Ejemplo n.º 1
0
static void *logfs_write_commit(struct super_block *sb, void *h,
		u16 *type, size_t *len)
{
	struct logfs_super *super = logfs_super(sb);

	*type = JE_COMMIT;
	*len = super->s_no_je * sizeof(__be64);
	return super->s_je_array;
}
Ejemplo n.º 2
0
void logfs_cleanup_journal(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);

	btree_grim_visitor32(&super->s_reserved_segments, 0, NULL);

	kfree(super->s_compressed_je);
	kfree(super->s_je);
}
Ejemplo n.º 3
0
static void read_erasecount(struct super_block *sb,
		struct logfs_je_journal_ec *ec)
{
	struct logfs_super *super = logfs_super(sb);
	int i;

	journal_for_each(i)
		super->s_journal_ec[i] = be32_to_cpu(ec->ec[i]);
}
Ejemplo n.º 4
0
int logfs_erase_segment(struct super_block *sb, u32 segno, int ensure_erase)
{
	struct logfs_super *super = logfs_super(sb);

	super->s_gec++;

	return super->s_devops->erase(sb, (u64)segno << super->s_segshift,
			super->s_segsize, ensure_erase);
}
Ejemplo n.º 5
0
/* called with inode->i_lock held */
static int logfs_drop_inode(struct inode *inode)
{
	struct logfs_super *super = logfs_super(inode->i_sb);
	struct logfs_inode *li = logfs_inode(inode);

	spin_lock(&logfs_inode_lock);
	list_move(&li->li_freeing_list, &super->s_freeing_list);
	spin_unlock(&logfs_inode_lock);
	return generic_drop_inode(inode);
}
Ejemplo n.º 6
0
static int __logfs_create(struct inode *dir, struct dentry *dentry,
		struct inode *inode, const char *dest, long destlen)
{
	struct logfs_super *super = logfs_super(dir->i_sb);
	struct logfs_inode *li = logfs_inode(inode);
	struct logfs_transaction *ta;
	int ret;

	ta = kzalloc(sizeof(*ta), GFP_KERNEL);
	if (!ta)
		return -ENOMEM;

	ta->state = CREATE_1;
	ta->ino = inode->i_ino;
	mutex_lock(&super->s_dirop_mutex);
	logfs_add_transaction(inode, ta);

	if (dest) {
		/* symlink */
		ret = logfs_inode_write(inode, dest, destlen, 0, WF_LOCK, NULL);
		if (!ret)
			ret = write_inode(inode);
	} else {
		/* creat/mkdir/mknod */
		ret = write_inode(inode);
	}
	if (ret) {
		abort_transaction(inode, ta);
		li->li_flags |= LOGFS_IF_STILLBORN;
		/* FIXME: truncate symlink */
		inode->i_nlink--;
		iput(inode);
		goto out;
	}

	ta->state = CREATE_2;
	logfs_add_transaction(dir, ta);
	ret = logfs_write_dir(dir, dentry, inode);
	/* sync directory */
	if (!ret)
		ret = write_inode(dir);

	if (ret) {
		logfs_del_transaction(dir, ta);
		ta->state = CREATE_2;
		logfs_add_transaction(inode, ta);
		logfs_remove_inode(inode);
		iput(inode);
		goto out;
	}
	d_instantiate(dentry, inode);
out:
	mutex_unlock(&super->s_dirop_mutex);
	return ret;
}
Ejemplo n.º 7
0
static int logfs_write_je(struct super_block *sb,
		void* (*write)(struct super_block *sb, void *scratch,
			u16 *type, size_t *len))
{
	void *buf;
	size_t len;
	u16 type;

	buf = write(sb, logfs_super(sb)->s_je, &type, &len);
	return logfs_write_je_buf(sb, buf, type, len);
}
Ejemplo n.º 8
0
static s64 logfs_get_free_bytes(struct logfs_area *area, size_t bytes)
{
	s32 ofs;

	logfs_open_area(area, bytes);

	ofs = area->a_used_bytes;
	area->a_used_bytes += bytes;
	BUG_ON(area->a_used_bytes >= logfs_super(area->a_sb)->s_segsize);

