xnu-1504.9.26.tar.gz

[apple/xnu.git] / osfmk / vm / memory_object.c

/*
 * Copyright (c) 2000-2008 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 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@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */
/*
 *      File:   vm/memory_object.c
 *      Author: Michael Wayne Young
 *
 *      External memory management interface control functions.
 */

#include <advisory_pageout.h>

/*
 *      Interface dependencies:
 */

#include <mach/std_types.h>     /* For pointer_t */
#include <mach/mach_types.h>

#include <mach/mig.h>
#include <mach/kern_return.h>
#include <mach/memory_object.h>
#include <mach/memory_object_default.h>
#include <mach/memory_object_control_server.h>
#include <mach/host_priv_server.h>
#include <mach/boolean.h>
#include <mach/vm_prot.h>
#include <mach/message.h>

/*
 *      Implementation dependencies:
 */
#include <string.h>             /* For memcpy() */

#include <kern/xpr.h>           
#include <kern/host.h>
#include <kern/thread.h>        /* For current_thread() */
#include <kern/ipc_mig.h>
#include <kern/misc_protos.h>

#include <vm/vm_object.h>
#include <vm/vm_fault.h>
#include <vm/memory_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/pmap.h>            /* For pmap_clear_modify */
#include <vm/vm_kern.h>         /* For kernel_map, vm_move */
#include <vm/vm_map.h>          /* For vm_map_pageable */
#include <vm/vm_purgeable_internal.h>   /* Needed by some vm_page.h macros */

#if     MACH_PAGEMAP
#include <vm/vm_external.h>
#endif  /* MACH_PAGEMAP */

#include <vm/vm_protos.h>


memory_object_default_t memory_manager_default = MEMORY_OBJECT_DEFAULT_NULL;
decl_lck_mtx_data(,     memory_manager_default_lock)


/*
 *      Routine:        memory_object_should_return_page
 *
 *      Description:
 *              Determine whether the given page should be returned,
 *              based on the page's state and on the given return policy.
 *
 *              We should return the page if one of the following is true:
 *
 *              1. Page is dirty and should_return is not RETURN_NONE.
 *              2. Page is precious and should_return is RETURN_ALL.
 *              3. Should_return is RETURN_ANYTHING.
 *
 *              As a side effect, m->dirty will be made consistent
 *              with pmap_is_modified(m), if should_return is not
 *              MEMORY_OBJECT_RETURN_NONE.
 */

#define memory_object_should_return_page(m, should_return) \
    (should_return != MEMORY_OBJECT_RETURN_NONE && \
     (((m)->dirty || ((m)->dirty = pmap_is_modified((m)->phys_page))) || \
      ((m)->precious && (should_return) == MEMORY_OBJECT_RETURN_ALL) || \
      (should_return) == MEMORY_OBJECT_RETURN_ANYTHING))

typedef int     memory_object_lock_result_t;

#define MEMORY_OBJECT_LOCK_RESULT_DONE          0
#define MEMORY_OBJECT_LOCK_RESULT_MUST_BLOCK    1
#define MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN    2
#define MEMORY_OBJECT_LOCK_RESULT_MUST_RETURN   3

memory_object_lock_result_t memory_object_lock_page(
                                vm_page_t               m,
                                memory_object_return_t  should_return,
                                boolean_t               should_flush,
                                vm_prot_t               prot);

/*
 *      Routine:        memory_object_lock_page
 *
 *      Description:
 *              Perform the appropriate lock operations on the
 *              given page.  See the description of
 *              "memory_object_lock_request" for the meanings
 *              of the arguments.
 *
 *              Returns an indication that the operation
 *              completed, blocked, or that the page must
 *              be cleaned.
 */
memory_object_lock_result_t
memory_object_lock_page(
        vm_page_t               m,
        memory_object_return_t  should_return,
        boolean_t               should_flush,
        vm_prot_t               prot)
{
        XPR(XPR_MEMORY_OBJECT,
            "m_o_lock_page, page 0x%X rtn %d flush %d prot %d\n",
            m, should_return, should_flush, prot, 0);

        /*
         *      If we cannot change access to the page,
         *      either because a mapping is in progress
         *      (busy page) or because a mapping has been
         *      wired, then give up.
         */

        if (m->busy || m->cleaning) {
                if (m->list_req_pending && (m->pageout || m->cleaning) &&
                    should_return == MEMORY_OBJECT_RETURN_NONE &&
                    should_flush == TRUE) {
                        /*
                         * if pageout is set, page was earmarked by vm_pageout_scan
                         * to be cleaned and stolen... if cleaning is set, we're
                         * pre-cleaning pages for a hibernate...
                         * in either case, we're going
                         * to take it back since we are being asked to
                         * flush the page w/o cleaning it (i.e. we don't
                         * care that it's dirty, we want it gone from
                         * the cache) and we don't want to stall
                         * waiting for it to be cleaned for 2 reasons...
                         * 1 - no use paging it out since we're probably
                         *     shrinking the file at this point or we no
                         *     longer care about the data in the page
                         * 2 - if we stall, we may casue a deadlock in
                         *     the FS trying to acquire its locks
                         *     on the VNOP_PAGEOUT path presuming that
                         *     those locks are already held on the truncate
                         *     path before calling through to this function
                         *
                         * so undo all of the state that vm_pageout_scan
                         * hung on this page
                         */
                        m->busy = FALSE;

                        vm_pageout_queue_steal(m, FALSE);
                } else
                        return(MEMORY_OBJECT_LOCK_RESULT_MUST_BLOCK);
        }

        /*
         *      Don't worry about pages for which the kernel
         *      does not have any data.
         */

        if (m->absent || m->error || m->restart) {
                if(m->error && should_flush) {
                        /* dump the page, pager wants us to */
                        /* clean it up and there is no      */
                        /* relevant data to return */
                        if ( !VM_PAGE_WIRED(m)) {
                                VM_PAGE_FREE(m);
                                return(MEMORY_OBJECT_LOCK_RESULT_DONE);
                        }
                } else {
                        return(MEMORY_OBJECT_LOCK_RESULT_DONE);
                }
        }

        assert(!m->fictitious);

        /*
         *      If the page is wired, just clean or return the page if needed.
         *      Wired pages don't get flushed or disconnected from the pmap.
         */

        if (VM_PAGE_WIRED(m)) {
                if (memory_object_should_return_page(m, should_return)) {
                        if (m->dirty)
                                return(MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN);
                        else
                                return(MEMORY_OBJECT_LOCK_RESULT_MUST_RETURN);
                }

                return(MEMORY_OBJECT_LOCK_RESULT_DONE);
        }

        /*
         *      If the page is to be flushed, allow
         *      that to be done as part of the protection.
         */

        if (should_flush)
                prot = VM_PROT_ALL;

        /*
         *      Set the page lock.
         *
         *      If we are decreasing permission, do it now;
         *      let the fault handler take care of increases
         *      (pmap_page_protect may not increase protection).
         */

        if (prot != VM_PROT_NO_CHANGE) {
                pmap_page_protect(m->phys_page, VM_PROT_ALL & ~prot);

                PAGE_WAKEUP(m);
        }

        /*
         *      Handle page returning.
         */
        if (memory_object_should_return_page(m, should_return)) {

                /*
                 *      If we weren't planning
                 *      to flush the page anyway,
                 *      we may need to remove the
                 *      page from the pageout
                 *      system and from physical
                 *      maps now.
                 */
                
                vm_page_lockspin_queues();
                VM_PAGE_QUEUES_REMOVE(m);
                vm_page_unlock_queues();

                if (!should_flush)
                        pmap_disconnect(m->phys_page);

                if (m->dirty)
                        return(MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN);
                else
                        return(MEMORY_OBJECT_LOCK_RESULT_MUST_RETURN);
        }

