1 /* 2 * Copyright (c) 1994 Jan-Simon Pendry 3 * Copyright (c) 1994 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Jan-Simon Pendry. 8 * 9 * %sccs.include.redist.c% 10 * 11 * @(#)union_subr.c 8.7 (Berkeley) 05/07/94 12 */ 13 14 #include <sys/param.h> 15 #include <sys/systm.h> 16 #include <sys/time.h> 17 #include <sys/kernel.h> 18 #include <sys/vnode.h> 19 #include <sys/namei.h> 20 #include <sys/malloc.h> 21 #include <sys/file.h> 22 #include <sys/filedesc.h> 23 #include <sys/queue.h> 24 #include <sys/mount.h> 25 #include <vm/vm.h> /* for vnode_pager_setsize */ 26 #include <miscfs/union/union.h> 27 28 #ifdef DIAGNOSTIC 29 #include <sys/proc.h> 30 #endif 31 32 /* must be power of two, otherwise change UNION_HASH() */ 33 #define NHASH 32 34 35 /* unsigned int ... */ 36 #define UNION_HASH(u, l) \ 37 (((((unsigned long) (u)) + ((unsigned long) l)) >> 8) & (NHASH-1)) 38 39 static LIST_HEAD(unhead, union_node) unhead[NHASH]; 40 static int unvplock[NHASH]; 41 42 int 43 union_init() 44 { 45 int i; 46 47 for (i = 0; i < NHASH; i++) 48 LIST_INIT(&unhead[i]); 49 bzero((caddr_t) unvplock, sizeof(unvplock)); 50 } 51 52 static int 53 union_list_lock(ix) 54 int ix; 55 { 56 57 if (unvplock[ix] & UN_LOCKED) { 58 unvplock[ix] |= UN_WANT; 59 sleep((caddr_t) &unvplock[ix], PINOD); 60 return (1); 61 } 62 63 unvplock[ix] |= UN_LOCKED; 64 65 return (0); 66 } 67 68 static void 69 union_list_unlock(ix) 70 int ix; 71 { 72 73 unvplock[ix] &= ~UN_LOCKED; 74 75 if (unvplock[ix] & UN_WANT) { 76 unvplock[ix] &= ~UN_WANT; 77 wakeup((caddr_t) &unvplock[ix]); 78 } 79 } 80 81 void 82 union_updatevp(un, uppervp, lowervp) 83 struct union_node *un; 84 struct vnode *uppervp; 85 struct vnode *lowervp; 86 { 87 int ohash = UNION_HASH(un->un_uppervp, un->un_lowervp); 88 int nhash = UNION_HASH(uppervp, lowervp); 89 int docache = (lowervp != NULLVP || uppervp != NULLVP); 90 91 /* 92 * Ensure locking is ordered from lower to higher 93 * to avoid deadlocks. 94 */ 95 if (nhash < ohash) { 96 int t = ohash; 97 ohash = nhash; 98 nhash = t; 99 } 100 101 if (ohash != nhash) 102 while (union_list_lock(ohash)) 103 continue; 104 105 while (union_list_lock(nhash)) 106 continue; 107 108 if (ohash != nhash || !docache) { 109 if (un->un_flags & UN_CACHED) { 110 LIST_REMOVE(un, un_cache); 111 un->un_flags &= ~UN_CACHED; 112 } 113 } 114 115 if (ohash != nhash) 116 union_list_unlock(ohash); 117 118 if (un->un_lowervp != lowervp) { 119 if (un->un_lowervp) { 120 vrele(un->un_lowervp); 121 if (un->un_path) { 122 free(un->un_path, M_TEMP); 123 un->un_path = 0; 124 } 125 if (un->un_dirvp) { 126 vrele(un->un_dirvp); 127 un->un_dirvp = NULLVP; 128 } 129 } 130 un->un_lowervp = lowervp; 131 un->un_lowersz = VNOVAL; 132 } 133 134 if (un->un_uppervp != uppervp) { 135 if (un->un_uppervp) 136 vrele(un->un_uppervp); 137 138 un->un_uppervp = uppervp; 139 un->un_uppersz = VNOVAL; 140 } 141 142 if (docache && (ohash != nhash)) { 143 LIST_INSERT_HEAD(&unhead[nhash], un, un_cache); 144 un->un_flags |= UN_CACHED; 145 } 146 147 union_list_unlock(nhash); 148 } 149 150 void 151 union_newlower(un, lowervp) 152 struct union_node *un; 153 struct vnode *lowervp; 154 { 155 156 union_updatevp(un, un->un_uppervp, lowervp); 157 } 158 159 void 160 union_newupper(un, uppervp) 161 struct union_node *un; 162 struct vnode *uppervp; 163 { 164 165 union_updatevp(un, uppervp, un->un_lowervp); 166 } 167 168 /* 169 * Keep track of size changes in the underlying vnodes. 