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 = kmalloc(sizeof(struct iattr), GFP_KERNEL);
  58                 if (!sd_iattr)
  59                         return -ENOMEM;
  60                 /* assign default attributes */
  61                 memset(sd_iattr, 0, sizeof(struct iattr));
  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 struct inode * sysfs_new_inode(mode_t mode, struct sysfs_dirent * sd)
 114 {
 115         struct inode * inode = new_inode(sysfs_sb);
 116         if (inode) {
 117                 inode->i_blksize = PAGE_CACHE_SIZE;
 118                 inode->i_blocks = 0;
 119                 inode->i_mapping->a_ops = &sysfs_aops;
 120                 inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 121                 inode->i_op = &sysfs_inode_operations;
 122
 123                 if (sd->s_iattr) {
 124                         /* sysfs_dirent has non-default attributes
 125                          * get them for the new inode from persistent copy
 126                          * in sysfs_dirent
 127                          */
 128                         set_inode_attr(inode, sd->s_iattr);
 129                 } else
 130                         set_default_inode_attr(inode, mode);
 131         }
 132         return inode;
 133 }
 134
 135 int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
 136 {
 137         int error = 0;
 138         struct inode * inode = NULL;
 139         if (dentry) {
 140                 if (!dentry->d_inode) {
 141                         struct sysfs_dirent * sd = dentry->d_fsdata;
 142                         if ((inode = sysfs_new_inode(mode, sd))) {
 143                                 if (dentry->d_parent && dentry->d_parent->d_inode) {
 144                                         struct inode *p_inode = dentry->d_parent->d_inode;
 145                                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
 146                                 }
 147                                 goto Proceed;
 148                         }
 149                         else
 150                                 error = -ENOMEM;
 151                 } else
 152                         error = -EEXIST;
 153         } else
 154                 error = -ENOENT;
 155         goto Done;
 156
 157  Proceed:
 158         if (init)
 159                 error = init(inode);
 160         if (!error) {
 161                 d_instantiate(dentry, inode);
 162                 if (S_ISDIR(mode))
 163                         dget(dentry);  /* pin only directory dentry in core */
 164         } else
 165                 iput(inode);
 166  Done:
 167         return error;
 168 }
 169
 170 /*
 171  * Get the name for corresponding element represented by the given sysfs_dirent
 172  */
 173 const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
 174 {
 175         struct attribute * attr;
 176         struct bin_attribute * bin_attr;
 177         struct sysfs_symlink  * sl;
 178
 179         if (!sd || !sd->s_element)
 180                 BUG();
 181
 182         switch (sd->s_type) {
 183                 case SYSFS_DIR:
 184                         /* Always have a dentry so use that */
 185                         return sd->s_dentry->d_name.name;
 186
 187                 case SYSFS_KOBJ_ATTR:
 188                         attr = sd->s_element;
 189                         return attr->name;
 190
 191                 case SYSFS_KOBJ_BIN_ATTR:
 192                         bin_attr = sd->s_element;
 193                         return bin_attr->attr.name;
 194
 195                 case SYSFS_KOBJ_LINK:
 196                         sl = sd->s_element;
 197                         return sl->link_name;
 198         }
 199         return NULL;
 200 }
 201
 202
 203 /*
 204  * Unhashes the dentry corresponding to given sysfs_dirent
 205  * Called with parent inode's i_mutex held.
 206  */
 207 void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
 208 {
 209         struct dentry * dentry = sd->s_dentry;
 210
 211         if (dentry) {
 212                 spin_lock(&dcache_lock);
 213                 spin_lock(&dentry->d_lock);
 214                 if (!(d_unhashed(dentry) && dentry->d_inode)) {
 215                         dget_locked(dentry);
 216                         __d_drop(dentry);
 217                         spin_unlock(&dentry->d_lock);
 218                         spin_unlock(&dcache_lock);
 219                         simple_unlink(parent->d_inode, dentry);
 220                 } else {
 221                         spin_unlock(&dentry->d_lock);
 222                         spin_unlock(&dcache_lock);
 223                 }
 224         }
 225 }
 226
 227 void sysfs_hash_and_remove(struct dentry * dir, const char * name)
 228 {
 229         struct sysfs_dirent * sd;
 230         struct sysfs_dirent * parent_sd = dir->d_fsdata;
 231
 232         if (dir->d_inode == NULL)
 233                 /* no inode means this hasn't been made visible yet */
 234                 return;
 235
 236         mutex_lock(&dir->d_inode->i_mutex);
 237         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 238                 if (!sd->s_element)
 239                         continue;
 240                 if (!strcmp(sysfs_get_name(sd), name)) {
 241                         list_del_init(&sd->s_sibling);
 242                         sysfs_drop_dentry(sd, dir);
 243                         sysfs_put(sd);
 244                         break;
 245                 }
 246         }
 247         mutex_unlock(&dir->d_inode->i_mutex);
 248 }