1 /*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * John Heidemann of the UCLA Ficus project. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)null_vnops.c 8.6 (Berkeley) 5/27/95 33 * 34 * Ancestors: 35 * @(#)lofs_vnops.c 1.2 (Berkeley) 6/18/92 36 * ...and... 37 * @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project 38 * 39 * $FreeBSD$ 40 */ 41 42 /* 43 * Null Layer 44 * 45 * (See mount_nullfs(8) for more information.) 46 * 47 * The null layer duplicates a portion of the filesystem 48 * name space under a new name. In this respect, it is 49 * similar to the loopback filesystem. It differs from 50 * the loopback fs in two respects: it is implemented using 51 * a stackable layers techniques, and its "null-node"s stack above 52 * all lower-layer vnodes, not just over directory vnodes. 53 * 54 * The null layer has two purposes. First, it serves as a demonstration 55 * of layering by proving a layer which does nothing. (It actually 56 * does everything the loopback filesystem does, which is slightly 57 * more than nothing.) Second, the null layer can serve as a prototype 58 * layer. Since it provides all necessary layer framework, 59 * new filesystem layers can be created very easily be starting 60 * with a null layer. 61 * 62 * The remainder of this man page examines the null layer as a basis 63 * for constructing new layers. 64 * 65 * 66 * INSTANTIATING NEW NULL LAYERS 67 * 68 * New null layers are created with mount_nullfs(8). 69 * Mount_nullfs(8) takes two arguments, the pathname 70 * of the lower vfs (target-pn) and the pathname where the null 71 * layer will appear in the namespace (alias-pn). After 72 * the null layer is put into place, the contents 73 * of target-pn subtree will be aliased under alias-pn. 74 * 75 * 76 * OPERATION OF A NULL LAYER 77 * 78 * The null layer is the minimum filesystem layer, 79 * simply bypassing all possible operations to the lower layer 80 * for processing there. The majority of its activity centers 81 * on the bypass routine, through which nearly all vnode operations 82 * pass. 83 * 84 * The bypass routine accepts arbitrary vnode operations for 85 * handling by the lower layer. It begins by examing vnode 86 * operation arguments and replacing any null-nodes by their 87 * lower-layer equivlants. It then invokes the operation 88 * on the lower layer. Finally, it replaces the null-nodes 89 * in the arguments and, if a vnode is return by the operation, 90 * stacks a null-node on top of the returned vnode. 91 * 92 * Although bypass handles most operations, vop_getattr, vop_lock, 93 * vop_unlock, vop_inactive, vop_reclaim, and vop_print are not 94 * bypassed. Vop_getattr must change the fsid being returned. 95 * Vop_lock and vop_unlock must handle any locking for the 96 * current vnode as well as pass the lock request down. 97 * Vop_inactive and vop_reclaim are not bypassed so that 98 * they can handle freeing null-layer specific data. Vop_print 99 * is not bypassed to avoid excessive debugging information. 100 * Also, certain vnode operations change the locking state within 101 * the operation (create, mknod, remove, link, rename, mkdir, rmdir, 102 * and symlink). Ideally these operations should not change the 103 * lock state, but should be changed to let the caller of the 104 * function unlock them. Otherwise all intermediate vnode layers 105 * (such as union, umapfs, etc) must catch these functions to do 106 * the necessary locking at their layer. 107 * 108 * 109 * INSTANTIATING VNODE STACKS 110 * 111 * Mounting associates the null layer with a lower layer, 112 * effect stacking two VFSes. Vnode stacks are instead 113 * created on demand as files are accessed. 