fs/nilfs2/dat.c - kernel/quantenna - Git at Google

 /*
  * dat.c - NILFS disk address translation.
  *
  * 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.
  *
  * Written by Koji Sato.
  */

 #include <linux/types.h>
 #include <linux/buffer_head.h>
 #include <linux/string.h>
 #include <linux/errno.h>
 #include "nilfs.h"
 #include "mdt.h"
 #include "alloc.h"
 #include "dat.h"


 #define NILFS_CNO_MIN	((__u64)1)
 #define NILFS_CNO_MAX	(~(__u64)0)

 /**
  * struct nilfs_dat_info - on-memory private data of DAT file
  * @mi: on-memory private data of metadata file
  * @palloc_cache: persistent object allocator cache of DAT file
  * @shadow: shadow map of DAT file
  */
 struct nilfs_dat_info {
 	struct nilfs_mdt_info mi;
 	struct nilfs_palloc_cache palloc_cache;
 	struct nilfs_shadow_map shadow;
 };

 static inline struct nilfs_dat_info *NILFS_DAT_I(struct inode *dat)
 {
 	return (struct nilfs_dat_info *)NILFS_MDT(dat);
 }

 static int nilfs_dat_prepare_entry(struct inode *dat,
 				   struct nilfs_palloc_req *req, int create)
 {
 	return nilfs_palloc_get_entry_block(dat, req->pr_entry_nr,
 					    create, &req->pr_entry_bh);
 }

 static void nilfs_dat_commit_entry(struct inode *dat,
 				   struct nilfs_palloc_req *req)
 {
 	mark_buffer_dirty(req->pr_entry_bh);
 	nilfs_mdt_mark_dirty(dat);
 	brelse(req->pr_entry_bh);
 }

 static void nilfs_dat_abort_entry(struct inode *dat,
 				  struct nilfs_palloc_req *req)
 {
 	brelse(req->pr_entry_bh);
 }

 int nilfs_dat_prepare_alloc(struct inode *dat, struct nilfs_palloc_req *req)
 {
 	int ret;

 	ret = nilfs_palloc_prepare_alloc_entry(dat, req);
 	if (ret < 0)
 		return ret;

 	ret = nilfs_dat_prepare_entry(dat, req, 1);
 	if (ret < 0)
 		nilfs_palloc_abort_alloc_entry(dat, req);

 	return ret;
 }

 void nilfs_dat_commit_alloc(struct inode *dat, struct nilfs_palloc_req *req)
 {
 	struct nilfs_dat_entry *entry;
 	void *kaddr;

 	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
 					     req->pr_entry_bh, kaddr);
 	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
 	entry->de_end = cpu_to_le64(NILFS_CNO_MAX);
 	entry->de_blocknr = cpu_to_le64(0);
 	kunmap_atomic(kaddr);

 	nilfs_palloc_commit_alloc_entry(dat, req);
 	nilfs_dat_commit_entry(dat, req);
 }

 void nilfs_dat_abort_alloc(struct inode *dat, struct nilfs_palloc_req *req)
 {
 	nilfs_dat_abort_entry(dat, req);
 	nilfs_palloc_abort_alloc_entry(dat, req);
 }

 static void nilfs_dat_commit_free(struct inode *dat,
 				  struct nilfs_palloc_req *req)
 {
 	struct nilfs_dat_entry *entry;
 	void *kaddr;

 	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
 					     req->pr_entry_bh, kaddr);
 	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
 	entry->de_end = cpu_to_le64(NILFS_CNO_MIN);
 	entry->de_blocknr = cpu_to_le64(0);
 	kunmap_atomic(kaddr);

 	nilfs_dat_commit_entry(dat, req);
 	nilfs_palloc_commit_free_entry(dat, req);
 }

 int nilfs_dat_prepare_start(struct inode *dat, struct nilfs_palloc_req *req)
 {
 	int ret;

 	ret = nilfs_dat_prepare_entry(dat, req, 0);
 	WARN_ON(ret == -ENOENT);
 	return ret;
 }

 void nilfs_dat_commit_start(struct inode *dat, struct nilfs_palloc_req *req,
 			    sector_t blocknr)
 {
 	struct nilfs_dat_entry *entry;
 	void *kaddr;

