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Rewrote MAP_PRIVATE case of vm_mmap() - all of the COW portion of this

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routine was highly convoluted.

Submitted by:	John Dyson
This commit is contained in:
David Greenman 1995-02-22 08:40:54 +00:00
parent 6f05a6e836
commit 50ce2102e1
1 changed files with 52 additions and 53 deletions
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105
sys/vm/vm_mmap.c
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@ -38,7 +38,7 @@
* from: Utah $Hdr: vm_mmap.c 1.6 91/10/21$
*
* @(#)vm_mmap.c 8.4 (Berkeley) 1/12/94
* $Id: vm_mmap.c,v 1.9 1995/02/15 09:22:17 davidg Exp $
* $Id: vm_mmap.c,v 1.10 1995/02/21 01:22:46 davidg Exp $
*/
/*
@ -678,70 +678,69 @@ vm_mmap(map, addr, size, prot, maxprot, flags, handle, foff)
}
}
/*
* A COW regular file
* mmap a COW regular file
*/
else {
vm_map_t tmap;
vm_offset_t off;
vm_map_entry_t entry;
/* locate and allocate the target address space */
rv = vm_map_find(map, NULL, 0, addr, size, fitit);
if (rv != KERN_SUCCESS) {
vm_object_deallocate(object);
goto out;
}
if (flags & MAP_COPY) {
/* locate and allocate the target address space */
rv = vm_map_find(map, NULL, 0, addr, size, fitit);
if (rv != KERN_SUCCESS) {
vm_object_deallocate(object);
goto out;
}
off = VM_MIN_ADDRESS;
tmap = vm_map_create(NULL, off, off + size, TRUE);
rv = vm_map_find(tmap, object, foff, &off, size, FALSE);
if (rv != KERN_SUCCESS) {
vm_object_deallocate(object);
off = VM_MIN_ADDRESS;
tmap = vm_map_create(NULL, off, off + size, TRUE);
rv = vm_map_find(tmap, object, foff, &off, size, FALSE);
if (rv != KERN_SUCCESS) {
vm_object_deallocate(object);
vm_map_deallocate(tmap);
goto out;
}
rv = vm_map_copy(map, tmap, *addr, size, off,
FALSE, FALSE);
vm_map_deallocate(tmap);
goto out;
if (rv != KERN_SUCCESS)
goto out;
} else {
vm_object_t user_object;
user_object = vm_object_allocate( size);
user_object->shadow = object;
TAILQ_INSERT_TAIL(&object->reverse_shadow_head,
user_object, reverse_shadow_list);
object->ref_count += 1;
rv = vm_map_find(map, user_object, foff, addr, size, fitit);
if( rv != KERN_SUCCESS) {
vm_object_deallocate(user_object);
vm_object_deallocate(object);
goto out;
}
/*
* this is a consistancy check, gets the map entry, and should
* never fail
*/
if (!vm_map_lookup_entry(map, *addr, &entry)) {
panic("vm_mmap: missing map entry!!!\n");
}
entry->copy_on_write = TRUE;
}
/*
* (XXX) MAP_PRIVATE implies that we see changes made
* by others. To ensure that we need to guarentee
* that no copy object is created (otherwise original
* pages would be pushed to the copy object and we
* would never see changes made by others). We
* totally sleeze it right now by marking the object
* internal temporarily.
*/
if ((flags & MAP_COPY) == 0)
object->flags |= OBJ_INTERNAL;
rv = vm_map_copy(map, tmap, *addr, size, off,
FALSE, FALSE);
object->flags &= ~OBJ_INTERNAL;
/*
* (XXX) My oh my, this only gets worse... Force
* creation of a shadow object so that vm_map_fork
* will do the right thing.
*/
if ((flags & MAP_COPY) == 0) {
vm_map_t tmap;
vm_map_entry_t tentry;
vm_object_t tobject;
vm_offset_t toffset;
vm_prot_t tprot;
boolean_t twired, tsu;
tmap = map;
vm_map_lookup(&tmap, *addr, VM_PROT_WRITE,
&tentry, &tobject, &toffset,
&tprot, &twired, &tsu);
vm_map_lookup_done(tmap, tentry);
}
/*
* (XXX) Map copy code cannot detect sharing unless a
* sharing map is involved. So we cheat and write
* protect everything ourselves.
* set pages COW and protect for read access only
*/
vm_object_pmap_copy(object, foff, foff + size);
vm_map_deallocate(tmap);
if (rv != KERN_SUCCESS)
goto out;
}
/*