fs/ocfs2/suballoc.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * suballoc.c
 *
 * metadata alloc and free
 * Inspired by ext3 block groups.
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 *
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>

#define MLOG_MASK_PREFIX ML_DISK_ALLOC
#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "blockcheck.h"
#include "dlmglue.h"
#include "inode.h"
#include "journal.h"
#include "localalloc.h"
#include "suballoc.h"
#include "super.h"
#include "sysfile.h"
#include "uptodate.h"

#include "buffer_head_io.h"

#define NOT_ALLOC_NEW_GROUP		0
#define ALLOC_NEW_GROUP			0x1
#define ALLOC_GROUPS_FROM_GLOBAL	0x2

#define OCFS2_MAX_TO_STEAL		1024

struct ocfs2_suballoc_result {
	u64		sr_bg_blkno;	/* The bg we allocated from.  Set
					   to 0 when a block group is
					   contiguous. */
	u64		sr_blkno;	/* The first allocated block */
	unsigned int	sr_bit_offset;	/* The bit in the bg */
	unsigned int	sr_bits;	/* How many bits we claimed */
};

static u64 ocfs2_group_from_res(struct ocfs2_suballoc_result *res)
{
	if (res->sr_blkno == 0)
		return 0;

	if (res->sr_bg_blkno)
		return res->sr_bg_blkno;

	return ocfs2_which_suballoc_group(res->sr_blkno, res->sr_bit_offset);
}

static inline void ocfs2_debug_bg(struct ocfs2_group_desc *bg);
static inline void ocfs2_debug_suballoc_inode(struct ocfs2_dinode *fe);
static inline u16 ocfs2_find_victim_chain(struct ocfs2_chain_list *cl);
static int ocfs2_block_group_fill(handle_t *handle,
				  struct inode *alloc_inode,
				  struct buffer_head *bg_bh,
				  u64 group_blkno,
				  unsigned int group_clusters,
				  u16 my_chain,
				  struct ocfs2_chain_list *cl);
static int ocfs2_block_group_alloc(struct ocfs2_super *osb,
				   struct inode *alloc_inode,
				   struct buffer_head *bh,
				   u64 max_block,
				   u64 *last_alloc_group,
				   int flags);

static int ocfs2_cluster_group_search(struct inode *inode,
				      struct buffer_head *group_bh,
				      u32 bits_wanted, u32 min_bits,
				      u64 max_block,
				      struct ocfs2_suballoc_result *res);
static int ocfs2_block_group_search(struct inode *inode,
				    struct buffer_head *group_bh,
				    u32 bits_wanted, u32 min_bits,
				    u64 max_block,
				    struct ocfs2_suballoc_result *res);
static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
				     handle_t *handle,
				     u32 bits_wanted,
				     u32 min_bits,
				     struct ocfs2_suballoc_result *res);
static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,
					 int nr);
static inline int ocfs2_block_group_set_bits(handle_t *handle,
					     struct inode *alloc_inode,
					     struct ocfs2_group_desc *bg,
					     struct buffer_head *group_bh,
					     unsigned int bit_off,
					     unsigned int num_bits);
static int ocfs2_relink_block_group(handle_t *handle,
				    struct inode *alloc_inode,
				    struct buffer_head *fe_bh,
				    struct buffer_head *bg_bh,
				    struct buffer_head *prev_bg_bh,
				    u16 chain);
static inline int ocfs2_block_group_reasonably_empty(struct ocfs2_group_desc *bg,
						     u32 wanted);
static inline u32 ocfs2_desc_bitmap_to_cluster_off(struct inode *inode,
						   u64 bg_blkno,
						   u16 bg_bit_off);
static inline void ocfs2_block_to_cluster_group(struct inode *inode,
						u64 data_blkno,
						u64 *bg_blkno,
						u16 *bg_bit_off);
static int ocfs2_reserve_clusters_with_limit(struct ocfs2_super *osb,
					     u32 bits_wanted, u64 max_block,
					     int flags,
					     struct ocfs2_alloc_context **ac);

void ocfs2_free_ac_resource(struct ocfs2_alloc_context *ac)
{
	struct inode *inode = ac->ac_inode;

	if (inode) {
		if (ac->ac_which != OCFS2_AC_USE_LOCAL)
			ocfs2_inode_unlock(inode, 1);

		mutex_unlock(&inode->i_mutex);

		iput(inode);
		ac->ac_inode = NULL;
	}
	brelse(ac->ac_bh);
	ac->ac_bh = NULL;
	ac->ac_resv = NULL;
}

void ocfs2_free_alloc_context(struct ocfs2_alloc_context *ac)
{
	ocfs2_free_ac_resource(ac);
	kfree(ac);
}

static u32 ocfs2_bits_per_group(struct ocfs2_chain_list *cl)
{
	return (u32)le16_to_cpu(cl->cl_cpg) * (u32)le16_to_cpu(cl->cl_bpc);
}

#define do_error(fmt, ...)						\
	do{								\
		if (resize)					\
			mlog(ML_ERROR, fmt "\n", ##__VA_ARGS__);	\
		else							\
			ocfs2_error(sb, fmt, ##__VA_ARGS__);		\
	} while (0)

static int ocfs2_validate_gd_self(struct super_block *sb,
				  struct buffer_head *bh,
				  int resize)
{
	struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data;

	if (!OCFS2_IS_VALID_GROUP_DESC(gd)) {
		do_error("Group descriptor #%llu has bad signature %.*s",
			 (unsigned long long)bh->b_blocknr, 7,
			 gd->bg_signature);
		return -EINVAL;
	}

	if (le64_to_cpu(gd->bg_blkno) != bh->b_blocknr) {
		do_error("Group descriptor #%llu has an invalid bg_blkno "
			 "of %llu",
			 (unsigned long long)bh->b_blocknr,
			 (unsigned long long)le64_to_cpu(gd->bg_blkno));
		return -EINVAL;
	}

	if (le32_to_cpu(gd->bg_generation) != OCFS2_SB(sb)->fs_generation) {
		do_error("Group descriptor #%llu has an invalid "
			 "fs_generation of #%u",
			 (unsigned long long)bh->b_blocknr,
			 le32_to_cpu(gd->bg_generation));
		return -EINVAL;
	}

	if (le16_to_cpu(gd->bg_free_bits_count) > le16_to_cpu(gd->bg_bits)) {
		do_error("Group descriptor #%llu has bit count %u but "
			 "claims that %u are free",
			 (unsigned long long)bh->b_blocknr,
			 le16_to_cpu(gd->bg_bits),
			 le16_to_cpu(gd->bg_free_bits_count));
		return -EINVAL;
	}

	if (le16_to_cpu(gd->bg_bits) > (8 * le16_to_cpu(gd->bg_size))) {
		do_error("Group descriptor #%llu has bit count %u but "
			 "max bitmap bits of %u",
			 (unsigned long long)bh->b_blocknr,
			 le16_to_cpu(gd->bg_bits),
			 8 * le16_to_cpu(gd->bg_size));
		return -EINVAL;
	}

	return 0;
}

static int ocfs2_validate_gd_parent(struct super_block *sb,
				    struct ocfs2_dinode *di,
				    struct buffer_head *bh,
				    int resize)
{
	unsigned int max_bits;
	struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data;

	if (di->i_blkno != gd->bg_parent_dinode) {
		do_error("Group descriptor #%llu has bad parent "
			 "pointer (%llu, expected %llu)",
			 (unsigned long long)bh->b_blocknr,
			 (unsigned long long)le64_to_cpu(gd->bg_parent_dinode),
			 (unsigned long long)le64_to_cpu(di->i_blkno));
		return -EINVAL;
	}

	max_bits = le16_to_cpu(di->id2.i_chain.cl_cpg) * le16_to_cpu(di->id2.i_chain.cl_bpc);
	if (le16_to_cpu(gd->bg_bits) > max_bits) {
		do_error("Group descriptor #%llu has bit count of %u",
			 (unsigned long long)bh->b_blocknr,
			 le16_to_cpu(gd->bg_bits));
		return -EINVAL;
	}

	/* In resize, we may meet the case bg_chain == cl_next_free_rec. */
	if ((le16_to_cpu(gd->bg_chain) >
	     le16_to_cpu(di->id2.i_chain.cl_next_free_rec)) ||
	    ((le16_to_cpu(gd->bg_chain) ==
	     le16_to_cpu(di->id2.i_chain.cl_next_free_rec)) && !resize)) {
		do_error("Group descriptor #%llu has bad chain %u",
			 (unsigned long long)bh->b_blocknr,
			 le16_to_cpu(gd->bg_chain));
		return -EINVAL;
	}

	return 0;
}

#undef do_error

/*
 * This version only prints errors.  It does not fail the filesystem, and
 * exists only for resize.
 */
int ocfs2_check_group_descriptor(struct super_block *sb,
				 struct ocfs2_dinode *di,
				 struct buffer_head *bh)
{
	int rc;
	struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data;

	BUG_ON(!buffer_uptodate(bh));

	/*
	 * If the ecc fails, we return the error but otherwise
	 * leave the filesystem running.  We know any error is
	 * local to this block.
	 */
	rc = ocfs2_validate_meta_ecc(sb, bh->b_data, &gd->bg_check);
	if (rc) {
		mlog(ML_ERROR,
		     "Checksum failed for group descriptor %llu\n",
		     (unsigned long long)bh->b_blocknr);
	} else
		rc = ocfs2_validate_gd_self(sb, bh, 1);
	if (!rc)
		rc = ocfs2_validate_gd_parent(sb, di, bh, 1);

	return rc;
}

static int ocfs2_validate_group_descriptor(struct super_block *sb,
					   struct buffer_head *bh)
{
	int rc;
	struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data;

	mlog(0, "Validating group descriptor %llu\n",
	     (unsigned long long)bh->b_blocknr);

	BUG_ON(!buffer_uptodate(bh));

	/*
	 * If the ecc fails, we return the error but otherwise
	 * leave the filesystem running.  We know any error is
	 * local to this block.
	 */
	rc = ocfs2_validate_meta_ecc(sb, bh->b_data, &gd->bg_check);
	if (rc)
		return rc;

	/*
	 * Errors after here are fatal.
	 */

	return ocfs2_validate_gd_self(sb, bh, 0);
}

int ocfs2_read_group_descriptor(struct inode *inode, struct ocfs2_dinode *di,
				u64 gd_blkno, struct buffer_head **bh)
{
	int rc;
	struct buffer_head *tmp = *bh;

	rc = ocfs2_read_block(INODE_CACHE(inode), gd_blkno, &tmp,
			      ocfs2_validate_group_descriptor);
	if (rc)
		goto out;

	rc = ocfs2_validate_gd_parent(inode->i_sb, di, tmp, 0);
	if (rc) {
		brelse(tmp);
		goto out;
	}

	/* If ocfs2_read_block() got us a new bh, pass it up. */
	if (!*bh)
		*bh = tmp;

out:
	return rc;
}

static void ocfs2_bg_discontig_add_extent(struct ocfs2_super *osb,
					  struct ocfs2_group_desc *bg,
					  struct ocfs2_chain_list *cl,
					  u64 p_blkno, u32 clusters)
{
	struct ocfs2_extent_list *el = &bg->bg_list;
	struct ocfs2_extent_rec *rec;