114 * 115 * The initial mount creates a single vnode stack for the 116 * root of the new null layer. All other vnode stacks 117 * are created as a result of vnode operations on 118 * this or other null vnode stacks. 119 * 120 * New vnode stacks come into existance as a result of 121 * an operation which returns a vnode. 122 * The bypass routine stacks a null-node above the new 123 * vnode before returning it to the caller. 124 * 125 * For example, imagine mounting a null layer with 126 * "mount_nullfs /usr/include /dev/layer/null". 127 * Changing directory to /dev/layer/null will assign 128 * the root null-node (which was created when the null layer was mounted). 129 * Now consider opening "sys". A vop_lookup would be 130 * done on the root null-node. This operation would bypass through 131 * to the lower layer which would return a vnode representing 132 * the UFS "sys". Null_bypass then builds a null-node 133 * aliasing the UFS "sys" and returns this to the caller. 134 * Later operations on the null-node "sys" will repeat this 135 * process when constructing other vnode stacks. 136 * 137 * 138 * CREATING OTHER FILE SYSTEM LAYERS 139 * 140 * One of the easiest ways to construct new filesystem layers is to make 141 * a copy of the null layer, rename all files and variables, and 142 * then begin modifing the copy. Sed can be used to easily rename 143 * all variables. 144 * 145 * The umap layer is an example of a layer descended from the 146 * null layer. 147 * 148 * 149 * INVOKING OPERATIONS ON LOWER LAYERS 150 * 151 * There are two techniques to invoke operations on a lower layer 152 * when the operation cannot be completely bypassed. Each method 153 * is appropriate in different situations. In both cases, 154 * it is the responsibility of the aliasing layer to make 155 * the operation arguments "correct" for the lower layer 156 * by mapping a vnode arguments to the lower layer. 157 * 158 * The first approach is to call the aliasing layer's bypass routine. 159 * This method is most suitable when you wish to invoke the operation 160 * currently being handled on the lower layer. It has the advantage 161 * that the bypass routine already must do argument mapping. 162 * An example of this is null_getattrs in the null layer. 163 * 164 * A second approach is to directly invoke vnode operations on 165 * the lower layer with the VOP_OPERATIONNAME interface. 166 * The advantage of this method is that it is easy to invoke 167 * arbitrary operations on the lower layer. The disadvantage 168 * is that vnode arguments must be manualy mapped. 169 * 170 */ 171 172 #include <sys/param.h> 173 #include <sys/systm.h> 174 #include <sys/conf.h> 175 #include <sys/kernel.h> 176 #include <sys/lock.h> 177 #include <sys/malloc.h> 178 #include <sys/mount.h> 179 #include <sys/mutex.h> 180 #include <sys/namei.h> 181 #include <sys/sysctl.h> 182 #include <sys/vnode.h> 183 184 #include <fs/nullfs/null.h> 185 186 #include <vm/vm.h> 187 #include <vm/vm_extern.h> 188 #include <vm/vm_object.h> 189 #include <vm/vnode_pager.h> 190 191 static int null_bug_bypass = 0; /* for debugging: enables bypass printf'ing */ 192 SYSCTL_INT(_debug, OID_AUTO, nullfs_bug_bypass, CTLFLAG_RW, 193 &null_bug_bypass, 0, ""); 194 195 /* 196 * This is the 10-Apr-92 bypass routine. 197 * This version has been optimized for speed, throwing away some 198 * safety checks. It should still always work, but it's not as 199 * robust to programmer errors. 200 * 201 * In general, we map all vnodes going down and unmap them on the way back. 202 * As an exception to this, vnodes can be marked "unmapped" by setting 203 * the Nth bit in operation's vdesc_flags. 