/*
   * sufile.c - NILFS segment usage file.
   *
   * Copyright (C) 2006-2008 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 Koji Sato <koji@osrg.net>.
   * Revised by Ryusuke Konishi <ryusuke@osrg.net>.
   */
  
  #include <linux/kernel.h>
  #include <linux/fs.h>
  #include <linux/string.h>
  #include <linux/buffer_head.h>
  #include <linux/errno.h>
  #include <linux/nilfs2_fs.h>
  #include "mdt.h"
  #include "sufile.h"
  
  #include <trace/events/nilfs2.h>
  
  /**
   * struct nilfs_sufile_info - on-memory private data of sufile
   * @mi: on-memory private data of metadata file
   * @ncleansegs: number of clean segments
   * @allocmin: lower limit of allocatable segment range
   * @allocmax: upper limit of allocatable segment range
   */
  struct nilfs_sufile_info {
  	struct nilfs_mdt_info mi;
  	unsigned long ncleansegs;/* number of clean segments */
  	__u64 allocmin;		/* lower limit of allocatable segment range */
  	__u64 allocmax;		/* upper limit of allocatable segment range */
  };
  
  static inline struct nilfs_sufile_info *NILFS_SUI(struct inode *sufile)
  {
  	return (struct nilfs_sufile_info *)NILFS_MDT(sufile);
  }
  
  static inline unsigned long
  nilfs_sufile_segment_usages_per_block(const struct inode *sufile)
  {
  	return NILFS_MDT(sufile)->mi_entries_per_block;
  }
  
  static unsigned long
  nilfs_sufile_get_blkoff(const struct inode *sufile, __u64 segnum)
  {
  	__u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
  	do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
  	return (unsigned long)t;
  }
  
  static unsigned long
  nilfs_sufile_get_offset(const struct inode *sufile, __u64 segnum)
  {
  	__u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
  	return do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
  }
  
  static unsigned long
  nilfs_sufile_segment_usages_in_block(const struct inode *sufile, __u64 curr,
  				     __u64 max)
  {
  	return min_t(unsigned long,
  		     nilfs_sufile_segment_usages_per_block(sufile) -
  		     nilfs_sufile_get_offset(sufile, curr),
  		     max - curr + 1);
  }
  
  static struct nilfs_segment_usage *
  nilfs_sufile_block_get_segment_usage(const struct inode *sufile, __u64 segnum,
  				     struct buffer_head *bh, void *kaddr)
  {
  	return kaddr + bh_offset(bh) +
  		nilfs_sufile_get_offset(sufile, segnum) *
  		NILFS_MDT(sufile)->mi_entry_size;
  }
  
  static inline int nilfs_sufile_get_header_block(struct inode *sufile,
  						struct buffer_head **bhp)
  {
  	return nilfs_mdt_get_block(sufile, 0, 0, NULL, bhp);
  }
  
  static inline int
  nilfs_sufile_get_segment_usage_block(struct inode *sufile, __u64 segnum,
  				     int create, struct buffer_head **bhp)
  {
  	return nilfs_mdt_get_block(sufile,
  				   nilfs_sufile_get_blkoff(sufile, segnum),
  				   create, NULL, bhp);
  }
  
  static int nilfs_sufile_delete_segment_usage_block(struct inode *sufile,
  						   __u64 segnum)
  {
  	return nilfs_mdt_delete_block(sufile,
  				      nilfs_sufile_get_blkoff(sufile, segnum));
  }
  
  static void nilfs_sufile_mod_counter(struct buffer_head *header_bh,
  				     u64 ncleanadd, u64 ndirtyadd)
  {
  	struct nilfs_sufile_header *header;
  	void *kaddr;
  
  	kaddr = kmap_atomic(header_bh->b_page);
  	header = kaddr + bh_offset(header_bh);
  	le64_add_cpu(&header->sh_ncleansegs, ncleanadd);
  	le64_add_cpu(&header->sh_ndirtysegs, ndirtyadd);
  	kunmap_atomic(kaddr);
  
  	mark_buffer_dirty(header_bh);
  }
  
  /**
   * nilfs_sufile_get_ncleansegs - return the number of clean segments
   * @sufile: inode of segment usage file
   */
  unsigned long nilfs_sufile_get_ncleansegs(struct inode *sufile)
  {
  	return NILFS_SUI(sufile)->ncleansegs;
  }
  
