nilfs2: super block operations
Ryusuke Konishi [Tue, 7 Apr 2009 02:01:35 +0000 (19:01 -0700)]
This adds super block operations for the nilfs2 file system.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/super.c [new file with mode: 0644]

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
new file mode 100644 (file)
index 0000000..10e82c0
--- /dev/null
@@ -0,0 +1,1366 @@
+/*
+ * 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 "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_VERSION(NILFS_VERSION);
+MODULE_LICENSE("GPL");
+
+static int nilfs_remount(struct super_block *sb, int *flags, char *data);
+static int test_exclusive_mount(struct file_system_type *fs_type,
+                               struct block_device *bdev, int flags);
+
+/**
+ * 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->s_state |= cpu_to_le16(NILFS_ERROR_FS);
+                       nilfs_commit_super(sbi);
+               }
+               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(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->vfs_inode.i_version = 1;
+       nilfs_btnode_cache_init(&ii->i_btnode_cache);
+       return &ii->vfs_inode;
+}
+
+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);
+       struct nilfs_transaction_info ti;
+       struct nilfs_sb_info *sbi = NILFS_SB(inode->i_sb);
+
+#ifdef CONFIG_NILFS_POSIX_ACL
+       if (ii->i_acl && ii->i_acl != NILFS_ACL_NOT_CACHED) {
+               posix_acl_release(ii->i_acl);
+               ii->i_acl = NILFS_ACL_NOT_CACHED;
+       }
+       if (ii->i_default_acl && ii->i_default_acl != NILFS_ACL_NOT_CACHED) {
+               posix_acl_release(ii->i_default_acl);
+               ii->i_default_acl = NILFS_ACL_NOT_CACHED;
+       }
+#endif
+       /*
+        * Free resources allocated in nilfs_read_inode(), here.
+        */
+       nilfs_transaction_begin(inode->i_sb, &ti, 0);
+
+       spin_lock(&sbi->s_inode_lock);
+       if (!list_empty(&ii->i_dirty))
+               list_del_init(&ii->i_dirty);
+       brelse(ii->i_bh);
+       ii->i_bh = NULL;
+       spin_unlock(&sbi->s_inode_lock);
+
+       if (test_bit(NILFS_I_BMAP, &ii->i_state))
+               nilfs_bmap_clear(ii->i_bmap);
+
+       nilfs_btnode_cache_clear(&ii->i_btnode_cache);
+
+       nilfs_transaction_end(inode->i_sb, 0);
+}
+
+/**
+ * nilfs_update_last_segment - change pointer to the latest segment
+ * @sbi: nilfs_sb_info
+ * @update_cno: flag whether to update checkpoint number.
+ *
+ * nilfs_update_last_segment() changes information in the super block
+ * after a partial segment is written out successfully. The super
+ * block is marked dirty. It will be written out at the next VFS sync
+ * operations such as sync_supers() and generic_shutdown_super().
