Re: [PATCH] mm/page_alloc: Harmonize should_compact_retry() type

[Brendan Jackman <jackmanb@google.com>]

On Wed Aug 27, 2025 at 2:13 AM UTC, Andrew Morton wrote:
> On Tue, 26 Aug 2025 14:06:54 +0000 Brendan Jackman <jackmanb@google.com> wrote:
>
>> Currently order is signed in one version of the function and unsigned in
>> the other. Tidy that up.
>> 
>> In page_alloc.c, order is unsigned in the vast majority of cases. But,
>> there is a cluster of exceptions in compaction-related code (probably
>> stemming from the fact that compact_control.order is signed). So, prefer
>> local consistency and make this one signed too.
>> 
>
> grumble, pet peeve.  Negative orders make no sense.  Can we make
> cc->order unsigned in order (heh) to make everything nice?

I think we can't "just" do that:

/*
 * order == -1 is expected when compacting proactively via
 * 1. /proc/sys/vm/compact_memory
 * 2. /sys/devices/system/node/nodex/compact
 * 3. /proc/sys/vm/compaction_proactiveness
 */
static inline bool is_via_compact_memory(int order)
{
	return order == -1;
}