// SPDX-License-Identifier: GPL-2.0
/*
 * fs/f2fs/gc.c
 *
 * Copyright (c) 2012 Samsung Electronics Co., Ltd.
 *             http://www.samsung.com/
 */
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/backing-dev.h>
#include <linux/init.h>
#include <linux/f2fs_fs.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/freezer.h>
#include <linux/sched/signal.h>

#include "f2fs.h"
#include "node.h"
#include "segment.h"
#include "gc.h"
#include <trace/events/f2fs.h>

static struct kmem_cache *victim_entry_slab;

static unsigned int count_bits(const unsigned long *addr,
                                unsigned int offset, unsigned int len);

static int gc_thread_func(void *data)
{
        struct f2fs_sb_info *sbi = data;
        struct f2fs_gc_kthread *gc_th = sbi->gc_thread;
        wait_queue_head_t *wq = &sbi->gc_thread->gc_wait_queue_head;
        wait_queue_head_t *fggc_wq = &sbi->gc_thread->fggc_wq;
        unsigned int wait_ms;

        wait_ms = gc_th->min_sleep_time;

        set_freezable();
        do {
                bool sync_mode, foreground = false;

                wait_event_interruptible_timeout(*wq,
                                kthread_should_stop() || freezing(current) ||
                                waitqueue_active(fggc_wq) ||
                                gc_th->gc_wake,
                                msecs_to_jiffies(wait_ms));

                if (test_opt(sbi, GC_MERGE) && waitqueue_active(fggc_wq))
                        foreground = true;

                /* give it a try one time */
                if (gc_th->gc_wake)
                        gc_th->gc_wake = 0;

                if (try_to_freeze()) {
                        stat_other_skip_bggc_count(sbi);
                        continue;
                }
                if (kthread_should_stop())
                        break;

                if (sbi->sb->s_writers.frozen >= SB_FREEZE_WRITE) {
                        increase_sleep_time(gc_th, &wait_ms);
                        stat_other_skip_bggc_count(sbi);
                        continue;
                }

                if (time_to_inject(sbi, FAULT_CHECKPOINT)) {
                        f2fs_show_injection_info(sbi, FAULT_CHECKPOINT);
                        f2fs_stop_checkpoint(sbi, false);
                }

                if (!sb_start_write_trylock(sbi->sb)) {
                        stat_other_skip_bggc_count(sbi);
                        continue;
                }

                /*
                 * [GC triggering condition]
                 * 0. GC is not conducted currently.
                 * 1. There are enough dirty segments.
                 * 2. IO subsystem is idle by checking the # of writeback pages.
                 * 3. IO subsystem is idle by checking the # of requests in
                 *    bdev's request list.
                 *
                 * Note) We have to avoid triggering GCs frequently.
                 * Because it is possible that some segments can be
                 * invalidated soon after by user update or deletion.
                 * So, I'd like to wait some time to collect dirty segments.
                 */
                if (sbi->gc_mode == GC_URGENT_HIGH) {
                        wait_ms = gc_th->urgent_sleep_time;
                        down_write(&sbi->gc_lock);
                        goto do_gc;
                }

                if (foreground) {
                        down_write(&sbi->gc_lock);
                        goto do_gc;
                } else if (!down_write_trylock(&sbi->gc_lock)) {
                        stat_other_skip_bggc_count(sbi);
                        goto next;
                }

                if (!is_idle(sbi, GC_TIME)) {
                        increase_sleep_time(gc_th, &wait_ms);
                        up_write(&sbi->gc_lock);
                        stat_io_skip_bggc_count(sbi);
                        goto next;
                }

                if (has_enough_invalid_blocks(sbi))
                        decrease_sleep_time(gc_th, &wait_ms);
                else
                        increase_sleep_time(gc_th, &wait_ms);
do_gc:
                if (!foreground)
                        stat_inc_bggc_count(sbi->stat_info);

                sync_mode = F2FS_OPTION(sbi).bggc_mode == BGGC_MODE_SYNC;

                /* foreground GC was been triggered via f2fs_balance_fs() */
                if (foreground)
                        sync_mode = false;

                /* if return value is not zero, no victim was selected */
                if (f2fs_gc(sbi, sync_mode, !foreground, false, NULL_SEGNO))
                        wait_ms = gc_th->no_gc_sleep_time;

                if (foreground)
                        wake_up_all(&gc_th->fggc_wq);

                trace_f2fs_background_gc(sbi->sb, wait_ms,
                                prefree_segments(sbi), free_segments(sbi));

                /* balancing f2fs's metadata periodically */
                f2fs_balance_fs_bg(sbi, true);
next:
                sb_end_write(sbi->sb);

        } while (!kthread_should_stop());
        return 0;
}

int f2fs_start_gc_thread(struct f2fs_sb_info *sbi)
{
        struct f2fs_gc_kthread *gc_th;
        dev_t dev = sbi->sb->s_bdev->bd_dev;
        int err = 0;

        gc_th = f2fs_kmalloc(sbi, sizeof(struct f2fs_gc_kthread), GFP_KERNEL);
        if (!gc_th) {
                err = -ENOMEM;
                goto out;
        }

        gc_th->urgent_sleep_time = DEF_GC_THREAD_URGENT_SLEEP_TIME;
        gc_th->min_sleep_time = DEF_GC_THREAD_MIN_SLEEP_TIME;
        gc_th->max_sleep_time = DEF_GC_THREAD_MAX_SLEEP_TIME;
        gc_th->no_gc_sleep_time = DEF_GC_THREAD_NOGC_SLEEP_TIME;

        gc_th->gc_wake = 0;

        sbi->gc_thread = gc_th;
        init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
        init_waitqueue_head(&sbi->gc_thread->fggc_wq);
        sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi,
                        "f2fs_gc-%u:%u", MAJOR(dev), MINOR(dev));
        if (IS_ERR(gc_th->f2fs_gc_task)) {
                err = PTR_ERR(gc_th->f2fs_gc_task);
                kfree(gc_th);
                sbi->gc_thread = NULL;
        }
out:
        return err;
}

void f2fs_stop_gc_thread(struct f2fs_sb_info *sbi)
{
        struct f2fs_gc_kthread *gc_th = sbi->gc_thread;

        if (!gc_th)
                return;
        kthread_stop(gc_th->f2fs_gc_task);
        wake_up_all(&gc_th->fggc_wq);
        kfree(gc_th);
        sbi->gc_thread = NULL;
}

static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
{
        int gc_mode;

        if (gc_type == BG_GC) {
                if (sbi->am.atgc_enabled)
                        gc_mode = GC_AT;
                else
                        gc_mode = GC_CB;
        } else {
                gc_mode = GC_GREEDY;
        }

        switch (sbi->gc_mode) {
        case GC_IDLE_CB:
                gc_mode = GC_CB;
                break;
        case GC_IDLE_GREEDY:
        case GC_URGENT_HIGH:
                gc_mode = GC_GREEDY;
                break;
        case GC_IDLE_AT:
                gc_mode = GC_AT;
                break;
        }

        return gc_mode;
}

static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
                        int type, struct victim_sel_policy *p)
{
        struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);

        if (p->alloc_mode == SSR) {
                p->gc_mode = GC_GREEDY;
                p->dirty_bitmap = dirty_i->dirty_segmap[type];
                p->max_search = dirty_i->nr_dirty[type];
                p->ofs_unit = 1;
        } else if (p->alloc_mode == AT_SSR) {
                p->gc_mode = GC_GREEDY;
                p->dirty_bitmap = dirty_i->dirty_segmap[type];
                p->max_search = dirty_i->nr_dirty[type];
                p->ofs_unit = 1;
        } else {
                p->gc_mode = select_gc_type(sbi, gc_type);
                p->ofs_unit = sbi->segs_per_sec;
                if (__is_large_section(sbi)) {
                        p->dirty_bitmap = dirty_i->dirty_secmap;
                        p->max_search = count_bits(p->dirty_bitmap,
                                                0, MAIN_SECS(sbi));
                } else {
                        p->dirty_bitmap = dirty_i->dirty_segmap[DIRTY];
                        p->max_search = dirty_i->nr_dirty[DIRTY];
                }
        }

