xref: /src/sys/uvm/uvm_page.c

/*	$NetBSD: uvm_page.c,v 1.4 1998/02/07 11:09:19 mrg Exp $	*/

/*
 * XXXCDC: "ROUGH DRAFT" QUALITY UVM PRE-RELEASE FILE!
 *         >>>USE AT YOUR OWN RISK, WORK IS NOT FINISHED<<<
 */
/*
 * Copyright (c) 1997 Charles D. Cranor and Washington University.
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by Charles D. Cranor,
 *      Washington University, the University of California, Berkeley and
 *      its contributors.
 * 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.
 *
 *	@(#)vm_page.c   8.3 (Berkeley) 3/21/94
 * from: Id: uvm_page.c,v 1.1.2.18 1998/02/06 05:24:42 chs Exp
 *
 *
 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
 * All rights reserved.
 *
 * 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 (at) 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.
 */

/*
 * uvm_page.c: page ops.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>

#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_kern.h>

#include <sys/syscallargs.h>

#define UVM_PAGE                /* pull in uvm_page.h functions */
#include <uvm/uvm.h>

/*
 * global vars... XXXCDC: move to uvm. structure.
 */

/*
 * physical memory config is stored in vm_physmem.
 */

struct vm_physseg vm_physmem[VM_PHYSSEG_MAX];	/* XXXCDC: uvm.physmem */
int vm_nphysseg = 0;				/* XXXCDC: uvm.nphysseg */

/*
 * local variables
 */

/*
 * these variables record the values returned by vm_page_bootstrap,
 * for debugging purposes.  The implementation of uvm_pageboot_alloc
 * and pmap_startup here also uses them internally.
 */

static vm_offset_t      virtual_space_start;
static vm_offset_t      virtual_space_end;

/*
 * we use a hash table with only one bucket during bootup.  we will
 * later rehash (resize) the hash table once malloc() is ready.
 * we static allocate the bootstrap bucket below...
 */

static struct pglist uvm_bootbucket;

/*
 * local prototypes
 */

static void uvm_pageinsert __P((struct vm_page *));
#if !defined(PMAP_STEAL_MEMORY)
static boolean_t uvm_page_physget __P((vm_offset_t *));
#endif


/*
 * inline functions
 */

/*
 * uvm_pageinsert: insert a page in the object and the hash table
 *
 * => caller must lock object
 * => caller must lock page queues
 * => call should have already set pg's object and offset pointers
 *    and bumped the version counter
 */

__inline static void uvm_pageinsert(pg)

struct vm_page *pg;

{
  struct pglist *buck;
  int s;

#ifdef DIAGNOSTIC
  if (pg->flags & PG_TABLED)
    panic("uvm_pageinsert: already inserted");
#endif

  buck = &uvm.page_hash[uvm_pagehash(pg->uobject,pg->offset)];
  s = splimp();
  simple_lock(&uvm.hashlock);
  TAILQ_INSERT_TAIL(buck, pg, hashq);	/* put in hash */
  simple_unlock(&uvm.hashlock);
  splx(s);

  TAILQ_INSERT_TAIL(&pg->uobject->memq, pg, listq);	/* put in object */
  pg->flags |= PG_TABLED;
  pg->uobject->uo_npages++;

}

/*
 * uvm_page_remove: remove page from object and hash
 *
 * => caller must lock object
 * => caller must lock page queues
 */

void __inline uvm_pageremove(pg)

struct vm_page *pg;

{
  struct pglist *buck;
  int s;

#ifdef DIAGNOSTIC
  if ((pg->flags & (PG_FAULTING)) != 0)
    panic("uvm_pageremove: page is faulting");
#endif

  if ((pg->flags & PG_TABLED) == 0)
    return;				/* XXX: log */

  buck = &uvm.page_hash[uvm_pagehash(pg->uobject,pg->offset)];
  s = splimp();
  simple_lock(&uvm.hashlock);
  TAILQ_REMOVE(buck, pg, hashq);
  simple_unlock(&uvm.hashlock);
  splx(s);

