nilfs2: meta data file

This adds the meta data file, which serves common buffer functions to the
DAT, sufile, cpfile, ifile, and so forth.

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>

2 files changed, 687 insertions, 0 deletions

diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
new file mode 100644
index 000000000000..6ab847578615
--- /dev/null
+++ b/fs/nilfs2/mdt.c
@@ -0,0 +1,562 @@
+/*
+ * mdt.c - meta data file for NILFS
+ *
+ * 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>
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/mpage.h>
+#include <linux/mm.h>
+#include <linux/writeback.h>
+#include <linux/backing-dev.h>
+#include <linux/swap.h>
+#include "nilfs.h"
+#include "segment.h"
+#include "page.h"
+#include "mdt.h"
+
+
+#define NILFS_MDT_MAX_RA_BLOCKS         (16 - 1)
+
+#define INIT_UNUSED_INODE_FIELDS
+
+static int
+nilfs_mdt_insert_new_block(struct inode *inode, unsigned long block,
+                           struct buffer_head *bh,
+                           void (*init_block)(struct inode *,
+                                              struct buffer_head *, void *))
+{
+        struct nilfs_inode_info *ii = NILFS_I(inode);
+        void *kaddr;
+        int ret;
+
+        /* Caller exclude read accesses using page lock */
+
+        /* set_buffer_new(bh); */
+        bh->b_blocknr = 0;
+
+        ret = nilfs_bmap_insert(ii->i_bmap, block, (unsigned long)bh);
+        if (unlikely(ret))
+                return ret;
+
+        set_buffer_mapped(bh);
+
+        kaddr = kmap_atomic(bh->b_page, KM_USER0);
+        memset(kaddr + bh_offset(bh), 0, 1 << inode->i_blkbits);
+        if (init_block)
+                init_block(inode, bh, kaddr);
+        flush_dcache_page(bh->b_page);
+        kunmap_atomic(kaddr, KM_USER0);
+
+        set_buffer_uptodate(bh);
+        nilfs_mark_buffer_dirty(bh);
+        nilfs_mdt_mark_dirty(inode);
+        return 0;
+}
+
+static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
+                                  struct buffer_head **out_bh,
+                                  void (*init_block)(struct inode *,
+                                                     struct buffer_head *,
+                                                     void *))
+{
+        struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs;
+        struct nilfs_sb_info *writer = NULL;
+        struct super_block *sb = inode->i_sb;
+        struct nilfs_transaction_info ti;
+        struct buffer_head *bh;
+        int err;
+
+        if (!sb) {
+                writer = nilfs_get_writer(nilfs);
+                if (!writer) {
+                        err = -EROFS;
+                        goto out;
+                }
+                sb = writer->s_super;
+        }
+
+        nilfs_transaction_begin(sb, &ti, 0);
+
+        err = -ENOMEM;
+        bh = nilfs_grab_buffer(inode, inode->i_mapping, block, 0);
+        if (unlikely(!bh))
+                goto failed_unlock;
+
+        err = -EEXIST;
+        if (buffer_uptodate(bh) || buffer_mapped(bh))
+                goto failed_bh;
+#if 0
+        /* The uptodate flag is not protected by the page lock, but
+           the mapped flag is.  Thus, we don't have to wait the buffer. */
+        wait_on_buffer(bh);
+        if (buffer_uptodate(bh))
+                goto failed_bh;
+#endif
+
+        bh->b_bdev = nilfs->ns_bdev;
+        err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
+        if (likely(!err)) {
+                get_bh(bh);
+                *out_bh = bh;
+        }
+
+ failed_bh:
+        unlock_page(bh->b_page);
+        page_cache_release(bh->b_page);
+        brelse(bh);
+
+ failed_unlock:
+        nilfs_transaction_end(sb, !err);
+        if (writer)
+                nilfs_put_writer(nilfs);
+ out:
+        return err;
+}
+
+static int
+nilfs_mdt_submit_block(struct inode *inode, unsigned long blkoff,
+                       int mode, struct buffer_head **out_bh)
+{
+        struct buffer_head *bh;
+        unsigned long blknum = 0;
+        int ret = -ENOMEM;
+
+        bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
+        if (unlikely(!bh))
+                goto failed;
+
+        ret = -EEXIST; /* internal code */
+        if (buffer_uptodate(bh))
+                goto out;
+
+        if (mode == READA) {
+                if (!trylock_buffer(bh)) {
+                        ret = -EBUSY;
+                        goto failed_bh;
+                }
+        } else {
+                BUG_ON(mode != READ);
+                lock_buffer(bh);
+        }
+
+        if (buffer_uptodate(bh)) {
+                unlock_buffer(bh);
+                goto out;
+        }