  /**
   * nilfs_sufile_updatev - modify multiple segment usages at a time
   * @sufile: inode of segment usage file
   * @segnumv: array of segment numbers
   * @nsegs: size of @segnumv array
   * @create: creation flag
   * @ndone: place to store number of modified segments on @segnumv
   * @dofunc: primitive operation for the update
   *
   * Description: nilfs_sufile_updatev() repeatedly calls @dofunc
   * against the given array of segments.  The @dofunc is called with
   * buffers of a header block and the sufile block in which the target
   * segment usage entry is contained.  If @ndone is given, the number
   * of successfully modified segments from the head is stored in the
   * place @ndone points to.
   *
   * Return Value: On success, zero is returned.  On error, one of the
   * following negative error codes is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   *
   * %-ENOENT - Given segment usage is in hole block (may be returned if
   *            @create is zero)
   *
   * %-EINVAL - Invalid segment usage number
   */
  int nilfs_sufile_updatev(struct inode *sufile, __u64 *segnumv, size_t nsegs,
  			 int create, size_t *ndone,
  			 void (*dofunc)(struct inode *, __u64,
  					struct buffer_head *,
  					struct buffer_head *))
  {
  	struct buffer_head *header_bh, *bh;
  	unsigned long blkoff, prev_blkoff;
  	__u64 *seg;
  	size_t nerr = 0, n = 0;
  	int ret = 0;
  
  	if (unlikely(nsegs == 0))
  		goto out;
  
  	down_write(&NILFS_MDT(sufile)->mi_sem);
  	for (seg = segnumv; seg < segnumv + nsegs; seg++) {
  		if (unlikely(*seg >= nilfs_sufile_get_nsegments(sufile))) {
  			printk(KERN_WARNING
  			       "%s: invalid segment number: %llu
  ", __func__,
  			       (unsigned long long)*seg);
  			nerr++;
  		}
  	}
  	if (nerr > 0) {
  		ret = -EINVAL;
  		goto out_sem;
  	}
  
  	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (ret < 0)
  		goto out_sem;
  
  	seg = segnumv;
  	blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
  	ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
  	if (ret < 0)
  		goto out_header;
  
  	for (;;) {
  		dofunc(sufile, *seg, header_bh, bh);
  
  		if (++seg >= segnumv + nsegs)
  			break;
  		prev_blkoff = blkoff;
  		blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
  		if (blkoff == prev_blkoff)
  			continue;
  
  		/* get different block */
  		brelse(bh);
  		ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
  		if (unlikely(ret < 0))
  			goto out_header;
  	}
  	brelse(bh);
  
   out_header:
  	n = seg - segnumv;
  	brelse(header_bh);
   out_sem:
  	up_write(&NILFS_MDT(sufile)->mi_sem);
   out:
  	if (ndone)
  		*ndone = n;
  	return ret;
  }
  
  int nilfs_sufile_update(struct inode *sufile, __u64 segnum, int create,
  			void (*dofunc)(struct inode *, __u64,
  				       struct buffer_head *,
  				       struct buffer_head *))
  {
  	struct buffer_head *header_bh, *bh;
  	int ret;
  
  	if (unlikely(segnum >= nilfs_sufile_get_nsegments(sufile))) {
  		printk(KERN_WARNING "%s: invalid segment number: %llu
  ",
  		       __func__, (unsigned long long)segnum);
  		return -EINVAL;
  	}
  	down_write(&NILFS_MDT(sufile)->mi_sem);
  
  	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (ret < 0)
  		goto out_sem;
  
  	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, create, &bh);
  	if (!ret) {
  		dofunc(sufile, segnum, header_bh, bh);
  		brelse(bh);
  	}
  	brelse(header_bh);
  
   out_sem:
  	up_write(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  /**
   * nilfs_sufile_set_alloc_range - limit range of segment to be allocated
   * @sufile: inode of segment usage file
   * @start: minimum segment number of allocatable region (inclusive)
   * @end: maximum segment number of allocatable region (inclusive)
   *
   * Return Value: On success, 0 is returned.  On error, one of the
   * following negative error codes is returned.
   *
   * %-ERANGE - invalid segment region
   */
  int nilfs_sufile_set_alloc_range(struct inode *sufile, __u64 start, __u64 end)
  {
  	struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
  	__u64 nsegs;
  	int ret = -ERANGE;
  
  	down_write(&NILFS_MDT(sufile)->mi_sem);
  	nsegs = nilfs_sufile_get_nsegments(sufile);
  
  	if (start <= end && end < nsegs) {
  		sui->allocmin = start;
  		sui->allocmax = end;
  		ret = 0;
  	}
  	up_write(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  /**
   * nilfs_sufile_alloc - allocate a segment
   * @sufile: inode of segment usage file
   * @segnump: pointer to segment number
   *
   * Description: nilfs_sufile_alloc() allocates a clean segment.
   *
   * Return Value: On success, 0 is returned and the segment number of the
   * allocated segment is stored in the place pointed by @segnump. On error, one
   * of the following negative error codes is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   *
   * %-ENOSPC - No clean segment left.
   */
  int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
  {
  	struct buffer_head *header_bh, *su_bh;
  	struct nilfs_sufile_header *header;
  	struct nilfs_segment_usage *su;
  	struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
  	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
  	__u64 segnum, maxsegnum, last_alloc;
  	void *kaddr;
  	unsigned long nsegments, nsus, cnt;
  	int ret, j;
  
  	down_write(&NILFS_MDT(sufile)->mi_sem);
  