	BUG_ON(!ocfs2_supports_discontig_bg(osb));
	if (!el->l_next_free_rec)
		el->l_count = cpu_to_le16(ocfs2_extent_recs_per_gd(osb->sb));
	rec = &el->l_recs[le16_to_cpu(el->l_next_free_rec)];
	rec->e_blkno = cpu_to_le64(p_blkno);
	rec->e_cpos = cpu_to_le32(le16_to_cpu(bg->bg_bits) /
				  le16_to_cpu(cl->cl_bpc));
	rec->e_leaf_clusters = cpu_to_le32(clusters);
	le16_add_cpu(&bg->bg_bits, clusters * le16_to_cpu(cl->cl_bpc));
	le16_add_cpu(&bg->bg_free_bits_count,
		     clusters * le16_to_cpu(cl->cl_bpc));
	le16_add_cpu(&el->l_next_free_rec, 1);
}

static int ocfs2_block_group_fill(handle_t *handle,
				  struct inode *alloc_inode,
				  struct buffer_head *bg_bh,
				  u64 group_blkno,
				  unsigned int group_clusters,
				  u16 my_chain,
				  struct ocfs2_chain_list *cl)
{
	int status = 0;
	struct ocfs2_super *osb = OCFS2_SB(alloc_inode->i_sb);
	struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) bg_bh->b_data;
	struct super_block * sb = alloc_inode->i_sb;

	mlog_entry_void();

	if (((unsigned long long) bg_bh->b_blocknr) != group_blkno) {
		ocfs2_error(alloc_inode->i_sb, "group block (%llu) != "
			    "b_blocknr (%llu)",
			    (unsigned long long)group_blkno,
			    (unsigned long long) bg_bh->b_blocknr);
		status = -EIO;
		goto bail;
	}

	status = ocfs2_journal_access_gd(handle,
					 INODE_CACHE(alloc_inode),
					 bg_bh,
					 OCFS2_JOURNAL_ACCESS_CREATE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	memset(bg, 0, sb->s_blocksize);
	strcpy(bg->bg_signature, OCFS2_GROUP_DESC_SIGNATURE);
	bg->bg_generation = cpu_to_le32(OCFS2_SB(sb)->fs_generation);
	bg->bg_size = cpu_to_le16(ocfs2_group_bitmap_size(sb, 1,
						osb->s_feature_incompat));
	bg->bg_chain = cpu_to_le16(my_chain);
	bg->bg_next_group = cl->cl_recs[my_chain].c_blkno;
	bg->bg_parent_dinode = cpu_to_le64(OCFS2_I(alloc_inode)->ip_blkno);
	bg->bg_blkno = cpu_to_le64(group_blkno);
	if (group_clusters == le16_to_cpu(cl->cl_cpg))
		bg->bg_bits = cpu_to_le16(ocfs2_bits_per_group(cl));
	else
		ocfs2_bg_discontig_add_extent(osb, bg, cl, group_blkno,
					      group_clusters);

	/* set the 1st bit in the bitmap to account for the descriptor block */
	ocfs2_set_bit(0, (unsigned long *)bg->bg_bitmap);
	bg->bg_free_bits_count = cpu_to_le16(le16_to_cpu(bg->bg_bits) - 1);

	ocfs2_journal_dirty(handle, bg_bh);

	/* There is no need to zero out or otherwise initialize the
	 * other blocks in a group - All valid FS metadata in a block
	 * group stores the superblock fs_generation value at
	 * allocation time. */

bail:
	mlog_exit(status);
	return status;
}

static inline u16 ocfs2_find_smallest_chain(struct ocfs2_chain_list *cl)
{
	u16 curr, best;

	best = curr = 0;
	while (curr < le16_to_cpu(cl->cl_count)) {
		if (le32_to_cpu(cl->cl_recs[best].c_total) >
		    le32_to_cpu(cl->cl_recs[curr].c_total))
			best = curr;
		curr++;
	}
	return best;
}

static struct buffer_head *
ocfs2_block_group_alloc_contig(struct ocfs2_super *osb, handle_t *handle,
			       struct inode *alloc_inode,
			       struct ocfs2_alloc_context *ac,
			       struct ocfs2_chain_list *cl)
{
	int status;
	u32 bit_off, num_bits;
	u64 bg_blkno;
	struct buffer_head *bg_bh;
	unsigned int alloc_rec = ocfs2_find_smallest_chain(cl);

	status = ocfs2_claim_clusters(handle, ac,
				      le16_to_cpu(cl->cl_cpg), &bit_off,
				      &num_bits);
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}

	/* setup the group */
	bg_blkno = ocfs2_clusters_to_blocks(osb->sb, bit_off);
	mlog(0, "new descriptor, record %u, at block %llu\n",
	     alloc_rec, (unsigned long long)bg_blkno);

	bg_bh = sb_getblk(osb->sb, bg_blkno);
	if (!bg_bh) {
		status = -EIO;
		mlog_errno(status);
		goto bail;
	}
	ocfs2_set_new_buffer_uptodate(INODE_CACHE(alloc_inode), bg_bh);

	status = ocfs2_block_group_fill(handle, alloc_inode, bg_bh,
					bg_blkno, num_bits, alloc_rec, cl);
	if (status < 0) {
		brelse(bg_bh);
		mlog_errno(status);
	}

bail:
	return status ? ERR_PTR(status) : bg_bh;
}

static int ocfs2_block_group_claim_bits(struct ocfs2_super *osb,
					handle_t *handle,
					struct ocfs2_alloc_context *ac,
					unsigned int min_bits,
					u32 *bit_off, u32 *num_bits)
{
	int status = 0;

	while (min_bits) {
		status = ocfs2_claim_clusters(handle, ac, min_bits,
					      bit_off, num_bits);
		if (status != -ENOSPC)
			break;

		min_bits >>= 1;
	}

	return status;
}

static int ocfs2_block_group_grow_discontig(handle_t *handle,
					    struct inode *alloc_inode,
					    struct buffer_head *bg_bh,
					    struct ocfs2_alloc_context *ac,
					    struct ocfs2_chain_list *cl,
					    unsigned int min_bits)
{
	int status;
	struct ocfs2_super *osb = OCFS2_SB(alloc_inode->i_sb);
	struct ocfs2_group_desc *bg =
		(struct ocfs2_group_desc *)bg_bh->b_data;
	unsigned int needed = le16_to_cpu(cl->cl_cpg) -
			 le16_to_cpu(bg->bg_bits) / le16_to_cpu(cl->cl_bpc);
	u32 p_cpos, clusters;
	u64 p_blkno;
	struct ocfs2_extent_list *el = &bg->bg_list;

	status = ocfs2_journal_access_gd(handle,
					 INODE_CACHE(alloc_inode),
					 bg_bh,
					 OCFS2_JOURNAL_ACCESS_CREATE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	while ((needed > 0) && (le16_to_cpu(el->l_next_free_rec) <
				le16_to_cpu(el->l_count))) {
		if (min_bits > needed)
			min_bits = needed;
		status = ocfs2_block_group_claim_bits(osb, handle, ac,
						      min_bits, &p_cpos,
						      &clusters);
		if (status < 0) {
			if (status != -ENOSPC)
				mlog_errno(status);
			goto bail;
		}
		p_blkno = ocfs2_clusters_to_blocks(osb->sb, p_cpos);
		ocfs2_bg_discontig_add_extent(osb, bg, cl, p_blkno,
					      clusters);

		min_bits = clusters;
		needed = le16_to_cpu(cl->cl_cpg) -
			 le16_to_cpu(bg->bg_bits) / le16_to_cpu(cl->cl_bpc);
	}

	if (needed > 0) {
		/*
		 * We have used up all the extent rec but can't fill up
		 * the cpg. So bail out.
		 */
		status = -ENOSPC;
		goto bail;
	}

	ocfs2_journal_dirty(handle, bg_bh);

bail:
	return status;
}

static void ocfs2_bg_alloc_cleanup(handle_t *handle,
				   struct ocfs2_alloc_context *cluster_ac,
				   struct inode *alloc_inode,
				   struct buffer_head *bg_bh)
{
	int i, ret;
	struct ocfs2_group_desc *bg;
	struct ocfs2_extent_list *el;
	struct ocfs2_extent_rec *rec;

	if (!bg_bh)
		return;

	bg = (struct ocfs2_group_desc *)bg_bh->b_data;
	el = &bg->bg_list;
	for (i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
		rec = &el->l_recs[i];
		ret = ocfs2_free_clusters(handle, cluster_ac->ac_inode,
					  cluster_ac->ac_bh,
					  le64_to_cpu(rec->e_blkno),
					  le32_to_cpu(rec->e_leaf_clusters));
		if (ret)
			mlog_errno(ret);
		/* Try all the clusters to free */
	}

	ocfs2_remove_from_cache(INODE_CACHE(alloc_inode), bg_bh);
	brelse(bg_bh);
}

static struct buffer_head *
ocfs2_block_group_alloc_discontig(handle_t *handle,
				  struct inode *alloc_inode,
				  struct ocfs2_alloc_context *ac,
				  struct ocfs2_chain_list *cl)
{
	int status;
	u32 bit_off, num_bits;
	u64 bg_blkno;
	unsigned int min_bits = le16_to_cpu(cl->cl_cpg) >> 1;
	struct buffer_head *bg_bh = NULL;
	unsigned int alloc_rec = ocfs2_find_smallest_chain(cl);
	struct ocfs2_super *osb = OCFS2_SB(alloc_inode->i_sb);

	if (!ocfs2_supports_discontig_bg(osb)) {
		status = -ENOSPC;
		goto bail;
	}

	status = ocfs2_extend_trans(handle,
				    ocfs2_calc_bg_discontig_credits(osb->sb));
	if (status) {
		mlog_errno(status);
		goto bail;
	}

	/*
	 * We're going to be grabbing from multiple cluster groups.
	 * We don't have enough credits to relink them all, and the
	 * cluster groups will be staying in cache for the duration of
	 * this operation.
	 */
	ac->ac_allow_chain_relink = 0;

	/* Claim the first region */
	status = ocfs2_block_group_claim_bits(osb, handle, ac, min_bits,
					      &bit_off, &num_bits);
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}
	min_bits = num_bits;

	/* setup the group */
	bg_blkno = ocfs2_clusters_to_blocks(osb->sb, bit_off);
	mlog(0, "new descriptor, record %u, at block %llu\n",
	     alloc_rec, (unsigned long long)bg_blkno);

	bg_bh = sb_getblk(osb->sb, bg_blkno);
	if (!bg_bh) {
		status = -EIO;
		mlog_errno(status);
		goto bail;
	}
	ocfs2_set_new_buffer_uptodate(INODE_CACHE(alloc_inode), bg_bh);

	status = ocfs2_block_group_fill(handle, alloc_inode, bg_bh,
					bg_blkno, num_bits, alloc_rec, cl);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	status = ocfs2_block_group_grow_discontig(handle, alloc_inode,
						  bg_bh, ac, cl, min_bits);
	if (status)
		mlog_errno(status);

bail:
	if (status)
		ocfs2_bg_alloc_cleanup(handle, ac, alloc_inode, bg_bh);
	return status ? ERR_PTR(status) : bg_bh;
}

/*
 * We expect the block group allocator to already be locked.
 */
static int ocfs2_block_group_alloc(struct ocfs2_super *osb,
				   struct inode *alloc_inode,
				   struct buffer_head *bh,
				   u64 max_block,
				   u64 *last_alloc_group,
				   int flags)
{
	int status, credits;
	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) bh->b_data;
	struct ocfs2_chain_list *cl;
	struct ocfs2_alloc_context *ac = NULL;
	handle_t *handle = NULL;
	u16 alloc_rec;
	struct buffer_head *bg_bh = NULL;
	struct ocfs2_group_desc *bg;

