1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1992, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software donated to Berkeley by 8 * Jan-Simon Pendry. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 /* 36 * Null Layer 37 * (See null_vnops.c for a description of what this does.) 38 */ 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/fcntl.h> 43 #include <sys/kernel.h> 44 #include <sys/lock.h> 45 #include <sys/malloc.h> 46 #include <sys/mount.h> 47 #include <sys/namei.h> 48 #include <sys/proc.h> 49 #include <sys/sysctl.h> 50 #include <sys/vnode.h> 51 #include <sys/jail.h> 52 53 #include <fs/nullfs/null.h> 54 55 static MALLOC_DEFINE(M_NULLFSMNT, "nullfs_mount", "NULLFS mount structure"); 56 57 static vfs_fhtovp_t nullfs_fhtovp; 58 static vfs_mount_t nullfs_mount; 59 static vfs_quotactl_t nullfs_quotactl; 60 static vfs_root_t nullfs_root; 61 static vfs_sync_t nullfs_sync; 62 static vfs_statfs_t nullfs_statfs; 63 static vfs_unmount_t nullfs_unmount; 64 static vfs_vget_t nullfs_vget; 65 static vfs_extattrctl_t nullfs_extattrctl; 66 67 SYSCTL_NODE(_vfs, OID_AUTO, nullfs, CTLFLAG_RW, 0, "nullfs"); 68 69 static bool null_cache_vnodes = true; 70 SYSCTL_BOOL(_vfs_nullfs, OID_AUTO, cache_vnodes, CTLFLAG_RWTUN, 71 &null_cache_vnodes, 0, 72 "cache free nullfs vnodes"); 73 74 /* 75 * Mount null layer 76 */ 77 static int 78 nullfs_mount(struct mount *mp) 79 { 80 struct vnode *lowerrootvp; 81 struct vnode *nullm_rootvp; 82 struct null_mount *xmp; 83 struct null_node *nn; 84 struct nameidata nd, *ndp; 85 char *target; 86 int error, len; 87 bool isvnunlocked; 88 static const char cache_opt_name[] = "cache"; 89 static const char nocache_opt_name[] = "nocache"; 90 static const char unixbypass_opt_name[] = "unixbypass"; 91 static const char nounixbypass_opt_name[] = "nounixbypass"; 92 93 NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp); 94 95 if (mp->mnt_flag & MNT_ROOTFS) 96 return (EOPNOTSUPP); 97 98 /* 99 * Update is a no-op 100 */ 101 if (mp->mnt_flag & MNT_UPDATE) { 102 /* 103 * Only support update mounts for NFS export. 104 */ 105 if (vfs_flagopt(mp->mnt_optnew, "export", NULL, 0)) 106 return (0); 107 else 108 return (EOPNOTSUPP); 109 } 110 111 /* 112 * Get argument 113 */ 114 error = vfs_getopt(mp->mnt_optnew, "from", (void **)&target, &len); 115 if (error != 0) 116 error = vfs_getopt(mp->mnt_optnew, "target", (void **)&target, &len); 117 if (error || target[len - 1] != '\0') 118 return (EINVAL); 119 120 /* 121 * Unlock lower node to avoid possible deadlock. 122 */ 123 if (null_is_nullfs_vnode(mp->mnt_vnodecovered) && 124 VOP_ISLOCKED(mp->mnt_vnodecovered) == LK_EXCLUSIVE) { 125 VOP_UNLOCK(mp->mnt_vnodecovered); 126 isvnunlocked = true; 127 } else { 128 isvnunlocked = false; 129 } 130 131 /* 132 * Find lower node 133 */ 134 ndp = &nd; 135 NDINIT(ndp, LOOKUP, FOLLOW|LOCKLEAF, UIO_SYSSPACE, target); 136 error = namei(ndp); 137 138 /* 139 * Re-lock vnode. 140 * XXXKIB This is deadlock-prone as well. 141 */ 142 if (isvnunlocked) 143 vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY); 144 145 if (error) 146 return (error); 147 NDFREE_PNBUF(ndp); 148 149 /* 150 * Sanity check on lower vnode 151 */ 152 lowerrootvp = ndp->ni_vp; 153 154 /* 155 * Check multi null mount to avoid `lock against myself' panic. 