1. 根目录:
2. fs
3. f2fs
4. segment.h

/*
 * fs/f2fs/segment.h
 *
 * 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/blkdev.h>
#include <linux/backing-dev.h>

/* constant macro */
#define NULL_SEGNO			((unsigned int)(~0))
#define NULL_SECNO			((unsigned int)(~0))

#define DEF_RECLAIM_PREFREE_SEGMENTS	5	/* 5% over total segments */

/* L: Logical segment # in volume, R: Relative segment # in main area */
#define GET_L2R_SEGNO(free_i, segno)	(segno - free_i->start_segno)
#define GET_R2L_SEGNO(free_i, segno)	(segno + free_i->start_segno)

#define IS_DATASEG(t)	(t <= CURSEG_COLD_DATA)
#define IS_NODESEG(t)	(t >= CURSEG_HOT_NODE)

#define IS_CURSEG(sbi, seg)						\
	((seg == CURSEG_I(sbi, CURSEG_HOT_DATA)->segno) ||	\
	 (seg == CURSEG_I(sbi, CURSEG_WARM_DATA)->segno) ||	\
	 (seg == CURSEG_I(sbi, CURSEG_COLD_DATA)->segno) ||	\
	 (seg == CURSEG_I(sbi, CURSEG_HOT_NODE)->segno) ||	\
	 (seg == CURSEG_I(sbi, CURSEG_WARM_NODE)->segno) ||	\
	 (seg == CURSEG_I(sbi, CURSEG_COLD_NODE)->segno))

#define IS_CURSEC(sbi, secno)						\
	((secno == CURSEG_I(sbi, CURSEG_HOT_DATA)->segno /		\
	  sbi->segs_per_sec) ||	\
	 (secno == CURSEG_I(sbi, CURSEG_WARM_DATA)->segno /		\
	  sbi->segs_per_sec) ||	\
	 (secno == CURSEG_I(sbi, CURSEG_COLD_DATA)->segno /		\
	  sbi->segs_per_sec) ||	\
	 (secno == CURSEG_I(sbi, CURSEG_HOT_NODE)->segno /		\
	  sbi->segs_per_sec) ||	\
	 (secno == CURSEG_I(sbi, CURSEG_WARM_NODE)->segno /		\
	  sbi->segs_per_sec) ||	\
	 (secno == CURSEG_I(sbi, CURSEG_COLD_NODE)->segno /		\
	  sbi->segs_per_sec))	\

#define MAIN_BLKADDR(sbi)	(SM_I(sbi)->main_blkaddr)
#define SEG0_BLKADDR(sbi)	(SM_I(sbi)->seg0_blkaddr)

#define MAIN_SEGS(sbi)	(SM_I(sbi)->main_segments)
#define MAIN_SECS(sbi)	(sbi->total_sections)

#define TOTAL_SEGS(sbi)	(SM_I(sbi)->segment_count)
#define TOTAL_BLKS(sbi)	(TOTAL_SEGS(sbi) << sbi->log_blocks_per_seg)

#define MAX_BLKADDR(sbi)	(SEG0_BLKADDR(sbi) + TOTAL_BLKS(sbi))
#define SEGMENT_SIZE(sbi)	(1ULL << (sbi->log_blocksize +		\
					sbi->log_blocks_per_seg))

#define START_BLOCK(sbi, segno)	(SEG0_BLKADDR(sbi) +			\
	 (GET_R2L_SEGNO(FREE_I(sbi), segno) << sbi->log_blocks_per_seg))

#define NEXT_FREE_BLKADDR(sbi, curseg)					\
	(START_BLOCK(sbi, curseg->segno) + curseg->next_blkoff)

#define GET_SEGOFF_FROM_SEG0(sbi, blk_addr)	((blk_addr) - SEG0_BLKADDR(sbi))
#define GET_SEGNO_FROM_SEG0(sbi, blk_addr)				\
	(GET_SEGOFF_FROM_SEG0(sbi, blk_addr) >> sbi->log_blocks_per_seg)
#define GET_BLKOFF_FROM_SEG0(sbi, blk_addr)				\
	(GET_SEGOFF_FROM_SEG0(sbi, blk_addr) & (sbi->blocks_per_seg - 1))

