1 files changed, 395 insertions, 0 deletions
diff --git a/mm/page_ext.c b/mm/page_ext.c
new file mode 100644
index 0000000..514a3bc
--- /dev/null
+++ b/mm/page_ext.c
@@ -0,0 +1,395 @@
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/bootmem.h>
+#include <linux/page_ext.h>
+#include <linux/memory.h>
+#include <linux/vmalloc.h>
+#include <linux/kmemleak.h>
+
+/*
+ * struct page extension
+ *
+ * This is the feature to manage memory for extended data per page.
+ *
+ * Until now, we must modify struct page itself to store extra data per page.
+ * This requires rebuilding the kernel and it is really time consuming process.
+ * And, sometimes, rebuild is impossible due to third party module dependency.
+ * At last, enlarging struct page could cause un-wanted system behaviour change.
+ *
+ * This feature is intended to overcome above mentioned problems. This feature
+ * allocates memory for extended data per page in certain place rather than
+ * the struct page itself. This memory can be accessed by the accessor
+ * functions provided by this code. During the boot process, it checks whether
+ * allocation of huge chunk of memory is needed or not. If not, it avoids
+ * allocating memory at all. With this advantage, we can include this feature
+ * into the kernel in default and can avoid rebuild and solve related problems.
+ *
+ * To help these things to work well, there are two callbacks for clients. One
+ * is the need callback which is mandatory if user wants to avoid useless
+ * memory allocation at boot-time. The other is optional, init callback, which
+ * is used to do proper initialization after memory is allocated.
+ *
+ * The need callback is used to decide whether extended memory allocation is
+ * needed or not. Sometimes users want to deactivate some features in this
+ * boot and extra memory would be unneccessary. In this case, to avoid
+ * allocating huge chunk of memory, each clients represent their need of
+ * extra memory through the need callback. If one of the need callbacks
+ * returns true, it means that someone needs extra memory so that
+ * page extension core should allocates memory for page extension. If
+ * none of need callbacks return true, memory isn't needed at all in this boot
+ * and page extension core can skip to allocate memory. As result,
+ * none of memory is wasted.
+ *
+ * The init callback is used to do proper initialization after page extension
+ * is completely initialized. In sparse memory system, extra memory is
+ * allocated some time later than memmap is allocated. In other words, lifetime
+ * of memory for page extension isn't same with memmap for struct page.
+ * Therefore, clients can't store extra data until page extension is
+ * initialized, even if pages are allocated and used freely. This could
+ * cause inadequate state of extra data per page, so, to prevent it, client
+ * can utilize this callback to initialize the state of it correctly.
+ */
+
+static struct page_ext_operations *page_ext_ops[] = {
+};
+
+static unsigned long total_usage;
+
+static bool __init invoke_need_callbacks(void)
+{
+	int i;
+	int entries = ARRAY_SIZE(page_ext_ops);
+
+	for (i = 0; i < entries; i++) {
+		if (page_ext_ops[i]->need && page_ext_ops[i]->need())
+			return true;
+	}
+
+	return false;
+}
+
+static void __init invoke_init_callbacks(void)
+{
+	int i;
+	int entries = ARRAY_SIZE(page_ext_ops);
+
+	for (i = 0; i < entries; i++) {
+		if (page_ext_ops[i]->init)
+			page_ext_ops[i]->init();
+	}
+}
+
+#if !defined(CONFIG_SPARSEMEM)
+
+
+void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
+{
+	pgdat->node_page_ext = NULL;
+}
+
+struct page_ext *lookup_page_ext(struct page *page)
+{
+	unsigned long pfn = page_to_pfn(page);
+	unsigned long offset;
+	struct page_ext *base;
+
+	base = NODE_DATA(page_to_nid(page))->node_page_ext;
+#ifdef CONFIG_DEBUG_VM
+	/*
+	 * The sanity checks the page allocator does upon freeing a
+	 * page can reach here before the page_ext arrays are
+	 * allocated when feeding a range of pages to the allocator
+	 * for the first time during bootup or memory hotplug.