  	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (ret < 0)
  		goto out_sem;
  	kaddr = kmap_atomic(header_bh->b_page);
  	header = kaddr + bh_offset(header_bh);
  	last_alloc = le64_to_cpu(header->sh_last_alloc);
  	kunmap_atomic(kaddr);
  
  	nsegments = nilfs_sufile_get_nsegments(sufile);
  	maxsegnum = sui->allocmax;
  	segnum = last_alloc + 1;
  	if (segnum < sui->allocmin || segnum > sui->allocmax)
  		segnum = sui->allocmin;
  
  	for (cnt = 0; cnt < nsegments; cnt += nsus) {
  		if (segnum > maxsegnum) {
  			if (cnt < sui->allocmax - sui->allocmin + 1) {
  				/*
  				 * wrap around in the limited region.
  				 * if allocation started from
  				 * sui->allocmin, this never happens.
  				 */
  				segnum = sui->allocmin;
  				maxsegnum = last_alloc;
  			} else if (segnum > sui->allocmin &&
  				   sui->allocmax + 1 < nsegments) {
  				segnum = sui->allocmax + 1;
  				maxsegnum = nsegments - 1;
  			} else if (sui->allocmin > 0)  {
  				segnum = 0;
  				maxsegnum = sui->allocmin - 1;
  			} else {
  				break; /* never happens */
  			}
  		}
  		trace_nilfs2_segment_usage_check(sufile, segnum, cnt);
  		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1,
  							   &su_bh);
  		if (ret < 0)
  			goto out_header;
  		kaddr = kmap_atomic(su_bh->b_page);
  		su = nilfs_sufile_block_get_segment_usage(
  			sufile, segnum, su_bh, kaddr);
  
  		nsus = nilfs_sufile_segment_usages_in_block(
  			sufile, segnum, maxsegnum);
  		for (j = 0; j < nsus; j++, su = (void *)su + susz, segnum++) {
  			if (!nilfs_segment_usage_clean(su))
  				continue;
  			/* found a clean segment */
  			nilfs_segment_usage_set_dirty(su);
  			kunmap_atomic(kaddr);
  
  			kaddr = kmap_atomic(header_bh->b_page);
  			header = kaddr + bh_offset(header_bh);
  			le64_add_cpu(&header->sh_ncleansegs, -1);
  			le64_add_cpu(&header->sh_ndirtysegs, 1);
  			header->sh_last_alloc = cpu_to_le64(segnum);
  			kunmap_atomic(kaddr);
  
  			sui->ncleansegs--;
  			mark_buffer_dirty(header_bh);
  			mark_buffer_dirty(su_bh);
  			nilfs_mdt_mark_dirty(sufile);
  			brelse(su_bh);
  			*segnump = segnum;
  
  			trace_nilfs2_segment_usage_allocated(sufile, segnum);
  
  			goto out_header;
  		}
  
  		kunmap_atomic(kaddr);
  		brelse(su_bh);
  	}
  
  	/* no segments left */
  	ret = -ENOSPC;
  
   out_header:
  	brelse(header_bh);
  
   out_sem:
  	up_write(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  void nilfs_sufile_do_cancel_free(struct inode *sufile, __u64 segnum,
  				 struct buffer_head *header_bh,
  				 struct buffer_head *su_bh)
  {
  	struct nilfs_segment_usage *su;
  	void *kaddr;
  
  	kaddr = kmap_atomic(su_bh->b_page);
  	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
  	if (unlikely(!nilfs_segment_usage_clean(su))) {
  		printk(KERN_WARNING "%s: segment %llu must be clean
  ",
  		       __func__, (unsigned long long)segnum);
  		kunmap_atomic(kaddr);
  		return;
  	}
  	nilfs_segment_usage_set_dirty(su);
  	kunmap_atomic(kaddr);
  
  	nilfs_sufile_mod_counter(header_bh, -1, 1);
  	NILFS_SUI(sufile)->ncleansegs--;
  
  	mark_buffer_dirty(su_bh);
  	nilfs_mdt_mark_dirty(sufile);
  }
  
  void nilfs_sufile_do_scrap(struct inode *sufile, __u64 segnum,
  			   struct buffer_head *header_bh,
  			   struct buffer_head *su_bh)
  {
  	struct nilfs_segment_usage *su;
  	void *kaddr;
  	int clean, dirty;
  
  	kaddr = kmap_atomic(su_bh->b_page);
  	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
  	if (su->su_flags == cpu_to_le32(1UL << NILFS_SEGMENT_USAGE_DIRTY) &&
  	    su->su_nblocks == cpu_to_le32(0)) {
  		kunmap_atomic(kaddr);
  		return;
  	}
  	clean = nilfs_segment_usage_clean(su);
  	dirty = nilfs_segment_usage_dirty(su);
  
