The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/vm/vnode_pager.c

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    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: head/sys/vm/vnode_pager.c 302343 2016-07-05 11:21:02Z kib $");
   55 
   56 #include "opt_vm.h"
   57 
   58 #include <sys/param.h>
   59 #include <sys/systm.h>
   60 #include <sys/proc.h>
   61 #include <sys/vnode.h>
   62 #include <sys/mount.h>
   63 #include <sys/bio.h>
   64 #include <sys/buf.h>
   65 #include <sys/vmmeter.h>
   66 #include <sys/limits.h>
   67 #include <sys/conf.h>
   68 #include <sys/rwlock.h>
   69 #include <sys/sf_buf.h>
   70 
   71 #include <machine/atomic.h>
   72 
   73 #include <vm/vm.h>
   74 #include <vm/vm_param.h>
   75 #include <vm/vm_object.h>
   76 #include <vm/vm_page.h>
   77 #include <vm/vm_pager.h>
   78 #include <vm/vm_map.h>
   79 #include <vm/vnode_pager.h>
   80 #include <vm/vm_extern.h>
   81 
   82 static int vnode_pager_addr(struct vnode *vp, vm_ooffset_t address,
   83     daddr_t *rtaddress, int *run);
   84 static int vnode_pager_input_smlfs(vm_object_t object, vm_page_t m);
   85 static int vnode_pager_input_old(vm_object_t object, vm_page_t m);
   86 static void vnode_pager_dealloc(vm_object_t);
   87 static int vnode_pager_getpages(vm_object_t, vm_page_t *, int, int *, int *);
   88 static int vnode_pager_getpages_async(vm_object_t, vm_page_t *, int, int *,
   89     int *, vop_getpages_iodone_t, void *);
   90 static void vnode_pager_putpages(vm_object_t, vm_page_t *, int, int, int *);
   91 static boolean_t vnode_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
   92 static vm_object_t vnode_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
   93     vm_ooffset_t, struct ucred *cred);
   94 static int vnode_pager_generic_getpages_done(struct buf *);
   95 static void vnode_pager_generic_getpages_done_async(struct buf *);
   96 
   97 struct pagerops vnodepagerops = {
   98         .pgo_alloc =    vnode_pager_alloc,
   99         .pgo_dealloc =  vnode_pager_dealloc,
  100         .pgo_getpages = vnode_pager_getpages,
  101         .pgo_getpages_async = vnode_pager_getpages_async,
  102         .pgo_putpages = vnode_pager_putpages,
  103         .pgo_haspage =  vnode_pager_haspage,
  104 };
  105 
  106 int vnode_pbuf_freecnt;
  107 int vnode_async_pbuf_freecnt;
  108 
  109 /* Create the VM system backing object for this vnode */
  110 int
  111 vnode_create_vobject(struct vnode *vp, off_t isize, struct thread *td)
  112 {
  113         vm_object_t object;
  114         vm_ooffset_t size = isize;
  115         struct vattr va;
  116 
  117         if (!vn_isdisk(vp, NULL) && vn_canvmio(vp) == FALSE)
  118                 return (0);
  119 
  120         while ((object = vp->v_object) != NULL) {
  121                 VM_OBJECT_WLOCK(object);
  122                 if (!(object->flags & OBJ_DEAD)) {
  123                         VM_OBJECT_WUNLOCK(object);
  124                         return (0);
  125                 }
  126                 VOP_UNLOCK(vp, 0);
  127                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
  128                 VM_OBJECT_SLEEP(object, object, PDROP | PVM, "vodead", 0);
  129                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  130         }
  131 
  132         if (size == 0) {
  133                 if (vn_isdisk(vp, NULL)) {
  134                         size = IDX_TO_OFF(INT_MAX);
  135                 } else {
  136                         if (VOP_GETATTR(vp, &va, td->td_ucred))
  137                                 return (0);
  138                         size = va.va_size;
  139                 }
  140         }
  141 
  142         object = vnode_pager_alloc(vp, size, 0, 0, td->td_ucred);
  143         /*
  144          * Dereference the reference we just created.  This assumes
  145          * that the object is associated with the vp.
  146          */
  147         VM_OBJECT_WLOCK(object);
  148         object->ref_count--;
  149         VM_OBJECT_WUNLOCK(object);
  150         vrele(vp);
  151 
  152         KASSERT(vp->v_object != NULL, ("vnode_create_vobject: NULL object"));
  153 
  154         return (0);
  155 }
  156 
  157 void
  158 vnode_destroy_vobject(struct vnode *vp)
  159 {
  160         struct vm_object *obj;
  161 
  162         obj = vp->v_object;
  163         if (obj == NULL)
  164                 return;
  165         ASSERT_VOP_ELOCKED(vp, "vnode_destroy_vobject");
  166         VM_OBJECT_WLOCK(obj);
  167         umtx_shm_object_terminated(obj);
  168         if (obj->ref_count == 0) {
  169                 /*
  170                  * don't double-terminate the object
  171                  */
  172                 if ((obj->flags & OBJ_DEAD) == 0) {
  173                         vm_object_terminate(obj);
  174                 } else {
  175                         /*
  176                          * Waiters were already handled during object
  177                          * termination.  The exclusive vnode lock hopefully
  178                          * prevented new waiters from referencing the dying
  179                          * object.
  180                          */
  181                         KASSERT((obj->flags & OBJ_DISCONNECTWNT) == 0,
  182                             ("OBJ_DISCONNECTWNT set obj %p flags %x",
  183                             obj, obj->flags));
  184                         vp->v_object = NULL;
  185                         VM_OBJECT_WUNLOCK(obj);
  186                 }
  187         } else {
  188                 /*
  189                  * Woe to the process that tries to page now :-).
  190                  */
  191                 vm_pager_deallocate(obj);
  192                 VM_OBJECT_WUNLOCK(obj);
  193         }
  194         KASSERT(vp->v_object == NULL, ("vp %p obj %p", vp, vp->v_object));
  195 }
  196 
  197 
  198 /*
  199  * Allocate (or lookup) pager for a vnode.
  200  * Handle is a vnode pointer.
  201  *
  202  * MPSAFE
  203  */
  204 vm_object_t
  205 vnode_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
  206     vm_ooffset_t offset, struct ucred *cred)
  207 {
  208         vm_object_t object;
  209         struct vnode *vp;
  210 
  211         /*
  212          * Pageout to vnode, no can do yet.
  213          */
  214         if (handle == NULL)
  215                 return (NULL);
  216 
  217         vp = (struct vnode *) handle;
  218 
  219         /*
  220          * If the object is being terminated, wait for it to
  221          * go away.
