/*
 * 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/crc32.h>
#include <linux/vfs.h>
#include <linux/writeback.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include "nilfs.h"
#include "export.h"
#include "mdt.h"
#include "alloc.h"
#include "btree.h"
#include "btnode.h"
#include "page.h"
#include "cpfile.h"
#include "sufile.h" /* nilfs_sufile_resize(), nilfs_sufile_set_alloc_range() */
#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 struct kmem_cache *nilfs_inode_cachep;
struct kmem_cache *nilfs_transaction_cachep;
struct kmem_cache *nilfs_segbuf_cachep;
struct kmem_cache *nilfs_btree_path_cache;

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

static void nilfs_set_error(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;

        down_write(&nilfs->ns_sem);
        if (!(nilfs->ns_mount_state & NILFS_ERROR_FS)) {
                nilfs->ns_mount_state |= NILFS_ERROR_FS;
                sbp = nilfs_prepare_super(sb, 0);
                if (likely(sbp)) {
                        sbp[0]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
                        if (sbp[1])
                                sbp[1]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
                        nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
                }
        }
        up_write(&nilfs->ns_sem);
}

/**
 * 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 the_nilfs *nilfs = sb->s_fs_info;
        struct va_format vaf;
        va_list args;

        va_start(args, fmt);

        vaf.fmt = fmt;
        vaf.va = &args;

        printk(KERN_CRIT "NILFS error (device %s): %s: %pV\n",
               sb->s_id, function, &vaf);

        va_end(args);

        if (!(sb->s_flags & MS_RDONLY)) {
                nilfs_set_error(sb);

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

        if (nilfs_test_opt(nilfs, 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, ...)
{
        struct va_format vaf;
        va_list args;

        va_start(args, fmt);

        vaf.fmt = fmt;
        vaf.va = &args;

        printk(KERN_WARNING "NILFS warning (device %s): %s: %pV\n",
               sb->s_id, function, &vaf);

        va_end(args);
}


struct inode *nilfs_alloc_inode(struct super_block *sb)
{
        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->i_cno = 0;
        ii->vfs_inode.i_version = 1;
        nilfs_mapping_init(&ii->i_btnode_cache, &ii->vfs_inode, sb->s_bdi);
        return &ii->vfs_inode;
}

static void nilfs_i_callback(struct rcu_head *head)
{
        struct inode *inode = container_of(head, struct inode, i_rcu);
        struct nilfs_mdt_info *mdi = NILFS_MDT(inode);

        if (mdi) {
                kfree(mdi->mi_bgl); /* kfree(NULL) is safe */
                kfree(mdi);
        }
        kmem_cache_free(nilfs_inode_cachep, NILFS_I(inode));
}

void nilfs_destroy_inode(struct inode *inode)
{
        call_rcu(&inode->i_rcu, nilfs_i_callback);
}

static int nilfs_sync_super(struct super_block *sb, int flag)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        int err;

 retry:
        set_buffer_dirty(nilfs->ns_sbh[0]);
        if (nilfs_test_opt(nilfs, BARRIER)) {
                err = __sync_dirty_buffer(nilfs->ns_sbh[0],
                                          WRITE_SYNC | WRITE_FLUSH_FUA);
        } else {
                err = sync_dirty_buffer(nilfs->ns_sbh[0]);
        }

        if (unlikely(err)) {
                printk(KERN_ERR
                       "NILFS: unable to write superblock (err=%d)\n", err);
                if (err == -EIO && nilfs->ns_sbh[1]) {
                        /*
                         * sbp[0] points to newer log than sbp[1],
                         * so copy sbp[0] to sbp[1] to take over sbp[0].
                         */
                        memcpy(nilfs->ns_sbp[1], nilfs->ns_sbp[0],
                               nilfs->ns_sbsize);
                        nilfs_fall_back_super_block(nilfs);
                        goto retry;
                }
        } else {
                struct nilfs_super_block *sbp = nilfs->ns_sbp[0];

                nilfs->ns_sbwcount++;

                /*
                 * 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]) {
                        if (flag == NILFS_SB_COMMIT_ALL) {
                                set_buffer_dirty(nilfs->ns_sbh[1]);
                                if (sync_dirty_buffer(nilfs->ns_sbh[1]) < 0)
                                        goto out;
                        }
                        if (le64_to_cpu(nilfs->ns_sbp[1]->s_last_cno) <
                            le64_to_cpu(nilfs->ns_sbp[0]->s_last_cno))
                                sbp = nilfs->ns_sbp[1];
                }

                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);
        }
 out:
        return err;
}

void nilfs_set_log_cursor(struct nilfs_super_block *sbp,
                          struct the_nilfs *nilfs)
{
        sector_t nfreeblocks;