 	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
 					     req->pr_entry_bh, kaddr);
 	entry->de_start = cpu_to_le64(nilfs_mdt_cno(dat));
 	entry->de_blocknr = cpu_to_le64(blocknr);
 	kunmap_atomic(kaddr);

 	nilfs_dat_commit_entry(dat, req);
 }

 int nilfs_dat_prepare_end(struct inode *dat, struct nilfs_palloc_req *req)
 {
 	struct nilfs_dat_entry *entry;
 	sector_t blocknr;
 	void *kaddr;
 	int ret;

 	ret = nilfs_dat_prepare_entry(dat, req, 0);
 	if (ret < 0) {
 		WARN_ON(ret == -ENOENT);
 		return ret;
 	}

 	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
 					     req->pr_entry_bh, kaddr);
 	blocknr = le64_to_cpu(entry->de_blocknr);
 	kunmap_atomic(kaddr);

 	if (blocknr == 0) {
 		ret = nilfs_palloc_prepare_free_entry(dat, req);
 		if (ret < 0) {
 			nilfs_dat_abort_entry(dat, req);
 			return ret;
 		}
 	}

 	return 0;
 }

 void nilfs_dat_commit_end(struct inode *dat, struct nilfs_palloc_req *req,
 			  int dead)
 {
 	struct nilfs_dat_entry *entry;
 	__u64 start, end;
 	sector_t blocknr;
 	void *kaddr;

 	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
 					     req->pr_entry_bh, kaddr);
 	end = start = le64_to_cpu(entry->de_start);
 	if (!dead) {
 		end = nilfs_mdt_cno(dat);
 		WARN_ON(start > end);
 	}
 	entry->de_end = cpu_to_le64(end);
 	blocknr = le64_to_cpu(entry->de_blocknr);
 	kunmap_atomic(kaddr);

 	if (blocknr == 0)
 		nilfs_dat_commit_free(dat, req);
 	else
 		nilfs_dat_commit_entry(dat, req);
 }

 void nilfs_dat_abort_end(struct inode *dat, struct nilfs_palloc_req *req)
 {
 	struct nilfs_dat_entry *entry;
 	__u64 start;
 	sector_t blocknr;
 	void *kaddr;

 	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
 					     req->pr_entry_bh, kaddr);
 	start = le64_to_cpu(entry->de_start);
 	blocknr = le64_to_cpu(entry->de_blocknr);
 	kunmap_atomic(kaddr);

 	if (start == nilfs_mdt_cno(dat) && blocknr == 0)
 		nilfs_palloc_abort_free_entry(dat, req);
 	nilfs_dat_abort_entry(dat, req);
 }

 int nilfs_dat_prepare_update(struct inode *dat,
 			     struct nilfs_palloc_req *oldreq,
 			     struct nilfs_palloc_req *newreq)
 {
 	int ret;

 	ret = nilfs_dat_prepare_end(dat, oldreq);
 	if (!ret) {
 		ret = nilfs_dat_prepare_alloc(dat, newreq);
 		if (ret < 0)
 			nilfs_dat_abort_end(dat, oldreq);
 	}
 	return ret;
 }

 void nilfs_dat_commit_update(struct inode *dat,
 			     struct nilfs_palloc_req *oldreq,
 			     struct nilfs_palloc_req *newreq, int dead)
 {
 	nilfs_dat_commit_end(dat, oldreq, dead);
 	nilfs_dat_commit_alloc(dat, newreq);
 }

 void nilfs_dat_abort_update(struct inode *dat,
 			    struct nilfs_palloc_req *oldreq,
 			    struct nilfs_palloc_req *newreq)
 {
 	nilfs_dat_abort_end(dat, oldreq);
 	nilfs_dat_abort_alloc(dat, newreq);
 }