	return dev_ofs(area->a_sb, area->a_segno, ofs);
}
Ejemplo n.º 9
0
static void read_dynsb(struct super_block *sb,
		struct logfs_je_dynsb *dynsb)
{
	struct logfs_super *super = logfs_super(sb);

	super->s_gec		= be64_to_cpu(dynsb->ds_gec);
	super->s_sweeper	= be64_to_cpu(dynsb->ds_sweeper);
	super->s_victim_ino	= be64_to_cpu(dynsb->ds_victim_ino);
	super->s_rename_dir	= be64_to_cpu(dynsb->ds_rename_dir);
	super->s_rename_pos	= be64_to_cpu(dynsb->ds_rename_pos);
	super->s_used_bytes	= be64_to_cpu(dynsb->ds_used_bytes);
	super->s_generation	= be32_to_cpu(dynsb->ds_generation);
}
Ejemplo n.º 10
0
static void writeseg_end_io(struct bio *bio)
{
	struct bio_vec *bvec;
	int i;
	struct super_block *sb = bio->bi_private;
	struct logfs_super *super = logfs_super(sb);

	BUG_ON(bio->bi_error); /* FIXME: Retry io or write elsewhere */

	bio_for_each_segment_all(bvec, bio, i) {
		end_page_writeback(bvec->bv_page);
		page_cache_release(bvec->bv_page);
	}
Ejemplo n.º 11
0
static void *logfs_write_erasecount(struct super_block *sb, void *_ec,
		u16 *type, size_t *len)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_je_journal_ec *ec = _ec;
	int i;

	journal_for_each(i)
		ec->ec[i] = cpu_to_be32(super->s_journal_ec[i]);
	*type = JE_ERASECOUNT;
	*len = logfs_journal_erasecount_size(super);
	return ec;
}
Ejemplo n.º 12
0
static int logfs_read_segment(struct super_block *sb, u32 segno)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_journal_header *jh = super->s_compressed_je;
	u64 ofs, seg_ofs = dev_ofs(sb, segno, 0);
	u32 h_ofs, last_ofs = 0;
	u16 len, datalen, last_len = 0;
	int i, err;

	
	for (h_ofs = 0; h_ofs < super->s_segsize; h_ofs += sizeof(*jh)) {
		ofs = seg_ofs + h_ofs;
		err = __read_je_header(sb, ofs, jh);
		if (err)
			continue;
		if (jh->h_type != cpu_to_be16(JE_COMMIT))
			continue;
		err = __read_je_payload(sb, ofs, jh);
		if (err)
			continue;
		len = be16_to_cpu(jh->h_len);
		datalen = be16_to_cpu(jh->h_datalen);
		if ((datalen > sizeof(super->s_je_array)) ||
				(datalen % sizeof(__be64)))
			continue;
		last_ofs = h_ofs;
		last_len = datalen;
		h_ofs += ALIGN(len, sizeof(*jh)) - sizeof(*jh);
	}
	
	if (last_ofs == 0)
		return -ENOENT;
	ofs = seg_ofs + last_ofs;
	log_journal("Read commit from %llx\n", ofs);
	err = __read_je(sb, ofs, jh);
	BUG_ON(err); 
	if (err)
		return err;
	
	unpack(jh, super->s_je_array);
	super->s_no_je = last_len / sizeof(__be64);
	
	for (i = 0; i < super->s_no_je; i++) {
		err = read_je(sb, be64_to_cpu(super->s_je_array[i]));
		if (err)
			return err;
	}
	super->s_journal_area->a_segno = segno;
	return 0;
}
Ejemplo n.º 13
0
static int logfs_unlink(struct inode *dir, struct dentry *dentry)
{
	struct logfs_super *super = logfs_super(dir->i_sb);
	struct inode *inode = dentry->d_inode;
	struct logfs_transaction *ta;
	struct page *page;
	pgoff_t index;
	int ret;

	ta = kzalloc(sizeof(*ta), GFP_KERNEL);
	if (!ta)
		return -ENOMEM;