        /*
         *      Handle flushing
         */
        if (should_flush) {
                VM_PAGE_FREE(m);
        } else {
                /*
                 *      XXX Make clean but not flush a paging hint,
                 *      and deactivate the pages.  This is a hack
                 *      because it overloads flush/clean with
                 *      implementation-dependent meaning.  This only
                 *      happens to pages that are already clean.
                 */

                if (vm_page_deactivate_hint &&
                    (should_return != MEMORY_OBJECT_RETURN_NONE)) {
                        vm_page_lockspin_queues();
                        vm_page_deactivate(m);
                        vm_page_unlock_queues();
                }
        }

        return(MEMORY_OBJECT_LOCK_RESULT_DONE);
}

#define LIST_REQ_PAGEOUT_PAGES(object, data_cnt, action, po, ro, ioerr, iosync)    \
MACRO_BEGIN                                                             \
                                                                        \
        register int            upl_flags;                              \
        memory_object_t         pager;                                  \
                                                                        \
        if ((pager = (object)->pager) != MEMORY_OBJECT_NULL) {          \
                vm_object_paging_begin(object);                         \
                vm_object_unlock(object);                               \
                                                                        \
                if (iosync)                                             \
                        upl_flags = UPL_MSYNC | UPL_IOSYNC;             \
                else                                                    \
                        upl_flags = UPL_MSYNC;                          \
                                                                        \
                (void) memory_object_data_return(pager,                 \
                        po,                                             \
                        (memory_object_cluster_size_t)data_cnt,                                 \
                        ro,                                             \
                        ioerr,                                          \
                        (action) == MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN,\
                        !should_flush,                                  \
                        upl_flags);                                     \
                                                                        \
                vm_object_lock(object);                                 \
                vm_object_paging_end(object);                           \
        }                                                               \
MACRO_END

/*
 *      Routine:        memory_object_lock_request [user interface]
 *
 *      Description:
 *              Control use of the data associated with the given
 *              memory object.  For each page in the given range,
 *              perform the following operations, in order:
 *                      1)  restrict access to the page (disallow
 *                          forms specified by "prot");
 *                      2)  return data to the manager (if "should_return"
 *                          is RETURN_DIRTY and the page is dirty, or
 *                          "should_return" is RETURN_ALL and the page
 *                          is either dirty or precious); and,
 *                      3)  flush the cached copy (if "should_flush"
 *                          is asserted).
 *              The set of pages is defined by a starting offset
 *              ("offset") and size ("size").  Only pages with the
 *              same page alignment as the starting offset are
 *              considered.
 *
 *              A single acknowledgement is sent (to the "reply_to"
 *              port) when these actions are complete.  If successful,
 *              the naked send right for reply_to is consumed.
 */

kern_return_t
memory_object_lock_request(
        memory_object_control_t         control,
        memory_object_offset_t          offset,
        memory_object_size_t            size,
        memory_object_offset_t  *       resid_offset,
        int                     *       io_errno,
        memory_object_return_t          should_return,
        int                             flags,
        vm_prot_t                       prot)
{
        vm_object_t     object;

        /*
         *      Check for bogus arguments.
         */
        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        if ((prot & ~VM_PROT_ALL) != 0 && prot != VM_PROT_NO_CHANGE)
                return (KERN_INVALID_ARGUMENT);

        size = round_page_64(size);

        /*
         *      Lock the object, and acquire a paging reference to
         *      prevent the memory_object reference from being released.
         */
        vm_object_lock(object);
        vm_object_paging_begin(object);

        if (flags & MEMORY_OBJECT_DATA_FLUSH_ALL) {
                if ((should_return != MEMORY_OBJECT_RETURN_NONE) || offset || object->copy) {
                        flags &= ~MEMORY_OBJECT_DATA_FLUSH_ALL;
                        flags |= MEMORY_OBJECT_DATA_FLUSH;
                }
        }
        offset -= object->paging_offset;

        if (flags & MEMORY_OBJECT_DATA_FLUSH_ALL)
                vm_object_reap_pages(object, REAP_DATA_FLUSH);
        else
                (void)vm_object_update(object, offset, size, resid_offset,
                                       io_errno, should_return, flags, prot);

        vm_object_paging_end(object);
        vm_object_unlock(object);

        return (KERN_SUCCESS);
}

/*
 *      memory_object_release_name:  [interface]
 *
 *      Enforces name semantic on memory_object reference count decrement
 *      This routine should not be called unless the caller holds a name
 *      reference gained through the memory_object_named_create or the
 *      memory_object_rename call.
 *      If the TERMINATE_IDLE flag is set, the call will return if the
 *      reference count is not 1. i.e. idle with the only remaining reference
 *      being the name.
 *      If the decision is made to proceed the name field flag is set to
 *      false and the reference count is decremented.  If the RESPECT_CACHE
 *      flag is set and the reference count has gone to zero, the 
 *      memory_object is checked to see if it is cacheable otherwise when
 *      the reference count is zero, it is simply terminated.
 */

kern_return_t
memory_object_release_name(
        memory_object_control_t control,
        int                             flags)
{
        vm_object_t     object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        return vm_object_release_name(object, flags);
}



/*
 *      Routine:        memory_object_destroy [user interface]
 *      Purpose:
 *              Shut down a memory object, despite the
 *              presence of address map (or other) references
 *              to the vm_object.
 */
kern_return_t
memory_object_destroy(
        memory_object_control_t control,
        kern_return_t           reason)
{
        vm_object_t             object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        return (vm_object_destroy(object, reason));
}

/*
 *      Routine:        vm_object_sync
 *
 *      Kernel internal function to synch out pages in a given
 *      range within an object to its memory manager.  Much the
 *      same as memory_object_lock_request but page protection
 *      is not changed.
 *
 *      If the should_flush and should_return flags are true pages
 *      are flushed, that is dirty & precious pages are written to
 *      the memory manager and then discarded.  If should_return
 *      is false, only precious pages are returned to the memory
 *      manager.
 *
 *      If should flush is false and should_return true, the memory
 *      manager's copy of the pages is updated.  If should_return
 *      is also false, only the precious pages are updated.  This
 *      last option is of limited utility.
 *
 *      Returns:
 *      FALSE           if no pages were returned to the pager
 *      TRUE            otherwise.
 */

boolean_t
vm_object_sync(
        vm_object_t             object,
        vm_object_offset_t      offset,
        vm_object_size_t        size,
        boolean_t               should_flush,
        boolean_t               should_return,
        boolean_t               should_iosync)
{
        boolean_t       rv;
        int             flags;

        XPR(XPR_VM_OBJECT,
            "vm_o_sync, object 0x%X, offset 0x%X size 0x%x flush %d rtn %d\n",
            object, offset, size, should_flush, should_return);

        /*
         * Lock the object, and acquire a paging reference to
         * prevent the memory_object and control ports from
         * being destroyed.
         */
        vm_object_lock(object);
        vm_object_paging_begin(object);

        if (should_flush)
                flags = MEMORY_OBJECT_DATA_FLUSH;
        else
                flags = 0;

        if (should_iosync)
                flags |= MEMORY_OBJECT_IO_SYNC;

        rv = vm_object_update(object, offset, (vm_object_size_t)size, NULL, NULL,
                (should_return) ?
                        MEMORY_OBJECT_RETURN_ALL :
                        MEMORY_OBJECT_RETURN_NONE,
                flags,
                VM_PROT_NO_CHANGE);


        vm_object_paging_end(object);
        vm_object_unlock(object);
        return rv;
}




static int
vm_object_update_extent(
        vm_object_t             object,
        vm_object_offset_t      offset,
        vm_object_offset_t      offset_end,
        vm_object_offset_t      *offset_resid,
        int                     *io_errno,
        boolean_t               should_flush,
        memory_object_return_t  should_return,
        boolean_t               should_iosync, 
        vm_prot_t               prot)
{
        vm_page_t       m;
        int             retval = 0;
        memory_object_cluster_size_t    data_cnt = 0;
        vm_object_offset_t      paging_offset = 0;
        vm_object_offset_t      next_offset = offset;
        memory_object_lock_result_t     page_lock_result;
        memory_object_lock_result_t     pageout_action;
        
        pageout_action = MEMORY_OBJECT_LOCK_RESULT_DONE;

        for (;
             offset < offset_end && object->resident_page_count;
             offset += PAGE_SIZE_64) {

                /*
                 * Limit the number of pages to be cleaned at once to a contiguous
                 * run, or at most MAX_UPL_TRANSFER size
                 */
                if (data_cnt) {
                        if ((data_cnt >= PAGE_SIZE * MAX_UPL_TRANSFER) || (next_offset != offset)) {
                                LIST_REQ_PAGEOUT_PAGES(object, data_cnt, 
                                                       pageout_action, paging_offset, offset_resid, io_errno, should_iosync);
                                data_cnt = 0;
                        }
                }

                while ((m = vm_page_lookup(object, offset)) != VM_PAGE_NULL) {
                        page_lock_result = memory_object_lock_page(m, should_return, should_flush, prot);