170 * If the size changes, then callback to the vm layer 171 * giving priority to the upper layer size. 172 */ 173 void 174 union_newsize(vp, uppersz, lowersz) 175 struct vnode *vp; 176 off_t uppersz, lowersz; 177 { 178 struct union_node *un; 179 off_t sz; 180 181 /* only interested in regular files */ 182 if (vp->v_type != VREG) 183 return; 184 185 un = VTOUNION(vp); 186 sz = VNOVAL; 187 188 if ((uppersz != VNOVAL) && (un->un_uppersz != uppersz)) { 189 un->un_uppersz = uppersz; 190 if (sz == VNOVAL) 191 sz = un->un_uppersz; 192 } 193 194 if ((lowersz != VNOVAL) && (un->un_lowersz != lowersz)) { 195 un->un_lowersz = lowersz; 196 if (sz == VNOVAL) 197 sz = un->un_lowersz; 198 } 199 200 if (sz != VNOVAL) { 201 #ifdef UNION_DIAGNOSTIC 202 printf("union: %s size now %ld\n", 203 uppersz != VNOVAL ? "upper" : "lower", (long) sz); 204 #endif 205 vnode_pager_setsize(vp, sz); 206 } 207 } 208 209 /* 210 * allocate a union_node/vnode pair. the vnode is 211 * referenced and locked. the new vnode is returned 212 * via (vpp). (mp) is the mountpoint of the union filesystem, 213 * (dvp) is the parent directory where the upper layer object 214 * should exist (but doesn't) and (cnp) is the componentname 215 * information which is partially copied to allow the upper 216 * layer object to be created at a later time. (uppervp) 217 * and (lowervp) reference the upper and lower layer objects 218 * being mapped. either, but not both, can be nil. 219 * if supplied, (uppervp) is locked. 220 * the reference is either maintained in the new union_node 221 * object which is allocated, or they are vrele'd. 222 * 223 * all union_nodes are maintained on a singly-linked 224 * list. new nodes are only allocated when they cannot 225 * be found on this list. entries on the list are 226 * removed when the vfs reclaim entry is called. 227 * 228 * a single lock is kept for the entire list. this is 229 * needed because the getnewvnode() function can block 230 * waiting for a vnode to become free, in which case there 231 * may be more than one process trying to get the same 232 * vnode. this lock is only taken if we are going to 233 * call getnewvnode, since the kernel itself is single-threaded. 234 * 235 * if an entry is found on the list, then call vget() to 236 * take a reference. this is done because there may be 237 * zero references to it and so it needs to removed from 238 * the vnode free list. 239 */ 240 int 241 union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp) 242 struct vnode **vpp; 243 struct mount *mp; 244 struct vnode *undvp; 245 struct vnode *dvp; /* may be null */ 246 struct componentname *cnp; /* may be null */ 247 struct vnode *uppervp; /* may be null */ 248 struct vnode *lowervp; /* may be null */ 249 { 250 int error; 251 struct union_node *un; 252 struct union_node **pp; 253 struct vnode *xlowervp = NULLVP; 254 struct union_mount *um = MOUNTTOUNIONMOUNT(mp); 255 int hash; 256 int vflag; 257 int try; 258 259 if (uppervp == NULLVP && lowervp == NULLVP) 260 panic("union: unidentifiable allocation"); 261 262 if (uppervp && lowervp && (uppervp->v_type != lowervp->v_type)) { 