fs/f2fs/gc.c - nest-learning-thermostat/5.9.1/linux-imx-ul - Git at Google

 /*
  * fs/f2fs/gc.c
  *
  * Copyright (c) 2012 Samsung Electronics Co., Ltd.
  *             http://www.samsung.com/
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
 #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/blkdev.h>

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

 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;
 	long wait_ms;

 	wait_ms = gc_th->min_sleep_time;

 	do {
 		if (try_to_freeze())
 			continue;
 		else
 			wait_event_interruptible_timeout(*wq,
 						kthread_should_stop(),
 						msecs_to_jiffies(wait_ms));
 		if (kthread_should_stop())
 			break;

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

 		if (!is_idle(sbi)) {
 			increase_sleep_time(gc_th, &wait_ms);
 			mutex_unlock(&sbi->gc_mutex);
 			continue;
 		}

 		if (has_enough_invalid_blocks(sbi))
 			decrease_sleep_time(gc_th, &wait_ms);
 		else
 			increase_sleep_time(gc_th, &wait_ms);

 		stat_inc_bggc_count(sbi);

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

 		/* balancing f2fs's metadata periodically */
 		f2fs_balance_fs_bg(sbi);

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

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

 	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_idle = 0;

 	sbi->gc_thread = gc_th;
 	init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
 	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 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);
 	kfree(gc_th);
 	sbi->gc_thread = NULL;
 }

 static int select_gc_type(struct f2fs_gc_kthread *gc_th, int gc_type)
 {
 	int gc_mode = (gc_type == BG_GC) ? GC_CB : GC_GREEDY;

 	if (gc_th && gc_th->gc_idle) {
 		if (gc_th->gc_idle == 1)
 			gc_mode = GC_CB;
 		else if (gc_th->gc_idle == 2)
 			gc_mode = GC_GREEDY;
 	}
 	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_segmap = 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_thread, gc_type);
 		p->dirty_segmap = dirty_i->dirty_segmap[DIRTY];
 		p->max_search = dirty_i->nr_dirty[DIRTY];
 		p->ofs_unit = sbi->segs_per_sec;
 	}

 	if (p->max_search > sbi->max_victim_search)
 		p->max_search = sbi->max_victim_search;

 	p->offset = 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 1 << sbi->log_blocks_per_seg;
 	if (p->gc_mode == GC_GREEDY)
 		return (1 << sbi->log_blocks_per_seg) * p->ofs_unit;
 	else if (p->gc_mode == GC_CB)
 		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 secno * sbi->segs_per_sec;
 	}
 	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_SECNO(sbi, segno);
 	unsigned int start = secno * sbi->segs_per_sec;
 	unsigned long long mtime = 0;
 	unsigned int vblocks;
 	unsigned char age = 0;
 	unsigned char u;
 	unsigned int i;

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

 	mtime = div_u64(mtime, sbi->segs_per_sec);
 	vblocks = div_u64(vblocks, sbi->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, sbi->segs_per_sec);
 	else
 		return get_cb_cost(sbi, segno);
 }

 /*
  * 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)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
 	struct victim_sel_policy p;
 	unsigned int secno, max_cost;
 	int nsearched = 0;

 	mutex_lock(&dirty_i->seglist_lock);

 	p.alloc_mode = alloc_mode;
 	select_policy(sbi, gc_type, type, &p);

 	p.min_segno = NULL_SEGNO;
 	p.min_cost = max_cost = get_max_cost(sbi, &p);

 	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;
 		unsigned int segno;

 		segno = find_next_bit(p.dirty_segmap, MAIN_SEGS(sbi), p.offset);
 		if (segno >= MAIN_SEGS(sbi)) {
 			if (sbi->last_victim[p.gc_mode]) {
 				sbi->last_victim[p.gc_mode] = 0;
 				p.offset = 0;
 				continue;
 			}
 			break;
 		}

 		p.offset = segno + p.ofs_unit;
 		if (p.ofs_unit > 1)
 			p.offset -= segno % p.ofs_unit;

 		secno = GET_SECNO(sbi, segno);

 		if (sec_usage_check(sbi, secno))
 			continue;
 		if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
 			continue;

