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

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    1 /*-
    2  * SPDX-License-Identifier: BSD-4-Clause
    3  *
    4  * Copyright (c) 1990 University of Utah.
    5  * Copyright (c) 1991 The Regents of the University of California.
    6  * All rights reserved.
    7  * Copyright (c) 1993, 1994 John S. Dyson
    8  * Copyright (c) 1995, David Greenman
    9  *
   10  * This code is derived from software contributed to Berkeley by
   11  * the Systems Programming Group of the University of Utah Computer
   12  * Science Department.
   13  *
   14  * Redistribution and use in source and binary forms, with or without
   15  * modification, are permitted provided that the following conditions
   16  * are met:
   17  * 1. Redistributions of source code must retain the above copyright
   18  *    notice, this list of conditions and the following disclaimer.
   19  * 2. Redistributions in binary form must reproduce the above copyright
   20  *    notice, this list of conditions and the following disclaimer in the
   21  *    documentation and/or other materials provided with the distribution.
   22  * 3. All advertising materials mentioning features or use of this software
   23  *    must display the following acknowledgement:
   24  *      This product includes software developed by the University of
   25  *      California, Berkeley and its contributors.
   26  * 4. Neither the name of the University nor the names of its contributors
   27  *    may be used to endorse or promote products derived from this software
   28  *    without specific prior written permission.
   29  *
   30  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   31  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   32  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   33  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   34  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   35  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   36  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   37  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   38  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   39  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   40  * SUCH DAMAGE.
   41  *
   42  *      from: @(#)vnode_pager.c 7.5 (Berkeley) 4/20/91
   43  */
   44 
   45 /*
   46  * Page to/from files (vnodes).
   47  */
   48 
   49 /*
   50  * TODO:
   51  *      Implement VOP_GETPAGES/PUTPAGES interface for filesystems. Will
   52  *      greatly re-simplify the vnode_pager.
   53  */
   54 
   55 #include <sys/cdefs.h>
   56 __FBSDID("$FreeBSD: head/sys/vm/vnode_pager.c 344561 2019-02-26 04:50:46Z jah $");
   57 
   58 #include "opt_vm.h"
   59 
   60 #include <sys/param.h>
   61 #include <sys/kernel.h>
   62 #include <sys/systm.h>
   63 #include <sys/sysctl.h>
   64 #include <sys/proc.h>
   65 #include <sys/vnode.h>
   66 #include <sys/mount.h>
   67 #include <sys/bio.h>
   68 #include <sys/buf.h>
   69 #include <sys/vmmeter.h>
   70 #include <sys/limits.h>
   71 #include <sys/conf.h>
   72 #include <sys/rwlock.h>
   73 #include <sys/sf_buf.h>
   74 #include <sys/domainset.h>
   75 
   76 #include <machine/atomic.h>
   77 
   78 #include <vm/vm.h>
   79 #include <vm/vm_param.h>
   80 #include <vm/vm_object.h>
   81 #include <vm/vm_page.h>
   82 #include <vm/vm_pager.h>
   83 #include <vm/vm_map.h>
   84 #include <vm/vnode_pager.h>
   85 #include <vm/vm_extern.h>
   86 #include <vm/uma.h>
   87 
   88 static int vnode_pager_addr(struct vnode *vp, vm_ooffset_t address,
   89     daddr_t *rtaddress, int *run);
   90 static int vnode_pager_input_smlfs(vm_object_t object, vm_page_t m);
   91 static int vnode_pager_input_old(vm_object_t object, vm_page_t m);
   92 static void vnode_pager_dealloc(vm_object_t);
   93 static int vnode_pager_getpages(vm_object_t, vm_page_t *, int, int *, int *);
   94 static int vnode_pager_getpages_async(vm_object_t, vm_page_t *, int, int *,
   95     int *, vop_getpages_iodone_t, void *);
   96 static void vnode_pager_putpages(vm_object_t, vm_page_t *, int, int, int *);
   97 static boolean_t vnode_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
   98 static vm_object_t vnode_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
   99     vm_ooffset_t, struct ucred *cred);
  100 static int vnode_pager_generic_getpages_done(struct buf *);
  101 static void vnode_pager_generic_getpages_done_async(struct buf *);
  102 
  103 struct pagerops vnodepagerops = {
  104         .pgo_alloc =    vnode_pager_alloc,
  105         .pgo_dealloc =  vnode_pager_dealloc,
  106         .pgo_getpages = vnode_pager_getpages,
  107         .pgo_getpages_async = vnode_pager_getpages_async,
  108         .pgo_putpages = vnode_pager_putpages,
  109         .pgo_haspage =  vnode_pager_haspage,
  110 };
  111 
  112 static struct domainset *vnode_domainset = NULL;
  113 
  114 SYSCTL_PROC(_debug, OID_AUTO, vnode_domainset, CTLTYPE_STRING | CTLFLAG_RW,
  115     &vnode_domainset, 0, sysctl_handle_domainset, "A",
  116     "Default vnode NUMA policy");
  117 
  118 static int nvnpbufs;
  119 SYSCTL_INT(_vm, OID_AUTO, vnode_pbufs, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
  120     &nvnpbufs, 0, "number of physical buffers allocated for vnode pager");
  121 
  122 static uma_zone_t vnode_pbuf_zone;
  123 
  124 static void
  125 vnode_pager_init(void *dummy)
  126 {
  127 
  128 #ifdef __LP64__
  129         nvnpbufs = nswbuf * 2;
  130 #else
  131         nvnpbufs = nswbuf / 2;
  132 #endif
  133         TUNABLE_INT_FETCH("vm.vnode_pbufs", &nvnpbufs);
  134         vnode_pbuf_zone = pbuf_zsecond_create("vnpbuf", nvnpbufs);
  135 }
  136 SYSINIT(vnode_pager, SI_SUB_CPU, SI_ORDER_ANY, vnode_pager_init, NULL);
  137 
  138 /* Create the VM system backing object for this vnode */
  139 int
  140 vnode_create_vobject(struct vnode *vp, off_t isize, struct thread *td)
  141 {
  142         vm_object_t object;
  143         vm_ooffset_t size = isize;
  144         struct vattr va;
  145 
  146         if (!vn_isdisk(vp, NULL) && vn_canvmio(vp) == FALSE)
  147                 return (0);
  148 
  149         while ((object = vp->v_object) != NULL) {
  150                 VM_OBJECT_WLOCK(object);
  151                 if (!(object->flags & OBJ_DEAD)) {
  152                         VM_OBJECT_WUNLOCK(object);
  153                         return (0);
  154                 }
  155                 VOP_UNLOCK(vp, 0);
  156                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
  157                 VM_OBJECT_SLEEP(object, object, PDROP | PVM, "vodead", 0);
  158                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  159         }
  160 
  161         if (size == 0) {
  162                 if (vn_isdisk(vp, NULL)) {
  163                         size = IDX_TO_OFF(INT_MAX);
  164                 } else {
  165                         if (VOP_GETATTR(vp, &va, td->td_ucred))
  166                                 return (0);
  167                         size = va.va_size;
  168                 }
  169         }
  170 
  171         object = vnode_pager_alloc(vp, size, 0, 0, td->td_ucred);
  172         /*
  173          * Dereference the reference we just created.  This assumes
  174          * that the object is associated with the vp.
  175          */
  176         VM_OBJECT_WLOCK(object);
  177         object->ref_count--;
  178         VM_OBJECT_WUNLOCK(object);
  179         vrele(vp);
  180 
  181         KASSERT(vp->v_object != NULL, ("vnode_create_vobject: NULL object"));
  182 
  183         return (0);
  184 }
  185 
  186 void
  187 vnode_destroy_vobject(struct vnode *vp)
  188 {
  189         struct vm_object *obj;
  190 
  191         obj = vp->v_object;
  192         if (obj == NULL)
  193                 return;
  194         ASSERT_VOP_ELOCKED(vp, "vnode_destroy_vobject");
  195         VM_OBJECT_WLOCK(obj);
  196         umtx_shm_object_terminated(obj);
  197         if (obj->ref_count == 0) {
  198                 /*
  199                  * don't double-terminate the object
  200                  */
  201                 if ((obj->flags & OBJ_DEAD) == 0) {
  202                         vm_object_terminate(obj);
  203                 } else {
  204                         /*
  205                          * Waiters were already handled during object
  206                          * termination.  The exclusive vnode lock hopefully
  207                          * prevented new waiters from referencing the dying
  208                          * object.
