fs/nilfs2/the_nilfs.h - kernel/skids - Git at Google

 /*
  * the_nilfs.h - the_nilfs shared structure.
  *
  * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  *
  * Written by Ryusuke Konishi <ryusuke@osrg.net>
  *
  */

 #ifndef _THE_NILFS_H
 #define _THE_NILFS_H

 #include <linux/types.h>
 #include <linux/buffer_head.h>
 #include <linux/fs.h>
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
 #include <linux/slab.h>
 #include "sb.h"

 /* the_nilfs struct */
 enum {
 	THE_NILFS_INIT = 0,     /* Information from super_block is set */
 	THE_NILFS_LOADED,       /* Roll-back/roll-forward has done and
 				   the latest checkpoint was loaded */
 	THE_NILFS_DISCONTINUED,	/* 'next' pointer chain has broken */
 	THE_NILFS_GC_RUNNING,	/* gc process is running */
 	THE_NILFS_SB_DIRTY,	/* super block is dirty */
 };

 /**
  * struct the_nilfs - struct to supervise multiple nilfs mount points
  * @ns_flags: flags
  * @ns_count: reference count
  * @ns_list: list head for nilfs_list
  * @ns_bdev: block device
  * @ns_bdi: backing dev info
  * @ns_writer: back pointer to writable nilfs_sb_info
  * @ns_sem: semaphore for shared states
  * @ns_super_sem: semaphore for global operations across super block instances
  * @ns_mount_mutex: mutex protecting mount process of nilfs
  * @ns_writer_sem: semaphore protecting ns_writer attach/detach
  * @ns_current: back pointer to current mount
  * @ns_sbh: buffer heads of on-disk super blocks
  * @ns_sbp: pointers to super block data
  * @ns_sbwtime: previous write time of super blocks
  * @ns_sbsize: size of valid data in super block
  * @ns_supers: list of nilfs super block structs
  * @ns_seg_seq: segment sequence counter
  * @ns_segnum: index number of the latest full segment.
  * @ns_nextnum: index number of the full segment index to be used next
  * @ns_pseg_offset: offset of next partial segment in the current full segment
  * @ns_cno: next checkpoint number
  * @ns_ctime: write time of the last segment
  * @ns_nongc_ctime: write time of the last segment not for cleaner operation
  * @ns_ndirtyblks: Number of dirty data blocks
  * @ns_last_segment_lock: lock protecting fields for the latest segment
  * @ns_last_pseg: start block number of the latest segment
  * @ns_last_seq: sequence value of the latest segment
  * @ns_last_cno: checkpoint number of the latest segment
  * @ns_prot_seq: least sequence number of segments which must not be reclaimed
  * @ns_free_segments_count: counter of free segments
  * @ns_segctor_sem: segment constructor semaphore
  * @ns_dat: DAT file inode
  * @ns_cpfile: checkpoint file inode
  * @ns_sufile: segusage file inode
  * @ns_gc_dat: shadow inode of the DAT file inode for GC
  * @ns_gc_inodes: dummy inodes to keep live blocks
  * @ns_gc_inodes_h: hash list to keep dummy inode holding live blocks
  * @ns_blocksize_bits: bit length of block size
  * @ns_nsegments: number of segments in filesystem
  * @ns_blocks_per_segment: number of blocks per segment
  * @ns_r_segments_percentage: reserved segments percentage
  * @ns_nrsvsegs: number of reserved segments
  * @ns_first_data_block: block number of first data block
  * @ns_inode_size: size of on-disk inode
  * @ns_first_ino: first not-special inode number
  * @ns_crc_seed: seed value of CRC32 calculation
  */
 struct the_nilfs {
 	unsigned long		ns_flags;
 	atomic_t		ns_count;
 	struct list_head	ns_list;

 	struct block_device    *ns_bdev;
 	struct backing_dev_info *ns_bdi;
 	struct nilfs_sb_info   *ns_writer;
 	struct rw_semaphore	ns_sem;
 	struct rw_semaphore	ns_super_sem;
 	struct mutex		ns_mount_mutex;
 	struct rw_semaphore	ns_writer_sem;

 	/*
 	 * components protected by ns_super_sem
 	 */
 	struct nilfs_sb_info   *ns_current;
 	struct list_head	ns_supers;

