linux-kernel - [PATCH 15/28] maple_tree: Add gap support, slot and pivot sizes for maple copy

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Message-ID: <20260115193647.1695937-16-Liam.Howlett@oracle.com>
Date: Thu, 15 Jan 2026 14:36:34 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Suren Baghdasaryan <surenb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Alice Ryhl <aliceryhl@...gle.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>, Christian Kujau <lists@...dbynature.de>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH 15/28] maple_tree: Add gap support, slot and pivot sizes for maple copy

Add plumbing work for using maple copy as a normal node for a source of
copy operations.  This is needed later.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 include/linux/maple_tree.h | 1 +
 lib/maple_tree.c           | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index e99e16ac1c6da..db6a02788902a 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -165,6 +165,7 @@ struct maple_copy {
 	} src[4];
 	/* Simulated node */
 	void __rcu *slot[3];
+	unsigned long gap[3];
 	unsigned long min;
 	union {
 		unsigned long pivot[3];
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 366202dc22343..a9d4f3ef8e888 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -101,6 +101,7 @@ static const unsigned long mt_max[] = {
 	[maple_leaf_64]		= ULONG_MAX,
 	[maple_range_64]	= ULONG_MAX,
 	[maple_arange_64]	= ULONG_MAX,
+	[maple_copy]		= ULONG_MAX,
 };
 #define mt_node_max(x) mt_max[mte_node_type(x)]
 #endif
@@ -110,6 +111,7 @@ static const unsigned char mt_slots[] = {
 	[maple_leaf_64]		= MAPLE_RANGE64_SLOTS,
 	[maple_range_64]	= MAPLE_RANGE64_SLOTS,
 	[maple_arange_64]	= MAPLE_ARANGE64_SLOTS,
+	[maple_copy]		= 3,
 };
 #define mt_slot_count(x) mt_slots[mte_node_type(x)]
 
@@ -118,6 +120,7 @@ static const unsigned char mt_pivots[] = {
 	[maple_leaf_64]		= MAPLE_RANGE64_SLOTS - 1,
 	[maple_range_64]	= MAPLE_RANGE64_SLOTS - 1,
 	[maple_arange_64]	= MAPLE_ARANGE64_SLOTS - 1,
+	[maple_copy]		= 3,
 };
 #define mt_pivot_count(x) mt_pivots[mte_node_type(x)]
 
@@ -126,6 +129,7 @@ static const unsigned char mt_min_slots[] = {
 	[maple_leaf_64]		= (MAPLE_RANGE64_SLOTS / 2) - 2,
 	[maple_range_64]	= (MAPLE_RANGE64_SLOTS / 2) - 2,
 	[maple_arange_64]	= (MAPLE_ARANGE64_SLOTS / 2) - 1,
+	[maple_copy]		= 1, /* Should never be used */
 };
 #define mt_min_slot_count(x) mt_min_slots[mte_node_type(x)]
 
@@ -627,6 +631,7 @@ static inline unsigned long *ma_gaps(struct maple_node *node,
 	case maple_arange_64:
 		return node->ma64.gap;
 	case maple_copy:
+		return node->cp.gap;
 	case maple_range_64:
 	case maple_leaf_64:
 	case maple_dense:
-- 
2.47.3