/*
   * the_nilfs.c - the_nilfs shared structure.
   *
   * 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/slab.h>
  #include <linux/blkdev.h>
  #include <linux/backing-dev.h>

  #include <linux/random.h>

  #include <linux/crc32.h>

  #include "nilfs.h"
  #include "segment.h"
  #include "alloc.h"
  #include "cpfile.h"
  #include "sufile.h"
  #include "dat.h"

  #include "segbuf.h"

  static int nilfs_valid_sb(struct nilfs_super_block *sbp);

  void nilfs_set_last_segment(struct the_nilfs *nilfs,
  			    sector_t start_blocknr, u64 seq, __u64 cno)
  {
  	spin_lock(&nilfs->ns_last_segment_lock);
  	nilfs->ns_last_pseg = start_blocknr;
  	nilfs->ns_last_seq = seq;
  	nilfs->ns_last_cno = cno;

  
  	if (!nilfs_sb_dirty(nilfs)) {
  		if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
  			goto stay_cursor;
  
  		set_nilfs_sb_dirty(nilfs);
  	}
  	nilfs->ns_prev_seq = nilfs->ns_last_seq;
  
   stay_cursor:

  	spin_unlock(&nilfs->ns_last_segment_lock);
  }
  
  /**

   * alloc_nilfs - allocate a nilfs object

   * @bdev: block device to which the_nilfs is related
   *

   * Return Value: On success, pointer to the_nilfs is returned.
   * On error, NULL is returned.
   */

  struct the_nilfs *alloc_nilfs(struct block_device *bdev)

  {
  	struct the_nilfs *nilfs;
  
  	nilfs = kzalloc(sizeof(*nilfs), GFP_KERNEL);
  	if (!nilfs)
  		return NULL;
  
  	nilfs->ns_bdev = bdev;

  	atomic_set(&nilfs->ns_ndirtyblks, 0);
  	init_rwsem(&nilfs->ns_sem);

  	INIT_LIST_HEAD(&nilfs->ns_dirty_files);

  	INIT_LIST_HEAD(&nilfs->ns_gc_inodes);

  	spin_lock_init(&nilfs->ns_inode_lock);

  	spin_lock_init(&nilfs->ns_next_gen_lock);

  	spin_lock_init(&nilfs->ns_last_segment_lock);

  	nilfs->ns_cptree = RB_ROOT;
  	spin_lock_init(&nilfs->ns_cptree_lock);

  	init_rwsem(&nilfs->ns_segctor_sem);

  
  	return nilfs;
  }
  
  /**

   * destroy_nilfs - destroy nilfs object
   * @nilfs: nilfs object to be released

   */

  void destroy_nilfs(struct the_nilfs *nilfs)

  {

  	might_sleep();

  	if (nilfs_init(nilfs)) {

  		brelse(nilfs->ns_sbh[0]);
  		brelse(nilfs->ns_sbh[1]);

  	}
  	kfree(nilfs);
  }

  static int nilfs_load_super_root(struct the_nilfs *nilfs,
  				 struct super_block *sb, sector_t sr_block)

  {
  	struct buffer_head *bh_sr;
  	struct nilfs_super_root *raw_sr;

  	struct nilfs_super_block **sbp = nilfs->ns_sbp;

  	struct nilfs_inode *rawi;

  	unsigned dat_entry_size, segment_usage_size, checkpoint_size;
  	unsigned inode_size;
  	int err;

  	err = nilfs_read_super_root_block(nilfs, sr_block, &bh_sr, 1);

  	if (unlikely(err))
  		return err;
  
  	down_read(&nilfs->ns_sem);

  	dat_entry_size = le16_to_cpu(sbp[0]->s_dat_entry_size);
  	checkpoint_size = le16_to_cpu(sbp[0]->s_checkpoint_size);
  	segment_usage_size = le16_to_cpu(sbp[0]->s_segment_usage_size);

