[PATCH] OCFS2: The Second Oracle Cluster Filesystem

The OCFS2 file system module.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>

1 files changed, 1651 insertions, 0 deletions

diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
new file mode 100644
index 0000000..c46c164
--- /dev/null
+++ b/fs/ocfs2/suballoc.c
@@ -0,0 +1,1651 @@
+/* -*- 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 "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"
+
+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(struct ocfs2_journal_handle *handle,
+				  struct inode *alloc_inode,
+				  struct buffer_head *bg_bh,
+				  u64 group_blkno,
+				  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);
+
+static int ocfs2_reserve_suballoc_bits(struct ocfs2_super *osb,
+				       struct ocfs2_alloc_context *ac);
+
+static int ocfs2_cluster_group_search(struct inode *inode,
+				      struct buffer_head *group_bh,
+				      u32 bits_wanted, u32 min_bits,
+				      u16 *bit_off, u16 *bits_found);
+static int ocfs2_block_group_search(struct inode *inode,
+				    struct buffer_head *group_bh,
+				    u32 bits_wanted, u32 min_bits,
+				    u16 *bit_off, u16 *bits_found);
+static int ocfs2_search_chain(struct ocfs2_alloc_context *ac,
+			      u32 bits_wanted,
+			      u32 min_bits,
+			      u16 *bit_off,
+			      unsigned int *num_bits,
+			      u64 *bg_blkno);
+static int ocfs2_claim_suballoc_bits(struct ocfs2_super *osb,
+				     struct ocfs2_alloc_context *ac,
+				     u32 bits_wanted,
+				     u32 min_bits,
+				     u16 *bit_off,
+				     unsigned int *num_bits,
+				     u64 *bg_blkno);
+static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,
+					 int nr);
+static int ocfs2_block_group_find_clear_bits(struct ocfs2_super *osb,
+					     struct buffer_head *bg_bh,
+					     unsigned int bits_wanted,
+					     u16 *bit_off,
+					     u16 *bits_found);
+static inline int ocfs2_block_group_set_bits(struct ocfs2_journal_handle *handle,
+					     struct inode *alloc_inode,
+					     struct ocfs2_group_desc *bg,
+					     struct buffer_head *group_bh,
+					     unsigned int bit_off,
+					     unsigned int num_bits);
+static inline int ocfs2_block_group_clear_bits(struct ocfs2_journal_handle *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(struct ocfs2_journal_handle *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 int ocfs2_free_suballoc_bits(struct ocfs2_journal_handle *handle,
+				    struct inode *alloc_inode,
+				    struct buffer_head *alloc_bh,
+				    unsigned int start_bit,
+				    u64 bg_blkno,
+				    unsigned int count);
+static inline u64 ocfs2_which_suballoc_group(u64 block,
+					     unsigned int bit);
+static inline u32 ocfs2_desc_bitmap_to_cluster_off(struct inode *inode,
+						   u64 bg_blkno,
+						   u16 bg_bit_off);
+static inline u64 ocfs2_which_cluster_group(struct inode *inode,
+					    u32 cluster);
+static inline void ocfs2_block_to_cluster_group(struct inode *inode,
+						u64 data_blkno,
+						u64 *bg_blkno,
+						u16 *bg_bit_off);
+
+void ocfs2_free_alloc_context(struct ocfs2_alloc_context *ac)
+{
+	if (ac->ac_inode)
+		iput(ac->ac_inode);
+	if (ac->ac_bh)
+		brelse(ac->ac_bh);
+	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);
+}
+
+static int ocfs2_block_group_fill(struct ocfs2_journal_handle *handle,
+				  struct inode *alloc_inode,
+				  struct buffer_head *bg_bh,
+				  u64 group_blkno,
+				  u16 my_chain,
+				  struct ocfs2_chain_list *cl)
+{
+	int status = 0;
+	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 (%"MLFu64") "
+			    "!= b_blocknr (%llu)", group_blkno,
+			    (unsigned long long) bg_bh->b_blocknr);
+		status = -EIO;
+		goto bail;
+	}
+
+	status = ocfs2_journal_access(handle,
+				      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));
