mm: fix dirty_bytes/dirty_background_bytes sysctls on 64bit arches

mm: fix dirty_bytes/dirty_background_bytes sysctls on 64bit arches

We need to pass an unsigned long as the minimum, because it gets casted
to an unsigned long in the sysctl handler. If we pass an int, we'll
access four more bytes on 64bit arches, resulting in a random minimum
value.

[[email protected]: fix type of `old_bytes']
Signed-off-by: Sven Wegener <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>