nilfs2: segment buffer

This adds the segment buffer which is used to constuct logs.

[akpm@linux-foundation.org: BIO_RW_SYNC got removed]
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, 664 insertions, 0 deletions

diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
new file mode 100644
index 000000000000..3d3ea8351f6d
--- /dev/null
+++ b/fs/nilfs2/segbuf.c
@@ -0,0 +1,461 @@
+/*
+ * segbuf.c - NILFS segment buffer
+ *
+ * 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/writeback.h>
+#include <linux/crc32.h>
+#include "page.h"
+#include "segbuf.h"
+#include "seglist.h"
+
+
+static struct kmem_cache *nilfs_segbuf_cachep;
+
+static void nilfs_segbuf_init_once(void *obj)
+{
+        memset(obj, 0, sizeof(struct nilfs_segment_buffer));
+}
+
+int __init nilfs_init_segbuf_cache(void)
+{
+        nilfs_segbuf_cachep =
+                kmem_cache_create("nilfs2_segbuf_cache",
+                                  sizeof(struct nilfs_segment_buffer),
+                                  0, SLAB_RECLAIM_ACCOUNT,
+                                  nilfs_segbuf_init_once);
+
+        return (nilfs_segbuf_cachep == NULL) ? -ENOMEM : 0;
+}
+
+void nilfs_destroy_segbuf_cache(void)
+{
+        kmem_cache_destroy(nilfs_segbuf_cachep);
+}
+
+struct nilfs_segment_buffer *nilfs_segbuf_new(struct super_block *sb)
+{
+        struct nilfs_segment_buffer *segbuf;
+
+        segbuf = kmem_cache_alloc(nilfs_segbuf_cachep, GFP_NOFS);
+        if (unlikely(!segbuf))
+                return NULL;
+
+        segbuf->sb_super = sb;
+        INIT_LIST_HEAD(&segbuf->sb_list);
+        INIT_LIST_HEAD(&segbuf->sb_segsum_buffers);
+        INIT_LIST_HEAD(&segbuf->sb_payload_buffers);
+        segbuf->sb_segent = NULL;
+        return segbuf;
+}
+
+void nilfs_segbuf_free(struct nilfs_segment_buffer *segbuf)
+{
+        struct nilfs_segment_entry *ent = segbuf->sb_segent;
+
+        if (ent != NULL && list_empty(&ent->list)) {
+                /* free isolated segment list head */
+                nilfs_free_segment_entry(segbuf->sb_segent);
+                segbuf->sb_segent = NULL;
+        }
+        kmem_cache_free(nilfs_segbuf_cachep, segbuf);
+}
+
+int nilfs_segbuf_map(struct nilfs_segment_buffer *segbuf, __u64 segnum,
+                     unsigned long offset, struct the_nilfs *nilfs)
+{
+        struct nilfs_segment_entry *ent;
+
+        segbuf->sb_segnum = segnum;
+        nilfs_get_segment_range(nilfs, segnum, &segbuf->sb_fseg_start,
+                                &segbuf->sb_fseg_end);
+
+        segbuf->sb_pseg_start = segbuf->sb_fseg_start + offset;
+        segbuf->sb_rest_blocks =
+                segbuf->sb_fseg_end - segbuf->sb_pseg_start + 1;
+
+        /* Attach a segment list head */
+        ent = segbuf->sb_segent;
+        if (ent == NULL) {
+                segbuf->sb_segent = nilfs_alloc_segment_entry(segnum);
+                if (unlikely(!segbuf->sb_segent))
+                        return -ENOMEM;
+        } else {
+                BUG_ON(ent->bh_su || !list_empty(&ent->list));
+                ent->segnum = segnum;
+        }
+        return 0;
+}
+
+void nilfs_segbuf_set_next_segnum(struct nilfs_segment_buffer *segbuf,
+                                  __u64 nextnum, struct the_nilfs *nilfs)
+{
+        segbuf->sb_nextnum = nextnum;
+        segbuf->sb_sum.next = nilfs_get_segment_start_blocknr(nilfs, nextnum);
+}
+
+int nilfs_segbuf_extend_segsum(struct nilfs_segment_buffer *segbuf)
+{
+        struct buffer_head *bh;
+
+        bh = sb_getblk(segbuf->sb_super,
+                       segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk);
