/*
 * super.c - NILFS module and super block management.
 *
 * 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>
 */
/*
 *  linux/fs/ext2/super.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/parser.h>
#include <linux/random.h>
#include <linux/crc32.h>
#include <linux/smp_lock.h>
#include <linux/vfs.h>
#include <linux/writeback.h>
#include <linux/kobject.h>
#include <linux/exportfs.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include "nilfs.h"
#include "mdt.h"
#include "alloc.h"
#include "page.h"
#include "cpfile.h"
#include "ifile.h"
#include "dat.h"
#include "segment.h"
#include "segbuf.h"

MODULE_AUTHOR("NTT Corp.");
MODULE_DESCRIPTION("A New Implementation of the Log-structured Filesystem "
                   "(NILFS)");
MODULE_LICENSE("GPL");

static int nilfs_remount(struct super_block *sb, int *flags, char *data);

/**
 * nilfs_error() - report failure condition on a filesystem
 *
 * nilfs_error() sets an ERROR_FS flag on the superblock as well as
 * reporting an error message.  It should be called when NILFS detects
 * incoherences or defects of meta data on disk.  As for sustainable
 * errors such as a single-shot I/O error, nilfs_warning() or the printk()
 * function should be used instead.
 *
 * The segment constructor must not call this function because it can
 * kill itself.
 */
void nilfs_error(struct super_block *sb, const char *function,
                 const char *fmt, ...)
{
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        va_list args;

        va_start(args, fmt);
        printk(KERN_CRIT "NILFS error (device %s): %s: ", sb->s_id, function);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);

        if (!(sb->s_flags & MS_RDONLY)) {
                struct the_nilfs *nilfs = sbi->s_nilfs;

                if (!nilfs_test_opt(sbi, ERRORS_CONT))
                        nilfs_detach_segment_constructor(sbi);

                down_write(&nilfs->ns_sem);
                if (!(nilfs->ns_mount_state & NILFS_ERROR_FS)) {
                        nilfs->ns_mount_state |= NILFS_ERROR_FS;
                        nilfs->ns_sbp[0]->s_state |=
                                cpu_to_le16(NILFS_ERROR_FS);
                        nilfs_commit_super(sbi, 1);
                }
                up_write(&nilfs->ns_sem);

                if (nilfs_test_opt(sbi, ERRORS_RO)) {
                        printk(KERN_CRIT "Remounting filesystem read-only\n");
                        sb->s_flags |= MS_RDONLY;
                }
        }

        if (nilfs_test_opt(sbi, ERRORS_PANIC))
                panic("NILFS (device %s): panic forced after error\n",
                      sb->s_id);
}

void nilfs_warning(struct super_block *sb, const char *function,
                   const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        printk(KERN_WARNING "NILFS warning (device %s): %s: ",
               sb->s_id, function);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);
}

static struct kmem_cache *nilfs_inode_cachep;

struct inode *nilfs_alloc_inode_common(struct the_nilfs *nilfs)
{
        struct nilfs_inode_info *ii;

        ii = kmem_cache_alloc(nilfs_inode_cachep, GFP_NOFS);
        if (!ii)
                return NULL;
        ii->i_bh = NULL;
        ii->i_state = 0;
        ii->vfs_inode.i_version = 1;
        nilfs_btnode_cache_init(&ii->i_btnode_cache, nilfs->ns_bdi);
        return &ii->vfs_inode;
}

struct inode *nilfs_alloc_inode(struct super_block *sb)
{
        return nilfs_alloc_inode_common(NILFS_SB(sb)->s_nilfs);
}

void nilfs_destroy_inode(struct inode *inode)
{
        kmem_cache_free(nilfs_inode_cachep, NILFS_I(inode));
}

static void init_once(void *obj)
{
        struct nilfs_inode_info *ii = obj;

        INIT_LIST_HEAD(&ii->i_dirty);
#ifdef CONFIG_NILFS_XATTR
        init_rwsem(&ii->xattr_sem);
#endif
        nilfs_btnode_cache_init_once(&ii->i_btnode_cache);
        ii->i_bmap = (struct nilfs_bmap *)&ii->i_bmap_union;
        inode_init_once(&ii->vfs_inode);
}

static int nilfs_init_inode_cache(void)
{
        nilfs_inode_cachep = kmem_cache_create("nilfs2_inode_cache",
                                               sizeof(struct nilfs_inode_info),
                                               0, SLAB_RECLAIM_ACCOUNT,
                                               init_once);

        return (nilfs_inode_cachep == NULL) ? -ENOMEM : 0;
}

static inline void nilfs_destroy_inode_cache(void)
{
        kmem_cache_destroy(nilfs_inode_cachep);
}

static void nilfs_clear_inode(struct inode *inode)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);