+	 */
+	if (unlikely(!base))
+		return NULL;
+#endif
+	offset = pfn - round_down(node_start_pfn(page_to_nid(page)),
+					MAX_ORDER_NR_PAGES);
+	return base + offset;
+}
+
+static int __init alloc_node_page_ext(int nid)
+{
+	struct page_ext *base;
+	unsigned long table_size;
+	unsigned long nr_pages;
+
+	nr_pages = NODE_DATA(nid)->node_spanned_pages;
+	if (!nr_pages)
+		return 0;
+
+	/*
+	 * Need extra space if node range is not aligned with
+	 * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
+	 * checks buddy's status, range could be out of exact node range.
+	 */
+	if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
+		!IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
+		nr_pages += MAX_ORDER_NR_PAGES;
+
+	table_size = sizeof(struct page_ext) * nr_pages;
+
+	base = memblock_virt_alloc_try_nid_nopanic(
+			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
+			BOOTMEM_ALLOC_ACCESSIBLE, nid);
+	if (!base)
+		return -ENOMEM;
+	NODE_DATA(nid)->node_page_ext = base;
+	total_usage += table_size;
+	return 0;
+}
+
+void __init page_ext_init_flatmem(void)
+{
+
+	int nid, fail;
+
+	if (!invoke_need_callbacks())
+		return;
+
+	for_each_online_node(nid)  {
+		fail = alloc_node_page_ext(nid);
+		if (fail)
+			goto fail;
+	}
+	pr_info("allocated %ld bytes of page_ext\n", total_usage);
+	invoke_init_callbacks();
+	return;
+
+fail:
+	pr_crit("allocation of page_ext failed.\n");
+	panic("Out of memory");
+}
+
+#else /* CONFIG_FLAT_NODE_MEM_MAP */
+
+struct page_ext *lookup_page_ext(struct page *page)
+{
+	unsigned long pfn = page_to_pfn(page);
+	struct mem_section *section = __pfn_to_section(pfn);
+#ifdef CONFIG_DEBUG_VM
+	/*
+	 * The sanity checks the page allocator does upon freeing a
+	 * page can reach here before the page_ext arrays are
+	 * allocated when feeding a range of pages to the allocator
+	 * for the first time during bootup or memory hotplug.
+	 */
+	if (!section->page_ext)
+		return NULL;
+#endif
+	return section->page_ext + pfn;
+}
+
+static void *__meminit alloc_page_ext(size_t size, int nid)
+{
+	gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
+	void *addr = NULL;
+
+	addr = alloc_pages_exact_nid(nid, size, flags);
+	if (addr) {
+		kmemleak_alloc(addr, size, 1, flags);
+		return addr;
+	}
+
+	if (node_state(nid, N_HIGH_MEMORY))
+		addr = vzalloc_node(size, nid);
+	else
+		addr = vzalloc(size);
+
+	return addr;
+}
+
+static int __meminit init_section_page_ext(unsigned long pfn, int nid)
+{
+	struct mem_section *section;
+	struct page_ext *base;
+	unsigned long table_size;
+
+	section = __pfn_to_section(pfn);
+
+	if (section->page_ext)
+		return 0;
+
+	table_size = sizeof(struct page_ext) * PAGES_PER_SECTION;
+	base = alloc_page_ext(table_size, nid);
+
+	/*
+	 * The value stored in section->page_ext is (base - pfn)
+	 * and it does not point to the memory block allocated above,
+	 * causing kmemleak false positives.
+	 */
+	kmemleak_not_leak(base);
+
+	if (!base) {
+		pr_err("page ext allocation failure\n");
+		return -ENOMEM;
+	}
+
+	/*
+	 * The passed "pfn" may not be aligned to SECTION.  For the calculation
+	 * we need to apply a mask.
