/*
   * segment.c - NILFS segment constructor.
   *
   * 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/pagemap.h>
  #include <linux/buffer_head.h>
  #include <linux/writeback.h>
  #include <linux/bio.h>
  #include <linux/completion.h>
  #include <linux/blkdev.h>
  #include <linux/backing-dev.h>
  #include <linux/freezer.h>
  #include <linux/kthread.h>
  #include <linux/crc32.h>
  #include <linux/pagevec.h>

  #include <linux/slab.h>

  #include "nilfs.h"
  #include "btnode.h"
  #include "page.h"
  #include "segment.h"
  #include "sufile.h"
  #include "cpfile.h"
  #include "ifile.h"

  #include "segbuf.h"
  
  
  /*
   * Segment constructor
   */
  #define SC_N_INODEVEC	16   /* Size of locally allocated inode vector */
  
  #define SC_MAX_SEGDELTA 64   /* Upper limit of the number of segments
  				appended in collection retry loop */
  
  /* Construction mode */
  enum {
  	SC_LSEG_SR = 1,	/* Make a logical segment having a super root */
  	SC_LSEG_DSYNC,	/* Flush data blocks of a given file and make
  			   a logical segment without a super root */
  	SC_FLUSH_FILE,	/* Flush data files, leads to segment writes without
  			   creating a checkpoint */
  	SC_FLUSH_DAT,	/* Flush DAT file. This also creates segments without
  			   a checkpoint */
  };
  
  /* Stage numbers of dirty block collection */
  enum {
  	NILFS_ST_INIT = 0,
  	NILFS_ST_GC,		/* Collecting dirty blocks for GC */
  	NILFS_ST_FILE,

  	NILFS_ST_IFILE,
  	NILFS_ST_CPFILE,
  	NILFS_ST_SUFILE,
  	NILFS_ST_DAT,
  	NILFS_ST_SR,		/* Super root */
  	NILFS_ST_DSYNC,		/* Data sync blocks */
  	NILFS_ST_DONE,
  };
  
  /* State flags of collection */
  #define NILFS_CF_NODE		0x0001	/* Collecting node blocks */
  #define NILFS_CF_IFILE_STARTED	0x0002	/* IFILE stage has started */

  #define NILFS_CF_SUFREED	0x0004	/* segment usages has been freed */
  #define NILFS_CF_HISTORY_MASK	(NILFS_CF_IFILE_STARTED | NILFS_CF_SUFREED)

  
  /* Operations depending on the construction mode and file type */
  struct nilfs_sc_operations {
  	int (*collect_data)(struct nilfs_sc_info *, struct buffer_head *,
  			    struct inode *);
  	int (*collect_node)(struct nilfs_sc_info *, struct buffer_head *,
  			    struct inode *);
  	int (*collect_bmap)(struct nilfs_sc_info *, struct buffer_head *,
  			    struct inode *);
  	void (*write_data_binfo)(struct nilfs_sc_info *,
  				 struct nilfs_segsum_pointer *,
  				 union nilfs_binfo *);
  	void (*write_node_binfo)(struct nilfs_sc_info *,
  				 struct nilfs_segsum_pointer *,
  				 union nilfs_binfo *);
  };
  
  /*
   * Other definitions
   */
  static void nilfs_segctor_start_timer(struct nilfs_sc_info *);
  static void nilfs_segctor_do_flush(struct nilfs_sc_info *, int);
  static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *);

  static void nilfs_dispose_list(struct the_nilfs *, struct list_head *, int);

  
  #define nilfs_cnt32_gt(a, b)   \
  	(typecheck(__u32, a) && typecheck(__u32, b) && \
  	 ((__s32)(b) - (__s32)(a) < 0))
  #define nilfs_cnt32_ge(a, b)   \
  	(typecheck(__u32, a) && typecheck(__u32, b) && \
  	 ((__s32)(a) - (__s32)(b) >= 0))
  #define nilfs_cnt32_lt(a, b)  nilfs_cnt32_gt(b, a)
  #define nilfs_cnt32_le(a, b)  nilfs_cnt32_ge(b, a)

  static int nilfs_prepare_segment_lock(struct nilfs_transaction_info *ti)
  {
  	struct nilfs_transaction_info *cur_ti = current->journal_info;
  	void *save = NULL;
  
  	if (cur_ti) {
  		if (cur_ti->ti_magic == NILFS_TI_MAGIC)
  			return ++cur_ti->ti_count;
  		else {
  			/*
  			 * If journal_info field is occupied by other FS,

  			 * it is saved and will be restored on
  			 * nilfs_transaction_commit().

  			 */
  			printk(KERN_WARNING
  			       "NILFS warning: journal info from a different "
  			       "FS
  ");
  			save = current->journal_info;
  		}
  	}
  	if (!ti) {
  		ti = kmem_cache_alloc(nilfs_transaction_cachep, GFP_NOFS);
  		if (!ti)
  			return -ENOMEM;
  		ti->ti_flags = NILFS_TI_DYNAMIC_ALLOC;
  	} else {
  		ti->ti_flags = 0;
  	}
  	ti->ti_count = 0;
  	ti->ti_save = save;
  	ti->ti_magic = NILFS_TI_MAGIC;
  	current->journal_info = ti;
  	return 0;
  }
  
  /**
   * nilfs_transaction_begin - start indivisible file operations.
   * @sb: super block
   * @ti: nilfs_transaction_info
   * @vacancy_check: flags for vacancy rate checks
   *
   * nilfs_transaction_begin() acquires a reader/writer semaphore, called
   * the segment semaphore, to make a segment construction and write tasks

   * exclusive.  The function is used with nilfs_transaction_commit() in pairs.

   * The region enclosed by these two functions can be nested.  To avoid a
   * deadlock, the semaphore is only acquired or released in the outermost call.
   *
   * This function allocates a nilfs_transaction_info struct to keep context
   * information on it.  It is initialized and hooked onto the current task in
   * the outermost call.  If a pre-allocated struct is given to @ti, it is used

   * instead; otherwise a new struct is assigned from a slab.

   *
   * When @vacancy_check flag is set, this function will check the amount of
   * free space, and will wait for the GC to reclaim disk space if low capacity.
   *
   * Return Value: On success, 0 is returned. On error, one of the following
   * negative error code is returned.
   *
   * %-ENOMEM - Insufficient memory available.
   *

   * %-ENOSPC - No space left on device
   */
  int nilfs_transaction_begin(struct super_block *sb,
  			    struct nilfs_transaction_info *ti,
  			    int vacancy_check)
  {

  	struct the_nilfs *nilfs;
  	int ret = nilfs_prepare_segment_lock(ti);
  
  	if (unlikely(ret < 0))
  		return ret;
  	if (ret > 0)
  		return 0;

  	sb_start_intwrite(sb);

  	nilfs = sb->s_fs_info;

  	down_read(&nilfs->ns_segctor_sem);
  	if (vacancy_check && nilfs_near_disk_full(nilfs)) {
  		up_read(&nilfs->ns_segctor_sem);
  		ret = -ENOSPC;
  		goto failed;
  	}
  	return 0;
  
   failed:
  	ti = current->journal_info;
  	current->journal_info = ti->ti_save;
  	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
  		kmem_cache_free(nilfs_transaction_cachep, ti);

  	sb_end_intwrite(sb);

  	return ret;
  }
  
  /**

   * nilfs_transaction_commit - commit indivisible file operations.

   * @sb: super block

   *

   * nilfs_transaction_commit() releases the read semaphore which is
   * acquired by nilfs_transaction_begin(). This is only performed
   * in outermost call of this function.  If a commit flag is set,
   * nilfs_transaction_commit() sets a timer to start the segment
   * constructor.  If a sync flag is set, it starts construction
   * directly.

   */

  int nilfs_transaction_commit(struct super_block *sb)

  {
  	struct nilfs_transaction_info *ti = current->journal_info;

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	int err = 0;
  
  	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);

  	ti->ti_flags |= NILFS_TI_COMMIT;

  	if (ti->ti_count > 0) {
  		ti->ti_count--;
  		return 0;
  	}

  	if (nilfs->ns_writer) {
  		struct nilfs_sc_info *sci = nilfs->ns_writer;

  		if (ti->ti_flags & NILFS_TI_COMMIT)
  			nilfs_segctor_start_timer(sci);

  		if (atomic_read(&nilfs->ns_ndirtyblks) > sci->sc_watermark)

  			nilfs_segctor_do_flush(sci, 0);
  	}

  	up_read(&nilfs->ns_segctor_sem);

  	current->journal_info = ti->ti_save;
  
  	if (ti->ti_flags & NILFS_TI_SYNC)
  		err = nilfs_construct_segment(sb);
  	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
  		kmem_cache_free(nilfs_transaction_cachep, ti);

  	sb_end_intwrite(sb);

  	return err;
  }

  void nilfs_transaction_abort(struct super_block *sb)
  {
  	struct nilfs_transaction_info *ti = current->journal_info;

  	struct the_nilfs *nilfs = sb->s_fs_info;

  
  	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
  	if (ti->ti_count > 0) {
  		ti->ti_count--;
  		return;
  	}

  	up_read(&nilfs->ns_segctor_sem);

  
  	current->journal_info = ti->ti_save;
  	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
  		kmem_cache_free(nilfs_transaction_cachep, ti);

  	sb_end_intwrite(sb);

  }

  void nilfs_relax_pressure_in_lock(struct super_block *sb)
  {

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	struct nilfs_sc_info *sci = nilfs->ns_writer;

  
  	if (!sci || !sci->sc_flush_request)
  		return;
  
  	set_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
  	up_read(&nilfs->ns_segctor_sem);
  
  	down_write(&nilfs->ns_segctor_sem);
  	if (sci->sc_flush_request &&
  	    test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags)) {
  		struct nilfs_transaction_info *ti = current->journal_info;
  
  		ti->ti_flags |= NILFS_TI_WRITER;
  		nilfs_segctor_do_immediate_flush(sci);
  		ti->ti_flags &= ~NILFS_TI_WRITER;
  	}
  	downgrade_write(&nilfs->ns_segctor_sem);
  }

  static void nilfs_transaction_lock(struct super_block *sb,

  				   struct nilfs_transaction_info *ti,
  				   int gcflag)
  {
  	struct nilfs_transaction_info *cur_ti = current->journal_info;

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	struct nilfs_sc_info *sci = nilfs->ns_writer;

  	WARN_ON(cur_ti);

  	ti->ti_flags = NILFS_TI_WRITER;
  	ti->ti_count = 0;
  	ti->ti_save = cur_ti;
  	ti->ti_magic = NILFS_TI_MAGIC;
  	INIT_LIST_HEAD(&ti->ti_garbage);
  	current->journal_info = ti;
  
  	for (;;) {

  		down_write(&nilfs->ns_segctor_sem);
  		if (!test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags))

  			break;

  		nilfs_segctor_do_immediate_flush(sci);

  		up_write(&nilfs->ns_segctor_sem);

  		yield();
  	}
  	if (gcflag)
  		ti->ti_flags |= NILFS_TI_GC;
  }

  static void nilfs_transaction_unlock(struct super_block *sb)

  {
  	struct nilfs_transaction_info *ti = current->journal_info;

  	struct the_nilfs *nilfs = sb->s_fs_info;

  
  	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
  	BUG_ON(ti->ti_count > 0);

  	up_write(&nilfs->ns_segctor_sem);

  	current->journal_info = ti->ti_save;
  	if (!list_empty(&ti->ti_garbage))

  		nilfs_dispose_list(nilfs, &ti->ti_garbage, 0);