  	/* make the segment garbage */
  	su->su_lastmod = cpu_to_le64(0);
  	su->su_nblocks = cpu_to_le32(0);
  	su->su_flags = cpu_to_le32(1UL << NILFS_SEGMENT_USAGE_DIRTY);
  	kunmap_atomic(kaddr);
  
  	nilfs_sufile_mod_counter(header_bh, clean ? (u64)-1 : 0, dirty ? 0 : 1);
  	NILFS_SUI(sufile)->ncleansegs -= clean;
  
  	mark_buffer_dirty(su_bh);
  	nilfs_mdt_mark_dirty(sufile);
  }
  
  void nilfs_sufile_do_free(struct inode *sufile, __u64 segnum,
  			  struct buffer_head *header_bh,
  			  struct buffer_head *su_bh)
  {
  	struct nilfs_segment_usage *su;
  	void *kaddr;
  	int sudirty;
  
  	kaddr = kmap_atomic(su_bh->b_page);
  	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
  	if (nilfs_segment_usage_clean(su)) {
  		printk(KERN_WARNING "%s: segment %llu is already clean
  ",
  		       __func__, (unsigned long long)segnum);
  		kunmap_atomic(kaddr);
  		return;
  	}
  	WARN_ON(nilfs_segment_usage_error(su));
  	WARN_ON(!nilfs_segment_usage_dirty(su));
  
  	sudirty = nilfs_segment_usage_dirty(su);
  	nilfs_segment_usage_set_clean(su);
  	kunmap_atomic(kaddr);
  	mark_buffer_dirty(su_bh);
  
  	nilfs_sufile_mod_counter(header_bh, 1, sudirty ? (u64)-1 : 0);
  	NILFS_SUI(sufile)->ncleansegs++;
  
  	nilfs_mdt_mark_dirty(sufile);
  
  	trace_nilfs2_segment_usage_freed(sufile, segnum);
  }
  
  /**
   * nilfs_sufile_mark_dirty - mark the buffer having a segment usage dirty
   * @sufile: inode of segment usage file
   * @segnum: segment number
   */
  int nilfs_sufile_mark_dirty(struct inode *sufile, __u64 segnum)
  {
  	struct buffer_head *bh;
  	int ret;
  
  	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &bh);
  	if (!ret) {
  		mark_buffer_dirty(bh);
  		nilfs_mdt_mark_dirty(sufile);
  		brelse(bh);
  	}
  	return ret;
  }
  
  /**
   * nilfs_sufile_set_segment_usage - set usage of a segment
   * @sufile: inode of segment usage file
   * @segnum: segment number
   * @nblocks: number of live blocks in the segment
   * @modtime: modification time (option)
   */
  int nilfs_sufile_set_segment_usage(struct inode *sufile, __u64 segnum,
  				   unsigned long nblocks, time_t modtime)
  {
  	struct buffer_head *bh;
  	struct nilfs_segment_usage *su;
  	void *kaddr;
  	int ret;
  
  	down_write(&NILFS_MDT(sufile)->mi_sem);
  	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &bh);
  	if (ret < 0)
  		goto out_sem;
  
  	kaddr = kmap_atomic(bh->b_page);
  	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr);
  	WARN_ON(nilfs_segment_usage_error(su));
  	if (modtime)
  		su->su_lastmod = cpu_to_le64(modtime);
  	su->su_nblocks = cpu_to_le32(nblocks);
  	kunmap_atomic(kaddr);
  
  	mark_buffer_dirty(bh);
  	nilfs_mdt_mark_dirty(sufile);
  	brelse(bh);
  
   out_sem:
  	up_write(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  /**
   * nilfs_sufile_get_stat - get segment usage statistics
   * @sufile: inode of segment usage file
   * @stat: pointer to a structure of segment usage statistics
   *
   * Description: nilfs_sufile_get_stat() returns information about segment
   * usage.
   *
   * Return Value: On success, 0 is returned, and segment usage information is
   * stored in the place pointed by @stat. On error, one of the following
   * negative error codes is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   */
  int nilfs_sufile_get_stat(struct inode *sufile, struct nilfs_sustat *sustat)
  {
  	struct buffer_head *header_bh;
  	struct nilfs_sufile_header *header;
  	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
  	void *kaddr;
  	int ret;
  
  	down_read(&NILFS_MDT(sufile)->mi_sem);
  
  	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (ret < 0)
  		goto out_sem;
  
  	kaddr = kmap_atomic(header_bh->b_page);
  	header = kaddr + bh_offset(header_bh);
  	sustat->ss_nsegs = nilfs_sufile_get_nsegments(sufile);
  	sustat->ss_ncleansegs = le64_to_cpu(header->sh_ncleansegs);
  	sustat->ss_ndirtysegs = le64_to_cpu(header->sh_ndirtysegs);
  	sustat->ss_ctime = nilfs->ns_ctime;
  	sustat->ss_nongc_ctime = nilfs->ns_nongc_ctime;
  	spin_lock(&nilfs->ns_last_segment_lock);
  	sustat->ss_prot_seq = nilfs->ns_prot_seq;
  	spin_unlock(&nilfs->ns_last_segment_lock);
  	kunmap_atomic(kaddr);
  	brelse(header_bh);
  
   out_sem:
  	up_read(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  void nilfs_sufile_do_set_error(struct inode *sufile, __u64 segnum,
  			       struct buffer_head *header_bh,
  			       struct buffer_head *su_bh)
  {
  	struct nilfs_segment_usage *su;
  	void *kaddr;
  	int suclean;
  
  	kaddr = kmap_atomic(su_bh->b_page);
  	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
  	if (nilfs_segment_usage_error(su)) {
  		kunmap_atomic(kaddr);
  		return;
  	}
  	suclean = nilfs_segment_usage_clean(su);
  	nilfs_segment_usage_set_error(su);
  	kunmap_atomic(kaddr);
  
  	if (suclean) {
  		nilfs_sufile_mod_counter(header_bh, -1, 0);
  		NILFS_SUI(sufile)->ncleansegs--;
  	}
  	mark_buffer_dirty(su_bh);
  	nilfs_mdt_mark_dirty(sufile);
  }
  