        /*
         * Free resources allocated in nilfs_read_inode(), here.
         */
        BUG_ON(!list_empty(&ii->i_dirty));
        brelse(ii->i_bh);
        ii->i_bh = NULL;

        if (test_bit(NILFS_I_BMAP, &ii->i_state))
                nilfs_bmap_clear(ii->i_bmap);

        nilfs_btnode_cache_clear(&ii->i_btnode_cache);
}

static int nilfs_sync_super(struct nilfs_sb_info *sbi, int dupsb)
{
        struct the_nilfs *nilfs = sbi->s_nilfs;
        int err;
        int barrier_done = 0;

        if (nilfs_test_opt(sbi, BARRIER)) {
                set_buffer_ordered(nilfs->ns_sbh[0]);
                barrier_done = 1;
        }
 retry:
        set_buffer_dirty(nilfs->ns_sbh[0]);
        err = sync_dirty_buffer(nilfs->ns_sbh[0]);
        if (err == -EOPNOTSUPP && barrier_done) {
                nilfs_warning(sbi->s_super, __func__,
                              "barrier-based sync failed. "
                              "disabling barriers\n");
                nilfs_clear_opt(sbi, BARRIER);
                barrier_done = 0;
                clear_buffer_ordered(nilfs->ns_sbh[0]);
                goto retry;
        }
        if (unlikely(err)) {
                printk(KERN_ERR
                       "NILFS: unable to write superblock (err=%d)\n", err);
                if (err == -EIO && nilfs->ns_sbh[1]) {
                        nilfs_fall_back_super_block(nilfs);
                        goto retry;
                }
        } else {
                struct nilfs_super_block *sbp = nilfs->ns_sbp[0];

                /*
                 * The latest segment becomes trailable from the position
                 * written in superblock.
                 */
                clear_nilfs_discontinued(nilfs);

                /* update GC protection for recent segments */
                if (nilfs->ns_sbh[1]) {
                        sbp = NULL;
                        if (dupsb) {
                                set_buffer_dirty(nilfs->ns_sbh[1]);
                                if (!sync_dirty_buffer(nilfs->ns_sbh[1]))
                                        sbp = nilfs->ns_sbp[1];
                        }
                }
                if (sbp) {
                        spin_lock(&nilfs->ns_last_segment_lock);
                        nilfs->ns_prot_seq = le64_to_cpu(sbp->s_last_seq);
                        spin_unlock(&nilfs->ns_last_segment_lock);
                }
        }

        return err;
}

int nilfs_commit_super(struct nilfs_sb_info *sbi, int dupsb)
{
        struct the_nilfs *nilfs = sbi->s_nilfs;
        struct nilfs_super_block **sbp = nilfs->ns_sbp;
        sector_t nfreeblocks;
        time_t t;
        int err;

        /* nilfs->sem must be locked by the caller. */
        if (sbp[0]->s_magic != NILFS_SUPER_MAGIC) {
                if (sbp[1] && sbp[1]->s_magic == NILFS_SUPER_MAGIC)
                        nilfs_swap_super_block(nilfs);
                else {
                        printk(KERN_CRIT "NILFS: superblock broke on dev %s\n",
                               sbi->s_super->s_id);
                        return -EIO;
                }
        }
        err = nilfs_count_free_blocks(nilfs, &nfreeblocks);
        if (unlikely(err)) {
                printk(KERN_ERR "NILFS: failed to count free blocks\n");
                return err;
        }
        spin_lock(&nilfs->ns_last_segment_lock);
        sbp[0]->s_last_seq = cpu_to_le64(nilfs->ns_last_seq);
        sbp[0]->s_last_pseg = cpu_to_le64(nilfs->ns_last_pseg);
        sbp[0]->s_last_cno = cpu_to_le64(nilfs->ns_last_cno);
        spin_unlock(&nilfs->ns_last_segment_lock);

        t = get_seconds();
        nilfs->ns_sbwtime[0] = t;
        sbp[0]->s_free_blocks_count = cpu_to_le64(nfreeblocks);
        sbp[0]->s_wtime = cpu_to_le64(t);
        sbp[0]->s_sum = 0;
        sbp[0]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
                                             (unsigned char *)sbp[0],
                                             nilfs->ns_sbsize));
        if (dupsb && sbp[1]) {
                memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
                nilfs->ns_sbwtime[1] = t;
        }
        sbi->s_super->s_dirt = 0;
        return nilfs_sync_super(sbi, dupsb);
}

static void nilfs_put_super(struct super_block *sb)
{
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        struct the_nilfs *nilfs = sbi->s_nilfs;

        lock_kernel();

        nilfs_detach_segment_constructor(sbi);

        if (!(sb->s_flags & MS_RDONLY)) {
                down_write(&nilfs->ns_sem);
                nilfs->ns_sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
                nilfs_commit_super(sbi, 1);
                up_write(&nilfs->ns_sem);
        }
        down_write(&nilfs->ns_super_sem);
        if (nilfs->ns_current == sbi)
                nilfs->ns_current = NULL;
        up_write(&nilfs->ns_super_sem);

        nilfs_detach_checkpoint(sbi);
        put_nilfs(sbi->s_nilfs);
        sbi->s_super = NULL;
        sb->s_fs_info = NULL;
        nilfs_put_sbinfo(sbi);

        unlock_kernel();
}

static int nilfs_sync_fs(struct super_block *sb, int wait)
{
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        struct the_nilfs *nilfs = sbi->s_nilfs;
        int err = 0;