+	bg->bg_bits = cpu_to_le16(ocfs2_bits_per_group(cl));
+	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);
+	/* 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);
+
+	status = ocfs2_journal_dirty(handle, bg_bh);
+	if (status < 0)
+		mlog_errno(status);
+
+	/* 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;
+}
+
+/*
+ * 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)
+{
+	int status, credits;
+	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) bh->b_data;
+	struct ocfs2_chain_list *cl;
+	struct ocfs2_alloc_context *ac = NULL;
+	struct ocfs2_journal_handle *handle = NULL;
+	u32 bit_off, num_bits;
+	u16 alloc_rec;
+	u64 bg_blkno;
+	struct buffer_head *bg_bh = NULL;
+	struct ocfs2_group_desc *bg;
+
+	BUG_ON(ocfs2_is_cluster_bitmap(alloc_inode));
+
+	mlog_entry_void();
+
+	handle = ocfs2_alloc_handle(osb);
+	if (!handle) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	cl = &fe->id2.i_chain;
+	status = ocfs2_reserve_clusters(osb,
+					handle,
+					le16_to_cpu(cl->cl_cpg),
+					&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, handle, credits);
+	if (IS_ERR(handle)) {
+		status = PTR_ERR(handle);
+		handle = NULL;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	status = ocfs2_claim_clusters(osb,
+				      handle,
+				      ac,
+				      le16_to_cpu(cl->cl_cpg),
+				      &bit_off,
+				      &num_bits);
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto bail;
+	}
+
+	alloc_rec = ocfs2_find_smallest_chain(cl);
+
+	/* setup the group */
+	bg_blkno = ocfs2_clusters_to_blocks(osb->sb, bit_off);
+	mlog(0, "new descriptor, record %u, at block %"MLFu64"\n",
+	     alloc_rec, 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(alloc_inode, bg_bh);
+
+	status = ocfs2_block_group_fill(handle,
+					alloc_inode,
+					bg_bh,
+					bg_blkno,
+					alloc_rec,
+					cl);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	bg = (struct ocfs2_group_desc *) bg_bh->b_data;
+
+	status = ocfs2_journal_access(handle, alloc_inode,
+				      bh, OCFS2_JOURNAL_ACCESS_WRITE);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	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  = cpu_to_le64(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));
+
+	status = ocfs2_journal_dirty(handle, bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	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_align_bytes_to_sectors(i_size_read(alloc_inode));
+
+	status = 0;
+bail:
+	if (handle)
+		ocfs2_commit_trans(handle);
+
+	if (ac)
+		ocfs2_free_alloc_context(ac);
+
+	if (bg_bh)
+		brelse(bg_bh);
+
+	mlog_exit(status);
+	return status;
+}
+
+static int ocfs2_reserve_suballoc_bits(struct ocfs2_super *osb,
+				       struct ocfs2_alloc_context *ac)
+{
+	int status;
+	u32 bits_wanted = ac->ac_bits_wanted;
+	struct inode *alloc_inode = ac->ac_inode;
+	struct buffer_head *bh = NULL;
+	struct ocfs2_journal_handle *handle = ac->ac_handle;
+	struct ocfs2_dinode *fe;
+	u32 free_bits;
+
+	mlog_entry_void();
+
+	BUG_ON(handle->flags & OCFS2_HANDLE_STARTED);
+
+	ocfs2_handle_add_inode(handle, alloc_inode);
+	status = ocfs2_meta_lock(alloc_inode, handle, &bh, 1);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	fe = (struct ocfs2_dinode *) bh->b_data;
+	if (!OCFS2_IS_VALID_DINODE(fe)) {
+		OCFS2_RO_ON_INVALID_DINODE(alloc_inode->i_sb, fe);
+		status = -EIO;
+		goto bail;
+	}
+	if (!(fe->i_flags & cpu_to_le32(OCFS2_CHAIN_FL))) {
+		ocfs2_error(alloc_inode->i_sb, "Invalid chain allocator "
+			    "# %"MLFu64, 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;
+		}
+
+		status = ocfs2_block_group_alloc(osb, alloc_inode, bh);
+		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:
+	if (bh)
+		brelse(bh);
+
+	mlog_exit(status);
+	return status;
+}
+
+int ocfs2_reserve_new_metadata(struct ocfs2_super *osb,