+        if (unlikely(!bh))
+                return -ENOMEM;
+
+        nilfs_segbuf_add_segsum_buffer(segbuf, bh);
+        return 0;
+}
+
+int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *segbuf,
+                                struct buffer_head **bhp)
+{
+        struct buffer_head *bh;
+
+        bh = sb_getblk(segbuf->sb_super,
+                       segbuf->sb_pseg_start + segbuf->sb_sum.nblocks);
+        if (unlikely(!bh))
+                return -ENOMEM;
+
+        nilfs_segbuf_add_payload_buffer(segbuf, bh);
+        *bhp = bh;
+        return 0;
+}
+
+int nilfs_segbuf_reset(struct nilfs_segment_buffer *segbuf, unsigned flags,
+                       time_t ctime)
+{
+        int err;
+
+        segbuf->sb_sum.nblocks = segbuf->sb_sum.nsumblk = 0;
+        err = nilfs_segbuf_extend_segsum(segbuf);
+        if (unlikely(err))
+                return err;
+
+        segbuf->sb_sum.flags = flags;
+        segbuf->sb_sum.sumbytes = sizeof(struct nilfs_segment_summary);
+        segbuf->sb_sum.nfinfo = segbuf->sb_sum.nfileblk = 0;
+        segbuf->sb_sum.ctime = ctime;
+
+        segbuf->sb_io_error = 0;
+        return 0;
+}
+
+/*
+ * Setup segument summary
+ */
+void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *segbuf)
+{
+        struct nilfs_segment_summary *raw_sum;
+        struct buffer_head *bh_sum;
+
+        bh_sum = list_entry(segbuf->sb_segsum_buffers.next,
+                            struct buffer_head, b_assoc_buffers);
+        raw_sum = (struct nilfs_segment_summary *)bh_sum->b_data;
+
+        raw_sum->ss_magic    = cpu_to_le32(NILFS_SEGSUM_MAGIC);
+        raw_sum->ss_bytes    = cpu_to_le16(sizeof(*raw_sum));
+        raw_sum->ss_flags    = cpu_to_le16(segbuf->sb_sum.flags);
+        raw_sum->ss_seq      = cpu_to_le64(segbuf->sb_sum.seg_seq);
+        raw_sum->ss_create   = cpu_to_le64(segbuf->sb_sum.ctime);
+        raw_sum->ss_next     = cpu_to_le64(segbuf->sb_sum.next);
+        raw_sum->ss_nblocks  = cpu_to_le32(segbuf->sb_sum.nblocks);
+        raw_sum->ss_nfinfo   = cpu_to_le32(segbuf->sb_sum.nfinfo);
+        raw_sum->ss_sumbytes = cpu_to_le32(segbuf->sb_sum.sumbytes);
+        raw_sum->ss_pad      = 0;
+}
+
+/*
+ * CRC calculation routines
+ */
+void nilfs_segbuf_fill_in_segsum_crc(struct nilfs_segment_buffer *segbuf,
+                                     u32 seed)
+{
+        struct buffer_head *bh;
+        struct nilfs_segment_summary *raw_sum;
+        unsigned long size, bytes = segbuf->sb_sum.sumbytes;
+        u32 crc;
+
+        bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
+                        b_assoc_buffers);
+
+        raw_sum = (struct nilfs_segment_summary *)bh->b_data;
+        size = min_t(unsigned long, bytes, bh->b_size);
+        crc = crc32_le(seed,
+                       (unsigned char *)raw_sum +
+                       sizeof(raw_sum->ss_datasum) + sizeof(raw_sum->ss_sumsum),
+                       size - (sizeof(raw_sum->ss_datasum) +
+                               sizeof(raw_sum->ss_sumsum)));
+
+        list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
+                                     b_assoc_buffers) {
+                bytes -= size;
+                size = min_t(unsigned long, bytes, bh->b_size);
+                crc = crc32_le(crc, bh->b_data, size);
+        }
+        raw_sum->ss_sumsum = cpu_to_le32(crc);
+}
+
+void nilfs_segbuf_fill_in_data_crc(struct nilfs_segment_buffer *segbuf,
+                                   u32 seed)
+{
+        struct buffer_head *bh;
+        struct nilfs_segment_summary *raw_sum;
+        void *kaddr;
+        u32 crc;
+