 	/*
 	 * used for
 	 * - loading the latest checkpoint exclusively.
 	 * - allocating a new full segment.
 	 * - protecting s_dirt in the super_block struct
 	 *   (see nilfs_write_super) and the following fields.
 	 */
 	struct buffer_head     *ns_sbh[2];
 	struct nilfs_super_block *ns_sbp[2];
 	time_t			ns_sbwtime[2];
 	unsigned		ns_sbsize;
 	unsigned		ns_mount_state;

 	/*
 	 * Following fields are dedicated to a writable FS-instance.
 	 * Except for the period seeking checkpoint, code outside the segment
 	 * constructor must lock a segment semaphore while accessing these
 	 * fields.
 	 * The writable FS-instance is sole during a lifetime of the_nilfs.
 	 */
 	u64			ns_seg_seq;
 	__u64			ns_segnum;
 	__u64			ns_nextnum;
 	unsigned long		ns_pseg_offset;
 	__u64			ns_cno;
 	time_t			ns_ctime;
 	time_t			ns_nongc_ctime;
 	atomic_t		ns_ndirtyblks;

 	/*
 	 * The following fields hold information on the latest partial segment
 	 * written to disk with a super root.  These fields are protected by
 	 * ns_last_segment_lock.
 	 */
 	spinlock_t		ns_last_segment_lock;
 	sector_t		ns_last_pseg;
 	u64			ns_last_seq;
 	__u64			ns_last_cno;
 	u64			ns_prot_seq;
 	unsigned long		ns_free_segments_count;

 	struct rw_semaphore	ns_segctor_sem;

 	/*
 	 * Following fields are lock free except for the period before
 	 * the_nilfs is initialized.
 	 */
 	struct inode	       *ns_dat;
 	struct inode	       *ns_cpfile;
 	struct inode	       *ns_sufile;
 	struct inode	       *ns_gc_dat;

 	/* GC inode list and hash table head */
 	struct list_head	ns_gc_inodes;
 	struct hlist_head      *ns_gc_inodes_h;

 	/* Disk layout information (static) */
 	unsigned int		ns_blocksize_bits;
 	unsigned long		ns_nsegments;
 	unsigned long		ns_blocks_per_segment;
 	unsigned long		ns_r_segments_percentage;
 	unsigned long		ns_nrsvsegs;
 	unsigned long		ns_first_data_block;
 	int			ns_inode_size;
 	int			ns_first_ino;
 	u32			ns_crc_seed;
 };

 #define NILFS_GCINODE_HASH_BITS		8
 #define NILFS_GCINODE_HASH_SIZE		(1<<NILFS_GCINODE_HASH_BITS)

 #define THE_NILFS_FNS(bit, name)					\
 static inline void set_nilfs_##name(struct the_nilfs *nilfs)		\
 {									\
 	set_bit(THE_NILFS_##bit, &(nilfs)->ns_flags);			\
 }									\
 static inline void clear_nilfs_##name(struct the_nilfs *nilfs)		\
 {									\
 	clear_bit(THE_NILFS_##bit, &(nilfs)->ns_flags);			\
 }									\
 static inline int nilfs_##name(struct the_nilfs *nilfs)			\
 {									\
 	return test_bit(THE_NILFS_##bit, &(nilfs)->ns_flags);		\
 }

 THE_NILFS_FNS(INIT, init)
 THE_NILFS_FNS(LOADED, loaded)
 THE_NILFS_FNS(DISCONTINUED, discontinued)
 THE_NILFS_FNS(GC_RUNNING, gc_running)
 THE_NILFS_FNS(SB_DIRTY, sb_dirty)

