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: releng/9.0/sys/vm/vm_pager.c 217529 2011-01-18 04:54:43Z alc $");
   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 int cluster_pbuf_freecnt = -1;  /* unlimited to begin with */
   86 
   87 static int dead_pager_getpages(vm_object_t, vm_page_t *, int, int);
   88 static vm_object_t dead_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
   89     vm_ooffset_t, struct ucred *);
   90 static void dead_pager_putpages(vm_object_t, vm_page_t *, int, int, int *);
   91 static boolean_t dead_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
   92 static void dead_pager_dealloc(vm_object_t);
   93 
   94 static int
   95 dead_pager_getpages(obj, ma, count, req)
   96         vm_object_t obj;
   97         vm_page_t *ma;
   98         int count;
   99         int req;
  100 {
  101         return VM_PAGER_FAIL;
  102 }
  103 
  104 static vm_object_t
  105 dead_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
  106     vm_ooffset_t off, struct ucred *cred)
  107 {
  108         return NULL;
  109 }
  110 
  111 static void
  112 dead_pager_putpages(object, m, count, flags, rtvals)
  113         vm_object_t object;
  114         vm_page_t *m;
  115         int count;
  116         int flags;
  117         int *rtvals;
  118 {
  119         int i;
  120 
  121         for (i = 0; i < count; i++) {
  122                 rtvals[i] = VM_PAGER_AGAIN;
  123         }
  124 }
  125 
  126 static int
  127 dead_pager_haspage(object, pindex, prev, next)
  128         vm_object_t object;
  129         vm_pindex_t pindex;
  130         int *prev;
  131         int *next;
  132 {
  133         if (prev)
  134                 *prev = 0;
  135         if (next)
  136                 *next = 0;
  137         return FALSE;
  138 }
  139 
  140 static void
  141 dead_pager_dealloc(object)
  142         vm_object_t object;
  143 {
  144         return;
  145 }
  146 
  147 static struct pagerops deadpagerops = {
  148         .pgo_alloc =    dead_pager_alloc,
  149         .pgo_dealloc =  dead_pager_dealloc,
  150         .pgo_getpages = dead_pager_getpages,
  151         .pgo_putpages = dead_pager_putpages,
  152         .pgo_haspage =  dead_pager_haspage,
  153 };
  154 
  155 struct pagerops *pagertab[] = {
  156         &defaultpagerops,       /* OBJT_DEFAULT */
  157         &swappagerops,          /* OBJT_SWAP */
  158         &vnodepagerops,         /* OBJT_VNODE */
  159         &devicepagerops,        /* OBJT_DEVICE */
  160         &physpagerops,          /* OBJT_PHYS */
  161         &deadpagerops,          /* OBJT_DEAD */
  162         &sgpagerops             /* OBJT_SG */
  163 };
  164 
  165 static const int npagers = sizeof(pagertab) / sizeof(pagertab[0]);
  166 
  167 /*
  168  * Kernel address space for mapping pages.
  169  * Used by pagers where KVAs are needed for IO.
  170  *
  171  * XXX needs to be large enough to support the number of pending async
  172  * cleaning requests (NPENDINGIO == 64) * the maximum swap cluster size
  173  * (MAXPHYS == 64k) if you want to get the most efficiency.
  174  */
  175 vm_map_t pager_map;
  176 static int bswneeded;
  177 static vm_offset_t swapbkva;            /* swap buffers kva */
  178 struct mtx pbuf_mtx;
  179 static TAILQ_HEAD(swqueue, buf) bswlist;
  180 
  181 void
  182 vm_pager_init()
  183 {
  184         struct pagerops **pgops;
  185 
  186         TAILQ_INIT(&bswlist);
  187         /*
  188          * Initialize known pagers
  189          */
  190         for (pgops = pagertab; pgops < &pagertab[npagers]; pgops++)
  191                 if (pgops && ((*pgops)->pgo_init != NULL))
  192                         (*(*pgops)->pgo_init) ();
  193 }
  194 
  195 void
  196 vm_pager_bufferinit()
  197 {
  198         struct buf *bp;
  199         int i;
  200 
  201         mtx_init(&pbuf_mtx, "pbuf mutex", NULL, MTX_DEF);
  202         bp = swbuf;
  203         /*
  204          * Now set up swap and physical I/O buffer headers.