263 xlowervp = lowervp; 264 lowervp = NULLVP; 265 } 266 267 /* detect the root vnode (and aliases) */ 268 vflag = 0; 269 if ((uppervp == um->um_uppervp) && 270 ((lowervp == NULLVP) || lowervp == um->um_lowervp)) { 271 if (lowervp == NULLVP) { 272 lowervp = um->um_lowervp; 273 VREF(lowervp); 274 } 275 vflag = VROOT; 276 } 277 278 loop: 279 for (try = 0; try < 3; try++) { 280 switch (try) { 281 case 0: 282 if (lowervp == NULLVP) 283 continue; 284 hash = UNION_HASH(uppervp, lowervp); 285 break; 286 287 case 1: 288 if (uppervp == NULLVP) 289 continue; 290 hash = UNION_HASH(uppervp, NULLVP); 291 break; 292 293 case 2: 294 if (lowervp == NULLVP) 295 continue; 296 hash = UNION_HASH(NULLVP, lowervp); 297 break; 298 } 299 300 while (union_list_lock(hash)) 301 continue; 302 303 for (un = unhead[hash].lh_first; un != 0; 304 un = un->un_cache.le_next) { 305 if ((un->un_lowervp == lowervp || 306 un->un_lowervp == NULLVP) && 307 (un->un_uppervp == uppervp || 308 un->un_uppervp == NULLVP) && 309 (UNIONTOV(un)->v_mount == mp)) { 310 if (vget(UNIONTOV(un), 0)) { 311 union_list_unlock(hash); 312 goto loop; 313 } 314 break; 315 } 316 } 317 318 union_list_unlock(hash); 319 320 if (un) 321 break; 322 } 323 324 if (un) { 325 /* 326 * Obtain a lock on the union_node. 327 * uppervp is locked, though un->un_uppervp 328 * may not be. this doesn't break the locking 329 * hierarchy since in the case that un->un_uppervp 330 * is not yet locked it will be vrele'd and replaced 331 * with uppervp. 332 */ 333 334 if ((dvp != NULLVP) && (uppervp == dvp)) { 335 /* 336 * Access ``.'', so (un) will already 337 * be locked. Since this process has 338 * the lock on (uppervp) no other 339 * process can hold the lock on (un). 340 */ 341 #ifdef DIAGNOSTIC 342 if ((un->un_flags & UN_LOCKED) == 0) 343 panic("union: . not locked"); 344 else if (curproc && un->un_pid != curproc->p_pid && 345 un->un_pid > -1 && curproc->p_pid > -1) 346 panic("union: allocvp not lock owner"); 347 #endif 348 } else { 349 if (un->un_flags & UN_LOCKED) { 350 vrele(UNIONTOV(un)); 351 un->un_flags |= UN_WANT; 352 sleep((caddr_t) &un->un_flags, PINOD); 353 goto loop; 354 } 355 un->un_flags |= UN_LOCKED; 356 357 #ifdef DIAGNOSTIC 358 if (curproc) 359 un->un_pid = curproc->p_pid; 360 else 361 un->un_pid = -1; 362 #endif 363 } 364 365 /* 366 * At this point, the union_node is locked, 367 * un->un_uppervp may not be locked, and uppervp 368 * is locked or nil. 369 */ 370 371 /* 372 * Save information about the upper layer. 373 */ 374 if (uppervp != un->un_uppervp) { 375 union_newupper(un, uppervp); 376 } else if (uppervp) { 377 vrele(uppervp); 378 } 379 380 if (un->un_uppervp) { 381 un->un_flags |= UN_ULOCK; 382 un->un_flags &= ~UN_KLOCK; 383 } 384 385 /* 386 * Save information about the lower layer. 387 * This needs to keep track of pathname 388 * and directory information which union_vn_create 389 * might need. 390 */ 391 if (lowervp != un->un_lowervp) { 392 union_newlower(un, lowervp); 393 if (cnp && (lowervp != NULLVP) && 394 (lowervp->v_type == VREG)) { 395 un->un_hash = cnp->cn_hash; 396 un->un_path = malloc(cnp->cn_namelen+1, 397 M_TEMP, M_WAITOK); 398 bcopy(cnp->cn_nameptr, un->un_path, 399 cnp->cn_namelen); 400 un->un_path[cnp->cn_namelen] = '\0'; 401 VREF(dvp); 402 un->un_dirvp = dvp; 403 } 404 } else if (lowervp) { 405 vrele(lowervp); 406 } 407 *vpp = UNIONTOV(un); 408 return (0); 409 } 410 411 /* 412 * otherwise lock the vp list while we call getnewvnode 413 * since that can block. 