uvm_anon.c

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    1 /*      $NetBSD: uvm_anon.c,v 1.51 2008/01/18 10:48:23 yamt Exp $       */
    2 
    3 /*
    4  *
    5  * Copyright (c) 1997 Charles D. Cranor and Washington University.
    6  * All rights reserved.
    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 Charles D. Cranor and
   19  *      Washington University.
   20  * 4. The name of the author may not be used to endorse or promote products
   21  *    derived from this software without specific prior written permission.
   22  *
   23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   33  */
   34 
   35 /*
   36  * uvm_anon.c: uvm anon ops
   37  */
   38 
   39 #include <sys/cdefs.h>
   40 __KERNEL_RCSID(0, "$NetBSD: uvm_anon.c,v 1.51 2008/01/18 10:48:23 yamt Exp $");
   41 
   42 #include "opt_uvmhist.h"
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/proc.h>
   47 #include <sys/malloc.h>
   48 #include <sys/pool.h>
   49 #include <sys/kernel.h>
   50 
   51 #include <uvm/uvm.h>
   52 #include <uvm/uvm_swap.h>
   53 #include <uvm/uvm_pdpolicy.h>
   54 
   55 static struct pool_cache uvm_anon_cache;
   56 
   57 static int uvm_anon_ctor(void *, void *, int);
   58 static void uvm_anon_dtor(void *, void *);
   59 
   60 /*
   61  * allocate anons
   62  */
   63 void
   64 uvm_anon_init(void)
   65 {
   66 
   67         pool_cache_bootstrap(&uvm_anon_cache, sizeof(struct vm_anon), 0, 0,
   68             PR_LARGECACHE, "anonpl", NULL, IPL_NONE, uvm_anon_ctor,
   69             uvm_anon_dtor, NULL);
   70 }
   71 
   72 static int
   73 uvm_anon_ctor(void *arg, void *object, int flags)
   74 {
   75         struct vm_anon *anon = object;
   76 
   77         anon->an_ref = 0;
   78         mutex_init(&anon->an_lock, MUTEX_DEFAULT, IPL_NONE);
   79         anon->an_page = NULL;
   80 #if defined(VMSWAP)
   81         anon->an_swslot = 0;
   82 #endif /* defined(VMSWAP) */
   83 
   84         return 0;
   85 }
   86 
   87 static void
   88 uvm_anon_dtor(void *arg, void *object)
   89 {
   90         struct vm_anon *anon = object;
   91 
   92         mutex_destroy(&anon->an_lock);
   93 }
   94 
   95 /*
   96  * allocate an anon
   97  *
   98  * => new anon is returned locked!
   99  */
  100 struct vm_anon *
  101 uvm_analloc(void)
  102 {
  103         struct vm_anon *anon;
  104 
  105         anon = pool_cache_get(&uvm_anon_cache, PR_NOWAIT);
  106         if (anon) {
  107                 KASSERT(anon->an_ref == 0);
  108                 KASSERT(anon->an_page == NULL);
  109 #if defined(VMSWAP)
  110                 KASSERT(anon->an_swslot == 0);
  111 #endif /* defined(VMSWAP) */
  112                 anon->an_ref = 1;
  113                 mutex_enter(&anon->an_lock);
  114         }
  115         return anon;
  116 }
  117 
  118 /*
  119  * uvm_anfree: free a single anon structure
  120  *
  121  * => caller must remove anon from its amap before calling (if it was in
  122  *      an amap).
  123  * => anon must be unlocked and have a zero reference count.
  124  * => we may lock the pageq's.
  125  */
  126 
  127 void
  128 uvm_anfree(struct vm_anon *anon)
  129 {
  130         struct vm_page *pg;
  131         UVMHIST_FUNC("uvm_anfree"); UVMHIST_CALLED(maphist);
  132         UVMHIST_LOG(maphist,"(anon=0x%x)", anon, 0,0,0);
  133 
  134         KASSERT(anon->an_ref == 0);
  135         KASSERT(!mutex_owned(&anon->an_lock));
  136 
  137         /*
  138          * get page
  139          */
  140 
  141         pg = anon->an_page;
  142 
  143         /*
  144          * if there is a resident page and it is loaned, then anon may not
  145          * own it.   call out to uvm_anon_lockpage() to ensure the real owner
  146          * of the page has been identified and locked.
  147          */
  148 
  149         if (pg && pg->loan_count) {
  150                 mutex_enter(&anon->an_lock);
  151                 pg = uvm_anon_lockloanpg(anon);
  152                 mutex_exit(&anon->an_lock);
  153         }
  154 
  155         /*
  156          * if we have a resident page, we must dispose of it before freeing
  157          * the anon.
  158          */
  159 
  160         if (pg) {
  161 
  162                 /*
  163                  * if the page is owned by a uobject (now locked), then we must
  164                  * kill the loan on the page rather than free it.
