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
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