Re: [patch 2/5] setup_per_zone_lowmem_reserve() oops fix

[Nick Piggin <nickpiggin@yahoo.com.au>]

akpm@osdl.org wrote:
> If you do 'echo 0 0 > /proc/sys/vm/lowmem_reserve_ratio' the kernel gets a
> divide-by-zero.
> 
> Prevent that, and fiddle with some whitespace too.
> 
> Signed-off-by: Andrew Morton <akpm@osdl.org>

Can we instead have a patch that makes the value zero turn off the
lowmem reserve entirely if it is set to zero?

Just now I was just testing, and found no easy way to do this other
than to make the value large enough that the reserve is insignificant.

So the loop would be something like:

  			for (idx = j-1; idx >= 0; idx--) {
				struct zone *lower_zone;
				lower_zone = pgdat->node_zones + idx;

				lower_zone->lowmem_reserve[j] = 0;
				if (sysctl_lowmem_reserve_ratio[idx] > 0)
					lower_zone->lowmem_reserve[j] = present_pages /
						sysctl_lowmem_reserve_ratio[idx];

				present_pages += lower_zone->present_pages;
			}