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/sf_buf.h>
  67
  68 #include <machine/atomic.h>
  69
  70 #include <vm/vm.h>
  71 #include <vm/vm_param.h>
  72 #include <vm/vm_object.h>
  73 #include <vm/vm_page.h>
  74 #include <vm/vm_pager.h>
  75 #include <vm/vm_map.h>
  76 #include <vm/vnode_pager.h>
  77 #include <vm/vm_extern.h>
  78
  79 static int vnode_pager_addr(struct vnode *vp, vm_ooffset_t address,
  80     daddr_t *rtaddress, int *run);
  81 static int vnode_pager_input_smlfs(vm_object_t object, vm_page_t m);
  82 static int vnode_pager_input_old(vm_object_t object, vm_page_t m);
  83 static void vnode_pager_dealloc(vm_object_t);
  84 static int vnode_pager_getpages(vm_object_t, vm_page_t *, int, int);
  85 static void vnode_pager_putpages(vm_object_t, vm_page_t *, int, boolean_t, int *);
  86 static boolean_t vnode_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
  87 static vm_object_t vnode_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
  88     vm_ooffset_t, struct ucred *cred);
  89
  90 struct pagerops vnodepagerops = {
  91         .pgo_alloc =    vnode_pager_alloc,
  92         .pgo_dealloc =  vnode_pager_dealloc,
  93         .pgo_getpages = vnode_pager_getpages,
  94         .pgo_putpages = vnode_pager_putpages,
  95         .pgo_haspage =  vnode_pager_haspage,
  96 };
  97
  98 int vnode_pbuf_freecnt;
  99
 100 /* Create the VM system backing object for this vnode */
 101 int
 102 vnode_create_vobject(struct vnode *vp, off_t isize, struct thread *td)
 103 {
 104         vm_object_t object;
 105         vm_ooffset_t size = isize;
 106         struct vattr va;
 107
 108         if (!vn_isdisk(vp, NULL) && vn_canvmio(vp) == FALSE)
 109                 return (0);
 110
 111         while ((object = vp->v_object) != NULL) {
 112                 VM_OBJECT_LOCK(object);
 113                 if (!(object->flags & OBJ_DEAD)) {
 114                         VM_OBJECT_UNLOCK(object);
 115                         return (0);
 116                 }
 117                 VOP_UNLOCK(vp, 0);
 118                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
 119                 msleep(object, VM_OBJECT_MTX(object), PDROP | PVM, "vodead", 0);
 120                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 121         }
 122
 123         if (size == 0) {
 124                 if (vn_isdisk(vp, NULL)) {
 125                         size = IDX_TO_OFF(INT_MAX);
 126                 } else {
 127                         if (VOP_GETATTR(vp, &va, td->td_ucred))
 128                                 return (0);
 129                         size = va.va_size;
 130                 }
 131         }
 132
 133         object = vnode_pager_alloc(vp, size, 0, 0, td->td_ucred);
 134         /*
 135          * Dereference the reference we just created.  This assumes
 136          * that the object is associated with the vp.
 137          */
 138         VM_OBJECT_LOCK(object);
 139         object->ref_count--;
 140         VM_OBJECT_UNLOCK(object);
 141         vrele(vp);
 142
 143         KASSERT(vp->v_object != NULL, ("vnode_create_vobject: NULL object"));
 144
 145         return (0);
 146 }
 147
 148 void
 149 vnode_destroy_vobject(struct vnode *vp)
 150 {
 151         struct vm_object *obj;
 152
 153         obj = vp->v_object;
 154         if (obj == NULL)
 155                 return;
 156         ASSERT_VOP_ELOCKED(vp, "vnode_destroy_vobject");
 157         VM_OBJECT_LOCK(obj);
 158         if (obj->ref_count == 0) {
 159                 /*
 160                  * vclean() may be called twice. The first time
 161                  * removes the primary reference to the object,
 162                  * the second time goes one further and is a
 163                  * special-case to terminate the object.
 164                  *
 165                  * don't double-terminate the object
 166                  */
 167                 if ((obj->flags & OBJ_DEAD) == 0)
 168                         vm_object_terminate(obj);
 169                 else
 170                         VM_OBJECT_UNLOCK(obj);
 171         } else {
 172                 /*
 173                  * Woe to the process that tries to page now :-).
 174                  */
 175                 vm_pager_deallocate(obj);
 176                 VM_OBJECT_UNLOCK(obj);
 177         }
 178         vp->v_object = NULL;
 179 }
 180
 181
 182 /*
 183  * Allocate (or lookup) pager for a vnode.
 184  * Handle is a vnode pointer.
 185  *
 186  * MPSAFE
 187  */
 188 vm_object_t
 189 vnode_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
 190     vm_ooffset_t offset, struct ucred *cred)
 191 {
 192         vm_object_t object;
 193         struct vnode *vp;
 194
 195         /*
 196          * Pageout to vnode, no can do yet.
 197          */
 198         if (handle == NULL)
 199                 return (NULL);
 200
 201         vp = (struct vnode *) handle;
 202
 203         /*
 204          * If the object is being terminated, wait for it to
 205          * go away.
 206          */
 207 retry:
 208         while ((object = vp->v_object) != NULL) {
 209                 VM_OBJECT_LOCK(object);
 210                 if ((object->flags & OBJ_DEAD) == 0)
 211                         break;
 212                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
 213                 msleep(object, VM_OBJECT_MTX(object), PDROP | PVM, "vadead", 0);
 214         }
 215
 216         KASSERT(vp->v_usecount != 0, ("vnode_pager_alloc: no vnode reference"));
 217
 218         if (object == NULL) {
 219                 /*
 220                  * Add an object of the appropriate size
 221                  */
 222                 object = vm_object_allocate(OBJT_VNODE, OFF_TO_IDX(round_page(size)));
 223
 224                 object->un_pager.vnp.vnp_size = size;
 225                 object->un_pager.vnp.writemappings = 0;
 226
 227                 object->handle = handle;
 228                 VI_LOCK(vp);
 229                 if (vp->v_object != NULL) {
 230                         /*
 231                          * Object has been created while we were sleeping
 232                          */
 233                         VI_UNLOCK(vp);
 234                         VM_OBJECT_LOCK(object);
 235                         KASSERT(object->ref_count == 1,
 236                             ("leaked ref %p %d", object, object->ref_count));
 237                         object->type = OBJT_DEAD;
 238                         object->ref_count = 0;
 239                         VM_OBJECT_UNLOCK(object);
 240                         vm_object_destroy(object);
 241                         goto retry;
 242                 }
 243                 vp->v_object = object;
 244                 VI_UNLOCK(vp);
 245         } else {
 246                 object->ref_count++;
 247                 VM_OBJECT_UNLOCK(object);
 248         }
 249         vref(vp);
 250         return (object);
 251 }
 252
 253 /*
 254  *      The object must be locked.
