fs/fuse/control.c

   1 /*
   2   FUSE: Filesystem in Userspace
   3   Copyright (C) 2001-2006  Miklos Szeredi <miklos@szeredi.hu>
   4
   5   This program can be distributed under the terms of the GNU GPL.
   6   See the file COPYING.
   7 */
   8
   9 #include "fuse_i.h"
  10
  11 #include <linux/init.h>
  12 #include <linux/module.h>
  13
  14 #define FUSE_CTL_SUPER_MAGIC 0x65735543
  15
  16 /*
  17  * This is non-NULL when the single instance of the control filesystem
  18  * exists.  Protected by fuse_mutex
  19  */
  20 static struct super_block *fuse_control_sb;
  21
  22 static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
  23 {
  24         struct fuse_conn *fc;
  25         mutex_lock(&fuse_mutex);
  26         fc = file->f_dentry->d_inode->u.generic_ip;
  27         if (fc)
  28                 fc = fuse_conn_get(fc);
  29         mutex_unlock(&fuse_mutex);
  30         return fc;
  31 }
  32
  33 static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
  34                                      size_t count, loff_t *ppos)
  35 {
  36         struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  37         if (fc) {
  38                 fuse_abort_conn(fc);
  39                 fuse_conn_put(fc);
  40         }
  41         return count;
  42 }
  43
  44 static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
  45                                       size_t len, loff_t *ppos)
  46 {
  47         char tmp[32];
  48         size_t size;
  49
  50         if (!*ppos) {
  51                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  52                 if (!fc)
  53                         return 0;
  54
  55                 file->private_data=(void *)(long)atomic_read(&fc->num_waiting);
  56                 fuse_conn_put(fc);
  57         }
  58         size = sprintf(tmp, "%ld\n", (long)file->private_data);
  59         return simple_read_from_buffer(buf, len, ppos, tmp, size);
  60 }
  61
  62 static const struct file_operations fuse_ctl_abort_ops = {
  63         .open = nonseekable_open,
  64         .write = fuse_conn_abort_write,
  65 };
  66
  67 static const struct file_operations fuse_ctl_waiting_ops = {
  68         .open = nonseekable_open,
  69         .read = fuse_conn_waiting_read,
  70 };
  71
  72 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
  73                                           struct fuse_conn *fc,
  74                                           const char *name,
  75                                           int mode, int nlink,
  76                                           struct inode_operations *iop,
  77                                           const struct file_operations *fop)
  78 {
  79         struct dentry *dentry;
  80         struct inode *inode;
  81
  82         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
  83         dentry = d_alloc_name(parent, name);
  84         if (!dentry)
  85                 return NULL;
  86
  87         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
  88         inode = new_inode(fuse_control_sb);
  89         if (!inode)
  90                 return NULL;
  91
  92         inode->i_mode = mode;
  93         inode->i_uid = fc->user_id;
  94         inode->i_gid = fc->group_id;
  95         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  96         /* setting ->i_op to NULL is not allowed */
  97         if (iop)
  98                 inode->i_op = iop;
  99         inode->i_fop = fop;
 100         inode->i_nlink = nlink;
 101         inode->u.generic_ip = fc;
 102         d_add(dentry, inode);
 103         return dentry;
 104 }
 105
 106 /*
 107  * Add a connection to the control filesystem (if it exists).  Caller
 108  * must host fuse_mutex
 109  */
 110 int fuse_ctl_add_conn(struct fuse_conn *fc)
 111 {
 112         struct dentry *parent;
 113         char name[32];
 114
 115         if (!fuse_control_sb)
 116                 return 0;
 117
 118         parent = fuse_control_sb->s_root;
 119         parent->d_inode->i_nlink++;
 120         sprintf(name, "%llu", (unsigned long long) fc->id);
 121         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
 122                                      &simple_dir_inode_operations,
 123                                      &simple_dir_operations);
 124         if (!parent)
 125                 goto err;
 126
 127         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
 128                                 NULL, &fuse_ctl_waiting_ops) ||
 129             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
 130                                  NULL, &fuse_ctl_abort_ops))
 131                 goto err;
 132
 133         return 0;
 134
 135  err:
 136         fuse_ctl_remove_conn(fc);
 137         return -ENOMEM;
 138 }
 139
 140 /*
 141  * Remove a connection from the control filesystem (if it exists).
 142  * Caller must host fuse_mutex
 143  */
 144 void fuse_ctl_remove_conn(struct fuse_conn *fc)
 145 {
 146         int i;
 147
 148         if (!fuse_control_sb)
 149                 return;
 150
 151         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
 152                 struct dentry *dentry = fc->ctl_dentry[i];
 153                 dentry->d_inode->u.generic_ip = NULL;
 154                 d_drop(dentry);
 155                 dput(dentry);
 156         }
 157         fuse_control_sb->s_root->d_inode->i_nlink--;
 158 }
 159
 160 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
 161 {
 162         struct tree_descr empty_descr = {""};
 163         struct fuse_conn *fc;
 164         int err;
 165
 166         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
 167         if (err)
 168                 return err;
 169
 170         mutex_lock(&fuse_mutex);
 171         BUG_ON(fuse_control_sb);
 172         fuse_control_sb = sb;
 173         list_for_each_entry(fc, &fuse_conn_list, entry) {
 174                 err = fuse_ctl_add_conn(fc);
 175                 if (err) {
 176                         fuse_control_sb = NULL;
 177                         mutex_unlock(&fuse_mutex);
 178                         return err;
 179                 }
 180         }
 181         mutex_unlock(&fuse_mutex);
 182
 183         return 0;
 184 }
 185
 186 static int fuse_ctl_get_sb(struct file_system_type *fs_type, int flags,
 187                         const char *dev_name, void *raw_data,
 188                         struct vfsmount *mnt)
 189 {
 190         return get_sb_single(fs_type, flags, raw_data,
 191                                 fuse_ctl_fill_super, mnt);
 192 }
 193
 194 static void fuse_ctl_kill_sb(struct super_block *sb)
 195 {
 196         mutex_lock(&fuse_mutex);
 197         fuse_control_sb = NULL;
 198         mutex_unlock(&fuse_mutex);
 199
 200         kill_litter_super(sb);
 201 }
 202
 203 static struct file_system_type fuse_ctl_fs_type = {
 204         .owner          = THIS_MODULE,
 205         .name           = "fusectl",
 206         .get_sb         = fuse_ctl_get_sb,
 207         .kill_sb        = fuse_ctl_kill_sb,
 208 };
 209
 210 int __init fuse_ctl_init(void)
 211 {
 212         return register_filesystem(&fuse_ctl_fs_type);
 213 }
 214
 215 void fuse_ctl_cleanup(void)
 216 {
 217         unregister_filesystem(&fuse_ctl_fs_type);
 218 }