	ta->state = UNLINK_1;
	ta->ino = inode->i_ino;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;

	page = logfs_get_dd_page(dir, dentry);
	if (!page) {
		kfree(ta);
		return -ENOENT;
	}
	if (IS_ERR(page)) {
		kfree(ta);
		return PTR_ERR(page);
	}
	index = page->index;
	page_cache_release(page);

	mutex_lock(&super->s_dirop_mutex);
	logfs_add_transaction(dir, ta);

	ret = logfs_delete(dir, index, NULL);
	if (!ret)
		ret = write_inode(dir);

	if (ret) {
		abort_transaction(dir, ta);
		printk(KERN_ERR"LOGFS: unable to delete inode\n");
		goto out;
	}

	ta->state = UNLINK_2;
	logfs_add_transaction(inode, ta);
	ret = logfs_remove_inode(inode);
out:
	mutex_unlock(&super->s_dirop_mutex);
	return ret;
}
Ejemplo n.º 14
0
/* No locking done here, as this is called before .get_sb() returns. */
int logfs_replay_journal(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	struct inode *inode;
	u64 ino, pos;
	int err;

	if (super->s_victim_ino) {
		/* delete victim inode */
		ino = super->s_victim_ino;
		printk(KERN_INFO"LogFS: delete unmapped inode #%llx\n", ino);
		inode = logfs_iget(sb, ino);
		if (IS_ERR(inode))
			goto fail;

		LOGFS_BUG_ON(i_size_read(inode) > 0, sb);
		super->s_victim_ino = 0;
		err = logfs_remove_inode(inode);
		iput(inode);
		if (err) {
			super->s_victim_ino = ino;
			goto fail;
		}
	}
	if (super->s_rename_dir) {
		/* delete old dd from rename */
		ino = super->s_rename_dir;
		pos = super->s_rename_pos;
		printk(KERN_INFO"LogFS: delete unbacked dentry (%llx, %llx)\n",
				ino, pos);
		inode = logfs_iget(sb, ino);
		if (IS_ERR(inode))
			goto fail;

		super->s_rename_dir = 0;
		super->s_rename_pos = 0;
		err = logfs_delete_dd(inode, pos);
		iput(inode);
		if (err) {
			super->s_rename_dir = ino;
			super->s_rename_pos = pos;
			goto fail;
		}
	}
	return 0;
fail:
	LOGFS_BUG(sb);
	return -EIO;
}
Ejemplo n.º 15
0
/*
 * FIXME: There should be a reserve for root, similar to ext2.
 */
int logfs_statfs(struct dentry *dentry, struct kstatfs *stats)
{
	struct super_block *sb = dentry->d_sb;
	struct logfs_super *super = logfs_super(sb);

	stats->f_type		= LOGFS_MAGIC_U32;
	stats->f_bsize		= sb->s_blocksize;
	stats->f_blocks		= super->s_size >> LOGFS_BLOCK_BITS >> 3;
	stats->f_bfree		= super->s_free_bytes >> sb->s_blocksize_bits;
	stats->f_bavail		= super->s_free_bytes >> sb->s_blocksize_bits;
	stats->f_files		= 0;
	stats->f_ffree		= 0;
	stats->f_namelen	= LOGFS_MAX_NAMELEN;
	return 0;
}
Ejemplo n.º 16
0
/*
 * Cross-directory rename, target does not exist.  Just a little nasty.
 * Create a new dentry in the target dir, then remove the old dentry,
 * all the while taking care to remember our operation in the journal.
 */
static int logfs_rename_cross(struct inode *old_dir, struct dentry *old_dentry,
			      struct inode *new_dir, struct dentry *new_dentry)
{
	struct logfs_super *super = logfs_super(old_dir->i_sb);
	struct logfs_disk_dentry dd;
	struct logfs_transaction *ta;
	loff_t pos;
	int err;