  209                          */
  210                         KASSERT((obj->flags & OBJ_DISCONNECTWNT) == 0,
  211                             ("OBJ_DISCONNECTWNT set obj %p flags %x",
  212                             obj, obj->flags));
  213                         vp->v_object = NULL;
  214                         VM_OBJECT_WUNLOCK(obj);
  215                 }
  216         } else {
  217                 /*
  218                  * Woe to the process that tries to page now :-).
  219                  */
  220                 vm_pager_deallocate(obj);
  221                 VM_OBJECT_WUNLOCK(obj);
  222         }
  223         KASSERT(vp->v_object == NULL, ("vp %p obj %p", vp, vp->v_object));
  224 }
  225 
  226 
  227 /*
  228  * Allocate (or lookup) pager for a vnode.
  229  * Handle is a vnode pointer.
  230  *
  231  * MPSAFE
  232  */
  233 vm_object_t
  234 vnode_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
  235     vm_ooffset_t offset, struct ucred *cred)
  236 {
  237         vm_object_t object;
  238         struct vnode *vp;
  239 
  240         /*
  241          * Pageout to vnode, no can do yet.
  242          */
  243         if (handle == NULL)
  244                 return (NULL);
  245 
  246         vp = (struct vnode *) handle;
  247 
  248         /*
  249          * If the object is being terminated, wait for it to
  250          * go away.
  251          */
  252 retry:
  253         while ((object = vp->v_object) != NULL) {
  254                 VM_OBJECT_WLOCK(object);
  255                 if ((object->flags & OBJ_DEAD) == 0)
  256                         break;
  257                 vm_object_set_flag(object, OBJ_DISCONNECTWNT);
  258                 VM_OBJECT_SLEEP(object, object, PDROP | PVM, "vadead", 0);
  259         }
  260 
  261         KASSERT(vp->v_usecount != 0, ("vnode_pager_alloc: no vnode reference"));
  262 
  263         if (object == NULL) {
  264                 /*
  265                  * Add an object of the appropriate size
  266                  */
  267                 object = vm_object_allocate(OBJT_VNODE, OFF_TO_IDX(round_page(size)));
  268 
  269                 object->un_pager.vnp.vnp_size = size;
  270                 object->un_pager.vnp.writemappings = 0;
  271                 object->domain.dr_policy = vnode_domainset;
  272 
  273                 object->handle = handle;
  274                 VI_LOCK(vp);
  275                 if (vp->v_object != NULL) {
  276                         /*
  277                          * Object has been created while we were sleeping
  278                          */
  279                         VI_UNLOCK(vp);
  280                         VM_OBJECT_WLOCK(object);
  281                         KASSERT(object->ref_count == 1,
  282                             ("leaked ref %p %d", object, object->ref_count));
  283                         object->type = OBJT_DEAD;
  284                         object->ref_count = 0;
  285                         VM_OBJECT_WUNLOCK(object);
  286                         vm_object_destroy(object);
  287                         goto retry;
  288                 }
  289                 vp->v_object = object;
  290                 VI_UNLOCK(vp);
  291         } else {
  292                 object->ref_count++;
  293 #if VM_NRESERVLEVEL > 0
  294                 vm_object_color(object, 0);
  295 #endif
  296                 VM_OBJECT_WUNLOCK(object);
  297         }
  298         vrefact(vp);
  299         return (object);
  300 }
  301 
  302 /*
  303  *      The object must be locked.
  304  */
  305 static void
  306 vnode_pager_dealloc(vm_object_t object)
  307 {
  308         struct vnode *vp;
  309         int refs;
  310 
  311         vp = object->handle;
  312         if (vp == NULL)
  313                 panic("vnode_pager_dealloc: pager already dealloced");
  314 
  315         VM_OBJECT_ASSERT_WLOCKED(object);
  316         vm_object_pip_wait(object, "vnpdea");
  317         refs = object->ref_count;
  318 
  319         object->handle = NULL;
  320         object->type = OBJT_DEAD;
  321         if (object->flags & OBJ_DISCONNECTWNT) {
  322                 vm_object_clear_flag(object, OBJ_DISCONNECTWNT);
  323                 wakeup(object);
  324         }
  325         ASSERT_VOP_ELOCKED(vp, "vnode_pager_dealloc");
  326         if (object->un_pager.vnp.writemappings > 0) {
  327                 object->un_pager.vnp.writemappings = 0;
  328                 VOP_ADD_WRITECOUNT(vp, -1);
  329                 CTR3(KTR_VFS, "%s: vp %p v_writecount decreased to %d",
  330                     __func__, vp, vp->v_writecount);
  331         }
  332         vp->v_object = NULL;
  333         VOP_UNSET_TEXT(vp);
  334         VM_OBJECT_WUNLOCK(object);
  335         while (refs-- > 0)
  336                 vunref(vp);
  337         VM_OBJECT_WLOCK(object);
  338 }
  339 
  340 static boolean_t
  341 vnode_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
  342     int *after)
  343 {
  344         struct vnode *vp = object->handle;
  345         daddr_t bn;
  346         int err;
  347         daddr_t reqblock;
  348         int poff;
  349         int bsize;
  350         int pagesperblock, blocksperpage;
  351 
  352         VM_OBJECT_ASSERT_WLOCKED(object);
  353         /*
  354          * If no vp or vp is doomed or marked transparent to VM, we do not
  355          * have the page.
  356          */
  357         if (vp == NULL || vp->v_iflag & VI_DOOMED)
  358                 return FALSE;
  359         /*
  360          * If the offset is beyond end of file we do
  361          * not have the page.
  362          */
  363         if (IDX_TO_OFF(pindex) >= object->un_pager.vnp.vnp_size)
  364                 return FALSE;
  365 
  366         bsize = vp->v_mount->mnt_stat.f_iosize;
  367         pagesperblock = bsize / PAGE_SIZE;
  368         blocksperpage = 0;
  369         if (pagesperblock > 0) {
  370                 reqblock = pindex / pagesperblock;
  371         } else {
  372                 blocksperpage = (PAGE_SIZE / bsize);
  373                 reqblock = pindex * blocksperpage;
  374         }
  375         VM_OBJECT_WUNLOCK(object);
  376         err = VOP_BMAP(vp, reqblock, NULL, &bn, after, before);
  377         VM_OBJECT_WLOCK(object);
  378         if (err)
  379                 return TRUE;
  380         if (bn == -1)
  381                 return FALSE;
  382         if (pagesperblock > 0) {
  383                 poff = pindex - (reqblock * pagesperblock);
  384                 if (before) {
  385                         *before *= pagesperblock;
  386                         *before += poff;
  387                 }
  388                 if (after) {
  389                         /*
  390                          * The BMAP vop can report a partial block in the
  391                          * 'after', but must not report blocks after EOF.
  392                          * Assert the latter, and truncate 'after' in case
  393                          * of the former.
  394                          */
  395                         KASSERT((reqblock + *after) * pagesperblock <
  396                             roundup2(object->size, pagesperblock),
  397                             ("%s: reqblock %jd after %d size %ju", __func__,
  398                             (intmax_t )reqblock, *after,
  399                             (uintmax_t )object->size));
  400                         *after *= pagesperblock;
  401                         *after += pagesperblock - (poff + 1);
  402                         if (pindex + *after >= object->size)
  403                                 *after = object->size - 1 - pindex;
  404                 }
  405         } else {
  406                 if (before) {
  407                         *before /= blocksperpage;
  408                 }
  409 
  410                 if (after) {
  411                         *after /= blocksperpage;
  412                 }
  413         }
  414         return TRUE;
  415 }
  416 
  417 /*
  418  * Lets the VM system know about a change in size for a file.
  419  * We adjust our own internal size and flush any cached pages in
  420  * the associated object that are affected by the size change.
  421  *
  422  * Note: this routine may be invoked as a result of a pager put
  423  * operation (possibly at object termination time), so we must be careful.
