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  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      from: @(#)vm_pager.c    8.6 (Berkeley) 1/12/94
   33  *
   34  *
   35  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   36  * All rights reserved.
   37  *
   38  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   39  *
   40  * Permission to use, copy, modify and distribute this software and
   41  * its documentation is hereby granted, provided that both the copyright
   42  * notice and this permission notice appear in all copies of the
   43  * software, derivative works or modified versions, and any portions
   44  * thereof, and that both notices appear in supporting documentation.
   45  *
   46  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   47  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   48  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   49  *
   50  * Carnegie Mellon requests users of this software to return to
   51  *
   52  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   53  *  School of Computer Science
   54  *  Carnegie Mellon University
   55  *  Pittsburgh PA 15213-3890
   56  *
   57  * any improvements or extensions that they make and grant Carnegie the
   58  * rights to redistribute these changes.
   59  */
   60 
   61 /*
   62  *      Paging space routine stubs.  Emulates a matchmaker-like interface
   63  *      for builtin pagers.
   64  */
   65 
   66 #include <sys/cdefs.h>
   67 __FBSDID("$FreeBSD$");
   68 
   69 #include <sys/param.h>
   70 #include <sys/systm.h>
   71 #include <sys/kernel.h>
   72 #include <sys/vnode.h>
   73 #include <sys/bio.h>
   74 #include <sys/buf.h>
   75 #include <sys/ucred.h>
   76 #include <sys/malloc.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_extern.h>
   84 
   85 MALLOC_DEFINE(M_VMPGDATA, "vm_pgdata", "XXX: VM pager private data");
   86 
   87 int cluster_pbuf_freecnt = -1;  /* unlimited to begin with */
   88 
   89 static int dead_pager_getpages(vm_object_t, vm_page_t *, int, int);
   90 static vm_object_t dead_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
   91         vm_ooffset_t);
   92 static void dead_pager_putpages(vm_object_t, vm_page_t *, int, int, int *);
   93 static boolean_t dead_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
   94 static void dead_pager_dealloc(vm_object_t);
   95 
   96 static int
   97 dead_pager_getpages(obj, ma, count, req)
   98         vm_object_t obj;
   99         vm_page_t *ma;
  100         int count;
  101         int req;
  102 {
  103         return VM_PAGER_FAIL;
  104 }
  105 
  106 static vm_object_t
  107 dead_pager_alloc(handle, size, prot, off)
  108         void *handle;
  109         vm_ooffset_t size;
  110         vm_prot_t prot;
  111         vm_ooffset_t off;
  112 {
  113         return NULL;
  114 }
  115 
  116 static void
  117 dead_pager_putpages(object, m, count, flags, rtvals)
  118         vm_object_t object;
  119         vm_page_t *m;
  120         int count;
  121         int flags;
  122         int *rtvals;
  123 {
  124         int i;
  125 
  126         for (i = 0; i < count; i++) {
  127                 rtvals[i] = VM_PAGER_AGAIN;
  128         }
  129 }
  130 
  131 static int
  132 dead_pager_haspage(object, pindex, prev, next)
  133         vm_object_t object;
  134         vm_pindex_t pindex;
  135         int *prev;
  136         int *next;
  137 {
  138         if (prev)
  139                 *prev = 0;
  140         if (next)
  141                 *next = 0;
  142         return FALSE;
  143 }
  144 
  145 static void
  146 dead_pager_dealloc(object)
  147         vm_object_t object;
  148 {
  149         return;
  150 }
  151 
  152 static struct pagerops deadpagerops = {
  153         .pgo_alloc =    dead_pager_alloc,
  154         .pgo_dealloc =  dead_pager_dealloc,
  155         .pgo_getpages = dead_pager_getpages,
  156         .pgo_putpages = dead_pager_putpages,
  157         .pgo_haspage =  dead_pager_haspage,
  158 };
  159 
  160 struct pagerops *pagertab[] = {
  161         &defaultpagerops,       /* OBJT_DEFAULT */
  162         &swappagerops,          /* OBJT_SWAP */
  163         &vnodepagerops,         /* OBJT_VNODE */
  164         &devicepagerops,        /* OBJT_DEVICE */
  165         &physpagerops,          /* OBJT_PHYS */
  166         &deadpagerops           /* OBJT_DEAD */
  167 };
  168 
  169 static const int npagers = sizeof(pagertab) / sizeof(pagertab[0]);
  170 
  171 /*
  172  * Kernel address space for mapping pages.