	BUG_ON(ocfs2_is_cluster_bitmap(alloc_inode));

	mlog_entry_void();

	cl = &fe->id2.i_chain;
	status = ocfs2_reserve_clusters_with_limit(osb,
						   le16_to_cpu(cl->cl_cpg),
						   max_block, flags, &ac);
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}

	credits = ocfs2_calc_group_alloc_credits(osb->sb,
						 le16_to_cpu(cl->cl_cpg));
	handle = ocfs2_start_trans(osb, credits);
	if (IS_ERR(handle)) {
		status = PTR_ERR(handle);
		handle = NULL;
		mlog_errno(status);
		goto bail;
	}

	if (last_alloc_group && *last_alloc_group != 0) {
		mlog(0, "use old allocation group %llu for block group alloc\n",
		     (unsigned long long)*last_alloc_group);
		ac->ac_last_group = *last_alloc_group;
	}

	bg_bh = ocfs2_block_group_alloc_contig(osb, handle, alloc_inode,
					       ac, cl);
	if (IS_ERR(bg_bh) && (PTR_ERR(bg_bh) == -ENOSPC))
		bg_bh = ocfs2_block_group_alloc_discontig(handle,
							  alloc_inode,
							  ac, cl);
	if (IS_ERR(bg_bh)) {
		status = PTR_ERR(bg_bh);
		bg_bh = NULL;
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}
	bg = (struct ocfs2_group_desc *) bg_bh->b_data;

	status = ocfs2_journal_access_di(handle, INODE_CACHE(alloc_inode),
					 bh, OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	alloc_rec = le16_to_cpu(bg->bg_chain);
	le32_add_cpu(&cl->cl_recs[alloc_rec].c_free,
		     le16_to_cpu(bg->bg_free_bits_count));
	le32_add_cpu(&cl->cl_recs[alloc_rec].c_total,
		     le16_to_cpu(bg->bg_bits));
	cl->cl_recs[alloc_rec].c_blkno = bg->bg_blkno;
	if (le16_to_cpu(cl->cl_next_free_rec) < le16_to_cpu(cl->cl_count))
		le16_add_cpu(&cl->cl_next_free_rec, 1);

	le32_add_cpu(&fe->id1.bitmap1.i_used, le16_to_cpu(bg->bg_bits) -
					le16_to_cpu(bg->bg_free_bits_count));
	le32_add_cpu(&fe->id1.bitmap1.i_total, le16_to_cpu(bg->bg_bits));
	le32_add_cpu(&fe->i_clusters, le16_to_cpu(cl->cl_cpg));

	ocfs2_journal_dirty(handle, bh);

	spin_lock(&OCFS2_I(alloc_inode)->ip_lock);
	OCFS2_I(alloc_inode)->ip_clusters = le32_to_cpu(fe->i_clusters);
	fe->i_size = cpu_to_le64(ocfs2_clusters_to_bytes(alloc_inode->i_sb,
					     le32_to_cpu(fe->i_clusters)));
	spin_unlock(&OCFS2_I(alloc_inode)->ip_lock);
	i_size_write(alloc_inode, le64_to_cpu(fe->i_size));
	alloc_inode->i_blocks = ocfs2_inode_sector_count(alloc_inode);

	status = 0;

	/* save the new last alloc group so that the caller can cache it. */
	if (last_alloc_group)
		*last_alloc_group = ac->ac_last_group;

bail:
	if (handle)
		ocfs2_commit_trans(osb, handle);

	if (ac)
		ocfs2_free_alloc_context(ac);

	brelse(bg_bh);

	mlog_exit(status);
	return status;
}

static int ocfs2_reserve_suballoc_bits(struct ocfs2_super *osb,
				       struct ocfs2_alloc_context *ac,
				       int type,
				       u32 slot,
				       u64 *last_alloc_group,
				       int flags)
{
	int status;
	u32 bits_wanted = ac->ac_bits_wanted;
	struct inode *alloc_inode;
	struct buffer_head *bh = NULL;
	struct ocfs2_dinode *fe;
	u32 free_bits;

	mlog_entry_void();

	alloc_inode = ocfs2_get_system_file_inode(osb, type, slot);
	if (!alloc_inode) {
		mlog_errno(-EINVAL);
		return -EINVAL;
	}

	mutex_lock(&alloc_inode->i_mutex);

	status = ocfs2_inode_lock(alloc_inode, &bh, 1);
	if (status < 0) {
		mutex_unlock(&alloc_inode->i_mutex);
		iput(alloc_inode);

		mlog_errno(status);
		return status;
	}

	ac->ac_inode = alloc_inode;
	ac->ac_alloc_slot = slot;

	fe = (struct ocfs2_dinode *) bh->b_data;

	/* The bh was validated by the inode read inside
	 * ocfs2_inode_lock().  Any corruption is a code bug. */
	BUG_ON(!OCFS2_IS_VALID_DINODE(fe));

	if (!(fe->i_flags & cpu_to_le32(OCFS2_CHAIN_FL))) {
		ocfs2_error(alloc_inode->i_sb, "Invalid chain allocator %llu",
			    (unsigned long long)le64_to_cpu(fe->i_blkno));
		status = -EIO;
		goto bail;
	}

	free_bits = le32_to_cpu(fe->id1.bitmap1.i_total) -
		le32_to_cpu(fe->id1.bitmap1.i_used);

	if (bits_wanted > free_bits) {
		/* cluster bitmap never grows */
		if (ocfs2_is_cluster_bitmap(alloc_inode)) {
			mlog(0, "Disk Full: wanted=%u, free_bits=%u\n",
			     bits_wanted, free_bits);
			status = -ENOSPC;
			goto bail;
		}

		if (!(flags & ALLOC_NEW_GROUP)) {
			mlog(0, "Alloc File %u Full: wanted=%u, free_bits=%u, "
			     "and we don't alloc a new group for it.\n",
			     slot, bits_wanted, free_bits);
			status = -ENOSPC;
			goto bail;
		}

		status = ocfs2_block_group_alloc(osb, alloc_inode, bh,
						 ac->ac_max_block,
						 last_alloc_group, flags);
		if (status < 0) {
			if (status != -ENOSPC)
				mlog_errno(status);
			goto bail;
		}
		atomic_inc(&osb->alloc_stats.bg_extends);

		/* You should never ask for this much metadata */
		BUG_ON(bits_wanted >
		       (le32_to_cpu(fe->id1.bitmap1.i_total)
			- le32_to_cpu(fe->id1.bitmap1.i_used)));
	}

	get_bh(bh);
	ac->ac_bh = bh;
bail:
	brelse(bh);

	mlog_exit(status);
	return status;
}

static void ocfs2_init_inode_steal_slot(struct ocfs2_super *osb)
{
	spin_lock(&osb->osb_lock);
	osb->s_inode_steal_slot = OCFS2_INVALID_SLOT;
	spin_unlock(&osb->osb_lock);
	atomic_set(&osb->s_num_inodes_stolen, 0);
}

static void ocfs2_init_meta_steal_slot(struct ocfs2_super *osb)
{
	spin_lock(&osb->osb_lock);
	osb->s_meta_steal_slot = OCFS2_INVALID_SLOT;
	spin_unlock(&osb->osb_lock);
	atomic_set(&osb->s_num_meta_stolen, 0);
}

void ocfs2_init_steal_slots(struct ocfs2_super *osb)
{
	ocfs2_init_inode_steal_slot(osb);
	ocfs2_init_meta_steal_slot(osb);
}

static void __ocfs2_set_steal_slot(struct ocfs2_super *osb, int slot, int type)
{
	spin_lock(&osb->osb_lock);
	if (type == INODE_ALLOC_SYSTEM_INODE)
		osb->s_inode_steal_slot = slot;
	else if (type == EXTENT_ALLOC_SYSTEM_INODE)
		osb->s_meta_steal_slot = slot;
	spin_unlock(&osb->osb_lock);
}

static int __ocfs2_get_steal_slot(struct ocfs2_super *osb, int type)
{
	int slot = OCFS2_INVALID_SLOT;

	spin_lock(&osb->osb_lock);
	if (type == INODE_ALLOC_SYSTEM_INODE)
		slot = osb->s_inode_steal_slot;
	else if (type == EXTENT_ALLOC_SYSTEM_INODE)
		slot = osb->s_meta_steal_slot;
	spin_unlock(&osb->osb_lock);

	return slot;
}

static int ocfs2_get_inode_steal_slot(struct ocfs2_super *osb)
{
	return __ocfs2_get_steal_slot(osb, INODE_ALLOC_SYSTEM_INODE);
}

static int ocfs2_get_meta_steal_slot(struct ocfs2_super *osb)
{
	return __ocfs2_get_steal_slot(osb, EXTENT_ALLOC_SYSTEM_INODE);
}

static int ocfs2_steal_resource(struct ocfs2_super *osb,
				struct ocfs2_alloc_context *ac,
				int type)
{
	int i, status = -ENOSPC;
	int slot = __ocfs2_get_steal_slot(osb, type);

	/* Start to steal resource from the first slot after ours. */
	if (slot == OCFS2_INVALID_SLOT)
		slot = osb->slot_num + 1;

	for (i = 0; i < osb->max_slots; i++, slot++) {
		if (slot == osb->max_slots)
			slot = 0;

		if (slot == osb->slot_num)
			continue;

		status = ocfs2_reserve_suballoc_bits(osb, ac,
						     type,
						     (u32)slot, NULL,
						     NOT_ALLOC_NEW_GROUP);
		if (status >= 0) {
			__ocfs2_set_steal_slot(osb, slot, type);
			break;
		}

		ocfs2_free_ac_resource(ac);
	}

	return status;
}

static int ocfs2_steal_inode(struct ocfs2_super *osb,
			     struct ocfs2_alloc_context *ac)
{
	return ocfs2_steal_resource(osb, ac, INODE_ALLOC_SYSTEM_INODE);
}

static int ocfs2_steal_meta(struct ocfs2_super *osb,
			    struct ocfs2_alloc_context *ac)
{
	return ocfs2_steal_resource(osb, ac, EXTENT_ALLOC_SYSTEM_INODE);
}

int ocfs2_reserve_new_metadata_blocks(struct ocfs2_super *osb,
				      int blocks,
				      struct ocfs2_alloc_context **ac)
{
	int status;
	int slot = ocfs2_get_meta_steal_slot(osb);

	*ac = kzalloc(sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
	if (!(*ac)) {
		status = -ENOMEM;
		mlog_errno(status);
		goto bail;
	}

	(*ac)->ac_bits_wanted = blocks;
	(*ac)->ac_which = OCFS2_AC_USE_META;
	(*ac)->ac_group_search = ocfs2_block_group_search;

	if (slot != OCFS2_INVALID_SLOT &&
		atomic_read(&osb->s_num_meta_stolen) < OCFS2_MAX_TO_STEAL)
		goto extent_steal;

	atomic_set(&osb->s_num_meta_stolen, 0);
	status = ocfs2_reserve_suballoc_bits(osb, (*ac),
					     EXTENT_ALLOC_SYSTEM_INODE,
					     (u32)osb->slot_num, NULL,
					     ALLOC_GROUPS_FROM_GLOBAL|ALLOC_NEW_GROUP);


	if (status >= 0) {
		status = 0;
		if (slot != OCFS2_INVALID_SLOT)
			ocfs2_init_meta_steal_slot(osb);
		goto bail;
	} else if (status < 0 && status != -ENOSPC) {
		mlog_errno(status);
		goto bail;
	}

	ocfs2_free_ac_resource(*ac);

extent_steal:
	status = ocfs2_steal_meta(osb, *ac);
	atomic_inc(&osb->s_num_meta_stolen);
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}

	status = 0;
bail:
	if ((status < 0) && *ac) {
		ocfs2_free_alloc_context(*ac);
		*ac = NULL;
	}

	mlog_exit(status);
	return status;
}

int ocfs2_reserve_new_metadata(struct ocfs2_super *osb,
			       struct ocfs2_extent_list *root_el,
			       struct ocfs2_alloc_context **ac)
{
	return ocfs2_reserve_new_metadata_blocks(osb,
					ocfs2_extend_meta_needed(root_el),
					ac);
}

int ocfs2_reserve_new_inode(struct ocfs2_super *osb,
			    struct ocfs2_alloc_context **ac)
{
	int status;
	int slot = ocfs2_get_inode_steal_slot(osb);
	u64 alloc_group;