                        XPR(XPR_MEMORY_OBJECT,
                            "m_o_update: lock_page, obj 0x%X offset 0x%X result %d\n",
                            object, offset, page_lock_result, 0, 0);

                        switch (page_lock_result)
                        {
                          case MEMORY_OBJECT_LOCK_RESULT_DONE:
                            /*
                             *  End of a cluster of dirty pages.
                             */
                            if (data_cnt) {
                                    LIST_REQ_PAGEOUT_PAGES(object, 
                                                           data_cnt, pageout_action, 
                                                           paging_offset, offset_resid, io_errno, should_iosync);
                                    data_cnt = 0;
                                    continue;
                            }
                            break;

                          case MEMORY_OBJECT_LOCK_RESULT_MUST_BLOCK:
                            /*
                             *  Since it is necessary to block,
                             *  clean any dirty pages now.
                             */
                            if (data_cnt) {
                                    LIST_REQ_PAGEOUT_PAGES(object,
                                                           data_cnt, pageout_action, 
                                                           paging_offset, offset_resid, io_errno, should_iosync);
                                    data_cnt = 0;
                                    continue;
                            }
                            PAGE_SLEEP(object, m, THREAD_UNINT);
                            continue;

                          case MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN:
                          case MEMORY_OBJECT_LOCK_RESULT_MUST_RETURN:
                            /*
                             * The clean and return cases are similar.
                             *
                             * if this would form a discontiguous block,
                             * clean the old pages and start anew.
                             */
                            if (data_cnt && pageout_action != page_lock_result) {
                                    LIST_REQ_PAGEOUT_PAGES(object, 
                                                           data_cnt, pageout_action, 
                                                           paging_offset, offset_resid, io_errno, should_iosync);
                                    data_cnt = 0;
                                    continue;
                            }
                            if (m->cleaning) {
                                    PAGE_SLEEP(object, m, THREAD_UNINT);
                                    continue;
                            }
                            if (data_cnt == 0) {
                                    pageout_action = page_lock_result;
                                    paging_offset = offset;
                            }
                            data_cnt += PAGE_SIZE;
                            next_offset = offset + PAGE_SIZE_64;

                            /*
                             * Clean
                             */
                            m->list_req_pending = TRUE;
                            m->cleaning = TRUE;

                            if (should_flush &&
                                /* let's not flush a wired page... */
                                !VM_PAGE_WIRED(m)) {
                                    /*
                                     * and add additional state
                                     * for the flush
                                     */
                                    m->busy = TRUE;
                                    m->pageout = TRUE;

                                    vm_page_lockspin_queues();
                                    vm_page_wire(m);
                                    vm_page_unlock_queues();
                            }

                            retval = 1;
                            break;
                        }
                        break;
                }
        }
        /*
         *      We have completed the scan for applicable pages.
         *      Clean any pages that have been saved.
         */
        if (data_cnt) {
                LIST_REQ_PAGEOUT_PAGES(object,
                                       data_cnt, pageout_action, paging_offset, offset_resid, io_errno, should_iosync);
        }
        return (retval);
}



/*
 *      Routine:        vm_object_update
 *      Description:
 *              Work function for m_o_lock_request(), vm_o_sync().
 *
 *              Called with object locked and paging ref taken.
 */
kern_return_t
vm_object_update(
        register vm_object_t            object,
        register vm_object_offset_t     offset,
        register vm_object_size_t       size,
        register vm_object_offset_t     *resid_offset,
        int                             *io_errno,
        memory_object_return_t          should_return,
        int                             flags,
        vm_prot_t                       protection)
{
        vm_object_t             copy_object = VM_OBJECT_NULL;
        boolean_t               data_returned = FALSE;
        boolean_t               update_cow;
        boolean_t               should_flush = (flags & MEMORY_OBJECT_DATA_FLUSH) ? TRUE : FALSE;
        boolean_t               should_iosync = (flags & MEMORY_OBJECT_IO_SYNC) ? TRUE : FALSE;
        vm_fault_return_t       result;
        int                     num_of_extents;
        int                     n;
#define MAX_EXTENTS     8
#define EXTENT_SIZE     (1024 * 1024 * 256)
#define RESIDENT_LIMIT  (1024 * 32)
        struct extent {
                vm_object_offset_t e_base;
                vm_object_offset_t e_min;
                vm_object_offset_t e_max;
        } extents[MAX_EXTENTS];

        /*
         *      To avoid blocking while scanning for pages, save
         *      dirty pages to be cleaned all at once.
         *
         *      XXXO A similar strategy could be used to limit the
         *      number of times that a scan must be restarted for
         *      other reasons.  Those pages that would require blocking
         *      could be temporarily collected in another list, or
         *      their offsets could be recorded in a small array.
         */

        /*
         * XXX  NOTE: May want to consider converting this to a page list
         * XXX  vm_map_copy interface.  Need to understand object
         * XXX  coalescing implications before doing so.
         */

        update_cow = ((flags & MEMORY_OBJECT_DATA_FLUSH) 
                        && (!(flags & MEMORY_OBJECT_DATA_NO_CHANGE) &&
                                        !(flags & MEMORY_OBJECT_DATA_PURGE)))
                                || (flags & MEMORY_OBJECT_COPY_SYNC);
                        
        if (update_cow || (flags & (MEMORY_OBJECT_DATA_PURGE | MEMORY_OBJECT_DATA_SYNC))) {
                int collisions = 0;

                while ((copy_object = object->copy) != VM_OBJECT_NULL) {
                        /*
                         * need to do a try here since we're swimming upstream
                         * against the normal lock ordering... however, we need
                         * to hold the object stable until we gain control of the
                         * copy object so we have to be careful how we approach this
                         */
                        if (vm_object_lock_try(copy_object)) {
                               /*
                                * we 'won' the lock on the copy object...
                                * no need to hold the object lock any longer...
                                * take a real reference on the copy object because
                                * we're going to call vm_fault_page on it which may
                                * under certain conditions drop the lock and the paging
                                * reference we're about to take... the reference
                                * will keep the copy object from going away if that happens
                                */
                               vm_object_unlock(object);
                               vm_object_reference_locked(copy_object);
                               break;
                        }
                        vm_object_unlock(object);

                        collisions++;
                        mutex_pause(collisions);

                        vm_object_lock(object);
                }
        }
        if ((copy_object != VM_OBJECT_NULL && update_cow) || (flags & MEMORY_OBJECT_DATA_SYNC)) {
                vm_map_size_t           i;
                vm_map_size_t           copy_size;
                vm_map_offset_t         copy_offset;
                vm_prot_t               prot;
                vm_page_t               page;
                vm_page_t               top_page;
                kern_return_t           error = 0;
                struct vm_object_fault_info fault_info;

                if (copy_object != VM_OBJECT_NULL) {
                        /*
                         * translate offset with respect to shadow's offset
                         */
                        copy_offset = (offset >= copy_object->shadow_offset) ?
                          (vm_map_offset_t)(offset - copy_object->shadow_offset) :
                          (vm_map_offset_t) 0;

                        if (copy_offset > copy_object->size)
                                copy_offset = copy_object->size;

                        /*
                         * clip size with respect to shadow offset
                         */
                        if (offset >= copy_object->shadow_offset) {
                                copy_size = size;
                        } else if (size >= copy_object->shadow_offset - offset) {
                                copy_size = size - (copy_object->shadow_offset - offset);
                        } else {
                                copy_size = 0;
                        }
                        
                        if (copy_offset + copy_size > copy_object->size) {
                                if (copy_object->size >= copy_offset) {
                                        copy_size = copy_object->size - copy_offset;
                                } else {
                                        copy_size = 0;
                                }
                        }
                        copy_size+=copy_offset;

                } else {
                        copy_object = object;

