On 05.06.19 10:58, David Hildenbrand wrote:

quoted

quoted

/*
 * For now, we have a linear search to go find the appropriate
 * memory_block corresponding to a particular phys_index. If

@@ -658,6 +670,11 @@ static int init_memory_block(struct memory_block **memory, int block_id,

	unsigned long start_pfn;
	int ret = 0;

+	mem = find_memory_block_by_id(block_id, NULL);
+	if (mem) {
+		put_device(&mem->dev);
+		return -EEXIST;
+	}

find_memory_block_by_id() is not that close to the main idea in this patch.
Would it be better to split this part?

I played with that but didn't like the temporary results (e.g. having to
export find_memory_block_by_id()). I'll stick to this for now.

quoted

quoted

	mem = kzalloc(sizeof(*mem), GFP_KERNEL);
	if (!mem)
		return -ENOMEM;

@@ -699,44 +716,53 @@ static int add_memory_block(int base_section_nr)

	return 0;
}

+static void unregister_memory(struct memory_block *memory)
+{
+	if (WARN_ON_ONCE(memory->dev.bus != &memory_subsys))
+		return;
+
+	/* drop the ref. we got via find_memory_block() */
+	put_device(&memory->dev);
+	device_unregister(&memory->dev);
+}
+
/*
- * need an interface for the VM to add new memory regions,
- * but without onlining it.
+ * Create memory block devices for the given memory area. Start and size
+ * have to be aligned to memory block granularity. Memory block devices
+ * will be initialized as offline.
 */
-int hotplug_memory_register(int nid, struct mem_section *section)
+int create_memory_block_devices(unsigned long start, unsigned long size)
{
-	int block_id = base_memory_block_id(__section_nr(section));
-	int ret = 0;
+	const int start_block_id = pfn_to_block_id(PFN_DOWN(start));
+	int end_block_id = pfn_to_block_id(PFN_DOWN(start + size));
	struct memory_block *mem;
+	unsigned long block_id;
+	int ret = 0;

-	mutex_lock(&mem_sysfs_mutex);
+	if (WARN_ON_ONCE(!IS_ALIGNED(start, memory_block_size_bytes()) ||
+			 !IS_ALIGNED(size, memory_block_size_bytes())))
+		return -EINVAL;

-	mem = find_memory_block(section);
-	if (mem) {
-		mem->section_count++;
-		put_device(&mem->dev);
-	} else {
+	mutex_lock(&mem_sysfs_mutex);
+	for (block_id = start_block_id; block_id != end_block_id; block_id++) {
		ret = init_memory_block(&mem, block_id, MEM_OFFLINE);
		if (ret)
-			goto out;
-		mem->section_count++;
+			break;
+		mem->section_count = sections_per_block;
+	}
+	if (ret) {
+		end_block_id = block_id;
+		for (block_id = start_block_id; block_id != end_block_id;
+		     block_id++) {
+			mem = find_memory_block_by_id(block_id, NULL);
+			mem->section_count = 0;
+			unregister_memory(mem);
+		}
	}

Would it be better to do this in reverse order?

And unregister_memory() would free mem, so it is still necessary to set
section_count to 0?

1. I kept the existing behavior (setting it to 0) for now. I am planning
to eventually remove the section count completely (it could be
beneficial to detect removing of partially populated memory blocks).

Correction: We already use it to block offlining of partially populated
memory blocks \o/

2. Reverse order: We would have to start with "block_id - 1", I don't
like that better.

Thanks for having a look!

-- 

Thanks,

David / dhildenb