+			       struct ocfs2_journal_handle *handle,
+			       struct ocfs2_dinode *fe,
+			       struct ocfs2_alloc_context **ac)
+{
+	int status;
+	struct inode *alloc_inode = NULL;
+
+	*ac = kcalloc(1, sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
+	if (!(*ac)) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	(*ac)->ac_bits_wanted = ocfs2_extend_meta_needed(fe);
+	(*ac)->ac_handle = handle;
+	(*ac)->ac_which = OCFS2_AC_USE_META;
+
+#ifndef OCFS2_USE_ALL_METADATA_SUBALLOCATORS
+	alloc_inode = ocfs2_get_system_file_inode(osb,
+						  EXTENT_ALLOC_SYSTEM_INODE,
+						  0);
+#else
+	alloc_inode = ocfs2_get_system_file_inode(osb,
+						  EXTENT_ALLOC_SYSTEM_INODE,
+						  osb->slot_num);
+#endif
+	if (!alloc_inode) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	(*ac)->ac_inode = igrab(alloc_inode);
+	(*ac)->ac_group_search = ocfs2_block_group_search;
+
+	status = ocfs2_reserve_suballoc_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 (alloc_inode)
+		iput(alloc_inode);
+
+	mlog_exit(status);
+	return status;
+}
+
+int ocfs2_reserve_new_inode(struct ocfs2_super *osb,
+			    struct ocfs2_journal_handle *handle,
+			    struct ocfs2_alloc_context **ac)
+{
+	int status;
+	struct inode *alloc_inode = NULL;
+
+	*ac = kcalloc(1, sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
+	if (!(*ac)) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	(*ac)->ac_bits_wanted = 1;
+	(*ac)->ac_handle = handle;
+	(*ac)->ac_which = OCFS2_AC_USE_INODE;
+
+	alloc_inode = ocfs2_get_system_file_inode(osb,
+						  INODE_ALLOC_SYSTEM_INODE,
+						  osb->slot_num);
+	if (!alloc_inode) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	(*ac)->ac_inode = igrab(alloc_inode);
+	(*ac)->ac_group_search = ocfs2_block_group_search;
+
+	status = ocfs2_reserve_suballoc_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 (alloc_inode)
+		iput(alloc_inode);
+
+	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_inode = ocfs2_get_system_file_inode(osb,
+						   GLOBAL_BITMAP_SYSTEM_INODE,
+						   OCFS2_INVALID_SLOT);
+	if (!ac->ac_inode) {
+		status = -EINVAL;
+		mlog(ML_ERROR, "Could not get bitmap inode!\n");
+		goto bail;
+	}
+	ac->ac_which = OCFS2_AC_USE_MAIN;
+	ac->ac_group_search = ocfs2_cluster_group_search;
+
+	status = ocfs2_reserve_suballoc_bits(osb, ac);
+	if (status < 0 && status != -ENOSPC)
+		mlog_errno(status);
+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. */
+int ocfs2_reserve_clusters(struct ocfs2_super *osb,
+			   struct ocfs2_journal_handle *handle,
+			   u32 bits_wanted,
+			   struct ocfs2_alloc_context **ac)
+{
+	int status;
+
+	mlog_entry_void();
+
+	BUG_ON(!handle);
+
+	*ac = kcalloc(1, sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
+	if (!(*ac)) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	(*ac)->ac_bits_wanted = bits_wanted;
+	(*ac)->ac_handle = handle;
+
+	status = -ENOSPC;
+	if (ocfs2_alloc_should_use_local(osb, bits_wanted)) {
+		status = ocfs2_reserve_local_alloc_bits(osb,
+							handle,
+							bits_wanted,
+							*ac);
+		if ((status < 0) && (status != -ENOSPC)) {
+			mlog_errno(status);
+			goto bail;
+		} else if (status == -ENOSPC) {
+			/* reserve_local_bits will return enospc with
+			 * the local alloc inode still locked, so we
+			 * can change this safely here. */
+			mlog(0, "Disabling local alloc\n");
+			/* We set to OCFS2_LA_DISABLED so that umount
+			 * can clean up what's left of the local
+			 * allocation */
+			osb->local_alloc_state = OCFS2_LA_DISABLED;
+		}
+	}
+
+	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;
+}
+
+/*
+ * 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 seperate 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;
+
+	if (ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap))
+		return 0;
+	if (!buffer_jbd(bg_bh) || !bh2jh(bg_bh)->b_committed_data)
