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

     /*
      * (MPSAFE)
      *
      * Copyright (c) 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * The Mach Operating System project at Carnegie-Mellon University.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#)vm_pager.c    8.6 (Berkeley) 1/12/94
     *
     *
     * Copyright (c) 1987, 1990 Carnegie-Mellon University.
     * All rights reserved.
     *
     * Authors: Avadis Tevanian, Jr., Michael Wayne Young
     *
     * Permission to use, copy, modify and distribute this software and
     * its documentation is hereby granted, provided that both the copyright
     * notice and this permission notice appear in all copies of the
     * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     *
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     *
     * Carnegie Mellon requests users of this software to return to
     *
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     *
     * any improvements or extensions that they make and grant Carnegie the
     * rights to redistribute these changes.
     *
     * $FreeBSD: src/sys/vm/vm_pager.c,v 1.54.2.2 2001/11/18 07:11:00 dillon Exp $
     */
    
    /*
     *      Paging space routine stubs.  Emulates a matchmaker-like interface
     *      for builtin pagers.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/vnode.h>
    #include <sys/buf.h>
    #include <sys/ucred.h>
    #include <sys/dsched.h>
    #include <sys/proc.h>
    #include <sys/sysctl.h>
    #include <sys/thread2.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pager.h>
    #include <vm/vm_extern.h>
    
    #include <sys/buf2.h>
    
    extern struct pagerops defaultpagerops;
    extern struct pagerops swappagerops;
    extern struct pagerops vnodepagerops;
    extern struct pagerops devicepagerops;
    extern struct pagerops physpagerops;
    
    int cluster_pbuf_freecnt = -1;  /* unlimited to begin with */
    
    static int dead_pager_getpage (vm_object_t, vm_page_t *, int);
   static void dead_pager_putpages (vm_object_t, vm_page_t *, int, int, int *);
   static boolean_t dead_pager_haspage (vm_object_t, vm_pindex_t);
   static void dead_pager_dealloc (vm_object_t);
   
   /*
    * No requirements.
    */
   static int
   dead_pager_getpage(vm_object_t obj, vm_page_t *mpp, int seqaccess)
   {
           return VM_PAGER_FAIL;
   }
   
   /*
    * No requirements.
    */
   static void
   dead_pager_putpages(vm_object_t object, vm_page_t *m, int count, int flags,
                       int *rtvals)
   {
           int i;
   
           for (i = 0; i < count; i++) {
                   rtvals[i] = VM_PAGER_AGAIN;
           }
   }
   
   /*
    * No requirements.
    */
   static int
   dead_pager_haspage(vm_object_t object, vm_pindex_t pindex)
   {
           return FALSE;
   }
   
   /*
    * No requirements.
    */
   static void
   dead_pager_dealloc(vm_object_t object)
   {
           KKASSERT(object->swblock_count == 0);
           return;
   }
   
   static struct pagerops deadpagerops = {
           dead_pager_dealloc,
           dead_pager_getpage,
           dead_pager_putpages,
           dead_pager_haspage
   };
   
   struct pagerops *pagertab[] = {
           &defaultpagerops,       /* OBJT_DEFAULT */
           &swappagerops,          /* OBJT_SWAP */
           &vnodepagerops,         /* OBJT_VNODE */
           &devicepagerops,        /* OBJT_DEVICE */
           &devicepagerops,        /* OBJT_MGTDEVICE */
           &physpagerops,          /* OBJT_PHYS */
           &deadpagerops           /* OBJT_DEAD */
   };
   
   int npagers = NELEM(pagertab);
   
   /*
    * Kernel address space for mapping pages.
    * Used by pagers where KVAs are needed for IO.
    *
    * XXX needs to be large enough to support the number of pending async
    * cleaning requests (NPENDINGIO == 64) * the maximum swap cluster size
    * (MAXPHYS == 64k) if you want to get the most efficiency.
    */
   #define PAGER_MAP_SIZE  (8 * 1024 * 1024)
   
   TAILQ_HEAD(swqueue, buf);
   
   int pager_map_size = PAGER_MAP_SIZE;
   struct vm_map pager_map;
   
   static int bswneeded_raw;
   static int bswneeded_kva;
   static long nswbuf_raw;
   static struct buf *swbuf_raw;
   static vm_offset_t swapbkva;            /* swap buffers kva */
   static struct swqueue bswlist_raw;      /* without kva */
   static struct swqueue bswlist_kva;      /* with kva */
   static struct spinlock bswspin = SPINLOCK_INITIALIZER(&bswspin);
   static int pbuf_raw_count;
   static int pbuf_kva_count;
   
   SYSCTL_INT(_vfs, OID_AUTO, pbuf_raw_count, CTLFLAG_RD, &pbuf_raw_count, 0,
       "Kernel virtual address space reservations");
   SYSCTL_INT(_vfs, OID_AUTO, pbuf_kva_count, CTLFLAG_RD, &pbuf_kva_count, 0,
       "Kernel raw address space reservations");
   