  TAILQ_REMOVE(&pg->uobject->memq, pg, listq);/* object should be locked */

  pg->flags &= ~PG_TABLED;
  pg->uobject->uo_npages--;
  pg->uobject = NULL;
  pg->version++;

}

/*
 * uvm_page_init: init the page system.   called from uvm_init().
 *
 * => we return the range of kernel virtual memory in kvm_startp/kvm_endp
 */

void uvm_page_init(kvm_startp, kvm_endp)

vm_offset_t *kvm_startp, *kvm_endp;

{
  int freepages, pagecount;
  vm_page_t pagearray;
  int lcv, n, i;
  vm_offset_t paddr;


  /*
   * step 1: init the page queues and page queue locks
   */

  TAILQ_INIT(&uvm.page_free);
  TAILQ_INIT(&uvm.page_active);
  TAILQ_INIT(&uvm.page_inactive_swp);
  TAILQ_INIT(&uvm.page_inactive_obj);
  simple_lock_init(&uvm.pageqlock);
  simple_lock_init(&uvm.fpageqlock);

  /*
   * step 2: init the <obj,offset> => <page> hash table. for now
   * we just have one bucket (the bootstrap bucket).   later on we
   * will malloc() new buckets as we dynamically resize the hash table.
   */

  uvm.page_nhash = 1;			/* 1 bucket */
  uvm.page_hashmask = 0;		/* mask for hash function */
  uvm.page_hash = &uvm_bootbucket;	/* install bootstrap bucket */
  TAILQ_INIT(uvm.page_hash);		/* init hash table */
  simple_lock_init(&uvm.hashlock);	/* init hash table lock */

  /*
   * step 3: allocate vm_page structures.
   */

  /*
   * sanity check:
   * before calling this function the MD code is expected to register
   * some free RAM with the uvm_page_physload() function.   our job
   * now is to allocate vm_page structures for this memory.
   */

  if (vm_nphysseg == 0)
    panic("vm_page_bootstrap: no memory pre-allocated");

  /*
   * first calculate the number of free pages...
   *
   * note that we use start/end rather than avail_start/avail_end.
   * this allows us to allocate extra vm_page structures in case we
   * want to return some memory to the pool after booting.
   */

  freepages = 0;
  for (lcv = 0 ; lcv < vm_nphysseg ; lcv++) {
    freepages = freepages + (vm_physmem[lcv].end - vm_physmem[lcv].start);
  }

  /*
   * we now know we have (PAGE_SIZE * freepages) bytes of memory we can
   * use.   for each page of memory we use we need a vm_page structure.
   * thus, the total number of pages we can use is the total size of
   * the memory divided by the PAGE_SIZE plus the size of the vm_page
   * structure.   we add one to freepages as a fudge factor to avoid
   * truncation errors (since we can only allocate in terms of whole
   * pages).
   */

  pagecount = (PAGE_SIZE * (freepages + 1)) /
    (PAGE_SIZE + sizeof(struct vm_page));
  pagearray = (vm_page_t)uvm_pageboot_alloc(pagecount * sizeof(struct vm_page));
  bzero(pagearray, pagecount * sizeof(struct vm_page));

  /*
   * step 4: init the vm_page structures and put them in the correct
   * place...
   */

  for (lcv = 0 ; lcv < vm_nphysseg ; lcv++) {

    n = vm_physmem[lcv].end - vm_physmem[lcv].start;
    if (n > pagecount) {
      printf("uvm_page_init: lost %d page(s) in init\n", n - pagecount);
      panic("uvm_page_init");  /* XXXCDC: shouldn't happen? */
      /* n = pagecount; */
    }
    /* set up page array pointers */
    vm_physmem[lcv].pgs = pagearray;
    pagearray += n;
    pagecount -= n;
    vm_physmem[lcv].lastpg = vm_physmem[lcv].pgs + (n - 1);

