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 drop_nlink(fuse_control_sb->s_root->d_inode); 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 } 225