  424  */
  425 void
  426 vnode_pager_setsize(struct vnode *vp, vm_ooffset_t nsize)
  427 {
  428         vm_object_t object;
  429         vm_page_t m;
  430         vm_pindex_t nobjsize;
  431 
  432         if ((object = vp->v_object) == NULL)
  433                 return;
  434 /*      ASSERT_VOP_ELOCKED(vp, "vnode_pager_setsize and not locked vnode"); */
  435         VM_OBJECT_WLOCK(object);
  436         if (object->type == OBJT_DEAD) {
  437                 VM_OBJECT_WUNLOCK(object);
  438                 return;
  439         }
  440         KASSERT(object->type == OBJT_VNODE,
  441             ("not vnode-backed object %p", object));
  442         if (nsize == object->un_pager.vnp.vnp_size) {
  443                 /*
  444                  * Hasn't changed size
  445                  */
  446                 VM_OBJECT_WUNLOCK(object);
  447                 return;
  448         }
  449         nobjsize = OFF_TO_IDX(nsize + PAGE_MASK);
  450         if (nsize < object->un_pager.vnp.vnp_size) {
  451                 /*
  452                  * File has shrunk. Toss any cached pages beyond the new EOF.
  453                  */
  454                 if (nobjsize < object->size)
  455                         vm_object_page_remove(object, nobjsize, object->size,
  456                             0);
  457                 /*
  458                  * this gets rid of garbage at the end of a page that is now
  459                  * only partially backed by the vnode.
  460                  *
  461                  * XXX for some reason (I don't know yet), if we take a
  462                  * completely invalid page and mark it partially valid
  463                  * it can screw up NFS reads, so we don't allow the case.
  464                  */
  465                 if ((nsize & PAGE_MASK) &&
  466                     (m = vm_page_lookup(object, OFF_TO_IDX(nsize))) != NULL &&
  467                     m->valid != 0) {
  468                         int base = (int)nsize & PAGE_MASK;
  469                         int size = PAGE_SIZE - base;
  470 
  471                         /*
  472                          * Clear out partial-page garbage in case
  473                          * the page has been mapped.
  474                          */
  475                         pmap_zero_page_area(m, base, size);
  476 
  477                         /*
  478                          * Update the valid bits to reflect the blocks that
  479                          * have been zeroed.  Some of these valid bits may
  480                          * have already been set.
  481                          */
  482                         vm_page_set_valid_range(m, base, size);
  483 
  484                         /*
  485                          * Round "base" to the next block boundary so that the
  486                          * dirty bit for a partially zeroed block is not
  487                          * cleared.
  488                          */
  489                         base = roundup2(base, DEV_BSIZE);
  490 
  491                         /*
  492                          * Clear out partial-page dirty bits.
  493                          *
  494                          * note that we do not clear out the valid
  495                          * bits.  This would prevent bogus_page
  496                          * replacement from working properly.
  497                          */
  498                         vm_page_clear_dirty(m, base, PAGE_SIZE - base);
  499                 }
  500         }
  501         object->un_pager.vnp.vnp_size = nsize;
  502         object->size = nobjsize;
  503         VM_OBJECT_WUNLOCK(object);
  504 }
  505 
  506 /*
  507  * calculate the linear (byte) disk address of specified virtual
  508  * file address
  509  */
  510 static int
  511 vnode_pager_addr(struct vnode *vp, vm_ooffset_t address, daddr_t *rtaddress,
  512     int *run)
  513 {
  514         int bsize;
  515         int err;
  516         daddr_t vblock;
  517         daddr_t voffset;
  518 
  519         if (address < 0)
  520                 return -1;
  521 
  522         if (vp->v_iflag & VI_DOOMED)
  523                 return -1;
  524 
  525         bsize = vp->v_mount->mnt_stat.f_iosize;
  526         vblock = address / bsize;
  527         voffset = address % bsize;
  528 
  529         err = VOP_BMAP(vp, vblock, NULL, rtaddress, run, NULL);
  530         if (err == 0) {
  531                 if (*rtaddress != -1)
  532                         *rtaddress += voffset / DEV_BSIZE;
  533                 if (run) {
  534                         *run += 1;
  535                         *run *= bsize/PAGE_SIZE;
  536                         *run -= voffset/PAGE_SIZE;
  537                 }
  538         }
  539 
  540         return (err);
  541 }
  542 
  543 /*
  544  * small block filesystem vnode pager input
  545  */
  546 static int
  547 vnode_pager_input_smlfs(vm_object_t object, vm_page_t m)
  548 {
  549         struct vnode *vp;
  550         struct bufobj *bo;
  551         struct buf *bp;
  552         struct sf_buf *sf;
  553         daddr_t fileaddr;
  554         vm_offset_t bsize;
  555         vm_page_bits_t bits;
  556         int error, i;
  557 
  558         error = 0;
  559         vp = object->handle;
  560         if (vp->v_iflag & VI_DOOMED)
  561                 return VM_PAGER_BAD;
  562 
  563         bsize = vp->v_mount->mnt_stat.f_iosize;
  564 
  565         VOP_BMAP(vp, 0, &bo, 0, NULL, NULL);
  566 
  567         sf = sf_buf_alloc(m, 0);
  568 
  569         for (i = 0; i < PAGE_SIZE / bsize; i++) {
  570                 vm_ooffset_t address;
  571 
  572                 bits = vm_page_bits(i * bsize, bsize);
  573                 if (m->valid & bits)
  574                         continue;
  575 
  576                 address = IDX_TO_OFF(m->pindex) + i * bsize;
  577                 if (address >= object->un_pager.vnp.vnp_size) {
  578                         fileaddr = -1;
  579                 } else {
  580                         error = vnode_pager_addr(vp, address, &fileaddr, NULL);
  581                         if (error)
  582                                 break;
  583                 }
  584                 if (fileaddr != -1) {
  585                         bp = uma_zalloc(vnode_pbuf_zone, M_WAITOK);
  586 
  587                         /* build a minimal buffer header */
  588                         bp->b_iocmd = BIO_READ;
  589                         bp->b_iodone = bdone;
  590                         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
  591                         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
  592                         bp->b_rcred = crhold(curthread->td_ucred);
  593                         bp->b_wcred = crhold(curthread->td_ucred);
  594                         bp->b_data = (caddr_t)sf_buf_kva(sf) + i * bsize;
  595                         bp->b_blkno = fileaddr;
  596                         pbgetbo(bo, bp);
  597                         bp->b_vp = vp;
  598                         bp->b_bcount = bsize;
  599                         bp->b_bufsize = bsize;
  600                         bp->b_runningbufspace = bp->b_bufsize;
  601                         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
  602 
  603                         /* do the input */
  604                         bp->b_iooffset = dbtob(bp->b_blkno);
  605                         bstrategy(bp);
  606 
  607                         bwait(bp, PVM, "vnsrd");
  608 
  609                         if ((bp->b_ioflags & BIO_ERROR) != 0)
  610                                 error = EIO;
  611 
  612                         /*
  613                          * free the buffer header back to the swap buffer pool
  614                          */
  615                         bp->b_vp = NULL;
  616                         pbrelbo(bp);
  617                         uma_zfree(vnode_pbuf_zone, bp);
  618                         if (error)
  619                                 break;
  620                 } else
  621                         bzero((caddr_t)sf_buf_kva(sf) + i * bsize, bsize);
  622                 KASSERT((m->dirty & bits) == 0,
  623                     ("vnode_pager_input_smlfs: page %p is dirty", m));
  624                 VM_OBJECT_WLOCK(object);
  625                 m->valid |= bits;
  626                 VM_OBJECT_WUNLOCK(object);
  627         }
  628         sf_buf_free(sf);
  629         if (error) {
  630                 return VM_PAGER_ERROR;
  631         }
  632         return VM_PAGER_OK;
  633 }
  634 
  635 /*
  636  * old style vnode pager input routine
  637  */
  638 static int
  639 vnode_pager_input_old(vm_object_t object, vm_page_t m)
  640 {
  641         struct uio auio;
  642         struct iovec aiov;
  643         int error;
  644         int size;
  645         struct sf_buf *sf;
  646         struct vnode *vp;
  647 
  648         VM_OBJECT_ASSERT_WLOCKED(object);
  649         error = 0;
  650 
  651         /*
  652          * Return failure if beyond current EOF
  653          */
  654         if (IDX_TO_OFF(m->pindex) >= object->un_pager.vnp.vnp_size) {
  655                 return VM_PAGER_BAD;
  656         } else {
  657                 size = PAGE_SIZE;
  658                 if (IDX_TO_OFF(m->pindex) + size > object->un_pager.vnp.vnp_size)
  659                         size = object->un_pager.vnp.vnp_size - IDX_TO_OFF(m->pindex);
  660                 vp = object->handle;
  661                 VM_OBJECT_WUNLOCK(object);
  662 
  663                 /*
  664                  * Allocate a kernel virtual address and initialize so that
  665                  * we can use VOP_READ/WRITE routines.