  }
  
  static void *nilfs_segctor_map_segsum_entry(struct nilfs_sc_info *sci,
  					    struct nilfs_segsum_pointer *ssp,
  					    unsigned bytes)
  {
  	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
  	unsigned blocksize = sci->sc_super->s_blocksize;
  	void *p;
  
  	if (unlikely(ssp->offset + bytes > blocksize)) {
  		ssp->offset = 0;
  		BUG_ON(NILFS_SEGBUF_BH_IS_LAST(ssp->bh,
  					       &segbuf->sb_segsum_buffers));
  		ssp->bh = NILFS_SEGBUF_NEXT_BH(ssp->bh);
  	}
  	p = ssp->bh->b_data + ssp->offset;
  	ssp->offset += bytes;
  	return p;
  }
  
  /**
   * nilfs_segctor_reset_segment_buffer - reset the current segment buffer
   * @sci: nilfs_sc_info
   */
  static int nilfs_segctor_reset_segment_buffer(struct nilfs_sc_info *sci)
  {
  	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
  	struct buffer_head *sumbh;
  	unsigned sumbytes;
  	unsigned flags = 0;
  	int err;
  
  	if (nilfs_doing_gc())
  		flags = NILFS_SS_GC;

  	err = nilfs_segbuf_reset(segbuf, flags, sci->sc_seg_ctime, sci->sc_cno);

  	if (unlikely(err))
  		return err;
  
  	sumbh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
  	sumbytes = segbuf->sb_sum.sumbytes;
  	sci->sc_finfo_ptr.bh = sumbh;  sci->sc_finfo_ptr.offset = sumbytes;
  	sci->sc_binfo_ptr.bh = sumbh;  sci->sc_binfo_ptr.offset = sumbytes;
  	sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
  	return 0;
  }
  
  static int nilfs_segctor_feed_segment(struct nilfs_sc_info *sci)
  {
  	sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
  	if (NILFS_SEGBUF_IS_LAST(sci->sc_curseg, &sci->sc_segbufs))
  		return -E2BIG; /* The current segment is filled up
  				  (internal code) */
  	sci->sc_curseg = NILFS_NEXT_SEGBUF(sci->sc_curseg);
  	return nilfs_segctor_reset_segment_buffer(sci);
  }
  
  static int nilfs_segctor_add_super_root(struct nilfs_sc_info *sci)
  {
  	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
  	int err;
  
  	if (segbuf->sb_sum.nblocks >= segbuf->sb_rest_blocks) {
  		err = nilfs_segctor_feed_segment(sci);
  		if (err)
  			return err;
  		segbuf = sci->sc_curseg;
  	}

  	err = nilfs_segbuf_extend_payload(segbuf, &segbuf->sb_super_root);

  	if (likely(!err))
  		segbuf->sb_sum.flags |= NILFS_SS_SR;
  	return err;
  }
  
  /*
   * Functions for making segment summary and payloads
   */
  static int nilfs_segctor_segsum_block_required(
  	struct nilfs_sc_info *sci, const struct nilfs_segsum_pointer *ssp,
  	unsigned binfo_size)
  {
  	unsigned blocksize = sci->sc_super->s_blocksize;
  	/* Size of finfo and binfo is enough small against blocksize */
  
  	return ssp->offset + binfo_size +
  		(!sci->sc_blk_cnt ? sizeof(struct nilfs_finfo) : 0) >
  		blocksize;
  }
  
  static void nilfs_segctor_begin_finfo(struct nilfs_sc_info *sci,
  				      struct inode *inode)
  {
  	sci->sc_curseg->sb_sum.nfinfo++;
  	sci->sc_binfo_ptr = sci->sc_finfo_ptr;
  	nilfs_segctor_map_segsum_entry(
  		sci, &sci->sc_binfo_ptr, sizeof(struct nilfs_finfo));

  	if (NILFS_I(inode)->i_root &&
  	    !test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))

  		set_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);

  	/* skip finfo */
  }
  
  static void nilfs_segctor_end_finfo(struct nilfs_sc_info *sci,
  				    struct inode *inode)
  {
  	struct nilfs_finfo *finfo;
  	struct nilfs_inode_info *ii;
  	struct nilfs_segment_buffer *segbuf;

  	__u64 cno;

  
  	if (sci->sc_blk_cnt == 0)
  		return;
  
  	ii = NILFS_I(inode);

  
  	if (test_bit(NILFS_I_GCINODE, &ii->i_state))
  		cno = ii->i_cno;
  	else if (NILFS_ROOT_METADATA_FILE(inode->i_ino))
  		cno = 0;
  	else
  		cno = sci->sc_cno;

  	finfo = nilfs_segctor_map_segsum_entry(sci, &sci->sc_finfo_ptr,
  						 sizeof(*finfo));
  	finfo->fi_ino = cpu_to_le64(inode->i_ino);
  	finfo->fi_nblocks = cpu_to_le32(sci->sc_blk_cnt);
  	finfo->fi_ndatablk = cpu_to_le32(sci->sc_datablk_cnt);

  	finfo->fi_cno = cpu_to_le64(cno);

  
  	segbuf = sci->sc_curseg;
  	segbuf->sb_sum.sumbytes = sci->sc_binfo_ptr.offset +
  		sci->sc_super->s_blocksize * (segbuf->sb_sum.nsumblk - 1);
  	sci->sc_finfo_ptr = sci->sc_binfo_ptr;
  	sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
  }
  
  static int nilfs_segctor_add_file_block(struct nilfs_sc_info *sci,
  					struct buffer_head *bh,
  					struct inode *inode,
  					unsigned binfo_size)
  {
  	struct nilfs_segment_buffer *segbuf;
  	int required, err = 0;
  
   retry:
  	segbuf = sci->sc_curseg;
  	required = nilfs_segctor_segsum_block_required(
  		sci, &sci->sc_binfo_ptr, binfo_size);
  	if (segbuf->sb_sum.nblocks + required + 1 > segbuf->sb_rest_blocks) {
  		nilfs_segctor_end_finfo(sci, inode);
  		err = nilfs_segctor_feed_segment(sci);
  		if (err)
  			return err;
  		goto retry;
  	}
  	if (unlikely(required)) {
  		err = nilfs_segbuf_extend_segsum(segbuf);
  		if (unlikely(err))
  			goto failed;
  	}
  	if (sci->sc_blk_cnt == 0)
  		nilfs_segctor_begin_finfo(sci, inode);
  
  	nilfs_segctor_map_segsum_entry(sci, &sci->sc_binfo_ptr, binfo_size);
  	/* Substitution to vblocknr is delayed until update_blocknr() */
  	nilfs_segbuf_add_file_buffer(segbuf, bh);
  	sci->sc_blk_cnt++;
   failed:
  	return err;
  }

  /*
   * Callback functions that enumerate, mark, and collect dirty blocks
   */
  static int nilfs_collect_file_data(struct nilfs_sc_info *sci,
  				   struct buffer_head *bh, struct inode *inode)
  {
  	int err;

  	err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);

  	if (err < 0)
  		return err;

  
  	err = nilfs_segctor_add_file_block(sci, bh, inode,
  					   sizeof(struct nilfs_binfo_v));
  	if (!err)
  		sci->sc_datablk_cnt++;
  	return err;
  }
  
  static int nilfs_collect_file_node(struct nilfs_sc_info *sci,
  				   struct buffer_head *bh,
  				   struct inode *inode)
  {

  	return nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);

  }
  
  static int nilfs_collect_file_bmap(struct nilfs_sc_info *sci,
  				   struct buffer_head *bh,
  				   struct inode *inode)
  {

  	WARN_ON(!buffer_dirty(bh));

  	return nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
  }
  
  static void nilfs_write_file_data_binfo(struct nilfs_sc_info *sci,
  					struct nilfs_segsum_pointer *ssp,
  					union nilfs_binfo *binfo)
  {
  	struct nilfs_binfo_v *binfo_v = nilfs_segctor_map_segsum_entry(
  		sci, ssp, sizeof(*binfo_v));
  	*binfo_v = binfo->bi_v;
  }
  
  static void nilfs_write_file_node_binfo(struct nilfs_sc_info *sci,
  					struct nilfs_segsum_pointer *ssp,
  					union nilfs_binfo *binfo)
  {
  	__le64 *vblocknr = nilfs_segctor_map_segsum_entry(
  		sci, ssp, sizeof(*vblocknr));
  	*vblocknr = binfo->bi_v.bi_vblocknr;
  }

  static struct nilfs_sc_operations nilfs_sc_file_ops = {

  	.collect_data = nilfs_collect_file_data,
  	.collect_node = nilfs_collect_file_node,
  	.collect_bmap = nilfs_collect_file_bmap,
  	.write_data_binfo = nilfs_write_file_data_binfo,
  	.write_node_binfo = nilfs_write_file_node_binfo,
  };
  
  static int nilfs_collect_dat_data(struct nilfs_sc_info *sci,
  				  struct buffer_head *bh, struct inode *inode)
  {
  	int err;
  
  	err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);

  	if (err < 0)
  		return err;

  
  	err = nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
  	if (!err)
  		sci->sc_datablk_cnt++;
  	return err;
  }
  
  static int nilfs_collect_dat_bmap(struct nilfs_sc_info *sci,
  				  struct buffer_head *bh, struct inode *inode)
  {

  	WARN_ON(!buffer_dirty(bh));

  	return nilfs_segctor_add_file_block(sci, bh, inode,
  					    sizeof(struct nilfs_binfo_dat));
  }
  
  static void nilfs_write_dat_data_binfo(struct nilfs_sc_info *sci,
  				       struct nilfs_segsum_pointer *ssp,
  				       union nilfs_binfo *binfo)
  {
  	__le64 *blkoff = nilfs_segctor_map_segsum_entry(sci, ssp,
  							  sizeof(*blkoff));
  	*blkoff = binfo->bi_dat.bi_blkoff;
  }
  
  static void nilfs_write_dat_node_binfo(struct nilfs_sc_info *sci,
  				       struct nilfs_segsum_pointer *ssp,
  				       union nilfs_binfo *binfo)
  {
  	struct nilfs_binfo_dat *binfo_dat =
  		nilfs_segctor_map_segsum_entry(sci, ssp, sizeof(*binfo_dat));
  	*binfo_dat = binfo->bi_dat;
  }

  static struct nilfs_sc_operations nilfs_sc_dat_ops = {

  	.collect_data = nilfs_collect_dat_data,
  	.collect_node = nilfs_collect_file_node,
  	.collect_bmap = nilfs_collect_dat_bmap,
  	.write_data_binfo = nilfs_write_dat_data_binfo,
  	.write_node_binfo = nilfs_write_dat_node_binfo,
  };

  static struct nilfs_sc_operations nilfs_sc_dsync_ops = {

  	.collect_data = nilfs_collect_file_data,
  	.collect_node = NULL,
  	.collect_bmap = NULL,
  	.write_data_binfo = nilfs_write_file_data_binfo,
  	.write_node_binfo = NULL,
  };

  static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
  					      struct list_head *listp,
  					      size_t nlimit,
  					      loff_t start, loff_t end)