  165                  */
  166 
  167                 if (pg->uobject) {
  168                         mutex_enter(&uvm_pageqlock);
  169                         KASSERT(pg->loan_count > 0);
  170                         pg->loan_count--;
  171                         pg->uanon = NULL;
  172                         mutex_exit(&uvm_pageqlock);
  173                         mutex_exit(&pg->uobject->vmobjlock);
  174                 } else {
  175 
  176                         /*
  177                          * page has no uobject, so we must be the owner of it.
  178                          */
  179 
  180                         KASSERT((pg->flags & PG_RELEASED) == 0);
  181                         mutex_enter(&anon->an_lock);
  182                         pmap_page_protect(pg, VM_PROT_NONE);
  183 
  184                         /*
  185                          * if the page is busy, mark it as PG_RELEASED
  186                          * so that uvm_anon_release will release it later.
  187                          */
  188 
  189                         if (pg->flags & PG_BUSY) {
  190                                 pg->flags |= PG_RELEASED;
  191                                 mutex_exit(&anon->an_lock);
  192                                 return;
  193                         }
  194                         mutex_enter(&uvm_pageqlock);
  195                         uvm_pagefree(pg);
  196                         mutex_exit(&uvm_pageqlock);
  197                         mutex_exit(&anon->an_lock);
  198                         UVMHIST_LOG(maphist, "anon 0x%x, page 0x%x: "
  199                                     "freed now!", anon, pg, 0, 0);
  200                 }
  201         }
  202 #if defined(VMSWAP)
  203         if (pg == NULL && anon->an_swslot > 0) {
  204                 /* this page is no longer only in swap. */
  205                 mutex_enter(&uvm_swap_data_lock);
  206                 KASSERT(uvmexp.swpgonly > 0);
  207                 uvmexp.swpgonly--;
  208                 mutex_exit(&uvm_swap_data_lock);
  209         }
  210 #endif /* defined(VMSWAP) */
  211 
  212         /*
  213          * free any swap resources.
  214          */
  215 
  216         uvm_anon_dropswap(anon);
  217 
  218         /*
  219          * give a page replacement hint.
  220          */
  221 
  222         uvmpdpol_anfree(anon);
  223 
  224         /*
  225          * now that we've stripped the data areas from the anon,
  226          * free the anon itself.
  227          */
  228 
  229         KASSERT(anon->an_page == NULL);
  230 #if defined(VMSWAP)
  231         KASSERT(anon->an_swslot == 0);
  232 #endif /* defined(VMSWAP) */
  233 
  234         pool_cache_put(&uvm_anon_cache, anon);
  235         UVMHIST_LOG(maphist,"<- done!",0,0,0,0);
  236 }
  237 
  238 #if defined(VMSWAP)
  239 
  240 /*
  241  * uvm_anon_dropswap:  release any swap resources from this anon.
  242  *
  243  * => anon must be locked or have a reference count of 0.
  244  */
  245 void
  246 uvm_anon_dropswap(struct vm_anon *anon)
  247 {
  248         UVMHIST_FUNC("uvm_anon_dropswap"); UVMHIST_CALLED(maphist);
  249 
  250         if (anon->an_swslot == 0)
  251                 return;
  252 
  253         UVMHIST_LOG(maphist,"freeing swap for anon %p, paged to swslot 0x%x",
  254                     anon, anon->an_swslot, 0, 0);
  255         uvm_swap_free(anon->an_swslot, 1);
  256         anon->an_swslot = 0;
  257 }
  258 
  259 #endif /* defined(VMSWAP) */
  260 
  261 /*
  262  * uvm_anon_lockloanpg: given a locked anon, lock its resident page
  263  *
  264  * => anon is locked by caller
  265  * => on return: anon is locked
  266  *               if there is a resident page:
  267  *                      if it has a uobject, it is locked by us
  268  *                      if it is ownerless, we take over as owner
  269  *               we return the resident page (it can change during
  270  *               this function)
  271  * => note that the only time an anon has an ownerless resident page
  272  *      is if the page was loaned from a uvm_object and the uvm_object
  273  *      disowned it
  274  * => this only needs to be called when you want to do an operation
  275  *      on an anon's resident page and that page has a non-zero loan
  276  *      count.
  277  */
  278 struct vm_page *
  279 uvm_anon_lockloanpg(struct vm_anon *anon)
  280 {
  281         struct vm_page *pg;
  282         bool locked = false;
  283 
  284         KASSERT(mutex_owned(&anon->an_lock));
  285 
  286         /*
  287          * loop while we have a resident page that has a non-zero loan count.
  288          * if we successfully get our lock, we will "break" the loop.
  289          * note that the test for pg->loan_count is not protected -- this
  290          * may produce false positive results.   note that a false positive
  291          * result may cause us to do more work than we need to, but it will
  292          * not produce an incorrect result.
  293          */
  294 
  295         while (((pg = anon->an_page) != NULL) && pg->loan_count != 0) {
  296 
  297                 /*
  298                  * quickly check to see if the page has an object before
  299                  * bothering to lock the page queues.   this may also produce
  300                  * a false positive result, but that's ok because we do a real
  301                  * check after that.
