sys/vm/vnode_pager.c

   1 /*-
   2  * Copyright (c) 1990 University of Utah.
   3  * Copyright (c) 1991 The Regents of the University of California.
   4  * All rights reserved.
   5  * Copyright (c) 1993, 1994 John S. Dyson
   6  * Copyright (c) 1995, David Greenman
   7  *
   8  * This code is derived from software contributed to Berkeley by
   9  * the Systems Programming Group of the University of Utah Computer
  10  * Science Department.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. All advertising materials mentioning features or use of this software
  21  *    must display the following acknowledgement:
  22  *      This product includes software developed by the University of
  23  *      California, Berkeley and its contributors.
  24  * 4. Neither the name of the University nor the names of its contributors
  25  *    may be used to endorse or promote products derived from this software
  26  *    without specific prior written permission.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  38  * SUCH DAMAGE.
  39  *
  40  *      from: @(#)vnode_pager.c 7.5 (Berkeley) 4/20/91
  41  */
  42
  43 /*
  44  * Page to/from files (vnodes).
  45  */
  46
  47 /*
  48  * TODO:
  49  *      Implement VOP_GETPAGES/PUTPAGES interface for filesystems. Will
  50  *      greatly re-simplify the vnode_pager.
  51  */
  52
  53 #include <sys/cdefs.h>
  54 __FBSDID("$FreeBSD$");
  55
  56 #include <sys/param.h>
  57 #include <sys/systm.h>
  58 #include <sys/proc.h>
  59 #include <sys/vnode.h>
  60 #include <sys/mount.h>
  61 #include <sys/bio.h>
  62 #include <sys/buf.h>
  63 #include <sys/vmmeter.h>
  64 #include <sys/limits.h>
  65 #include <sys/conf.h>
  66 #include <sys/rwlock.h>
  67 #include <sys/sf_buf.h>
  68
  69 #include <machine/atomic.h>
  70
  71 #include <vm/vm.h>
  72 #include <vm/vm_param.h>
  73 #include <vm/vm_object.h>
  74 #include <vm/vm_page.h>
  75 #include <vm/vm_pager.h>
  76 #include <vm/vm_map.h>
  77 #include <vm/vnode_pager.h>
  78 #include <vm/vm_extern.h>
  79
  80 static int vnode_pager_addr(struct vnode *vp, vm_ooffset_t address,
  81     daddr_t *rtaddress, int *run);
  82 static int vnode_pager_input_smlfs(vm_object_t object, vm_page_t m);
  83 static int vnode_pager_input_old(vm_object_t object, vm_page_t m);
  84 static void vnode_pager_dealloc(vm_object_t);
  85 static int vnode_pager_getpages(vm_object_t, vm_page_t *, int, int);
  86 static void vnode_pager_putpages(vm_object_t, vm_page_t *, int, boolean_t, int *);
  87 static boolean_t vnode_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
  88 static vm_object_t vnode_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
  89     vm_ooffset_t, struct ucred *cred);
  90
  91 struct pagerops vnodepagerops = {
  92         .pgo_alloc =    vnode_pager_alloc,
  93         .pgo_dealloc =  vnode_pager_dealloc,
  94         .pgo_getpages = vnode_pager_getpages,
  95         .pgo_putpages = vnode_pager_putpages,
  96         .pgo_haspage =  vnode_pager_haspage,
  97 };
  98
  99 int vnode_pbuf_freecnt;
 100
 101 /* Create the VM system backing object for this vnode */
 102 int
 103 vnode_create_vobject(struct vnode *vp, off_t isize, struct thread *td)
 104 {
 105         vm_object_t object;
 106         vm_ooffset_t size = isize;
 107         struct vattr va;
 108
 109         if (!vn_isdisk(vp, NULL) && vn_canvmio(vp) == FALSE)
 110                 return (0);
 111
 112         while ((object = vp->v_object) != NULL) {
 113                 VM_OBJECT_WLOCK(object);
 114                 if (!(object->flags & OBJ_DEAD)) {
 115                         VM_OBJECT_WUNLOCK(object);
 116                         return (0);
 117                 }
 118                 VOP_UNLOCK(vp, 0);
 119                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
 120                 VM_OBJECT_SLEEP(object, object, PDROP | PVM, "vodead", 0);
 121                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 122         }
 123
 124         if (size == 0) {
 125                 if (vn_isdisk(vp, NULL)) {
 126                         size = IDX_TO_OFF(INT_MAX);
 127                 } else {
 128                         if (VOP_GETATTR(vp, &va, td->td_ucred))
 129                                 return (0);
 130                         size = va.va_size;
 131                 }
 132         }
 133
 134         object = vnode_pager_alloc(vp, size, 0, 0, td->td_ucred);
 135         /*
 136          * Dereference the reference we just created.  This assumes
 137          * that the object is associated with the vp.
 138          */
 139         VM_OBJECT_WLOCK(object);
 140         object->ref_count--;
 141         VM_OBJECT_WUNLOCK(object);
 142         vrele(vp);
 143
 144         KASSERT(vp->v_object != NULL, ("vnode_create_vobject: NULL object"));
 145
 146         return (0);
 147 }
 148
 149 void
 150 vnode_destroy_vobject(struct vnode *vp)
 151 {
 152         struct vm_object *obj;
 153
 154         obj = vp->v_object;
 155         if (obj == NULL)
 156                 return;
 157         ASSERT_VOP_ELOCKED(vp, "vnode_destroy_vobject");
 158         VM_OBJECT_WLOCK(obj);
 159         if (obj->ref_count == 0) {
 160                 /*
 161                  * don't double-terminate the object
 162                  */
 163                 if ((obj->flags & OBJ_DEAD) == 0)
 164                         vm_object_terminate(obj);
 165                 else
 166                         VM_OBJECT_WUNLOCK(obj);
 167         } else {
 168                 /*
 169                  * Woe to the process that tries to page now :-).
 170                  */
 171                 vm_pager_deallocate(obj);
 172                 VM_OBJECT_WUNLOCK(obj);
 173         }
 174         vp->v_object = NULL;
 175 }
 176
 177
 178 /*
 179  * Allocate (or lookup) pager for a vnode.
 180  * Handle is a vnode pointer.