        /* nilfs->ns_sem must be locked by the caller. */
        nilfs_count_free_blocks(nilfs, &nfreeblocks);
        sbp->s_free_blocks_count = cpu_to_le64(nfreeblocks);

        spin_lock(&nilfs->ns_last_segment_lock);
        sbp->s_last_seq = cpu_to_le64(nilfs->ns_last_seq);
        sbp->s_last_pseg = cpu_to_le64(nilfs->ns_last_pseg);
        sbp->s_last_cno = cpu_to_le64(nilfs->ns_last_cno);
        spin_unlock(&nilfs->ns_last_segment_lock);
}

struct nilfs_super_block **nilfs_prepare_super(struct super_block *sb,
                                               int flip)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp = nilfs->ns_sbp;

        /* nilfs->ns_sem must be locked by the caller. */
        if (sbp[0]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
                if (sbp[1] &&
                    sbp[1]->s_magic == cpu_to_le16(NILFS_SUPER_MAGIC)) {
                        memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
                } else {
                        printk(KERN_CRIT "NILFS: superblock broke on dev %s\n",
                               sb->s_id);
                        return NULL;
                }
        } else if (sbp[1] &&
                   sbp[1]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
                        memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
        }

        if (flip && sbp[1])
                nilfs_swap_super_block(nilfs);

        return sbp;
}

int nilfs_commit_super(struct super_block *sb, int flag)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp = nilfs->ns_sbp;
        time_t t;

        /* nilfs->ns_sem must be locked by the caller. */
        t = get_seconds();
        nilfs->ns_sbwtime = t;
        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 (flag == NILFS_SB_COMMIT_ALL && sbp[1]) {
                sbp[1]->s_wtime = sbp[0]->s_wtime;
                sbp[1]->s_sum = 0;
                sbp[1]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
                                            (unsigned char *)sbp[1],
                                            nilfs->ns_sbsize));
        }
        clear_nilfs_sb_dirty(nilfs);
        nilfs->ns_flushed_device = 1;
        /* make sure store to ns_flushed_device cannot be reordered */
        smp_wmb();
        return nilfs_sync_super(sb, flag);
}

/**
 * nilfs_cleanup_super() - write filesystem state for cleanup
 * @sb: super block instance to be unmounted or degraded to read-only
 *
 * This function restores state flags in the on-disk super block.
 * This will set "clean" flag (i.e. NILFS_VALID_FS) unless the
 * filesystem was not clean previously.
 */
int nilfs_cleanup_super(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        int flag = NILFS_SB_COMMIT;
        int ret = -EIO;

        sbp = nilfs_prepare_super(sb, 0);
        if (sbp) {
                sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
                nilfs_set_log_cursor(sbp[0], nilfs);
                if (sbp[1] && sbp[0]->s_last_cno == sbp[1]->s_last_cno) {
                        /*
                         * make the "clean" flag also to the opposite
                         * super block if both super blocks point to
                         * the same checkpoint.
                         */
                        sbp[1]->s_state = sbp[0]->s_state;
                        flag = NILFS_SB_COMMIT_ALL;
                }
                ret = nilfs_commit_super(sb, flag);
        }
        return ret;
}

/**
 * nilfs_move_2nd_super - relocate secondary super block
 * @sb: super block instance
 * @sb2off: new offset of the secondary super block (in bytes)
 */
static int nilfs_move_2nd_super(struct super_block *sb, loff_t sb2off)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct buffer_head *nsbh;
        struct nilfs_super_block *nsbp;
        sector_t blocknr, newblocknr;
        unsigned long offset;
        int sb2i = -1;  /* array index of the secondary superblock */
        int ret = 0;

        /* nilfs->ns_sem must be locked by the caller. */
        if (nilfs->ns_sbh[1] &&
            nilfs->ns_sbh[1]->b_blocknr > nilfs->ns_first_data_block) {
                sb2i = 1;
                blocknr = nilfs->ns_sbh[1]->b_blocknr;
        } else if (nilfs->ns_sbh[0]->b_blocknr > nilfs->ns_first_data_block) {
                sb2i = 0;
                blocknr = nilfs->ns_sbh[0]->b_blocknr;
        }
        if (sb2i >= 0 && (u64)blocknr << nilfs->ns_blocksize_bits == sb2off)
                goto out;  /* super block location is unchanged */

