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From:   Pankaj Suryawanshi <pankaj.suryawanshi@einfochips.com>
To:     Michal Hocko <mhocko@kernel.org>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "minchan@kernel.org" <minchan@kernel.org>
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
Thread-Topic: [External] Re: vmscan: Reclaim unevictable pages
Thread-Index: AQHU2jnLyCfGly2dbEuVu40O8aA4saYKwYIOgAACnP2AAArTAIAAAt0e
Date:   Thu, 14 Mar 2019 08:52:37 +0000
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I am using kernel version 4.14.65 (on Android pie [ARM]).

No additional patches applied on top of vanilla.(Core MM).

If=A0 I change in the vmscan.c as below patch, it will work.=20

Regards,
Pankaj=20
=20

 =20
From: Michal Hocko <mhocko@kernel.org>
Sent: 14 March 2019 14:11:20
To: Pankaj Suryawanshi
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: [External] Re: vmscan: Reclaim unevictable pages
=A0=20

CAUTION: This email originated from outside of the organization. Do not cli=
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On Thu 14-03-19 08:23:10, Pankaj Suryawanshi wrote:
>
> Below is the Error Msg :
>
> [=A0=A0 24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || P=
ageUnevictable(page))
> [=A0=A0 24.726949] page->mem_cgroup:bd008c00
> [=A0=A0 24.730693] ------------[ cut here ]------------
> [=A0=A0 24.735304] kernel BUG at mm/vmscan.c:1350!
> [=A0=A0 24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM

Just curious. Which kernel version is that? Are there any addional
patches applied on top of vanilla?

> Solved the issue by below patch.
>
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index be56e2e..2e51edc 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_h=
ead *page_list,
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 page =3D lru_to_page(page=
_list);
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 list_del(&page->lru);
>
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (!trylock_page(page)) {
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 g=
oto keep;
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 }
>
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 VM_BUG_ON_PAGE(PageActive=
(page), page);
>
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 sc->nr_scanned++;
>
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (unlikely(!page_evicta=
ble(page)))
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 goto =
activate_locked;
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 goto cul=
l_mlocked;
>
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (!sc->may_unmap && pag=
e_mapped(page))
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 g=
oto keep_locked;
> @@ -1331,6 +1333,12 @@ static unsigned long shrink_page_list(struct list_=
head *page_list,
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 } else
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 l=
ist_add(&page->lru, &free_pages);
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 continue;
> +cull_mlocked:
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (PageSwapCache(page))
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 tr=
y_to_free_swap(page);
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 unlock_page(page);
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 list_add(&page->lru, &ret_=
pages);
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 continue;
>
>=A0 activate_locked:
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 /* Not a candidate for sw=
apping, so reclaim swap space. */
>
>
>
>
> From: Pankaj Suryawanshi
> Sent: 14 March 2019 13:23:53
> To: linux-kernel@vger.kernel.org
> Cc: minchan@kernel.org
> Subject: vmscan: Reclaim unevictable pages
>
>
>
> Hello ,
>
> shrink_page_list() returns , number of pages reclaimed, when pages is une=
victable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),p=
age);
>
> We can add the unevictable pages in reclaim list in shrink_page_list(), r=
eturn total number of reclaim pages including unevictable pages, let the ca=
ller handle unevictable pages.
>
> Regards,
> Pankaj
>
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--
Michal Hocko
SUSE Labs
    =