        /* This function is called when super block should be written back */
        if (wait)
                err = nilfs_construct_segment(sb);

        down_write(&nilfs->ns_sem);
        if (sb->s_dirt)
                nilfs_commit_super(sbi, 1);
        up_write(&nilfs->ns_sem);

        return err;
}

int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno)
{
        struct the_nilfs *nilfs = sbi->s_nilfs;
        struct nilfs_checkpoint *raw_cp;
        struct buffer_head *bh_cp;
        int err;

        down_write(&nilfs->ns_super_sem);
        list_add(&sbi->s_list, &nilfs->ns_supers);
        up_write(&nilfs->ns_super_sem);

        sbi->s_ifile = nilfs_mdt_new(nilfs, sbi->s_super, NILFS_IFILE_INO);
        if (!sbi->s_ifile)
                return -ENOMEM;

        err = nilfs_palloc_init_blockgroup(sbi->s_ifile, nilfs->ns_inode_size);
        if (unlikely(err))
                goto failed;

        down_read(&nilfs->ns_segctor_sem);
        err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, cno, 0, &raw_cp,
                                          &bh_cp);
        up_read(&nilfs->ns_segctor_sem);
        if (unlikely(err)) {
                if (err == -ENOENT || err == -EINVAL) {
                        printk(KERN_ERR
                               "NILFS: Invalid checkpoint "
                               "(checkpoint number=%llu)\n",
                               (unsigned long long)cno);
                        err = -EINVAL;
                }
                goto failed;
        }
        err = nilfs_read_inode_common(sbi->s_ifile, &raw_cp->cp_ifile_inode);
        if (unlikely(err))
                goto failed_bh;
        atomic_set(&sbi->s_inodes_count, le64_to_cpu(raw_cp->cp_inodes_count));
        atomic_set(&sbi->s_blocks_count, le64_to_cpu(raw_cp->cp_blocks_count));

        nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
        return 0;

 failed_bh:
        nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
 failed:
        nilfs_mdt_destroy(sbi->s_ifile);
        sbi->s_ifile = NULL;

        down_write(&nilfs->ns_super_sem);
        list_del_init(&sbi->s_list);
        up_write(&nilfs->ns_super_sem);

        return err;
}

void nilfs_detach_checkpoint(struct nilfs_sb_info *sbi)
{
        struct the_nilfs *nilfs = sbi->s_nilfs;

        nilfs_mdt_clear(sbi->s_ifile);
        nilfs_mdt_destroy(sbi->s_ifile);
        sbi->s_ifile = NULL;
        down_write(&nilfs->ns_super_sem);
        list_del_init(&sbi->s_list);
        up_write(&nilfs->ns_super_sem);
}

static int nilfs_mark_recovery_complete(struct nilfs_sb_info *sbi)
{
        struct the_nilfs *nilfs = sbi->s_nilfs;
        int err = 0;

        down_write(&nilfs->ns_sem);
        if (!(nilfs->ns_mount_state & NILFS_VALID_FS)) {
                nilfs->ns_mount_state |= NILFS_VALID_FS;
                err = nilfs_commit_super(sbi, 1);
                if (likely(!err))
                        printk(KERN_INFO "NILFS: recovery complete.\n");
        }
        up_write(&nilfs->ns_sem);
        return err;
}

static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct super_block *sb = dentry->d_sb;
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        struct the_nilfs *nilfs = sbi->s_nilfs;
        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
        unsigned long long blocks;
        unsigned long overhead;
        unsigned long nrsvblocks;
        sector_t nfreeblocks;
        int err;

        /*
         * Compute all of the segment blocks
         *
         * The blocks before first segment and after last segment
         * are excluded.
         */
        blocks = nilfs->ns_blocks_per_segment * nilfs->ns_nsegments
                - nilfs->ns_first_data_block;
        nrsvblocks = nilfs->ns_nrsvsegs * nilfs->ns_blocks_per_segment;