 /**
  * nilfs_dat_mark_dirty -
  * @dat: DAT file inode
  * @vblocknr: virtual block 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_dat_mark_dirty(struct inode *dat, __u64 vblocknr)
 {
 	struct nilfs_palloc_req req;
 	int ret;

 	req.pr_entry_nr = vblocknr;
 	ret = nilfs_dat_prepare_entry(dat, &req, 0);
 	if (ret == 0)
 		nilfs_dat_commit_entry(dat, &req);
 	return ret;
 }

 /**
  * nilfs_dat_freev - free virtual block numbers
  * @dat: DAT file inode
  * @vblocknrs: array of virtual block numbers
  * @nitems: number of virtual block numbers
  *
  * Description: nilfs_dat_freev() frees the virtual block numbers specified by
  * @vblocknrs and @nitems.
  *
  * 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.
  *
  * %-ENOENT - The virtual block number have not been allocated.
  */
 int nilfs_dat_freev(struct inode *dat, __u64 *vblocknrs, size_t nitems)
 {
 	return nilfs_palloc_freev(dat, vblocknrs, nitems);
 }

 /**
  * nilfs_dat_move - change a block number
  * @dat: DAT file inode
  * @vblocknr: virtual block number
  * @blocknr: block number
  *
  * Description: nilfs_dat_move() changes the block number associated with
  * @vblocknr to @blocknr.
  *
  * 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_dat_move(struct inode *dat, __u64 vblocknr, sector_t blocknr)
 {
 	struct buffer_head *entry_bh;
 	struct nilfs_dat_entry *entry;
 	void *kaddr;
 	int ret;

 	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
 	if (ret < 0)
 		return ret;

 	/*
 	 * The given disk block number (blocknr) is not yet written to
 	 * the device at this point.
 	 *
 	 * To prevent nilfs_dat_translate() from returning the
 	 * uncommitted block number, this makes a copy of the entry
 	 * buffer and redirects nilfs_dat_translate() to the copy.
 	 */
 	if (!buffer_nilfs_redirected(entry_bh)) {
 		ret = nilfs_mdt_freeze_buffer(dat, entry_bh);
 		if (ret) {
 			brelse(entry_bh);
 			return ret;
 		}
 	}

 	kaddr = kmap_atomic(entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
 	if (unlikely(entry->de_blocknr == cpu_to_le64(0))) {
 		printk(KERN_CRIT "%s: vbn = %llu, [%llu, %llu)\n", __func__,
 		       (unsigned long long)vblocknr,
 		       (unsigned long long)le64_to_cpu(entry->de_start),
 		       (unsigned long long)le64_to_cpu(entry->de_end));
 		kunmap_atomic(kaddr);
 		brelse(entry_bh);
 		return -EINVAL;
 	}
 	WARN_ON(blocknr == 0);
 	entry->de_blocknr = cpu_to_le64(blocknr);
 	kunmap_atomic(kaddr);

 	mark_buffer_dirty(entry_bh);
 	nilfs_mdt_mark_dirty(dat);

 	brelse(entry_bh);

 	return 0;
 }

 /**
  * nilfs_dat_translate - translate a virtual block number to a block number
  * @dat: DAT file inode
  * @vblocknr: virtual block number
  * @blocknrp: pointer to a block number
  *
  * Description: nilfs_dat_translate() maps the virtual block number @vblocknr
  * to the corresponding block number.
  *
  * Return Value: On success, 0 is returned and the block number associated
  * with @vblocknr is stored in the place pointed by @blocknrp. On error, one
  * of the following negative error codes is returned.
  *
  * %-EIO - I/O error.
  *
  * %-ENOMEM - Insufficient amount of memory available.
  *
  * %-ENOENT - A block number associated with @vblocknr does not exist.
  */
 int nilfs_dat_translate(struct inode *dat, __u64 vblocknr, sector_t *blocknrp)
 {
 	struct buffer_head *entry_bh, *bh;
 	struct nilfs_dat_entry *entry;
 	sector_t blocknr;
 	void *kaddr;
 	int ret;

