powerpc/mm: Track backing pages allocated by vmemmap_populate() (91eea67c) · Commits · 戴 / test

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>

arch/powerpc/include/asm/pgalloc-64.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -11,6 +11,12 @@
		#include <linux/cpumask.h>
		#include <linux/percpu.h>

		struct vmemmap_backing {
		struct vmemmap_backing *list;
		unsigned long phys;
		unsigned long virt_addr;
		};

		/*
		* Functions that deal with pagetables that could be at any level of
		* the table need to be passed an "index_size" so they know how to

arch/powerpc/mm/init_64.c

+43 −0

Original line number	Diff line number	Diff line
		@@ -252,6 +252,47 @@ static void __meminit vmemmap_create_mapping(unsigned long start,
		}
		#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 @@ int __meminit vmemmap_populate(struct page *start_page,
		if (!p)
		return -ENOMEM;

		vmemmap_list_populate(__pa(p), start, node);

		pr_debug(" * %016lx..%016lx allocated at %p\n",
		start, start + page_size, p);

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