        /*
         * adjust candidates range, should select all dirty segments for
         * foreground GC and urgent GC cases.
         */
        if (gc_type != FG_GC &&
                        (sbi->gc_mode != GC_URGENT_HIGH) &&
                        (p->gc_mode != GC_AT && p->alloc_mode != AT_SSR) &&
                        p->max_search > sbi->max_victim_search)
                p->max_search = sbi->max_victim_search;

        /* let's select beginning hot/small space first in no_heap mode*/
        if (test_opt(sbi, NOHEAP) &&
                (type == CURSEG_HOT_DATA || IS_NODESEG(type)))
                p->offset = 0;
        else
                p->offset = SIT_I(sbi)->last_victim[p->gc_mode];
}

static unsigned int get_max_cost(struct f2fs_sb_info *sbi,
                                struct victim_sel_policy *p)
{
        /* SSR allocates in a segment unit */
        if (p->alloc_mode == SSR)
                return sbi->blocks_per_seg;
        else if (p->alloc_mode == AT_SSR)
                return UINT_MAX;

        /* LFS */
        if (p->gc_mode == GC_GREEDY)
                return 2 * sbi->blocks_per_seg * p->ofs_unit;
        else if (p->gc_mode == GC_CB)
                return UINT_MAX;
        else if (p->gc_mode == GC_AT)
                return UINT_MAX;
        else /* No other gc_mode */
                return 0;
}

static unsigned int check_bg_victims(struct f2fs_sb_info *sbi)
{
        struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
        unsigned int secno;

        /*
         * If the gc_type is FG_GC, we can select victim segments
         * selected by background GC before.
         * Those segments guarantee they have small valid blocks.
         */
        for_each_set_bit(secno, dirty_i->victim_secmap, MAIN_SECS(sbi)) {
                if (sec_usage_check(sbi, secno))
                        continue;
                clear_bit(secno, dirty_i->victim_secmap);
                return GET_SEG_FROM_SEC(sbi, secno);
        }
        return NULL_SEGNO;
}

static unsigned int get_cb_cost(struct f2fs_sb_info *sbi, unsigned int segno)
{
        struct sit_info *sit_i = SIT_I(sbi);
        unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
        unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
        unsigned long long mtime = 0;
        unsigned int vblocks;
        unsigned char age = 0;
        unsigned char u;
        unsigned int i;
        unsigned int usable_segs_per_sec = f2fs_usable_segs_in_sec(sbi, segno);

        for (i = 0; i < usable_segs_per_sec; i++)
                mtime += get_seg_entry(sbi, start + i)->mtime;
        vblocks = get_valid_blocks(sbi, segno, true);

        mtime = div_u64(mtime, usable_segs_per_sec);
        vblocks = div_u64(vblocks, usable_segs_per_sec);

        u = (vblocks * 100) >> sbi->log_blocks_per_seg;

        /* Handle if the system time has changed by the user */
        if (mtime < sit_i->min_mtime)
                sit_i->min_mtime = mtime;
        if (mtime > sit_i->max_mtime)
                sit_i->max_mtime = mtime;
        if (sit_i->max_mtime != sit_i->min_mtime)
                age = 100 - div64_u64(100 * (mtime - sit_i->min_mtime),
                                sit_i->max_mtime - sit_i->min_mtime);

        return UINT_MAX - ((100 * (100 - u) * age) / (100 + u));
}

static inline unsigned int get_gc_cost(struct f2fs_sb_info *sbi,
                        unsigned int segno, struct victim_sel_policy *p)
{
        if (p->alloc_mode == SSR)
                return get_seg_entry(sbi, segno)->ckpt_valid_blocks;

        /* alloc_mode == LFS */
        if (p->gc_mode == GC_GREEDY)
                return get_valid_blocks(sbi, segno, true);
        else if (p->gc_mode == GC_CB)
                return get_cb_cost(sbi, segno);

        f2fs_bug_on(sbi, 1);
        return 0;
}

static unsigned int count_bits(const unsigned long *addr,
                                unsigned int offset, unsigned int len)
{
        unsigned int end = offset + len, sum = 0;

        while (offset < end) {
                if (test_bit(offset++, addr))
                        ++sum;
        }
        return sum;
}

static struct victim_entry *attach_victim_entry(struct f2fs_sb_info *sbi,
                                unsigned long long mtime, unsigned int segno,
                                struct rb_node *parent, struct rb_node **p,
                                bool left_most)
{
        struct atgc_management *am = &sbi->am;
        struct victim_entry *ve;

        ve =  f2fs_kmem_cache_alloc(victim_entry_slab, GFP_NOFS);

        ve->mtime = mtime;
        ve->segno = segno;

        rb_link_node(&ve->rb_node, parent, p);
        rb_insert_color_cached(&ve->rb_node, &am->root, left_most);

        list_add_tail(&ve->list, &am->victim_list);

        am->victim_count++;

        return ve;
}

static void insert_victim_entry(struct f2fs_sb_info *sbi,
                                unsigned long long mtime, unsigned int segno)
{
        struct atgc_management *am = &sbi->am;
        struct rb_node **p;
        struct rb_node *parent = NULL;
        bool left_most = true;

        p = f2fs_lookup_rb_tree_ext(sbi, &am->root, &parent, mtime, &left_most);
        attach_victim_entry(sbi, mtime, segno, parent, p, left_most);
}

static void add_victim_entry(struct f2fs_sb_info *sbi,
                                struct victim_sel_policy *p, unsigned int segno)
{
        struct sit_info *sit_i = SIT_I(sbi);
        unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
        unsigned int start = GET_SEG_FROM_SEC(sbi, secno);
        unsigned long long mtime = 0;
        unsigned int i;

        if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
                if (p->gc_mode == GC_AT &&
                        get_valid_blocks(sbi, segno, true) == 0)
                        return;
        }

        for (i = 0; i < sbi->segs_per_sec; i++)
                mtime += get_seg_entry(sbi, start + i)->mtime;
        mtime = div_u64(mtime, sbi->segs_per_sec);

        /* Handle if the system time has changed by the user */
        if (mtime < sit_i->min_mtime)
                sit_i->min_mtime = mtime;
        if (mtime > sit_i->max_mtime)
                sit_i->max_mtime = mtime;
        if (mtime < sit_i->dirty_min_mtime)
                sit_i->dirty_min_mtime = mtime;
        if (mtime > sit_i->dirty_max_mtime)
                sit_i->dirty_max_mtime = mtime;

        /* don't choose young section as candidate */
        if (sit_i->dirty_max_mtime - mtime < p->age_threshold)
                return;

        insert_victim_entry(sbi, mtime, segno);
}

static struct rb_node *lookup_central_victim(struct f2fs_sb_info *sbi,
                                                struct victim_sel_policy *p)
{
        struct atgc_management *am = &sbi->am;
        struct rb_node *parent = NULL;
        bool left_most;

        f2fs_lookup_rb_tree_ext(sbi, &am->root, &parent, p->age, &left_most);

        return parent;
}

static void atgc_lookup_victim(struct f2fs_sb_info *sbi,
                                                struct victim_sel_policy *p)
{
        struct sit_info *sit_i = SIT_I(sbi);
        struct atgc_management *am = &sbi->am;
        struct rb_root_cached *root = &am->root;
        struct rb_node *node;
        struct rb_entry *re;
        struct victim_entry *ve;
        unsigned long long total_time;
        unsigned long long age, u, accu;
        unsigned long long max_mtime = sit_i->dirty_max_mtime;
        unsigned long long min_mtime = sit_i->dirty_min_mtime;
        unsigned int sec_blocks = BLKS_PER_SEC(sbi);
        unsigned int vblocks;
        unsigned int dirty_threshold = max(am->max_candidate_count,
                                        am->candidate_ratio *
                                        am->victim_count / 100);
        unsigned int age_weight = am->age_weight;
        unsigned int cost;
        unsigned int iter = 0;

        if (max_mtime < min_mtime)
                return;

        max_mtime += 1;
        total_time = max_mtime - min_mtime;

        accu = div64_u64(ULLONG_MAX, total_time);
        accu = min_t(unsigned long long, div_u64(accu, 100),
                                        DEFAULT_ACCURACY_CLASS);

        node = rb_first_cached(root);
next:
        re = rb_entry_safe(node, struct rb_entry, rb_node);
        if (!re)
                return;

        ve = (struct victim_entry *)re;

        if (ve->mtime >= max_mtime || ve->mtime < min_mtime)
                goto skip;

