/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * suballoc.c
 *
 * metadata alloc and free
 * Inspired by ext3 block groups.
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

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

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "blockcheck.h"
#include "dlmglue.h"
#include "inode.h"
#include "journal.h"
#include "localalloc.h"
#include "suballoc.h"
#include "super.h"
#include "sysfile.h"
#include "uptodate.h"
#include "ocfs2_trace.h"

#include "buffer_head_io.h"

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

#define OCFS2_MAX_TO_STEAL              1024

struct ocfs2_suballoc_result {
        u64             sr_bg_blkno;    /* The bg we allocated from.  Set
                                           to 0 when a block group is
                                           contiguous. */
        u64             sr_bg_stable_blkno; /*
                                             * Doesn't change, always
                                             * set to target block
                                             * group descriptor
                                             * block.
                                             */
        u64             sr_blkno;       /* The first allocated block */
        unsigned int    sr_bit_offset;  /* The bit in the bg */
        unsigned int    sr_bits;        /* How many bits we claimed */
};

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

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

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

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

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

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

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

                inode_unlock(inode);

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

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

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

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

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

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

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

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

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

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

        return 0;
}

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

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

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

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

        return 0;
}

#undef do_error

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

        BUG_ON(!buffer_uptodate(bh));

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

        return rc;
}

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

        trace_ocfs2_validate_group_descriptor(
                                        (unsigned long long)bh->b_blocknr);

        BUG_ON(!buffer_uptodate(bh));

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

        /*
         * Errors after here are fatal.
         */

        return ocfs2_validate_gd_self(sb, bh, 0);
}

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

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

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

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

out:
        return rc;
}

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

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

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

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

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

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

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

        ocfs2_journal_dirty(handle, bg_bh);

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

bail:
        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

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

        /* setup the group */
        bg_blkno = ocfs2_clusters_to_blocks(osb->sb, bit_off);
        trace_ocfs2_block_group_alloc_contig(
             (unsigned long long)bg_blkno, alloc_rec);

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

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

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

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

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

                min_bits >>= 1;
        }

        return status;
}

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

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

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

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

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

        ocfs2_journal_dirty(handle, bg_bh);

bail:
        return status;
}

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

        if (!bg_bh)
                return;

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

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

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

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

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

        /*
         * We're going to be grabbing from multiple cluster groups.
         * We don't have enough credits to relink them all, and the
         * cluster groups will be staying in cache for the duration of
         * this operation.
         */
        ac->ac_disable_chain_relink = 1;

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

        /* setup the group */
        bg_blkno = ocfs2_clusters_to_blocks(osb->sb, bit_off);
        trace_ocfs2_block_group_alloc_discontig(
                                (unsigned long long)bg_blkno, alloc_rec);

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

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

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

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

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

        BUG_ON(ocfs2_is_cluster_bitmap(alloc_inode));

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

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

        if (last_alloc_group && *last_alloc_group != 0) {
                trace_ocfs2_block_group_alloc(
                                (unsigned long long)*last_alloc_group);
                ac->ac_last_group = *last_alloc_group;
        }

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

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

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

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

        ocfs2_journal_dirty(handle, bh);

        spin_lock(&OCFS2_I(alloc_inode)->ip_lock);
        OCFS2_I(alloc_inode)->ip_clusters = le32_to_cpu(fe->i_clusters);
        fe->i_size = cpu_to_le64(ocfs2_clusters_to_bytes(alloc_inode->i_sb,
                                             le32_to_cpu(fe->i_clusters)));
        spin_unlock(&OCFS2_I(alloc_inode)->ip_lock);
        i_size_write(alloc_inode, le64_to_cpu(fe->i_size));
        alloc_inode->i_blocks = ocfs2_inode_sector_count(alloc_inode);
        ocfs2_update_inode_fsync_trans(handle, alloc_inode, 0);

        status = 0;

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

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

        if (ac)
                ocfs2_free_alloc_context(ac);

        brelse(bg_bh);

        if (status)
                mlog_errno(status);
        return status;
}

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

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

        inode_lock(alloc_inode);

        status = ocfs2_inode_lock(alloc_inode, &bh, 1);
        if (status < 0) {
                inode_unlock(alloc_inode);
                iput(alloc_inode);

                mlog_errno(status);
                return status;
        }

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

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

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

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

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

        if (bits_wanted > free_bits) {
                /* cluster bitmap never grows */
                if (ocfs2_is_cluster_bitmap(alloc_inode)) {
                        trace_ocfs2_reserve_suballoc_bits_nospc(bits_wanted,
                                                                free_bits);
                        status = -ENOSPC;
                        goto bail;
                }

                if (!(flags & ALLOC_NEW_GROUP)) {
                        trace_ocfs2_reserve_suballoc_bits_no_new_group(
                                                slot, bits_wanted, free_bits);
                        status = -ENOSPC;
                        goto bail;
                }

