/*
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
* Copyright (c) 1994 John S. Dyson
* All rights reserved.
* Copyright (c) 1994 David Greenman
* 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 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.
*
* from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*
* $Id: vm_fault.c,v 1.35 1995/11/02 06:42:47 davidg Exp $
*/
/*
* Page fault handling module.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/resource.h>
#include <sys/signalvar.h>
#include <sys/resourcevar.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_kern.h>
#include <vm/vm_pager.h>
#include <vm/vnode_pager.h>
#include <vm/swap_pager.h>
int vm_fault_additional_pages __P((vm_page_t, int, int, vm_page_t *, int *));
#define VM_FAULT_READ_AHEAD 4
#define VM_FAULT_READ_BEHIND 3
#define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
/*
* vm_fault:
*
* Handle a page fault occuring at the given address,
* requiring the given permissions, in the map specified.
* If successful, the page is inserted into the
* associated physical map.
*
* NOTE: the given address should be truncated to the
* proper page address.
*
* KERN_SUCCESS is returned if the page fault is handled; otherwise,
* a standard error specifying why the fault is fatal is returned.
*
*
* The map in question must be referenced, and remains so.
* Caller may hold no locks.
*/
int
vm_fault(map, vaddr, fault_type, change_wiring)
vm_map_t map;
vm_offset_t vaddr;
vm_prot_t fault_type;
boolean_t change_wiring;
{
vm_object_t first_object;
vm_offset_t first_offset;
vm_map_entry_t entry;
register vm_object_t object;
register vm_offset_t offset;
vm_page_t m;
vm_page_t first_m;
vm_prot_t prot;
int result;
boolean_t wired;
boolean_t su;
boolean_t lookup_still_valid;
boolean_t page_exists;
vm_page_t old_m;
vm_object_t next_object;
vm_page_t marray[VM_FAULT_READ];
int spl;
int hardfault = 0;
struct vnode *vp = NULL;
cnt.v_vm_faults++; /* needs lock XXX */
/*
* Recovery actions
*/
#define FREE_PAGE(m) { \
PAGE_WAKEUP(m); \
vm_page_free(m); \
}
#define RELEASE_PAGE(m) { \
PAGE_WAKEUP(m); \
if ((m->flags & PG_ACTIVE) == 0) vm_page_activate(m); \
}
#define UNLOCK_MAP { \
if (lookup_still_valid) { \
vm_map_lookup_done(map, entry); \
lookup_still_valid = FALSE; \
} \
}
#define UNLOCK_THINGS { \
vm_object_pip_wakeup(object); \
if (object != first_object) { \
FREE_PAGE(first_m); \
vm_object_pip_wakeup(first_object); \
} \
UNLOCK_MAP; \
if (vp != NULL) VOP_UNLOCK(vp); \
}
#define UNLOCK_AND_DEALLOCATE { \
UNLOCK_THINGS; \
vm_object_deallocate(first_object); \
}
RetryFault:;
/*
* Find the backing store object and offset into it to begin the
* search.
*/
if ((result = vm_map_lookup(&map, vaddr,
fault_type, &entry, &first_object,
&first_offset, &prot, &wired, &su)) != KERN_SUCCESS) {
return (result);
}
vp = vnode_pager_lock(first_object);
lookup_still_valid = TRUE;
if (wired)
fault_type = prot;
first_m = NULL;
/*
* Make a reference to this object to prevent its disposal while we
* are messing with it. Once we have the reference, the map is free
* to be diddled. Since objects reference their shadows (and copies),
* they will stay around as well.
*/
first_object->ref_count++;
first_object->paging_in_progress++;
/*
* INVARIANTS (through entire routine):
*
* 1) At all times, we must either have the object lock or a busy
* page in some object to prevent some other process from trying to
* bring in the same page.
*
* Note that we cannot hold any locks during the pager access or when
* waiting for memory, so we use a busy page then.
*
* Note also that we aren't as concerned about more than one thead
* attempting to pager_data_unlock the same page at once, so we don't
* hold the page as busy then, but do record the highest unlock value
* so far. [Unlock requests may also be delivered out of order.]
*
* 2) Once we have a busy page, we must remove it from the pageout
* queues, so that the pageout daemon will not grab it away.
*
* 3) To prevent another process from racing us down the shadow chain
* and entering a new page in the top object before we do, we must
* keep a busy page in the top object while following the shadow
* chain.
*
* 4) We must increment paging_in_progress on any object for which
* we have a busy page, to prevent vm_object_collapse from removing
* the busy page without our noticing.
