[Stable 4.4 - NEEDS REVIEW - 0/3] mm: working set fixes

[Michal Hocko]

Hi Johannes,
this is my attempt to backport your 22f2ac51b6d6 ("mm: workingset: fix
crash in shadow node shrinker caused by replace_page_cache_page()")
which has been marked for 3.15+ stable trees. There are 2 follow up
fixes for this patch d3798ae8c6f3 ("mm: filemap: don't plant shadow
entries without radix tree node") and 3ddf40e8c319 ("mm: filemap: fix
mapping->nrpages double accounting in fuse") which are backported here
as well.

This is not an area I would feel really strongly so I would highly
appreciate if you could review these backports. The first two needed
quite some tweaking.

Thanks!