#define GET_SEGNO(sbi, blk_addr)					\
	(((blk_addr == NULL_ADDR) || (blk_addr == NEW_ADDR)) ?		\
	NULL_SEGNO : GET_L2R_SEGNO(FREE_I(sbi),			\
		GET_SEGNO_FROM_SEG0(sbi, blk_addr)))
#define GET_SECNO(sbi, segno)					\
	((segno) / sbi->segs_per_sec)
#define GET_ZONENO_FROM_SEGNO(sbi, segno)				\
	((segno / sbi->segs_per_sec) / sbi->secs_per_zone)

#define GET_SUM_BLOCK(sbi, segno)				\
	((sbi->sm_info->ssa_blkaddr) + segno)

#define GET_SUM_TYPE(footer) ((footer)->entry_type)
#define SET_SUM_TYPE(footer, type) ((footer)->entry_type = type)

#define SIT_ENTRY_OFFSET(sit_i, segno)					\
	(segno % sit_i->sents_per_block)
#define SIT_BLOCK_OFFSET(segno)					\
	(segno / SIT_ENTRY_PER_BLOCK)
#define	START_SEGNO(segno)		\
	(SIT_BLOCK_OFFSET(segno) * SIT_ENTRY_PER_BLOCK)
#define SIT_BLK_CNT(sbi)			\
	((MAIN_SEGS(sbi) + SIT_ENTRY_PER_BLOCK - 1) / SIT_ENTRY_PER_BLOCK)
#define f2fs_bitmap_size(nr)			\
	(BITS_TO_LONGS(nr) * sizeof(unsigned long))

#define SECTOR_FROM_BLOCK(blk_addr)					\
	(((sector_t)blk_addr) << F2FS_LOG_SECTORS_PER_BLOCK)
#define SECTOR_TO_BLOCK(sectors)					\
	(sectors >> F2FS_LOG_SECTORS_PER_BLOCK)
#define MAX_BIO_BLOCKS(sbi)						\
	((int)min((int)max_hw_blocks(sbi), BIO_MAX_PAGES))

/*
 * indicate a block allocation direction: RIGHT and LEFT.
 * RIGHT means allocating new sections towards the end of volume.
 * LEFT means the opposite direction.
 */
enum {
	ALLOC_RIGHT = 0,
	ALLOC_LEFT
};

/*
 * In the victim_sel_policy->alloc_mode, there are two block allocation modes.
 * LFS writes data sequentially with cleaning operations.
 * SSR (Slack Space Recycle) reuses obsolete space without cleaning operations.
 */
enum {
	LFS = 0,
	SSR
};

/*
 * In the victim_sel_policy->gc_mode, there are two gc, aka cleaning, modes.
 * GC_CB is based on cost-benefit algorithm.
 * GC_GREEDY is based on greedy algorithm.
 */
enum {
	GC_CB = 0,
	GC_GREEDY
};

/*
 * BG_GC means the background cleaning job.
 * FG_GC means the on-demand cleaning job.
 * FORCE_FG_GC means on-demand cleaning job in background.
 */
enum {
	BG_GC = 0,
	FG_GC,
	FORCE_FG_GC,
};

/* for a function parameter to select a victim segment */
struct victim_sel_policy {
	int alloc_mode;			/* LFS or SSR */
	int gc_mode;			/* GC_CB or GC_GREEDY */
	unsigned long *dirty_segmap;	/* dirty segment bitmap */
	unsigned int max_search;	/* maximum # of segments to search */
	unsigned int offset;		/* last scanned bitmap offset */
	unsigned int ofs_unit;		/* bitmap search unit */
	unsigned int min_cost;		/* minimum cost */
	unsigned int min_segno;		/* segment # having min. cost */
};

struct seg_entry {
	unsigned short valid_blocks;	/* # of valid blocks */
	unsigned char *cur_valid_map;	/* validity bitmap of blocks */
	/*
	 * # of valid blocks and the validity bitmap stored in the the last
	 * checkpoint pack. This information is used by the SSR mode.
	 */
	unsigned short ckpt_valid_blocks;
	unsigned char *ckpt_valid_map;
	unsigned char *discard_map;
	unsigned char type;		/* segment type like CURSEG_XXX_TYPE */
	unsigned long long mtime;	/* modification time of the segment */
};

struct sec_entry {
	unsigned int valid_blocks;	/* # of valid blocks in a section */
};

struct segment_allocation {
	void (*allocate_segment)(struct f2fs_sb_info *, int, bool);
};