  {

  	struct address_space *mapping = inode->i_mapping;
  	struct pagevec pvec;

  	pgoff_t index = 0, last = ULONG_MAX;
  	size_t ndirties = 0;
  	int i;

  	if (unlikely(start != 0 || end != LLONG_MAX)) {
  		/*
  		 * A valid range is given for sync-ing data pages. The
  		 * range is rounded to per-page; extra dirty buffers
  		 * may be included if blocksize < pagesize.
  		 */
  		index = start >> PAGE_SHIFT;
  		last = end >> PAGE_SHIFT;
  	}

  	pagevec_init(&pvec, 0);
   repeat:

  	if (unlikely(index > last) ||
  	    !pagevec_lookup_tag(&pvec, mapping, &index, PAGECACHE_TAG_DIRTY,
  				min_t(pgoff_t, last - index,
  				      PAGEVEC_SIZE - 1) + 1))
  		return ndirties;

  
  	for (i = 0; i < pagevec_count(&pvec); i++) {
  		struct buffer_head *bh, *head;
  		struct page *page = pvec.pages[i];

  		if (unlikely(page->index > last))
  			break;

  		lock_page(page);
  		if (!page_has_buffers(page))
  			create_empty_buffers(page, 1 << inode->i_blkbits, 0);
  		unlock_page(page);

  
  		bh = head = page_buffers(page);
  		do {

  			if (!buffer_dirty(bh) || buffer_async_write(bh))

  				continue;
  			get_bh(bh);
  			list_add_tail(&bh->b_assoc_buffers, listp);
  			ndirties++;
  			if (unlikely(ndirties >= nlimit)) {
  				pagevec_release(&pvec);
  				cond_resched();
  				return ndirties;

  			}

  		} while (bh = bh->b_this_page, bh != head);

  	}
  	pagevec_release(&pvec);
  	cond_resched();

  	goto repeat;

  }
  
  static void nilfs_lookup_dirty_node_buffers(struct inode *inode,
  					    struct list_head *listp)
  {
  	struct nilfs_inode_info *ii = NILFS_I(inode);
  	struct address_space *mapping = &ii->i_btnode_cache;
  	struct pagevec pvec;
  	struct buffer_head *bh, *head;
  	unsigned int i;
  	pgoff_t index = 0;
  
  	pagevec_init(&pvec, 0);
  
  	while (pagevec_lookup_tag(&pvec, mapping, &index, PAGECACHE_TAG_DIRTY,
  				  PAGEVEC_SIZE)) {
  		for (i = 0; i < pagevec_count(&pvec); i++) {
  			bh = head = page_buffers(pvec.pages[i]);
  			do {

  				if (buffer_dirty(bh) &&
  						!buffer_async_write(bh)) {

  					get_bh(bh);
  					list_add_tail(&bh->b_assoc_buffers,
  						      listp);
  				}
  				bh = bh->b_this_page;
  			} while (bh != head);
  		}
  		pagevec_release(&pvec);
  		cond_resched();
  	}
  }

  static void nilfs_dispose_list(struct the_nilfs *nilfs,

  			       struct list_head *head, int force)
  {
  	struct nilfs_inode_info *ii, *n;
  	struct nilfs_inode_info *ivec[SC_N_INODEVEC], **pii;
  	unsigned nv = 0;
  
  	while (!list_empty(head)) {

  		spin_lock(&nilfs->ns_inode_lock);

  		list_for_each_entry_safe(ii, n, head, i_dirty) {
  			list_del_init(&ii->i_dirty);
  			if (force) {
  				if (unlikely(ii->i_bh)) {
  					brelse(ii->i_bh);
  					ii->i_bh = NULL;
  				}
  			} else if (test_bit(NILFS_I_DIRTY, &ii->i_state)) {
  				set_bit(NILFS_I_QUEUED, &ii->i_state);
  				list_add_tail(&ii->i_dirty,

  					      &nilfs->ns_dirty_files);

  				continue;
  			}
  			ivec[nv++] = ii;
  			if (nv == SC_N_INODEVEC)
  				break;
  		}

  		spin_unlock(&nilfs->ns_inode_lock);

  
  		for (pii = ivec; nv > 0; pii++, nv--)
  			iput(&(*pii)->vfs_inode);
  	}
  }

  static int nilfs_test_metadata_dirty(struct the_nilfs *nilfs,
  				     struct nilfs_root *root)

  {

  	int ret = 0;

  	if (nilfs_mdt_fetch_dirty(root->ifile))

  		ret++;
  	if (nilfs_mdt_fetch_dirty(nilfs->ns_cpfile))
  		ret++;
  	if (nilfs_mdt_fetch_dirty(nilfs->ns_sufile))
  		ret++;

  	if ((ret || nilfs_doing_gc()) && nilfs_mdt_fetch_dirty(nilfs->ns_dat))
  		ret++;

  	return ret;
  }
  
  static int nilfs_segctor_clean(struct nilfs_sc_info *sci)
  {
  	return list_empty(&sci->sc_dirty_files) &&
  		!test_bit(NILFS_SC_DIRTY, &sci->sc_flags) &&

  		sci->sc_nfreesegs == 0 &&

  		(!nilfs_doing_gc() || list_empty(&sci->sc_gc_inodes));
  }
  
  static int nilfs_segctor_confirm(struct nilfs_sc_info *sci)
  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	int ret = 0;

  	if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))

  		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);

  	spin_lock(&nilfs->ns_inode_lock);
  	if (list_empty(&nilfs->ns_dirty_files) && nilfs_segctor_clean(sci))

  		ret++;

  	spin_unlock(&nilfs->ns_inode_lock);

  	return ret;
  }
  
  static void nilfs_segctor_clear_metadata_dirty(struct nilfs_sc_info *sci)
  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	nilfs_mdt_clear_dirty(sci->sc_root->ifile);

  	nilfs_mdt_clear_dirty(nilfs->ns_cpfile);
  	nilfs_mdt_clear_dirty(nilfs->ns_sufile);

  	nilfs_mdt_clear_dirty(nilfs->ns_dat);

  }
  
  static int nilfs_segctor_create_checkpoint(struct nilfs_sc_info *sci)
  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	struct buffer_head *bh_cp;
  	struct nilfs_checkpoint *raw_cp;
  	int err;
  
  	/* XXX: this interface will be changed */
  	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 1,
  					  &raw_cp, &bh_cp);
  	if (likely(!err)) {
  		/* The following code is duplicated with cpfile.  But, it is
  		   needed to collect the checkpoint even if it was not newly
  		   created */

  		mark_buffer_dirty(bh_cp);

  		nilfs_mdt_mark_dirty(nilfs->ns_cpfile);
  		nilfs_cpfile_put_checkpoint(
  			nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);

  	} else
  		WARN_ON(err == -EINVAL || err == -ENOENT);

  	return err;
  }
  
  static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	struct buffer_head *bh_cp;
  	struct nilfs_checkpoint *raw_cp;
  	int err;
  
  	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 0,
  					  &raw_cp, &bh_cp);
  	if (unlikely(err)) {

  		WARN_ON(err == -EINVAL || err == -ENOENT);

  		goto failed_ibh;
  	}
  	raw_cp->cp_snapshot_list.ssl_next = 0;
  	raw_cp->cp_snapshot_list.ssl_prev = 0;
  	raw_cp->cp_inodes_count =

  		cpu_to_le64(atomic64_read(&sci->sc_root->inodes_count));

  	raw_cp->cp_blocks_count =

  		cpu_to_le64(atomic64_read(&sci->sc_root->blocks_count));

  	raw_cp->cp_nblk_inc =
  		cpu_to_le64(sci->sc_nblk_inc + sci->sc_nblk_this_inc);
  	raw_cp->cp_create = cpu_to_le64(sci->sc_seg_ctime);
  	raw_cp->cp_cno = cpu_to_le64(nilfs->ns_cno);

  	if (test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
  		nilfs_checkpoint_clear_minor(raw_cp);
  	else
  		nilfs_checkpoint_set_minor(raw_cp);

  	nilfs_write_inode_common(sci->sc_root->ifile,
  				 &raw_cp->cp_ifile_inode, 1);

  	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
  	return 0;
  
   failed_ibh:
  	return err;
  }
  
  static void nilfs_fill_in_file_bmap(struct inode *ifile,
  				    struct nilfs_inode_info *ii)
  
  {
  	struct buffer_head *ibh;
  	struct nilfs_inode *raw_inode;
  
  	if (test_bit(NILFS_I_BMAP, &ii->i_state)) {
  		ibh = ii->i_bh;
  		BUG_ON(!ibh);
  		raw_inode = nilfs_ifile_map_inode(ifile, ii->vfs_inode.i_ino,
  						  ibh);
  		nilfs_bmap_write(ii->i_bmap, raw_inode);
  		nilfs_ifile_unmap_inode(ifile, ii->vfs_inode.i_ino, ibh);
  	}
  }

  static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci)

  {
  	struct nilfs_inode_info *ii;
  
  	list_for_each_entry(ii, &sci->sc_dirty_files, i_dirty) {

  		nilfs_fill_in_file_bmap(sci->sc_root->ifile, ii);

  		set_bit(NILFS_I_COLLECTED, &ii->i_state);
  	}

  }

  static void nilfs_segctor_fill_in_super_root(struct nilfs_sc_info *sci,
  					     struct the_nilfs *nilfs)
  {

  	struct buffer_head *bh_sr;
  	struct nilfs_super_root *raw_sr;

  	unsigned isz, srsz;

  	bh_sr = NILFS_LAST_SEGBUF(&sci->sc_segbufs)->sb_super_root;
  	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;

  	isz = nilfs->ns_inode_size;
  	srsz = NILFS_SR_BYTES(isz);

  	raw_sr->sr_bytes = cpu_to_le16(srsz);

  	raw_sr->sr_nongc_ctime
  		= cpu_to_le64(nilfs_doing_gc() ?
  			      nilfs->ns_nongc_ctime : sci->sc_seg_ctime);
  	raw_sr->sr_flags = 0;

  	nilfs_write_inode_common(nilfs->ns_dat, (void *)raw_sr +

  				 NILFS_SR_DAT_OFFSET(isz), 1);
  	nilfs_write_inode_common(nilfs->ns_cpfile, (void *)raw_sr +
  				 NILFS_SR_CPFILE_OFFSET(isz), 1);
  	nilfs_write_inode_common(nilfs->ns_sufile, (void *)raw_sr +
  				 NILFS_SR_SUFILE_OFFSET(isz), 1);

  	memset((void *)raw_sr + srsz, 0, nilfs->ns_blocksize - srsz);

  }
  
  static void nilfs_redirty_inodes(struct list_head *head)
  {
  	struct nilfs_inode_info *ii;
  
  	list_for_each_entry(ii, head, i_dirty) {
  		if (test_bit(NILFS_I_COLLECTED, &ii->i_state))
  			clear_bit(NILFS_I_COLLECTED, &ii->i_state);
  	}
  }
  
  static void nilfs_drop_collected_inodes(struct list_head *head)
  {
  	struct nilfs_inode_info *ii;
  
  	list_for_each_entry(ii, head, i_dirty) {
  		if (!test_and_clear_bit(NILFS_I_COLLECTED, &ii->i_state))
  			continue;
  
  		clear_bit(NILFS_I_INODE_DIRTY, &ii->i_state);
  		set_bit(NILFS_I_UPDATED, &ii->i_state);
  	}
  }

  static int nilfs_segctor_apply_buffers(struct nilfs_sc_info *sci,
  				       struct inode *inode,
  				       struct list_head *listp,
  				       int (*collect)(struct nilfs_sc_info *,
  						      struct buffer_head *,
  						      struct inode *))
  {
  	struct buffer_head *bh, *n;
  	int err = 0;
  
  	if (collect) {
  		list_for_each_entry_safe(bh, n, listp, b_assoc_buffers) {
  			list_del_init(&bh->b_assoc_buffers);
  			err = collect(sci, bh, inode);
  			brelse(bh);
  			if (unlikely(err))
  				goto dispose_buffers;
  		}
  		return 0;
  	}
  
   dispose_buffers:
  	while (!list_empty(listp)) {

  		bh = list_first_entry(listp, struct buffer_head,
  				      b_assoc_buffers);

  		list_del_init(&bh->b_assoc_buffers);
  		brelse(bh);
  	}
  	return err;
  }

  static size_t nilfs_segctor_buffer_rest(struct nilfs_sc_info *sci)
  {
  	/* Remaining number of blocks within segment buffer */
  	return sci->sc_segbuf_nblocks -
  		(sci->sc_nblk_this_inc + sci->sc_curseg->sb_sum.nblocks);
  }