        /*
         * Compute the overhead
         *
         * When distributing meta data blocks outside semgent structure,
         * We must count them as the overhead.
         */
        overhead = 0;

        err = nilfs_count_free_blocks(nilfs, &nfreeblocks);
        if (unlikely(err))
                return err;

        buf->f_type = NILFS_SUPER_MAGIC;
        buf->f_bsize = sb->s_blocksize;
        buf->f_blocks = blocks - overhead;
        buf->f_bfree = nfreeblocks;
        buf->f_bavail = (buf->f_bfree >= nrsvblocks) ?
                (buf->f_bfree - nrsvblocks) : 0;
        buf->f_files = atomic_read(&sbi->s_inodes_count);
        buf->f_ffree = 0; /* nilfs_count_free_inodes(sb); */
        buf->f_namelen = NILFS_NAME_LEN;
        buf->f_fsid.val[0] = (u32)id;
        buf->f_fsid.val[1] = (u32)(id >> 32);

        return 0;
}

static int nilfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
        struct super_block *sb = vfs->mnt_sb;
        struct nilfs_sb_info *sbi = NILFS_SB(sb);

        if (!nilfs_test_opt(sbi, BARRIER))
                seq_printf(seq, ",barrier=off");
        if (nilfs_test_opt(sbi, SNAPSHOT))
                seq_printf(seq, ",cp=%llu",
                           (unsigned long long int)sbi->s_snapshot_cno);
        if (nilfs_test_opt(sbi, ERRORS_RO))
                seq_printf(seq, ",errors=remount-ro");
        if (nilfs_test_opt(sbi, ERRORS_PANIC))
                seq_printf(seq, ",errors=panic");
        if (nilfs_test_opt(sbi, STRICT_ORDER))
                seq_printf(seq, ",order=strict");

        return 0;
}

static const struct super_operations nilfs_sops = {
        .alloc_inode    = nilfs_alloc_inode,
        .destroy_inode  = nilfs_destroy_inode,
        .dirty_inode    = nilfs_dirty_inode,
        /* .write_inode    = nilfs_write_inode, */
        /* .put_inode      = nilfs_put_inode, */
        /* .drop_inode    = nilfs_drop_inode, */
        .delete_inode   = nilfs_delete_inode,
        .put_super      = nilfs_put_super,
        /* .write_super    = nilfs_write_super, */
        .sync_fs        = nilfs_sync_fs,
        /* .write_super_lockfs */
        /* .unlockfs */
        .statfs         = nilfs_statfs,
        .remount_fs     = nilfs_remount,
        .clear_inode    = nilfs_clear_inode,
        /* .umount_begin */
        .show_options = nilfs_show_options
};

static struct inode *
nilfs_nfs_get_inode(struct super_block *sb, u64 ino, u32 generation)
{
        struct inode *inode;

        if (ino < NILFS_FIRST_INO(sb) && ino != NILFS_ROOT_INO &&
            ino != NILFS_SKETCH_INO)
                return ERR_PTR(-ESTALE);

        inode = nilfs_iget(sb, ino);
        if (IS_ERR(inode))
                return ERR_CAST(inode);
        if (generation && inode->i_generation != generation) {
                iput(inode);
                return ERR_PTR(-ESTALE);
        }

        return inode;
}

static struct dentry *
nilfs_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len,
                   int fh_type)
{
        return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
                                    nilfs_nfs_get_inode);
}

static struct dentry *
nilfs_fh_to_parent(struct super_block *sb, struct fid *fid, int fh_len,
                   int fh_type)
{
        return generic_fh_to_parent(sb, fid, fh_len, fh_type,
                                    nilfs_nfs_get_inode);
}

static const struct export_operations nilfs_export_ops = {
        .fh_to_dentry = nilfs_fh_to_dentry,
        .fh_to_parent = nilfs_fh_to_parent,
        .get_parent = nilfs_get_parent,
};

enum {
        Opt_err_cont, Opt_err_panic, Opt_err_ro,
        Opt_barrier, Opt_snapshot, Opt_order,
        Opt_err,
};

static match_table_t tokens = {
        {Opt_err_cont, "errors=continue"},
        {Opt_err_panic, "errors=panic"},
        {Opt_err_ro, "errors=remount-ro"},
        {Opt_barrier, "barrier=%s"},
        {Opt_snapshot, "cp=%u"},
        {Opt_order, "order=%s"},
        {Opt_err, NULL}
};

static int match_bool(substring_t *s, int *result)
{
        int len = s->to - s->from;

        if (strncmp(s->from, "on", len) == 0)
                *result = 1;
        else if (strncmp(s->from, "off", len) == 0)
                *result = 0;
        else
                return 1;
        return 0;
}

static int parse_options(char *options, struct super_block *sb)
{
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        char *p;
        substring_t args[MAX_OPT_ARGS];
        int option;

        if (!options)
                return 1;