  666                  */
  667                 sf = sf_buf_alloc(m, 0);
  668 
  669                 aiov.iov_base = (caddr_t)sf_buf_kva(sf);
  670                 aiov.iov_len = size;
  671                 auio.uio_iov = &aiov;
  672                 auio.uio_iovcnt = 1;
  673                 auio.uio_offset = IDX_TO_OFF(m->pindex);
  674                 auio.uio_segflg = UIO_SYSSPACE;
  675                 auio.uio_rw = UIO_READ;
  676                 auio.uio_resid = size;
  677                 auio.uio_td = curthread;
  678 
  679                 error = VOP_READ(vp, &auio, 0, curthread->td_ucred);
  680                 if (!error) {
  681                         int count = size - auio.uio_resid;
  682 
  683                         if (count == 0)
  684                                 error = EINVAL;
  685                         else if (count != PAGE_SIZE)
  686                                 bzero((caddr_t)sf_buf_kva(sf) + count,
  687                                     PAGE_SIZE - count);
  688                 }
  689                 sf_buf_free(sf);
  690 
  691                 VM_OBJECT_WLOCK(object);
  692         }
  693         KASSERT(m->dirty == 0, ("vnode_pager_input_old: page %p is dirty", m));
  694         if (!error)
  695                 m->valid = VM_PAGE_BITS_ALL;
  696         return error ? VM_PAGER_ERROR : VM_PAGER_OK;
  697 }
  698 
  699 /*
  700  * generic vnode pager input routine
  701  */
  702 
  703 /*
  704  * Local media VFS's that do not implement their own VOP_GETPAGES
  705  * should have their VOP_GETPAGES call to vnode_pager_generic_getpages()
  706  * to implement the previous behaviour.
  707  *
  708  * All other FS's should use the bypass to get to the local media
  709  * backing vp's VOP_GETPAGES.
  710  */
  711 static int
  712 vnode_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
  713     int *rahead)
  714 {
  715         struct vnode *vp;
  716         int rtval;
  717 
  718         vp = object->handle;
  719         VM_OBJECT_WUNLOCK(object);
  720         rtval = VOP_GETPAGES(vp, m, count, rbehind, rahead);
  721         KASSERT(rtval != EOPNOTSUPP,
  722             ("vnode_pager: FS getpages not implemented\n"));
  723         VM_OBJECT_WLOCK(object);
  724         return rtval;
  725 }
  726 
  727 static int
  728 vnode_pager_getpages_async(vm_object_t object, vm_page_t *m, int count,
  729     int *rbehind, int *rahead, vop_getpages_iodone_t iodone, void *arg)
  730 {
  731         struct vnode *vp;
  732         int rtval;
  733 
  734         vp = object->handle;
  735         VM_OBJECT_WUNLOCK(object);
  736         rtval = VOP_GETPAGES_ASYNC(vp, m, count, rbehind, rahead, iodone, arg);
  737         KASSERT(rtval != EOPNOTSUPP,
  738             ("vnode_pager: FS getpages_async not implemented\n"));
  739         VM_OBJECT_WLOCK(object);
  740         return (rtval);
  741 }
  742 
  743 /*
  744  * The implementation of VOP_GETPAGES() and VOP_GETPAGES_ASYNC() for
  745  * local filesystems, where partially valid pages can only occur at
  746  * the end of file.
  747  */
  748 int
  749 vnode_pager_local_getpages(struct vop_getpages_args *ap)
  750 {
  751 
  752         return (vnode_pager_generic_getpages(ap->a_vp, ap->a_m, ap->a_count,
  753             ap->a_rbehind, ap->a_rahead, NULL, NULL));
  754 }
  755 
  756 int
  757 vnode_pager_local_getpages_async(struct vop_getpages_async_args *ap)
  758 {
  759 
  760         return (vnode_pager_generic_getpages(ap->a_vp, ap->a_m, ap->a_count,
  761             ap->a_rbehind, ap->a_rahead, ap->a_iodone, ap->a_arg));
  762 }
  763 
  764 /*
  765  * This is now called from local media FS's to operate against their
  766  * own vnodes if they fail to implement VOP_GETPAGES.
  767  */
  768 int
  769 vnode_pager_generic_getpages(struct vnode *vp, vm_page_t *m, int count,
  770     int *a_rbehind, int *a_rahead, vop_getpages_iodone_t iodone, void *arg)
  771 {
  772         vm_object_t object;
  773         struct bufobj *bo;
  774         struct buf *bp;
  775         off_t foff;
  776 #ifdef INVARIANTS
  777         off_t blkno0;
  778 #endif
  779         int bsize, pagesperblock;
  780         int error, before, after, rbehind, rahead, poff, i;
  781         int bytecount, secmask;
  782 
  783         KASSERT(vp->v_type != VCHR && vp->v_type != VBLK,
  784             ("%s does not support devices", __func__));
  785 
  786         if (vp->v_iflag & VI_DOOMED)
  787                 return (VM_PAGER_BAD);
  788 
  789         object = vp->v_object;
  790         foff = IDX_TO_OFF(m[0]->pindex);
  791         bsize = vp->v_mount->mnt_stat.f_iosize;
  792         pagesperblock = bsize / PAGE_SIZE;
  793 
  794         KASSERT(foff < object->un_pager.vnp.vnp_size,
  795             ("%s: page %p offset beyond vp %p size", __func__, m[0], vp));
  796         KASSERT(count <= nitems(bp->b_pages),
  797             ("%s: requested %d pages", __func__, count));
  798 
  799         /*
  800          * The last page has valid blocks.  Invalid part can only
  801          * exist at the end of file, and the page is made fully valid
  802          * by zeroing in vm_pager_get_pages().
  803          */
  804         if (m[count - 1]->valid != 0 && --count == 0) {
  805                 if (iodone != NULL)
  806                         iodone(arg, m, 1, 0);
  807                 return (VM_PAGER_OK);
  808         }
  809 
  810         bp = uma_zalloc(vnode_pbuf_zone, M_WAITOK);
  811 
  812         /*
  813          * Get the underlying device blocks for the file with VOP_BMAP().
  814          * If the file system doesn't support VOP_BMAP, use old way of
  815          * getting pages via VOP_READ.
  816          */
  817         error = VOP_BMAP(vp, foff / bsize, &bo, &bp->b_blkno, &after, &before);
  818         if (error == EOPNOTSUPP) {
  819                 uma_zfree(vnode_pbuf_zone, bp);
  820                 VM_OBJECT_WLOCK(object);
  821                 for (i = 0; i < count; i++) {
  822                         VM_CNT_INC(v_vnodein);
  823                         VM_CNT_INC(v_vnodepgsin);
  824                         error = vnode_pager_input_old(object, m[i]);
  825                         if (error)
  826                                 break;
  827                 }
  828                 VM_OBJECT_WUNLOCK(object);
  829                 return (error);
  830         } else if (error != 0) {
  831                 uma_zfree(vnode_pbuf_zone, bp);
  832                 return (VM_PAGER_ERROR);
  833         }
  834 
  835         /*
  836          * If the file system supports BMAP, but blocksize is smaller
  837          * than a page size, then use special small filesystem code.
  838          */
  839         if (pagesperblock == 0) {
  840                 uma_zfree(vnode_pbuf_zone, bp);
  841                 for (i = 0; i < count; i++) {
  842                         VM_CNT_INC(v_vnodein);
  843                         VM_CNT_INC(v_vnodepgsin);
  844                         error = vnode_pager_input_smlfs(object, m[i]);
  845                         if (error)
  846                                 break;
  847                 }
  848                 return (error);
  849         }
  850 
  851         /*
  852          * A sparse file can be encountered only for a single page request,
  853          * which may not be preceded by call to vm_pager_haspage().
