* vm_soft_fault() did not take into account that a cache's source can change while
traversing a cache chain.
* Now, we grab a reference to every cache we get before locking it, and
* no longer get the cache's source without having the cache locked.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@19571 a95241bf-73f2-0310-859d-f6bbb57e9c96