/*
   * 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 block
   * @ns_sbwcount: write count of super block

   * @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_prev_seq: base sequence number used to decide if advance log cursor

   * @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_blocksize: 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;
  	unsigned		ns_sbwcount;

  	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;

  	u64			ns_prev_seq;

  
  	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 int		ns_blocksize;

  	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

  static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
  {
  	u64 t = get_seconds();

  	return t < nilfs->ns_sbwtime || t > nilfs->ns_sbwtime + NILFS_SB_FREQ;

  }

  static inline int nilfs_sb_will_flip(struct the_nilfs *nilfs)

  {

  	int flip_bits = nilfs->ns_sbwcount & 0x0FL;
  	return (flip_bits != 0x08 && flip_bits != 0x0F);

  }

  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 */