*/
/*
* Search for the page at object/offset.
*/
object = first_object;
offset = first_offset;
/*
* See whether this page is resident
*/
while (TRUE) {
m = vm_page_lookup(object, offset);
if (m != NULL) {
/*
* If the page is being brought in, wait for it and
* then retry.
*/
if ((m->flags & PG_BUSY) || m->busy) {
int s;
UNLOCK_THINGS;
s = splhigh();
if ((m->flags & PG_BUSY) || m->busy) {
m->flags |= PG_WANTED | PG_REFERENCED;
cnt.v_intrans++;
tsleep(m, PSWP, "vmpfw", 0);
}
splx(s);
vm_object_deallocate(first_object);
goto RetryFault;
}
/*
* Mark page busy for other processes, and the pagedaemon.
*/
m->flags |= PG_BUSY;
if ((m->flags & PG_CACHE) &&
(cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_reserved) {
UNLOCK_AND_DEALLOCATE;
VM_WAIT;
PAGE_WAKEUP(m);
goto RetryFault;
}
if (m->valid && ((m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
m->object != kernel_object && m->object != kmem_object) {
goto readrest;
}
break;
}
if (((object->type != OBJT_DEFAULT) && (!change_wiring || wired))
|| (object == first_object)) {
if (offset >= object->size) {
UNLOCK_AND_DEALLOCATE;
return (KERN_PROTECTION_FAILURE);
}
/*
* Allocate a new page for this object/offset pair.
*/
m = vm_page_alloc(object, offset,
vp?VM_ALLOC_NORMAL:(VM_ALLOC_NORMAL|VM_ALLOC_ZERO));
if (m == NULL) {
UNLOCK_AND_DEALLOCATE;
VM_WAIT;
goto RetryFault;
}
}
readrest:
if (object->type != OBJT_DEFAULT && (!change_wiring || wired)) {
int rv;
int faultcount;
int reqpage;
/*
* now we find out if any other pages should be paged
* in at this time this routine checks to see if the
* pages surrounding this fault reside in the same
* object as the page for this fault. If they do,
* then they are faulted in also into the object. The
* array "marray" returned contains an array of
* vm_page_t structs where one of them is the
* vm_page_t passed to the routine. The reqpage
* return value is the index into the marray for the
* vm_page_t passed to the routine.
*/
faultcount = vm_fault_additional_pages(
m, VM_FAULT_READ_BEHIND, VM_FAULT_READ_AHEAD,
marray, &reqpage);
/*
* Call the pager to retrieve the data, if any, after
* releasing the lock on the map.
*/
UNLOCK_MAP;
rv = faultcount ?
vm_pager_get_pages(object, marray, faultcount,
reqpage) : VM_PAGER_FAIL;
if (rv == VM_PAGER_OK) {
/*
* Found the page. Leave it busy while we play
* with it.
*/
/*
* Relookup in case pager changed page. Pager
* is responsible for disposition of old page
* if moved.
*/
m = vm_page_lookup(object, offset);
if( !m) {
UNLOCK_AND_DEALLOCATE;
goto RetryFault;
}
hardfault++;
break;
}
/*
* Remove the bogus page (which does not exist at this
* object/offset); before doing so, we must get back
* our object lock to preserve our invariant.
*
* Also wake up any other process that may want to bring
* in this page.
*
* If this is the top-level object, we must leave the
* busy page to prevent another process from rushing
* past us, and inserting the page in that object at
* the same time that we are.
*/
if (rv == VM_PAGER_ERROR)
printf("vm_fault: pager input (probably hardware) error, PID %d failure\n",
curproc->p_pid);
/*
* Data outside the range of the pager or an I/O error
*/
/*
* XXX - the check for kernel_map is a kludge to work
* around having the machine panic on a kernel space
* fault w/ I/O error.
*/
if (((map != kernel_map) && (rv == VM_PAGER_ERROR)) || (rv == VM_PAGER_BAD)) {
FREE_PAGE(m);
UNLOCK_AND_DEALLOCATE;
return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
}
if (object != first_object) {
FREE_PAGE(m);
/*
* XXX - we cannot just fall out at this
* point, m has been freed and is invalid!
*/
}
}
/*
* We get here if the object has default pager (or unwiring) or the
* pager doesn't have the page.
*/
if (object == first_object)
first_m = m;
/*
* Move on to the next object. Lock the next object before
* unlocking the current one.
*/
offset += object->backing_object_offset;
next_object = object->backing_object;
if (next_object == NULL) {
/*
* If there's no object left, fill the page in the top
* object with zeros.
