The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_pager.c

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    1 /*
    2  * Copyright (c) 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * The Mach Operating System project at Carnegie-Mellon University.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. All advertising materials mentioning features or use of this software
   17  *    must display the following acknowledgement:
   18  *      This product includes software developed by the University of
   19  *      California, Berkeley and its contributors.
   20  * 4. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  *      from: @(#)vm_pager.c    8.6 (Berkeley) 1/12/94
   37  *
   38  *
   39  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   40  * All rights reserved.
   41  *
   42  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   43  *
   44  * Permission to use, copy, modify and distribute this software and
   45  * its documentation is hereby granted, provided that both the copyright
   46  * notice and this permission notice appear in all copies of the
   47  * software, derivative works or modified versions, and any portions
   48  * thereof, and that both notices appear in supporting documentation.
   49  *
   50  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   51  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   52  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   53  *
   54  * Carnegie Mellon requests users of this software to return to
   55  *
   56  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   57  *  School of Computer Science
   58  *  Carnegie Mellon University
   59  *  Pittsburgh PA 15213-3890
   60  *
   61  * any improvements or extensions that they make and grant Carnegie the
   62  * rights to redistribute these changes.
   63  *
   64  * $FreeBSD: releng/5.0/sys/vm/vm_pager.c 99196 2002-07-01 02:38:05Z alc $
   65  */
   66 
   67 /*
   68  *      Paging space routine stubs.  Emulates a matchmaker-like interface
   69  *      for builtin pagers.
   70  */
   71 
   72 #include <sys/param.h>
   73 #include <sys/systm.h>
   74 #include <sys/kernel.h>
   75 #include <sys/vnode.h>
   76 #include <sys/bio.h>
   77 #include <sys/buf.h>
   78 #include <sys/ucred.h>
   79 #include <sys/malloc.h>
   80 
   81 #include <vm/vm.h>
   82 #include <vm/vm_param.h>
   83 #include <vm/vm_object.h>
   84 #include <vm/vm_page.h>
   85 #include <vm/vm_pager.h>
   86 #include <vm/vm_extern.h>
   87 
   88 MALLOC_DEFINE(M_VMPGDATA, "VM pgdata", "XXX: VM pager private data");
   89 
   90 extern struct pagerops defaultpagerops;
   91 extern struct pagerops swappagerops;
   92 extern struct pagerops vnodepagerops;
   93 extern struct pagerops devicepagerops;
   94 extern struct pagerops physpagerops;
   95 
   96 int cluster_pbuf_freecnt = -1;  /* unlimited to begin with */
   97 
   98 static int dead_pager_getpages(vm_object_t, vm_page_t *, int, int);
   99 static vm_object_t dead_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
  100         vm_ooffset_t);
  101 static void dead_pager_putpages(vm_object_t, vm_page_t *, int, int, int *);
  102 static boolean_t dead_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
  103 static void dead_pager_dealloc(vm_object_t);
  104 
  105 static int
  106 dead_pager_getpages(obj, ma, count, req)
  107         vm_object_t obj;
  108         vm_page_t *ma;
  109         int count;
  110         int req;
  111 {
  112         return VM_PAGER_FAIL;
  113 }
  114 
  115 static vm_object_t
  116 dead_pager_alloc(handle, size, prot, off)
  117         void *handle;
  118         vm_ooffset_t size;
  119         vm_prot_t prot;
  120         vm_ooffset_t off;
  121 {
  122         return NULL;