+		return 1;
+
+	bg = (struct ocfs2_group_desc *) bh2jh(bg_bh)->b_committed_data;
+	return !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
+}
+
+static int ocfs2_block_group_find_clear_bits(struct ocfs2_super *osb,
+					     struct buffer_head *bg_bh,
+					     unsigned int bits_wanted,
+					     u16 *bit_off,
+					     u16 *bits_found)
+{
+	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;
+
+	if (!OCFS2_IS_VALID_GROUP_DESC(bg)) {
+		OCFS2_RO_ON_INVALID_GROUP_DESC(osb->sb, bg);
+		return -EIO;
+	}
+
+	found = start = best_offset = best_size = 0;
+	bitmap = bg->bg_bitmap;
+
+	while((offset = ocfs2_find_next_zero_bit(bitmap,
+						 le16_to_cpu(bg->bg_bits),
+						 start)) != -1) {
+		if (offset == le16_to_cpu(bg->bg_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;
+		}
+	}
+
+	/* XXX: I think the first clause is equivalent to the second
+	 * 	- jlbec */
+	if (found == bits_wanted) {
+		*bit_off = start - found;
+		*bits_found = found;
+	} else if (best_size) {
+		*bit_off = best_offset;
+		*bits_found = 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(struct ocfs2_journal_handle *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();
+
+	if (!OCFS2_IS_VALID_GROUP_DESC(bg)) {
+		OCFS2_RO_ON_INVALID_GROUP_DESC(alloc_inode->i_sb, bg);
+		status = -EIO;
+		goto bail;
+	}
+	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(handle,
+				      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);
+
+	status = ocfs2_journal_dirty(handle,
+				     group_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+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(struct ocfs2_journal_handle *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;
+
+	if (!OCFS2_IS_VALID_DINODE(fe)) {
+		OCFS2_RO_ON_INVALID_DINODE(alloc_inode->i_sb, fe);
+		status = -EIO;
+		goto out;
+	}
+	if (!OCFS2_IS_VALID_GROUP_DESC(bg)) {
+		OCFS2_RO_ON_INVALID_GROUP_DESC(alloc_inode->i_sb, bg);
+		status = -EIO;
+		goto out;
+	}
+	if (!OCFS2_IS_VALID_GROUP_DESC(prev_bg)) {
+		OCFS2_RO_ON_INVALID_GROUP_DESC(alloc_inode->i_sb, prev_bg);
+		status = -EIO;
+		goto out;
+	}
+
+	mlog(0, "In suballoc %"MLFu64", chain %u, move group %"MLFu64" to "
+	     "top, prev = %"MLFu64"\n",
+	     fe->i_blkno, chain, bg->bg_blkno, 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(handle, 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;
+
+	status = ocfs2_journal_dirty(handle, prev_bg_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto out_rollback;
+	}
+
+	status = ocfs2_journal_access(handle, 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;
+
+	status = ocfs2_journal_dirty(handle, bg_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto out_rollback;
+	}
+
+	status = ocfs2_journal_access(handle, 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;
+
+	status = ocfs2_journal_dirty(handle, fe_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto out_rollback;
+	}
+
+	status = 0;
+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);
+	}
+out:
+	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,
+				      u16 *bit_off, u16 *bits_found)
+{
+	int search = -ENOSPC;
+	int ret;
+	struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) group_bh->b_data;
+	u16 tmp_off, tmp_found;
+
+	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,
+							&tmp_off, &tmp_found);
+		if (ret)
+			return ret;
+
+		/* 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 <= tmp_found) {
+			*bit_off = tmp_off;
+			*bits_found = tmp_found;
+			search = 0; /* success */
+		}
+	}
+
+	return search;
+}
+
+static int ocfs2_block_group_search(struct inode *inode,
+				    struct buffer_head *group_bh,
+				    u32 bits_wanted, u32 min_bits,
+				    u16 *bit_off, u16 *bits_found)
+{
+	int ret = -ENOSPC;
+	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,
