nilfs2: super block operations

This adds super block operations for the nilfs2 file system.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/super.c

+/*
+ * 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)