#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 <linux/jump_label.h>
#include <linux/migrate.h>
#include <linux/stackdepot.h>
#include <linux/seq_file.h>

#include "internal.h"

/*
 * TODO: teach PAGE_OWNER_STACK_DEPTH (__dump_page_owner and save_stack)
 * to use off stack temporal storage
 */
#define PAGE_OWNER_STACK_DEPTH (16)

struct page_owner {
        unsigned int order;
        gfp_t gfp_mask;
        int last_migrate_reason;
        depot_stack_handle_t handle;
};

static bool page_owner_disabled = true;
DEFINE_STATIC_KEY_FALSE(page_owner_inited);

static depot_stack_handle_t dummy_handle;
static depot_stack_handle_t failure_handle;

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 noinline void register_dummy_stack(void)
{
        unsigned long entries[4];
        struct stack_trace dummy;

        dummy.nr_entries = 0;
        dummy.max_entries = ARRAY_SIZE(entries);
        dummy.entries = &entries[0];
        dummy.skip = 0;

        save_stack_trace(&dummy);
        dummy_handle = depot_save_stack(&dummy, GFP_KERNEL);
}

static noinline void register_failure_stack(void)
{
        unsigned long entries[4];
        struct stack_trace failure;

        failure.nr_entries = 0;
        failure.max_entries = ARRAY_SIZE(entries);
        failure.entries = &entries[0];
        failure.skip = 0;

        save_stack_trace(&failure);
        failure_handle = depot_save_stack(&failure, GFP_KERNEL);
}

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

        register_dummy_stack();
        register_failure_stack();
        static_branch_enable(&page_owner_inited);
        init_early_allocated_pages();
}

struct page_ext_operations page_owner_ops = {
        .size = sizeof(struct page_owner),
        .need = need_page_owner,
        .init = init_page_owner,
};

static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
{
        return (void *)page_ext + page_owner_ops.offset;
}

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);
                if (unlikely(!page_ext))
                        continue;
                __clear_bit(PAGE_EXT_OWNER, &page_ext->flags);
        }
}

static inline bool check_recursive_alloc(struct stack_trace *trace,
                                        unsigned long ip)
{
        int i, count;

        if (!trace->nr_entries)
                return false;

        for (i = 0, count = 0; i < trace->nr_entries; i++) {
                if (trace->entries[i] == ip && ++count == 2)
                        return true;
        }

        return false;
}

static noinline depot_stack_handle_t save_stack(gfp_t flags)
{
        unsigned long entries[PAGE_OWNER_STACK_DEPTH];
        struct stack_trace trace = {
                .nr_entries = 0,
                .entries = entries,
                .max_entries = PAGE_OWNER_STACK_DEPTH,
                .skip = 0
        };
        depot_stack_handle_t handle;

        save_stack_trace(&trace);
        if (trace.nr_entries != 0 &&
            trace.entries[trace.nr_entries-1] == ULONG_MAX)
                trace.nr_entries--;

        /*
         * We need to check recursion here because our request to stackdepot
         * could trigger memory allocation to save new entry. New memory
         * allocation would reach here and call depot_save_stack() again
         * if we don't catch it. There is still not enough memory in stackdepot
         * so it would try to allocate memory again and loop forever.
         */
        if (check_recursive_alloc(&trace, _RET_IP_))
                return dummy_handle;

        handle = depot_save_stack(&trace, flags);
        if (!handle)
                handle = failure_handle;

        return handle;
}

noinline void __set_page_owner(struct page *page, unsigned int order,
                                        gfp_t gfp_mask)
{
        struct page_ext *page_ext = lookup_page_ext(page);
        struct page_owner *page_owner;

        if (unlikely(!page_ext))
                return;

        page_owner = get_page_owner(page_ext);
        page_owner->handle = save_stack(gfp_mask);
        page_owner->order = order;
        page_owner->gfp_mask = gfp_mask;
        page_owner->last_migrate_reason = -1;

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

void __set_page_owner_migrate_reason(struct page *page, int reason)
{
        struct page_ext *page_ext = lookup_page_ext(page);
        struct page_owner *page_owner;

        if (unlikely(!page_ext))
                return;

        page_owner = get_page_owner(page_ext);
        page_owner->last_migrate_reason = reason;
}

void __split_page_owner(struct page *page, unsigned int order)
{
        int i;
        struct page_ext *page_ext = lookup_page_ext(page);
        struct page_owner *page_owner;

        if (unlikely(!page_ext))
                return;

        page_owner = get_page_owner(page_ext);
        page_owner->order = 0;
        for (i = 1; i < (1 << order); i++)
                __copy_page_owner(page, page + i);
}

void __copy_page_owner(struct page *oldpage, struct page *newpage)
{
        struct page_ext *old_ext = lookup_page_ext(oldpage);
        struct page_ext *new_ext = lookup_page_ext(newpage);
        struct page_owner *old_page_owner, *new_page_owner;

        if (unlikely(!old_ext || !new_ext))
                return;

        old_page_owner = get_page_owner(old_ext);
        new_page_owner = get_page_owner(new_ext);
        new_page_owner->order = old_page_owner->order;
        new_page_owner->gfp_mask = old_page_owner->gfp_mask;
        new_page_owner->last_migrate_reason =
                old_page_owner->last_migrate_reason;
        new_page_owner->handle = old_page_owner->handle;