        while ((p = strsep(&options, ",")) != NULL) {
                int token;
                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_barrier:
                        if (match_bool(&args[0], &option))
                                return 0;
                        if (option)
                                nilfs_set_opt(sbi, BARRIER);
                        else
                                nilfs_clear_opt(sbi, BARRIER);
                        break;
                case Opt_order:
                        if (strcmp(args[0].from, "relaxed") == 0)
                                /* Ordered data semantics */
                                nilfs_clear_opt(sbi, STRICT_ORDER);
                        else if (strcmp(args[0].from, "strict") == 0)
                                /* Strict in-order semantics */
                                nilfs_set_opt(sbi, STRICT_ORDER);
                        else
                                return 0;
                        break;
                case Opt_err_panic:
                        nilfs_write_opt(sbi, ERROR_MODE, ERRORS_PANIC);
                        break;
                case Opt_err_ro:
                        nilfs_write_opt(sbi, ERROR_MODE, ERRORS_RO);
                        break;
                case Opt_err_cont:
                        nilfs_write_opt(sbi, ERROR_MODE, ERRORS_CONT);
                        break;
                case Opt_snapshot:
                        if (match_int(&args[0], &option) || option <= 0)
                                return 0;
                        if (!(sb->s_flags & MS_RDONLY))
                                return 0;
                        sbi->s_snapshot_cno = option;
                        nilfs_set_opt(sbi, SNAPSHOT);
                        break;
                default:
                        printk(KERN_ERR
                               "NILFS: Unrecognized mount option \"%s\"\n", p);
                        return 0;
                }
        }
        return 1;
}

static inline void
nilfs_set_default_options(struct nilfs_sb_info *sbi,
                          struct nilfs_super_block *sbp)
{
        sbi->s_mount_opt =
                NILFS_MOUNT_ERRORS_CONT | NILFS_MOUNT_BARRIER;
}

static int nilfs_setup_super(struct nilfs_sb_info *sbi)
{
        struct the_nilfs *nilfs = sbi->s_nilfs;
        struct nilfs_super_block *sbp = nilfs->ns_sbp[0];
        int max_mnt_count = le16_to_cpu(sbp->s_max_mnt_count);
        int mnt_count = le16_to_cpu(sbp->s_mnt_count);

        /* nilfs->sem must be locked by the caller. */
        if (!(nilfs->ns_mount_state & NILFS_VALID_FS)) {
                printk(KERN_WARNING "NILFS warning: mounting unchecked fs\n");
        } else if (nilfs->ns_mount_state & NILFS_ERROR_FS) {
                printk(KERN_WARNING
                       "NILFS warning: mounting fs with errors\n");
#if 0
        } else if (max_mnt_count >= 0 && mnt_count >= max_mnt_count) {
                printk(KERN_WARNING
                       "NILFS warning: maximal mount count reached\n");
#endif
        }
        if (!max_mnt_count)
                sbp->s_max_mnt_count = cpu_to_le16(NILFS_DFL_MAX_MNT_COUNT);

        sbp->s_mnt_count = cpu_to_le16(mnt_count + 1);
        sbp->s_state = cpu_to_le16(le16_to_cpu(sbp->s_state) & ~NILFS_VALID_FS);
        sbp->s_mtime = cpu_to_le64(get_seconds());
        return nilfs_commit_super(sbi, 1);
}

struct nilfs_super_block *nilfs_read_super_block(struct super_block *sb,
                                                 u64 pos, int blocksize,
                                                 struct buffer_head **pbh)
{
        unsigned long long sb_index = pos;
        unsigned long offset;

        offset = do_div(sb_index, blocksize);
        *pbh = sb_bread(sb, sb_index);
        if (!*pbh)
                return NULL;
        return (struct nilfs_super_block *)((char *)(*pbh)->b_data + offset);
}

int nilfs_store_magic_and_option(struct super_block *sb,
                                 struct nilfs_super_block *sbp,
                                 char *data)
{
        struct nilfs_sb_info *sbi = NILFS_SB(sb);

        sb->s_magic = le16_to_cpu(sbp->s_magic);

        /* FS independent flags */
#ifdef NILFS_ATIME_DISABLE
        sb->s_flags |= MS_NOATIME;
#endif

        nilfs_set_default_options(sbi, sbp);

        sbi->s_resuid = le16_to_cpu(sbp->s_def_resuid);
        sbi->s_resgid = le16_to_cpu(sbp->s_def_resgid);
        sbi->s_interval = le32_to_cpu(sbp->s_c_interval);
        sbi->s_watermark = le32_to_cpu(sbp->s_c_block_max);

        return !parse_options(data, sb) ? -EINVAL : 0 ;
}

/**
 * nilfs_fill_super() - initialize a super block instance
 * @sb: super_block
 * @data: mount options
 * @silent: silent mode flag
 * @nilfs: the_nilfs struct
 *
 * This function is called exclusively by nilfs->ns_mount_mutex.
 * So, the recovery process is protected from other simultaneous mounts.
 */
static int
nilfs_fill_super(struct super_block *sb, void *data, int silent,
                 struct the_nilfs *nilfs)
{
        struct nilfs_sb_info *sbi;
        struct inode *root;
        __u64 cno;
        int err;

        sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
        if (!sbi)
                return -ENOMEM;

        sb->s_fs_info = sbi;

        get_nilfs(nilfs);
        sbi->s_nilfs = nilfs;
        sbi->s_super = sb;
        atomic_set(&sbi->s_count, 1);

        err = init_nilfs(nilfs, sbi, (char *)data);
        if (err)
                goto failed_sbi;

        spin_lock_init(&sbi->s_inode_lock);
        INIT_LIST_HEAD(&sbi->s_dirty_files);
        INIT_LIST_HEAD(&sbi->s_list);