        /* Get new super block buffer */
        newblocknr = sb2off >> nilfs->ns_blocksize_bits;
        offset = sb2off & (nilfs->ns_blocksize - 1);
        nsbh = sb_getblk(sb, newblocknr);
        if (!nsbh) {
                printk(KERN_WARNING
                       "NILFS warning: unable to move secondary superblock "
                       "to block %llu\n", (unsigned long long)newblocknr);
                ret = -EIO;
                goto out;
        }
        nsbp = (void *)nsbh->b_data + offset;
        memset(nsbp, 0, nilfs->ns_blocksize);

        if (sb2i >= 0) {
                memcpy(nsbp, nilfs->ns_sbp[sb2i], nilfs->ns_sbsize);
                brelse(nilfs->ns_sbh[sb2i]);
                nilfs->ns_sbh[sb2i] = nsbh;
                nilfs->ns_sbp[sb2i] = nsbp;
        } else if (nilfs->ns_sbh[0]->b_blocknr < nilfs->ns_first_data_block) {
                /* secondary super block will be restored to index 1 */
                nilfs->ns_sbh[1] = nsbh;
                nilfs->ns_sbp[1] = nsbp;
        } else {
                brelse(nsbh);
        }
out:
        return ret;
}

/**
 * nilfs_resize_fs - resize the filesystem
 * @sb: super block instance
 * @newsize: new size of the filesystem (in bytes)
 */
int nilfs_resize_fs(struct super_block *sb, __u64 newsize)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        __u64 devsize, newnsegs;
        loff_t sb2off;
        int ret;

        ret = -ERANGE;
        devsize = i_size_read(sb->s_bdev->bd_inode);
        if (newsize > devsize)
                goto out;

        /*
         * Write lock is required to protect some functions depending
         * on the number of segments, the number of reserved segments,
         * and so forth.
         */
        down_write(&nilfs->ns_segctor_sem);

        sb2off = NILFS_SB2_OFFSET_BYTES(newsize);
        newnsegs = sb2off >> nilfs->ns_blocksize_bits;
        do_div(newnsegs, nilfs->ns_blocks_per_segment);

        ret = nilfs_sufile_resize(nilfs->ns_sufile, newnsegs);
        up_write(&nilfs->ns_segctor_sem);
        if (ret < 0)
                goto out;

        ret = nilfs_construct_segment(sb);
        if (ret < 0)
                goto out;

        down_write(&nilfs->ns_sem);
        nilfs_move_2nd_super(sb, sb2off);
        ret = -EIO;
        sbp = nilfs_prepare_super(sb, 0);
        if (likely(sbp)) {
                nilfs_set_log_cursor(sbp[0], nilfs);
                /*
                 * Drop NILFS_RESIZE_FS flag for compatibility with
                 * mount-time resize which may be implemented in a
                 * future release.
                 */
                sbp[0]->s_state = cpu_to_le16(le16_to_cpu(sbp[0]->s_state) &
                                              ~NILFS_RESIZE_FS);
                sbp[0]->s_dev_size = cpu_to_le64(newsize);
                sbp[0]->s_nsegments = cpu_to_le64(nilfs->ns_nsegments);
                if (sbp[1])
                        memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
                ret = nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
        }
        up_write(&nilfs->ns_sem);

        /*
         * Reset the range of allocatable segments last.  This order
         * is important in the case of expansion because the secondary
         * superblock must be protected from log write until migration
         * completes.
         */
        if (!ret)
                nilfs_sufile_set_alloc_range(nilfs->ns_sufile, 0, newnsegs - 1);
out:
        return ret;
}

static void nilfs_put_super(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;

        nilfs_detach_log_writer(sb);

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

        iput(nilfs->ns_sufile);
        iput(nilfs->ns_cpfile);
        iput(nilfs->ns_dat);

        destroy_nilfs(nilfs);
        sb->s_fs_info = NULL;
}

static int nilfs_sync_fs(struct super_block *sb, int wait)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        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 (nilfs_sb_dirty(nilfs)) {
                sbp = nilfs_prepare_super(sb, nilfs_sb_will_flip(nilfs));
                if (likely(sbp)) {
                        nilfs_set_log_cursor(sbp[0], nilfs);
                        nilfs_commit_super(sb, NILFS_SB_COMMIT);
                }
        }
        up_write(&nilfs->ns_sem);

        if (!err)
                err = nilfs_flush_device(nilfs);

        return err;
}

int nilfs_attach_checkpoint(struct super_block *sb, __u64 cno, int curr_mnt,
                            struct nilfs_root **rootp)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_root *root;
        struct nilfs_checkpoint *raw_cp;
        struct buffer_head *bh_cp;
        int err = -ENOMEM;

        root = nilfs_find_or_create_root(
                nilfs, curr_mnt ? NILFS_CPTREE_CURRENT_CNO : cno);
        if (!root)
                return err;

        if (root->ifile)
                goto reuse; /* already attached checkpoint */

        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_ifile_read(sb, root, nilfs->ns_inode_size,
                               &raw_cp->cp_ifile_inode, &root->ifile);
        if (err)
                goto failed_bh;

        atomic64_set(&root->inodes_count,
                        le64_to_cpu(raw_cp->cp_inodes_count));
        atomic64_set(&root->blocks_count,
                        le64_to_cpu(raw_cp->cp_blocks_count));