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

 		if (p.min_cost > cost) {
 			p.min_segno = segno;
 			p.min_cost = cost;
 		} else if (unlikely(cost == max_cost)) {
 			continue;
 		}

 		if (nsearched++ >= p.max_search) {
 			sbi->last_victim[p.gc_mode] = segno;
 			break;
 		}
 	}
 	if (p.min_segno != NULL_SEGNO) {
 got_it:
 		if (p.alloc_mode == LFS) {
 			secno = GET_SECNO(sbi, p.min_segno);
 			if (gc_type == FG_GC)
 				sbi->cur_victim_sec = secno;
 			else
 				set_bit(secno, dirty_i->victim_secmap);
 		}
 		*result = (p.min_segno / p.ofs_unit) * p.ofs_unit;

 		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 (p.min_segno == NULL_SEGNO) ? 0 : 1;
 }

 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(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(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;

 	mutex_lock(&sit_i->sentry_lock);
 	sentry = get_seg_entry(sbi, segno);
 	ret = f2fs_test_bit(offset, sentry->cur_valid_map);
 	mutex_unlock(&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 void gc_node_segment(struct f2fs_sb_info *sbi,
 		struct f2fs_summary *sum, unsigned int segno, int gc_type)
 {
 	bool initial = true;
 	struct f2fs_summary *entry;
 	int off;

 next_step:
 	entry = sum;

 	for (off = 0; off < sbi->blocks_per_seg; off++, entry++) {
 		nid_t nid = le32_to_cpu(entry->nid);
 		struct page *node_page;

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

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

 		if (initial) {
 			ra_node_page(sbi, nid);
 			continue;
 		}
 		node_page = get_node_page(sbi, nid);
 		if (IS_ERR(node_page))
 			continue;

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

 		/* set page dirty and write it */
 		if (gc_type == FG_GC) {
 			f2fs_wait_on_page_writeback(node_page, NODE);
 			set_page_dirty(node_page);
 		} else {
 			if (!PageWriteback(node_page))
 				set_page_dirty(node_page);
 		}
 		f2fs_put_page(node_page, 1);
 		stat_inc_node_blk_count(sbi, 1, gc_type);
 	}

 	if (initial) {
 		initial = false;
 		goto next_step;
 	}

 	if (gc_type == FG_GC) {
 		struct writeback_control wbc = {
 			.sync_mode = WB_SYNC_ALL,
 			.nr_to_write = LONG_MAX,
 			.for_reclaim = 0,
 		};
 		sync_node_pages(sbi, 0, &wbc);

 		/*
 		 * In the case of FG_GC, it'd be better to reclaim this victim
 		 * completely.
 		 */
 		if (get_valid_blocks(sbi, segno, 1) != 0)
 			goto next_step;
 	}
 }

 /*
  * 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 start_bidx_of_node(unsigned int node_ofs, struct f2fs_inode_info *fi)
 {
 	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 + ADDRS_PER_INODE(fi);
 }

 static int check_dnode(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 = get_node_page(sbi, nid);
 	if (IS_ERR(node_page))
 		return 0;

 	get_node_info(sbi, nid, dni);

 	if (sum->version != dni->version) {
 		f2fs_put_page(node_page, 1);
 		return 0;
 	}

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

 	if (source_blkaddr != blkaddr)
 		return 0;
 	return 1;
 }

 static void move_data_page(struct inode *inode, struct page *page, int gc_type)
 {
 	struct f2fs_io_info fio = {
 		.type = DATA,
 		.rw = WRITE_SYNC,
 	};

 	if (gc_type == BG_GC) {
 		if (PageWriteback(page))
 			goto out;
 		set_page_dirty(page);
 		set_cold_data(page);
 	} else {
 		f2fs_wait_on_page_writeback(page, DATA);

 		if (clear_page_dirty_for_io(page))
 			inode_dec_dirty_pages(inode);
 		set_cold_data(page);
 		do_write_data_page(page, &fio);
 		clear_cold_data(page);
 	}
 out:
 	f2fs_put_page(page, 1);
 }

 /*
  * 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 void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 		struct gc_inode_list *gc_list, unsigned int segno, int gc_type)
 {
 	struct super_block *sb = sbi->sb;
 	struct f2fs_summary *entry;
 	block_t start_addr;
 	int off;
 	int phase = 0;

 	start_addr = START_BLOCK(sbi, segno);

 next_step:
 	entry = sum;

 	for (off = 0; off < sbi->blocks_per_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;

