#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 void init_early_allocated_pages(void);

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;
        init_early_allocated_pages();
}

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 = lookup_page_ext(page);
        struct stack_trace trace = {
                .nr_entries = 0,
                .max_entries = ARRAY_SIZE(page_ext->trace_entries),
                .entries = &page_ext->trace_entries[0],
                .skip = 3,
        };

        save_stack_trace(&trace);

        page_ext->order = order;
        page_ext->gfp_mask = gfp_mask;
        page_ext->nr_entries = trace.nr_entries;

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

gfp_t __get_page_owner_gfp(struct page *page)
{
        struct page_ext *page_ext = lookup_page_ext(page);

        return page_ext->gfp_mask;
}

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;
        struct stack_trace trace = {
                .nr_entries = page_ext->nr_entries,
                .entries = &page_ext->trace_entries[0],
        };

        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, &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);

                /*
                 * Some pages could be missed by concurrent allocation or free,
                 * because we don't hold the zone lock.
                 */
                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 void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
{
        struct page *page;
        struct page_ext *page_ext;
        unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
        unsigned long end_pfn = pfn + zone->spanned_pages;
        unsigned long count = 0;

        /* Scan block by block. First and last block may be incomplete */
        pfn = zone->zone_start_pfn;

        /*
         * Walk the zone in pageblock_nr_pages steps. If a page block spans
         * a zone boundary, it will be double counted between zones. This does
         * not matter as the mixed block count will still be correct
         */
        for (; pfn < end_pfn; ) {
                if (!pfn_valid(pfn)) {
                        pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
                        continue;
                }

                block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
                block_end_pfn = min(block_end_pfn, end_pfn);

                page = pfn_to_page(pfn);

                for (; pfn < block_end_pfn; pfn++) {
                        if (!pfn_valid_within(pfn))
                                continue;

                        page = pfn_to_page(pfn);

                        /*
                         * We are safe to check buddy flag and order, because
                         * this is init stage and only single thread runs.
                         */
                        if (PageBuddy(page)) {
                                pfn += (1UL << page_order(page)) - 1;
                                continue;
                        }

                        if (PageReserved(page))
                                continue;

                        page_ext = lookup_page_ext(page);

                        /* Maybe overraping zone */
                        if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
                                continue;

                        /* Found early allocated page */
                        set_page_owner(page, 0, 0);
                        count++;
                }
        }

        pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
                pgdat->node_id, zone->name, count);
}

static void init_zones_in_node(pg_data_t *pgdat)
{
        struct zone *zone;
        struct zone *node_zones = pgdat->node_zones;
        unsigned long flags;

        for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
                if (!populated_zone(zone))
                        continue;

                spin_lock_irqsave(&zone->lock, flags);
                init_pages_in_zone(pgdat, zone);
                spin_unlock_irqrestore(&zone->lock, flags);
        }
}

static void init_early_allocated_pages(void)
{
        pg_data_t *pgdat;

        drain_all_pages(NULL);
        for_each_online_pgdat(pgdat)
                init_zones_in_node(pgdat);
}

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;
}
late_initcall(pageowner_init)