 	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
 	if (ret < 0)
 		return ret;

 	if (!nilfs_doing_gc() && buffer_nilfs_redirected(entry_bh)) {
 		bh = nilfs_mdt_get_frozen_buffer(dat, entry_bh);
 		if (bh) {
 			WARN_ON(!buffer_uptodate(bh));
 			brelse(entry_bh);
 			entry_bh = bh;
 		}
 	}

 	kaddr = kmap_atomic(entry_bh->b_page);
 	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
 	blocknr = le64_to_cpu(entry->de_blocknr);
 	if (blocknr == 0) {
 		ret = -ENOENT;
 		goto out;
 	}
 	*blocknrp = blocknr;

  out:
 	kunmap_atomic(kaddr);
 	brelse(entry_bh);
 	return ret;
 }

 ssize_t nilfs_dat_get_vinfo(struct inode *dat, void *buf, unsigned int visz,
 			    size_t nvi)
 {
 	struct buffer_head *entry_bh;
 	struct nilfs_dat_entry *entry;
 	struct nilfs_vinfo *vinfo = buf;
 	__u64 first, last;
 	void *kaddr;
 	unsigned long entries_per_block = NILFS_MDT(dat)->mi_entries_per_block;
 	int i, j, n, ret;

 	for (i = 0; i < nvi; i += n) {
 		ret = nilfs_palloc_get_entry_block(dat, vinfo->vi_vblocknr,
 						   0, &entry_bh);
 		if (ret < 0)
 			return ret;
 		kaddr = kmap_atomic(entry_bh->b_page);
 		/* last virtual block number in this block */
 		first = vinfo->vi_vblocknr;
 		do_div(first, entries_per_block);
 		first *= entries_per_block;
 		last = first + entries_per_block - 1;
 		for (j = i, n = 0;
 		     j < nvi && vinfo->vi_vblocknr >= first &&
 			     vinfo->vi_vblocknr <= last;
 		     j++, n++, vinfo = (void *)vinfo + visz) {
 			entry = nilfs_palloc_block_get_entry(
 				dat, vinfo->vi_vblocknr, entry_bh, kaddr);
 			vinfo->vi_start = le64_to_cpu(entry->de_start);
 			vinfo->vi_end = le64_to_cpu(entry->de_end);
 			vinfo->vi_blocknr = le64_to_cpu(entry->de_blocknr);
 		}
 		kunmap_atomic(kaddr);
 		brelse(entry_bh);
 	}

 	return nvi;
 }

 /**
  * nilfs_dat_read - read or get dat inode
  * @sb: super block instance
  * @entry_size: size of a dat entry
  * @raw_inode: on-disk dat inode
  * @inodep: buffer to store the inode
  */
 int nilfs_dat_read(struct super_block *sb, size_t entry_size,
 		   struct nilfs_inode *raw_inode, struct inode **inodep)
 {
 	static struct lock_class_key dat_lock_key;
 	struct inode *dat;
 	struct nilfs_dat_info *di;
 	int err;

 	if (entry_size > sb->s_blocksize) {
 		printk(KERN_ERR
 		       "NILFS: too large DAT entry size: %zu bytes.\n",
 		       entry_size);
 		return -EINVAL;
 	} else if (entry_size < NILFS_MIN_DAT_ENTRY_SIZE) {
 		printk(KERN_ERR
 		       "NILFS: too small DAT entry size: %zu bytes.\n",
 		       entry_size);
 		return -EINVAL;
 	}

 	dat = nilfs_iget_locked(sb, NULL, NILFS_DAT_INO);
 	if (unlikely(!dat))
 		return -ENOMEM;
 	if (!(dat->i_state & I_NEW))
 		goto out;

 	err = nilfs_mdt_init(dat, NILFS_MDT_GFP, sizeof(*di));
 	if (err)
 		goto failed;

 	err = nilfs_palloc_init_blockgroup(dat, entry_size);
 	if (err)
 		goto failed;

 	di = NILFS_DAT_I(dat);
 	lockdep_set_class(&di->mi.mi_sem, &dat_lock_key);
 	nilfs_palloc_setup_cache(dat, &di->palloc_cache);
 	nilfs_mdt_setup_shadow_map(dat, &di->shadow);

 	err = nilfs_read_inode_common(dat, raw_inode);
 	if (err)
 		goto failed;

 	unlock_new_inode(dat);
  out:
 	*inodep = dat;
 	return 0;
  failed:
 	iget_failed(dat);
 	return err;
 }
	/*
	* dat.c - NILFS disk address translation.
	*
	* 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.
	*
	* Written by Koji Sato.
	*/