  854          */
  855         if (bp->b_blkno == -1) {
  856                 KASSERT(count == 1,
  857                     ("%s: array[%d] request to a sparse file %p", __func__,
  858                     count, vp));
  859                 uma_zfree(vnode_pbuf_zone, bp);
  860                 pmap_zero_page(m[0]);
  861                 KASSERT(m[0]->dirty == 0, ("%s: page %p is dirty",
  862                     __func__, m[0]));
  863                 VM_OBJECT_WLOCK(object);
  864                 m[0]->valid = VM_PAGE_BITS_ALL;
  865                 VM_OBJECT_WUNLOCK(object);
  866                 return (VM_PAGER_OK);
  867         }
  868 
  869 #ifdef INVARIANTS
  870         blkno0 = bp->b_blkno;
  871 #endif
  872         bp->b_blkno += (foff % bsize) / DEV_BSIZE;
  873 
  874         /* Recalculate blocks available after/before to pages. */
  875         poff = (foff % bsize) / PAGE_SIZE;
  876         before *= pagesperblock;
  877         before += poff;
  878         after *= pagesperblock;
  879         after += pagesperblock - (poff + 1);
  880         if (m[0]->pindex + after >= object->size)
  881                 after = object->size - 1 - m[0]->pindex;
  882         KASSERT(count <= after + 1, ("%s: %d pages asked, can do only %d",
  883             __func__, count, after + 1));
  884         after -= count - 1;
  885 
  886         /* Trim requested rbehind/rahead to possible values. */   
  887         rbehind = a_rbehind ? *a_rbehind : 0;
  888         rahead = a_rahead ? *a_rahead : 0;
  889         rbehind = min(rbehind, before);
  890         rbehind = min(rbehind, m[0]->pindex);
  891         rahead = min(rahead, after);
  892         rahead = min(rahead, object->size - m[count - 1]->pindex);
  893         /*
  894          * Check that total amount of pages fit into buf.  Trim rbehind and
  895          * rahead evenly if not.
  896          */
  897         if (rbehind + rahead + count > nitems(bp->b_pages)) {
  898                 int trim, sum;
  899 
  900                 trim = rbehind + rahead + count - nitems(bp->b_pages) + 1;
  901                 sum = rbehind + rahead;
  902                 if (rbehind == before) {
  903                         /* Roundup rbehind trim to block size. */
  904                         rbehind -= roundup(trim * rbehind / sum, pagesperblock);
  905                         if (rbehind < 0)
  906                                 rbehind = 0;
  907                 } else
  908                         rbehind -= trim * rbehind / sum;
  909                 rahead -= trim * rahead / sum;
  910         }
  911         KASSERT(rbehind + rahead + count <= nitems(bp->b_pages),
  912             ("%s: behind %d ahead %d count %d", __func__,
  913             rbehind, rahead, count));
  914 
  915         /*
  916          * Fill in the bp->b_pages[] array with requested and optional   
  917          * read behind or read ahead pages.  Read behind pages are looked
  918          * up in a backward direction, down to a first cached page.  Same
  919          * for read ahead pages, but there is no need to shift the array
  920          * in case of encountering a cached page.
  921          */
  922         i = bp->b_npages = 0;
  923         if (rbehind) {
  924                 vm_pindex_t startpindex, tpindex;
  925                 vm_page_t p;
  926 
  927                 VM_OBJECT_WLOCK(object);
  928                 startpindex = m[0]->pindex - rbehind;
  929                 if ((p = TAILQ_PREV(m[0], pglist, listq)) != NULL &&
  930                     p->pindex >= startpindex)
  931                         startpindex = p->pindex + 1;
  932 
  933                 /* tpindex is unsigned; beware of numeric underflow. */
  934                 for (tpindex = m[0]->pindex - 1;
  935                     tpindex >= startpindex && tpindex < m[0]->pindex;
  936                     tpindex--, i++) {
  937                         p = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
  938                         if (p == NULL) {
  939                                 /* Shift the array. */
  940                                 for (int j = 0; j < i; j++)
  941                                         bp->b_pages[j] = bp->b_pages[j + 
  942                                             tpindex + 1 - startpindex]; 
  943                                 break;
  944                         }
  945                         bp->b_pages[tpindex - startpindex] = p;
  946                 }
  947 
  948                 bp->b_pgbefore = i;
  949                 bp->b_npages += i;
  950                 bp->b_blkno -= IDX_TO_OFF(i) / DEV_BSIZE;
  951         } else
  952                 bp->b_pgbefore = 0;
  953 
  954         /* Requested pages. */
  955         for (int j = 0; j < count; j++, i++)
  956                 bp->b_pages[i] = m[j];
  957         bp->b_npages += count;
  958 
  959         if (rahead) {
  960                 vm_pindex_t endpindex, tpindex;
  961                 vm_page_t p;
  962 
  963                 if (!VM_OBJECT_WOWNED(object))
  964                         VM_OBJECT_WLOCK(object);
  965                 endpindex = m[count - 1]->pindex + rahead + 1;
  966                 if ((p = TAILQ_NEXT(m[count - 1], listq)) != NULL &&
  967                     p->pindex < endpindex)
  968                         endpindex = p->pindex;
  969                 if (endpindex > object->size)
  970                         endpindex = object->size;
  971 
  972                 for (tpindex = m[count - 1]->pindex + 1;
  973                     tpindex < endpindex; i++, tpindex++) {
  974                         p = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
  975                         if (p == NULL)
  976                                 break;
  977                         bp->b_pages[i] = p;
  978                 }
  979 
  980                 bp->b_pgafter = i - bp->b_npages;
  981                 bp->b_npages = i;
  982         } else
  983                 bp->b_pgafter = 0;
  984 
  985         if (VM_OBJECT_WOWNED(object))
  986                 VM_OBJECT_WUNLOCK(object);
  987 
  988         /* Report back actual behind/ahead read. */
  989         if (a_rbehind)
  990                 *a_rbehind = bp->b_pgbefore;
  991         if (a_rahead)
  992                 *a_rahead = bp->b_pgafter;
  993 
  994 #ifdef INVARIANTS
  995         KASSERT(bp->b_npages <= nitems(bp->b_pages),
  996             ("%s: buf %p overflowed", __func__, bp));
  997         for (int j = 1, prev = 0; j < bp->b_npages; j++) {
  998                 if (bp->b_pages[j] == bogus_page)
  999                         continue;
 1000                 KASSERT(bp->b_pages[j]->pindex - bp->b_pages[prev]->pindex ==
 1001                     j - prev, ("%s: pages array not consecutive, bp %p",
 1002                      __func__, bp));
 1003                 prev = j;
 1004         }
 1005 #endif
 1006 
 1007         /*
 1008          * Recalculate first offset and bytecount with regards to read behind.
 1009          * Truncate bytecount to vnode real size and round up physical size
 1010          * for real devices.
 1011          */
 1012         foff = IDX_TO_OFF(bp->b_pages[0]->pindex);
 1013         bytecount = bp->b_npages << PAGE_SHIFT;
 1014         if ((foff + bytecount) > object->un_pager.vnp.vnp_size)
 1015                 bytecount = object->un_pager.vnp.vnp_size - foff;
 1016         secmask = bo->bo_bsize - 1;
 1017         KASSERT(secmask < PAGE_SIZE && secmask > 0,
 1018             ("%s: sector size %d too large", __func__, secmask + 1));
 1019         bytecount = (bytecount + secmask) & ~secmask;
 1020 
 1021         /*
 1022          * And map the pages to be read into the kva, if the filesystem
 1023          * requires mapped buffers.