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

 reuse:
        *rootp = root;
        return 0;

 failed_bh:
        nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
 failed:
        nilfs_put_root(root);

        return err;
}

static int nilfs_freeze(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        int err;

        if (sb->s_flags & MS_RDONLY)
                return 0;

        /* Mark super block clean */
        down_write(&nilfs->ns_sem);
        err = nilfs_cleanup_super(sb);
        up_write(&nilfs->ns_sem);
        return err;
}

static int nilfs_unfreeze(struct super_block *sb)
{
        struct the_nilfs *nilfs = sb->s_fs_info;

        if (sb->s_flags & MS_RDONLY)
                return 0;

        down_write(&nilfs->ns_sem);
        nilfs_setup_super(sb, false);
        up_write(&nilfs->ns_sem);
        return 0;
}

static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct super_block *sb = dentry->d_sb;
        struct nilfs_root *root = NILFS_I(dentry->d_inode)->i_root;
        struct the_nilfs *nilfs = root->nilfs;
        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
        unsigned long long blocks;
        unsigned long overhead;
        unsigned long nrsvblocks;
        sector_t nfreeblocks;
        u64 nmaxinodes, nfreeinodes;
        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 segment structure,
         * We must count them as the overhead.
         */
        overhead = 0;

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

        err = nilfs_ifile_count_free_inodes(root->ifile,
                                            &nmaxinodes, &nfreeinodes);
        if (unlikely(err)) {
                printk(KERN_WARNING
                        "NILFS warning: fail to count free inodes: err %d.\n",
                        err);
                if (err == -ERANGE) {
                        /*
                         * If nilfs_palloc_count_max_entries() returns
                         * -ERANGE error code then we simply treat
                         * curent inodes count as maximum possible and
                         * zero as free inodes value.
                         */
                        nmaxinodes = atomic64_read(&root->inodes_count);
                        nfreeinodes = 0;
                        err = 0;
                } else
                        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 = nmaxinodes;
        buf->f_ffree = nfreeinodes;
        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 dentry *dentry)
{
        struct super_block *sb = dentry->d_sb;
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_root *root = NILFS_I(dentry->d_inode)->i_root;

        if (!nilfs_test_opt(nilfs, BARRIER))
                seq_puts(seq, ",nobarrier");
        if (root->cno != NILFS_CPTREE_CURRENT_CNO)
                seq_printf(seq, ",cp=%llu", (unsigned long long)root->cno);
        if (nilfs_test_opt(nilfs, ERRORS_PANIC))
                seq_puts(seq, ",errors=panic");
        if (nilfs_test_opt(nilfs, ERRORS_CONT))
                seq_puts(seq, ",errors=continue");
        if (nilfs_test_opt(nilfs, STRICT_ORDER))
                seq_puts(seq, ",order=strict");
        if (nilfs_test_opt(nilfs, NORECOVERY))
                seq_puts(seq, ",norecovery");
        if (nilfs_test_opt(nilfs, DISCARD))
                seq_puts(seq, ",discard");

        return 0;
}

static const struct super_operations nilfs_sops = {
        .alloc_inode    = nilfs_alloc_inode,
        .destroy_inode  = nilfs_destroy_inode,
        .dirty_inode    = nilfs_dirty_inode,
        .evict_inode    = nilfs_evict_inode,
        .put_super      = nilfs_put_super,
        .sync_fs        = nilfs_sync_fs,
        .freeze_fs      = nilfs_freeze,
        .unfreeze_fs    = nilfs_unfreeze,
        .statfs         = nilfs_statfs,
        .remount_fs     = nilfs_remount,
        .show_options = nilfs_show_options
};

enum {
        Opt_err_cont, Opt_err_panic, Opt_err_ro,
        Opt_barrier, Opt_nobarrier, Opt_snapshot, Opt_order, Opt_norecovery,
        Opt_discard, Opt_nodiscard, 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"},
        {Opt_nobarrier, "nobarrier"},
        {Opt_snapshot, "cp=%u"},
        {Opt_order, "order=%s"},
        {Opt_norecovery, "norecovery"},
        {Opt_discard, "discard"},
        {Opt_nodiscard, "nodiscard"},
        {Opt_err, NULL}
};

static int parse_options(char *options, struct super_block *sb, int is_remount)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        char *p;
        substring_t args[MAX_OPT_ARGS];

