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 <asm/semaphore.h>
  17 #include "sysfs.h"
  18
  19 extern struct super_block * sysfs_sb;
  20
  21 static const struct address_space_operations sysfs_aops = {
  22         .readpage       = simple_readpage,
  23         .prepare_write  = simple_prepare_write,
  24         .commit_write   = simple_commit_write
  25 };
  26
  27 static struct backing_dev_info sysfs_backing_dev_info = {
  28         .ra_pages       = 0,    /* No readahead */
  29         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  30 };
  31
  32 static struct inode_operations sysfs_inode_operations ={
  33         .setattr        = sysfs_setattr,
  34 };
  35
  36 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  37 {
  38         struct inode * inode = dentry->d_inode;
  39         struct sysfs_dirent * sd = dentry->d_fsdata;
  40         struct iattr * sd_iattr;
  41         unsigned int ia_valid = iattr->ia_valid;
  42         int error;
  43
  44         if (!sd)
  45                 return -EINVAL;
  46
  47         sd_iattr = sd->s_iattr;
  48
  49         error = inode_change_ok(inode, iattr);
  50         if (error)
  51                 return error;
  52
  53         error = inode_setattr(inode, iattr);
  54         if (error)
  55                 return error;
  56
  57         if (!sd_iattr) {
  58                 /* setting attributes for the first time, allocate now */
  59                 sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
  60                 if (!sd_iattr)
  61                         return -ENOMEM;
  62                 /* assign default attributes */
  63                 sd_iattr->ia_mode = sd->s_mode;
  64                 sd_iattr->ia_uid = 0;
  65                 sd_iattr->ia_gid = 0;
  66                 sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
  67                 sd->s_iattr = sd_iattr;
  68         }
  69
  70         /* attributes were changed atleast once in past */
  71
  72         if (ia_valid & ATTR_UID)
  73                 sd_iattr->ia_uid = iattr->ia_uid;
  74         if (ia_valid & ATTR_GID)
  75                 sd_iattr->ia_gid = iattr->ia_gid;
  76         if (ia_valid & ATTR_ATIME)
  77                 sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
  78                                                 inode->i_sb->s_time_gran);
  79         if (ia_valid & ATTR_MTIME)
  80                 sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
  81                                                 inode->i_sb->s_time_gran);
  82         if (ia_valid & ATTR_CTIME)
  83                 sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
  84                                                 inode->i_sb->s_time_gran);
  85         if (ia_valid & ATTR_MODE) {
  86                 umode_t mode = iattr->ia_mode;
  87
  88                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
  89                         mode &= ~S_ISGID;
  90                 sd_iattr->ia_mode = sd->s_mode = mode;
  91         }
  92
  93         return error;
  94 }
  95
  96 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
  97 {
  98         inode->i_mode = mode;
  99         inode->i_uid = 0;
 100         inode->i_gid = 0;
 101         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 102 }
 103
 104 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 105 {
 106         inode->i_mode = iattr->ia_mode;
 107         inode->i_uid = iattr->ia_uid;
 108         inode->i_gid = iattr->ia_gid;
 109         inode->i_atime = iattr->ia_atime;
 110         inode->i_mtime = iattr->ia_mtime;
 111         inode->i_ctime = iattr->ia_ctime;
 112 }
 113
 114
 115 /*
 116  * sysfs has a different i_mutex lock order behavior for i_mutex than other
 117  * filesystems; sysfs i_mutex is called in many places with subsystem locks
 118  * held. At the same time, many of the VFS locking rules do not apply to
 119  * sysfs at all (cross directory rename for example). To untangle this mess
 120  * (which gives false positives in lockdep), we're giving sysfs inodes their
 121  * own class for i_mutex.
