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