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 89 NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp); 90 91 if (mp->mnt_flag & MNT_ROOTFS) 92 return (EOPNOTSUPP); 93 94 /* 95 * Update is a no-op 96 */ 97 if (mp->mnt_flag & MNT_UPDATE) { 98 /* 99 * Only support update mounts for NFS export. 100 */ 101 if (vfs_flagopt(mp->mnt_optnew, "export", NULL, 0)) 102 return (0); 103 else 104 return (EOPNOTSUPP); 105 } 106 107 /* 108 * Get argument 109 */ 110 error = vfs_getopt(mp->mnt_optnew, "from", (void **)&target, &len); 111 if (error != 0) 112 error = vfs_getopt(mp->mnt_optnew, "target", (void **)&target, &len); 113 if (error || target[len - 1] != '\0') 114 return (EINVAL); 115 116 /* 117 * Unlock lower node to avoid possible deadlock. 118 */ 119 if (mp->mnt_vnodecovered->v_op == &null_vnodeops && 120 VOP_ISLOCKED(mp->mnt_vnodecovered) == LK_EXCLUSIVE) { 121 VOP_UNLOCK(mp->mnt_vnodecovered); 122 isvnunlocked = true; 123 } else { 124 isvnunlocked = false; 125 } 126 127 /* 128 * Find lower node 129 */ 130 ndp = &nd; 131 NDINIT(ndp, LOOKUP, FOLLOW|LOCKLEAF, UIO_SYSSPACE, target); 132 error = namei(ndp); 133 134 /* 135 * Re-lock vnode. 136 * XXXKIB This is deadlock-prone as well. 137 */ 138 if (isvnunlocked) 139 vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY); 140 141 if (error) 142 return (error); 143 NDFREE_PNBUF(ndp); 144 145 /* 146 * Sanity check on lower vnode 147 */ 148 lowerrootvp = ndp->ni_vp; 149 150 /* 151 * Check multi null mount to avoid `lock against myself' panic. 152 */ 153 if (mp->mnt_vnodecovered->v_op == &null_vnodeops) { 154 nn = VTONULL(mp->mnt_vnodecovered); 155 if (nn == NULL || lowerrootvp == nn->null_lowervp) { 156 NULLFSDEBUG("nullfs_mount: multi null mount?\n"); 157 vput(lowerrootvp); 158 return (EDEADLK); 159 } 160 } 161 162 /* 163 * Lower vnode must be the same type as the covered vnode - we 164 * don't allow mounting directories to files or vice versa. 165 */ 166 if ((lowerrootvp->v_type != VDIR && lowerrootvp->v_type != VREG) || 167 lowerrootvp->v_type != mp->mnt_vnodecovered->v_type) { 168 NULLFSDEBUG("nullfs_mount: target must be same type as fspath"); 169 vput(lowerrootvp); 170 return (EINVAL); 171 } 172 173 xmp = malloc(sizeof(struct null_mount), M_NULLFSMNT, 174 M_WAITOK | M_ZERO); 175 176 /* 177 * Save pointer to underlying FS and the reference to the 178 * lower root vnode. 179 */ 180 xmp->nullm_vfs = vfs_register_upper_from_vp(lowerrootvp, mp, 181 &xmp->upper_node); 182 if (xmp->nullm_vfs == NULL) { 183 vput(lowerrootvp); 184 free(xmp, M_NULLFSMNT); 185 return (ENOENT); 186 } 187 vref(lowerrootvp); 188 xmp->nullm_lowerrootvp = lowerrootvp; 189 mp->mnt_data = xmp; 190 191 /* 192 * Make sure the node alias worked. 193 */ 194 error = null_nodeget(mp, lowerrootvp, &nullm_rootvp); 195 if (error != 0) { 196 vfs_unregister_upper(xmp->nullm_vfs, &xmp->upper_node); 197 vrele(lowerrootvp); 198 free(xmp, M_NULLFSMNT); 199 return (error); 200 } 201 202 if (NULLVPTOLOWERVP(nullm_rootvp)->v_mount->mnt_flag & MNT_LOCAL) { 203 MNT_ILOCK(mp); 204 mp->mnt_flag |= MNT_LOCAL; 205 MNT_IUNLOCK(mp); 206 } 207 208 if (vfs_getopt(mp->mnt_optnew, "cache", NULL, NULL) == 0) { 209 xmp->nullm_flags |= NULLM_CACHE; 210 } else if (vfs_getopt(mp->mnt_optnew, "nocache", NULL, NULL) == 0) { 211 ; 212 } else if (null_cache_vnodes && 213 (xmp->nullm_vfs->mnt_kern_flag & MNTK_NULL_NOCACHE) == 0) { 214 xmp->nullm_flags |= NULLM_CACHE; 215 } 216 217 if ((xmp->nullm_flags & NULLM_CACHE) != 0) { 218 vfs_register_for_notification(xmp->nullm_vfs, mp, 219 &xmp->notify_node); 220 } 221 222 if (lowerrootvp == mp->mnt_vnodecovered) { 223 vn_lock(lowerrootvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE); 224 lowerrootvp->v_vflag |= VV_CROSSLOCK; 225 