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