HWPOISON: Add PROC_FS dependency to hwpoison injector v2

The injector filter requires stable_page_flags() which is supplied
by procfs. So make it dependent on that.

Also add ifdefs around the filter code in memory-failure.c so that
when the filter is disabled due to missing dependencies the whole
code still builds.

Reported-by: Ingo Molnar
Signed-off-by: Andi Kleen <ak@linux.intel.com>

mm/Kconfig

@@ -253,7 +253,7 @@ config MEMORY_FAILURE
 
 config HWPOISON_INJECT
 	tristate "HWPoison pages injector"
-	depends on MEMORY_FAILURE && DEBUG_KERNEL
+	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 	select PROC_PAGE_MONITOR
 
 config NOMMU_INITIAL_TRIM_EXCESS

mm/memory-failure.c

@@ -52,6 +52,8 @@ int sysctl_memory_failure_recovery __read_mostly = 1;
 
 atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
 
+#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
+
 u32 hwpoison_filter_enable = 0;
 u32 hwpoison_filter_dev_major = ~0U;
 u32 hwpoison_filter_dev_minor = ~0U;
@@ -164,6 +166,13 @@ int hwpoison_filter(struct page *p)
 
 	return 0;
 }
+#else
+int hwpoison_filter(struct page *p)
+{
+	return 0;
+}
+#endif
+
 EXPORT_SYMBOL_GPL(hwpoison_filter);
 
 /*