[01/17] Remove open coded implementation of memclear_highpage flush

There are a series of open coded reimplementation of memclear_highpage_flush all over the page cache code. Call memclear_highpage_flush in those locations. Consolidates code and eases maintenance. [There seems to be a better patch in mm. This patch here is just to make things work against 2.6.21

[01/17] Remove open coded implementation of memclear_highpage flush

There are a series of open coded reimplementation of memclear_highpage_flush all over the page cache code. Call memclear_highpage_flush in those locations. Consolidates code and eases maintenance. [There seems to be a better patch in mm. This patch here is just to make things work against 2.6.21