written the page, we now do it before, so that it cannot lose any changed data
anymore; it doesn't matter if the page is written to while writing it back, the
worst thing that can happen is that we write the same page twice. Also, we don't
rely on the PAGE_MODIFIED bit anymore, we now check all mappings of that page
to find all modified pages, no matter how far the (currently disabled) page
daemon had come.
Also, destroying an area will now result in writing back changed pages - this
is only really important for memory mapped files, though, and should probably
be avoided for other vm_store types.
Minor cleanup.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@15597 a95241bf-73f2-0310-859d-f6bbb57e9c96
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