = 0;
 139
 140         for (child = sd->s_dir.children; child; child = child->s_sibling)
 141                 if (sysfs_type(child) == SYSFS_DIR)
 142                         nr++;
 143
 144         return nr + 2;
 145 }
 146
 147 static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 148 {
 149         struct bin_attribute *bin_attr;
 150
 151         inode->i_private = sysfs_get(sd);
 152         inode->i_mapping->a_ops = &sysfs_aops;
 153         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 154         inode->i_op = &sysfs_inode_operations;
 155         inode->i_ino = sd->s_ino;
 156         lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 157
 158         if (sd->s_iattr) {
 159                 /* sysfs_dirent has non-default attributes
 160                  * get them for the new inode from persistent copy
 161                  * in sysfs_dirent
 162                  */
 163                 set_inode_attr(inode, sd->s_iattr);
 164         } else
 165                 set_default_inode_attr(inode, sd->s_mode);
 166
 167
 168         /* initialize inode according to type */
 169         switch (sysfs_type(sd)) {
 170         case SYSFS_DIR:
 171                 inode->i_op = &sysfs_dir_inode_operations;
 172                 inode->i_fop = &sysfs_dir_operations;
 173                 inode->i_nlink = sysfs_count_nlink(sd);
 174                 break;
 175         case SYSFS_KOBJ_ATTR:
 176                 inode->i_size = PAGE_SIZE;
 177                 inode->i_fop = &sysfs_file_operations;
 178                 break;
 179         case SYSFS_KOBJ_BIN_ATTR:
 180                 bin_attr = sd->s_bin_attr.bin_attr;
 181                 inode->i_size = bin_attr->size;
 182                 inode->i_fop = &bin_fops;
 183                 break;
 184         case SYSFS_KOBJ_LINK:
 185                 inode->i_op = &sysfs_symlink_inode_operations;
 186                 break;
 187         default:
 188                 BUG();
 189         }
 190
 191         unlock_new_inode(inode);
 192 }
 193
 194 /**
 195  *      sysfs_get_inode - get inode for sysfs_dirent
 196  *      @sd: sysfs_dirent to allocate inode for
 197  *
 198  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 199  *      is allocated and basics are initialized.  New inode is
 200  *      returned locked.
 201  *
 202  *      LOCKING:
 203  *      Kernel thread context (may sleep).
 204  *
 205  *      RETURNS:
 206  *      Pointer to allocated inode on success, NULL on failure.
 207  */
 208 struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 209 {
 210         struct inode *inode;
 211
 212         inode = iget_locked(sysfs_sb, sd->s_ino);
 213         if (inode && (inode->i_state & I_NEW))
 214                 sysfs_init_inode(sd, inode);
 215
 216         return inode;
 217 }
 218
 219 /*
 220  * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
 221  * To prevent the sysfs inode numbers from being freed prematurely we take a
 222  * reference to sysfs_dirent from the sysfs inode.  A
 223  * super_operations.delete_inode() implementation is needed to drop that
 224  * reference upon inode destruction.
 225  */
 226 void sysfs_delete_inode(struct inode *inode)
 227 {
 228         struct sysfs_dirent *sd  = inode->i_private;
 229
 230         truncate_inode_pages(&inode->i_data, 0);
 231         clear_inode(inode);
 232         sysfs_put(sd);
 233 }
 234
 235 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
 236 {
 237         struct sysfs_addrm_cxt acxt;
 238         struct sysfs_dirent *sd;
 239
 240         if (!dir_sd)
 241                 return -ENOENT;
 242
 243         sysfs_addrm_start(&acxt, dir_sd);
 244
 245         sd = sysfs_find_dirent(dir_sd, name);
 246         if (sd)
 247                 sysfs_remove_one(&acxt, sd);
 248
 249         sysfs_addrm_finish(&acxt);
 250
 251         if (sd)
 252                 return 0;
 253         else
 254                 return -ENOENT;
 255 }