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

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

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

        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

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

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

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

        return slot;
}

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

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

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

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

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

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

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

                ocfs2_free_ac_resource(ac);
        }

        return status;
}

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

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

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

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

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

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

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


        if (status >= 0) {

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

        ocfs2_free_ac_resource(*ac);

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

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

        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

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

        (*ac)->ac_group_search = ocfs2_block_group_search;

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

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

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

                spin_lock(&osb->osb_lock);
                osb->osb_inode_alloc_group = alloc_group;
                spin_unlock(&osb->osb_lock);
                trace_ocfs2_reserve_new_inode_new_group(
                        (unsigned long long)alloc_group);

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

        ocfs2_free_ac_resource(*ac);

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

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

        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

        return status;
}

/* Callers don't need to care which bitmap (local alloc or main) to
 * use so we figure it out for them, but unfortunately this clutters
 * things a bit. */
static int ocfs2_reserve_clusters_with_limit(struct ocfs2_super *osb,
                                             u32 bits_wanted, u64 max_block,
                                             int flags,
                                             struct ocfs2_alloc_context **ac)
{
        int status, ret = 0;
        int retried = 0;

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

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

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

        if (status == -ENOSPC) {
retry:
                status = ocfs2_reserve_cluster_bitmap_bits(osb, *ac);
                /* Retry if there is sufficient space cached in truncate log */
                if (status == -ENOSPC && !retried) {
                        retried = 1;
                        ocfs2_inode_unlock((*ac)->ac_inode, 1);
                        inode_unlock((*ac)->ac_inode);

                        ret = ocfs2_try_to_free_truncate_log(osb, bits_wanted);
                        if (ret == 1) {
                                iput((*ac)->ac_inode);
                                (*ac)->ac_inode = NULL;
                                goto retry;
                        }

                        if (ret < 0)
                                mlog_errno(ret);

                        inode_lock((*ac)->ac_inode);
                        ret = ocfs2_inode_lock((*ac)->ac_inode, NULL, 1);
                        if (ret < 0) {
                                mlog_errno(ret);
                                inode_unlock((*ac)->ac_inode);
                                iput((*ac)->ac_inode);
                                (*ac)->ac_inode = NULL;
                                goto bail;
                        }
                }
                if (status < 0) {
                        if (status != -ENOSPC)
                                mlog_errno(status);
                        goto bail;
                }
        }

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

        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

        if (!buffer_jbd(bg_bh))
                return 1;

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

        return ret;
}

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

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

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

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

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

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

        return status;
}

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

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

        trace_ocfs2_block_group_set_bits(bit_off, num_bits);

        if (ocfs2_is_cluster_bitmap(alloc_inode))
                journal_type = OCFS2_JOURNAL_ACCESS_UNDO;

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

        le16_add_cpu(&bg->bg_free_bits_count, -num_bits);
        if (le16_to_cpu(bg->bg_free_bits_count) > le16_to_cpu(bg->bg_bits)) {
                return ocfs2_error(alloc_inode->i_sb, "Group descriptor # %llu has bit count %u but claims %u are freed. num_bits %d\n",
                                   (unsigned long long)le64_to_cpu(bg->bg_blkno),
                                   le16_to_cpu(bg->bg_bits),
                                   le16_to_cpu(bg->bg_free_bits_count),
                                   num_bits);
        }
        while(num_bits--)
                ocfs2_set_bit(bit_off++, bitmap);

        ocfs2_journal_dirty(handle, group_bh);

bail:
        return status;
}

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

        BUG_ON(!cl->cl_next_free_rec);

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

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

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

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

        trace_ocfs2_relink_block_group(
                (unsigned long long)le64_to_cpu(fe->i_blkno), chain,
                (unsigned long long)le64_to_cpu(bg->bg_blkno),
                (unsigned long long)le64_to_cpu(prev_bg->bg_blkno));

        bg_ptr = le64_to_cpu(bg->bg_next_group);
        prev_bg_ptr = le64_to_cpu(prev_bg->bg_next_group);

        status = ocfs2_journal_access_gd(handle, INODE_CACHE(alloc_inode),
                                         prev_bg_bh,
                                         OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0)
                goto out;

