ocfs2: Add extent tree operation for xattr value btrees

[linux-2.6/btrfs-unstable.git] / fs / ocfs2 / extent_map.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * extent_map.c
 *
 * Block/Cluster mapping functions
 *
 * Copyright (C) 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, version 2,  as published by the Free Software Foundation.
 *
 * 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/init.h>
#include <linux/types.h>
#include <linux/fiemap.h>

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

#include "ocfs2.h"

#include "alloc.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "inode.h"
#include "super.h"

#include "buffer_head_io.h"

/*
 * The extent caching implementation is intentionally trivial.
 *
 * We only cache a small number of extents stored directly on the
 * inode, so linear order operations are acceptable. If we ever want
 * to increase the size of the extent map, then these algorithms must
 * get smarter.
 */

void ocfs2_extent_map_init(struct inode *inode)
{
        struct ocfs2_inode_info *oi = OCFS2_I(inode);

        oi->ip_extent_map.em_num_items = 0;
        INIT_LIST_HEAD(&oi->ip_extent_map.em_list);
}

static void __ocfs2_extent_map_lookup(struct ocfs2_extent_map *em,
                                      unsigned int cpos,
                                      struct ocfs2_extent_map_item **ret_emi)
{
        unsigned int range;
        struct ocfs2_extent_map_item *emi;

        *ret_emi = NULL;

        list_for_each_entry(emi, &em->em_list, ei_list) {
                range = emi->ei_cpos + emi->ei_clusters;

                if (cpos >= emi->ei_cpos && cpos < range) {
                        list_move(&emi->ei_list, &em->em_list);

                        *ret_emi = emi;
                        break;
                }
        }
}

static int ocfs2_extent_map_lookup(struct inode *inode, unsigned int cpos,
                                   unsigned int *phys, unsigned int *len,
                                   unsigned int *flags)
{
        unsigned int coff;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct ocfs2_extent_map_item *emi;

        spin_lock(&oi->ip_lock);

        __ocfs2_extent_map_lookup(&oi->ip_extent_map, cpos, &emi);
        if (emi) {
                coff = cpos - emi->ei_cpos;
                *phys = emi->ei_phys + coff;
                if (len)
                        *len = emi->ei_clusters - coff;
                if (flags)
                        *flags = emi->ei_flags;
        }

        spin_unlock(&oi->ip_lock);

        if (emi == NULL)
                return -ENOENT;

        return 0;
}

/*
 * Forget about all clusters equal to or greater than cpos.
 */
void ocfs2_extent_map_trunc(struct inode *inode, unsigned int cpos)
{
        struct ocfs2_extent_map_item *emi, *n;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct ocfs2_extent_map *em = &oi->ip_extent_map;
        LIST_HEAD(tmp_list);
        unsigned int range;

        spin_lock(&oi->ip_lock);
        list_for_each_entry_safe(emi, n, &em->em_list, ei_list) {
                if (emi->ei_cpos >= cpos) {
                        /* Full truncate of this record. */
                        list_move(&emi->ei_list, &tmp_list);
                        BUG_ON(em->em_num_items == 0);
                        em->em_num_items--;
                        continue;
                }

                range = emi->ei_cpos + emi->ei_clusters;
                if (range > cpos) {
                        /* Partial truncate */
                        emi->ei_clusters = cpos - emi->ei_cpos;
                }
        }
        spin_unlock(&oi->ip_lock);

        list_for_each_entry_safe(emi, n, &tmp_list, ei_list) {
                list_del(&emi->ei_list);
                kfree(emi);
        }
}

/*
 * Is any part of emi2 contained within emi1
 */
static int ocfs2_ei_is_contained(struct ocfs2_extent_map_item *emi1,
                                 struct ocfs2_extent_map_item *emi2)
{
        unsigned int range1, range2;

        /*
         * Check if logical start of emi2 is inside emi1
         */
        range1 = emi1->ei_cpos + emi1->ei_clusters;
        if (emi2->ei_cpos >= emi1->ei_cpos && emi2->ei_cpos < range1)
                return 1;