    /* init and free vm_pages (we've already bzero'd them) */
    paddr = ptoa(vm_physmem[lcv].start);
    for (i = 0 ; i < n ; i++, paddr += PAGE_SIZE) {
      vm_physmem[lcv].pgs[i].phys_addr = paddr;
      if (atop(paddr) >= vm_physmem[lcv].avail_start &&
          atop(paddr) <= vm_physmem[lcv].avail_end) {
	uvmexp.npages++;
        uvm_pagefree(&vm_physmem[lcv].pgs[i]);	/* add page to free pool */
      }
    }
  }
  /*
   * step 5: pass up the values of virtual_space_start and
   * virtual_space_end (obtained by uvm_pageboot_alloc) to the upper
   * layers of the VM.
   */

  *kvm_startp = round_page(virtual_space_start);
  *kvm_endp = trunc_page(virtual_space_end);

  /*
   * step 6: init pagedaemon lock
   */

  simple_lock_init(&uvm.pagedaemon_lock);

  /*
   * step 7: init reserve thresholds
   * XXXCDC - values may need adjusting
   */
  uvmexp.reserve_pagedaemon = 1;
  uvmexp.reserve_kernel = 5;

  /*
   * done!
   */

}

/*
 * uvm_setpagesize: set the page size
 *
 * => sets page_shift and page_mask from uvmexp.pagesize.
 * => XXXCDC: move global vars.
 */

void uvm_setpagesize()
{
  if (uvmexp.pagesize == 0)
    uvmexp.pagesize = DEFAULT_PAGE_SIZE;
  uvmexp.pagemask = uvmexp.pagesize - 1;
  if ((uvmexp.pagemask & uvmexp.pagesize) != 0)
    panic("uvm_setpagesize: page size not a power of two");
  for (uvmexp.pageshift = 0; ; uvmexp.pageshift++)
    if ((1 << uvmexp.pageshift) == uvmexp.pagesize)
      break;
}

/*
 * uvm_pageboot_alloc: steal memory from physmem for bootstrapping
 */

vm_offset_t uvm_pageboot_alloc(size)

vm_size_t size;

{
#if defined(PMAP_STEAL_MEMORY)
  vm_offset_t addr;

  /*
   * defer bootstrap allocation to MD code (it may want to allocate
   * from a direct-mapped segment).  pmap_steal_memory should round
   * off virtual_space_start/virtual_space_end.
   */

  addr = pmap_steal_memory(size, &virtual_space_start, &virtual_space_end);

  return(addr);

#else /* !PMAP_STEAL_MEMORY */

  vm_offset_t addr, vaddr, paddr;

  /* round the size to an integer multiple */
  size = (size + 3) &~ 3; /* XXX */

  /*
   * on first call to this function init ourselves.   we detect this
   * by checking virtual_space_start/end which are in the zero'd BSS area.
   */

  if (virtual_space_start == virtual_space_end) {
    pmap_virtual_space(&virtual_space_start, &virtual_space_end);

    /* round it the way we like it */
    virtual_space_start = round_page(virtual_space_start);
    virtual_space_end = trunc_page(virtual_space_end);
  }

  /*
   * allocate virtual memory for this request
   */

  addr = virtual_space_start;
  virtual_space_start += size;

    /*
   * allocate and mapin physical pages to back new virtual pages
   */

  for (vaddr = round_page(addr) ; vaddr < addr + size ; vaddr += PAGE_SIZE) {

    if (!uvm_page_physget(&paddr))
      panic("uvm_pageboot_alloc: out of memory");

    /* XXX: should be wired, but some pmaps don't like that ... */
#if defined(PMAP_NEW)
    pmap_kenter_pa(vaddr, paddr, VM_PROT_READ|VM_PROT_WRITE);
#else
    pmap_enter(pmap_kernel(), vaddr, paddr,
               VM_PROT_READ|VM_PROT_WRITE, FALSE);
#endif