   /*
    * Initialize the swap buffer list.
    *
    * Called from the low level boot code only.
    */
   static void
   vm_pager_init(void *arg __unused)
   {
           TAILQ_INIT(&bswlist_raw);
           TAILQ_INIT(&bswlist_kva);
   }
   SYSINIT(vm_mem, SI_BOOT1_VM, SI_ORDER_SECOND, vm_pager_init, NULL)
   
   /*
    * Called from the low level boot code only.
    */
   static
   void
   vm_pager_bufferinit(void *dummy __unused)
   {
           struct buf *bp;
           long i;
   
           /*
            * Reserve KVM space for pbuf data.
            */
           swapbkva = kmem_alloc_pageable(&pager_map, nswbuf * MAXPHYS);
           if (!swapbkva)
                   panic("Not enough pager_map VM space for physical buffers");
   
           /*
            * Initial pbuf setup.  These pbufs have KVA reservations.
            */
           bp = swbuf;
           for (i = 0; i < nswbuf; ++i, ++bp) {
                   bp->b_kvabase = (caddr_t)((intptr_t)i * MAXPHYS) + swapbkva;
                   bp->b_kvasize = MAXPHYS;
                   BUF_LOCKINIT(bp);
                   buf_dep_init(bp);
                   TAILQ_INSERT_HEAD(&bswlist_kva, bp, b_freelist);
                   ++pbuf_kva_count;
           }
   
           /*
            * Initial pbuf setup.  These pbufs do not have KVA reservations,
            * so we can have a lot more of them.  These are typically used
            * to massage low level buf/bio requests.
            */
           nswbuf_raw = nbuf * 2;
           swbuf_raw = (void *)kmem_alloc(&kernel_map,
                                   round_page(nswbuf_raw * sizeof(struct buf)));
           bp = swbuf_raw;
           for (i = 0; i < nswbuf_raw; ++i, ++bp) {
                   BUF_LOCKINIT(bp);
                   buf_dep_init(bp);
                   TAILQ_INSERT_HEAD(&bswlist_raw, bp, b_freelist);
                   ++pbuf_raw_count;
           }
   
           /*
            * Allow the clustering code to use half of our pbufs.
            */
           cluster_pbuf_freecnt = nswbuf / 2;
   }
   
   SYSINIT(do_vmpg, SI_BOOT2_MACHDEP, SI_ORDER_FIRST, vm_pager_bufferinit, NULL);
   
   /*
    * No requirements.
    */
   void
   vm_pager_deallocate(vm_object_t object)
   {
           (*pagertab[object->type]->pgo_dealloc) (object);
   }
   
   /*
    * vm_pager_get_pages() - inline, see vm/vm_pager.h
    * vm_pager_put_pages() - inline, see vm/vm_pager.h
    * vm_pager_has_page() - inline, see vm/vm_pager.h
    * vm_pager_page_inserted() - inline, see vm/vm_pager.h
    * vm_pager_page_removed() - inline, see vm/vm_pager.h
    */
   
   /*
    * Search the specified pager object list for an object with the
    * specified handle.  If an object with the specified handle is found,
    * increase its reference count and return it.  Otherwise, return NULL.
    *
    * The pager object list must be locked.
    */
   vm_object_t
   vm_pager_object_lookup(struct pagerlst *pg_list, void *handle)
   {
           vm_object_t object;
   
           TAILQ_FOREACH(object, pg_list, pager_object_list) {
                   if (object->handle == handle) {
                           VM_OBJECT_LOCK(object);
                           if ((object->flags & OBJ_DEAD) == 0) {
                                   vm_object_reference_locked(object);
                                   VM_OBJECT_UNLOCK(object);
                                   break;
                           }
                           VM_OBJECT_UNLOCK(object);
                   }
           }
           return (object);
   }
   
   /*
    * Initialize a physical buffer.
    *
    * No requirements.
    */
   static void
   initpbuf(struct buf *bp)
   {
           bp->b_qindex = 0;               /* BQUEUE_NONE */
           bp->b_data = bp->b_kvabase;     /* NULL if pbuf sans kva */
           bp->b_flags = B_PAGING;
           bp->b_cmd = BUF_CMD_DONE;
           bp->b_error = 0;
           bp->b_bcount = 0;
           bp->b_bufsize = MAXPHYS;
           initbufbio(bp);
           xio_init(&bp->b_xio);
           BUF_LOCK(bp, LK_EXCLUSIVE);
   }
   
   /*
    * Allocate a physical buffer
    *
    *      There are a limited number (nswbuf) of physical buffers.  We need
    *      to make sure that no single subsystem is able to hog all of them,
    *      so each subsystem implements a counter which is typically initialized
    *      to 1/2 nswbuf.  getpbuf() decrements this counter in allocation and
    *      increments it on release, and blocks if the counter hits zero.  A
    *      subsystem may initialize the counter to -1 to disable the feature,
    *      but it must still be sure to match up all uses of getpbuf() with 
    *      relpbuf() using the same variable.
    *
    *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
    *      relatively soon when the rest of the subsystems get smart about it. XXX
    *
    *      Physical buffers can be with or without KVA space reserved.  There
    *      are severe limitations on the ones with KVA reserved, and fewer
    *      limitations on the ones without.  getpbuf() gets one without,
    *      getpbuf_kva() gets one with.
    *
    * No requirements.
    */
   struct buf *
   getpbuf(int *pfreecnt)
   {
           struct buf *bp;
   
           spin_lock(&bswspin);
   
           for (;;) {
                   if (pfreecnt) {
                           while (*pfreecnt == 0)
                                   ssleep(pfreecnt, &bswspin, 0, "wswbuf0", 0);
                   }
   