                        copy_size   = offset + size;
                        copy_offset = offset;
                }
                fault_info.interruptible = THREAD_UNINT;
                fault_info.behavior  = VM_BEHAVIOR_SEQUENTIAL;
                fault_info.user_tag  = 0;
                fault_info.lo_offset = copy_offset;
                fault_info.hi_offset = copy_size;
                fault_info.no_cache   = FALSE;
                fault_info.stealth = TRUE;
                fault_info.mark_zf_absent = FALSE;

                vm_object_paging_begin(copy_object);

                for (i = copy_offset; i < copy_size; i += PAGE_SIZE) {
        RETRY_COW_OF_LOCK_REQUEST:
                        fault_info.cluster_size = (vm_size_t) (copy_size - i);
                        assert(fault_info.cluster_size == copy_size - i);

                        prot =  VM_PROT_WRITE|VM_PROT_READ;
                        result = vm_fault_page(copy_object, i, 
                                               VM_PROT_WRITE|VM_PROT_READ,
                                               FALSE,
                                               &prot,
                                               &page,
                                               &top_page,
                                               (int *)0,
                                               &error,
                                               FALSE,
                                               FALSE, &fault_info);

                        switch (result) {
                        case VM_FAULT_SUCCESS:
                                if (top_page) {
                                        vm_fault_cleanup(
                                                page->object, top_page);
                                        vm_object_lock(copy_object);
                                        vm_object_paging_begin(copy_object);
                                }
                                if (!page->active &&
                                    !page->inactive &&
                                    !page->throttled) {
                                        vm_page_lockspin_queues();
                                        if (!page->active &&
                                            !page->inactive &&
                                            !page->throttled)
                                                vm_page_deactivate(page);
                                        vm_page_unlock_queues();
                                }
                                PAGE_WAKEUP_DONE(page);
                                break;
                        case VM_FAULT_RETRY:
                                prot =  VM_PROT_WRITE|VM_PROT_READ;
                                vm_object_lock(copy_object);
                                vm_object_paging_begin(copy_object);
                                goto RETRY_COW_OF_LOCK_REQUEST;
                        case VM_FAULT_INTERRUPTED:
                                prot =  VM_PROT_WRITE|VM_PROT_READ;
                                vm_object_lock(copy_object);
                                vm_object_paging_begin(copy_object);
                                goto RETRY_COW_OF_LOCK_REQUEST;
                        case VM_FAULT_MEMORY_SHORTAGE:
                                VM_PAGE_WAIT();
                                prot =  VM_PROT_WRITE|VM_PROT_READ;
                                vm_object_lock(copy_object);
                                vm_object_paging_begin(copy_object);
                                goto RETRY_COW_OF_LOCK_REQUEST;
                        case VM_FAULT_FICTITIOUS_SHORTAGE:
                                vm_page_more_fictitious();
                                prot =  VM_PROT_WRITE|VM_PROT_READ;
                                vm_object_lock(copy_object);
                                vm_object_paging_begin(copy_object);
                                goto RETRY_COW_OF_LOCK_REQUEST;
                        case VM_FAULT_SUCCESS_NO_VM_PAGE:
                                /* success but no VM page: fail */
                                vm_object_paging_end(copy_object);
                                vm_object_unlock(copy_object);
                                /*FALLTHROUGH*/
                        case VM_FAULT_MEMORY_ERROR:
                                if (object != copy_object)
                                        vm_object_deallocate(copy_object);
                                vm_object_lock(object);
                                goto BYPASS_COW_COPYIN;
                        default:
                                panic("vm_object_update: unexpected error 0x%x"
                                      " from vm_fault_page()\n", result);
                        }

                }
                vm_object_paging_end(copy_object);
        }
        if ((flags & (MEMORY_OBJECT_DATA_SYNC | MEMORY_OBJECT_COPY_SYNC))) {
                if (copy_object != VM_OBJECT_NULL && copy_object != object) {
                        vm_object_unlock(copy_object);
                        vm_object_deallocate(copy_object);
                        vm_object_lock(object);
                }
                return KERN_SUCCESS;
        }
        if (copy_object != VM_OBJECT_NULL && copy_object != object) {
                if ((flags & MEMORY_OBJECT_DATA_PURGE)) {
                        copy_object->shadow_severed = TRUE;
                        copy_object->shadowed = FALSE;
                        copy_object->shadow = NULL;
                        /*
                         * delete the ref the COW was holding on the target object
                         */
                        vm_object_deallocate(object);
                }
                vm_object_unlock(copy_object);
                vm_object_deallocate(copy_object);
                vm_object_lock(object);
        }
BYPASS_COW_COPYIN:

        /*
         * when we have a really large range to check relative
         * to the number of actual resident pages, we'd like
         * to use the resident page list to drive our checks
         * however, the object lock will get dropped while processing
         * the page which means the resident queue can change which
         * means we can't walk the queue as we process the pages
         * we also want to do the processing in offset order to allow
         * 'runs' of pages to be collected if we're being told to 
         * flush to disk... the resident page queue is NOT ordered.
         * 
         * a temporary solution (until we figure out how to deal with
         * large address spaces more generically) is to pre-flight
         * the resident page queue (if it's small enough) and develop
         * a collection of extents (that encompass actual resident pages)
         * to visit.  This will at least allow us to deal with some of the
         * more pathological cases in a more efficient manner.  The current
         * worst case (a single resident page at the end of an extremely large
         * range) can take minutes to complete for ranges in the terrabyte
         * category... since this routine is called when truncating a file,
         * and we currently support files up to 16 Tbytes in size, this
         * is not a theoretical problem
         */

        if ((object->resident_page_count < RESIDENT_LIMIT) && 
            (atop_64(size) > (unsigned)(object->resident_page_count/(8 * MAX_EXTENTS)))) {
                vm_page_t               next;
                vm_object_offset_t      start;
                vm_object_offset_t      end;
                vm_object_size_t        e_mask;
                vm_page_t               m;

                start = offset;
                end   = offset + size;
                num_of_extents = 0;
                e_mask = ~((vm_object_size_t)(EXTENT_SIZE - 1));

                m = (vm_page_t) queue_first(&object->memq);

                while (!queue_end(&object->memq, (queue_entry_t) m)) {
                        next = (vm_page_t) queue_next(&m->listq);

                        if ((m->offset >= start) && (m->offset < end)) {
                                /*
                                 * this is a page we're interested in
                                 * try to fit it into a current extent
                                 */
                                for (n = 0; n < num_of_extents; n++) {
                                        if ((m->offset & e_mask) == extents[n].e_base) {
                                                /*
                                                 * use (PAGE_SIZE - 1) to determine the
                                                 * max offset so that we don't wrap if
                                                 * we're at the last page of the space
                                                 */
                                                if (m->offset < extents[n].e_min)
                                                        extents[n].e_min = m->offset;
                                                else if ((m->offset + (PAGE_SIZE - 1)) > extents[n].e_max)
                                                        extents[n].e_max = m->offset + (PAGE_SIZE - 1);
                                                break;
                                        }
                                }
                                if (n == num_of_extents) {
                                        /*
                                         * didn't find a current extent that can encompass
                                         * this page
                                         */
                                        if (n < MAX_EXTENTS) {
                                                /*
                                                 * if we still have room, 
                                                 * create a new extent
                                                 */
                                                extents[n].e_base = m->offset & e_mask;
                                                extents[n].e_min  = m->offset;
                                                extents[n].e_max  = m->offset + (PAGE_SIZE - 1);

                                                num_of_extents++;
                                        } else {
                                                /*
                                                 * no room to create a new extent...
                                                 * fall back to a single extent based
                                                 * on the min and max page offsets 
                                                 * we find in the range we're interested in...
                                                 * first, look through the extent list and
                                                 * develop the overall min and max for the
                                                 * pages we've looked at up to this point
                                                 */                                             
                                                for (n = 1; n < num_of_extents; n++) {
                                                        if (extents[n].e_min < extents[0].e_min)
                                                                extents[0].e_min = extents[n].e_min;
                                                        if (extents[n].e_max > extents[0].e_max)
                                                                extents[0].e_max = extents[n].e_max;
                                                }
                                                /*
                                                 * now setup to run through the remaining pages
                                                 * to determine the overall min and max
                                                 * offset for the specified range
                                                 */
                                                extents[0].e_base = 0;
                                                e_mask = 0;
                                                num_of_extents = 1;

