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Subject[PATCH V2] mm/thp: Make ALLOC_SPLIT_PTLOCKS dependent on USE_SPLIT_PTE_PTLOCKS
Date
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. While here drop the spinlock_t element
from the struct page when USE_SPLIT_PTE_PTLOCKS is not enabled.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This applies on v5.13-rc2.

Changes in V2:

- Dropped spinlock_t element from struct page

Changes in V1:

https://lore.kernel.org/linux-mm/1620618390-9999-1-git-send-email-anshuman.khandual@arm.com/

include/linux/mm_types.h | 2 ++
include/linux/mm_types_task.h | 5 +++++
mm/memory.c | 2 +-
3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5aacc1c10a45..a0fd851c0a0c 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -152,10 +152,12 @@ struct page {
struct mm_struct *pt_mm; /* x86 pgds only */
atomic_t pt_frag_refcount; /* powerpc */
};
+#if USE_SPLIT_PTE_PTLOCKS
#if ALLOC_SPLIT_PTLOCKS
spinlock_t *ptl;
#else
spinlock_t ptl;
+#endif
#endif
};
struct { /* ZONE_DEVICE pages */
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
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