	#include <linux/types.h>
	#include <linux/buffer_head.h>
	#include <linux/string.h>
	#include <linux/errno.h>
	#include "nilfs.h"
	#include "mdt.h"
	#include "alloc.h"
	#include "dat.h"


	#define NILFS_CNO_MIN ((__u64)1)
	#define NILFS_CNO_MAX (~(__u64)0)

	/**
	* struct nilfs_dat_info - on-memory private data of DAT file
	* @mi: on-memory private data of metadata file
	* @palloc_cache: persistent object allocator cache of DAT file
	* @shadow: shadow map of DAT file
	*/
	struct nilfs_dat_info {
	struct nilfs_mdt_info mi;
	struct nilfs_palloc_cache palloc_cache;
	struct nilfs_shadow_map shadow;
	};

	static inline struct nilfs_dat_info NILFS_DAT_I(struct inode dat)
	{
	return (struct nilfs_dat_info *)NILFS_MDT(dat);
	}

	static int nilfs_dat_prepare_entry(struct inode *dat,
	struct nilfs_palloc_req *req, int create)
	{
	return nilfs_palloc_get_entry_block(dat, req->pr_entry_nr,
	create, &req->pr_entry_bh);
	}

	static void nilfs_dat_commit_entry(struct inode *dat,
	struct nilfs_palloc_req *req)
	{
	mark_buffer_dirty(req->pr_entry_bh);
	nilfs_mdt_mark_dirty(dat);
	brelse(req->pr_entry_bh);
	}

	static void nilfs_dat_abort_entry(struct inode *dat,
	struct nilfs_palloc_req *req)
	{
	brelse(req->pr_entry_bh);
	}

	int nilfs_dat_prepare_alloc(struct inode dat, struct nilfs_palloc_req req)
	{
	int ret;

	ret = nilfs_palloc_prepare_alloc_entry(dat, req);
	if (ret < 0)
	return ret;

	ret = nilfs_dat_prepare_entry(dat, req, 1);
	if (ret < 0)
	nilfs_palloc_abort_alloc_entry(dat, req);

	return ret;
	}

	void nilfs_dat_commit_alloc(struct inode dat, struct nilfs_palloc_req req)
	{
	struct nilfs_dat_entry *entry;
	void *kaddr;

	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
	req->pr_entry_bh, kaddr);
	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
	entry->de_end = cpu_to_le64(NILFS_CNO_MAX);
	entry->de_blocknr = cpu_to_le64(0);
	kunmap_atomic(kaddr);

	nilfs_palloc_commit_alloc_entry(dat, req);
	nilfs_dat_commit_entry(dat, req);
	}

	void nilfs_dat_abort_alloc(struct inode dat, struct nilfs_palloc_req req)
	{
	nilfs_dat_abort_entry(dat, req);
	nilfs_palloc_abort_alloc_entry(dat, req);
	}

	static void nilfs_dat_commit_free(struct inode *dat,
	struct nilfs_palloc_req *req)
	{
	struct nilfs_dat_entry *entry;
	void *kaddr;