 255  */
 256 static void
 257 vnode_pager_dealloc(object)
 258         vm_object_t object;
 259 {
 260         struct vnode *vp;
 261         int refs;
 262
 263         vp = object->handle;
 264         if (vp == NULL)
 265                 panic("vnode_pager_dealloc: pager already dealloced");
 266
 267         VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
 268         vm_object_pip_wait(object, "vnpdea");
 269         refs = object->ref_count;
 270
 271         object->handle = NULL;
 272         object->type = OBJT_DEAD;
 273         if (object->flags & OBJ_DISCONNECTWNT) {
 274                 vm_object_clear_flag(object, OBJ_DISCONNECTWNT);
 275                 wakeup(object);
 276         }
 277         ASSERT_VOP_ELOCKED(vp, "vnode_pager_dealloc");
 278         if (object->un_pager.vnp.writemappings > 0) {
 279                 object->un_pager.vnp.writemappings = 0;
 280                 VOP_ADD_WRITECOUNT(vp, -1);
 281         }
 282         vp->v_object = NULL;
 283         VOP_UNSET_TEXT(vp);
 284         VM_OBJECT_UNLOCK(object);
 285         while (refs-- > 0)
 286                 vunref(vp);
 287         VM_OBJECT_LOCK(object);
 288 }
 289
 290 static boolean_t
 291 vnode_pager_haspage(object, pindex, before, after)
 292         vm_object_t object;
 293         vm_pindex_t pindex;
 294         int *before;
 295         int *after;
 296 {
 297         struct vnode *vp = object->handle;
 298         daddr_t bn;
 299         int err;
 300         daddr_t reqblock;
 301         int poff;
 302         int bsize;
 303         int pagesperblock, blocksperpage;
 304         int vfslocked;
 305
 306         VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
 307         /*
 308          * If no vp or vp is doomed or marked transparent to VM, we do not
 309          * have the page.
 310          */
 311         if (vp == NULL || vp->v_iflag & VI_DOOMED)
 312                 return FALSE;
 313         /*
 314          * If the offset is beyond end of file we do
 315          * not have the page.
 316          */
 317         if (IDX_TO_OFF(pindex) >= object->un_pager.vnp.vnp_size)
 318                 return FALSE;
 319
 320         bsize = vp->v_mount->mnt_stat.f_iosize;
 321         pagesperblock = bsize / PAGE_SIZE;
 322         blocksperpage = 0;
 323         if (pagesperblock > 0) {
 324                 reqblock = pindex / pagesperblock;
 325         } else {
 326                 blocksperpage = (PAGE_SIZE / bsize);
 327                 reqblock = pindex * blocksperpage;
 328         }
 329         VM_OBJECT_UNLOCK(object);
 330         vfslocked = VFS_LOCK_GIANT(vp->v_mount);
 331         err = VOP_BMAP(vp, reqblock, NULL, &bn, after, before);
 332         VFS_UNLOCK_GIANT(vfslocked);
 333         VM_OBJECT_LOCK(object);
 334         if (err)
 335                 return TRUE;
 336         if (bn == -1)
 337                 return FALSE;
 338         if (pagesperblock > 0) {
 339                 poff = pindex - (reqblock * pagesperblock);
 340                 if (before) {
 341                         *before *= pagesperblock;
 342                         *before += poff;
 343                 }
 344                 if (after) {
 345                         int numafter;
 346                         *after *= pagesperblock;
 347                         numafter = pagesperblock - (poff + 1);
 348                         if (IDX_TO_OFF(pindex + numafter) >
 349                             object->un_pager.vnp.vnp_size) {
 350                                 numafter =
 351                                     OFF_TO_IDX(object->un_pager.vnp.vnp_size) -
 352                                     pindex;
 353                         }
 354                         *after += numafter;
 355                 }
 356         } else {
 357                 if (before) {
 358                         *before /= blocksperpage;
 359                 }
 360
 361                 if (after) {
 362                         *after /= blocksperpage;
 363                 }
 364         }
 365         return TRUE;
 366 }
 367
 368 /*
 369  * Lets the VM system know about a change in size for a file.
 370  * We adjust our own internal size and flush any cached pages in
 371  * the associated object that are affected by the size change.
 372  *
 373  * Note: this routine may be invoked as a result of a pager put
 374  * operation (possibly at object termination time), so we must be careful.
 375  */
 376 void
 377 vnode_pager_setsize(vp, nsize)
 378         struct vnode *vp;
 379         vm_ooffset_t nsize;
 380 {
 381         vm_object_t object;
 382         vm_page_t m;
 383         vm_pindex_t nobjsize;
 384
 385         if ((object = vp->v_object) == NULL)
 386                 return;
 387 /*      ASSERT_VOP_ELOCKED(vp, "vnode_pager_setsize and not locked vnode"); */
 388         VM_OBJECT_LOCK(object);
 389         if (object->type == OBJT_DEAD) {
 390                 VM_OBJECT_UNLOCK(object);
 391                 return;
 392         }
 393         KASSERT(object->type == OBJT_VNODE,
 394             ("not vnode-backed object %p", object));
 395         if (nsize == object->un_pager.vnp.vnp_size) {
 396                 /*
 397                  * Hasn't changed size
 398                  */
 399                 VM_OBJECT_UNLOCK(object);
 400                 return;
 401         }
 402         nobjsize = OFF_TO_IDX(nsize + PAGE_MASK);
 403         if (nsize < object->un_pager.vnp.vnp_size) {
 404                 /*
 405                  * File has shrunk. Toss any cached pages beyond the new EOF.