                                                /*
                                                 * by continuing, we'll reprocess the
                                                 * page that forced us to abandon trying
                                                 * to develop multiple extents
                                                 */
                                                continue;
                                        }
                                }
                        }
                        m = next;
                }
        } else {
                extents[0].e_min = offset;
                extents[0].e_max = offset + (size - 1);

                num_of_extents = 1;
        }
        for (n = 0; n < num_of_extents; n++) {
                if (vm_object_update_extent(object, extents[n].e_min, extents[n].e_max, resid_offset, io_errno,
                                            should_flush, should_return, should_iosync, protection))
                        data_returned = TRUE;
        }
        return (data_returned);
}


/*
 *      Routine:        memory_object_synchronize_completed [user interface]
 *
 *      Tell kernel that previously synchronized data
 *      (memory_object_synchronize) has been queue or placed on the
 *      backing storage.
 *
 *      Note: there may be multiple synchronize requests for a given
 *      memory object outstanding but they will not overlap.
 */

kern_return_t
memory_object_synchronize_completed(
        memory_object_control_t control,
        memory_object_offset_t  offset,
        memory_object_size_t    length)
{
        vm_object_t                     object;
        msync_req_t                     msr;

        object = memory_object_control_to_vm_object(control);

        XPR(XPR_MEMORY_OBJECT,
            "m_o_sync_completed, object 0x%X, offset 0x%X length 0x%X\n",
            object, offset, length, 0, 0);

        /*
         *      Look for bogus arguments
         */

        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        vm_object_lock(object);

/*
 *      search for sync request structure
 */
        queue_iterate(&object->msr_q, msr, msync_req_t, msr_q) {
                if (msr->offset == offset && msr->length == length) {
                        queue_remove(&object->msr_q, msr, msync_req_t, msr_q);
                        break;
                }
        }/* queue_iterate */

        if (queue_end(&object->msr_q, (queue_entry_t)msr)) {
                vm_object_unlock(object);
                return KERN_INVALID_ARGUMENT;
        }

        msr_lock(msr);
        vm_object_unlock(object);
        msr->flag = VM_MSYNC_DONE;
        msr_unlock(msr);
        thread_wakeup((event_t) msr);

        return KERN_SUCCESS;
}/* memory_object_synchronize_completed */

static kern_return_t
vm_object_set_attributes_common(
        vm_object_t     object,
        boolean_t       may_cache,
        memory_object_copy_strategy_t copy_strategy,
        boolean_t       temporary,
        boolean_t       silent_overwrite,
        boolean_t       advisory_pageout)
{
        boolean_t       object_became_ready;

        XPR(XPR_MEMORY_OBJECT,
            "m_o_set_attr_com, object 0x%X flg %x strat %d\n",
            object, (may_cache&1)|((temporary&1)<1), copy_strategy, 0, 0);

        if (object == VM_OBJECT_NULL)
                return(KERN_INVALID_ARGUMENT);

        /*
         *      Verify the attributes of importance
         */

        switch(copy_strategy) {
                case MEMORY_OBJECT_COPY_NONE:
                case MEMORY_OBJECT_COPY_DELAY:
                        break;
                default:
                        return(KERN_INVALID_ARGUMENT);
        }

#if     !ADVISORY_PAGEOUT
        if (silent_overwrite || advisory_pageout)
                return(KERN_INVALID_ARGUMENT);

#endif  /* !ADVISORY_PAGEOUT */
        if (may_cache)
                may_cache = TRUE;
        if (temporary)
                temporary = TRUE;

        vm_object_lock(object);

        /*
         *      Copy the attributes
         */
        assert(!object->internal);
        object_became_ready = !object->pager_ready;
        object->copy_strategy = copy_strategy;
        object->can_persist = may_cache;
        object->temporary = temporary;
        object->silent_overwrite = silent_overwrite;
        object->advisory_pageout = advisory_pageout;

        /*
         *      Wake up anyone waiting for the ready attribute
         *      to become asserted.
         */

        if (object_became_ready) {
                object->pager_ready = TRUE;
                vm_object_wakeup(object, VM_OBJECT_EVENT_PAGER_READY);
        }

        vm_object_unlock(object);

        return(KERN_SUCCESS);
}

/*
 *      Set the memory object attribute as provided.
 *
 *      XXX This routine cannot be completed until the vm_msync, clean 
 *           in place, and cluster work is completed. See ifdef notyet
 *           below and note that vm_object_set_attributes_common()
 *           may have to be expanded.
 */
kern_return_t
memory_object_change_attributes(
        memory_object_control_t         control,
        memory_object_flavor_t          flavor,
        memory_object_info_t            attributes,
        mach_msg_type_number_t          count)
{
        vm_object_t                     object;
        kern_return_t                   result = KERN_SUCCESS;
        boolean_t                       temporary;
        boolean_t                       may_cache;
        boolean_t                       invalidate;
        memory_object_copy_strategy_t   copy_strategy;
        boolean_t                       silent_overwrite;
        boolean_t                       advisory_pageout;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        vm_object_lock(object);

        temporary = object->temporary;
        may_cache = object->can_persist;
        copy_strategy = object->copy_strategy;
        silent_overwrite = object->silent_overwrite;
        advisory_pageout = object->advisory_pageout;
#if notyet
        invalidate = object->invalidate;
#endif
        vm_object_unlock(object);       

        switch (flavor) {
            case OLD_MEMORY_OBJECT_BEHAVIOR_INFO:
            {
                old_memory_object_behave_info_t     behave;

                if (count != OLD_MEMORY_OBJECT_BEHAVE_INFO_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
                        break;
                }

                behave = (old_memory_object_behave_info_t) attributes;

                temporary = behave->temporary;
                invalidate = behave->invalidate;
                copy_strategy = behave->copy_strategy;

                break;
            }

            case MEMORY_OBJECT_BEHAVIOR_INFO:
            {
                memory_object_behave_info_t     behave;

                if (count != MEMORY_OBJECT_BEHAVE_INFO_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
                        break;
                }

                behave = (memory_object_behave_info_t) attributes;

                temporary = behave->temporary;
                invalidate = behave->invalidate;
                copy_strategy = behave->copy_strategy;
                silent_overwrite = behave->silent_overwrite;
                advisory_pageout = behave->advisory_pageout;
                break;
            }

            case MEMORY_OBJECT_PERFORMANCE_INFO:
            {
                memory_object_perf_info_t       perf;

                if (count != MEMORY_OBJECT_PERF_INFO_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
                        break;
                }

                perf = (memory_object_perf_info_t) attributes;

                may_cache = perf->may_cache;

                break;
            }

            case OLD_MEMORY_OBJECT_ATTRIBUTE_INFO:
            {
                old_memory_object_attr_info_t   attr;

                if (count != OLD_MEMORY_OBJECT_ATTR_INFO_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
                        break;
                }

                attr = (old_memory_object_attr_info_t) attributes;

                may_cache = attr->may_cache;
                copy_strategy = attr->copy_strategy;

                break;
            }

            case MEMORY_OBJECT_ATTRIBUTE_INFO:
            {
                memory_object_attr_info_t       attr;

                if (count != MEMORY_OBJECT_ATTR_INFO_COUNT) {
                        result = KERN_INVALID_ARGUMENT;
                        break;
                }

                attr = (memory_object_attr_info_t) attributes;

                copy_strategy = attr->copy_strategy;
                may_cache = attr->may_cache_object;
                temporary = attr->temporary;

                break;
            }

            default:
                result = KERN_INVALID_ARGUMENT;
                break;
        }

        if (result != KERN_SUCCESS)
                return(result);

        if (copy_strategy == MEMORY_OBJECT_COPY_TEMPORARY) {
                copy_strategy = MEMORY_OBJECT_COPY_DELAY;
                temporary = TRUE;
        } else {
                temporary = FALSE;
        }

        /*
         * XXX  may_cache may become a tri-valued variable to handle
         * XXX  uncache if not in use.
         */
        return (vm_object_set_attributes_common(object,
                                                     may_cache,
                                                     copy_strategy,
                                                     temporary,
                                                     silent_overwrite,
                                                     advisory_pageout));
}

kern_return_t
memory_object_get_attributes(
        memory_object_control_t control,
        memory_object_flavor_t  flavor,
        memory_object_info_t    attributes,     /* pointer to OUT array */
        mach_msg_type_number_t  *count)         /* IN/OUT */
{
        kern_return_t           ret = KERN_SUCCESS;
        vm_object_t             object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        vm_object_lock(object);

        switch (flavor) {
            case OLD_MEMORY_OBJECT_BEHAVIOR_INFO:
            {
                old_memory_object_behave_info_t behave;

                if (*count < OLD_MEMORY_OBJECT_BEHAVE_INFO_COUNT) {
                        ret = KERN_INVALID_ARGUMENT;
                        break;
                }

                behave = (old_memory_object_behave_info_t) attributes;
                behave->copy_strategy = object->copy_strategy;
                behave->temporary = object->temporary;
#if notyet      /* remove when vm_msync complies and clean in place fini */
                behave->invalidate = object->invalidate;
#else
                behave->invalidate = FALSE;
#endif

