mm: batch radix tree operations when truncating pages [jack@suse.cz: convert delete_from_page_cache_batch... ...kernel.org/r/20171018111648.13714-1-jack@suse.cz ...kernel.org/r/20171010151937.26984-8-jack@suse.cz Signed-off-by: Jan Kara <jack@suse.cz>