                   /* get a bp from the swap buffer header pool */
                   if ((bp = TAILQ_FIRST(&bswlist_raw)) != NULL)
                           break;
                   bswneeded_raw = 1;
                   ssleep(&bswneeded_raw, &bswspin, 0, "wswbuf1", 0);
                   /* loop in case someone else grabbed one */
           }
           TAILQ_REMOVE(&bswlist_raw, bp, b_freelist);
           --pbuf_raw_count;
           if (pfreecnt)
                   --*pfreecnt;
   
           spin_unlock(&bswspin);
   
           initpbuf(bp);
           KKASSERT(dsched_is_clear_buf_priv(bp));
   
           return (bp);
   }
   
   struct buf *
   getpbuf_kva(int *pfreecnt)
   {
           struct buf *bp;
   
           spin_lock(&bswspin);
   
           for (;;) {
                   if (pfreecnt) {
                           while (*pfreecnt == 0)
                                   ssleep(pfreecnt, &bswspin, 0, "wswbuf0", 0);
                   }
   
                   /* get a bp from the swap buffer header pool */
                   if ((bp = TAILQ_FIRST(&bswlist_kva)) != NULL)
                           break;
                   bswneeded_kva = 1;
                   ssleep(&bswneeded_kva, &bswspin, 0, "wswbuf1", 0);
                   /* loop in case someone else grabbed one */
           }
           TAILQ_REMOVE(&bswlist_kva, bp, b_freelist);
           --pbuf_kva_count;
           if (pfreecnt)
                   --*pfreecnt;
   
           spin_unlock(&bswspin);
   
           initpbuf(bp);
           KKASSERT(dsched_is_clear_buf_priv(bp));
   
           return (bp);
   }
   
   /*
    * Allocate a physical buffer, if one is available.
    *
    *      Note that there is no NULL hack here - all subsystems using this
    *      call understand how to use pfreecnt.
    *
    * No requirements.
    */
   struct buf *
   trypbuf(int *pfreecnt)
   {
           struct buf *bp;
   
           spin_lock(&bswspin);
   
           if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist_raw)) == NULL) {
                   spin_unlock(&bswspin);
                   return NULL;
           }
           TAILQ_REMOVE(&bswlist_raw, bp, b_freelist);
           --pbuf_raw_count;
           --*pfreecnt;
   
           spin_unlock(&bswspin);
   
           initpbuf(bp);
   
           return bp;
   }
   
   struct buf *
   trypbuf_kva(int *pfreecnt)
   {
           struct buf *bp;
   
           spin_lock(&bswspin);
   
           if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist_kva)) == NULL) {
                   spin_unlock(&bswspin);
                   return NULL;
           }
           TAILQ_REMOVE(&bswlist_kva, bp, b_freelist);
           --pbuf_kva_count;
           --*pfreecnt;
   
           spin_unlock(&bswspin);
   
           initpbuf(bp);
   
           return bp;
   }
   
   /*
    * Release a physical buffer
    *
    *      NOTE: pfreecnt can be NULL, but this 'feature' will be removed
    *      relatively soon when the rest of the subsystems get smart about it. XXX
    *
    * No requirements.
    */
   void
   relpbuf(struct buf *bp, int *pfreecnt)
   {
           int wake_bsw_kva = 0;
           int wake_bsw_raw = 0;
           int wake_freecnt = 0;
   
           KKASSERT(bp->b_flags & B_PAGING);
           dsched_exit_buf(bp);
   
           BUF_UNLOCK(bp);
   
           spin_lock(&bswspin);
           if (bp->b_kvabase) {
                   TAILQ_INSERT_HEAD(&bswlist_kva, bp, b_freelist);
                   ++pbuf_kva_count;
           } else {
                   TAILQ_INSERT_HEAD(&bswlist_raw, bp, b_freelist);
                   ++pbuf_raw_count;
           }
           if (bswneeded_kva) {
                   bswneeded_kva = 0;
                   wake_bsw_kva = 1;
           }
           if (bswneeded_raw) {
                   bswneeded_raw = 0;
                   wake_bsw_raw = 1;
           }
           if (pfreecnt) {
                   if (++*pfreecnt == 1)
                           wake_freecnt = 1;
           }
           spin_unlock(&bswspin);
   
           if (wake_bsw_kva)
                   wakeup(&bswneeded_kva);
           if (wake_bsw_raw)
                   wakeup(&bswneeded_raw);
           if (wake_freecnt)
                   wakeup(pfreecnt);
   }
   
   void
   pbuf_adjcount(int *pfreecnt, int n)
   {
           if (n) {
                   spin_lock(&bswspin);
                   *pfreecnt += n;
                   spin_unlock(&bswspin);
                   wakeup(pfreecnt);
           }
   }

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