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 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 filler_t *filler; 67 size_t size; 68 char *buf; 69 int ret; 70 71 _enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique); 72 73 /* read the contents of the symlink into the pagecache */ 74 filler = (filler_t *) AFS_VNODE_TO_I(vnode)->i_mapping->a_ops->readpage; 75 76 page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, 77 filler, NULL); 78 if (IS_ERR(page)) { 79 ret = PTR_ERR(page); 80 goto out; 81 } 82 83 ret = -EIO; 84 wait_on_page_locked(page); 85 buf = kmap(page); 86 if (!PageUptodate(page)) 87 goto out_free; 88 if (PageError(page)) 89 goto out_free; 90 91 /* examine the symlink's contents */ 92 size = vnode->status.size; 93 _debug("symlink to %*.*s", size, (int) size, buf); 94 95 if (size > 2 && 96 (buf[0] == '%' || buf[0] == '#') && 97 buf[size - 1] == '.' 98 ) { 99 _debug("symlink is a mountpoint"); 100 spin_lock(&vnode->lock); 101 vnode->flags |= AFS_VNODE_MOUNTPOINT; 102 spin_unlock(&vnode->lock); 103 } 104 105 ret = 0; 106 107 out_free: 108 kunmap(page); 109 page_cache_release(page); 110 out: 111 _leave(" = %d", ret); 112 return ret; 113 114 } /* end afs_mntpt_check_symlink() */ 115 116 /*****************************************************************************/ 117 /* 118 * no valid lookup procedure on this sort of dir 119 */ 120 static struct dentry *afs_mntpt_lookup(struct inode *dir, 121 struct dentry *dentry, 122 struct nameidata *nd) 123 { 124 kenter("%p,%p{%p{%s},%s}", 125 dir, 126 dentry, 127 dentry->d_parent, 128 dentry->d_parent ? 129 dentry->d_parent->d_name.name : (const unsigned char *) "", 130 dentry->d_name.name); 131 132 return ERR_PTR(-EREMOTE); 133 } /* end afs_mntpt_lookup() */ 134 135 /*****************************************************************************/ 136 /* 137 * no valid open procedure on this sort of dir 138 */ 139 static int afs_mntpt_open(struct inode *inode, struct file *file) 140 { 141 kenter("%p,%p{%p{%s},%s}", 142 inode, file, 143 file->f_dentry->d_parent, 144 file->f_dentry->d_parent ? 145 file->f_dentry->d_parent->d_name.name : 146 (const unsigned char *) "", 147 file->f_dentry->d_name.name); 148 149 return -EREMOTE; 150 } /* end afs_mntpt_open() */ 151 152 /*****************************************************************************/ 153 /* 154 * create a vfsmount to be automounted 155 */ 156 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt) 157 { 158 struct afs_super_info *super; 159 struct vfsmount *mnt; 160 struct page *page = NULL; 161 size_t size; 162 char *buf, *devname = NULL, *options = NULL; 163 filler_t *filler; 164 int ret; 165 166 kenter("{%s}", mntpt->d_name.name); 167 168 BUG_ON(!mntpt->d_inode); 169 170 ret = -EINVAL; 171 size = mntpt->d_inode->i_size; 172 if (size > PAGE_SIZE - 1) 173 goto error; 174 175 ret = -ENOMEM; 176 devname = (char *) get_zeroed_page(GFP_KERNEL); 177 if (!devname) 178 goto error; 179 180 options = (char *) get_zeroed_page(GFP_KERNEL); 181 if (!options) 182 goto error; 183 184 /* read the contents of the AFS special symlink */ 185 filler = (filler_t *)mntpt->d_inode->i_mapping->a_ops->readpage; 186 187 page = read_cache_page(mntpt->d_inode->i_mapping, 0, filler, NULL); 188 if (IS_ERR(page)) { 189 ret = PTR_ERR(page); 190 goto error; 191 } 192 193 ret = -EIO; 194 wait_on_page_locked(page); 195 if (!PageUptodate(page) || PageError(page)) 196 goto error; 197 198 buf = kmap(page); 199 memcpy(devname, buf, size); 200 kunmap(page); 201 page_cache_release(page); 202 page = NULL; 203 204 /* work out what options we want */ 205 super = AFS_FS_S(mntpt->d_sb); 206 memcpy(options, "cell=", 5); 207 strcpy(options + 5, super->volume->cell->name); 208 if (super->volume->type == AFSVL_RWVOL) 209 strcat(options, ",rwpath"); 210 211 /* try and do the mount */ 212 kdebug("--- attempting mount %s -o %s ---", devname, options); 213 mnt = do_kern_mount("afs", 0, devname, options); 214 kdebug("--- mount result %p ---", mnt); 215 216 free_page((unsigned long) devname); 217 free_page((unsigned long) options); 218 kleave(" = %p", mnt); 219 return mnt; 220 221 error: 222 if (page) 223 page_cache_release(page); 224 if (devname) 225 free_page((unsigned long) devname); 226 if (options) 227 free_page((unsigned long) options); 228 kleave(" = %d", ret); 229 return ERR_PTR(ret); 230 } /* end afs_mntpt_do_automount() */ 231 232 /*****************************************************************************/ 233 /* 234 * follow a link from a mountpoint directory, thus causing it to be mounted 235 */ 236 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd) 237 { 238 struct vfsmount *newmnt; 239 struct dentry *old_dentry; 240 int err; 241 242 kenter("%p{%s},{%s:%p{%s}}", 243 dentry, 244 dentry->d_name.name, 245 nd->mnt->mnt_devname, 246 dentry, 247 nd->dentry->d_name.name); 248 249 newmnt = afs_mntpt_do_automount(dentry); 250 if (IS_ERR(newmnt)) { 251 path_release(nd); 252 return (void *)newmnt; 253 } 254 255 old_dentry = nd->dentry; 256 nd->dentry = dentry; 257 err = do_add_mount(newmnt, nd, 0, &afs_vfsmounts); 258 nd->dentry = old_dentry; 259 260 path_release(nd); 261 262 if (!err) { 263 mntget(newmnt); 264 nd->mnt = newmnt; 265 dget(newmnt->mnt_root); 266 nd->dentry = newmnt->mnt_root; 267 } 268 269 kleave(" = %d", err); 270 return ERR_PTR(err); 271 } /* end afs_mntpt_follow_link() */ 272 273 /*****************************************************************************/ 274 /* 275 * handle mountpoint expiry timer going off 276 */ 277 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer) 278 { 279 kenter(""); 280 281 mark_mounts_for_expiry(&afs_vfsmounts); 282 283 afs_kafstimod_add_timer(&afs_mntpt_expiry_timer, 284 afs_mntpt_expiry_timeout * HZ); 285 286 kleave(""); 287 } /* end afs_mntpt_expiry_timed_out() */ 288