        /*
         * Following initialization is overlapped because
         * nilfs_sb_info structure has been cleared at the beginning.
         * But we reserve them to keep our interest and make ready
         * for the future change.
         */
        get_random_bytes(&sbi->s_next_generation,
                         sizeof(sbi->s_next_generation));
        spin_lock_init(&sbi->s_next_gen_lock);

        sb->s_op = &nilfs_sops;
        sb->s_export_op = &nilfs_export_ops;
        sb->s_root = NULL;
        sb->s_time_gran = 1;

        if (!nilfs_loaded(nilfs)) {
                err = load_nilfs(nilfs, sbi);
                if (err)
                        goto failed_sbi;
        }
        cno = nilfs_last_cno(nilfs);

        if (sb->s_flags & MS_RDONLY) {
                if (nilfs_test_opt(sbi, SNAPSHOT)) {
                        down_read(&nilfs->ns_segctor_sem);
                        err = nilfs_cpfile_is_snapshot(nilfs->ns_cpfile,
                                                       sbi->s_snapshot_cno);
                        up_read(&nilfs->ns_segctor_sem);
                        if (err < 0) {
                                if (err == -ENOENT)
                                        err = -EINVAL;
                                goto failed_sbi;
                        }
                        if (!err) {
                                printk(KERN_ERR
                                       "NILFS: The specified checkpoint is "
                                       "not a snapshot "
                                       "(checkpoint number=%llu).\n",
                                       (unsigned long long)sbi->s_snapshot_cno);
                                err = -EINVAL;
                                goto failed_sbi;
                        }
                        cno = sbi->s_snapshot_cno;
                } else
                        /* Read-only mount */
                        sbi->s_snapshot_cno = cno;
        }

        err = nilfs_attach_checkpoint(sbi, cno);
        if (err) {
                printk(KERN_ERR "NILFS: error loading a checkpoint"
                       " (checkpoint number=%llu).\n", (unsigned long long)cno);
                goto failed_sbi;
        }

        if (!(sb->s_flags & MS_RDONLY)) {
                err = nilfs_attach_segment_constructor(sbi);
                if (err)
                        goto failed_checkpoint;
        }

        root = nilfs_iget(sb, NILFS_ROOT_INO);
        if (IS_ERR(root)) {
                printk(KERN_ERR "NILFS: get root inode failed\n");
                err = PTR_ERR(root);
                goto failed_segctor;
        }
        if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
                iput(root);
                printk(KERN_ERR "NILFS: corrupt root inode.\n");
                err = -EINVAL;
                goto failed_segctor;
        }
        sb->s_root = d_alloc_root(root);
        if (!sb->s_root) {
                iput(root);
                printk(KERN_ERR "NILFS: get root dentry failed\n");
                err = -ENOMEM;
                goto failed_segctor;
        }

        if (!(sb->s_flags & MS_RDONLY)) {
                down_write(&nilfs->ns_sem);
                nilfs_setup_super(sbi);
                up_write(&nilfs->ns_sem);
        }

        err = nilfs_mark_recovery_complete(sbi);
        if (unlikely(err)) {
                printk(KERN_ERR "NILFS: recovery failed.\n");
                goto failed_root;
        }

        down_write(&nilfs->ns_super_sem);
        if (!nilfs_test_opt(sbi, SNAPSHOT))
                nilfs->ns_current = sbi;
        up_write(&nilfs->ns_super_sem);

        return 0;

 failed_root:
        dput(sb->s_root);
        sb->s_root = NULL;

 failed_segctor:
        nilfs_detach_segment_constructor(sbi);

 failed_checkpoint:
        nilfs_detach_checkpoint(sbi);

 failed_sbi:
        put_nilfs(nilfs);
        sb->s_fs_info = NULL;
        nilfs_put_sbinfo(sbi);
        return err;
}

static int nilfs_remount(struct super_block *sb, int *flags, char *data)
{
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        struct nilfs_super_block *sbp;
        struct the_nilfs *nilfs = sbi->s_nilfs;
        unsigned long old_sb_flags;
        struct nilfs_mount_options old_opts;
        int err;

        lock_kernel();

        down_write(&nilfs->ns_super_sem);
        old_sb_flags = sb->s_flags;
        old_opts.mount_opt = sbi->s_mount_opt;
        old_opts.snapshot_cno = sbi->s_snapshot_cno;

        if (!parse_options(data, sb)) {
                err = -EINVAL;
                goto restore_opts;
        }
        sb->s_flags = (sb->s_flags & ~MS_POSIXACL);

        if ((*flags & MS_RDONLY) &&
            sbi->s_snapshot_cno != old_opts.snapshot_cno) {
                printk(KERN_WARNING "NILFS (device %s): couldn't "
                       "remount to a different snapshot. \n",
                       sb->s_id);
                err = -EINVAL;
                goto restore_opts;
        }

        if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
                goto out;
        if (*flags & MS_RDONLY) {
                /* Shutting down the segment constructor */
                nilfs_detach_segment_constructor(sbi);
                sb->s_flags |= MS_RDONLY;

                sbi->s_snapshot_cno = nilfs_last_cno(nilfs);
                /* nilfs_set_opt(sbi, SNAPSHOT); */

