[PATCH] setup_per_zone_pages_min() overflow fix

[PATCH] setup_per_zone_pages_min() overflow fix

As pointed out in http://bugzilla.kernel.org/show_bug.cgi?id=6490, this
function can experience overflows on 32-bit machines, causing our response to
changed values of min_free_kbytes to go whacky.

Fixing it efficiently is all too hard, so fix it with 64-bit math instead.

Cc: Ake Sandgren <[email protected]>
Cc: Martin Bligh <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>