 1024          */
 1025         if ((vp->v_mount->mnt_kern_flag & MNTK_UNMAPPED_BUFS) != 0 &&
 1026             unmapped_buf_allowed) {
 1027                 bp->b_data = unmapped_buf;
 1028                 bp->b_offset = 0;
 1029         } else {
 1030                 bp->b_data = bp->b_kvabase;
 1031                 pmap_qenter((vm_offset_t)bp->b_data, bp->b_pages, bp->b_npages);
 1032         }
 1033 
 1034         /* Build a minimal buffer header. */
 1035         bp->b_iocmd = BIO_READ;
 1036         KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
 1037         KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
 1038         bp->b_rcred = crhold(curthread->td_ucred);
 1039         bp->b_wcred = crhold(curthread->td_ucred);
 1040         pbgetbo(bo, bp);
 1041         bp->b_vp = vp;
 1042         bp->b_bcount = bp->b_bufsize = bp->b_runningbufspace = bytecount;
 1043         bp->b_iooffset = dbtob(bp->b_blkno);
 1044         KASSERT(IDX_TO_OFF(m[0]->pindex - bp->b_pages[0]->pindex) ==
 1045             (blkno0 - bp->b_blkno) * DEV_BSIZE +
 1046             IDX_TO_OFF(m[0]->pindex) % bsize,
 1047             ("wrong offsets bsize %d m[0] %ju b_pages[0] %ju "
 1048             "blkno0 %ju b_blkno %ju", bsize,
 1049             (uintmax_t)m[0]->pindex, (uintmax_t)bp->b_pages[0]->pindex,
 1050             (uintmax_t)blkno0, (uintmax_t)bp->b_blkno));
 1051 
 1052         atomic_add_long(&runningbufspace, bp->b_runningbufspace);
 1053         VM_CNT_INC(v_vnodein);
 1054         VM_CNT_ADD(v_vnodepgsin, bp->b_npages);
 1055 
 1056         if (iodone != NULL) { /* async */
 1057                 bp->b_pgiodone = iodone;
 1058                 bp->b_caller1 = arg;
 1059                 bp->b_iodone = vnode_pager_generic_getpages_done_async;
 1060                 bp->b_flags |= B_ASYNC;
 1061                 BUF_KERNPROC(bp);
 1062                 bstrategy(bp);
 1063                 return (VM_PAGER_OK);
 1064         } else {
 1065                 bp->b_iodone = bdone;
 1066                 bstrategy(bp);
 1067                 bwait(bp, PVM, "vnread");
 1068                 error = vnode_pager_generic_getpages_done(bp);
 1069                 for (i = 0; i < bp->b_npages; i++)
 1070                         bp->b_pages[i] = NULL;
 1071                 bp->b_vp = NULL;
 1072                 pbrelbo(bp);
 1073                 uma_zfree(vnode_pbuf_zone, bp);
 1074                 return (error != 0 ? VM_PAGER_ERROR : VM_PAGER_OK);
 1075         }
 1076 }
 1077 
 1078 static void
 1079 vnode_pager_generic_getpages_done_async(struct buf *bp)
 1080 {
 1081         int error;
 1082 
 1083         error = vnode_pager_generic_getpages_done(bp);
 1084         /* Run the iodone upon the requested range. */
 1085         bp->b_pgiodone(bp->b_caller1, bp->b_pages + bp->b_pgbefore,
 1086             bp->b_npages - bp->b_pgbefore - bp->b_pgafter, error);
 1087         for (int i = 0; i < bp->b_npages; i++)
 1088                 bp->b_pages[i] = NULL;
 1089         bp->b_vp = NULL;
 1090         pbrelbo(bp);
 1091         uma_zfree(vnode_pbuf_zone, bp);
 1092 }
 1093 
 1094 static int
 1095 vnode_pager_generic_getpages_done(struct buf *bp)
 1096 {
 1097         vm_object_t object;
 1098         off_t tfoff, nextoff;
 1099         int i, error;
 1100 
 1101         error = (bp->b_ioflags & BIO_ERROR) != 0 ? EIO : 0;
 1102         object = bp->b_vp->v_object;
 1103 
 1104         if (error == 0 && bp->b_bcount != bp->b_npages * PAGE_SIZE) {
 1105                 if (!buf_mapped(bp)) {
 1106                         bp->b_data = bp->b_kvabase;
 1107                         pmap_qenter((vm_offset_t)bp->b_data, bp->b_pages,
 1108                             bp->b_npages);
 1109                 }
 1110                 bzero(bp->b_data + bp->b_bcount,
 1111                     PAGE_SIZE * bp->b_npages - bp->b_bcount);
 1112         }
 1113         if (buf_mapped(bp)) {
 1114                 pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages);
 1115                 bp->b_data = unmapped_buf;
 1116         }
 1117 
 1118         VM_OBJECT_WLOCK(object);
 1119         for (i = 0, tfoff = IDX_TO_OFF(bp->b_pages[0]->pindex);
 1120             i < bp->b_npages; i++, tfoff = nextoff) {
 1121                 vm_page_t mt;
 1122 
 1123                 nextoff = tfoff + PAGE_SIZE;
 1124                 mt = bp->b_pages[i];
 1125 
 1126                 if (nextoff <= object->un_pager.vnp.vnp_size) {
 1127                         /*
 1128                          * Read filled up entire page.
 1129                          */
 1130                         mt->valid = VM_PAGE_BITS_ALL;
 1131                         KASSERT(mt->dirty == 0,
 1132                             ("%s: page %p is dirty", __func__, mt));
 1133                         KASSERT(!pmap_page_is_mapped(mt),
 1134                             ("%s: page %p is mapped", __func__, mt));
 1135                 } else {
 1136                         /*
 1137                          * Read did not fill up entire page.
 1138                          *
 1139                          * Currently we do not set the entire page valid,
 1140                          * we just try to clear the piece that we couldn't
 1141                          * read.
 1142                          */
 1143                         vm_page_set_valid_range(mt, 0,
 1144                             object->un_pager.vnp.vnp_size - tfoff);
 1145                         KASSERT((mt->dirty & vm_page_bits(0,
 1146                             object->un_pager.vnp.vnp_size - tfoff)) == 0,
 1147                             ("%s: page %p is dirty", __func__, mt));
 1148                 }
 1149 
 1150                 if (i < bp->b_pgbefore || i >= bp->b_npages - bp->b_pgafter)
 1151                         vm_page_readahead_finish(mt);
 1152         }
 1153         VM_OBJECT_WUNLOCK(object);
 1154         if (error != 0)
 1155                 printf("%s: I/O read error %d\n", __func__, error);
 1156 
 1157         return (error);
 1158 }
 1159 
 1160 /*
 1161  * EOPNOTSUPP is no longer legal.  For local media VFS's that do not
 1162  * implement their own VOP_PUTPAGES, their VOP_PUTPAGES should call to
 1163  * vnode_pager_generic_putpages() to implement the previous behaviour.
 1164  *
 1165  * All other FS's should use the bypass to get to the local media
 1166  * backing vp's VOP_PUTPAGES.
 1167  */
 1168 static void
 1169 vnode_pager_putpages(vm_object_t object, vm_page_t *m, int count,
 1170     int flags, int *rtvals)
 1171 {
 1172         int rtval;
 1173         struct vnode *vp;
 1174         int bytes = count * PAGE_SIZE;
 1175 
 1176         /*
 1177          * Force synchronous operation if we are extremely low on memory
 1178          * to prevent a low-memory deadlock.  VOP operations often need to
 1179          * allocate more memory to initiate the I/O ( i.e. do a BMAP
 1180          * operation ).  The swapper handles the case by limiting the amount
 1181          * of asynchronous I/O, but that sort of solution doesn't scale well
 1182          * for the vnode pager without a lot of work.
 1183          *
 1184          * Also, the backing vnode's iodone routine may not wake the pageout
 1185          * daemon up.  This should be probably be addressed XXX.
 1186          */
 1187 
 1188         if (vm_page_count_min())
 1189                 flags |= VM_PAGER_PUT_SYNC;
 1190 
 1191         /*
 1192          * Call device-specific putpages function
 1193          */
 1194         vp = object->handle;
 1195         VM_OBJECT_WUNLOCK(object);
 1196         rtval = VOP_PUTPAGES(vp, m, bytes, flags, rtvals);
 1197         KASSERT(rtval != EOPNOTSUPP, 
 1198             ("vnode_pager: stale FS putpages\n"));
 1199         VM_OBJECT_WLOCK(object);
 1200 }
 1201 
 1202 static int
 1203 vn_off2bidx(vm_ooffset_t offset)
 1204 {
 1205 
 1206         return ((offset & PAGE_MASK) / DEV_BSIZE);
 1207 }
 1208 
 1209 static bool
 1210 vn_dirty_blk(vm_page_t m, vm_ooffset_t offset)
 1211 {
 1212 
 1213         KASSERT(IDX_TO_OFF(m->pindex) <= offset &&
 1214             offset < IDX_TO_OFF(m->pindex + 1),
 1215             ("page %p pidx %ju offset %ju", m, (uintmax_t)m->pindex,
 1216             (uintmax_t)offset));
 1217         return ((m->dirty & ((vm_page_bits_t)1 << vn_off2bidx(offset))) != 0);
 1218 }
 1219 
 1220 /*
 1221  * This is now called from local media FS's to operate against their
 1222  * own vnodes if they fail to implement VOP_PUTPAGES.