                *count = OLD_MEMORY_OBJECT_BEHAVE_INFO_COUNT;
                break;
            }

            case MEMORY_OBJECT_BEHAVIOR_INFO:
            {
                memory_object_behave_info_t     behave;

                if (*count < MEMORY_OBJECT_BEHAVE_INFO_COUNT) {
                        ret = KERN_INVALID_ARGUMENT;
                        break;
                }

                behave = (memory_object_behave_info_t) attributes;
                behave->copy_strategy = object->copy_strategy;
                behave->temporary = object->temporary;
#if notyet      /* remove when vm_msync complies and clean in place fini */
                behave->invalidate = object->invalidate;
#else
                behave->invalidate = FALSE;
#endif
                behave->advisory_pageout = object->advisory_pageout;
                behave->silent_overwrite = object->silent_overwrite;
                *count = MEMORY_OBJECT_BEHAVE_INFO_COUNT;
                break;
            }

            case MEMORY_OBJECT_PERFORMANCE_INFO:
            {
                memory_object_perf_info_t       perf;

                if (*count < MEMORY_OBJECT_PERF_INFO_COUNT) {
                        ret = KERN_INVALID_ARGUMENT;
                        break;
                }

                perf = (memory_object_perf_info_t) attributes;
                perf->cluster_size = PAGE_SIZE;
                perf->may_cache = object->can_persist;

                *count = MEMORY_OBJECT_PERF_INFO_COUNT;
                break;
            }

            case OLD_MEMORY_OBJECT_ATTRIBUTE_INFO:
            {
                old_memory_object_attr_info_t       attr;

                if (*count < OLD_MEMORY_OBJECT_ATTR_INFO_COUNT) {
                        ret = KERN_INVALID_ARGUMENT;
                        break;
                }

                attr = (old_memory_object_attr_info_t) attributes;
                attr->may_cache = object->can_persist;
                attr->copy_strategy = object->copy_strategy;

                *count = OLD_MEMORY_OBJECT_ATTR_INFO_COUNT;
                break;
            }

            case MEMORY_OBJECT_ATTRIBUTE_INFO:
            {
                memory_object_attr_info_t       attr;

                if (*count < MEMORY_OBJECT_ATTR_INFO_COUNT) {
                        ret = KERN_INVALID_ARGUMENT;
                        break;
                }

                attr = (memory_object_attr_info_t) attributes;
                attr->copy_strategy = object->copy_strategy;
                attr->cluster_size = PAGE_SIZE;
                attr->may_cache_object = object->can_persist;
                attr->temporary = object->temporary;

                *count = MEMORY_OBJECT_ATTR_INFO_COUNT;
                break;
            }

            default:
                ret = KERN_INVALID_ARGUMENT;
                break;
        }

        vm_object_unlock(object);

        return(ret);
}


kern_return_t
memory_object_iopl_request(
        ipc_port_t              port,
        memory_object_offset_t  offset,
        upl_size_t              *upl_size,
        upl_t                   *upl_ptr,
        upl_page_info_array_t   user_page_list,
        unsigned int            *page_list_count,
        int                     *flags)
{
        vm_object_t             object;
        kern_return_t           ret;
        int                     caller_flags;

        caller_flags = *flags;

        if (caller_flags & ~UPL_VALID_FLAGS) {
                /*
                 * For forward compatibility's sake,
                 * reject any unknown flag.
                 */
                return KERN_INVALID_VALUE;
        }

        if (ip_kotype(port) == IKOT_NAMED_ENTRY) {
                vm_named_entry_t        named_entry;

                named_entry = (vm_named_entry_t)port->ip_kobject;
                /* a few checks to make sure user is obeying rules */
                if(*upl_size == 0) {
                        if(offset >= named_entry->size)
                                return(KERN_INVALID_RIGHT);
                        *upl_size = (upl_size_t)(named_entry->size - offset);
                        if (*upl_size != named_entry->size - offset)
                                return KERN_INVALID_ARGUMENT;
                }
                if(caller_flags & UPL_COPYOUT_FROM) {
                        if((named_entry->protection & VM_PROT_READ) 
                                                != VM_PROT_READ) {
                                return(KERN_INVALID_RIGHT);
                        }
                } else {
                        if((named_entry->protection & 
                                (VM_PROT_READ | VM_PROT_WRITE)) 
                                != (VM_PROT_READ | VM_PROT_WRITE)) {
                                return(KERN_INVALID_RIGHT);
                        }
                }
                if(named_entry->size < (offset + *upl_size))
                        return(KERN_INVALID_ARGUMENT);

                /* the callers parameter offset is defined to be the */
                /* offset from beginning of named entry offset in object */
                offset = offset + named_entry->offset;

                if(named_entry->is_sub_map) 
                        return (KERN_INVALID_ARGUMENT);
                
                named_entry_lock(named_entry);

                if (named_entry->is_pager) {
                        object = vm_object_enter(named_entry->backing.pager, 
                                        named_entry->offset + named_entry->size, 
                                        named_entry->internal, 
                                        FALSE,
                                        FALSE);
                        if (object == VM_OBJECT_NULL) {
                                named_entry_unlock(named_entry);
                                return(KERN_INVALID_OBJECT);
                        }

                        /* JMM - drop reference on pager here? */

                        /* create an extra reference for the named entry */
                        vm_object_lock(object);
                        vm_object_reference_locked(object);
                        named_entry->backing.object = object;
                        named_entry->is_pager = FALSE;
                        named_entry_unlock(named_entry);

                        /* wait for object to be ready */
                        while (!object->pager_ready) {
                                vm_object_wait(object,
                                                VM_OBJECT_EVENT_PAGER_READY,
                                                THREAD_UNINT);
                                vm_object_lock(object);
                        }
                        vm_object_unlock(object);
                } else {
                        /* This is the case where we are going to map */
                        /* an already mapped object.  If the object is */
                        /* not ready it is internal.  An external     */
                        /* object cannot be mapped until it is ready  */
                        /* we can therefore avoid the ready check     */
                        /* in this case.  */
                        object = named_entry->backing.object;
                        vm_object_reference(object);
                        named_entry_unlock(named_entry);
                }
        } else if (ip_kotype(port) == IKOT_MEM_OBJ_CONTROL) {
                memory_object_control_t control;
                control = (memory_object_control_t) port;
                if (control == NULL)
                        return (KERN_INVALID_ARGUMENT);
                object = memory_object_control_to_vm_object(control);
                if (object == VM_OBJECT_NULL)
                        return (KERN_INVALID_ARGUMENT);
                vm_object_reference(object);
        } else {
                return KERN_INVALID_ARGUMENT;
        }
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        if (!object->private) {
                if (*upl_size > (MAX_UPL_TRANSFER*PAGE_SIZE))
                        *upl_size = (MAX_UPL_TRANSFER*PAGE_SIZE);
                if (object->phys_contiguous) {
                        *flags = UPL_PHYS_CONTIG;
                } else {
                        *flags = 0;
                }
        } else {
                *flags = UPL_DEV_MEMORY | UPL_PHYS_CONTIG;
        }

        ret = vm_object_iopl_request(object,
                                     offset,
                                     *upl_size,
                                     upl_ptr,
                                     user_page_list,
                                     page_list_count,
                                     caller_flags);
        vm_object_deallocate(object);
        return ret;
}

/*  
 *      Routine:        memory_object_upl_request [interface]
 *      Purpose:
 *              Cause the population of a portion of a vm_object.
 *              Depending on the nature of the request, the pages
 *              returned may be contain valid data or be uninitialized.
 *
 */

kern_return_t
memory_object_upl_request(
        memory_object_control_t control,
        memory_object_offset_t  offset,
        upl_size_t              size,
        upl_t                   *upl_ptr,
        upl_page_info_array_t   user_page_list,
        unsigned int            *page_list_count,
        int                     cntrl_flags)
{
        vm_object_t             object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_TERMINATED);

        return vm_object_upl_request(object,
                                     offset,
                                     size,
                                     upl_ptr,
                                     user_page_list,
                                     page_list_count,
                                     cntrl_flags);
}