/*
 * this value is set in page as a private data which indicate that
 * the page is atomically written, and it is in inmem_pages list.
 */
#define ATOMIC_WRITTEN_PAGE		0x0000ffff

#define IS_ATOMIC_WRITTEN_PAGE(page)			\
		(page_private(page) == (unsigned long)ATOMIC_WRITTEN_PAGE)

struct inmem_pages {
	struct list_head list;
	struct page *page;
};

struct sit_info {
	const struct segment_allocation *s_ops;

	block_t sit_base_addr;		/* start block address of SIT area */
	block_t sit_blocks;		/* # of blocks used by SIT area */
	block_t written_valid_blocks;	/* # of valid blocks in main area */
	char *sit_bitmap;		/* SIT bitmap pointer */
	unsigned int bitmap_size;	/* SIT bitmap size */

	unsigned long *tmp_map;			/* bitmap for temporal use */
	unsigned long *dirty_sentries_bitmap;	/* bitmap for dirty sentries */
	unsigned int dirty_sentries;		/* # of dirty sentries */
	unsigned int sents_per_block;		/* # of SIT entries per block */
	struct mutex sentry_lock;		/* to protect SIT cache */
	struct seg_entry *sentries;		/* SIT segment-level cache */
	struct sec_entry *sec_entries;		/* SIT section-level cache */

	/* for cost-benefit algorithm in cleaning procedure */
	unsigned long long elapsed_time;	/* elapsed time after mount */
	unsigned long long mounted_time;	/* mount time */
	unsigned long long min_mtime;		/* min. modification time */
	unsigned long long max_mtime;		/* max. modification time */
};

struct free_segmap_info {
	unsigned int start_segno;	/* start segment number logically */
	unsigned int free_segments;	/* # of free segments */
	unsigned int free_sections;	/* # of free sections */
	spinlock_t segmap_lock;		/* free segmap lock */
	unsigned long *free_segmap;	/* free segment bitmap */
	unsigned long *free_secmap;	/* free section bitmap */
};

/* Notice: The order of dirty type is same with CURSEG_XXX in f2fs.h */
enum dirty_type {
	DIRTY_HOT_DATA,		/* dirty segments assigned as hot data logs */
	DIRTY_WARM_DATA,	/* dirty segments assigned as warm data logs */
	DIRTY_COLD_DATA,	/* dirty segments assigned as cold data logs */
	DIRTY_HOT_NODE,		/* dirty segments assigned as hot node logs */
	DIRTY_WARM_NODE,	/* dirty segments assigned as warm node logs */
	DIRTY_COLD_NODE,	/* dirty segments assigned as cold node logs */
	DIRTY,			/* to count # of dirty segments */
	PRE,			/* to count # of entirely obsolete segments */
	NR_DIRTY_TYPE
};

struct dirty_seglist_info {
	const struct victim_selection *v_ops;	/* victim selction operation */
	unsigned long *dirty_segmap[NR_DIRTY_TYPE];
	struct mutex seglist_lock;		/* lock for segment bitmaps */
	int nr_dirty[NR_DIRTY_TYPE];		/* # of dirty segments */
	unsigned long *victim_secmap;		/* background GC victims */
};

/* victim selection function for cleaning and SSR */
struct victim_selection {
	int (*get_victim)(struct f2fs_sb_info *, unsigned int *,
							int, int, char);
};

/* for active log information */
struct curseg_info {
	struct mutex curseg_mutex;		/* lock for consistency */
	struct f2fs_summary_block *sum_blk;	/* cached summary block */
	unsigned char alloc_type;		/* current allocation type */
	unsigned int segno;			/* current segment number */
	unsigned short next_blkoff;		/* next block offset to write */
	unsigned int zone;			/* current zone number */
	unsigned int next_segno;		/* preallocated segment */
};

struct sit_entry_set {
	struct list_head set_list;	/* link with all sit sets */
	unsigned int start_segno;	/* start segno of sits in set */
	unsigned int entry_cnt;		/* the # of sit entries in set */
};