204 * 205 * Also, some BSD vnode operations have the side effect of vrele'ing 206 * their arguments. With stacking, the reference counts are held 207 * by the upper node, not the lower one, so we must handle these 208 * side-effects here. This is not of concern in Sun-derived systems 209 * since there are no such side-effects. 210 * 211 * This makes the following assumptions: 212 * - only one returned vpp 213 * - no INOUT vpp's (Sun's vop_open has one of these) 214 * - the vnode operation vector of the first vnode should be used 215 * to determine what implementation of the op should be invoked 216 * - all mapped vnodes are of our vnode-type (NEEDSWORK: 217 * problems on rmdir'ing mount points and renaming?) 218 */ 219 int 220 null_bypass(struct vop_generic_args *ap) 221 { 222 struct vnode **this_vp_p; 223 int error; 224 struct vnode *old_vps[VDESC_MAX_VPS]; 225 struct vnode **vps_p[VDESC_MAX_VPS]; 226 struct vnode ***vppp; 227 struct vnodeop_desc *descp = ap->a_desc; 228 int reles, i; 229 230 if (null_bug_bypass) 231 printf ("null_bypass: %s\n", descp->vdesc_name); 232 233 #ifdef DIAGNOSTIC 234 /* 235 * We require at least one vp. 236 */ 237 if (descp->vdesc_vp_offsets == NULL || 238 descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET) 239 panic ("null_bypass: no vp's in map"); 240 #endif 241 242 /* 243 * Map the vnodes going in. 244 * Later, we'll invoke the operation based on 245 * the first mapped vnode's operation vector. 246 */ 247 reles = descp->vdesc_flags; 248 for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) { 249 if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET) 250 break; /* bail out at end of list */ 251 vps_p[i] = this_vp_p = 252 VOPARG_OFFSETTO(struct vnode**,descp->vdesc_vp_offsets[i],ap); 253 /* 254 * We're not guaranteed that any but the first vnode 255 * are of our type. Check for and don't map any 256 * that aren't. (We must always map first vp or vclean fails.) 257 */ 258 if (i && (*this_vp_p == NULLVP || 259 (*this_vp_p)->v_op != &null_vnodeops)) { 260 old_vps[i] = NULLVP; 261 } else { 262 old_vps[i] = *this_vp_p; 263 *(vps_p[i]) = NULLVPTOLOWERVP(*this_vp_p); 264 /* 265 * XXX - Several operations have the side effect 266 * of vrele'ing their vp's. We must account for 267 * that. (This should go away in the future.) 268 */ 269 if (reles & VDESC_VP0_WILLRELE) 270 VREF(*this_vp_p); 271 } 272 273 } 274 275 /* 276 * Call the operation on the lower layer 277 * with the modified argument structure. 278 */ 279 if (vps_p[0] && *vps_p[0]) 280 error = VCALL(ap); 281 else { 282 printf("null_bypass: no map for %s\n", descp->vdesc_name); 283 error = EINVAL; 284 } 285 286 /* 287 * Maintain the illusion of call-by-value 288 * by restoring vnodes in the argument structure 289 * to their original value. 290 */ 291 reles = descp->vdesc_flags; 292 for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) { 293 if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET) 294 break; /* bail out at end of list */ 295 if (old_vps[i]) { 296 *(vps_p[i]) = old_vps[i]; 297 #if 0 298 if (reles & VDESC_VP0_WILLUNLOCK) 299 VOP_UNLOCK(*(vps_p[i]), 0); 300 #endif 301 if (reles & VDESC_VP0_WILLRELE) 302 vrele(*(vps_p[i])); 303 } 304 } 305 306 /* 307 * Map the possible out-going vpp 308 * (Assumes that the lower layer always returns 309 * a VREF'ed vpp unless it gets an error.) 310 */ 311 if (descp->vdesc_vpp_offset != VDESC_NO_OFFSET && 312 !(descp->vdesc_flags & VDESC_NOMAP_VPP) && 313 !error) { 314 /* 315 * XXX - even though some ops have vpp returned vp's, 316 * several ops actually vrele this before returning. 