 406                  */
 407                 if (nobjsize < object->size)
 408                         vm_object_page_remove(object, nobjsize, object->size,
 409                             0);
 410                 /*
 411                  * this gets rid of garbage at the end of a page that is now
 412                  * only partially backed by the vnode.
 413                  *
 414                  * XXX for some reason (I don't know yet), if we take a
 415                  * completely invalid page and mark it partially valid
 416                  * it can screw up NFS reads, so we don't allow the case.
 417                  */
 418                 if ((nsize & PAGE_MASK) &&
 419                     (m = vm_page_lookup(object, OFF_TO_IDX(nsize))) != NULL &&
 420                     m->valid != 0) {
 421                         int base = (int)nsize & PAGE_MASK;
 422                         int size = PAGE_SIZE - base;
 423
 424                         /*
 425                          * Clear out partial-page garbage in case
 426                          * the page has been mapped.
 427                          */
 428                         pmap_zero_page_area(m, base, size);
 429
 430                         /*
 431                          * Update the valid bits to reflect the blocks that
 432                          * have been zeroed.  Some of these valid bits may
 433                          * have already been set.
 434                          */
 435                         vm_page_set_valid(m, base, size);
 436
 437                         /*
 438                          * Round "base" to the next block boundary so that the
 439                          * dirty bit for a partially zeroed block is not
 440                          * cleared.
 441                          */
 442                         base = roundup2(base, DEV_BSIZE);
 443
 444                         /*
 445                          * Clear out partial-page dirty bits.
 446                          *
 447                          * note that we do not clear out the valid
 448                          * bits.  This would prevent bogus_page
 449                          * replacement from working properly.
 450                          */
 451                         vm_page_clear_dirty(m, base, PAGE_SIZE - base);
 452                 } else if ((nsize & PAGE_MASK) &&
 453                     __predict_false(object->cache != NULL)) {
 454                         vm_page_cache_free(object, OFF_TO_IDX(nsize),
 455                             nobjsize);
 456                 }
 457         }
 458         object->un_pager.vnp.vnp_size = nsize;
 459         object->size = nobjsize;
 460         VM_OBJECT_UNLOCK(object);
 461 }
 462
 463 /*
 464  * calculate the linear (byte) disk address of specified virtual
 465  * file address
 466  */
 467 static int
 468 vnode_pager_addr(struct vnode *vp, vm_ooffset_t address, daddr_t *rtaddress,
 469     int *run)
 470 {
 471         int bsize;
 472         int err;
 473         daddr_t vblock;
 474         daddr_t voffset;
 475
 476         if (address < 0)
 477                 return -1;
 478
 479         if (vp->v_iflag & VI_DOOMED)
 480                 return -1;
 481
 482         bsize = vp->v_mount->mnt_stat.f_iosize;
 483         vblock = address / bsize;
 484         voffset = address % bsize;
 485
 486         err = VOP_BMAP(vp, vblock, NULL, rtaddress, run, NULL);
 487         if (err == 0) {
 488                 if (*rtaddress != -1)
 489                         *rtaddress += voffset / DEV_BSIZE;
 490                 if (run) {
 491                         *run += 1;
 492                         *run *= bsize/PAGE_SIZE;
 493                         *run -= voffset/PAGE_SIZE;
 494                 }
 495         }
 496
 497         return (err);
 498 }
 499
 500 /*
 501  * small block filesystem vnode pager input
 502  */
 503 static int
 504 vnode_pager_input_smlfs(object, m)
 505         vm_object_t object;
 506         vm_page_t m;
 507 {
 508         struct vnode *vp;
 509         struct bufobj *bo;
 510         struct buf *bp;
 511         struct sf_buf *sf;
 512         daddr_t fileaddr;
 513         vm_offset_t bsize;
 514         vm_page_bits_t bits;
 515         int error, i;
 516
 517         error = 0;
 518         vp = object->handle;
 519         if (vp->v_iflag & VI_DOOMED)
 520                 return VM_PAGER_BAD;
 521
 522         bsize = vp->v_mount->mnt_stat.f_iosize;
 523
 524         VOP_BMAP(vp, 0, &bo, 0, NULL, NULL);
 525
 526         sf = sf_buf_alloc(m, 0);
 527
 528         for (i = 0; i < PAGE_SIZE / bsize; i++) {
 529                 vm_ooffset_t address;
 530
 531                 bits = vm_page_bits(i * bsize, bsize);
 532                 if (m->valid & bits)
 533                         continue;
 534
 535                 address = IDX_TO_OFF(m->pindex) + i * bsize;
 536                 if (address >= object->un_pager.vnp.vnp_size) {
 537                         fileaddr = -1;
 538                 } else {
 539                         error = vnode_pager_addr(vp, address, &fileaddr, NULL);
 540                         if (error)
 541                                 break;
 542                 }
 543                 if (fileaddr != -1) {
 544                         bp = getpbuf(&vnode_pbuf_freecnt);
 545
 546                         /* build a minimal buffer header */
 547                         bp->b_iocmd = BIO_READ;
 548                         bp->b_iodone = bdone;
 549                         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
 550                         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
 551                         bp->b_rcred = crhold(curthread->td_ucred);
 552                         bp->b_wcred = crhold(curthread->td_ucred);
 553                         bp->b_data = (caddr_t)sf_buf_kva(sf) + i * bsize;
 554                         bp->b_blkno = fileaddr;
 555                         pbgetbo(bo, bp);
 556                         bp->b_vp = vp;
 557                         bp->b_bcount = bsize;
 558                         bp->b_bufsize = bsize;
 559                         bp->b_runningbufspace = bp->b_bufsize;
 560                         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
