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 "sysfs.h"
  16
  17 extern struct super_block * sysfs_sb;
  18
  19 static struct address_space_operations sysfs_aops = {
  20         .readpage       = simple_readpage,
  21         .prepare_write  = simple_prepare_write,
  22         .commit_write   = simple_commit_write
  23 };
  24
  25 static struct backing_dev_info sysfs_backing_dev_info = {
  26         .ra_pages       = 0,    /* No readahead */
  27         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  28 };
  29
  30 static struct inode_operations sysfs_inode_operations ={
  31         .setattr        = sysfs_setattr,
  32 };
  33
  34 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  35 {
  36         struct inode * inode = dentry->d_inode;
  37         struct sysfs_dirent * sd = dentry->d_fsdata;
  38         struct iattr * sd_iattr;
  39         unsigned int ia_valid = iattr->ia_valid;
  40         int error;
  41
  42         if (!sd)
  43                 return -EINVAL;
  44
  45         sd_iattr = sd->s_iattr;
  46
  47         error = inode_change_ok(inode, iattr);
  48         if (error)
  49                 return error;
  50
  51         error = inode_setattr(inode, iattr);
  52         if (error)
  53                 return error;
  54
  55         if (!sd_iattr) {
  56                 /* setting attributes for the first time, allocate now */
  57                 sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
  58                 if (!sd_iattr)
  59                         return -ENOMEM;
  60                 /* assign default attributes */
  61                 sd_iattr->ia_mode = sd->s_mode;
  62                 sd_iattr->ia_uid = 0;
  63                 sd_iattr->ia_gid = 0;
  64                 sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
  65                 sd->s_iattr = sd_iattr;
  66         }
  67
  68         /* attributes were changed atleast once in past */
  69
  70         if (ia_valid & ATTR_UID)
  71                 sd_iattr->ia_uid = iattr->ia_uid;
  72         if (ia_valid & ATTR_GID)
  73                 sd_iattr->ia_gid = iattr->ia_gid;
  74         if (ia_valid & ATTR_ATIME)
  75                 sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
  76                                                 inode->i_sb->s_time_gran);
  77         if (ia_valid & ATTR_MTIME)
  78                 sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
  79                                                 inode->i_sb->s_time_gran);
  80         if (ia_valid & ATTR_CTIME)
  81                 sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
  82                                                 inode->i_sb->s_time_gran);
  83         if (ia_valid & ATTR_MODE) {
  84                 umode_t mode = iattr->ia_mode;
  85
  86                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
  87                         mode &= ~S_ISGID;
  88                 sd_iattr->ia_mode = sd->s_mode = mode;
  89         }
  90
  91         return error;
  92 }
  93
  94 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
  95 {
  96         inode->i_mode = mode;
  97         inode->i_uid = 0;
  98         inode->i_gid = 0;
  99         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 100 }
 101
 102 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 103 {
 104         inode->i_mode = iattr->ia_mode;
 105         inode->i_uid = iattr->ia_uid;
 106         inode->i_gid = iattr->ia_gid;
 107         inode->i_atime = iattr->ia_atime;
 108         inode->i_mtime = iattr->ia_mtime;
 109         inode->i_ctime = iattr->ia_ctime;
 110 }
 111
 112 struct inode * sysfs_new_inode(mode_t mode, struct sysfs_dirent * sd)
 113 {
 114         struct inode * inode = new_inode(sysfs_sb);
 115         if (inode) {
 116                 inode->i_blksize = PAGE_CACHE_SIZE;
 117                 inode->i_blocks = 0;
 118                 inode->i_mapping->a_ops = &sysfs_aops;
 119                 inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 120                 inode->i_op = &sysfs_inode_operations;
 121
 122                 if (sd->s_iattr) {
 123                         /* sysfs_dirent has non-default attributes
 124                          * get them for the new inode from persistent copy
 125                          * in sysfs_dirent
 126                          */
 127                         set_inode_attr(inode, sd->s_iattr);
 128                 } else