*/
if (object != first_object) {
vm_object_pip_wakeup(object);
object = first_object;
offset = first_offset;
m = first_m;
}
first_m = NULL;
if ((m->flags & PG_ZERO) == 0)
vm_page_zero_fill(m);
m->valid = VM_PAGE_BITS_ALL;
cnt.v_zfod++;
break;
} else {
if (object != first_object) {
vm_object_pip_wakeup(object);
}
object = next_object;
object->paging_in_progress++;
}
}
if ((m->flags & PG_BUSY) == 0)
panic("vm_fault: not busy after main loop");
/*
* PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
* is held.]
*/
old_m = m; /* save page that would be copied */
/*
* If the page is being written, but isn't already owned by the
* top-level object, we have to copy it into a new page owned by the
* top-level object.
*/
if (object != first_object) {
/*
* We only really need to copy if we want to write it.
*/
if (fault_type & VM_PROT_WRITE) {
/*
* If we try to collapse first_object at this point,
* we may deadlock when we try to get the lock on an
* intermediate object (since we have the bottom
* object locked). We can't unlock the bottom object,
* because the page we found may move (by collapse) if
* we do.
*
* Instead, we first copy the page. Then, when we have
* no more use for the bottom object, we unlock it and
* try to collapse.
*
* Note that we copy the page even if we didn't need
* to... that's the breaks.
*/
/*
* We already have an empty page in first_object - use
* it.
*/
vm_page_copy(m, first_m);
first_m->valid = VM_PAGE_BITS_ALL;
/*
* If another map is truly sharing this page with us,
* we have to flush all uses of the original page,
* since we can't distinguish those which want the
* original from those which need the new copy.
*
* XXX If we know that only one map has access to this
* page, then we could avoid the pmap_page_protect()
* call.
*/
if ((m->flags & PG_ACTIVE) == 0)
vm_page_activate(m);
vm_page_protect(m, VM_PROT_NONE);
/*
* We no longer need the old page or object.
*/
PAGE_WAKEUP(m);
vm_object_pip_wakeup(object);
/*
* Only use the new page below...
*/
cnt.v_cow_faults++;
m = first_m;
object = first_object;
offset = first_offset;
/*
* Now that we've gotten the copy out of the way,
* let's try to collapse the top object.
*
* But we have to play ugly games with
* paging_in_progress to do that...
*/
vm_object_pip_wakeup(object);
vm_object_collapse(object);
object->paging_in_progress++;
} else {
prot &= ~VM_PROT_WRITE;
}
}
/*
* We must verify that the maps have not changed since our last
* lookup.
*/
if (!lookup_still_valid) {
vm_object_t retry_object;
vm_offset_t retry_offset;
vm_prot_t retry_prot;
/*
* Since map entries may be pageable, make sure we can take a
* page fault on them.
*/
/*
* To avoid trying to write_lock the map while another process
* has it read_locked (in vm_map_pageable), we do not try for
* write permission. If the page is still writable, we will
* get write permission. If it is not, or has been marked
* needs_copy, we enter the mapping without write permission,
* and will merely take another fault.
*/
result = vm_map_lookup(&map, vaddr, fault_type & ~VM_PROT_WRITE,
&entry, &retry_object, &retry_offset, &retry_prot, &wired, &su);
/*
* If we don't need the page any longer, put it on the active
* list (the easiest thing to do here). If no one needs it,
* pageout will grab it eventually.
*/
if (result != KERN_SUCCESS) {
RELEASE_PAGE(m);
UNLOCK_AND_DEALLOCATE;
return (result);
}
lookup_still_valid = TRUE;
if ((retry_object != first_object) ||
(retry_offset != first_offset)) {
RELEASE_PAGE(m);
UNLOCK_AND_DEALLOCATE;
goto RetryFault;
}
/*
* Check whether the protection has changed or the object has
* been copied while we left the map unlocked. Changing from
* read to write permission is OK - we leave the page
* write-protected, and catch the write fault. Changing from
* write to read permission means that we can't mark the page
* write-enabled after all.
*/
prot &= retry_prot;
}
/*
* (the various bits we're fiddling with here are locked by the
* object's lock)
*/
/*
* It's critically important that a wired-down page be faulted only
* once in each map for which it is wired.
*/
/*
* Put this page into the physical map. We had to do the unlock above
* because pmap_enter may cause other faults. We don't put the page
* back on the active queue until later so that the page-out daemon
* won't find us (yet).