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

        status = ocfs2_journal_access_gd(handle, INODE_CACHE(alloc_inode),
                                         bg_bh, OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0)
                goto out_rollback_prev_bg;

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

        status = ocfs2_journal_access_di(handle, INODE_CACHE(alloc_inode),
                                         fe_bh, OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0)
                goto out_rollback_bg;

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

out:
        if (status < 0)
                mlog_errno(status);
        return status;

out_rollback_bg:
        bg->bg_next_group = cpu_to_le64(bg_ptr);
out_rollback_prev_bg:
        prev_bg->bg_next_group = cpu_to_le64(prev_bg_ptr);
        goto out;
}

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

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

        BUG_ON(!ocfs2_is_cluster_bitmap(inode));

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

                /* Tail groups in cluster bitmaps which aren't cpg
                 * aligned are prone to partial extension by a failed
                 * fs resize. If the file system resize never got to
                 * update the dinode cluster count, then we don't want
                 * to trust any clusters past it, regardless of what
                 * the group descriptor says. */
                gd_cluster_off = ocfs2_blocks_to_clusters(inode->i_sb,
                                                          le64_to_cpu(gd->bg_blkno));
                if ((gd_cluster_off + max_bits) >
                    OCFS2_I(inode)->ip_clusters) {
                        max_bits = OCFS2_I(inode)->ip_clusters - gd_cluster_off;
                        trace_ocfs2_cluster_group_search_wrong_max_bits(
                                (unsigned long long)le64_to_cpu(gd->bg_blkno),
                                le16_to_cpu(gd->bg_bits),
                                OCFS2_I(inode)->ip_clusters, max_bits);
                }

                ret = ocfs2_block_group_find_clear_bits(osb,
                                                        group_bh, bits_wanted,
                                                        max_bits, res);
                if (ret)
                        return ret;

                if (max_block) {
                        blkoff = ocfs2_clusters_to_blocks(inode->i_sb,
                                                          gd_cluster_off +
                                                          res->sr_bit_offset +
                                                          res->sr_bits);
                        trace_ocfs2_cluster_group_search_max_block(
                                (unsigned long long)blkoff,
                                (unsigned long long)max_block);
                        if (blkoff > max_block)
                                return -ENOSPC;
                }

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

        return search;
}

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

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

        if (bg->bg_free_bits_count) {
                ret = ocfs2_block_group_find_clear_bits(OCFS2_SB(inode->i_sb),
                                                        group_bh, bits_wanted,
                                                        le16_to_cpu(bg->bg_bits),
                                                        res);
                if (!ret && max_block) {
                        blkoff = le64_to_cpu(bg->bg_blkno) +
                                res->sr_bit_offset + res->sr_bits;
                        trace_ocfs2_block_group_search_max_block(
                                (unsigned long long)blkoff,
                                (unsigned long long)max_block);
                        if (blkoff > max_block)
                                ret = -ENOSPC;
                }
        }

        return ret;
}

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

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

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

out:
        return ret;
}

void ocfs2_rollback_alloc_dinode_counts(struct inode *inode,
                                       struct buffer_head *di_bh,
                                       u32 num_bits,
                                       u16 chain)
{
        u32 tmp_used;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *) di_bh->b_data;
        struct ocfs2_chain_list *cl;

        cl = (struct ocfs2_chain_list *)&di->id2.i_chain;
        tmp_used = le32_to_cpu(di->id1.bitmap1.i_used);
        di->id1.bitmap1.i_used = cpu_to_le32(tmp_used - num_bits);
        le32_add_cpu(&cl->cl_recs[chain].c_free, num_bits);
}

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

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

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

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

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

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

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

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

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

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

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

        if (ac->ac_find_loc_only)
                goto out_loc_only;

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

        ret = ocfs2_block_group_set_bits(handle, alloc_inode, gd, group_bh,
                                         res->sr_bit_offset, res->sr_bits);
        if (ret < 0) {
                ocfs2_rollback_alloc_dinode_counts(alloc_inode, ac->ac_bh,
                                               res->sr_bits,
                                               le16_to_cpu(gd->bg_chain));
                mlog_errno(ret);
        }

out_loc_only:
        *bits_left = le16_to_cpu(gd->bg_free_bits_count);

out:
        brelse(group_bh);

        return ret;
}

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

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

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

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

                brelse(prev_group_bh);
                prev_group_bh = NULL;

