fs/sysfs/inode.c

   1 /*
   2  * inode.c - basic inode and dentry operations.
   3  *
   4  * sysfs is Copyright (c) 2001-3 Patrick Mochel
   5  *
   6  * Please see Documentation/filesystems/sysfs.txt for more information.
   7  */
   8
   9 #undef DEBUG
  10
  11 #include <linux/pagemap.h>
  12 #include <linux/namei.h>
  13 #include <linux/backing-dev.h>
  14 #include <linux/capability.h>
  15 #include <linux/errno.h>
  16 #include <linux/sched.h>
  17 #include <asm/semaphore.h>
  18 #include "sysfs.h"
  19
  20 extern struct super_block * sysfs_sb;
  21
  22 static const struct address_space_operations sysfs_aops = {
  23         .readpage       = simple_readpage,
  24         .prepare_write  = simple_prepare_write,
  25         .commit_write   = simple_commit_write
  26 };
  27
  28 static struct backing_dev_info sysfs_backing_dev_info = {
  29         .ra_pages       = 0,    /* No readahead */
  30         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  31 };
  32
  33 static const struct inode_operations sysfs_inode_operations ={
  34         .setattr        = sysfs_setattr,
  35 };
  36
  37 void sysfs_delete_inode(struct inode *inode)
  38 {
  39         /* Free the shadowed directory inode operations */
  40         if (sysfs_is_shadowed_inode(inode)) {
  41                 kfree(inode->i_op);
  42                 inode->i_op = NULL;
  43         }
  44         return generic_delete_inode(inode);
  45 }
  46
  47 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  48 {
  49         struct inode * inode = dentry->d_inode;
  50         struct sysfs_dirent * sd = dentry->d_fsdata;
  51         struct iattr * sd_iattr;
  52         unsigned int ia_valid = iattr->ia_valid;
  53         int error;
  54
  55         if (!sd)
  56                 return -EINVAL;
  57
  58         sd_iattr = sd->s_iattr;
  59
  60         error = inode_change_ok(inode, iattr);
  61         if (error)
  62                 return error;
  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_uid = 0;
 111         inode->i_gid = 0;
 112         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 113 }
 114
 115 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 116 {
 117         inode->i_mode = iattr->ia_mode;
 118         inode->i_uid = iattr->ia_uid;
 119         inode->i_gid = iattr->ia_gid;
 120         inode->i_atime = iattr->ia_atime;
 121         inode->i_mtime = iattr->ia_mtime;
 122         inode->i_ctime = iattr->ia_ctime;
 123 }
 124
 125
 126 /*
 127  * sysfs has a different i_mutex lock order behavior for i_mutex than other
 128  * filesystems; sysfs i_mutex is called in many places with subsystem locks
 129  * held. At the same time, many of the VFS locking rules do not apply to
 130  * sysfs at all (cross directory rename for example). To untangle this mess
 131  * (which gives false positives in lockdep), we're giving sysfs inodes their
 132  * own class for i_mutex.
 133  */
 134 static struct lock_class_key sysfs_inode_imutex_key;
 135
 136 struct inode * sysfs_new_inode(mode_t mode, struct sysfs_dirent * sd)
 137 {
 138         struct inode * inode = new_inode(sysfs_sb);
 139         if (inode) {
 140                 inode->i_blocks = 0;
 141                 inode->i_mapping->a_ops = &sysfs_aops;
 142                 inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 143                 inode->i_op = &sysfs_inode_operations;
 144                 lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 145
 146                 if (sd->s_iattr) {
 147                         /* sysfs_dirent has non-default attributes
 148                          * get them for the new inode from persistent copy
 149                          * in sysfs_dirent
 150                          */
 151                         set_inode_attr(inode, sd->s_iattr);
 152                 } else
 153                         set_default_inode_attr(inode, mode);
 154         }
 155         return inode;
 156 }
 157
 158 int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
 159 {
 160         int error = 0;
 161         struct inode * inode = NULL;
 162         if (dentry) {
 163                 if (!dentry->d_inode) {
 164                         struct sysfs_dirent * sd = dentry->d_fsdata;
 165                         if ((inode = sysfs_new_inode(mode, sd))) {
 166                                 if (dentry->d_parent && dentry->d_parent->d_inode) {
 167                                         struct inode *p_inode = dentry->d_parent->d_inode;
 168                                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
 169                                 }
 170                                 goto Proceed;