/*
 * inline functions
 */
static inline struct curseg_info *CURSEG_I(struct f2fs_sb_info *sbi, int type)
{
	return (struct curseg_info *)(SM_I(sbi)->curseg_array + type);
}

static inline struct seg_entry *get_seg_entry(struct f2fs_sb_info *sbi,
						unsigned int segno)
{
	struct sit_info *sit_i = SIT_I(sbi);
	return &sit_i->sentries[segno];
}

static inline struct sec_entry *get_sec_entry(struct f2fs_sb_info *sbi,
						unsigned int segno)
{
	struct sit_info *sit_i = SIT_I(sbi);
	return &sit_i->sec_entries[GET_SECNO(sbi, segno)];
}

static inline unsigned int get_valid_blocks(struct f2fs_sb_info *sbi,
				unsigned int segno, int section)
{
	/*
	 * In order to get # of valid blocks in a section instantly from many
	 * segments, f2fs manages two counting structures separately.
	 */
	if (section > 1)
		return get_sec_entry(sbi, segno)->valid_blocks;
	else
		return get_seg_entry(sbi, segno)->valid_blocks;
}

static inline void seg_info_from_raw_sit(struct seg_entry *se,
					struct f2fs_sit_entry *rs)
{
	se->valid_blocks = GET_SIT_VBLOCKS(rs);
	se->ckpt_valid_blocks = GET_SIT_VBLOCKS(rs);
	memcpy(se->cur_valid_map, rs->valid_map, SIT_VBLOCK_MAP_SIZE);
	memcpy(se->ckpt_valid_map, rs->valid_map, SIT_VBLOCK_MAP_SIZE);
	se->type = GET_SIT_TYPE(rs);
	se->mtime = le64_to_cpu(rs->mtime);
}

static inline void seg_info_to_raw_sit(struct seg_entry *se,
					struct f2fs_sit_entry *rs)
{
	unsigned short raw_vblocks = (se->type << SIT_VBLOCKS_SHIFT) |
					se->valid_blocks;
	rs->vblocks = cpu_to_le16(raw_vblocks);
	memcpy(rs->valid_map, se->cur_valid_map, SIT_VBLOCK_MAP_SIZE);
	memcpy(se->ckpt_valid_map, rs->valid_map, SIT_VBLOCK_MAP_SIZE);
	se->ckpt_valid_blocks = se->valid_blocks;
	rs->mtime = cpu_to_le64(se->mtime);
}

static inline unsigned int find_next_inuse(struct free_segmap_info *free_i,
		unsigned int max, unsigned int segno)
{
	unsigned int ret;
	spin_lock(&free_i->segmap_lock);
	ret = find_next_bit(free_i->free_segmap, max, segno);
	spin_unlock(&free_i->segmap_lock);
	return ret;
}

static inline void __set_free(struct f2fs_sb_info *sbi, unsigned int segno)
{
	struct free_segmap_info *free_i = FREE_I(sbi);
	unsigned int secno = segno / sbi->segs_per_sec;
	unsigned int start_segno = secno * sbi->segs_per_sec;
	unsigned int next;

	spin_lock(&free_i->segmap_lock);
	clear_bit(segno, free_i->free_segmap);
	free_i->free_segments++;

	next = find_next_bit(free_i->free_segmap,
			start_segno + sbi->segs_per_sec, start_segno);
	if (next >= start_segno + sbi->segs_per_sec) {
		clear_bit(secno, free_i->free_secmap);
		free_i->free_sections++;
	}
	spin_unlock(&free_i->segmap_lock);
}

static inline void __set_inuse(struct f2fs_sb_info *sbi,
		unsigned int segno)
{
	struct free_segmap_info *free_i = FREE_I(sbi);
	unsigned int secno = segno / sbi->segs_per_sec;
	set_bit(segno, free_i->free_segmap);
	free_i->free_segments--;
	if (!test_and_set_bit(secno, free_i->free_secmap))
		free_i->free_sections--;
}

static inline void __set_test_and_free(struct f2fs_sb_info *sbi,
		unsigned int segno)
{
	struct free_segmap_info *free_i = FREE_I(sbi);
	unsigned int secno = segno / sbi->segs_per_sec;
	unsigned int start_segno = secno * sbi->segs_per_sec;
	unsigned int next;

