linux-kernel - Re: [PATCH] mm/page_alloc: only set ALLOC_HIGHATOMIC for __GPF

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Message-ID: <aLGBTPAphSP84jZ8@quatroqueijos.cascardo.eti.br>
Date: Fri, 29 Aug 2025 07:30:36 -0300
From: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>, Zi Yan <ziy@...dia.com>,
	Mel Gorman <mgorman@...hsingularity.net>, kernel-dev@...lia.com,
	Helen Koike <koike@...lia.com>,
	Matthew Wilcox <willy@...radead.org>,
	Thierry Reding <thierry.reding@...il.com>, neil@...wn.name
Subject: Re: [PATCH] mm/page_alloc: only set ALLOC_HIGHATOMIC for __GPF_HIGH
 allocations

On Fri, Aug 29, 2025 at 11:30:17AM +0200, Vlastimil Babka wrote:
> On 8/29/25 10:56, Sergey Senozhatsky wrote:
> > On (25/08/29 10:38), Vlastimil Babka wrote:
> >> On 8/29/25 10:36, Vlastimil Babka wrote:
> >> > On 8/14/25 19:22, Thadeu Lima de Souza Cascardo wrote:
> > [..]
> >> > Agreed with others that this change matches the original intention and it
> >> > must have been an oversight. Also found nothing to the contrary in the
> >> > original threads.
> >> 
> >> Oops, forgot to add
> >> 
> >> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
> > 
> > Thank you!
> > 
> > FWIW
> > Tested-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> > 
> > This needs Cc: stable@...r.kernel.org  all the way down to 5.15,
> > as far as I can tell.
> 
> If that problem bothers users of LTS kernels in that range, we can do that.
> I wonder a bit how it was only found out now as a regression in the
> browser/desktop environment test if it's that old? Is there another factor
> i.e. some new frequesnt source of allocations that trigger it?

That is not. It is just that there was an upgrade all the way back from 5.4
and, then, I caught this while doing some code inspection and reviewing the
patchset I referred to.

Well, I also tested that it really happens and caught a unix socket skb
allocation triggering that as it masks off __GFP_DIRECT_RECLAIM.

Cascardo.