  123 }
  124 
  125 static void
  126 dead_pager_putpages(object, m, count, flags, rtvals)
  127         vm_object_t object;
  128         vm_page_t *m;
  129         int count;
  130         int flags;
  131         int *rtvals;
  132 {
  133         int i;
  134 
  135         for (i = 0; i < count; i++) {
  136                 rtvals[i] = VM_PAGER_AGAIN;
  137         }
  138 }
  139 
  140 static int
  141 dead_pager_haspage(object, pindex, prev, next)
  142         vm_object_t object;
  143         vm_pindex_t pindex;
  144         int *prev;
  145         int *next;
  146 {
  147         if (prev)
  148                 *prev = 0;
  149         if (next)
  150                 *next = 0;
  151         return FALSE;
  152 }
  153 
  154 static void
  155 dead_pager_dealloc(object)
  156         vm_object_t object;
  157 {
  158         return;
  159 }
  160 
  161 static struct pagerops deadpagerops = {
  162         NULL,
  163         dead_pager_alloc,
  164         dead_pager_dealloc,
  165         dead_pager_getpages,
  166         dead_pager_putpages,
  167         dead_pager_haspage,
  168         NULL
  169 };
  170 
  171 struct pagerops *pagertab[] = {
  172         &defaultpagerops,       /* OBJT_DEFAULT */
  173         &swappagerops,          /* OBJT_SWAP */
  174         &vnodepagerops,         /* OBJT_VNODE */
  175         &devicepagerops,        /* OBJT_DEVICE */
  176         &physpagerops,          /* OBJT_PHYS */
  177         &deadpagerops           /* OBJT_DEAD */
  178 };
  179 
  180 int npagers = sizeof(pagertab) / sizeof(pagertab[0]);
  181 
  182 /*
  183  * Kernel address space for mapping pages.
  184  * Used by pagers where KVAs are needed for IO.
  185  *
  186  * XXX needs to be large enough to support the number of pending async
  187  * cleaning requests (NPENDINGIO == 64) * the maximum swap cluster size
  188  * (MAXPHYS == 64k) if you want to get the most efficiency.
  189  */
  190 #define PAGER_MAP_SIZE  (8 * 1024 * 1024)
  191 
  192 int pager_map_size = PAGER_MAP_SIZE;
  193 vm_map_t pager_map;
  194 static int bswneeded;
  195 static vm_offset_t swapbkva;            /* swap buffers kva */
  196 struct mtx pbuf_mtx;
  197 static TAILQ_HEAD(swqueue, buf) bswlist;
  198 
  199 void
  200 vm_pager_init()
  201 {
  202         struct pagerops **pgops;
  203 
  204         TAILQ_INIT(&bswlist);
  205         /*
  206          * Initialize known pagers
  207          */
  208         for (pgops = pagertab; pgops < &pagertab[npagers]; pgops++)
  209                 if (pgops && ((*pgops)->pgo_init != NULL))
  210                         (*(*pgops)->pgo_init) ();
  211 }
  212 
  213 void
  214 vm_pager_bufferinit()
  215 {
  216         struct buf *bp;
  217         int i;
  218 
  219         mtx_init(&pbuf_mtx, "pbuf mutex", NULL, MTX_DEF);
  220         bp = swbuf;
  221         /*
  222          * Now set up swap and physical I/O buffer headers.
  223          */
  224         for (i = 0; i < nswbuf; i++, bp++) {
  225                 TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
  226                 BUF_LOCKINIT(bp);
  227                 LIST_INIT(&bp->b_dep);
  228                 bp->b_rcred = bp->b_wcred = NOCRED;
  229                 bp->b_xflags = 0;
  230         }
  231 
  232         cluster_pbuf_freecnt = nswbuf / 2;
  233 
  234         swapbkva = kmem_alloc_pageable(pager_map, nswbuf * MAXPHYS);
  235         if (!swapbkva)
  236                 panic("Not enough pager_map VM space for physical buffers");
  237 }
  238 
  239 /*
  240  * Allocate an instance of a pager of the given type.
  241  * Size, protection and offset parameters are passed in for pagers that
  242  * need to perform page-level validation (e.g. the device pager).