156 */ 157 if (null_is_nullfs_vnode(mp->mnt_vnodecovered)) { 158 nn = VTONULL(mp->mnt_vnodecovered); 159 if (nn == NULL || lowerrootvp == nn->null_lowervp) { 160 NULLFSDEBUG("nullfs_mount: multi null mount?\n"); 161 vput(lowerrootvp); 162 return (EDEADLK); 163 } 164 } 165 166 /* 167 * Lower vnode must be the same type as the covered vnode - we 168 * don't allow mounting directories to files or vice versa. 169 */ 170 if ((lowerrootvp->v_type != VDIR && lowerrootvp->v_type != VREG) || 171 lowerrootvp->v_type != mp->mnt_vnodecovered->v_type) { 172 NULLFSDEBUG("nullfs_mount: target must be same type as fspath"); 173 vput(lowerrootvp); 174 return (EINVAL); 175 } 176 177 xmp = malloc(sizeof(struct null_mount), M_NULLFSMNT, 178 M_WAITOK | M_ZERO); 179 180 /* 181 * Save pointer to underlying FS and the reference to the 182 * lower root vnode. 183 */ 184 xmp->nullm_vfs = vfs_register_upper_from_vp(lowerrootvp, mp, 185 &xmp->upper_node); 186 if (xmp->nullm_vfs == NULL) { 187 vput(lowerrootvp); 188 free(xmp, M_NULLFSMNT); 189 return (ENOENT); 190 } 191 vref(lowerrootvp); 192 xmp->nullm_lowerrootvp = lowerrootvp; 193 mp->mnt_data = xmp; 194 195 /* 196 * Make sure the node alias worked. 197 */ 198 error = null_nodeget(mp, lowerrootvp, &nullm_rootvp); 199 if (error != 0) { 200 vfs_unregister_upper(xmp->nullm_vfs, &xmp->upper_node); 201 vrele(lowerrootvp); 202 free(xmp, M_NULLFSMNT); 203 return (error); 204 } 205 206 if (NULLVPTOLOWERVP(nullm_rootvp)->v_mount->mnt_flag & MNT_LOCAL) { 207 MNT_ILOCK(mp); 208 mp->mnt_flag |= MNT_LOCAL; 209 MNT_IUNLOCK(mp); 210 } 211 212 if (vfs_getopt(mp->mnt_optnew, cache_opt_name, NULL, NULL) == 0) { 213 xmp->nullm_flags |= NULLM_CACHE; 214 } else if (vfs_getopt(mp->mnt_optnew, nocache_opt_name, NULL, 215 NULL) == 0) { 216 ; 217 } else if (null_cache_vnodes && 218 (xmp->nullm_vfs->mnt_kern_flag & MNTK_NULL_NOCACHE) == 0) { 219 xmp->nullm_flags |= NULLM_CACHE; 220 } 221 222 if ((xmp->nullm_flags & NULLM_CACHE) != 0) { 223 vfs_register_for_notification(xmp->nullm_vfs, mp, 224 &xmp->notify_node); 225 } 226 227 if (vfs_getopt(mp->mnt_optnew, unixbypass_opt_name, NULL, NULL) == 0) { 228 ; 229 } else if (vfs_getopt(mp->mnt_optnew, nounixbypass_opt_name, NULL, 230 NULL) == 0) { 231 xmp->nullm_flags |= NULLM_NOUNPBYPASS; 232 } 233 234 if (lowerrootvp == mp->mnt_vnodecovered) { 235 vn_lock(lowerrootvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE); 236 lowerrootvp->v_vflag |= VV_CROSSLOCK; 237 VOP_UNLOCK(lowerrootvp); 238 } 239 240 MNT_ILOCK(mp); 241 if ((xmp->nullm_flags & NULLM_CACHE) != 0) { 242 mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag & 243 (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED | 244 MNTK_EXTENDED_SHARED); 245 } 246 mp->mnt_kern_flag |= MNTK_NOMSYNC | MNTK_UNLOCKED_INSMNTQUE; 247 mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag & 248 (MNTK_USES_BCACHE | MNTK_NO_IOPF | MNTK_UNMAPPED_BUFS); 249 MNT_IUNLOCK(mp); 250 vfs_getnewfsid(mp); 251 vfs_mountedfrom(mp, target); 252 vput(nullm_rootvp); 253 254 NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n", 255 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname); 256 return (0); 257 } 258 259 /* 260 * Free reference to null layer 261 */ 262 static int 263 nullfs_unmount(struct mount *mp, int mntflags) 264 { 265 struct null_mount *mntdata; 266 int