path: root/fs/f2fs/gc.c

/*
 * 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 "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;
	unsigned int wait_ms;

	wait_ms = gc_th->min_sleep_time;

	set_freezable();
	do {
		wait_event_interruptible_timeout(*wq,
				kthread_should_stop() || freezing(current) ||
				gc_th->gc_wake,
				msecs_to_jiffies(wait_ms));

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

		if (try_to_freeze())
			continue;
		if (kthread_should_stop())
			break;

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

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

		if (!sb_start_write_trylock(sbi->sb))
			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) {
			wait_ms = gc_th->urgent_sleep_time;
			mutex_lock(&sbi->gc_mutex);
			goto do_gc;
		}

		if (!mutex_trylock(&sbi->gc_mutex))
			goto next;

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

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

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

		/* bala