	/* 1. locate source dd */
	err = logfs_get_dd(old_dir, old_dentry, &dd, &pos);
	if (err)
		return err;

	ta = kzalloc(sizeof(*ta), GFP_KERNEL);
	if (!ta)
		return -ENOMEM;

	ta->state = CROSS_RENAME_1;
	ta->dir = old_dir->i_ino;
	ta->pos = pos;

	/* 2. write target dd */
	mutex_lock(&super->s_dirop_mutex);
	logfs_add_transaction(new_dir, ta);
	err = logfs_write_dir(new_dir, new_dentry, old_dentry->d_inode);
	if (!err)
		err = write_inode(new_dir);

	if (err) {
		super->s_rename_dir = 0;
		super->s_rename_pos = 0;
		abort_transaction(new_dir, ta);
		goto out;
	}

	/* 3. remove source dd */
	ta->state = CROSS_RENAME_2;
	logfs_add_transaction(old_dir, ta);
	err = logfs_delete_dd(old_dir, pos);
	if (!err)
		err = write_inode(old_dir);
	LOGFS_BUG_ON(err, old_dir->i_sb);
out:
	mutex_unlock(&super->s_dirop_mutex);
	return err;
}
Ejemplo n.º 17
0
static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
		size_t nr_pages)
{
	struct logfs_super *super = logfs_super(sb);
	struct address_space *mapping = super->s_mapping_inode->i_mapping;
	struct bio *bio;
	struct page *page;
	struct request_queue *q = bdev_get_queue(sb->s_bdev);
	unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9);
	int i;

	if (max_pages > BIO_MAX_PAGES)
		max_pages = BIO_MAX_PAGES;
	bio = bio_alloc(GFP_NOFS, max_pages);
	BUG_ON(!bio);

	for (i = 0; i < nr_pages; i++) {
		if (i >= max_pages) {
			/* Block layer cannot split bios :( */
			bio->bi_vcnt = i;
			bio->bi_idx = 0;
			bio->bi_size = i * PAGE_SIZE;
			bio->bi_bdev = super->s_bdev;
			bio->bi_sector = ofs >> 9;
			bio->bi_private = sb;
			bio->bi_end_io = writeseg_end_io;
			atomic_inc(&super->s_pending_writes);
			submit_bio(WRITE, bio);

			ofs += i * PAGE_SIZE;
			index += i;
			nr_pages -= i;
			i = 0;

			bio = bio_alloc(GFP_NOFS, max_pages);
			BUG_ON(!bio);
		}
		page = find_lock_page(mapping, index + i);
		BUG_ON(!page);
		bio->bi_io_vec[i].bv_page = page;
		bio->bi_io_vec[i].bv_len = PAGE_SIZE;
		bio->bi_io_vec[i].bv_offset = 0;

		BUG_ON(PageWriteback(page));
		set_page_writeback(page);
		unlock_page(page);
	}
Ejemplo n.º 18
0
static int logfs_read_sb(struct super_block *sb, int read_only)
{
	struct logfs_super *super = logfs_super(sb);
	int ret;
	
	super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
	if (!super->s_btree_pool)
		return -ENOMEM;

	btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
	btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
	btree_init_mempool32(&super->s_shadow_tree.segment_map,
			super->s_btree_pool);
	
	ret = logfs_init_mapping(sb);
	if (ret)
		return ret;
	
	ret = __logfs_read_sb(sb);
	if (ret)
		return ret;
	
	if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
		return -EIO;
	if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
			!read_only)
		return -EIO;

	ret = logfs_init_rw(sb);
	if (ret)
		return ret;
	
	ret = logfs_init_areas(sb);
	if (ret)
		return ret;

	/*
	ret = logfs_init_gc(sb);
	if (ret)
		return ret;
	*/
	ret = logfs_init_journal(sb);
	if (ret)
		return ret;

	return 0;
}
Ejemplo n.º 19
0
static struct page *get_mapping_page(struct super_block *sb, pgoff_t index,
		int use_filler)
{
	struct logfs_super *super = logfs_super(sb);
	struct address_space *mapping = super->s_mapping_inode->i_mapping;
	filler_t *filler = super->s_devops->readpage;
	struct page *page;