        /* age = 10000 * x% * 60 */
        age = div64_u64(accu * (max_mtime - ve->mtime), total_time) *
                                                                age_weight;

        vblocks = get_valid_blocks(sbi, ve->segno, true);
        f2fs_bug_on(sbi, !vblocks || vblocks == sec_blocks);

        /* u = 10000 * x% * 40 */
        u = div64_u64(accu * (sec_blocks - vblocks), sec_blocks) *
                                                        (100 - age_weight);

        f2fs_bug_on(sbi, age + u >= UINT_MAX);

        cost = UINT_MAX - (age + u);
        iter++;

        if (cost < p->min_cost ||
                        (cost == p->min_cost && age > p->oldest_age)) {
                p->min_cost = cost;
                p->oldest_age = age;
                p->min_segno = ve->segno;
        }
skip:
        if (iter < dirty_threshold) {
                node = rb_next(node);
                goto next;
        }
}

/*
 * select candidates around source section in range of
 * [target - dirty_threshold, target + dirty_threshold]
 */
static void atssr_lookup_victim(struct f2fs_sb_info *sbi,
                                                struct victim_sel_policy *p)
{
        struct sit_info *sit_i = SIT_I(sbi);
        struct atgc_management *am = &sbi->am;
        struct rb_node *node;
        struct rb_entry *re;
        struct victim_entry *ve;
        unsigned long long age;
        unsigned long long max_mtime = sit_i->dirty_max_mtime;
        unsigned long long min_mtime = sit_i->dirty_min_mtime;
        unsigned int seg_blocks = sbi->blocks_per_seg;
        unsigned int vblocks;
        unsigned int dirty_threshold = max(am->max_candidate_count,
                                        am->candidate_ratio *
                                        am->victim_count / 100);
        unsigned int cost;
        unsigned int iter = 0;
        int stage = 0;

        if (max_mtime < min_mtime)
                return;
        max_mtime += 1;
next_stage:
        node = lookup_central_victim(sbi, p);
next_node:
        re = rb_entry_safe(node, struct rb_entry, rb_node);
        if (!re) {
                if (stage == 0)
                        goto skip_stage;
                return;
        }

        ve = (struct victim_entry *)re;

        if (ve->mtime >= max_mtime || ve->mtime < min_mtime)
                goto skip_node;

        age = max_mtime - ve->mtime;

        vblocks = get_seg_entry(sbi, ve->segno)->ckpt_valid_blocks;
        f2fs_bug_on(sbi, !vblocks);

        /* rare case */
        if (vblocks == seg_blocks)
                goto skip_node;

        iter++;

        age = max_mtime - abs(p->age - age);
        cost = UINT_MAX - vblocks;

        if (cost < p->min_cost ||
                        (cost == p->min_cost && age > p->oldest_age)) {
                p->min_cost = cost;
                p->oldest_age = age;
                p->min_segno = ve->segno;
        }
skip_node:
        if (iter < dirty_threshold) {
                if (stage == 0)
                        node = rb_prev(node);
                else if (stage == 1)
                        node = rb_next(node);
                goto next_node;
        }
skip_stage:
        if (stage < 1) {
                stage++;
                iter = 0;
                goto next_stage;
        }
}
static void lookup_victim_by_age(struct f2fs_sb_info *sbi,
                                                struct victim_sel_policy *p)
{
        f2fs_bug_on(sbi, !f2fs_check_rb_tree_consistence(sbi,
                                                &sbi->am.root, true));

        if (p->gc_mode == GC_AT)
                atgc_lookup_victim(sbi, p);
        else if (p->alloc_mode == AT_SSR)
                atssr_lookup_victim(sbi, p);
        else
                f2fs_bug_on(sbi, 1);
}

static void release_victim_entry(struct f2fs_sb_info *sbi)
{
        struct atgc_management *am = &sbi->am;
        struct victim_entry *ve, *tmp;

        list_for_each_entry_safe(ve, tmp, &am->victim_list, list) {
                list_del(&ve->list);
                kmem_cache_free(victim_entry_slab, ve);
                am->victim_count--;
        }

        am->root = RB_ROOT_CACHED;

        f2fs_bug_on(sbi, am->victim_count);
        f2fs_bug_on(sbi, !list_empty(&am->victim_list));
}

/*
 * This function is called from two paths.
 * One is garbage collection and the other is SSR segment selection.
 * When it is called during GC, it just gets a victim segment
 * and it does not remove it from dirty seglist.
 * When it is called from SSR segment selection, it finds a segment
 * which has minimum valid blocks and removes it from dirty seglist.
 */
static int get_victim_by_default(struct f2fs_sb_info *sbi,
                        unsigned int *result, int gc_type, int type,
                        char alloc_mode, unsigned long long age)
{
        struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
        struct sit_info *sm = SIT_I(sbi);
        struct victim_sel_policy p;
        unsigned int secno, last_victim;
        unsigned int last_segment;
        unsigned int nsearched;
        bool is_atgc;
        int ret = 0;

        mutex_lock(&dirty_i->seglist_lock);
        last_segment = MAIN_SECS(sbi) * sbi->segs_per_sec;

        p.alloc_mode = alloc_mode;
        p.age = age;
        p.age_threshold = sbi->am.age_threshold;

retry:
        select_policy(sbi, gc_type, type, &p);
        p.min_segno = NULL_SEGNO;
        p.oldest_age = 0;
        p.min_cost = get_max_cost(sbi, &p);

        is_atgc = (p.gc_mode == GC_AT || p.alloc_mode == AT_SSR);
        nsearched = 0;

        if (is_atgc)
                SIT_I(sbi)->dirty_min_mtime = ULLONG_MAX;

        if (*result != NULL_SEGNO) {
                if (!get_valid_blocks(sbi, *result, false)) {
                        ret = -ENODATA;
                        goto out;
                }

                if (sec_usage_check(sbi, GET_SEC_FROM_SEG(sbi, *result)))
                        ret = -EBUSY;
                else
                        p.min_segno = *result;
                goto out;
        }

        ret = -ENODATA;
        if (p.max_search == 0)
                goto out;

        if (__is_large_section(sbi) && p.alloc_mode == LFS) {
                if (sbi->next_victim_seg[BG_GC] != NULL_SEGNO) {
                        p.min_segno = sbi->next_victim_seg[BG_GC];
                        *result = p.min_segno;
                        sbi->next_victim_seg[BG_GC] = NULL_SEGNO;
                        goto got_result;
                }
                if (gc_type == FG_GC &&
                                sbi->next_victim_seg[FG_GC] != NULL_SEGNO) {
                        p.min_segno = sbi->next_victim_seg[FG_GC];
                        *result = p.min_segno;
                        sbi->next_victim_seg[FG_GC] = NULL_SEGNO;
                        goto got_result;
                }
        }

        last_victim = sm->last_victim[p.gc_mode];
        if (p.alloc_mode == LFS && gc_type == FG_GC) {
                p.min_segno = check_bg_victims(sbi);
                if (p.min_segno != NULL_SEGNO)
                        goto got_it;
        }

        while (1) {
                unsigned long cost, *dirty_bitmap;
                unsigned int unit_no, segno;

                dirty_bitmap = p.dirty_bitmap;
                unit_no = find_next_bit(dirty_bitmap,
                                last_segment / p.ofs_unit,
                                p.offset / p.ofs_unit);
                segno = unit_no * p.ofs_unit;
                if (segno >= last_segment) {
                        if (sm->last_victim[p.gc_mode]) {
                                last_segment =
                                        sm->last_victim[p.gc_mode];
                                sm->last_victim[p.gc_mode] = 0;
                                p.offset = 0;
                                continue;
                        }
                        break;
                }

                p.offset = segno + p.ofs_unit;
                nsearched++;

#ifdef CONFIG_F2FS_CHECK_FS
                /*
                 * skip selecting the invalid segno (that is failed due to block
                 * validity check failure during GC) to avoid endless GC loop in
                 * such cases.
                 */
                if (test_bit(segno, sm->invalid_segmap))
                        goto next;
#endif

                secno = GET_SEC_FROM_SEG(sbi, segno);

                if (sec_usage_check(sbi, secno))
                        goto next;

