mm/memory-failure: send SIGBUS in the event of thp split fail

mm/memory-failure: send SIGBUS in the event of thp split fail

While handling hwpoison in a THP page, it is possible that
try_to_split_thp_page() fails.  For example, when the THP page has been
RDMA pinned.  At this point, the kernel cannot isolate the poisoned THP
page, all it could do is to send a SIGBUS to the user process with
meaningful payload to give user-level recovery a chance.

Link: https://lkml.kernel.org/r/20240524215306.2705454-6-jane.chu@oracle.com
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <oalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>