mm, hwpoison: use num_poisoned_pages_sub() to decrease num_poisoned_pages

Use num_poisoned_pages_sub() to combine multiple atomic ops into one. Also
num_poisoned_pages_dec() can be killed as there's no caller now.

Link: https://lkml.kernel.org/r/20220830123604.25763-4-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>

include/linux/swapops.h

@@ -485,11 +485,6 @@ static inline void num_poisoned_pages_inc(void)
 	atomic_long_inc(&num_poisoned_pages);
 }
 
-static inline void num_poisoned_pages_dec(void)
-{
-	atomic_long_dec(&num_poisoned_pages);
-}
-
 static inline void num_poisoned_pages_sub(long i)
 {
 	atomic_long_sub(i, &num_poisoned_pages);

mm/memory-failure.c

@@ -2602,7 +2602,7 @@ int soft_offline_page(unsigned long pfn, int flags)
 
 void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 {
-	int i;
+	int i, total = 0;
 
 	/*
 	 * A further optimization is to have per section refcounted
@@ -2615,8 +2615,10 @@ void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 
 	for (i = 0; i < nr_pages; i++) {
 		if (PageHWPoison(&memmap[i])) {
-			num_poisoned_pages_dec();
+			total++;
 			ClearPageHWPoison(&memmap[i]);
 		}
 	}
+	if (total)
+		num_poisoned_pages_sub(total);
 }