  243  */
  244 vm_object_t
  245 vm_pager_allocate(objtype_t type, void *handle, vm_ooffset_t size,
  246                   vm_prot_t prot, vm_ooffset_t off)
  247 {
  248         vm_object_t ret;
  249         struct pagerops *ops;
  250 
  251         ops = pagertab[type];
  252         if (ops)
  253                 ret = (*ops->pgo_alloc) (handle, size, prot, off);
  254         else
  255                 ret = NULL;
  256         return (ret);
  257 }
  258 
  259 void
  260 vm_pager_deallocate(object)
  261         vm_object_t object;
  262 {
  263         (*pagertab[object->type]->pgo_dealloc) (object);
  264 }
  265 
  266 /*
  267  *      vm_pager_strategy:
  268  *
  269  *      called with no specific spl
  270  *      Execute strategy routine directly to pager.
  271  */
  272 void
  273 vm_pager_strategy(vm_object_t object, struct bio *bp)
  274 {
  275         if (pagertab[object->type]->pgo_strategy) {
  276                 (*pagertab[object->type]->pgo_strategy)(object, bp);
  277         } else {
  278                 bp->bio_flags |= BIO_ERROR;
  279                 bp->bio_error = ENXIO;
  280                 biodone(bp);
  281         }
  282 }
  283 
  284 /*
  285  * vm_pager_get_pages() - inline, see vm/vm_pager.h
  286  * vm_pager_put_pages() - inline, see vm/vm_pager.h
  287  * vm_pager_has_page() - inline, see vm/vm_pager.h
  288  * vm_pager_page_inserted() - inline, see vm/vm_pager.h
  289  * vm_pager_page_removed() - inline, see vm/vm_pager.h
  290  */
  291 
  292 vm_offset_t
  293 vm_pager_map_page(m)
  294         vm_page_t m;
  295 {
  296         vm_offset_t kva;
  297 
  298         kva = kmem_alloc_wait(pager_map, PAGE_SIZE);
  299         pmap_qenter(kva, &m, 1);
  300         return (kva);
  301 }
  302 
  303 void
  304 vm_pager_unmap_page(kva)
  305         vm_offset_t kva;
  306 {
  307 
  308         pmap_qremove(kva, 1);
  309         kmem_free_wakeup(pager_map, kva, PAGE_SIZE);
  310 }
  311 
  312 vm_object_t
  313 vm_pager_object_lookup(pg_list, handle)
  314         struct pagerlst *pg_list;
  315         void *handle;
  316 {
  317         vm_object_t object;
  318 
  319         TAILQ_FOREACH(object, pg_list, pager_object_list)
  320                 if (object->handle == handle)
  321                         return (object);
  322         return (NULL);
  323 }
  324 
  325 /*
  326  * initialize a physical buffer
  327  */
  328 
  329 /*
  330  * XXX This probably belongs in vfs_bio.c
  331  */
  332 static void
  333 initpbuf(struct buf *bp)
  334 {
  335         bp->b_rcred = NOCRED;
  336         bp->b_wcred = NOCRED;
  337         bp->b_qindex = 0;       /* On no queue (QUEUE_NONE) */
  338         bp->b_data = (caddr_t) (MAXPHYS * (bp - swbuf)) + swapbkva;
  339         bp->b_kvabase = bp->b_data;
  340         bp->b_kvasize = MAXPHYS;
  341         bp->b_xflags = 0;
  342         bp->b_flags = 0;
  343         bp->b_ioflags = 0;
  344         bp->b_iodone = NULL;
  345         bp->b_error = 0;
  346         bp->b_magic = B_MAGIC_BIO;
  347         bp->b_op = &buf_ops_bio;
  348         BUF_LOCK(bp, LK_EXCLUSIVE);
  349 }
  350 
  351 /*
  352  * allocate a physical buffer
  353  *
  354  *      There are a limited number (nswbuf) of physical buffers.  We need
  355  *      to make sure that no single subsystem is able to hog all of them,
  356  *      so each subsystem implements a counter which is typically initialized
  357  *      to 1/2 nswbuf.  getpbuf() decrements this counter in allocation and
  358  *      increments it on release, and blocks if the counter hits zero.  A
  359  *      subsystem may initialize the counter to -1 to disable the feature,
  360  *      but it must still be sure to match up all uses of getpbuf() with 
  361  *      relpbuf() using the same variable.