	*ac = kzalloc(sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
	if (!(*ac)) {
		status = -ENOMEM;
		mlog_errno(status);
		goto bail;
	}

	(*ac)->ac_bits_wanted = 1;
	(*ac)->ac_which = OCFS2_AC_USE_INODE;

	(*ac)->ac_group_search = ocfs2_block_group_search;

	/*
	 * stat(2) can't handle i_ino > 32bits, so we tell the
	 * lower levels not to allocate us a block group past that
	 * limit.  The 'inode64' mount option avoids this behavior.
	 */
	if (!(osb->s_mount_opt & OCFS2_MOUNT_INODE64))
		(*ac)->ac_max_block = (u32)~0U;

	/*
	 * slot is set when we successfully steal inode from other nodes.
	 * It is reset in 3 places:
	 * 1. when we flush the truncate log
	 * 2. when we complete local alloc recovery.
	 * 3. when we successfully allocate from our own slot.
	 * After it is set, we will go on stealing inodes until we find the
	 * need to check our slots to see whether there is some space for us.
	 */
	if (slot != OCFS2_INVALID_SLOT &&
	    atomic_read(&osb->s_num_inodes_stolen) < OCFS2_MAX_TO_STEAL)
		goto inode_steal;

	atomic_set(&osb->s_num_inodes_stolen, 0);
	alloc_group = osb->osb_inode_alloc_group;
	status = ocfs2_reserve_suballoc_bits(osb, *ac,
					     INODE_ALLOC_SYSTEM_INODE,
					     (u32)osb->slot_num,
					     &alloc_group,
					     ALLOC_NEW_GROUP |
					     ALLOC_GROUPS_FROM_GLOBAL);
	if (status >= 0) {
		status = 0;

		spin_lock(&osb->osb_lock);
		osb->osb_inode_alloc_group = alloc_group;
		spin_unlock(&osb->osb_lock);
		mlog(0, "after reservation, new allocation group is "
		     "%llu\n", (unsigned long long)alloc_group);

		/*
		 * Some inodes must be freed by us, so try to allocate
		 * from our own next time.
		 */
		if (slot != OCFS2_INVALID_SLOT)
			ocfs2_init_inode_steal_slot(osb);
		goto bail;
	} else if (status < 0 && status != -ENOSPC) {
		mlog_errno(status);
		goto bail;
	}

	ocfs2_free_ac_resource(*ac);

inode_steal:
	status = ocfs2_steal_inode(osb, *ac);
	atomic_inc(&osb->s_num_inodes_stolen);
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}

	status = 0;
bail:
	if ((status < 0) && *ac) {
		ocfs2_free_alloc_context(*ac);
		*ac = NULL;
	}

	mlog_exit(status);
	return status;
}

/* local alloc code has to do the same thing, so rather than do this
 * twice.. */
int ocfs2_reserve_cluster_bitmap_bits(struct ocfs2_super *osb,
				      struct ocfs2_alloc_context *ac)
{
	int status;

	ac->ac_which = OCFS2_AC_USE_MAIN;
	ac->ac_group_search = ocfs2_cluster_group_search;

	status = ocfs2_reserve_suballoc_bits(osb, ac,
					     GLOBAL_BITMAP_SYSTEM_INODE,
					     OCFS2_INVALID_SLOT, NULL,
					     ALLOC_NEW_GROUP);
	if (status < 0 && status != -ENOSPC) {
		mlog_errno(status);
		goto bail;
	}

bail:
	return status;
}

/* Callers don't need to care which bitmap (local alloc or main) to
 * use so we figure it out for them, but unfortunately this clutters
 * things a bit. */
static int ocfs2_reserve_clusters_with_limit(struct ocfs2_super *osb,
					     u32 bits_wanted, u64 max_block,
					     int flags,
					     struct ocfs2_alloc_context **ac)
{
	int status;

	mlog_entry_void();

	*ac = kzalloc(sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
	if (!(*ac)) {
		status = -ENOMEM;
		mlog_errno(status);
		goto bail;
	}

	(*ac)->ac_bits_wanted = bits_wanted;
	(*ac)->ac_max_block = max_block;

	status = -ENOSPC;
	if (!(flags & ALLOC_GROUPS_FROM_GLOBAL) &&
	    ocfs2_alloc_should_use_local(osb, bits_wanted)) {
		status = ocfs2_reserve_local_alloc_bits(osb,
							bits_wanted,
							*ac);
		if ((status < 0) && (status != -ENOSPC)) {
			mlog_errno(status);
			goto bail;
		}
	}

	if (status == -ENOSPC) {
		status = ocfs2_reserve_cluster_bitmap_bits(osb, *ac);
		if (status < 0) {
			if (status != -ENOSPC)
				mlog_errno(status);
			goto bail;
		}
	}

	status = 0;
bail:
	if ((status < 0) && *ac) {
		ocfs2_free_alloc_context(*ac);
		*ac = NULL;
	}

	mlog_exit(status);
	return status;
}

int ocfs2_reserve_clusters(struct ocfs2_super *osb,
			   u32 bits_wanted,
			   struct ocfs2_alloc_context **ac)
{
	return ocfs2_reserve_clusters_with_limit(osb, bits_wanted, 0,
						 ALLOC_NEW_GROUP, ac);
}

/*
 * More or less lifted from ext3. I'll leave their description below:
 *
 * "For ext3 allocations, we must not reuse any blocks which are
 * allocated in the bitmap buffer's "last committed data" copy.  This
 * prevents deletes from freeing up the page for reuse until we have
 * committed the delete transaction.
 *
 * If we didn't do this, then deleting something and reallocating it as
 * data would allow the old block to be overwritten before the
 * transaction committed (because we force data to disk before commit).
 * This would lead to corruption if we crashed between overwriting the
 * data and committing the delete.
 *
 * @@@ We may want to make this allocation behaviour conditional on
 * data-writes at some point, and disable it for metadata allocations or
 * sync-data inodes."
 *
 * Note: OCFS2 already does this differently for metadata vs data
 * allocations, as those bitmaps are separate and undo access is never
 * called on a metadata group descriptor.
 */
static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,
					 int nr)
{
	struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) bg_bh->b_data;
	int ret;

	if (ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap))
		return 0;

	if (!buffer_jbd(bg_bh))
		return 1;

	jbd_lock_bh_state(bg_bh);
	bg = (struct ocfs2_group_desc *) bh2jh(bg_bh)->b_committed_data;
	if (bg)
		ret = !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
	else
		ret = 1;
	jbd_unlock_bh_state(bg_bh);

	return ret;
}

static int ocfs2_block_group_find_clear_bits(struct ocfs2_super *osb,
					     struct buffer_head *bg_bh,
					     unsigned int bits_wanted,
					     unsigned int total_bits,
					     struct ocfs2_suballoc_result *res)
{
	void *bitmap;
	u16 best_offset, best_size;
	int offset, start, found, status = 0;
	struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) bg_bh->b_data;

	/* Callers got this descriptor from
	 * ocfs2_read_group_descriptor().  Any corruption is a code bug. */
	BUG_ON(!OCFS2_IS_VALID_GROUP_DESC(bg));

	found = start = best_offset = best_size = 0;
	bitmap = bg->bg_bitmap;

	while((offset = ocfs2_find_next_zero_bit(bitmap, total_bits, start)) != -1) {
		if (offset == total_bits)
			break;

		if (!ocfs2_test_bg_bit_allocatable(bg_bh, offset)) {
			/* We found a zero, but we can't use it as it
			 * hasn't been put to disk yet! */
			found = 0;
			start = offset + 1;
		} else if (offset == start) {
			/* we found a zero */
			found++;
			/* move start to the next bit to test */
			start++;
		} else {
			/* got a zero after some ones */
			found = 1;
			start = offset + 1;
		}
		if (found > best_size) {
			best_size = found;
			best_offset = start - found;
		}
		/* we got everything we needed */
		if (found == bits_wanted) {
			/* mlog(0, "Found it all!\n"); */
			break;
		}
	}

	if (best_size) {
		res->sr_bit_offset = best_offset;
		res->sr_bits = best_size;
	} else {
		status = -ENOSPC;
		/* No error log here -- see the comment above
		 * ocfs2_test_bg_bit_allocatable */
	}

	return status;
}

static inline int ocfs2_block_group_set_bits(handle_t *handle,
					     struct inode *alloc_inode,
					     struct ocfs2_group_desc *bg,
					     struct buffer_head *group_bh,
					     unsigned int bit_off,
					     unsigned int num_bits)
{
	int status;
	void *bitmap = bg->bg_bitmap;
	int journal_type = OCFS2_JOURNAL_ACCESS_WRITE;

	mlog_entry_void();

	/* All callers get the descriptor via
	 * ocfs2_read_group_descriptor().  Any corruption is a code bug. */
	BUG_ON(!OCFS2_IS_VALID_GROUP_DESC(bg));
	BUG_ON(le16_to_cpu(bg->bg_free_bits_count) < num_bits);

	mlog(0, "block_group_set_bits: off = %u, num = %u\n", bit_off,
	     num_bits);

	if (ocfs2_is_cluster_bitmap(alloc_inode))
		journal_type = OCFS2_JOURNAL_ACCESS_UNDO;

	status = ocfs2_journal_access_gd(handle,
					 INODE_CACHE(alloc_inode),
					 group_bh,
					 journal_type);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	le16_add_cpu(&bg->bg_free_bits_count, -num_bits);
	while(num_bits--)
		ocfs2_set_bit(bit_off++, bitmap);

	ocfs2_journal_dirty(handle, group_bh);

bail:
	mlog_exit(status);
	return status;
}

/* find the one with the most empty bits */
static inline u16 ocfs2_find_victim_chain(struct ocfs2_chain_list *cl)
{
	u16 curr, best;

	BUG_ON(!cl->cl_next_free_rec);

	best = curr = 0;
	while (curr < le16_to_cpu(cl->cl_next_free_rec)) {
		if (le32_to_cpu(cl->cl_recs[curr].c_free) >
		    le32_to_cpu(cl->cl_recs[best].c_free))
			best = curr;
		curr++;
	}

	BUG_ON(best >= le16_to_cpu(cl->cl_next_free_rec));
	return best;
}

static int ocfs2_relink_block_group(handle_t *handle,
				    struct inode *alloc_inode,
				    struct buffer_head *fe_bh,
				    struct buffer_head *bg_bh,
				    struct buffer_head *prev_bg_bh,
				    u16 chain)
{
	int status;
	/* there is a really tiny chance the journal calls could fail,
	 * but we wouldn't want inconsistent blocks in *any* case. */
	u64 fe_ptr, bg_ptr, prev_bg_ptr;
	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) fe_bh->b_data;
	struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) bg_bh->b_data;
	struct ocfs2_group_desc *prev_bg = (struct ocfs2_group_desc *) prev_bg_bh->b_data;