  /**
    * nilfs_sufile_truncate_range - truncate range of segment array
    * @sufile: inode of segment usage file
    * @start: start segment number (inclusive)
    * @end: end segment number (inclusive)
    *
    * Return Value: On success, 0 is returned.  On error, one of the
    * following negative error codes is returned.
    *
    * %-EIO - I/O error.
    *
    * %-ENOMEM - Insufficient amount of memory available.
    *
    * %-EINVAL - Invalid number of segments specified
    *
    * %-EBUSY - Dirty or active segments are present in the range
    */
  static int nilfs_sufile_truncate_range(struct inode *sufile,
  				       __u64 start, __u64 end)
  {
  	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
  	struct buffer_head *header_bh;
  	struct buffer_head *su_bh;
  	struct nilfs_segment_usage *su, *su2;
  	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
  	unsigned long segusages_per_block;
  	unsigned long nsegs, ncleaned;
  	__u64 segnum;
  	void *kaddr;
  	ssize_t n, nc;
  	int ret;
  	int j;
  
  	nsegs = nilfs_sufile_get_nsegments(sufile);
  
  	ret = -EINVAL;
  	if (start > end || start >= nsegs)
  		goto out;
  
  	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (ret < 0)
  		goto out;
  
  	segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
  	ncleaned = 0;
  
  	for (segnum = start; segnum <= end; segnum += n) {
  		n = min_t(unsigned long,
  			  segusages_per_block -
  				  nilfs_sufile_get_offset(sufile, segnum),
  			  end - segnum + 1);
  		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
  							   &su_bh);
  		if (ret < 0) {
  			if (ret != -ENOENT)
  				goto out_header;
  			/* hole */
  			continue;
  		}
  		kaddr = kmap_atomic(su_bh->b_page);
  		su = nilfs_sufile_block_get_segment_usage(
  			sufile, segnum, su_bh, kaddr);
  		su2 = su;
  		for (j = 0; j < n; j++, su = (void *)su + susz) {
  			if ((le32_to_cpu(su->su_flags) &
  			     ~(1UL << NILFS_SEGMENT_USAGE_ERROR)) ||
  			    nilfs_segment_is_active(nilfs, segnum + j)) {
  				ret = -EBUSY;
  				kunmap_atomic(kaddr);
  				brelse(su_bh);
  				goto out_header;
  			}
  		}
  		nc = 0;
  		for (su = su2, j = 0; j < n; j++, su = (void *)su + susz) {
  			if (nilfs_segment_usage_error(su)) {
  				nilfs_segment_usage_set_clean(su);
  				nc++;
  			}
  		}
  		kunmap_atomic(kaddr);
  		if (nc > 0) {
  			mark_buffer_dirty(su_bh);
  			ncleaned += nc;
  		}
  		brelse(su_bh);
  
  		if (n == segusages_per_block) {
  			/* make hole */
  			nilfs_sufile_delete_segment_usage_block(sufile, segnum);
  		}
  	}
  	ret = 0;
  
  out_header:
  	if (ncleaned > 0) {
  		NILFS_SUI(sufile)->ncleansegs += ncleaned;
  		nilfs_sufile_mod_counter(header_bh, ncleaned, 0);
  		nilfs_mdt_mark_dirty(sufile);
  	}
  	brelse(header_bh);
  out:
  	return ret;
  }
  
  /**
   * nilfs_sufile_resize - resize segment array
   * @sufile: inode of segment usage file
   * @newnsegs: new number of segments
   *
   * Return Value: On success, 0 is returned.  On error, one of the
   * following negative error codes is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   *
   * %-ENOSPC - Enough free space is not left for shrinking
   *
   * %-EBUSY - Dirty or active segments exist in the region to be truncated
   */
  int nilfs_sufile_resize(struct inode *sufile, __u64 newnsegs)
  {
  	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
  	struct buffer_head *header_bh;
  	struct nilfs_sufile_header *header;
  	struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
  	void *kaddr;
  	unsigned long nsegs, nrsvsegs;
  	int ret = 0;
  
  	down_write(&NILFS_MDT(sufile)->mi_sem);
  
  	nsegs = nilfs_sufile_get_nsegments(sufile);
  	if (nsegs == newnsegs)
  		goto out;
  
  	ret = -ENOSPC;
  	nrsvsegs = nilfs_nrsvsegs(nilfs, newnsegs);
  	if (newnsegs < nsegs && nsegs - newnsegs + nrsvsegs > sui->ncleansegs)
  		goto out;
  