                /* Don't touch checkpointed data */
                if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
                        if (p.alloc_mode == LFS) {
                                /*
                                 * LFS is set to find source section during GC.
                                 * The victim should have no checkpointed data.
                                 */
                                if (get_ckpt_valid_blocks(sbi, segno, true))
                                        goto next;
                        } else {
                                /*
                                 * SSR | AT_SSR are set to find target segment
                                 * for writes which can be full by checkpointed
                                 * and newly written blocks.
                                 */
                                if (!f2fs_segment_has_free_slot(sbi, segno))
                                        goto next;
                        }
                }

                if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
                        goto next;

                if (is_atgc) {
                        add_victim_entry(sbi, &p, segno);
                        goto next;
                }

                cost = get_gc_cost(sbi, segno, &p);

                if (p.min_cost > cost) {
                        p.min_segno = segno;
                        p.min_cost = cost;
                }
next:
                if (nsearched >= p.max_search) {
                        if (!sm->last_victim[p.gc_mode] && segno <= last_victim)
                                sm->last_victim[p.gc_mode] =
                                        last_victim + p.ofs_unit;
                        else
                                sm->last_victim[p.gc_mode] = segno + p.ofs_unit;
                        sm->last_victim[p.gc_mode] %=
                                (MAIN_SECS(sbi) * sbi->segs_per_sec);
                        break;
                }
        }

        /* get victim for GC_AT/AT_SSR */
        if (is_atgc) {
                lookup_victim_by_age(sbi, &p);
                release_victim_entry(sbi);
        }

        if (is_atgc && p.min_segno == NULL_SEGNO &&
                        sm->elapsed_time < p.age_threshold) {
                p.age_threshold = 0;
                goto retry;
        }

        if (p.min_segno != NULL_SEGNO) {
got_it:
                *result = (p.min_segno / p.ofs_unit) * p.ofs_unit;
got_result:
                if (p.alloc_mode == LFS) {
                        secno = GET_SEC_FROM_SEG(sbi, p.min_segno);
                        if (gc_type == FG_GC)
                                sbi->cur_victim_sec = secno;
                        else
                                set_bit(secno, dirty_i->victim_secmap);
                }
                ret = 0;

        }
out:
        if (p.min_segno != NULL_SEGNO)
                trace_f2fs_get_victim(sbi->sb, type, gc_type, &p,
                                sbi->cur_victim_sec,
                                prefree_segments(sbi), free_segments(sbi));
        mutex_unlock(&dirty_i->seglist_lock);

        return ret;
}

static const struct victim_selection default_v_ops = {
        .get_victim = get_victim_by_default,
};

static struct inode *find_gc_inode(struct gc_inode_list *gc_list, nid_t ino)
{
        struct inode_entry *ie;

        ie = radix_tree_lookup(&gc_list->iroot, ino);
        if (ie)
                return ie->inode;
        return NULL;
}

static void add_gc_inode(struct gc_inode_list *gc_list, struct inode *inode)
{
        struct inode_entry *new_ie;

        if (inode == find_gc_inode(gc_list, inode->i_ino)) {
                iput(inode);
                return;
        }
        new_ie = f2fs_kmem_cache_alloc(f2fs_inode_entry_slab, GFP_NOFS);
        new_ie->inode = inode;

        f2fs_radix_tree_insert(&gc_list->iroot, inode->i_ino, new_ie);
        list_add_tail(&new_ie->list, &gc_list->ilist);
}

static void put_gc_inode(struct gc_inode_list *gc_list)
{
        struct inode_entry *ie, *next_ie;

        list_for_each_entry_safe(ie, next_ie, &gc_list->ilist, list) {
                radix_tree_delete(&gc_list->iroot, ie->inode->i_ino);
                iput(ie->inode);
                list_del(&ie->list);
                kmem_cache_free(f2fs_inode_entry_slab, ie);
        }
}

static int check_valid_map(struct f2fs_sb_info *sbi,
                                unsigned int segno, int offset)
{
        struct sit_info *sit_i = SIT_I(sbi);
        struct seg_entry *sentry;
        int ret;

        down_read(&sit_i->sentry_lock);
        sentry = get_seg_entry(sbi, segno);
        ret = f2fs_test_bit(offset, sentry->cur_valid_map);
        up_read(&sit_i->sentry_lock);
        return ret;
}

/*
 * This function compares node address got in summary with that in NAT.
 * On validity, copy that node with cold status, otherwise (invalid node)
 * ignore that.
 */
static int gc_node_segment(struct f2fs_sb_info *sbi,
                struct f2fs_summary *sum, unsigned int segno, int gc_type)
{
        struct f2fs_summary *entry;
        block_t start_addr;
        int off;
        int phase = 0;
        bool fggc = (gc_type == FG_GC);
        int submitted = 0;
        unsigned int usable_blks_in_seg = f2fs_usable_blks_in_seg(sbi, segno);

        start_addr = START_BLOCK(sbi, segno);

next_step:
        entry = sum;

        if (fggc && phase == 2)
                atomic_inc(&sbi->wb_sync_req[NODE]);

        for (off = 0; off < usable_blks_in_seg; off++, entry++) {
                nid_t nid = le32_to_cpu(entry->nid);
                struct page *node_page;
                struct node_info ni;
                int err;

                /* stop BG_GC if there is not enough free sections. */
                if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0))
                        return submitted;

                if (check_valid_map(sbi, segno, off) == 0)
                        continue;

                if (phase == 0) {
                        f2fs_ra_meta_pages(sbi, NAT_BLOCK_OFFSET(nid), 1,
                                                        META_NAT, true);
                        continue;
                }

                if (phase == 1) {
                        f2fs_ra_node_page(sbi, nid);
                        continue;
                }

                /* phase == 2 */
                node_page = f2fs_get_node_page(sbi, nid);
                if (IS_ERR(node_page))
                        continue;

                /* block may become invalid during f2fs_get_node_page */
                if (check_valid_map(sbi, segno, off) == 0) {
                        f2fs_put_page(node_page, 1);
                        continue;
                }

                if (f2fs_get_node_info(sbi, nid, &ni)) {
                        f2fs_put_page(node_page, 1);
                        continue;
                }

                if (ni.blk_addr != start_addr + off) {
                        f2fs_put_page(node_page, 1);
                        continue;
                }

                err = f2fs_move_node_page(node_page, gc_type);
                if (!err && gc_type == FG_GC)
                        submitted++;
                stat_inc_node_blk_count(sbi, 1, gc_type);
        }

        if (++phase < 3)
                goto next_step;

        if (fggc)
                atomic_dec(&sbi->wb_sync_req[NODE]);
        return submitted;
}

/*
 * Calculate start block index indicating the given node offset.
 * Be careful, caller should give this node offset only indicating direct node
 * blocks. If any node offsets, which point the other types of node blocks such
 * as indirect or double indirect node blocks, are given, it must be a caller's
 * bug.
 */
block_t f2fs_start_bidx_of_node(unsigned int node_ofs, struct inode *inode)
{
        unsigned int indirect_blks = 2 * NIDS_PER_BLOCK + 4;
        unsigned int bidx;

        if (node_ofs == 0)
                return 0;

        if (node_ofs <= 2) {
                bidx = node_ofs - 1;
        } else if (node_ofs <= indirect_blks) {
                int dec = (node_ofs - 4) / (NIDS_PER_BLOCK + 1);

                bidx = node_ofs - 2 - dec;
        } else {
                int dec = (node_ofs - indirect_blks - 3) / (NIDS_PER_BLOCK + 1);

                bidx = node_ofs - 5 - dec;
        }
        return bidx * ADDRS_PER_BLOCK(inode) + ADDRS_PER_INODE(inode);
}

static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
                struct node_info *dni, block_t blkaddr, unsigned int *nofs)
{
        struct page *node_page;

        nid_t nid;
        unsigned int ofs_in_node;
        block_t source_blkaddr;

        nid = le32_to_cpu(sum->nid);
        ofs_in_node = le16_to_cpu(sum->ofs_in_node);

        node_page = f2fs_get_node_page(sbi, nid);
        if (IS_ERR(node_page))
                return false;

        if (f2fs_get_node_info(sbi, nid, dni)) {
                f2fs_put_page(node_page, 1);
                return false;
        }

        if (sum->version != dni->version) {
                f2fs_warn(sbi, "%s: valid data with mismatched node version.",
                          __func__);
                set_sbi_flag(sbi, SBI_NEED_FSCK);
        }

