fs/nilfs2/sufile.c - kernel/msm - Gitiles

 /*
  * 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>.
  */

 #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"


 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 inline struct nilfs_sufile_header *
 nilfs_sufile_block_get_header(const struct inode *sufile,
 			      struct buffer_head *bh,
 			      void *kaddr)
 {
 	return kaddr + bh_offset(bh);
 }

 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 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, KM_USER0);
 	header = kaddr + bh_offset(header_bh);
 	le64_add_cpu(&header->sh_ncleansegs, ncleanadd);
 	le64_add_cpu(&header->sh_ndirtysegs, ndirtyadd);
 	kunmap_atomic(kaddr, KM_USER0);

 	nilfs_mdt_mark_buffer_dirty(header_bh);
 }

 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\n",
 		       __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_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;
 	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
 	__u64 segnum, maxsegnum, last_alloc;
 	void *kaddr;
 	unsigned long nsegments, ncleansegs, nsus;
 	int ret, i, 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, KM_USER0);
 	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
 	ncleansegs = le64_to_cpu(header->sh_ncleansegs);
 	last_alloc = le64_to_cpu(header->sh_last_alloc);
 	kunmap_atomic(kaddr, KM_USER0);

 	nsegments = nilfs_sufile_get_nsegments(sufile);
 	segnum = last_alloc + 1;
 	maxsegnum = nsegments - 1;
 	for (i = 0; i < nsegments; i += nsus) {
 		if (segnum >= nsegments) {
 			/* wrap around */
 			segnum = 0;
 			maxsegnum = last_alloc;
 		}
 		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, KM_USER0);
 		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, KM_USER0);

 			kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 			header = nilfs_sufile_block_get_header(
 				sufile, header_bh, kaddr);
 			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, KM_USER0);

 			nilfs_mdt_mark_buffer_dirty(header_bh);
 			nilfs_mdt_mark_buffer_dirty(su_bh);
 			nilfs_mdt_mark_dirty(sufile);
 			brelse(su_bh);
 			*segnump = segnum;
 			goto out_header;
 		}

 		kunmap_atomic(kaddr, KM_USER0);
 		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, KM_USER0);
 	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\n",
 		       __func__, (unsigned long long)segnum);
 		kunmap_atomic(kaddr, KM_USER0);
 		return;
 	}
 	nilfs_segment_usage_set_dirty(su);
 	kunmap_atomic(kaddr, KM_USER0);

 	nilfs_sufile_mod_counter(header_bh, -1, 1);
 	nilfs_mdt_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, KM_USER0);
 	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, KM_USER0);
 		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, KM_USER0);

 	nilfs_sufile_mod_counter(header_bh, clean ? (u64)-1 : 0, dirty ? 0 : 1);
 	nilfs_mdt_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, KM_USER0);
 	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\n",
 		       __func__, (unsigned long long)segnum);
 		kunmap_atomic(kaddr, KM_USER0);
 		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, KM_USER0);
 	nilfs_mdt_mark_buffer_dirty(su_bh);

 	nilfs_sufile_mod_counter(header_bh, 1, sudirty ? (u64)-1 : 0);
 	nilfs_mdt_mark_dirty(sufile);
 }

 /**
  * nilfs_sufile_get_segment_usage - get a segment usage
  * @sufile: inode of segment usage file
  * @segnum: segment number
  * @sup: pointer to segment usage
  * @bhp: pointer to buffer head
  *
  * Description: nilfs_sufile_get_segment_usage() acquires the segment usage
  * specified by @segnum.
  *
  * Return Value: On success, 0 is returned, and the segment usage and the
  * buffer head of the buffer on which the segment usage is located are stored
  * in the place pointed by @sup and @bhp, respectively. On error, one of the
  * following negative error codes is returned.
  *
  * %-EIO - I/O error.
  *
  * %-ENOMEM - Insufficient amount of memory available.
  *
  * %-EINVAL - Invalid segment usage number.
  */
 int nilfs_sufile_get_segment_usage(struct inode *sufile, __u64 segnum,
 				   struct nilfs_segment_usage **sup,
 				   struct buffer_head **bhp)
 {
 	struct buffer_head *bh;
 	struct nilfs_segment_usage *su;
 	void *kaddr;
 	int ret;

