[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 000000000000..c46c164aefbb
--- /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);
+        }
+}