+        bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
+                        b_assoc_buffers);
+        raw_sum = (struct nilfs_segment_summary *)bh->b_data;
+        crc = crc32_le(seed,
+                       (unsigned char *)raw_sum + sizeof(raw_sum->ss_datasum),
+                       bh->b_size - sizeof(raw_sum->ss_datasum));
+
+        list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
+                                     b_assoc_buffers) {
+                crc = crc32_le(crc, bh->b_data, bh->b_size);
+        }
+        list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
+                kaddr = kmap_atomic(bh->b_page, KM_USER0);
+                crc = crc32_le(crc, kaddr + bh_offset(bh), bh->b_size);
+                kunmap_atomic(kaddr, KM_USER0);
+        }
+        raw_sum->ss_datasum = cpu_to_le32(crc);
+}
+
+void nilfs_release_buffers(struct list_head *list)
+{
+        struct buffer_head *bh, *n;
+
+        list_for_each_entry_safe(bh, n, list, b_assoc_buffers) {
+                list_del_init(&bh->b_assoc_buffers);
+                if (buffer_nilfs_allocated(bh)) {
+                        struct page *clone_page = bh->b_page;
+
+                        /* remove clone page */
+                        brelse(bh);
+                        page_cache_release(clone_page); /* for each bh */
+                        if (page_count(clone_page) <= 2) {
+                                lock_page(clone_page);
+                                nilfs_free_private_page(clone_page);
+                        }
+                        continue;
+                }
+                brelse(bh);
+        }
+}
+
+/*
+ * BIO operations
+ */
+static void nilfs_end_bio_write(struct bio *bio, int err)
+{
+        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+        struct nilfs_write_info *wi = bio->bi_private;
+
+        if (err == -EOPNOTSUPP) {
+                set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
+                bio_put(bio);
+                /* to be detected by submit_seg_bio() */
+        }
+
+        if (!uptodate)
+                atomic_inc(&wi->err);
+
+        bio_put(bio);
+        complete(&wi->bio_event);
+}
+
+static int nilfs_submit_seg_bio(struct nilfs_write_info *wi, int mode)
+{
+        struct bio *bio = wi->bio;
+        int err;
+
+        if (wi->nbio > 0 && bdi_write_congested(wi->bdi)) {
+                wait_for_completion(&wi->bio_event);
+                wi->nbio--;
+                if (unlikely(atomic_read(&wi->err))) {
+                        bio_put(bio);
+                        err = -EIO;
+                        goto failed;
+                }
+        }
+
+        bio->bi_end_io = nilfs_end_bio_write;
+        bio->bi_private = wi;
+        bio_get(bio);
+        submit_bio(mode, bio);
+        if (bio_flagged(bio, BIO_EOPNOTSUPP)) {
+                bio_put(bio);
+                err = -EOPNOTSUPP;
+                goto failed;
+        }
+        wi->nbio++;
+        bio_put(bio);
+
+        wi->bio = NULL;
+        wi->rest_blocks -= wi->end - wi->start;
+        wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
+        wi->start = wi->end;
+        return 0;
+
+ failed:
+        wi->bio = NULL;
+        return err;
+}
+
+/**
+ * nilfs_alloc_seg_bio - allocate a bio for writing segment.
+ * @sb: super block
+ * @start: beginning disk block number of this BIO.
+ * @nr_vecs: request size of page vector.
+ *
+ * alloc_seg_bio() allocates a new BIO structure and initialize it.
+ *
+ * Return Value: On success, pointer to the struct bio is returned.
+ * On error, NULL is returned.