        /*
         * Check if logical end of emi2 is inside emi1
         */
        range2 = emi2->ei_cpos + emi2->ei_clusters;
        if (range2 > emi1->ei_cpos && range2 <= range1)
                return 1;

        return 0;
}

static void ocfs2_copy_emi_fields(struct ocfs2_extent_map_item *dest,
                                  struct ocfs2_extent_map_item *src)
{
        dest->ei_cpos = src->ei_cpos;
        dest->ei_phys = src->ei_phys;
        dest->ei_clusters = src->ei_clusters;
        dest->ei_flags = src->ei_flags;
}

/*
 * Try to merge emi with ins. Returns 1 if merge succeeds, zero
 * otherwise.
 */
static int ocfs2_try_to_merge_extent_map(struct ocfs2_extent_map_item *emi,
                                         struct ocfs2_extent_map_item *ins)
{
        /*
         * Handle contiguousness
         */
        if (ins->ei_phys == (emi->ei_phys + emi->ei_clusters) &&
            ins->ei_cpos == (emi->ei_cpos + emi->ei_clusters) &&
            ins->ei_flags == emi->ei_flags) {
                emi->ei_clusters += ins->ei_clusters;
                return 1;
        } else if ((ins->ei_phys + ins->ei_clusters) == emi->ei_phys &&
                   (ins->ei_cpos + ins->ei_clusters) == emi->ei_phys &&
                   ins->ei_flags == emi->ei_flags) {
                emi->ei_phys = ins->ei_phys;
                emi->ei_cpos = ins->ei_cpos;
                emi->ei_clusters += ins->ei_clusters;
                return 1;
        }

        /*
         * Overlapping extents - this shouldn't happen unless we've
         * split an extent to change it's flags. That is exceedingly
         * rare, so there's no sense in trying to optimize it yet.
         */
        if (ocfs2_ei_is_contained(emi, ins) ||
            ocfs2_ei_is_contained(ins, emi)) {
                ocfs2_copy_emi_fields(emi, ins);
                return 1;
        }

        /* No merge was possible. */
        return 0;
}

/*
 * In order to reduce complexity on the caller, this insert function
 * is intentionally liberal in what it will accept.
 *
 * The only rule is that the truncate call *must* be used whenever
 * records have been deleted. This avoids inserting overlapping
 * records with different physical mappings.
 */
void ocfs2_extent_map_insert_rec(struct inode *inode,
                                 struct ocfs2_extent_rec *rec)
{
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct ocfs2_extent_map *em = &oi->ip_extent_map;
        struct ocfs2_extent_map_item *emi, *new_emi = NULL;
        struct ocfs2_extent_map_item ins;

        ins.ei_cpos = le32_to_cpu(rec->e_cpos);
        ins.ei_phys = ocfs2_blocks_to_clusters(inode->i_sb,
                                               le64_to_cpu(rec->e_blkno));
        ins.ei_clusters = le16_to_cpu(rec->e_leaf_clusters);
        ins.ei_flags = rec->e_flags;

search:
        spin_lock(&oi->ip_lock);

        list_for_each_entry(emi, &em->em_list, ei_list) {
                if (ocfs2_try_to_merge_extent_map(emi, &ins)) {
                        list_move(&emi->ei_list, &em->em_list);
                        spin_unlock(&oi->ip_lock);
                        goto out;
                }
        }

        /*
         * No item could be merged.
         *
         * Either allocate and add a new item, or overwrite the last recently
         * inserted.
         */

        if (em->em_num_items < OCFS2_MAX_EXTENT_MAP_ITEMS) {
                if (new_emi == NULL) {
                        spin_unlock(&oi->ip_lock);

                        new_emi = kmalloc(sizeof(*new_emi), GFP_NOFS);
                        if (new_emi == NULL)
                                goto out;

