1 /* mntpt.c: mountpoint management 2 * 3 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/kernel.h> 13 #include <linux/module.h> 14 #include <linux/init.h> 15 #include <linux/sched.h> 16 #include <linux/slab.h> 17 #include <linux/fs.h> 18 #include <linux/pagemap.h> 19 #include <linux/mount.h> 20 #include <linux/namei.h> 21 #include <linux/namespace.h> 22 #include "super.h" 23 #include "cell.h" 24 #include "volume.h" 25 #include "vnode.h" 26 #include "internal.h" 27 28 29 static struct dentry *afs_mntpt_lookup(struct inode *dir, 30 struct dentry *dentry, 31 struct nameidata *nd); 32 static int afs_mntpt_open(struct inode *inode, struct file *file); 33 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd); 34 35 const struct file_operations afs_mntpt_file_operations = { 36 .open = afs_mntpt_open, 37 }; 38 39 struct inode_operations afs_mntpt_inode_operations = { 40 .lookup = afs_mntpt_lookup, 41 .follow_link = afs_mntpt_follow_link, 42 .readlink = page_readlink, 43 .getattr = afs_inode_getattr, 44 }; 45 46 static LIST_HEAD(afs_vfsmounts); 47 48 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer); 49 50 struct afs_timer_ops afs_mntpt_expiry_timer_ops = { 51 .timed_out = afs_mntpt_expiry_timed_out, 52 }; 53 54 struct afs_timer afs_mntpt_expiry_timer; 55 56 unsigned long afs_mntpt_expiry_timeout = 20; 57 58 /*****************************************************************************/ 59 /* 60 * check a symbolic link to see whether it actually encodes a mountpoint 61 * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately 62 */ 63 int afs_mntpt_check_symlink(struct afs_vnode *vnode) 64 { 65 struct page *page; 66 size_t size; 67 char *buf; 68 int ret; 69 70 _enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique); 71 72 /* read the contents of the symlink into the pagecache */ 73 page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, NULL); 74 if (IS_ERR(page)) { 75 ret = PTR_ERR(page); 76 goto out; 77 } 78 79 ret = -EIO; 80 wait_on_page_locked(page); 81 buf = kmap(page); 82 if (!PageUptodate(page)) 83 goto out_free; 84 if (PageError(page)) 85 goto out_free; 86 87 /* examine the symlink's contents */ 88 size = vnode->status.size; 89 _debug("symlink to %*.*s", size, (int) size, buf); 90 91 if (size > 2 && 92 (buf[0] == '%' || buf[0] == '#') && 93 buf[size - 1] == '.' 94 ) { 95 _debug("symlink is a mountpoint"); 96 spin_lock(&vnode->lock); 97 vnode->flags |= AFS_VNODE_MOUNTPOINT; 98 spin_unlock(&vnode->lock); 99 } 100 101 ret = 0; 102 103 out_free: 104 kunmap(page); 105 page_cache_release(page); 106 out: 107 _leave(" = %d", ret); 108 return ret; 109 110 } /* end afs_mntpt_check_symlink() */ 111 112 /*****************************************************************************/ 113 /* 114 * no valid lookup procedure on this sort of dir 115 */ 116 static struct dentry *afs_mntpt_lookup(struct inode *dir, 117 struct dentry *dentry, 118 struct nameidata *nd) 119 { 120 kenter("%p,%p{%p{%s},%s}", 121 dir, 122 dentry, 123 dentry->d_parent, 124 dentry->d_parent ? 125 dentry->d_parent->d_name.name : (const unsigned char *) "", 126 dentry->d_name.name); 127 128 return ERR_PTR(-EREMOTE); 129 } /* end afs_mntpt_lookup() */ 130 131 /*****************************************************************************/ 132 /* 133 * no valid open procedure on this sort of dir 134 */ 135 static int afs_mntpt_open(struct inode *inode, struct file *file) 136 { 137 kenter("%p,%p{%p{%s},%s}", 138 inode, file, 139 file->f_dentry->d_parent, 140 file->f_dentry->d_parent ? 