  222          */
  223 retry:
  224         while ((object = vp->v_object) != NULL) {
  225                 VM_OBJECT_WLOCK(object);
  226                 if ((object->flags & OBJ_DEAD) == 0)
  227                         break;
  228                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
  229                 VM_OBJECT_SLEEP(object, object, PDROP | PVM, "vadead", 0);
  230         }
  231 
  232         KASSERT(vp->v_usecount != 0, ("vnode_pager_alloc: no vnode reference"));
  233 
  234         if (object == NULL) {
  235                 /*
  236                  * Add an object of the appropriate size
  237                  */
  238                 object = vm_object_allocate(OBJT_VNODE, OFF_TO_IDX(round_page(size)));
  239 
  240                 object->un_pager.vnp.vnp_size = size;
  241                 object->un_pager.vnp.writemappings = 0;
  242 
  243                 object->handle = handle;
  244                 VI_LOCK(vp);
  245                 if (vp->v_object != NULL) {
  246                         /*
  247                          * Object has been created while we were sleeping
  248                          */
  249                         VI_UNLOCK(vp);
  250                         VM_OBJECT_WLOCK(object);
  251                         KASSERT(object->ref_count == 1,
  252                             ("leaked ref %p %d", object, object->ref_count));
  253                         object->type = OBJT_DEAD;
  254                         object->ref_count = 0;
  255                         VM_OBJECT_WUNLOCK(object);
  256                         vm_object_destroy(object);
  257                         goto retry;
  258                 }
  259                 vp->v_object = object;
  260                 VI_UNLOCK(vp);
  261         } else {
  262                 object->ref_count++;
  263 #if VM_NRESERVLEVEL > 0
  264                 vm_object_color(object, 0);
  265 #endif
  266                 VM_OBJECT_WUNLOCK(object);
  267         }
  268         vref(vp);
  269         return (object);
  270 }
  271 
  272 /*
  273  *      The object must be locked.
  274  */
  275 static void
  276 vnode_pager_dealloc(vm_object_t object)
  277 {
  278         struct vnode *vp;
  279         int refs;
  280 
  281         vp = object->handle;
  282         if (vp == NULL)
  283                 panic("vnode_pager_dealloc: pager already dealloced");
  284 
  285         VM_OBJECT_ASSERT_WLOCKED(object);
  286         vm_object_pip_wait(object, "vnpdea");
  287         refs = object->ref_count;
  288 
  289         object->handle = NULL;
  290         object->type = OBJT_DEAD;
  291         if (object->flags & OBJ_DISCONNECTWNT) {
  292                 vm_object_clear_flag(object, OBJ_DISCONNECTWNT);
  293                 wakeup(object);
  294         }
  295         ASSERT_VOP_ELOCKED(vp, "vnode_pager_dealloc");
  296         if (object->un_pager.vnp.writemappings > 0) {
  297                 object->un_pager.vnp.writemappings = 0;
  298                 VOP_ADD_WRITECOUNT(vp, -1);
  299                 CTR3(KTR_VFS, "%s: vp %p v_writecount decreased to %d",
  300                     __func__, vp, vp->v_writecount);
  301         }
  302         vp->v_object = NULL;
  303         VOP_UNSET_TEXT(vp);
  304         VM_OBJECT_WUNLOCK(object);
  305         while (refs-- > 0)
  306                 vunref(vp);
  307         VM_OBJECT_WLOCK(object);
  308 }
  309 
  310 static boolean_t
  311 vnode_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
  312     int *after)
  313 {
  314         struct vnode *vp = object->handle;
  315         daddr_t bn;
  316         int err;
  317         daddr_t reqblock;
  318         int poff;
  319         int bsize;
  320         int pagesperblock, blocksperpage;
  321 
  322         VM_OBJECT_ASSERT_WLOCKED(object);
  323         /*
  324          * If no vp or vp is doomed or marked transparent to VM, we do not
  325          * have the page.
  326          */
  327         if (vp == NULL || vp->v_iflag & VI_DOOMED)
  328                 return FALSE;
  329         /*
  330          * If the offset is beyond end of file we do
  331          * not have the page.
  332          */
  333         if (IDX_TO_OFF(pindex) >= object->un_pager.vnp.vnp_size)
  334                 return FALSE;
  335 
  336         bsize = vp->v_mount->mnt_stat.f_iosize;
  337         pagesperblock = bsize / PAGE_SIZE;
  338         blocksperpage = 0;
  339         if (pagesperblock > 0) {
  340                 reqblock = pindex / pagesperblock;
  341         } else {
  342                 blocksperpage = (PAGE_SIZE / bsize);
  343                 reqblock = pindex * blocksperpage;
  344         }
  345         VM_OBJECT_WUNLOCK(object);
  346         err = VOP_BMAP(vp, reqblock, NULL, &bn, after, before);
  347         VM_OBJECT_WLOCK(object);
  348         if (err)
  349                 return TRUE;
  350         if (bn == -1)
  351                 return FALSE;
  352         if (pagesperblock > 0) {
  353                 poff = pindex - (reqblock * pagesperblock);
  354                 if (before) {
  355                         *before *= pagesperblock;
  356                         *before += poff;
  357                 }
  358                 if (after) {
  359                         /*
  360                          * The BMAP vop can report a partial block in the
  361                          * 'after', but must not report blocks after EOF.
  362                          * Assert the latter, and truncate 'after' in case
  363                          * of the former.
  364                          */
  365                         KASSERT((reqblock + *after) * pagesperblock <
  366                             roundup2(object->size, pagesperblock),
  367                             ("%s: reqblock %jd after %d size %ju", __func__,
  368                             (intmax_t )reqblock, *after,
  369                             (uintmax_t )object->size));
  370                         *after *= pagesperblock;
  371                         *after += pagesperblock - (poff + 1);
  372                         if (pindex + *after >= object->size)
  373                                 *after = object->size - 1 - pindex;
  374                 }
  375         } else {
  376                 if (before) {
  377                         *before /= blocksperpage;
  378                 }
  379 
  380                 if (after) {
  381                         *after /= blocksperpage;
  382                 }
  383         }
  384         return TRUE;
  385 }
  386 
  387 /*
  388  * Lets the VM system know about a change in size for a file.
  389  * We adjust our own internal size and flush any cached pages in
  390  * the associated object that are affected by the size change.
  391  *
  392  * Note: this routine may be invoked as a result of a pager put
  393  * operation (possibly at object termination time), so we must be careful.
  394  */
  395 void
  396 vnode_pager_setsize(struct vnode *vp, vm_ooffset_t nsize)
  397 {
  398         vm_object_t object;
  399         vm_page_t m;
  400         vm_pindex_t nobjsize;
  401 
  402         if ((object = vp->v_object) == NULL)
  403                 return;
  404 /*      ASSERT_VOP_ELOCKED(vp, "vnode_pager_setsize and not locked vnode"); */
  405         VM_OBJECT_WLOCK(object);
  406         if (object->type == OBJT_DEAD) {
  407                 VM_OBJECT_WUNLOCK(object);
  408                 return;
  409         }
  410         KASSERT(object->type == OBJT_VNODE,
  411             ("not vnode-backed object %p", object));
  412         if (nsize == object->un_pager.vnp.vnp_size) {
  413                 /*
  414                  * Hasn't changed size
  415                  */
  416                 VM_OBJECT_WUNLOCK(object);
  417                 return;
  418         }
  419         nobjsize = OFF_TO_IDX(nsize + PAGE_MASK);
  420         if (nsize < object->un_pager.vnp.vnp_size) {
  421                 /*
  422                  * File has shrunk. Toss any cached pages beyond the new EOF.