                        goto search;
                }

                ocfs2_copy_emi_fields(new_emi, &ins);
                list_add(&new_emi->ei_list, &em->em_list);
                em->em_num_items++;
                new_emi = NULL;
        } else {
                BUG_ON(list_empty(&em->em_list) || em->em_num_items == 0);
                emi = list_entry(em->em_list.prev,
                                 struct ocfs2_extent_map_item, ei_list);
                list_move(&emi->ei_list, &em->em_list);
                ocfs2_copy_emi_fields(emi, &ins);
        }

        spin_unlock(&oi->ip_lock);

out:
        if (new_emi)
                kfree(new_emi);
}

static int ocfs2_last_eb_is_empty(struct inode *inode,
                                  struct ocfs2_dinode *di)
{
        int ret, next_free;
        u64 last_eb_blk = le64_to_cpu(di->i_last_eb_blk);
        struct buffer_head *eb_bh = NULL;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list *el;

        ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), last_eb_blk,
                               &eb_bh, OCFS2_BH_CACHED, inode);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        eb = (struct ocfs2_extent_block *) eb_bh->b_data;
        el = &eb->h_list;

        if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
                ret = -EROFS;
                OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
                goto out;
        }

        if (el->l_tree_depth) {
                ocfs2_error(inode->i_sb,
                            "Inode %lu has non zero tree depth in "
                            "leaf block %llu\n", inode->i_ino,
                            (unsigned long long)eb_bh->b_blocknr);
                ret = -EROFS;
                goto out;
        }

        next_free = le16_to_cpu(el->l_next_free_rec);

        if (next_free == 0 ||
            (next_free == 1 && ocfs2_is_empty_extent(&el->l_recs[0])))
                ret = 1;

out:
        brelse(eb_bh);
        return ret;
}

/*
 * Return the 1st index within el which contains an extent start
 * larger than v_cluster.
 */
static int ocfs2_search_for_hole_index(struct ocfs2_extent_list *el,
                                       u32 v_cluster)
{
        int i;
        struct ocfs2_extent_rec *rec;

        for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
                rec = &el->l_recs[i];

                if (v_cluster < le32_to_cpu(rec->e_cpos))
                        break;
        }

        return i;
}

/*
 * Figure out the size of a hole which starts at v_cluster within the given
 * extent list.
 *
 * If there is no more allocation past v_cluster, we return the maximum
 * cluster size minus v_cluster.
 *
 * If we have in-inode extents, then el points to the dinode list and
 * eb_bh is NULL. Otherwise, eb_bh should point to the extent block
 * containing el.
 */
static int ocfs2_figure_hole_clusters(struct inode *inode,
                                      struct ocfs2_extent_list *el,
                                      struct buffer_head *eb_bh,
                                      u32 v_cluster,
                                      u32 *num_clusters)
{
        int ret, i;
        struct buffer_head *next_eb_bh = NULL;
        struct ocfs2_extent_block *eb, *next_eb;

        i = ocfs2_search_for_hole_index(el, v_cluster);

        if (i == le16_to_cpu(el->l_next_free_rec) && eb_bh) {
                eb = (struct ocfs2_extent_block *)eb_bh->b_data;

                /*
                 * Check the next leaf for any extents.
                 */

                if (le64_to_cpu(eb->h_next_leaf_blk) == 0ULL)
                        goto no_more_extents;

                ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
                                       le64_to_cpu(eb->h_next_leaf_blk),
                                       &next_eb_bh, OCFS2_BH_CACHED, inode);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
                next_eb = (struct ocfs2_extent_block *)next_eb_bh->b_data;

                if (!OCFS2_IS_VALID_EXTENT_BLOCK(next_eb)) {
                        ret = -EROFS;
                        OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, next_eb);
                        goto out;
                }

                el = &next_eb->h_list;

                i = ocfs2_search_for_hole_index(el, v_cluster);
        }

no_more_extents:
        if (i == le16_to_cpu(el->l_next_free_rec)) {
                /*
                 * We're at the end of our existing allocation. Just
                 * return the maximum number of clusters we could
                 * possibly allocate.
                 */
                *num_clusters = UINT_MAX - v_cluster;
        } else {
                *num_clusters = le32_to_cpu(el->l_recs[i].e_cpos) - v_cluster;
        }