 /* Minimum interval of periodical update of superblocks (in seconds) */
 #define NILFS_SB_FREQ		10
 #define NILFS_ALTSB_FREQ	60  /* spare superblock */

 static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
 {
 	u64 t = get_seconds();
 	return t < nilfs->ns_sbwtime[0] ||
 		 t > nilfs->ns_sbwtime[0] + NILFS_SB_FREQ;
 }

 static inline int nilfs_altsb_need_update(struct the_nilfs *nilfs)
 {
 	u64 t = get_seconds();
 	struct nilfs_super_block **sbp = nilfs->ns_sbp;
 	return sbp[1] && t > nilfs->ns_sbwtime[1] + NILFS_ALTSB_FREQ;
 }

 void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
 struct the_nilfs *find_or_create_nilfs(struct block_device *);
 void put_nilfs(struct the_nilfs *);
 int init_nilfs(struct the_nilfs *, struct nilfs_sb_info *, char *);
 int load_nilfs(struct the_nilfs *, struct nilfs_sb_info *);
 int nilfs_discard_segments(struct the_nilfs *, __u64 *, size_t);
 int nilfs_count_free_blocks(struct the_nilfs *, sector_t *);
 struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *, int, __u64);
 int nilfs_checkpoint_is_mounted(struct the_nilfs *, __u64, int);
 int nilfs_near_disk_full(struct the_nilfs *);
 void nilfs_fall_back_super_block(struct the_nilfs *);
 void nilfs_swap_super_block(struct the_nilfs *);


 static inline void get_nilfs(struct the_nilfs *nilfs)
 {
 	/* Caller must have at least one reference of the_nilfs. */
 	atomic_inc(&nilfs->ns_count);
 }

 static inline void
 nilfs_attach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 {
 	down_write(&nilfs->ns_writer_sem);
 	nilfs->ns_writer = sbi;
 	up_write(&nilfs->ns_writer_sem);
 }

 static inline void
 nilfs_detach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 {
 	down_write(&nilfs->ns_writer_sem);
 	if (sbi == nilfs->ns_writer)
 		nilfs->ns_writer = NULL;
 	up_write(&nilfs->ns_writer_sem);
 }

 static inline void nilfs_put_sbinfo(struct nilfs_sb_info *sbi)
 {
 	if (atomic_dec_and_test(&sbi->s_count))
 		kfree(sbi);
 }

 static inline int nilfs_valid_fs(struct the_nilfs *nilfs)
 {
 	unsigned valid_fs;

 	down_read(&nilfs->ns_sem);
 	valid_fs = (nilfs->ns_mount_state & NILFS_VALID_FS);
 	up_read(&nilfs->ns_sem);
 	return valid_fs;
 }

 static inline void
 nilfs_get_segment_range(struct the_nilfs *nilfs, __u64 segnum,
 			sector_t *seg_start, sector_t *seg_end)
 {
 	*seg_start = (sector_t)nilfs->ns_blocks_per_segment * segnum;
 	*seg_end = *seg_start + nilfs->ns_blocks_per_segment - 1;
 	if (segnum == 0)
 		*seg_start = nilfs->ns_first_data_block;
 }

 static inline sector_t
 nilfs_get_segment_start_blocknr(struct the_nilfs *nilfs, __u64 segnum)
 {
 	return (segnum == 0) ? nilfs->ns_first_data_block :
 		(sector_t)nilfs->ns_blocks_per_segment * segnum;
 }

 static inline __u64
 nilfs_get_segnum_of_block(struct the_nilfs *nilfs, sector_t blocknr)
 {
 	sector_t segnum = blocknr;

 	sector_div(segnum, nilfs->ns_blocks_per_segment);
 	return segnum;
 }

 static inline void
 nilfs_terminate_segment(struct the_nilfs *nilfs, sector_t seg_start,
 			sector_t seg_end)
 {
 	/* terminate the current full segment (used in case of I/O-error) */
 	nilfs->ns_pseg_offset = seg_end - seg_start + 1;
 }

 static inline void nilfs_shift_to_next_segment(struct the_nilfs *nilfs)
 {
 	/* move forward with a full segment */
 	nilfs->ns_segnum = nilfs->ns_nextnum;
 	nilfs->ns_pseg_offset = 0;
 	nilfs->ns_seg_seq++;
 }

 static inline __u64 nilfs_last_cno(struct the_nilfs *nilfs)
 {
 	__u64 cno;

 	spin_lock(&nilfs->ns_last_segment_lock);
 	cno = nilfs->ns_last_cno;
 	spin_unlock(&nilfs->ns_last_segment_lock);
 	return cno;
 }

 static inline int nilfs_segment_is_active(struct the_nilfs *nilfs, __u64 n)
 {
 	return n == nilfs->ns_segnum || n == nilfs->ns_nextnum;
 }

