HWPOISON: Turn ref argument into flags argument

Now that "ref" is just a boolean turn it into
a flags argument. First step is only a single flag
that makes the code's intention more clear, but more
may follow.
Signed-off-by: Andi Kleen <ak@linux.intel.com>

include/linux/mm.h

@@ -1331,8 +1331,11 @@ extern int account_locked_memory(struct mm_struct *mm, struct rlimit *rlim,
 				 size_t size);
 extern void refund_locked_memory(struct mm_struct *mm, size_t size);
 
+enum mf_flags {
+	MF_COUNT_INCREASED = 1 << 0,
+};
 extern void memory_failure(unsigned long pfn, int trapno);
-extern int __memory_failure(unsigned long pfn, int trapno, int ref);
+extern int __memory_failure(unsigned long pfn, int trapno, int flags);
 extern int sysctl_memory_failure_early_kill;
 extern int sysctl_memory_failure_recovery;
 extern void shake_page(struct page *p);

mm/madvise.c

@@ -237,7 +237,7 @@ static int madvise_hwpoison(unsigned long start, unsigned long end)
 		printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
 		       page_to_pfn(p), start);
 		/* Ignore return value for now */
-		__memory_failure(page_to_pfn(p), 0, 1);
+		__memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED);
 	}
 	return ret;
 }

mm/memory-failure.c

@@ -737,7 +737,7 @@ static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
 		      ret != SWAP_SUCCESS, pfn);
 }
 
-int __memory_failure(unsigned long pfn, int trapno, int ref)
+int __memory_failure(unsigned long pfn, int trapno, int flags)
 {
 	unsigned long lru_flag;
 	struct page_state *ps;
@@ -773,7 +773,8 @@ int __memory_failure(unsigned long pfn, int trapno, int ref)
 	 * In fact it's dangerous to directly bump up page count from 0,
 	 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
 	 */
-	if (!ref && !get_page_unless_zero(compound_head(p))) {
+	if (!(flags & MF_COUNT_INCREASED) &&
+		!get_page_unless_zero(compound_head(p))) {
 		action_result(pfn, "free or high order kernel", IGNORED);
 		return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
 	}