414 */ 415 hash = UNION_HASH(uppervp, lowervp); 416 417 if (union_list_lock(hash)) 418 goto loop; 419 420 error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp); 421 if (error) { 422 if (uppervp) { 423 if (dvp == uppervp) 424 vrele(uppervp); 425 else 426 vput(uppervp); 427 } 428 if (lowervp) 429 vrele(lowervp); 430 431 goto out; 432 } 433 434 MALLOC((*vpp)->v_data, void *, sizeof(struct union_node), 435 M_TEMP, M_WAITOK); 436 437 (*vpp)->v_flag |= vflag; 438 if (uppervp) 439 (*vpp)->v_type = uppervp->v_type; 440 else 441 (*vpp)->v_type = lowervp->v_type; 442 un = VTOUNION(*vpp); 443 un->un_vnode = *vpp; 444 un->un_uppervp = uppervp; 445 un->un_uppersz = VNOVAL; 446 un->un_lowervp = lowervp; 447 un->un_lowersz = VNOVAL; 448 un->un_openl = 0; 449 un->un_flags = UN_LOCKED; 450 if (un->un_uppervp) 451 un->un_flags |= UN_ULOCK; 452 #ifdef DIAGNOSTIC 453 if (curproc) 454 un->un_pid = curproc->p_pid; 455 else 456 un->un_pid = -1; 457 #endif 458 if (cnp && (lowervp != NULLVP) && (lowervp->v_type == VREG)) { 459 un->un_hash = cnp->cn_hash; 460 un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK); 461 bcopy(cnp->cn_nameptr, un->un_path, cnp->cn_namelen); 462 un->un_path[cnp->cn_namelen] = '\0'; 463 VREF(dvp); 464 un->un_dirvp = dvp; 465 } else { 466 un->un_hash = 0; 467 un->un_path = 0; 468 un->un_dirvp = 0; 469 } 470 471 LIST_INSERT_HEAD(&unhead[hash], un, un_cache); 472 un->un_flags |= UN_CACHED; 473 474 if (xlowervp) 475 vrele(xlowervp); 476 477 out: 478 union_list_unlock(hash); 479 480 return (error); 481 } 482 483 int 484 union_freevp(vp) 485 struct vnode *vp; 486 { 487 struct union_node *un = VTOUNION(vp); 488 489 if (un->un_flags & UN_CACHED) { 490 LIST_REMOVE(un, un_cache); 491 un->un_flags &= ~UN_CACHED; 492 } 493 494 if (un->un_uppervp != NULLVP) 495 vrele(un->un_uppervp); 496 if (un->un_lowervp != NULLVP) 497 vrele(un->un_lowervp); 498 if (un->un_dirvp != NULLVP) 499 vrele(un->un_dirvp); 500 if (un->un_path) 501 free(un->un_path, M_TEMP); 502 503 FREE(vp->v_data, M_TEMP); 504 vp->v_data = 0; 505 506 return (0); 507 } 508 509 /* 510 * copyfile. copy the vnode (fvp) to the vnode (tvp) 511 * using a sequence of reads and writes. both (fvp) 512 * and (tvp) are locked on entry and exit. 513 */ 514 int 515 union_copyfile(p, cred, fvp, tvp) 516 struct proc *p; 517 struct ucred *cred; 518 struct vnode *fvp; 519 struct vnode *tvp; 520 { 521 char *buf; 522 struct uio uio; 523 struct iovec iov; 524 int error = 0; 525 526 /* 527 * strategy: 528 * allocate a buffer of size MAXBSIZE. 529 * loop doing reads and writes, keeping track 530 * of the current uio offset. 531 * give up at the first sign of trouble. 