  	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (ret < 0)
  		goto out;
  
  	if (newnsegs > nsegs) {
  		sui->ncleansegs += newnsegs - nsegs;
  	} else /* newnsegs < nsegs */ {
  		ret = nilfs_sufile_truncate_range(sufile, newnsegs, nsegs - 1);
  		if (ret < 0)
  			goto out_header;
  
  		sui->ncleansegs -= nsegs - newnsegs;
  	}
  
  	kaddr = kmap_atomic(header_bh->b_page);
  	header = kaddr + bh_offset(header_bh);
  	header->sh_ncleansegs = cpu_to_le64(sui->ncleansegs);
  	kunmap_atomic(kaddr);
  
  	mark_buffer_dirty(header_bh);
  	nilfs_mdt_mark_dirty(sufile);
  	nilfs_set_nsegments(nilfs, newnsegs);
  
  out_header:
  	brelse(header_bh);
  out:
  	up_write(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  /**
   * nilfs_sufile_get_suinfo -
   * @sufile: inode of segment usage file
   * @segnum: segment number to start looking
   * @buf: array of suinfo
   * @sisz: byte size of suinfo
   * @nsi: size of suinfo array
   *
   * Description:
   *
   * Return Value: On success, 0 is returned and .... On error, one of the
   * following negative error codes is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   */
  ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
  				unsigned sisz, size_t nsi)
  {
  	struct buffer_head *su_bh;
  	struct nilfs_segment_usage *su;
  	struct nilfs_suinfo *si = buf;
  	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
  	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
  	void *kaddr;
  	unsigned long nsegs, segusages_per_block;
  	ssize_t n;
  	int ret, i, j;
  
  	down_read(&NILFS_MDT(sufile)->mi_sem);
  
  	segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
  	nsegs = min_t(unsigned long,
  		      nilfs_sufile_get_nsegments(sufile) - segnum,
  		      nsi);
  	for (i = 0; i < nsegs; i += n, segnum += n) {
  		n = min_t(unsigned long,
  			  segusages_per_block -
  				  nilfs_sufile_get_offset(sufile, segnum),
  			  nsegs - i);
  		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
  							   &su_bh);
  		if (ret < 0) {
  			if (ret != -ENOENT)
  				goto out;
  			/* hole */
  			memset(si, 0, sisz * n);
  			si = (void *)si + sisz * n;
  			continue;
  		}
  
  		kaddr = kmap_atomic(su_bh->b_page);
  		su = nilfs_sufile_block_get_segment_usage(
  			sufile, segnum, su_bh, kaddr);
  		for (j = 0; j < n;
  		     j++, su = (void *)su + susz, si = (void *)si + sisz) {
  			si->sui_lastmod = le64_to_cpu(su->su_lastmod);
  			si->sui_nblocks = le32_to_cpu(su->su_nblocks);
  			si->sui_flags = le32_to_cpu(su->su_flags) &
  				~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
  			if (nilfs_segment_is_active(nilfs, segnum + j))
  				si->sui_flags |=
  					(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
  		}
  		kunmap_atomic(kaddr);
  		brelse(su_bh);
  	}
  	ret = nsegs;
  
   out:
  	up_read(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  /**
   * nilfs_sufile_set_suinfo - sets segment usage info
   * @sufile: inode of segment usage file
   * @buf: array of suinfo_update
   * @supsz: byte size of suinfo_update
   * @nsup: size of suinfo_update array
   *
   * Description: Takes an array of nilfs_suinfo_update structs and updates
   * segment usage accordingly. Only the fields indicated by the sup_flags
   * are updated.
   *
   * Return Value: On success, 0 is returned. On error, one of the
   * following negative error codes is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   *
   * %-EINVAL - Invalid values in input (segment number, flags or nblocks)
   */
  ssize_t nilfs_sufile_set_suinfo(struct inode *sufile, void *buf,
  				unsigned supsz, size_t nsup)
  {
  	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
  	struct buffer_head *header_bh, *bh;
  	struct nilfs_suinfo_update *sup, *supend = buf + supsz * nsup;
  	struct nilfs_segment_usage *su;
  	void *kaddr;
  	unsigned long blkoff, prev_blkoff;
  	int cleansi, cleansu, dirtysi, dirtysu;
  	long ncleaned = 0, ndirtied = 0;
  	int ret = 0;
  
  	if (unlikely(nsup == 0))
  		return ret;
  
  	for (sup = buf; sup < supend; sup = (void *)sup + supsz) {
  		if (sup->sup_segnum >= nilfs->ns_nsegments
  			|| (sup->sup_flags &
  				(~0UL << __NR_NILFS_SUINFO_UPDATE_FIELDS))
  			|| (nilfs_suinfo_update_nblocks(sup) &&
  				sup->sup_sui.sui_nblocks >
  				nilfs->ns_blocks_per_segment))
  			return -EINVAL;
  	}
  
  	down_write(&NILFS_MDT(sufile)->mi_sem);
  