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

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

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

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

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

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

        if (ac->ac_find_loc_only)
                goto out_loc_only;

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

        status = ocfs2_block_group_set_bits(handle,
                                            alloc_inode,
                                            bg,
                                            group_bh,
                                            res->sr_bit_offset,
                                            res->sr_bits);
        if (status < 0) {
                ocfs2_rollback_alloc_dinode_counts(alloc_inode,
                                        ac->ac_bh, res->sr_bits, chain);
                mlog_errno(status);
                goto bail;
        }

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

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

        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

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

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

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

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

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

        status = ocfs2_search_chain(ac, handle, bits_wanted, min_bits,
                                    res, &bits_left);
        if (!status) {
                if (ocfs2_is_cluster_bitmap(ac->ac_inode))
                        hint = res->sr_bg_blkno;
                else
                        hint = ocfs2_group_from_res(res);
                goto set_hint;
        }
        if (status < 0 && status != -ENOSPC) {
                mlog_errno(status);
                goto bail;
        }

        trace_ocfs2_claim_suballoc_bits(victim);

        /* If we didn't pick a good victim, then just default to
         * searching each chain in order. Don't allow chain relinking
         * because we only calculate enough journal credits for one
         * relink per alloc. */
        ac->ac_disable_chain_relink = 1;
        for (i = 0; i < le16_to_cpu(cl->cl_next_free_rec); i ++) {
                if (i == victim)
                        continue;
                if (!cl->cl_recs[i].c_free)
                        continue;

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

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

bail:
        if (status)
                mlog_errno(status);
        return status;
}

int ocfs2_claim_metadata(handle_t *handle,

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

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

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

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

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

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

int ocfs2_find_new_inode_loc(struct inode *dir,
                             struct buffer_head *parent_fe_bh,
                             struct ocfs2_alloc_context *ac,
                             u64 *fe_blkno)
{
        int ret;
        handle_t *handle = NULL;
        struct ocfs2_suballoc_result *res;

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

        res = kzalloc(sizeof(*res), GFP_NOFS);
        if (res == NULL) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        ocfs2_init_inode_ac_group(dir, parent_fe_bh, ac);

        /*
         * The handle started here is for chain relink. Alternatively,
         * we could just disable relink for these calls.
         */
        handle = ocfs2_start_trans(OCFS2_SB(dir->i_sb), OCFS2_SUBALLOC_ALLOC);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                handle = NULL;
                mlog_errno(ret);
                goto out;
        }

        /*
         * This will instruct ocfs2_claim_suballoc_bits and
         * ocfs2_search_one_group to search but save actual allocation
         * for later.
         */
        ac->ac_find_loc_only = 1;

        ret = ocfs2_claim_suballoc_bits(ac, handle, 1, 1, res);
        if (ret < 0) {
                mlog_errno(ret);
                goto out;
        }

        ac->ac_find_loc_priv = res;
        *fe_blkno = res->sr_blkno;
        ocfs2_update_inode_fsync_trans(handle, dir, 0);
out:
        if (handle)
                ocfs2_commit_trans(OCFS2_SB(dir->i_sb), handle);

        if (ret)
                kfree(res);

        return ret;
}

int ocfs2_claim_new_inode_at_loc(handle_t *handle,
                                 struct inode *dir,
                                 struct ocfs2_alloc_context *ac,
                                 u64 *suballoc_loc,
                                 u16 *suballoc_bit,
                                 u64 di_blkno)
{
        int ret;
        u16 chain;
        struct ocfs2_suballoc_result *res = ac->ac_find_loc_priv;
        struct buffer_head *bg_bh = NULL;
        struct ocfs2_group_desc *bg;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *) ac->ac_bh->b_data;