+							bit_off, bits_found);
+
+	return ret;
+}
+
+static int ocfs2_search_chain(struct ocfs2_alloc_context *ac,
+			      u32 bits_wanted,
+			      u32 min_bits,
+			      u16 *bit_off,
+			      unsigned int *num_bits,
+			      u64 *bg_blkno)
+{
+	int status;
+	u16 chain, tmp_bits;
+	u32 tmp_used;
+	u64 next_group;
+	struct ocfs2_journal_handle *handle = ac->ac_handle;
+	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 %"MLFu64"\n",
+	     bits_wanted, chain, OCFS2_I(alloc_inode)->ip_blkno);
+
+	status = ocfs2_read_block(OCFS2_SB(alloc_inode->i_sb),
+				  le64_to_cpu(cl->cl_recs[chain].c_blkno),
+				  &group_bh, OCFS2_BH_CACHED, alloc_inode);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+	bg = (struct ocfs2_group_desc *) group_bh->b_data;
+	if (!OCFS2_IS_VALID_GROUP_DESC(bg)) {
+		OCFS2_RO_ON_INVALID_GROUP_DESC(alloc_inode->i_sb, bg);
+		status = -EIO;
+		goto bail;
+	}
+
+	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, bit_off,
+					     &tmp_bits)) == -ENOSPC) {
+		if (!bg->bg_next_group)
+			break;
+
+		if (prev_group_bh) {
+			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_block(OCFS2_SB(alloc_inode->i_sb),
+					  next_group, &group_bh,
+					  OCFS2_BH_CACHED, alloc_inode);
+		if (status < 0) {
+			mlog_errno(status);
+			goto bail;
+		}
+		bg = (struct ocfs2_group_desc *) group_bh->b_data;
+		if (!OCFS2_IS_VALID_GROUP_DESC(bg)) {
+			OCFS2_RO_ON_INVALID_GROUP_DESC(alloc_inode->i_sb, bg);
+			status = -EIO;
+			goto bail;
+		}
+	}
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto bail;
+	}
+
+	mlog(0, "alloc succeeds: we give %u bits from block group %"MLFu64"\n",
+	     tmp_bits, bg->bg_blkno);
+
+	*num_bits = tmp_bits;
+
+	BUG_ON(*num_bits == 0);
+
+	/*
+	 * 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, *num_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(handle,
+				      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(*num_bits + tmp_used);
+	le32_add_cpu(&cl->cl_recs[chain].c_free, -(*num_bits));
+
+	status = ocfs2_journal_dirty(handle,
+				     ac->ac_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	status = ocfs2_block_group_set_bits(handle,
+					    alloc_inode,
+					    bg,
+					    group_bh,
+					    *bit_off,
+					    *num_bits);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	mlog(0, "Allocated %u bits from suballocator %"MLFu64"\n",
+	     *num_bits, fe->i_blkno);
+
+	*bg_blkno = le64_to_cpu(bg->bg_blkno);
+bail:
+	if (group_bh)
+		brelse(group_bh);
+	if (prev_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_super *osb,
+				     struct ocfs2_alloc_context *ac,
+				     u32 bits_wanted,
+				     u32 min_bits,
+				     u16 *bit_off,
+				     unsigned int *num_bits,
+				     u64 *bg_blkno)
+{
+	int status;
+	u16 victim, i;
+	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;
+	if (!OCFS2_IS_VALID_DINODE(fe)) {
+		OCFS2_RO_ON_INVALID_DINODE(osb->sb, fe);
+		status = -EIO;
+		goto bail;
+	}
+	if (le32_to_cpu(fe->id1.bitmap1.i_used) >=
+	    le32_to_cpu(fe->id1.bitmap1.i_total)) {
+		ocfs2_error(osb->sb, "Chain allocator dinode %"MLFu64" has %u"
+			    "used bits but only %u total.",
+			    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;
+	}
+
+	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, bits_wanted, min_bits, bit_off,
+				    num_bits, bg_blkno);
+	if (!status)
+		goto bail;
+	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, bits_wanted, min_bits,
+					    bit_off, num_bits,
+					    bg_blkno);
+		if (!status)
+			break;
+		if (status < 0 && status != -ENOSPC) {
+			mlog_errno(status);
+			goto bail;
+		}
+	}
+bail:
+
+	mlog_exit(status);
+	return status;
+}
+
+int ocfs2_claim_metadata(struct ocfs2_super *osb,
+			 struct ocfs2_journal_handle *handle,
+			 struct ocfs2_alloc_context *ac,
