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

     /*-
      * 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.
     * 4. 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.
     */
    
    /*
     *      Paging space routine stubs.  Emulates a matchmaker-like interface
     *      for builtin pagers.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: src/sys/vm/vm_pager.c,v 1.95.2.3 2005/08/16 15:09:44 sobomax Exp $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/vnode.h>
    #include <sys/bio.h>
    #include <sys/buf.h>
    #include <sys/ucred.h>
    #include <sys/malloc.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pager.h>
    #include <vm/vm_extern.h>
    
    MALLOC_DEFINE(M_VMPGDATA, "VM pgdata", "XXX: VM pager private data");
    
    int cluster_pbuf_freecnt = -1;  /* unlimited to begin with */
    
    static int dead_pager_getpages(vm_object_t, vm_page_t *, int, int);
    static vm_object_t dead_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
            vm_ooffset_t);
    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, int *, int *);
    static void dead_pager_dealloc(vm_object_t);
    
    static int
    dead_pager_getpages(obj, ma, count, req)
            vm_object_t obj;
            vm_page_t *ma;
           int count;
           int req;
   {
           return VM_PAGER_FAIL;
   }
   
   static vm_object_t
   dead_pager_alloc(handle, size, prot, off)
           void *handle;
           vm_ooffset_t size;
           vm_prot_t prot;
           vm_ooffset_t off;
   {
           return NULL;
   }
   
   static void
   dead_pager_putpages(object, m, count, flags, rtvals)
           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;
           }
   }
   
   static int
   dead_pager_haspage(object, pindex, prev, next)
           vm_object_t object;
           vm_pindex_t pindex;
           int *prev;
           int *next;
   {
           if (prev)
                   *prev = 0;
           if (next)
                   *next = 0;
           return FALSE;
   }
   
   static void
   dead_pager_dealloc(object)
           vm_object_t object;
   {
           return;
   }
   
   static struct pagerops deadpagerops = {
           .pgo_alloc =    dead_pager_alloc,
           .pgo_dealloc =  dead_pager_dealloc,
           .pgo_getpages = dead_pager_getpages,
           .pgo_putpages = dead_pager_putpages,
           .pgo_haspage =  dead_pager_haspage,
   };
   
   struct pagerops *pagertab[] = {
           &defaultpagerops,       /* OBJT_DEFAULT */
           &swappagerops,          /* OBJT_SWAP */
           &vnodepagerops,         /* OBJT_VNODE */
           &devicepagerops,        /* OBJT_DEVICE */
           &physpagerops,          /* OBJT_PHYS */
           &deadpagerops           /* OBJT_DEAD */
   };
   
   static const int npagers = sizeof(pagertab) / sizeof(pagertab[0]);
   
   /*
    * 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.
    */
   vm_map_t pager_map;
   static int bswneeded;
   static vm_offset_t swapbkva;            /* swap buffers kva */
   struct mtx pbuf_mtx;
   static TAILQ_HEAD(swqueue, buf) bswlist;
   
   void
   vm_pager_init()
   {
           struct pagerops **pgops;
   
           TAILQ_INIT(&bswlist);
           /*
            * Initialize known pagers
            */
           for (pgops = pagertab; pgops < &pagertab[npagers]; pgops++)
                   if (pgops && ((*pgops)->pgo_init != NULL))
                           (*(*pgops)->pgo_init) ();
   }
   
   void
   vm_pager_bufferinit()
   {
           struct buf *bp;
           int i;
   
           mtx_init(&pbuf_mtx, "pbuf mutex", NULL, MTX_DEF);
           bp = swbuf;
           /*
            * Now set up swap and physical I/O buffer headers.
            */
           for (i = 0; i < nswbuf; i++, bp++) {
                   TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
                   BUF_LOCKINIT(bp);
                   LIST_INIT(&bp->b_dep);
                   bp->b_rcred = bp->b_wcred = NOCRED;
                   bp->b_xflags = 0;
           }
   
           cluster_pbuf_freecnt = nswbuf / 2;
           vnode_pbuf_freecnt = nswbuf / 2 + 1;
   
           swapbkva = kmem_alloc_nofault(pager_map, nswbuf * MAXPHYS);
           if (!swapbkva)
                   panic("Not enough pager_map VM space for physical buffers");
   }
   