 129                         set_default_inode_attr(inode, mode);
 130         }
 131         return inode;
 132 }
 133
 134 int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
 135 {
 136         int error = 0;
 137         struct inode * inode = NULL;
 138         if (dentry) {
 139                 if (!dentry->d_inode) {
 140                         struct sysfs_dirent * sd = dentry->d_fsdata;
 141                         if ((inode = sysfs_new_inode(mode, sd))) {
 142                                 if (dentry->d_parent && dentry->d_parent->d_inode) {
 143                                         struct inode *p_inode = dentry->d_parent->d_inode;
 144                                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
 145                                 }
 146                                 goto Proceed;
 147                         }
 148                         else
 149                                 error = -ENOMEM;
 150                 } else
 151                         error = -EEXIST;
 152         } else
 153                 error = -ENOENT;
 154         goto Done;
 155
 156  Proceed:
 157         if (init)
 158                 error = init(inode);
 159         if (!error) {
 160                 d_instantiate(dentry, inode);
 161                 if (S_ISDIR(mode))
 162                         dget(dentry);  /* pin only directory dentry in core */
 163         } else
 164                 iput(inode);
 165  Done:
 166         return error;
 167 }
 168
 169 /*
 170  * Get the name for corresponding element represented by the given sysfs_dirent
 171  */
 172 const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
 173 {
 174         struct attribute * attr;
 175         struct bin_attribute * bin_attr;
 176         struct sysfs_symlink  * sl;
 177
 178         BUG_ON(!sd || !sd->s_element);
 179
 180         switch (sd->s_type) {
 181                 case SYSFS_DIR:
 182                         /* Always have a dentry so use that */
 183                         return sd->s_dentry->d_name.name;
 184
 185                 case SYSFS_KOBJ_ATTR:
 186                         attr = sd->s_element;
 187                         return attr->name;
 188
 189                 case SYSFS_KOBJ_BIN_ATTR:
 190                         bin_attr = sd->s_element;
 191                         return bin_attr->attr.name;
 192
 193                 case SYSFS_KOBJ_LINK:
 194                         sl = sd->s_element;
 195                         return sl->link_name;
 196         }
 197         return NULL;
 198 }
 199
 200
 201 /*
 202  * Unhashes the dentry corresponding to given sysfs_dirent
 203  * Called with parent inode's i_mutex held.
 204  */
 205 void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
 206 {
 207         struct dentry * dentry = sd->s_dentry;
 208
 209         if (dentry) {
 210                 spin_lock(&dcache_lock);
 211                 spin_lock(&dentry->d_lock);
 212                 if (!(d_unhashed(dentry) && dentry->d_inode)) {
 213                         dget_locked(dentry);
 214                         __d_drop(dentry);
 215                         spin_unlock(&dentry->d_lock);
 216                         spin_unlock(&dcache_lock);
 217                         simple_unlink(parent->d_inode, dentry);
 218                 } else {
 219                         spin_unlock(&dentry->d_lock);
 220                         spin_unlock(&dcache_lock);
 221                 }
 222         }
 223 }
 224
 225 void sysfs_hash_and_remove(struct dentry * dir, const char * name)
 226 {
 227         struct sysfs_dirent * sd;
 228         struct sysfs_dirent * parent_sd;
 229
 230         if (!dir)
 231                 return;
 232
 233         if (dir->d_inode == NULL)
 234                 /* no inode means this hasn't been made visible yet */
 235                 return;
 236
 237         parent_sd = dir->d_fsdata;
 238         mutex_lock(&dir->d_inode->i_mutex);
 239         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 240                 if (!sd->s_element)
 241                         continue;
 242                 if (!strcmp(sysfs_get_name(sd), name)) {
 243                         list_del_init(&sd->s_sibling);
 244                         sysfs_drop_dentry(sd, dir);
 245                         sysfs_put(sd);
 246                         break;
 247                 }
 248         }
 249         mutex_unlock(&dir->d_inode->i_mutex);
 250 }