  173  * Used by pagers where KVAs are needed for IO.
  174  *
  175  * XXX needs to be large enough to support the number of pending async
  176  * cleaning requests (NPENDINGIO == 64) * the maximum swap cluster size
  177  * (MAXPHYS == 64k) if you want to get the most efficiency.
  178  */
  179 vm_map_t pager_map;
  180 static int bswneeded;
  181 static vm_offset_t swapbkva;            /* swap buffers kva */
  182 struct mtx pbuf_mtx;
  183 static TAILQ_HEAD(swqueue, buf) bswlist;
  184 
  185 void
  186 vm_pager_init()
  187 {
  188         struct pagerops **pgops;
  189 
  190         TAILQ_INIT(&bswlist);
  191         /*
  192          * Initialize known pagers
  193          */
  194         for (pgops = pagertab; pgops < &pagertab[npagers]; pgops++)
  195                 if (pgops && ((*pgops)->pgo_init != NULL))
  196                         (*(*pgops)->pgo_init) ();
  197 }
  198 
  199 void
  200 vm_pager_bufferinit()
  201 {
  202         struct buf *bp;
  203         int i;
  204 
  205         mtx_init(&pbuf_mtx, "pbuf mutex", NULL, MTX_DEF);
  206         bp = swbuf;
  207         /*
  208          * Now set up swap and physical I/O buffer headers.
  209          */
  210         for (i = 0; i < nswbuf; i++, bp++) {
  211                 TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
  212                 BUF_LOCKINIT(bp);
  213                 LIST_INIT(&bp->b_dep);
  214                 bp->b_rcred = bp->b_wcred = NOCRED;
  215                 bp->b_xflags = 0;
  216         }
  217 
  218         cluster_pbuf_freecnt = nswbuf / 2;
  219         vnode_pbuf_freecnt = nswbuf / 2 + 1;
  220 
  221         swapbkva = kmem_alloc_nofault(pager_map, nswbuf * MAXPHYS);
  222         if (!swapbkva)
  223                 panic("Not enough pager_map VM space for physical buffers");
  224 }
  225 
  226 /*
  227  * Allocate an instance of a pager of the given type.
  228  * Size, protection and offset parameters are passed in for pagers that
  229  * need to perform page-level validation (e.g. the device pager).
  230  */
  231 vm_object_t
  232 vm_pager_allocate(objtype_t type, void *handle, vm_ooffset_t size,
  233                   vm_prot_t prot, vm_ooffset_t off)
  234 {
  235         vm_object_t ret;
  236         struct pagerops *ops;
  237 
  238         ops = pagertab[type];
  239         if (ops)
  240                 ret = (*ops->pgo_alloc) (handle, size, prot, off);
  241         else
  242                 ret = NULL;
  243         return (ret);
  244 }
  245 
  246 /*
  247  *      The object must be locked.
  248  */
  249 void
  250 vm_pager_deallocate(object)
  251         vm_object_t object;
  252 {
  253 
  254         VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
  255         (*pagertab[object->type]->pgo_dealloc) (object);
  256 }
  257 
  258 /*
  259  * vm_pager_get_pages() - inline, see vm/vm_pager.h
  260  * vm_pager_put_pages() - inline, see vm/vm_pager.h
  261  * vm_pager_has_page() - inline, see vm/vm_pager.h
  262  */
  263 
  264 /*
  265  * Search the specified pager object list for an object with the
  266  * specified handle.  If an object with the specified handle is found,
  267  * increase its reference count and return it.  Otherwise, return NULL.
  268  *
  269  * The pager object list must be locked.