  423                  */
  424                 if (nobjsize < object->size)
  425                         vm_object_page_remove(object, nobjsize, object->size,
  426                             0);
  427                 /*
  428                  * this gets rid of garbage at the end of a page that is now
  429                  * only partially backed by the vnode.
  430                  *
  431                  * XXX for some reason (I don't know yet), if we take a
  432                  * completely invalid page and mark it partially valid
  433                  * it can screw up NFS reads, so we don't allow the case.
  434                  */
  435                 if ((nsize & PAGE_MASK) &&
  436                     (m = vm_page_lookup(object, OFF_TO_IDX(nsize))) != NULL &&
  437                     m->valid != 0) {
  438                         int base = (int)nsize & PAGE_MASK;
  439                         int size = PAGE_SIZE - base;
  440 
  441                         /*
  442                          * Clear out partial-page garbage in case
  443                          * the page has been mapped.
  444                          */
  445                         pmap_zero_page_area(m, base, size);
  446 
  447                         /*
  448                          * Update the valid bits to reflect the blocks that
  449                          * have been zeroed.  Some of these valid bits may
  450                          * have already been set.
  451                          */
  452                         vm_page_set_valid_range(m, base, size);
  453 
  454                         /*
  455                          * Round "base" to the next block boundary so that the
  456                          * dirty bit for a partially zeroed block is not
  457                          * cleared.
  458                          */
  459                         base = roundup2(base, DEV_BSIZE);
  460 
  461                         /*
  462                          * Clear out partial-page dirty bits.
  463                          *
  464                          * note that we do not clear out the valid
  465                          * bits.  This would prevent bogus_page
  466                          * replacement from working properly.
  467                          */
  468                         vm_page_clear_dirty(m, base, PAGE_SIZE - base);
  469                 } else if ((nsize & PAGE_MASK) &&
  470                     vm_page_is_cached(object, OFF_TO_IDX(nsize))) {
  471                         vm_page_cache_free(object, OFF_TO_IDX(nsize),
  472                             nobjsize);
  473                 }
  474         }
  475         object->un_pager.vnp.vnp_size = nsize;
  476         object->size = nobjsize;
  477         VM_OBJECT_WUNLOCK(object);
  478 }
  479 
  480 /*
  481  * calculate the linear (byte) disk address of specified virtual
  482  * file address
  483  */
  484 static int
  485 vnode_pager_addr(struct vnode *vp, vm_ooffset_t address, daddr_t *rtaddress,
  486     int *run)
  487 {
  488         int bsize;
  489         int err;
  490         daddr_t vblock;
  491         daddr_t voffset;
  492 
  493         if (address < 0)
  494                 return -1;
  495 
  496         if (vp->v_iflag & VI_DOOMED)
  497                 return -1;
  498 
  499         bsize = vp->v_mount->mnt_stat.f_iosize;
  500         vblock = address / bsize;
  501         voffset = address % bsize;
  502 
  503         err = VOP_BMAP(vp, vblock, NULL, rtaddress, run, NULL);
  504         if (err == 0) {
  505                 if (*rtaddress != -1)
  506                         *rtaddress += voffset / DEV_BSIZE;
  507                 if (run) {
  508                         *run += 1;
  509                         *run *= bsize/PAGE_SIZE;
  510                         *run -= voffset/PAGE_SIZE;
  511                 }
  512         }
  513 
  514         return (err);
  515 }
  516 
  517 /*
  518  * small block filesystem vnode pager input
  519  */
  520 static int
  521 vnode_pager_input_smlfs(vm_object_t object, vm_page_t m)
  522 {
  523         struct vnode *vp;
  524         struct bufobj *bo;
  525         struct buf *bp;
  526         struct sf_buf *sf;
  527         daddr_t fileaddr;
  528         vm_offset_t bsize;
  529         vm_page_bits_t bits;
  530         int error, i;
  531 
  532         error = 0;
  533         vp = object->handle;
  534         if (vp->v_iflag & VI_DOOMED)
  535                 return VM_PAGER_BAD;
  536 
  537         bsize = vp->v_mount->mnt_stat.f_iosize;
  538 
  539         VOP_BMAP(vp, 0, &bo, 0, NULL, NULL);
  540 
  541         sf = sf_buf_alloc(m, 0);
  542 
  543         for (i = 0; i < PAGE_SIZE / bsize; i++) {
  544                 vm_ooffset_t address;
  545 
  546                 bits = vm_page_bits(i * bsize, bsize);
  547                 if (m->valid & bits)
  548                         continue;
  549 
  550                 address = IDX_TO_OFF(m->pindex) + i * bsize;
  551                 if (address >= object->un_pager.vnp.vnp_size) {
  552                         fileaddr = -1;
  553                 } else {
  554                         error = vnode_pager_addr(vp, address, &fileaddr, NULL);
  555                         if (error)
  556                                 break;
  557                 }
  558                 if (fileaddr != -1) {
  559                         bp = getpbuf(&vnode_pbuf_freecnt);
  560 
  561                         /* build a minimal buffer header */
  562                         bp->b_iocmd = BIO_READ;
  563                         bp->b_iodone = bdone;
  564                         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
  565                         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
  566                         bp->b_rcred = crhold(curthread->td_ucred);
  567                         bp->b_wcred = crhold(curthread->td_ucred);
  568                         bp->b_data = (caddr_t)sf_buf_kva(sf) + i * bsize;
  569                         bp->b_blkno = fileaddr;
  570                         pbgetbo(bo, bp);
  571                         bp->b_vp = vp;
  572                         bp->b_bcount = bsize;
  573                         bp->b_bufsize = bsize;
  574                         bp->b_runningbufspace = bp->b_bufsize;
  575                         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
  576 
  577                         /* do the input */
  578                         bp->b_iooffset = dbtob(bp->b_blkno);
  579                         bstrategy(bp);
  580 
  581                         bwait(bp, PVM, "vnsrd");
  582 
  583                         if ((bp->b_ioflags & BIO_ERROR) != 0)
  584                                 error = EIO;
  585 
  586                         /*
  587                          * free the buffer header back to the swap buffer pool
  588                          */
  589                         bp->b_vp = NULL;
  590                         pbrelbo(bp);
  591                         relpbuf(bp, &vnode_pbuf_freecnt);
  592                         if (error)
  593                                 break;
  594                 } else
  595                         bzero((caddr_t)sf_buf_kva(sf) + i * bsize, bsize);
  596                 KASSERT((m->dirty & bits) == 0,
  597                     ("vnode_pager_input_smlfs: page %p is dirty", m));
  598                 VM_OBJECT_WLOCK(object);
  599                 m->valid |= bits;
  600                 VM_OBJECT_WUNLOCK(object);
  601         }
  602         sf_buf_free(sf);
  603         if (error) {
  604                 return VM_PAGER_ERROR;
  605         }
  606         return VM_PAGER_OK;
  607 }
  608 
  609 /*
  610  * old style vnode pager input routine
  611  */
  612 static int
  613 vnode_pager_input_old(vm_object_t object, vm_page_t m)
  614 {
  615         struct uio auio;
  616         struct iovec aiov;
  617         int error;
  618         int size;
  619         struct sf_buf *sf;
  620         struct vnode *vp;
  621 
  622         VM_OBJECT_ASSERT_WLOCKED(object);
  623         error = 0;
  624 
  625         /*
  626          * Return failure if beyond current EOF
  627          */
  628         if (IDX_TO_OFF(m->pindex) >= object->un_pager.vnp.vnp_size) {
  629                 return VM_PAGER_BAD;
  630         } else {
  631                 size = PAGE_SIZE;
  632                 if (IDX_TO_OFF(m->pindex) + size > object->un_pager.vnp.vnp_size)
  633                         size = object->un_pager.vnp.vnp_size - IDX_TO_OFF(m->pindex);
  634                 vp = object->handle;
  635                 VM_OBJECT_WUNLOCK(object);
  636 
  637                 /*
  638                  * Allocate a kernel virtual address and initialize so that
  639                  * we can use VOP_READ/WRITE routines.