+			 u32 bits_wanted,
+			 u16 *suballoc_bit_start,
+			 unsigned int *num_bits,
+			 u64 *blkno_start)
+{
+	int status;
+	u64 bg_blkno;
+
+	BUG_ON(!ac);
+	BUG_ON(ac->ac_bits_wanted < (ac->ac_bits_given + bits_wanted));
+	BUG_ON(ac->ac_which != OCFS2_AC_USE_META);
+	BUG_ON(ac->ac_handle != handle);
+
+	status = ocfs2_claim_suballoc_bits(osb,
+					   ac,
+					   bits_wanted,
+					   1,
+					   suballoc_bit_start,
+					   num_bits,
+					   &bg_blkno);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+	atomic_inc(&osb->alloc_stats.bg_allocs);
+
+	*blkno_start = bg_blkno + (u64) *suballoc_bit_start;
+	ac->ac_bits_given += (*num_bits);
+	status = 0;
+bail:
+	mlog_exit(status);
+	return status;
+}
+
+int ocfs2_claim_new_inode(struct ocfs2_super *osb,
+			  struct ocfs2_journal_handle *handle,
+			  struct ocfs2_alloc_context *ac,
+			  u16 *suballoc_bit,
+			  u64 *fe_blkno)
+{
+	int status;
+	unsigned int num_bits;
+	u64 bg_blkno;
+
+	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);
+	BUG_ON(ac->ac_handle != handle);
+
+	status = ocfs2_claim_suballoc_bits(osb,
+					   ac,
+					   1,
+					   1,
+					   suballoc_bit,
+					   &num_bits,
+					   &bg_blkno);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+	atomic_inc(&osb->alloc_stats.bg_allocs);
+
+	BUG_ON(num_bits != 1);
+
+	*fe_blkno = bg_blkno + (u64) (*suballoc_bit);
+	ac->ac_bits_given++;
+	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. */
+static inline 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(struct ocfs2_super *osb,
+			 struct ocfs2_journal_handle *handle,
+			 struct ocfs2_alloc_context *ac,
+			 u32 min_clusters,
+			 u32 *cluster_start,
+			 u32 *num_clusters)
+{
+	int status;
+	unsigned int bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;
+	u64 bg_blkno;
+	u16 bg_bit_off;
+
+	mlog_entry_void();
+
+	BUG_ON(!ac);
+	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);
+	BUG_ON(ac->ac_handle != handle);
+
+	if (ac->ac_which == OCFS2_AC_USE_LOCAL) {
+		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 exceeds "
+				       "group bitmap size!");
+			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(osb,
+						   ac,
+						   bits_wanted,
+						   min_clusters,
+						   &bg_bit_off,
+						   num_clusters,
+						   &bg_blkno);
+		if (!status) {
+			*cluster_start =
+				ocfs2_desc_bitmap_to_cluster_off(ac->ac_inode,
+								 bg_blkno,
+								 bg_bit_off);
+			atomic_inc(&osb->alloc_stats.bitmap_data);
+		}
+	}
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto bail;
+	}
+
+	ac->ac_bits_given += *num_clusters;
+
+bail:
+	mlog_exit(status);
+	return status;
+}
+
+static inline int ocfs2_block_group_clear_bits(struct ocfs2_journal_handle *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;
+	unsigned int tmp;
+	int journal_type = OCFS2_JOURNAL_ACCESS_WRITE;
+	struct ocfs2_group_desc *undo_bg = NULL;
+
+	mlog_entry_void();
+
+	if (!OCFS2_IS_VALID_GROUP_DESC(bg)) {
+		OCFS2_RO_ON_INVALID_GROUP_DESC(alloc_inode->i_sb, bg);
+		status = -EIO;
+		goto bail;
+	}
+
+	mlog(0, "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(handle, alloc_inode, group_bh,
+				      journal_type);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	if (ocfs2_is_cluster_bitmap(alloc_inode))
+		undo_bg = (struct ocfs2_group_desc *) bh2jh(group_bh)->b_committed_data;
+
+	tmp = num_bits;
+	while(tmp--) {
+		ocfs2_clear_bit((bit_off + tmp),
+				(unsigned long *) bg->bg_bitmap);
+		if (ocfs2_is_cluster_bitmap(alloc_inode))
+			ocfs2_set_bit(bit_off + tmp,
+				      (unsigned long *) undo_bg->bg_bitmap);
+	}
+	le16_add_cpu(&bg->bg_free_bits_count, num_bits);
+
+	status = ocfs2_journal_dirty(handle, group_bh);
+	if (status < 0)
+		mlog_errno(status);
+bail:
+	return status;
+}
+
+/*
+ * expects the suballoc inode to already be locked.