        ret = 0;
out:
        brelse(next_eb_bh);
        return ret;
}

static int ocfs2_get_clusters_nocache(struct inode *inode,
                                      struct buffer_head *di_bh,
                                      u32 v_cluster, unsigned int *hole_len,
                                      struct ocfs2_extent_rec *ret_rec,
                                      unsigned int *is_last)
{
        int i, ret, tree_height, len;
        struct ocfs2_dinode *di;
        struct ocfs2_extent_block *uninitialized_var(eb);
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_rec *rec;
        struct buffer_head *eb_bh = NULL;

        memset(ret_rec, 0, sizeof(*ret_rec));
        if (is_last)
                *is_last = 0;

        di = (struct ocfs2_dinode *) di_bh->b_data;
        el = &di->id2.i_list;
        tree_height = le16_to_cpu(el->l_tree_depth);

        if (tree_height > 0) {
                ret = ocfs2_find_leaf(inode, el, v_cluster, &eb_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                eb = (struct ocfs2_extent_block *) eb_bh->b_data;
                el = &eb->h_list;

                if (el->l_tree_depth) {
                        ocfs2_error(inode->i_sb,
                                    "Inode %lu has non zero tree depth in "
                                    "leaf block %llu\n", inode->i_ino,
                                    (unsigned long long)eb_bh->b_blocknr);
                        ret = -EROFS;
                        goto out;
                }
        }

        i = ocfs2_search_extent_list(el, v_cluster);
        if (i == -1) {
                /*
                 * Holes can be larger than the maximum size of an
                 * extent, so we return their lengths in a seperate
                 * field.
                 */
                if (hole_len) {
                        ret = ocfs2_figure_hole_clusters(inode, el, eb_bh,
                                                         v_cluster, &len);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }

                        *hole_len = len;
                }
                goto out_hole;
        }

        rec = &el->l_recs[i];

        BUG_ON(v_cluster < le32_to_cpu(rec->e_cpos));

        if (!rec->e_blkno) {
                ocfs2_error(inode->i_sb, "Inode %lu has bad extent "
                            "record (%u, %u, 0)", inode->i_ino,
                            le32_to_cpu(rec->e_cpos),
                            ocfs2_rec_clusters(el, rec));
                ret = -EROFS;
                goto out;
        }

        *ret_rec = *rec;

        /*
         * Checking for last extent is potentially expensive - we
         * might have to look at the next leaf over to see if it's
         * empty.
         *
         * The first two checks are to see whether the caller even
         * cares for this information, and if the extent is at least
         * the last in it's list.
         *
         * If those hold true, then the extent is last if any of the
         * additional conditions hold true:
         *  - Extent list is in-inode
         *  - Extent list is right-most
         *  - Extent list is 2nd to rightmost, with empty right-most
         */
        if (is_last) {
                if (i == (le16_to_cpu(el->l_next_free_rec) - 1)) {
                        if (tree_height == 0)
                                *is_last = 1;
                        else if (eb->h_blkno == di->i_last_eb_blk)
                                *is_last = 1;
                        else if (eb->h_next_leaf_blk == di->i_last_eb_blk) {
                                ret = ocfs2_last_eb_is_empty(inode, di);
                                if (ret < 0) {
                                        mlog_errno(ret);
                                        goto out;
                                }
                                if (ret == 1)
                                        *is_last = 1;
                        }
                }
        }

out_hole:
        ret = 0;
out:
        brelse(eb_bh);
        return ret;
}

static void ocfs2_relative_extent_offsets(struct super_block *sb,
                                          u32 v_cluster,
                                          struct ocfs2_extent_rec *rec,
                                          u32 *p_cluster, u32 *num_clusters)

{
        u32 coff = v_cluster - le32_to_cpu(rec->e_cpos);