  }

  return(addr);
#endif	/* PMAP_STEAL_MEMORY */
}

#if !defined(PMAP_STEAL_MEMORY)
/*
 * uvm_page_physget: "steal" one page from the vm_physmem structure.
 *
 * => attempt to allocate it off the end of a segment in which the "avail"
 *    values match the start/end values.   if we can't do that, then we
 *    will advance both values (making them equal, and removing some
 *    vm_page structures from the non-avail area).
 * => return false if out of memory.
 */

static boolean_t uvm_page_physget(paddrp)

vm_offset_t *paddrp;

{
  int lcv, x;

  /* pass 1: try allocating from a matching end */
#if (VM_PHYSSEG_STRAT == VM_PSTRAT_BIGFIRST)
  for (lcv = vm_nphysseg - 1 ; lcv >= 0 ; lcv--)
#else
  for (lcv = 0 ; lcv < vm_nphysseg ; lcv++)
#endif
  {

    if (vm_physmem[lcv].pgs)
      panic("vm_page_physget: called _after_ bootstrap");

    /* try from front */
    if (vm_physmem[lcv].avail_start == vm_physmem[lcv].start &&
        vm_physmem[lcv].avail_start < vm_physmem[lcv].avail_end) {
      *paddrp = ptoa(vm_physmem[lcv].avail_start);
      vm_physmem[lcv].avail_start++;
      vm_physmem[lcv].start++;
      /* nothing left?   nuke it */
      if (vm_physmem[lcv].avail_start == vm_physmem[lcv].end) {
        if (vm_nphysseg == 1)
          panic("vm_page_physget: out of memory!");
        vm_nphysseg--;
        for (x = lcv ; x < vm_nphysseg ; x++)
          vm_physmem[x] = vm_physmem[x+1];  /* structure copy */
      }
      return(TRUE);
    }

    /* try from rear */
    if (vm_physmem[lcv].avail_end == vm_physmem[lcv].end &&
        vm_physmem[lcv].avail_start < vm_physmem[lcv].avail_end) {
      *paddrp = ptoa(vm_physmem[lcv].avail_end - 1);
      vm_physmem[lcv].avail_end--;
      vm_physmem[lcv].end--;
      /* nothing left?   nuke it */
      if (vm_physmem[lcv].avail_end == vm_physmem[lcv].start) {
        if (vm_nphysseg == 1)
          panic("vm_page_physget: out of memory!");
        vm_nphysseg--;
        for (x = lcv ; x < vm_nphysseg ; x++)
          vm_physmem[x] = vm_physmem[x+1];  /* structure copy */
      }
      return(TRUE);
    }
  }

  /* pass2: forget about matching ends, just allocate something */
#if (VM_PHYSSEG_STRAT == VM_PSTRAT_BIGFIRST)
  for (lcv = vm_nphysseg - 1 ; lcv >= 0 ; lcv--)
#else
  for (lcv = 0 ; lcv < vm_nphysseg ; lcv++)
#endif
  {

    /* any room in this bank? */
    if (vm_physmem[lcv].avail_start >= vm_physmem[lcv].avail_end)
      continue;  /* nope */

    *paddrp = ptoa(vm_physmem[lcv].avail_start);
    vm_physmem[lcv].avail_start++;
    vm_physmem[lcv].start = vm_physmem[lcv].avail_start; /* truncate! */
    /* nothing left?   nuke it */
    if (vm_physmem[lcv].avail_start == vm_physmem[lcv].end) {
      if (vm_nphysseg == 1)
        panic("vm_page_physget: out of memory!");
      vm_nphysseg--;
      for (x = lcv ; x < vm_nphysseg ; x++)
        vm_physmem[x] = vm_physmem[x+1];  /* structure copy */
    }
    return(TRUE);
  }

  return(FALSE);        /* whoops! */
}
#endif /* PMAP_STEAL_MEMORY */

/*
 * uvm_page_physload: load physical memory into VM system
 *
 * => all args are PFs
 * => all pages in start/end get vm_page structures
 * => areas marked by avail_start/avail_end get added to the free page pool
 * => we are limited to VM_PHYSSEG_MAX physical memory segments
 */

void uvm_page_physload(start, end, avail_start, avail_end)

vm_offset_t start, end, avail_start, avail_end;

