nilfs2: segment usage file

This adds a meta data file which stores the allocation state of segments.

[konishi.ryusuke@lab.ntt.co.jp: fix wrong counting of checkpoints and dirty segments]
Signed-off-by: Koji Sato <sato.koji@lab.ntt.co.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/cpfile.c

@@ -357,7 +357,7 @@ int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
 		kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 		header = nilfs_cpfile_block_get_header(cpfile, header_bh,
 						       kaddr);
-		le64_add_cpu(&header->ch_ncheckpoints, -tnicps);
+		le64_add_cpu(&header->ch_ncheckpoints, -(u64)tnicps);
 		nilfs_mdt_mark_buffer_dirty(header_bh);
 		nilfs_mdt_mark_dirty(cpfile);
 		kunmap_atomic(kaddr, KM_USER0);

fs/nilfs2/sufile.c

+/*
+ * 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);
+}
+
+/**
+ * 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 the_nilfs *nilfs;
+	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);
+
+	nilfs = NILFS_MDT(sufile)->mi_nilfs;
+
+	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_active(su);
+			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;
+}
+
+/**
+ * nilfs_sufile_cancel_free -
+ * @sufile: inode of segment usage file
+ * @segnum: segment number
+ *
+ * Description:
+ *
+ * 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.
+ */
+int nilfs_sufile_cancel_free(struct inode *sufile, __u64 segnum)
+{
+	struct buffer_head *header_bh, *su_bh;
+	struct the_nilfs *nilfs;
+	struct nilfs_sufile_header *header;
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	int ret;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+
+	nilfs = NILFS_MDT(sufile)->mi_nilfs;
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+
+	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &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);
+	if (!nilfs_segment_usage_clean(su)) {
+		printk(KERN_CRIT "%s: segment %llu must be clean\n",
+		       __func__, (unsigned long long)segnum);
+		BUG();
+	}
+	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);
+	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);
+
+ out_header:
+	brelse(header_bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_freev - free segments
+ * @sufile: inode of segment usage file
+ * @segnum: array of segment numbers
+ * @nsegs: number of segments
+ *
+ * Description: nilfs_sufile_freev() frees segments specified by @segnum and
+ * @nsegs, which must have been returned by a previous call to
+ * nilfs_sufile_alloc().
+ *
+ * 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.
+ */
+#define NILFS_SUFILE_FREEV_PREALLOC	16
+int nilfs_sufile_freev(struct inode *sufile, __u64 *segnum, size_t nsegs)
+{
+	struct buffer_head *header_bh, **su_bh,
+		*su_bh_prealloc[NILFS_SUFILE_FREEV_PREALLOC];
+	struct the_nilfs *nilfs;
+	struct nilfs_sufile_header *header;
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	int ret, i;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+
+	nilfs = NILFS_MDT(sufile)->mi_nilfs;
+
+	/* prepare resources */
+	if (nsegs <= NILFS_SUFILE_FREEV_PREALLOC)
+		su_bh = su_bh_prealloc;
+	else {
+		su_bh = kmalloc(sizeof(*su_bh) * nsegs, GFP_NOFS);
+		if (su_bh == NULL) {
+			ret = -ENOMEM;
+			goto out_sem;
+		}
+	}
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out_su_bh;
+	for (i = 0; i < nsegs; i++) {
+		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum[i],
+							   0, &su_bh[i]);
+		if (ret < 0)
+			goto out_bh;
+	}
+
+	/* free segments */
+	for (i = 0; i < nsegs; i++) {
+		kaddr = kmap_atomic(su_bh[i]->b_page, KM_USER0);
+		su = nilfs_sufile_block_get_segment_usage(
+			sufile, segnum[i], su_bh[i], kaddr);
+		BUG_ON(nilfs_segment_usage_error(su));
+		nilfs_segment_usage_set_clean(su);
+		kunmap_atomic(kaddr, KM_USER0);
+		nilfs_mdt_mark_buffer_dirty(su_bh[i]);
+	}
+	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, nsegs);
+	le64_add_cpu(&header->sh_ndirtysegs, -(u64)nsegs);
+	kunmap_atomic(kaddr, KM_USER0);
+	nilfs_mdt_mark_buffer_dirty(header_bh);
+	nilfs_mdt_mark_dirty(sufile);
+
+ out_bh:
+	for (i--; i >= 0; i--)
+		brelse(su_bh[i]);
+	brelse(header_bh);
+
+ out_su_bh:
+	if (su_bh != su_bh_prealloc)
+		kfree(su_bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_free -
+ * @sufile:
+ * @segnum:
+ */
+int nilfs_sufile_free(struct inode *sufile, __u64 segnum)
+{
+	return nilfs_sufile_freev(sufile, &segnum, 1);
+}
+
+/**
+ * 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 */
+	BUG_ON(segnum >= nilfs_sufile_get_nsegments(sufile));
+
+	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;
+	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_MDT(sufile)->mi_nilfs->ns_ctime;
+	sustat->ss_nongc_ctime = NILFS_MDT(sufile)->mi_nilfs->ns_nongc_ctime;
+	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;
+}
+
+/**
+ * nilfs_sufile_set_error - mark a segment as erroneous
+ * @sufile: inode of segment usage file
+ * @segnum: segment number
+ *
+ * Description: nilfs_sufile_set_error() marks the segment specified by
+ * @segnum as erroneous. The error segment will never be used again.
+ *
+ * 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.
+ */
+int nilfs_sufile_set_error(struct inode *sufile, __u64 segnum)
+{
+	struct buffer_head *header_bh, *su_bh;
+	struct nilfs_segment_usage *su;
+	struct nilfs_sufile_header *header;
+	void *kaddr;
+	int ret;
+
+	BUG_ON(segnum >= nilfs_sufile_get_nsegments(sufile));
+
+	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, 0, &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);
+	if (nilfs_segment_usage_error(su)) {
+		kunmap_atomic(kaddr, KM_USER0);
+		brelse(su_bh);
+		goto out_header;
+	}
+
+	nilfs_segment_usage_set_error(su);
+	kunmap_atomic(kaddr, KM_USER0);
+	brelse(su_bh);
+
+	kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
+	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
+	le64_add_cpu(&header->sh_ndirtysegs, -1);
+	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);
+
+ out_header:
+	brelse(header_bh);
+
+ out_sem:
+	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
+ * @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;
+	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);
+		}
+		kunmap_atomic(kaddr, KM_USER0);
+		brelse(su_bh);
+	}
+	ret = nsegs;
+
+ out:
+	up_read(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}