        *p_cluster = ocfs2_blocks_to_clusters(sb, le64_to_cpu(rec->e_blkno));
        *p_cluster = *p_cluster + coff;

        if (num_clusters)
                *num_clusters = le16_to_cpu(rec->e_leaf_clusters) - coff;
}

int ocfs2_xattr_get_clusters(struct inode *inode, u32 v_cluster,
                             u32 *p_cluster, u32 *num_clusters,
                             struct ocfs2_extent_list *el)
{
        int ret = 0, i;
        struct buffer_head *eb_bh = NULL;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_rec *rec;
        u32 coff;

        if (el->l_tree_depth) {
                ret = ocfs2_find_leaf(inode, el, v_cluster, &eb_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                eb = (struct ocfs2_extent_block *) eb_bh->b_data;
                el = &eb->h_list;

                if (el->l_tree_depth) {
                        ocfs2_error(inode->i_sb,
                                    "Inode %lu has non zero tree depth in "
                                    "xattr leaf block %llu\n", inode->i_ino,
                                    (unsigned long long)eb_bh->b_blocknr);
                        ret = -EROFS;
                        goto out;
                }
        }

        i = ocfs2_search_extent_list(el, v_cluster);
        if (i == -1) {
                ret = -EROFS;
                mlog_errno(ret);
                goto out;
        } else {
                rec = &el->l_recs[i];
                BUG_ON(v_cluster < le32_to_cpu(rec->e_cpos));

                if (!rec->e_blkno) {
                        ocfs2_error(inode->i_sb, "Inode %lu has bad extent "
                                    "record (%u, %u, 0) in xattr", inode->i_ino,
                                    le32_to_cpu(rec->e_cpos),
                                    ocfs2_rec_clusters(el, rec));
                        ret = -EROFS;
                        goto out;
                }
                coff = v_cluster - le32_to_cpu(rec->e_cpos);
                *p_cluster = ocfs2_blocks_to_clusters(inode->i_sb,
                                                    le64_to_cpu(rec->e_blkno));
                *p_cluster = *p_cluster + coff;
                if (num_clusters)
                        *num_clusters = ocfs2_rec_clusters(el, rec) - coff;
        }
out:
        if (eb_bh)
                brelse(eb_bh);
        return ret;
}

int ocfs2_get_clusters(struct inode *inode, u32 v_cluster,
                       u32 *p_cluster, u32 *num_clusters,
                       unsigned int *extent_flags)
{
        int ret;
        unsigned int uninitialized_var(hole_len), flags = 0;
        struct buffer_head *di_bh = NULL;
        struct ocfs2_extent_rec rec;

        if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
                ret = -ERANGE;
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_extent_map_lookup(inode, v_cluster, p_cluster,
                                      num_clusters, extent_flags);
        if (ret == 0)
                goto out;

        ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), OCFS2_I(inode)->ip_blkno,
                               &di_bh, OCFS2_BH_CACHED, inode);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_get_clusters_nocache(inode, di_bh, v_cluster, &hole_len,
                                         &rec, NULL);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        if (rec.e_blkno == 0ULL) {
                /*
                 * A hole was found. Return some canned values that
                 * callers can key on. If asked for, num_clusters will
                 * be populated with the size of the hole.
                 */
                *p_cluster = 0;
                if (num_clusters) {
                        *num_clusters = hole_len;
                }
        } else {
                ocfs2_relative_extent_offsets(inode->i_sb, v_cluster, &rec,
                                              p_cluster, num_clusters);
                flags = rec.e_flags;

                ocfs2_extent_map_insert_rec(inode, &rec);
        }

        if (extent_flags)
                *extent_flags = flags;

out:
        brelse(di_bh);
        return ret;
}

/*
 * This expects alloc_sem to be held. The allocation cannot change at
 * all while the map is in the process of being updated.
 */
int ocfs2_extent_map_get_blocks(struct inode *inode, u64 v_blkno, u64 *p_blkno,
                                u64 *ret_count, unsigned int *extent_flags)
{
        int ret;
        int bpc = ocfs2_clusters_to_blocks(inode->i_sb, 1);
        u32 cpos, num_clusters, p_cluster;
        u64 boff = 0;

        cpos = ocfs2_blocks_to_clusters(inode->i_sb, v_blkno);

        ret = ocfs2_get_clusters(inode, cpos, &p_cluster, &num_clusters,
                                 extent_flags);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /*
         * p_cluster == 0 indicates a hole.
         */
        if (p_cluster) {
                boff = ocfs2_clusters_to_blocks(inode->i_sb, p_cluster);
                boff += (v_blkno & (u64)(bpc - 1));
        }

