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 extern struct super_block * sysfs_sb;
  15
  16 static struct address_space_operations sysfs_aops = {
  17         .readpage       = simple_readpage,
  18         .prepare_write  = simple_prepare_write,
  19         .commit_write   = simple_commit_write
  20 };
  21
  22 static struct backing_dev_info sysfs_backing_dev_info = {
  23         .ra_pages       = 0,    /* No readahead */
  24         .memory_backed  = 1,    /* Does not contribute to dirty memory */
  25 };
  26
  27 struct inode * sysfs_new_inode(mode_t mode)
  28 {
  29         struct inode * inode = new_inode(sysfs_sb);
  30         if (inode) {
  31                 inode->i_mode = mode;
  32                 inode->i_uid = current->fsuid;
  33                 inode->i_gid = current->fsgid;
  34                 inode->i_blksize = PAGE_CACHE_SIZE;
  35                 inode->i_blocks = 0;
  36                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  37                 inode->i_mapping->a_ops = &sysfs_aops;
  38                 inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
  39         }
  40         return inode;
  41 }
  42
  43 int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
  44 {
  45         int error = 0;
  46         struct inode * inode = NULL;
  47         if (dentry) {
  48                 if (!dentry->d_inode) {
  49                         if ((inode = sysfs_new_inode(mode)))
  50                                 goto Proceed;
  51                         else
  52                                 error = -ENOMEM;
  53                 } else
  54                         error = -EEXIST;
  55         } else
  56                 error = -ENOENT;
  57         goto Done;
  58
  59  Proceed:
  60         if (init)
  61                 error = init(inode);
  62         if (!error) {
  63                 d_instantiate(dentry, inode);
  64                 dget(dentry); /* Extra count - pin the dentry in core */
  65         } else
  66                 iput(inode);
  67  Done:
  68         return error;
  69 }
  70
  71 int sysfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
  72 {
  73         return sysfs_create(dentry, mode, NULL);
  74 }
  75
  76 struct dentry * sysfs_get_dentry(struct dentry * parent, const char * name)
  77 {
  78         struct qstr qstr;
  79
  80         qstr.name = name;
  81         qstr.len = strlen(name);
  82         qstr.hash = full_name_hash(name,qstr.len);
  83         return lookup_hash(&qstr,parent);
  84 }
  85
  86 void sysfs_hash_and_remove(struct dentry * dir, const char * name)
  87 {
  88         struct dentry * victim;
  89
  90         down(&dir->d_inode->i_sem);
  91         victim = sysfs_get_dentry(dir,name);
  92         if (!IS_ERR(victim)) {
  93                 /* make sure dentry is really there */
  94                 if (victim->d_inode &&
  95                     (victim->d_parent->d_inode == dir->d_inode)) {
  96                         pr_debug("sysfs: Removing %s (%d)\n", victim->d_name.name,
  97                                  atomic_read(&victim->d_count));
  98
  99                         d_drop(victim);
 100                         /* release the target kobject in case of
 101                          * a symlink
 102                          */
 103                         if (S_ISLNK(victim->d_inode->i_mode))
 104                                 kobject_put(victim->d_fsdata);
 105                         simple_unlink(dir->d_inode,victim);
 106                 }
 107                 /*
 108                  * Drop reference from sysfs_get_dentry() above.
 109                  */
 110                 dput(victim);
 111         }
 112         up(&dir->d_inode->i_sem);
 113 }
 114
 115