  640                  */
  641                 sf = sf_buf_alloc(m, 0);
  642 
  643                 aiov.iov_base = (caddr_t)sf_buf_kva(sf);
  644                 aiov.iov_len = size;
  645                 auio.uio_iov = &aiov;
  646                 auio.uio_iovcnt = 1;
  647                 auio.uio_offset = IDX_TO_OFF(m->pindex);
  648                 auio.uio_segflg = UIO_SYSSPACE;
  649                 auio.uio_rw = UIO_READ;
  650                 auio.uio_resid = size;
  651                 auio.uio_td = curthread;
  652 
  653                 error = VOP_READ(vp, &auio, 0, curthread->td_ucred);
  654                 if (!error) {
  655                         int count = size - auio.uio_resid;
  656 
  657                         if (count == 0)
  658                                 error = EINVAL;
  659                         else if (count != PAGE_SIZE)
  660                                 bzero((caddr_t)sf_buf_kva(sf) + count,
  661                                     PAGE_SIZE - count);
  662                 }
  663                 sf_buf_free(sf);
  664 
  665                 VM_OBJECT_WLOCK(object);
  666         }
  667         KASSERT(m->dirty == 0, ("vnode_pager_input_old: page %p is dirty", m));
  668         if (!error)
  669                 m->valid = VM_PAGE_BITS_ALL;
  670         return error ? VM_PAGER_ERROR : VM_PAGER_OK;
  671 }
  672 
  673 /*
  674  * generic vnode pager input routine
  675  */
  676 
  677 /*
  678  * Local media VFS's that do not implement their own VOP_GETPAGES
  679  * should have their VOP_GETPAGES call to vnode_pager_generic_getpages()
  680  * to implement the previous behaviour.
  681  *
  682  * All other FS's should use the bypass to get to the local media
  683  * backing vp's VOP_GETPAGES.
  684  */
  685 static int
  686 vnode_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
  687     int *rahead)
  688 {
  689         struct vnode *vp;
  690         int rtval;
  691 
  692         vp = object->handle;
  693         VM_OBJECT_WUNLOCK(object);
  694         rtval = VOP_GETPAGES(vp, m, count, rbehind, rahead);
  695         KASSERT(rtval != EOPNOTSUPP,
  696             ("vnode_pager: FS getpages not implemented\n"));
  697         VM_OBJECT_WLOCK(object);
  698         return rtval;
  699 }
  700 
  701 static int
  702 vnode_pager_getpages_async(vm_object_t object, vm_page_t *m, int count,
  703     int *rbehind, int *rahead, vop_getpages_iodone_t iodone, void *arg)
  704 {
  705         struct vnode *vp;
  706         int rtval;
  707 
  708         vp = object->handle;
  709         VM_OBJECT_WUNLOCK(object);
  710         rtval = VOP_GETPAGES_ASYNC(vp, m, count, rbehind, rahead, iodone, arg);
  711         KASSERT(rtval != EOPNOTSUPP,
  712             ("vnode_pager: FS getpages_async not implemented\n"));
  713         VM_OBJECT_WLOCK(object);
  714         return (rtval);
  715 }
  716 
  717 /*
  718  * The implementation of VOP_GETPAGES() and VOP_GETPAGES_ASYNC() for
  719  * local filesystems, where partially valid pages can only occur at
  720  * the end of file.
  721  */
  722 int
  723 vnode_pager_local_getpages(struct vop_getpages_args *ap)
  724 {
  725 
  726         return (vnode_pager_generic_getpages(ap->a_vp, ap->a_m, ap->a_count,
  727             ap->a_rbehind, ap->a_rahead, NULL, NULL));
  728 }
  729 
  730 int
  731 vnode_pager_local_getpages_async(struct vop_getpages_async_args *ap)
  732 {
  733 
  734         return (vnode_pager_generic_getpages(ap->a_vp, ap->a_m, ap->a_count,
  735             ap->a_rbehind, ap->a_rahead, ap->a_iodone, ap->a_arg));
  736 }
  737 
  738 /*
  739  * This is now called from local media FS's to operate against their
  740  * own vnodes if they fail to implement VOP_GETPAGES.
  741  */
  742 int
  743 vnode_pager_generic_getpages(struct vnode *vp, vm_page_t *m, int count,
  744     int *a_rbehind, int *a_rahead, vop_getpages_iodone_t iodone, void *arg)
  745 {
  746         vm_object_t object;
  747         struct bufobj *bo;
  748         struct buf *bp;
  749         off_t foff;
  750         int bsize, pagesperblock, *freecnt;
  751         int error, before, after, rbehind, rahead, poff, i;
  752         int bytecount, secmask;
  753 
  754         KASSERT(vp->v_type != VCHR && vp->v_type != VBLK,
  755             ("%s does not support devices", __func__));
  756 
  757         if (vp->v_iflag & VI_DOOMED)
  758                 return (VM_PAGER_BAD);
  759 
  760         object = vp->v_object;
  761         foff = IDX_TO_OFF(m[0]->pindex);
  762         bsize = vp->v_mount->mnt_stat.f_iosize;
  763         pagesperblock = bsize / PAGE_SIZE;
  764 
  765         KASSERT(foff < object->un_pager.vnp.vnp_size,
  766             ("%s: page %p offset beyond vp %p size", __func__, m[0], vp));
  767         KASSERT(count <= sizeof(bp->b_pages),
  768             ("%s: requested %d pages", __func__, count));
  769 
  770         /*
  771          * The last page has valid blocks.  Invalid part can only
  772          * exist at the end of file, and the page is made fully valid
  773          * by zeroing in vm_pager_get_pages().