*/
if (prot & VM_PROT_WRITE) {
m->flags |= PG_WRITEABLE;
m->object->flags |= OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY;
/*
* If the fault is a write, we know that this page is being
* written NOW. This will save on the pmap_is_modified() calls
* later.
*/
if (fault_type & VM_PROT_WRITE) {
m->dirty = VM_PAGE_BITS_ALL;
}
}
m->flags |= PG_MAPPED|PG_REFERENCED;
m->flags &= ~PG_ZERO;
pmap_enter(map->pmap, vaddr, VM_PAGE_TO_PHYS(m), prot, wired);
#if 0
if (change_wiring == 0 && wired == 0)
pmap_prefault(map->pmap, vaddr, entry, first_object);
#endif
/*
* If the page is not wired down, then put it where the pageout daemon
* can find it.
*/
if (change_wiring) {
if (wired)
vm_page_wire(m);
else
vm_page_unwire(m);
} else {
if ((m->flags & PG_ACTIVE) == 0)
vm_page_activate(m);
}
if (curproc && (curproc->p_flag & P_INMEM) && curproc->p_stats) {
if (hardfault) {
curproc->p_stats->p_ru.ru_majflt++;
} else {
curproc->p_stats->p_ru.ru_minflt++;
}
}
if ((m->flags & PG_BUSY) == 0)
printf("page not busy: %d\n", m->offset);
/*
* Unlock everything, and return
*/
PAGE_WAKEUP(m);
UNLOCK_AND_DEALLOCATE;
return (KERN_SUCCESS);
}
/*
* vm_fault_wire:
*
* Wire down a range of virtual addresses in a map.
*/
int
vm_fault_wire(map, start, end)
vm_map_t map;
vm_offset_t start, end;
{
register vm_offset_t va;
register pmap_t pmap;
int rv;
pmap = vm_map_pmap(map);
/*
* Inform the physical mapping system that the range of addresses may
* not fault, so that page tables and such can be locked down as well.
*/
pmap_pageable(pmap, start, end, FALSE);
/*
* We simulate a fault to get the page and enter it in the physical
* map.
*/
for (va = start; va < end; va += PAGE_SIZE) {
while( curproc != pageproc &&
(cnt.v_free_count <= cnt.v_pageout_free_min))
VM_WAIT;
rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE, TRUE);
if (rv) {
if (va != start)
vm_fault_unwire(map, start, va);
return (rv);
}
}
return (KERN_SUCCESS);
}
/*
* vm_fault_unwire:
*
* Unwire a range of virtual addresses in a map.
*/
void
vm_fault_unwire(map, start, end)
vm_map_t map;
vm_offset_t start, end;
{
register vm_offset_t va, pa;
register pmap_t pmap;
pmap = vm_map_pmap(map);
/*
* Since the pages are wired down, we must be able to get their
* mappings from the physical map system.
*/
for (va = start; va < end; va += PAGE_SIZE) {
pa = pmap_extract(pmap, va);
if (pa == (vm_offset_t) 0) {
panic("unwire: page not in pmap");
}
pmap_change_wiring(pmap, va, FALSE);
vm_page_unwire(PHYS_TO_VM_PAGE(pa));
}
/*
* Inform the physical mapping system that the range of addresses may
* fault, so that page tables and such may be unwired themselves.
*/
pmap_pageable(pmap, start, end, TRUE);
}
/*
* Routine:
* vm_fault_copy_entry
* Function:
* Copy all of the pages from a wired-down map entry to another.
*
* In/out conditions:
* The source and destination maps must be locked for write.
* The source map entry must be wired down (or be a sharing map
* entry corresponding to a main map entry that is wired down).
*/
void
vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry)
vm_map_t dst_map;
vm_map_t src_map;
vm_map_entry_t dst_entry;
vm_map_entry_t src_entry;
{
vm_object_t dst_object;
vm_object_t src_object;
vm_offset_t dst_offset;
vm_offset_t src_offset;
vm_prot_t prot;
vm_offset_t vaddr;
vm_page_t dst_m;
vm_page_t src_m;
#ifdef lint
src_map++;
#endif /* lint */
src_object = src_entry->object.vm_object;
src_offset = src_entry->offset;
/*
* Create the top-level object for the destination entry. (Doesn't
* actually shadow anything - we copy the pages directly.)
*/
dst_object = vm_object_allocate(OBJT_DEFAULT,
(vm_size_t) (dst_entry->end - dst_entry->start));
dst_entry->object.vm_object = dst_object;
dst_entry->offset = 0;
prot = dst_entry->max_protection;
/*
* Loop through all of the pages in the entry's range, copying each
* one from the source object (it should be there) to the destination
* object.