        /*
         * We don't clear the bit on the oldpage as it's going to be freed
         * after migration. Until then, the info can be useful in case of
         * a bug, and the overal stats will be off a bit only temporarily.
         * Also, migrate_misplaced_transhuge_page() can still fail the
         * migration and then we want the oldpage to retain the info. But
         * in that case we also don't need to explicitly clear the info from
         * the new page, which will be freed.
         */
        __set_bit(PAGE_EXT_OWNER, &new_ext->flags);
}

void pagetypeinfo_showmixedcount_print(struct seq_file *m,
                                       pg_data_t *pgdat, struct zone *zone)
{
        struct page *page;
        struct page_ext *page_ext;
        struct page_owner *page_owner;
        unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
        unsigned long end_pfn = pfn + zone->spanned_pages;
        unsigned long count[MIGRATE_TYPES] = { 0, };
        int pageblock_mt, page_mt;
        int i;

        /* 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);
                pageblock_mt = get_pageblock_migratetype(page);

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

                        page = pfn_to_page(pfn);

                        if (page_zone(page) != zone)
                                continue;

                        if (PageBuddy(page)) {
                                pfn += (1UL << page_order(page)) - 1;
                                continue;
                        }

                        if (PageReserved(page))
                                continue;

                        page_ext = lookup_page_ext(page);
                        if (unlikely(!page_ext))
                                continue;

                        if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
                                continue;

                        page_owner = get_page_owner(page_ext);
                        page_mt = gfpflags_to_migratetype(
                                        page_owner->gfp_mask);
                        if (pageblock_mt != page_mt) {
                                if (is_migrate_cma(pageblock_mt))
                                        count[MIGRATE_MOVABLE]++;
                                else
                                        count[pageblock_mt]++;

                                pfn = block_end_pfn;
                                break;
                        }
                        pfn += (1UL << page_owner->order) - 1;
                }
        }

        /* Print counts */
        seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
        for (i = 0; i < MIGRATE_TYPES; i++)
                seq_printf(m, "%12lu ", count[i]);
        seq_putc(m, '\n');
}

static ssize_t
print_page_owner(char __user *buf, size_t count, unsigned long pfn,
                struct page *page, struct page_owner *page_owner,
                depot_stack_handle_t handle)
{
        int ret;
        int pageblock_mt, page_mt;
        char *kbuf;
        unsigned long entries[PAGE_OWNER_STACK_DEPTH];
        struct stack_trace trace = {
                .nr_entries = 0,
                .entries = entries,
                .max_entries = PAGE_OWNER_STACK_DEPTH,
                .skip = 0
        };

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

        ret = snprintf(kbuf, count,
                        "Page allocated via order %u, mask %#x(%pGg)\n",
                        page_owner->order, page_owner->gfp_mask,
                        &page_owner->gfp_mask);

        if (ret >= count)
                goto err;

        /* Print information relevant to grouping pages by mobility */
        pageblock_mt = get_pageblock_migratetype(page);
        page_mt  = gfpflags_to_migratetype(page_owner->gfp_mask);
        ret += snprintf(kbuf + ret, count - ret,
                        "PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)\n",
                        pfn,
                        migratetype_names[page_mt],
                        pfn >> pageblock_order,
                        migratetype_names[pageblock_mt],
                        page->flags, &page->flags);

        if (ret >= count)
                goto err;

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

        if (page_owner->last_migrate_reason != -1) {
                ret += snprintf(kbuf + ret, count - ret,
                        "Page has been migrated, last migrate reason: %s\n",
                        migrate_reason_names[page_owner->last_migrate_reason]);
                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;
}

void __dump_page_owner(struct page *page)
{
        struct page_ext *page_ext = lookup_page_ext(page);
        struct page_owner *page_owner;
        unsigned long entries[PAGE_OWNER_STACK_DEPTH];
        struct stack_trace trace = {
                .nr_entries = 0,
                .entries = entries,
                .max_entries = PAGE_OWNER_STACK_DEPTH,
                .skip = 0
        };
        depot_stack_handle_t handle;
        gfp_t gfp_mask;
        int mt;

        if (unlikely(!page_ext)) {
                pr_alert("There is not page extension available.\n");
                return;
        }

        page_owner = get_page_owner(page_ext);
        gfp_mask = page_owner->gfp_mask;
        mt = gfpflags_to_migratetype(gfp_mask);

        if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
                pr_alert("page_owner info is not active (free page?)\n");
                return;
        }

        handle = READ_ONCE(page_owner->handle);
        if (!handle) {
                pr_alert("page_owner info is not active (free page?)\n");
                return;
        }

        depot_fetch_stack(handle, &trace);
        pr_alert("page allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)\n",
                 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask);
        print_stack_trace(&trace, 0);

        if (page_owner->last_migrate_reason != -1)
                pr_alert("page has been migrated, last migrate reason: %s\n",
                        migrate_reason_names[page_owner->last_migrate_reason]);
}

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;
        struct page_owner *page_owner;
        depot_stack_handle_t handle;

        if (!static_branch_unlikely(&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);
                if (unlikely(!page_ext))
                        continue;

                /*
                 * 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;

                page_owner = get_page_owner(page_ext);

                /*
                 * Access to page_ext->handle isn't synchronous so we should
                 * be careful to access it.
                 */
                handle = READ_ONCE(page_owner->handle);
                if (!handle)
                        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_owner, handle);
        }

        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);

                        if (page_zone(page) != zone)
                                continue;

                        /*
                         * 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);
                        if (unlikely(!page_ext))
                                continue;

                        /* 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 (!static_branch_unlikely(&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)