 181  *
 182  * MPSAFE
 183  */
 184 vm_object_t
 185 vnode_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
 186     vm_ooffset_t offset, struct ucred *cred)
 187 {
 188         vm_object_t object;
 189         struct vnode *vp;
 190
 191         /*
 192          * Pageout to vnode, no can do yet.
 193          */
 194         if (handle == NULL)
 195                 return (NULL);
 196
 197         vp = (struct vnode *) handle;
 198
 199         /*
 200          * If the object is being terminated, wait for it to
 201          * go away.
 202          */
 203 retry:
 204         while ((object = vp->v_object) != NULL) {
 205                 VM_OBJECT_WLOCK(object);
 206                 if ((object->flags & OBJ_DEAD) == 0)
 207                         break;
 208                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
 209                 VM_OBJECT_SLEEP(object, object, PDROP | PVM, "vadead", 0);
 210         }
 211
 212         KASSERT(vp->v_usecount != 0, ("vnode_pager_alloc: no vnode reference"));
 213
 214         if (object == NULL) {
 215                 /*
 216                  * Add an object of the appropriate size
 217                  */
 218                 object = vm_object_allocate(OBJT_VNODE, OFF_TO_IDX(round_page(size)));
 219
 220                 object->un_pager.vnp.vnp_size = size;
 221                 object->un_pager.vnp.writemappings = 0;
 222
 223                 object->handle = handle;
 224                 VI_LOCK(vp);
 225                 if (vp->v_object != NULL) {
 226                         /*
 227                          * Object has been created while we were sleeping
 228                          */
 229                         VI_UNLOCK(vp);
 230                         vm_object_destroy(object);
 231                         goto retry;
 232                 }
 233                 vp->v_object = object;
 234                 VI_UNLOCK(vp);
 235         } else {
 236                 object->ref_count++;
 237                 VM_OBJECT_WUNLOCK(object);
 238         }
 239         vref(vp);
 240         return (object);
 241 }
 242
 243 /*
 244  *      The object must be locked.
 245  */
 246 static void
 247 vnode_pager_dealloc(object)
 248         vm_object_t object;
 249 {
 250         struct vnode *vp;
 251         int refs;
 252
 253         vp = object->handle;
 254         if (vp == NULL)
 255                 panic("vnode_pager_dealloc: pager already dealloced");
 256
 257         VM_OBJECT_ASSERT_WLOCKED(object);
 258         vm_object_pip_wait(object, "vnpdea");
 259         refs = object->ref_count;
 260
 261         object->handle = NULL;
 262         object->type = OBJT_DEAD;
 263         if (object->flags & OBJ_DISCONNECTWNT) {
 264                 vm_object_clear_flag(object, OBJ_DISCONNECTWNT);
 265                 wakeup(object);
 266         }
 267         ASSERT_VOP_ELOCKED(vp, "vnode_pager_dealloc");
 268         if (object->un_pager.vnp.writemappings > 0) {
 269                 object->un_pager.vnp.writemappings = 0;
 270                 VOP_ADD_WRITECOUNT(vp, -1);
 271                 CTR3(KTR_VFS, "%s: vp %p v_writecount decreased to %d",
 272                     __func__, vp, vp->v_writecount);
 273         }
 274         vp->v_object = NULL;
 275         VOP_UNSET_TEXT(vp);
 276         VM_OBJECT_WUNLOCK(object);
 277         while (refs-- > 0)
 278                 vunref(vp);
 279         VM_OBJECT_WLOCK(object);
 280 }
 281
 282 static boolean_t
 283 vnode_pager_haspage(object, pindex, before, after)
 284         vm_object_t object;
 285         vm_pindex_t pindex;
 286         int *before;
 287         int *after;
 288 {
 289         struct vnode *vp = object->handle;
 290         daddr_t bn;
 291         int err;
 292         daddr_t reqblock;
 293         int poff;
 294         int bsize;
 295         int pagesperblock, blocksperpage;
 296
 297         VM_OBJECT_ASSERT_WLOCKED(object);
 298         /*
 299          * If no vp or vp is doomed or marked transparent to VM, we do not
 300          * have the page.
 301          */
 302         if (vp == NULL || vp->v_iflag & VI_DOOMED)
 303                 return FALSE;
 304         /*
 305          * If the offset is beyond end of file we do
 306          * not have the page.
 307          */
 308         if (IDX_TO_OFF(pindex) >= object->un_pager.vnp.vnp_size)
 309                 return FALSE;
 310
 311         bsize = vp->v_mount->mnt_stat.f_iosize;
 312         pagesperblock = bsize / PAGE_SIZE;
 313         blocksperpage = 0;
 314         if (pagesperblock > 0) {
 315                 reqblock = pindex / pagesperblock;
 316         } else {
 317                 blocksperpage = (PAGE_SIZE / bsize);
 318                 reqblock = pindex * blocksperpage;
 319         }
 320         VM_OBJECT_WUNLOCK(object);
 321         err = VOP_BMAP(vp, reqblock, NULL, &bn, after, before);
 322         VM_OBJECT_WLOCK(object);
 323         if (err)
 324                 return TRUE;
 325         if (bn == -1)
 326                 return FALSE;
 327         if (pagesperblock > 0) {
 328                 poff = pindex - (reqblock * pagesperblock);
 329                 if (before) {
 330                         *before *= pagesperblock;
 331                         *before += poff;
 332                 }
 333                 if (after) {
 334                         int numafter;
 335                         *after *= pagesperblock;
 336                         numafter = pagesperblock - (poff + 1);
 337                         if (IDX_TO_OFF(pindex + numafter) >
 338                             object->un_pager.vnp.vnp_size) {
 339                                 numafter =
 340                                     OFF_TO_IDX(object->un_pager.vnp.vnp_size) -
 341                                     pindex;
 342                         }
 343                         *after += numafter;
 344                 }
 345         } else {
 346                 if (before) {
 347                         *before /= blocksperpage;
 348                 }
 349
 350                 if (after) {
 351                         *after /= blocksperpage;
 352                 }
 353         }
 354         return TRUE;
 355 }
 356
 357 /*
 358  * Lets the VM system know about a change in size for a file.
 359  * We adjust our own internal size and flush any cached pages in
 360  * the associated object that are affected by the size change.
 361  *
 362  * Note: this routine may be invoked as a result of a pager put
 363  * operation (possibly at object termination time), so we must be careful.
