linux-kernel - [PATCH] fixup: mm: memcontrol: Unbreak memcontrol build when THP is disabled

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Message-ID: <20190131160802.GA5777@chrisdown.name>
Date:   Thu, 31 Jan 2019 11:08:02 -0500
From:   Chris Down <chris@...isdown.name>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>,
        Roman Gushchin <guro@...com>, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-mm@...ck.org, kernel-team@...com
Subject: [PATCH] fixup: mm: memcontrol: Unbreak memcontrol build when THP is
 disabled

This can be folded into "mm: memcontrol: Expose THP events on a
per-memcg basis"
(mm-memcontrol-expose-thp-events-on-a-per-memcg-basis.patch).

kbuild points out that this patch can't be built with
CONFIG_TRANSPARENT_HUGEPAGE not set. I had originally worried about
this, but had only checked NR_ANON_THPS (which is not ifdeffed), not the
event counters.

NR_ANON_THPS is not #ifdeffed in node_stat_item, so we don't need to
also guard MEMCG_RSS_HUGE to futureproof it.

Signed-off-by: Chris Down <chris@...isdown.name>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Roman Gushchin <guro@...com>
Cc: linux-kernel@...r.kernel.org
Cc: cgroups@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: kernel-team@...com
---
 Documentation/admin-guide/cgroup-v2.rst | 8 +++++---
 mm/memcontrol.c                         | 2 ++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index b6989b39ed8e..53d3288c328b 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1255,12 +1255,14 @@ PAGE_SIZE multiple when read back.
 	  thp_fault_alloc
 
 		Number of transparent hugepages which were allocated to satisfy
-		a page fault, including COW faults
+		a page fault, including COW faults. This counter is not present
+		when CONFIG_TRANSPARENT_HUGEPAGE is not set.
 
 	  thp_collapse_alloc
 
-		Number of transparent hugepages which were allocated to
-		allow collapsing an existing range of pages
+		Number of transparent hugepages which were allocated to allow
+		collapsing an existing range of pages. This counter is not
+		present when CONFIG_TRANSPARENT_HUGEPAGE is not set.
 
   memory.swap.current
 	A read-only single value file which exists on non-root
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2f4fe2fb9046..bc4da016b8ce 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5643,9 +5643,11 @@ static int memory_stat_show(struct seq_file *m, void *v)
 	seq_printf(m, "pglazyfree %lu\n", acc.events[PGLAZYFREE]);
 	seq_printf(m, "pglazyfreed %lu\n", acc.events[PGLAZYFREED]);
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	seq_printf(m, "thp_fault_alloc %lu\n", acc.events[THP_FAULT_ALLOC]);
 	seq_printf(m, "thp_collapse_alloc %lu\n",
 		   acc.events[THP_COLLAPSE_ALLOC]);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 	return 0;
 }
-- 
2.20.1