	/* The caller got these descriptors from
	 * ocfs2_read_group_descriptor().  Any corruption is a code bug. */
	BUG_ON(!OCFS2_IS_VALID_GROUP_DESC(bg));
	BUG_ON(!OCFS2_IS_VALID_GROUP_DESC(prev_bg));

	mlog(0, "Suballoc %llu, chain %u, move group %llu to top, prev = %llu\n",
	     (unsigned long long)le64_to_cpu(fe->i_blkno), chain,
	     (unsigned long long)le64_to_cpu(bg->bg_blkno),
	     (unsigned long long)le64_to_cpu(prev_bg->bg_blkno));

	fe_ptr = le64_to_cpu(fe->id2.i_chain.cl_recs[chain].c_blkno);
	bg_ptr = le64_to_cpu(bg->bg_next_group);
	prev_bg_ptr = le64_to_cpu(prev_bg->bg_next_group);

	status = ocfs2_journal_access_gd(handle, INODE_CACHE(alloc_inode),
					 prev_bg_bh,
					 OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto out_rollback;
	}

	prev_bg->bg_next_group = bg->bg_next_group;
	ocfs2_journal_dirty(handle, prev_bg_bh);

	status = ocfs2_journal_access_gd(handle, INODE_CACHE(alloc_inode),
					 bg_bh, OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto out_rollback;
	}

	bg->bg_next_group = fe->id2.i_chain.cl_recs[chain].c_blkno;
	ocfs2_journal_dirty(handle, bg_bh);

	status = ocfs2_journal_access_di(handle, INODE_CACHE(alloc_inode),
					 fe_bh, OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto out_rollback;
	}

	fe->id2.i_chain.cl_recs[chain].c_blkno = bg->bg_blkno;
	ocfs2_journal_dirty(handle, fe_bh);

out_rollback:
	if (status < 0) {
		fe->id2.i_chain.cl_recs[chain].c_blkno = cpu_to_le64(fe_ptr);
		bg->bg_next_group = cpu_to_le64(bg_ptr);
		prev_bg->bg_next_group = cpu_to_le64(prev_bg_ptr);
	}

	mlog_exit(status);
	return status;
}

static inline int ocfs2_block_group_reasonably_empty(struct ocfs2_group_desc *bg,
						     u32 wanted)
{
	return le16_to_cpu(bg->bg_free_bits_count) > wanted;
}

/* return 0 on success, -ENOSPC to keep searching and any other < 0
 * value on error. */
static int ocfs2_cluster_group_search(struct inode *inode,
				      struct buffer_head *group_bh,
				      u32 bits_wanted, u32 min_bits,
				      u64 max_block,
				      struct ocfs2_suballoc_result *res)
{
	int search = -ENOSPC;
	int ret;
	u64 blkoff;
	struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *) group_bh->b_data;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	unsigned int max_bits, gd_cluster_off;

	BUG_ON(!ocfs2_is_cluster_bitmap(inode));

	if (gd->bg_free_bits_count) {
		max_bits = le16_to_cpu(gd->bg_bits);

		/* Tail groups in cluster bitmaps which aren't cpg
		 * aligned are prone to partial extention by a failed
		 * fs resize. If the file system resize never got to
		 * update the dinode cluster count, then we don't want
		 * to trust any clusters past it, regardless of what
		 * the group descriptor says. */
		gd_cluster_off = ocfs2_blocks_to_clusters(inode->i_sb,
							  le64_to_cpu(gd->bg_blkno));
		if ((gd_cluster_off + max_bits) >
		    OCFS2_I(inode)->ip_clusters) {
			max_bits = OCFS2_I(inode)->ip_clusters - gd_cluster_off;
			mlog(0, "Desc %llu, bg_bits %u, clusters %u, use %u\n",
			     (unsigned long long)le64_to_cpu(gd->bg_blkno),
			     le16_to_cpu(gd->bg_bits),
			     OCFS2_I(inode)->ip_clusters, max_bits);
		}

		ret = ocfs2_block_group_find_clear_bits(OCFS2_SB(inode->i_sb),
							group_bh, bits_wanted,
							max_bits, res);
		if (ret)
			return ret;

		if (max_block) {
			blkoff = ocfs2_clusters_to_blocks(inode->i_sb,
							  gd_cluster_off +
							  res->sr_bit_offset +
							  res->sr_bits);
			mlog(0, "Checking %llu against %llu\n",
			     (unsigned long long)blkoff,
			     (unsigned long long)max_block);
			if (blkoff > max_block)
				return -ENOSPC;
		}

		/* ocfs2_block_group_find_clear_bits() might
		 * return success, but we still want to return
		 * -ENOSPC unless it found the minimum number
		 * of bits. */
		if (min_bits <= res->sr_bits)
			search = 0; /* success */
		else if (res->sr_bits) {
			/*
			 * Don't show bits which we'll be returning
			 * for allocation to the local alloc bitmap.
			 */
			ocfs2_local_alloc_seen_free_bits(osb, res->sr_bits);
		}
	}

	return search;
}

static int ocfs2_block_group_search(struct inode *inode,
				    struct buffer_head *group_bh,
				    u32 bits_wanted, u32 min_bits,
				    u64 max_block,
				    struct ocfs2_suballoc_result *res)
{
	int ret = -ENOSPC;
	u64 blkoff;
	struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) group_bh->b_data;

	BUG_ON(min_bits != 1);
	BUG_ON(ocfs2_is_cluster_bitmap(inode));

	if (bg->bg_free_bits_count) {
		ret = ocfs2_block_group_find_clear_bits(OCFS2_SB(inode->i_sb),
							group_bh, bits_wanted,
							le16_to_cpu(bg->bg_bits),
							res);
		if (!ret && max_block) {
			blkoff = le64_to_cpu(bg->bg_blkno) +
				res->sr_bit_offset + res->sr_bits;
			mlog(0, "Checking %llu against %llu\n",
			     (unsigned long long)blkoff,
			     (unsigned long long)max_block);
			if (blkoff > max_block)
				ret = -ENOSPC;
		}
	}

	return ret;
}

static int ocfs2_alloc_dinode_update_counts(struct inode *inode,
				       handle_t *handle,
				       struct buffer_head *di_bh,
				       u32 num_bits,
				       u16 chain)
{
	int ret;
	u32 tmp_used;
	struct ocfs2_dinode *di = (struct ocfs2_dinode *) di_bh->b_data;
	struct ocfs2_chain_list *cl = (struct ocfs2_chain_list *) &di->id2.i_chain;

	ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
				      OCFS2_JOURNAL_ACCESS_WRITE);
	if (ret < 0) {
		mlog_errno(ret);
		goto out;
	}

	tmp_used = le32_to_cpu(di->id1.bitmap1.i_used);
	di->id1.bitmap1.i_used = cpu_to_le32(num_bits + tmp_used);
	le32_add_cpu(&cl->cl_recs[chain].c_free, -num_bits);
	ocfs2_journal_dirty(handle, di_bh);

out:
	return ret;
}

static int ocfs2_bg_discontig_fix_by_rec(struct ocfs2_suballoc_result *res,
					 struct ocfs2_extent_rec *rec,
					 struct ocfs2_chain_list *cl)
{
	unsigned int bpc = le16_to_cpu(cl->cl_bpc);
	unsigned int bitoff = le32_to_cpu(rec->e_cpos) * bpc;
	unsigned int bitcount = le32_to_cpu(rec->e_leaf_clusters) * bpc;

	if (res->sr_bit_offset < bitoff)
		return 0;
	if (res->sr_bit_offset >= (bitoff + bitcount))
		return 0;
	res->sr_blkno = le64_to_cpu(rec->e_blkno) +
		(res->sr_bit_offset - bitoff);
	if ((res->sr_bit_offset + res->sr_bits) > (bitoff + bitcount))
		res->sr_bits = (bitoff + bitcount) - res->sr_bit_offset;
	return 1;
}

static void ocfs2_bg_discontig_fix_result(struct ocfs2_alloc_context *ac,
					  struct ocfs2_group_desc *bg,
					  struct ocfs2_suballoc_result *res)
{
	int i;
	u64 bg_blkno = res->sr_bg_blkno;  /* Save off */
	struct ocfs2_extent_rec *rec;
	struct ocfs2_dinode *di = (struct ocfs2_dinode *)ac->ac_bh->b_data;
	struct ocfs2_chain_list *cl = &di->id2.i_chain;

	if (ocfs2_is_cluster_bitmap(ac->ac_inode)) {
		res->sr_blkno = 0;
		return;
	}

	res->sr_blkno = res->sr_bg_blkno + res->sr_bit_offset;
	res->sr_bg_blkno = 0;  /* Clear it for contig block groups */
	if (!ocfs2_supports_discontig_bg(OCFS2_SB(ac->ac_inode->i_sb)) ||
	    !bg->bg_list.l_next_free_rec)
		return;

	for (i = 0; i < le16_to_cpu(bg->bg_list.l_next_free_rec); i++) {
		rec = &bg->bg_list.l_recs[i];
		if (ocfs2_bg_discontig_fix_by_rec(res, rec, cl)) {
			res->sr_bg_blkno = bg_blkno;  /* Restore */
			break;
		}
	}
}

static int ocfs2_search_one_group(struct ocfs2_alloc_context *ac,
				  handle_t *handle,
				  u32 bits_wanted,
				  u32 min_bits,
				  struct ocfs2_suballoc_result *res,
				  u16 *bits_left)
{
	int ret;
	struct buffer_head *group_bh = NULL;
	struct ocfs2_group_desc *gd;
	struct ocfs2_dinode *di = (struct ocfs2_dinode *)ac->ac_bh->b_data;
	struct inode *alloc_inode = ac->ac_inode;

	ret = ocfs2_read_group_descriptor(alloc_inode, di,
					  res->sr_bg_blkno, &group_bh);
	if (ret < 0) {
		mlog_errno(ret);
		return ret;
	}

	gd = (struct ocfs2_group_desc *) group_bh->b_data;
	ret = ac->ac_group_search(alloc_inode, group_bh, bits_wanted, min_bits,
				  ac->ac_max_block, res);
	if (ret < 0) {
		if (ret != -ENOSPC)
			mlog_errno(ret);
		goto out;
	}

	if (!ret)
		ocfs2_bg_discontig_fix_result(ac, gd, res);

	ret = ocfs2_alloc_dinode_update_counts(alloc_inode, handle, ac->ac_bh,
					       res->sr_bits,
					       le16_to_cpu(gd->bg_chain));
	if (ret < 0) {
		mlog_errno(ret);
		goto out;
	}

	ret = ocfs2_block_group_set_bits(handle, alloc_inode, gd, group_bh,
					 res->sr_bit_offset, res->sr_bits);
	if (ret < 0)
		mlog_errno(ret);