	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
	req->pr_entry_bh, kaddr);
	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
	entry->de_end = cpu_to_le64(NILFS_CNO_MIN);
	entry->de_blocknr = cpu_to_le64(0);
	kunmap_atomic(kaddr);

	nilfs_dat_commit_entry(dat, req);
	nilfs_palloc_commit_free_entry(dat, req);
	}

	int nilfs_dat_prepare_start(struct inode dat, struct nilfs_palloc_req req)
	{
	int ret;

	ret = nilfs_dat_prepare_entry(dat, req, 0);
	WARN_ON(ret == -ENOENT);
	return ret;
	}

	void nilfs_dat_commit_start(struct inode dat, struct nilfs_palloc_req req,
	sector_t blocknr)
	{
	struct nilfs_dat_entry *entry;
	void *kaddr;

	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
	req->pr_entry_bh, kaddr);
	entry->de_start = cpu_to_le64(nilfs_mdt_cno(dat));
	entry->de_blocknr = cpu_to_le64(blocknr);
	kunmap_atomic(kaddr);

	nilfs_dat_commit_entry(dat, req);
	}

	int nilfs_dat_prepare_end(struct inode dat, struct nilfs_palloc_req req)
	{
	struct nilfs_dat_entry *entry;
	sector_t blocknr;
	void *kaddr;
	int ret;

	ret = nilfs_dat_prepare_entry(dat, req, 0);
	if (ret < 0) {
	WARN_ON(ret == -ENOENT);
	return ret;
	}

	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
	req->pr_entry_bh, kaddr);
	blocknr = le64_to_cpu(entry->de_blocknr);
	kunmap_atomic(kaddr);

	if (blocknr == 0) {
	ret = nilfs_palloc_prepare_free_entry(dat, req);
	if (ret < 0) {
	nilfs_dat_abort_entry(dat, req);
	return ret;
	}
	}

	return 0;
	}

	void nilfs_dat_commit_end(struct inode dat, struct nilfs_palloc_req req,
	int dead)
	{
	struct nilfs_dat_entry *entry;
	__u64 start, end;
	sector_t blocknr;
	void *kaddr;

	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
	req->pr_entry_bh, kaddr);
	end = start = le64_to_cpu(entry->de_start);
	if (!dead) {
	end = nilfs_mdt_cno(dat);
	WARN_ON(start > end);
	}
	entry->de_end = cpu_to_le64(end);
	blocknr = le64_to_cpu(entry->de_blocknr);
	kunmap_atomic(kaddr);

	if (blocknr == 0)
	nilfs_dat_commit_free(dat, req);
	else
	nilfs_dat_commit_entry(dat, req);
	}

	void nilfs_dat_abort_end(struct inode dat, struct nilfs_palloc_req req)
	{
	struct nilfs_dat_entry *entry;
	__u64 start;
	sector_t blocknr;
	void *kaddr;

	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
	req->pr_entry_bh, kaddr);
	start = le64_to_cpu(entry->de_start);
	blocknr = le64_to_cpu(entry->de_blocknr);
	kunmap_atomic(kaddr);

	if (start == nilfs_mdt_cno(dat) && blocknr == 0)
	nilfs_palloc_abort_free_entry(dat, req);
	nilfs_dat_abort_entry(dat, req);
	}

	int nilfs_dat_prepare_update(struct inode *dat,
	struct nilfs_palloc_req *oldreq,
	struct nilfs_palloc_req *newreq)
	{
	int ret;

	ret = nilfs_dat_prepare_end(dat, oldreq);
	if (!ret) {
	ret = nilfs_dat_prepare_alloc(dat, newreq);
	if (ret < 0)
	nilfs_dat_abort_end(dat, oldreq);
	}
	return ret;
	}

	void nilfs_dat_commit_update(struct inode *dat,
	struct nilfs_palloc_req *oldreq,
	struct nilfs_palloc_req *newreq, int dead)
	{
	nilfs_dat_commit_end(dat, oldreq, dead);
	nilfs_dat_commit_alloc(dat, newreq);
	}

	void nilfs_dat_abort_update(struct inode *dat,
	struct nilfs_palloc_req *oldreq,
	struct nilfs_palloc_req *newreq)
	{
	nilfs_dat_abort_end(dat, oldreq);
	nilfs_dat_abort_alloc(dat, newreq);
	}

