Re: [syzbot] [mm?] general protection fault in swap_reclaim_full_clusters

[Matteo Croce]

Il giorno ven 8 nov 2024 alle ore 18:35 Johannes Weiner
<hannes@xxxxxxxxxxx> ha scritto:
> The syzbot console output indicates a virtual environment where
> swapfile is on a rotational device. In this case, clusters aren't
> actually used, and si->full_clusters is not initialized. Daan's report
> is from qemu, so likely rotational too.
>
> Make sure to only schedule the cluster reclaim work when clusters are
> actually in use.
>
> Link: https://lore.kernel.org/lkml/672ac50b.050a0220.2edce.1517.GAE@xxxxxxxxxx/
> Link: https://github.com/systemd/systemd/issues/35044
> Fixes: 5168a68eb78f ("mm, swap: avoid over reclaim of full clusters")
> Reported-by: syzbot+078be8bfa863cb9e0c6b@xxxxxxxxxxxxxxxxxxxxxxxxx
> Reported-by: Daan De Meyer <daan.j.demeyer@xxxxxxxxx>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> ---
>  mm/swapfile.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 46bd4b1a3c07..9c85bd46ab7f 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -929,7 +929,7 @@ static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
>                 si->highest_bit = 0;
>                 del_from_avail_list(si);
>
> -               if (vm_swap_full())
> +               if (si->cluster_info && vm_swap_full())
>                         schedule_work(&si->reclaim_work);
>         }
>  }
> --

I've tested the patch and now the oomd test passes:

1/1 systemd:integration-tests / TEST-55-OOMD OK               63.48s

Tested-by: Matteo Croce <teknoraver@xxxxxxxx>

-- 
Matteo Croce

perl -e 'for($t=0;;$t++){print chr($t*($t>>8|$t>>13)&255)}' |aplay