  	up_read(&nilfs->ns_sem);
  
  	inode_size = nilfs->ns_inode_size;

  	rawi = (void *)bh_sr->b_data + NILFS_SR_DAT_OFFSET(inode_size);
  	err = nilfs_dat_read(sb, dat_entry_size, rawi, &nilfs->ns_dat);
  	if (err)

  		goto failed;

  	rawi = (void *)bh_sr->b_data + NILFS_SR_CPFILE_OFFSET(inode_size);
  	err = nilfs_cpfile_read(sb, checkpoint_size, rawi, &nilfs->ns_cpfile);
  	if (err)

  		goto failed_dat;

  	rawi = (void *)bh_sr->b_data + NILFS_SR_SUFILE_OFFSET(inode_size);
  	err = nilfs_sufile_read(sb, segment_usage_size, rawi,
  				&nilfs->ns_sufile);
  	if (err)

  		goto failed_cpfile;

  	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
  	nilfs->ns_nongc_ctime = le64_to_cpu(raw_sr->sr_nongc_ctime);
  
   failed:
  	brelse(bh_sr);
  	return err;

   failed_cpfile:

  	iput(nilfs->ns_cpfile);

  
   failed_dat:

  	iput(nilfs->ns_dat);

  	goto failed;
  }
  
  static void nilfs_init_recovery_info(struct nilfs_recovery_info *ri)
  {
  	memset(ri, 0, sizeof(*ri));
  	INIT_LIST_HEAD(&ri->ri_used_segments);
  }
  
  static void nilfs_clear_recovery_info(struct nilfs_recovery_info *ri)
  {
  	nilfs_dispose_segment_list(&ri->ri_used_segments);
  }
  
  /**

   * nilfs_store_log_cursor - load log cursor from a super block
   * @nilfs: nilfs object
   * @sbp: buffer storing super block to be read
   *
   * nilfs_store_log_cursor() reads the last position of the log
   * containing a super root from a given super block, and initializes
   * relevant information on the nilfs object preparatory for log
   * scanning and recovery.
   */
  static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
  				  struct nilfs_super_block *sbp)
  {
  	int ret = 0;
  
  	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
  	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
  	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);

  	nilfs->ns_prev_seq = nilfs->ns_last_seq;

  	nilfs->ns_seg_seq = nilfs->ns_last_seq;
  	nilfs->ns_segnum =
  		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
  	nilfs->ns_cno = nilfs->ns_last_cno + 1;
  	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
  		printk(KERN_ERR "NILFS invalid last segment number.
  ");
  		ret = -EINVAL;
  	}
  	return ret;
  }
  
  /**

   * load_nilfs - load and recover the nilfs
   * @nilfs: the_nilfs structure to be released

   * @sb: super block isntance used to recover past segment

   *
   * load_nilfs() searches and load the latest super root,
   * attaches the last segment, and does recovery if needed.
   * The caller must call this exclusively for simultaneous mounts.
   */

  int load_nilfs(struct the_nilfs *nilfs, struct super_block *sb)

  {
  	struct nilfs_recovery_info ri;

  	unsigned int s_flags = sb->s_flags;

  	int really_read_only = bdev_read_only(nilfs->ns_bdev);

  	int valid_fs = nilfs_valid_fs(nilfs);

  	int err;

  	if (!valid_fs) {
  		printk(KERN_WARNING "NILFS warning: mounting unchecked fs
  ");
  		if (s_flags & MS_RDONLY) {
  			printk(KERN_INFO "NILFS: INFO: recovery "
  			       "required for readonly filesystem.
  ");
  			printk(KERN_INFO "NILFS: write access will "
  			       "be enabled during recovery.
  ");