error, flags; 267 268 NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp); 269 270 if (mntflags & MNT_FORCE) 271 flags = FORCECLOSE; 272 else 273 flags = 0; 274 275 for (;;) { 276 /* There is 1 extra root vnode reference (nullm_rootvp). */ 277 error = vflush(mp, 0, flags, curthread); 278 if (error) 279 return (error); 280 MNT_ILOCK(mp); 281 if (mp->mnt_nvnodelistsize == 0) { 282 MNT_IUNLOCK(mp); 283 break; 284 } 285 MNT_IUNLOCK(mp); 286 if ((mntflags & MNT_FORCE) == 0) 287 return (EBUSY); 288 } 289 290 /* 291 * Finally, throw away the null_mount structure 292 */ 293 mntdata = mp->mnt_data; 294 if ((mntdata->nullm_flags & NULLM_CACHE) != 0) { 295 vfs_unregister_for_notification(mntdata->nullm_vfs, 296 &mntdata->notify_node); 297 } 298 if (mntdata->nullm_lowerrootvp == mp->mnt_vnodecovered) { 299 vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE); 300 mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK; 301 VOP_UNLOCK(mp->mnt_vnodecovered); 302 } 303 vfs_unregister_upper(mntdata->nullm_vfs, &mntdata->upper_node); 304 vrele(mntdata->nullm_lowerrootvp); 305 mp->mnt_data = NULL; 306 free(mntdata, M_NULLFSMNT); 307 return (0); 308 } 309 310 static int 311 nullfs_root(struct mount *mp, int flags, struct vnode **vpp) 312 { 313 struct vnode *vp; 314 struct null_mount *mntdata; 315 int error; 316 317 mntdata = MOUNTTONULLMOUNT(mp); 318 NULLFSDEBUG("nullfs_root(mp = %p, vp = %p)\n", mp, 319 mntdata->nullm_lowerrootvp); 320 321 error = vget(mntdata->nullm_lowerrootvp, flags); 322 if (error == 0) { 323 error = null_nodeget(mp, mntdata->nullm_lowerrootvp, &vp); 324 if (error == 0) { 325 *vpp = vp; 326 } 327 } 328 return (error); 329 } 330 331 static int 332 nullfs_quotactl(struct mount *mp, int cmd, uid_t uid, void *arg, bool *mp_busy) 333 { 334 struct mount *lowermp; 335 struct null_mount *mntdata; 336 int error; 337 bool unbusy; 338 339 mntdata = MOUNTTONULLMOUNT(mp); 340 lowermp = atomic_load_ptr(&mntdata->nullm_vfs); 341 KASSERT(*mp_busy == true, ("upper mount not busy")); 342 /* 343 * See comment in sys_quotactl() for an explanation of why the 344 * lower mount needs to be busied by the caller of VFS_QUOTACTL() 345 * but may be unbusied by the implementation. We must unbusy 346 * the upper mount for the same reason; otherwise a namei lookup 347 * issued by the VFS_QUOTACTL() implementation could traverse the 348 * upper mount and deadlock. 349 */ 350 vfs_unbusy(mp); 351 *mp_busy = false; 352 unbusy = true; 353 error = vfs_busy(lowermp, 0); 354 if (error == 0) 355 error = VFS_QUOTACTL(lowermp, cmd, uid, arg, &unbusy); 356 if (unbusy) 357 vfs_unbusy(lowermp); 358 359 return (error); 360 } 361 362 static int 363 nullfs_statfs(struct mount *mp, struct statfs *sbp) 364 { 365 int error; 366 struct statfs *mstat; 367 368 NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p->%p)\n", (void *)mp, 369 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp, 370 (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp)); 371 372 mstat = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK | M_ZERO); 373 374 error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, mstat); 375 if (error) { 376 free(mstat, M_STATFS); 377 return (error); 378 } 379 380 sbp->f_type = mstat->f_type; 381 sbp->f_bsize = mstat->f_bsize; 382 sbp->f_iosize = mstat->f_iosize; 383 sbp->f_blocks = mstat->f_blocks; 384 sbp->f_bfree = mstat->f_bfree; 385 sbp->f_bavail = mstat->f_bavail; 386 sbp->f_files = mstat->f_files; 387 sbp->f_ffree = mstat->f_ffree; 388 389 free(mstat, M_STATFS); 390 return (0); 391 } 392 393 static int 394 nullfs_sync(struct mount *mp, int waitfor) 395 { 396 /* 397 * XXX - Assumes no data cached at null layer. 