        *nofs = ofs_of_node(node_page);
        source_blkaddr = data_blkaddr(NULL, node_page, ofs_in_node);
        f2fs_put_page(node_page, 1);

        if (source_blkaddr != blkaddr) {
#ifdef CONFIG_F2FS_CHECK_FS
                unsigned int segno = GET_SEGNO(sbi, blkaddr);
                unsigned long offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);

                if (unlikely(check_valid_map(sbi, segno, offset))) {
                        if (!test_and_set_bit(segno, SIT_I(sbi)->invalid_segmap)) {
                                f2fs_err(sbi, "mismatched blkaddr %u (source_blkaddr %u) in seg %u",
                                         blkaddr, source_blkaddr, segno);
                                f2fs_bug_on(sbi, 1);
                        }
                }
#endif
                return false;
        }
        return true;
}

static int ra_data_block(struct inode *inode, pgoff_t index)
{
        struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
        struct address_space *mapping = inode->i_mapping;
        struct dnode_of_data dn;
        struct page *page;
        struct extent_info ei = {0, 0, 0};
        struct f2fs_io_info fio = {
                .sbi = sbi,
                .ino = inode->i_ino,
                .type = DATA,
                .temp = COLD,
                .op = REQ_OP_READ,
                .op_flags = 0,
                .encrypted_page = NULL,
                .in_list = false,
                .retry = false,
        };
        int err;

        page = f2fs_grab_cache_page(mapping, index, true);
        if (!page)
                return -ENOMEM;

        if (f2fs_lookup_extent_cache(inode, index, &ei)) {
                dn.data_blkaddr = ei.blk + index - ei.fofs;
                if (unlikely(!f2fs_is_valid_blkaddr(sbi, dn.data_blkaddr,
                                                DATA_GENERIC_ENHANCE_READ))) {
                        err = -EFSCORRUPTED;
                        goto put_page;
                }
                goto got_it;
        }

        set_new_dnode(&dn, inode, NULL, NULL, 0);
        err = f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE);
        if (err)
                goto put_page;
        f2fs_put_dnode(&dn);

        if (!__is_valid_data_blkaddr(dn.data_blkaddr)) {
                err = -ENOENT;
                goto put_page;
        }
        if (unlikely(!f2fs_is_valid_blkaddr(sbi, dn.data_blkaddr,
                                                DATA_GENERIC_ENHANCE))) {
                err = -EFSCORRUPTED;
                goto put_page;
        }
got_it:
        /* read page */
        fio.page = page;
        fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;

        /*
         * don't cache encrypted data into meta inode until previous dirty
         * data were writebacked to avoid racing between GC and flush.
         */
        f2fs_wait_on_page_writeback(page, DATA, true, true);

        f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);

        fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(sbi),
                                        dn.data_blkaddr,
                                        FGP_LOCK | FGP_CREAT, GFP_NOFS);
        if (!fio.encrypted_page) {
                err = -ENOMEM;
                goto put_page;
        }

        err = f2fs_submit_page_bio(&fio);
        if (err)
                goto put_encrypted_page;
        f2fs_put_page(fio.encrypted_page, 0);
        f2fs_put_page(page, 1);

        f2fs_update_iostat(sbi, FS_DATA_READ_IO, F2FS_BLKSIZE);
        f2fs_update_iostat(sbi, FS_GDATA_READ_IO, F2FS_BLKSIZE);

        return 0;
put_encrypted_page:
        f2fs_put_page(fio.encrypted_page, 1);
put_page:
        f2fs_put_page(page, 1);
        return err;
}

/*
 * Move data block via META_MAPPING while keeping locked data page.
 * This can be used to move blocks, aka LBAs, directly on disk.
 */
static int move_data_block(struct inode *inode, block_t bidx,
                                int gc_type, unsigned int segno, int off)
{
        struct f2fs_io_info fio = {
                .sbi = F2FS_I_SB(inode),
                .ino = inode->i_ino,
                .type = DATA,
                .temp = COLD,
                .op = REQ_OP_READ,
                .op_flags = 0,
                .encrypted_page = NULL,
                .in_list = false,
                .retry = false,
        };
        struct dnode_of_data dn;
        struct f2fs_summary sum;
        struct node_info ni;
        struct page *page, *mpage;
        block_t newaddr;
        int err = 0;
        bool lfs_mode = f2fs_lfs_mode(fio.sbi);
        int type = fio.sbi->am.atgc_enabled && (gc_type == BG_GC) &&
                                (fio.sbi->gc_mode != GC_URGENT_HIGH) ?
                                CURSEG_ALL_DATA_ATGC : CURSEG_COLD_DATA;

        /* do not read out */
        page = f2fs_grab_cache_page(inode->i_mapping, bidx, false);
        if (!page)
                return -ENOMEM;

        if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
                err = -ENOENT;
                goto out;
        }

        if (f2fs_is_atomic_file(inode)) {
                F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
                F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
                err = -EAGAIN;
                goto out;
        }

        if (f2fs_is_pinned_file(inode)) {
                f2fs_pin_file_control(inode, true);
                err = -EAGAIN;
                goto out;
        }

        set_new_dnode(&dn, inode, NULL, NULL, 0);
        err = f2fs_get_dnode_of_data(&dn, bidx, LOOKUP_NODE);
        if (err)
                goto out;

        if (unlikely(dn.data_blkaddr == NULL_ADDR)) {
                ClearPageUptodate(page);
                err = -ENOENT;
                goto put_out;
        }

        /*
         * don't cache encrypted data into meta inode until previous dirty
         * data were writebacked to avoid racing between GC and flush.
         */
        f2fs_wait_on_page_writeback(page, DATA, true, true);

        f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);

        err = f2fs_get_node_info(fio.sbi, dn.nid, &ni);
        if (err)
                goto put_out;

        /* read page */
        fio.page = page;
        fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;

        if (lfs_mode)
                down_write(&fio.sbi->io_order_lock);

        mpage = f2fs_grab_cache_page(META_MAPPING(fio.sbi),
                                        fio.old_blkaddr, false);
        if (!mpage) {
                err = -ENOMEM;
                goto up_out;
        }

        fio.encrypted_page = mpage;

        /* read source block in mpage */
        if (!PageUptodate(mpage)) {
                err = f2fs_submit_page_bio(&fio);
                if (err) {
                        f2fs_put_page(mpage, 1);
                        goto up_out;
                }

                f2fs_update_iostat(fio.sbi, FS_DATA_READ_IO, F2FS_BLKSIZE);
                f2fs_update_iostat(fio.sbi, FS_GDATA_READ_IO, F2FS_BLKSIZE);

                lock_page(mpage);
                if (unlikely(mpage->mapping != META_MAPPING(fio.sbi) ||
                                                !PageUptodate(mpage))) {
                        err = -EIO;
                        f2fs_put_page(mpage, 1);
                        goto up_out;
                }
        }

        set_summary(&sum, dn.nid, dn.ofs_in_node, ni.version);

        /* allocate block address */
        f2fs_allocate_data_block(fio.sbi, NULL, fio.old_blkaddr, &newaddr,
                                &sum, type, NULL);

        fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(fio.sbi),
                                newaddr, FGP_LOCK | FGP_CREAT, GFP_NOFS);
        if (!fio.encrypted_page) {
                err = -ENOMEM;
                f2fs_put_page(mpage, 1);
                goto recover_block;
        }