 364  */
 365 void
 366 vnode_pager_setsize(vp, nsize)
 367         struct vnode *vp;
 368         vm_ooffset_t nsize;
 369 {
 370         vm_object_t object;
 371         vm_page_t m;
 372         vm_pindex_t nobjsize;
 373
 374         if ((object = vp->v_object) == NULL)
 375                 return;
 376 /*      ASSERT_VOP_ELOCKED(vp, "vnode_pager_setsize and not locked vnode"); */
 377         VM_OBJECT_WLOCK(object);
 378         if (object->type == OBJT_DEAD) {
 379                 VM_OBJECT_WUNLOCK(object);
 380                 return;
 381         }
 382         KASSERT(object->type == OBJT_VNODE,
 383             ("not vnode-backed object %p", object));
 384         if (nsize == object->un_pager.vnp.vnp_size) {
 385                 /*
 386                  * Hasn't changed size
 387                  */
 388                 VM_OBJECT_WUNLOCK(object);
 389                 return;
 390         }
 391         nobjsize = OFF_TO_IDX(nsize + PAGE_MASK);
 392         if (nsize < object->un_pager.vnp.vnp_size) {
 393                 /*
 394                  * File has shrunk. Toss any cached pages beyond the new EOF.
 395                  */
 396                 if (nobjsize < object->size)
 397                         vm_object_page_remove(object, nobjsize, object->size,
 398                             0);
 399                 /*
 400                  * this gets rid of garbage at the end of a page that is now
 401                  * only partially backed by the vnode.
 402                  *
 403                  * XXX for some reason (I don't know yet), if we take a
 404                  * completely invalid page and mark it partially valid
 405                  * it can screw up NFS reads, so we don't allow the case.
 406                  */
 407                 if ((nsize & PAGE_MASK) &&
 408                     (m = vm_page_lookup(object, OFF_TO_IDX(nsize))) != NULL &&
 409                     m->valid != 0) {
 410                         int base = (int)nsize & PAGE_MASK;
 411                         int size = PAGE_SIZE - base;
 412
 413                         /*
 414                          * Clear out partial-page garbage in case
 415                          * the page has been mapped.
 416                          */
 417                         pmap_zero_page_area(m, base, size);
 418
 419                         /*
 420                          * Update the valid bits to reflect the blocks that
 421                          * have been zeroed.  Some of these valid bits may
 422                          * have already been set.
 423                          */
 424                         vm_page_set_valid_range(m, base, size);
 425
 426                         /*
 427                          * Round "base" to the next block boundary so that the
 428                          * dirty bit for a partially zeroed block is not
 429                          * cleared.
 430                          */
 431                         base = roundup2(base, DEV_BSIZE);
 432
 433                         /*
 434                          * Clear out partial-page dirty bits.
 435                          *
 436                          * note that we do not clear out the valid
 437                          * bits.  This would prevent bogus_page
 438                          * replacement from working properly.
 439                          */
 440                         vm_page_clear_dirty(m, base, PAGE_SIZE - base);
 441                 } else if ((nsize & PAGE_MASK) &&
 442                     vm_page_is_cached(object, OFF_TO_IDX(nsize))) {
 443                         vm_page_cache_free(object, OFF_TO_IDX(nsize),
 444                             nobjsize);
 445                 }
 446         }
 447         object->un_pager.vnp.vnp_size = nsize;
 448         object->size = nobjsize;
 449         VM_OBJECT_WUNLOCK(object);
 450 }
 451
 452 /*
 453  * calculate the linear (byte) disk address of specified virtual
 454  * file address
 455  */
 456 static int
 457 vnode_pager_addr(struct vnode *vp, vm_ooffset_t address, daddr_t *rtaddress,
 458     int *run)
 459 {
 460         int bsize;
 461         int err;
 462         daddr_t vblock;
 463         daddr_t voffset;
 464
 465         if (address < 0)
 466                 return -1;
 467
 468         if (vp->v_iflag & VI_DOOMED)
 469                 return -1;
 470
 471         bsize = vp->v_mount->mnt_stat.f_iosize;
 472         vblock = address / bsize;
 473         voffset = address % bsize;
 474
 475         err = VOP_BMAP(vp, vblock, NULL, rtaddress, run, NULL);
 476         if (err == 0) {
 477                 if (*rtaddress != -1)
 478                         *rtaddress += voffset / DEV_BSIZE;
 479                 if (run) {
 480                         *run += 1;
 481                         *run *= bsize/PAGE_SIZE;
 482                         *run -= voffset/PAGE_SIZE;
 483                 }
 484         }
 485
 486         return (err);
 487 }
 488
 489 /*
 490  * small block filesystem vnode pager input
 491  */
 492 static int
 493 vnode_pager_input_smlfs(object, m)
 494         vm_object_t object;
 495         vm_page_t m;
 496 {
 497         struct vnode *vp;
 498         struct bufobj *bo;
 499         struct buf *bp;
 500         struct sf_buf *sf;
 501         daddr_t fileaddr;
 502         vm_offset_t bsize;
 503         vm_page_bits_t bits;
 504         int error, i;
 505
 506         error = 0;
 507         vp = object->handle;
 508         if (vp->v_iflag & VI_DOOMED)
 509                 return VM_PAGER_BAD;
 510
 511         bsize = vp->v_mount->mnt_stat.f_iosize;
 512
 513         VOP_BMAP(vp, 0, &bo, 0, NULL, NULL);
 514
 515         sf = sf_buf_alloc(m, 0);
 516
 517         for (i = 0; i < PAGE_SIZE / bsize; i++) {
 518                 vm_ooffset_t address;
 519
 520                 bits = vm_page_bits(i * bsize, bsize);
 521                 if (m->valid & bits)
 522                         continue;
 523
 524                 address = IDX_TO_OFF(m->pindex) + i * bsize;
 525                 if (address >= object->un_pager.vnp.vnp_size) {
 526                         fileaddr = -1;