  		}

  	}

  	nilfs_init_recovery_info(&ri);

  	err = nilfs_search_super_root(nilfs, &ri);

  	if (unlikely(err)) {

  		struct nilfs_super_block **sbp = nilfs->ns_sbp;
  		int blocksize;
  
  		if (err != -EINVAL)
  			goto scan_error;
  
  		if (!nilfs_valid_sb(sbp[1])) {
  			printk(KERN_WARNING
  			       "NILFS warning: unable to fall back to spare"
  			       "super block
  ");
  			goto scan_error;
  		}
  		printk(KERN_INFO
  		       "NILFS: try rollback from an earlier position
  ");
  
  		/*
  		 * restore super block with its spare and reconfigure
  		 * relevant states of the nilfs object.
  		 */
  		memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
  		nilfs->ns_crc_seed = le32_to_cpu(sbp[0]->s_crc_seed);
  		nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
  
  		/* verify consistency between two super blocks */
  		blocksize = BLOCK_SIZE << le32_to_cpu(sbp[0]->s_log_block_size);
  		if (blocksize != nilfs->ns_blocksize) {
  			printk(KERN_WARNING
  			       "NILFS warning: blocksize differs between "
  			       "two super blocks (%d != %d)
  ",
  			       blocksize, nilfs->ns_blocksize);
  			goto scan_error;
  		}
  
  		err = nilfs_store_log_cursor(nilfs, sbp[0]);
  		if (err)
  			goto scan_error;
  
  		/* drop clean flag to allow roll-forward and recovery */
  		nilfs->ns_mount_state &= ~NILFS_VALID_FS;
  		valid_fs = 0;
  
  		err = nilfs_search_super_root(nilfs, &ri);
  		if (err)
  			goto scan_error;

  	}

  	err = nilfs_load_super_root(nilfs, sb, ri.ri_super_root);

  	if (unlikely(err)) {
  		printk(KERN_ERR "NILFS: error loading super root.
  ");
  		goto failed;
  	}

  	if (valid_fs)
  		goto skip_recovery;
  
  	if (s_flags & MS_RDONLY) {

  		__u64 features;

  		if (nilfs_test_opt(nilfs, NORECOVERY)) {

  			printk(KERN_INFO "NILFS: norecovery option specified. "
  			       "skipping roll-forward recovery
  ");
  			goto skip_recovery;
  		}

  		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
  			~NILFS_FEATURE_COMPAT_RO_SUPP;
  		if (features) {
  			printk(KERN_ERR "NILFS: couldn't proceed with "
  			       "recovery because of unsupported optional "
  			       "features (%llx)
  ",
  			       (unsigned long long)features);
  			err = -EROFS;
  			goto failed_unload;
  		}

  		if (really_read_only) {
  			printk(KERN_ERR "NILFS: write access "
  			       "unavailable, cannot proceed.
  ");
  			err = -EROFS;
  			goto failed_unload;

  		}

  		sb->s_flags &= ~MS_RDONLY;

  	} else if (nilfs_test_opt(nilfs, NORECOVERY)) {

  		printk(KERN_ERR "NILFS: recovery cancelled because norecovery "
  		       "option was specified for a read/write mount
  ");
  		err = -EINVAL;
  		goto failed_unload;

  	}

  	err = nilfs_salvage_orphan_logs(nilfs, sb, &ri);

  	if (err)
  		goto failed_unload;
  
  	down_write(&nilfs->ns_sem);

  	nilfs->ns_mount_state |= NILFS_VALID_FS; /* set "clean" flag */

  	err = nilfs_cleanup_super(sb);

  	up_write(&nilfs->ns_sem);
  
  	if (err) {
  		printk(KERN_ERR "NILFS: failed to update super block. "
  		       "recovery unfinished.
  ");
  		goto failed_unload;