        /* write target block */
        f2fs_wait_on_page_writeback(fio.encrypted_page, DATA, true, true);
        memcpy(page_address(fio.encrypted_page),
                                page_address(mpage), PAGE_SIZE);
        f2fs_put_page(mpage, 1);
        invalidate_mapping_pages(META_MAPPING(fio.sbi),
                                fio.old_blkaddr, fio.old_blkaddr);
        f2fs_invalidate_compress_page(fio.sbi, fio.old_blkaddr);

        set_page_dirty(fio.encrypted_page);
        if (clear_page_dirty_for_io(fio.encrypted_page))
                dec_page_count(fio.sbi, F2FS_DIRTY_META);

        set_page_writeback(fio.encrypted_page);
        ClearPageError(page);

        fio.op = REQ_OP_WRITE;
        fio.op_flags = REQ_SYNC;
        fio.new_blkaddr = newaddr;
        f2fs_submit_page_write(&fio);
        if (fio.retry) {
                err = -EAGAIN;
                if (PageWriteback(fio.encrypted_page))
                        end_page_writeback(fio.encrypted_page);
                goto put_page_out;
        }

        f2fs_update_iostat(fio.sbi, FS_GC_DATA_IO, F2FS_BLKSIZE);

        f2fs_update_data_blkaddr(&dn, newaddr);
        set_inode_flag(inode, FI_APPEND_WRITE);
        if (page->index == 0)
                set_inode_flag(inode, FI_FIRST_BLOCK_WRITTEN);
put_page_out:
        f2fs_put_page(fio.encrypted_page, 1);
recover_block:
        if (err)
                f2fs_do_replace_block(fio.sbi, &sum, newaddr, fio.old_blkaddr,
                                                        true, true, true);
up_out:
        if (lfs_mode)
                up_write(&fio.sbi->io_order_lock);
put_out:
        f2fs_put_dnode(&dn);
out:
        f2fs_put_page(page, 1);
        return err;
}

static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
                                                        unsigned int segno, int off)
{
        struct page *page;
        int err = 0;

        page = f2fs_get_lock_data_page(inode, bidx, true);
        if (IS_ERR(page))
                return PTR_ERR(page);

        if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
                err = -ENOENT;
                goto out;
        }

        if (f2fs_is_atomic_file(inode)) {
                F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
                F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
                err = -EAGAIN;
                goto out;
        }
        if (f2fs_is_pinned_file(inode)) {
                if (gc_type == FG_GC)
                        f2fs_pin_file_control(inode, true);
                err = -EAGAIN;
                goto out;
        }

        if (gc_type == BG_GC) {
                if (PageWriteback(page)) {
                        err = -EAGAIN;
                        goto out;
                }
                set_page_dirty(page);
                set_page_private_gcing(page);
        } else {
                struct f2fs_io_info fio = {
                        .sbi = F2FS_I_SB(inode),
                        .ino = inode->i_ino,
                        .type = DATA,
                        .temp = COLD,
                        .op = REQ_OP_WRITE,
                        .op_flags = REQ_SYNC,
                        .old_blkaddr = NULL_ADDR,
                        .page = page,
                        .encrypted_page = NULL,
                        .need_lock = LOCK_REQ,
                        .io_type = FS_GC_DATA_IO,
                };
                bool is_dirty = PageDirty(page);

retry:
                f2fs_wait_on_page_writeback(page, DATA, true, true);

                set_page_dirty(page);
                if (clear_page_dirty_for_io(page)) {
                        inode_dec_dirty_pages(inode);
                        f2fs_remove_dirty_inode(inode);
                }

                set_page_private_gcing(page);

                err = f2fs_do_write_data_page(&fio);
                if (err) {
                        clear_page_private_gcing(page);
                        if (err == -ENOMEM) {
                                congestion_wait(BLK_RW_ASYNC,
                                                DEFAULT_IO_TIMEOUT);
                                goto retry;
                        }
                        if (is_dirty)
                                set_page_dirty(page);
                }
        }
out:
        f2fs_put_page(page, 1);
        return err;
}

/*
 * This function tries to get parent node of victim data block, and identifies
 * data block validity. If the block is valid, copy that with cold status and
 * modify parent node.
 * If the parent node is not valid or the data block address is different,
 * the victim data block is ignored.
 */
static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
                struct gc_inode_list *gc_list, unsigned int segno, int gc_type,
                bool force_migrate)
{
        struct super_block *sb = sbi->sb;
        struct f2fs_summary *entry;
        block_t start_addr;
        int off;
        int phase = 0;
        int submitted = 0;
        unsigned int usable_blks_in_seg = f2fs_usable_blks_in_seg(sbi, segno);

        start_addr = START_BLOCK(sbi, segno);

next_step:
        entry = sum;

        for (off = 0; off < usable_blks_in_seg; off++, entry++) {
                struct page *data_page;
                struct inode *inode;
                struct node_info dni; /* dnode info for the data */
                unsigned int ofs_in_node, nofs;
                block_t start_bidx;
                nid_t nid = le32_to_cpu(entry->nid);

                /*
                 * stop BG_GC if there is not enough free sections.
                 * Or, stop GC if the segment becomes fully valid caused by
                 * race condition along with SSR block allocation.
                 */
                if ((gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0)) ||
                        (!force_migrate && get_valid_blocks(sbi, segno, true) ==
                                                        BLKS_PER_SEC(sbi)))
                        return submitted;

                if (check_valid_map(sbi, segno, off) == 0)
                        continue;

                if (phase == 0) {
                        f2fs_ra_meta_pages(sbi, NAT_BLOCK_OFFSET(nid), 1,
                                                        META_NAT, true);
                        continue;
                }

                if (phase == 1) {
                        f2fs_ra_node_page(sbi, nid);
                        continue;
                }

                /* Get an inode by ino with checking validity */
                if (!is_alive(sbi, entry, &dni, start_addr + off, &nofs))
                        continue;

                if (phase == 2) {
                        f2fs_ra_node_page(sbi, dni.ino);
                        continue;
                }

                ofs_in_node = le16_to_cpu(entry->ofs_in_node);

                if (phase == 3) {
                        inode = f2fs_iget(sb, dni.ino);
                        if (IS_ERR(inode) || is_bad_inode(inode))
                                continue;

                        if (!down_write_trylock(
                                &F2FS_I(inode)->i_gc_rwsem[WRITE])) {
                                iput(inode);
                                sbi->skipped_gc_rwsem++;
                                continue;
                        }

                        start_bidx = f2fs_start_bidx_of_node(nofs, inode) +
                                                                ofs_in_node;

                        if (f2fs_post_read_required(inode)) {
                                int err = ra_data_block(inode, start_bidx);

                                up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
                                if (err) {
                                        iput(inode);
                                        continue;
                                }
                                add_gc_inode(gc_list, inode);
                                continue;
                        }

                        data_page = f2fs_get_read_data_page(inode,
                                                start_bidx, REQ_RAHEAD, true);
                        up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
                        if (IS_ERR(data_page)) {
                                iput(inode);
                                continue;
                        }

                        f2fs_put_page(data_page, 0);
                        add_gc_inode(gc_list, inode);
                        continue;
                }

                /* phase 4 */
                inode = find_gc_inode(gc_list, dni.ino);
                if (inode) {
                        struct f2fs_inode_info *fi = F2FS_I(inode);
                        bool locked = false;
                        int err;

                        if (S_ISREG(inode->i_mode)) {
                                if (!down_write_trylock(&fi->i_gc_rwsem[READ]))
                                        continue;
                                if (!down_write_trylock(
                                                &fi->i_gc_rwsem[WRITE])) {
                                        sbi->skipped_gc_rwsem++;
                                        up_write(&fi->i_gc_rwsem[READ]);
                                        continue;
                                }
                                locked = true;

                                /* wait for all inflight aio data */
                                inode_dio_wait(inode);
                        }

                        start_bidx = f2fs_start_bidx_of_node(nofs, inode)
                                                                + ofs_in_node;
                        if (f2fs_post_read_required(inode))
                                err = move_data_block(inode, start_bidx,
                                                        gc_type, segno, off);
                        else
                                err = move_data_page(inode, start_bidx, gc_type,
                                                                segno, off);

                        if (!err && (gc_type == FG_GC ||
                                        f2fs_post_read_required(inode)))
                                submitted++;

                        if (locked) {
                                up_write(&fi->i_gc_rwsem[WRITE]);
                                up_write(&fi->i_gc_rwsem[READ]);
                        }