{
  int preload, lcv, npages;
  struct vm_page *pgs;
  struct vm_physseg *ps;

  if (uvmexp.pagesize == 0)
    panic("vm_page_physload: page size not set!");

  /*
   * do we have room?
   */
  if (vm_nphysseg == VM_PHYSSEG_MAX) {
    printf("vm_page_physload: unable to load physical memory segment\n");
    printf("\t%d segments allocated, ignoring 0x%lx -> 0x%lx\n",
           VM_PHYSSEG_MAX, start, end);
    return;
  }

  /*
   * check to see if this is a "preload" (i.e. uvm_mem_init hasn't been
   * called yet, so malloc is not available).
   */
  for (lcv = 0 ; lcv < vm_nphysseg ; lcv++) {
    if (vm_physmem[lcv].pgs)
      break;
  }
  preload = (lcv == vm_nphysseg);

  /*
   * if VM is already running, attempt to malloc() vm_page structures
   */
  if (!preload) {
#if defined(VM_PHYSSEG_NOADD)
    panic("vm_page_physload: tried to add RAM after vm_mem_init");
#else
    /* XXXCDC: need some sort of lockout for this case */
    vm_offset_t paddr;
    npages = end - start;  /* # of pages */
    MALLOC(pgs, struct vm_page *, sizeof(struct vm_page) * npages,
           M_VMPAGE, M_NOWAIT);
    if (pgs == NULL) {
      printf("vm_page_physload: can not malloc vm_page structs for segment\n");
      printf("\tignoring 0x%lx -> 0x%lx\n", start, end);
      return;
    }
    /* zero data, init phys_addr, and free pages */
    bzero(pgs, sizeof(struct vm_page) * npages);
    for (lcv = 0, paddr = ptoa(start) ;
         lcv < npages ; lcv++, paddr += PAGE_SIZE) {
      pgs[lcv].phys_addr = paddr;
      if (atop(paddr) >= avail_start && atop(paddr) <= avail_end)
        vm_page_free(&pgs[i]);
    }
    /* XXXCDC: incomplete: need to update uvmexp.free, what else? */
    /* XXXCDC: need hook to tell pmap to rebuild pv_list, etc... */
#endif
  } else {

    /* gcc complains if these don't get init'd */
    pgs = NULL;
    npages = 0;

  }

  /*
   * now insert us in the proper place in vm_physmem[]
   */

#if (VM_PHYSSEG_STRAT == VM_PSTRAT_RANDOM)

  /* random: put it at the end (easy!) */
  ps = &vm_physmem[vm_nphysseg];

#elif (VM_PHYSSEG_STRAT == VM_PSTRAT_BSEARCH)

  {
    int x;
    /* sort by address for binary search */
    for (lcv = 0 ; lcv < vm_nphysseg ; lcv++)
      if (start < vm_physmem[lcv].start)
        break;
    ps = &vm_physmem[lcv];
    /* move back other entries, if necessary ... */
    for (x = vm_nphysseg ; x > lcv ; x--)
      vm_physmem[x] = vm_physmem[x - 1];        /* structure copy */
  }

#elif (VM_PHYSSEG_STRAT == VM_PSTRAT_BIGFIRST)

  {
    int x;
    /* sort by largest segment first */
    for (lcv = 0 ; lcv < vm_nphysseg ; lcv++)
      if ((end - start) > (vm_physmem[lcv].end - vm_physmem[lcv].start))
        break;
    ps = &vm_physmem[lcv];
    /* move back other entries, if necessary ... */
    for (x = vm_nphysseg ; x > lcv ; x--)
      vm_physmem[x] = vm_physmem[x - 1];        /* structure copy */
  }

#else

  panic("vm_page_physload: unknown physseg strategy selected!");