  	}

  	printk(KERN_INFO "NILFS: recovery complete.
  ");

   skip_recovery:

  	nilfs_clear_recovery_info(&ri);

  	sb->s_flags = s_flags;

  	return 0;

   scan_error:
  	printk(KERN_ERR "NILFS: error searching super root.
  ");
  	goto failed;

   failed_unload:

  	iput(nilfs->ns_cpfile);
  	iput(nilfs->ns_sufile);
  	iput(nilfs->ns_dat);

  
   failed:
  	nilfs_clear_recovery_info(&ri);

  	sb->s_flags = s_flags;

  	return err;
  }
  
  static unsigned long long nilfs_max_size(unsigned int blkbits)
  {
  	unsigned int max_bits;
  	unsigned long long res = MAX_LFS_FILESIZE; /* page cache limit */
  
  	max_bits = blkbits + NILFS_BMAP_KEY_BIT; /* bmap size limit */
  	if (max_bits < 64)
  		res = min_t(unsigned long long, res, (1ULL << max_bits) - 1);
  	return res;
  }

  /**
   * nilfs_nrsvsegs - calculate the number of reserved segments
   * @nilfs: nilfs object
   * @nsegs: total number of segments
   */
  unsigned long nilfs_nrsvsegs(struct the_nilfs *nilfs, unsigned long nsegs)
  {
  	return max_t(unsigned long, NILFS_MIN_NRSVSEGS,
  		     DIV_ROUND_UP(nsegs * nilfs->ns_r_segments_percentage,
  				  100));
  }
  
  void nilfs_set_nsegments(struct the_nilfs *nilfs, unsigned long nsegs)
  {
  	nilfs->ns_nsegments = nsegs;
  	nilfs->ns_nrsvsegs = nilfs_nrsvsegs(nilfs, nsegs);
  }

  static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
  				   struct nilfs_super_block *sbp)

  {

  	if (le32_to_cpu(sbp->s_rev_level) < NILFS_MIN_SUPP_REV) {
  		printk(KERN_ERR "NILFS: unsupported revision "

  		       "(superblock rev.=%d.%d, current rev.=%d.%d). "
  		       "Please check the version of mkfs.nilfs.
  ",
  		       le32_to_cpu(sbp->s_rev_level),
  		       le16_to_cpu(sbp->s_minor_rev_level),
  		       NILFS_CURRENT_REV, NILFS_MINOR_REV);
  		return -EINVAL;
  	}

  	nilfs->ns_sbsize = le16_to_cpu(sbp->s_bytes);
  	if (nilfs->ns_sbsize > BLOCK_SIZE)
  		return -EINVAL;

  	nilfs->ns_inode_size = le16_to_cpu(sbp->s_inode_size);
  	nilfs->ns_first_ino = le32_to_cpu(sbp->s_first_ino);
  
  	nilfs->ns_blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
  	if (nilfs->ns_blocks_per_segment < NILFS_SEG_MIN_BLOCKS) {

  		printk(KERN_ERR "NILFS: too short segment.
  ");

  		return -EINVAL;
  	}
  
  	nilfs->ns_first_data_block = le64_to_cpu(sbp->s_first_data_block);

  	nilfs->ns_r_segments_percentage =
  		le32_to_cpu(sbp->s_r_segments_percentage);

  	nilfs_set_nsegments(nilfs, le64_to_cpu(sbp->s_nsegments));

  	nilfs->ns_crc_seed = le32_to_cpu(sbp->s_crc_seed);
  	return 0;
  }

  static int nilfs_valid_sb(struct nilfs_super_block *sbp)
  {
  	static unsigned char sum[4];
  	const int sumoff = offsetof(struct nilfs_super_block, s_sum);
  	size_t bytes;
  	u32 crc;
  
  	if (!sbp || le16_to_cpu(sbp->s_magic) != NILFS_SUPER_MAGIC)
  		return 0;
  	bytes = le16_to_cpu(sbp->s_bytes);
  	if (bytes > BLOCK_SIZE)
  		return 0;
  	crc = crc32_le(le32_to_cpu(sbp->s_crc_seed), (unsigned char *)sbp,
  		       sumoff);
  	crc = crc32_le(crc, sum, 4);
  	crc = crc32_le(crc, (unsigned char *)sbp + sumoff + 4,
  		       bytes - sumoff - 4);
  	return crc == le32_to_cpu(sbp->s_sum);
  }
  