 1223  *
 1224  * This is typically called indirectly via the pageout daemon and
 1225  * clustering has already typically occurred, so in general we ask the
 1226  * underlying filesystem to write the data out asynchronously rather
 1227  * then delayed.
 1228  */
 1229 int
 1230 vnode_pager_generic_putpages(struct vnode *vp, vm_page_t *ma, int bytecount,
 1231     int flags, int *rtvals)
 1232 {
 1233         vm_object_t object;
 1234         vm_page_t m;
 1235         vm_ooffset_t maxblksz, next_offset, poffset, prev_offset;
 1236         struct uio auio;
 1237         struct iovec aiov;
 1238         off_t prev_resid, wrsz;
 1239         int count, error, i, maxsize, ncount, pgoff, ppscheck;
 1240         bool in_hole;
 1241         static struct timeval lastfail;
 1242         static int curfail;
 1243 
 1244         object = vp->v_object;
 1245         count = bytecount / PAGE_SIZE;
 1246 
 1247         for (i = 0; i < count; i++)
 1248                 rtvals[i] = VM_PAGER_ERROR;
 1249 
 1250         if ((int64_t)ma[0]->pindex < 0) {
 1251                 printf("vnode_pager_generic_putpages: "
 1252                     "attempt to write meta-data 0x%jx(%lx)\n",
 1253                     (uintmax_t)ma[0]->pindex, (u_long)ma[0]->dirty);
 1254                 rtvals[0] = VM_PAGER_BAD;
 1255                 return (VM_PAGER_BAD);
 1256         }
 1257 
 1258         maxsize = count * PAGE_SIZE;
 1259         ncount = count;
 1260 
 1261         poffset = IDX_TO_OFF(ma[0]->pindex);
 1262 
 1263         /*
 1264          * If the page-aligned write is larger then the actual file we
 1265          * have to invalidate pages occurring beyond the file EOF.  However,
 1266          * there is an edge case where a file may not be page-aligned where
 1267          * the last page is partially invalid.  In this case the filesystem
 1268          * may not properly clear the dirty bits for the entire page (which
 1269          * could be VM_PAGE_BITS_ALL due to the page having been mmap()d).
 1270          * With the page locked we are free to fix-up the dirty bits here.
 1271          *
 1272          * We do not under any circumstances truncate the valid bits, as
 1273          * this will screw up bogus page replacement.
 1274          */
 1275         VM_OBJECT_RLOCK(object);
 1276         if (maxsize + poffset > object->un_pager.vnp.vnp_size) {
 1277                 if (!VM_OBJECT_TRYUPGRADE(object)) {
 1278                         VM_OBJECT_RUNLOCK(object);
 1279                         VM_OBJECT_WLOCK(object);
 1280                         if (maxsize + poffset <= object->un_pager.vnp.vnp_size)
 1281                                 goto downgrade;
 1282                 }
 1283                 if (object->un_pager.vnp.vnp_size > poffset) {
 1284                         maxsize = object->un_pager.vnp.vnp_size - poffset;
 1285                         ncount = btoc(maxsize);
 1286                         if ((pgoff = (int)maxsize & PAGE_MASK) != 0) {
 1287                                 pgoff = roundup2(pgoff, DEV_BSIZE);
 1288 
 1289                                 /*
 1290                                  * If the object is locked and the following
 1291                                  * conditions hold, then the page's dirty
 1292                                  * field cannot be concurrently changed by a
 1293                                  * pmap operation.
 1294                                  */
 1295                                 m = ma[ncount - 1];
 1296                                 vm_page_assert_sbusied(m);
 1297                                 KASSERT(!pmap_page_is_write_mapped(m),
 1298                 ("vnode_pager_generic_putpages: page %p is not read-only", m));
 1299                                 MPASS(m->dirty != 0);
 1300                                 vm_page_clear_dirty(m, pgoff, PAGE_SIZE -
 1301                                     pgoff);
 1302                         }
 1303                 } else {
 1304                         maxsize = 0;
 1305                         ncount = 0;
 1306                 }
 1307                 for (i = ncount; i < count; i++)
 1308                         rtvals[i] = VM_PAGER_BAD;
 1309 downgrade:
 1310                 VM_OBJECT_LOCK_DOWNGRADE(object);
 1311         }
 1312 
 1313         auio.uio_iov = &aiov;
 1314         auio.uio_segflg = UIO_NOCOPY;
 1315         auio.uio_rw = UIO_WRITE;
 1316         auio.uio_td = NULL;
 1317         maxblksz = roundup2(poffset + maxsize, DEV_BSIZE);
 1318 
 1319         for (prev_offset = poffset; prev_offset < maxblksz;) {
 1320                 /* Skip clean blocks. */
 1321                 for (in_hole = true; in_hole && prev_offset < maxblksz;) {
 1322                         m = ma[OFF_TO_IDX(prev_offset - poffset)];
 1323                         for (i = vn_off2bidx(prev_offset);
 1324                             i < sizeof(vm_page_bits_t) * NBBY &&
 1325                             prev_offset < maxblksz; i++) {
 1326                                 if (vn_dirty_blk(m, prev_offset)) {
 1327                                         in_hole = false;
 1328                                         break;
 1329                                 }
 1330                                 prev_offset += DEV_BSIZE;
 1331                         }
 1332                 }
 1333                 if (in_hole)
 1334                         goto write_done;
 1335 
 1336                 /* Find longest run of dirty blocks. */
 1337                 for (next_offset = prev_offset; next_offset < maxblksz;) {
 1338                         m = ma[OFF_TO_IDX(next_offset - poffset)];
 1339                         for (i = vn_off2bidx(next_offset);
 1340                             i < sizeof(vm_page_bits_t) * NBBY &&
 1341                             next_offset < maxblksz; i++) {
 1342                                 if (!vn_dirty_blk(m, next_offset))
 1343                                         goto start_write;
 1344                                 next_offset += DEV_BSIZE;
 1345                         }
 1346                 }
 1347 start_write:
 1348                 if (next_offset > poffset + maxsize)
 1349                         next_offset = poffset + maxsize;
 1350 
 1351                 /*
 1352                  * Getting here requires finding a dirty block in the
 1353                  * 'skip clean blocks' loop.
 1354                  */
 1355                 MPASS(prev_offset < next_offset);
 1356 
 1357                 VM_OBJECT_RUNLOCK(object);
 1358                 aiov.iov_base = NULL;
 1359                 auio.uio_iovcnt = 1;
 1360                 auio.uio_offset = prev_offset;
 1361                 prev_resid = auio.uio_resid = aiov.iov_len = next_offset -
 1362                     prev_offset;
 1363                 error = VOP_WRITE(vp, &auio,
 1364                     vnode_pager_putpages_ioflags(flags), curthread->td_ucred);
 1365 
 1366                 wrsz = prev_resid - auio.uio_resid;
 1367                 if (wrsz == 0) {
 1368                         if (ppsratecheck(&lastfail, &curfail, 1) != 0) {
 1369                                 vn_printf(vp, "vnode_pager_putpages: "
 1370                                     "zero-length write at %ju resid %zd\n",
 1371                                     auio.uio_offset, auio.uio_resid);
 1372                         }
 1373                         VM_OBJECT_RLOCK(object);
 1374                         break;
 1375                 }
 1376 
 1377                 /* Adjust the starting offset for next iteration. */
 1378                 prev_offset += wrsz;
 1379                 MPASS(auio.uio_offset == prev_offset);
 1380 
 1381                 ppscheck = 0;
 1382                 if (error != 0 && (ppscheck = ppsratecheck(&lastfail,
 1383                     &curfail, 1)) != 0)
 1384                         vn_printf(vp, "vnode_pager_putpages: I/O error %d\n",
 1385                             error);
 1386                 if (auio.uio_resid != 0 && (ppscheck != 0 ||
 1387                     ppsratecheck(&lastfail, &curfail, 1) != 0))
 1388                         vn_printf(vp, "vnode_pager_putpages: residual I/O %zd "
 1389                             "at %ju\n", auio.uio_resid,
 1390                             (uintmax_t)ma[0]->pindex);
 1391                 VM_OBJECT_RLOCK(object);
 1392                 if (error != 0 || auio.uio_resid != 0)
 1393                         break;
 1394         }
 1395 write_done:
 1396         /* Mark completely processed pages. */
 1397         for (i = 0; i < OFF_TO_IDX(prev_offset - poffset); i++)
 1398                 rtvals[i] = VM_PAGER_OK;
 1399         /* Mark partial EOF page. */
 1400         if (prev_offset == poffset + maxsize && (prev_offset & PAGE_MASK) != 0)
 1401                 rtvals[i++] = VM_PAGER_OK;
 1402         /* Unwritten pages in range, free bonus if the page is clean. */
 1403         for (; i < ncount; i++)
 1404                 rtvals[i] = ma[i]->dirty == 0 ? VM_PAGER_OK : VM_PAGER_ERROR;
 1405         VM_OBJECT_RUNLOCK(object);
 1406         VM_CNT_ADD(v_vnodepgsout, i);
 1407         VM_CNT_INC(v_vnodeout);
 1408         return (rtvals[0]);
 1409 }
 1410 
 1411 int
 1412 vnode_pager_putpages_ioflags(int pager_flags)
 1413 {
 1414         int ioflags;
 1415 
 1416         /*
 1417          * Pageouts are already clustered, use IO_ASYNC to force a
 1418          * bawrite() rather then a bdwrite() to prevent paging I/O
 1419          * from saturating the buffer cache.  Dummy-up the sequential
 1420          * heuristic to cause large ranges to cluster.  If neither
 1421          * IO_SYNC or IO_ASYNC is set, the system decides how to
 1422          * cluster.