/*  
 *      Routine:        memory_object_super_upl_request [interface]
 *      Purpose:
 *              Cause the population of a portion of a vm_object
 *              in much the same way as memory_object_upl_request.
 *              Depending on the nature of the request, the pages
 *              returned may be contain valid data or be uninitialized.
 *              However, the region may be expanded up to the super
 *              cluster size provided.
 */

kern_return_t
memory_object_super_upl_request(
        memory_object_control_t control,
        memory_object_offset_t  offset,
        upl_size_t              size,
        upl_size_t              super_cluster,
        upl_t                   *upl,
        upl_page_info_t         *user_page_list,
        unsigned int            *page_list_count,
        int                     cntrl_flags)
{
        vm_object_t             object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        return vm_object_super_upl_request(object,
                                           offset,
                                           size,
                                           super_cluster,
                                           upl,
                                           user_page_list,
                                           page_list_count,
                                           cntrl_flags);
}

kern_return_t
memory_object_cluster_size(memory_object_control_t control, memory_object_offset_t *start,
                           vm_size_t *length, uint32_t *io_streaming, memory_object_fault_info_t fault_info)
{
        vm_object_t             object;

        object = memory_object_control_to_vm_object(control);

        if (object == VM_OBJECT_NULL || object->paging_offset > *start)
                return (KERN_INVALID_ARGUMENT);

        *start -= object->paging_offset;

        vm_object_cluster_size(object, (vm_object_offset_t *)start, length, (vm_object_fault_info_t)fault_info, io_streaming);

        *start += object->paging_offset;

        return (KERN_SUCCESS);
}


int vm_stat_discard_cleared_reply = 0;
int vm_stat_discard_cleared_unset = 0;
int vm_stat_discard_cleared_too_late = 0;



/*
 *      Routine:        host_default_memory_manager [interface]
 *      Purpose:
 *              set/get the default memory manager port and default cluster
 *              size.
 *
 *              If successful, consumes the supplied naked send right.
 */
kern_return_t
host_default_memory_manager(
        host_priv_t             host_priv,
        memory_object_default_t *default_manager,
        __unused memory_object_cluster_size_t cluster_size)
{
        memory_object_default_t current_manager;
        memory_object_default_t new_manager;
        memory_object_default_t returned_manager;
        kern_return_t result = KERN_SUCCESS;

        if (host_priv == HOST_PRIV_NULL)
                return(KERN_INVALID_HOST);

        assert(host_priv == &realhost);

        new_manager = *default_manager;
        lck_mtx_lock(&memory_manager_default_lock);
        current_manager = memory_manager_default;
        returned_manager = MEMORY_OBJECT_DEFAULT_NULL;

        if (new_manager == MEMORY_OBJECT_DEFAULT_NULL) {
                /*
                 *      Retrieve the current value.
                 */
                returned_manager = current_manager;
                memory_object_default_reference(returned_manager);
        } else {

                /*
                 *      If this is the first non-null manager, start
                 *      up the internal pager support.
                 */
                if (current_manager == MEMORY_OBJECT_DEFAULT_NULL) {
                        result = vm_pageout_internal_start();
                        if (result != KERN_SUCCESS)
                                goto out;
                }

                /*
                 *      Retrieve the current value,
                 *      and replace it with the supplied value.
                 *      We return the old reference to the caller
                 *      but we have to take a reference on the new
                 *      one.
                 */
                returned_manager = current_manager;
                memory_manager_default = new_manager;
                memory_object_default_reference(new_manager);

                /*
                 *      In case anyone's been waiting for a memory
                 *      manager to be established, wake them up.
                 */

                thread_wakeup((event_t) &memory_manager_default);

                /*
                 * Now that we have a default pager for anonymous memory,
                 * reactivate all the throttled pages (i.e. dirty pages with
                 * no pager).
                 */
                if (current_manager == MEMORY_OBJECT_DEFAULT_NULL) {
                        vm_page_reactivate_all_throttled();
                }
        }
 out:
        lck_mtx_unlock(&memory_manager_default_lock);

        *default_manager = returned_manager;
        return(result);
}

/*
 *      Routine:        memory_manager_default_reference
 *      Purpose:
 *              Returns a naked send right for the default
 *              memory manager.  The returned right is always
 *              valid (not IP_NULL or IP_DEAD).
 */

__private_extern__ memory_object_default_t
memory_manager_default_reference(void)
{
        memory_object_default_t current_manager;

        lck_mtx_lock(&memory_manager_default_lock);
        current_manager = memory_manager_default;
        while (current_manager == MEMORY_OBJECT_DEFAULT_NULL) {
                wait_result_t res;

                res = lck_mtx_sleep(&memory_manager_default_lock,
                                        LCK_SLEEP_DEFAULT,
                                        (event_t) &memory_manager_default,
                                        THREAD_UNINT);
                assert(res == THREAD_AWAKENED);
                current_manager = memory_manager_default;
        }
        memory_object_default_reference(current_manager);
        lck_mtx_unlock(&memory_manager_default_lock);

        return current_manager;
}

/*
 *      Routine:        memory_manager_default_check
 *
 *      Purpose:
 *              Check whether a default memory manager has been set
 *              up yet, or not. Returns KERN_SUCCESS if dmm exists,
 *              and KERN_FAILURE if dmm does not exist.
 *
 *              If there is no default memory manager, log an error,
 *              but only the first time.
 *
 */
__private_extern__ kern_return_t
memory_manager_default_check(void)
{
        memory_object_default_t current;

        lck_mtx_lock(&memory_manager_default_lock);
        current = memory_manager_default;
        if (current == MEMORY_OBJECT_DEFAULT_NULL) {
                static boolean_t logged;        /* initialized to 0 */
                boolean_t       complain = !logged;
                logged = TRUE;
                lck_mtx_unlock(&memory_manager_default_lock);
                if (complain)
                        printf("Warning: No default memory manager\n");
                return(KERN_FAILURE);
        } else {
                lck_mtx_unlock(&memory_manager_default_lock);
                return(KERN_SUCCESS);
        }
}

__private_extern__ void
memory_manager_default_init(void)
{
        memory_manager_default = MEMORY_OBJECT_DEFAULT_NULL;
        lck_mtx_init(&memory_manager_default_lock, &vm_object_lck_grp, &vm_object_lck_attr);
}



/* Allow manipulation of individual page state.  This is actually part of */
/* the UPL regimen but takes place on the object rather than on a UPL */

kern_return_t
memory_object_page_op(
        memory_object_control_t control,
        memory_object_offset_t  offset,
        int                     ops,
        ppnum_t                 *phys_entry,
        int                     *flags)
{
        vm_object_t             object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        return vm_object_page_op(object, offset, ops, phys_entry, flags);
}

/*
 * memory_object_range_op offers performance enhancement over 
 * memory_object_page_op for page_op functions which do not require page 
 * level state to be returned from the call.  Page_op was created to provide 
 * a low-cost alternative to page manipulation via UPLs when only a single 
 * page was involved.  The range_op call establishes the ability in the _op 
 * family of functions to work on multiple pages where the lack of page level
 * state handling allows the caller to avoid the overhead of the upl structures.
 */

kern_return_t
memory_object_range_op(
        memory_object_control_t control,
        memory_object_offset_t  offset_beg,
        memory_object_offset_t  offset_end,
        int                     ops,
        int                     *range)
{
        vm_object_t             object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        return vm_object_range_op(object,
                                  offset_beg,
                                  offset_end,
                                  ops,
                                  (uint32_t *) range);
}


kern_return_t
memory_object_pages_resident(
        memory_object_control_t control,
        boolean_t                       *       has_pages_resident)
{
        vm_object_t             object;

        *has_pages_resident = FALSE;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return (KERN_INVALID_ARGUMENT);

        if (object->resident_page_count)
                *has_pages_resident = TRUE;
        
        return (KERN_SUCCESS);
}

kern_return_t
memory_object_signed(
        memory_object_control_t control,
        boolean_t               is_signed)
{
        vm_object_t     object;

        object = memory_object_control_to_vm_object(control);
        if (object == VM_OBJECT_NULL)
                return KERN_INVALID_ARGUMENT;

        vm_object_lock(object);
        object->code_signed = is_signed;
        vm_object_unlock(object);

        return KERN_SUCCESS;
}

static zone_t mem_obj_control_zone;