  774          */
  775         if (m[count - 1]->valid != 0 && --count == 0) {
  776                 if (iodone != NULL)
  777                         iodone(arg, m, 1, 0);
  778                 return (VM_PAGER_OK);
  779         }
  780 
  781         /*
  782          * Synchronous and asynchronous paging operations use different
  783          * free pbuf counters.  This is done to avoid asynchronous requests
  784          * to consume all pbufs.
  785          * Allocate the pbuf at the very beginning of the function, so that
  786          * if we are low on certain kind of pbufs don't even proceed to BMAP,
  787          * but sleep.
  788          */
  789         freecnt = iodone != NULL ?
  790             &vnode_async_pbuf_freecnt : &vnode_pbuf_freecnt;
  791         bp = getpbuf(freecnt);
  792 
  793         /*
  794          * Get the underlying device blocks for the file with VOP_BMAP().
  795          * If the file system doesn't support VOP_BMAP, use old way of
  796          * getting pages via VOP_READ.
  797          */
  798         error = VOP_BMAP(vp, foff / bsize, &bo, &bp->b_blkno, &after, &before);
  799         if (error == EOPNOTSUPP) {
  800                 relpbuf(bp, freecnt);
  801                 VM_OBJECT_WLOCK(object);
  802                 for (i = 0; i < count; i++) {
  803                         PCPU_INC(cnt.v_vnodein);
  804                         PCPU_INC(cnt.v_vnodepgsin);
  805                         error = vnode_pager_input_old(object, m[i]);
  806                         if (error)
  807                                 break;
  808                 }
  809                 VM_OBJECT_WUNLOCK(object);
  810                 return (error);
  811         } else if (error != 0) {
  812                 relpbuf(bp, freecnt);
  813                 return (VM_PAGER_ERROR);
  814         }
  815 
  816         /*
  817          * If the file system supports BMAP, but blocksize is smaller
  818          * than a page size, then use special small filesystem code.
  819          */
  820         if (pagesperblock == 0) {
  821                 relpbuf(bp, freecnt);
  822                 for (i = 0; i < count; i++) {
  823                         PCPU_INC(cnt.v_vnodein);
  824                         PCPU_INC(cnt.v_vnodepgsin);
  825                         error = vnode_pager_input_smlfs(object, m[i]);
  826                         if (error)
  827                                 break;
  828                 }
  829                 return (error);
  830         }
  831 
  832         /*
  833          * A sparse file can be encountered only for a single page request,
  834          * which may not be preceded by call to vm_pager_haspage().
  835          */
  836         if (bp->b_blkno == -1) {
  837                 KASSERT(count == 1,
  838                     ("%s: array[%d] request to a sparse file %p", __func__,
  839                     count, vp));
  840                 relpbuf(bp, freecnt);
  841                 pmap_zero_page(m[0]);
  842                 KASSERT(m[0]->dirty == 0, ("%s: page %p is dirty",
  843                     __func__, m[0]));
  844                 VM_OBJECT_WLOCK(object);
  845                 m[0]->valid = VM_PAGE_BITS_ALL;
  846                 VM_OBJECT_WUNLOCK(object);
  847                 return (VM_PAGER_OK);
  848         }
  849 
  850         bp->b_blkno += (foff % bsize) / DEV_BSIZE;
  851 
  852         /* Recalculate blocks available after/before to pages. */
  853         poff = (foff % bsize) / PAGE_SIZE;
  854         before *= pagesperblock;
  855         before += poff;
  856         after *= pagesperblock;
  857         after += pagesperblock - (poff + 1);
  858         if (m[0]->pindex + after >= object->size)
  859                 after = object->size - 1 - m[0]->pindex;
  860         KASSERT(count <= after + 1, ("%s: %d pages asked, can do only %d",
  861             __func__, count, after + 1));
  862         after -= count - 1;
  863 
  864         /* Trim requested rbehind/rahead to possible values. */   
  865         rbehind = a_rbehind ? *a_rbehind : 0;
  866         rahead = a_rahead ? *a_rahead : 0;
  867         rbehind = min(rbehind, before);
  868         rbehind = min(rbehind, m[0]->pindex);
  869         rahead = min(rahead, after);
  870         rahead = min(rahead, object->size - m[count - 1]->pindex);
  871         KASSERT(rbehind + rahead + count <= sizeof(bp->b_pages),
  872             ("%s: behind %d ahead %d count %d", __func__,
  873             rbehind, rahead, count));
  874 
  875         /*
  876          * Fill in the bp->b_pages[] array with requested and optional   
  877          * read behind or read ahead pages.  Read behind pages are looked
  878          * up in a backward direction, down to a first cached page.  Same
  879          * for read ahead pages, but there is no need to shift the array
  880          * in case of encountering a cached page.
  881          */
  882         i = bp->b_npages = 0;
  883         if (rbehind) {
  884                 vm_pindex_t startpindex, tpindex;
  885                 vm_page_t p;
  886 
  887                 VM_OBJECT_WLOCK(object);
  888                 startpindex = m[0]->pindex - rbehind;
  889                 if ((p = TAILQ_PREV(m[0], pglist, listq)) != NULL &&
  890                     p->pindex >= startpindex)
  891                         startpindex = p->pindex + 1;
  892 
  893                 /* tpindex is unsigned; beware of numeric underflow. */
  894                 for (tpindex = m[0]->pindex - 1;
  895                     tpindex >= startpindex && tpindex < m[0]->pindex;
  896                     tpindex--, i++) {
  897                         p = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
  898                             VM_ALLOC_IFNOTCACHED);
  899                         if (p == NULL) {
  900                                 /* Shift the array. */
  901                                 for (int j = 0; j < i; j++)
  902                                         bp->b_pages[j] = bp->b_pages[j + 
  903                                             tpindex + 1 - startpindex]; 
  904                                 break;
  905                         }
  906                         bp->b_pages[tpindex - startpindex] = p;
  907                 }
  908 
  909                 bp->b_pgbefore = i;
  910                 bp->b_npages += i;
  911                 bp->b_blkno -= IDX_TO_OFF(i) / DEV_BSIZE;
  912         } else
  913                 bp->b_pgbefore = 0;
  914 
  915         /* Requested pages. */
  916         for (int j = 0; j < count; j++, i++)
  917                 bp->b_pages[i] = m[j];
  918         bp->b_npages += count;
  919 
  920         if (rahead) {
  921                 vm_pindex_t endpindex, tpindex;
  922                 vm_page_t p;
  923 
  924                 if (!VM_OBJECT_WOWNED(object))
  925                         VM_OBJECT_WLOCK(object);
  926                 endpindex = m[count - 1]->pindex + rahead + 1;
  927                 if ((p = TAILQ_NEXT(m[count - 1], listq)) != NULL &&
  928                     p->pindex < endpindex)
  929                         endpindex = p->pindex;
  930                 if (endpindex > object->size)
  931                         endpindex = object->size;
  932 
  933                 for (tpindex = m[count - 1]->pindex + 1;
  934                     tpindex < endpindex; i++, tpindex++) {
  935                         p = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
  936                             VM_ALLOC_IFNOTCACHED);
  937                         if (p == NULL)
  938                                 break;
  939                         bp->b_pages[i] = p;
  940                 }
  941 
  942                 bp->b_pgafter = i - bp->b_npages;
  943                 bp->b_npages = i;
  944         } else
  945                 bp->b_pgafter = 0;
  946 
  947         if (VM_OBJECT_WOWNED(object))
  948                 VM_OBJECT_WUNLOCK(object);
  949 
  950         /* Report back actual behind/ahead read. */
  951         if (a_rbehind)
  952                 *a_rbehind = bp->b_pgbefore;
  953         if (a_rahead)
  954                 *a_rahead = bp->b_pgafter;
  955 
  956         KASSERT(bp->b_npages <= sizeof(bp->b_pages),
  957             ("%s: buf %p overflowed", __func__, bp));
  958 
  959         /*
  960          * Recalculate first offset and bytecount with regards to read behind.
