Re: [PATCH] mm, page_alloc: do not break __GFP_THISNODE by zonelist reset

[Vlastimil Babka]

On 05/25/2018 09:43 PM, Andrew Morton wrote:
> On Fri, 25 May 2018 15:08:53 +0200 Vlastimil Babka <vbabka@xxxxxxx> wrote:
> 
>> we might consider this for 4.17 although I don't know if there's anything
>> currently broken. Stable backports should be more important, but will have to
>> be reviewed carefully, as the code went through many changes.
>> BTW I think that also the ac->preferred_zoneref reset is currently useless if
>> we don't also reset ac->nodemask from a mempolicy to NULL first (which we
>> probably should for the OOM victims etc?), but I would leave that for a
>> separate patch.
> 
> Confused.  If nothing is currently broken then why is a backport
> needed?  Presumably because we expect breakage in the future?  Can you
> expand on this?

I mean that SLAB is currently not affected, but in older kernels than
4.7 that don't yet have 511e3a058812 ("mm/slab: make cache_grow() handle
the page allocated on arbitrary node") it is. That's at least 4.4 LTS.
Older ones I'll have to check.