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

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

 		if (phase == 0) {
 			ra_node_page(sbi, le32_to_cpu(entry->nid));
 			continue;
 		}

 		/* Get an inode by ino with checking validity */
 		if (check_dnode(sbi, entry, &dni, start_addr + off, &nofs) == 0)
 			continue;

 		if (phase == 1) {
 			ra_node_page(sbi, dni.ino);
 			continue;
 		}

 		ofs_in_node = le16_to_cpu(entry->ofs_in_node);

 		if (phase == 2) {
 			inode = f2fs_iget(sb, dni.ino);
 			if (IS_ERR(inode) || is_bad_inode(inode))
 				continue;

 			start_bidx = start_bidx_of_node(nofs, F2FS_I(inode));

 			data_page = find_data_page(inode,
 					start_bidx + ofs_in_node, false);
 			if (IS_ERR(data_page)) {
 				iput(inode);
 				continue;
 			}

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

 		/* phase 3 */
 		inode = find_gc_inode(gc_list, dni.ino);
 		if (inode) {
 			start_bidx = start_bidx_of_node(nofs, F2FS_I(inode));
 			data_page = get_lock_data_page(inode,
 						start_bidx + ofs_in_node);
 			if (IS_ERR(data_page))
 				continue;
 			move_data_page(inode, data_page, gc_type);
 			stat_inc_data_blk_count(sbi, 1, gc_type);
 		}
 	}

 	if (++phase < 4)
 		goto next_step;

 	if (gc_type == FG_GC) {
 		f2fs_submit_merged_bio(sbi, DATA, WRITE);

 		/*
 		 * In the case of FG_GC, it'd be better to reclaim this victim
 		 * completely.
 		 */
 		if (get_valid_blocks(sbi, segno, 1) != 0) {
 			phase = 2;
 			goto next_step;
 		}
 	}
 }

 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;

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

 static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 				struct gc_inode_list *gc_list, int gc_type)
 {
 	struct page *sum_page;
 	struct f2fs_summary_block *sum;
 	struct blk_plug plug;

 	/* read segment summary of victim */
 	sum_page = get_sum_page(sbi, segno);

 	blk_start_plug(&plug);

 	sum = page_address(sum_page);

 	switch (GET_SUM_TYPE((&sum->footer))) {
 	case SUM_TYPE_NODE:
 		gc_node_segment(sbi, sum->entries, segno, gc_type);
 		break;
 	case SUM_TYPE_DATA:
 		gc_data_segment(sbi, sum->entries, gc_list, segno, gc_type);
 		break;
 	}
 	blk_finish_plug(&plug);

 	stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)), gc_type);
 	stat_inc_call_count(sbi->stat_info);

 	f2fs_put_page(sum_page, 1);
 }

 int f2fs_gc(struct f2fs_sb_info *sbi)
 {
 	unsigned int segno, i;
 	int gc_type = BG_GC;
 	int nfree = 0;
 	int ret = -1;
 	struct cp_control cpc;
 	struct gc_inode_list gc_list = {
 		.ilist = LIST_HEAD_INIT(gc_list.ilist),
 		.iroot = RADIX_TREE_INIT(GFP_NOFS),
 	};

 	cpc.reason = __get_cp_reason(sbi);
 gc_more:
 	if (unlikely(!(sbi->sb->s_flags & MS_ACTIVE)))
 		goto stop;
 	if (unlikely(f2fs_cp_error(sbi)))
 		goto stop;

 	if (gc_type == BG_GC && has_not_enough_free_secs(sbi, nfree)) {
 		gc_type = FG_GC;
 		write_checkpoint(sbi, &cpc);
 	}

 	if (!__get_victim(sbi, &segno, gc_type))
 		goto stop;
 	ret = 0;

