On Thu 25-03-21 17:36:22, Michal Hocko wrote:
> If all it takes is to make pfn_to_online_page work (and my
> previous attempt is incorrect because it should consult block rather
> than section pfn range)
This should work.
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 9697acfe96eb..e50d685be8ab 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -510,6 +510,23 @@ static struct memory_block *find_memory_block_by_id(unsigned long block_id)
return mem;
}
+struct page *is_vmemmap_page(unsigned long pfn)
+{
+ unsigned long nr = pfn_to_section_nr(pfn);
+ struct memory_block *mem;
+ unsigned long block_pfn;
+
+ mem = find_memory_block_by_id(memory_block_id(nr));
+ if (!mem || !mem->nr_vmemmap_pages)
+ return NULL;
+
+ block_pfn = section_nr_to_pfn(mem->start_section_nr);
+ if (pfn - block_pfn > mem->nr_vmemmap_pages)
+ return NULL;
+
+ return pfn_to_page(pfn);
+}
+
/*
* Called under device_hotplug_lock.
*/
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 754026a9164d..760bf3ad48d5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -304,8 +304,16 @@ struct page *pfn_to_online_page(unsigned long pfn)
return NULL;
ms = __nr_to_section(nr);
- if (!online_section(ms))
+ if (!online_section(ms)) {
+ /*
+ * vmemmap reserved space can eat up a whole section which then
+ * never gets onlined because it doesn't contain any memory to
+ * online.
+ */
+ if (memmap_on_memory)
+ return is_vmemmap_page(pfn);
return NULL;
+ }
/*
* Save some code text when online_section() +
--
Michal Hocko
SUSE Labs
