hwpoison, shmem: fix data lost issue for 5.15.y

[Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx>]

Hi,

I'd like to request the follow commits to be backported to 5.15.y.

- dd0f230a0a80 ("mm: hwpoison: refactor refcount check handling")
- 4966455d9100 ("mm: hwpoison: handle non-anonymous THP correctly")
- a76054266661 ("mm: shmem: don't truncate page if memory failure happens")

These patches fixed a data lost issue by preventing shmem pagecache from
being removed by memory error.  These were not tagged for stable originally,
but that's revisited recently.

Thanks,
Naoya Horiguchi