*/
for (vaddr = dst_entry->start, dst_offset = 0;
vaddr < dst_entry->end;
vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
/*
* Allocate a page in the destination object
*/
do {
dst_m = vm_page_alloc(dst_object, dst_offset, VM_ALLOC_NORMAL);
if (dst_m == NULL) {
VM_WAIT;
}
} while (dst_m == NULL);
/*
* Find the page in the source object, and copy it in.
* (Because the source is wired down, the page will be in
* memory.)
*/
src_m = vm_page_lookup(src_object, dst_offset + src_offset);
if (src_m == NULL)
panic("vm_fault_copy_wired: page missing");
vm_page_copy(src_m, dst_m);
/*
* Enter it in the pmap...
*/
dst_m->flags |= PG_WRITEABLE|PG_MAPPED;
dst_m->flags &= ~PG_ZERO;
pmap_enter(dst_map->pmap, vaddr, VM_PAGE_TO_PHYS(dst_m),
prot, FALSE);
/*
* Mark it no longer busy, and put it on the active list.
*/
vm_page_activate(dst_m);
PAGE_WAKEUP(dst_m);
}
}
/*
* This routine checks around the requested page for other pages that
* might be able to be faulted in. This routine brackets the viable
* pages for the pages to be paged in.
*
* Inputs:
* m, rbehind, rahead
*
* Outputs:
* marray (array of vm_page_t), reqpage (index of requested page)
*
* Return value:
* number of pages in marray
*/
int
vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
vm_page_t m;
int rbehind;
int rahead;
vm_page_t *marray;
int *reqpage;
{
int i;
vm_object_t object;
vm_offset_t offset, startoffset, endoffset, toffset, size;
vm_page_t rtm;
int treqpage;
int cbehind, cahead;
object = m->object;
offset = m->offset;
/*
* if the requested page is not available, then give up now
*/
if (!vm_pager_has_page(object,
object->paging_offset + offset, &cbehind, &cahead))
return 0;
if ((cbehind == 0) && (cahead == 0)) {
*reqpage = 0;
marray[0] = m;
return 1;
}
if (rahead > cahead) {
rahead = cahead;
}
if (rbehind > cbehind) {
rbehind = cbehind;
}
/*
* try to do any readahead that we might have free pages for.
*/
if ((rahead + rbehind) >
((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) {
pagedaemon_wakeup();
*reqpage = 0;
marray[0] = m;
return 1;
}
/*
* scan backward for the read behind pages -- in memory or on disk not
* in same object
*/
toffset = offset - PAGE_SIZE;
if (toffset < offset) {
if (rbehind * PAGE_SIZE > offset)
rbehind = offset / PAGE_SIZE;
startoffset = offset - rbehind * PAGE_SIZE;
while (toffset >= startoffset) {
if (vm_page_lookup( object, toffset)) {
startoffset = toffset + PAGE_SIZE;
break;
}
if (toffset == 0)
break;
toffset -= PAGE_SIZE;
}
} else {
startoffset = offset;
}
/*
* scan forward for the read ahead pages -- in memory or on disk not
* in same object
*/
toffset = offset + PAGE_SIZE;
endoffset = offset + (rahead + 1) * PAGE_SIZE;
if (endoffset > object->size)
endoffset = object->size;
while (toffset < endoffset) {
if ( vm_page_lookup(object, toffset)) {
break;
}
toffset += PAGE_SIZE;
}
endoffset = toffset;
/* calculate number of bytes of pages */
size = (endoffset - startoffset) / PAGE_SIZE;
/* calculate the page offset of the required page */
treqpage = (offset - startoffset) / PAGE_SIZE;
/* see if we have space (again) */
if ((cnt.v_free_count + cnt.v_cache_count) >
(cnt.v_free_reserved + size)) {
/*
* get our pages and don't block for them
*/
for (i = 0; i < size; i++) {
if (i != treqpage) {
rtm = vm_page_alloc(object,
startoffset + i * PAGE_SIZE,
VM_ALLOC_NORMAL);
if (rtm == NULL) {
if (i < treqpage) {
int j;
for (j = 0; j < i; j++) {
FREE_PAGE(marray[j]);
}
*reqpage = 0;
marray[0] = m;
return 1;
} else {
size = i;
*reqpage = treqpage;
return size;
}
}
marray[i] = rtm;
} else {
marray[i] = m;
}
}
*reqpage = treqpage;
return size;
}
*reqpage = 0;
marray[0] = m;
return 1;
}