 	/* readahead multi ssa blocks those have contiguous address */
 	if (sbi->segs_per_sec > 1)
 		ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno), sbi->segs_per_sec,
 								META_SSA);

 	for (i = 0; i < sbi->segs_per_sec; i++)
 		do_garbage_collect(sbi, segno + i, &gc_list, gc_type);

 	if (gc_type == FG_GC) {
 		sbi->cur_victim_sec = NULL_SEGNO;
 		nfree++;
 		WARN_ON(get_valid_blocks(sbi, segno, sbi->segs_per_sec));
 	}

 	if (has_not_enough_free_secs(sbi, nfree))
 		goto gc_more;

 	if (gc_type == FG_GC)
 		write_checkpoint(sbi, &cpc);
 stop:
 	mutex_unlock(&sbi->gc_mutex);

 	put_gc_inode(&gc_list);
 	return ret;
 }

 void build_gc_manager(struct f2fs_sb_info *sbi)
 {
 	DIRTY_I(sbi)->v_ops = &default_v_ops;
 }
	/*
	* fs/f2fs/gc.c
	*
	* Copyright (c) 2012 Samsung Electronics Co., Ltd.
	* http://www.samsung.com/
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/
	#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/blkdev.h>

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

	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;
	long wait_ms;

	wait_ms = gc_th->min_sleep_time;

	do {
	if (try_to_freeze())
	continue;
	else
	wait_event_interruptible_timeout(*wq,
	kthread_should_stop(),
	msecs_to_jiffies(wait_ms));
	if (kthread_should_stop())
	break;

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

	if (!is_idle(sbi)) {
	increase_sleep_time(gc_th, &wait_ms);
	mutex_unlock(&sbi->gc_mutex);
	continue;
	}

	if (has_enough_invalid_blocks(sbi))
	decrease_sleep_time(gc_th, &wait_ms);
	else
	increase_sleep_time(gc_th, &wait_ms);

	stat_inc_bggc_count(sbi);

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

	/* balancing f2fs's metadata periodically */
	f2fs_balance_fs_bg(sbi);

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

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

	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_idle = 0;

	sbi->gc_thread = gc_th;
	init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
	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 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);
	kfree(gc_th);
	sbi->gc_thread = NULL;
	}

	static int select_gc_type(struct f2fs_gc_kthread *gc_th, int gc_type)
	{
	int gc_mode = (gc_type == BG_GC) ? GC_CB : GC_GREEDY;

	if (gc_th && gc_th->gc_idle) {
	if (gc_th->gc_idle == 1)
	gc_mode = GC_CB;
	else if (gc_th->gc_idle == 2)
	gc_mode = GC_GREEDY;
	}
	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_segmap = 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_thread, gc_type);
	p->dirty_segmap = dirty_i->dirty_segmap[DIRTY];
	p->max_search = dirty_i->nr_dirty[DIRTY];
	p->ofs_unit = sbi->segs_per_sec;
	}

	if (p->max_search > sbi->max_victim_search)
	p->max_search = sbi->max_victim_search;

	p->offset = 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 1 << sbi->log_blocks_per_seg;
	if (p->gc_mode == GC_GREEDY)
	return (1 << sbi->log_blocks_per_seg) * p->ofs_unit;
	else if (p->gc_mode == GC_CB)
	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 secno * sbi->segs_per_sec;
	}
	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_SECNO(sbi, segno);
	unsigned int start = secno * sbi->segs_per_sec;
	unsigned long long mtime = 0;
	unsigned int vblocks;
	unsigned char age = 0;
	unsigned char u;
	unsigned int i;

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

	mtime = div_u64(mtime, sbi->segs_per_sec);
	vblocks = div_u64(vblocks, sbi->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, sbi->segs_per_sec);
	else
	return get_cb_cost(sbi, segno);
	}

	/*
	* 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)
	{
	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
	struct victim_sel_policy p;
	unsigned int secno, max_cost;
	int nsearched = 0;

	mutex_lock(&dirty_i->seglist_lock);

	p.alloc_mode = alloc_mode;
	select_policy(sbi, gc_type, type, &p);

	p.min_segno = NULL_SEGNO;
	p.min_cost = max_cost = get_max_cost(sbi, &p);

	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;
	unsigned int segno;

	segno = find_next_bit(p.dirty_segmap, MAIN_SEGS(sbi), p.offset);
	if (segno >= MAIN_SEGS(sbi)) {
	if (sbi->last_victim[p.gc_mode]) {
	sbi->last_victim[p.gc_mode] = 0;
	p.offset = 0;
	continue;
	}
	break;
	}

	p.offset = segno + p.ofs_unit;
	if (p.ofs_unit > 1)
	p.offset -= segno % p.ofs_unit;

	secno = GET_SECNO(sbi, segno);

	if (sec_usage_check(sbi, secno))
	continue;
	if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
	continue;