317 * We must avoid these ops. 318 * (This should go away when these ops are regularized.) 319 */ 320 if (descp->vdesc_flags & VDESC_VPP_WILLRELE) 321 goto out; 322 vppp = VOPARG_OFFSETTO(struct vnode***, 323 descp->vdesc_vpp_offset,ap); 324 if (*vppp) 325 error = null_nodeget(old_vps[0]->v_mount, **vppp, *vppp); 326 } 327 328 out: 329 return (error); 330 } 331 332 /* 333 * We have to carry on the locking protocol on the null layer vnodes 334 * as we progress through the tree. We also have to enforce read-only 335 * if this layer is mounted read-only. 336 */ 337 static int 338 null_lookup(struct vop_lookup_args *ap) 339 { 340 struct componentname *cnp = ap->a_cnp; 341 struct vnode *dvp = ap->a_dvp; 342 int flags = cnp->cn_flags; 343 struct vnode *vp, *ldvp, *lvp; 344 int error; 345 346 if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) && 347 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 348 return (EROFS); 349 /* 350 * Although it is possible to call null_bypass(), we'll do 351 * a direct call to reduce overhead 352 */ 353 ldvp = NULLVPTOLOWERVP(dvp); 354 vp = lvp = NULL; 355 error = VOP_LOOKUP(ldvp, &lvp, cnp); 356 if (error == EJUSTRETURN && (flags & ISLASTCN) && 357 (dvp->v_mount->mnt_flag & MNT_RDONLY) && 358 (cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME)) 359 error = EROFS; 360 361 if ((error == 0 || error == EJUSTRETURN) && lvp != NULL) { 362 if (ldvp == lvp) { 363 *ap->a_vpp = dvp; 364 VREF(dvp); 365 vrele(lvp); 366 } else { 367 error = null_nodeget(dvp->v_mount, lvp, &vp); 368 if (error) 369 vput(lvp); 370 else 371 *ap->a_vpp = vp; 372 } 373 } 374 return (error); 375 } 376 377 static int 378 null_open(struct vop_open_args *ap) 379 { 380 int retval; 381 struct vnode *vp, *ldvp; 382 383 vp = ap->a_vp; 384 ldvp = NULLVPTOLOWERVP(vp); 385 retval = null_bypass(&ap->a_gen); 386 if (retval == 0) 387 vp->v_object = ldvp->v_object; 388 return (retval); 389 } 390 391 /* 392 * Setattr call. Disallow write attempts if the layer is mounted read-only. 393 */ 394 static int 395 null_setattr(struct vop_setattr_args *ap) 396 { 397 struct vnode *vp = ap->a_vp; 398 struct vattr *vap = ap->a_vap; 399 400 if ((vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL || 401 vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL || 402 vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL) && 403 (vp->v_mount->mnt_flag & MNT_RDONLY)) 404 return (EROFS); 405 if (vap->va_size != VNOVAL) { 406 switch (vp->v_type) { 407 case VDIR: 408 return (EISDIR); 409 case VCHR: 410 case VBLK: 411 case VSOCK: 412 case VFIFO: 413 if (vap->va_flags != VNOVAL) 414 return (EOPNOTSUPP); 415 return (0); 416 case VREG: 417 case VLNK: 418 default: 419 /* 420 * Disallow write attempts if the filesystem is 421 * mounted read-only. 422 */ 423 if (vp->v_mount->mnt_flag & MNT_RDONLY) 424 return (EROFS); 425 } 426 } 427 428 return (null_bypass((struct vop_generic_args *)ap)); 429 } 430 431 /* 432 * We handle getattr only to change the fsid. 433 */ 434 static int 435 null_getattr(struct vop_getattr_args *ap) 436 { 437 int error; 438 439 if ((error = null_bypass((struct vop_generic_args *)ap)) != 0) 440 return (error); 441 442 ap->a_vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0]; 443 return (0); 444 } 445 446 /* 447 * Handle to disallow write access if mounted read-only. 448 */ 449 static int 450 null_access(struct vop_access_args *ap) 451 { 452 struct vnode *vp = ap->a_vp; 453 accmode_t accmode = ap->a_accmode; 454 455 /* 456 * Disallow write attempts on read-only layers; 457 * unless the file is a socket, fifo, or a block or 458 * character device resident on the filesystem. 