  205          */
  206         for (i = 0; i < nswbuf; i++, bp++) {
  207                 TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
  208                 BUF_LOCKINIT(bp);
  209                 LIST_INIT(&bp->b_dep);
  210                 bp->b_rcred = bp->b_wcred = NOCRED;
  211                 bp->b_xflags = 0;
  212         }
  213 
  214         cluster_pbuf_freecnt = nswbuf / 2;
  215         vnode_pbuf_freecnt = nswbuf / 2 + 1;
  216 
  217         swapbkva = kmem_alloc_nofault(pager_map, nswbuf * MAXPHYS);
  218         if (!swapbkva)
  219                 panic("Not enough pager_map VM space for physical buffers");
  220 }
  221 
  222 /*
  223  * Allocate an instance of a pager of the given type.
  224  * Size, protection and offset parameters are passed in for pagers that
  225  * need to perform page-level validation (e.g. the device pager).
  226  */
  227 vm_object_t
  228 vm_pager_allocate(objtype_t type, void *handle, vm_ooffset_t size,
  229     vm_prot_t prot, vm_ooffset_t off, struct ucred *cred)
  230 {
  231         vm_object_t ret;
  232         struct pagerops *ops;
  233 
  234         ops = pagertab[type];
  235         if (ops)
  236                 ret = (*ops->pgo_alloc) (handle, size, prot, off, cred);
  237         else
  238                 ret = NULL;
  239         return (ret);
  240 }
  241 
  242 /*
  243  *      The object must be locked.
  244  */
  245 void
  246 vm_pager_deallocate(object)
  247         vm_object_t object;
  248 {
  249 
  250         VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
  251         (*pagertab[object->type]->pgo_dealloc) (object);
  252 }
  253 
  254 /*
  255  * vm_pager_get_pages() - inline, see vm/vm_pager.h
  256  * vm_pager_put_pages() - inline, see vm/vm_pager.h
  257  * vm_pager_has_page() - inline, see vm/vm_pager.h
  258  */
  259 
  260 /*
  261  * Search the specified pager object list for an object with the
  262  * specified handle.  If an object with the specified handle is found,
  263  * increase its reference count and return it.  Otherwise, return NULL.
  264  *
  265  * The pager object list must be locked.
  266  */
  267 vm_object_t
  268 vm_pager_object_lookup(struct pagerlst *pg_list, void *handle)
  269 {
  270         vm_object_t object;
  271 
  272         TAILQ_FOREACH(object, pg_list, pager_object_list) {
  273                 VM_OBJECT_LOCK(object);
  274                 if (object->handle == handle &&
  275                     (object->flags & OBJ_DEAD) == 0) {
  276                         vm_object_reference_locked(object);
  277                         VM_OBJECT_UNLOCK(object);
  278                         break;
  279                 }
  280                 VM_OBJECT_UNLOCK(object);
  281         }
  282         return (object);
  283 }
  284 
  285 /*
  286  * initialize a physical buffer
  287  */
  288 
  289 /*
  290  * XXX This probably belongs in vfs_bio.c
  291  */
  292 static void
  293 initpbuf(struct buf *bp)
  294 {
  295         KASSERT(bp->b_bufobj == NULL, ("initpbuf with bufobj"));
  296         KASSERT(bp->b_vp == NULL, ("initpbuf with vp"));
  297         bp->b_rcred = NOCRED;
  298         bp->b_wcred = NOCRED;
  299         bp->b_qindex = 0;       /* On no queue (QUEUE_NONE) */
  300         bp->b_saveaddr = (caddr_t) (MAXPHYS * (bp - swbuf)) + swapbkva;
  301         bp->b_data = bp->b_saveaddr;
  302         bp->b_kvabase = bp->b_saveaddr;
  303         bp->b_kvasize = MAXPHYS;
  304         bp->b_xflags = 0;
  305         bp->b_flags = 0;
  306         bp->b_ioflags = 0;
  307         bp->b_iodone = NULL;
  308         bp->b_error = 0;
  309         BUF_LOCK(bp, LK_EXCLUSIVE, NULL);
  310 }
  311 
  312 /*
  313  * allocate a physical buffer
  314  *
