* Removed the vm_cache/vm_store ref_count duality that besides being a bit ugly
also created the page dameon cache retrieval problem: now, only areas (and
cache consumers) retrieve a reference to the store (and therefore, the vnode).
The page daemon doesn't need to care about this at all anymore, and the pseudo
references of the vm_cache could be removed again.
* Rearranged deletion of vnodes such that its ID can be reused directly after
fs_remove_vnode() has been called.
* vm_page_allocate_page() no longer panics when it runs out of pages, but just
waits for new pages to become available using the new sFreeCondition condition
variable - to make sure this happens in an acceptable time frame, it'll
trigger a run of the low memory handlers.
* Implemented a page_thief() that steals inactive pages from caches and puts
them into the free queue. It runs as a low memory handler.
* The file cache now sets the usage count on the pages it inserts into the
cache (needs some rework though, cache_io() doesn't do it yet).
* Instead of panicking, the kernel will currently dead lock in low memory
situations, since BFS does a bit too much in bfs_release_vnode().
* Some minor cleanup.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22315 a95241bf-73f2-0310-859d-f6bbb57e9c96
6d4aea4796