                        stat_inc_data_blk_count(sbi, 1, gc_type);
                }
        }

        if (++phase < 5)
                goto next_step;

        return submitted;
}

static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
                        int gc_type)
{
        struct sit_info *sit_i = SIT_I(sbi);
        int ret;

        down_write(&sit_i->sentry_lock);
        ret = DIRTY_I(sbi)->v_ops->get_victim(sbi, victim, gc_type,
                                              NO_CHECK_TYPE, LFS, 0);
        up_write(&sit_i->sentry_lock);
        return ret;
}

static int do_garbage_collect(struct f2fs_sb_info *sbi,
                                unsigned int start_segno,
                                struct gc_inode_list *gc_list, int gc_type,
                                bool force_migrate)
{
        struct page *sum_page;
        struct f2fs_summary_block *sum;
        struct blk_plug plug;
        unsigned int segno = start_segno;
        unsigned int end_segno = start_segno + sbi->segs_per_sec;
        int seg_freed = 0, migrated = 0;
        unsigned char type = IS_DATASEG(get_seg_entry(sbi, segno)->type) ?
                                                SUM_TYPE_DATA : SUM_TYPE_NODE;
        int submitted = 0;

        if (__is_large_section(sbi))
                end_segno = rounddown(end_segno, sbi->segs_per_sec);

        /*
         * zone-capacity can be less than zone-size in zoned devices,
         * resulting in less than expected usable segments in the zone,
         * calculate the end segno in the zone which can be garbage collected
         */
        if (f2fs_sb_has_blkzoned(sbi))
                end_segno -= sbi->segs_per_sec -
                                        f2fs_usable_segs_in_sec(sbi, segno);

        sanity_check_seg_type(sbi, get_seg_entry(sbi, segno)->type);

        /* readahead multi ssa blocks those have contiguous address */
        if (__is_large_section(sbi))
                f2fs_ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno),
                                        end_segno - segno, META_SSA, true);

        /* reference all summary page */
        while (segno < end_segno) {
                sum_page = f2fs_get_sum_page(sbi, segno++);
                if (IS_ERR(sum_page)) {
                        int err = PTR_ERR(sum_page);

                        end_segno = segno - 1;
                        for (segno = start_segno; segno < end_segno; segno++) {
                                sum_page = find_get_page(META_MAPPING(sbi),
                                                GET_SUM_BLOCK(sbi, segno));
                                f2fs_put_page(sum_page, 0);
                                f2fs_put_page(sum_page, 0);
                        }
                        return err;
                }
                unlock_page(sum_page);
        }

        blk_start_plug(&plug);

        for (segno = start_segno; segno < end_segno; segno++) {

                /* find segment summary of victim */
                sum_page = find_get_page(META_MAPPING(sbi),
                                        GET_SUM_BLOCK(sbi, segno));
                f2fs_put_page(sum_page, 0);

                if (get_valid_blocks(sbi, segno, false) == 0)
                        goto freed;
                if (gc_type == BG_GC && __is_large_section(sbi) &&
                                migrated >= sbi->migration_granularity)
                        goto skip;
                if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi)))
                        goto skip;

                sum = page_address(sum_page);
                if (type != GET_SUM_TYPE((&sum->footer))) {
                        f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SSA and SIT",
                                 segno, type, GET_SUM_TYPE((&sum->footer)));
                        set_sbi_flag(sbi, SBI_NEED_FSCK);
                        f2fs_stop_checkpoint(sbi, false);
                        goto skip;
                }

                /*
                 * this is to avoid deadlock:
                 * - lock_page(sum_page)         - f2fs_replace_block
                 *  - check_valid_map()            - down_write(sentry_lock)
                 *   - down_read(sentry_lock)     - change_curseg()
                 *                                  - lock_page(sum_page)
                 */
                if (type == SUM_TYPE_NODE)
                        submitted += gc_node_segment(sbi, sum->entries, segno,
                                                                gc_type);
                else
                        submitted += gc_data_segment(sbi, sum->entries, gc_list,
                                                        segno, gc_type,
                                                        force_migrate);

                stat_inc_seg_count(sbi, type, gc_type);
                migrated++;

freed:
                if (gc_type == FG_GC &&
                                get_valid_blocks(sbi, segno, false) == 0)
                        seg_freed++;

                if (__is_large_section(sbi) && segno + 1 < end_segno)
                        sbi->next_victim_seg[gc_type] = segno + 1;
skip:
                f2fs_put_page(sum_page, 0);
        }

        if (submitted)
                f2fs_submit_merged_write(sbi,
                                (type == SUM_TYPE_NODE) ? NODE : DATA);

        blk_finish_plug(&plug);

        stat_inc_call_count(sbi->stat_info);

        return seg_freed;
}

int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
                        bool background, bool force, unsigned int segno)
{
        int gc_type = sync ? FG_GC : BG_GC;
        int sec_freed = 0, seg_freed = 0, total_freed = 0;
        int ret = 0;
        struct cp_control cpc;
        unsigned int init_segno = segno;
        struct gc_inode_list gc_list = {
                .ilist = LIST_HEAD_INIT(gc_list.ilist),
                .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
        };
        unsigned long long last_skipped = sbi->skipped_atomic_files[FG_GC];
        unsigned long long first_skipped;
        unsigned int skipped_round = 0, round = 0;

        trace_f2fs_gc_begin(sbi->sb, sync, background,
                                get_pages(sbi, F2FS_DIRTY_NODES),
                                get_pages(sbi, F2FS_DIRTY_DENTS),
                                get_pages(sbi, F2FS_DIRTY_IMETA),
                                free_sections(sbi),
                                free_segments(sbi),
                                reserved_segments(sbi),
                                prefree_segments(sbi));

        cpc.reason = __get_cp_reason(sbi);
        sbi->skipped_gc_rwsem = 0;
        first_skipped = last_skipped;
gc_more:
        if (unlikely(!(sbi->sb->s_flags & SB_ACTIVE))) {
                ret = -EINVAL;
                goto stop;
        }
        if (unlikely(f2fs_cp_error(sbi))) {
                ret = -EIO;
                goto stop;
        }

        if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0)) {
                /*
                 * For example, if there are many prefree_segments below given
                 * threshold, we can make them free by checkpoint. Then, we
                 * secure free segments which doesn't need fggc any more.
                 */
                if (prefree_segments(sbi) &&
                                !is_sbi_flag_set(sbi, SBI_CP_DISABLED)) {
                        ret = f2fs_write_checkpoint(sbi, &cpc);
                        if (ret)
                                goto stop;
                }
                if (has_not_enough_free_secs(sbi, 0, 0))
                        gc_type = FG_GC;
        }

        /* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
        if (gc_type == BG_GC && !background) {
                ret = -EINVAL;
                goto stop;
        }
        ret = __get_victim(sbi, &segno, gc_type);
        if (ret)
                goto stop;

        seg_freed = do_garbage_collect(sbi, segno, &gc_list, gc_type, force);
        if (gc_type == FG_GC &&
                seg_freed == f2fs_usable_segs_in_sec(sbi, segno))
                sec_freed++;
        total_freed += seg_freed;

        if (gc_type == FG_GC) {
                if (sbi->skipped_atomic_files[FG_GC] > last_skipped ||
                                                sbi->skipped_gc_rwsem)
                        skipped_round++;
                last_skipped = sbi->skipped_atomic_files[FG_GC];
                round++;
        }

        if (gc_type == FG_GC && seg_freed)
                sbi->cur_victim_sec = NULL_SEGNO;

        if (sync)
                goto stop;

        if (has_not_enough_free_secs(sbi, sec_freed, 0)) {
                if (skipped_round <= MAX_SKIP_GC_COUNT ||
                                        skipped_round * 2 < round) {
                        segno = NULL_SEGNO;
                        goto gc_more;
                }

                if (first_skipped < last_skipped &&
                                (last_skipped - first_skipped) >
                                                sbi->skipped_gc_rwsem) {
                        f2fs_drop_inmem_pages_all(sbi, true);
                        segno = NULL_SEGNO;
                        goto gc_more;
                }
                if (gc_type == FG_GC && !is_sbi_flag_set(sbi, SBI_CP_DISABLED))
                        ret = f2fs_write_checkpoint(sbi, &cpc);
        }
stop:
        SIT_I(sbi)->last_victim[ALLOC_NEXT] = 0;
        SIT_I(sbi)->last_victim[FLUSH_DEVICE] = init_segno;

        trace_f2fs_gc_end(sbi->sb, ret, total_freed, sec_freed,
                                get_pages(sbi, F2FS_DIRTY_NODES),
                                get_pages(sbi, F2FS_DIRTY_DENTS),
                                get_pages(sbi, F2FS_DIRTY_IMETA),
                                free_sections(sbi),
                                free_segments(sbi),
                                reserved_segments(sbi),
                                prefree_segments(sbi));