+ */
+static struct bio *nilfs_alloc_seg_bio(struct super_block *sb, sector_t start,
+                                       int nr_vecs)
+{
+        struct bio *bio;
+
+        bio = bio_alloc(GFP_NOWAIT, nr_vecs);
+        if (bio == NULL) {
+                while (!bio && (nr_vecs >>= 1))
+                        bio = bio_alloc(GFP_NOWAIT, nr_vecs);
+        }
+        if (likely(bio)) {
+                bio->bi_bdev = sb->s_bdev;
+                bio->bi_sector = (sector_t)start << (sb->s_blocksize_bits - 9);
+        }
+        return bio;
+}
+
+void nilfs_segbuf_prepare_write(struct nilfs_segment_buffer *segbuf,
+                                struct nilfs_write_info *wi)
+{
+        wi->bio = NULL;
+        wi->rest_blocks = segbuf->sb_sum.nblocks;
+        wi->max_pages = bio_get_nr_vecs(wi->sb->s_bdev);
+        wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
+        wi->start = wi->end = 0;
+        wi->nbio = 0;
+        wi->blocknr = segbuf->sb_pseg_start;
+
+        atomic_set(&wi->err, 0);
+        init_completion(&wi->bio_event);
+}
+
+static int nilfs_submit_bh(struct nilfs_write_info *wi, struct buffer_head *bh,
+                           int mode)
+{
+        int len, err;
+
+        BUG_ON(wi->nr_vecs <= 0);
+ repeat:
+        if (!wi->bio) {
+                wi->bio = nilfs_alloc_seg_bio(wi->sb, wi->blocknr + wi->end,
+                                              wi->nr_vecs);
+                if (unlikely(!wi->bio))
+                        return -ENOMEM;
+        }
+
+        len = bio_add_page(wi->bio, bh->b_page, bh->b_size, bh_offset(bh));
+        if (len == bh->b_size) {
+                wi->end++;
+                return 0;
+        }
+        /* bio is FULL */
+        err = nilfs_submit_seg_bio(wi, mode);
+        /* never submit current bh */
+        if (likely(!err))
+                goto repeat;
+        return err;
+}
+
+int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
+                       struct nilfs_write_info *wi)
+{
+        struct buffer_head *bh;
+        int res, rw = WRITE;
+
+        list_for_each_entry(bh, &segbuf->sb_segsum_buffers, b_assoc_buffers) {
+                res = nilfs_submit_bh(wi, bh, rw);
+                if (unlikely(res))
+                        goto failed_bio;
+        }
+
+        list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
+                res = nilfs_submit_bh(wi, bh, rw);
+                if (unlikely(res))
+                        goto failed_bio;
+        }
+
+        if (wi->bio) {
+                /*
+                 * Last BIO is always sent through the following
+                 * submission.
+                 */
+                rw |= (1 << BIO_RW_SYNCIO);
+                res = nilfs_submit_seg_bio(wi, rw);
+                if (unlikely(res))
+                        goto failed_bio;
+        }
+
+        res = 0;
+ out:
+        return res;
+
+ failed_bio:
+        atomic_inc(&wi->err);
+        goto out;
+}
+
+/**
+ * nilfs_segbuf_wait - wait for completion of requested BIOs
+ * @wi: nilfs_write_info
+ *
+ * Return Value: On Success, 0 is returned. On Error, one of the following
+ * negative error code is returned.
