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 "sysfs.h"
  15
  16 extern struct super_block * sysfs_sb;
  17
  18 static struct address_space_operations sysfs_aops = {
  19         .readpage       = simple_readpage,
  20         .prepare_write  = simple_prepare_write,
  21         .commit_write   = simple_commit_write
  22 };
  23
  24 static struct backing_dev_info sysfs_backing_dev_info = {
  25         .ra_pages       = 0,    /* No readahead */
  26         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  27 };
  28
  29 static struct inode_operations sysfs_inode_operations ={
  30         .setattr        = sysfs_setattr,
  31 };
  32
  33 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  34 {
  35         struct inode * inode = dentry->d_inode;
  36         struct sysfs_dirent * sd = dentry->d_fsdata;
  37         struct iattr * sd_iattr;
  38         unsigned int ia_valid = iattr->ia_valid;
  39         int error;
  40
  41         if (!sd)
  42                 return -EINVAL;
  43
  44         sd_iattr = sd->s_iattr;
  45
  46         error = inode_change_ok(inode, iattr);
  47         if (error)
  48                 return error;
  49
  50         error = inode_setattr(inode, iattr);
  51         if (error)
  52                 return error;
  53
  54         if (!sd_iattr) {
  55                 /* setting attributes for the first time, allocate now */
  56                 sd_iattr = kmalloc(sizeof(struct iattr), GFP_KERNEL);
  57                 if (!sd_iattr)
  58                         return -ENOMEM;
  59                 /* assign default attributes */
  60                 memset(sd_iattr, 0, sizeof(struct iattr));
  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 = mode;
  89         }
  90
  91         return error;
  92 }
  93
  94 struct inode * sysfs_new_inode(mode_t mode)
  95 {
  96         struct inode * inode = new_inode(sysfs_sb);
  97         if (inode) {
  98                 inode->i_mode = mode;
  99                 inode->i_uid = 0;
 100                 inode->i_gid = 0;
 101                 inode->i_blksize = PAGE_CACHE_SIZE;
 102                 inode->i_blocks = 0;
 103                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 104                 inode->i_mapping->a_ops = &sysfs_aops;
 105                 inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 106         }
 107         return inode;
 108 }
 109
 110 int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
 111 {
 112         int error = 0;
 113         struct inode * inode = NULL;
 114         if (dentry) {
 115                 if (!dentry->d_inode) {
 116                         if ((inode = sysfs_new_inode(mode))) {
 117                                 if (dentry->d_parent && dentry->d_parent->d_inode) {
 118                                         struct inode *p_inode = dentry->d_parent->d_inode;
 119                                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
 120                                 }
 121                                 goto Proceed;
 122                         }
 123                         else
 124                                 error = -ENOMEM;
 125                 } else
 126                         error = -EEXIST;
 127         } else
 128                 error = -ENOENT;
 129         goto Done;
 130
 131  Proceed:
 132         if (init)
 133                 error = init(inode);
 134         if (!error) {
 135                 d_instantiate(dentry, inode);
 136                 if (S_ISDIR(mode))
 137                         dget(dentry);  /* pin only directory dentry in core */
 138         } else
 139                 iput(inode);
 140  Done:
 141         return error;
 142 }
 143
 144 struct dentry * sysfs_get_dentry(struct dentry * parent, const char * name)
 145 {
 146         struct qstr qstr;
 147
 148         qstr.name = name;
 149         qstr.len = strlen(name);
 150         qstr.hash = full_name_hash(name,qstr.len);
 151         return lookup_hash(&qstr,parent);
 152 }
 153
 154 /*
 155  * Get the name for corresponding element represented by the given sysfs_dirent
 156  */
 157 const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
 158 {
 159         struct attribute * attr;
 160         struct bin_attribute * bin_attr;
 161         struct sysfs_symlink  * sl;
 162
 163         if (!sd || !sd->s_element)
 164                 BUG();
 165
 166         switch (sd->s_type) {
 167                 case SYSFS_DIR:
 168                         /* Always have a dentry so use that */
 169                         return sd->s_dentry->d_name.name;
 170
 171                 case SYSFS_KOBJ_ATTR:
 172                         attr = sd->s_element;
 173                         return attr->name;
 174
 175                 case SYSFS_KOBJ_BIN_ATTR:
 176                         bin_attr = sd->s_element;
 177                         return bin_attr->attr.name;
 178
 179                 case SYSFS_KOBJ_LINK:
 180                         sl = sd->s_element;
 181                         return sl->link_name;
 182         }
 183         return NULL;
 184 }
 185
 186
 187 /*
 188  * Unhashes the dentry corresponding to given sysfs_dirent
 189  * Called with parent inode's i_sem held.
 190  */
 191 void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
 192 {
 193         struct dentry * dentry = sd->s_dentry;
 194
 195         if (dentry) {
 196                 spin_lock(&dcache_lock);
 197                 spin_lock(&dentry->d_lock);
 198                 if (!(d_unhashed(dentry) && dentry->d_inode)) {
 199                         dget_locked(dentry);
 200                         __d_drop(dentry);
 201                         spin_unlock(&dentry->d_lock);
 202                         spin_unlock(&dcache_lock);
 203                         simple_unlink(parent->d_inode, dentry);
 204                 } else {
 205                         spin_unlock(&dentry->d_lock);
 206                         spin_unlock(&dcache_lock);
 207                 }
 208         }
 209 }
 210
 211 void sysfs_hash_and_remove(struct dentry * dir, const char * name)
 212 {
 213         struct sysfs_dirent * sd;
 214         struct sysfs_dirent * parent_sd = dir->d_fsdata;
 215
 216         down(&dir->d_inode->i_sem);
 217         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 218                 if (!sd->s_element)
 219                         continue;
 220                 if (!strcmp(sysfs_get_name(sd), name)) {
 221                         list_del_init(&sd->s_sibling);
 222                         sysfs_drop_dentry(sd, dir);
 223                         sysfs_put(sd);
 224                         break;
 225                 }
 226         }
 227         up(&dir->d_inode->i_sem);
 228 }
 229
 230