        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:
                        nilfs_set_opt(nilfs, BARRIER);
                        break;
                case Opt_nobarrier:
                        nilfs_clear_opt(nilfs, BARRIER);
                        break;
                case Opt_order:
                        if (strcmp(args[0].from, "relaxed") == 0)
                                /* Ordered data semantics */
                                nilfs_clear_opt(nilfs, STRICT_ORDER);
                        else if (strcmp(args[0].from, "strict") == 0)
                                /* Strict in-order semantics */
                                nilfs_set_opt(nilfs, STRICT_ORDER);
                        else
                                return 0;
                        break;
                case Opt_err_panic:
                        nilfs_write_opt(nilfs, ERROR_MODE, ERRORS_PANIC);
                        break;
                case Opt_err_ro:
                        nilfs_write_opt(nilfs, ERROR_MODE, ERRORS_RO);
                        break;
                case Opt_err_cont:
                        nilfs_write_opt(nilfs, ERROR_MODE, ERRORS_CONT);
                        break;
                case Opt_snapshot:
                        if (is_remount) {
                                printk(KERN_ERR
                                       "NILFS: \"%s\" option is invalid "
                                       "for remount.\n", p);
                                return 0;
                        }
                        break;
                case Opt_norecovery:
                        nilfs_set_opt(nilfs, NORECOVERY);
                        break;
                case Opt_discard:
                        nilfs_set_opt(nilfs, DISCARD);
                        break;
                case Opt_nodiscard:
                        nilfs_clear_opt(nilfs, DISCARD);
                        break;
                default:
                        printk(KERN_ERR
                               "NILFS: Unrecognized mount option \"%s\"\n", p);
                        return 0;
                }
        }
        return 1;
}

static inline void
nilfs_set_default_options(struct super_block *sb,
                          struct nilfs_super_block *sbp)
{
        struct the_nilfs *nilfs = sb->s_fs_info;

        nilfs->ns_mount_opt =
                NILFS_MOUNT_ERRORS_RO | NILFS_MOUNT_BARRIER;
}

static int nilfs_setup_super(struct super_block *sb, int is_mount)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_super_block **sbp;
        int max_mnt_count;
        int mnt_count;

        /* nilfs->ns_sem must be locked by the caller. */
        sbp = nilfs_prepare_super(sb, 0);
        if (!sbp)
                return -EIO;

        if (!is_mount)
                goto skip_mount_setup;

        max_mnt_count = le16_to_cpu(sbp[0]->s_max_mnt_count);
        mnt_count = le16_to_cpu(sbp[0]->s_mnt_count);

        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[0]->s_max_mnt_count = cpu_to_le16(NILFS_DFL_MAX_MNT_COUNT);

        sbp[0]->s_mnt_count = cpu_to_le16(mnt_count + 1);
        sbp[0]->s_mtime = cpu_to_le64(get_seconds());

skip_mount_setup:
        sbp[0]->s_state =
                cpu_to_le16(le16_to_cpu(sbp[0]->s_state) & ~NILFS_VALID_FS);
        /* synchronize sbp[1] with sbp[0] */
        if (sbp[1])
                memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
        return nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
}

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 the_nilfs *nilfs = sb->s_fs_info;

        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(sb, sbp);

        nilfs->ns_resuid = le16_to_cpu(sbp->s_def_resuid);
        nilfs->ns_resgid = le16_to_cpu(sbp->s_def_resgid);
        nilfs->ns_interval = le32_to_cpu(sbp->s_c_interval);
        nilfs->ns_watermark = le32_to_cpu(sbp->s_c_block_max);

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

int nilfs_check_feature_compatibility(struct super_block *sb,
                                      struct nilfs_super_block *sbp)
{
        __u64 features;

        features = le64_to_cpu(sbp->s_feature_incompat) &
                ~NILFS_FEATURE_INCOMPAT_SUPP;
        if (features) {
                printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
                       "optional features (%llx)\n",
                       (unsigned long long)features);
                return -EINVAL;
        }
        features = le64_to_cpu(sbp->s_feature_compat_ro) &
                ~NILFS_FEATURE_COMPAT_RO_SUPP;
        if (!(sb->s_flags & MS_RDONLY) && features) {
                printk(KERN_ERR "NILFS: couldn't mount RDWR because of "
                       "unsupported optional features (%llx)\n",
                       (unsigned long long)features);
                return -EINVAL;
        }
        return 0;
}

static int nilfs_get_root_dentry(struct super_block *sb,
                                 struct nilfs_root *root,
                                 struct dentry **root_dentry)
{
        struct inode *inode;
        struct dentry *dentry;
        int ret = 0;