	spin_lock(&free_i->segmap_lock);
	if (test_and_clear_bit(segno, free_i->free_segmap)) {
		free_i->free_segments++;

		next = find_next_bit(free_i->free_segmap,
				start_segno + sbi->segs_per_sec, start_segno);
		if (next >= start_segno + sbi->segs_per_sec) {
			if (test_and_clear_bit(secno, free_i->free_secmap))
				free_i->free_sections++;
		}
	}
	spin_unlock(&free_i->segmap_lock);
}

static inline void __set_test_and_inuse(struct f2fs_sb_info *sbi,
		unsigned int segno)
{
	struct free_segmap_info *free_i = FREE_I(sbi);
	unsigned int secno = segno / sbi->segs_per_sec;
	spin_lock(&free_i->segmap_lock);
	if (!test_and_set_bit(segno, free_i->free_segmap)) {
		free_i->free_segments--;
		if (!test_and_set_bit(secno, free_i->free_secmap))
			free_i->free_sections--;
	}
	spin_unlock(&free_i->segmap_lock);
}

static inline void get_sit_bitmap(struct f2fs_sb_info *sbi,
		void *dst_addr)
{
	struct sit_info *sit_i = SIT_I(sbi);
	memcpy(dst_addr, sit_i->sit_bitmap, sit_i->bitmap_size);
}

static inline block_t written_block_count(struct f2fs_sb_info *sbi)
{
	return SIT_I(sbi)->written_valid_blocks;
}

static inline unsigned int free_segments(struct f2fs_sb_info *sbi)
{
	return FREE_I(sbi)->free_segments;
}

static inline int reserved_segments(struct f2fs_sb_info *sbi)
{
	return SM_I(sbi)->reserved_segments;
}

static inline unsigned int free_sections(struct f2fs_sb_info *sbi)
{
	return FREE_I(sbi)->free_sections;
}

static inline unsigned int prefree_segments(struct f2fs_sb_info *sbi)
{
	return DIRTY_I(sbi)->nr_dirty[PRE];
}

static inline unsigned int dirty_segments(struct f2fs_sb_info *sbi)
{
	return DIRTY_I(sbi)->nr_dirty[DIRTY_HOT_DATA] +
		DIRTY_I(sbi)->nr_dirty[DIRTY_WARM_DATA] +
		DIRTY_I(sbi)->nr_dirty[DIRTY_COLD_DATA] +
		DIRTY_I(sbi)->nr_dirty[DIRTY_HOT_NODE] +
		DIRTY_I(sbi)->nr_dirty[DIRTY_WARM_NODE] +
		DIRTY_I(sbi)->nr_dirty[DIRTY_COLD_NODE];
}

static inline int overprovision_segments(struct f2fs_sb_info *sbi)
{
	return SM_I(sbi)->ovp_segments;
}

static inline int overprovision_sections(struct f2fs_sb_info *sbi)
{
	return ((unsigned int) overprovision_segments(sbi)) / sbi->segs_per_sec;
}

static inline int reserved_sections(struct f2fs_sb_info *sbi)
{
	return ((unsigned int) reserved_segments(sbi)) / sbi->segs_per_sec;
}

static inline bool need_SSR(struct f2fs_sb_info *sbi)
{
	int node_secs = get_blocktype_secs(sbi, F2FS_DIRTY_NODES);
	int dent_secs = get_blocktype_secs(sbi, F2FS_DIRTY_DENTS);
	return free_sections(sbi) <= (node_secs + 2 * dent_secs +
						reserved_sections(sbi) + 1);
}

static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi, int freed)
{
	int node_secs = get_blocktype_secs(sbi, F2FS_DIRTY_NODES);
	int dent_secs = get_blocktype_secs(sbi, F2FS_DIRTY_DENTS);

	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
		return false;

	return (free_sections(sbi) + freed) <= (node_secs + 2 * dent_secs +
						reserved_sections(sbi));
}

static inline bool excess_prefree_segs(struct f2fs_sb_info *sbi)
{
	return prefree_segments(sbi) > SM_I(sbi)->rec_prefree_segments;
}

static inline int utilization(struct f2fs_sb_info *sbi)
{
	return div_u64((u64)valid_user_blocks(sbi) * 100,
					sbi->user_block_count);
}