532 */ 533 534 uio.uio_procp = p; 535 uio.uio_segflg = UIO_SYSSPACE; 536 uio.uio_offset = 0; 537 538 VOP_UNLOCK(fvp); /* XXX */ 539 LEASE_CHECK(fvp, p, cred, LEASE_READ); 540 VOP_LOCK(fvp); /* XXX */ 541 VOP_UNLOCK(tvp); /* XXX */ 542 LEASE_CHECK(tvp, p, cred, LEASE_WRITE); 543 VOP_LOCK(tvp); /* XXX */ 544 545 buf = malloc(MAXBSIZE, M_TEMP, M_WAITOK); 546 547 /* ugly loop follows... */ 548 do { 549 off_t offset = uio.uio_offset; 550 551 uio.uio_iov = &iov; 552 uio.uio_iovcnt = 1; 553 iov.iov_base = buf; 554 iov.iov_len = MAXBSIZE; 555 uio.uio_resid = iov.iov_len; 556 uio.uio_rw = UIO_READ; 557 error = VOP_READ(fvp, &uio, 0, cred); 558 559 if (error == 0) { 560 uio.uio_iov = &iov; 561 uio.uio_iovcnt = 1; 562 iov.iov_base = buf; 563 iov.iov_len = MAXBSIZE - uio.uio_resid; 564 uio.uio_offset = offset; 565 uio.uio_rw = UIO_WRITE; 566 uio.uio_resid = iov.iov_len; 567 568 if (uio.uio_resid == 0) 569 break; 570 571 do { 572 error = VOP_WRITE(tvp, &uio, 0, cred); 573 } while ((uio.uio_resid > 0) && (error == 0)); 574 } 575 576 } while (error == 0); 577 578 free(buf, M_TEMP); 579 return (error); 580 } 581 582 /* 583 * Create a shadow directory in the upper layer. 584 * The new vnode is returned locked. 585 * 586 * (um) points to the union mount structure for access to the 587 * the mounting process's credentials. 588 * (dvp) is the directory in which to create the shadow directory. 589 * it is unlocked on entry and exit. 590 * (cnp) is the componentname to be created. 591 * (vpp) is the returned newly created shadow directory, which 592 * is returned locked. 593 */ 594 int 595 union_mkshadow(um, dvp, cnp, vpp) 596 struct union_mount *um; 597 struct vnode *dvp; 598 struct componentname *cnp; 599 struct vnode **vpp; 600 { 601 int error; 602 struct vattr va; 603 struct proc *p = cnp->cn_proc; 604 struct componentname cn; 605 606 /* 607 * policy: when creating the shadow directory in the 608 * upper layer, create it owned by the user who did 609 * the mount, group from parent directory, and mode 610 * 777 modified by umask (ie mostly identical to the 611 * mkdir syscall). (jsp, kb) 612 */ 613 614 /* 615 * A new componentname structure must be faked up because 616 * there is no way to know where the upper level cnp came 617 * from or what it is being used for. This must duplicate 618 * some of the work done by NDINIT, some of the work done 619 * by namei, some of the work done by lookup and some of 620 * the work done by VOP_LOOKUP when given a CREATE flag. 621 * Conclusion: Horrible. 622 * 623 * The pathname buffer will be FREEed by VOP_MKDIR. 624 */ 625 cn.cn_pnbuf = malloc(cnp->cn_namelen+1, M_NAMEI, M_WAITOK); 626 bcopy(cnp->cn_nameptr, cn.cn_pnbuf, cnp->cn_namelen); 627 cn.cn_pnbuf[cnp->cn_namelen] = '\0'; 628 629 cn.cn_nameiop = CREATE; 630 cn.cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN); 631 cn.cn_proc = cnp->cn_proc; 632 if (um->um_op == UNMNT_ABOVE) 633 cn.cn_cred = cnp->cn_cred; 634 else 635 cn.cn_cred = um->um_cred; 636 cn.cn_nameptr = cn.cn_pnbuf; 637 cn.cn_namelen = cnp->cn_namelen; 638 cn.cn_hash = cnp->cn_hash; 639 cn.cn_consume = cnp->cn_consume; 640 641 VREF(dvp); 642 if (error = relookup(dvp, vpp, &cn)) 643 return (error); 644 vrele(dvp); 645 646 if (*vpp) { 647 VOP_ABORTOP(dvp, &cn); 648 VOP_UNLOCK(dvp); 649 vrele(*vpp); 650 *vpp = NULLVP; 651 return (EEXIST); 652 } 653 654 VATTR_NULL(&va); 655 va.va_type = VDIR; 656 va.va_mode = um->um_cmode; 657 658 /* LEASE_CHECK: dvp is locked */ 659 LEASE_CHECK(dvp, p, p->p_ucred, LEASE_WRITE); 660 661 error = VOP_MKDIR(dvp, vpp, &cn, &va); 662 return (error); 663 } 664 665 /* 666 * union_vn_create: creates and opens a new shadow file 667 * on the upper union layer. this function is similar 668 * in spirit to calling vn_open but it avoids calling namei(). 