141 file->f_dentry->d_parent->d_name.name : 142 (const unsigned char *) "", 143 file->f_dentry->d_name.name); 144 145 return -EREMOTE; 146 } /* end afs_mntpt_open() */ 147 148 /*****************************************************************************/ 149 /* 150 * create a vfsmount to be automounted 151 */ 152 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt) 153 { 154 struct afs_super_info *super; 155 struct vfsmount *mnt; 156 struct page *page = NULL; 157 size_t size; 158 char *buf, *devname = NULL, *options = NULL; 159 int ret; 160 161 kenter("{%s}", mntpt->d_name.name); 162 163 BUG_ON(!mntpt->d_inode); 164 165 ret = -EINVAL; 166 size = mntpt->d_inode->i_size; 167 if (size > PAGE_SIZE - 1) 168 goto error; 169 170 ret = -ENOMEM; 171 devname = (char *) get_zeroed_page(GFP_KERNEL); 172 if (!devname) 173 goto error; 174 175 options = (char *) get_zeroed_page(GFP_KERNEL); 176 if (!options) 177 goto error; 178 179 /* read the contents of the AFS special symlink */ 180 page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL); 181 if (IS_ERR(page)) { 182 ret = PTR_ERR(page); 183 goto error; 184 } 185 186 ret = -EIO; 187 wait_on_page_locked(page); 188 if (!PageUptodate(page) || PageError(page)) 189 goto error; 190 191 buf = kmap(page); 192 memcpy(devname, buf, size); 193 kunmap(page); 194 page_cache_release(page); 195 page = NULL; 196 197 /* work out what options we want */ 198 super = AFS_FS_S(mntpt->d_sb); 199 memcpy(options, "cell=", 5); 200 strcpy(options + 5, super->volume->cell->name); 201 if (super->volume->type == AFSVL_RWVOL) 202 strcat(options, ",rwpath"); 203 204 /* try and do the mount */ 205 kdebug("--- attempting mount %s -o %s ---", devname, options); 206 mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options); 207 kdebug("--- mount result %p ---", mnt); 208 209 free_page((unsigned long) devname); 210 free_page((unsigned long) options); 211 kleave(" = %p", mnt); 212 return mnt; 213 214 error: 215 if (page) 216 page_cache_release(page); 217 if (devname) 218 free_page((unsigned long) devname); 219 if (options) 220 free_page((unsigned long) options); 221 kleave(" = %d", ret); 222 return ERR_PTR(ret); 223 } /* end afs_mntpt_do_automount() */ 224 225 /*****************************************************************************/ 226 /* 227 * follow a link from a mountpoint directory, thus causing it to be mounted 228 */ 229 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd) 230 { 231 struct vfsmount *newmnt; 232 struct dentry *old_dentry; 233 int err; 234 235 kenter("%p{%s},{%s:%p{%s}}", 236 dentry, 237 dentry->d_name.name, 238 nd->mnt->mnt_devname, 239 dentry, 240 nd->dentry->d_name.name); 241 242 newmnt = afs_mntpt_do_automount(dentry); 243 if (IS_ERR(newmnt)) { 244 path_release(nd); 245 return (void *)newmnt; 246 } 247 248 old_dentry = nd->dentry; 249 nd->dentry = dentry; 250 err = do_add_mount(newmnt, nd, 0, &afs_vfsmounts); 251 nd->dentry = old_dentry; 252 253 path_release(nd); 254 255 if (!err) { 256 mntget(newmnt); 257 nd->mnt = newmnt; 258 dget(newmnt->mnt_root); 259 nd->dentry = newmnt->mnt_root; 260 } 261 262 kleave(" = %d", err); 263 return ERR_PTR(err); 264 } /* end afs_mntpt_follow_link() */ 265 266 /*****************************************************************************/ 267 /* 268 * handle mountpoint expiry timer going off 269 */ 270 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer) 271 { 272 kenter(""); 273 274 mark_mounts_for_expiry(&afs_vfsmounts); 275 276 afs_kafstimod_add_timer(&afs_mntpt_expiry_timer, 277 afs_mntpt_expiry_timeout * HZ); 278 279 kleave(""); 280 } /* end afs_mntpt_expiry_timed_out() */ 281