mm: oom analysis: add buffer cache information to show_free_areas()

It is often useful to know the statistics for all pages that are handled
like page cache pages when looking at OOM log output.

Therefore show_free_areas() should also display buffer cache statistics.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -2137,7 +2137,7 @@ void show_free_areas(void)
 	printk("Active_anon:%lu active_file:%lu inactive_anon:%lu\n"
 		" inactive_file:%lu"
 		" unevictable:%lu"
-		" dirty:%lu writeback:%lu unstable:%lu\n"
+		" dirty:%lu writeback:%lu unstable:%lu buffer:%lu\n"
 		" free:%lu slab_reclaimable:%lu slab_unreclaimable:%lu\n"
 		" mapped:%lu pagetables:%lu bounce:%lu\n",
 		global_page_state(NR_ACTIVE_ANON),
@@ -2148,6 +2148,7 @@ void show_free_areas(void)
 		global_page_state(NR_FILE_DIRTY),
 		global_page_state(NR_WRITEBACK),
 		global_page_state(NR_UNSTABLE_NFS),
+		nr_blockdev_pages(),
 		global_page_state(NR_FREE_PAGES),
 		global_page_state(NR_SLAB_RECLAIMABLE),
 		global_page_state(NR_SLAB_UNRECLAIMABLE),