  static int nilfs_segctor_scan_file(struct nilfs_sc_info *sci,
  				   struct inode *inode,
  				   struct nilfs_sc_operations *sc_ops)
  {
  	LIST_HEAD(data_buffers);
  	LIST_HEAD(node_buffers);

  	int err;

  
  	if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {

  		size_t n, rest = nilfs_segctor_buffer_rest(sci);
  
  		n = nilfs_lookup_dirty_data_buffers(
  			inode, &data_buffers, rest + 1, 0, LLONG_MAX);
  		if (n > rest) {
  			err = nilfs_segctor_apply_buffers(

  				sci, inode, &data_buffers,

  				sc_ops->collect_data);
  			BUG_ON(!err); /* always receive -E2BIG or true error */

  			goto break_or_fail;
  		}
  	}
  	nilfs_lookup_dirty_node_buffers(inode, &node_buffers);
  
  	if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {
  		err = nilfs_segctor_apply_buffers(
  			sci, inode, &data_buffers, sc_ops->collect_data);
  		if (unlikely(err)) {
  			/* dispose node list */
  			nilfs_segctor_apply_buffers(
  				sci, inode, &node_buffers, NULL);
  			goto break_or_fail;
  		}
  		sci->sc_stage.flags |= NILFS_CF_NODE;
  	}
  	/* Collect node */
  	err = nilfs_segctor_apply_buffers(
  		sci, inode, &node_buffers, sc_ops->collect_node);
  	if (unlikely(err))
  		goto break_or_fail;
  
  	nilfs_bmap_lookup_dirty_buffers(NILFS_I(inode)->i_bmap, &node_buffers);
  	err = nilfs_segctor_apply_buffers(
  		sci, inode, &node_buffers, sc_ops->collect_bmap);
  	if (unlikely(err))
  		goto break_or_fail;
  
  	nilfs_segctor_end_finfo(sci, inode);
  	sci->sc_stage.flags &= ~NILFS_CF_NODE;
  
   break_or_fail:
  	return err;
  }
  
  static int nilfs_segctor_scan_file_dsync(struct nilfs_sc_info *sci,
  					 struct inode *inode)
  {
  	LIST_HEAD(data_buffers);

  	size_t n, rest = nilfs_segctor_buffer_rest(sci);
  	int err;

  	n = nilfs_lookup_dirty_data_buffers(inode, &data_buffers, rest + 1,
  					    sci->sc_dsync_start,
  					    sci->sc_dsync_end);
  
  	err = nilfs_segctor_apply_buffers(sci, inode, &data_buffers,
  					  nilfs_collect_file_data);
  	if (!err) {

  		nilfs_segctor_end_finfo(sci, inode);

  		BUG_ON(n > rest);
  		/* always receive -E2BIG or true error if n > rest */
  	}

  	return err;
  }
  
  static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	struct list_head *head;
  	struct nilfs_inode_info *ii;

  	size_t ndone;

  	int err = 0;
  
  	switch (sci->sc_stage.scnt) {
  	case NILFS_ST_INIT:
  		/* Pre-processes */
  		sci->sc_stage.flags = 0;
  
  		if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags)) {
  			sci->sc_nblk_inc = 0;
  			sci->sc_curseg->sb_sum.flags = NILFS_SS_LOGBGN;
  			if (mode == SC_LSEG_DSYNC) {
  				sci->sc_stage.scnt = NILFS_ST_DSYNC;
  				goto dsync_mode;
  			}
  		}
  
  		sci->sc_stage.dirty_file_ptr = NULL;
  		sci->sc_stage.gc_inode_ptr = NULL;
  		if (mode == SC_FLUSH_DAT) {
  			sci->sc_stage.scnt = NILFS_ST_DAT;
  			goto dat_stage;
  		}
  		sci->sc_stage.scnt++;  /* Fall through */
  	case NILFS_ST_GC:
  		if (nilfs_doing_gc()) {
  			head = &sci->sc_gc_inodes;
  			ii = list_prepare_entry(sci->sc_stage.gc_inode_ptr,
  						head, i_dirty);
  			list_for_each_entry_continue(ii, head, i_dirty) {
  				err = nilfs_segctor_scan_file(
  					sci, &ii->vfs_inode,
  					&nilfs_sc_file_ops);
  				if (unlikely(err)) {
  					sci->sc_stage.gc_inode_ptr = list_entry(
  						ii->i_dirty.prev,
  						struct nilfs_inode_info,
  						i_dirty);
  					goto break_or_fail;
  				}
  				set_bit(NILFS_I_COLLECTED, &ii->i_state);
  			}
  			sci->sc_stage.gc_inode_ptr = NULL;
  		}
  		sci->sc_stage.scnt++;  /* Fall through */
  	case NILFS_ST_FILE:
  		head = &sci->sc_dirty_files;
  		ii = list_prepare_entry(sci->sc_stage.dirty_file_ptr, head,
  					i_dirty);
  		list_for_each_entry_continue(ii, head, i_dirty) {
  			clear_bit(NILFS_I_DIRTY, &ii->i_state);
  
  			err = nilfs_segctor_scan_file(sci, &ii->vfs_inode,
  						      &nilfs_sc_file_ops);
  			if (unlikely(err)) {
  				sci->sc_stage.dirty_file_ptr =
  					list_entry(ii->i_dirty.prev,
  						   struct nilfs_inode_info,
  						   i_dirty);
  				goto break_or_fail;
  			}
  			/* sci->sc_stage.dirty_file_ptr = NILFS_I(inode); */
  			/* XXX: required ? */
  		}
  		sci->sc_stage.dirty_file_ptr = NULL;
  		if (mode == SC_FLUSH_FILE) {
  			sci->sc_stage.scnt = NILFS_ST_DONE;
  			return 0;
  		}

  		sci->sc_stage.scnt++;
  		sci->sc_stage.flags |= NILFS_CF_IFILE_STARTED;
  		/* Fall through */
  	case NILFS_ST_IFILE:

  		err = nilfs_segctor_scan_file(sci, sci->sc_root->ifile,

  					      &nilfs_sc_file_ops);
  		if (unlikely(err))
  			break;
  		sci->sc_stage.scnt++;
  		/* Creating a checkpoint */
  		err = nilfs_segctor_create_checkpoint(sci);
  		if (unlikely(err))
  			break;
  		/* Fall through */
  	case NILFS_ST_CPFILE:
  		err = nilfs_segctor_scan_file(sci, nilfs->ns_cpfile,
  					      &nilfs_sc_file_ops);
  		if (unlikely(err))
  			break;
  		sci->sc_stage.scnt++;  /* Fall through */
  	case NILFS_ST_SUFILE:

  		err = nilfs_sufile_freev(nilfs->ns_sufile, sci->sc_freesegs,
  					 sci->sc_nfreesegs, &ndone);
  		if (unlikely(err)) {
  			nilfs_sufile_cancel_freev(nilfs->ns_sufile,
  						  sci->sc_freesegs, ndone,
  						  NULL);

  			break;

  		}
  		sci->sc_stage.flags |= NILFS_CF_SUFREED;

  		err = nilfs_segctor_scan_file(sci, nilfs->ns_sufile,
  					      &nilfs_sc_file_ops);
  		if (unlikely(err))
  			break;
  		sci->sc_stage.scnt++;  /* Fall through */
  	case NILFS_ST_DAT:
   dat_stage:

  		err = nilfs_segctor_scan_file(sci, nilfs->ns_dat,

  					      &nilfs_sc_dat_ops);
  		if (unlikely(err))
  			break;
  		if (mode == SC_FLUSH_DAT) {
  			sci->sc_stage.scnt = NILFS_ST_DONE;
  			return 0;
  		}
  		sci->sc_stage.scnt++;  /* Fall through */
  	case NILFS_ST_SR:
  		if (mode == SC_LSEG_SR) {
  			/* Appending a super root */
  			err = nilfs_segctor_add_super_root(sci);
  			if (unlikely(err))
  				break;
  		}
  		/* End of a logical segment */
  		sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
  		sci->sc_stage.scnt = NILFS_ST_DONE;
  		return 0;
  	case NILFS_ST_DSYNC:
   dsync_mode:
  		sci->sc_curseg->sb_sum.flags |= NILFS_SS_SYNDT;

  		ii = sci->sc_dsync_inode;

  		if (!test_bit(NILFS_I_BUSY, &ii->i_state))
  			break;
  
  		err = nilfs_segctor_scan_file_dsync(sci, &ii->vfs_inode);
  		if (unlikely(err))
  			break;

  		sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
  		sci->sc_stage.scnt = NILFS_ST_DONE;
  		return 0;
  	case NILFS_ST_DONE:
  		return 0;
  	default:
  		BUG();
  	}
  
   break_or_fail:
  	return err;
  }

  /**
   * nilfs_segctor_begin_construction - setup segment buffer to make a new log
   * @sci: nilfs_sc_info
   * @nilfs: nilfs object
   */

  static int nilfs_segctor_begin_construction(struct nilfs_sc_info *sci,
  					    struct the_nilfs *nilfs)
  {

  	struct nilfs_segment_buffer *segbuf, *prev;

  	__u64 nextnum;

  	int err, alloc = 0;

  	segbuf = nilfs_segbuf_new(sci->sc_super);
  	if (unlikely(!segbuf))
  		return -ENOMEM;

  	if (list_empty(&sci->sc_write_logs)) {
  		nilfs_segbuf_map(segbuf, nilfs->ns_segnum,
  				 nilfs->ns_pseg_offset, nilfs);
  		if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
  			nilfs_shift_to_next_segment(nilfs);
  			nilfs_segbuf_map(segbuf, nilfs->ns_segnum, 0, nilfs);
  		}

  		segbuf->sb_sum.seg_seq = nilfs->ns_seg_seq;
  		nextnum = nilfs->ns_nextnum;
  
  		if (nilfs->ns_segnum == nilfs->ns_nextnum)
  			/* Start from the head of a new full segment */
  			alloc++;
  	} else {
  		/* Continue logs */
  		prev = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
  		nilfs_segbuf_map_cont(segbuf, prev);
  		segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq;
  		nextnum = prev->sb_nextnum;
  
  		if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
  			nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
  			segbuf->sb_sum.seg_seq++;
  			alloc++;
  		}

  	}

  	err = nilfs_sufile_mark_dirty(nilfs->ns_sufile, segbuf->sb_segnum);

  	if (err)
  		goto failed;

  	if (alloc) {

  		err = nilfs_sufile_alloc(nilfs->ns_sufile, &nextnum);

  		if (err)
  			goto failed;
  	}

  	nilfs_segbuf_set_next_segnum(segbuf, nextnum, nilfs);

  	BUG_ON(!list_empty(&sci->sc_segbufs));
  	list_add_tail(&segbuf->sb_list, &sci->sc_segbufs);
  	sci->sc_segbuf_nblocks = segbuf->sb_rest_blocks;

  	return 0;

  
   failed:
  	nilfs_segbuf_free(segbuf);
  	return err;

  }
  
  static int nilfs_segctor_extend_segments(struct nilfs_sc_info *sci,
  					 struct the_nilfs *nilfs, int nadd)
  {

  	struct nilfs_segment_buffer *segbuf, *prev;

  	struct inode *sufile = nilfs->ns_sufile;
  	__u64 nextnextnum;
  	LIST_HEAD(list);
  	int err, ret, i;
  
  	prev = NILFS_LAST_SEGBUF(&sci->sc_segbufs);
  	/*
  	 * Since the segment specified with nextnum might be allocated during
  	 * the previous construction, the buffer including its segusage may
  	 * not be dirty.  The following call ensures that the buffer is dirty
  	 * and will pin the buffer on memory until the sufile is written.
  	 */

  	err = nilfs_sufile_mark_dirty(sufile, prev->sb_nextnum);

  	if (unlikely(err))
  		return err;
  
  	for (i = 0; i < nadd; i++) {
  		/* extend segment info */
  		err = -ENOMEM;
  		segbuf = nilfs_segbuf_new(sci->sc_super);
  		if (unlikely(!segbuf))
  			goto failed;
  
