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From:   Zi Yan <ziy@nvidia.com>
To:     Qian Cai <quic_qiancai@quicinc.com>
Cc:     David Hildenbrand <david@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Vlastimil Babka <vbabka@suse.cz>,
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        Mike Rapoport <rppt@kernel.org>,
        Oscar Salvador <osalvador@suse.de>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v11 0/6] Use pageblock_order for cma and alloc_contig_range alignment.
Date:   Sun, 22 May 2022 15:33:30 -0400
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On 22 May 2022, at 12:54, Zi Yan wrote:

> On 20 May 2022, at 19:41, Qian Cai wrote:
>
>> On Fri, May 20, 2022 at 05:56:52PM -0400, Zi Yan wrote:
>>> Do you have the page information like refcount, map count, mapping, i=
ndex, and
>>> page flags? That would be more helpful. Thanks.
>>
>> page:fffffc200c7f8000 refcount:393 mapcount:1 mapping:0000000000000000=
 index:0xffffbb800 pfn:0x8039fe00
>> head:fffffc200c7f8000 order:9 compound_mapcount:0 compound_pincount:0
>> memcg:ffff40026005a000
>> anon flags: 0xbfffc000009001c(uptodate|dirty|lru|head|swapbacked|node=3D=
0|zone=3D2|lastcpupid=3D0xffff)
>> raw: 0bfffc000009001c fffffc2007b74048 fffffc2009c087c8 ffff08038dab91=
89
>> raw: 0000000ffffbb800 0000000000000000 0000018900000000 ffff40026005a0=
00

OK. I replicated two scenarios, which can have the above page dump:
1. a PTE-mapped THP with 393 subpages mapped without any extra pin,
2. a PTE-mapped THP with 392 subpages mapped with an extra pin on the fir=
st subpage.

For scenario 1, there is no infinite looping on next-20220519 and next-20=
220520.

For scenario 2, an infinite loop happens on next-20220519, next-20220520,=
 and next-20220520
with my fixup patch from another email, when the memory block, in which t=
he page resides,
is being offlined. However, after reverting all my patches, the infinite =
loop remains.

So it looks to me that having an infinite loop during memory offline is n=
ot a regression
based on the experiments I have done. David Hildenbranch can correct me i=
f I am wrong.
A better issue description, other than infinite loop during memory offlin=
ing, and a
better reproducer are needed for me to identify potential bugs in my code=
 and fix them.

Of course, my fixup patch should be applied anyway.

Thanks for your testing.


--
Best Regards,
Yan, Zi

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