/* -*- 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>

  #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 "ocfs2_trace.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_bg_stable_blkno; /*
  					     * Doesn't change, always
  					     * set to target block
  					     * group descriptor
  					     * block.
  					     */

  	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;

  	if (ac->ac_find_loc_priv) {
  		kfree(ac->ac_find_loc_priv);
  		ac->ac_find_loc_priv = 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 "
  ", ##__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
  ",
  		     (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;

  	trace_ocfs2_validate_group_descriptor(
  					(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, unsigned int 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_le16(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;

  	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:

  	if (status)
  		mlog_errno(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);

  	trace_ocfs2_block_group_alloc_contig(
  	     (unsigned long long)bg_blkno, alloc_rec);

  
  	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);

  	trace_ocfs2_block_group_alloc_discontig(
  				(unsigned long long)bg_blkno, alloc_rec);

  
  	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));

  	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) {

  		trace_ocfs2_block_group_alloc(
  				(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);

  	if (status)
  		mlog_errno(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;

  	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)) {

  			trace_ocfs2_reserve_suballoc_bits_nospc(bits_wanted,
  								free_bits);

  			status = -ENOSPC;
  			goto bail;
  		}

  		if (!(flags & ALLOC_NEW_GROUP)) {

  			trace_ocfs2_reserve_suballoc_bits_no_new_group(
  						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);

  	if (status)
  		mlog_errno(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;
  	}

  	if (status)
  		mlog_errno(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);

  		trace_ocfs2_reserve_new_inode_new_group(
  			(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;
  	}

  	if (status)
  		mlog_errno(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;

  	*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;
  	}

  	if (status)
  		mlog_errno(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!
  "); */
  			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;

  	/* 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);

  	trace_ocfs2_block_group_set_bits(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);

  	if (le16_to_cpu(bg->bg_free_bits_count) > le16_to_cpu(bg->bg_bits)) {
  		ocfs2_error(alloc_inode->i_sb, "Group descriptor # %llu has bit"
  			    " count %u but claims %u are freed. num_bits %d",
  			    (unsigned long long)le64_to_cpu(bg->bg_blkno),
  			    le16_to_cpu(bg->bg_bits),
  			    le16_to_cpu(bg->bg_free_bits_count), num_bits);
  		return -EROFS;
  	}

  	while(num_bits--)
  		ocfs2_set_bit(bit_off++, bitmap);

  	ocfs2_journal_dirty(handle, group_bh);

  
  bail:

  	if (status)
  		mlog_errno(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));

  	trace_ocfs2_relink_block_group(
  		(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);
  	}

  	if (status)
  		mlog_errno(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 extension 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;

  			trace_ocfs2_cluster_group_search_wrong_max_bits(
  				(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);

  			trace_ocfs2_cluster_group_search_max_block(
  				(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;

  			trace_ocfs2_block_group_search_max_block(
  				(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);

  	/*
  	 * sr_bg_blkno might have been changed by
  	 * ocfs2_bg_discontig_fix_result
  	 */
  	res->sr_bg_stable_blkno = group_bh->b_blocknr;
  
  	if (ac->ac_find_loc_only)
  		goto out_loc_only;

  	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);

  out_loc_only:

  	*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;

  	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;

  	trace_ocfs2_search_chain_begin(
  		(unsigned long long)OCFS2_I(alloc_inode)->ip_blkno,
  		bits_wanted, chain);

  	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;
  	}

  	trace_ocfs2_search_chain_succ(
  		(unsigned long long)le64_to_cpu(bg->bg_blkno), res->sr_bits);

  	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);

  	/*
  	 * sr_bg_blkno might have been changed by
  	 * ocfs2_bg_discontig_fix_result
  	 */
  	res->sr_bg_stable_blkno = group_bh->b_blocknr;

  
  	/*
  	 * 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;
  		}
  	}

  	if (ac->ac_find_loc_only)
  		goto out_loc_only;

  	status = ocfs2_alloc_dinode_update_counts(alloc_inode, handle,
  						  ac->ac_bh, res->sr_bits,
  						  chain);
  	if (status) {

  		mlog_errno(status);
  		goto bail;
  	}

  	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;
  	}

  	trace_ocfs2_search_chain_end(
  			(unsigned long long)le64_to_cpu(fe->i_blkno),
  			res->sr_bits);

  out_loc_only:

  	*bits_left = le16_to_cpu(bg->bg_free_bits_count);

  bail:

  	brelse(group_bh);
  	brelse(prev_group_bh);

  	if (status)
  		mlog_errno(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;

  	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 maintain 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;
  	}

  	trace_ocfs2_claim_suballoc_bits(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:

  	if (status)
  		mlog_errno(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:

  	if (status)
  		mlog_errno(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_find_new_inode_loc(struct inode *dir,
  			     struct buffer_head *parent_fe_bh,
  			     struct ocfs2_alloc_context *ac,
  			     u64 *fe_blkno)
  {
  	int ret;
  	handle_t *handle = NULL;
  	struct ocfs2_suballoc_result *res;
  
  	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);
  
  	res = kzalloc(sizeof(*res), GFP_NOFS);
  	if (res == NULL) {
  		ret = -ENOMEM;
  		mlog_errno(ret);
  		goto out;
  	}
  
  	ocfs2_init_inode_ac_group(dir, parent_fe_bh, ac);
  
  	/*
  	 * The handle started here is for chain relink. Alternatively,
  	 * we could just disable relink for these calls.
  	 */
  	handle = ocfs2_start_trans(OCFS2_SB(dir->i_sb), OCFS2_SUBALLOC_ALLOC);
  	if (IS_ERR(handle)) {
  		ret = PTR_ERR(handle);
  		handle = NULL;
  		mlog_errno(ret);
  		goto out;
  	}
  
  	/*
  	 * This will instruct ocfs2_claim_suballoc_bits and
  	 * ocfs2_search_one_group to search but save actual allocation
  	 * for later.
  	 */
  	ac->ac_find_loc_only = 1;
  
  	ret = ocfs2_claim_suballoc_bits(ac, handle, 1, 1, res);
  	if (ret < 0) {
  		mlog_errno(ret);
  		goto out;
  	}
  
  	ac->ac_find_loc_priv = res;
  	*fe_blkno = res->sr_blkno;
  
  out:
  	if (handle)
  		ocfs2_commit_trans(OCFS2_SB(dir->i_sb), handle);
  
  	if (ret)
  		kfree(res);
  
  	return ret;
  }
  
  int ocfs2_claim_new_inode_at_loc(handle_t *handle,
  				 struct inode *dir,
  				 struct ocfs2_alloc_context *ac,
  				 u64 *suballoc_loc,
  				 u16 *suballoc_bit,
  				 u64 di_blkno)
  {
  	int ret;
  	u16 chain;
  	struct ocfs2_suballoc_result *res = ac->ac_find_loc_priv;
  	struct buffer_head *bg_bh = NULL;
  	struct ocfs2_group_desc *bg;
  	struct ocfs2_dinode *di = (struct ocfs2_dinode *) ac->ac_bh->b_data;
  
  	/*
  	 * Since di_blkno is being passed back in, we check for any
  	 * inconsistencies which may have happened between
  	 * calls. These are code bugs as di_blkno is not expected to
  	 * change once returned from ocfs2_find_new_inode_loc()
  	 */
  	BUG_ON(res->sr_blkno != di_blkno);
  
  	ret = ocfs2_read_group_descriptor(ac->ac_inode, di,
  					  res->sr_bg_stable_blkno, &bg_bh);
  	if (ret) {
  		mlog_errno(ret);
  		goto out;
  	}
  
  	bg = (struct ocfs2_group_desc *) bg_bh->b_data;
  	chain = le16_to_cpu(bg->bg_chain);
  
  	ret = ocfs2_alloc_dinode_update_counts(ac->ac_inode, handle,
  					       ac->ac_bh, res->sr_bits,
  					       chain);
  	if (ret) {
  		mlog_errno(ret);
  		goto out;
  	}
  
  	ret = ocfs2_block_group_set_bits(handle,
  					 ac->ac_inode,
  					 bg,
  					 bg_bh,
  					 res->sr_bit_offset,
  					 res->sr_bits);
  	if (ret < 0) {
  		mlog_errno(ret);
  		goto out;
  	}

  	trace_ocfs2_claim_new_inode_at_loc((unsigned long long)di_blkno,
  					   res->sr_bits);

  
  	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;
  	ac->ac_bits_given++;
  	ocfs2_save_inode_ac_group(dir, ac);
  
  out:
  	brelse(bg_bh);
  
  	return ret;
  }

  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;

  	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:

  	if (status)
  		mlog_errno(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);

  	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!
  ", 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 */