/*
 * Sometimes f2fs may be better to drop out-of-place update policy.
 * And, users can control the policy through sysfs entries.
 * There are five policies with triggering conditions as follows.
 * F2FS_IPU_FORCE - all the time,
 * F2FS_IPU_SSR - if SSR mode is activated,
 * F2FS_IPU_UTIL - if FS utilization is over threashold,
 * F2FS_IPU_SSR_UTIL - if SSR mode is activated and FS utilization is over
 *                     threashold,
 * F2FS_IPU_FSYNC - activated in fsync path only for high performance flash
 *                     storages. IPU will be triggered only if the # of dirty
 *                     pages over min_fsync_blocks.
 * F2FS_IPUT_DISABLE - disable IPU. (=default option)
 */
#define DEF_MIN_IPU_UTIL	70
#define DEF_MIN_FSYNC_BLOCKS	8

enum {
	F2FS_IPU_FORCE,
	F2FS_IPU_SSR,
	F2FS_IPU_UTIL,
	F2FS_IPU_SSR_UTIL,
	F2FS_IPU_FSYNC,
};

static inline bool need_inplace_update(struct inode *inode)
{
	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
	unsigned int policy = SM_I(sbi)->ipu_policy;

	/* IPU can be done only for the user data */
	if (S_ISDIR(inode->i_mode) || f2fs_is_atomic_file(inode))
		return false;

	if (policy & (0x1 << F2FS_IPU_FORCE))
		return true;
	if (policy & (0x1 << F2FS_IPU_SSR) && need_SSR(sbi))
		return true;
	if (policy & (0x1 << F2FS_IPU_UTIL) &&
			utilization(sbi) > SM_I(sbi)->min_ipu_util)
		return true;
	if (policy & (0x1 << F2FS_IPU_SSR_UTIL) && need_SSR(sbi) &&
			utilization(sbi) > SM_I(sbi)->min_ipu_util)
		return true;

	/* this is only set during fdatasync */
	if (policy & (0x1 << F2FS_IPU_FSYNC) &&
			is_inode_flag_set(F2FS_I(inode), FI_NEED_IPU))
		return true;

	return false;
}

static inline unsigned int curseg_segno(struct f2fs_sb_info *sbi,
		int type)
{
	struct curseg_info *curseg = CURSEG_I(sbi, type);
	return curseg->segno;
}

static inline unsigned char curseg_alloc_type(struct f2fs_sb_info *sbi,
		int type)
{
	struct curseg_info *curseg = CURSEG_I(sbi, type);
	return curseg->alloc_type;
}

static inline unsigned short curseg_blkoff(struct f2fs_sb_info *sbi, int type)
{
	struct curseg_info *curseg = CURSEG_I(sbi, type);
	return curseg->next_blkoff;
}

static inline void check_seg_range(struct f2fs_sb_info *sbi, unsigned int segno)
{
	f2fs_bug_on(sbi, segno > TOTAL_SEGS(sbi) - 1);
}

static inline void verify_block_addr(struct f2fs_sb_info *sbi, block_t blk_addr)
{
	f2fs_bug_on(sbi, blk_addr < SEG0_BLKADDR(sbi)
					|| blk_addr >= MAX_BLKADDR(sbi));
}

/*
 * Summary block is always treated as an invalid block
 */
static inline void check_block_count(struct f2fs_sb_info *sbi,
		int segno, struct f2fs_sit_entry *raw_sit)
{
#ifdef CONFIG_F2FS_CHECK_FS
	bool is_valid  = test_bit_le(0, raw_sit->valid_map) ? true : false;
	int valid_blocks = 0;
	int cur_pos = 0, next_pos;

	/* check bitmap with valid block count */
	do {
		if (is_valid) {
			next_pos = find_next_zero_bit_le(&raw_sit->valid_map,
					sbi->blocks_per_seg,
					cur_pos);
			valid_blocks += next_pos - cur_pos;
		} else
			next_pos = find_next_bit_le(&raw_sit->valid_map,
					sbi->blocks_per_seg,
					cur_pos);
		cur_pos = next_pos;
		is_valid = !is_valid;
	} while (cur_pos < sbi->blocks_per_seg);
	BUG_ON(GET_SIT_VBLOCKS(raw_sit) != valid_blocks);
#endif
	/* check segment usage, and check boundary of a given segment number */
	f2fs_bug_on(sbi, GET_SIT_VBLOCKS(raw_sit) > sbi->blocks_per_seg
					|| segno > TOTAL_SEGS(sbi) - 1);
}

static inline pgoff_t current_sit_addr(struct f2fs_sb_info *sbi,
						unsigned int start)
{
	struct sit_info *sit_i = SIT_I(sbi);
	unsigned int offset = SIT_BLOCK_OFFSET(start);
	block_t blk_addr = sit_i->sit_base_addr + offset;

	check_seg_range(sbi, start);