+ */
+void nilfs_update_last_segment(struct nilfs_sb_info *sbi, int update_cno)
+{
+       struct the_nilfs *nilfs = sbi->s_nilfs;
+       struct nilfs_super_block *sbp = nilfs->ns_sbp;
+
+       /* nilfs->sem must be locked by the caller. */
+       spin_lock(&nilfs->ns_last_segment_lock);
+       if (update_cno)
+               nilfs->ns_last_cno = nilfs->ns_cno++;
+       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);
+
+       sbi->s_super->s_dirt = 1; /* must be set if delaying the call of
+                                    nilfs_commit_super() */
+}
+
+static int nilfs_sync_super(struct nilfs_sb_info *sbi)
+{
+       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);
+               barrier_done = 1;
+       }
+ retry:
+       set_buffer_dirty(nilfs->ns_sbh);
+       err = sync_dirty_buffer(nilfs->ns_sbh);
+       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);
+               goto retry;
+       }
+       if (unlikely(err))
+               printk(KERN_ERR
+                      "NILFS: unable to write superblock (err=%d)\n", err);
+       else {
+               nilfs_dispose_used_segments(nilfs);
+               clear_nilfs_discontinued(nilfs);
+       }
+
+       return err;
+}
+
+int nilfs_commit_super(struct nilfs_sb_info *sbi)
+{
+       struct the_nilfs *nilfs = sbi->s_nilfs;
+       struct nilfs_super_block *sbp = nilfs->ns_sbp;
+       sector_t nfreeblocks;
+       int err;
+
+       /* nilfs->sem must be locked by the caller. */
+       err = nilfs_count_free_blocks(nilfs, &nfreeblocks);
+       if (unlikely(err)) {
+               printk(KERN_ERR "NILFS: failed to count free blocks\n");
+               return err;
+       }
+       sbp->s_free_blocks_count = cpu_to_le64(nfreeblocks);
+       sbp->s_wtime = cpu_to_le64(get_seconds());
+       sbp->s_sum = 0;
+       sbp->s_sum = crc32_le(nilfs->ns_crc_seed, (unsigned char *)sbp,
+                             le16_to_cpu(sbp->s_bytes));
+
+       sbi->s_super->s_dirt = 0;
+       return nilfs_sync_super(sbi);
+}
+
+static void nilfs_put_super(struct super_block *sb)
+{
+       struct nilfs_sb_info *sbi = NILFS_SB(sb);
+       struct the_nilfs *nilfs = sbi->s_nilfs;
+
+       nilfs_detach_segment_constructor(sbi);
+
+       if (!(sb->s_flags & MS_RDONLY)) {
+               down_write(&nilfs->ns_sem);
+               nilfs->ns_sbp->s_state = cpu_to_le16(nilfs->ns_mount_state);
+               nilfs_commit_super(sbi);
+               up_write(&nilfs->ns_sem);
+       }
+
+       nilfs_detach_checkpoint(sbi);
+       put_nilfs(sbi->s_nilfs);
+       sbi->s_super = NULL;
+       sb->s_fs_info = NULL;
+       kfree(sbi);
+}
+
+/**
+ * nilfs_write_super - write super block(s) of NILFS
+ * @sb: super_block
+ *
+ * nilfs_write_super() gets a fs-dependent lock, writes super block(s), and
+ * clears s_dirt.  This function is called in the section protected by
+ * lock_super().
+ *
+ * The s_dirt flag is managed by each filesystem and we protect it by ns_sem
+ * of the struct the_nilfs.  Lock order must be as follows:
+ *
+ *   1. lock_super()
+ *   2.    down_write(&nilfs->ns_sem)
+ *
+ * Inside NILFS, locking ns_sem is enough to protect s_dirt and the buffer
+ * of the super block (nilfs->ns_sbp).
+ *
+ * In most cases, VFS functions call lock_super() before calling these
+ * methods.  So we must be careful not to bring on deadlocks when using
+ * lock_super();  see generic_shutdown_super(), write_super(), and so on.
+ *
+ * Note that order of lock_kernel() and lock_super() depends on contexts
+ * of VFS.  We should also note that lock_kernel() can be used in its
+ * protective section and only the outermost one has an effect.