 561
 562                         /* do the input */
 563                         bp->b_iooffset = dbtob(bp->b_blkno);
 564                         bstrategy(bp);
 565
 566                         bwait(bp, PVM, "vnsrd");
 567
 568                         if ((bp->b_ioflags & BIO_ERROR) != 0)
 569                                 error = EIO;
 570
 571                         /*
 572                          * free the buffer header back to the swap buffer pool
 573                          */
 574                         bp->b_vp = NULL;
 575                         pbrelbo(bp);
 576                         relpbuf(bp, &vnode_pbuf_freecnt);
 577                         if (error)
 578                                 break;
 579                 } else
 580                         bzero((caddr_t)sf_buf_kva(sf) + i * bsize, bsize);
 581                 KASSERT((m->dirty & bits) == 0,
 582                     ("vnode_pager_input_smlfs: page %p is dirty", m));
 583                 VM_OBJECT_LOCK(object);
 584                 m->valid |= bits;
 585                 VM_OBJECT_UNLOCK(object);
 586         }
 587         sf_buf_free(sf);
 588         if (error) {
 589                 return VM_PAGER_ERROR;
 590         }
 591         return VM_PAGER_OK;
 592 }
 593
 594 /*
 595  * old style vnode pager input routine
 596  */
 597 static int
 598 vnode_pager_input_old(object, m)
 599         vm_object_t object;
 600         vm_page_t m;
 601 {
 602         struct uio auio;
 603         struct iovec aiov;
 604         int error;
 605         int size;
 606         struct sf_buf *sf;
 607         struct vnode *vp;
 608
 609         VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
 610         error = 0;
 611
 612         /*
 613          * Return failure if beyond current EOF
 614          */
 615         if (IDX_TO_OFF(m->pindex) >= object->un_pager.vnp.vnp_size) {
 616                 return VM_PAGER_BAD;
 617         } else {
 618                 size = PAGE_SIZE;
 619                 if (IDX_TO_OFF(m->pindex) + size > object->un_pager.vnp.vnp_size)
 620                         size = object->un_pager.vnp.vnp_size - IDX_TO_OFF(m->pindex);
 621                 vp = object->handle;
 622                 VM_OBJECT_UNLOCK(object);
 623
 624                 /*
 625                  * Allocate a kernel virtual address and initialize so that
 626                  * we can use VOP_READ/WRITE routines.
 627                  */
 628                 sf = sf_buf_alloc(m, 0);
 629
 630                 aiov.iov_base = (caddr_t)sf_buf_kva(sf);
 631                 aiov.iov_len = size;
 632                 auio.uio_iov = &aiov;
 633                 auio.uio_iovcnt = 1;
 634                 auio.uio_offset = IDX_TO_OFF(m->pindex);
 635                 auio.uio_segflg = UIO_SYSSPACE;
 636                 auio.uio_rw = UIO_READ;
 637                 auio.uio_resid = size;
 638                 auio.uio_td = curthread;
 639
 640                 error = VOP_READ(vp, &auio, 0, curthread->td_ucred);
 641                 if (!error) {
 642                         int count = size - auio.uio_resid;
 643
 644                         if (count == 0)
 645                                 error = EINVAL;
 646                         else if (count != PAGE_SIZE)
 647                                 bzero((caddr_t)sf_buf_kva(sf) + count,
 648                                     PAGE_SIZE - count);
 649                 }
 650                 sf_buf_free(sf);
 651
 652                 VM_OBJECT_LOCK(object);
 653         }
 654         KASSERT(m->dirty == 0, ("vnode_pager_input_old: page %p is dirty", m));
 655         if (!error)
 656                 m->valid = VM_PAGE_BITS_ALL;
 657         return error ? VM_PAGER_ERROR : VM_PAGER_OK;
 658 }
 659
 660 /*
 661  * generic vnode pager input routine
 662  */
 663
 664 /*
 665  * Local media VFS's that do not implement their own VOP_GETPAGES
 666  * should have their VOP_GETPAGES call to vnode_pager_generic_getpages()
 667  * to implement the previous behaviour.
 668  *
 669  * All other FS's should use the bypass to get to the local media
 670  * backing vp's VOP_GETPAGES.
 671  */
 672 static int
 673 vnode_pager_getpages(object, m, count, reqpage)
 674         vm_object_t object;
 675         vm_page_t *m;
 676         int count;
 677         int reqpage;
 678 {
 679         int rtval;
 680         struct vnode *vp;
 681         int bytes = count * PAGE_SIZE;
 682         int vfslocked;
 683
 684         vp = object->handle;
 685         VM_OBJECT_UNLOCK(object);
 686         vfslocked = VFS_LOCK_GIANT(vp->v_mount);
 687         rtval = VOP_GETPAGES(vp, m, bytes, reqpage, 0);
 688         KASSERT(rtval != EOPNOTSUPP,
 689             ("vnode_pager: FS getpages not implemented\n"));
 690         VFS_UNLOCK_GIANT(vfslocked);
 691         VM_OBJECT_LOCK(object);
 692         return rtval;
 693 }
 694
 695 /*
 696  * This is now called from local media FS's to operate against their
 697  * own vnodes if they fail to implement VOP_GETPAGES.
 698  */
 699 int
 700 vnode_pager_generic_getpages(vp, m, bytecount, reqpage)
 701         struct vnode *vp;
 702         vm_page_t *m;
 703         int bytecount;
 704         int reqpage;
 705 {
 706         vm_object_t object;
 707         vm_offset_t kva;
 708         off_t foff, tfoff, nextoff;
 709         int i, j, size, bsize, first;
 710         daddr_t firstaddr, reqblock;
 711         struct bufobj *bo;
 712         int runpg;
 713         int runend;
 714         struct buf *bp;
 715         struct mount *mp;
 716         int count;
 717         int error;
 718
 719         object = vp->v_object;
 720         count = bytecount / PAGE_SIZE;
 721
 722         KASSERT(vp->v_type != VCHR && vp->v_type != VBLK,
 723             ("vnode_pager_generic_getpages does not support devices"));
 724         if (vp->v_iflag & VI_DOOMED)
 725                 return VM_PAGER_BAD;
 726
 727         bsize = vp->v_mount->mnt_stat.f_iosize;
 728
 729         /* get the UNDERLYING device for the file with VOP_BMAP() */
 730
 731         /*
 732          * originally, we did not check for an error return value -- assuming
 733          * an fs always has a bmap entry point -- that assumption is wrong!!!