  static int nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
  {
  	return offset < ((le64_to_cpu(sbp->s_nsegments) *
  			  le32_to_cpu(sbp->s_blocks_per_segment)) <<
  			 (le32_to_cpu(sbp->s_log_block_size) + 10));
  }
  
  static void nilfs_release_super_block(struct the_nilfs *nilfs)
  {
  	int i;
  
  	for (i = 0; i < 2; i++) {
  		if (nilfs->ns_sbp[i]) {
  			brelse(nilfs->ns_sbh[i]);
  			nilfs->ns_sbh[i] = NULL;
  			nilfs->ns_sbp[i] = NULL;
  		}
  	}
  }
  
  void nilfs_fall_back_super_block(struct the_nilfs *nilfs)
  {
  	brelse(nilfs->ns_sbh[0]);
  	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
  	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
  	nilfs->ns_sbh[1] = NULL;
  	nilfs->ns_sbp[1] = NULL;
  }
  
  void nilfs_swap_super_block(struct the_nilfs *nilfs)
  {
  	struct buffer_head *tsbh = nilfs->ns_sbh[0];
  	struct nilfs_super_block *tsbp = nilfs->ns_sbp[0];
  
  	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
  	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
  	nilfs->ns_sbh[1] = tsbh;
  	nilfs->ns_sbp[1] = tsbp;
  }
  
  static int nilfs_load_super_block(struct the_nilfs *nilfs,
  				  struct super_block *sb, int blocksize,
  				  struct nilfs_super_block **sbpp)
  {
  	struct nilfs_super_block **sbp = nilfs->ns_sbp;
  	struct buffer_head **sbh = nilfs->ns_sbh;
  	u64 sb2off = NILFS_SB2_OFFSET_BYTES(nilfs->ns_bdev->bd_inode->i_size);
  	int valid[2], swp = 0;
  
  	sbp[0] = nilfs_read_super_block(sb, NILFS_SB_OFFSET_BYTES, blocksize,
  					&sbh[0]);
  	sbp[1] = nilfs_read_super_block(sb, sb2off, blocksize, &sbh[1]);
  
  	if (!sbp[0]) {
  		if (!sbp[1]) {
  			printk(KERN_ERR "NILFS: unable to read superblock
  ");
  			return -EIO;
  		}
  		printk(KERN_WARNING

  		       "NILFS warning: unable to read primary superblock "
  		       "(blocksize = %d)
  ", blocksize);
  	} else if (!sbp[1]) {

  		printk(KERN_WARNING

  		       "NILFS warning: unable to read secondary superblock "
  		       "(blocksize = %d)
  ", blocksize);
  	}

  	/*
  	 * Compare two super blocks and set 1 in swp if the secondary
  	 * super block is valid and newer.  Otherwise, set 0 in swp.
  	 */

  	valid[0] = nilfs_valid_sb(sbp[0]);
  	valid[1] = nilfs_valid_sb(sbp[1]);

  	swp = valid[1] && (!valid[0] ||
  			   le64_to_cpu(sbp[1]->s_last_cno) >
  			   le64_to_cpu(sbp[0]->s_last_cno));

  
  	if (valid[swp] && nilfs_sb2_bad_offset(sbp[swp], sb2off)) {
  		brelse(sbh[1]);
  		sbh[1] = NULL;
  		sbp[1] = NULL;
  		swp = 0;
  	}
  	if (!valid[swp]) {
  		nilfs_release_super_block(nilfs);
  		printk(KERN_ERR "NILFS: Can't find nilfs on dev %s.
  ",
  		       sb->s_id);
  		return -EINVAL;
  	}

  	if (!valid[!swp])

  		printk(KERN_WARNING "NILFS warning: broken superblock. "