  315  *      There are a limited number (nswbuf) of physical buffers.  We need
  316  *      to make sure that no single subsystem is able to hog all of them,
  317  *      so each subsystem implements a counter which is typically initialized
  318  *      to 1/2 nswbuf.  getpbuf() decrements this counter in allocation and
  319  *      increments it on release, and blocks if the counter hits zero.  A
  320  *      subsystem may initialize the counter to -1 to disable the feature,
  321  *      but it must still be sure to match up all uses of getpbuf() with 
  322  *      relpbuf() using the same variable.
  323  *
  324  *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  325  *      relatively soon when the rest of the subsystems get smart about it. XXX
  326  */
  327 struct buf *
  328 getpbuf(int *pfreecnt)
  329 {
  330         struct buf *bp;
  331 
  332         mtx_lock(&pbuf_mtx);
  333 
  334         for (;;) {
  335                 if (pfreecnt) {
  336                         while (*pfreecnt == 0) {
  337                                 msleep(pfreecnt, &pbuf_mtx, PVM, "wswbuf0", 0);
  338                         }
  339                 }
  340 
  341                 /* get a bp from the swap buffer header pool */
  342                 if ((bp = TAILQ_FIRST(&bswlist)) != NULL)
  343                         break;
  344 
  345                 bswneeded = 1;
  346                 msleep(&bswneeded, &pbuf_mtx, PVM, "wswbuf1", 0);
  347                 /* loop in case someone else grabbed one */
  348         }
  349         TAILQ_REMOVE(&bswlist, bp, b_freelist);
  350         if (pfreecnt)
  351                 --*pfreecnt;
  352         mtx_unlock(&pbuf_mtx);
  353 
  354         initpbuf(bp);
  355         return bp;
  356 }
  357 
  358 /*
  359  * allocate a physical buffer, if one is available.
  360  *
  361  *      Note that there is no NULL hack here - all subsystems using this
  362  *      call understand how to use pfreecnt.
  363  */
  364 struct buf *
  365 trypbuf(int *pfreecnt)
  366 {
  367         struct buf *bp;
  368 
  369         mtx_lock(&pbuf_mtx);
  370         if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist)) == NULL) {
  371                 mtx_unlock(&pbuf_mtx);
  372                 return NULL;
  373         }
  374         TAILQ_REMOVE(&bswlist, bp, b_freelist);
  375 
  376         --*pfreecnt;
  377 
  378         mtx_unlock(&pbuf_mtx);
  379 
  380         initpbuf(bp);
  381 
  382         return bp;
  383 }
  384 
  385 /*
  386  * release a physical buffer
  387  *
  388  *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  389  *      relatively soon when the rest of the subsystems get smart about it. XXX
  390  */
  391 void
  392 relpbuf(struct buf *bp, int *pfreecnt)
  393 {
  394 
  395         if (bp->b_rcred != NOCRED) {
  396                 crfree(bp->b_rcred);
  397                 bp->b_rcred = NOCRED;
  398         }
  399         if (bp->b_wcred != NOCRED) {
  400                 crfree(bp->b_wcred);
  401                 bp->b_wcred = NOCRED;
  402         }
  403 
  404         KASSERT(bp->b_vp == NULL, ("relpbuf with vp"));
  405         KASSERT(bp->b_bufobj == NULL, ("relpbuf with bufobj"));
  406 
  407         BUF_UNLOCK(bp);
  408 
  409         mtx_lock(&pbuf_mtx);
  410         TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
  411 
  412         if (bswneeded) {
  413                 bswneeded = 0;
  414                 wakeup(&bswneeded);
  415         }
  416         if (pfreecnt) {
  417                 if (++*pfreecnt == 1)
  418                         wakeup(pfreecnt);
  419         }
  420         mtx_unlock(&pbuf_mtx);
  421 }
  422 
  423 /*
  424  * Associate a p-buffer with a vnode.