	/* calculate sit block address */
	if (f2fs_test_bit(offset, sit_i->sit_bitmap))
		blk_addr += sit_i->sit_blocks;

	return blk_addr;
}

static inline pgoff_t next_sit_addr(struct f2fs_sb_info *sbi,
						pgoff_t block_addr)
{
	struct sit_info *sit_i = SIT_I(sbi);
	block_addr -= sit_i->sit_base_addr;
	if (block_addr < sit_i->sit_blocks)
		block_addr += sit_i->sit_blocks;
	else
		block_addr -= sit_i->sit_blocks;

	return block_addr + sit_i->sit_base_addr;
}

static inline void set_to_next_sit(struct sit_info *sit_i, unsigned int start)
{
	unsigned int block_off = SIT_BLOCK_OFFSET(start);

	f2fs_change_bit(block_off, sit_i->sit_bitmap);
}

static inline unsigned long long get_mtime(struct f2fs_sb_info *sbi)
{
	struct sit_info *sit_i = SIT_I(sbi);
	return sit_i->elapsed_time + CURRENT_TIME_SEC.tv_sec -
						sit_i->mounted_time;
}

static inline void set_summary(struct f2fs_summary *sum, nid_t nid,
			unsigned int ofs_in_node, unsigned char version)
{
	sum->nid = cpu_to_le32(nid);
	sum->ofs_in_node = cpu_to_le16(ofs_in_node);
	sum->version = version;
}

static inline block_t start_sum_block(struct f2fs_sb_info *sbi)
{
	return __start_cp_addr(sbi) +
		le32_to_cpu(F2FS_CKPT(sbi)->cp_pack_start_sum);
}

static inline block_t sum_blk_addr(struct f2fs_sb_info *sbi, int base, int type)
{
	return __start_cp_addr(sbi) +
		le32_to_cpu(F2FS_CKPT(sbi)->cp_pack_total_block_count)
				- (base + 1) + type;
}

static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned int secno)
{
	if (IS_CURSEC(sbi, secno) || (sbi->cur_victim_sec == secno))
		return true;
	return false;
}

static inline unsigned int max_hw_blocks(struct f2fs_sb_info *sbi)
{
	struct block_device *bdev = sbi->sb->s_bdev;
	struct request_queue *q = bdev_get_queue(bdev);
	return SECTOR_TO_BLOCK(queue_max_sectors(q));
}

/*
 * It is very important to gather dirty pages and write at once, so that we can
 * submit a big bio without interfering other data writes.
 * By default, 512 pages for directory data,
 * 512 pages (2MB) * 3 for three types of nodes, and
 * max_bio_blocks for meta are set.
 */
static inline int nr_pages_to_skip(struct f2fs_sb_info *sbi, int type)
{
	if (sbi->sb->s_bdi->wb.dirty_exceeded)
		return 0;

	if (type == DATA)
		return sbi->blocks_per_seg;
	else if (type == NODE)
		return 3 * sbi->blocks_per_seg;
	else if (type == META)
		return MAX_BIO_BLOCKS(sbi);
	else
		return 0;
}

/*
 * When writing pages, it'd better align nr_to_write for segment size.
 */
static inline long nr_pages_to_write(struct f2fs_sb_info *sbi, int type,
					struct writeback_control *wbc)
{
	long nr_to_write, desired;

	if (wbc->sync_mode != WB_SYNC_NONE)
		return 0;

	nr_to_write = wbc->nr_to_write;

	if (type == DATA)
		desired = 4096;
	else if (type == NODE)
		desired = 3 * max_hw_blocks(sbi);
	else
		desired = MAX_BIO_BLOCKS(sbi);

	wbc->nr_to_write = desired;
	return desired - nr_to_write;
}