	BUG_ON(mapping_gfp_mask(mapping) & __GFP_FS);
	if (use_filler)
		page = read_cache_page(mapping, index, filler, sb);
	else {
		page = find_or_create_page(mapping, index, GFP_NOFS);
		unlock_page(page);
	}
	return page;
}
Ejemplo n.º 20
0
static void account_shadows(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	struct inode *inode = super->s_master_inode;
	struct logfs_inode *li = logfs_inode(inode);
	struct shadow_tree *tree = &super->s_shadow_tree;

	btree_grim_visitor64(&tree->new, (unsigned long)sb, account_shadow);
	btree_grim_visitor64(&tree->old, (unsigned long)sb, account_shadow);
	btree_grim_visitor32(&tree->segment_map, 0, NULL);
	tree->no_shadowed_segments = 0;

	if (li->li_block) {
		li->li_block->ops->free_block(sb, li->li_block);
	}
	BUG_ON((s64)li->li_used_bytes < 0);
}
Ejemplo n.º 21
0
static int bdev_readpage(void *_sb, struct page *page)
{
	struct super_block *sb = _sb;
	struct block_device *bdev = logfs_super(sb)->s_bdev;
	int err;

	err = sync_request(page, bdev, READ);
	if (err) {
		ClearPageUptodate(page);
		SetPageError(page);
	} else {
		SetPageUptodate(page);
		ClearPageError(page);
	}
	unlock_page(page);
	return err;
}
Ejemplo n.º 22
0
static void read_anchor(struct super_block *sb,
		struct logfs_je_anchor *da)
{
	struct logfs_super *super = logfs_super(sb);
	struct inode *inode = super->s_master_inode;
	struct logfs_inode *li = logfs_inode(inode);
	int i;

	super->s_last_ino = be64_to_cpu(da->da_last_ino);
	li->li_flags	= 0;
	li->li_height	= da->da_height;
	i_size_write(inode, be64_to_cpu(da->da_size));
	li->li_used_bytes = be64_to_cpu(da->da_used_bytes);

	for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
		li->li_data[i] = be64_to_cpu(da->da_data[i]);
}
Ejemplo n.º 23
0
static void *logfs_write_dynsb(struct super_block *sb, void *_dynsb,
		u16 *type, size_t *len)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_je_dynsb *dynsb = _dynsb;

	dynsb->ds_gec		= cpu_to_be64(super->s_gec);
	dynsb->ds_sweeper	= cpu_to_be64(super->s_sweeper);
	dynsb->ds_victim_ino	= cpu_to_be64(super->s_victim_ino);
	dynsb->ds_rename_dir	= cpu_to_be64(super->s_rename_dir);
	dynsb->ds_rename_pos	= cpu_to_be64(super->s_rename_pos);
	dynsb->ds_used_bytes	= cpu_to_be64(super->s_used_bytes);
	dynsb->ds_generation	= cpu_to_be32(super->s_generation);
	*type = JE_DYNSB;
	*len = sizeof(*dynsb);
	return dynsb;
}
Ejemplo n.º 24
0
static int logfs_get_sb_final(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	struct inode *rootdir;
	int err;

	/* root dir */
	rootdir = logfs_iget(sb, LOGFS_INO_ROOT);
	if (IS_ERR(rootdir))
	  //goto fail;
	  return -EIO;

	sb->s_root = d_make_root(rootdir);
	if (!sb->s_root)
	  //goto fail;
	  return -EIO;

	
	// at that point we know that ->put_super() will be called
	super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
	if (!super->s_erase_page)
		return -ENOMEM;
	memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);
	
	/*
	// FIXME: check for read-only mounts
	err = logfs_make_writeable(sb);
	if (err) {
		__free_page(super->s_erase_page);
		return err;
	}
	*/
	
	
	log_super("LogFS: Finished mounting\n");
	return 0;
	