  425  *
  426  * Also sets B_PAGING flag to indicate that vnode is not fully associated
  427  * with the buffer.  i.e. the bp has not been linked into the vnode or
  428  * ref-counted.
  429  */
  430 void
  431 pbgetvp(struct vnode *vp, struct buf *bp)
  432 {
  433 
  434         KASSERT(bp->b_vp == NULL, ("pbgetvp: not free"));
  435         KASSERT(bp->b_bufobj == NULL, ("pbgetvp: not free (bufobj)"));
  436 
  437         bp->b_vp = vp;
  438         bp->b_flags |= B_PAGING;
  439         bp->b_bufobj = &vp->v_bufobj;
  440 }
  441 
  442 /*
  443  * Associate a p-buffer with a vnode.
  444  *
  445  * Also sets B_PAGING flag to indicate that vnode is not fully associated
  446  * with the buffer.  i.e. the bp has not been linked into the vnode or
  447  * ref-counted.
  448  */
  449 void
  450 pbgetbo(struct bufobj *bo, struct buf *bp)
  451 {
  452 
  453         KASSERT(bp->b_vp == NULL, ("pbgetbo: not free (vnode)"));
  454         KASSERT(bp->b_bufobj == NULL, ("pbgetbo: not free (bufobj)"));
  455 
  456         bp->b_flags |= B_PAGING;
  457         bp->b_bufobj = bo;
  458 }
  459 
  460 /*
  461  * Disassociate a p-buffer from a vnode.
  462  */
  463 void
  464 pbrelvp(struct buf *bp)
  465 {
  466 
  467         KASSERT(bp->b_vp != NULL, ("pbrelvp: NULL"));
  468         KASSERT(bp->b_bufobj != NULL, ("pbrelvp: NULL bufobj"));
  469 
  470         /* XXX REMOVE ME */
  471         BO_LOCK(bp->b_bufobj);
  472         if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
  473                 panic(
  474                     "relpbuf(): b_vp was probably reassignbuf()d %p %x",
  475                     bp,
  476                     (int)bp->b_flags
  477                 );
  478         }
  479         BO_UNLOCK(bp->b_bufobj);
  480         bp->b_vp = NULL;
  481         bp->b_bufobj = NULL;
  482         bp->b_flags &= ~B_PAGING;
  483 }
  484 
  485 /*
  486  * Disassociate a p-buffer from a bufobj.
  487  */
  488 void
  489 pbrelbo(struct buf *bp)
  490 {
  491 
  492         KASSERT(bp->b_vp == NULL, ("pbrelbo: vnode"));
  493         KASSERT(bp->b_bufobj != NULL, ("pbrelbo: NULL bufobj"));
  494 
  495         /* XXX REMOVE ME */
  496         BO_LOCK(bp->b_bufobj);
  497         if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
  498                 panic(
  499                     "relpbuf(): b_vp was probably reassignbuf()d %p %x",
  500                     bp,
  501                     (int)bp->b_flags
  502                 );
  503         }
  504         BO_UNLOCK(bp->b_bufobj);
  505         bp->b_bufobj = NULL;
  506         bp->b_flags &= ~B_PAGING;
  507 }

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