 #endif /* _THE_NILFS_H */
	/*
	* the_nilfs.h - the_nilfs shared structure.
	*
	* Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	*
	* Written by Ryusuke Konishi <ryusuke@osrg.net>
	*
	*/

	#ifndef _THE_NILFS_H
	#define _THE_NILFS_H

	#include <linux/types.h>
	#include <linux/buffer_head.h>
	#include <linux/fs.h>
	#include <linux/blkdev.h>
	#include <linux/backing-dev.h>
	#include <linux/slab.h>
	#include "sb.h"

	/* the_nilfs struct */
	enum {
	THE_NILFS_INIT = 0, /* Information from super_block is set */
	THE_NILFS_LOADED, /* Roll-back/roll-forward has done and
	the latest checkpoint was loaded */
	THE_NILFS_DISCONTINUED, /* 'next' pointer chain has broken */
	THE_NILFS_GC_RUNNING, /* gc process is running */
	THE_NILFS_SB_DIRTY, /* super block is dirty */
	};

	/**
	* struct the_nilfs - struct to supervise multiple nilfs mount points
	* @ns_flags: flags
	* @ns_count: reference count
	* @ns_list: list head for nilfs_list
	* @ns_bdev: block device
	* @ns_bdi: backing dev info
	* @ns_writer: back pointer to writable nilfs_sb_info
	* @ns_sem: semaphore for shared states
	* @ns_super_sem: semaphore for global operations across super block instances
	* @ns_mount_mutex: mutex protecting mount process of nilfs
	* @ns_writer_sem: semaphore protecting ns_writer attach/detach
	* @ns_current: back pointer to current mount
	* @ns_sbh: buffer heads of on-disk super blocks
	* @ns_sbp: pointers to super block data
	* @ns_sbwtime: previous write time of super blocks
	* @ns_sbsize: size of valid data in super block
	* @ns_supers: list of nilfs super block structs
	* @ns_seg_seq: segment sequence counter
	* @ns_segnum: index number of the latest full segment.
	* @ns_nextnum: index number of the full segment index to be used next
	* @ns_pseg_offset: offset of next partial segment in the current full segment
	* @ns_cno: next checkpoint number
	* @ns_ctime: write time of the last segment
	* @ns_nongc_ctime: write time of the last segment not for cleaner operation
	* @ns_ndirtyblks: Number of dirty data blocks
	* @ns_last_segment_lock: lock protecting fields for the latest segment
	* @ns_last_pseg: start block number of the latest segment
	* @ns_last_seq: sequence value of the latest segment
	* @ns_last_cno: checkpoint number of the latest segment
	* @ns_prot_seq: least sequence number of segments which must not be reclaimed
	* @ns_free_segments_count: counter of free segments
	* @ns_segctor_sem: segment constructor semaphore
	* @ns_dat: DAT file inode
	* @ns_cpfile: checkpoint file inode
	* @ns_sufile: segusage file inode
	* @ns_gc_dat: shadow inode of the DAT file inode for GC
	* @ns_gc_inodes: dummy inodes to keep live blocks
	* @ns_gc_inodes_h: hash list to keep dummy inode holding live blocks
	* @ns_blocksize_bits: bit length of block size
	* @ns_nsegments: number of segments in filesystem
	* @ns_blocks_per_segment: number of blocks per segment
	* @ns_r_segments_percentage: reserved segments percentage
	* @ns_nrsvsegs: number of reserved segments
	* @ns_first_data_block: block number of first data block
	* @ns_inode_size: size of on-disk inode
	* @ns_first_ino: first not-special inode number
	* @ns_crc_seed: seed value of CRC32 calculation
	*/
	struct the_nilfs {
	unsigned long ns_flags;
	atomic_t ns_count;
	struct list_head ns_list;

	struct block_device *ns_bdev;
	struct backing_dev_info *ns_bdi;
	struct nilfs_sb_info *ns_writer;
	struct rw_semaphore ns_sem;
	struct rw_semaphore ns_super_sem;
	struct mutex ns_mount_mutex;
	struct rw_semaphore ns_writer_sem;