  961          * Truncate bytecount to vnode real size and round up physical size
  962          * for real devices.
  963          */
  964         foff = IDX_TO_OFF(bp->b_pages[0]->pindex);
  965         bytecount = bp->b_npages << PAGE_SHIFT;
  966         if ((foff + bytecount) > object->un_pager.vnp.vnp_size)
  967                 bytecount = object->un_pager.vnp.vnp_size - foff;
  968         secmask = bo->bo_bsize - 1;
  969         KASSERT(secmask < PAGE_SIZE && secmask > 0,
  970             ("%s: sector size %d too large", __func__, secmask + 1));
  971         bytecount = (bytecount + secmask) & ~secmask;
  972 
  973         /*
  974          * And map the pages to be read into the kva, if the filesystem
  975          * requires mapped buffers.
  976          */
  977         if ((vp->v_mount->mnt_kern_flag & MNTK_UNMAPPED_BUFS) != 0 &&
  978             unmapped_buf_allowed) {
  979                 bp->b_data = unmapped_buf;
  980                 bp->b_offset = 0;
  981         } else {
  982                 bp->b_data = bp->b_kvabase;
  983                 pmap_qenter((vm_offset_t)bp->b_data, bp->b_pages, bp->b_npages);
  984         }
  985 
  986         /* Build a minimal buffer header. */
  987         bp->b_iocmd = BIO_READ;
  988         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
  989         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
  990         bp->b_rcred = crhold(curthread->td_ucred);
  991         bp->b_wcred = crhold(curthread->td_ucred);
  992         pbgetbo(bo, bp);
  993         bp->b_vp = vp;
  994         bp->b_bcount = bp->b_bufsize = bp->b_runningbufspace = bytecount;
  995         bp->b_iooffset = dbtob(bp->b_blkno);
  996 
  997         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
  998         PCPU_INC(cnt.v_vnodein);
  999         PCPU_ADD(cnt.v_vnodepgsin, bp->b_npages);
 1000 
 1001         if (iodone != NULL) { /* async */
 1002                 bp->b_pgiodone = iodone;
 1003                 bp->b_caller1 = arg;
 1004                 bp->b_iodone = vnode_pager_generic_getpages_done_async;
 1005                 bp->b_flags |= B_ASYNC;
 1006                 BUF_KERNPROC(bp);
 1007                 bstrategy(bp);
 1008                 return (VM_PAGER_OK);
 1009         } else {
 1010                 bp->b_iodone = bdone;
 1011                 bstrategy(bp);
 1012                 bwait(bp, PVM, "vnread");
 1013                 error = vnode_pager_generic_getpages_done(bp);
 1014                 for (i = 0; i < bp->b_npages; i++)
 1015                         bp->b_pages[i] = NULL;
 1016                 bp->b_vp = NULL;
 1017                 pbrelbo(bp);
 1018                 relpbuf(bp, &vnode_pbuf_freecnt);
 1019                 return (error != 0 ? VM_PAGER_ERROR : VM_PAGER_OK);
 1020         }
 1021 }
 1022 
 1023 static void
 1024 vnode_pager_generic_getpages_done_async(struct buf *bp)
 1025 {
 1026         int error;
 1027 
 1028         error = vnode_pager_generic_getpages_done(bp);
 1029         /* Run the iodone upon the requested range. */
 1030         bp->b_pgiodone(bp->b_caller1, bp->b_pages + bp->b_pgbefore,
 1031             bp->b_npages - bp->b_pgbefore - bp->b_pgafter, error);
 1032         for (int i = 0; i < bp->b_npages; i++)
 1033                 bp->b_pages[i] = NULL;
 1034         bp->b_vp = NULL;
 1035         pbrelbo(bp);
 1036         relpbuf(bp, &vnode_async_pbuf_freecnt);
 1037 }
 1038 
 1039 static int
 1040 vnode_pager_generic_getpages_done(struct buf *bp)
 1041 {
 1042         vm_object_t object;
 1043         off_t tfoff, nextoff;
 1044         int i, error;
 1045 
 1046         error = (bp->b_ioflags & BIO_ERROR) != 0 ? EIO : 0;
 1047         object = bp->b_vp->v_object;
 1048 
 1049         if (error == 0 && bp->b_bcount != bp->b_npages * PAGE_SIZE) {
 1050                 if (!buf_mapped(bp)) {
 1051                         bp->b_data = bp->b_kvabase;
 1052                         pmap_qenter((vm_offset_t)bp->b_data, bp->b_pages,
 1053                             bp->b_npages);
 1054                 }
 1055                 bzero(bp->b_data + bp->b_bcount,
 1056                     PAGE_SIZE * bp->b_npages - bp->b_bcount);
 1057         }
 1058         if (buf_mapped(bp)) {
 1059                 pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages);
 1060                 bp->b_data = unmapped_buf;
 1061         }
 1062 
 1063         VM_OBJECT_WLOCK(object);
 1064         for (i = 0, tfoff = IDX_TO_OFF(bp->b_pages[0]->pindex);
 1065             i < bp->b_npages; i++, tfoff = nextoff) {
 1066                 vm_page_t mt;
 1067 
 1068                 nextoff = tfoff + PAGE_SIZE;
 1069                 mt = bp->b_pages[i];
 1070 
 1071                 if (nextoff <= object->un_pager.vnp.vnp_size) {
 1072                         /*
 1073                          * Read filled up entire page.