 734          */
 735         foff = IDX_TO_OFF(m[reqpage]->pindex);
 736
 737         /*
 738          * if we can't bmap, use old VOP code
 739          */
 740         error = VOP_BMAP(vp, foff / bsize, &bo, &reqblock, NULL, NULL);
 741         if (error == EOPNOTSUPP) {
 742                 VM_OBJECT_LOCK(object);
 743
 744                 for (i = 0; i < count; i++)
 745                         if (i != reqpage) {
 746                                 vm_page_lock(m[i]);
 747                                 vm_page_free(m[i]);
 748                                 vm_page_unlock(m[i]);
 749                         }
 750                 PCPU_INC(cnt.v_vnodein);
 751                 PCPU_INC(cnt.v_vnodepgsin);
 752                 error = vnode_pager_input_old(object, m[reqpage]);
 753                 VM_OBJECT_UNLOCK(object);
 754                 return (error);
 755         } else if (error != 0) {
 756                 VM_OBJECT_LOCK(object);
 757                 for (i = 0; i < count; i++)
 758                         if (i != reqpage) {
 759                                 vm_page_lock(m[i]);
 760                                 vm_page_free(m[i]);
 761                                 vm_page_unlock(m[i]);
 762                         }
 763                 VM_OBJECT_UNLOCK(object);
 764                 return (VM_PAGER_ERROR);
 765
 766                 /*
 767                  * if the blocksize is smaller than a page size, then use
 768                  * special small filesystem code.  NFS sometimes has a small
 769                  * blocksize, but it can handle large reads itself.
 770                  */
 771         } else if ((PAGE_SIZE / bsize) > 1 &&
 772             (vp->v_mount->mnt_stat.f_type != nfs_mount_type)) {
 773                 VM_OBJECT_LOCK(object);
 774                 for (i = 0; i < count; i++)
 775                         if (i != reqpage) {
 776                                 vm_page_lock(m[i]);
 777                                 vm_page_free(m[i]);
 778                                 vm_page_unlock(m[i]);
 779                         }
 780                 VM_OBJECT_UNLOCK(object);
 781                 PCPU_INC(cnt.v_vnodein);
 782                 PCPU_INC(cnt.v_vnodepgsin);
 783                 return vnode_pager_input_smlfs(object, m[reqpage]);
 784         }
 785
 786         /*
 787          * If we have a completely valid page available to us, we can
 788          * clean up and return.  Otherwise we have to re-read the
 789          * media.
 790          */
 791         VM_OBJECT_LOCK(object);
 792         if (m[reqpage]->valid == VM_PAGE_BITS_ALL) {
 793                 for (i = 0; i < count; i++)
 794                         if (i != reqpage) {
 795                                 vm_page_lock(m[i]);
 796                                 vm_page_free(m[i]);
 797                                 vm_page_unlock(m[i]);
 798                         }
 799                 VM_OBJECT_UNLOCK(object);
 800                 return VM_PAGER_OK;
 801         } else if (reqblock == -1) {
 802                 pmap_zero_page(m[reqpage]);
 803                 KASSERT(m[reqpage]->dirty == 0,
 804                     ("vnode_pager_generic_getpages: page %p is dirty", m));
 805                 m[reqpage]->valid = VM_PAGE_BITS_ALL;
 806                 for (i = 0; i < count; i++)
 807                         if (i != reqpage) {
 808                                 vm_page_lock(m[i]);
 809                                 vm_page_free(m[i]);
 810                                 vm_page_unlock(m[i]);
 811                         }
 812                 VM_OBJECT_UNLOCK(object);
 813                 return (VM_PAGER_OK);
 814         }
 815         m[reqpage]->valid = 0;
 816         VM_OBJECT_UNLOCK(object);
 817
 818         /*
 819          * here on direct device I/O
 820          */
 821         firstaddr = -1;
 822
 823         /*
 824          * calculate the run that includes the required page
 825          */
 826         for (first = 0, i = 0; i < count; i = runend) {
 827                 if (vnode_pager_addr(vp, IDX_TO_OFF(m[i]->pindex), &firstaddr,
 828                     &runpg) != 0) {
 829                         VM_OBJECT_LOCK(object);
 830                         for (; i < count; i++)
 831                                 if (i != reqpage) {
 832                                         vm_page_lock(m[i]);
 833                                         vm_page_free(m[i]);
 834                                         vm_page_unlock(m[i]);
 835                                 }
 836                         VM_OBJECT_UNLOCK(object);
 837                         return (VM_PAGER_ERROR);
 838                 }
 839                 if (firstaddr == -1) {
 840                         VM_OBJECT_LOCK(object);
 841                         if (i == reqpage && foff < object->un_pager.vnp.vnp_size) {
 842                                 panic("vnode_pager_getpages: unexpected missing page: firstaddr: %jd, foff: 0x%jx%08jx, vnp_size: 0x%jx%08jx",
 843                                     (intmax_t)firstaddr, (uintmax_t)(foff >> 32),
 844                                     (uintmax_t)foff,
 845                                     (uintmax_t)
 846                                     (object->un_pager.vnp.vnp_size >> 32),
 847                                     (uintmax_t)object->un_pager.vnp.vnp_size);
 848                         }
 849                         vm_page_lock(m[i]);
 850                         vm_page_free(m[i]);
 851                         vm_page_unlock(m[i]);
 852                         VM_OBJECT_UNLOCK(object);
 853                         runend = i + 1;
 854                         first = runend;
 855                         continue;
 856                 }
 857                 runend = i + runpg;
 858                 if (runend <= reqpage) {
 859                         VM_OBJECT_LOCK(object);
 860                         for (j = i; j < runend; j++) {
 861                                 vm_page_lock(m[j]);
 862                                 vm_page_free(m[j]);
 863                                 vm_page_unlock(m[j]);
 864                         }
 865                         VM_OBJECT_UNLOCK(object);
 866                 } else {
 867                         if (runpg < (count - first)) {
 868                                 VM_OBJECT_LOCK(object);
 869                                 for (i = first + runpg; i < count; i++) {
 870                                         vm_page_lock(m[i]);
 871                                         vm_page_free(m[i]);
 872                                         vm_page_unlock(m[i]);
 873                                 }
 874                                 VM_OBJECT_UNLOCK(object);
 875                                 count = first + runpg;
 876                         }
 877                         break;
 878                 }
 879                 first = runend;
 880         }
 881
 882         /*
 883          * the first and last page have been calculated now, move input pages
 884          * to be zero based...
