// SPDX-License-Identifier: GPL-2.0
/*
 * DAMON Code for The Physical Address Space
 *
 * Author: SeongJae Park <sj@kernel.org>
 */

#define pr_fmt(fmt) "damon-pa: " fmt

#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/memory-tiers.h>
#include <linux/mm_inline.h>

#include "../internal.h"
#include "ops-common.h"

static phys_addr_t damon_pa_phys_addr(
                unsigned long addr, unsigned long addr_unit)
{
        return (phys_addr_t)addr * addr_unit;
}

static unsigned long damon_pa_core_addr(
                phys_addr_t pa, unsigned long addr_unit)
{
        /*
         * Use div_u64() for avoiding linking errors related with __udivdi3,
         * __aeabi_uldivmod, or similar problems.  This should also improve the
         * performance optimization (read div_u64() comment for the detail).
         */
        if (sizeof(pa) == 8 && sizeof(addr_unit) == 4)
                return div_u64(pa, addr_unit);
        return pa / addr_unit;
}

static void damon_pa_mkold(phys_addr_t paddr)
{
        struct folio *folio = damon_get_folio(PHYS_PFN(paddr));

        if (!folio)
                return;

        damon_folio_mkold(folio);
        folio_put(folio);
}

static void __damon_pa_prepare_access_check(struct damon_region *r,
                unsigned long addr_unit)
{
        r->sampling_addr = damon_rand(r->ar.start, r->ar.end);

        damon_pa_mkold(damon_pa_phys_addr(r->sampling_addr, addr_unit));
}

static void damon_pa_prepare_access_checks(struct damon_ctx *ctx)
{
        struct damon_target *t;
        struct damon_region *r;

        damon_for_each_target(t, ctx) {
                damon_for_each_region(r, t)
                        __damon_pa_prepare_access_check(r, ctx->addr_unit);
        }
}

static bool damon_pa_young(phys_addr_t paddr, unsigned long *folio_sz)
{
        struct folio *folio = damon_get_folio(PHYS_PFN(paddr));
        bool accessed;

        if (!folio)
                return false;

        accessed = damon_folio_young(folio);
        *folio_sz = folio_size(folio);
        folio_put(folio);
        return accessed;
}

static void __damon_pa_check_access(struct damon_region *r,
                struct damon_attrs *attrs, unsigned long addr_unit)
{
        static phys_addr_t last_addr;
        static unsigned long last_folio_sz = PAGE_SIZE;
        static bool last_accessed;
        phys_addr_t sampling_addr = damon_pa_phys_addr(
                        r->sampling_addr, addr_unit);

        /* If the region is in the last checked page, reuse the result */
        if (ALIGN_DOWN(last_addr, last_folio_sz) ==
                                ALIGN_DOWN(sampling_addr, last_folio_sz)) {
                damon_update_region_access_rate(r, last_accessed, attrs);
                return;
        }

        last_accessed = damon_pa_young(sampling_addr, &last_folio_sz);
        damon_update_region_access_rate(r, last_accessed, attrs);

        last_addr = sampling_addr;
}

static unsigned int damon_pa_check_accesses(struct damon_ctx *ctx)
{
        struct damon_target *t;
        struct damon_region *r;
        unsigned int max_nr_accesses = 0;

        damon_for_each_target(t, ctx) {
                damon_for_each_region(r, t) {
                        __damon_pa_check_access(
                                        r, &ctx->attrs, ctx->addr_unit);
                        max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
                }
        }

        return max_nr_accesses;
}

/*
 * damos_pa_filter_out - Return true if the page should be filtered out.
 */
static bool damos_pa_filter_out(struct damos *scheme, struct folio *folio)
{
        struct damos_filter *filter;

        if (scheme->core_filters_allowed)
                return false;

        damos_for_each_ops_filter(filter, scheme) {
                if (damos_folio_filter_match(filter, folio))
                        return !filter->allow;
        }
        return scheme->ops_filters_default_reject;
}