669 * the problem with calling namei is that a) it locks too many 670 * things, and b) it doesn't start at the "right" directory, 671 * whereas relookup is told where to start. 672 */ 673 int 674 union_vn_create(vpp, un, p) 675 struct vnode **vpp; 676 struct union_node *un; 677 struct proc *p; 678 { 679 struct vnode *vp; 680 struct ucred *cred = p->p_ucred; 681 struct vattr vat; 682 struct vattr *vap = &vat; 683 int fmode = FFLAGS(O_WRONLY|O_CREAT|O_TRUNC|O_EXCL); 684 int error; 685 int cmode = UN_FILEMODE & ~p->p_fd->fd_cmask; 686 char *cp; 687 struct componentname cn; 688 689 *vpp = NULLVP; 690 691 /* 692 * Build a new componentname structure (for the same 693 * reasons outlines in union_mkshadow). 694 * The difference here is that the file is owned by 695 * the current user, rather than by the person who 696 * did the mount, since the current user needs to be 697 * able to write the file (that's why it is being 698 * copied in the first place). 699 */ 700 cn.cn_namelen = strlen(un->un_path); 701 cn.cn_pnbuf = (caddr_t) malloc(cn.cn_namelen, M_NAMEI, M_WAITOK); 702 bcopy(un->un_path, cn.cn_pnbuf, cn.cn_namelen+1); 703 cn.cn_nameiop = CREATE; 704 cn.cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN); 705 cn.cn_proc = p; 706 cn.cn_cred = p->p_ucred; 707 cn.cn_nameptr = cn.cn_pnbuf; 708 cn.cn_hash = un->un_hash; 709 cn.cn_consume = 0; 710 711 VREF(un->un_dirvp); 712 if (error = relookup(un->un_dirvp, &vp, &cn)) 713 return (error); 714 vrele(un->un_dirvp); 715 716 if (vp) { 717 VOP_ABORTOP(un->un_dirvp, &cn); 718 if (un->un_dirvp == vp) 719 vrele(un->un_dirvp); 720 else 721 vput(un->un_dirvp); 722 vrele(vp); 723 return (EEXIST); 724 } 725 726 /* 727 * Good - there was no race to create the file 728 * so go ahead and create it. The permissions 729 * on the file will be 0666 modified by the 730 * current user's umask. Access to the file, while 731 * it is unioned, will require access to the top *and* 732 * bottom files. Access when not unioned will simply 733 * require access to the top-level file. 734 * TODO: confirm choice of access permissions. 735 */ 736 VATTR_NULL(vap); 737 vap->va_type = VREG; 738 vap->va_mode = cmode; 739 LEASE_CHECK(un->un_dirvp, p, cred, LEASE_WRITE); 740 if (error = VOP_CREATE(un->un_dirvp, &vp, &cn, vap)) 741 return (error); 742 743 if (error = VOP_OPEN(vp, fmode, cred, p)) { 744 vput(vp); 745 return (error); 746 } 747 748 vp->v_writecount++; 749 *vpp = vp; 750 return (0); 751 } 752 753 int 754 union_vn_close(vp, fmode, cred, p) 755 struct vnode *vp; 756 int fmode; 757 struct ucred *cred; 758 struct proc *p; 759 { 760 if (fmode & FWRITE) 761 --vp->v_writecount; 762 return (VOP_CLOSE(vp, fmode)); 763 } 764 765 void 766 union_removed_upper(un) 767 struct union_node *un; 768 { 769 if (un->un_flags & UN_ULOCK) { 770 un->un_flags &= ~UN_ULOCK; 771 VOP_UNLOCK(un->un_uppervp); 772 } 773 774 union_newupper(un, NULLVP); 775 } 776 777 struct vnode * 778 union_lowervp(vp) 779 struct vnode *vp; 780 { 781 struct union_node *un = VTOUNION(vp); 782 783 if (un->un_lowervp && (vp->v_type == un->un_lowervp->v_type)) { 784 if (vget(un->un_lowervp, 0)) 785 return (NULLVP); 786 } 787 788 return (un->un_lowervp); 789 } 790