 527                 } else {
 528                         error = vnode_pager_addr(vp, address, &fileaddr, NULL);
 529                         if (error)
 530                                 break;
 531                 }
 532                 if (fileaddr != -1) {
 533                         bp = getpbuf(&vnode_pbuf_freecnt);
 534
 535                         /* build a minimal buffer header */
 536                         bp->b_iocmd = BIO_READ;
 537                         bp->b_iodone = bdone;
 538                         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
 539                         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
 540                         bp->b_rcred = crhold(curthread->td_ucred);
 541                         bp->b_wcred = crhold(curthread->td_ucred);
 542                         bp->b_data = (caddr_t)sf_buf_kva(sf) + i * bsize;
 543                         bp->b_blkno = fileaddr;
 544                         pbgetbo(bo, bp);
 545                         bp->b_vp = vp;
 546                         bp->b_bcount = bsize;
 547                         bp->b_bufsize = bsize;
 548                         bp->b_runningbufspace = bp->b_bufsize;
 549                         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
 550
 551                         /* do the input */
 552                         bp->b_iooffset = dbtob(bp->b_blkno);
 553                         bstrategy(bp);
 554
 555                         bwait(bp, PVM, "vnsrd");
 556
 557                         if ((bp->b_ioflags & BIO_ERROR) != 0)
 558                                 error = EIO;
 559
 560                         /*
 561                          * free the buffer header back to the swap buffer pool
 562                          */
 563                         bp->b_vp = NULL;
 564                         pbrelbo(bp);
 565                         relpbuf(bp, &vnode_pbuf_freecnt);
 566                         if (error)
 567                                 break;
 568                 } else
 569                         bzero((caddr_t)sf_buf_kva(sf) + i * bsize, bsize);
 570                 KASSERT((m->dirty & bits) == 0,
 571                     ("vnode_pager_input_smlfs: page %p is dirty", m));
 572                 VM_OBJECT_WLOCK(object);
 573                 m->valid |= bits;
 574                 VM_OBJECT_WUNLOCK(object);
 575         }
 576         sf_buf_free(sf);
 577         if (error) {
 578                 return VM_PAGER_ERROR;
 579         }
 580         return VM_PAGER_OK;
 581 }
 582
 583 /*
 584  * old style vnode pager input routine
 585  */
 586 static int
 587 vnode_pager_input_old(object, m)
 588         vm_object_t object;
 589         vm_page_t m;
 590 {
 591         struct uio auio;
 592         struct iovec aiov;
 593         int error;
 594         int size;
 595         struct sf_buf *sf;
 596         struct vnode *vp;
 597
 598         VM_OBJECT_ASSERT_WLOCKED(object);
 599         error = 0;
 600
 601         /*
 602          * Return failure if beyond current EOF
 603          */
 604         if (IDX_TO_OFF(m->pindex) >= object->un_pager.vnp.vnp_size) {
 605                 return VM_PAGER_BAD;
 606         } else {
 607                 size = PAGE_SIZE;
 608                 if (IDX_TO_OFF(m->pindex) + size > object->un_pager.vnp.vnp_size)
 609                         size = object->un_pager.vnp.vnp_size - IDX_TO_OFF(m->pindex);
 610                 vp = object->handle;
 611                 VM_OBJECT_WUNLOCK(object);
 612
 613                 /*
 614                  * Allocate a kernel virtual address and initialize so that
 615                  * we can use VOP_READ/WRITE routines.
 616                  */
 617                 sf = sf_buf_alloc(m, 0);
 618
 619                 aiov.iov_base = (caddr_t)sf_buf_kva(sf);
 620                 aiov.iov_len = size;
 621                 auio.uio_iov = &aiov;
 622                 auio.uio_iovcnt = 1;
 623                 auio.uio_offset = IDX_TO_OFF(m->pindex);
 624                 auio.uio_segflg = UIO_SYSSPACE;
 625                 auio.uio_rw = UIO_READ;
 626                 auio.uio_resid = size;
 627                 auio.uio_td = curthread;
 628
 629                 error = VOP_READ(vp, &auio, 0, curthread->td_ucred);
 630                 if (!error) {
 631                         int count = size - auio.uio_resid;
 632
 633                         if (count == 0)
 634                                 error = EINVAL;
 635                         else if (count != PAGE_SIZE)
 636                                 bzero((caddr_t)sf_buf_kva(sf) + count,
 637                                     PAGE_SIZE - count);
 638                 }
 639                 sf_buf_free(sf);
 640
 641                 VM_OBJECT_WLOCK(object);
 642         }
 643         KASSERT(m->dirty == 0, ("vnode_pager_input_old: page %p is dirty", m));
 644         if (!error)
 645                 m->valid = VM_PAGE_BITS_ALL;
 646         return error ? VM_PAGER_ERROR : VM_PAGER_OK;
 647 }
 648
 649 /*
 650  * generic vnode pager input routine
 651  */
 652
 653 /*
 654  * Local media VFS's that do not implement their own VOP_GETPAGES
 655  * should have their VOP_GETPAGES call to vnode_pager_generic_getpages()
 656  * to implement the previous behaviour.
 657  *
 658  * All other FS's should use the bypass to get to the local media
 659  * backing vp's VOP_GETPAGES.
 660  */
 661 static int
 662 vnode_pager_getpages(object, m, count, reqpage)
 663         vm_object_t object;
 664         vm_page_t *m;
 665         int count;
 666         int reqpage;
 667 {
 668         int rtval;
 669         struct vnode *vp;
 670         int bytes = count * PAGE_SIZE;
 671
 672         vp = object->handle;
 673         VM_OBJECT_WUNLOCK(object);
 674         rtval = VOP_GETPAGES(vp, m, bytes, reqpage, 0);
 675         KASSERT(rtval != EOPNOTSUPP,
 676             ("vnode_pager: FS getpages not implemented\n"));
 677         VM_OBJECT_WLOCK(object);
 678         return rtval;
 679 }
 680
 681 /*
 682  * This is now called from local media FS's to operate against their
 683  * own vnodes if they fail to implement VOP_GETPAGES.