398 */ 399 return (0); 400 } 401 402 static int 403 nullfs_vget(struct mount *mp, ino_t ino, int flags, struct vnode **vpp) 404 { 405 int error; 406 407 KASSERT((flags & LK_TYPE_MASK) != 0, 408 ("nullfs_vget: no lock requested")); 409 410 error = VFS_VGET(MOUNTTONULLMOUNT(mp)->nullm_vfs, ino, flags, vpp); 411 if (error != 0) 412 return (error); 413 return (null_nodeget(mp, *vpp, vpp)); 414 } 415 416 static int 417 nullfs_fhtovp(struct mount *mp, struct fid *fidp, int flags, struct vnode **vpp) 418 { 419 int error; 420 421 error = VFS_FHTOVP(MOUNTTONULLMOUNT(mp)->nullm_vfs, fidp, flags, 422 vpp); 423 if (error != 0) 424 return (error); 425 return (null_nodeget(mp, *vpp, vpp)); 426 } 427 428 static int 429 nullfs_extattrctl(struct mount *mp, int cmd, struct vnode *filename_vp, 430 int namespace, const char *attrname) 431 { 432 433 return (VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, 434 filename_vp, namespace, attrname)); 435 } 436 437 static void 438 nullfs_reclaim_lowervp(struct mount *mp, struct vnode *lowervp) 439 { 440 struct vnode *vp; 441 442 vp = null_hashget(mp, lowervp); 443 if (vp == NULL) 444 return; 445 VTONULL(vp)->null_flags |= NULLV_NOUNLOCK; 446 vgone(vp); 447 vput(vp); 448 } 449 450 static void 451 nullfs_unlink_lowervp(struct mount *mp, struct vnode *lowervp) 452 { 453 struct vnode *vp; 454 struct null_node *xp; 455 456 vp = null_hashget(mp, lowervp); 457 if (vp == NULL) 458 return; 459 xp = VTONULL(vp); 460 xp->null_flags |= NULLV_DROP | NULLV_NOUNLOCK; 461 vhold(vp); 462 vunref(vp); 463 464 if (vp->v_usecount == 0) { 465 /* 466 * If vunref() dropped the last use reference on the 467 * nullfs vnode, it must be reclaimed, and its lock 468 * was split from the lower vnode lock. Need to do 469 * extra unlock before allowing the final vdrop() to 470 * free the vnode. 471 */ 472 KASSERT(VN_IS_DOOMED(vp), 473 ("not reclaimed nullfs vnode %p", vp)); 474 VOP_UNLOCK(vp); 475 } else { 476 /* 477 * Otherwise, the nullfs vnode still shares the lock 478 * with the lower vnode, and must not be unlocked. 479 * Also clear the NULLV_NOUNLOCK, the flag is not 480 * relevant for future reclamations. 481 */ 482 ASSERT_VOP_ELOCKED(vp, "unlink_lowervp"); 483 KASSERT(!VN_IS_DOOMED(vp), 484 ("reclaimed nullfs vnode %p", vp)); 485 xp->null_flags &= ~NULLV_NOUNLOCK; 486 } 487 vdrop(vp); 488 } 489 490 static struct vfsops null_vfsops = { 491 .vfs_extattrctl = nullfs_extattrctl, 492 .vfs_fhtovp = nullfs_fhtovp, 493 .vfs_init = nullfs_init, 494 .vfs_mount = nullfs_mount, 495 .vfs_quotactl = nullfs_quotactl, 496 .vfs_root = nullfs_root, 497 .vfs_statfs = nullfs_statfs, 498 .vfs_sync = nullfs_sync, 499 .vfs_uninit = nullfs_uninit, 500 .vfs_unmount = nullfs_unmount, 501 .vfs_vget = nullfs_vget, 502 .vfs_reclaim_lowervp = nullfs_reclaim_lowervp, 503 .vfs_unlink_lowervp = nullfs_unlink_lowervp, 504 }; 505 506 VFS_SET(null_vfsops, nullfs, VFCF_LOOPBACK | VFCF_JAIL | VFCF_FILEMOUNT); 507