+        if (!buffer_mapped(bh)) { /* unused buffer */
+                ret = nilfs_bmap_lookup(NILFS_I(inode)->i_bmap, blkoff,
+                                        &blknum);
+                if (unlikely(ret)) {
+                        unlock_buffer(bh);
+                        goto failed_bh;
+                }
+                bh->b_bdev = NILFS_MDT(inode)->mi_nilfs->ns_bdev;
+                bh->b_blocknr = blknum;
+                set_buffer_mapped(bh);
+        }
+
+        bh->b_end_io = end_buffer_read_sync;
+        get_bh(bh);
+        submit_bh(mode, bh);
+        ret = 0;
+ out:
+        get_bh(bh);
+        *out_bh = bh;
+
+ failed_bh:
+        unlock_page(bh->b_page);
+        page_cache_release(bh->b_page);
+        brelse(bh);
+ failed:
+        return ret;
+}
+
+static int nilfs_mdt_read_block(struct inode *inode, unsigned long block,
+                                struct buffer_head **out_bh)
+{
+        struct buffer_head *first_bh, *bh;
+        unsigned long blkoff;
+        int i, nr_ra_blocks = NILFS_MDT_MAX_RA_BLOCKS;
+        int err;
+
+        err = nilfs_mdt_submit_block(inode, block, READ, &first_bh);
+        if (err == -EEXIST) /* internal code */
+                goto out;
+
+        if (unlikely(err))
+                goto failed;
+
+        blkoff = block + 1;
+        for (i = 0; i < nr_ra_blocks; i++, blkoff++) {
+                err = nilfs_mdt_submit_block(inode, blkoff, READA, &bh);
+                if (likely(!err || err == -EEXIST))
+                        brelse(bh);
+                else if (err != -EBUSY)
+                        break; /* abort readahead if bmap lookup failed */
+
+                if (!buffer_locked(first_bh))
+                        goto out_no_wait;
+        }
+
+        wait_on_buffer(first_bh);
+
+ out_no_wait:
+        err = -EIO;
+        if (!buffer_uptodate(first_bh))
+                goto failed_bh;
+ out:
+        *out_bh = first_bh;
+        return 0;
+
+ failed_bh:
+        brelse(first_bh);
+ failed:
+        return err;
+}
+
+/**
+ * nilfs_mdt_get_block - read or create a buffer on meta data file.
+ * @inode: inode of the meta data file
+ * @blkoff: block offset
+ * @create: create flag
+ * @init_block: initializer used for newly allocated block
+ * @out_bh: output of a pointer to the buffer_head
+ *
+ * nilfs_mdt_get_block() looks up the specified buffer and tries to create
+ * a new buffer if @create is not zero.  On success, the returned buffer is
+ * assured to be either existing or formatted using a buffer lock on success.
+ * @out_bh is substituted only when zero is returned.
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - the specified block does not exist (hole block)
+ *
+ * %-EINVAL - bmap is broken. (the caller should call nilfs_error())
+ *
+ * %-EROFS - Read only filesystem (for create mode)
+ */
+int nilfs_mdt_get_block(struct inode *inode, unsigned long blkoff, int create,
+                        void (*init_block)(struct inode *,
+                                           struct buffer_head *, void *),
+                        struct buffer_head **out_bh)
+{
+        int ret;
+
+        /* Should be rewritten with merging nilfs_mdt_read_block() */
+ retry:
+        ret = nilfs_mdt_read_block(inode, blkoff, out_bh);
+        if (!create || ret != -ENOENT)
+                return ret;
+
+        ret = nilfs_mdt_create_block(inode, blkoff, out_bh, init_block);
+        if (unlikely(ret == -EEXIST)) {
+                /* create = 0; */  /* limit read-create loop retries */
+                goto retry;
+        }
+        return ret;
+}
+
+/**
+ * nilfs_mdt_delete_block - make a hole on the meta data file.
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * Return Value: On success, zero is returned.
+ * On error, one of the following negative error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-EINVAL - bmap is broken. (the caller should call nilfs_error())
+ */
+int nilfs_mdt_delete_block(struct inode *inode, unsigned long block)
+{
+        struct nilfs_inode_info *ii = NILFS_I(inode);
+        int err;
+
+        err = nilfs_bmap_delete(ii->i_bmap, block);
+        if (likely(!err)) {
+                nilfs_mdt_mark_dirty(inode);
+                nilfs_mdt_forget_block(inode, block);
+        }
+        return err;
+}
+
+/**
+ * nilfs_mdt_forget_block - discard dirty state and try to remove the page
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * nilfs_mdt_forget_block() clears a dirty flag of the specified buffer, and
+ * tries to release the page including the buffer from a page cache.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error code is returned.