  	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (ret < 0)
  		goto out_sem;
  
  	sup = buf;
  	blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
  	ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
  	if (ret < 0)
  		goto out_header;
  
  	for (;;) {
  		kaddr = kmap_atomic(bh->b_page);
  		su = nilfs_sufile_block_get_segment_usage(
  			sufile, sup->sup_segnum, bh, kaddr);
  
  		if (nilfs_suinfo_update_lastmod(sup))
  			su->su_lastmod = cpu_to_le64(sup->sup_sui.sui_lastmod);
  
  		if (nilfs_suinfo_update_nblocks(sup))
  			su->su_nblocks = cpu_to_le32(sup->sup_sui.sui_nblocks);
  
  		if (nilfs_suinfo_update_flags(sup)) {
  			/*
  			 * Active flag is a virtual flag projected by running
  			 * nilfs kernel code - drop it not to write it to
  			 * disk.
  			 */
  			sup->sup_sui.sui_flags &=
  					~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
  
  			cleansi = nilfs_suinfo_clean(&sup->sup_sui);
  			cleansu = nilfs_segment_usage_clean(su);
  			dirtysi = nilfs_suinfo_dirty(&sup->sup_sui);
  			dirtysu = nilfs_segment_usage_dirty(su);
  
  			if (cleansi && !cleansu)
  				++ncleaned;
  			else if (!cleansi && cleansu)
  				--ncleaned;
  
  			if (dirtysi && !dirtysu)
  				++ndirtied;
  			else if (!dirtysi && dirtysu)
  				--ndirtied;
  
  			su->su_flags = cpu_to_le32(sup->sup_sui.sui_flags);
  		}
  
  		kunmap_atomic(kaddr);
  
  		sup = (void *)sup + supsz;
  		if (sup >= supend)
  			break;
  
  		prev_blkoff = blkoff;
  		blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
  		if (blkoff == prev_blkoff)
  			continue;
  
  		/* get different block */
  		mark_buffer_dirty(bh);
  		put_bh(bh);
  		ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
  		if (unlikely(ret < 0))
  			goto out_mark;
  	}
  	mark_buffer_dirty(bh);
  	put_bh(bh);
  
   out_mark:
  	if (ncleaned || ndirtied) {
  		nilfs_sufile_mod_counter(header_bh, (u64)ncleaned,
  				(u64)ndirtied);
  		NILFS_SUI(sufile)->ncleansegs += ncleaned;
  	}
  	nilfs_mdt_mark_dirty(sufile);
   out_header:
  	put_bh(header_bh);
   out_sem:
  	up_write(&NILFS_MDT(sufile)->mi_sem);
  	return ret;
  }
  
  /**
   * nilfs_sufile_trim_fs() - trim ioctl handle function
   * @sufile: inode of segment usage file
   * @range: fstrim_range structure
   *
   * start:	First Byte to trim
   * len:		number of Bytes to trim from start
   * minlen:	minimum extent length in Bytes
   *
   * Decription: nilfs_sufile_trim_fs goes through all segments containing bytes
   * from start to start+len. start is rounded up to the next block boundary
   * and start+len is rounded down. For each clean segment blkdev_issue_discard
   * function is invoked.
   *
   * Return Value: On success, 0 is returned or negative error code, otherwise.
   */
  int nilfs_sufile_trim_fs(struct inode *sufile, struct fstrim_range *range)
  {
  	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
  	struct buffer_head *su_bh;
  	struct nilfs_segment_usage *su;
  	void *kaddr;
  	size_t n, i, susz = NILFS_MDT(sufile)->mi_entry_size;
  	sector_t seg_start, seg_end, start_block, end_block;
  	sector_t start = 0, nblocks = 0;
  	u64 segnum, segnum_end, minlen, len, max_blocks, ndiscarded = 0;
  	int ret = 0;
  	unsigned int sects_per_block;
  
  	sects_per_block = (1 << nilfs->ns_blocksize_bits) /
  			bdev_logical_block_size(nilfs->ns_bdev);
  	len = range->len >> nilfs->ns_blocksize_bits;
  	minlen = range->minlen >> nilfs->ns_blocksize_bits;
  	max_blocks = ((u64)nilfs->ns_nsegments * nilfs->ns_blocks_per_segment);
  
  	if (!len || range->start >= max_blocks << nilfs->ns_blocksize_bits)
  		return -EINVAL;
  
  	start_block = (range->start + nilfs->ns_blocksize - 1) >>
  			nilfs->ns_blocksize_bits;
  
  	/*
  	 * range->len can be very large (actually, it is set to
  	 * ULLONG_MAX by default) - truncate upper end of the range
  	 * carefully so as not to overflow.
  	 */
  	if (max_blocks - start_block < len)
  		end_block = max_blocks - 1;
  	else
  		end_block = start_block + len - 1;
  
  	segnum = nilfs_get_segnum_of_block(nilfs, start_block);
  	segnum_end = nilfs_get_segnum_of_block(nilfs, end_block);
  
  	down_read(&NILFS_MDT(sufile)->mi_sem);
  
  	while (segnum <= segnum_end) {
  		n = nilfs_sufile_segment_usages_in_block(sufile, segnum,
  				segnum_end);
  