459 */ 460 if (accmode & VWRITE) { 461 switch (vp->v_type) { 462 case VDIR: 463 case VLNK: 464 case VREG: 465 if (vp->v_mount->mnt_flag & MNT_RDONLY) 466 return (EROFS); 467 break; 468 default: 469 break; 470 } 471 } 472 return (null_bypass((struct vop_generic_args *)ap)); 473 } 474 475 /* 476 * We handle this to eliminate null FS to lower FS 477 * file moving. Don't know why we don't allow this, 478 * possibly we should. 479 */ 480 static int 481 null_rename(struct vop_rename_args *ap) 482 { 483 struct vnode *tdvp = ap->a_tdvp; 484 struct vnode *fvp = ap->a_fvp; 485 struct vnode *fdvp = ap->a_fdvp; 486 struct vnode *tvp = ap->a_tvp; 487 488 /* Check for cross-device rename. */ 489 if ((fvp->v_mount != tdvp->v_mount) || 490 (tvp && (fvp->v_mount != tvp->v_mount))) { 491 if (tdvp == tvp) 492 vrele(tdvp); 493 else 494 vput(tdvp); 495 if (tvp) 496 vput(tvp); 497 vrele(fdvp); 498 vrele(fvp); 499 return (EXDEV); 500 } 501 502 return (null_bypass((struct vop_generic_args *)ap)); 503 } 504 505 /* 506 * We need to process our own vnode lock and then clear the 507 * interlock flag as it applies only to our vnode, not the 508 * vnodes below us on the stack. 509 */ 510 static int 511 null_lock(struct vop_lock1_args *ap) 512 { 513 struct vnode *vp = ap->a_vp; 514 int flags = ap->a_flags; 515 struct null_node *nn; 516 struct vnode *lvp; 517 int error; 518 519 520 if ((flags & LK_INTERLOCK) == 0) { 521 VI_LOCK(vp); 522 ap->a_flags = flags |= LK_INTERLOCK; 523 } 524 nn = VTONULL(vp); 525 /* 526 * If we're still active we must ask the lower layer to 527 * lock as ffs has special lock considerations in it's 528 * vop lock. 529 */ 530 if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) { 531 VI_LOCK_FLAGS(lvp, MTX_DUPOK); 532 VI_UNLOCK(vp); 533 /* 534 * We have to hold the vnode here to solve a potential 535 * reclaim race. If we're forcibly vgone'd while we 536 * still have refs, a thread could be sleeping inside 537 * the lowervp's vop_lock routine. When we vgone we will 538 * drop our last ref to the lowervp, which would allow it 539 * to be reclaimed. The lowervp could then be recycled, 540 * in which case it is not legal to be sleeping in it's VOP. 541 * We prevent it from being recycled by holding the vnode 542 * here. 543 */ 544 vholdl(lvp); 545 error = VOP_LOCK(lvp, flags); 546 547 /* 548 * We might have slept to get the lock and someone might have 549 * clean our vnode already, switching vnode lock from one in 550 * lowervp to v_lock in our own vnode structure. Handle this 551 * case by reacquiring correct lock in requested mode. 552 */ 553 if (VTONULL(vp) == NULL && error == 0) { 554 ap->a_flags &= ~(LK_TYPE_MASK | LK_INTERLOCK); 555 switch (flags & LK_TYPE_MASK) { 556 case LK_SHARED: 557 ap->a_flags |= LK_SHARED; 558 break; 559 case LK_UPGRADE: 560 case LK_EXCLUSIVE: 561 ap->a_flags |= LK_EXCLUSIVE; 562 break; 563 default: 564 panic("Unsupported lock request %d\n", 565 ap->a_flags); 566 } 567 VOP_UNLOCK(lvp, 0); 568 error = vop_stdlock(ap); 569 } 570 vdrop(lvp); 571 } else 572 error = vop_stdlock(ap); 573 574 return (error); 575 } 576 577 /* 578 * We need to process our own vnode unlock and then clear the 579 * interlock flag as it applies only to our vnode, not the 580 * vnodes below us on the stack. 