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 void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 137 {
 138         inode->i_blocks = 0;
 139         inode->i_mapping->a_ops = &sysfs_aops;
 140         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 141         inode->i_op = &sysfs_inode_operations;
 142         inode->i_ino = sd->s_ino;
 143         lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 144
 145         if (sd->s_iattr) {
 146                 /* sysfs_dirent has non-default attributes
 147                  * get them for the new inode from persistent copy
 148                  * in sysfs_dirent
 149                  */
 150                 set_inode_attr(inode, sd->s_iattr);
 151         } else
 152                 set_default_inode_attr(inode, sd->s_mode);
 153 }
 154
 155 /**
 156  *      sysfs_get_inode - get inode for sysfs_dirent
 157  *      @sd: sysfs_dirent to allocate inode for
 158  *
 159  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 160  *      is allocated and basics are initialized.  New inode is
 161  *      returned locked.
 162  *
 163  *      LOCKING:
 164  *      Kernel thread context (may sleep).
 165  *
 166  *      RETURNS:
 167  *      Pointer to allocated inode on success, NULL on failure.
 168  */
 169 struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 170 {
 171         struct inode *inode;
 172
 173         inode = iget_locked(sysfs_sb, sd->s_ino);
 174         if (inode && (inode->i_state & I_NEW))
 175                 sysfs_init_inode(sd, inode);
 176
 177         return inode;
 178 }
 179
 180 /**
 181  *      sysfs_instantiate - instantiate dentry
 182  *      @dentry: dentry to be instantiated
 183  *      @inode: inode associated with @sd
 184  *
 185  *      Unlock @inode if locked and instantiate @dentry with @inode.
 186  *
 187  *      LOCKING:
 188  *      None.
 189  */
 190 void sysfs_instantiate(struct dentry *dentry, struct inode *inode)
 191 {
 192         BUG_ON(!dentry || dentry->d_inode);
 193
 194         if (inode->i_state & I_NEW) {
 195                 unlock_new_inode(inode);
 196
 197                 if (dentry->d_parent && dentry->d_parent->d_inode) {
 198                         struct inode *p_inode = dentry->d_parent->d_inode;
 199                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
 200                 }
 201         }
 202
 203         d_instantiate(dentry, inode);
 204 }
 205
 206 /**
 207  *      sysfs_drop_dentry - drop dentry for the specified sysfs_dirent
 208  *      @sd: target sysfs_dirent
 209  *
 210  *      Drop dentry for @sd.  @sd must have been unlinked from its
 211  *      parent on entry to this function such that it can't be looked
 212  *      up anymore.
 213  *
 214  *      @sd->s_dentry which is protected with sysfs_lock points to the
 215  *      currently associated dentry but we're not holding a reference
 216  *      to it and racing with dput().  Grab dcache_lock and verify
 217  *      dentry before dropping it.  If @sd->s_dentry is NULL or dput()
 218  *      beats us, no need to bother.
 219  */
 220 void sysfs_drop_dentry(struct sysfs_dirent *sd)
 221 {
 222         struct dentry *dentry = NULL;
 223         struct timespec curtime;
 224         struct inode *inode;
 225
 226         /* We're not holding a reference to ->s_dentry dentry but the
 227          * field will stay valid as long as sysfs_lock is held.
 228          */
 229         spin_lock(&sysfs_lock);
 230         spin_lock(&dcache_lock);
 231
 232         /* drop dentry if it's there and dput() didn't kill it yet */
 233         if (sd->s_dentry && sd->s_dentry->d_inode) {
 234                 dentry = dget_locked(sd->s_dentry);
 235                 spin_lock(&dentry->d_lock);
 236                 __d_drop(dentry);
 237                 spin_unlock(&dentry->d_lock);
 238         }
 239
 240         spin_unlock(&dcache_lock);
 241         spin_unlock(&sysfs_lock);
 242
 243         dput(dentry);
 244         /* XXX: unpin if directory, this will go away soon */
 245         if (sysfs_type(sd) == SYSFS_DIR)
 246                 dput(dentry);
 247
 248         /* adjust nlink and update timestamp */
 249         curtime = CURRENT_TIME;
 250
 251         inode = ilookup(sysfs_sb, sd->s_ino);
 252         if (inode) {
 253                 mutex_lock(&inode->i_mutex);
 254
 255                 inode->i_ctime = curtime;
 256                 drop_nlink(inode);
 257                 if (sysfs_type(sd) == SYSFS_DIR)
 258                         drop_nlink(inode);
 259
 260                 mutex_unlock(&inode->i_mutex);
 261                 iput(inode);
 262         }
 263
 264         /* adjust nlink and udpate timestamp of the parent */
 265         inode = ilookup(sysfs_sb, sd->s_parent->s_ino);
 266         if (inode) {
 267                 mutex_lock(&inode->i_mutex);
 268
 269                 inode->i_ctime = inode->i_mtime = curtime;
 270                 if (sysfs_type(sd) == SYSFS_DIR)
 271                         drop_nlink(inode);
 272
 273                 mutex_unlock(&inode->i_mutex);
 274                 iput(inode);
 275         }
 276 }
 277
 278 int sysfs_hash_and_remove(struct dentry * dir, const char * name)
 279 {
 280         struct sysfs_dirent **pos, *sd;
 281         struct sysfs_dirent *parent_sd;
 282         int found = 0;
 283
 284         if (!dir)
 285                 return -ENOENT;
 286
 287         if (dir->d_inode == NULL)
 288                 /* no inode means this hasn't been made visible yet */
 289                 return -ENOENT;
 290
 291         parent_sd = dir->d_fsdata;
 292         mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 293         for (pos = &parent_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
 294                 sd = *pos;
 295
 296                 if (!sysfs_type(sd))
 297                         continue;
 298                 if (!strcmp(sd->s_name, name)) {
 299                         *pos = sd->s_sibling;
 300                         sd->s_sibling = NULL;
 301                         found = 1;
 302                         break;
 303                 }
 304         }
 305         mutex_unlock(&dir->d_inode->i_mutex);
 306
 307         if (!found)
 308                 return -ENOENT;
 309
 310         sysfs_drop_dentry(sd);
 311         sysfs_deactivate(sd);
 312         sysfs_put(sd);
 313
 314         return 0;
 315 }