static bool damon_pa_invalid_damos_folio(struct folio *folio, struct damos *s)
{
        if (!folio)
                return true;
        if (folio == s->last_applied) {
                folio_put(folio);
                return true;
        }
        return false;
}

static unsigned long damon_pa_pageout(struct damon_region *r,
                unsigned long addr_unit, struct damos *s,
                unsigned long *sz_filter_passed)
{
        phys_addr_t addr, applied;
        LIST_HEAD(folio_list);
        bool install_young_filter = true;
        struct damos_filter *filter;
        struct folio *folio = NULL;

        /* check access in page level again by default */
        damos_for_each_ops_filter(filter, s) {
                if (filter->type == DAMOS_FILTER_TYPE_YOUNG) {
                        install_young_filter = false;
                        break;
                }
        }
        if (install_young_filter) {
                filter = damos_new_filter(
                                DAMOS_FILTER_TYPE_YOUNG, true, false);
                if (!filter)
                        return 0;
                damos_add_filter(s, filter);
        }

        addr = damon_pa_phys_addr(r->ar.start, addr_unit);
        while (addr < damon_pa_phys_addr(r->ar.end, addr_unit)) {
                folio = damon_get_folio(PHYS_PFN(addr));
                if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }

                if (damos_pa_filter_out(s, folio))
                        goto put_folio;
                else
                        *sz_filter_passed += folio_size(folio) / addr_unit;

                folio_clear_referenced(folio);
                folio_test_clear_young(folio);
                if (!folio_isolate_lru(folio))
                        goto put_folio;
                if (folio_test_unevictable(folio))
                        folio_putback_lru(folio);
                else
                        list_add(&folio->lru, &folio_list);
put_folio:
                addr += folio_size(folio);
                folio_put(folio);
        }
        if (install_young_filter)
                damos_destroy_filter(filter);
        applied = reclaim_pages(&folio_list);
        cond_resched();
        s->last_applied = folio;
        return damon_pa_core_addr(applied * PAGE_SIZE, addr_unit);
}

static inline unsigned long damon_pa_de_activate(
                struct damon_region *r, unsigned long addr_unit,
                struct damos *s, bool activate,
                unsigned long *sz_filter_passed)
{
        phys_addr_t addr, applied = 0;
        struct folio *folio = NULL;

        addr = damon_pa_phys_addr(r->ar.start, addr_unit);
        while (addr < damon_pa_phys_addr(r->ar.end, addr_unit)) {
                folio = damon_get_folio(PHYS_PFN(addr));
                if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }

                if (damos_pa_filter_out(s, folio))
                        goto put_folio;
                else
                        *sz_filter_passed += folio_size(folio) / addr_unit;

                if (activate)
                        folio_activate(folio);
                else
                        folio_deactivate(folio);
                applied += folio_nr_pages(folio);
put_folio:
                addr += folio_size(folio);
                folio_put(folio);
        }
        s->last_applied = folio;
        return damon_pa_core_addr(applied * PAGE_SIZE, addr_unit);
}

static unsigned long damon_pa_activate_pages(struct damon_region *r,
                unsigned long addr_unit, struct damos *s,
                unsigned long *sz_filter_passed)
{
        return damon_pa_de_activate(r, addr_unit, s, true, sz_filter_passed);
}

static unsigned long damon_pa_deactivate_pages(struct damon_region *r,
                unsigned long addr_unit, struct damos *s,
                unsigned long *sz_filter_passed)
{
        return damon_pa_de_activate(r, addr_unit, s, false, sz_filter_passed);
}

static unsigned long damon_pa_migrate(struct damon_region *r,
                unsigned long addr_unit, struct damos *s,
                unsigned long *sz_filter_passed)
{
        phys_addr_t addr, applied;
        LIST_HEAD(folio_list);
        struct folio *folio = NULL;

