// SPDX-License-Identifier: GPL-2.0
#include <linux/debugfs.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/memblock.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 <linux/sched/clock.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 short order;
        short last_migrate_reason;
        gfp_t gfp_mask;
        depot_stack_handle_t handle;
        depot_stack_handle_t free_handle;
        u64 ts_nsec;
        u64 free_ts_nsec;
        pid_t pid;
};

static bool page_owner_enabled = false;
DEFINE_STATIC_KEY_FALSE(page_owner_inited);

static depot_stack_handle_t dummy_handle;
static depot_stack_handle_t failure_handle;
static depot_stack_handle_t early_handle;

static void init_early_allocated_pages(void);

static int __init early_page_owner_param(char *buf)
{
        return kstrtobool(buf, &page_owner_enabled);
}
early_param("page_owner", early_page_owner_param);

static bool need_page_owner(void)
{
        return page_owner_enabled;
}

static __always_inline depot_stack_handle_t create_dummy_stack(void)
{
        unsigned long entries[4];
        unsigned int nr_entries;

        nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
        return stack_depot_save(entries, nr_entries, GFP_KERNEL);
}

static noinline void register_dummy_stack(void)
{
        dummy_handle = create_dummy_stack();
}

static noinline void register_failure_stack(void)
{
        failure_handle = create_dummy_stack();
}

static noinline void register_early_stack(void)
{
        early_handle = create_dummy_stack();
}

static void init_page_owner(void)
{
        if (!page_owner_enabled)
                return;

        register_dummy_stack();
        register_failure_stack();
        register_early_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;
}

static noinline depot_stack_handle_t save_stack(gfp_t flags)
{
        unsigned long entries[PAGE_OWNER_STACK_DEPTH];
        depot_stack_handle_t handle;
        unsigned int nr_entries;

        /*
         * Avoid recursion.
         *
         * Sometimes page metadata allocation tracking requires more
         * memory to be allocated:
         * - when new stack trace is saved to stack depot
         * - when backtrace itself is calculated (ia64)
         */
        if (current->in_page_owner)
                return dummy_handle;
        current->in_page_owner = 1;

        nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
        handle = stack_depot_save(entries, nr_entries, flags);
        if (!handle)
                handle = failure_handle;

        current->in_page_owner = 0;
        return handle;
}

void __reset_page_owner(struct page *page, unsigned int order)
{
        int i;
        struct page_ext *page_ext;
        depot_stack_handle_t handle;
        struct page_owner *page_owner;
        u64 free_ts_nsec = local_clock();

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

        handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
        for (i = 0; i < (1 << order); i++) {
                __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
                page_owner = get_page_owner(page_ext);
                page_owner->free_handle = handle;
                page_owner->free_ts_nsec = free_ts_nsec;
                page_ext = page_ext_next(page_ext);
        }
}

static inline void __set_page_owner_handle(struct page_ext *page_ext,
                                        depot_stack_handle_t handle,
                                        unsigned int order, gfp_t gfp_mask)
{
        struct page_owner *page_owner;
        int i;

        for (i = 0; i < (1 << order); i++) {
                page_owner = get_page_owner(page_ext);
                page_owner->handle = handle;
                page_owner->order = order;
                page_owner->gfp_mask = gfp_mask;
                page_owner->last_migrate_reason = -1;
                page_owner->pid = current->pid;
                page_owner->ts_nsec = local_clock();
                __set_bit(PAGE_EXT_OWNER, &page_ext->flags);
                __set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);

                page_ext = page_ext_next(page_ext);
        }
}

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

        if (unlikely(!page_ext))
                return;

        handle = save_stack(gfp_mask);
        __set_page_owner_handle(page_ext, handle, order, gfp_mask);
}

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 nr)
{
        int i;
        struct page_ext *page_ext = lookup_page_ext(page);
        struct page_owner *page_owner;

        if (unlikely(!page_ext))
                return;

        for (i = 0; i < nr; i++) {
                page_owner = get_page_owner(page_ext);
                page_owner->order = 0;
                page_ext = page_ext_next(page_ext);
        }
}

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;
        new_page_owner->pid = old_page_owner->pid;
        new_page_owner->ts_nsec = old_page_owner->ts_nsec;
        new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;