VOP_UNLOCK(lowerrootvp); 226 } 227 228 MNT_ILOCK(mp); 229 if ((xmp->nullm_flags & NULLM_CACHE) != 0) { 230 mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag & 231 (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED | 232 MNTK_EXTENDED_SHARED); 233 } 234 mp->mnt_kern_flag |= MNTK_NOMSYNC | MNTK_UNLOCKED_INSMNTQUE; 235 mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag & 236 (MNTK_USES_BCACHE | MNTK_NO_IOPF | MNTK_UNMAPPED_BUFS); 237 MNT_IUNLOCK(mp); 238 vfs_getnewfsid(mp); 239 vfs_mountedfrom(mp, target); 240 vput(nullm_rootvp); 241 242 NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n", 243 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname); 244 return (0); 245 } 246 247 /* 248 * Free reference to null layer 249 */ 250 static int 251 nullfs_unmount(struct mount *mp, int mntflags) 252 { 253 struct null_mount *mntdata; 254 int error, flags; 255 256 NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp); 257 258 if (mntflags & MNT_FORCE) 259 flags = FORCECLOSE; 260 else 261 flags = 0; 262 263 for (;;) { 264 /* There is 1 extra root vnode reference (nullm_rootvp). */ 265 error = vflush(mp, 0, flags, curthread); 266 if (error) 267 return (error); 268 MNT_ILOCK(mp); 269 if (mp->mnt_nvnodelistsize == 0) { 270 MNT_IUNLOCK(mp); 271 break; 272 } 273 MNT_IUNLOCK(mp); 274 if ((mntflags & MNT_FORCE) == 0) 275 return (EBUSY); 276 } 277 278 /* 279 * Finally, throw away the null_mount structure 280 */ 281 mntdata = mp->mnt_data; 282 if ((mntdata->nullm_flags & NULLM_CACHE) != 0) { 283 vfs_unregister_for_notification(mntdata->nullm_vfs, 284 &mntdata->notify_node); 285 } 286 if (mntdata->nullm_lowerrootvp == mp->mnt_vnodecovered) { 287 vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE); 288 mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK; 289 VOP_UNLOCK(mp->mnt_vnodecovered); 290 } 291 vfs_unregister_upper(mntdata->nullm_vfs, &mntdata->upper_node); 292 vrele(mntdata->nullm_lowerrootvp); 293 mp->mnt_data = NULL; 294 free(mntdata, M_NULLFSMNT); 295 return (0); 296 } 297 298 static int 299 nullfs_root(struct mount *mp, int flags, struct vnode **vpp) 300 { 301 struct vnode *vp; 302 struct null_mount *mntdata; 303 int error; 304 305 mntdata = MOUNTTONULLMOUNT(mp); 306 NULLFSDEBUG("nullfs_root(mp = %p, vp = %p)\n", mp, 307 mntdata->nullm_lowerrootvp); 308 309 error = vget(mntdata->nullm_lowerrootvp, flags); 310 if (error == 0) { 311 error = null_nodeget(mp, mntdata->nullm_lowerrootvp, &vp); 312 if (error == 0) { 313 *vpp = vp; 314 } 315 } 316 return (error); 317 } 318 319 static int 320 nullfs_quotactl(struct mount *mp, int cmd, uid_t uid, void *arg, bool *mp_busy) 321 { 322 struct mount *lowermp; 323 struct null_mount *mntdata; 324 int error; 325 bool unbusy; 326 327 mntdata = MOUNTTONULLMOUNT(mp); 328 lowermp = atomic_load_ptr(&mntdata->nullm_vfs); 329 KASSERT(*mp_busy == true, ("upper mount not busy")); 330 /* 331 * See comment in sys_quotactl() for an explanation of why the 332 * lower mount needs to be busied by the caller of VFS_QUOTACTL() 333 * but may be unbusied by the implementation. We must unbusy 334 * the upper mount for the same reason; otherwise a namei lookup 335 * issued by the VFS_QUOTACTL() implementation could traverse the 336 * upper mount and deadlock. 