+ */
+static void nilfs_write_super(struct super_block *sb)
+{
+       struct nilfs_sb_info *sbi = NILFS_SB(sb);
+       struct the_nilfs *nilfs = sbi->s_nilfs;
+
+       down_write(&nilfs->ns_sem);
+       if (!(sb->s_flags & MS_RDONLY))
+               nilfs_commit_super(sbi);
+       sb->s_dirt = 0;
+       up_write(&nilfs->ns_sem);
+}
+
+static int nilfs_sync_fs(struct super_block *sb, int wait)
+{
+       int err = 0;
+
+       /* This function is called when super block should be written back */
+       if (wait)
+               err = nilfs_construct_segment(sb);
+       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_sem);
+       list_add(&sbi->s_list, &nilfs->ns_supers);
+       up_write(&nilfs->ns_sem);
+
+       sbi->s_ifile = nilfs_mdt_new(
+               nilfs, sbi->s_super, NILFS_IFILE_INO, NILFS_IFILE_GFP);
+       if (!sbi->s_ifile)
+               return -ENOMEM;
+
+       err = nilfs_palloc_init_blockgroup(sbi->s_ifile, nilfs->ns_inode_size);
+       if (unlikely(err))
+               goto failed;
+
+       err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, cno, 0, &raw_cp,
+                                         &bh_cp);
+       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_sem);
+       list_del_init(&sbi->s_list);
+       up_write(&nilfs->ns_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_sem);
+       list_del_init(&sbi->s_list);
+       up_write(&nilfs->ns_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);
+               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);
+       unsigned long long blocks;
+       unsigned long overhead;
+       unsigned long nrsvblocks;
+       sector_t nfreeblocks;
+       struct the_nilfs *nilfs = sbi->s_nilfs;
+       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;
+       return 0;
+}
+
+static 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 */
+};
+
+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 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;
+       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);
+}
+
+struct nilfs_super_block *
+nilfs_load_super_block(struct super_block *sb, struct buffer_head **pbh)
+{
+       int blocksize;
+       unsigned long offset, sb_index;
+
+       /*
+        * Adjusting block size
+        * Blocksize will be enlarged when it is smaller than hardware
+        * sector size.
+        * Disk format of superblock does not change.
+        */
+       blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
+       if (!blocksize) {
+               printk(KERN_ERR
+                      "NILFS: unable to set blocksize of superblock\n");
+               return NULL;
+       }
+       sb_index = NILFS_SB_OFFSET_BYTES / blocksize;
+       offset = NILFS_SB_OFFSET_BYTES % blocksize;
+
+       *pbh = sb_bread(sb, sb_index);
+       if (!*pbh) {
+               printk(KERN_ERR "NILFS: unable to read superblock\n");
+               return NULL;
+       }
+       return (struct nilfs_super_block *)((char *)(*pbh)->b_data + offset);
+}
+
+struct nilfs_super_block *
+nilfs_reload_super_block(struct super_block *sb, struct buffer_head **pbh,
+                        int blocksize)
+{
+       struct nilfs_super_block *sbp;
+       unsigned long offset, sb_index;
+       int hw_blocksize = bdev_hardsect_size(sb->s_bdev);
+
+       if (blocksize < hw_blocksize) {
+               printk(KERN_ERR
+                      "NILFS: blocksize %d too small for device "
+                      "(sector-size = %d).\n",
+                      blocksize, hw_blocksize);
+               goto failed_sbh;
+       }
+       brelse(*pbh);
+       sb_set_blocksize(sb, blocksize);
+
+       sb_index = NILFS_SB_OFFSET_BYTES / blocksize;
+       offset = NILFS_SB_OFFSET_BYTES % blocksize;
+
+       *pbh = sb_bread(sb, sb_index);
+       if (!*pbh) {
+               printk(KERN_ERR
+                      "NILFS: cannot read superblock on 2nd try.\n");
+               goto failed;
+       }
+
+       sbp = (struct nilfs_super_block *)((char *)(*pbh)->b_data + offset);
+       if (sbp->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
+               printk(KERN_ERR
+                      "NILFS: !? Magic mismatch on 2nd try.\n");
+               goto failed_sbh;
+       }
+       return sbp;
+
+ failed_sbh:
+       brelse(*pbh);
+
+ failed:
+       return NULL;
+}
+
+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);
+
+       /* trying to fill super (1st stage) */
+       sb->s_magic = le16_to_cpu(sbp->s_magic);
+
+       /* FS independent flags */
+#ifdef NILFS_ATIME_DISABLE
+       sb->s_flags |= MS_NOATIME;
+#endif
+
+       if (sb->s_magic != NILFS_SUPER_MAGIC) {
+               printk("NILFS: Can't find nilfs on dev %s.\n", sb->s_id);
+               return -EINVAL;
+       }
+
+       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);
+
+       if (!parse_options(data, sb))
+               return -EINVAL;
+
+       return 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 bd_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;
+
+       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;
+
+       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)) {
+                       if (!nilfs_cpfile_is_snapshot(nilfs->ns_cpfile,
+                                                     sbi->s_snapshot_cno)) {
+                               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, NULL);
+               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;
+       }
+
+       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;
+       kfree(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;
+
+       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;
+               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);
+               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.)
