/*
 * 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 "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 */
};

/**
 * 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)

/* 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_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 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 */