                /*
                 * Remounting a valid RW partition RDONLY, so set
                 * the RDONLY flag and then mark the partition as valid again.
                 */
                down_write(&nilfs->ns_sem);
                sbp = nilfs->ns_sbp[0];
                if (!(sbp->s_state & le16_to_cpu(NILFS_VALID_FS)) &&
                    (nilfs->ns_mount_state & NILFS_VALID_FS))
                        sbp->s_state = cpu_to_le16(nilfs->ns_mount_state);
                sbp->s_mtime = cpu_to_le64(get_seconds());
                nilfs_commit_super(sbi, 1);
                up_write(&nilfs->ns_sem);
        } else {
                /*
                 * Mounting a RDONLY partition read-write, so reread and
                 * store the current valid flag.  (It may have been changed
                 * by fsck since we originally mounted the partition.)
                 */
                if (nilfs->ns_current && nilfs->ns_current != sbi) {
                        printk(KERN_WARNING "NILFS (device %s): couldn't "
                               "remount because an RW-mount exists.\n",
                               sb->s_id);
                        err = -EBUSY;
                        goto restore_opts;
                }
                if (sbi->s_snapshot_cno != nilfs_last_cno(nilfs)) {
                        printk(KERN_WARNING "NILFS (device %s): couldn't "
                               "remount because the current RO-mount is not "
                               "the latest one.\n",
                               sb->s_id);
                        err = -EINVAL;
                        goto restore_opts;
                }
                sb->s_flags &= ~MS_RDONLY;
                nilfs_clear_opt(sbi, SNAPSHOT);
                sbi->s_snapshot_cno = 0;

                err = nilfs_attach_segment_constructor(sbi);
                if (err)
                        goto restore_opts;

                down_write(&nilfs->ns_sem);
                nilfs_setup_super(sbi);
                up_write(&nilfs->ns_sem);

                nilfs->ns_current = sbi;
        }
 out:
        up_write(&nilfs->ns_super_sem);
        unlock_kernel();
        return 0;

 restore_opts:
        sb->s_flags = old_sb_flags;
        sbi->s_mount_opt = old_opts.mount_opt;
        sbi->s_snapshot_cno = old_opts.snapshot_cno;
        up_write(&nilfs->ns_super_sem);
        unlock_kernel();
        return err;
}

struct nilfs_super_data {
        struct block_device *bdev;
        struct nilfs_sb_info *sbi;
        __u64 cno;
        int flags;
};

/**
 * nilfs_identify - pre-read mount options needed to identify mount instance
 * @data: mount options
 * @sd: nilfs_super_data
 */

static int nilfs_identify(char *data, struct nilfs_super_data *sd)
{
        char *p, *options = data;
        substring_t args[MAX_OPT_ARGS];
        int option, token;
        int ret = 0;

        do {
                p = strsep(&options, ",");
                if (p != NULL && *p) {
                        token = match_token(p, tokens, args);
                        if (token == Opt_snapshot) {
                                if (!(sd->flags & MS_RDONLY))
                                        ret++;
                                else {
                                        ret = match_int(&args[0], &option);
                                        if (!ret) {
                                                if (option > 0)
                                                        sd->cno = option;
                                                else
                                                        ret++;
                                        }
                                }
                        }
                        if (ret)
                                printk(KERN_ERR
                                       "NILFS: invalid mount option: %s\n", p);
                }
                if (!options)
                        break;
                BUG_ON(options == data);
                *(options - 1) = ',';
        } while (!ret);
        return ret;
}

static int nilfs_set_bdev_super(struct super_block *s, void *data)
{
        struct nilfs_super_data *sd = data;

        s->s_bdev = sd->bdev;
        s->s_dev = s->s_bdev->bd_dev;
        return 0;
}

static int nilfs_test_bdev_super(struct super_block *s, void *data)
{
        struct nilfs_super_data *sd = data;

        return sd->sbi && s->s_fs_info == (void *)sd->sbi;
}

static int
nilfs_get_sb(struct file_system_type *fs_type, int flags,
             const char *dev_name, void *data, struct vfsmount *mnt)
{
        struct nilfs_super_data sd;
        struct super_block *s;
        struct the_nilfs *nilfs;
        int err, need_to_close = 1;

        sd.bdev = open_bdev_exclusive(dev_name, flags, fs_type);
        if (IS_ERR(sd.bdev))
                return PTR_ERR(sd.bdev);