+                */
+               down(&sb->s_bdev->bd_mount_sem);
+               /* Check existing RW-mount */
+               if (test_exclusive_mount(sb->s_type, sb->s_bdev, 0)) {
+                       printk(KERN_WARNING "NILFS (device %s): couldn't "
+                              "remount because a RW-mount exists.\n",
+                              sb->s_id);
+                       err = -EBUSY;
+                       goto rw_remount_failed;
+               }
+               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 rw_remount_failed;
+               }
+               sb->s_flags &= ~MS_RDONLY;
+               nilfs_clear_opt(sbi, SNAPSHOT);
+               sbi->s_snapshot_cno = 0;
+
+               err = nilfs_attach_segment_constructor(sbi, NULL);
+               if (err)
+                       goto rw_remount_failed;
+
+               down_write(&nilfs->ns_sem);
+               nilfs_setup_super(sbi);
+               up_write(&nilfs->ns_sem);
+
+               up(&sb->s_bdev->bd_mount_sem);
+       }
+ out:
+       return 0;
+
+ rw_remount_failed:
+       up(&sb->s_bdev->bd_mount_sem);
+ restore_opts:
+       sb->s_flags = old_sb_flags;
+       sbi->s_mount_opt = old_opts.mount_opt;
+       sbi->s_snapshot_cno = old_opts.snapshot_cno;
+       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 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 s->s_bdev == sd->bdev;
+}
+
+static int nilfs_test_bdev_super2(struct super_block *s, void *data)
+{
+       struct nilfs_super_data *sd = data;
+       int ret;
+
+       if (s->s_bdev != sd->bdev)
+               return 0;
+
+       if (!((s->s_flags | sd->flags) & MS_RDONLY))
+               return 1; /* Reuse an old R/W-mode super_block */
+
+       if (s->s_flags & sd->flags & MS_RDONLY) {
+               if (down_read_trylock(&s->s_umount)) {
+                       ret = s->s_root &&
+                               (sd->cno == NILFS_SB(s)->s_snapshot_cno);
+                       up_read(&s->s_umount);
+                       /*
+                        * This path is locked with sb_lock by sget().
+                        * So, drop_super() causes deadlock.
+                        */
+                       return ret;
+               }
+       }
+       return 0;
+}
+
+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, *s2;
+       struct the_nilfs *nilfs = NULL;
+       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.
+        * The results are passed in sget() using nilfs_super_data.
+        */
+       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
+        */
+       down(&sd.bdev->bd_mount_sem);
+       if (!sd.cno &&
+           (err = test_exclusive_mount(fs_type, sd.bdev, flags ^ MS_RDONLY))) {
+               err = (err < 0) ? : -EBUSY;
+               goto failed_unlock;
+       }
+
+       /*
+        * Phase-1: search any existent instance and get the_nilfs
+        */
+       s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
+       if (IS_ERR(s))
+               goto error_s;
+
+       if (!s->s_root) {
+               err = -ENOMEM;
+               nilfs = alloc_nilfs(sd.bdev);
+               if (!nilfs)
+                       goto cancel_new;
+       } else {
+               struct nilfs_sb_info *sbi = NILFS_SB(s);
+
+               BUG_ON(!sbi || !sbi->s_nilfs);
+               /*
+                * s_umount protects super_block from unmount process;
+                * It covers pointers of nilfs_sb_info and the_nilfs.