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

        if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
                dentry = d_find_alias(inode);
                if (!dentry) {
                        dentry = d_make_root(inode);
                        if (!dentry) {
                                ret = -ENOMEM;
                                goto failed_dentry;
                        }
                } else {
                        iput(inode);
                }
        } else {
                dentry = d_obtain_root(inode);
                if (IS_ERR(dentry)) {
                        ret = PTR_ERR(dentry);
                        goto failed_dentry;
                }
        }
        *root_dentry = dentry;
 out:
        return ret;

 failed_dentry:
        printk(KERN_ERR "NILFS: get root dentry failed\n");
        goto out;
}

static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
                                 struct dentry **root_dentry)
{
        struct the_nilfs *nilfs = s->s_fs_info;
        struct nilfs_root *root;
        int ret;

        mutex_lock(&nilfs->ns_snapshot_mount_mutex);

        down_read(&nilfs->ns_segctor_sem);
        ret = nilfs_cpfile_is_snapshot(nilfs->ns_cpfile, cno);
        up_read(&nilfs->ns_segctor_sem);
        if (ret < 0) {
                ret = (ret == -ENOENT) ? -EINVAL : ret;
                goto out;
        } else if (!ret) {
                printk(KERN_ERR "NILFS: The specified checkpoint is "
                       "not a snapshot (checkpoint number=%llu).\n",
                       (unsigned long long)cno);
                ret = -EINVAL;
                goto out;
        }

        ret = nilfs_attach_checkpoint(s, cno, false, &root);
        if (ret) {
                printk(KERN_ERR "NILFS: error loading snapshot "
                       "(checkpoint number=%llu).\n",
               (unsigned long long)cno);
                goto out;
        }
        ret = nilfs_get_root_dentry(s, root, root_dentry);
        nilfs_put_root(root);
 out:
        mutex_unlock(&nilfs->ns_snapshot_mount_mutex);
        return ret;

}

/**
 * nilfs_tree_is_busy() - try to shrink dentries of a checkpoint
 * @root_dentry: root dentry of the tree to be shrunk
 *
 * This function returns true if the tree was in-use.
 */
static bool nilfs_tree_is_busy(struct dentry *root_dentry)
{
        shrink_dcache_parent(root_dentry);
        return d_count(root_dentry) > 1;
}

int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        struct nilfs_root *root;
        struct inode *inode;
        struct dentry *dentry;
        int ret;

        if (cno < 0 || cno > nilfs->ns_cno)
                return false;

        if (cno >= nilfs_last_cno(nilfs))
                return true;    /* protect recent checkpoints */

        ret = false;
        root = nilfs_lookup_root(nilfs, cno);
        if (root) {
                inode = nilfs_ilookup(sb, root, NILFS_ROOT_INO);
                if (inode) {
                        dentry = d_find_alias(inode);
                        if (dentry) {
                                ret = nilfs_tree_is_busy(dentry);
                                dput(dentry);
                        }
                        iput(inode);
                }
                nilfs_put_root(root);
        }
        return ret;
}

/**
 * nilfs_fill_super() - initialize a super block instance
 * @sb: super_block
 * @data: mount options
 * @silent: silent mode flag
 *
 * 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_root *fsroot;
        struct backing_dev_info *bdi;
        __u64 cno;
        int err;

        nilfs = alloc_nilfs(sb->s_bdev);
        if (!nilfs)
                return -ENOMEM;

        sb->s_fs_info = nilfs;

        err = init_nilfs(nilfs, sb, (char *)data);
        if (err)
                goto failed_nilfs;

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

        bdi = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
        sb->s_bdi = bdi ? : &default_backing_dev_info;

        err = load_nilfs(nilfs, sb);
        if (err)
                goto failed_nilfs;

        cno = nilfs_last_cno(nilfs);
        err = nilfs_attach_checkpoint(sb, cno, true, &fsroot);
        if (err) {
                printk(KERN_ERR "NILFS: error loading last checkpoint "
                       "(checkpoint number=%llu).\n", (unsigned long long)cno);
                goto failed_unload;
        }

        if (!(sb->s_flags & MS_RDONLY)) {
                err = nilfs_attach_log_writer(sb, fsroot);
                if (err)
                        goto failed_checkpoint;
        }

        err = nilfs_get_root_dentry(sb, fsroot, &sb->s_root);
        if (err)
                goto failed_segctor;

        nilfs_put_root(fsroot);