	/*
	* components protected by ns_super_sem
	*/
	struct nilfs_sb_info *ns_current;
	struct list_head ns_supers;

	/*
	* used for
	* - loading the latest checkpoint exclusively.
	* - allocating a new full segment.
	* - protecting s_dirt in the super_block struct
	* (see nilfs_write_super) and the following fields.
	*/
	struct buffer_head *ns_sbh[2];
	struct nilfs_super_block *ns_sbp[2];
	time_t ns_sbwtime[2];
	unsigned ns_sbsize;
	unsigned ns_mount_state;

	/*
	* Following fields are dedicated to a writable FS-instance.
	* Except for the period seeking checkpoint, code outside the segment
	* constructor must lock a segment semaphore while accessing these
	* fields.
	* The writable FS-instance is sole during a lifetime of the_nilfs.
	*/
	u64 ns_seg_seq;
	__u64 ns_segnum;
	__u64 ns_nextnum;
	unsigned long ns_pseg_offset;
	__u64 ns_cno;
	time_t ns_ctime;
	time_t ns_nongc_ctime;
	atomic_t ns_ndirtyblks;

	/*
	* The following fields hold information on the latest partial segment
	* written to disk with a super root. These fields are protected by
	* ns_last_segment_lock.
	*/
	spinlock_t ns_last_segment_lock;
	sector_t ns_last_pseg;
	u64 ns_last_seq;
	__u64 ns_last_cno;
	u64 ns_prot_seq;
	unsigned long ns_free_segments_count;

	struct rw_semaphore ns_segctor_sem;

	/*
	* Following fields are lock free except for the period before
	* the_nilfs is initialized.
	*/
	struct inode *ns_dat;
	struct inode *ns_cpfile;
	struct inode *ns_sufile;
	struct inode *ns_gc_dat;

	/* GC inode list and hash table head */
	struct list_head ns_gc_inodes;
	struct hlist_head *ns_gc_inodes_h;

	/* Disk layout information (static) */
	unsigned int ns_blocksize_bits;
	unsigned long ns_nsegments;
	unsigned long ns_blocks_per_segment;
	unsigned long ns_r_segments_percentage;
	unsigned long ns_nrsvsegs;
	unsigned long ns_first_data_block;
	int ns_inode_size;
	int ns_first_ino;
	u32 ns_crc_seed;
	};

	#define NILFS_GCINODE_HASH_BITS 8
	#define NILFS_GCINODE_HASH_SIZE (1<<NILFS_GCINODE_HASH_BITS)

	#define THE_NILFS_FNS(bit, name) \
	static inline void set_nilfs_##name(struct the_nilfs *nilfs) \
	{ \
	set_bit(THE_NILFS_##bit, &(nilfs)->ns_flags); \
	} \
	static inline void clear_nilfs_##name(struct the_nilfs *nilfs) \
	{ \
	clear_bit(THE_NILFS_##bit, &(nilfs)->ns_flags); \
	} \
	static inline int nilfs_##name(struct the_nilfs *nilfs) \
	{ \
	return test_bit(THE_NILFS_##bit, &(nilfs)->ns_flags); \
	}

	THE_NILFS_FNS(INIT, init)
	THE_NILFS_FNS(LOADED, loaded)
	THE_NILFS_FNS(DISCONTINUED, discontinued)
	THE_NILFS_FNS(GC_RUNNING, gc_running)
	THE_NILFS_FNS(SB_DIRTY, sb_dirty)

	/* Minimum interval of periodical update of superblocks (in seconds) */
	#define NILFS_SB_FREQ 10
	#define NILFS_ALTSB_FREQ 60 /* spare superblock */

	static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
	{
	u64 t = get_seconds();
	return t < nilfs->ns_sbwtime[0] \|\|
	t > nilfs->ns_sbwtime[0] + NILFS_SB_FREQ;
	}

	static inline int nilfs_altsb_need_update(struct the_nilfs *nilfs)
	{
	u64 t = get_seconds();
	struct nilfs_super_block **sbp = nilfs->ns_sbp;
	return sbp[1] && t > nilfs->ns_sbwtime[1] + NILFS_ALTSB_FREQ;
	}