  270  */
  271 vm_object_t
  272 vm_pager_object_lookup(struct pagerlst *pg_list, void *handle)
  273 {
  274         vm_object_t object;
  275 
  276         TAILQ_FOREACH(object, pg_list, pager_object_list) {
  277                 VM_OBJECT_LOCK(object);
  278                 if (object->handle == handle &&
  279                     (object->flags & OBJ_DEAD) == 0) {
  280                         vm_object_reference_locked(object);
  281                         VM_OBJECT_UNLOCK(object);
  282                         break;
  283                 }
  284                 VM_OBJECT_UNLOCK(object);
  285         }
  286         return (object);
  287 }
  288 
  289 /*
  290  * initialize a physical buffer
  291  */
  292 
  293 /*
  294  * XXX This probably belongs in vfs_bio.c
  295  */
  296 static void
  297 initpbuf(struct buf *bp)
  298 {
  299         KASSERT(bp->b_bufobj == NULL, ("initpbuf with bufobj"));
  300         KASSERT(bp->b_vp == NULL, ("initpbuf with vp"));
  301         bp->b_rcred = NOCRED;
  302         bp->b_wcred = NOCRED;
  303         bp->b_qindex = 0;       /* On no queue (QUEUE_NONE) */
  304         bp->b_saveaddr = (caddr_t) (MAXPHYS * (bp - swbuf)) + swapbkva;
  305         bp->b_data = bp->b_saveaddr;
  306         bp->b_kvabase = bp->b_saveaddr;
  307         bp->b_kvasize = MAXPHYS;
  308         bp->b_xflags = 0;
  309         bp->b_flags = 0;
  310         bp->b_ioflags = 0;
  311         bp->b_iodone = NULL;
  312         bp->b_error = 0;
  313         BUF_LOCK(bp, LK_EXCLUSIVE, NULL);
  314 }
  315 
  316 /*
  317  * allocate a physical buffer
  318  *
  319  *      There are a limited number (nswbuf) of physical buffers.  We need
  320  *      to make sure that no single subsystem is able to hog all of them,
  321  *      so each subsystem implements a counter which is typically initialized
  322  *      to 1/2 nswbuf.  getpbuf() decrements this counter in allocation and
  323  *      increments it on release, and blocks if the counter hits zero.  A
  324  *      subsystem may initialize the counter to -1 to disable the feature,
  325  *      but it must still be sure to match up all uses of getpbuf() with 
  326  *      relpbuf() using the same variable.
  327  *
  328  *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  329  *      relatively soon when the rest of the subsystems get smart about it. XXX
  330  */
  331 struct buf *
  332 getpbuf(int *pfreecnt)
  333 {
  334         struct buf *bp;
  335 
  336         mtx_lock(&pbuf_mtx);
  337 
  338         for (;;) {
  339                 if (pfreecnt) {
  340                         while (*pfreecnt == 0) {
  341                                 msleep(pfreecnt, &pbuf_mtx, PVM, "wswbuf0", 0);
  342                         }
  343                 }
  344 
  345                 /* get a bp from the swap buffer header pool */
  346                 if ((bp = TAILQ_FIRST(&bswlist)) != NULL)
  347                         break;
  348 
  349                 bswneeded = 1;
  350                 msleep(&bswneeded, &pbuf_mtx, PVM, "wswbuf1", 0);
  351                 /* loop in case someone else grabbed one */
  352         }
  353         TAILQ_REMOVE(&bswlist, bp, b_freelist);
  354         if (pfreecnt)
  355                 --*pfreecnt;
  356         mtx_unlock(&pbuf_mtx);
  357 
  358         initpbuf(bp);
  359         return bp;
  360 }
  361 
  362 /*
  363  * allocate a physical buffer, if one is available.
  364  *
  365  *      Note that there is no NULL hack here - all subsystems using this
  366  *      call understand how to use pfreecnt.
