This patch should fix the remap_file_pages problem for object-based rmap.
I added a function that converts an object-based page to a pte_chain-based
page.  It's a little tricky because it has to preallocated all the
pte_chains it needs before taking the lock since the page can't be allowed
outside the lock in an intermediate state.  Fortunately I know how many
pte_chains are needed in advance.

I also condensed some of the common code and added comments.  One side
effect is I removed taking the page_table_lock during the pte lookups.
I've convinced myself that anyone else trying to touch those areas will
block on the locks I already hold.  It survives the abuse test I've thrown
at it.

Dave McCracken

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Dave McCracken          IBM Linux Base Kernel Team      1-512-838-3059
dmccr@us.ibm.com                                        T/L   678-3059