	void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
	struct the_nilfs find_or_create_nilfs(struct block_device );
	void put_nilfs(struct the_nilfs *);
	int init_nilfs(struct the_nilfs , struct nilfs_sb_info , char *);
	int load_nilfs(struct the_nilfs , struct nilfs_sb_info );
	int nilfs_discard_segments(struct the_nilfs , __u64 , size_t);
	int nilfs_count_free_blocks(struct the_nilfs , sector_t );
	struct nilfs_sb_info nilfs_find_sbinfo(struct the_nilfs , int, __u64);
	int nilfs_checkpoint_is_mounted(struct the_nilfs *, __u64, int);
	int nilfs_near_disk_full(struct the_nilfs *);
	void nilfs_fall_back_super_block(struct the_nilfs *);
	void nilfs_swap_super_block(struct the_nilfs *);


	static inline void get_nilfs(struct the_nilfs *nilfs)
	{
	/* Caller must have at least one reference of the_nilfs. */
	atomic_inc(&nilfs->ns_count);
	}

	static inline void
	nilfs_attach_writer(struct the_nilfs nilfs, struct nilfs_sb_info sbi)
	{
	down_write(&nilfs->ns_writer_sem);
	nilfs->ns_writer = sbi;
	up_write(&nilfs->ns_writer_sem);
	}

	static inline void
	nilfs_detach_writer(struct the_nilfs nilfs, struct nilfs_sb_info sbi)
	{
	down_write(&nilfs->ns_writer_sem);
	if (sbi == nilfs->ns_writer)
	nilfs->ns_writer = NULL;
	up_write(&nilfs->ns_writer_sem);
	}

	static inline void nilfs_put_sbinfo(struct nilfs_sb_info *sbi)
	{
	if (atomic_dec_and_test(&sbi->s_count))
	kfree(sbi);
	}

	static inline int nilfs_valid_fs(struct the_nilfs *nilfs)
	{
	unsigned valid_fs;

	down_read(&nilfs->ns_sem);
	valid_fs = (nilfs->ns_mount_state & NILFS_VALID_FS);
	up_read(&nilfs->ns_sem);
	return valid_fs;
	}

	static inline void
	nilfs_get_segment_range(struct the_nilfs *nilfs, __u64 segnum,
	sector_t seg_start, sector_t seg_end)
	{
	seg_start = (sector_t)nilfs->ns_blocks_per_segment segnum;
	seg_end = seg_start + nilfs->ns_blocks_per_segment - 1;
	if (segnum == 0)
	*seg_start = nilfs->ns_first_data_block;
	}

	static inline sector_t
	nilfs_get_segment_start_blocknr(struct the_nilfs *nilfs, __u64 segnum)
	{
	return (segnum == 0) ? nilfs->ns_first_data_block :
	(sector_t)nilfs->ns_blocks_per_segment * segnum;
	}

	static inline __u64
	nilfs_get_segnum_of_block(struct the_nilfs *nilfs, sector_t blocknr)
	{
	sector_t segnum = blocknr;

	sector_div(segnum, nilfs->ns_blocks_per_segment);
	return segnum;
	}

	static inline void
	nilfs_terminate_segment(struct the_nilfs *nilfs, sector_t seg_start,
	sector_t seg_end)
	{
	/* terminate the current full segment (used in case of I/O-error) */
	nilfs->ns_pseg_offset = seg_end - seg_start + 1;
	}

	static inline void nilfs_shift_to_next_segment(struct the_nilfs *nilfs)
	{
	/* move forward with a full segment */
	nilfs->ns_segnum = nilfs->ns_nextnum;
	nilfs->ns_pseg_offset = 0;
	nilfs->ns_seg_seq++;
	}

	static inline __u64 nilfs_last_cno(struct the_nilfs *nilfs)
	{
	__u64 cno;

	spin_lock(&nilfs->ns_last_segment_lock);
	cno = nilfs->ns_last_cno;
	spin_unlock(&nilfs->ns_last_segment_lock);
	return cno;
	}

	static inline int nilfs_segment_is_active(struct the_nilfs *nilfs, __u64 n)
	{
	return n == nilfs->ns_segnum \|\| n == nilfs->ns_nextnum;
	}

	#endif /* _THE_NILFS_H */