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

        return 0;

 failed_segctor:
        nilfs_detach_log_writer(sb);

 failed_checkpoint:
        nilfs_put_root(fsroot);

 failed_unload:
        iput(nilfs->ns_sufile);
        iput(nilfs->ns_cpfile);
        iput(nilfs->ns_dat);

 failed_nilfs:
        destroy_nilfs(nilfs);
        return err;
}

static int nilfs_remount(struct super_block *sb, int *flags, char *data)
{
        struct the_nilfs *nilfs = sb->s_fs_info;
        unsigned long old_sb_flags;
        unsigned long old_mount_opt;
        int err;

        sync_filesystem(sb);
        old_sb_flags = sb->s_flags;
        old_mount_opt = nilfs->ns_mount_opt;

        if (!parse_options(data, sb, 1)) {
                err = -EINVAL;
                goto restore_opts;
        }
        sb->s_flags = (sb->s_flags & ~MS_POSIXACL);

        err = -EINVAL;

        if (!nilfs_valid_fs(nilfs)) {
                printk(KERN_WARNING "NILFS (device %s): couldn't "
                       "remount because the filesystem is in an "
                       "incomplete recovery state.\n", sb->s_id);
                goto restore_opts;
        }

        if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
                goto out;
        if (*flags & MS_RDONLY) {
                /* Shutting down log writer */
                nilfs_detach_log_writer(sb);
                sb->s_flags |= MS_RDONLY;

                /*
                 * Remounting a valid RW partition RDONLY, so set
                 * the RDONLY flag and then mark the partition as valid again.
                 */
                down_write(&nilfs->ns_sem);
                nilfs_cleanup_super(sb);
                up_write(&nilfs->ns_sem);
        } else {
                __u64 features;
                struct nilfs_root *root;

                /*
                 * 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.)
                 */
                down_read(&nilfs->ns_sem);
                features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
                        ~NILFS_FEATURE_COMPAT_RO_SUPP;
                up_read(&nilfs->ns_sem);
                if (features) {
                        printk(KERN_WARNING "NILFS (device %s): couldn't "
                               "remount RDWR because of unsupported optional "
                               "features (%llx)\n",
                               sb->s_id, (unsigned long long)features);
                        err = -EROFS;
                        goto restore_opts;
                }

                sb->s_flags &= ~MS_RDONLY;

                root = NILFS_I(sb->s_root->d_inode)->i_root;
                err = nilfs_attach_log_writer(sb, root);
                if (err)
                        goto restore_opts;

                down_write(&nilfs->ns_sem);
                nilfs_setup_super(sb, true);
                up_write(&nilfs->ns_sem);
        }
 out:
        return 0;

 restore_opts:
        sb->s_flags = old_sb_flags;
        nilfs->ns_mount_opt = old_mount_opt;
        return err;
}

struct nilfs_super_data {
        struct block_device *bdev;
        __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 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 {
                                        sd->cno = simple_strtoull(args[0].from,
                                                                  NULL, 0);
                                        /*
                                         * No need to see the end pointer;
                                         * match_token() has done syntax
                                         * checking.
                                         */
                                        if (sd->cno == 0)
                                                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)
{
        s->s_bdev = data;
        s->s_dev = s->s_bdev->bd_dev;
        return 0;
}

static int nilfs_test_bdev_super(struct super_block *s, void *data)
{
        return (void *)s->s_bdev == data;
}

static struct dentry *
nilfs_mount(struct file_system_type *fs_type, int flags,
             const char *dev_name, void *data)
{
        struct nilfs_super_data sd;
        struct super_block *s;
        fmode_t mode = FMODE_READ | FMODE_EXCL;
        struct dentry *root_dentry;
        int err, s_new = false;

        if (!(flags & MS_RDONLY))
                mode |= FMODE_WRITE;

        sd.bdev = blkdev_get_by_path(dev_name, mode, fs_type);
        if (IS_ERR(sd.bdev))
                return ERR_CAST(sd.bdev);

        sd.cno = 0;
        sd.flags = flags;
        if (nilfs_identify((char *)data, &sd)) {
                err = -EINVAL;
                goto failed;
        }

        /*
         * once the super is inserted into the list by sget, s_umount
         * will protect the lockfs code from trying to start a snapshot
         * while we are mounting
         */
        mutex_lock(&sd.bdev->bd_fsfreeze_mutex);
        if (sd.bdev->bd_fsfreeze_count > 0) {
                mutex_unlock(&sd.bdev->bd_fsfreeze_mutex);
                err = -EBUSY;
                goto failed;
        }
        s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, flags,
                 sd.bdev);
        mutex_unlock(&sd.bdev->bd_fsfreeze_mutex);
        if (IS_ERR(s)) {
                err = PTR_ERR(s);
                goto failed;
        }