  		/* map this buffer to region of segment on-disk */

  		nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);

  		sci->sc_segbuf_nblocks += segbuf->sb_rest_blocks;
  
  		/* allocate the next next full segment */
  		err = nilfs_sufile_alloc(sufile, &nextnextnum);
  		if (unlikely(err))
  			goto failed_segbuf;
  
  		segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq + 1;
  		nilfs_segbuf_set_next_segnum(segbuf, nextnextnum, nilfs);
  
  		list_add_tail(&segbuf->sb_list, &list);
  		prev = segbuf;
  	}

  	list_splice_tail(&list, &sci->sc_segbufs);

  	return 0;
  
   failed_segbuf:
  	nilfs_segbuf_free(segbuf);
   failed:

  	list_for_each_entry(segbuf, &list, sb_list) {

  		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);

  		WARN_ON(ret); /* never fails */

  	}

  	nilfs_destroy_logs(&list);

  	return err;
  }

  static void nilfs_free_incomplete_logs(struct list_head *logs,
  				       struct the_nilfs *nilfs)

  {

  	struct nilfs_segment_buffer *segbuf, *prev;
  	struct inode *sufile = nilfs->ns_sufile;

  	int ret;

  	segbuf = NILFS_FIRST_SEGBUF(logs);

  	if (nilfs->ns_nextnum != segbuf->sb_nextnum) {

  		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);

  		WARN_ON(ret); /* never fails */

  	}

  	if (atomic_read(&segbuf->sb_err)) {

  		/* Case 1: The first segment failed */
  		if (segbuf->sb_pseg_start != segbuf->sb_fseg_start)
  			/* Case 1a:  Partial segment appended into an existing
  			   segment */
  			nilfs_terminate_segment(nilfs, segbuf->sb_fseg_start,
  						segbuf->sb_fseg_end);
  		else /* Case 1b:  New full segment */
  			set_nilfs_discontinued(nilfs);

  	}

  	prev = segbuf;
  	list_for_each_entry_continue(segbuf, logs, sb_list) {
  		if (prev->sb_nextnum != segbuf->sb_nextnum) {
  			ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
  			WARN_ON(ret); /* never fails */
  		}

  		if (atomic_read(&segbuf->sb_err) &&
  		    segbuf->sb_segnum != nilfs->ns_nextnum)
  			/* Case 2: extended segment (!= next) failed */

  			nilfs_sufile_set_error(sufile, segbuf->sb_segnum);
  		prev = segbuf;

  	}

  }
  
  static void nilfs_segctor_update_segusage(struct nilfs_sc_info *sci,
  					  struct inode *sufile)
  {
  	struct nilfs_segment_buffer *segbuf;

  	unsigned long live_blocks;
  	int ret;
  
  	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {

  		live_blocks = segbuf->sb_sum.nblocks +
  			(segbuf->sb_pseg_start - segbuf->sb_fseg_start);

  		ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
  						     live_blocks,
  						     sci->sc_seg_ctime);
  		WARN_ON(ret); /* always succeed because the segusage is dirty */

  	}
  }

  static void nilfs_cancel_segusage(struct list_head *logs, struct inode *sufile)

  {
  	struct nilfs_segment_buffer *segbuf;

  	int ret;

  	segbuf = NILFS_FIRST_SEGBUF(logs);

  	ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
  					     segbuf->sb_pseg_start -
  					     segbuf->sb_fseg_start, 0);
  	WARN_ON(ret); /* always succeed because the segusage is dirty */

  	list_for_each_entry_continue(segbuf, logs, sb_list) {

  		ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
  						     0, 0);

  		WARN_ON(ret); /* always succeed */

  	}
  }
  
  static void nilfs_segctor_truncate_segments(struct nilfs_sc_info *sci,
  					    struct nilfs_segment_buffer *last,
  					    struct inode *sufile)
  {

  	struct nilfs_segment_buffer *segbuf = last;

  	int ret;

  	list_for_each_entry_continue(segbuf, &sci->sc_segbufs, sb_list) {

  		sci->sc_segbuf_nblocks -= segbuf->sb_rest_blocks;
  		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);

  		WARN_ON(ret);

  	}

  	nilfs_truncate_logs(&sci->sc_segbufs, last);

  }
  
  
  static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
  				 struct the_nilfs *nilfs, int mode)
  {
  	struct nilfs_cstage prev_stage = sci->sc_stage;
  	int err, nadd = 1;
  
  	/* Collection retry loop */
  	for (;;) {

  		sci->sc_nblk_this_inc = 0;
  		sci->sc_curseg = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
  
  		err = nilfs_segctor_reset_segment_buffer(sci);
  		if (unlikely(err))
  			goto failed;
  
  		err = nilfs_segctor_collect_blocks(sci, mode);
  		sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
  		if (!err)
  			break;
  
  		if (unlikely(err != -E2BIG))
  			goto failed;
  
  		/* The current segment is filled up */
  		if (mode != SC_LSEG_SR || sci->sc_stage.scnt < NILFS_ST_CPFILE)
  			break;

  		nilfs_clear_logs(&sci->sc_segbufs);

  		if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
  			err = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
  							sci->sc_freesegs,
  							sci->sc_nfreesegs,
  							NULL);
  			WARN_ON(err); /* do not happen */

  			sci->sc_stage.flags &= ~NILFS_CF_SUFREED;

  		}

  
  		err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
  		if (unlikely(err))
  			return err;

  		nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
  		sci->sc_stage = prev_stage;
  	}
  	nilfs_segctor_truncate_segments(sci, sci->sc_curseg, nilfs->ns_sufile);
  	return 0;
  
   failed:
  	return err;
  }
  
  static void nilfs_list_replace_buffer(struct buffer_head *old_bh,
  				      struct buffer_head *new_bh)
  {
  	BUG_ON(!list_empty(&new_bh->b_assoc_buffers));
  
  	list_replace_init(&old_bh->b_assoc_buffers, &new_bh->b_assoc_buffers);
  	/* The caller must release old_bh */
  }
  
  static int
  nilfs_segctor_update_payload_blocknr(struct nilfs_sc_info *sci,
  				     struct nilfs_segment_buffer *segbuf,
  				     int mode)
  {
  	struct inode *inode = NULL;
  	sector_t blocknr;
  	unsigned long nfinfo = segbuf->sb_sum.nfinfo;
  	unsigned long nblocks = 0, ndatablk = 0;
  	struct nilfs_sc_operations *sc_op = NULL;
  	struct nilfs_segsum_pointer ssp;
  	struct nilfs_finfo *finfo = NULL;
  	union nilfs_binfo binfo;
  	struct buffer_head *bh, *bh_org;
  	ino_t ino = 0;
  	int err = 0;
  
  	if (!nfinfo)
  		goto out;
  
  	blocknr = segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk;
  	ssp.bh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
  	ssp.offset = sizeof(struct nilfs_segment_summary);
  
  	list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {

  		if (bh == segbuf->sb_super_root)

  			break;
  		if (!finfo) {
  			finfo =	nilfs_segctor_map_segsum_entry(
  				sci, &ssp, sizeof(*finfo));
  			ino = le64_to_cpu(finfo->fi_ino);
  			nblocks = le32_to_cpu(finfo->fi_nblocks);
  			ndatablk = le32_to_cpu(finfo->fi_ndatablk);

  			inode = bh->b_page->mapping->host;

  
  			if (mode == SC_LSEG_DSYNC)
  				sc_op = &nilfs_sc_dsync_ops;
  			else if (ino == NILFS_DAT_INO)
  				sc_op = &nilfs_sc_dat_ops;
  			else /* file blocks */
  				sc_op = &nilfs_sc_file_ops;
  		}
  		bh_org = bh;
  		get_bh(bh_org);
  		err = nilfs_bmap_assign(NILFS_I(inode)->i_bmap, &bh, blocknr,
  					&binfo);
  		if (bh != bh_org)
  			nilfs_list_replace_buffer(bh_org, bh);
  		brelse(bh_org);
  		if (unlikely(err))
  			goto failed_bmap;
  
  		if (ndatablk > 0)
  			sc_op->write_data_binfo(sci, &ssp, &binfo);
  		else
  			sc_op->write_node_binfo(sci, &ssp, &binfo);
  
  		blocknr++;
  		if (--nblocks == 0) {
  			finfo = NULL;
  			if (--nfinfo == 0)
  				break;
  		} else if (ndatablk > 0)
  			ndatablk--;
  	}
   out:
  	return 0;
  
   failed_bmap:

  	return err;
  }
  
  static int nilfs_segctor_assign(struct nilfs_sc_info *sci, int mode)
  {
  	struct nilfs_segment_buffer *segbuf;
  	int err;
  
  	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
  		err = nilfs_segctor_update_payload_blocknr(sci, segbuf, mode);
  		if (unlikely(err))
  			return err;
  		nilfs_segbuf_fill_in_segsum(segbuf);
  	}
  	return 0;
  }

  static void nilfs_begin_page_io(struct page *page)

  {
  	if (!page || PageWriteback(page))
  		/* For split b-tree node pages, this function may be called
  		   twice.  We ignore the 2nd or later calls by this check. */

  		return;

  
  	lock_page(page);
  	clear_page_dirty_for_io(page);
  	set_page_writeback(page);
  	unlock_page(page);

  }

  static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)

  {
  	struct nilfs_segment_buffer *segbuf;
  	struct page *bd_page = NULL, *fs_page = NULL;

  	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
  		struct buffer_head *bh;
  
  		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
  				    b_assoc_buffers) {

  			set_buffer_async_write(bh);

  			if (bh->b_page != bd_page) {
  				if (bd_page) {
  					lock_page(bd_page);
  					clear_page_dirty_for_io(bd_page);
  					set_page_writeback(bd_page);
  					unlock_page(bd_page);
  				}
  				bd_page = bh->b_page;
  			}
  		}
  
  		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
  				    b_assoc_buffers) {

  			set_buffer_async_write(bh);

  			if (bh == segbuf->sb_super_root) {

  				if (bh->b_page != bd_page) {
  					lock_page(bd_page);
  					clear_page_dirty_for_io(bd_page);
  					set_page_writeback(bd_page);
  					unlock_page(bd_page);
  					bd_page = bh->b_page;
  				}
  				break;
  			}
  			if (bh->b_page != fs_page) {

  				nilfs_begin_page_io(fs_page);

  				fs_page = bh->b_page;
  			}
  		}
  	}
  	if (bd_page) {
  		lock_page(bd_page);
  		clear_page_dirty_for_io(bd_page);
  		set_page_writeback(bd_page);
  		unlock_page(bd_page);
  	}

  	nilfs_begin_page_io(fs_page);

  }
  
  static int nilfs_segctor_write(struct nilfs_sc_info *sci,

  			       struct the_nilfs *nilfs)

  {

  	int ret;

  	ret = nilfs_write_logs(&sci->sc_segbufs, nilfs);

  	list_splice_tail_init(&sci->sc_segbufs, &sci->sc_write_logs);
  	return ret;

