Re: [PATCH v4 4/4] Use 2GB memory block size on large-memory x86-64 systems

[Yinghai Lu]

On Mon, Aug 24, 2015 at 4:41 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> On Mon, Aug 24, 2015 at 3:39 PM, Tony Luck <tony.luck@xxxxxxxxx> wrote:
>> On Mon, Aug 24, 2015 at 2:25 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
>>
>>> Can you boot with "debug ignore_loglevel" so we can see following print out
>>> for vmemmap?
>>
>> See attached. There are a few extra messages from my own debug printk()
>> calls. It seems that we successfully deal with node 0 from topology_init()
>> but die walking node 1. I see that the NODE_DATA limits for memory
>> on node 1 were from 1d70000 to 3a00000. But when we get into
>> register_mem_sect_under_node() we have rounded the start pfn down to
>> 1d00000 ... and we panic processing that range (which is in a hole in e820).
>>
>> We seem to die here:
>>
>>         for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
>>                 int page_nid;
>>
>>                 page_nid = get_nid_for_pfn(pfn);
>
> oh, no.
> register_mem_sect_under_node() is assuming:
> first section in the block is present and first page in that section is present.

attached should fix the problem:
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 31df474d..cc910ad 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -390,8 +390,14 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
 	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
 	sect_end_pfn += PAGES_PER_SECTION - 1;
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
-		int page_nid;
+		int page_nid, scn_nr;
 
+		scn_nr = pfn_to_section_nr(pfn);
+		if (!present_section_nr(scn_nr)) {
+			pfn = round_down(pfn + PAGES_PER_SECTION,
+					 PAGES_PER_SECTION) - 1;
+			continue;
+		}
 		page_nid = get_nid_for_pfn(pfn);
 		if (page_nid < 0)
 			continue;
@@ -426,10 +432,18 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
 		return -ENOMEM;
 	nodes_clear(*unlinked_nodes);
 
-	sect_start_pfn = section_nr_to_pfn(phys_index);
-	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
+	sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
+	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
+	sect_end_pfn += PAGES_PER_SECTION - 1;
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
-		int nid;
+		int nid, scn_nr;
+
+		scn_nr = pfn_to_section_nr(pfn);
+		if (!present_section_nr(scn_nr)) {
+			pfn = round_down(pfn + PAGES_PER_SECTION,
+					 PAGES_PER_SECTION) - 1;
+			continue;
+		}
 
 		nid = get_nid_for_pfn(pfn);
 		if (nid < 0)