 	/* segnum is 0 origin */
 	if (segnum >= nilfs_sufile_get_nsegments(sufile))
 		return -EINVAL;
 	down_write(&NILFS_MDT(sufile)->mi_sem);
 	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1, &bh);
 	if (ret < 0)
 		goto out_sem;
 	kaddr = kmap(bh->b_page);
 	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr);
 	if (nilfs_segment_usage_error(su)) {
 		kunmap(bh->b_page);
 		brelse(bh);
 		ret = -EINVAL;
 		goto out_sem;
 	}

 	if (sup != NULL)
 		*sup = su;
 	*bhp = bh;

  out_sem:
 	up_write(&NILFS_MDT(sufile)->mi_sem);
 	return ret;
 }

 /**
  * nilfs_sufile_put_segment_usage - put a segment usage
  * @sufile: inode of segment usage file
  * @segnum: segment number
  * @bh: buffer head
  *
  * Description: nilfs_sufile_put_segment_usage() releases the segment usage
  * specified by @segnum. @bh must be the buffer head which have been returned
  * by a previous call to nilfs_sufile_get_segment_usage() with @segnum.
  */
 void nilfs_sufile_put_segment_usage(struct inode *sufile, __u64 segnum,
 				    struct buffer_head *bh)
 {
 	kunmap(bh->b_page);
 	brelse(bh);
 }

 /**
  * 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 = NILFS_MDT(sufile)->mi_nilfs;
 	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, KM_USER0);
 	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
 	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, KM_USER0);
 	brelse(header_bh);

  out_sem:
 	up_read(&NILFS_MDT(sufile)->mi_sem);
 	return ret;
 }

 /**
  * nilfs_sufile_get_ncleansegs - get the number of clean segments
  * @sufile: inode of segment usage file
  * @nsegsp: pointer to the number of clean segments
  *
  * Description: nilfs_sufile_get_ncleansegs() acquires the number of clean
  * segments.
  *
  * Return Value: On success, 0 is returned and the number of clean segments is
  * stored in the place pointed by @nsegsp. 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_ncleansegs(struct inode *sufile, unsigned long *nsegsp)
 {
 	struct nilfs_sustat sustat;
 	int ret;

 	ret = nilfs_sufile_get_stat(sufile, &sustat);
 	if (ret == 0)
 		*nsegsp = sustat.ss_ncleansegs;
 	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, KM_USER0);
 	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
 	if (nilfs_segment_usage_error(su)) {
 		kunmap_atomic(kaddr, KM_USER0);
 		return;
 	}
 	suclean = nilfs_segment_usage_clean(su);
 	nilfs_segment_usage_set_error(su);
 	kunmap_atomic(kaddr, KM_USER0);

 	if (suclean)
 		nilfs_sufile_mod_counter(header_bh, -1, 0);
 	nilfs_mdt_mark_buffer_dirty(su_bh);
 	nilfs_mdt_mark_dirty(sufile);
 }

 /**
  * nilfs_sufile_get_suinfo -
  * @sufile: inode of segment usage file
  * @segnum: segment number to start looking
  * @si: array 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,
 				struct nilfs_suinfo *si, size_t nsi)
 {
 	struct buffer_head *su_bh;
 	struct nilfs_segment_usage *su;
 	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
 	struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
 	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[i], 0, sizeof(struct nilfs_suinfo) * n);
 			continue;
 		}

 		kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
 		su = nilfs_sufile_block_get_segment_usage(
 			sufile, segnum, su_bh, kaddr);
 		for (j = 0; j < n; j++, su = (void *)su + susz) {
 			si[i + j].sui_lastmod = le64_to_cpu(su->su_lastmod);
 			si[i + j].sui_nblocks = le32_to_cpu(su->su_nblocks);
 			si[i + j].sui_flags = le32_to_cpu(su->su_flags) &
 				~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
 			if (nilfs_segment_is_active(nilfs, segnum + j))
 				si[i + j].sui_flags |=
 					(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
 		}
 		kunmap_atomic(kaddr, KM_USER0);
 		brelse(su_bh);
 	}
 	ret = nsegs;

  out:
 	up_read(&NILFS_MDT(sufile)->mi_sem);
 	return ret;
 }
	/*
	* 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>.
	*/