  367  */
  368 struct buf *
  369 trypbuf(int *pfreecnt)
  370 {
  371         struct buf *bp;
  372 
  373         mtx_lock(&pbuf_mtx);
  374         if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist)) == NULL) {
  375                 mtx_unlock(&pbuf_mtx);
  376                 return NULL;
  377         }
  378         TAILQ_REMOVE(&bswlist, bp, b_freelist);
  379 
  380         --*pfreecnt;
  381 
  382         mtx_unlock(&pbuf_mtx);
  383 
  384         initpbuf(bp);
  385 
  386         return bp;
  387 }
  388 
  389 /*
  390  * release a physical buffer
  391  *
  392  *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  393  *      relatively soon when the rest of the subsystems get smart about it. XXX
  394  */
  395 void
  396 relpbuf(struct buf *bp, int *pfreecnt)
  397 {
  398 
  399         if (bp->b_rcred != NOCRED) {
  400                 crfree(bp->b_rcred);
  401                 bp->b_rcred = NOCRED;
  402         }
  403         if (bp->b_wcred != NOCRED) {
  404                 crfree(bp->b_wcred);
  405                 bp->b_wcred = NOCRED;
  406         }
  407 
  408         KASSERT(bp->b_vp == NULL, ("relpbuf with vp"));
  409         KASSERT(bp->b_bufobj == NULL, ("relpbuf with bufobj"));
  410 
  411         BUF_UNLOCK(bp);
  412 
  413         mtx_lock(&pbuf_mtx);
  414         TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
  415 
  416         if (bswneeded) {
  417                 bswneeded = 0;
  418                 wakeup(&bswneeded);
  419         }
  420         if (pfreecnt) {
  421                 if (++*pfreecnt == 1)
  422                         wakeup(pfreecnt);
  423         }
  424         mtx_unlock(&pbuf_mtx);
  425 }
  426 
  427 /*
  428  * Associate a p-buffer with a vnode.
  429  *
  430  * Also sets B_PAGING flag to indicate that vnode is not fully associated
  431  * with the buffer.  i.e. the bp has not been linked into the vnode or
  432  * ref-counted.
  433  */
  434 void
  435 pbgetvp(struct vnode *vp, struct buf *bp)
  436 {
  437 
  438         KASSERT(bp->b_vp == NULL, ("pbgetvp: not free"));
  439         KASSERT(bp->b_bufobj == NULL, ("pbgetvp: not free (bufobj)"));
  440 
  441         bp->b_vp = vp;
  442         bp->b_flags |= B_PAGING;
  443         bp->b_bufobj = &vp->v_bufobj;
  444 }
  445 
  446 /*
  447  * Associate a p-buffer with a vnode.
  448  *
  449  * Also sets B_PAGING flag to indicate that vnode is not fully associated
  450  * with the buffer.  i.e. the bp has not been linked into the vnode or
  451  * ref-counted.
  452  */
  453 void
  454 pbgetbo(struct bufobj *bo, struct buf *bp)
  455 {
  456 
  457         KASSERT(bp->b_vp == NULL, ("pbgetbo: not free (vnode)"));
  458         KASSERT(bp->b_bufobj == NULL, ("pbgetbo: not free (bufobj)"));
  459 
  460         bp->b_flags |= B_PAGING;
  461         bp->b_bufobj = bo;
  462 }
  463 
  464 /*
  465  * Disassociate a p-buffer from a vnode.
  466  */
  467 void
  468 pbrelvp(struct buf *bp)
  469 {
  470 
  471         KASSERT(bp->b_vp != NULL, ("pbrelvp: NULL"));
  472         KASSERT(bp->b_bufobj != NULL, ("pbrelvp: NULL bufobj"));
  473 
  474         /* XXX REMOVE ME */
  475         BO_LOCK(bp->b_bufobj);
  476         if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
  477                 panic(
  478                     "relpbuf(): b_vp was probably reassignbuf()d %p %x",
  479                     bp,
  480                     (int)bp->b_flags
  481                 );
  482         }
  483         BO_UNLOCK(bp->b_bufobj);
  484         bp->b_vp = NULL;
  485         bp->b_bufobj = NULL;
  486         bp->b_flags &= ~B_PAGING;
  487 }
  488 
  489 /*
  490  * Disassociate a p-buffer from a bufobj.
  491  */
  492 void
  493 pbrelbo(struct buf *bp)
  494 {
  495 
  496         KASSERT(bp->b_vp == NULL, ("pbrelbo: vnode"));
  497         KASSERT(bp->b_bufobj != NULL, ("pbrelbo: NULL bufobj"));
  498 
  499         /* XXX REMOVE ME */
  500         BO_LOCK(bp->b_bufobj);
  501         if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
  502                 panic(
  503                     "relpbuf(): b_vp was probably reassignbuf()d %p %x",
  504                     bp,
  505                     (int)bp->b_flags
  506                 );
  507         }
  508         BO_UNLOCK(bp->b_bufobj);
  509         bp->b_bufobj = NULL;
  510         bp->b_flags &= ~B_PAGING;
  511 }

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