 885          */
 886         if (first != 0) {
 887                 m += first;
 888                 count -= first;
 889                 reqpage -= first;
 890         }
 891
 892         /*
 893          * calculate the file virtual address for the transfer
 894          */
 895         foff = IDX_TO_OFF(m[0]->pindex);
 896
 897         /*
 898          * calculate the size of the transfer
 899          */
 900         size = count * PAGE_SIZE;
 901         KASSERT(count > 0, ("zero count"));
 902         if ((foff + size) > object->un_pager.vnp.vnp_size)
 903                 size = object->un_pager.vnp.vnp_size - foff;
 904         KASSERT(size > 0, ("zero size"));
 905
 906         /*
 907          * round up physical size for real devices.
 908          */
 909         if (1) {
 910                 int secmask = bo->bo_bsize - 1;
 911                 KASSERT(secmask < PAGE_SIZE && secmask > 0,
 912                     ("vnode_pager_generic_getpages: sector size %d too large",
 913                     secmask + 1));
 914                 size = (size + secmask) & ~secmask;
 915         }
 916
 917         bp = getpbuf(&vnode_pbuf_freecnt);
 918         kva = (vm_offset_t)bp->b_data;
 919
 920         /*
 921          * and map the pages to be read into the kva, if the filesystem
 922          * requires mapped buffers.
 923          */
 924         mp = vp->v_mount;
 925         if (mp != NULL && (mp->mnt_kern_flag & MNTK_UNMAPPED_BUFS) != 0 &&
 926             unmapped_buf_allowed) {
 927                 bp->b_data = unmapped_buf;
 928                 bp->b_kvabase = unmapped_buf;
 929                 bp->b_offset = 0;
 930                 bp->b_flags |= B_UNMAPPED;
 931                 bp->b_npages = count;
 932                 for (i = 0; i < count; i++)
 933                         bp->b_pages[i] = m[i];
 934         } else
 935                 pmap_qenter(kva, m, count);
 936
 937         /* build a minimal buffer header */
 938         bp->b_iocmd = BIO_READ;
 939         bp->b_iodone = bdone;
 940         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
 941         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
 942         bp->b_rcred = crhold(curthread->td_ucred);
 943         bp->b_wcred = crhold(curthread->td_ucred);
 944         bp->b_blkno = firstaddr;
 945         pbgetbo(bo, bp);
 946         bp->b_vp = vp;
 947         bp->b_bcount = size;
 948         bp->b_bufsize = size;
 949         bp->b_runningbufspace = bp->b_bufsize;
 950         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
 951
 952         PCPU_INC(cnt.v_vnodein);
 953         PCPU_ADD(cnt.v_vnodepgsin, count);
 954
 955         /* do the input */
 956         bp->b_iooffset = dbtob(bp->b_blkno);
 957         bstrategy(bp);
 958
 959         bwait(bp, PVM, "vnread");
 960
 961         if ((bp->b_ioflags & BIO_ERROR) != 0)
 962                 error = EIO;
 963
 964         if (error == 0 && size != count * PAGE_SIZE) {
 965                 if ((bp->b_flags & B_UNMAPPED) != 0) {
 966                         bp->b_flags &= ~B_UNMAPPED;
 967                         pmap_qenter(kva, m, count);
 968                 }
 969                 bzero((caddr_t)kva + size, PAGE_SIZE * count - size);
 970         }
 971         if ((bp->b_flags & B_UNMAPPED) == 0)
 972                 pmap_qremove(kva, count);
 973         if (mp != NULL && (mp->mnt_kern_flag & MNTK_UNMAPPED_BUFS) != 0) {
 974                 bp->b_data = (caddr_t)kva;
 975                 bp->b_kvabase = (caddr_t)kva;
 976                 bp->b_flags &= ~B_UNMAPPED;
 977                 for (i = 0; i < count; i++)
 978                         bp->b_pages[i] = NULL;
 979         }
 980
 981         /*
 982          * free the buffer header back to the swap buffer pool
 983          */
 984         bp->b_vp = NULL;
 985         pbrelbo(bp);
 986         relpbuf(bp, &vnode_pbuf_freecnt);
 987
 988         VM_OBJECT_LOCK(object);
 989         for (i = 0, tfoff = foff; i < count; i++, tfoff = nextoff) {
 990                 vm_page_t mt;
 991
 992                 nextoff = tfoff + PAGE_SIZE;
 993                 mt = m[i];
 994
 995                 if (nextoff <= object->un_pager.vnp.vnp_size) {
 996                         /*
 997                          * Read filled up entire page.
 998                          */
 999                         mt->valid = VM_PAGE_BITS_ALL;
1000                         KASSERT(mt->dirty == 0,
1001                             ("vnode_pager_generic_getpages: page %p is dirty",
1002                             mt));
1003                         KASSERT(!pmap_page_is_mapped(mt),
1004                             ("vnode_pager_generic_getpages: page %p is mapped",
1005                             mt));
1006                 } else {
1007                         /*
1008                          * Read did not fill up entire page.
1009                          *
1010                          * Currently we do not set the entire page valid,
1011                          * we just try to clear the piece that we couldn't
1012                          * read.
