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 *
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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#include <sys/kdb.h> 184 185#include <fs/nullfs/null.h> 186 187#include <vm/vm.h> 188#include <vm/vm_extern.h> 189#include <vm/vm_object.h> 190#include <vm/vnode_pager.h> 191 192static int null_bug_bypass = 0; /* for debugging: enables bypass printf'ing */ 193SYSCTL_INT(_debug, OID_AUTO, nullfs_bug_bypass, CTLFLAG_RW, 194 &null_bug_bypass, 0, ""); 195 196/* 197 * This is the 10-Apr-92 bypass routine. 198 * This version has been optimized for speed, throwing away some 199 * safety checks. It should still always work, but it's not as 200 * robust to programmer errors. 201 * 202 * In general, we map all vnodes going down and unmap them on the way back. 203 * As an exception to this, vnodes can be marked "unmapped" by setting 204 * the Nth bit in operation's vdesc_flags. 205 * 206 * Also, some BSD vnode operations have the side effect of vrele'ing 207 * their arguments. With stacking, the reference counts are held 208 * by the upper node, not the lower one, so we must handle these 209 * side-effects here. This is not of concern in Sun-derived systems 210 * since there are no such side-effects. 211 * 212 * This makes the following assumptions: 213 * - only one returned vpp 214 * - no INOUT vpp's (Sun's vop_open has one of these) 215 * - the vnode operation vector of the first vnode should be used 216 * to determine what implementation of the op should be invoked 217 * - all mapped vnodes are of our vnode-type (NEEDSWORK: 218 * problems on rmdir'ing mount points and renaming?) 219 */ 220int 221null_bypass(struct vop_generic_args *ap) 222{ 223 struct vnode **this_vp_p; 224 int error; 225 struct vnode *old_vps[VDESC_MAX_VPS]; 226 struct vnode **vps_p[VDESC_MAX_VPS]; 227 struct vnode ***vppp; 228 struct vnodeop_desc *descp = ap->a_desc; 229 int reles, i; 230 231 if (null_bug_bypass) 232 printf ("null_bypass: %s\n", descp->vdesc_name); 233 234#ifdef DIAGNOSTIC 235 /* 236 * We require at least one vp. 237 */ 238 if (descp->vdesc_vp_offsets == NULL || 239 descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET) 240 panic ("null_bypass: no vp's in map"); 241#endif 242 243 /* 244 * Map the vnodes going in. 245 * Later, we'll invoke the operation based on 246 * the first mapped vnode's operation vector. 247 */ 248 reles = descp->vdesc_flags; 249 for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) { 250 if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET) 251 break; /* bail out at end of list */ 252 vps_p[i] = this_vp_p = 253 VOPARG_OFFSETTO(struct vnode**,descp->vdesc_vp_offsets[i],ap); 254 /* 255 * We're not guaranteed that any but the first vnode 256 * are of our type. Check for and don't map any 257 * that aren't. (We must always map first vp or vclean fails.) 258 */ 259 if (i && (*this_vp_p == NULLVP || 260 (*this_vp_p)->v_op != &null_vnodeops)) { 261 old_vps[i] = NULLVP; 262 } else { 263 old_vps[i] = *this_vp_p; 264 *(vps_p[i]) = NULLVPTOLOWERVP(*this_vp_p); 265 /* 266 * XXX - Several operations have the side effect 267 * of vrele'ing their vp's. We must account for 268 * that. (This should go away in the future.) 269 */ 270 if (reles & VDESC_VP0_WILLRELE) 271 VREF(*this_vp_p); 272 } 273 274 } 275 276 /* 277 * Call the operation on the lower layer 278 * with the modified argument structure. 279 */ 280 if (vps_p[0] && *vps_p[0]) 281 error = VCALL(ap); 282 else { 283 printf("null_bypass: no map for %s\n", descp->vdesc_name); 284 error = EINVAL; 285 } 286 287 /* 288 * Maintain the illusion of call-by-value 289 * by restoring vnodes in the argument structure 290 * to their original value. 