581 */ 582 static int 583 null_unlock(struct vop_unlock_args *ap) 584 { 585 struct vnode *vp = ap->a_vp; 586 int flags = ap->a_flags; 587 int mtxlkflag = 0; 588 struct null_node *nn; 589 struct vnode *lvp; 590 int error; 591 592 if ((flags & LK_INTERLOCK) != 0) 593 mtxlkflag = 1; 594 else if (mtx_owned(VI_MTX(vp)) == 0) { 595 VI_LOCK(vp); 596 mtxlkflag = 2; 597 } 598 nn = VTONULL(vp); 599 if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) { 600 VI_LOCK_FLAGS(lvp, MTX_DUPOK); 601 flags |= LK_INTERLOCK; 602 vholdl(lvp); 603 VI_UNLOCK(vp); 604 error = VOP_UNLOCK(lvp, flags); 605 vdrop(lvp); 606 if (mtxlkflag == 0) 607 VI_LOCK(vp); 608 } else { 609 if (mtxlkflag == 2) 610 VI_UNLOCK(vp); 611 error = vop_stdunlock(ap); 612 } 613 614 return (error); 615 } 616 617 static int 618 null_islocked(struct vop_islocked_args *ap) 619 { 620 struct vnode *vp = ap->a_vp; 621 622 return (lockstatus(vp->v_vnlock)); 623 } 624 625 /* 626 * There is no way to tell that someone issued remove/rmdir operation 627 * on the underlying filesystem. For now we just have to release lowervp 628 * as soon as possible. 629 * 630 * Note, we can't release any resources nor remove vnode from hash before 631 * appropriate VXLOCK stuff is is done because other process can find this 632 * vnode in hash during inactivation and may be sitting in vget() and waiting 633 * for null_inactive to unlock vnode. Thus we will do all those in VOP_RECLAIM. 634 */ 635 static int 636 null_inactive(struct vop_inactive_args *ap) 637 { 638 struct vnode *vp = ap->a_vp; 639 struct thread *td = ap->a_td; 640 641 vp->v_object = NULL; 642 643 /* 644 * If this is the last reference, then free up the vnode 645 * so as not to tie up the lower vnodes. 646 */ 647 vrecycle(vp, td); 648 649 return (0); 650 } 651 652 /* 653 * Now, the VXLOCK is in force and we're free to destroy the null vnode. 654 */ 655 static int 656 null_reclaim(struct vop_reclaim_args *ap) 657 { 658 struct vnode *vp = ap->a_vp; 659 struct null_node *xp = VTONULL(vp); 660 struct vnode *lowervp = xp->null_lowervp; 661 662 if (lowervp) 663 null_hashrem(xp); 664 /* 665 * Use the interlock to protect the clearing of v_data to 666 * prevent faults in null_lock(). 667 */ 668 VI_LOCK(vp); 669 vp->v_data = NULL; 670 vp->v_object = NULL; 671 vp->v_vnlock = &vp->v_lock; 672 if (lowervp) { 673 lockmgr(vp->v_vnlock, LK_EXCLUSIVE | LK_INTERLOCK, VI_MTX(vp)); 674 vput(lowervp); 675 } else 676 panic("null_reclaim: reclaiming a node with no lowervp"); 677 free(xp, M_NULLFSNODE); 678 679 return (0); 680 } 681 682 static int 683 null_print(struct vop_print_args *ap) 684 { 685 struct vnode *vp = ap->a_vp; 686 687 printf("\tvp=%p, lowervp=%p\n", vp, NULLVPTOLOWERVP(vp)); 688 return (0); 689 } 690 691 /* ARGSUSED */ 692 static int 693 null_getwritemount(struct vop_getwritemount_args *ap) 694 { 695 struct null_node *xp; 696 struct vnode *lowervp; 697 struct vnode *vp; 698 699 vp = ap->a_vp; 700 VI_LOCK(vp); 701 xp = VTONULL(vp); 702 if (xp && (lowervp = xp->null_lowervp)) { 703 VI_LOCK_FLAGS(lowervp, MTX_DUPOK); 704 VI_UNLOCK(vp); 705 vholdl(lowervp); 706 VI_UNLOCK(lowervp); 707 VOP_GETWRITEMOUNT(lowervp, ap->a_mpp); 708 vdrop(lowervp); 709 } else { 710 VI_UNLOCK(vp); 711 *(ap->a_mpp) = NULL; 712 } 713 return (0); 714 } 715 716 static int 717 null_vptofh(struct vop_vptofh_args *ap) 718 { 719 struct vnode *lvp; 720 721 lvp = NULLVPTOLOWERVP(ap->a_vp); 722 return VOP_VPTOFH(lvp, ap->a_fhp); 723 } 724 725 /* 726 * Global vfs data structures 727 */ 728 struct vop_vector null_vnodeops = { 729 .vop_bypass = null_bypass, 730 .vop_access = null_access, 731 .vop_bmap = VOP_EOPNOTSUPP, 732 .vop_getattr = null_getattr, 733 .vop_getwritemount = null_getwritemount, 734 .vop_inactive = null_inactive, 735 .vop_islocked = null_islocked, 736 .vop_lock1 = null_lock, 737 .vop_lookup = null_lookup, 738 .vop_open = null_open, 739 .vop_print = null_print, 740 .vop_reclaim = null_reclaim, 741 .vop_rename = null_rename, 742 .vop_setattr = null_setattr, 743 .vop_strategy = VOP_EOPNOTSUPP, 744 .vop_unlock = null_unlock, 745 .vop_vptofh = null_vptofh, 746 }; 747