linux-kernel - [PATCH 08/30] Introduce CONFIG_RADIX_TREE

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Date:	Wed,  6 Apr 2016 17:21:17 -0400
From:	Matthew Wilcox <willy@...ux.intel.com>
To:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matthew Wilcox <willy@...ux.intel.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	Jan Kara <jack@...e.com>, Neil Brown <neilb@...e.de>
Subject: [PATCH 08/30] Introduce CONFIG_RADIX_TREE_MULTIORDER

I've been receiving increasingly concerned notes from 0day about how much
my recent changes have been bloating the radix tree.  Make it happier by
only including multiorder support if CONFIG_TRANSPARENT_HUGEPAGES is set.
This is an independent Kconfig option, so other radix tree users can
also set it if they have a need.

Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 lib/Kconfig                             |  3 +++
 lib/radix-tree.c                        | 25 +++++++++++++++++--------
 mm/Kconfig                              |  1 +
 tools/testing/radix-tree/linux/kernel.h |  1 +
 4 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/lib/Kconfig b/lib/Kconfig
index 3cca1222578e..56403a6fba41 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -362,6 +362,9 @@ config INTERVAL_TREE
 
 	  for more information.
 
+config RADIX_TREE_MULTIORDER
+	bool
+
 config ASSOCIATIVE_ARRAY
 	bool
 	help
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 1624c4117961..ae53ad56e01e 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -484,6 +484,7 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 		slot = node->slots[offset];
 	}
 
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
 	/* Insert pointers to the canonical entry */
 	if ((shift - order) > 0) {
 		int i, n = 1 << (shift - order);
@@ -499,6 +500,7 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 			node->count++;
 		}
 	}
+#endif
 
 	if (nodep)
 		*nodep = node;
@@ -1469,6 +1471,19 @@ bool __radix_tree_delete_node(struct radix_tree_root *root,
 	return deleted;
 }
 
+static inline void delete_sibling_entries(struct radix_tree_node *node,
+					void *ptr, unsigned offset)
+{
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+	int i;
+	for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
+		if (node->slots[offset + i] != ptr)
+			break;
+		node->slots[offset + i] = NULL;
+		node->count--;
+	}
+#endif
+}
 /**
  *	radix_tree_delete_item    -    delete an item from a radix tree
  *	@root:		radix tree root
@@ -1484,7 +1499,7 @@ void *radix_tree_delete_item(struct radix_tree_root *root,
 			     unsigned long index, void *item)
 {
 	struct radix_tree_node *node;
-	unsigned int offset, i;
+	unsigned int offset;
 	void **slot;
 	void *entry;
 	int tag;
@@ -1513,13 +1528,7 @@ void *radix_tree_delete_item(struct radix_tree_root *root,
 			radix_tree_tag_clear(root, index, tag);
 	}
 
-	/* Delete any sibling slots pointing to this slot */
-	for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
-		if (node->slots[offset + i] != ptr_to_indirect(slot))
-			break;
-		node->slots[offset + i] = NULL;
-		node->count--;
-	}
+	delete_sibling_entries(node, ptr_to_indirect(slot), offset);
 	node->slots[offset] = NULL;
 	node->count--;
 
diff --git a/mm/Kconfig b/mm/Kconfig
index 989f8f3d77e0..6d5b39e6d326 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -393,6 +393,7 @@ config TRANSPARENT_HUGEPAGE
 	bool "Transparent Hugepage Support"
 	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select COMPACTION
+	select RADIX_TREE_MULTIORDER
 	help
 	  Transparent Hugepages allows the kernel to use huge pages and
 	  huge tlb transparently to the applications whenever possible.
diff --git a/tools/testing/radix-tree/linux/kernel.h b/tools/testing/radix-tree/linux/kernel.h
index 31fe2c77d7ae..8ea0ed450810 100644
--- a/tools/testing/radix-tree/linux/kernel.h
+++ b/tools/testing/radix-tree/linux/kernel.h
@@ -9,6 +9,7 @@
 
 #include "../../include/linux/compiler.h"
 
+#define CONFIG_RADIX_TREE_MULTIORDER
 #define CONFIG_SHMEM
 #define CONFIG_SWAP
 
-- 
2.8.0.rc3