	*bits_left = le16_to_cpu(gd->bg_free_bits_count);

out:
	brelse(group_bh);

	return ret;
}

static int ocfs2_search_chain(struct ocfs2_alloc_context *ac,
			      handle_t *handle,
			      u32 bits_wanted,
			      u32 min_bits,
			      struct ocfs2_suballoc_result *res,
			      u16 *bits_left)
{
	int status;
	u16 chain;
	u32 tmp_used;
	u64 next_group;
	struct inode *alloc_inode = ac->ac_inode;
	struct buffer_head *group_bh = NULL;
	struct buffer_head *prev_group_bh = NULL;
	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) ac->ac_bh->b_data;
	struct ocfs2_chain_list *cl = (struct ocfs2_chain_list *) &fe->id2.i_chain;
	struct ocfs2_group_desc *bg;

	chain = ac->ac_chain;
	mlog(0, "trying to alloc %u bits from chain %u, inode %llu\n",
	     bits_wanted, chain,
	     (unsigned long long)OCFS2_I(alloc_inode)->ip_blkno);

	status = ocfs2_read_group_descriptor(alloc_inode, fe,
					     le64_to_cpu(cl->cl_recs[chain].c_blkno),
					     &group_bh);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}
	bg = (struct ocfs2_group_desc *) group_bh->b_data;

	status = -ENOSPC;
	/* for now, the chain search is a bit simplistic. We just use
	 * the 1st group with any empty bits. */
	while ((status = ac->ac_group_search(alloc_inode, group_bh,
					     bits_wanted, min_bits,
					     ac->ac_max_block,
					     res)) == -ENOSPC) {
		if (!bg->bg_next_group)
			break;

		brelse(prev_group_bh);
		prev_group_bh = NULL;

		next_group = le64_to_cpu(bg->bg_next_group);
		prev_group_bh = group_bh;
		group_bh = NULL;
		status = ocfs2_read_group_descriptor(alloc_inode, fe,
						     next_group, &group_bh);
		if (status < 0) {
			mlog_errno(status);
			goto bail;
		}
		bg = (struct ocfs2_group_desc *) group_bh->b_data;
	}
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}

	mlog(0, "alloc succeeds: we give %u bits from block group %llu\n",
	     res->sr_bits, (unsigned long long)le64_to_cpu(bg->bg_blkno));

	res->sr_bg_blkno = le64_to_cpu(bg->bg_blkno);

	BUG_ON(res->sr_bits == 0);
	if (!status)
		ocfs2_bg_discontig_fix_result(ac, bg, res);


	/*
	 * Keep track of previous block descriptor read. When
	 * we find a target, if we have read more than X
	 * number of descriptors, and the target is reasonably
	 * empty, relink him to top of his chain.
	 *
	 * We've read 0 extra blocks and only send one more to
	 * the transaction, yet the next guy to search has a
	 * much easier time.
	 *
	 * Do this *after* figuring out how many bits we're taking out
	 * of our target group.
	 */
	if (ac->ac_allow_chain_relink &&
	    (prev_group_bh) &&
	    (ocfs2_block_group_reasonably_empty(bg, res->sr_bits))) {
		status = ocfs2_relink_block_group(handle, alloc_inode,
						  ac->ac_bh, group_bh,
						  prev_group_bh, chain);
		if (status < 0) {
			mlog_errno(status);
			goto bail;
		}
	}

	/* Ok, claim our bits now: set the info on dinode, chainlist
	 * and then the group */
	status = ocfs2_journal_access_di(handle,
					 INODE_CACHE(alloc_inode),
					 ac->ac_bh,
					 OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	tmp_used = le32_to_cpu(fe->id1.bitmap1.i_used);
	fe->id1.bitmap1.i_used = cpu_to_le32(res->sr_bits + tmp_used);
	le32_add_cpu(&cl->cl_recs[chain].c_free, -res->sr_bits);
	ocfs2_journal_dirty(handle, ac->ac_bh);

	status = ocfs2_block_group_set_bits(handle,
					    alloc_inode,
					    bg,
					    group_bh,
					    res->sr_bit_offset,
					    res->sr_bits);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	mlog(0, "Allocated %u bits from suballocator %llu\n", res->sr_bits,
	     (unsigned long long)le64_to_cpu(fe->i_blkno));

	*bits_left = le16_to_cpu(bg->bg_free_bits_count);
bail:
	brelse(group_bh);
	brelse(prev_group_bh);

	mlog_exit(status);
	return status;
}

/* will give out up to bits_wanted contiguous bits. */
static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
				     handle_t *handle,
				     u32 bits_wanted,
				     u32 min_bits,
				     struct ocfs2_suballoc_result *res)
{
	int status;
	u16 victim, i;
	u16 bits_left = 0;
	u64 hint = ac->ac_last_group;
	struct ocfs2_chain_list *cl;
	struct ocfs2_dinode *fe;

	mlog_entry_void();

	BUG_ON(ac->ac_bits_given >= ac->ac_bits_wanted);
	BUG_ON(bits_wanted > (ac->ac_bits_wanted - ac->ac_bits_given));
	BUG_ON(!ac->ac_bh);

	fe = (struct ocfs2_dinode *) ac->ac_bh->b_data;

	/* The bh was validated by the inode read during
	 * ocfs2_reserve_suballoc_bits().  Any corruption is a code bug. */
	BUG_ON(!OCFS2_IS_VALID_DINODE(fe));

	if (le32_to_cpu(fe->id1.bitmap1.i_used) >=
	    le32_to_cpu(fe->id1.bitmap1.i_total)) {
		ocfs2_error(ac->ac_inode->i_sb,
			    "Chain allocator dinode %llu has %u used "
			    "bits but only %u total.",
			    (unsigned long long)le64_to_cpu(fe->i_blkno),
			    le32_to_cpu(fe->id1.bitmap1.i_used),
			    le32_to_cpu(fe->id1.bitmap1.i_total));
		status = -EIO;
		goto bail;
	}

	res->sr_bg_blkno = hint;
	if (res->sr_bg_blkno) {
		/* Attempt to short-circuit the usual search mechanism
		 * by jumping straight to the most recently used
		 * allocation group. This helps us mantain some
		 * contiguousness across allocations. */
		status = ocfs2_search_one_group(ac, handle, bits_wanted,
						min_bits, res, &bits_left);
		if (!status)
			goto set_hint;
		if (status < 0 && status != -ENOSPC) {
			mlog_errno(status);
			goto bail;
		}
	}

	cl = (struct ocfs2_chain_list *) &fe->id2.i_chain;

	victim = ocfs2_find_victim_chain(cl);
	ac->ac_chain = victim;
	ac->ac_allow_chain_relink = 1;

	status = ocfs2_search_chain(ac, handle, bits_wanted, min_bits,
				    res, &bits_left);
	if (!status) {
		hint = ocfs2_group_from_res(res);
		goto set_hint;
	}
	if (status < 0 && status != -ENOSPC) {
		mlog_errno(status);
		goto bail;
	}

	mlog(0, "Search of victim chain %u came up with nothing, "
	     "trying all chains now.\n", victim);

	/* If we didn't pick a good victim, then just default to
	 * searching each chain in order. Don't allow chain relinking
	 * because we only calculate enough journal credits for one
	 * relink per alloc. */
	ac->ac_allow_chain_relink = 0;
	for (i = 0; i < le16_to_cpu(cl->cl_next_free_rec); i ++) {
		if (i == victim)
			continue;
		if (!cl->cl_recs[i].c_free)
			continue;

		ac->ac_chain = i;
		status = ocfs2_search_chain(ac, handle, bits_wanted, min_bits,
					    res, &bits_left);
		if (!status) {
			hint = ocfs2_group_from_res(res);
			break;
		}
		if (status < 0 && status != -ENOSPC) {
			mlog_errno(status);
			goto bail;
		}
	}

set_hint:
	if (status != -ENOSPC) {
		/* If the next search of this group is not likely to
		 * yield a suitable extent, then we reset the last
		 * group hint so as to not waste a disk read */
		if (bits_left < min_bits)
			ac->ac_last_group = 0;
		else
			ac->ac_last_group = hint;
	}

bail:
	mlog_exit(status);
	return status;
}

int ocfs2_claim_metadata(handle_t *handle,
			 struct ocfs2_alloc_context *ac,
			 u32 bits_wanted,
			 u64 *suballoc_loc,
			 u16 *suballoc_bit_start,
			 unsigned int *num_bits,
			 u64 *blkno_start)
{
	int status;
	struct ocfs2_suballoc_result res = { .sr_blkno = 0, };

	BUG_ON(!ac);
	BUG_ON(ac->ac_bits_wanted < (ac->ac_bits_given + bits_wanted));
	BUG_ON(ac->ac_which != OCFS2_AC_USE_META);

	status = ocfs2_claim_suballoc_bits(ac,
					   handle,
					   bits_wanted,
					   1,
					   &res);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}
	atomic_inc(&OCFS2_SB(ac->ac_inode->i_sb)->alloc_stats.bg_allocs);

	*suballoc_loc = res.sr_bg_blkno;
	*suballoc_bit_start = res.sr_bit_offset;
	*blkno_start = res.sr_blkno;
	ac->ac_bits_given += res.sr_bits;
	*num_bits = res.sr_bits;
	status = 0;
bail:
	mlog_exit(status);
	return status;
}

static void ocfs2_init_inode_ac_group(struct inode *dir,
				      struct buffer_head *parent_di_bh,
				      struct ocfs2_alloc_context *ac)
{
	struct ocfs2_dinode *di = (struct ocfs2_dinode *)parent_di_bh->b_data;
	/*
	 * Try to allocate inodes from some specific group.
	 *
	 * If the parent dir has recorded the last group used in allocation,
	 * cool, use it. Otherwise if we try to allocate new inode from the
	 * same slot the parent dir belongs to, use the same chunk.
	 *
	 * We are very careful here to avoid the mistake of setting
	 * ac_last_group to a group descriptor from a different (unlocked) slot.
	 */
	if (OCFS2_I(dir)->ip_last_used_group &&
	    OCFS2_I(dir)->ip_last_used_slot == ac->ac_alloc_slot)
		ac->ac_last_group = OCFS2_I(dir)->ip_last_used_group;
	else if (le16_to_cpu(di->i_suballoc_slot) == ac->ac_alloc_slot) {
		if (di->i_suballoc_loc)
			ac->ac_last_group = le64_to_cpu(di->i_suballoc_loc);
		else
			ac->ac_last_group = ocfs2_which_suballoc_group(
					le64_to_cpu(di->i_blkno),
					le16_to_cpu(di->i_suballoc_bit));
	}
}

static inline void ocfs2_save_inode_ac_group(struct inode *dir,
					     struct ocfs2_alloc_context *ac)
{
	OCFS2_I(dir)->ip_last_used_group = ac->ac_last_group;
	OCFS2_I(dir)->ip_last_used_slot = ac->ac_alloc_slot;
}

int ocfs2_claim_new_inode(handle_t *handle,
			  struct inode *dir,
			  struct buffer_head *parent_fe_bh,
			  struct ocfs2_alloc_context *ac,
			  u64 *suballoc_loc,
			  u16 *suballoc_bit,
			  u64 *fe_blkno)
{
	int status;
	struct ocfs2_suballoc_result res;

	mlog_entry_void();

	BUG_ON(!ac);
	BUG_ON(ac->ac_bits_given != 0);
	BUG_ON(ac->ac_bits_wanted != 1);
	BUG_ON(ac->ac_which != OCFS2_AC_USE_INODE);

	ocfs2_init_inode_ac_group(dir, parent_fe_bh, ac);

	status = ocfs2_claim_suballoc_bits(ac,
					   handle,
					   1,
					   1,
					   &res);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}
	atomic_inc(&OCFS2_SB(ac->ac_inode->i_sb)->alloc_stats.bg_allocs);

	BUG_ON(res.sr_bits != 1);

	*suballoc_loc = res.sr_bg_blkno;
	*suballoc_bit = res.sr_bit_offset;
	*fe_blkno = res.sr_blkno;
	ac->ac_bits_given++;
	ocfs2_save_inode_ac_group(dir, ac);
	status = 0;
bail:
	mlog_exit(status);
	return status;
}

/* translate a group desc. blkno and it's bitmap offset into
 * disk cluster offset. */
static inline u32 ocfs2_desc_bitmap_to_cluster_off(struct inode *inode,
						   u64 bg_blkno,
						   u16 bg_bit_off)
{
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	u32 cluster = 0;

	BUG_ON(!ocfs2_is_cluster_bitmap(inode));

	if (bg_blkno != osb->first_cluster_group_blkno)
		cluster = ocfs2_blocks_to_clusters(inode->i_sb, bg_blkno);
	cluster += (u32) bg_bit_off;
	return cluster;
}