291 */ 292 reles = descp->vdesc_flags; 293 for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) { 294 if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET) 295 break; /* bail out at end of list */ 296 if (old_vps[i]) { 297 *(vps_p[i]) = old_vps[i]; 298#if 0 299 if (reles & VDESC_VP0_WILLUNLOCK) 300 VOP_UNLOCK(*(vps_p[i]), 0, curthread); 301#endif 302 if (reles & VDESC_VP0_WILLRELE) 303 vrele(*(vps_p[i])); 304 } 305 } 306 307 /* 308 * Map the possible out-going vpp 309 * (Assumes that the lower layer always returns 310 * a VREF'ed vpp unless it gets an error.) 311 */ 312 if (descp->vdesc_vpp_offset != VDESC_NO_OFFSET && 313 !(descp->vdesc_flags & VDESC_NOMAP_VPP) && 314 !error) { 315 /* 316 * XXX - even though some ops have vpp returned vp's, 317 * several ops actually vrele this before returning. 318 * We must avoid these ops. 319 * (This should go away when these ops are regularized.) 320 */ 321 if (descp->vdesc_flags & VDESC_VPP_WILLRELE) 322 goto out; 323 vppp = VOPARG_OFFSETTO(struct vnode***, 324 descp->vdesc_vpp_offset,ap); 325 if (*vppp) 326 error = null_nodeget(old_vps[0]->v_mount, **vppp, *vppp); 327 } 328 329 out: 330 return (error); 331} 332 333/* 334 * We have to carry on the locking protocol on the null layer vnodes 335 * as we progress through the tree. We also have to enforce read-only 336 * if this layer is mounted read-only. 337 */ 338static int 339null_lookup(struct vop_lookup_args *ap) 340{ 341 struct componentname *cnp = ap->a_cnp; 342 struct vnode *dvp = ap->a_dvp; 343 int flags = cnp->cn_flags; 344 struct vnode *vp, *ldvp, *lvp; 345 int error; 346 347 if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) && 348 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 349 return (EROFS); 350 /* 351 * Although it is possible to call null_bypass(), we'll do 352 * a direct call to reduce overhead 353 */ 354 ldvp = NULLVPTOLOWERVP(dvp); 355 vp = lvp = NULL; 356 error = VOP_LOOKUP(ldvp, &lvp, cnp); 357 if (error == EJUSTRETURN && (flags & ISLASTCN) && 358 (dvp->v_mount->mnt_flag & MNT_RDONLY) && 359 (cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME)) 360 error = EROFS; 361 362 if ((error == 0 || error == EJUSTRETURN) && lvp != NULL) { 363 if (ldvp == lvp) { 364 *ap->a_vpp = dvp; 365 VREF(dvp); 366 vrele(lvp); 367 } else { 368 error = null_nodeget(dvp->v_mount, lvp, &vp); 369 if (error) { 370 /* XXX Cleanup needed... */ 371 panic("null_nodeget failed"); 372 } 373 *ap->a_vpp = vp; 374 } 375 } 376 return (error); 377} 378 379static int 380null_open(struct vop_open_args *ap) 381{ 382 int retval; 383 struct vnode *vp, *ldvp; 384 385 vp = ap->a_vp; 386 ldvp = NULLVPTOLOWERVP(vp); 387 retval = null_bypass(&ap->a_gen); 388 if (retval == 0) 389 vp->v_object = ldvp->v_object; 390 return (retval); 391} 392 393/* 394 * Setattr call. Disallow write attempts if the layer is mounted read-only. 395 */ 396static int 397null_setattr(struct vop_setattr_args *ap) 398{ 399 struct vnode *vp = ap->a_vp; 400 struct vattr *vap = ap->a_vap; 401 402 if ((vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL || 403 vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL || 404 vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL) && 405 (vp->v_mount->mnt_flag & MNT_RDONLY)) 406 return (EROFS); 407 if (vap->va_size != VNOVAL) { 408 switch (vp->v_type) { 409 case VDIR: 410 return (EISDIR); 411 case VCHR: 412 case VBLK: 413 case VSOCK: 414 case VFIFO: 415 if (vap->va_flags != VNOVAL) 416 return (EOPNOTSUPP); 417 return (0); 418 case VREG: 419 case VLNK: 420 default: 421 /* 422 * Disallow write attempts if the filesystem is 423 * mounted read-only. 424 */ 425 if (vp->v_mount->mnt_flag & MNT_RDONLY) 426 return (EROFS); 427 } 428 } 429 430 return (null_bypass((struct vop_generic_args *)ap)); 431} 432 433/* 434 * We handle getattr only to change the fsid. 435 */ 436static int 437null_getattr(struct vop_getattr_args *ap) 438{ 439 int error; 440 441 if ((error = null_bypass((struct vop_generic_args *)ap)) != 0) 442 return (error); 443 444 ap->a_vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0]; 445 return (0); 446} 447 448/* 449 * Handle to disallow write access if mounted read-only. 450 */ 451static int 452null_access(struct vop_access_args *ap) 453{ 454 struct vnode *vp = ap->a_vp; 455 mode_t mode = ap->a_mode; 456 457 /* 458 * Disallow write attempts on read-only layers; 459 * unless the file is a socket, fifo, or a block or 460 * character device resident on the filesystem. 461 */ 462 if (mode & VWRITE) { 463 switch (vp->v_type) { 464 case VDIR: 465 case VLNK: 466 case VREG: 467 if (vp->v_mount->mnt_flag & MNT_RDONLY) 468 return (EROFS); 469 break; 470 default: 471 break; 472 } 473 } 474 return (null_bypass((struct vop_generic_args *)ap)); 475} 476 477/* 478 * We handle this to eliminate null FS to lower FS 479 * file moving. Don't know why we don't allow this, 480 * possibly we should. 481 */ 482static int 483null_rename(struct vop_rename_args *ap) 484{ 485 struct vnode *tdvp = ap->a_tdvp; 486 struct vnode *fvp = ap->a_fvp; 487 struct vnode *fdvp = ap->a_fdvp; 488 struct vnode *tvp = ap->a_tvp; 489 490 /* Check for cross-device rename. */ 491 if ((fvp->v_mount != tdvp->v_mount) || 492 (tvp && (fvp->v_mount != tvp->v_mount))) { 493 if (tdvp == tvp) 494 vrele(tdvp); 495 else 496 vput(tdvp); 497 if (tvp) 498 vput(tvp); 499 vrele(fdvp); 500 vrele(fvp); 501 return (EXDEV); 502 } 503 504 return (null_bypass((struct vop_generic_args *)ap)); 505} 506 507/* 508 * We need to process our own vnode lock and then clear the 509 * interlock flag as it applies only to our vnode, not the 510 * vnodes below us on the stack. 511 */ 512static int 513null_lock(struct _vop_lock_args *ap) 514{ 515 struct vnode *vp = ap->a_vp; 516 int flags = ap->a_flags; 517 struct thread *td = ap->a_td; 518 struct null_node *nn; 519 struct vnode *lvp; 520 int error; 521 522 523 if ((flags & LK_INTERLOCK) == 0) { 524 VI_LOCK(vp); 525 ap->a_flags = flags |= LK_INTERLOCK; 526 } 527 nn = VTONULL(vp); 528 /* 529 * If we're still active we must ask the lower layer to 530 * lock as ffs has special lock considerations in it's 531 * vop lock. 532 */ 533 if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) { 534 VI_LOCK_FLAGS(lvp, MTX_DUPOK); 535 VI_UNLOCK(vp); 536 /* 537 * We have to hold the vnode here to solve a potential 538 * reclaim race. If we're forcibly vgone'd while we 539 * still have refs, a thread could be sleeping inside 540 * the lowervp's vop_lock routine. When we vgone we will 541 * drop our last ref to the lowervp, which would allow it 542 * to be reclaimed. The lowervp could then be recycled, 543 * in which case it is not legal to be sleeping in it's VOP. 544 * We prevent it from being recycled by holding the vnode 545 * here. 546 */ 547 vholdl(lvp); 548 error = VOP_LOCK(lvp, flags, td); 549 550 /* 551 * We might have slept to get the lock and someone might have 552 * clean our vnode already, switching vnode lock from one in 553 * lowervp to v_lock in our own vnode structure. Handle this 554 * case by reacquiring correct lock in requested mode. 555 */ 556 if (VTONULL(vp) == NULL && error == 0) { 557 ap->a_flags &= ~(LK_TYPE_MASK | LK_INTERLOCK); 558 switch (flags & LK_TYPE_MASK) { 559 case LK_SHARED: 560 ap->a_flags |= LK_SHARED; 561 break; 562 case LK_UPGRADE: 563 case LK_EXCLUSIVE: 564 ap->a_flags |= LK_EXCLUSIVE; 565 break; 566 default: 567 panic("Unsupported lock request %d\n", 568 ap->a_flags); 569 } 570 VOP_UNLOCK(lvp, 0, td); 571 error = vop_stdlock(ap); 572 } 573 vdrop(lvp); 574 } else 575 error = vop_stdlock(ap); 576 577 return (error); 578} 579 580/* 581 * We need to process our own vnode unlock and then clear the 582 * interlock flag as it applies only to our vnode, not the 583 * vnodes below us on the stack. 