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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>
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2 changed files with 49 additions and 0 deletions
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@ -11,6 +11,12 @@
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#include <linux/cpumask.h>
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#include <linux/percpu.h>
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struct vmemmap_backing {
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struct vmemmap_backing *list;
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unsigned long phys;
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unsigned long virt_addr;
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};
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/*
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* Functions that deal with pagetables that could be at any level of
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* the table need to be passed an "index_size" so they know how to
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@ -252,6 +252,47 @@ static void __meminit vmemmap_create_mapping(unsigned long start,
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}
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#endif /* CONFIG_PPC_BOOK3E */
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struct vmemmap_backing *vmemmap_list;
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static __meminit struct vmemmap_backing * vmemmap_list_alloc(int node)
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{
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static struct vmemmap_backing *next;
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static int num_left;
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/* allocate a page when required and hand out chunks */
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if (!next || !num_left) {
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next = vmemmap_alloc_block(PAGE_SIZE, node);
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if (unlikely(!next)) {
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WARN_ON(1);
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return NULL;
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}
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num_left = PAGE_SIZE / sizeof(struct vmemmap_backing);
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}
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num_left--;
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return next++;
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}
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static __meminit void vmemmap_list_populate(unsigned long phys,
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unsigned long start,
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int node)
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{
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struct vmemmap_backing *vmem_back;
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vmem_back = vmemmap_list_alloc(node);
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if (unlikely(!vmem_back)) {
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WARN_ON(1);
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return;
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}
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vmem_back->phys = phys;
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vmem_back->virt_addr = start;
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vmem_back->list = vmemmap_list;
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vmemmap_list = vmem_back;
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}
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int __meminit vmemmap_populate(struct page *start_page,
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unsigned long nr_pages, int node)
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{
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@ -276,6 +317,8 @@ int __meminit vmemmap_populate(struct page *start_page,
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if (!p)
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return -ENOMEM;
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vmemmap_list_populate(__pa(p), start, node);
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pr_debug(" * %016lx..%016lx allocated at %p\n",
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start, start + page_size, p);
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