From: Hugh Dickins <hugh@veritas.com>

anon_vma will need to pass vma to put_dirty_page, so change it and its
various callers (setup_arg_pages and its 32-on-64-bit arch variants); and
please, let's rename it to install_arg_page.

Earlier attempt to do this (rmap 26 __setup_arg_pages) tried to clean up
those callers instead, but failed to boot: so now apply rmap 27's memset
initialization of vmas to these callers too; which relieves them from
needing the recently included linux/mempolicy.h.

While there, moved install_arg_page's flush_dcache_page up before
page_table_lock - doesn't in fact matter at all, just saves one worry when
researching flush_dcache_page locking constraints.