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

                s_new = true;

                /* New superblock instance created */
                s->s_mode = mode;
                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_SILENT ? 1 : 0);
                if (err)
                        goto failed_super;

                s->s_flags |= MS_ACTIVE;
        } else if (!sd.cno) {
                if (nilfs_tree_is_busy(s->s_root)) {
                        if ((flags ^ s->s_flags) & MS_RDONLY) {
                                printk(KERN_ERR "NILFS: the device already "
                                       "has a %s mount.\n",
                                       (s->s_flags & MS_RDONLY) ?
                                       "read-only" : "read/write");
                                err = -EBUSY;
                                goto failed_super;
                        }
                } else {
                        /*
                         * Try remount to setup mount states if the current
                         * tree is not mounted and only snapshots use this sb.
                         */
                        err = nilfs_remount(s, &flags, data);
                        if (err)
                                goto failed_super;
                }
        }

        if (sd.cno) {
                err = nilfs_attach_snapshot(s, sd.cno, &root_dentry);
                if (err)
                        goto failed_super;
        } else {
                root_dentry = dget(s->s_root);
        }

        if (!s_new)
                blkdev_put(sd.bdev, mode);

        return root_dentry;

 failed_super:
        deactivate_locked_super(s);

 failed:
        if (!s_new)
                blkdev_put(sd.bdev, mode);
        return ERR_PTR(err);
}

struct file_system_type nilfs_fs_type = {
        .owner    = THIS_MODULE,
        .name     = "nilfs2",
        .mount    = nilfs_mount,
        .kill_sb  = kill_block_super,
        .fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("nilfs2");

static void nilfs_inode_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
        address_space_init_once(&ii->i_btnode_cache);
        ii->i_bmap = &ii->i_bmap_data;
        inode_init_once(&ii->vfs_inode);
}

static void nilfs_segbuf_init_once(void *obj)
{
        memset(obj, 0, sizeof(struct nilfs_segment_buffer));
}

static void nilfs_destroy_cachep(void)
{
        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();

        if (nilfs_inode_cachep)
                kmem_cache_destroy(nilfs_inode_cachep);
        if (nilfs_transaction_cachep)
                kmem_cache_destroy(nilfs_transaction_cachep);
        if (nilfs_segbuf_cachep)
                kmem_cache_destroy(nilfs_segbuf_cachep);
        if (nilfs_btree_path_cache)
                kmem_cache_destroy(nilfs_btree_path_cache);
}

static int __init nilfs_init_cachep(void)
{
        nilfs_inode_cachep = kmem_cache_create("nilfs2_inode_cache",
                        sizeof(struct nilfs_inode_info), 0,
                        SLAB_RECLAIM_ACCOUNT, nilfs_inode_init_once);
        if (!nilfs_inode_cachep)
                goto fail;

        nilfs_transaction_cachep = kmem_cache_create("nilfs2_transaction_cache",
                        sizeof(struct nilfs_transaction_info), 0,
                        SLAB_RECLAIM_ACCOUNT, NULL);
        if (!nilfs_transaction_cachep)
                goto fail;

        nilfs_segbuf_cachep = kmem_cache_create("nilfs2_segbuf_cache",
                        sizeof(struct nilfs_segment_buffer), 0,
                        SLAB_RECLAIM_ACCOUNT, nilfs_segbuf_init_once);
        if (!nilfs_segbuf_cachep)
                goto fail;

        nilfs_btree_path_cache = kmem_cache_create("nilfs2_btree_path_cache",
                        sizeof(struct nilfs_btree_path) * NILFS_BTREE_LEVEL_MAX,
                        0, 0, NULL);
        if (!nilfs_btree_path_cache)
                goto fail;

        return 0;

fail:
        nilfs_destroy_cachep();
        return -ENOMEM;
}

static int __init init_nilfs_fs(void)
{
        int err;

        err = nilfs_init_cachep();
        if (err)
                goto fail;

        err = nilfs_sysfs_init();
        if (err)
                goto free_cachep;

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

        printk(KERN_INFO "NILFS version 2 loaded\n");
        return 0;

deinit_sysfs_entry:
        nilfs_sysfs_exit();
free_cachep:
        nilfs_destroy_cachep();
fail:
        return err;
}

static void __exit exit_nilfs_fs(void)
{
        nilfs_destroy_cachep();
        nilfs_sysfs_exit();
        unregister_filesystem(&nilfs_fs_type);
}

module_init(init_nilfs_fs)
module_exit(exit_nilfs_fs)