fs/nilfs2/sufile.h

+/*
+ * sufile.h - 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>.
+ */
+
+#ifndef _NILFS_SUFILE_H
+#define _NILFS_SUFILE_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/nilfs2_fs.h>
+#include "mdt.h"
+
+#define NILFS_SUFILE_GFP	NILFS_MDT_GFP
+
+static inline unsigned long nilfs_sufile_get_nsegments(struct inode *sufile)
+{
+	return NILFS_MDT(sufile)->mi_nilfs->ns_nsegments;
+}
+
+int nilfs_sufile_alloc(struct inode *, __u64 *);
+int nilfs_sufile_cancel_free(struct inode *, __u64);
+int nilfs_sufile_freev(struct inode *, __u64 *, size_t);
+int nilfs_sufile_free(struct inode *, __u64);
+int nilfs_sufile_get_segment_usage(struct inode *, __u64,
+				   struct nilfs_segment_usage **,
+				   struct buffer_head **);
+void nilfs_sufile_put_segment_usage(struct inode *, __u64,
+				    struct buffer_head *);
+int nilfs_sufile_get_stat(struct inode *, struct nilfs_sustat *);
+int nilfs_sufile_get_ncleansegs(struct inode *, unsigned long *);
+int nilfs_sufile_set_error(struct inode *, __u64);
+ssize_t nilfs_sufile_get_suinfo(struct inode *, __u64, struct nilfs_suinfo *,
+				size_t);
+
+
+#endif	/* _NILFS_SUFILE_H */