  }

  static void nilfs_end_page_io(struct page *page, int err)
  {
  	if (!page)
  		return;

  	if (buffer_nilfs_node(page_buffers(page)) && !PageWriteback(page)) {

  		/*
  		 * For b-tree node pages, this function may be called twice
  		 * or more because they might be split in a segment.
  		 */

  		if (PageDirty(page)) {
  			/*
  			 * For pages holding split b-tree node buffers, dirty
  			 * flag on the buffers may be cleared discretely.
  			 * In that case, the page is once redirtied for
  			 * remaining buffers, and it must be cancelled if
  			 * all the buffers get cleaned later.
  			 */
  			lock_page(page);
  			if (nilfs_page_buffers_clean(page))
  				__nilfs_clear_page_dirty(page);
  			unlock_page(page);
  		}

  		return;

  	}

  	if (!err) {
  		if (!nilfs_page_buffers_clean(page))
  			__set_page_dirty_nobuffers(page);
  		ClearPageError(page);
  	} else {
  		__set_page_dirty_nobuffers(page);
  		SetPageError(page);

  	}

  
  	end_page_writeback(page);

  }

  static void nilfs_abort_logs(struct list_head *logs, int err)

  {
  	struct nilfs_segment_buffer *segbuf;
  	struct page *bd_page = NULL, *fs_page = NULL;

  	struct buffer_head *bh;

  	if (list_empty(logs))
  		return;

  	list_for_each_entry(segbuf, logs, sb_list) {

  		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
  				    b_assoc_buffers) {

  			clear_buffer_async_write(bh);

  			if (bh->b_page != bd_page) {
  				if (bd_page)
  					end_page_writeback(bd_page);
  				bd_page = bh->b_page;
  			}
  		}
  
  		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
  				    b_assoc_buffers) {

  			clear_buffer_async_write(bh);

  			if (bh == segbuf->sb_super_root) {

  				if (bh->b_page != bd_page) {
  					end_page_writeback(bd_page);
  					bd_page = bh->b_page;
  				}
  				break;
  			}
  			if (bh->b_page != fs_page) {
  				nilfs_end_page_io(fs_page, err);

  				fs_page = bh->b_page;
  			}
  		}
  	}
  	if (bd_page)
  		end_page_writeback(bd_page);
  
  	nilfs_end_page_io(fs_page, err);

  }
  
  static void nilfs_segctor_abort_construction(struct nilfs_sc_info *sci,
  					     struct the_nilfs *nilfs, int err)
  {
  	LIST_HEAD(logs);
  	int ret;
  
  	list_splice_tail_init(&sci->sc_write_logs, &logs);
  	ret = nilfs_wait_on_logs(&logs);

  	nilfs_abort_logs(&logs, ret ? : err);

  
  	list_splice_tail_init(&sci->sc_segbufs, &logs);
  	nilfs_cancel_segusage(&logs, nilfs->ns_sufile);
  	nilfs_free_incomplete_logs(&logs, nilfs);

  
  	if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
  		ret = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
  						sci->sc_freesegs,
  						sci->sc_nfreesegs,
  						NULL);
  		WARN_ON(ret); /* do not happen */
  	}
  
  	nilfs_destroy_logs(&logs);

  }
  
  static void nilfs_set_next_segment(struct the_nilfs *nilfs,
  				   struct nilfs_segment_buffer *segbuf)
  {
  	nilfs->ns_segnum = segbuf->sb_segnum;
  	nilfs->ns_nextnum = segbuf->sb_nextnum;
  	nilfs->ns_pseg_offset = segbuf->sb_pseg_start - segbuf->sb_fseg_start
  		+ segbuf->sb_sum.nblocks;
  	nilfs->ns_seg_seq = segbuf->sb_sum.seg_seq;
  	nilfs->ns_ctime = segbuf->sb_sum.ctime;
  }
  
  static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
  {
  	struct nilfs_segment_buffer *segbuf;
  	struct page *bd_page = NULL, *fs_page = NULL;

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	int update_sr = false;

  	list_for_each_entry(segbuf, &sci->sc_write_logs, sb_list) {

  		struct buffer_head *bh;
  
  		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
  				    b_assoc_buffers) {
  			set_buffer_uptodate(bh);
  			clear_buffer_dirty(bh);

  			clear_buffer_async_write(bh);

  			if (bh->b_page != bd_page) {
  				if (bd_page)
  					end_page_writeback(bd_page);
  				bd_page = bh->b_page;
  			}
  		}
  		/*
  		 * We assume that the buffers which belong to the same page
  		 * continue over the buffer list.
  		 * Under this assumption, the last BHs of pages is
  		 * identifiable by the discontinuity of bh->b_page
  		 * (page != fs_page).
  		 *
  		 * For B-tree node blocks, however, this assumption is not
  		 * guaranteed.  The cleanup code of B-tree node pages needs
  		 * special care.
  		 */
  		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
  				    b_assoc_buffers) {
  			set_buffer_uptodate(bh);
  			clear_buffer_dirty(bh);

  			clear_buffer_async_write(bh);

  			clear_buffer_delay(bh);

  			clear_buffer_nilfs_volatile(bh);

  			clear_buffer_nilfs_redirected(bh);

  			if (bh == segbuf->sb_super_root) {

  				if (bh->b_page != bd_page) {
  					end_page_writeback(bd_page);
  					bd_page = bh->b_page;
  				}

  				update_sr = true;

  				break;
  			}
  			if (bh->b_page != fs_page) {
  				nilfs_end_page_io(fs_page, 0);
  				fs_page = bh->b_page;
  			}
  		}

  		if (!nilfs_segbuf_simplex(segbuf)) {
  			if (segbuf->sb_sum.flags & NILFS_SS_LOGBGN) {

  				set_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
  				sci->sc_lseg_stime = jiffies;
  			}

  			if (segbuf->sb_sum.flags & NILFS_SS_LOGEND)

  				clear_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
  		}
  	}
  	/*
  	 * Since pages may continue over multiple segment buffers,
  	 * end of the last page must be checked outside of the loop.
  	 */
  	if (bd_page)
  		end_page_writeback(bd_page);
  
  	nilfs_end_page_io(fs_page, 0);

  	nilfs_drop_collected_inodes(&sci->sc_dirty_files);

  	if (nilfs_doing_gc())

  		nilfs_drop_collected_inodes(&sci->sc_gc_inodes);

  	else

  		nilfs->ns_nongc_ctime = sci->sc_seg_ctime;

  
  	sci->sc_nblk_inc += sci->sc_nblk_this_inc;

  	segbuf = NILFS_LAST_SEGBUF(&sci->sc_write_logs);

  	nilfs_set_next_segment(nilfs, segbuf);
  
  	if (update_sr) {
  		nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,

  				       segbuf->sb_sum.seg_seq, nilfs->ns_cno++);

  		clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);

  		clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
  		set_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);

  		nilfs_segctor_clear_metadata_dirty(sci);

  	} else
  		clear_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
  }

  static int nilfs_segctor_wait(struct nilfs_sc_info *sci)
  {
  	int ret;
  
  	ret = nilfs_wait_on_logs(&sci->sc_write_logs);
  	if (!ret) {
  		nilfs_segctor_complete_write(sci);
  		nilfs_destroy_logs(&sci->sc_write_logs);
  	}
  	return ret;
  }

  static int nilfs_segctor_collect_dirty_files(struct nilfs_sc_info *sci,
  					     struct the_nilfs *nilfs)

  {
  	struct nilfs_inode_info *ii, *n;

  	struct inode *ifile = sci->sc_root->ifile;

  	spin_lock(&nilfs->ns_inode_lock);

   retry:

  	list_for_each_entry_safe(ii, n, &nilfs->ns_dirty_files, i_dirty) {

  		if (!ii->i_bh) {
  			struct buffer_head *ibh;
  			int err;

  			spin_unlock(&nilfs->ns_inode_lock);

  			err = nilfs_ifile_get_inode_block(

  				ifile, ii->vfs_inode.i_ino, &ibh);

  			if (unlikely(err)) {

  				nilfs_warning(sci->sc_super, __func__,

  					      "failed to get inode block.
  ");
  				return err;
  			}

  			mark_buffer_dirty(ibh);

  			nilfs_mdt_mark_dirty(ifile);

  			spin_lock(&nilfs->ns_inode_lock);

  			if (likely(!ii->i_bh))
  				ii->i_bh = ibh;
  			else
  				brelse(ibh);
  			goto retry;
  		}

  
  		clear_bit(NILFS_I_QUEUED, &ii->i_state);
  		set_bit(NILFS_I_BUSY, &ii->i_state);

  		list_move_tail(&ii->i_dirty, &sci->sc_dirty_files);

  	}

  	spin_unlock(&nilfs->ns_inode_lock);

  	return 0;
  }

  static void nilfs_segctor_drop_written_files(struct nilfs_sc_info *sci,
  					     struct the_nilfs *nilfs)

  {
  	struct nilfs_transaction_info *ti = current->journal_info;
  	struct nilfs_inode_info *ii, *n;

  	spin_lock(&nilfs->ns_inode_lock);

  	list_for_each_entry_safe(ii, n, &sci->sc_dirty_files, i_dirty) {
  		if (!test_and_clear_bit(NILFS_I_UPDATED, &ii->i_state) ||

  		    test_bit(NILFS_I_DIRTY, &ii->i_state))

  			continue;

  		clear_bit(NILFS_I_BUSY, &ii->i_state);
  		brelse(ii->i_bh);
  		ii->i_bh = NULL;

  		list_move_tail(&ii->i_dirty, &ti->ti_garbage);

  	}

  	spin_unlock(&nilfs->ns_inode_lock);

  }
  
  /*

   * Main procedure of segment constructor
   */
  static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	int err;

  
  	sci->sc_stage.scnt = NILFS_ST_INIT;

  	sci->sc_cno = nilfs->ns_cno;

  	err = nilfs_segctor_collect_dirty_files(sci, nilfs);

  	if (unlikely(err))
  		goto out;

  	if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))

  		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
  
  	if (nilfs_segctor_clean(sci))
  		goto out;
  
  	do {
  		sci->sc_stage.flags &= ~NILFS_CF_HISTORY_MASK;
  
  		err = nilfs_segctor_begin_construction(sci, nilfs);
  		if (unlikely(err))
  			goto out;
  
  		/* Update time stamp */
  		sci->sc_seg_ctime = get_seconds();
  
  		err = nilfs_segctor_collect(sci, nilfs, mode);
  		if (unlikely(err))
  			goto failed;

  		/* Avoid empty segment */
  		if (sci->sc_stage.scnt == NILFS_ST_DONE &&

  		    nilfs_segbuf_empty(sci->sc_curseg)) {

  			nilfs_segctor_abort_construction(sci, nilfs, 1);

  			goto out;
  		}
  
  		err = nilfs_segctor_assign(sci, mode);
  		if (unlikely(err))
  			goto failed;

  		if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)

  			nilfs_segctor_fill_in_file_bmap(sci);

  		if (mode == SC_LSEG_SR &&
  		    sci->sc_stage.scnt >= NILFS_ST_CPFILE) {

  			err = nilfs_segctor_fill_in_checkpoint(sci);
  			if (unlikely(err))

  				goto failed_to_write;

  
  			nilfs_segctor_fill_in_super_root(sci, nilfs);
  		}
  		nilfs_segctor_update_segusage(sci, nilfs->ns_sufile);
  
  		/* Write partial segments */

  		nilfs_segctor_prepare_write(sci);

  
  		nilfs_add_checksums_on_logs(&sci->sc_segbufs,
  					    nilfs->ns_crc_seed);

  		err = nilfs_segctor_write(sci, nilfs);

  		if (unlikely(err))
  			goto failed_to_write;

  		if (sci->sc_stage.scnt == NILFS_ST_DONE ||
  		    nilfs->ns_blocksize_bits != PAGE_CACHE_SHIFT) {
  			/*
  			 * At this point, we avoid double buffering
  			 * for blocksize < pagesize because page dirty
  			 * flag is turned off during write and dirty
  			 * buffers are not properly collected for
  			 * pages crossing over segments.
  			 */
  			err = nilfs_segctor_wait(sci);
  			if (err)
  				goto failed_to_write;
  		}