584 */ 585static int 586null_unlock(struct vop_unlock_args *ap) 587{ 588 struct vnode *vp = ap->a_vp; 589 int flags = ap->a_flags; 590 struct thread *td = ap->a_td; 591 struct null_node *nn; 592 struct vnode *lvp; 593 int error; 594 595 if ((flags & LK_INTERLOCK) != 0) { 596 VI_UNLOCK(vp); 597 ap->a_flags = flags &= ~LK_INTERLOCK; 598 } 599 nn = VTONULL(vp); 600 if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) 601 error = VOP_UNLOCK(lvp, flags, td); 602 else 603 error = vop_stdunlock(ap); 604 605 return (error); 606} 607 608static int 609null_islocked(struct vop_islocked_args *ap) 610{ 611 struct vnode *vp = ap->a_vp; 612 struct thread *td = ap->a_td; 613 614 return (lockstatus(vp->v_vnlock, td)); 615} 616 617/* 618 * There is no way to tell that someone issued remove/rmdir operation 619 * on the underlying filesystem. For now we just have to release lowevrp 620 * as soon as possible. 621 * 622 * Note, we can't release any resources nor remove vnode from hash before 623 * appropriate VXLOCK stuff is is done because other process can find this 624 * vnode in hash during inactivation and may be sitting in vget() and waiting 625 * for null_inactive to unlock vnode. Thus we will do all those in VOP_RECLAIM. 626 */ 627static int 628null_inactive(struct vop_inactive_args *ap) 629{ 630 struct vnode *vp = ap->a_vp; 631 struct thread *td = ap->a_td; 632 633 vp->v_object = NULL; 634 635 /* 636 * If this is the last reference, then free up the vnode 637 * so as not to tie up the lower vnodes. 638 */ 639 vrecycle(vp, td); 640 641 return (0); 642} 643 644/* 645 * Now, the VXLOCK is in force and we're free to destroy the null vnode. 646 */ 647static int 648null_reclaim(struct vop_reclaim_args *ap) 649{ 650 struct vnode *vp = ap->a_vp; 651 struct null_node *xp = VTONULL(vp); 652 struct vnode *lowervp = xp->null_lowervp; 653 struct lock *vnlock; 654 655 if (lowervp) 656 null_hashrem(xp); 657 /* 658 * Use the interlock to protect the clearing of v_data to 659 * prevent faults in null_lock(). 660 */ 661 VI_LOCK(vp); 662 vp->v_data = NULL; 663 vp->v_object = NULL; 664 vnlock = vp->v_vnlock; 665 vp->v_vnlock = &vp->v_lock; 666 if (lowervp) { 667 lockmgr(vp->v_vnlock, 668 LK_EXCLUSIVE|LK_INTERLOCK, VI_MTX(vp), curthread); 669 vput(lowervp); 670 } else 671 panic("null_reclaim: reclaiming an node with now lowervp"); 672 FREE(xp, M_NULLFSNODE); 673 674 return (0); 675} 676 677static int 678null_print(struct vop_print_args *ap) 679{ 680 struct vnode *vp = ap->a_vp; 681 682 printf("\tvp=%p, lowervp=%p\n", vp, NULLVPTOLOWERVP(vp)); 683 return (0); 684} 685 686/* ARGSUSED */ 687static int 688null_getwritemount(struct vop_getwritemount_args *ap) 689{ 690 struct null_node *xp; 691 struct vnode *lowervp; 692 struct vnode *vp; 693 694 vp = ap->a_vp; 695 VI_LOCK(vp); 696 xp = VTONULL(vp); 697 if (xp && (lowervp = xp->null_lowervp)) { 698 VI_LOCK_FLAGS(lowervp, MTX_DUPOK); 699 VI_UNLOCK(vp); 700 vholdl(lowervp); 701 VI_UNLOCK(lowervp); 702 VOP_GETWRITEMOUNT(lowervp, ap->a_mpp); 703 vdrop(lowervp); 704 } else { 705 VI_UNLOCK(vp); 706 *(ap->a_mpp) = NULL; 707 } 708 return (0); 709} 710
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