 1423          */
 1424         ioflags = IO_VMIO;
 1425         if ((pager_flags & (VM_PAGER_PUT_SYNC | VM_PAGER_PUT_INVAL)) != 0)
 1426                 ioflags |= IO_SYNC;
 1427         else if ((pager_flags & VM_PAGER_CLUSTER_OK) == 0)
 1428                 ioflags |= IO_ASYNC;
 1429         ioflags |= (pager_flags & VM_PAGER_PUT_INVAL) != 0 ? IO_INVAL: 0;
 1430         ioflags |= (pager_flags & VM_PAGER_PUT_NOREUSE) != 0 ? IO_NOREUSE : 0;
 1431         ioflags |= IO_SEQMAX << IO_SEQSHIFT;
 1432         return (ioflags);
 1433 }
 1434 
 1435 /*
 1436  * vnode_pager_undirty_pages().
 1437  *
 1438  * A helper to mark pages as clean after pageout that was possibly
 1439  * done with a short write.  The lpos argument specifies the page run
 1440  * length in bytes, and the written argument specifies how many bytes
 1441  * were actually written.  eof is the offset past the last valid byte
 1442  * in the vnode using the absolute file position of the first byte in
 1443  * the run as the base from which it is computed.
 1444  */
 1445 void
 1446 vnode_pager_undirty_pages(vm_page_t *ma, int *rtvals, int written, off_t eof,
 1447     int lpos)
 1448 {
 1449         vm_object_t obj;
 1450         int i, pos, pos_devb;
 1451 
 1452         if (written == 0 && eof >= lpos)
 1453                 return;
 1454         obj = ma[0]->object;
 1455         VM_OBJECT_WLOCK(obj);
 1456         for (i = 0, pos = 0; pos < written; i++, pos += PAGE_SIZE) {
 1457                 if (pos < trunc_page(written)) {
 1458                         rtvals[i] = VM_PAGER_OK;
 1459                         vm_page_undirty(ma[i]);
 1460                 } else {
 1461                         /* Partially written page. */
 1462                         rtvals[i] = VM_PAGER_AGAIN;
 1463                         vm_page_clear_dirty(ma[i], 0, written & PAGE_MASK);
 1464                 }
 1465         }
 1466         if (eof >= lpos) /* avoid truncation */
 1467                 goto done;
 1468         for (pos = eof, i = OFF_TO_IDX(trunc_page(pos)); pos < lpos; i++) {
 1469                 if (pos != trunc_page(pos)) {
 1470                         /*
 1471                          * The page contains the last valid byte in
 1472                          * the vnode, mark the rest of the page as
 1473                          * clean, potentially making the whole page
 1474                          * clean.
 1475                          */
 1476                         pos_devb = roundup2(pos & PAGE_MASK, DEV_BSIZE);
 1477                         vm_page_clear_dirty(ma[i], pos_devb, PAGE_SIZE -
 1478                             pos_devb);
 1479 
 1480                         /*
 1481                          * If the page was cleaned, report the pageout
 1482                          * on it as successful.  msync() no longer
 1483                          * needs to write out the page, endlessly
 1484                          * creating write requests and dirty buffers.
 1485                          */
 1486                         if (ma[i]->dirty == 0)
 1487                                 rtvals[i] = VM_PAGER_OK;
 1488 
 1489                         pos = round_page(pos);
 1490                 } else {
 1491                         /* vm_pageout_flush() clears dirty */
 1492                         rtvals[i] = VM_PAGER_BAD;
 1493                         pos += PAGE_SIZE;
 1494                 }
 1495         }
 1496 done:
 1497         VM_OBJECT_WUNLOCK(obj);
 1498 }
 1499 
 1500 void
 1501 vnode_pager_update_writecount(vm_object_t object, vm_offset_t start,
 1502     vm_offset_t end)
 1503 {
 1504         struct vnode *vp;
 1505         vm_ooffset_t old_wm;
 1506 
 1507         VM_OBJECT_WLOCK(object);
 1508         if (object->type != OBJT_VNODE) {
 1509                 VM_OBJECT_WUNLOCK(object);
 1510                 return;
 1511         }
 1512         old_wm = object->un_pager.vnp.writemappings;
 1513         object->un_pager.vnp.writemappings += (vm_ooffset_t)end - start;
 1514         vp = object->handle;
 1515         if (old_wm == 0 && object->un_pager.vnp.writemappings != 0) {
 1516                 ASSERT_VOP_ELOCKED(vp, "v_writecount inc");
 1517                 VOP_ADD_WRITECOUNT(vp, 1);
 1518                 CTR3(KTR_VFS, "%s: vp %p v_writecount increased to %d",
 1519                     __func__, vp, vp->v_writecount);
 1520         } else if (old_wm != 0 && object->un_pager.vnp.writemappings == 0) {
 1521                 ASSERT_VOP_ELOCKED(vp, "v_writecount dec");
 1522                 VOP_ADD_WRITECOUNT(vp, -1);
 1523                 CTR3(KTR_VFS, "%s: vp %p v_writecount decreased to %d",
 1524                     __func__, vp, vp->v_writecount);
 1525         }
 1526         VM_OBJECT_WUNLOCK(object);
 1527 }
 1528 
 1529 void
 1530 vnode_pager_release_writecount(vm_object_t object, vm_offset_t start,
 1531     vm_offset_t end)
 1532 {
 1533         struct vnode *vp;
 1534         struct mount *mp;
 1535         vm_offset_t inc;
 1536 
 1537         VM_OBJECT_WLOCK(object);
 1538 
 1539         /*
 1540          * First, recheck the object type to account for the race when
 1541          * the vnode is reclaimed.
 1542          */
 1543         if (object->type != OBJT_VNODE) {
 1544                 VM_OBJECT_WUNLOCK(object);
 1545                 return;
 1546         }
 1547 
 1548         /*
 1549          * Optimize for the case when writemappings is not going to
 1550          * zero.
 1551          */
 1552         inc = end - start;
 1553         if (object->un_pager.vnp.writemappings != inc) {
 1554                 object->un_pager.vnp.writemappings -= inc;
 1555                 VM_OBJECT_WUNLOCK(object);
 1556                 return;
 1557         }
 1558 
 1559         vp = object->handle;
 1560         vhold(vp);
 1561         VM_OBJECT_WUNLOCK(object);
 1562         mp = NULL;
 1563         vn_start_write(vp, &mp, V_WAIT);
 1564         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 1565 
 1566         /*
 1567          * Decrement the object's writemappings, by swapping the start
 1568          * and end arguments for vnode_pager_update_writecount().  If
 1569          * there was not a race with vnode reclaimation, then the
 1570          * vnode's v_writecount is decremented.
 1571          */
 1572         vnode_pager_update_writecount(object, end, start);
 1573         VOP_UNLOCK(vp, 0);
 1574         vdrop(vp);
 1575         if (mp != NULL)
 1576                 vn_finished_write(mp);
 1577 }

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