mm: hwpoison: remove the unnecessary THP check

When handling THP hwpoison checked if the THP is in allocation or free
stage since hwpoison may mistreat it as hugetlb page.  After commit
415c64c145 ("mm/memory-failure: split thp earlier in memory error
handling") the problem has been fixed, so this check is no longer
needed.  Remove it.  The side effect of the removal is hwpoison may
report unsplit THP instead of unknown error for shmem THP.  It seems not
like a big deal.

The following patch "mm: filemap: check if THP has hwpoisoned subpage
for PMD page fault" depends on this, which fixes shmem THP with
hwpoisoned subpage(s) are mapped PMD wrongly.  So this patch needs to be
backported to -stable as well.

Link: https://lkml.kernel.org/r/20211020210755.23964-2-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Suggested-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -1147,20 +1147,6 @@ static int __get_hwpoison_page(struct page *page)
 	if (!HWPoisonHandlable(head))
 		return -EBUSY;
 
-	if (PageTransHuge(head)) {
-		/*
-		 * Non anonymous thp exists only in allocation/free time. We
-		 * can't handle such a case correctly, so let's give it up.
-		 * This should be better than triggering BUG_ON when kernel
-		 * tries to touch the "partially handled" page.
-		 */
-		if (!PageAnon(head)) {
-			pr_err("Memory failure: %#lx: non anonymous thp\n",
-				page_to_pfn(page));
-			return 0;
-		}
-	}
-
 	if (get_page_unless_zero(head)) {
 		if (head == compound_head(page))
 			return 1;