[PATCH v5 3/4] memblock: extend memblock_cap_memory_range to multiple ranges

[Chen Zhou <chenzhou10@huawei.com>]

The memblock_cap_memory_range() removes all the memory except the
range passed to it. Extend this function to receive an array of
memblock_regions that should be kept. This allows switching to
simple iteration over memblock arrays with 'for_each_mem_range_rev'
to remove the unneeded memory.

Enable use of this function in arm64 for reservation of multiple
regions for the crash kernel.

Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
---
 arch/arm64/mm/init.c     | 34 ++++++++++++++++++++++++----------
 include/linux/memblock.h |  2 +-
 mm/memblock.c            | 44 ++++++++++++++++++++------------------------
 3 files changed, 45 insertions(+), 35 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index f5dde73..7f999bf 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -64,6 +64,10 @@ EXPORT_SYMBOL(memstart_addr);
 phys_addr_t arm64_dma_phys_limit __ro_after_init;
 
 #ifdef CONFIG_KEXEC_CORE
+
+/* at most two crash kernel regions, low_region and high_region */
+#define CRASH_MAX_USABLE_RANGES	2
+
 /*
  * reserve_crashkernel() - reserves memory for crash kernel
  *
@@ -295,9 +299,9 @@ early_param("mem", early_mem);
 static int __init early_init_dt_scan_usablemem(unsigned long node,
 		const char *uname, int depth, void *data)
 {
-	struct memblock_region *usablemem = data;
-	const __be32 *reg;
-	int len;
+	struct memblock_type *usablemem = data;
+	const __be32 *reg, *endp;
+	int len, nr = 0;
 
 	if (depth != 1 || strcmp(uname, "chosen") != 0)
 		return 0;
@@ -306,22 +310,32 @@ static int __init early_init_dt_scan_usablemem(unsigned long node,
 	if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 		return 1;
 
-	usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
-	usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
+	endp = reg + (len / sizeof(__be32));
+	while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
+		unsigned long base = dt_mem_next_cell(dt_root_addr_cells, &reg);
+		unsigned long size = dt_mem_next_cell(dt_root_size_cells, &reg);
 
+		if (memblock_add_range(usablemem, base, size, NUMA_NO_NODE,
+				       MEMBLOCK_NONE))
+			return 0;
+		if (++nr >= CRASH_MAX_USABLE_RANGES)
+			break;
+	}
 	return 1;
 }
 
 static void __init fdt_enforce_memory_region(void)
 {
-	struct memblock_region reg = {
-		.size = 0,
+	struct memblock_region usable_regions[CRASH_MAX_USABLE_RANGES];
+	struct memblock_type usablemem = {
+		.max = CRASH_MAX_USABLE_RANGES,
+		.regions = usable_regions,
 	};
 
-	of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
+	of_scan_flat_dt(early_init_dt_scan_usablemem, &usablemem);
 
-	if (reg.size)
-		memblock_cap_memory_range(reg.base, reg.size);
+	if (usablemem.cnt)
+		memblock_cap_memory_ranges(usablemem.regions, usablemem.cnt);
 }
 
 void __init arm64_memblock_init(void)
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 47e3c06..e490a73 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -445,7 +445,7 @@ phys_addr_t memblock_mem_size(unsigned long limit_pfn);
 phys_addr_t memblock_start_of_DRAM(void);
 phys_addr_t memblock_end_of_DRAM(void);
 void memblock_enforce_memory_limit(phys_addr_t memory_limit);
-void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
+void memblock_cap_memory_ranges(struct memblock_region *regions, int count);
 void memblock_mem_limit_remove_map(phys_addr_t limit);
 bool memblock_is_memory(phys_addr_t addr);
 bool memblock_is_map_memory(phys_addr_t addr);
diff --git a/mm/memblock.c b/mm/memblock.c
index f315eca..08581b1 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1669,36 +1669,31 @@ void __init memblock_enforce_memory_limit(phys_addr_t limit)
 			      PHYS_ADDR_MAX);
 }
 
-void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
-{
-	int start_rgn, end_rgn;
-	int i, ret;
-
-	if (!size)
-		return;
-
-	ret = memblock_isolate_range(&memblock.memory, base, size,
-						&start_rgn, &end_rgn);
-	if (ret)
-		return;
-
-	/* remove all the MAP regions */
-	for (i = memblock.memory.cnt - 1; i >= end_rgn; i--)
-		if (!memblock_is_nomap(&memblock.memory.regions[i]))
-			memblock_remove_region(&memblock.memory, i);
+void __init memblock_cap_memory_ranges(struct memblock_region *regions,
+				       int count)
+{
+	struct memblock_type regions_to_keep = {
+		.max = count,
+		.cnt = count,
+		.regions = regions,
+	};
+	phys_addr_t start, end;
+	u64 i;
 
-	for (i = start_rgn - 1; i >= 0; i--)
-		if (!memblock_is_nomap(&memblock.memory.regions[i]))
-			memblock_remove_region(&memblock.memory, i);
+	/* truncate memory while skipping NOMAP regions */
+	for_each_mem_range_rev(i, &memblock.memory, &regions_to_keep,
+			       NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end, NULL)
+		memblock_remove(start, end - start);
 
 	/* truncate the reserved regions */
-	memblock_remove_range(&memblock.reserved, 0, base);
-	memblock_remove_range(&memblock.reserved,
-			base + size, PHYS_ADDR_MAX);
+	for_each_mem_range_rev(i, &memblock.reserved, &regions_to_keep,
+			       NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end, NULL)
+		memblock_remove_range(&memblock.reserved, start, end - start);
 }
 
 void __init memblock_mem_limit_remove_map(phys_addr_t limit)
 {
+	struct memblock_region region = { 0 };
 	phys_addr_t max_addr;
 
 	if (!limit)
@@ -1710,7 +1705,8 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
 	if (max_addr == PHYS_ADDR_MAX)
 		return;
 
-	memblock_cap_memory_range(0, max_addr);
+	region.size = max_addr;
+	memblock_cap_memory_ranges(&region, 1);
 }
 
 static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
-- 
2.7.4