 1074                          */
 1075                         mt->valid = VM_PAGE_BITS_ALL;
 1076                         KASSERT(mt->dirty == 0,
 1077                             ("%s: page %p is dirty", __func__, mt));
 1078                         KASSERT(!pmap_page_is_mapped(mt),
 1079                             ("%s: page %p is mapped", __func__, mt));
 1080                 } else {
 1081                         /*
 1082                          * Read did not fill up entire page.
 1083                          *
 1084                          * Currently we do not set the entire page valid,
 1085                          * we just try to clear the piece that we couldn't
 1086                          * read.
 1087                          */
 1088                         vm_page_set_valid_range(mt, 0,
 1089                             object->un_pager.vnp.vnp_size - tfoff);
 1090                         KASSERT((mt->dirty & vm_page_bits(0,
 1091                             object->un_pager.vnp.vnp_size - tfoff)) == 0,
 1092                             ("%s: page %p is dirty", __func__, mt));
 1093                 }
 1094 
 1095                 if (i < bp->b_pgbefore || i >= bp->b_npages - bp->b_pgafter)
 1096                         vm_page_readahead_finish(mt);
 1097         }
 1098         VM_OBJECT_WUNLOCK(object);
 1099         if (error != 0)
 1100                 printf("%s: I/O read error %d\n", __func__, error);
 1101 
 1102         return (error);
 1103 }
 1104 
 1105 /*
 1106  * EOPNOTSUPP is no longer legal.  For local media VFS's that do not
 1107  * implement their own VOP_PUTPAGES, their VOP_PUTPAGES should call to
 1108  * vnode_pager_generic_putpages() to implement the previous behaviour.
 1109  *
 1110  * All other FS's should use the bypass to get to the local media
 1111  * backing vp's VOP_PUTPAGES.
 1112  */
 1113 static void
 1114 vnode_pager_putpages(vm_object_t object, vm_page_t *m, int count,
 1115     int flags, int *rtvals)
 1116 {
 1117         int rtval;
 1118         struct vnode *vp;
 1119         int bytes = count * PAGE_SIZE;
 1120 
 1121         /*
 1122          * Force synchronous operation if we are extremely low on memory
 1123          * to prevent a low-memory deadlock.  VOP operations often need to
 1124          * allocate more memory to initiate the I/O ( i.e. do a BMAP
 1125          * operation ).  The swapper handles the case by limiting the amount
 1126          * of asynchronous I/O, but that sort of solution doesn't scale well
 1127          * for the vnode pager without a lot of work.
 1128          *
 1129          * Also, the backing vnode's iodone routine may not wake the pageout
 1130          * daemon up.  This should be probably be addressed XXX.
 1131          */
 1132 
 1133         if (vm_cnt.v_free_count + vm_cnt.v_cache_count <
 1134             vm_cnt.v_pageout_free_min)
 1135                 flags |= VM_PAGER_PUT_SYNC;
 1136 
 1137         /*
 1138          * Call device-specific putpages function
 1139          */
 1140         vp = object->handle;
 1141         VM_OBJECT_WUNLOCK(object);
 1142         rtval = VOP_PUTPAGES(vp, m, bytes, flags, rtvals);
 1143         KASSERT(rtval != EOPNOTSUPP, 
 1144             ("vnode_pager: stale FS putpages\n"));
 1145         VM_OBJECT_WLOCK(object);
 1146 }
 1147 
 1148 
 1149 /*
 1150  * This is now called from local media FS's to operate against their
 1151  * own vnodes if they fail to implement VOP_PUTPAGES.
 1152  *
 1153  * This is typically called indirectly via the pageout daemon and
 1154  * clustering has already typically occurred, so in general we ask the
 1155  * underlying filesystem to write the data out asynchronously rather
 1156  * then delayed.
 1157  */
 1158 int
 1159 vnode_pager_generic_putpages(struct vnode *vp, vm_page_t *ma, int bytecount,
 1160     int flags, int *rtvals)
 1161 {
 1162         int i;
 1163         vm_object_t object;
 1164         vm_page_t m;
 1165         int count;
 1166 
 1167         int maxsize, ncount;
 1168         vm_ooffset_t poffset;
 1169         struct uio auio;
 1170         struct iovec aiov;
 1171         int error;
 1172         int ioflags;
 1173         int ppscheck = 0;
 1174         static struct timeval lastfail;
 1175         static int curfail;
 1176 
 1177         object = vp->v_object;
 1178         count = bytecount / PAGE_SIZE;
 1179 
 1180         for (i = 0; i < count; i++)
 1181                 rtvals[i] = VM_PAGER_ERROR;
 1182 
 1183         if ((int64_t)ma[0]->pindex < 0) {
 1184                 printf("vnode_pager_putpages: attempt to write meta-data!!! -- 0x%lx(%lx)\n",
 1185                     (long)ma[0]->pindex, (u_long)ma[0]->dirty);
 1186                 rtvals[0] = VM_PAGER_BAD;
 1187                 return VM_PAGER_BAD;
 1188         }
 1189 
 1190         maxsize = count * PAGE_SIZE;
 1191         ncount = count;
 1192 
 1193         poffset = IDX_TO_OFF(ma[0]->pindex);
 1194 
 1195         /*
 1196          * If the page-aligned write is larger then the actual file we
 1197          * have to invalidate pages occurring beyond the file EOF.  However,
 1198          * there is an edge case where a file may not be page-aligned where
 1199          * the last page is partially invalid.  In this case the filesystem
 1200          * may not properly clear the dirty bits for the entire page (which
 1201          * could be VM_PAGE_BITS_ALL due to the page having been mmap()d).
 1202          * With the page locked we are free to fix-up the dirty bits here.
 1203          *
 1204          * We do not under any circumstances truncate the valid bits, as
 1205          * this will screw up bogus page replacement.
 1206          */
 1207         VM_OBJECT_WLOCK(object);
 1208         if (maxsize + poffset > object->un_pager.vnp.vnp_size) {
 1209                 if (object->un_pager.vnp.vnp_size > poffset) {
 1210                         int pgoff;
 1211 
 1212                         maxsize = object->un_pager.vnp.vnp_size - poffset;
 1213                         ncount = btoc(maxsize);
 1214                         if ((pgoff = (int)maxsize & PAGE_MASK) != 0) {
 1215                                 /*
 1216                                  * If the object is locked and the following
 1217                                  * conditions hold, then the page's dirty
 1218                                  * field cannot be concurrently changed by a
 1219                                  * pmap operation.