        /*
         * Since di_blkno is being passed back in, we check for any
         * inconsistencies which may have happened between
         * calls. These are code bugs as di_blkno is not expected to
         * change once returned from ocfs2_find_new_inode_loc()
         */
        BUG_ON(res->sr_blkno != di_blkno);

        ret = ocfs2_read_group_descriptor(ac->ac_inode, di,
                                          res->sr_bg_stable_blkno, &bg_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        bg = (struct ocfs2_group_desc *) bg_bh->b_data;
        chain = le16_to_cpu(bg->bg_chain);

        ret = ocfs2_alloc_dinode_update_counts(ac->ac_inode, handle,
                                               ac->ac_bh, res->sr_bits,
                                               chain);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_block_group_set_bits(handle,
                                         ac->ac_inode,
                                         bg,
                                         bg_bh,
                                         res->sr_bit_offset,
                                         res->sr_bits);
        if (ret < 0) {
                ocfs2_rollback_alloc_dinode_counts(ac->ac_inode,
                                               ac->ac_bh, res->sr_bits, chain);
                mlog_errno(ret);
                goto out;
        }

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

        atomic_inc(&OCFS2_SB(ac->ac_inode->i_sb)->alloc_stats.bg_allocs);

        BUG_ON(res->sr_bits != 1);

        *suballoc_loc = res->sr_bg_blkno;
        *suballoc_bit = res->sr_bit_offset;
        ac->ac_bits_given++;
        ocfs2_save_inode_ac_group(dir, ac);

out:
        brelse(bg_bh);

        return ret;
}

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

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

        ocfs2_init_inode_ac_group(dir, parent_fe_bh, ac);

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

        BUG_ON(res.sr_bits != 1);

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

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

        BUG_ON(!ocfs2_is_cluster_bitmap(inode));

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

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

        BUG_ON(!ocfs2_is_cluster_bitmap(inode));

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

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

        BUG_ON(!ocfs2_is_cluster_bitmap(inode));

        *bg_blkno = ocfs2_which_cluster_group(inode,
                                              data_cluster);

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

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

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

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

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

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

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

        ac->ac_bits_given += *num_clusters;

bail:
        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

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

        trace_ocfs2_block_group_clear_bits(bit_off, num_bits);

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

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

        tmp = num_bits;
        while(tmp--) {
                ocfs2_clear_bit((bit_off + tmp),
                                (unsigned long *) bg->bg_bitmap);
                if (undo_fn)
                        undo_fn(bit_off + tmp,
                                (unsigned long *) undo_bg->bg_bitmap);
        }
        le16_add_cpu(&bg->bg_free_bits_count, num_bits);
        if (le16_to_cpu(bg->bg_free_bits_count) > le16_to_cpu(bg->bg_bits)) {
                if (undo_fn)
                        jbd_unlock_bh_state(group_bh);
                return ocfs2_error(alloc_inode->i_sb, "Group descriptor # %llu has bit count %u but claims %u are freed. num_bits %d\n",
                                   (unsigned long long)le64_to_cpu(bg->bg_blkno),
                                   le16_to_cpu(bg->bg_bits),
                                   le16_to_cpu(bg->bg_free_bits_count),
                                   num_bits);
        }

        if (undo_fn)
                jbd_unlock_bh_state(group_bh);

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

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

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

        trace_ocfs2_free_suballoc_bits(
                (unsigned long long)OCFS2_I(alloc_inode)->ip_blkno,
                (unsigned long long)bg_blkno,
                start_bit, count);

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

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

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

        status = ocfs2_journal_access_di(handle, INODE_CACHE(alloc_inode),
                                         alloc_bh, OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                ocfs2_block_group_set_bits(handle, alloc_inode, group, group_bh,
                                start_bit, count);
                goto bail;
        }

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

bail:
        brelse(group_bh);

        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

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

        /* 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.
         * 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)));


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

        trace_ocfs2_free_clusters((unsigned long long)bg_blkno,
                        (unsigned long long)start_blk,
                        bg_start_bit, num_clusters);

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

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

out:
        if (status)
                mlog_errno(status);
        return status;
}

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

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

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

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

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

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

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

        if (clusters_to_add == 0)
                goto out;

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

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

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

        return ret;
}

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

        trace_ocfs2_get_suballoc_slot_bit((unsigned long long)blkno);

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

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

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

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

bail:
        brelse(inode_bh);

        if (status)
                mlog_errno(status);
        return status;
}

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

        trace_ocfs2_test_suballoc_bit((unsigned long long)blkno,
                                      (unsigned int)bit);

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

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

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

bail:
        brelse(group_bh);

        if (status)
                mlog_errno(status);
        return status;
}

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

        trace_ocfs2_test_inode_bit((unsigned long long)blkno);

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

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

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

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

        ocfs2_inode_unlock(inode_alloc_inode, 0);
        inode_unlock(inode_alloc_inode);

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