It's time to remove truncate_complete_page's BUG_ON(page_mapped(page)): it
was there to give confidence in the new vm_truncate_count mechanism. 
Earlier releases had no such check, and it wouldn't be at all helpful if it
ever bugged up file truncation on a production system - though we don't
know of any scenario in which that could happen now.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>