        /*
         * To get mount instance using sget() vfs-routine, NILFS needs
         * much more information than normal filesystems to identify mount
         * instance.  For snapshot mounts, not only a mount type (ro-mount
         * or rw-mount) but also a checkpoint number is required.
         */
        sd.cno = 0;
        sd.flags = flags;
        if (nilfs_identify((char *)data, &sd)) {
                err = -EINVAL;
                goto failed;
        }

        nilfs = find_or_create_nilfs(sd.bdev);
        if (!nilfs) {
                err = -ENOMEM;
                goto failed;
        }

        mutex_lock(&nilfs->ns_mount_mutex);

        if (!sd.cno) {
                /*
                 * Check if an exclusive mount exists or not.
                 * Snapshot mounts coexist with a current mount
                 * (i.e. rw-mount or ro-mount), whereas rw-mount and
                 * ro-mount are mutually exclusive.
                 */
                down_read(&nilfs->ns_super_sem);
                if (nilfs->ns_current &&
                    ((nilfs->ns_current->s_super->s_flags ^ flags)
                     & MS_RDONLY)) {
                        up_read(&nilfs->ns_super_sem);
                        err = -EBUSY;
                        goto failed_unlock;
                }
                up_read(&nilfs->ns_super_sem);
        }

        /*
         * Find existing nilfs_sb_info struct
         */
        sd.sbi = nilfs_find_sbinfo(nilfs, !(flags & MS_RDONLY), sd.cno);

        /*
         * Get super block instance holding the nilfs_sb_info struct.
         * A new instance is allocated if no existing mount is present or
         * existing instance has been unmounted.
         */
        s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
        if (sd.sbi)
                nilfs_put_sbinfo(sd.sbi);

        if (IS_ERR(s)) {
                err = PTR_ERR(s);
                goto failed_unlock;
        }

        if (!s->s_root) {
                char b[BDEVNAME_SIZE];

                /* New superblock instance created */
                s->s_flags = flags;
                strlcpy(s->s_id, bdevname(sd.bdev, b), sizeof(s->s_id));
                sb_set_blocksize(s, block_size(sd.bdev));

                err = nilfs_fill_super(s, data, flags & MS_VERBOSE, nilfs);
                if (err)
                        goto cancel_new;

                s->s_flags |= MS_ACTIVE;
                need_to_close = 0;
        }

        mutex_unlock(&nilfs->ns_mount_mutex);
        put_nilfs(nilfs);
        if (need_to_close)
                close_bdev_exclusive(sd.bdev, flags);
        simple_set_mnt(mnt, s);
        return 0;

 failed_unlock:
        mutex_unlock(&nilfs->ns_mount_mutex);
        put_nilfs(nilfs);
 failed:
        close_bdev_exclusive(sd.bdev, flags);

        return err;

 cancel_new:
        /* Abandoning the newly allocated superblock */
        mutex_unlock(&nilfs->ns_mount_mutex);
        put_nilfs(nilfs);
        up_write(&s->s_umount);
        deactivate_super(s);
        /*
         * deactivate_super() invokes close_bdev_exclusive().
         * We must finish all post-cleaning before this call;
         * put_nilfs() needs the block device.
         */
        return err;
}

struct file_system_type nilfs_fs_type = {
        .owner    = THIS_MODULE,
        .name     = "nilfs2",
        .get_sb   = nilfs_get_sb,
        .kill_sb  = kill_block_super,
        .fs_flags = FS_REQUIRES_DEV,
};

static int __init init_nilfs_fs(void)
{
        int err;

        err = nilfs_init_inode_cache();
        if (err)
                goto failed;

        err = nilfs_init_transaction_cache();
        if (err)
                goto failed_inode_cache;

        err = nilfs_init_segbuf_cache();
        if (err)
                goto failed_transaction_cache;

        err = nilfs_btree_path_cache_init();
        if (err)
                goto failed_segbuf_cache;

        err = register_filesystem(&nilfs_fs_type);
        if (err)
                goto failed_btree_path_cache;

        return 0;

 failed_btree_path_cache:
        nilfs_btree_path_cache_destroy();

 failed_segbuf_cache:
        nilfs_destroy_segbuf_cache();

 failed_transaction_cache:
        nilfs_destroy_transaction_cache();

 failed_inode_cache:
        nilfs_destroy_inode_cache();

 failed:
        return err;
}

static void __exit exit_nilfs_fs(void)
{
        nilfs_destroy_segbuf_cache();
        nilfs_destroy_transaction_cache();
        nilfs_destroy_inode_cache();
        nilfs_btree_path_cache_destroy();
        unregister_filesystem(&nilfs_fs_type);
}

module_init(init_nilfs_fs)
module_exit(exit_nilfs_fs)