   /*
    * Allocate an instance of a pager of the given type.
    * Size, protection and offset parameters are passed in for pagers that
    * need to perform page-level validation (e.g. the device pager).
    */
   vm_object_t
   vm_pager_allocate(objtype_t type, void *handle, vm_ooffset_t size,
                     vm_prot_t prot, vm_ooffset_t off)
   {
           vm_object_t ret;
           struct pagerops *ops;
   
           ops = pagertab[type];
           if (ops)
                   ret = (*ops->pgo_alloc) (handle, size, prot, off);
           else
                   ret = NULL;
           return (ret);
   }
   
   /*
    *      The object must be locked.
    */
   void
   vm_pager_deallocate(object)
           vm_object_t object;
   {
   
           VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
           (*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_object_t
   vm_pager_object_lookup(pg_list, handle)
           struct pagerlst *pg_list;
           void *handle;
   {
           vm_object_t object;
   
           TAILQ_FOREACH(object, pg_list, pager_object_list)
                   if (object->handle == handle)
                           return (object);
           return (NULL);
   }
   
   /*
    * initialize a physical buffer
    */
   
   /*
    * XXX This probably belongs in vfs_bio.c
    */
   static void
   initpbuf(struct buf *bp)
   {
           bp->b_rcred = NOCRED;
           bp->b_wcred = NOCRED;
           bp->b_qindex = 0;       /* On no queue (QUEUE_NONE) */
           bp->b_saveaddr = (caddr_t) (MAXPHYS * (bp - swbuf)) + swapbkva;
           bp->b_data = bp->b_saveaddr;
           bp->b_kvabase = bp->b_saveaddr;
           bp->b_kvasize = MAXPHYS;
           bp->b_xflags = 0;
           bp->b_flags = 0;
           bp->b_ioflags = 0;
           bp->b_iodone = NULL;
           bp->b_error = 0;
           bp->b_magic = B_MAGIC_BIO;
           bp->b_op = &buf_ops_bio;
           BUF_LOCK(bp, LK_EXCLUSIVE, NULL);
   }
   
   /*
    * 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
    */
   struct buf *
   getpbuf(int *pfreecnt)
   {
           int s;
           struct buf *bp;
   
           s = splvm();
           mtx_lock(&pbuf_mtx);
   
           for (;;) {
                   if (pfreecnt) {
                           while (*pfreecnt == 0) {
                                   msleep(pfreecnt, &pbuf_mtx, PVM, "wswbuf0", 0);
                           }
                   }
   
                   /* get a bp from the swap buffer header pool */
                   if ((bp = TAILQ_FIRST(&bswlist)) != NULL)
                           break;
   
                   bswneeded = 1;
                   msleep(&bswneeded, &pbuf_mtx, PVM, "wswbuf1", 0);
                   /* loop in case someone else grabbed one */
           }
           TAILQ_REMOVE(&bswlist, bp, b_freelist);
           if (pfreecnt)
                   --*pfreecnt;
           mtx_unlock(&pbuf_mtx);
           splx(s);
   
           initpbuf(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.
    */
   struct buf *
   trypbuf(int *pfreecnt)
   {
           int s;
           struct buf *bp;
   
           s = splvm();
           mtx_lock(&pbuf_mtx);
           if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist)) == NULL) {
                   mtx_unlock(&pbuf_mtx);
                   splx(s);
                   return NULL;
           }
           TAILQ_REMOVE(&bswlist, bp, b_freelist);
   
           --*pfreecnt;
   
           mtx_unlock(&pbuf_mtx);
           splx(s);
   
           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
    */
   void
   relpbuf(struct buf *bp, int *pfreecnt)
   {
           int s;
   
           s = splvm();
   
           if (bp->b_rcred != NOCRED) {
                   crfree(bp->b_rcred);
                   bp->b_rcred = NOCRED;
           }
           if (bp->b_wcred != NOCRED) {
                   crfree(bp->b_wcred);
                   bp->b_wcred = NOCRED;
           }
   
           if (bp->b_vp)
                   pbrelvp(bp);
   
           BUF_UNLOCK(bp);
   
           mtx_lock(&pbuf_mtx);
           TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
   
           if (bswneeded) {
                   bswneeded = 0;
                   wakeup(&bswneeded);
           }
           if (pfreecnt) {
                   if (++*pfreecnt == 1)
                           wakeup(pfreecnt);
           }
           mtx_unlock(&pbuf_mtx);
           splx(s);
   }

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