 171                         }
 172                         else
 173                                 error = -ENOMEM;
 174                 } else
 175                         error = -EEXIST;
 176         } else
 177                 error = -ENOENT;
 178         goto Done;
 179
 180  Proceed:
 181         if (init)
 182                 error = init(inode);
 183         if (!error) {
 184                 d_instantiate(dentry, inode);
 185                 if (S_ISDIR(mode))
 186                         dget(dentry);  /* pin only directory dentry in core */
 187         } else
 188                 iput(inode);
 189  Done:
 190         return error;
 191 }
 192
 193 /*
 194  * Get the name for corresponding element represented by the given sysfs_dirent
 195  */
 196 const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
 197 {
 198         struct attribute * attr;
 199         struct bin_attribute * bin_attr;
 200         struct sysfs_symlink  * sl;
 201
 202         BUG_ON(!sd || !sd->s_element);
 203
 204         switch (sd->s_type) {
 205                 case SYSFS_DIR:
 206                         /* Always have a dentry so use that */
 207                         return sd->s_dentry->d_name.name;
 208
 209                 case SYSFS_KOBJ_ATTR:
 210                         attr = sd->s_element;
 211                         return attr->name;
 212
 213                 case SYSFS_KOBJ_BIN_ATTR:
 214                         bin_attr = sd->s_element;
 215                         return bin_attr->attr.name;
 216
 217                 case SYSFS_KOBJ_LINK:
 218                         sl = sd->s_element;
 219                         return sl->link_name;
 220         }
 221         return NULL;
 222 }
 223
 224 static inline void orphan_all_buffers(struct inode *node)
 225 {
 226         struct sysfs_buffer_collection *set;
 227         struct sysfs_buffer *buf;
 228
 229         mutex_lock_nested(&node->i_mutex, I_MUTEX_CHILD);
 230         set = node->i_private;
 231         if (set) {
 232                 list_for_each_entry(buf, &set->associates, associates) {
 233                         down(&buf->sem);
 234                         buf->orphaned = 1;
 235                         up(&buf->sem);
 236                 }
 237         }
 238         mutex_unlock(&node->i_mutex);
 239 }
 240
 241
 242 /*
 243  * Unhashes the dentry corresponding to given sysfs_dirent
 244  * Called with parent inode's i_mutex held.
 245  */
 246 void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
 247 {
 248         struct dentry * dentry = sd->s_dentry;
 249         struct inode *inode;
 250
 251         if (dentry) {
 252                 spin_lock(&dcache_lock);
 253                 spin_lock(&dentry->d_lock);
 254                 if (!(d_unhashed(dentry) && dentry->d_inode)) {
 255                         inode = dentry->d_inode;
 256                         spin_lock(&inode->i_lock);
 257                         __iget(inode);
 258                         spin_unlock(&inode->i_lock);
 259                         dget_locked(dentry);
 260                         __d_drop(dentry);
 261                         spin_unlock(&dentry->d_lock);
 262                         spin_unlock(&dcache_lock);
 263                         simple_unlink(parent->d_inode, dentry);
 264                         orphan_all_buffers(inode);
 265                         iput(inode);
 266                 } else {
 267                         spin_unlock(&dentry->d_lock);
 268                         spin_unlock(&dcache_lock);
 269                 }
 270         }
 271 }
 272
 273 int sysfs_hash_and_remove(struct dentry * dir, const char * name)
 274 {
 275         struct sysfs_dirent * sd;
 276         struct sysfs_dirent * parent_sd;
 277         int found = 0;
 278
 279         if (!dir)
 280                 return -ENOENT;
 281
 282         if (dir->d_inode == NULL)
 283                 /* no inode means this hasn't been made visible yet */
 284                 return -ENOENT;
 285
 286         parent_sd = dir->d_fsdata;
 287         mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 288         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 289                 if (!sd->s_element)
 290                         continue;
 291                 if (!strcmp(sysfs_get_name(sd), name)) {
 292                         list_del_init(&sd->s_sibling);
 293                         sysfs_drop_dentry(sd, dir);
 294                         sysfs_put(sd);
 295                         found = 1;
 296                         break;
 297                 }
 298         }
 299         mutex_unlock(&dir->d_inode->i_mutex);
 300
 301         return found ? 0 : -ENOENT;
 302 }