  	} while (sci->sc_stage.scnt != NILFS_ST_DONE);

   out:

  	nilfs_segctor_drop_written_files(sci, nilfs);

  	return err;
  
   failed_to_write:

  	if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
  		nilfs_redirty_inodes(&sci->sc_dirty_files);

  
   failed:
  	if (nilfs_doing_gc())
  		nilfs_redirty_inodes(&sci->sc_gc_inodes);

  	nilfs_segctor_abort_construction(sci, nilfs, err);

  	goto out;
  }
  
  /**

   * nilfs_segctor_start_timer - set timer of background write

   * @sci: nilfs_sc_info
   *
   * If the timer has already been set, it ignores the new request.
   * This function MUST be called within a section locking the segment
   * semaphore.
   */
  static void nilfs_segctor_start_timer(struct nilfs_sc_info *sci)
  {
  	spin_lock(&sci->sc_state_lock);

  	if (!(sci->sc_state & NILFS_SEGCTOR_COMMIT)) {
  		sci->sc_timer.expires = jiffies + sci->sc_interval;
  		add_timer(&sci->sc_timer);

  		sci->sc_state |= NILFS_SEGCTOR_COMMIT;
  	}
  	spin_unlock(&sci->sc_state_lock);
  }
  
  static void nilfs_segctor_do_flush(struct nilfs_sc_info *sci, int bn)
  {
  	spin_lock(&sci->sc_state_lock);
  	if (!(sci->sc_flush_request & (1 << bn))) {
  		unsigned long prev_req = sci->sc_flush_request;
  
  		sci->sc_flush_request |= (1 << bn);
  		if (!prev_req)
  			wake_up(&sci->sc_wait_daemon);
  	}
  	spin_unlock(&sci->sc_state_lock);
  }
  
  /**
   * nilfs_flush_segment - trigger a segment construction for resource control
   * @sb: super block
   * @ino: inode number of the file to be flushed out.
   */
  void nilfs_flush_segment(struct super_block *sb, ino_t ino)
  {

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	struct nilfs_sc_info *sci = nilfs->ns_writer;

  
  	if (!sci || nilfs_doing_construction())
  		return;
  	nilfs_segctor_do_flush(sci, NILFS_MDT_INODE(sb, ino) ? ino : 0);
  					/* assign bit 0 to data files */
  }

  struct nilfs_segctor_wait_request {
  	wait_queue_t	wq;
  	__u32		seq;
  	int		err;
  	atomic_t	done;
  };
  
  static int nilfs_segctor_sync(struct nilfs_sc_info *sci)
  {
  	struct nilfs_segctor_wait_request wait_req;
  	int err = 0;
  
  	spin_lock(&sci->sc_state_lock);
  	init_wait(&wait_req.wq);
  	wait_req.err = 0;
  	atomic_set(&wait_req.done, 0);
  	wait_req.seq = ++sci->sc_seq_request;
  	spin_unlock(&sci->sc_state_lock);
  
  	init_waitqueue_entry(&wait_req.wq, current);
  	add_wait_queue(&sci->sc_wait_request, &wait_req.wq);
  	set_current_state(TASK_INTERRUPTIBLE);
  	wake_up(&sci->sc_wait_daemon);
  
  	for (;;) {
  		if (atomic_read(&wait_req.done)) {
  			err = wait_req.err;
  			break;
  		}
  		if (!signal_pending(current)) {
  			schedule();
  			continue;
  		}
  		err = -ERESTARTSYS;
  		break;
  	}
  	finish_wait(&sci->sc_wait_request, &wait_req.wq);
  	return err;
  }
  
  static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err)
  {
  	struct nilfs_segctor_wait_request *wrq, *n;
  	unsigned long flags;
  
  	spin_lock_irqsave(&sci->sc_wait_request.lock, flags);
  	list_for_each_entry_safe(wrq, n, &sci->sc_wait_request.task_list,
  				 wq.task_list) {
  		if (!atomic_read(&wrq->done) &&
  		    nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq)) {
  			wrq->err = err;
  			atomic_set(&wrq->done, 1);
  		}
  		if (atomic_read(&wrq->done)) {
  			wrq->wq.func(&wrq->wq,
  				     TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
  				     0, NULL);
  		}
  	}
  	spin_unlock_irqrestore(&sci->sc_wait_request.lock, flags);
  }
  
  /**
   * nilfs_construct_segment - construct a logical segment
   * @sb: super block
   *
   * Return Value: On success, 0 is retured. On errors, one of the following
   * negative error code is returned.
   *
   * %-EROFS - Read only filesystem.
   *
   * %-EIO - I/O error
   *
   * %-ENOSPC - No space left on device (only in a panic state).
   *
   * %-ERESTARTSYS - Interrupted.
   *
   * %-ENOMEM - Insufficient memory available.
   */
  int nilfs_construct_segment(struct super_block *sb)
  {

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	struct nilfs_sc_info *sci = nilfs->ns_writer;

  	struct nilfs_transaction_info *ti;
  	int err;
  
  	if (!sci)
  		return -EROFS;
  
  	/* A call inside transactions causes a deadlock. */
  	BUG_ON((ti = current->journal_info) && ti->ti_magic == NILFS_TI_MAGIC);
  
  	err = nilfs_segctor_sync(sci);
  	return err;
  }
  
  /**
   * nilfs_construct_dsync_segment - construct a data-only logical segment
   * @sb: super block

   * @inode: inode whose data blocks should be written out
   * @start: start byte offset
   * @end: end byte offset (inclusive)

   *
   * Return Value: On success, 0 is retured. On errors, one of the following
   * negative error code is returned.
   *
   * %-EROFS - Read only filesystem.
   *
   * %-EIO - I/O error
   *
   * %-ENOSPC - No space left on device (only in a panic state).
   *
   * %-ERESTARTSYS - Interrupted.
   *
   * %-ENOMEM - Insufficient memory available.
   */

  int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
  				  loff_t start, loff_t end)

  {

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	struct nilfs_sc_info *sci = nilfs->ns_writer;

  	struct nilfs_inode_info *ii;
  	struct nilfs_transaction_info ti;
  	int err = 0;
  
  	if (!sci)
  		return -EROFS;

  	nilfs_transaction_lock(sb, &ti, 0);

  
  	ii = NILFS_I(inode);
  	if (test_bit(NILFS_I_INODE_DIRTY, &ii->i_state) ||

  	    nilfs_test_opt(nilfs, STRICT_ORDER) ||

  	    test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||

  	    nilfs_discontinued(nilfs)) {

  		nilfs_transaction_unlock(sb);

  		err = nilfs_segctor_sync(sci);
  		return err;
  	}

  	spin_lock(&nilfs->ns_inode_lock);

  	if (!test_bit(NILFS_I_QUEUED, &ii->i_state) &&
  	    !test_bit(NILFS_I_BUSY, &ii->i_state)) {

  		spin_unlock(&nilfs->ns_inode_lock);

  		nilfs_transaction_unlock(sb);

  		return 0;
  	}

  	spin_unlock(&nilfs->ns_inode_lock);

  	sci->sc_dsync_inode = ii;
  	sci->sc_dsync_start = start;
  	sci->sc_dsync_end = end;

  
  	err = nilfs_segctor_do_construct(sci, SC_LSEG_DSYNC);

  	nilfs_transaction_unlock(sb);

  	return err;
  }

  #define FLUSH_FILE_BIT	(0x1) /* data file only */
  #define FLUSH_DAT_BIT	(1 << NILFS_DAT_INO) /* DAT only */

  /**
   * nilfs_segctor_accept - record accepted sequence count of log-write requests
   * @sci: segment constructor object
   */
  static void nilfs_segctor_accept(struct nilfs_sc_info *sci)

  {

  	spin_lock(&sci->sc_state_lock);

  	sci->sc_seq_accepted = sci->sc_seq_request;

  	spin_unlock(&sci->sc_state_lock);

  	del_timer_sync(&sci->sc_timer);

  }

  /**
   * nilfs_segctor_notify - notify the result of request to caller threads
   * @sci: segment constructor object
   * @mode: mode of log forming
   * @err: error code to be notified
   */
  static void nilfs_segctor_notify(struct nilfs_sc_info *sci, int mode, int err)

  {
  	/* Clear requests (even when the construction failed) */
  	spin_lock(&sci->sc_state_lock);

  	if (mode == SC_LSEG_SR) {

  		sci->sc_state &= ~NILFS_SEGCTOR_COMMIT;

  		sci->sc_seq_done = sci->sc_seq_accepted;
  		nilfs_segctor_wakeup(sci, err);

  		sci->sc_flush_request = 0;

  	} else {

  		if (mode == SC_FLUSH_FILE)

  			sci->sc_flush_request &= ~FLUSH_FILE_BIT;

  		else if (mode == SC_FLUSH_DAT)

  			sci->sc_flush_request &= ~FLUSH_DAT_BIT;
  
  		/* re-enable timer if checkpoint creation was not done */

  		if ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
  		    time_before(jiffies, sci->sc_timer.expires))
  			add_timer(&sci->sc_timer);

  	}

  	spin_unlock(&sci->sc_state_lock);
  }

  /**
   * nilfs_segctor_construct - form logs and write them to disk
   * @sci: segment constructor object
   * @mode: mode of log forming
   */
  static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)

  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	struct nilfs_super_block **sbp;

  	int err = 0;

  	nilfs_segctor_accept(sci);

  	if (nilfs_discontinued(nilfs))

  		mode = SC_LSEG_SR;
  	if (!nilfs_segctor_confirm(sci))
  		err = nilfs_segctor_do_construct(sci, mode);

  	if (likely(!err)) {

  		if (mode != SC_FLUSH_DAT)

  			atomic_set(&nilfs->ns_ndirtyblks, 0);
  		if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) &&
  		    nilfs_discontinued(nilfs)) {
  			down_write(&nilfs->ns_sem);

  			err = -EIO;

  			sbp = nilfs_prepare_super(sci->sc_super,

  						  nilfs_sb_will_flip(nilfs));
  			if (likely(sbp)) {
  				nilfs_set_log_cursor(sbp[0], nilfs);

  				err = nilfs_commit_super(sci->sc_super,
  							 NILFS_SB_COMMIT);

  			}

  			up_write(&nilfs->ns_sem);
  		}
  	}

  
  	nilfs_segctor_notify(sci, mode, err);

  	return err;
  }
  
  static void nilfs_construction_timeout(unsigned long data)
  {
  	struct task_struct *p = (struct task_struct *)data;
  	wake_up_process(p);
  }
  
  static void
  nilfs_remove_written_gcinodes(struct the_nilfs *nilfs, struct list_head *head)
  {
  	struct nilfs_inode_info *ii, *n;
  
  	list_for_each_entry_safe(ii, n, head, i_dirty) {
  		if (!test_bit(NILFS_I_UPDATED, &ii->i_state))
  			continue;

  		list_del_init(&ii->i_dirty);

  		truncate_inode_pages(&ii->vfs_inode.i_data, 0);
  		nilfs_btnode_cache_clear(&ii->i_btnode_cache);

  		iput(&ii->vfs_inode);

  	}
  }

  int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
  			 void **kbufs)