+ *
+ * %-EIO - I/O error
+ */
+int nilfs_segbuf_wait(struct nilfs_segment_buffer *segbuf,
+                      struct nilfs_write_info *wi)
+{
+        int err = 0;
+
+        if (!wi->nbio)
+                return 0;
+
+        do {
+                wait_for_completion(&wi->bio_event);
+        } while (--wi->nbio > 0);
+
+        if (unlikely(atomic_read(&wi->err) > 0)) {
+                printk(KERN_ERR "NILFS: IO error writing segment\n");
+                err = -EIO;
+                segbuf->sb_io_error = 1;
+        }
+        return err;
+}
diff --git a/fs/nilfs2/segbuf.h b/fs/nilfs2/segbuf.h
new file mode 100644
index 000000000000..25f2a5faa483
--- /dev/null
+++ b/fs/nilfs2/segbuf.h
@@ -0,0 +1,203 @@
+/*
+ * segbuf.h - NILFS Segment buffer prototypes 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_SEGBUF_H
+#define _NILFS_SEGBUF_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/bio.h>
+#include <linux/completion.h>
+#include <linux/backing-dev.h>
+
+/**
+ * struct nilfs_segsum_info - On-memory segment summary
+ * @flags: Flags
+ * @nfinfo: Number of file information structures
+ * @nblocks: Number of blocks included in the partial segment
+ * @nsumblk: Number of summary blocks
+ * @sumbytes: Byte count of segment summary
+ * @nfileblk: Total number of file blocks
+ * @seg_seq: Segment sequence number
+ * @ctime: Creation time
+ * @next: Block number of the next full segment
+ */
+struct nilfs_segsum_info {
+        unsigned int            flags;
+        unsigned long           nfinfo;
+        unsigned long           nblocks;
+        unsigned long           nsumblk;
+        unsigned long           sumbytes;
+        unsigned long           nfileblk;
+        u64                     seg_seq;
+        time_t                  ctime;
+        sector_t                next;
+};
+
+/* macro for the flags */
+#define NILFS_SEG_HAS_SR(sum)    ((sum)->flags & NILFS_SS_SR)
+#define NILFS_SEG_LOGBGN(sum)    ((sum)->flags & NILFS_SS_LOGBGN)
+#define NILFS_SEG_LOGEND(sum)    ((sum)->flags & NILFS_SS_LOGEND)
+#define NILFS_SEG_DSYNC(sum)     ((sum)->flags & NILFS_SS_SYNDT)
+#define NILFS_SEG_SIMPLEX(sum) \
+        (((sum)->flags & (NILFS_SS_LOGBGN | NILFS_SS_LOGEND)) == \
+         (NILFS_SS_LOGBGN | NILFS_SS_LOGEND))
+
+#define NILFS_SEG_EMPTY(sum)    ((sum)->nblocks == (sum)->nsumblk)
+
+/**
+ * struct nilfs_segment_buffer - Segment buffer
+ * @sb_super: back pointer to a superblock struct
+ * @sb_list: List head to chain this structure
+ * @sb_segent: Pointer for attaching a segment entry
+ * @sb_sum: On-memory segment summary
+ * @sb_segnum: Index number of the full segment
+ * @sb_nextnum: Index number of the next full segment
+ * @sb_fseg_start: Start block number of the full segment
+ * @sb_fseg_end: End block number of the full segment
+ * @sb_pseg_start: Disk block number of partial segment
+ * @sb_rest_blocks: Number of residual blocks in the current segment
+ * @sb_segsum_buffers: List of buffers for segment summaries
+ * @sb_payload_buffers: List of buffers for segment payload
+ * @sb_io_error: I/O error status
+ */
+struct nilfs_segment_buffer {
+        struct super_block     *sb_super;
+        struct list_head        sb_list;
+        struct nilfs_segment_entry *sb_segent;
+
+        /* Segment information */
+        struct nilfs_segsum_info sb_sum;
+        __u64                   sb_segnum;
+        __u64                   sb_nextnum;
+        sector_t                sb_fseg_start, sb_fseg_end;
+        sector_t                sb_pseg_start;
+        unsigned                sb_rest_blocks;
+
+        /* Buffers */
+        struct list_head        sb_segsum_buffers;
+        struct list_head        sb_payload_buffers; /* including super root */
+
+        /* io status */
+        int                     sb_io_error;
+};
+
+#define NILFS_LIST_SEGBUF(head)  \
+        list_entry((head), struct nilfs_segment_buffer, sb_list)