 684  */
 685 int
 686 vnode_pager_generic_getpages(vp, m, bytecount, reqpage)
 687         struct vnode *vp;
 688         vm_page_t *m;
 689         int bytecount;
 690         int reqpage;
 691 {
 692         vm_object_t object;
 693         vm_offset_t kva;
 694         off_t foff, tfoff, nextoff;
 695         int i, j, size, bsize, first;
 696         daddr_t firstaddr, reqblock;
 697         struct bufobj *bo;
 698         int runpg;
 699         int runend;
 700         struct buf *bp;
 701         struct mount *mp;
 702         int count;
 703         int error;
 704
 705         object = vp->v_object;
 706         count = bytecount / PAGE_SIZE;
 707
 708         KASSERT(vp->v_type != VCHR && vp->v_type != VBLK,
 709             ("vnode_pager_generic_getpages does not support devices"));
 710         if (vp->v_iflag & VI_DOOMED)
 711                 return VM_PAGER_BAD;
 712
 713         bsize = vp->v_mount->mnt_stat.f_iosize;
 714
 715         /* get the UNDERLYING device for the file with VOP_BMAP() */
 716
 717         /*
 718          * originally, we did not check for an error return value -- assuming
 719          * an fs always has a bmap entry point -- that assumption is wrong!!!
 720          */
 721         foff = IDX_TO_OFF(m[reqpage]->pindex);
 722
 723         /*
 724          * if we can't bmap, use old VOP code
 725          */
 726         error = VOP_BMAP(vp, foff / bsize, &bo, &reqblock, NULL, NULL);
 727         if (error == EOPNOTSUPP) {
 728                 VM_OBJECT_WLOCK(object);
 729
 730                 for (i = 0; i < count; i++)
 731                         if (i != reqpage) {
 732                                 vm_page_lock(m[i]);
 733                                 vm_page_free(m[i]);
 734                                 vm_page_unlock(m[i]);
 735                         }
 736                 PCPU_INC(cnt.v_vnodein);
 737                 PCPU_INC(cnt.v_vnodepgsin);
 738                 error = vnode_pager_input_old(object, m[reqpage]);
 739                 VM_OBJECT_WUNLOCK(object);
 740                 return (error);
 741         } else if (error != 0) {
 742                 VM_OBJECT_WLOCK(object);
 743                 for (i = 0; i < count; i++)
 744                         if (i != reqpage) {
 745                                 vm_page_lock(m[i]);
 746                                 vm_page_free(m[i]);
 747                                 vm_page_unlock(m[i]);
 748                         }
 749                 VM_OBJECT_WUNLOCK(object);
 750                 return (VM_PAGER_ERROR);
 751
 752                 /*
 753                  * if the blocksize is smaller than a page size, then use
 754                  * special small filesystem code.  NFS sometimes has a small
 755                  * blocksize, but it can handle large reads itself.
 756                  */
 757         } else if ((PAGE_SIZE / bsize) > 1 &&
 758             (vp->v_mount->mnt_stat.f_type != nfs_mount_type)) {
 759                 VM_OBJECT_WLOCK(object);
 760                 for (i = 0; i < count; i++)
 761                         if (i != reqpage) {
 762                                 vm_page_lock(m[i]);
 763                                 vm_page_free(m[i]);
 764                                 vm_page_unlock(m[i]);
 765                         }
 766                 VM_OBJECT_WUNLOCK(object);
 767                 PCPU_INC(cnt.v_vnodein);
 768                 PCPU_INC(cnt.v_vnodepgsin);
 769                 return vnode_pager_input_smlfs(object, m[reqpage]);
 770         }
 771
 772         /*
 773          * If we have a completely valid page available to us, we can
 774          * clean up and return.  Otherwise we have to re-read the
 775          * media.
 776          */
 777         VM_OBJECT_WLOCK(object);
 778         if (m[reqpage]->valid == VM_PAGE_BITS_ALL) {
 779                 for (i = 0; i < count; i++)
 780                         if (i != reqpage) {
 781                                 vm_page_lock(m[i]);
 782                                 vm_page_free(m[i]);
 783                                 vm_page_unlock(m[i]);
 784                         }
 785                 VM_OBJECT_WUNLOCK(object);
 786                 return VM_PAGER_OK;
 787         } else if (reqblock == -1) {
 788                 pmap_zero_page(m[reqpage]);
 789                 KASSERT(m[reqpage]->dirty == 0,
 790                     ("vnode_pager_generic_getpages: page %p is dirty", m));
 791                 m[reqpage]->valid = VM_PAGE_BITS_ALL;
 792                 for (i = 0; i < count; i++)
 793                         if (i != reqpage) {
 794                                 vm_page_lock(m[i]);
 795                                 vm_page_free(m[i]);
 796                                 vm_page_unlock(m[i]);
 797                         }
 798                 VM_OBJECT_WUNLOCK(object);
 799                 return (VM_PAGER_OK);
 800         }
 801         m[reqpage]->valid = 0;
 802         VM_OBJECT_WUNLOCK(object);
 803
 804         /*
 805          * here on direct device I/O
 806          */
 807         firstaddr = -1;
 808
 809         /*
 810          * calculate the run that includes the required page
 811          */
 812         for (first = 0, i = 0; i < count; i = runend) {
 813                 if (vnode_pager_addr(vp, IDX_TO_OFF(m[i]->pindex), &firstaddr,
 814                     &runpg) != 0) {
 815                         VM_OBJECT_WLOCK(object);
 816                         for (; i < count; i++)
 817                                 if (i != reqpage) {
 818                                         vm_page_lock(m[i]);
 819                                         vm_page_free(m[i]);
 820                                         vm_page_unlock(m[i]);
 821                                 }
 822                         VM_OBJECT_WUNLOCK(object);
 823                         return (VM_PAGER_ERROR);
 824                 }
 825                 if (firstaddr == -1) {
 826                         VM_OBJECT_WLOCK(object);
 827                         if (i == reqpage && foff < object->un_pager.vnp.vnp_size) {
 828                                 panic("vnode_pager_getpages: unexpected missing page: firstaddr: %jd, foff: 0x%jx%08jx, vnp_size: 0x%jx%08jx",
 829                                     (intmax_t)firstaddr, (uintmax_t)(foff >> 32),
 830                                     (uintmax_t)foff,
 831                                     (uintmax_t)
 832                                     (object->un_pager.vnp.vnp_size >> 32),
 833                                     (uintmax_t)object->un_pager.vnp.vnp_size);
 834                         }
 835                         vm_page_lock(m[i]);
 836                         vm_page_free(m[i]);
 837                         vm_page_unlock(m[i]);
 838                         VM_OBJECT_WUNLOCK(object);
 839                         runend = i + 1;
 840                         first = runend;
 841                         continue;
 842                 }
 843                 runend = i + runpg;
 844                 if (runend <= reqpage) {
 845                         VM_OBJECT_WLOCK(object);
 846                         for (j = i; j < runend; j++) {
 847                                 vm_page_lock(m[j]);
 848                                 vm_page_free(m[j]);
 849                                 vm_page_unlock(m[j]);
 850                         }
 851                         VM_OBJECT_WUNLOCK(object);
 852                 } else {
 853                         if (runpg < (count - first)) {
 854                                 VM_OBJECT_WLOCK(object);
 855                                 for (i = first + runpg; i < count; i++) {
 856                                         vm_page_lock(m[i]);
 857                                         vm_page_free(m[i]);
 858                                         vm_page_unlock(m[i]);
 859                                 }
 860                                 VM_OBJECT_WUNLOCK(object);
 861                                 count = first + runpg;
 862                         }
 863                         break;
 864                 }
 865                 first = runend;
 866         }
 867
 868         /*
 869          * the first and last page have been calculated now, move input pages
 870          * to be zero based...