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

	if (p.min_cost > cost) {
	p.min_segno = segno;
	p.min_cost = cost;
	} else if (unlikely(cost == max_cost)) {
	continue;
	}

	if (nsearched++ >= p.max_search) {
	sbi->last_victim[p.gc_mode] = segno;
	break;
	}
	}
	if (p.min_segno != NULL_SEGNO) {
	got_it:
	if (p.alloc_mode == LFS) {
	secno = GET_SECNO(sbi, p.min_segno);
	if (gc_type == FG_GC)
	sbi->cur_victim_sec = secno;
	else
	set_bit(secno, dirty_i->victim_secmap);
	}
	result = (p.min_segno / p.ofs_unit) p.ofs_unit;

	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 (p.min_segno == NULL_SEGNO) ? 0 : 1;
	}

	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(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(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;

	mutex_lock(&sit_i->sentry_lock);
	sentry = get_seg_entry(sbi, segno);
	ret = f2fs_test_bit(offset, sentry->cur_valid_map);
	mutex_unlock(&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 void gc_node_segment(struct f2fs_sb_info *sbi,
	struct f2fs_summary *sum, unsigned int segno, int gc_type)
	{
	bool initial = true;
	struct f2fs_summary *entry;
	int off;

	next_step:
	entry = sum;

	for (off = 0; off < sbi->blocks_per_seg; off++, entry++) {
	nid_t nid = le32_to_cpu(entry->nid);
	struct page *node_page;

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

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

	if (initial) {
	ra_node_page(sbi, nid);
	continue;
	}
	node_page = get_node_page(sbi, nid);
	if (IS_ERR(node_page))
	continue;

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

	/* set page dirty and write it */
	if (gc_type == FG_GC) {
	f2fs_wait_on_page_writeback(node_page, NODE);
	set_page_dirty(node_page);
	} else {
	if (!PageWriteback(node_page))
	set_page_dirty(node_page);
	}
	f2fs_put_page(node_page, 1);
	stat_inc_node_blk_count(sbi, 1, gc_type);
	}

	if (initial) {
	initial = false;
	goto next_step;
	}

	if (gc_type == FG_GC) {
	struct writeback_control wbc = {
	.sync_mode = WB_SYNC_ALL,
	.nr_to_write = LONG_MAX,
	.for_reclaim = 0,
	};
	sync_node_pages(sbi, 0, &wbc);

	/*
	* In the case of FG_GC, it'd be better to reclaim this victim
	* completely.
	*/
	if (get_valid_blocks(sbi, segno, 1) != 0)
	goto next_step;
	}
	}

	/*
	* 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 start_bidx_of_node(unsigned int node_ofs, struct f2fs_inode_info *fi)
	{
	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 + ADDRS_PER_INODE(fi);
	}

	static int check_dnode(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 = get_node_page(sbi, nid);
	if (IS_ERR(node_page))
	return 0;

	get_node_info(sbi, nid, dni);

	if (sum->version != dni->version) {
	f2fs_put_page(node_page, 1);
	return 0;
	}

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

	if (source_blkaddr != blkaddr)
	return 0;
	return 1;
	}

	static void move_data_page(struct inode inode, struct page page, int gc_type)
	{
	struct f2fs_io_info fio = {
	.type = DATA,
	.rw = WRITE_SYNC,
	};

	if (gc_type == BG_GC) {
	if (PageWriteback(page))
	goto out;
	set_page_dirty(page);
	set_cold_data(page);
	} else {
	f2fs_wait_on_page_writeback(page, DATA);

	if (clear_page_dirty_for_io(page))
	inode_dec_dirty_pages(inode);
	set_cold_data(page);
	do_write_data_page(page, &fio);
	clear_cold_data(page);
	}
	out:
	f2fs_put_page(page, 1);
	}

	/*
	* 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 void gc_data_segment(struct f2fs_sb_info sbi, struct f2fs_summary sum,
	struct gc_inode_list *gc_list, unsigned int segno, int gc_type)
	{
	struct super_block *sb = sbi->sb;
	struct f2fs_summary *entry;
	block_t start_addr;
	int off;
	int phase = 0;

	start_addr = START_BLOCK(sbi, segno);

	next_step:
	entry = sum;

	for (off = 0; off < sbi->blocks_per_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;