	/*
fail:
	iput(super->s_master_inode);
	iput(super->s_segfile_inode);
	iput(super->s_mapping_inode);
	return -EIO;
	*/
}
Ejemplo n.º 25
0
static void *logfs_write_area(struct super_block *sb, void *_a,
		u16 *type, size_t *len)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_area *area = super->s_area[super->s_sum_index];
	struct logfs_je_area *a = _a;

	a->vim = VIM_DEFAULT;
	a->gc_level = super->s_sum_index;
	a->used_bytes = cpu_to_be32(area->a_used_bytes);
	a->segno = cpu_to_be32(area->a_segno);
	if (super->s_writesize > 1)
		write_wbuf(sb, area, a + 1);

	*type = JE_AREA;
	*len = sizeof(*a) + super->s_writesize;
	return a;
}
Ejemplo n.º 26
0
static int logfs_write_obj_aliases(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	int err;

	log_journal("logfs_write_obj_aliases: %d aliases to write\n",
			super->s_no_object_aliases);
	super->s_je_fill = 0;
	err = logfs_write_obj_aliases_pagecache(sb);
	if (err)
		return err;

	if (super->s_je_fill)
		err = logfs_write_je_buf(sb, super->s_je, JE_OBJ_ALIAS,
				super->s_je_fill
				* sizeof(struct logfs_obj_alias));
	return err;
}
Ejemplo n.º 27
0
static void logfs_set_ino_generation(struct super_block *sb,
		struct inode *inode)
{
	struct logfs_super *super = logfs_super(sb);
	u64 ino;

	mutex_lock(&super->s_journal_mutex);
	ino = logfs_seek_hole(super->s_master_inode, super->s_last_ino + 1);
	super->s_last_ino = ino;
	super->s_inos_till_wrap--;
	if (super->s_inos_till_wrap < 0) {
		super->s_last_ino = LOGFS_RESERVED_INOS;
		super->s_generation++;
		super->s_inos_till_wrap = INOS_PER_WRAP;
	}
	inode->i_ino = ino;
	inode->i_generation = super->s_generation;
	mutex_unlock(&super->s_journal_mutex);
}
Ejemplo n.º 28
0
static void *__logfs_write_anchor(struct super_block *sb, void *_da,
		u16 *type, size_t *len)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_je_anchor *da = _da;
	struct inode *inode = super->s_master_inode;
	struct logfs_inode *li = logfs_inode(inode);
	int i;

	da->da_height	= li->li_height;
	da->da_last_ino = cpu_to_be64(super->s_last_ino);
	da->da_size	= cpu_to_be64(i_size_read(inode));
	da->da_used_bytes = cpu_to_be64(li->li_used_bytes);
	for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
		da->da_data[i] = cpu_to_be64(li->li_data[i]);
	*type = JE_ANCHOR;
	*len = sizeof(*da);
	return da;
}
Ejemplo n.º 29
0
void logfs_cleanup_gc(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	int i;

	if (!super->s_free_list.count)
		return;

	/*
	 * FIXME: The btree may still contain a single empty node.  So we
	 * call the grim visitor to clean up that mess.  Btree code should
	 * do it for us, really.
	 */
	btree_grim_visitor32(&super->s_cand_tree, 0, NULL);
	logfs_cleanup_list(sb, &super->s_free_list);
	logfs_cleanup_list(sb, &super->s_reserve_list);
	for_each_area(i)
		logfs_cleanup_list(sb, &super->s_low_list[i]);
	logfs_cleanup_list(sb, &super->s_ec_list);
}
Ejemplo n.º 30
0
static void write_wbuf(struct super_block *sb, struct logfs_area *area,
		void *wbuf)
{
	struct logfs_super *super = logfs_super(sb);
	struct address_space *mapping = super->s_mapping_inode->i_mapping;
	u64 ofs;
	pgoff_t index;
	int page_ofs;
	struct page *page;

	ofs = dev_ofs(sb, area->a_segno,
			area->a_used_bytes & ~(super->s_writesize - 1));
	index = ofs >> PAGE_SHIFT;
	page_ofs = ofs & (PAGE_SIZE - 1);

	page = find_lock_page(mapping, index);
	BUG_ON(!page);
	memcpy(wbuf, page_address(page) + page_ofs, super->s_writesize);
	unlock_page(page);
}