mm/memblock: remove empty dummy entry

The dummy entry is introduced in the initial implementation of lmb in
commit 7c8c6b97 ("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 784656f9
("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@gmail.com>
CC: Paul Mackerras <paulus@ozlabs.org>
CC: Tejun Heo <tj@kernel.org>
CC: Mike Rapoport <rppt@kernel.org>
Link: https://lore.kernel.org/r/20240405015821.13411-1-richard.weiyang@gmail.comSigned-off-by: Mike Rapoport (IBM) <rppt@kernel.org>

mm/memblock.c

@@ -114,12 +114,10 @@ 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.max		= INIT_MEMBLOCK_MEMORY_REGIONS,
 	.memory.name		= "memory",
 
 	.reserved.regions	= memblock_reserved_init_regions,
-	.reserved.cnt		= 1,	/* empty dummy entry */
 	.reserved.max		= INIT_MEMBLOCK_RESERVED_REGIONS,
 	.reserved.name		= "reserved",
 
@@ -130,7 +128,6 @@ 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 */
 	.max			= INIT_PHYSMEM_REGIONS,
 	.name			= "physmem",
 };
@@ -356,7 +353,6 @@ 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;
@@ -600,12 +596,13 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
 
 	/* special case for empty array */
 	if (type->regions[0].size == 0) {
-		WARN_ON(type->cnt != 1 || type->total_size);
+		WARN_ON(type->cnt != 0 || 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;
+		type->cnt = 1;
 		return 0;
 	}
 

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();

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;
 }