  		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
  							   &su_bh);
  		if (ret < 0) {
  			if (ret != -ENOENT)
  				goto out_sem;
  			/* hole */
  			segnum += n;
  			continue;
  		}
  
  		kaddr = kmap_atomic(su_bh->b_page);
  		su = nilfs_sufile_block_get_segment_usage(sufile, segnum,
  				su_bh, kaddr);
  		for (i = 0; i < n; ++i, ++segnum, su = (void *)su + susz) {
  			if (!nilfs_segment_usage_clean(su))
  				continue;
  
  			nilfs_get_segment_range(nilfs, segnum, &seg_start,
  						&seg_end);
  
  			if (!nblocks) {
  				/* start new extent */
  				start = seg_start;
  				nblocks = seg_end - seg_start + 1;
  				continue;
  			}
  
  			if (start + nblocks == seg_start) {
  				/* add to previous extent */
  				nblocks += seg_end - seg_start + 1;
  				continue;
  			}
  
  			/* discard previous extent */
  			if (start < start_block) {
  				nblocks -= start_block - start;
  				start = start_block;
  			}
  
  			if (nblocks >= minlen) {
  				kunmap_atomic(kaddr);
  
  				ret = blkdev_issue_discard(nilfs->ns_bdev,
  						start * sects_per_block,
  						nblocks * sects_per_block,
  						GFP_NOFS, 0);
  				if (ret < 0) {
  					put_bh(su_bh);
  					goto out_sem;
  				}
  
  				ndiscarded += nblocks;
  				kaddr = kmap_atomic(su_bh->b_page);
  				su = nilfs_sufile_block_get_segment_usage(
  					sufile, segnum, su_bh, kaddr);
  			}
  
  			/* start new extent */
  			start = seg_start;
  			nblocks = seg_end - seg_start + 1;
  		}
  		kunmap_atomic(kaddr);
  		put_bh(su_bh);
  	}
  
  
  	if (nblocks) {
  		/* discard last extent */
  		if (start < start_block) {
  			nblocks -= start_block - start;
  			start = start_block;
  		}
  		if (start + nblocks > end_block + 1)
  			nblocks = end_block - start + 1;
  
  		if (nblocks >= minlen) {
  			ret = blkdev_issue_discard(nilfs->ns_bdev,
  					start * sects_per_block,
  					nblocks * sects_per_block,
  					GFP_NOFS, 0);
  			if (!ret)
  				ndiscarded += nblocks;
  		}
  	}
  
  out_sem:
  	up_read(&NILFS_MDT(sufile)->mi_sem);
  
  	range->len = ndiscarded << nilfs->ns_blocksize_bits;
  	return ret;
  }
  
  /**
   * nilfs_sufile_read - read or get sufile inode
   * @sb: super block instance
   * @susize: size of a segment usage entry
   * @raw_inode: on-disk sufile inode
   * @inodep: buffer to store the inode
   */
  int nilfs_sufile_read(struct super_block *sb, size_t susize,
  		      struct nilfs_inode *raw_inode, struct inode **inodep)
  {
  	struct inode *sufile;
  	struct nilfs_sufile_info *sui;
  	struct buffer_head *header_bh;
  	struct nilfs_sufile_header *header;
  	void *kaddr;
  	int err;
  
  	if (susize > sb->s_blocksize) {
  		printk(KERN_ERR
  		       "NILFS: too large segment usage size: %zu bytes.
  ",
  		       susize);
  		return -EINVAL;
  	} else if (susize < NILFS_MIN_SEGMENT_USAGE_SIZE) {
  		printk(KERN_ERR
  		       "NILFS: too small segment usage size: %zu bytes.
  ",
  		       susize);
  		return -EINVAL;
  	}
  
  	sufile = nilfs_iget_locked(sb, NULL, NILFS_SUFILE_INO);
  	if (unlikely(!sufile))
  		return -ENOMEM;
  	if (!(sufile->i_state & I_NEW))
  		goto out;
  
  	err = nilfs_mdt_init(sufile, NILFS_MDT_GFP, sizeof(*sui));
  	if (err)
  		goto failed;
  
  	nilfs_mdt_set_entry_size(sufile, susize,
  				 sizeof(struct nilfs_sufile_header));
  
  	err = nilfs_read_inode_common(sufile, raw_inode);
  	if (err)
  		goto failed;
  
  	err = nilfs_sufile_get_header_block(sufile, &header_bh);
  	if (err)
  		goto failed;
  
  	sui = NILFS_SUI(sufile);
  	kaddr = kmap_atomic(header_bh->b_page);
  	header = kaddr + bh_offset(header_bh);
  	sui->ncleansegs = le64_to_cpu(header->sh_ncleansegs);
  	kunmap_atomic(kaddr);
  	brelse(header_bh);
  
  	sui->allocmax = nilfs_sufile_get_nsegments(sufile) - 1;
  	sui->allocmin = 0;
  
  	unlock_new_inode(sufile);
   out:
  	*inodep = sufile;
  	return 0;
   failed:
  	iget_failed(sufile);
  	return err;
  }