mm/memory-failure.c: remove PageSlab check in hwpoison_filter_dev

Since commit 03e5ac2f ("mm: fix crash when using XFS on loopback"),
page_mapping() can handle the Slab pages.  So remove this unnecessary
PageSlab check and obsolete comment.

Link: https://lkml.kernel.org/r/20220218090118.1105-6-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -130,12 +130,6 @@ static int hwpoison_filter_dev(struct page *p)
 	    hwpoison_filter_dev_minor == ~0U)
 		return 0;
 
-	/*
-	 * page_mapping() does not accept slab pages.
-	 */
-	if (PageSlab(p))
-		return -EINVAL;
-
 	mapping = page_mapping(p);
 	if (mapping == NULL || mapping->host == NULL)
 		return -EINVAL;