        up_write(&sbi->gc_lock);

        put_gc_inode(&gc_list);

        if (sync && !ret)
                ret = sec_freed ? 0 : -EAGAIN;
        return ret;
}

int __init f2fs_create_garbage_collection_cache(void)
{
        victim_entry_slab = f2fs_kmem_cache_create("f2fs_victim_entry",
                                        sizeof(struct victim_entry));
        if (!victim_entry_slab)
                return -ENOMEM;
        return 0;
}

void f2fs_destroy_garbage_collection_cache(void)
{
        kmem_cache_destroy(victim_entry_slab);
}

static void init_atgc_management(struct f2fs_sb_info *sbi)
{
        struct atgc_management *am = &sbi->am;

        if (test_opt(sbi, ATGC) &&
                SIT_I(sbi)->elapsed_time >= DEF_GC_THREAD_AGE_THRESHOLD)
                am->atgc_enabled = true;

        am->root = RB_ROOT_CACHED;
        INIT_LIST_HEAD(&am->victim_list);
        am->victim_count = 0;

        am->candidate_ratio = DEF_GC_THREAD_CANDIDATE_RATIO;
        am->max_candidate_count = DEF_GC_THREAD_MAX_CANDIDATE_COUNT;
        am->age_weight = DEF_GC_THREAD_AGE_WEIGHT;
        am->age_threshold = DEF_GC_THREAD_AGE_THRESHOLD;
}

void f2fs_build_gc_manager(struct f2fs_sb_info *sbi)
{
        DIRTY_I(sbi)->v_ops = &default_v_ops;

        sbi->gc_pin_file_threshold = DEF_GC_FAILED_PINNED_FILES;

        /* give warm/cold data area from slower device */
        if (f2fs_is_multi_device(sbi) && !__is_large_section(sbi))
                SIT_I(sbi)->last_victim[ALLOC_NEXT] =
                                GET_SEGNO(sbi, FDEV(0).end_blk) + 1;

        init_atgc_management(sbi);
}

static int free_segment_range(struct f2fs_sb_info *sbi,
                                unsigned int secs, bool gc_only)
{
        unsigned int segno, next_inuse, start, end;
        struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
        int gc_mode, gc_type;
        int err = 0;
        int type;

        /* Force block allocation for GC */
        MAIN_SECS(sbi) -= secs;
        start = MAIN_SECS(sbi) * sbi->segs_per_sec;
        end = MAIN_SEGS(sbi) - 1;

        mutex_lock(&DIRTY_I(sbi)->seglist_lock);
        for (gc_mode = 0; gc_mode < MAX_GC_POLICY; gc_mode++)
                if (SIT_I(sbi)->last_victim[gc_mode] >= start)
                        SIT_I(sbi)->last_victim[gc_mode] = 0;

        for (gc_type = BG_GC; gc_type <= FG_GC; gc_type++)
                if (sbi->next_victim_seg[gc_type] >= start)
                        sbi->next_victim_seg[gc_type] = NULL_SEGNO;
        mutex_unlock(&DIRTY_I(sbi)->seglist_lock);

        /* Move out cursegs from the target range */
        for (type = CURSEG_HOT_DATA; type < NR_CURSEG_PERSIST_TYPE; type++)
                f2fs_allocate_segment_for_resize(sbi, type, start, end);

        /* do GC to move out valid blocks in the range */
        for (segno = start; segno <= end; segno += sbi->segs_per_sec) {
                struct gc_inode_list gc_list = {
                        .ilist = LIST_HEAD_INIT(gc_list.ilist),
                        .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
                };

                do_garbage_collect(sbi, segno, &gc_list, FG_GC, true);
                put_gc_inode(&gc_list);

                if (!gc_only && get_valid_blocks(sbi, segno, true)) {
                        err = -EAGAIN;
                        goto out;
                }
                if (fatal_signal_pending(current)) {
                        err = -ERESTARTSYS;
                        goto out;
                }
        }
        if (gc_only)
                goto out;

        err = f2fs_write_checkpoint(sbi, &cpc);
        if (err)
                goto out;

        next_inuse = find_next_inuse(FREE_I(sbi), end + 1, start);
        if (next_inuse <= end) {
                f2fs_err(sbi, "segno %u should be free but still inuse!",
                         next_inuse);
                f2fs_bug_on(sbi, 1);
        }
out:
        MAIN_SECS(sbi) += secs;
        return err;
}

static void update_sb_metadata(struct f2fs_sb_info *sbi, int secs)
{
        struct f2fs_super_block *raw_sb = F2FS_RAW_SUPER(sbi);
        int section_count;
        int segment_count;
        int segment_count_main;
        long long block_count;
        int segs = secs * sbi->segs_per_sec;

        down_write(&sbi->sb_lock);

        section_count = le32_to_cpu(raw_sb->section_count);
        segment_count = le32_to_cpu(raw_sb->segment_count);
        segment_count_main = le32_to_cpu(raw_sb->segment_count_main);
        block_count = le64_to_cpu(raw_sb->block_count);

        raw_sb->section_count = cpu_to_le32(section_count + secs);
        raw_sb->segment_count = cpu_to_le32(segment_count + segs);
        raw_sb->segment_count_main = cpu_to_le32(segment_count_main + segs);
        raw_sb->block_count = cpu_to_le64(block_count +
                                        (long long)segs * sbi->blocks_per_seg);
        if (f2fs_is_multi_device(sbi)) {
                int last_dev = sbi->s_ndevs - 1;
                int dev_segs =
                        le32_to_cpu(raw_sb->devs[last_dev].total_segments);

                raw_sb->devs[last_dev].total_segments =
                                                cpu_to_le32(dev_segs + segs);
        }

        up_write(&sbi->sb_lock);
}

static void update_fs_metadata(struct f2fs_sb_info *sbi, int secs)
{
        int segs = secs * sbi->segs_per_sec;
        long long blks = (long long)segs * sbi->blocks_per_seg;
        long long user_block_count =
                                le64_to_cpu(F2FS_CKPT(sbi)->user_block_count);

        SM_I(sbi)->segment_count = (int)SM_I(sbi)->segment_count + segs;
        MAIN_SEGS(sbi) = (int)MAIN_SEGS(sbi) + segs;
        MAIN_SECS(sbi) += secs;
        FREE_I(sbi)->free_sections = (int)FREE_I(sbi)->free_sections + secs;
        FREE_I(sbi)->free_segments = (int)FREE_I(sbi)->free_segments + segs;
        F2FS_CKPT(sbi)->user_block_count = cpu_to_le64(user_block_count + blks);

        if (f2fs_is_multi_device(sbi)) {
                int last_dev = sbi->s_ndevs - 1;

                FDEV(last_dev).total_segments =
                                (int)FDEV(last_dev).total_segments + segs;
                FDEV(last_dev).end_blk =
                                (long long)FDEV(last_dev).end_blk + blks;
#ifdef CONFIG_BLK_DEV_ZONED
                FDEV(last_dev).nr_blkz = (int)FDEV(last_dev).nr_blkz +
                                        (int)(blks >> sbi->log_blocks_per_blkz);
#endif
        }
}

int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
{
        __u64 old_block_count, shrunk_blocks;
        struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
        unsigned int secs;
        int err = 0;
        __u32 rem;

        old_block_count = le64_to_cpu(F2FS_RAW_SUPER(sbi)->block_count);
        if (block_count > old_block_count)
                return -EINVAL;

        if (f2fs_is_multi_device(sbi)) {
                int last_dev = sbi->s_ndevs - 1;
                __u64 last_segs = FDEV(last_dev).total_segments;

                if (block_count + last_segs * sbi->blocks_per_seg <=
                                                                old_block_count)
                        return -EINVAL;
        }

        /* new fs size should align to section size */
        div_u64_rem(block_count, BLKS_PER_SEC(sbi), &rem);
        if (rem)
                return -EINVAL;

        if (block_count == old_block_count)
                return 0;

        if (is_sbi_flag_set(sbi, SBI_NEED_FSCK)) {
                f2fs_err(sbi, "Should run fsck to repair first.");
                return -EFSCORRUPTED;
        }