337 */ 338 vfs_unbusy(mp); 339 *mp_busy = false; 340 unbusy = true; 341 error = vfs_busy(lowermp, 0); 342 if (error == 0) 343 error = VFS_QUOTACTL(lowermp, cmd, uid, arg, &unbusy); 344 if (unbusy) 345 vfs_unbusy(lowermp); 346 347 return (error); 348 } 349 350 static int 351 nullfs_statfs(struct mount *mp, struct statfs *sbp) 352 { 353 int error; 354 struct statfs *mstat; 355 356 NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p->%p)\n", (void *)mp, 357 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp, 358 (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp)); 359 360 mstat = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK | M_ZERO); 361 362 error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, mstat); 363 if (error) { 364 free(mstat, M_STATFS); 365 return (error); 366 } 367 368 sbp->f_type = mstat->f_type; 369 sbp->f_bsize = mstat->f_bsize; 370 sbp->f_iosize = mstat->f_iosize; 371 sbp->f_blocks = mstat->f_blocks; 372 sbp->f_bfree = mstat->f_bfree; 373 sbp->f_bavail = mstat->f_bavail; 374 sbp->f_files = mstat->f_files; 375 sbp->f_ffree = mstat->f_ffree; 376 377 free(mstat, M_STATFS); 378 return (0); 379 } 380 381 static int 382 nullfs_sync(struct mount *mp, int waitfor) 383 { 384 /* 385 * XXX - Assumes no data cached at null layer. 386 */ 387 return (0); 388 } 389 390 static int 391 nullfs_vget(struct mount *mp, ino_t ino, int flags, struct vnode **vpp) 392 { 393 int error; 394 395 KASSERT((flags & LK_TYPE_MASK) != 0, 396 ("nullfs_vget: no lock requested")); 397 398 error = VFS_VGET(MOUNTTONULLMOUNT(mp)->nullm_vfs, ino, flags, vpp); 399 if (error != 0) 400 return (error); 401 return (null_nodeget(mp, *vpp, vpp)); 402 } 403 404 static int 405 nullfs_fhtovp(struct mount *mp, struct fid *fidp, int flags, struct vnode **vpp) 406 { 407 int error; 408 409 error = VFS_FHTOVP(MOUNTTONULLMOUNT(mp)->nullm_vfs, fidp, flags, 410 vpp); 411 if (error != 0) 412 return (error); 413 return (null_nodeget(mp, *vpp, vpp)); 414 } 415 416 static int 417 nullfs_extattrctl(struct mount *mp, int cmd, struct vnode *filename_vp, 418 int namespace, const char *attrname) 419 { 420 421 return (VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, 422 filename_vp, namespace, attrname)); 423 } 424 425 static void 426 nullfs_reclaim_lowervp(struct mount *mp, struct vnode *lowervp) 427 { 428 struct vnode *vp; 429 430 vp = null_hashget(mp, lowervp); 431 if (vp == NULL) 432 return; 433 VTONULL(vp)->null_flags |= NULLV_NOUNLOCK; 434 vgone(vp); 435 vput(vp); 436 } 437 438 static void 439 nullfs_unlink_lowervp(struct mount *mp, struct vnode *lowervp) 440 { 441 struct vnode *vp; 442 struct null_node *xp; 443 444 vp = null_hashget(mp, lowervp); 445 if (vp == NULL) 446 return; 447 xp = VTONULL(vp); 448 xp->null_flags |= NULLV_DROP | NULLV_NOUNLOCK; 449 vhold(vp); 450 vunref(vp); 451 452 if (vp->v_usecount == 0) { 453 /* 454 * If vunref() dropped the last use reference on the 455 * nullfs vnode, it must be reclaimed, and its lock 456 * was split from the lower vnode lock. Need to do 457 * extra unlock before allowing the final vdrop() to 458 * free the vnode. 459 */ 460 KASSERT(VN_IS_DOOMED(vp), 461 ("not reclaimed nullfs vnode %p", vp)); 462 VOP_UNLOCK(vp); 463 } else { 464 /* 465 * Otherwise, the nullfs vnode still shares the lock 466 * with the lower vnode, and must not be unlocked. 467 * Also clear the NULLV_NOUNLOCK, the flag is not 468 * relevant for future reclamations. 469 */ 470 ASSERT_VOP_ELOCKED(vp, "unlink_lowervp"); 471 KASSERT(!VN_IS_DOOMED(vp), 472 ("reclaimed nullfs vnode %p", vp)); 473 xp->null_flags &= ~NULLV_NOUNLOCK; 474 } 475 vdrop(vp); 476 } 477 478 static struct vfsops null_vfsops = { 479 .vfs_extattrctl = nullfs_extattrctl, 480 .vfs_fhtovp = nullfs_fhtovp, 481 .vfs_init = nullfs_init, 482 .vfs_mount = nullfs_mount, 483 .vfs_quotactl = nullfs_quotactl, 484 .vfs_root = nullfs_root, 485 .vfs_statfs = nullfs_statfs, 486 .vfs_sync = nullfs_sync, 487 .vfs_uninit = nullfs_uninit, 488 .vfs_unmount = nullfs_unmount, 489 .vfs_vget = nullfs_vget, 490 .vfs_reclaim_lowervp = nullfs_reclaim_lowervp, 491 .vfs_unlink_lowervp = nullfs_unlink_lowervp, 492 }; 493 494 VFS_SET(null_vfsops, nullfs, VFCF_LOOPBACK | VFCF_JAIL | VFCF_FILEMOUNT); 495