  302                  */
  303 
  304                 if (pg->uobject) {
  305                         mutex_enter(&uvm_pageqlock);
  306                         if (pg->uobject) {
  307                                 locked =
  308                                     mutex_tryenter(&pg->uobject->vmobjlock);
  309                         } else {
  310                                 /* object disowned before we got PQ lock */
  311                                 locked = true;
  312                         }
  313                         mutex_exit(&uvm_pageqlock);
  314 
  315                         /*
  316                          * if we didn't get a lock (try lock failed), then we
  317                          * toggle our anon lock and try again
  318                          */
  319 
  320                         if (!locked) {
  321                                 mutex_exit(&anon->an_lock);
  322 
  323                                 /*
  324                                  * someone locking the object has a chance to
  325                                  * lock us right now
  326                                  */
  327                                 /* XXX Better than yielding but inadequate. */
  328                                 kpause("livelock", false, 1, NULL);
  329 
  330                                 mutex_enter(&anon->an_lock);
  331                                 continue;
  332                         }
  333                 }
  334 
  335                 /*
  336                  * if page is un-owned [i.e. the object dropped its ownership],
  337                  * then we can take over as owner!
  338                  */
  339 
  340                 if (pg->uobject == NULL && (pg->pqflags & PQ_ANON) == 0) {
  341                         mutex_enter(&uvm_pageqlock);
  342                         pg->pqflags |= PQ_ANON;
  343                         pg->loan_count--;
  344                         mutex_exit(&uvm_pageqlock);
  345                 }
  346                 break;
  347         }
  348         return(pg);
  349 }
  350 
  351 #if defined(VMSWAP)
  352 
  353 /*
  354  * fetch an anon's page.
  355  *
  356  * => anon must be locked, and is unlocked upon return.
  357  * => returns true if pagein was aborted due to lack of memory.
  358  */
  359 
  360 bool
  361 uvm_anon_pagein(struct vm_anon *anon)
  362 {
  363         struct vm_page *pg;
  364         struct uvm_object *uobj;
  365         int rv;
  366 
  367         /* locked: anon */
  368         KASSERT(mutex_owned(&anon->an_lock));
  369 
  370         rv = uvmfault_anonget(NULL, NULL, anon);
  371 
  372         /*
  373          * if rv == 0, anon is still locked, else anon
  374          * is unlocked
  375          */
  376 
  377         switch (rv) {
  378         case 0:
  379                 break;
  380 
  381         case EIO:
  382         case ERESTART:
  383 
  384                 /*
  385                  * nothing more to do on errors.
  386                  * ERESTART can only mean that the anon was freed,
  387                  * so again there's nothing to do.
  388                  */
  389 
  390                 return false;
  391 
  392         default:
  393                 return true;
  394         }
  395 
  396         /*
  397          * ok, we've got the page now.
  398          * mark it as dirty, clear its swslot and un-busy it.
  399          */
  400 
  401         pg = anon->an_page;
  402         uobj = pg->uobject;
  403         if (anon->an_swslot > 0)
  404                 uvm_swap_free(anon->an_swslot, 1);
  405         anon->an_swslot = 0;
  406         pg->flags &= ~(PG_CLEAN);
  407 
  408         /*
  409          * deactivate the page (to put it on a page queue)
  410          */
  411 
  412         mutex_enter(&uvm_pageqlock);
  413         if (pg->wire_count == 0)
  414                 uvm_pagedeactivate(pg);
  415         mutex_exit(&uvm_pageqlock);
  416 
  417         if (pg->flags & PG_WANTED) {
  418                 wakeup(pg);
  419                 pg->flags &= ~(PG_WANTED);
  420         }
  421 
  422         /*
  423          * unlock the anon and we're done.
  424          */
  425 
  426         mutex_exit(&anon->an_lock);
  427         if (uobj) {
  428                 mutex_exit(&uobj->vmobjlock);
  429         }
  430         return false;
  431 }
  432 
  433 #endif /* defined(VMSWAP) */
  434 
  435 /*
  436  * uvm_anon_release: release an anon and its page.
  437  *
  438  * => caller must lock the anon.
  439  */
  440 
  441 void
  442 uvm_anon_release(struct vm_anon *anon)
  443 {
  444         struct vm_page *pg = anon->an_page;
  445 
  446         KASSERT(mutex_owned(&anon->an_lock));
  447         KASSERT(pg != NULL);
  448         KASSERT((pg->flags & PG_RELEASED) != 0);
  449         KASSERT((pg->flags & PG_BUSY) != 0);
  450         KASSERT(pg->uobject == NULL);
  451         KASSERT(pg->uanon == anon);
  452         KASSERT(pg->loan_count == 0);
  453         KASSERT(anon->an_ref == 0);
  454 
  455         mutex_enter(&uvm_pageqlock);
  456         uvm_pagefree(pg);
  457         mutex_exit(&uvm_pageqlock);
  458         mutex_exit(&anon->an_lock);
  459 
  460         KASSERT(anon->an_page == NULL);
  461 
  462         uvm_anfree(anon);
  463 }
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FreeBSD/Linux Kernel Cross Reference sys/uvm/uvm_anon.c

FreeBSD/Linux Kernel Cross Reference
sys/uvm/uvm_anon.c
