linux-kernel - [PATCH] mm/thp: Make ALLOC_SPLIT_PTLOCKS dependent on USE_SPLIT_PTE

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Date:   Mon, 10 May 2021 09:16:30 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org, akpm@...ux-foundation.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm/thp: Make ALLOC_SPLIT_PTLOCKS dependent on USE_SPLIT_PTE_PTLOCKS

Split ptlocks need not be defined and allocated unless they are being used.
ALLOC_SPLIT_PTLOCKS is inherently dependent on USE_SPLIT_PTE_PTLOCKS. This
just makes it explicit and clear.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 include/linux/mm_types_task.h | 5 +++++
 mm/memory.c                   | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h
index c1bc6731125c..1b222f8039d1 100644
--- a/include/linux/mm_types_task.h
+++ b/include/linux/mm_types_task.h
@@ -22,7 +22,12 @@
 #define USE_SPLIT_PTE_PTLOCKS	(NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS)
 #define USE_SPLIT_PMD_PTLOCKS	(USE_SPLIT_PTE_PTLOCKS && \
 		IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
+
+#if USE_SPLIT_PTE_PTLOCKS
 #define ALLOC_SPLIT_PTLOCKS	(SPINLOCK_SIZE > BITS_PER_LONG/8)
+#else
+#define ALLOC_SPLIT_PTLOCKS	0
+#endif
 
 /*
  * The per task VMA cache array:
diff --git a/mm/memory.c b/mm/memory.c
index 730daa00952b..9c3b63f11aee 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5250,7 +5250,7 @@ long copy_huge_page_from_user(struct page *dst_page,
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
 
-#if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS
+#if ALLOC_SPLIT_PTLOCKS
 
 static struct kmem_cache *page_ptl_cachep;
 
-- 
2.20.1