My usual tmpfs swapping loads on recent mmotms have oddly
aroused the OOM killer after an hour or two. Bisection led to
mm-return-boolean-from-page_is_file_cache.patch, but really it's
the prior mm-introduce-page_lru_base_type.patch that's at fault.
It converted page_lru() to use page_lru_base_type(), but forgot
to convert del_page_from_lru() - which then decremented the wrong
stats once page_is_file_cache() was changed to a boolean.
Fix that, move page_lru_base_type() before del_page_from_lru(),
and mark it "inline" like the other mm_inline.h functions.
Signed-off-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>