extent_map.c

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/* -*- 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/slab.h>
#include <linux/types.h>
#include <linux/fiemap.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "inode.h"
#include "super.h"
#include "symlink.h"
#include "ocfs2_trace.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_cpos &&
           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_extent_block(INODE_CACHE(inode), last_eb_blk, &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;
    }

    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.
 */
int ocfs2_figure_hole_clusters(struct ocfs2_caching_info *ci,
                   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_extent_block(ci,
                          le64_to_cpu(eb->h_next_leaf_blk),
                          &next_eb_bh);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        next_eb = (struct ocfs2_extent_block *)next_eb_bh->b_data;
        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_CACHE(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 separate
         * field.
         */
        if (hole_len) {
            ret = ocfs2_figure_hole_clusters(INODE_CACHE(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,
                 unsigned int *extent_flags)
{
    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_CACHE(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;

        if (extent_flags)
            *extent_flags = rec->e_flags;
    }
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_inode_block(inode, &di_bh);
    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;
}

/*
 * The ocfs2_fiemap_inline() may be a little bit misleading, since
 * it not only handles the fiemap for inlined files, but also deals
 * with the fast symlink, cause they have no difference for extent
 * mapping per se.
 */
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;
    if (ocfs2_inode_is_fast_symlink(inode))
        id_count = ocfs2_fast_symlink_chars(inode->i_sb);
    else
        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;
        if (ocfs2_inode_is_fast_symlink(inode))
            phys += offsetof(struct ocfs2_dinode, id2.i_symlink);
        else
            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 and fast symlink separately.
     */
    if ((OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) ||
        ocfs2_inode_is_fast_symlink(inode)) {
        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 (rec.e_flags & OCFS2_EXT_REFCOUNTED)
            fe_flags |= FIEMAP_EXTENT_SHARED;
        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;
}

int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int origin)
{
    struct inode *inode = file->f_mapping->host;
    int ret;
    unsigned int is_last = 0, is_data = 0;
    u16 cs_bits = OCFS2_SB(inode->i_sb)->s_clustersize_bits;
    u32 cpos, cend, clen, hole_size;
    u64 extoff, extlen;
    struct buffer_head *di_bh = NULL;
    struct ocfs2_extent_rec rec;

    BUG_ON(origin != SEEK_DATA && origin != SEEK_HOLE);

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

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

    if (*offset >= inode->i_size) {
        ret = -ENXIO;
        goto out_unlock;
    }

    if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
        if (origin == SEEK_HOLE)
            *offset = inode->i_size;
        goto out_unlock;
    }

    clen = 0;
    cpos = *offset >> cs_bits;
    cend = ocfs2_clusters_for_bytes(inode->i_sb, inode->i_size);

    while (cpos < cend && !is_last) {
        ret = ocfs2_get_clusters_nocache(inode, di_bh, cpos, &hole_size,
                         &rec, &is_last);
        if (ret) {
            mlog_errno(ret);
            goto out_unlock;
        }

        extoff = cpos;
        extoff <<= cs_bits;

        if (rec.e_blkno == 0ULL) {
            clen = hole_size;
            is_data = 0;
        } else {
            clen = le16_to_cpu(rec.e_leaf_clusters) -
                (cpos - le32_to_cpu(rec.e_cpos));
            is_data = (rec.e_flags & OCFS2_EXT_UNWRITTEN) ?  0 : 1;
        }

        if ((!is_data && origin == SEEK_HOLE) ||
            (is_data && origin == SEEK_DATA)) {
            if (extoff > *offset)
                *offset = extoff;
            goto out_unlock;
        }

        if (!is_last)
            cpos += clen;
    }

    if (origin == SEEK_HOLE) {
        extoff = cpos;
        extoff <<= cs_bits;
        extlen = clen;
        extlen <<=  cs_bits;

        if ((extoff + extlen) > inode->i_size)
            extlen = inode->i_size - extoff;
        extoff += extlen;
        if (extoff > *offset)
            *offset = extoff;
        goto out_unlock;
    }

    ret = -ENXIO;

out_unlock:

    brelse(di_bh);

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

    ocfs2_inode_unlock(inode, 0);
out:
    return ret;
}

int ocfs2_read_virt_blocks(struct inode *inode, u64 v_block, int nr,
               struct buffer_head *bhs[], int flags,
               int (*validate)(struct super_block *sb,
                       struct buffer_head *bh))
{
    int rc = 0;
    u64 p_block, p_count;
    int i, count, done = 0;

    trace_ocfs2_read_virt_blocks(
         inode, (unsigned long long)v_block, nr, bhs, flags,
         validate);

    if (((v_block + nr - 1) << inode->i_sb->s_blocksize_bits) >=
        i_size_read(inode)) {
        BUG_ON(!(flags & OCFS2_BH_READAHEAD));
        goto out;
    }

    while (done < nr) {
        down_read(&OCFS2_I(inode)->ip_alloc_sem);
        rc = ocfs2_extent_map_get_blocks(inode, v_block + done,
                         &p_block, &p_count, NULL);
        up_read(&OCFS2_I(inode)->ip_alloc_sem);
        if (rc) {
            mlog_errno(rc);
            break;
        }

        if (!p_block) {
            rc = -EIO;
            mlog(ML_ERROR,
                 "Inode #%llu contains a hole at offset %llu\n",
                 (unsigned long long)OCFS2_I(inode)->ip_blkno,
                 (unsigned long long)(v_block + done) <<
                 inode->i_sb->s_blocksize_bits);
            break;
        }

        count = nr - done;
        if (p_count < count)
            count = p_count;

        /*
         * If the caller passed us bhs, they should have come
         * from a previous readahead call to this function.  Thus,
         * they should have the right b_blocknr.
         */
        for (i = 0; i < count; i++) {
            if (!bhs[done + i])
                continue;
            BUG_ON(bhs[done + i]->b_blocknr != (p_block + i));
        }

        rc = ocfs2_read_blocks(INODE_CACHE(inode), p_block, count,
                       bhs + done, flags, validate);
        if (rc) {
            mlog_errno(rc);
            break;
        }
        done += count;
    }

out:
    return rc;
}