	#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"


	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 inline struct nilfs_sufile_header *
	nilfs_sufile_block_get_header(const struct inode *sufile,
	struct buffer_head *bh,
	void *kaddr)
	{
	return kaddr + bh_offset(bh);
	}

	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 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, KM_USER0);
	header = kaddr + bh_offset(header_bh);
	le64_add_cpu(&header->sh_ncleansegs, ncleanadd);
	le64_add_cpu(&header->sh_ndirtysegs, ndirtyadd);
	kunmap_atomic(kaddr, KM_USER0);

	nilfs_mdt_mark_buffer_dirty(header_bh);
	}

	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\n",
	__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_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;
	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
	__u64 segnum, maxsegnum, last_alloc;
	void *kaddr;
	unsigned long nsegments, ncleansegs, nsus;
	int ret, i, 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, KM_USER0);
	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
	ncleansegs = le64_to_cpu(header->sh_ncleansegs);
	last_alloc = le64_to_cpu(header->sh_last_alloc);
	kunmap_atomic(kaddr, KM_USER0);

	nsegments = nilfs_sufile_get_nsegments(sufile);
	segnum = last_alloc + 1;
	maxsegnum = nsegments - 1;
	for (i = 0; i < nsegments; i += nsus) {
	if (segnum >= nsegments) {
	/* wrap around */
	segnum = 0;
	maxsegnum = last_alloc;
	}
	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, KM_USER0);
	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, KM_USER0);

	kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
	header = nilfs_sufile_block_get_header(
	sufile, header_bh, kaddr);
	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, KM_USER0);

	nilfs_mdt_mark_buffer_dirty(header_bh);
	nilfs_mdt_mark_buffer_dirty(su_bh);
	nilfs_mdt_mark_dirty(sufile);
	brelse(su_bh);
	*segnump = segnum;
	goto out_header;
	}

	kunmap_atomic(kaddr, KM_USER0);
	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, KM_USER0);
	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\n",
	__func__, (unsigned long long)segnum);
	kunmap_atomic(kaddr, KM_USER0);
	return;
	}
	nilfs_segment_usage_set_dirty(su);
	kunmap_atomic(kaddr, KM_USER0);

	nilfs_sufile_mod_counter(header_bh, -1, 1);
	nilfs_mdt_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, KM_USER0);
	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, KM_USER0);
	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, KM_USER0);

	nilfs_sufile_mod_counter(header_bh, clean ? (u64)-1 : 0, dirty ? 0 : 1);
	nilfs_mdt_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, KM_USER0);
	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\n",
	__func__, (unsigned long long)segnum);
	kunmap_atomic(kaddr, KM_USER0);
	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, KM_USER0);
	nilfs_mdt_mark_buffer_dirty(su_bh);

	nilfs_sufile_mod_counter(header_bh, 1, sudirty ? (u64)-1 : 0);
	nilfs_mdt_mark_dirty(sufile);
	}

	/**
	* nilfs_sufile_get_segment_usage - get a segment usage
	* @sufile: inode of segment usage file
	* @segnum: segment number
	* @sup: pointer to segment usage
	* @bhp: pointer to buffer head
	*
	* Description: nilfs_sufile_get_segment_usage() acquires the segment usage
	* specified by @segnum.
	*
	* Return Value: On success, 0 is returned, and the segment usage and the
	* buffer head of the buffer on which the segment usage is located are stored
	* in the place pointed by @sup and @bhp, respectively. On error, one of the
	* following negative error codes is returned.
	*
	* %-EIO - I/O error.
	*
	* %-ENOMEM - Insufficient amount of memory available.
	*
	* %-EINVAL - Invalid segment usage number.
	*/
	int nilfs_sufile_get_segment_usage(struct inode *sufile, __u64 segnum,
	struct nilfs_segment_usage **sup,
	struct buffer_head **bhp)
	{
	struct buffer_head *bh;
	struct nilfs_segment_usage *su;
	void *kaddr;
	int ret;