#endif

  ps->start = start;
  ps->end = end;
  ps->avail_start = avail_start;
  ps->avail_end = avail_end;
  if (preload) {
    ps->pgs = NULL;
  } else {
    ps->pgs = pgs;
    ps->lastpg = pgs + npages - 1;
  }
  vm_nphysseg++;

  /*
   * done!
   */

  if (!preload)
    uvm_page_rehash();

  return;
}

/*
 * uvm_page_rehash: reallocate hash table based on number of free pages.
 */

void uvm_page_rehash()

{
  int freepages, lcv, bucketcount, s, oldcount;
  struct pglist *newbuckets, *oldbuckets;
  struct vm_page *pg;

  /*
   * compute number of pages that can go in the free pool
   */

  freepages = 0;
  for (lcv = 0 ; lcv < vm_nphysseg ; lcv++)
    freepages = freepages +
      (vm_physmem[lcv].avail_end - vm_physmem[lcv].avail_start);

  /*
   * compute number of buckets needed for this number of pages
   */

  bucketcount = 1;
  while (bucketcount < freepages)
    bucketcount = bucketcount * 2;

  /*
   * malloc new buckets
   */

  MALLOC(newbuckets, struct pglist *, sizeof(struct pglist) * bucketcount,
           M_VMPBUCKET, M_NOWAIT);
  if (newbuckets == NULL) {
    printf("vm_page_physrehash: WARNING: could not grow page hash table\n");
    return;
  }
  for (lcv = 0 ; lcv < bucketcount ; lcv++)
    TAILQ_INIT(&newbuckets[lcv]);

  /*
   * now replace the old buckets with the new ones and rehash everything
   */

  s = splimp();
  simple_lock(&uvm.hashlock);
  /* swap old for new ... */
  oldbuckets = uvm.page_hash;
  oldcount = uvm.page_nhash;
  uvm.page_hash = newbuckets;
  uvm.page_nhash = bucketcount;
  uvm.page_hashmask = bucketcount - 1;  /* power of 2 */

  /* ... and rehash */
  for (lcv = 0 ; lcv < oldcount ; lcv++) {
    while ((pg = oldbuckets[lcv].tqh_first) != NULL) {
      TAILQ_REMOVE(&oldbuckets[lcv], pg, hashq);
      TAILQ_INSERT_TAIL(
        &uvm.page_hash[uvm_pagehash(pg->uobject, pg->offset)], pg, hashq);
    }
  }
  simple_unlock(&uvm.hashlock);
  splx(s);

  /*
   * free old bucket array if we malloc'd it previously
   */

  if (oldbuckets != &uvm_bootbucket)
    FREE(oldbuckets, M_VMPBUCKET);

  /*
   * done
   */
  return;
}


#if 1 /* XXXCDC: TMP TMP TMP DEBUG DEBUG DEBUG */

void uvm_page_physdump __P((void)); /* SHUT UP GCC */

/* call from DDB */
void uvm_page_physdump() {
  int lcv;
  printf("rehash: physical memory config [segs=%d of %d]:\n",
         vm_nphysseg, VM_PHYSSEG_MAX);
  for (lcv = 0 ; lcv < vm_nphysseg ; lcv++)
    printf("0x%lx->0x%lx [0x%lx->0x%lx]\n", vm_physmem[lcv].start,
           vm_physmem[lcv].end, vm_physmem[lcv].avail_start,
           vm_physmem[lcv].avail_end);
  printf("STRATEGY = ");
  switch (VM_PHYSSEG_STRAT) {
  case VM_PSTRAT_RANDOM: printf("RANDOM\n"); break;
  case VM_PSTRAT_BSEARCH: printf("BSEARCH\n"); break;
  case VM_PSTRAT_BIGFIRST: printf("BIGFIRST\n"); break;
  default: printf("<<UNKNOWN>>!!!!\n");
  }
  printf("number of buckets = %d\n", uvm.page_nhash);
}
#endif

