v4.19.13 snapshot.
diff --git a/mm/page_ext.c b/mm/page_ext.c
new file mode 100644
index 0000000..a9826da
--- /dev/null
+++ b/mm/page_ext.c
@@ -0,0 +1,424 @@
+// SPDX-License-Identifier: GPL-2.0
+#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>
+#include <linux/page_owner.h>
+#include <linux/page_idle.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.
+ *
+ * When need callback returns true, page_ext checks if there is a request for
+ * extra memory through size in struct page_ext_operations. If it is non-zero,
+ * extra space is allocated for each page_ext entry and offset is returned to
+ * user through offset in struct page_ext_operations.
+ *
+ * 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[] = {
+#ifdef CONFIG_DEBUG_PAGEALLOC
+ &debug_guardpage_ops,
+#endif
+#ifdef CONFIG_PAGE_OWNER
+ &page_owner_ops,
+#endif
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
+ &page_idle_ops,
+#endif
+};
+
+static unsigned long total_usage;
+static unsigned long extra_mem;
+
+static bool __init invoke_need_callbacks(void)
+{
+ int i;
+ int entries = ARRAY_SIZE(page_ext_ops);
+ bool need = false;
+
+ for (i = 0; i < entries; i++) {
+ if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
+ page_ext_ops[i]->offset = sizeof(struct page_ext) +
+ extra_mem;
+ extra_mem += page_ext_ops[i]->size;
+ need = true;
+ }
+ }
+
+ return need;
+}
+
+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();
+ }
+}
+
+static unsigned long get_entry_size(void)
+{
+ return sizeof(struct page_ext) + extra_mem;
+}
+
+static inline struct page_ext *get_entry(void *base, unsigned long index)
+{
+ return base + get_entry_size() * index;
+}
+
+#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(const struct page *page)
+{
+ unsigned long pfn = page_to_pfn(page);
+ unsigned long index;
+ struct page_ext *base;
+
+ base = NODE_DATA(page_to_nid(page))->node_page_ext;
+ /*
+ * 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;
+ index = pfn - round_down(node_start_pfn(page_to_nid(page)),
+ MAX_ORDER_NR_PAGES);
+ return get_entry(base, index);
+}
+
+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 = get_entry_size() * 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(const struct page *page)
+{
+ unsigned long pfn = page_to_pfn(page);
+ struct mem_section *section = __pfn_to_section(pfn);
+ /*
+ * 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;
+ return get_entry(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;
+ }
+
+ addr = vzalloc_node(size, nid);
+
+ 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 = get_entry_size() * 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 = (void *)base - get_entry_size() * 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 = get_entry_size() * 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 = get_entry(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|....
+ *
+ * Take into account DEFERRED_STRUCT_PAGE_INIT.
+ */
+ if (early_pfn_to_nid(pfn) != nid)
+ continue;
+ if (init_section_page_ext(pfn, nid))
+ goto oom;
+ cond_resched();
+ }
+ }
+ 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