+ *
+ * %-EBUSY - page has an active buffer.
+ *
+ * %-ENOENT - page cache has no page addressed by the offset.
+ */
+int nilfs_mdt_forget_block(struct inode *inode, unsigned long block)
+{
+        pgoff_t index = (pgoff_t)block >>
+                (PAGE_CACHE_SHIFT - inode->i_blkbits);
+        struct page *page;
+        unsigned long first_block;
+        int ret = 0;
+        int still_dirty;
+
+        page = find_lock_page(inode->i_mapping, index);
+        if (!page)
+                return -ENOENT;
+
+        wait_on_page_writeback(page);
+
+        first_block = (unsigned long)index <<
+                (PAGE_CACHE_SHIFT - inode->i_blkbits);
+        if (page_has_buffers(page)) {
+                struct buffer_head *bh;
+
+                bh = nilfs_page_get_nth_block(page, block - first_block);
+                nilfs_forget_buffer(bh);
+        }
+        still_dirty = PageDirty(page);
+        unlock_page(page);
+        page_cache_release(page);
+
+        if (still_dirty ||
+            invalidate_inode_pages2_range(inode->i_mapping, index, index) != 0)
+                ret = -EBUSY;
+        return ret;
+}
+
+/**
+ * nilfs_mdt_mark_block_dirty - mark a block on the meta data file dirty.
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - the specified block does not exist (hole block)
+ *
+ * %-EINVAL - bmap is broken. (the caller should call nilfs_error())
+ */
+int nilfs_mdt_mark_block_dirty(struct inode *inode, unsigned long block)
+{
+        struct buffer_head *bh;
+        int err;
+
+        err = nilfs_mdt_read_block(inode, block, &bh);
+        if (unlikely(err))
+                return err;
+        nilfs_mark_buffer_dirty(bh);
+        nilfs_mdt_mark_dirty(inode);
+        brelse(bh);
+        return 0;
+}
+
+int nilfs_mdt_fetch_dirty(struct inode *inode)
+{
+        struct nilfs_inode_info *ii = NILFS_I(inode);
+
+        if (nilfs_bmap_test_and_clear_dirty(ii->i_bmap)) {
+                set_bit(NILFS_I_DIRTY, &ii->i_state);
+                return 1;
+        }
+        return test_bit(NILFS_I_DIRTY, &ii->i_state);
+}
+
+static int
+nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
+{
+        struct inode *inode = container_of(page->mapping,
+                                           struct inode, i_data);
+        struct super_block *sb = inode->i_sb;
+        struct nilfs_sb_info *writer = NULL;
+        int err = 0;
+
+        redirty_page_for_writepage(wbc, page);
+        unlock_page(page);
+
+        if (page->mapping->assoc_mapping)
+                return 0; /* Do not request flush for shadow page cache */
+        if (!sb) {
+                writer = nilfs_get_writer(NILFS_MDT(inode)->mi_nilfs);
+                if (!writer)
+                        return -EROFS;
+                sb = writer->s_super;
+        }
+
+        if (wbc->sync_mode == WB_SYNC_ALL)
+                err = nilfs_construct_segment(sb);
+        else if (wbc->for_reclaim)
+                nilfs_flush_segment(sb, inode->i_ino);
+
+        if (writer)
+                nilfs_put_writer(NILFS_MDT(inode)->mi_nilfs);
+        return err;
+}
+
+
+static struct address_space_operations def_mdt_aops = {
+        .writepage              = nilfs_mdt_write_page,
+};
+
+static struct inode_operations def_mdt_iops;
+static struct file_operations def_mdt_fops;
+
+/*
+ * NILFS2 uses pseudo inodes for meta data files such as DAT, cpfile, sufile,
+ * ifile, or gcinodes.  This allows the B-tree code and segment constructor
+ * to treat them like regular files, and this helps to simplify the
+ * implementation.
+ *   On the other hand, some of the pseudo inodes have an irregular point:
+ * They don't have valid inode->i_sb pointer because their lifetimes are
+ * longer than those of the super block structs; they may continue for
+ * several consecutive mounts/umounts.  This would need discussions.