	/* segnum is 0 origin */
	if (segnum >= nilfs_sufile_get_nsegments(sufile))
	return -EINVAL;
	down_write(&NILFS_MDT(sufile)->mi_sem);
	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1, &bh);
	if (ret < 0)
	goto out_sem;
	kaddr = kmap(bh->b_page);
	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr);
	if (nilfs_segment_usage_error(su)) {
	kunmap(bh->b_page);
	brelse(bh);
	ret = -EINVAL;
	goto out_sem;
	}

	if (sup != NULL)
	*sup = su;
	*bhp = bh;

	out_sem:
	up_write(&NILFS_MDT(sufile)->mi_sem);
	return ret;
	}

	/**
	* nilfs_sufile_put_segment_usage - put a segment usage
	* @sufile: inode of segment usage file
	* @segnum: segment number
	* @bh: buffer head
	*
	* Description: nilfs_sufile_put_segment_usage() releases the segment usage
	* specified by @segnum. @bh must be the buffer head which have been returned
	* by a previous call to nilfs_sufile_get_segment_usage() with @segnum.
	*/
	void nilfs_sufile_put_segment_usage(struct inode *sufile, __u64 segnum,
	struct buffer_head *bh)
	{
	kunmap(bh->b_page);
	brelse(bh);
	}

	/**
	* 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 = NILFS_MDT(sufile)->mi_nilfs;
	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, KM_USER0);
	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
	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, KM_USER0);
	brelse(header_bh);

	out_sem:
	up_read(&NILFS_MDT(sufile)->mi_sem);
	return ret;
	}

	/**
	* nilfs_sufile_get_ncleansegs - get the number of clean segments
	* @sufile: inode of segment usage file
	* @nsegsp: pointer to the number of clean segments
	*
	* Description: nilfs_sufile_get_ncleansegs() acquires the number of clean
	* segments.
	*
	* Return Value: On success, 0 is returned and the number of clean segments is
	* stored in the place pointed by @nsegsp. 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_ncleansegs(struct inode sufile, unsigned long nsegsp)
	{
	struct nilfs_sustat sustat;
	int ret;

	ret = nilfs_sufile_get_stat(sufile, &sustat);
	if (ret == 0)
	*nsegsp = sustat.ss_ncleansegs;
	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, KM_USER0);
	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
	if (nilfs_segment_usage_error(su)) {
	kunmap_atomic(kaddr, KM_USER0);
	return;
	}
	suclean = nilfs_segment_usage_clean(su);
	nilfs_segment_usage_set_error(su);
	kunmap_atomic(kaddr, KM_USER0);

	if (suclean)
	nilfs_sufile_mod_counter(header_bh, -1, 0);
	nilfs_mdt_mark_buffer_dirty(su_bh);
	nilfs_mdt_mark_dirty(sufile);
	}

	/**
	* nilfs_sufile_get_suinfo -
	* @sufile: inode of segment usage file
	* @segnum: segment number to start looking
	* @si: array 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,
	struct nilfs_suinfo *si, size_t nsi)
	{
	struct buffer_head *su_bh;
	struct nilfs_segment_usage *su;
	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
	struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
	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[i], 0, sizeof(struct nilfs_suinfo) * n);
	continue;
	}

	kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
	su = nilfs_sufile_block_get_segment_usage(
	sufile, segnum, su_bh, kaddr);
	for (j = 0; j < n; j++, su = (void *)su + susz) {
	si[i + j].sui_lastmod = le64_to_cpu(su->su_lastmod);
	si[i + j].sui_nblocks = le32_to_cpu(su->su_nblocks);
	si[i + j].sui_flags = le32_to_cpu(su->su_flags) &
	~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
	if (nilfs_segment_is_active(nilfs, segnum + j))
	si[i + j].sui_flags \|=
	(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
	}
	kunmap_atomic(kaddr, KM_USER0);
	brelse(su_bh);
	}
	ret = nsegs;

	out:
	up_read(&NILFS_MDT(sufile)->mi_sem);
	return ret;
	}