+#define NILFS_NEXT_SEGBUF(segbuf)  NILFS_LIST_SEGBUF((segbuf)->sb_list.next)
+#define NILFS_PREV_SEGBUF(segbuf)  NILFS_LIST_SEGBUF((segbuf)->sb_list.prev)
+#define NILFS_LAST_SEGBUF(head)    NILFS_LIST_SEGBUF((head)->prev)
+#define NILFS_FIRST_SEGBUF(head)   NILFS_LIST_SEGBUF((head)->next)
+#define NILFS_SEGBUF_IS_LAST(segbuf, head)  ((segbuf)->sb_list.next == (head))
+
+#define nilfs_for_each_segbuf_before(s, t, h) \
+        for ((s) = NILFS_FIRST_SEGBUF(h); (s) != (t); \
+             (s) = NILFS_NEXT_SEGBUF(s))
+
+#define NILFS_SEGBUF_FIRST_BH(head)  \
+        (list_entry((head)->next, struct buffer_head, b_assoc_buffers))
+#define NILFS_SEGBUF_NEXT_BH(bh)  \
+        (list_entry((bh)->b_assoc_buffers.next, struct buffer_head, \
+                    b_assoc_buffers))
+#define NILFS_SEGBUF_BH_IS_LAST(bh, head)  ((bh)->b_assoc_buffers.next == head)
+
+
+int __init nilfs_init_segbuf_cache(void);
+void nilfs_destroy_segbuf_cache(void);
+struct nilfs_segment_buffer *nilfs_segbuf_new(struct super_block *);
+void nilfs_segbuf_free(struct nilfs_segment_buffer *);
+int nilfs_segbuf_map(struct nilfs_segment_buffer *, __u64, unsigned long,
+                     struct the_nilfs *);
+void nilfs_segbuf_set_next_segnum(struct nilfs_segment_buffer *, __u64,
+                                  struct the_nilfs *);
+int nilfs_segbuf_reset(struct nilfs_segment_buffer *, unsigned, time_t);
+int nilfs_segbuf_extend_segsum(struct nilfs_segment_buffer *);
+int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *,
+                                struct buffer_head **);
+void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *);
+void nilfs_segbuf_fill_in_segsum_crc(struct nilfs_segment_buffer *, u32);
+void nilfs_segbuf_fill_in_data_crc(struct nilfs_segment_buffer *, u32);
+
+static inline void
+nilfs_segbuf_add_segsum_buffer(struct nilfs_segment_buffer *segbuf,
+                               struct buffer_head *bh)
+{
+        list_add_tail(&bh->b_assoc_buffers, &segbuf->sb_segsum_buffers);
+        segbuf->sb_sum.nblocks++;
+        segbuf->sb_sum.nsumblk++;
+}
+
+static inline void
+nilfs_segbuf_add_payload_buffer(struct nilfs_segment_buffer *segbuf,
+                                struct buffer_head *bh)
+{
+        list_add_tail(&bh->b_assoc_buffers, &segbuf->sb_payload_buffers);
+        segbuf->sb_sum.nblocks++;
+}
+
+static inline void
+nilfs_segbuf_add_file_buffer(struct nilfs_segment_buffer *segbuf,
+                             struct buffer_head *bh)
+{
+        get_bh(bh);
+        nilfs_segbuf_add_payload_buffer(segbuf, bh);
+        segbuf->sb_sum.nfileblk++;
+}
+
+void nilfs_release_buffers(struct list_head *);
+
+static inline void nilfs_segbuf_clear(struct nilfs_segment_buffer *segbuf)
+{
+        nilfs_release_buffers(&segbuf->sb_segsum_buffers);
+        nilfs_release_buffers(&segbuf->sb_payload_buffers);
+}
+
+struct nilfs_write_info {
+        struct bio             *bio;
+        int                     start, end; /* The region to be submitted */
+        int                     rest_blocks;
+        int                     max_pages;
+        int                     nr_vecs;
+        sector_t                blocknr;
+
+        int                     nbio;
+        atomic_t                err;
+        struct completion       bio_event;
+                                /* completion event of segment write */
+
+        /*
+         * The following fields must be set explicitly
+         */
+        struct super_block     *sb;
+        struct backing_dev_info *bdi; /* backing dev info */
+        struct buffer_head     *bh_sr;
+};
+
+
+void nilfs_segbuf_prepare_write(struct nilfs_segment_buffer *,
+                                struct nilfs_write_info *);
+int nilfs_segbuf_write(struct nilfs_segment_buffer *,
+                       struct nilfs_write_info *);
+int nilfs_segbuf_wait(struct nilfs_segment_buffer *,
+                      struct nilfs_write_info *);
+
+#endif /* _NILFS_SEGBUF_H */