/*
 * uvm_pagealloc: allocate vm_page.
 *
 * => return null if no pages free
 * => wake up pagedaemon if number of free pages drops below low water mark
 * => if obj != NULL, obj must be locked (to put in hash)
 * => if anon != NULL, anon must be locked (to put in anon)
 * => only one of obj or anon can be non-null
 * => caller must activate/deactivate page if it is not wired.
 */

struct vm_page *uvm_pagealloc(obj, off, anon)

struct uvm_object *obj;
vm_offset_t off;
struct vm_anon *anon;

{
  int s;
  struct vm_page *pg;

#ifdef DIAGNOSTIC
  /* sanity check */
  if (obj && anon)
    panic("uvm_pagealloc: obj and anon != NULL");
#endif

  s = splimp();

  uvm_lock_fpageq();		/* lock free page queue */

  /*
   * check to see if we need to generate some free pages waking
   * the pagedaemon.
   */

  if (uvmexp.free < uvmexp.freemin ||
      (uvmexp.free < uvmexp.freetarg && uvmexp.inactive < uvmexp.inactarg)) {

    thread_wakeup(&uvm.pagedaemon);
  }

  /*
   * fail if any of these conditions is true:
   * [1]  there really are no free pages, or
   * [2]  only kernel "reserved" pages remain and
   *        the page isn't being allocated to a kernel object.
   * [3]  only pagedaemon "reserved" pages remain and
   *        the requestor isn't the pagedaemon.
   */

  pg = uvm.page_free.tqh_first;
  if (pg == NULL ||
      (uvmexp.free <= uvmexp.reserve_kernel &&
       !(obj && obj->uo_refs == UVM_OBJ_KERN)) ||
      (uvmexp.free <= uvmexp.reserve_pagedaemon &&
       !(obj == uvmexp.kmem_object && curproc == uvm.pagedaemon_proc))) {
    uvm_unlock_fpageq();
    splx(s);
    return(NULL);
  }

  TAILQ_REMOVE(&uvm.page_free, pg, pageq);
  uvmexp.free--;

  uvm_unlock_fpageq();		/* unlock free page queue */
  splx(s);

  pg->offset = off;
  pg->uobject = obj;
  pg->uanon = anon;
  pg->flags = PG_BUSY|PG_CLEAN|PG_FAKE;
  pg->version++;
  pg->wire_count = 0;
  pg->loan_count = 0;
  if (anon) {
    anon->u.an_page = pg;
    pg->pqflags = PQ_ANON;
  } else {
    if (obj)
      uvm_pageinsert(pg);
    pg->pqflags = 0;
  }
#if defined(UVM_PAGE_TRKOWN)
  pg->owner_tag = NULL;
#endif
  UVM_PAGE_OWN(pg, "new alloc");

  return(pg);
}

/*
 * uvm_pagerealloc: reallocate a page from one object to another
 *
 * => both objects must be locked
 */

void uvm_pagerealloc(pg, newobj, newoff)

struct vm_page *pg;
struct uvm_object *newobj;
vm_offset_t newoff;

{
  /*
   * remove it from the old object
   */

  if (pg->uobject) {
    uvm_pageremove(pg);
  }

  /*
   * put it in the new object
   */

  if (newobj) {
    pg->uobject = newobj;
    pg->offset = newoff;
    pg->version++;
    uvm_pageinsert(pg);
  }

  return;
}


/*
 * uvm_pagefree: free page
 *
 * => erase page's identity (i.e. remove from hash/object)
 * => put page on free list
 * => caller must lock owning object (either anon or uvm_object)
 * => caller must lock page queues
 * => assumes all valid mappings of pg are gone
 */

void uvm_pagefree(pg)

struct vm_page *pg;

{
  int s;
  int saved_loan_count = pg->loan_count;

