From mboxrd@z Thu Jan  1 00:00:00 1970
From: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Subject: Re: [PATCH for 5.8] mm: do_swap_page fix up the error code
 instantiation
Date: Wed, 17 Jun 2020 09:34:30 -0400
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To: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>, Joonsoo Kim <js1304-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, "Kirill A. Shutemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>, Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org

On Wed, Jun 17, 2020 at 11:02:38AM +0200, Michal Hocko wrote:
> Damn, I forgot to commit my last change (s@err@ret@). Sorry about the
> noise.
> 
> From 50297dd026ebf71fe901e1945a9ce1e8d8aa083b Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>
> Date: Wed, 17 Jun 2020 10:40:47 +0200
> Subject: [PATCH] mm: do_swap_page fix up the error code
> 
> do_swap_page returns error codes from the VM_FAULT* space. try_charge
> might return -ENOMEM, though, and then do_swap_page simply returns 0
> which means a success.
> 
> We almost never return ENOMEM for GFP_KERNEL single page charge. Except
> for async OOM handling (oom_disabled v1). So this needs translation to
> VM_FAULT_OOM otherwise the the page fault path will not notify the
> userspace and wait for an action.
> 
> Fixes: 4c6355b25e8b ("mm: memcontrol: charge swapin pages on instantiation")
> Signed-off-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>

Good catch, thanks Michal.

Acked-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>