+	 */
+	pfn &= PAGE_SECTION_MASK;
+	section->page_ext = base - pfn;
+	total_usage += table_size;
+	return 0;
+}
+#ifdef CONFIG_MEMORY_HOTPLUG
+static void free_page_ext(void *addr)
+{
+	if (is_vmalloc_addr(addr)) {
+		vfree(addr);
+	} else {
+		struct page *page = virt_to_page(addr);
+		size_t table_size;
+
+		table_size = sizeof(struct page_ext) * PAGES_PER_SECTION;
+
+		BUG_ON(PageReserved(page));
+		free_pages_exact(addr, table_size);
+	}
+}
+
+static void __free_page_ext(unsigned long pfn)
+{
+	struct mem_section *ms;
+	struct page_ext *base;
+
+	ms = __pfn_to_section(pfn);
+	if (!ms || !ms->page_ext)
+		return;
+	base = ms->page_ext + pfn;
+	free_page_ext(base);
+	ms->page_ext = NULL;
+}
+
+static int __meminit online_page_ext(unsigned long start_pfn,
+				unsigned long nr_pages,
+				int nid)
+{
+	unsigned long start, end, pfn;
+	int fail = 0;
+
+	start = SECTION_ALIGN_DOWN(start_pfn);
+	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
+
+	if (nid == -1) {
+		/*
+		 * In this case, "nid" already exists and contains valid memory.
+		 * "start_pfn" passed to us is a pfn which is an arg for
+		 * online__pages(), and start_pfn should exist.
+		 */
+		nid = pfn_to_nid(start_pfn);
+		VM_BUG_ON(!node_state(nid, N_ONLINE));
+	}
+
+	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
+		if (!pfn_present(pfn))
+			continue;
+		fail = init_section_page_ext(pfn, nid);
+	}
+	if (!fail)
+		return 0;
+
+	/* rollback */
+	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
+		__free_page_ext(pfn);
+
+	return -ENOMEM;
+}
+
+static int __meminit offline_page_ext(unsigned long start_pfn,
+				unsigned long nr_pages, int nid)
+{
+	unsigned long start, end, pfn;
+
+	start = SECTION_ALIGN_DOWN(start_pfn);
+	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
+
+	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
+		__free_page_ext(pfn);
+	return 0;
+
+}
+
+static int __meminit page_ext_callback(struct notifier_block *self,
+			       unsigned long action, void *arg)
+{
+	struct memory_notify *mn = arg;
+	int ret = 0;
+
+	switch (action) {
+	case MEM_GOING_ONLINE:
+		ret = online_page_ext(mn->start_pfn,
+				   mn->nr_pages, mn->status_change_nid);
+		break;
+	case MEM_OFFLINE:
+		offline_page_ext(mn->start_pfn,
+				mn->nr_pages, mn->status_change_nid);
+		break;
+	case MEM_CANCEL_ONLINE:
+		offline_page_ext(mn->start_pfn,
+				mn->nr_pages, mn->status_change_nid);
+		break;
+	case MEM_GOING_OFFLINE:
+		break;
+	case MEM_ONLINE:
+	case MEM_CANCEL_OFFLINE:
+		break;
+	}
+
+	return notifier_from_errno(ret);
+}
+
+#endif
+
+void __init page_ext_init(void)
+{
+	unsigned long pfn;
+	int nid;
+
+	if (!invoke_need_callbacks())
+		return;
+
+	for_each_node_state(nid, N_MEMORY) {
+		unsigned long start_pfn, end_pfn;
+
+		start_pfn = node_start_pfn(nid);
+		end_pfn = node_end_pfn(nid);
+		/*
+		 * start_pfn and end_pfn may not be aligned to SECTION and the
+		 * page->flags of out of node pages are not initialized.  So we
+		 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
+		 */
+		for (pfn = start_pfn; pfn < end_pfn;
+			pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
+
+			if (!pfn_valid(pfn))
+				continue;
+			/*
+			 * Nodes's pfns can be overlapping.
+			 * We know some arch can have a nodes layout such as
+			 * -------------pfn-------------->
+			 * N0 | N1 | N2 | N0 | N1 | N2|....
+			 */
+			if (pfn_to_nid(pfn) != nid)
+				continue;
+			if (init_section_page_ext(pfn, nid))
+				goto oom;
+		}
+	}
+	hotplug_memory_notifier(page_ext_callback, 0);
+	pr_info("allocated %ld bytes of page_ext\n", total_usage);
+	invoke_init_callbacks();
+	return;
+
+oom:
+	panic("Out of memory");
+}
+
+void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
+{
+}
+
+#endif