/* given a cluster offset, calculate which block group it belongs to
 * and return that block offset. */
u64 ocfs2_which_cluster_group(struct inode *inode, u32 cluster)
{
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	u32 group_no;

	BUG_ON(!ocfs2_is_cluster_bitmap(inode));

	group_no = cluster / osb->bitmap_cpg;
	if (!group_no)
		return osb->first_cluster_group_blkno;
	return ocfs2_clusters_to_blocks(inode->i_sb,
					group_no * osb->bitmap_cpg);
}

/* given the block number of a cluster start, calculate which cluster
 * group and descriptor bitmap offset that corresponds to. */
static inline void ocfs2_block_to_cluster_group(struct inode *inode,
						u64 data_blkno,
						u64 *bg_blkno,
						u16 *bg_bit_off)
{
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	u32 data_cluster = ocfs2_blocks_to_clusters(osb->sb, data_blkno);

	BUG_ON(!ocfs2_is_cluster_bitmap(inode));

	*bg_blkno = ocfs2_which_cluster_group(inode,
					      data_cluster);

	if (*bg_blkno == osb->first_cluster_group_blkno)
		*bg_bit_off = (u16) data_cluster;
	else
		*bg_bit_off = (u16) ocfs2_blocks_to_clusters(osb->sb,
							     data_blkno - *bg_blkno);
}

/*
 * min_bits - minimum contiguous chunk from this total allocation we
 * can handle. set to what we asked for originally for a full
 * contig. allocation, set to '1' to indicate we can deal with extents
 * of any size.
 */
int __ocfs2_claim_clusters(handle_t *handle,
			   struct ocfs2_alloc_context *ac,
			   u32 min_clusters,
			   u32 max_clusters,
			   u32 *cluster_start,
			   u32 *num_clusters)
{
	int status;
	unsigned int bits_wanted = max_clusters;
	struct ocfs2_suballoc_result res = { .sr_blkno = 0, };
	struct ocfs2_super *osb = OCFS2_SB(ac->ac_inode->i_sb);

	mlog_entry_void();

	BUG_ON(ac->ac_bits_given >= ac->ac_bits_wanted);

	BUG_ON(ac->ac_which != OCFS2_AC_USE_LOCAL
	       && ac->ac_which != OCFS2_AC_USE_MAIN);

	if (ac->ac_which == OCFS2_AC_USE_LOCAL) {
		WARN_ON(min_clusters > 1);

		status = ocfs2_claim_local_alloc_bits(osb,
						      handle,
						      ac,
						      bits_wanted,
						      cluster_start,
						      num_clusters);
		if (!status)
			atomic_inc(&osb->alloc_stats.local_data);
	} else {
		if (min_clusters > (osb->bitmap_cpg - 1)) {
			/* The only paths asking for contiguousness
			 * should know about this already. */
			mlog(ML_ERROR, "minimum allocation requested %u exceeds "
			     "group bitmap size %u!\n", min_clusters,
			     osb->bitmap_cpg);
			status = -ENOSPC;
			goto bail;
		}
		/* clamp the current request down to a realistic size. */
		if (bits_wanted > (osb->bitmap_cpg - 1))
			bits_wanted = osb->bitmap_cpg - 1;

		status = ocfs2_claim_suballoc_bits(ac,
						   handle,
						   bits_wanted,
						   min_clusters,
						   &res);
		if (!status) {
			BUG_ON(res.sr_blkno); /* cluster alloc can't set */
			*cluster_start =
				ocfs2_desc_bitmap_to_cluster_off(ac->ac_inode,
								 res.sr_bg_blkno,
								 res.sr_bit_offset);
			atomic_inc(&osb->alloc_stats.bitmap_data);
			*num_clusters = res.sr_bits;
		}
	}
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto bail;
	}

	ac->ac_bits_given += *num_clusters;

bail:
	mlog_exit(status);
	return status;
}

int ocfs2_claim_clusters(handle_t *handle,
			 struct ocfs2_alloc_context *ac,
			 u32 min_clusters,
			 u32 *cluster_start,
			 u32 *num_clusters)
{
	unsigned int bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;

	return __ocfs2_claim_clusters(handle, ac, min_clusters,
				      bits_wanted, cluster_start, num_clusters);
}

static int ocfs2_block_group_clear_bits(handle_t *handle,
					struct inode *alloc_inode,
					struct ocfs2_group_desc *bg,
					struct buffer_head *group_bh,
					unsigned int bit_off,
					unsigned int num_bits,
					void (*undo_fn)(unsigned int bit,
							unsigned long *bmap))
{
	int status;
	unsigned int tmp;
	struct ocfs2_group_desc *undo_bg = NULL;

	mlog_entry_void();

	/* The caller got this descriptor from
	 * ocfs2_read_group_descriptor().  Any corruption is a code bug. */
	BUG_ON(!OCFS2_IS_VALID_GROUP_DESC(bg));

	mlog(0, "off = %u, num = %u\n", bit_off, num_bits);

	BUG_ON(undo_fn && !ocfs2_is_cluster_bitmap(alloc_inode));
	status = ocfs2_journal_access_gd(handle, INODE_CACHE(alloc_inode),
					 group_bh,
					 undo_fn ?
					 OCFS2_JOURNAL_ACCESS_UNDO :
					 OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	if (undo_fn) {
		jbd_lock_bh_state(group_bh);
		undo_bg = (struct ocfs2_group_desc *)
					bh2jh(group_bh)->b_committed_data;
		BUG_ON(!undo_bg);
	}

	tmp = num_bits;
	while(tmp--) {
		ocfs2_clear_bit((bit_off + tmp),
				(unsigned long *) bg->bg_bitmap);
		if (undo_fn)
			undo_fn(bit_off + tmp,
				(unsigned long *) undo_bg->bg_bitmap);
	}
	le16_add_cpu(&bg->bg_free_bits_count, num_bits);

	if (undo_fn)
		jbd_unlock_bh_state(group_bh);

	ocfs2_journal_dirty(handle, group_bh);
bail:
	return status;
}

/*
 * expects the suballoc inode to already be locked.
 */
static int _ocfs2_free_suballoc_bits(handle_t *handle,
				     struct inode *alloc_inode,
				     struct buffer_head *alloc_bh,
				     unsigned int start_bit,
				     u64 bg_blkno,
				     unsigned int count,
				     void (*undo_fn)(unsigned int bit,
						     unsigned long *bitmap))
{
	int status = 0;
	u32 tmp_used;
	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) alloc_bh->b_data;
	struct ocfs2_chain_list *cl = &fe->id2.i_chain;
	struct buffer_head *group_bh = NULL;
	struct ocfs2_group_desc *group;

	mlog_entry_void();

	/* The alloc_bh comes from ocfs2_free_dinode() or
	 * ocfs2_free_clusters().  The callers have all locked the
	 * allocator and gotten alloc_bh from the lock call.  This
	 * validates the dinode buffer.  Any corruption that has happended
	 * is a code bug. */
	BUG_ON(!OCFS2_IS_VALID_DINODE(fe));
	BUG_ON((count + start_bit) > ocfs2_bits_per_group(cl));

	mlog(0, "%llu: freeing %u bits from group %llu, starting at %u\n",
	     (unsigned long long)OCFS2_I(alloc_inode)->ip_blkno, count,
	     (unsigned long long)bg_blkno, start_bit);

	status = ocfs2_read_group_descriptor(alloc_inode, fe, bg_blkno,
					     &group_bh);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}
	group = (struct ocfs2_group_desc *) group_bh->b_data;

	BUG_ON((count + start_bit) > le16_to_cpu(group->bg_bits));

	status = ocfs2_block_group_clear_bits(handle, alloc_inode,
					      group, group_bh,
					      start_bit, count, undo_fn);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	status = ocfs2_journal_access_di(handle, INODE_CACHE(alloc_inode),
					 alloc_bh, OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	le32_add_cpu(&cl->cl_recs[le16_to_cpu(group->bg_chain)].c_free,
		     count);
	tmp_used = le32_to_cpu(fe->id1.bitmap1.i_used);
	fe->id1.bitmap1.i_used = cpu_to_le32(tmp_used - count);
	ocfs2_journal_dirty(handle, alloc_bh);

bail:
	brelse(group_bh);

	mlog_exit(status);
	return status;
}

int ocfs2_free_suballoc_bits(handle_t *handle,
			     struct inode *alloc_inode,
			     struct buffer_head *alloc_bh,
			     unsigned int start_bit,
			     u64 bg_blkno,
			     unsigned int count)
{
	return _ocfs2_free_suballoc_bits(handle, alloc_inode, alloc_bh,
					 start_bit, bg_blkno, count, NULL);
}

int ocfs2_free_dinode(handle_t *handle,
		      struct inode *inode_alloc_inode,
		      struct buffer_head *inode_alloc_bh,
		      struct ocfs2_dinode *di)
{
	u64 blk = le64_to_cpu(di->i_blkno);
	u16 bit = le16_to_cpu(di->i_suballoc_bit);
	u64 bg_blkno = ocfs2_which_suballoc_group(blk, bit);

	if (di->i_suballoc_loc)
		bg_blkno = le64_to_cpu(di->i_suballoc_loc);
	return ocfs2_free_suballoc_bits(handle, inode_alloc_inode,
					inode_alloc_bh, bit, bg_blkno, 1);
}

static int _ocfs2_free_clusters(handle_t *handle,
				struct inode *bitmap_inode,
				struct buffer_head *bitmap_bh,
				u64 start_blk,
				unsigned int num_clusters,
				void (*undo_fn)(unsigned int bit,
						unsigned long *bitmap))
{
	int status;
	u16 bg_start_bit;
	u64 bg_blkno;
	struct ocfs2_dinode *fe;

	/* You can't ever have a contiguous set of clusters
	 * bigger than a block group bitmap so we never have to worry
	 * about looping on them. */

	mlog_entry_void();

	/* This is expensive. We can safely remove once this stuff has
	 * gotten tested really well. */
	BUG_ON(start_blk != ocfs2_clusters_to_blocks(bitmap_inode->i_sb, ocfs2_blocks_to_clusters(bitmap_inode->i_sb, start_blk)));

	fe = (struct ocfs2_dinode *) bitmap_bh->b_data;

	ocfs2_block_to_cluster_group(bitmap_inode, start_blk, &bg_blkno,
				     &bg_start_bit);

	mlog(0, "want to free %u clusters starting at block %llu\n",
	     num_clusters, (unsigned long long)start_blk);
	mlog(0, "bg_blkno = %llu, bg_start_bit = %u\n",
	     (unsigned long long)bg_blkno, bg_start_bit);

	status = _ocfs2_free_suballoc_bits(handle, bitmap_inode, bitmap_bh,
					   bg_start_bit, bg_blkno,
					   num_clusters, undo_fn);
	if (status < 0) {
		mlog_errno(status);
		goto out;
	}

	ocfs2_local_alloc_seen_free_bits(OCFS2_SB(bitmap_inode->i_sb),
					 num_clusters);

out:
	mlog_exit(status);
	return status;
}

int ocfs2_free_clusters(handle_t *handle,
			struct inode *bitmap_inode,
			struct buffer_head *bitmap_bh,
			u64 start_blk,
			unsigned int num_clusters)
{
	return _ocfs2_free_clusters(handle, bitmap_inode, bitmap_bh,
				    start_blk, num_clusters,
				    _ocfs2_set_bit);
}