  		       "using spare superblock (blocksize = %d).
  ", blocksize);

  	if (swp)

  		nilfs_swap_super_block(nilfs);

  	nilfs->ns_sbwcount = 0;
  	nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);

  	nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
  	*sbpp = sbp[0];
  	return 0;
  }

  /**
   * init_nilfs - initialize a NILFS instance.
   * @nilfs: the_nilfs structure

   * @sb: super block
   * @data: mount options
   *
   * init_nilfs() performs common initialization per block device (e.g.
   * reading the super block, getting disk layout information, initializing

   * shared fields in the_nilfs).

   *
   * Return Value: On success, 0 is returned. On error, a negative error
   * code is returned.
   */

  int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data)

  {

  	struct nilfs_super_block *sbp;

  	int blocksize;

  	int err;

  
  	down_write(&nilfs->ns_sem);

  	blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);

  	if (!blocksize) {
  		printk(KERN_ERR "NILFS: unable to set blocksize
  ");

  		err = -EINVAL;
  		goto out;
  	}

  	err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
  	if (err)
  		goto out;

  	err = nilfs_store_magic_and_option(sb, sbp, data);
  	if (err)
  		goto failed_sbh;

  	err = nilfs_check_feature_compatibility(sb, sbp);
  	if (err)
  		goto failed_sbh;

  	blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);

  	if (blocksize < NILFS_MIN_BLOCK_SIZE ||
  	    blocksize > NILFS_MAX_BLOCK_SIZE) {
  		printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
  		       "filesystem blocksize %d
  ", blocksize);
  		err = -EINVAL;
  		goto failed_sbh;
  	}

  	if (sb->s_blocksize != blocksize) {

  		int hw_blocksize = bdev_logical_block_size(sb->s_bdev);

  
  		if (blocksize < hw_blocksize) {
  			printk(KERN_ERR
  			       "NILFS: blocksize %d too small for device "
  			       "(sector-size = %d).
  ",
  			       blocksize, hw_blocksize);

  			err = -EINVAL;

  			goto failed_sbh;
  		}
  		nilfs_release_super_block(nilfs);
  		sb_set_blocksize(sb, blocksize);
  
  		err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
  		if (err)

  			goto out;
  			/* not failed_sbh; sbh is released automatically
  			   when reloading fails. */

  	}
  	nilfs->ns_blocksize_bits = sb->s_blocksize_bits;

  	nilfs->ns_blocksize = blocksize;

  	get_random_bytes(&nilfs->ns_next_generation,
  			 sizeof(nilfs->ns_next_generation));

  	err = nilfs_store_disk_layout(nilfs, sbp);

  	if (err)
  		goto failed_sbh;
  
  	sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);
  
  	nilfs->ns_mount_state = le16_to_cpu(sbp->s_state);

  	err = nilfs_store_log_cursor(nilfs, sbp);
  	if (err)

  		goto failed_sbh;

  	set_nilfs_init(nilfs);
  	err = 0;
   out:
  	up_write(&nilfs->ns_sem);
  	return err;
  
   failed_sbh:

  	nilfs_release_super_block(nilfs);

  	goto out;
  }

  int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
  			    size_t nsegs)
  {
  	sector_t seg_start, seg_end;
  	sector_t start = 0, nblocks = 0;
  	unsigned int sects_per_block;
  	__u64 *sn;
  	int ret = 0;
  
  	sects_per_block = (1 << nilfs->ns_blocksize_bits) /
  		bdev_logical_block_size(nilfs->ns_bdev);
  	for (sn = segnump; sn < segnump + nsegs; sn++) {
  		nilfs_get_segment_range(nilfs, *sn, &seg_start, &seg_end);
  
  		if (!nblocks) {
  			start = seg_start;
  			nblocks = seg_end - seg_start + 1;
  		} else if (start + nblocks == seg_start) {
  			nblocks += seg_end - seg_start + 1;
  		} else {
  			ret = blkdev_issue_discard(nilfs->ns_bdev,
  						   start * sects_per_block,
  						   nblocks * sects_per_block,

