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From:   Pankaj Suryawanshi <pankaj.suryawanshi@einfochips.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     "minchan@kernel.org" <minchan@kernel.org>
Subject: Re: vmscan: Reclaim unevictable pages
Thread-Topic: vmscan: Reclaim unevictable pages
Thread-Index: AQHU2jnLyCfGly2dbEuVu40O8aA4saYKwYIOgAACnP0=
Date:   Thu, 14 Mar 2019 08:23:10 +0000
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Below is the Error Msg :

[   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUne=
victable(page))
[   24.726949] page->mem_cgroup:bd008c00
[   24.730693] ------------[ cut here ]------------
[   24.735304] kernel BUG at mm/vmscan.c:1350!
[   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM


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_hea=
d *page_list,
                page =3D lru_to_page(page_list);
                list_del(&page->lru);

               if (!trylock_page(page)) {
                        goto keep;
               }

                VM_BUG_ON_PAGE(PageActive(page), page);

                sc->nr_scanned++;

                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;

                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,6 +1333,12 @@ static unsigned long shrink_page_list(struct list_he=
ad *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;

 activate_locked:
                /* Not a candidate for swapping, 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 unevi=
ctable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),pag=
e);

We can add the unevictable pages in reclaim list in shrink_page_list(), ret=
urn total number of reclaim pages including unevictable pages, let the call=
er handle unevictable pages.

Regards,
Pankaj

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