fs/fuse/control.c

   1 /*
   2   FUSE: Filesystem in Userspace
   3   Copyright (C) 2001-2008  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_path.dentry->d_inode->i_private;
  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                 long value;
  52                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  53                 if (!fc)
  54                         return 0;
  55
  56                 value = atomic_read(&fc->num_waiting);
  57                 file->private_data = (void *)value;
  58                 fuse_conn_put(fc);
  59         }
  60         size = sprintf(tmp, "%ld\n", (long)file->private_data);
  61         return simple_read_from_buffer(buf, len, ppos, tmp, size);
  62 }
  63
  64 static const struct file_operations fuse_ctl_abort_ops = {
  65         .open = nonseekable_open,
  66         .write = fuse_conn_abort_write,
  67 };
  68
  69 static const struct file_operations fuse_ctl_waiting_ops = {
  70         .open = nonseekable_open,
  71         .read = fuse_conn_waiting_read,
  72 };
  73
  74 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
  75                                           struct fuse_conn *fc,
  76                                           const char *name,
  77                                           int mode, int nlink,
  78                                           const struct inode_operations *iop,
  79                                           const struct file_operations *fop)
  80 {
  81         struct dentry *dentry;
  82         struct inode *inode;
  83
  84         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
  85         dentry = d_alloc_name(parent, name);
  86         if (!dentry)
  87                 return NULL;
  88
  89         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
  90         inode = new_inode(fuse_control_sb);
  91         if (!inode)
  92                 return NULL;
  93
  94         inode->i_mode = mode;
  95         inode->i_uid = fc->user_id;
  96         inode->i_gid = fc->group_id;
  97         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  98         /* setting ->i_op to NULL is not allowed */
  99         if (iop)
 100                 inode->i_op = iop;
 101         inode->i_fop = fop;
 102         inode->i_nlink = nlink;
 103         inode->i_private = fc;
 104         d_add(dentry, inode);
 105         return dentry;
 106 }
 107
 108 /*
 109  * Add a connection to the control filesystem (if it exists).  Caller
 110  * must hold fuse_mutex
 111  */
 112 int fuse_ctl_add_conn(struct fuse_conn *fc)
 113 {
 114         struct dentry *parent;
 115         char name[32];
 116
 117         if (!fuse_control_sb)
 118                 return 0;
 119
 120         parent = fuse_control_sb->s_root;
 121         inc_nlink(parent->d_inode);
 122         sprintf(name, "%u", fc->dev);
 123         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
 124                                      &simple_dir_inode_operations,
 125                                      &simple_dir_operations);
 126         if (!parent)
 127                 goto err;
 128
 129         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
 130                                 NULL, &fuse_ctl_waiting_ops) ||
 131             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
 132                                  NULL, &fuse_ctl_abort_ops))
 133                 goto err;
 134
 135         return 0;
 136
 137  err:
 138         fuse_ctl_remove_conn(fc);
 139         return -ENOMEM;
 140 }
 141
 142 /*
 143  * Remove a connection from the control filesystem (if it exists).
 144  * Caller must hold fuse_mutex
 145  */
 146 void fuse_ctl_remove_conn(struct fuse_conn *fc)
 147 {
 148         int i;
 149
 150         if (!fuse_control_sb)
 151                 return;
 152
 153         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
 154                 struct dentry *dentry = fc->ctl_dentry[i];
 155                 dentry->d_inode->i_private = NULL;
 156                 d_drop(dentry);
 157                 dput(dentry);
 158         }
 159         fuse_control_sb->s_root->d_inode->i_nlink--;
 160 }
 161
 162 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
 163 {
 164         struct tree_descr empty_descr = {""};
 165         struct fuse_conn *fc;
 166         int err;
 167
 168         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
 169         if (err)
 170                 return err;
 171
 172         mutex_lock(&fuse_mutex);
 173         BUG_ON(fuse_control_sb);
 174         fuse_control_sb = sb;
 175         list_for_each_entry(fc, &fuse_conn_list, entry) {
 176                 err = fuse_ctl_add_conn(fc);
 177                 if (err) {
 178                         fuse_control_sb = NULL;
 179                         mutex_unlock(&fuse_mutex);
 180                         return err;
 181                 }
 182         }
 183         mutex_unlock(&fuse_mutex);
 184
 185         return 0;
 186 }
 187
 188 static int fuse_ctl_get_sb(struct file_system_type *fs_type, int flags,
 189                         const char *dev_name, void *raw_data,
 190                         struct vfsmount *mnt)
 191 {
 192         return get_sb_single(fs_type, flags, raw_data,
 193                                 fuse_ctl_fill_super, mnt);
 194 }
 195
 196 static void fuse_ctl_kill_sb(struct super_block *sb)
 197 {
 198         struct fuse_conn *fc;
 199
 200         mutex_lock(&fuse_mutex);
 201         fuse_control_sb = NULL;
 202         list_for_each_entry(fc, &fuse_conn_list, entry)
 203                 fc->ctl_ndents = 0;
 204         mutex_unlock(&fuse_mutex);
 205
 206         kill_litter_super(sb);
 207 }
 208
 209 static struct file_system_type fuse_ctl_fs_type = {
 210         .owner          = THIS_MODULE,
 211         .name           = "fusectl",
 212         .get_sb         = fuse_ctl_get_sb,
 213         .kill_sb        = fuse_ctl_kill_sb,
 214 };
 215
 216 int __init fuse_ctl_init(void)
 217 {
 218         return register_filesystem(&fuse_ctl_fs_type);
 219 }
 220
 221 void fuse_ctl_cleanup(void)
 222 {
 223         unregister_filesystem(&fuse_ctl_fs_type);
 224 }