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

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

	if (phase == 0) {
	ra_node_page(sbi, le32_to_cpu(entry->nid));
	continue;
	}

	/* Get an inode by ino with checking validity */
	if (check_dnode(sbi, entry, &dni, start_addr + off, &nofs) == 0)
	continue;

	if (phase == 1) {
	ra_node_page(sbi, dni.ino);
	continue;
	}

	ofs_in_node = le16_to_cpu(entry->ofs_in_node);

	if (phase == 2) {
	inode = f2fs_iget(sb, dni.ino);
	if (IS_ERR(inode) \|\| is_bad_inode(inode))
	continue;

	start_bidx = start_bidx_of_node(nofs, F2FS_I(inode));

	data_page = find_data_page(inode,
	start_bidx + ofs_in_node, false);
	if (IS_ERR(data_page)) {
	iput(inode);
	continue;
	}

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

	/* phase 3 */
	inode = find_gc_inode(gc_list, dni.ino);
	if (inode) {
	start_bidx = start_bidx_of_node(nofs, F2FS_I(inode));
	data_page = get_lock_data_page(inode,
	start_bidx + ofs_in_node);
	if (IS_ERR(data_page))
	continue;
	move_data_page(inode, data_page, gc_type);
	stat_inc_data_blk_count(sbi, 1, gc_type);
	}
	}

	if (++phase < 4)
	goto next_step;

	if (gc_type == FG_GC) {
	f2fs_submit_merged_bio(sbi, DATA, WRITE);

	/*
	* In the case of FG_GC, it'd be better to reclaim this victim
	* completely.
	*/
	if (get_valid_blocks(sbi, segno, 1) != 0) {
	phase = 2;
	goto next_step;
	}
	}
	}

	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;

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

	static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
	struct gc_inode_list *gc_list, int gc_type)
	{
	struct page *sum_page;
	struct f2fs_summary_block *sum;
	struct blk_plug plug;

	/* read segment summary of victim */
	sum_page = get_sum_page(sbi, segno);

	blk_start_plug(&plug);

	sum = page_address(sum_page);

	switch (GET_SUM_TYPE((&sum->footer))) {
	case SUM_TYPE_NODE:
	gc_node_segment(sbi, sum->entries, segno, gc_type);
	break;
	case SUM_TYPE_DATA:
	gc_data_segment(sbi, sum->entries, gc_list, segno, gc_type);
	break;
	}
	blk_finish_plug(&plug);

	stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)), gc_type);
	stat_inc_call_count(sbi->stat_info);

	f2fs_put_page(sum_page, 1);
	}

	int f2fs_gc(struct f2fs_sb_info *sbi)
	{
	unsigned int segno, i;
	int gc_type = BG_GC;
	int nfree = 0;
	int ret = -1;
	struct cp_control cpc;
	struct gc_inode_list gc_list = {
	.ilist = LIST_HEAD_INIT(gc_list.ilist),
	.iroot = RADIX_TREE_INIT(GFP_NOFS),
	};

	cpc.reason = __get_cp_reason(sbi);
	gc_more:
	if (unlikely(!(sbi->sb->s_flags & MS_ACTIVE)))
	goto stop;
	if (unlikely(f2fs_cp_error(sbi)))
	goto stop;

	if (gc_type == BG_GC && has_not_enough_free_secs(sbi, nfree)) {
	gc_type = FG_GC;
	write_checkpoint(sbi, &cpc);
	}

	if (!__get_victim(sbi, &segno, gc_type))
	goto stop;
	ret = 0;

	/* readahead multi ssa blocks those have contiguous address */
	if (sbi->segs_per_sec > 1)
	ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno), sbi->segs_per_sec,
	META_SSA);

	for (i = 0; i < sbi->segs_per_sec; i++)
	do_garbage_collect(sbi, segno + i, &gc_list, gc_type);

	if (gc_type == FG_GC) {
	sbi->cur_victim_sec = NULL_SEGNO;
	nfree++;
	WARN_ON(get_valid_blocks(sbi, segno, sbi->segs_per_sec));
	}

	if (has_not_enough_free_secs(sbi, nfree))
	goto gc_more;

	if (gc_type == FG_GC)
	write_checkpoint(sbi, &cpc);
	stop:
	mutex_unlock(&sbi->gc_mutex);

	put_gc_inode(&gc_list);
	return ret;
	}

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