mm/memory-failure: use folio_mapcount() in hwpoison_user_mappings()

We want to limit the use of page_mapcount() to the places where it is
absolutely necessary.  We can only unmap full folios; page_mapped(), which
we check here, is translated to folio_mapped() -- based on
folio_mapcount().  So let's print the folio mapcount instead.

Link: https://lkml.kernel.org/r/20240409192301.907377-10-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memory-failure.c

@@ -1634,8 +1634,8 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 
 	unmap_success = !page_mapped(p);
 	if (!unmap_success)
-		pr_err("%#lx: failed to unmap page (mapcount=%d)\n",
-		       pfn, page_mapcount(p));
+		pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
+		       pfn, folio_mapcount(page_folio(p)));
 
 	/*
 	 * try_to_unmap() might put mlocked page in lru cache, so call