Revert "When reading from large files through the generic file read functions into page cache we can detect when a file is so large that it is unlikely to be fully cached in ram. If that happens we can put it on the tail end of the inactive lru list so it can be the first thing evicted next time we need ram."

This reverts commit c33046ea8acc75e88259c9a4838c832fb83574ae.
mm: vmscan.c: remove undefined value

Signed-off-by: Willi Ye <williye97@gmail.com>