Re: [PATCH 2/2] mm, thp: consolidate THP gfp handling into alloc_hugepage_direct_gfpmask
From: Vlastimil Babka
Date: Thu Oct 25 2018 - 00:59:30 EST
On 10/25/18 1:17 AM, Andrew Morton wrote:
> On Mon, 22 Oct 2018 15:27:54 +0200 Vlastimil Babka <vbabka@xxxxxxx> wrote:
>>> : Moreover the oriinal code allowed to trigger
>>> : WARN_ON_ONCE(policy->mode == MPOL_BIND && (gfp & __GFP_THISNODE));
>>> : in policy_node if the requested node (e.g. cpu local one) was outside of
>>> : the mbind nodemask. This is not possible now. We haven't heard about any
>>> : such warning yet so it is unlikely that it happens but still a signal of
>>> : a wrong code layering.
>> Ah, as I said in the other mail, I think it's inaccurate, the warning
>> was not possible to hit.
>> There's also a slight difference wrt MPOL_BIND. The previous code would
>> avoid using __GFP_THISNODE if the local node was outside of
>> policy_nodemask(). After your patch __GFP_THISNODE is avoided for all
>> MPOL_BIND policies. So there's a difference that if local node is
>> actually allowed by the bind policy's nodemask, previously
>> __GFP_THISNODE would be added, but now it won't be. I don't think it
>> matters that much though, but maybe the changelog could say that
>> (instead of the inaccurate note about warning). Note the other policy
>> where nodemask is relevant is MPOL_INTERLEAVE, and that's unchanged by
>> this patch.
> So the above could go into the changelog, yes?
>> When that's addressed, you can add
> What is it that you'd like to see addressed? Purely changelog updates?
>> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>