	/**
	* nilfs_dat_mark_dirty -
	* @dat: DAT file inode
	* @vblocknr: virtual block 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_dat_mark_dirty(struct inode *dat, __u64 vblocknr)
	{
	struct nilfs_palloc_req req;
	int ret;

	req.pr_entry_nr = vblocknr;
	ret = nilfs_dat_prepare_entry(dat, &req, 0);
	if (ret == 0)
	nilfs_dat_commit_entry(dat, &req);
	return ret;
	}

	/**
	* nilfs_dat_freev - free virtual block numbers
	* @dat: DAT file inode
	* @vblocknrs: array of virtual block numbers
	* @nitems: number of virtual block numbers
	*
	* Description: nilfs_dat_freev() frees the virtual block numbers specified by
	* @vblocknrs and @nitems.
	*
	* 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.
	*
	* %-ENOENT - The virtual block number have not been allocated.
	*/
	int nilfs_dat_freev(struct inode dat, __u64 vblocknrs, size_t nitems)
	{
	return nilfs_palloc_freev(dat, vblocknrs, nitems);
	}

	/**
	* nilfs_dat_move - change a block number
	* @dat: DAT file inode
	* @vblocknr: virtual block number
	* @blocknr: block number
	*
	* Description: nilfs_dat_move() changes the block number associated with
	* @vblocknr to @blocknr.
	*
	* 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_dat_move(struct inode *dat, __u64 vblocknr, sector_t blocknr)
	{
	struct buffer_head *entry_bh;
	struct nilfs_dat_entry *entry;
	void *kaddr;
	int ret;

	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
	if (ret < 0)
	return ret;

	/*
	* The given disk block number (blocknr) is not yet written to
	* the device at this point.
	*
	* To prevent nilfs_dat_translate() from returning the
	* uncommitted block number, this makes a copy of the entry
	* buffer and redirects nilfs_dat_translate() to the copy.
	*/
	if (!buffer_nilfs_redirected(entry_bh)) {
	ret = nilfs_mdt_freeze_buffer(dat, entry_bh);
	if (ret) {
	brelse(entry_bh);
	return ret;
	}
	}

	kaddr = kmap_atomic(entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
	if (unlikely(entry->de_blocknr == cpu_to_le64(0))) {
	printk(KERN_CRIT "%s: vbn = %llu, [%llu, %llu)\n", __func__,
	(unsigned long long)vblocknr,
	(unsigned long long)le64_to_cpu(entry->de_start),
	(unsigned long long)le64_to_cpu(entry->de_end));
	kunmap_atomic(kaddr);
	brelse(entry_bh);
	return -EINVAL;
	}
	WARN_ON(blocknr == 0);
	entry->de_blocknr = cpu_to_le64(blocknr);
	kunmap_atomic(kaddr);

	mark_buffer_dirty(entry_bh);
	nilfs_mdt_mark_dirty(dat);

	brelse(entry_bh);

	return 0;
	}

	/**
	* nilfs_dat_translate - translate a virtual block number to a block number
	* @dat: DAT file inode
	* @vblocknr: virtual block number
	* @blocknrp: pointer to a block number
	*
	* Description: nilfs_dat_translate() maps the virtual block number @vblocknr
	* to the corresponding block number.
	*
	* Return Value: On success, 0 is returned and the block number associated
	* with @vblocknr is stored in the place pointed by @blocknrp. On error, one
	* of the following negative error codes is returned.
	*
	* %-EIO - I/O error.
	*
	* %-ENOMEM - Insufficient amount of memory available.
	*
	* %-ENOENT - A block number associated with @vblocknr does not exist.
	*/
	int nilfs_dat_translate(struct inode dat, __u64 vblocknr, sector_t blocknrp)
	{
	struct buffer_head entry_bh, bh;
	struct nilfs_dat_entry *entry;
	sector_t blocknr;
	void *kaddr;
	int ret;

