powerpc/mm: Track backing pages allocated by vmemmap_populate()
We need to keep track of the backing pages that get allocated by
vmemmap_populate() so that when we use kdump, the dump-capture kernel knows
where these pages are.
We use a simple linked list of structures that contain the physical address
of the backing page and corresponding virtual address to track the backing
pages.
To save space, we just use a pointer to the next struct vmemmap_backing. We
can also do this because we never remove nodes. We call the pointer "list"
to be compatible with changes made to the crash utility.
vmemmap_populate() is called either at boot-time or on a memory hotplug
operation. We don't have to worry about the boot-time calls because they
will be inherently single-threaded, and for a memory hotplug operation
vmemmap_populate() is called through:
sparse_add_one_section()
|
V
kmalloc_section_memmap()
|
V
sparse_mem_map_populate()
|
V
vmemmap_populate()
and in sparse_add_one_section() we're protected by pgdat_resize_lock().
So, we don't need a spinlock to protect the vmemmap_list.
We allocate space for the vmemmap_backing structs by allocating whole pages
in vmemmap_list_alloc() and then handing out chunks of this to
vmemmap_list_populate().
This means that we waste at most just under one page, but this keeps the code
is simple.
Signed-off-by: Mark Nelson <markn@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index d7fa50b..e267f22 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -252,6 +252,47 @@
}
#endif /* CONFIG_PPC_BOOK3E */
+struct vmemmap_backing *vmemmap_list;
+
+static __meminit struct vmemmap_backing * vmemmap_list_alloc(int node)
+{
+ static struct vmemmap_backing *next;
+ static int num_left;
+
+ /* allocate a page when required and hand out chunks */
+ if (!next || !num_left) {
+ next = vmemmap_alloc_block(PAGE_SIZE, node);
+ if (unlikely(!next)) {
+ WARN_ON(1);
+ return NULL;
+ }
+ num_left = PAGE_SIZE / sizeof(struct vmemmap_backing);
+ }
+
+ num_left--;
+
+ return next++;
+}
+
+static __meminit void vmemmap_list_populate(unsigned long phys,
+ unsigned long start,
+ int node)
+{
+ struct vmemmap_backing *vmem_back;
+
+ vmem_back = vmemmap_list_alloc(node);
+ if (unlikely(!vmem_back)) {
+ WARN_ON(1);
+ return;
+ }
+
+ vmem_back->phys = phys;
+ vmem_back->virt_addr = start;
+ vmem_back->list = vmemmap_list;
+
+ vmemmap_list = vmem_back;
+}
+
int __meminit vmemmap_populate(struct page *start_page,
unsigned long nr_pages, int node)
{
@@ -276,6 +317,8 @@
if (!p)
return -ENOMEM;
+ vmemmap_list_populate(__pa(p), start, node);
+
pr_debug(" * %016lx..%016lx allocated at %p\n",
start, start + page_size, p);