1013                          */
1014                         vm_page_set_valid(mt, 0,
1015                             object->un_pager.vnp.vnp_size - tfoff);
1016                         KASSERT((mt->dirty & vm_page_bits(0,
1017                             object->un_pager.vnp.vnp_size - tfoff)) == 0,
1018                             ("vnode_pager_generic_getpages: page %p is dirty",
1019                             mt));
1020                 }
1021
1022                 if (i != reqpage)
1023                         vm_page_readahead_finish(mt);
1024         }
1025         VM_OBJECT_UNLOCK(object);
1026         if (error) {
1027                 printf("vnode_pager_getpages: I/O read error\n");
1028         }
1029         return (error ? VM_PAGER_ERROR : VM_PAGER_OK);
1030 }
1031
1032 /*
1033  * EOPNOTSUPP is no longer legal.  For local media VFS's that do not
1034  * implement their own VOP_PUTPAGES, their VOP_PUTPAGES should call to
1035  * vnode_pager_generic_putpages() to implement the previous behaviour.
1036  *
1037  * All other FS's should use the bypass to get to the local media
1038  * backing vp's VOP_PUTPAGES.
1039  */
1040 static void
1041 vnode_pager_putpages(object, m, count, sync, rtvals)
1042         vm_object_t object;
1043         vm_page_t *m;
1044         int count;
1045         boolean_t sync;
1046         int *rtvals;
1047 {
1048         int rtval;
1049         struct vnode *vp;
1050         int bytes = count * PAGE_SIZE;
1051
1052         /*
1053          * Force synchronous operation if we are extremely low on memory
1054          * to prevent a low-memory deadlock.  VOP operations often need to
1055          * allocate more memory to initiate the I/O ( i.e. do a BMAP
1056          * operation ).  The swapper handles the case by limiting the amount
1057          * of asynchronous I/O, but that sort of solution doesn't scale well
1058          * for the vnode pager without a lot of work.
1059          *
1060          * Also, the backing vnode's iodone routine may not wake the pageout
1061          * daemon up.  This should be probably be addressed XXX.
1062          */
1063
1064         if ((cnt.v_free_count + cnt.v_cache_count) < cnt.v_pageout_free_min)
1065                 sync |= OBJPC_SYNC;
1066
1067         /*
1068          * Call device-specific putpages function
1069          */
1070         vp = object->handle;
1071         VM_OBJECT_UNLOCK(object);
1072         rtval = VOP_PUTPAGES(vp, m, bytes, sync, rtvals, 0);
1073         KASSERT(rtval != EOPNOTSUPP,
1074             ("vnode_pager: stale FS putpages\n"));
1075         VM_OBJECT_LOCK(object);
1076 }
1077
1078
1079 /*
1080  * This is now called from local media FS's to operate against their
1081  * own vnodes if they fail to implement VOP_PUTPAGES.
1082  *
1083  * This is typically called indirectly via the pageout daemon and
1084  * clustering has already typically occured, so in general we ask the
1085  * underlying filesystem to write the data out asynchronously rather
1086  * then delayed.
1087  */
1088 int
1089 vnode_pager_generic_putpages(struct vnode *vp, vm_page_t *ma, int bytecount,
1090     int flags, int *rtvals)
1091 {
1092         int i;
1093         vm_object_t object;
1094         vm_page_t m;
1095         int count;
1096
1097         int maxsize, ncount;
1098         vm_ooffset_t poffset;
1099         struct uio auio;
1100         struct iovec aiov;
1101         int error;
1102         int ioflags;
1103         int ppscheck = 0;
1104         static struct timeval lastfail;
1105         static int curfail;
1106
1107         object = vp->v_object;
1108         count = bytecount / PAGE_SIZE;
1109
1110         for (i = 0; i < count; i++)
1111                 rtvals[i] = VM_PAGER_ERROR;
1112
1113         if ((int64_t)ma[0]->pindex < 0) {
1114                 printf("vnode_pager_putpages: attempt to write meta-data!!! -- 0x%lx(%lx)\n",
1115                     (long)ma[0]->pindex, (u_long)ma[0]->dirty);
1116                 rtvals[0] = VM_PAGER_BAD;
1117                 return VM_PAGER_BAD;
1118         }
1119
1120         maxsize = count * PAGE_SIZE;
1121         ncount = count;
1122
1123         poffset = IDX_TO_OFF(ma[0]->pindex);
1124
1125         /*
1126          * If the page-aligned write is larger then the actual file we
1127          * have to invalidate pages occuring beyond the file EOF.  However,
1128          * there is an edge case where a file may not be page-aligned where
1129          * the last page is partially invalid.  In this case the filesystem
1130          * may not properly clear the dirty bits for the entire page (which
1131          * could be VM_PAGE_BITS_ALL due to the page having been mmap()d).
1132          * With the page locked we are free to fix-up the dirty bits here.
1133          *
1134          * We do not under any circumstances truncate the valid bits, as
1135          * this will screw up bogus page replacement.
1136          */
1137         VM_OBJECT_LOCK(object);
1138         if (maxsize + poffset > object->un_pager.vnp.vnp_size) {
1139                 if (object->un_pager.vnp.vnp_size > poffset) {
1140                         int pgoff;
1141
1142                         maxsize = object->un_pager.vnp.vnp_size - poffset;
1143                         ncount = btoc(maxsize);
1144                         if ((pgoff = (int)maxsize & PAGE_MASK) != 0) {
1145                                 /*
1146                                  * If the object is locked and the following
1147                                  * conditions hold, then the page's dirty
1148                                  * field cannot be concurrently changed by a
1149                                  * pmap operation.
1150                                  */
1151                                 m = ma[ncount - 1];
1152                                 KASSERT(m->busy > 0,
1153                 ("vnode_pager_generic_putpages: page %p is not busy", m));
1154                                 KASSERT(!pmap_page_is_write_mapped(m),
1155                 ("vnode_pager_generic_putpages: page %p is not read-only", m));
1156                                 vm_page_clear_dirty(m, pgoff, PAGE_SIZE -
1157                                     pgoff);
1158                         }
1159                 } else {
1160                         maxsize = 0;
1161                         ncount = 0;
1162                 }
1163                 if (ncount < count) {
1164                         for (i = ncount; i < count; i++) {
1165                                 rtvals[i] = VM_PAGER_BAD;
1166                         }
1167                 }
1168         }
1169         VM_OBJECT_UNLOCK(object);
1170
1171         /*
1172          * pageouts are already clustered, use IO_ASYNC t o force a bawrite()
1173          * rather then a bdwrite() to prevent paging I/O from saturating
1174          * the buffer cache.  Dummy-up the sequential heuristic to cause
1175          * large ranges to cluster.  If neither IO_SYNC or IO_ASYNC is set,
1176          * the system decides how to cluster.
