[PATCH] mm/memblock: remove empty dummy entry

[Wei Yang <richard.weiyang@xxxxxxxxx>]

The dummy entry is introduced in the initial implementation of lmb in
commit 7c8c6b9776fb ("powerpc: Merge lmb.c and make MM initialization
use it.").

As the comment says the empty dummy entry is to simplify the code.

	/* Create a dummy zero size LMB which will get coalesced away later.
         * This simplifies the lmb_add() code below...
         */

While current code is reimplemented by Tejun in commit 784656f9c680
("memblock: Reimplement memblock_add_region()"). This empty dummy entry
seems not benefit the code any more.

Let's remove it.

Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
CC: Paul Mackerras <paulus@xxxxxxxxxx>
CC: Tejun Heo <tj@xxxxxxxxxx>
CC: Mike Rapoport <rppt@xxxxxxxxxx>
---
 mm/memblock.c                            | 18 +++---------------
 tools/testing/memblock/tests/basic_api.c |  8 ++++----
 tools/testing/memblock/tests/common.c    |  4 ++--
 3 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index d09136e040d3..100d3b7ab499 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -114,12 +114,12 @@ static struct memblock_region memblock_physmem_init_regions[INIT_PHYSMEM_REGIONS
 
 struct memblock memblock __initdata_memblock = {
 	.memory.regions		= memblock_memory_init_regions,
-	.memory.cnt		= 1,	/* empty dummy entry */
+	.memory.cnt		= 0,
 	.memory.max		= INIT_MEMBLOCK_MEMORY_REGIONS,
 	.memory.name		= "memory",
 
 	.reserved.regions	= memblock_reserved_init_regions,
-	.reserved.cnt		= 1,	/* empty dummy entry */
+	.reserved.cnt		= 0,
 	.reserved.max		= INIT_MEMBLOCK_RESERVED_REGIONS,
 	.reserved.name		= "reserved",
 
@@ -130,7 +130,7 @@ struct memblock memblock __initdata_memblock = {
 #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
 struct memblock_type physmem = {
 	.regions		= memblock_physmem_init_regions,
-	.cnt			= 1,	/* empty dummy entry */
+	.cnt			= 0,
 	.max			= INIT_PHYSMEM_REGIONS,
 	.name			= "physmem",
 };
@@ -356,7 +356,6 @@ static void __init_memblock memblock_remove_region(struct memblock_type *type, u
 	/* Special case for empty arrays */
 	if (type->cnt == 0) {
 		WARN_ON(type->total_size != 0);
-		type->cnt = 1;
 		type->regions[0].base = 0;
 		type->regions[0].size = 0;
 		type->regions[0].flags = 0;
@@ -598,17 +597,6 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
 	if (!size)
 		return 0;
 
-	/* special case for empty array */
-	if (type->regions[0].size == 0) {
-		WARN_ON(type->cnt != 1 || type->total_size);
-		type->regions[0].base = base;
-		type->regions[0].size = size;
-		type->regions[0].flags = flags;
-		memblock_set_region_node(&type->regions[0], nid);
-		type->total_size = size;
-		return 0;
-	}
-
 	/*
 	 * The worst case is when new range overlaps all existing regions,
 	 * then we'll need type->cnt + 1 empty regions in @type. So if
diff --git a/tools/testing/memblock/tests/basic_api.c b/tools/testing/memblock/tests/basic_api.c
index 57bf2688edfd..f317fe691fc4 100644
--- a/tools/testing/memblock/tests/basic_api.c
+++ b/tools/testing/memblock/tests/basic_api.c
@@ -15,12 +15,12 @@ static int memblock_initialization_check(void)
 	PREFIX_PUSH();
 
 	ASSERT_NE(memblock.memory.regions, NULL);
-	ASSERT_EQ(memblock.memory.cnt, 1);
+	ASSERT_EQ(memblock.memory.cnt, 0);
 	ASSERT_EQ(memblock.memory.max, EXPECTED_MEMBLOCK_REGIONS);
 	ASSERT_EQ(strcmp(memblock.memory.name, "memory"), 0);
 
 	ASSERT_NE(memblock.reserved.regions, NULL);
-	ASSERT_EQ(memblock.reserved.cnt, 1);
+	ASSERT_EQ(memblock.reserved.cnt, 0);
 	ASSERT_EQ(memblock.memory.max, EXPECTED_MEMBLOCK_REGIONS);
 	ASSERT_EQ(strcmp(memblock.reserved.name, "reserved"), 0);
 
@@ -1295,7 +1295,7 @@ static int memblock_remove_only_region_check(void)
 	ASSERT_EQ(rgn->base, 0);
 	ASSERT_EQ(rgn->size, 0);
 
-	ASSERT_EQ(memblock.memory.cnt, 1);
+	ASSERT_EQ(memblock.memory.cnt, 0);
 	ASSERT_EQ(memblock.memory.total_size, 0);
 
 	test_pass_pop();
@@ -1723,7 +1723,7 @@ static int memblock_free_only_region_check(void)
 	ASSERT_EQ(rgn->base, 0);
 	ASSERT_EQ(rgn->size, 0);
 
-	ASSERT_EQ(memblock.reserved.cnt, 1);
+	ASSERT_EQ(memblock.reserved.cnt, 0);
 	ASSERT_EQ(memblock.reserved.total_size, 0);
 
 	test_pass_pop();
diff --git a/tools/testing/memblock/tests/common.c b/tools/testing/memblock/tests/common.c
index f43b6f414983..4fa94b281280 100644
--- a/tools/testing/memblock/tests/common.c
+++ b/tools/testing/memblock/tests/common.c
@@ -40,13 +40,13 @@ void reset_memblock_regions(void)
 {
 	memset(memblock.memory.regions, 0,
 	       memblock.memory.cnt * sizeof(struct memblock_region));
-	memblock.memory.cnt	= 1;
+	memblock.memory.cnt	= 0;
 	memblock.memory.max	= INIT_MEMBLOCK_REGIONS;
 	memblock.memory.total_size = 0;
 
 	memset(memblock.reserved.regions, 0,
 	       memblock.reserved.cnt * sizeof(struct memblock_region));
-	memblock.reserved.cnt	= 1;
+	memblock.reserved.cnt	= 0;
 	memblock.reserved.max	= INIT_MEMBLOCK_RESERVED_REGIONS;
 	memblock.reserved.total_size = 0;
 }
-- 
2.34.1