  362  *
  363  *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  364  *      relatively soon when the rest of the subsystems get smart about it. XXX
  365  */
  366 struct buf *
  367 getpbuf(pfreecnt)
  368         int *pfreecnt;
  369 {
  370         int s;
  371         struct buf *bp;
  372 
  373         s = splvm();
  374         GIANT_REQUIRED;
  375         mtx_lock(&pbuf_mtx);
  376 
  377         for (;;) {
  378                 if (pfreecnt) {
  379                         while (*pfreecnt == 0) {
  380                                 msleep(pfreecnt, &pbuf_mtx, PVM, "wswbuf0", 0);
  381                         }
  382                 }
  383 
  384                 /* get a bp from the swap buffer header pool */
  385                 if ((bp = TAILQ_FIRST(&bswlist)) != NULL)
  386                         break;
  387 
  388                 bswneeded = 1;
  389                 msleep(&bswneeded, &pbuf_mtx, PVM, "wswbuf1", 0);
  390                 /* loop in case someone else grabbed one */
  391         }
  392         TAILQ_REMOVE(&bswlist, bp, b_freelist);
  393         if (pfreecnt)
  394                 --*pfreecnt;
  395         mtx_unlock(&pbuf_mtx);
  396         splx(s);
  397 
  398         initpbuf(bp);
  399         return bp;
  400 }
  401 
  402 /*
  403  * allocate a physical buffer, if one is available.
  404  *
  405  *      Note that there is no NULL hack here - all subsystems using this
  406  *      call understand how to use pfreecnt.
  407  */
  408 struct buf *
  409 trypbuf(pfreecnt)
  410         int *pfreecnt;
  411 {
  412         int s;
  413         struct buf *bp;
  414 
  415         s = splvm();
  416         mtx_lock(&pbuf_mtx);
  417         if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist)) == NULL) {
  418                 mtx_unlock(&pbuf_mtx);
  419                 splx(s);
  420                 return NULL;
  421         }
  422         TAILQ_REMOVE(&bswlist, bp, b_freelist);
  423 
  424         --*pfreecnt;
  425 
  426         mtx_unlock(&pbuf_mtx);
  427         splx(s);
  428 
  429         initpbuf(bp);
  430 
  431         return bp;
  432 }
  433 
  434 /*
  435  * release a physical buffer
  436  *
  437  *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  438  *      relatively soon when the rest of the subsystems get smart about it. XXX
  439  */
  440 void
  441 relpbuf(bp, pfreecnt)
  442         struct buf *bp;
  443         int *pfreecnt;
  444 {
  445         int s;
  446 
  447         s = splvm();
  448         mtx_lock(&pbuf_mtx);
  449 
  450         if (bp->b_rcred != NOCRED) {
  451                 crfree(bp->b_rcred);
  452                 bp->b_rcred = NOCRED;
  453         }
  454         if (bp->b_wcred != NOCRED) {
  455                 crfree(bp->b_wcred);
  456                 bp->b_wcred = NOCRED;
  457         }
  458 
  459         if (bp->b_vp)
  460                 pbrelvp(bp);
  461 
  462         BUF_UNLOCK(bp);
  463 
  464         TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
  465 
  466         if (bswneeded) {
  467                 bswneeded = 0;
  468                 wakeup(&bswneeded);
  469         }
  470         if (pfreecnt) {
  471                 if (++*pfreecnt == 1)
  472                         wakeup(pfreecnt);
  473         }
  474         mtx_unlock(&pbuf_mtx);
  475         splx(s);
  476 }

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