+ */
+struct inode *
+nilfs_mdt_new_common(struct the_nilfs *nilfs, struct super_block *sb,
+                     ino_t ino, gfp_t gfp_mask)
+{
+        struct inode *inode = nilfs_alloc_inode(sb);
+
+        if (!inode)
+                return NULL;
+        else {
+                struct address_space * const mapping = &inode->i_data;
+                struct nilfs_mdt_info *mi = kzalloc(sizeof(*mi), GFP_NOFS);
+
+                if (!mi) {
+                        nilfs_destroy_inode(inode);
+                        return NULL;
+                }
+                mi->mi_nilfs = nilfs;
+                init_rwsem(&mi->mi_sem);
+
+                inode->i_sb = sb; /* sb may be NULL for some meta data files */
+                inode->i_blkbits = nilfs->ns_blocksize_bits;
+                inode->i_flags = 0;
+                atomic_set(&inode->i_count, 1);
+                inode->i_nlink = 1;
+                inode->i_ino = ino;
+                inode->i_mode = S_IFREG;
+                inode->i_private = mi;
+
+#ifdef INIT_UNUSED_INODE_FIELDS
+                atomic_set(&inode->i_writecount, 0);
+                inode->i_size = 0;
+                inode->i_blocks = 0;
+                inode->i_bytes = 0;
+                inode->i_generation = 0;
+#ifdef CONFIG_QUOTA
+                memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
+#endif
+                inode->i_pipe = NULL;
+                inode->i_bdev = NULL;
+                inode->i_cdev = NULL;
+                inode->i_rdev = 0;
+#ifdef CONFIG_SECURITY
+                inode->i_security = NULL;
+#endif
+                inode->dirtied_when = 0;
+
+                INIT_LIST_HEAD(&inode->i_list);
+                INIT_LIST_HEAD(&inode->i_sb_list);
+                inode->i_state = 0;
+#endif
+
+                spin_lock_init(&inode->i_lock);
+                mutex_init(&inode->i_mutex);
+                init_rwsem(&inode->i_alloc_sem);
+
+                mapping->host = NULL;  /* instead of inode */
+                mapping->flags = 0;
+                mapping_set_gfp_mask(mapping, gfp_mask);
+                mapping->assoc_mapping = NULL;
+                mapping->backing_dev_info = nilfs->ns_bdi;
+
+                inode->i_mapping = mapping;
+        }
+
+        return inode;
+}
+
+struct inode *nilfs_mdt_new(struct the_nilfs *nilfs, struct super_block *sb,
+                            ino_t ino, gfp_t gfp_mask)
+{
+        struct inode *inode = nilfs_mdt_new_common(nilfs, sb, ino, gfp_mask);
+
+        if (!inode)
+                return NULL;
+
+        inode->i_op = &def_mdt_iops;
+        inode->i_fop = &def_mdt_fops;
+        inode->i_mapping->a_ops = &def_mdt_aops;
+        return inode;
+}
+
+void nilfs_mdt_set_entry_size(struct inode *inode, unsigned entry_size,
+                              unsigned header_size)
+{
+        struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+
+        mi->mi_entry_size = entry_size;
+        mi->mi_entries_per_block = (1 << inode->i_blkbits) / entry_size;
+        mi->mi_first_entry_offset = DIV_ROUND_UP(header_size, entry_size);
+}
+
+void nilfs_mdt_set_shadow(struct inode *orig, struct inode *shadow)
+{
+        shadow->i_mapping->assoc_mapping = orig->i_mapping;
+        NILFS_I(shadow)->i_btnode_cache.assoc_mapping =
+                &NILFS_I(orig)->i_btnode_cache;
+}
+
+void nilfs_mdt_clear(struct inode *inode)
+{
+        struct nilfs_inode_info *ii = NILFS_I(inode);
+
+        invalidate_mapping_pages(inode->i_mapping, 0, -1);
+        truncate_inode_pages(inode->i_mapping, 0);
+
+        nilfs_bmap_clear(ii->i_bmap);
+        nilfs_btnode_cache_clear(&ii->i_btnode_cache);
+}
+
+void nilfs_mdt_destroy(struct inode *inode)
+{
+        struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
+
+        kfree(mdi->mi_bgl); /* kfree(NULL) is safe */
+        kfree(mdi);
+        nilfs_destroy_inode(inode);
+}