 1220                                  */
 1221                                 m = ma[ncount - 1];
 1222                                 vm_page_assert_sbusied(m);
 1223                                 KASSERT(!pmap_page_is_write_mapped(m),
 1224                 ("vnode_pager_generic_putpages: page %p is not read-only", m));
 1225                                 vm_page_clear_dirty(m, pgoff, PAGE_SIZE -
 1226                                     pgoff);
 1227                         }
 1228                 } else {
 1229                         maxsize = 0;
 1230                         ncount = 0;
 1231                 }
 1232                 if (ncount < count) {
 1233                         for (i = ncount; i < count; i++) {
 1234                                 rtvals[i] = VM_PAGER_BAD;
 1235                         }
 1236                 }
 1237         }
 1238         VM_OBJECT_WUNLOCK(object);
 1239 
 1240         /*
 1241          * pageouts are already clustered, use IO_ASYNC to force a bawrite()
 1242          * rather then a bdwrite() to prevent paging I/O from saturating 
 1243          * the buffer cache.  Dummy-up the sequential heuristic to cause
 1244          * large ranges to cluster.  If neither IO_SYNC or IO_ASYNC is set,
 1245          * the system decides how to cluster.
 1246          */
 1247         ioflags = IO_VMIO;
 1248         if (flags & (VM_PAGER_PUT_SYNC | VM_PAGER_PUT_INVAL))
 1249                 ioflags |= IO_SYNC;
 1250         else if ((flags & VM_PAGER_CLUSTER_OK) == 0)
 1251                 ioflags |= IO_ASYNC;
 1252         ioflags |= (flags & VM_PAGER_PUT_INVAL) ? IO_INVAL: 0;
 1253         ioflags |= IO_SEQMAX << IO_SEQSHIFT;
 1254 
 1255         aiov.iov_base = (caddr_t) 0;
 1256         aiov.iov_len = maxsize;
 1257         auio.uio_iov = &aiov;
 1258         auio.uio_iovcnt = 1;
 1259         auio.uio_offset = poffset;
 1260         auio.uio_segflg = UIO_NOCOPY;
 1261         auio.uio_rw = UIO_WRITE;
 1262         auio.uio_resid = maxsize;
 1263         auio.uio_td = (struct thread *) 0;
 1264         error = VOP_WRITE(vp, &auio, ioflags, curthread->td_ucred);
 1265         PCPU_INC(cnt.v_vnodeout);
 1266         PCPU_ADD(cnt.v_vnodepgsout, ncount);
 1267 
 1268         if (error) {
 1269                 if ((ppscheck = ppsratecheck(&lastfail, &curfail, 1)))
 1270                         printf("vnode_pager_putpages: I/O error %d\n", error);
 1271         }
 1272         if (auio.uio_resid) {
 1273                 if (ppscheck || ppsratecheck(&lastfail, &curfail, 1))
 1274                         printf("vnode_pager_putpages: residual I/O %zd at %lu\n",
 1275                             auio.uio_resid, (u_long)ma[0]->pindex);
 1276         }
 1277         for (i = 0; i < ncount; i++) {
 1278                 rtvals[i] = VM_PAGER_OK;
 1279         }
 1280         return rtvals[0];
 1281 }
 1282 
 1283 void
 1284 vnode_pager_undirty_pages(vm_page_t *ma, int *rtvals, int written)
 1285 {
 1286         vm_object_t obj;
 1287         int i, pos;
 1288 
 1289         if (written == 0)
 1290                 return;
 1291         obj = ma[0]->object;
 1292         VM_OBJECT_WLOCK(obj);
 1293         for (i = 0, pos = 0; pos < written; i++, pos += PAGE_SIZE) {
 1294                 if (pos < trunc_page(written)) {
 1295                         rtvals[i] = VM_PAGER_OK;
 1296                         vm_page_undirty(ma[i]);
 1297                 } else {
 1298                         /* Partially written page. */
 1299                         rtvals[i] = VM_PAGER_AGAIN;
 1300                         vm_page_clear_dirty(ma[i], 0, written & PAGE_MASK);
 1301                 }
 1302         }
 1303         VM_OBJECT_WUNLOCK(obj);
 1304 }
 1305 
 1306 void
 1307 vnode_pager_update_writecount(vm_object_t object, vm_offset_t start,
 1308     vm_offset_t end)
 1309 {
 1310         struct vnode *vp;
 1311         vm_ooffset_t old_wm;
 1312 
 1313         VM_OBJECT_WLOCK(object);
 1314         if (object->type != OBJT_VNODE) {
 1315                 VM_OBJECT_WUNLOCK(object);
 1316                 return;
 1317         }
 1318         old_wm = object->un_pager.vnp.writemappings;
 1319         object->un_pager.vnp.writemappings += (vm_ooffset_t)end - start;
 1320         vp = object->handle;
 1321         if (old_wm == 0 && object->un_pager.vnp.writemappings != 0) {
 1322                 ASSERT_VOP_ELOCKED(vp, "v_writecount inc");
 1323                 VOP_ADD_WRITECOUNT(vp, 1);
 1324                 CTR3(KTR_VFS, "%s: vp %p v_writecount increased to %d",
 1325                     __func__, vp, vp->v_writecount);
 1326         } else if (old_wm != 0 && object->un_pager.vnp.writemappings == 0) {
 1327                 ASSERT_VOP_ELOCKED(vp, "v_writecount dec");
 1328                 VOP_ADD_WRITECOUNT(vp, -1);
 1329                 CTR3(KTR_VFS, "%s: vp %p v_writecount decreased to %d",
 1330                     __func__, vp, vp->v_writecount);
 1331         }
 1332         VM_OBJECT_WUNLOCK(object);
 1333 }
 1334 
 1335 void
 1336 vnode_pager_release_writecount(vm_object_t object, vm_offset_t start,
 1337     vm_offset_t end)
 1338 {
 1339         struct vnode *vp;
 1340         struct mount *mp;
 1341         vm_offset_t inc;
 1342 
 1343         VM_OBJECT_WLOCK(object);
 1344 
 1345         /*
 1346          * First, recheck the object type to account for the race when
 1347          * the vnode is reclaimed.
 1348          */
 1349         if (object->type != OBJT_VNODE) {
 1350                 VM_OBJECT_WUNLOCK(object);
 1351                 return;
 1352         }
 1353 
 1354         /*
 1355          * Optimize for the case when writemappings is not going to
 1356          * zero.
 1357          */
 1358         inc = end - start;
 1359         if (object->un_pager.vnp.writemappings != inc) {
 1360                 object->un_pager.vnp.writemappings -= inc;
 1361                 VM_OBJECT_WUNLOCK(object);
 1362                 return;
 1363         }
 1364 
 1365         vp = object->handle;
 1366         vhold(vp);
 1367         VM_OBJECT_WUNLOCK(object);
 1368         mp = NULL;
 1369         vn_start_write(vp, &mp, V_WAIT);
 1370         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 1371 
 1372         /*
 1373          * Decrement the object's writemappings, by swapping the start
 1374          * and end arguments for vnode_pager_update_writecount().  If
 1375          * there was not a race with vnode reclaimation, then the
 1376          * vnode's v_writecount is decremented.
 1377          */
 1378         vnode_pager_update_writecount(object, end, start);
 1379         VOP_UNLOCK(vp, 0);
 1380         vdrop(vp);
 1381         if (mp != NULL)
 1382                 vn_finished_write(mp);
 1383 }

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