        *p_blkno = boff;

        if (ret_count) {
                *ret_count = ocfs2_clusters_to_blocks(inode->i_sb, num_clusters);
                *ret_count -= v_blkno & (u64)(bpc - 1);
        }

out:
        return ret;
}

static int ocfs2_fiemap_inline(struct inode *inode, struct buffer_head *di_bh,
                               struct fiemap_extent_info *fieinfo,
                               u64 map_start)
{
        int ret;
        unsigned int id_count;
        struct ocfs2_dinode *di;
        u64 phys;
        u32 flags = FIEMAP_EXTENT_DATA_INLINE|FIEMAP_EXTENT_LAST;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);

        di = (struct ocfs2_dinode *)di_bh->b_data;
        id_count = le16_to_cpu(di->id2.i_data.id_count);

        if (map_start < id_count) {
                phys = oi->ip_blkno << inode->i_sb->s_blocksize_bits;
                phys += offsetof(struct ocfs2_dinode, id2.i_data.id_data);

                ret = fiemap_fill_next_extent(fieinfo, 0, phys, id_count,
                                              flags);
                if (ret < 0)
                        return ret;
        }

        return 0;
}

#define OCFS2_FIEMAP_FLAGS      (FIEMAP_FLAG_SYNC)

int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                 u64 map_start, u64 map_len)
{
        int ret, is_last;
        u32 mapping_end, cpos;
        unsigned int hole_size;
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
        u64 len_bytes, phys_bytes, virt_bytes;
        struct buffer_head *di_bh = NULL;
        struct ocfs2_extent_rec rec;

        ret = fiemap_check_flags(fieinfo, OCFS2_FIEMAP_FLAGS);
        if (ret)
                return ret;

        ret = ocfs2_inode_lock(inode, &di_bh, 0);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        down_read(&OCFS2_I(inode)->ip_alloc_sem);

        /*
         * Handle inline-data separately.
         */
        if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
                ret = ocfs2_fiemap_inline(inode, di_bh, fieinfo, map_start);
                goto out_unlock;
        }

        cpos = map_start >> osb->s_clustersize_bits;
        mapping_end = ocfs2_clusters_for_bytes(inode->i_sb,
                                               map_start + map_len);
        mapping_end -= cpos;
        is_last = 0;
        while (cpos < mapping_end && !is_last) {
                u32 fe_flags;

                ret = ocfs2_get_clusters_nocache(inode, di_bh, cpos,
                                                 &hole_size, &rec, &is_last);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                if (rec.e_blkno == 0ULL) {
                        cpos += hole_size;
                        continue;
                }

                fe_flags = 0;
                if (rec.e_flags & OCFS2_EXT_UNWRITTEN)
                        fe_flags |= FIEMAP_EXTENT_UNWRITTEN;
                if (is_last)
                        fe_flags |= FIEMAP_EXTENT_LAST;
                len_bytes = (u64)le16_to_cpu(rec.e_leaf_clusters) << osb->s_clustersize_bits;
                phys_bytes = le64_to_cpu(rec.e_blkno) << osb->sb->s_blocksize_bits;
                virt_bytes = (u64)le32_to_cpu(rec.e_cpos) << osb->s_clustersize_bits;

                ret = fiemap_fill_next_extent(fieinfo, virt_bytes, phys_bytes,
                                              len_bytes, fe_flags);
                if (ret)
                        break;

                cpos = le32_to_cpu(rec.e_cpos)+ le16_to_cpu(rec.e_leaf_clusters);
        }

        if (ret > 0)
                ret = 0;

out_unlock:
        brelse(di_bh);

        up_read(&OCFS2_I(inode)->ip_alloc_sem);

        ocfs2_inode_unlock(inode, 0);
out:

        return ret;
}