diff --git a/fs/nilfs2/mdt.h b/fs/nilfs2/mdt.h
new file mode 100644
index 000000000000..df683e0bca6a
--- /dev/null
+++ b/fs/nilfs2/mdt.h
@@ -0,0 +1,125 @@
+/*
+ * mdt.h - NILFS meta data file prototype and definitions
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * Written by Ryusuke Konishi <ryusuke@osrg.net>
+ */
+
+#ifndef _NILFS_MDT_H
+#define _NILFS_MDT_H
+
+#include <linux/buffer_head.h>
+#include <linux/blockgroup_lock.h>
+#include "nilfs.h"
+#include "page.h"
+
+/**
+ * struct nilfs_mdt_info - on-memory private data of meta data files
+ * @mi_nilfs: back pointer to the_nilfs struct
+ * @mi_sem: reader/writer semaphore for meta data operations
+ * @mi_bgl: per-blockgroup locking
+ * @mi_entry_size: size of an entry
+ * @mi_first_entry_offset: offset to the first entry
+ * @mi_entries_per_block: number of entries in a block
+ * @mi_blocks_per_group: number of blocks in a group
+ * @mi_blocks_per_desc_block: number of blocks per descriptor block
+ */
+struct nilfs_mdt_info {
+        struct the_nilfs       *mi_nilfs;
+        struct rw_semaphore     mi_sem;
+        struct blockgroup_lock *mi_bgl;
+        unsigned                mi_entry_size;
+        unsigned                mi_first_entry_offset;
+        unsigned long           mi_entries_per_block;
+        unsigned long           mi_blocks_per_group;
+        unsigned long           mi_blocks_per_desc_block;
+};
+
+static inline struct nilfs_mdt_info *NILFS_MDT(const struct inode *inode)
+{
+        return inode->i_private;
+}
+
+static inline struct the_nilfs *NILFS_I_NILFS(struct inode *inode)
+{
+        struct super_block *sb = inode->i_sb;
+
+        return sb ? NILFS_SB(sb)->s_nilfs : NILFS_MDT(inode)->mi_nilfs;
+}
+
+/* Default GFP flags using highmem */
+#define NILFS_MDT_GFP      (__GFP_WAIT | __GFP_IO | __GFP_HIGHMEM)
+
+int nilfs_mdt_get_block(struct inode *, unsigned long, int,
+                        void (*init_block)(struct inode *,
+                                           struct buffer_head *, void *),
+                        struct buffer_head **);
+int nilfs_mdt_delete_block(struct inode *, unsigned long);
+int nilfs_mdt_forget_block(struct inode *, unsigned long);
+int nilfs_mdt_mark_block_dirty(struct inode *, unsigned long);
+int nilfs_mdt_fetch_dirty(struct inode *);
+
+struct inode *nilfs_mdt_new(struct the_nilfs *, struct super_block *, ino_t,
+                            gfp_t);
+struct inode *nilfs_mdt_new_common(struct the_nilfs *, struct super_block *,
+                                   ino_t, gfp_t);
+void nilfs_mdt_destroy(struct inode *);
+void nilfs_mdt_clear(struct inode *);
+void nilfs_mdt_set_entry_size(struct inode *, unsigned, unsigned);
+void nilfs_mdt_set_shadow(struct inode *, struct inode *);
+
+
+#define nilfs_mdt_mark_buffer_dirty(bh) nilfs_mark_buffer_dirty(bh)
+
+static inline void nilfs_mdt_mark_dirty(struct inode *inode)
+{
+        if (!test_bit(NILFS_I_DIRTY, &NILFS_I(inode)->i_state))
+                set_bit(NILFS_I_DIRTY, &NILFS_I(inode)->i_state);
+}
+
+static inline void nilfs_mdt_clear_dirty(struct inode *inode)
+{
+        clear_bit(NILFS_I_DIRTY, &NILFS_I(inode)->i_state);
+}
+
+static inline __u64 nilfs_mdt_cno(struct inode *inode)
+{
+        return NILFS_MDT(inode)->mi_nilfs->ns_cno;
+}
+
+#define nilfs_mdt_bgl_lock(inode, bg) \
+        (&NILFS_MDT(inode)->mi_bgl->locks[(bg) & (NR_BG_LOCKS-1)].lock)
+
+
+static inline int
+nilfs_mdt_read_inode_direct(struct inode *inode, struct buffer_head *bh,
+                            unsigned n)
+{
+        return nilfs_read_inode_common(
+                inode, (struct nilfs_inode *)(bh->b_data + n));
+}
+
+static inline void
+nilfs_mdt_write_inode_direct(struct inode *inode, struct buffer_head *bh,
+                             unsigned n)
+{
+        nilfs_write_inode_common(
+                inode, (struct nilfs_inode *)(bh->b_data + n), 1);
+}
+
+#endif /* _NILFS_MDT_H */