+ */
+static int ocfs2_free_suballoc_bits(struct ocfs2_journal_handle *handle,
+				    struct inode *alloc_inode,
+				    struct buffer_head *alloc_bh,
+				    unsigned int start_bit,
+				    u64 bg_blkno,
+				    unsigned int count)
+{
+	int status = 0;
+	u32 tmp_used;
+	struct ocfs2_super *osb = OCFS2_SB(alloc_inode->i_sb);
+	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();
+
+	if (!OCFS2_IS_VALID_DINODE(fe)) {
+		OCFS2_RO_ON_INVALID_DINODE(alloc_inode->i_sb, fe);
+		status = -EIO;
+		goto bail;
+	}
+	BUG_ON((count + start_bit) > ocfs2_bits_per_group(cl));
+
+	mlog(0, "suballocator %"MLFu64": freeing %u bits from group %"MLFu64
+	     ", starting at %u\n",
+	     OCFS2_I(alloc_inode)->ip_blkno, count, bg_blkno,
+	     start_bit);
+
+	status = ocfs2_read_block(osb, bg_blkno, &group_bh, OCFS2_BH_CACHED,
+				  alloc_inode);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	group = (struct ocfs2_group_desc *) group_bh->b_data;
+	if (!OCFS2_IS_VALID_GROUP_DESC(group)) {
+		OCFS2_RO_ON_INVALID_GROUP_DESC(alloc_inode->i_sb, group);
+		status = -EIO;
+		goto bail;
+	}
+	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);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	status = ocfs2_journal_access(handle, 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);
+
+	status = ocfs2_journal_dirty(handle, alloc_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+bail:
+	if (group_bh)
+		brelse(group_bh);
+
+	mlog_exit(status);
+	return status;
+}
+
+static inline u64 ocfs2_which_suballoc_group(u64 block, unsigned int bit)
+{
+	u64 group = block - (u64) bit;
+
+	return group;
+}
+
+int ocfs2_free_dinode(struct ocfs2_journal_handle *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);
+
+	return ocfs2_free_suballoc_bits(handle, inode_alloc_inode,
+					inode_alloc_bh, bit, bg_blkno, 1);
+}
+
+int ocfs2_free_extent_block(struct ocfs2_journal_handle *handle,
+			    struct inode *eb_alloc_inode,
+			    struct buffer_head *eb_alloc_bh,
+			    struct ocfs2_extent_block *eb)
+{
+	u64 blk = le64_to_cpu(eb->h_blkno);
+	u16 bit = le16_to_cpu(eb->h_suballoc_bit);
+	u64 bg_blkno = ocfs2_which_suballoc_group(blk, bit);
+
+	return ocfs2_free_suballoc_bits(handle, eb_alloc_inode, eb_alloc_bh,
+					bit, bg_blkno, 1);
+}
+
+int ocfs2_free_clusters(struct ocfs2_journal_handle *handle,
+		       struct inode *bitmap_inode,
+		       struct buffer_head *bitmap_bh,
+		       u64 start_blk,
+		       unsigned int num_clusters)
+{
+	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 %"MLFu64"\n",
+	     num_clusters, start_blk);
+	mlog(0, "bg_blkno = %"MLFu64", bg_start_bit = %u\n",
+	     bg_blkno, bg_start_bit);
+
+	status = ocfs2_free_suballoc_bits(handle, bitmap_inode, bitmap_bh,
+					  bg_start_bit, bg_blkno,
+					  num_clusters);
+	if (status < 0)
+		mlog_errno(status);
+
+	mlog_exit(status);
+	return status;
+}
+
+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:      %"MLFu64"\n", bg->bg_next_group);
+	printk("bg_parent_dinode:   %"MLFu64"\n", bg->bg_parent_dinode);
+	printk("bg_blkno:           %"MLFu64"\n", bg->bg_blkno);
+}
+
+static inline void ocfs2_debug_suballoc_inode(struct ocfs2_dinode *fe)
+{
+	int i;
+
+	printk("Suballoc Inode %"MLFu64":\n", fe->i_blkno);
+	printk("i_signature:                  %s\n", fe->i_signature);
+	printk("i_size:                       %"MLFu64"\n", 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: %"MLFu64"\n", i,
+		       fe->id2.i_chain.cl_recs[i].c_blkno);
+	}
+}