/*
 * Give never-used clusters back to the global bitmap.  We don't need
 * to protect these bits in the undo buffer.
 */
int ocfs2_release_clusters(handle_t *handle,
			   struct inode *bitmap_inode,
			   struct buffer_head *bitmap_bh,
			   u64 start_blk,
			   unsigned int num_clusters)
{
	return _ocfs2_free_clusters(handle, bitmap_inode, bitmap_bh,
				    start_blk, num_clusters,
				    _ocfs2_clear_bit);
}

static inline void ocfs2_debug_bg(struct ocfs2_group_desc *bg)
{
	printk("Block Group:\n");
	printk("bg_signature:       %s\n", bg->bg_signature);
	printk("bg_size:            %u\n", bg->bg_size);
	printk("bg_bits:            %u\n", bg->bg_bits);
	printk("bg_free_bits_count: %u\n", bg->bg_free_bits_count);
	printk("bg_chain:           %u\n", bg->bg_chain);
	printk("bg_generation:      %u\n", le32_to_cpu(bg->bg_generation));
	printk("bg_next_group:      %llu\n",
	       (unsigned long long)bg->bg_next_group);
	printk("bg_parent_dinode:   %llu\n",
	       (unsigned long long)bg->bg_parent_dinode);
	printk("bg_blkno:           %llu\n",
	       (unsigned long long)bg->bg_blkno);
}

static inline void ocfs2_debug_suballoc_inode(struct ocfs2_dinode *fe)
{
	int i;

	printk("Suballoc Inode %llu:\n", (unsigned long long)fe->i_blkno);
	printk("i_signature:                  %s\n", fe->i_signature);
	printk("i_size:                       %llu\n",
	       (unsigned long long)fe->i_size);
	printk("i_clusters:                   %u\n", fe->i_clusters);
	printk("i_generation:                 %u\n",
	       le32_to_cpu(fe->i_generation));
	printk("id1.bitmap1.i_used:           %u\n",
	       le32_to_cpu(fe->id1.bitmap1.i_used));
	printk("id1.bitmap1.i_total:          %u\n",
	       le32_to_cpu(fe->id1.bitmap1.i_total));
	printk("id2.i_chain.cl_cpg:           %u\n", fe->id2.i_chain.cl_cpg);
	printk("id2.i_chain.cl_bpc:           %u\n", fe->id2.i_chain.cl_bpc);
	printk("id2.i_chain.cl_count:         %u\n", fe->id2.i_chain.cl_count);
	printk("id2.i_chain.cl_next_free_rec: %u\n",
	       fe->id2.i_chain.cl_next_free_rec);
	for(i = 0; i < fe->id2.i_chain.cl_next_free_rec; i++) {
		printk("fe->id2.i_chain.cl_recs[%d].c_free:  %u\n", i,
		       fe->id2.i_chain.cl_recs[i].c_free);
		printk("fe->id2.i_chain.cl_recs[%d].c_total: %u\n", i,
		       fe->id2.i_chain.cl_recs[i].c_total);
		printk("fe->id2.i_chain.cl_recs[%d].c_blkno: %llu\n", i,
		       (unsigned long long)fe->id2.i_chain.cl_recs[i].c_blkno);
	}
}

/*
 * For a given allocation, determine which allocators will need to be
 * accessed, and lock them, reserving the appropriate number of bits.
 *
 * Sparse file systems call this from ocfs2_write_begin_nolock()
 * and ocfs2_allocate_unwritten_extents().
 *
 * File systems which don't support holes call this from
 * ocfs2_extend_allocation().
 */
int ocfs2_lock_allocators(struct inode *inode,
			  struct ocfs2_extent_tree *et,
			  u32 clusters_to_add, u32 extents_to_split,
			  struct ocfs2_alloc_context **data_ac,
			  struct ocfs2_alloc_context **meta_ac)
{
	int ret = 0, num_free_extents;
	unsigned int max_recs_needed = clusters_to_add + 2 * extents_to_split;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

	*meta_ac = NULL;
	if (data_ac)
		*data_ac = NULL;

	BUG_ON(clusters_to_add != 0 && data_ac == NULL);

	num_free_extents = ocfs2_num_free_extents(osb, et);
	if (num_free_extents < 0) {
		ret = num_free_extents;
		mlog_errno(ret);
		goto out;
	}

	/*
	 * Sparse allocation file systems need to be more conservative
	 * with reserving room for expansion - the actual allocation
	 * happens while we've got a journal handle open so re-taking
	 * a cluster lock (because we ran out of room for another
	 * extent) will violate ordering rules.
	 *
	 * Most of the time we'll only be seeing this 1 cluster at a time
	 * anyway.
	 *
	 * Always lock for any unwritten extents - we might want to
	 * add blocks during a split.
	 */
	if (!num_free_extents ||
	    (ocfs2_sparse_alloc(osb) && num_free_extents < max_recs_needed)) {
		ret = ocfs2_reserve_new_metadata(osb, et->et_root_el, meta_ac);
		if (ret < 0) {
			if (ret != -ENOSPC)
				mlog_errno(ret);
			goto out;
		}
	}

	if (clusters_to_add == 0)
		goto out;

	ret = ocfs2_reserve_clusters(osb, clusters_to_add, data_ac);
	if (ret < 0) {
		if (ret != -ENOSPC)
			mlog_errno(ret);
		goto out;
	}

out:
	if (ret) {
		if (*meta_ac) {
			ocfs2_free_alloc_context(*meta_ac);
			*meta_ac = NULL;
		}

		/*
		 * We cannot have an error and a non null *data_ac.
		 */
	}

	return ret;
}

/*
 * Read the inode specified by blkno to get suballoc_slot and
 * suballoc_bit.
 */
static int ocfs2_get_suballoc_slot_bit(struct ocfs2_super *osb, u64 blkno,
				       u16 *suballoc_slot, u64 *group_blkno,
				       u16 *suballoc_bit)
{
	int status;
	struct buffer_head *inode_bh = NULL;
	struct ocfs2_dinode *inode_fe;

	mlog_entry("blkno: %llu\n", (unsigned long long)blkno);

	/* dirty read disk */
	status = ocfs2_read_blocks_sync(osb, blkno, 1, &inode_bh);
	if (status < 0) {
		mlog(ML_ERROR, "read block %llu failed %d\n",
		     (unsigned long long)blkno, status);
		goto bail;
	}

	inode_fe = (struct ocfs2_dinode *) inode_bh->b_data;
	if (!OCFS2_IS_VALID_DINODE(inode_fe)) {
		mlog(ML_ERROR, "invalid inode %llu requested\n",
		     (unsigned long long)blkno);
		status = -EINVAL;
		goto bail;
	}

	if (le16_to_cpu(inode_fe->i_suballoc_slot) != (u16)OCFS2_INVALID_SLOT &&
	    (u32)le16_to_cpu(inode_fe->i_suballoc_slot) > osb->max_slots - 1) {
		mlog(ML_ERROR, "inode %llu has invalid suballoc slot %u\n",
		     (unsigned long long)blkno,
		     (u32)le16_to_cpu(inode_fe->i_suballoc_slot));
		status = -EINVAL;
		goto bail;
	}

	if (suballoc_slot)
		*suballoc_slot = le16_to_cpu(inode_fe->i_suballoc_slot);
	if (suballoc_bit)
		*suballoc_bit = le16_to_cpu(inode_fe->i_suballoc_bit);
	if (group_blkno)
		*group_blkno = le64_to_cpu(inode_fe->i_suballoc_loc);

bail:
	brelse(inode_bh);

	mlog_exit(status);
	return status;
}

/*
 * test whether bit is SET in allocator bitmap or not.  on success, 0
 * is returned and *res is 1 for SET; 0 otherwise.  when fails, errno
 * is returned and *res is meaningless.  Call this after you have
 * cluster locked against suballoc, or you may get a result based on
 * non-up2date contents
 */
static int ocfs2_test_suballoc_bit(struct ocfs2_super *osb,
				   struct inode *suballoc,
				   struct buffer_head *alloc_bh,
				   u64 group_blkno, u64 blkno,
				   u16 bit, int *res)
{
	struct ocfs2_dinode *alloc_di;
	struct ocfs2_group_desc *group;
	struct buffer_head *group_bh = NULL;
	u64 bg_blkno;
	int status;

	mlog_entry("blkno: %llu bit: %u\n", (unsigned long long)blkno,
		   (unsigned int)bit);

	alloc_di = (struct ocfs2_dinode *)alloc_bh->b_data;
	if ((bit + 1) > ocfs2_bits_per_group(&alloc_di->id2.i_chain)) {
		mlog(ML_ERROR, "suballoc bit %u out of range of %u\n",
		     (unsigned int)bit,
		     ocfs2_bits_per_group(&alloc_di->id2.i_chain));
		status = -EINVAL;
		goto bail;
	}

	bg_blkno = group_blkno ? group_blkno :
		   ocfs2_which_suballoc_group(blkno, bit);
	status = ocfs2_read_group_descriptor(suballoc, alloc_di, bg_blkno,
					     &group_bh);
	if (status < 0) {
		mlog(ML_ERROR, "read group %llu failed %d\n",
		     (unsigned long long)bg_blkno, status);
		goto bail;
	}

	group = (struct ocfs2_group_desc *) group_bh->b_data;
	*res = ocfs2_test_bit(bit, (unsigned long *)group->bg_bitmap);

bail:
	brelse(group_bh);

	mlog_exit(status);
	return status;
}

/*
 * Test if the bit representing this inode (blkno) is set in the
 * suballocator.
 *
 * On success, 0 is returned and *res is 1 for SET; 0 otherwise.
 *
 * In the event of failure, a negative value is returned and *res is
 * meaningless.
 *
 * Callers must make sure to hold nfs_sync_lock to prevent
 * ocfs2_delete_inode() on another node from accessing the same
 * suballocator concurrently.
 */
int ocfs2_test_inode_bit(struct ocfs2_super *osb, u64 blkno, int *res)
{
	int status;
	u64 group_blkno = 0;
	u16 suballoc_bit = 0, suballoc_slot = 0;
	struct inode *inode_alloc_inode;
	struct buffer_head *alloc_bh = NULL;

	mlog_entry("blkno: %llu", (unsigned long long)blkno);

	status = ocfs2_get_suballoc_slot_bit(osb, blkno, &suballoc_slot,
					     &group_blkno, &suballoc_bit);
	if (status < 0) {
		mlog(ML_ERROR, "get alloc slot and bit failed %d\n", status);
		goto bail;
	}

	inode_alloc_inode =
		ocfs2_get_system_file_inode(osb, INODE_ALLOC_SYSTEM_INODE,
					    suballoc_slot);
	if (!inode_alloc_inode) {
		/* the error code could be inaccurate, but we are not able to
		 * get the correct one. */
		status = -EINVAL;
		mlog(ML_ERROR, "unable to get alloc inode in slot %u\n",
		     (u32)suballoc_slot);
		goto bail;
	}

	mutex_lock(&inode_alloc_inode->i_mutex);
	status = ocfs2_inode_lock(inode_alloc_inode, &alloc_bh, 0);
	if (status < 0) {
		mutex_unlock(&inode_alloc_inode->i_mutex);
		mlog(ML_ERROR, "lock on alloc inode on slot %u failed %d\n",
		     (u32)suballoc_slot, status);
		goto bail;
	}

	status = ocfs2_test_suballoc_bit(osb, inode_alloc_inode, alloc_bh,
					 group_blkno, blkno, suballoc_bit, res);
	if (status < 0)
		mlog(ML_ERROR, "test suballoc bit failed %d\n", status);

	ocfs2_inode_unlock(inode_alloc_inode, 0);
	mutex_unlock(&inode_alloc_inode->i_mutex);

	iput(inode_alloc_inode);
	brelse(alloc_bh);
bail:
	mlog_exit(status);
	return status;
}