+                */
+               nilfs = sbi->s_nilfs;
+               get_nilfs(nilfs);
+               up_write(&s->s_umount);
+
+               /*
+                * Phase-2: search specified snapshot or R/W mode super_block
+                */
+               if (!sd.cno)
+                       /* trying to get the latest checkpoint.  */
+                       sd.cno = nilfs_last_cno(nilfs);
+
+               s2 = sget(fs_type, nilfs_test_bdev_super2,
+                         nilfs_set_bdev_super, &sd);
+               deactivate_super(s);
+               /*
+                * Although deactivate_super() invokes close_bdev_exclusive() at
+                * kill_block_super().  Here, s is an existent mount; we need
+                * one more close_bdev_exclusive() call.
+                */
+               s = s2;
+               if (IS_ERR(s))
+                       goto error_s;
+       }
+
+       if (!s->s_root) {
+               char b[BDEVNAME_SIZE];
+
+               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;
+       } else if (!(s->s_flags & MS_RDONLY)) {
+               err = -EBUSY;
+       }
+
+       up(&sd.bdev->bd_mount_sem);
+       put_nilfs(nilfs);
+       if (need_to_close)
+               close_bdev_exclusive(sd.bdev, flags);
+       simple_set_mnt(mnt, s);
+       return 0;
+
+ error_s:
+       up(&sd.bdev->bd_mount_sem);
+       if (nilfs)
+               put_nilfs(nilfs);
+       close_bdev_exclusive(sd.bdev, flags);
+       return PTR_ERR(s);
+
+ failed_unlock:
+       up(&sd.bdev->bd_mount_sem);
+ failed:
+       close_bdev_exclusive(sd.bdev, flags);
+
+       return err;
+
+ cancel_new:
+       /* Abandoning the newly allocated superblock */
+       up(&sd.bdev->bd_mount_sem);
+       if (nilfs)
+               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() and unlocking bd_mount_sem need the block device.
+        */
+       return err;
+}
+
+static int nilfs_test_bdev_super3(struct super_block *s, void *data)
+{
+       struct nilfs_super_data *sd = data;
+       int ret;
+
+       if (s->s_bdev != sd->bdev)
+               return 0;
+       if (down_read_trylock(&s->s_umount)) {
+               ret = (s->s_flags & MS_RDONLY) && s->s_root &&
+                       nilfs_test_opt(NILFS_SB(s), SNAPSHOT);
+               up_read(&s->s_umount);
+               if (ret)
+                       return 0; /* ignore snapshot mounts */
+       }
+       return !((sd->flags ^ s->s_flags) & MS_RDONLY);
+}
+
+static int __false_bdev_super(struct super_block *s, void *data)
+{
+#if 0 /* XXX: workaround for lock debug. This is not good idea */
+       up_write(&s->s_umount);
+#endif
+       return -EFAULT;
+}
+
+/**
+ * test_exclusive_mount - check whether an exclusive RW/RO mount exists or not.
+ * fs_type: filesystem type
+ * bdev: block device
+ * flag: 0 (check rw-mount) or MS_RDONLY (check ro-mount)
+ * res: pointer to an integer to store result
+ *
+ * This function must be called within a section protected by bd_mount_mutex.
+ */
+static int test_exclusive_mount(struct file_system_type *fs_type,
+                               struct block_device *bdev, int flags)
+{
+       struct super_block *s;
+       struct nilfs_super_data sd = { .flags = flags, .bdev = bdev };
+
+       s = sget(fs_type, nilfs_test_bdev_super3, __false_bdev_super, &sd);
+       if (IS_ERR(s)) {
+               if (PTR_ERR(s) != -EFAULT)
+                       return PTR_ERR(s);
+               return 0;  /* Not found */
+       }
+       up_write(&s->s_umount);
+       deactivate_super(s);
+       return 1;  /* Found */
+}
+
+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)