  /*
   * if the page was an object page (and thus "TABLED"), remove it
   * from the object.
   */

  if (pg->flags & PG_TABLED) {

    /*
     * if the object page is on loan we are going to drop ownership.
     * it is possible that an anon will take over as owner for this
     * page later on.   the anon will want a !PG_CLEAN page so that
     * it knows it needs to allocate swap if it wants to page the
     * page out.
     */

    if (saved_loan_count)
      pg->flags &= ~PG_CLEAN;	/* in case an anon takes over */

    uvm_pageremove(pg);

    /*
     * if our page was on loan, then we just lost control over it
     * (in fact, if it was loaned to an anon, the anon may have
     * already taken over ownership of the page by now and thus
     * changed the loan_count [e.g. in uvmfault_anonget()]) we just
     * return (when the last loan is dropped, then the page can be
     * freed by whatever was holding the last loan).
     */
    if (saved_loan_count)
      return;

  } else if (saved_loan_count && (pg->pqflags & PQ_ANON)) {

    /*
     * if our page is owned by an anon and is loaned out to the kernel
     * then we just want to drop ownership and return.   the kernel
     * must free the page when all its loans clear ...  note that the
     * kernel can't change the loan status of our page as long as we
     * are holding PQ lock.
     */
    pg->pqflags &= ~PQ_ANON;
    pg->uanon = NULL;
    return;

  }

#ifdef DIAGNOSTIC
  if (saved_loan_count) {
    printf("uvm_pagefree: warning: freeing page with a loan count of %d\n",
	saved_loan_count);
    panic("uvm_pagefree: loan count");
  }
#endif


  /*
   * now remove the page from the queues
   */

  if (pg->pqflags & PQ_ACTIVE) {
    TAILQ_REMOVE(&uvm.page_active, pg, pageq);
    pg->pqflags &= ~PQ_ACTIVE;
    uvmexp.active--;
  }
  if (pg->pqflags & PQ_INACTIVE) {
    if (pg->pqflags & PQ_SWAPBACKED)
      TAILQ_REMOVE(&uvm.page_inactive_swp, pg, pageq);
    else
      TAILQ_REMOVE(&uvm.page_inactive_obj, pg, pageq);
    pg->pqflags &= ~PQ_INACTIVE;
    uvmexp.inactive--;
  }

  /*
   * if the page was wired, unwire it now.
   */
  if (pg->wire_count)
  {
      pg->wire_count = 0;
      uvmexp.wired--;
  }

  /*
   * and put on free queue
   */

  s = splimp();
  uvm_lock_fpageq();
  TAILQ_INSERT_TAIL(&uvm.page_free, pg, pageq);
  pg->pqflags = PQ_FREE;
#ifdef DEBUG
  pg->uobject = (void *)0xdeadbeef;
  pg->offset = 0xdeadbeef;
  pg->uanon = (void *)0xdeadbeef;
#endif
  uvmexp.free++;
  uvm_unlock_fpageq();
  splx(s);
}

#if defined(UVM_PAGE_TRKOWN)
/*
 * uvm_page_own: set or release page ownership
 *
 * => this is a debugging function that keeps track of who sets PG_BUSY
 *	and where they do it.   it can be used to track down problems
 *	such a process setting "PG_BUSY" and never releasing it.
 * => page's object [if any] must be locked
 * => if "tag" is NULL then we are releasing page ownership
 */
void uvm_page_own(pg, tag)

struct vm_page *pg;
char *tag;

{
  /* gain ownership? */
  if (tag) {
    if (pg->owner_tag) {
      printf("uvm_page_own: page %p already owned by proc %d [%s]\n", pg,
	     pg->owner, pg->owner_tag);
      panic("uvm_page_own");
    }
    pg->owner = (curproc) ? curproc->p_pid :  (pid_t) -1;
    pg->owner_tag = tag;
    return;
  }

  /* drop ownership */
  if (pg->owner_tag == NULL) {
    printf("uvm_page_own: dropping ownership of an non-owned page (%p)\n", pg);
    panic("uvm_page_own");
  }
  pg->owner_tag = NULL;
  return;
}
#endif