hwpoison, hugetlbfs: fix RSS-counter warning

Memory error handling on hugepages can break a RSS counter, which emits a
message like "Bad rss-counter state mm:ffff88040abecac0 idx:1 val:-1".
This is because PageAnon returns true for hugepage (this behavior is
necessary for reverse mapping to work on hugetlbfs).

[akpm@linux-foundation.org: clean up code layout]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/rmap.c

@@ -1249,12 +1249,14 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 	update_hiwater_rss(mm);
 
 	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
-		if (PageAnon(page))
-			dec_mm_counter(mm, MM_ANONPAGES);
-		else
-			dec_mm_counter(mm, MM_FILEPAGES);
+		if (!PageHuge(page)) {
+			if (PageAnon(page))
+				dec_mm_counter(mm, MM_ANONPAGES);
+			else
+				dec_mm_counter(mm, MM_FILEPAGES);
+		}
 		set_pte_at(mm, address, pte,
-				swp_entry_to_pte(make_hwpoison_entry(page)));
+			   swp_entry_to_pte(make_hwpoison_entry(page)));
 	} else if (PageAnon(page)) {
 		swp_entry_t entry = { .val = page_private(page) };