        addr = damon_pa_phys_addr(r->ar.start, addr_unit);
        while (addr < damon_pa_phys_addr(r->ar.end, addr_unit)) {
                folio = damon_get_folio(PHYS_PFN(addr));
                if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }

                if (damos_pa_filter_out(s, folio))
                        goto put_folio;
                else
                        *sz_filter_passed += folio_size(folio) / addr_unit;

                if (!folio_isolate_lru(folio))
                        goto put_folio;
                list_add(&folio->lru, &folio_list);
put_folio:
                addr += folio_size(folio);
                folio_put(folio);
        }
        applied = damon_migrate_pages(&folio_list, s->target_nid);
        cond_resched();
        s->last_applied = folio;
        return damon_pa_core_addr(applied * PAGE_SIZE, addr_unit);
}

static unsigned long damon_pa_stat(struct damon_region *r,
                unsigned long addr_unit, struct damos *s,
                unsigned long *sz_filter_passed)
{
        phys_addr_t addr;
        struct folio *folio = NULL;

        if (!damos_ops_has_filter(s))
                return 0;

        addr = damon_pa_phys_addr(r->ar.start, addr_unit);
        while (addr < damon_pa_phys_addr(r->ar.end, addr_unit)) {
                folio = damon_get_folio(PHYS_PFN(addr));
                if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }

                if (!damos_pa_filter_out(s, folio))
                        *sz_filter_passed += folio_size(folio) / addr_unit;
                addr += folio_size(folio);
                folio_put(folio);
        }
        s->last_applied = folio;
        return 0;
}

static unsigned long damon_pa_apply_scheme(struct damon_ctx *ctx,
                struct damon_target *t, struct damon_region *r,
                struct damos *scheme, unsigned long *sz_filter_passed)
{
        unsigned long aunit = ctx->addr_unit;

        switch (scheme->action) {
        case DAMOS_PAGEOUT:
                return damon_pa_pageout(r, aunit, scheme, sz_filter_passed);
        case DAMOS_LRU_PRIO:
                return damon_pa_activate_pages(r, aunit, scheme,
                                sz_filter_passed);
        case DAMOS_LRU_DEPRIO:
                return damon_pa_deactivate_pages(r, aunit, scheme,
                                sz_filter_passed);
        case DAMOS_MIGRATE_HOT:
        case DAMOS_MIGRATE_COLD:
                return damon_pa_migrate(r, aunit, scheme, sz_filter_passed);
        case DAMOS_STAT:
                return damon_pa_stat(r, aunit, scheme, sz_filter_passed);
        default:
                /* DAMOS actions that not yet supported by 'paddr'. */
                break;
        }
        return 0;
}

static int damon_pa_scheme_score(struct damon_ctx *context,
                struct damon_target *t, struct damon_region *r,
                struct damos *scheme)
{
        switch (scheme->action) {
        case DAMOS_PAGEOUT:
                return damon_cold_score(context, r, scheme);
        case DAMOS_LRU_PRIO:
                return damon_hot_score(context, r, scheme);
        case DAMOS_LRU_DEPRIO:
                return damon_cold_score(context, r, scheme);
        case DAMOS_MIGRATE_HOT:
                return damon_hot_score(context, r, scheme);
        case DAMOS_MIGRATE_COLD:
                return damon_cold_score(context, r, scheme);
        default:
                break;
        }

        return DAMOS_MAX_SCORE;
}

static int __init damon_pa_initcall(void)
{
        struct damon_operations ops = {
                .id = DAMON_OPS_PADDR,
                .init = NULL,
                .update = NULL,
                .prepare_access_checks = damon_pa_prepare_access_checks,
                .check_accesses = damon_pa_check_accesses,
                .target_valid = NULL,
                .apply_scheme = damon_pa_apply_scheme,
                .get_scheme_score = damon_pa_scheme_score,
        };

        return damon_register_ops(&ops);
};

subsys_initcall(damon_pa_initcall);