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                 inode->i_ino = sd->s_ino;
 145                 lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 146
 147                 if (sd->s_iattr) {
 148                         /* sysfs_dirent has non-default attributes
 149                          * get them for the new inode from persistent copy
 150                          * in sysfs_dirent
 151                          */
 152                         set_inode_attr(inode, sd->s_iattr);
 153                 } else
 154                         set_default_inode_attr(inode, mode);
 155         }
 156         return inode;
 157 }
 158
 159 int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
 160 {
 161         int error = 0;
 162         struct inode * inode = NULL;
 163         if (dentry) {
 164                 if (!dentry->d_inode) {
 165                         struct sysfs_dirent * sd = dentry->d_fsdata;
 166                         if ((inode = sysfs_new_inode(mode, sd))) {
 167                                 if (dentry->d_parent && dentry->d_parent->d_inode) {
 168                                         struct inode *p_inode = dentry->d_parent->d_inode;
 169                                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
 170                                 }
 171                                 goto Proceed;
 172                         }
 173                         else
 174                                 error = -ENOMEM;
 175                 } else
 176                         error = -EEXIST;
 177         } else
 178                 error = -ENOENT;
 179         goto Done;
 180
 181  Proceed:
 182         if (init)
 183                 error = init(inode);
 184         if (!error) {
 185                 d_instantiate(dentry, inode);
 186                 if (S_ISDIR(mode))
 187                         dget(dentry);  /* pin only directory dentry in core */
 188         } else
 189                 iput(inode);
 190  Done:
 191         return error;
 192 }
 193
 194 /*
 195  * Get the name for corresponding element represented by the given sysfs_dirent
 196  */
 197 const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
 198 {
 199         struct attribute * attr;
 200         struct bin_attribute * bin_attr;
 201         struct sysfs_symlink  * sl;
 202
 203         BUG_ON(!sd || !sd->s_element);
 204
 205         switch (sd->s_type) {
 206                 case SYSFS_DIR:
 207                         /* Always have a dentry so use that */
 208                         return sd->s_dentry->d_name.name;
 209
 210                 case SYSFS_KOBJ_ATTR:
 211                         attr = sd->s_element;
 212                         return attr->name;
 213
 214                 case SYSFS_KOBJ_BIN_ATTR:
 215                         bin_attr = sd->s_element;
 216                         return bin_attr->attr.name;
 217
 218                 case SYSFS_KOBJ_LINK:
 219                         sl = sd->s_element;
 220                         return sl->link_name;
 221         }
 222         return NULL;
 223 }
 224
 225 static inline void orphan_all_buffers(struct inode *node)
 226 {
 227         struct sysfs_buffer_collection *set;
 228         struct sysfs_buffer *buf;
 229
 230         mutex_lock_nested(&node->i_mutex, I_MUTEX_CHILD);
 231         set = node->i_private;
 232         if (set) {
 233                 list_for_each_entry(buf, &set->associates, associates) {
 234                         down(&buf->sem);
 235                         buf->orphaned = 1;
 236                         up(&buf->sem);
 237                 }
 238         }
 239         mutex_unlock(&node->i_mutex);
 240 }
 241
 242
 243 /*
 244  * Unhashes the dentry corresponding to given sysfs_dirent
 245  * Called with parent inode's i_mutex held.
 246  */
 247 void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
 248 {
 249         struct dentry *dentry = NULL;
 250         struct inode *inode;
 251
 252         /* We're not holding a reference to ->s_dentry dentry but the
 253          * field will stay valid as long as sysfs_lock is held.
 254          */
 255         spin_lock(&sysfs_lock);
 256         spin_lock(&dcache_lock);
 257
 258         /* dget dentry if it's still alive */
 259         if (sd->s_dentry && sd->s_dentry->d_inode)
 260                 dentry = dget_locked(sd->s_dentry);
 261
 262         spin_unlock(&dcache_lock);
 263         spin_unlock(&sysfs_lock);
 264
 265         /* drop dentry */
 266         if (dentry) {
 267                 spin_lock(&dcache_lock);
 268                 spin_lock(&dentry->d_lock);
 269                 if (!d_unhashed(dentry) && dentry->d_inode) {
 270                         inode = dentry->d_inode;
 271                         spin_lock(&inode->i_lock);
 272                         __iget(inode);
 273                         spin_unlock(&inode->i_lock);
 274                         dget_locked(dentry);
 275                         __d_drop(dentry);
 276                         spin_unlock(&dentry->d_lock);
 277                         spin_unlock(&dcache_lock);
 278                         simple_unlink(parent->d_inode, dentry);
 279                         orphan_all_buffers(inode);
 280                         iput(inode);
 281                 } else {
 282                         spin_unlock(&dentry->d_lock);
 283                         spin_unlock(&dcache_lock);
 284                 }
 285
 286                 dput(dentry);
 287         }
 288 }
 289
 290 int sysfs_hash_and_remove(struct dentry * dir, const char * name)
 291 {
 292         struct sysfs_dirent * sd;
 293         struct sysfs_dirent * parent_sd;
 294         int found = 0;
 295
 296         if (!dir)
 297                 return -ENOENT;
 298
 299         if (dir->d_inode == NULL)
 300                 /* no inode means this hasn't been made visible yet */
 301                 return -ENOENT;
 302
 303         parent_sd = dir->d_fsdata;
 304         mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 305         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 306                 if (!sd->s_element)
 307                         continue;
 308                 if (!strcmp(sysfs_get_name(sd), name)) {
 309                         list_del_init(&sd->s_sibling);
 310                         sysfs_drop_dentry(sd, dir);
 311                         sysfs_put(sd);
 312                         found = 1;
 313                         break;
 314                 }
 315         }
 316         mutex_unlock(&dir->d_inode->i_mutex);
 317
 318         return found ? 0 : -ENOENT;
 319 }