1177          */
1178         ioflags = IO_VMIO;
1179         if (flags & (VM_PAGER_PUT_SYNC | VM_PAGER_PUT_INVAL))
1180                 ioflags |= IO_SYNC;
1181         else if ((flags & VM_PAGER_CLUSTER_OK) == 0)
1182                 ioflags |= IO_ASYNC;
1183         ioflags |= (flags & VM_PAGER_PUT_INVAL) ? IO_INVAL: 0;
1184         ioflags |= IO_SEQMAX << IO_SEQSHIFT;
1185
1186         aiov.iov_base = (caddr_t) 0;
1187         aiov.iov_len = maxsize;
1188         auio.uio_iov = &aiov;
1189         auio.uio_iovcnt = 1;
1190         auio.uio_offset = poffset;
1191         auio.uio_segflg = UIO_NOCOPY;
1192         auio.uio_rw = UIO_WRITE;
1193         auio.uio_resid = maxsize;
1194         auio.uio_td = (struct thread *) 0;
1195         error = VOP_WRITE(vp, &auio, ioflags, curthread->td_ucred);
1196         PCPU_INC(cnt.v_vnodeout);
1197         PCPU_ADD(cnt.v_vnodepgsout, ncount);
1198
1199         if (error) {
1200                 if ((ppscheck = ppsratecheck(&lastfail, &curfail, 1)))
1201                         printf("vnode_pager_putpages: I/O error %d\n", error);
1202         }
1203         if (auio.uio_resid) {
1204                 if (ppscheck || ppsratecheck(&lastfail, &curfail, 1))
1205                         printf("vnode_pager_putpages: residual I/O %zd at %lu\n",
1206                             auio.uio_resid, (u_long)ma[0]->pindex);
1207         }
1208         for (i = 0; i < ncount; i++) {
1209                 rtvals[i] = VM_PAGER_OK;
1210         }
1211         return rtvals[0];
1212 }
1213
1214 void
1215 vnode_pager_undirty_pages(vm_page_t *ma, int *rtvals, int written)
1216 {
1217         vm_object_t obj;
1218         int i, pos;
1219
1220         if (written == 0)
1221                 return;
1222         obj = ma[0]->object;
1223         VM_OBJECT_LOCK(obj);
1224         for (i = 0, pos = 0; pos < written; i++, pos += PAGE_SIZE) {
1225                 if (pos < trunc_page(written)) {
1226                         rtvals[i] = VM_PAGER_OK;
1227                         vm_page_undirty(ma[i]);
1228                 } else {
1229                         /* Partially written page. */
1230                         rtvals[i] = VM_PAGER_AGAIN;
1231                         vm_page_clear_dirty(ma[i], 0, written & PAGE_MASK);
1232                 }
1233         }
1234         VM_OBJECT_UNLOCK(obj);
1235 }
1236
1237 void
1238 vnode_pager_update_writecount(vm_object_t object, vm_offset_t start,
1239     vm_offset_t end)
1240 {
1241         struct vnode *vp;
1242         vm_ooffset_t old_wm;
1243
1244         VM_OBJECT_LOCK(object);
1245         if (object->type != OBJT_VNODE) {
1246                 VM_OBJECT_UNLOCK(object);
1247                 return;
1248         }
1249         old_wm = object->un_pager.vnp.writemappings;
1250         object->un_pager.vnp.writemappings += (vm_ooffset_t)end - start;
1251         vp = object->handle;
1252         if (old_wm == 0 && object->un_pager.vnp.writemappings != 0) {
1253                 ASSERT_VOP_ELOCKED(vp, "v_writecount inc");
1254                 VOP_ADD_WRITECOUNT(vp, 1);
1255         } else if (old_wm != 0 && object->un_pager.vnp.writemappings == 0) {
1256                 ASSERT_VOP_ELOCKED(vp, "v_writecount dec");
1257                 VOP_ADD_WRITECOUNT(vp, -1);
1258         }
1259         VM_OBJECT_UNLOCK(object);
1260 }
1261
1262 void
1263 vnode_pager_release_writecount(vm_object_t object, vm_offset_t start,
1264     vm_offset_t end)
1265 {
1266         struct vnode *vp;
1267         struct mount *mp;
1268         vm_offset_t inc;
1269         int vfslocked;
1270
1271         VM_OBJECT_LOCK(object);
1272
1273         /*
1274          * First, recheck the object type to account for the race when
1275          * the vnode is reclaimed.
1276          */
1277         if (object->type != OBJT_VNODE) {
1278                 VM_OBJECT_UNLOCK(object);
1279                 return;
1280         }
1281
1282         /*
1283          * Optimize for the case when writemappings is not going to
1284          * zero.
1285          */
1286         inc = end - start;
1287         if (object->un_pager.vnp.writemappings != inc) {
1288                 object->un_pager.vnp.writemappings -= inc;
1289                 VM_OBJECT_UNLOCK(object);
1290                 return;
1291         }
1292
1293         vp = object->handle;
1294         vhold(vp);
1295         VM_OBJECT_UNLOCK(object);
1296         vfslocked = VFS_LOCK_GIANT(vp->v_mount);
1297         mp = NULL;
1298         vn_start_write(vp, &mp, V_WAIT);
1299         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
1300
1301         /*
1302          * Decrement the object's writemappings, by swapping the start
1303          * and end arguments for vnode_pager_update_writecount().  If
1304          * there was not a race with vnode reclaimation, then the
1305          * vnode's v_writecount is decremented.
1306          */
1307         vnode_pager_update_writecount(object, end, start);
1308         VOP_UNLOCK(vp, 0);
1309         vdrop(vp);
1310         if (mp != NULL)
1311                 vn_finished_write(mp);
1312         VFS_UNLOCK_GIANT(vfslocked);
1313 }