* Mapping a page might actually need memory - since we usually have locks that

interfere with the page thief, we always need to have reserved a page for
  this upfront. I introduced a function to the vm_translation_map layer that
  estimates how much pages a mapping might need at maximum. All functions that
  map a page now call this and reserve the needed pages upfront.
  It might not be a nice solution, but it works.
* The page thief could run into a panic when trying to call vm_cache_release_ref()
  on a non-existing (NULL) cache.
* Also, it will now ignore wired active pages.
* There is still a race condition between the page writer and the vnode
  destruction - writing a page back needs a valid vnode, but that might just
  have been deleted.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22455 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/vm_translation_map.h

@@ -30,6 +30,7 @@ typedef struct vm_translation_map_ops {
 	void (*destroy)(vm_translation_map *map);
 	status_t (*lock)(vm_translation_map *map);
 	status_t (*unlock)(vm_translation_map *map);
+	size_t (*map_max_pages_need)(vm_translation_map *map, addr_t start, addr_t end);
 	status_t (*map)(vm_translation_map *map, addr_t va, addr_t pa,
 				uint32 attributes);
 	status_t (*unmap)(vm_translation_map *map, addr_t start, addr_t end);