	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
	if (ret < 0)
	return ret;

	if (!nilfs_doing_gc() && buffer_nilfs_redirected(entry_bh)) {
	bh = nilfs_mdt_get_frozen_buffer(dat, entry_bh);
	if (bh) {
	WARN_ON(!buffer_uptodate(bh));
	brelse(entry_bh);
	entry_bh = bh;
	}
	}

	kaddr = kmap_atomic(entry_bh->b_page);
	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
	blocknr = le64_to_cpu(entry->de_blocknr);
	if (blocknr == 0) {
	ret = -ENOENT;
	goto out;
	}
	*blocknrp = blocknr;

	out:
	kunmap_atomic(kaddr);
	brelse(entry_bh);
	return ret;
	}

	ssize_t nilfs_dat_get_vinfo(struct inode dat, void buf, unsigned int visz,
	size_t nvi)
	{
	struct buffer_head *entry_bh;
	struct nilfs_dat_entry *entry;
	struct nilfs_vinfo *vinfo = buf;
	__u64 first, last;
	void *kaddr;
	unsigned long entries_per_block = NILFS_MDT(dat)->mi_entries_per_block;
	int i, j, n, ret;

	for (i = 0; i < nvi; i += n) {
	ret = nilfs_palloc_get_entry_block(dat, vinfo->vi_vblocknr,
	0, &entry_bh);
	if (ret < 0)
	return ret;
	kaddr = kmap_atomic(entry_bh->b_page);
	/* last virtual block number in this block */
	first = vinfo->vi_vblocknr;
	do_div(first, entries_per_block);
	first *= entries_per_block;
	last = first + entries_per_block - 1;
	for (j = i, n = 0;
	j < nvi && vinfo->vi_vblocknr >= first &&
	vinfo->vi_vblocknr <= last;
	j++, n++, vinfo = (void *)vinfo + visz) {
	entry = nilfs_palloc_block_get_entry(
	dat, vinfo->vi_vblocknr, entry_bh, kaddr);
	vinfo->vi_start = le64_to_cpu(entry->de_start);
	vinfo->vi_end = le64_to_cpu(entry->de_end);
	vinfo->vi_blocknr = le64_to_cpu(entry->de_blocknr);
	}
	kunmap_atomic(kaddr);
	brelse(entry_bh);
	}

	return nvi;
	}

	/**
	* nilfs_dat_read - read or get dat inode
	* @sb: super block instance
	* @entry_size: size of a dat entry
	* @raw_inode: on-disk dat inode
	* @inodep: buffer to store the inode
	*/
	int nilfs_dat_read(struct super_block *sb, size_t entry_size,
	struct nilfs_inode raw_inode, struct inode *inodep)
	{
	static struct lock_class_key dat_lock_key;
	struct inode *dat;
	struct nilfs_dat_info *di;
	int err;

	if (entry_size > sb->s_blocksize) {
	printk(KERN_ERR
	"NILFS: too large DAT entry size: %zu bytes.\n",
	entry_size);
	return -EINVAL;
	} else if (entry_size < NILFS_MIN_DAT_ENTRY_SIZE) {
	printk(KERN_ERR
	"NILFS: too small DAT entry size: %zu bytes.\n",
	entry_size);
	return -EINVAL;
	}

	dat = nilfs_iget_locked(sb, NULL, NILFS_DAT_INO);
	if (unlikely(!dat))
	return -ENOMEM;
	if (!(dat->i_state & I_NEW))
	goto out;

	err = nilfs_mdt_init(dat, NILFS_MDT_GFP, sizeof(*di));
	if (err)
	goto failed;

	err = nilfs_palloc_init_blockgroup(dat, entry_size);
	if (err)
	goto failed;

	di = NILFS_DAT_I(dat);
	lockdep_set_class(&di->mi.mi_sem, &dat_lock_key);
	nilfs_palloc_setup_cache(dat, &di->palloc_cache);
	nilfs_mdt_setup_shadow_map(dat, &di->shadow);

	err = nilfs_read_inode_common(dat, raw_inode);
	if (err)
	goto failed;

	unlock_new_inode(dat);
	out:
	*inodep = dat;
	return 0;
	failed:
	iget_failed(dat);
	return err;
	}