        /*
         * 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 overall 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);
        __set_bit(PAGE_EXT_OWNER_ALLOCATED, &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, block_end_pfn;
        unsigned long end_pfn = zone_end_pfn(zone);
        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; ) {
                page = pfn_to_online_page(pfn);
                if (!page) {
                        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);

                pageblock_mt = get_pageblock_migratetype(page);

                for (; pfn < block_end_pfn; pfn++) {
                        /* The pageblock is online, no need to recheck. */
                        page = pfn_to_page(pfn);

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

                        if (PageBuddy(page)) {
                                unsigned long freepage_order;

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

                        if (PageReserved(page))
                                continue;

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

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

                        page_owner = get_page_owner(page_ext);
                        page_mt = gfp_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, pageblock_mt, page_mt;
        unsigned long *entries;
        unsigned int nr_entries;
        char *kbuf;

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

        ret = snprintf(kbuf, count,
                        "Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, free_ts %llu ns\n",
                        page_owner->order, page_owner->gfp_mask,
                        &page_owner->gfp_mask, page_owner->pid,
                        page_owner->ts_nsec, page_owner->free_ts_nsec);

        if (ret >= count)
                goto err;

        /* Print information relevant to grouping pages by mobility */
        pageblock_mt = get_pageblock_migratetype(page);
        page_mt  = gfp_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;

        nr_entries = stack_depot_fetch(handle, &entries);
        ret += stack_trace_snprint(kbuf + ret, count - ret, entries, nr_entries, 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(const struct page *page)
{
        struct page_ext *page_ext = lookup_page_ext(page);
        struct page_owner *page_owner;
        depot_stack_handle_t handle;
        unsigned long *entries;
        unsigned int nr_entries;
        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 = gfp_migratetype(gfp_mask);

        if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
                pr_alert("page_owner info is not present (never set?)\n");
                return;
        }

        if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
                pr_alert("page_owner tracks the page as allocated\n");
        else
                pr_alert("page_owner tracks the page as freed\n");

        pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d, ts %llu, free_ts %llu\n",
                 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
                 page_owner->pid, page_owner->ts_nsec, page_owner->free_ts_nsec);

        handle = READ_ONCE(page_owner->handle);
        if (!handle) {
                pr_alert("page_owner allocation stack trace missing\n");
        } else {
                nr_entries = stack_depot_fetch(handle, &entries);
                stack_trace_print(entries, nr_entries, 0);
        }

        handle = READ_ONCE(page_owner->free_handle);
        if (!handle) {
                pr_alert("page_owner free stack trace missing\n");
        } else {
                nr_entries = stack_depot_fetch(handle, &entries);
                pr_alert("page last free stack trace:\n");
                stack_trace_print(entries, nr_entries, 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;
                }

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

                /*
                 * Although we do have the info about past allocation of free
                 * pages, it's not relevant for current memory usage.
                 */
                if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
                        continue;

                page_owner = get_page_owner(page_ext);

                /*
                 * Don't print "tail" pages of high-order allocations as that
                 * would inflate the stats.
                 */
                if (!IS_ALIGNED(pfn, 1 << page_owner->order))
                        continue;

                /*
                 * 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)
{
        unsigned long pfn = zone->zone_start_pfn;
        unsigned long end_pfn = zone_end_pfn(zone);
        unsigned long count = 0;

        /*
         * 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; ) {
                unsigned long block_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);

                for (; pfn < block_end_pfn; pfn++) {
                        struct page *page = pfn_to_page(pfn);
                        struct page_ext *page_ext;

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

                        /*
                         * To avoid having to grab zone->lock, be a little
                         * careful when reading buddy page order. The only
                         * danger is that we skip too much and potentially miss
                         * some early allocated pages, which is better than
                         * heavy lock contention.
                         */
                        if (PageBuddy(page)) {
                                unsigned long order = buddy_order_unsafe(page);

                                if (order > 0 && order < MAX_ORDER)
                                        pfn += (1UL << order) - 1;
                                continue;
                        }

                        if (PageReserved(page))
                                continue;

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

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

                        /* Found early allocated page */
                        __set_page_owner_handle(page_ext, early_handle,
                                                0, 0);
                        count++;
                }
                cond_resched();
        }

        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;

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

                init_pages_in_zone(pgdat, zone);
        }
}

static void init_early_allocated_pages(void)
{
        pg_data_t *pgdat;

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

        debugfs_create_file("page_owner", 0400, NULL, NULL,
                            &proc_page_owner_operations);

        return 0;
}
late_initcall(pageowner_init)