 122  */
 123 static struct lock_class_key sysfs_inode_imutex_key;
 124
 125 struct inode * sysfs_new_inode(mode_t mode, struct sysfs_dirent * sd)
 126 {
 127         struct inode * inode = new_inode(sysfs_sb);
 128         if (inode) {
 129                 inode->i_blocks = 0;
 130                 inode->i_mapping->a_ops = &sysfs_aops;
 131                 inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 132                 inode->i_op = &sysfs_inode_operations;
 133                 lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 134
 135                 if (sd->s_iattr) {
 136                         /* sysfs_dirent has non-default attributes
 137                          * get them for the new inode from persistent copy
 138                          * in sysfs_dirent
 139                          */
 140                         set_inode_attr(inode, sd->s_iattr);
 141                 } else
 142                         set_default_inode_attr(inode, mode);
 143         }
 144         return inode;
 145 }
 146
 147 int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
 148 {
 149         int error = 0;
 150         struct inode * inode = NULL;
 151         if (dentry) {
 152                 if (!dentry->d_inode) {
 153                         struct sysfs_dirent * sd = dentry->d_fsdata;
 154                         if ((inode = sysfs_new_inode(mode, sd))) {
 155                                 if (dentry->d_parent && dentry->d_parent->d_inode) {
 156                                         struct inode *p_inode = dentry->d_parent->d_inode;
 157                                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
 158                                 }
 159                                 goto Proceed;
 160                         }
 161                         else
 162                                 error = -ENOMEM;
 163                 } else
 164                         error = -EEXIST;
 165         } else
 166                 error = -ENOENT;
 167         goto Done;
 168
 169  Proceed:
 170         if (init)
 171                 error = init(inode);
 172         if (!error) {
 173                 d_instantiate(dentry, inode);
 174                 if (S_ISDIR(mode))
 175                         dget(dentry);  /* pin only directory dentry in core */
 176         } else
 177                 iput(inode);
 178  Done:
 179         return error;
 180 }
 181
 182 /*
 183  * Get the name for corresponding element represented by the given sysfs_dirent
 184  */
 185 const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
 186 {
 187         struct attribute * attr;
 188         struct bin_attribute * bin_attr;
 189         struct sysfs_symlink  * sl;
 190
 191         BUG_ON(!sd || !sd->s_element);
 192
 193         switch (sd->s_type) {
 194                 case SYSFS_DIR:
 195                         /* Always have a dentry so use that */
 196                         return sd->s_dentry->d_name.name;
 197
 198                 case SYSFS_KOBJ_ATTR:
 199                         attr = sd->s_element;
 200                         return attr->name;
 201
 202                 case SYSFS_KOBJ_BIN_ATTR:
 203                         bin_attr = sd->s_element;
 204                         return bin_attr->attr.name;
 205
 206                 case SYSFS_KOBJ_LINK:
 207                         sl = sd->s_element;
 208                         return sl->link_name;
 209         }
 210         return NULL;
 211 }
 212
 213 static inline void orphan_all_buffers(struct inode *node)
 214 {
 215         struct sysfs_buffer_collection *set = node->i_private;
 216         struct sysfs_buffer *buf;
 217
 218         mutex_lock_nested(&node->i_mutex, I_MUTEX_CHILD);
 219         if (node->i_private) {
 220                 list_for_each_entry(buf, &set->associates, associates) {
 221                         down(&buf->sem);
 222                         buf->orphaned = 1;
 223                         up(&buf->sem);
 224                 }
 225         }
 226         mutex_unlock(&node->i_mutex);
 227 }
 228
 229
 230 /*
 231  * Unhashes the dentry corresponding to given sysfs_dirent
 232  * Called with parent inode's i_mutex held.
 233  */
 234 void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
 235 {
 236         struct dentry * dentry = sd->s_dentry;
 237         struct inode *inode;
 238
 239         if (dentry) {
 240                 spin_lock(&dcache_lock);
 241                 spin_lock(&dentry->d_lock);
 242                 if (!(d_unhashed(dentry) && dentry->d_inode)) {
 243                         inode = dentry->d_inode;
 244                         spin_lock(&inode->i_lock);
 245                         __iget(inode);
 246                         spin_unlock(&inode->i_lock);
 247                         dget_locked(dentry);
 248                         __d_drop(dentry);
 249                         spin_unlock(&dentry->d_lock);
 250                         spin_unlock(&dcache_lock);
 251                         simple_unlink(parent->d_inode, dentry);
 252                         orphan_all_buffers(inode);
 253                         iput(inode);
 254                 } else {
 255                         spin_unlock(&dentry->d_lock);
 256                         spin_unlock(&dcache_lock);
 257                 }
 258         }
 259 }
 260
 261 int sysfs_hash_and_remove(struct dentry * dir, const char * name)
 262 {
 263         struct sysfs_dirent * sd;
 264         struct sysfs_dirent * parent_sd;
 265         int found = 0;
 266
 267         if (!dir)
 268                 return -ENOENT;
 269
 270         if (dir->d_inode == NULL)
 271                 /* no inode means this hasn't been made visible yet */
 272                 return -ENOENT;
 273
 274         parent_sd = dir->d_fsdata;
 275         mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 276         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 277                 if (!sd->s_element)
 278                         continue;
 279                 if (!strcmp(sysfs_get_name(sd), name)) {
 280                         list_del_init(&sd->s_sibling);
 281                         sysfs_drop_dentry(sd, dir);
 282                         sysfs_put(sd);
 283                         found = 1;
 284                         break;
 285                 }
 286         }
 287         mutex_unlock(&dir->d_inode->i_mutex);
 288
 289         return found ? 0 : -ENOENT;
 290 }