__private_extern__ void
memory_object_control_bootstrap(void)
{
        int     i;

        i = (vm_size_t) sizeof (struct memory_object_control);
        mem_obj_control_zone = zinit (i, 8192*i, 4096, "mem_obj_control");
        zone_change(mem_obj_control_zone, Z_NOENCRYPT, TRUE);
        return;
}

__private_extern__ memory_object_control_t
memory_object_control_allocate(
        vm_object_t             object)
{                      
        memory_object_control_t control;

        control = (memory_object_control_t)zalloc(mem_obj_control_zone);
        if (control != MEMORY_OBJECT_CONTROL_NULL) {
                control->moc_object = object;
                control->moc_ikot = IKOT_MEM_OBJ_CONTROL; /* fake ip_kotype */
        }
        return (control);
}

__private_extern__ void
memory_object_control_collapse(
        memory_object_control_t control,                       
        vm_object_t             object)
{                      
        assert((control->moc_object != VM_OBJECT_NULL) &&
               (control->moc_object != object));
        control->moc_object = object;
}

__private_extern__ vm_object_t
memory_object_control_to_vm_object(
        memory_object_control_t control)
{
        if (control == MEMORY_OBJECT_CONTROL_NULL ||
            control->moc_ikot != IKOT_MEM_OBJ_CONTROL)
                return VM_OBJECT_NULL;

        return (control->moc_object);
}

memory_object_control_t
convert_port_to_mo_control(
        __unused mach_port_t    port)
{
        return MEMORY_OBJECT_CONTROL_NULL;
}


mach_port_t
convert_mo_control_to_port(
        __unused memory_object_control_t        control)
{
        return MACH_PORT_NULL;
}

void
memory_object_control_reference(
        __unused memory_object_control_t        control)
{
        return;
}

/*
 * We only every issue one of these references, so kill it
 * when that gets released (should switch the real reference
 * counting in true port-less EMMI).
 */
void
memory_object_control_deallocate(
        memory_object_control_t control)
{
        zfree(mem_obj_control_zone, control);
}

void
memory_object_control_disable(
        memory_object_control_t control)
{
        assert(control->moc_object != VM_OBJECT_NULL);
        control->moc_object = VM_OBJECT_NULL;
}

void
memory_object_default_reference(
        memory_object_default_t dmm)
{
        ipc_port_make_send(dmm);
}

void
memory_object_default_deallocate(
        memory_object_default_t dmm)
{
        ipc_port_release_send(dmm);
}

memory_object_t
convert_port_to_memory_object(
        __unused mach_port_t    port)
{
        return (MEMORY_OBJECT_NULL);
}


mach_port_t
convert_memory_object_to_port(
        __unused memory_object_t        object)
{
        return (MACH_PORT_NULL);
}


/* Routine memory_object_reference */
void memory_object_reference(
        memory_object_t memory_object)
{
        (memory_object->mo_pager_ops->memory_object_reference)(
                memory_object);
}

/* Routine memory_object_deallocate */
void memory_object_deallocate(
        memory_object_t memory_object)
{
        (memory_object->mo_pager_ops->memory_object_deallocate)(
                 memory_object);
}


/* Routine memory_object_init */
kern_return_t memory_object_init
(
        memory_object_t memory_object,
        memory_object_control_t memory_control,
        memory_object_cluster_size_t memory_object_page_size
)
{
        return (memory_object->mo_pager_ops->memory_object_init)(
                memory_object,
                memory_control,
                memory_object_page_size);
}

/* Routine memory_object_terminate */
kern_return_t memory_object_terminate
(
        memory_object_t memory_object
)
{
        return (memory_object->mo_pager_ops->memory_object_terminate)(
                memory_object);
}

/* Routine memory_object_data_request */
kern_return_t memory_object_data_request
(
        memory_object_t memory_object,
        memory_object_offset_t offset,
        memory_object_cluster_size_t length,
        vm_prot_t desired_access,
        memory_object_fault_info_t fault_info
)
{
        return (memory_object->mo_pager_ops->memory_object_data_request)(
                memory_object,
                offset, 
                length,
                desired_access,
                fault_info);
}

/* Routine memory_object_data_return */
kern_return_t memory_object_data_return
(
        memory_object_t memory_object,
        memory_object_offset_t offset,
        memory_object_cluster_size_t size,
        memory_object_offset_t *resid_offset,
        int     *io_error,
        boolean_t dirty,
        boolean_t kernel_copy,
        int     upl_flags
)
{
        return (memory_object->mo_pager_ops->memory_object_data_return)(
                memory_object,
                offset,
                size,
                resid_offset,
                io_error,
                dirty,
                kernel_copy,
                upl_flags);
}

/* Routine memory_object_data_initialize */
kern_return_t memory_object_data_initialize
(
        memory_object_t memory_object,
        memory_object_offset_t offset,
        memory_object_cluster_size_t size
)
{
        return (memory_object->mo_pager_ops->memory_object_data_initialize)(
                memory_object,
                offset,
                size);
}

/* Routine memory_object_data_unlock */
kern_return_t memory_object_data_unlock
(
        memory_object_t memory_object,
        memory_object_offset_t offset,
        memory_object_size_t size,
        vm_prot_t desired_access
)
{
        return (memory_object->mo_pager_ops->memory_object_data_unlock)(
                memory_object,
                offset,
                size,
                desired_access);
}

/* Routine memory_object_synchronize */
kern_return_t memory_object_synchronize
(
        memory_object_t memory_object,
        memory_object_offset_t offset,
        memory_object_size_t size,
        vm_sync_t sync_flags
)
{
        return (memory_object->mo_pager_ops->memory_object_synchronize)(
                memory_object,
                offset,
                size,
                sync_flags);
}


/*
 * memory_object_map() is called by VM (in vm_map_enter() and its variants)
 * each time a "named" VM object gets mapped directly or indirectly
 * (copy-on-write mapping).  A "named" VM object has an extra reference held
 * by the pager to keep it alive until the pager decides that the 
 * memory object (and its VM object) can be reclaimed.
 * VM calls memory_object_last_unmap() (in vm_object_deallocate()) when all
 * the mappings of that memory object have been removed.
 *
 * For a given VM object, calls to memory_object_map() and memory_object_unmap()
 * are serialized (through object->mapping_in_progress), to ensure that the
 * pager gets a consistent view of the mapping status of the memory object.
 *
 * This allows the pager to keep track of how many times a memory object
 * has been mapped and with which protections, to decide when it can be
 * reclaimed.
 */

/* Routine memory_object_map */
kern_return_t memory_object_map
(
        memory_object_t memory_object,
        vm_prot_t prot
)
{
        return (memory_object->mo_pager_ops->memory_object_map)(
                memory_object,
                prot);
}

/* Routine memory_object_last_unmap */
kern_return_t memory_object_last_unmap
(
        memory_object_t memory_object
)
{
        return (memory_object->mo_pager_ops->memory_object_last_unmap)(
                memory_object);
}

/* Routine memory_object_create */
kern_return_t memory_object_create
(
        memory_object_default_t default_memory_manager,
        vm_size_t new_memory_object_size,
        memory_object_t *new_memory_object
)
{
        return default_pager_memory_object_create(default_memory_manager,
                                                  new_memory_object_size,
                                                  new_memory_object);
}

upl_t
convert_port_to_upl(
        ipc_port_t      port)
{
        upl_t upl;

        ip_lock(port);
        if (!ip_active(port) || (ip_kotype(port) != IKOT_UPL)) {
                        ip_unlock(port);
                        return (upl_t)NULL;
        }
        upl = (upl_t) port->ip_kobject;
        ip_unlock(port);
        upl_lock(upl);
        upl->ref_count+=1;
        upl_unlock(upl);
        return upl;
}

mach_port_t
convert_upl_to_port(
        __unused upl_t          upl)
{
        return MACH_PORT_NULL;
}

__private_extern__ void
upl_no_senders(
        __unused ipc_port_t                             port,
        __unused mach_port_mscount_t    mscount)
{
        return;
}