#include <linux/debugfs.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/bootmem.h>
#include <linux/stacktrace.h>
#include <linux/page_owner.h>
#include "internal.h"

static bool page_owner_disabled = true;
bool page_owner_inited __read_mostly;

static int early_page_owner_param(char *buf)
{
	if (!buf)
		return -EINVAL;

	if (strcmp(buf, "on") == 0)
		page_owner_disabled = false;

	return 0;
}
early_param("page_owner", early_page_owner_param);

static bool need_page_owner(void)
{
	if (page_owner_disabled)
		return false;

	return true;
}

static void init_page_owner(void)
{
	if (page_owner_disabled)
		return;

	page_owner_inited = true;
}

struct page_ext_operations page_owner_ops = {
	.need = need_page_owner,
	.init = init_page_owner,
};

void __reset_page_owner(struct page *page, unsigned int order)
{
	int i;
	struct page_ext *page_ext;

	for (i = 0; i < (1 << order); i++) {
		page_ext = lookup_page_ext(page + i);
		__clear_bit(PAGE_EXT_OWNER, &page_ext->flags);
	}
}

void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
{
	struct page_ext *page_ext;
	struct stack_trace *trace;

	page_ext = lookup_page_ext(page);

	trace = &page_ext->trace;
	trace->nr_entries = 0;
	trace->max_entries = ARRAY_SIZE(page_ext->trace_entries);
	trace->entries = &page_ext->trace_entries[0];
	trace->skip = 3;
	save_stack_trace(&page_ext->trace);

	page_ext->order = order;
	page_ext->gfp_mask = gfp_mask;

	__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
}

static ssize_t
print_page_owner(char __user *buf, size_t count, unsigned long pfn,
		struct page *page, struct page_ext *page_ext)
{
	int ret;
	int pageblock_mt, page_mt;
	char *kbuf;

	kbuf = kmalloc(count, GFP_KERNEL);
	if (!kbuf)
		return -ENOMEM;

	ret = snprintf(kbuf, count,
			"Page allocated via order %u, mask 0x%x\n",
			page_ext->order, page_ext->gfp_mask);

	if (ret >= count)
		goto err;

	/* Print information relevant to grouping pages by mobility */
	pageblock_mt = get_pfnblock_migratetype(page, pfn);
	page_mt  = gfpflags_to_migratetype(page_ext->gfp_mask);
	ret += snprintf(kbuf + ret, count - ret,
			"PFN %lu Block %lu type %d %s Flags %s%s%s%s%s%s%s%s%s%s%s%s\n",
			pfn,
			pfn >> pageblock_order,
			pageblock_mt,
			pageblock_mt != page_mt ? "Fallback" : "        ",
			PageLocked(page)	? "K" : " ",
			PageError(page)		? "E" : " ",
			PageReferenced(page)	? "R" : " ",
			PageUptodate(page)	? "U" : " ",
			PageDirty(page)		? "D" : " ",
			PageLRU(page)		? "L" : " ",
			PageActive(page)	? "A" : " ",
			PageSlab(page)		? "S" : " ",
			PageWriteback(page)	? "W" : " ",
			PageCompound(page)	? "C" : " ",
			PageSwapCache(page)	? "B" : " ",
			PageMappedToDisk(page)	? "M" : " ");

	if (ret >= count)
		goto err;

	ret += snprint_stack_trace(kbuf + ret, count - ret,
					&page_ext->trace, 0);
	if (ret >= count)
		goto err;

	ret += snprintf(kbuf + ret, count - ret, "\n");
	if (ret >= count)
		goto err;

	if (copy_to_user(buf, kbuf, ret))
		ret = -EFAULT;

	kfree(kbuf);
	return ret;

err:
	kfree(kbuf);
	return -ENOMEM;
}

static ssize_t
read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	unsigned long pfn;
	struct page *page;
	struct page_ext *page_ext;

	if (!page_owner_inited)
		return -EINVAL;

	page = NULL;
	pfn = min_low_pfn + *ppos;

	/* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
	while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
		pfn++;

	drain_all_pages(NULL);

	/* Find an allocated page */
	for (; pfn < max_pfn; pfn++) {
		/*
		 * If the new page is in a new MAX_ORDER_NR_PAGES area,
		 * validate the area as existing, skip it if not
		 */
		if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
			pfn += MAX_ORDER_NR_PAGES - 1;
			continue;
		}

		/* Check for holes within a MAX_ORDER area */
		if (!pfn_valid_within(pfn))
			continue;

		page = pfn_to_page(pfn);
		if (PageBuddy(page)) {
			unsigned long freepage_order = page_order_unsafe(page);

			if (freepage_order < MAX_ORDER)
				pfn += (1UL << freepage_order) - 1;
			continue;
		}

		page_ext = lookup_page_ext(page);

		/*
		 * Pages allocated before initialization of page_owner are
		 * non-buddy and have no page_owner info.
		 */
		if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
			continue;

		/* Record the next PFN to read in the file offset */
		*ppos = (pfn - min_low_pfn) + 1;

		return print_page_owner(buf, count, pfn, page, page_ext);
	}

	return 0;
}

static const struct file_operations proc_page_owner_operations = {
	.read		= read_page_owner,
};

static int __init pageowner_init(void)
{
	struct dentry *dentry;

	if (!page_owner_inited) {
		pr_info("page_owner is disabled\n");
		return 0;
	}

	dentry = debugfs_create_file("page_owner", S_IRUSR, NULL,
			NULL, &proc_page_owner_operations);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	return 0;
}
module_init(pageowner_init)