 871          */
 872         if (first != 0) {
 873                 m += first;
 874                 count -= first;
 875                 reqpage -= first;
 876         }
 877
 878         /*
 879          * calculate the file virtual address for the transfer
 880          */
 881         foff = IDX_TO_OFF(m[0]->pindex);
 882
 883         /*
 884          * calculate the size of the transfer
 885          */
 886         size = count * PAGE_SIZE;
 887         KASSERT(count > 0, ("zero count"));
 888         if ((foff + size) > object->un_pager.vnp.vnp_size)
 889                 size = object->un_pager.vnp.vnp_size - foff;
 890         KASSERT(size > 0, ("zero size"));
 891
 892         /*
 893          * round up physical size for real devices.
 894          */
 895         if (1) {
 896                 int secmask = bo->bo_bsize - 1;
 897                 KASSERT(secmask < PAGE_SIZE && secmask > 0,
 898                     ("vnode_pager_generic_getpages: sector size %d too large",
 899                     secmask + 1));
 900                 size = (size + secmask) & ~secmask;
 901         }
 902
 903         bp = getpbuf(&vnode_pbuf_freecnt);
 904         kva = (vm_offset_t)bp->b_data;
 905
 906         /*
 907          * and map the pages to be read into the kva, if the filesystem
 908          * requires mapped buffers.
 909          */
 910         mp = vp->v_mount;
 911         if (mp != NULL && (mp->mnt_kern_flag & MNTK_UNMAPPED_BUFS) != 0 &&
 912             unmapped_buf_allowed) {
 913                 bp->b_data = unmapped_buf;
 914                 bp->b_kvabase = unmapped_buf;
 915                 bp->b_offset = 0;
 916                 bp->b_flags |= B_UNMAPPED;
 917                 bp->b_npages = count;
 918                 for (i = 0; i < count; i++)
 919                         bp->b_pages[i] = m[i];
 920         } else
 921                 pmap_qenter(kva, m, count);
 922
 923         /* build a minimal buffer header */
 924         bp->b_iocmd = BIO_READ;
 925         bp->b_iodone = bdone;
 926         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
 927         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
 928         bp->b_rcred = crhold(curthread->td_ucred);
 929         bp->b_wcred = crhold(curthread->td_ucred);
 930         bp->b_blkno = firstaddr;
 931         pbgetbo(bo, bp);
 932         bp->b_vp = vp;
 933         bp->b_bcount = size;
 934         bp->b_bufsize = size;
 935         bp->b_runningbufspace = bp->b_bufsize;
 936         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
 937
 938         PCPU_INC(cnt.v_vnodein);
 939         PCPU_ADD(cnt.v_vnodepgsin, count);
 940
 941         /* do the input */
 942         bp->b_iooffset = dbtob(bp->b_blkno);
 943         bstrategy(bp);
 944
 945         bwait(bp, PVM, "vnread");
 946
 947         if ((bp->b_ioflags & BIO_ERROR) != 0)
 948                 error = EIO;
 949
 950         if (error == 0 && size != count * PAGE_SIZE) {
 951                 if ((bp->b_flags & B_UNMAPPED) != 0) {
 952                         bp->b_flags &= ~B_UNMAPPED;
 953                         pmap_qenter(kva, m, count);
 954                 }
 955                 bzero((caddr_t)kva + size, PAGE_SIZE * count - size);
 956         }
 957         if ((bp->b_flags & B_UNMAPPED) == 0)
 958                 pmap_qremove(kva, count);
 959         if (mp != NULL && (mp->mnt_kern_flag & MNTK_UNMAPPED_BUFS) != 0) {
 960                 bp->b_data = (caddr_t)kva;
 961                 bp->b_kvabase = (caddr_t)kva;
 962                 bp->b_flags &= ~B_UNMAPPED;
 963                 for (i = 0; i < count; i++)
 964                         bp->b_pages[i] = NULL;
 965         }
 966
 967         /*
 968          * free the buffer header back to the swap buffer pool
 969          */
 970         bp->b_vp = NULL;
 971         pbrelbo(bp);
 972         relpbuf(bp, &vnode_pbuf_freecnt);
 973
 974         VM_OBJECT_WLOCK(object);
 975         for (i = 0, tfoff = foff; i < count; i++, tfoff = nextoff) {
 976                 vm_page_t mt;
 977
 978                 nextoff = tfoff + PAGE_SIZE;
 979                 mt = m[i];
 980
 981                 if (nextoff <= object->un_pager.vnp.vnp_size) {
 982                         /*
 983                          * Read filled up entire page.
 984                          */
 985                         mt->valid = VM_PAGE_BITS_ALL;
 986                         KASSERT(mt->dirty == 0,
 987                             ("vnode_pager_generic_getpages: page %p is dirty",
 988                             mt));
 989                         KASSERT(!pmap_page_is_mapped(mt),
 990                             ("vnode_pager_generic_getpages: page %p is mapped",
 991                             mt));
 992                 } else {
 993                         /*
 994                          * Read did not fill up entire page.
 995                          *
 996                          * Currently we do not set the entire page valid,
 997                          * we just try to clear the piece that we couldn't
 998                          * read.