  {

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	struct nilfs_sc_info *sci = nilfs->ns_writer;

  	struct nilfs_transaction_info ti;

  	int err;
  
  	if (unlikely(!sci))
  		return -EROFS;

  	nilfs_transaction_lock(sb, &ti, 1);

  	err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat);

  	if (unlikely(err))
  		goto out_unlock;

  	err = nilfs_ioctl_prepare_clean_segments(nilfs, argv, kbufs);

  	if (unlikely(err)) {
  		nilfs_mdt_restore_from_shadow_map(nilfs->ns_dat);

  		goto out_unlock;

  	}

  	sci->sc_freesegs = kbufs[4];
  	sci->sc_nfreesegs = argv[4].v_nmembs;

  	list_splice_tail_init(&nilfs->ns_gc_inodes, &sci->sc_gc_inodes);

  
  	for (;;) {

  		err = nilfs_segctor_construct(sci, SC_LSEG_SR);

  		nilfs_remove_written_gcinodes(nilfs, &sci->sc_gc_inodes);

  
  		if (likely(!err))
  			break;
  
  		nilfs_warning(sb, __func__,
  			      "segment construction failed. (err=%d)", err);
  		set_current_state(TASK_INTERRUPTIBLE);
  		schedule_timeout(sci->sc_interval);
  	}

  	if (nilfs_test_opt(nilfs, DISCARD)) {

  		int ret = nilfs_discard_segments(nilfs, sci->sc_freesegs,
  						 sci->sc_nfreesegs);
  		if (ret) {
  			printk(KERN_WARNING
  			       "NILFS warning: error %d on discard request, "
  			       "turning discards off for the device
  ", ret);

  			nilfs_clear_opt(nilfs, DISCARD);

  		}
  	}

  
   out_unlock:

  	sci->sc_freesegs = NULL;
  	sci->sc_nfreesegs = 0;

  	nilfs_mdt_clear_shadow_map(nilfs->ns_dat);

  	nilfs_transaction_unlock(sb);

  	return err;
  }
  
  static void nilfs_segctor_thread_construct(struct nilfs_sc_info *sci, int mode)
  {

  	struct nilfs_transaction_info ti;

  	nilfs_transaction_lock(sci->sc_super, &ti, 0);

  	nilfs_segctor_construct(sci, mode);

  
  	/*
  	 * Unclosed segment should be retried.  We do this using sc_timer.
  	 * Timeout of sc_timer will invoke complete construction which leads
  	 * to close the current logical segment.
  	 */
  	if (test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags))
  		nilfs_segctor_start_timer(sci);

  	nilfs_transaction_unlock(sci->sc_super);

  }
  
  static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *sci)
  {
  	int mode = 0;
  	int err;
  
  	spin_lock(&sci->sc_state_lock);
  	mode = (sci->sc_flush_request & FLUSH_DAT_BIT) ?
  		SC_FLUSH_DAT : SC_FLUSH_FILE;
  	spin_unlock(&sci->sc_state_lock);
  
  	if (mode) {
  		err = nilfs_segctor_do_construct(sci, mode);
  
  		spin_lock(&sci->sc_state_lock);
  		sci->sc_flush_request &= (mode == SC_FLUSH_FILE) ?
  			~FLUSH_FILE_BIT : ~FLUSH_DAT_BIT;
  		spin_unlock(&sci->sc_state_lock);
  	}
  	clear_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
  }
  
  static int nilfs_segctor_flush_mode(struct nilfs_sc_info *sci)
  {
  	if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
  	    time_before(jiffies, sci->sc_lseg_stime + sci->sc_mjcp_freq)) {
  		if (!(sci->sc_flush_request & ~FLUSH_FILE_BIT))
  			return SC_FLUSH_FILE;
  		else if (!(sci->sc_flush_request & ~FLUSH_DAT_BIT))
  			return SC_FLUSH_DAT;
  	}
  	return SC_LSEG_SR;
  }
  
  /**
   * nilfs_segctor_thread - main loop of the segment constructor thread.
   * @arg: pointer to a struct nilfs_sc_info.
   *
   * nilfs_segctor_thread() initializes a timer and serves as a daemon
   * to execute segment constructions.
   */
  static int nilfs_segctor_thread(void *arg)
  {
  	struct nilfs_sc_info *sci = (struct nilfs_sc_info *)arg;

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	int timeout = 0;

  	sci->sc_timer.data = (unsigned long)current;
  	sci->sc_timer.function = nilfs_construction_timeout;

  
  	/* start sync. */
  	sci->sc_task = current;
  	wake_up(&sci->sc_wait_task); /* for nilfs_segctor_start_thread() */
  	printk(KERN_INFO
  	       "segctord starting. Construction interval = %lu seconds, "
  	       "CP frequency < %lu seconds
  ",
  	       sci->sc_interval / HZ, sci->sc_mjcp_freq / HZ);
  
  	spin_lock(&sci->sc_state_lock);
   loop:
  	for (;;) {
  		int mode;
  
  		if (sci->sc_state & NILFS_SEGCTOR_QUIT)
  			goto end_thread;
  
  		if (timeout || sci->sc_seq_request != sci->sc_seq_done)
  			mode = SC_LSEG_SR;
  		else if (!sci->sc_flush_request)
  			break;
  		else
  			mode = nilfs_segctor_flush_mode(sci);
  
  		spin_unlock(&sci->sc_state_lock);
  		nilfs_segctor_thread_construct(sci, mode);
  		spin_lock(&sci->sc_state_lock);
  		timeout = 0;
  	}
  
  
  	if (freezing(current)) {
  		spin_unlock(&sci->sc_state_lock);

  		try_to_freeze();

  		spin_lock(&sci->sc_state_lock);
  	} else {
  		DEFINE_WAIT(wait);
  		int should_sleep = 1;
  
  		prepare_to_wait(&sci->sc_wait_daemon, &wait,
  				TASK_INTERRUPTIBLE);
  
  		if (sci->sc_seq_request != sci->sc_seq_done)
  			should_sleep = 0;
  		else if (sci->sc_flush_request)
  			should_sleep = 0;
  		else if (sci->sc_state & NILFS_SEGCTOR_COMMIT)
  			should_sleep = time_before(jiffies,

  					sci->sc_timer.expires);

  
  		if (should_sleep) {
  			spin_unlock(&sci->sc_state_lock);
  			schedule();
  			spin_lock(&sci->sc_state_lock);
  		}
  		finish_wait(&sci->sc_wait_daemon, &wait);
  		timeout = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&

  			   time_after_eq(jiffies, sci->sc_timer.expires));

  
  		if (nilfs_sb_dirty(nilfs) && nilfs_sb_need_update(nilfs))

  			set_nilfs_discontinued(nilfs);

  	}
  	goto loop;
  
   end_thread:
  	spin_unlock(&sci->sc_state_lock);

  
  	/* end sync. */
  	sci->sc_task = NULL;
  	wake_up(&sci->sc_wait_task); /* for nilfs_segctor_kill_thread() */
  	return 0;
  }
  
  static int nilfs_segctor_start_thread(struct nilfs_sc_info *sci)
  {
  	struct task_struct *t;
  
  	t = kthread_run(nilfs_segctor_thread, sci, "segctord");
  	if (IS_ERR(t)) {
  		int err = PTR_ERR(t);
  
  		printk(KERN_ERR "NILFS: error %d creating segctord thread
  ",
  		       err);
  		return err;
  	}
  	wait_event(sci->sc_wait_task, sci->sc_task != NULL);
  	return 0;
  }
  
  static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)

  	__acquires(&sci->sc_state_lock)
  	__releases(&sci->sc_state_lock)

  {
  	sci->sc_state |= NILFS_SEGCTOR_QUIT;
  
  	while (sci->sc_task) {
  		wake_up(&sci->sc_wait_daemon);
  		spin_unlock(&sci->sc_state_lock);
  		wait_event(sci->sc_wait_task, sci->sc_task == NULL);
  		spin_lock(&sci->sc_state_lock);
  	}
  }

  /*
   * Setup & clean-up functions
   */

  static struct nilfs_sc_info *nilfs_segctor_new(struct super_block *sb,

  					       struct nilfs_root *root)

  {

  	struct the_nilfs *nilfs = sb->s_fs_info;

  	struct nilfs_sc_info *sci;
  
  	sci = kzalloc(sizeof(*sci), GFP_KERNEL);
  	if (!sci)
  		return NULL;

  	sci->sc_super = sb;

  	nilfs_get_root(root);
  	sci->sc_root = root;

  	init_waitqueue_head(&sci->sc_wait_request);
  	init_waitqueue_head(&sci->sc_wait_daemon);
  	init_waitqueue_head(&sci->sc_wait_task);
  	spin_lock_init(&sci->sc_state_lock);
  	INIT_LIST_HEAD(&sci->sc_dirty_files);
  	INIT_LIST_HEAD(&sci->sc_segbufs);

  	INIT_LIST_HEAD(&sci->sc_write_logs);

  	INIT_LIST_HEAD(&sci->sc_gc_inodes);

  	init_timer(&sci->sc_timer);

  
  	sci->sc_interval = HZ * NILFS_SC_DEFAULT_TIMEOUT;
  	sci->sc_mjcp_freq = HZ * NILFS_SC_DEFAULT_SR_FREQ;
  	sci->sc_watermark = NILFS_SC_DEFAULT_WATERMARK;

  	if (nilfs->ns_interval)

  		sci->sc_interval = HZ * nilfs->ns_interval;

  	if (nilfs->ns_watermark)
  		sci->sc_watermark = nilfs->ns_watermark;

  	return sci;
  }
  
  static void nilfs_segctor_write_out(struct nilfs_sc_info *sci)
  {
  	int ret, retrycount = NILFS_SC_CLEANUP_RETRY;
  
  	/* The segctord thread was stopped and its timer was removed.
  	   But some tasks remain. */
  	do {

  		struct nilfs_transaction_info ti;

  		nilfs_transaction_lock(sci->sc_super, &ti, 0);

  		ret = nilfs_segctor_construct(sci, SC_LSEG_SR);

  		nilfs_transaction_unlock(sci->sc_super);

  
  	} while (ret && retrycount-- > 0);
  }
  
  /**
   * nilfs_segctor_destroy - destroy the segment constructor.
   * @sci: nilfs_sc_info
   *
   * nilfs_segctor_destroy() kills the segctord thread and frees
   * the nilfs_sc_info struct.
   * Caller must hold the segment semaphore.
   */
  static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
  {

  	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;

  	int flag;

  	up_write(&nilfs->ns_segctor_sem);

  
  	spin_lock(&sci->sc_state_lock);
  	nilfs_segctor_kill_thread(sci);
  	flag = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) || sci->sc_flush_request
  		|| sci->sc_seq_request != sci->sc_seq_done);
  	spin_unlock(&sci->sc_state_lock);

  	if (flag || !nilfs_segctor_confirm(sci))

  		nilfs_segctor_write_out(sci);

  	if (!list_empty(&sci->sc_dirty_files)) {

  		nilfs_warning(sci->sc_super, __func__,

  			      "dirty file(s) after the final construction
  ");

  		nilfs_dispose_list(nilfs, &sci->sc_dirty_files, 1);

  	}

  	WARN_ON(!list_empty(&sci->sc_segbufs));

  	WARN_ON(!list_empty(&sci->sc_write_logs));

  	nilfs_put_root(sci->sc_root);

  	down_write(&nilfs->ns_segctor_sem);

  	del_timer_sync(&sci->sc_timer);

  	kfree(sci);
  }
  
  /**

   * nilfs_attach_log_writer - attach log writer
   * @sb: super block instance

   * @root: root object of the current filesystem tree

   *

   * This allocates a log writer object, initializes it, and starts the
   * log writer.

   *
   * Return Value: On success, 0 is returned. On error, one of the following
   * negative error code is returned.
   *
   * %-ENOMEM - Insufficient memory available.
   */

  int nilfs_attach_log_writer(struct super_block *sb, struct nilfs_root *root)

  {