  						   GFP_NOFS, 0);

  			if (ret < 0)
  				return ret;
  			nblocks = 0;
  		}
  	}
  	if (nblocks)
  		ret = blkdev_issue_discard(nilfs->ns_bdev,
  					   start * sects_per_block,
  					   nblocks * sects_per_block,

  					   GFP_NOFS, 0);

  	return ret;
  }

  int nilfs_count_free_blocks(struct the_nilfs *nilfs, sector_t *nblocks)
  {

  	unsigned long ncleansegs;

  	down_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);

  	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);

  	up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);

  	*nblocks = (sector_t)ncleansegs * nilfs->ns_blocks_per_segment;
  	return 0;

  }

  int nilfs_near_disk_full(struct the_nilfs *nilfs)
  {

  	unsigned long ncleansegs, nincsegs;

  
  	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
  	nincsegs = atomic_read(&nilfs->ns_ndirtyblks) /
  		nilfs->ns_blocks_per_segment + 1;
  
  	return ncleansegs <= nilfs->ns_nrsvsegs + nincsegs;

  }

  struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno)

  {

  	struct rb_node *n;
  	struct nilfs_root *root;
  
  	spin_lock(&nilfs->ns_cptree_lock);
  	n = nilfs->ns_cptree.rb_node;
  	while (n) {
  		root = rb_entry(n, struct nilfs_root, rb_node);
  
  		if (cno < root->cno) {
  			n = n->rb_left;
  		} else if (cno > root->cno) {
  			n = n->rb_right;
  		} else {
  			atomic_inc(&root->count);
  			spin_unlock(&nilfs->ns_cptree_lock);
  			return root;
  		}

  	}

  	spin_unlock(&nilfs->ns_cptree_lock);

  	return NULL;

  }

  struct nilfs_root *
  nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)

  {

  	struct rb_node **p, *parent;
  	struct nilfs_root *root, *new;

  	root = nilfs_lookup_root(nilfs, cno);
  	if (root)
  		return root;

  	new = kmalloc(sizeof(*root), GFP_KERNEL);
  	if (!new)
  		return NULL;
  
  	spin_lock(&nilfs->ns_cptree_lock);
  
  	p = &nilfs->ns_cptree.rb_node;
  	parent = NULL;
  
  	while (*p) {
  		parent = *p;
  		root = rb_entry(parent, struct nilfs_root, rb_node);
  
  		if (cno < root->cno) {
  			p = &(*p)->rb_left;
  		} else if (cno > root->cno) {
  			p = &(*p)->rb_right;
  		} else {
  			atomic_inc(&root->count);
  			spin_unlock(&nilfs->ns_cptree_lock);
  			kfree(new);
  			return root;

  		}
  	}

  	new->cno = cno;
  	new->ifile = NULL;
  	new->nilfs = nilfs;
  	atomic_set(&new->count, 1);
  	atomic_set(&new->inodes_count, 0);
  	atomic_set(&new->blocks_count, 0);
  
  	rb_link_node(&new->rb_node, parent, p);
  	rb_insert_color(&new->rb_node, &nilfs->ns_cptree);
  
  	spin_unlock(&nilfs->ns_cptree_lock);
  
  	return new;
  }
  
  void nilfs_put_root(struct nilfs_root *root)
  {
  	if (atomic_dec_and_test(&root->count)) {
  		struct the_nilfs *nilfs = root->nilfs;
  
  		spin_lock(&nilfs->ns_cptree_lock);
  		rb_erase(&root->rb_node, &nilfs->ns_cptree);
  		spin_unlock(&nilfs->ns_cptree_lock);
  		if (root->ifile)

  			iput(root->ifile);

  
  		kfree(root);
  	}

  }