 999                          */
1000                         vm_page_set_valid_range(mt, 0,
1001                             object->un_pager.vnp.vnp_size - tfoff);
1002                         KASSERT((mt->dirty & vm_page_bits(0,
1003                             object->un_pager.vnp.vnp_size - tfoff)) == 0,
1004                             ("vnode_pager_generic_getpages: page %p is dirty",
1005                             mt));
1006                 }
1007
1008                 if (i != reqpage)
1009                         vm_page_readahead_finish(mt);
1010         }
1011         VM_OBJECT_WUNLOCK(object);
1012         if (error) {
1013                 printf("vnode_pager_getpages: I/O read error\n");
1014         }
1015         return (error ? VM_PAGER_ERROR : VM_PAGER_OK);
1016 }
1017
1018 /*
1019  * EOPNOTSUPP is no longer legal.  For local media VFS's that do not
1020  * implement their own VOP_PUTPAGES, their VOP_PUTPAGES should call to
1021  * vnode_pager_generic_putpages() to implement the previous behaviour.
1022  *
1023  * All other FS's should use the bypass to get to the local media
1024  * backing vp's VOP_PUTPAGES.
1025  */
1026 static void
1027 vnode_pager_putpages(object, m, count, sync, rtvals)
1028         vm_object_t object;
1029         vm_page_t *m;
1030         int count;
1031         boolean_t sync;
1032         int *rtvals;
1033 {
1034         int rtval;
1035         struct vnode *vp;
1036         int bytes = count * PAGE_SIZE;
1037
1038         /*
1039          * Force synchronous operation if we are extremely low on memory
1040          * to prevent a low-memory deadlock.  VOP operations often need to
1041          * allocate more memory to initiate the I/O ( i.e. do a BMAP
1042          * operation ).  The swapper handles the case by limiting the amount
1043          * of asynchronous I/O, but that sort of solution doesn't scale well
1044          * for the vnode pager without a lot of work.
1045          *
1046          * Also, the backing vnode's iodone routine may not wake the pageout
1047          * daemon up.  This should be probably be addressed XXX.
1048          */
1049
1050         if ((cnt.v_free_count + cnt.v_cache_count) < cnt.v_pageout_free_min)
1051                 sync |= OBJPC_SYNC;
1052
1053         /*
1054          * Call device-specific putpages function
1055          */
1056         vp = object->handle;
1057         VM_OBJECT_WUNLOCK(object);
1058         rtval = VOP_PUTPAGES(vp, m, bytes, sync, rtvals, 0);
1059         KASSERT(rtval != EOPNOTSUPP,
1060             ("vnode_pager: stale FS putpages\n"));
1061         VM_OBJECT_WLOCK(object);
1062 }
1063
1064
1065 /*
1066  * This is now called from local media FS's to operate against their
1067  * own vnodes if they fail to implement VOP_PUTPAGES.
1068  *
1069  * This is typically called indirectly via the pageout daemon and
1070  * clustering has already typically occured, so in general we ask the
1071  * underlying filesystem to write the data out asynchronously rather
1072  * then delayed.
1073  */
1074 int
1075 vnode_pager_generic_putpages(struct vnode *vp, vm_page_t *ma, int bytecount,
1076     int flags, int *rtvals)
1077 {
1078         int i;
1079         vm_object_t object;
1080         vm_page_t m;
1081         int count;
1082
1083         int maxsize, ncount;
1084         vm_ooffset_t poffset;
1085         struct uio auio;
1086         struct iovec aiov;
1087         int error;
1088         int ioflags;
1089         int ppscheck = 0;
1090         static struct timeval lastfail;
1091         static int curfail;
1092
1093         object = vp->v_object;
1094         count = bytecount / PAGE_SIZE;
1095
1096         for (i = 0; i < count; i++)
1097                 rtvals[i] = VM_PAGER_ERROR;
1098
1099         if ((int64_t)ma[0]->pindex < 0) {
1100                 printf("vnode_pager_putpages: attempt to write meta-data!!! -- 0x%lx(%lx)\n",
1101                     (long)ma[0]->pindex, (u_long)ma[0]->dirty);
1102                 rtvals[0] = VM_PAGER_BAD;
1103                 return VM_PAGER_BAD;
1104         }
1105
1106         maxsize = count * PAGE_SIZE;
1107         ncount = count;
1108
1109         poffset = IDX_TO_OFF(ma[0]->pindex);
1110
1111         /*
1112          * If the page-aligned write is larger then the actual file we
1113          * have to invalidate pages occuring beyond the file EOF.  However,
1114          * there is an edge case where a file may not be page-aligned where
1115          * the last page is partially invalid.  In this case the filesystem
1116          * may not properly clear the dirty bits for the entire page (which
1117          * could be VM_PAGE_BITS_ALL due to the page having been mmap()d).
1118          * With the page locked we are free to fix-up the dirty bits here.
1119          *
1120          * We do not under any circumstances truncate the valid bits, as
1121          * this will screw up bogus page replacement.
1122          */
1123         VM_OBJECT_WLOCK(object);
1124         if (maxsize + poffset > object->un_pager.vnp.vnp_size) {
1125                 if (object->un_pager.vnp.vnp_size > poffset) {
1126                         int pgoff;
1127
1128                         maxsize = object->un_pager.vnp.vnp_size - poffset;
1129                         ncount = btoc(maxsize);
1130                         if ((pgoff = (int)maxsize & PAGE_MASK) != 0) {
1131                                 /*
1132                                  * If the object is locked and the following
1133                                  * conditions hold, then the page's dirty
1134                                  * field cannot be concurrently changed by a
1135                                  * pmap operation.
1136                                  */
1137                                 m = ma[ncount - 1];
1138                                 vm_page_assert_sbusied(m);
1139                                 KASSERT(!pmap_page_is_write_mapped(m),
1140                 ("vnode_pager_generic_putpages: page %p is not read-only", m));
1141                                 vm_page_clear_dirty(m, pgoff, PAGE_SIZE -
1142                                     pgoff);
1143                         }
1144                 } else {
1145                         maxsize = 0;
1146                         ncount = 0;
1147                 }
1148                 if (ncount < count) {
1149                         for (i = ncount; i < count; i++) {
1150                                 rtvals[i] = VM_PAGER_BAD;
1151                         }
1152                 }
1153         }
1154         VM_OBJECT_WUNLOCK(object);
1155
1156         /*
1157          * pageouts are already clustered, use IO_ASYNC to force a bawrite()
1158          * rather then a bdwrite() to prevent paging I/O from saturating
1159          * the buffer cache.  Dummy-up the sequential heuristic to cause
1160          * large ranges to cluster.  If neither IO_SYNC or IO_ASYNC is set,
1161          * the system decides how to cluster.
1162          */
1163         ioflags = IO_VMIO;
1164         if (flags & (VM_PAGER_PUT_SYNC | VM_PAGER_PUT_INVAL))
1165                 ioflags |= IO_SYNC;
1166         else if ((flags & VM_PAGER_CLUSTER_OK) == 0)
1167                 ioflags |= IO_ASYNC;
1168         ioflags |= (flags & VM_PAGER_PUT_INVAL) ? IO_INVAL: 0;
1169         ioflags |= IO_SEQMAX << IO_SEQSHIFT;
1170
1171         aiov.iov_base = (caddr_t) 0;
1172         aiov.iov_len = maxsize;
1173         auio.uio_iov = &aiov;
1174         auio.uio_iovcnt = 1;
1175         auio.uio_offset = poffset;
1176         auio.uio_segflg = UIO_NOCOPY;
1177         auio.uio_rw = UIO_WRITE;
1178         auio.uio_resid = maxsize;
1179         auio.uio_td = (struct thread *) 0;
1180         error = VOP_WRITE(vp, &auio, ioflags, curthread->td_ucred);
1181         PCPU_INC(cnt.v_vnodeout);
1182         PCPU_ADD(cnt.v_vnodepgsout, ncount);
1183
1184         if (error) {
1185                 if ((ppscheck = ppsratecheck(&lastfail, &curfail, 1)))
1186                         printf("vnode_pager_putpages: I/O error %d\n", error);
1187         }
1188         if (auio.uio_resid) {
1189                 if (ppscheck || ppsratecheck(&lastfail, &curfail, 1))
1190                         printf("vnode_pager_putpages: residual I/O %zd at %lu\n",
1191                             auio.uio_resid, (u_long)ma[0]->pindex);
1192         }
1193         for (i = 0; i < ncount; i++) {
1194                 rtvals[i] = VM_PAGER_OK;
1195         }
1196         return rtvals[0];
1197 }
1198
1199 void
1200 vnode_pager_undirty_pages(vm_page_t *ma, int *rtvals, int written)
1201 {
1202         vm_object_t obj;
1203         int i, pos;
1204
1205         if (written == 0)
1206                 return;
1207         obj = ma[0]->object;
1208         VM_OBJECT_WLOCK(obj);
1209         for (i = 0, pos = 0; pos < written; i++, pos += PAGE_SIZE) {
1210                 if (pos < trunc_page(written)) {
1211                         rtvals[i] = VM_PAGER_OK;
1212                         vm_page_undirty(ma[i]);
1213                 } else {
1214                         /* Partially written page. */
1215                         rtvals[i] = VM_PAGER_AGAIN;
1216                         vm_page_clear_dirty(ma[i], 0, written & PAGE_MASK);
1217                 }
1218         }
1219         VM_OBJECT_WUNLOCK(obj);
1220 }
1221
1222 void
1223 vnode_pager_update_writecount(vm_object_t object, vm_offset_t start,
1224     vm_offset_t end)
1225 {
1226         struct vnode *vp;
1227         vm_ooffset_t old_wm;
1228
1229         VM_OBJECT_WLOCK(object);
1230         if (object->type != OBJT_VNODE) {
1231                 VM_OBJECT_WUNLOCK(object);
1232                 return;
1233         }
1234         old_wm = object->un_pager.vnp.writemappings;
1235         object->un_pager.vnp.writemappings += (vm_ooffset_t)end - start;
1236         vp = object->handle;
1237         if (old_wm == 0 && object->un_pager.vnp.writemappings != 0) {
1238                 ASSERT_VOP_ELOCKED(vp, "v_writecount inc");
1239                 VOP_ADD_WRITECOUNT(vp, 1);
1240                 CTR3(KTR_VFS, "%s: vp %p v_writecount increased to %d",
1241                     __func__, vp, vp->v_writecount);
1242         } else if (old_wm != 0 && object->un_pager.vnp.writemappings == 0) {
1243                 ASSERT_VOP_ELOCKED(vp, "v_writecount dec");
1244                 VOP_ADD_WRITECOUNT(vp, -1);
1245                 CTR3(KTR_VFS, "%s: vp %p v_writecount decreased to %d",
1246                     __func__, vp, vp->v_writecount);
1247         }
1248         VM_OBJECT_WUNLOCK(object);
1249 }
1250
1251 void
1252 vnode_pager_release_writecount(vm_object_t object, vm_offset_t start,
1253     vm_offset_t end)
1254 {
1255         struct vnode *vp;
1256         struct mount *mp;
1257         vm_offset_t inc;
1258
1259         VM_OBJECT_WLOCK(object);
1260
1261         /*
1262          * First, recheck the object type to account for the race when
1263          * the vnode is reclaimed.
1264          */
1265         if (object->type != OBJT_VNODE) {
1266                 VM_OBJECT_WUNLOCK(object);
1267                 return;
1268         }
1269
1270         /*
1271          * Optimize for the case when writemappings is not going to
1272          * zero.
1273          */
1274         inc = end - start;
1275         if (object->un_pager.vnp.writemappings != inc) {
1276                 object->un_pager.vnp.writemappings -= inc;
1277                 VM_OBJECT_WUNLOCK(object);
1278                 return;
1279         }
1280
1281         vp = object->handle;
1282         vhold(vp);
1283         VM_OBJECT_WUNLOCK(object);
1284         mp = NULL;
1285         vn_start_write(vp, &mp, V_WAIT);
1286         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
1287
1288         /*
1289          * Decrement the object's writemappings, by swapping the start
1290          * and end arguments for vnode_pager_update_writecount().  If
1291          * there was not a race with vnode reclaimation, then the
1292          * vnode's v_writecount is decremented.
1293          */
1294         vnode_pager_update_writecount(object, end, start);
1295         VOP_UNLOCK(vp, 0);
1296         vdrop(vp);
1297         if (mp != NULL)
1298                 vn_finished_write(mp);
1299 }