usbloadergx/source/libntfs/lcnalloc.c

/**
 * lcnalloc.c - Cluster (de)allocation code. Originated from the Linux-NTFS project.
 *
 * Copyright (c) 2002-2004 Anton Altaparmakov
 * Copyright (c) 2004 Yura Pakhuchiy
 * Copyright (c) 2004-2008 Szabolcs Szakacsits
 * Copyright (c) 2008-2009 Jean-Pierre Andre
 *
 * This program/include file 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/include file 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 (in the main directory of the NTFS-3G
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STDIO_H
#include <stdio.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif

#include "types.h"
#include "attrib.h"
#include "bitmap.h"
#include "debug.h"
#include "runlist.h"
#include "volume.h"
#include "lcnalloc.h"
#include "logging.h"
#include "misc.h"

/*
 * Plenty possibilities for big optimizations all over in the cluster
 * allocation, however at the moment the dominant bottleneck (~ 90%) is
 * the update of the mapping pairs which converges to the cubic Faulhaber's
 * formula as the function of the number of extents (fragments, runs).
 */
#define NTFS_LCNALLOC_BSIZE 4096
#define NTFS_LCNALLOC_SKIP  NTFS_LCNALLOC_BSIZE

enum
{
    ZONE_MFT = 1,
    ZONE_DATA1 = 2,
    ZONE_DATA2 = 4
} ;

static void ntfs_cluster_set_zone_pos( LCN start, LCN end, LCN *pos, LCN tc )
{
    ntfs_log_trace( "pos: %lld  tc: %lld\n", ( long long )*pos, ( long long )tc );

    if ( tc >= end )
        *pos = start;
    else if ( tc >= start )
        *pos = tc;
}

static void ntfs_cluster_update_zone_pos( ntfs_volume *vol, u8 zone, LCN tc )
{
    ntfs_log_trace( "tc = %lld, zone = %d\n", ( long long )tc, zone );

    if ( zone == ZONE_MFT )
        ntfs_cluster_set_zone_pos( vol->mft_lcn, vol->mft_zone_end,
                                   &vol->mft_zone_pos, tc );
    else if ( zone == ZONE_DATA1 )
        ntfs_cluster_set_zone_pos( vol->mft_zone_end, vol->nr_clusters,
                                   &vol->data1_zone_pos, tc );
    else /* zone == ZONE_DATA2 */
        ntfs_cluster_set_zone_pos( 0, vol->mft_zone_start,
                                   &vol->data2_zone_pos, tc );
}

/*
 *      Unmark full zones when a cluster has been freed in a full zone
 *
 *  Next allocation will reuse the freed cluster
 */

static void update_full_status( ntfs_volume *vol, LCN lcn )
{
    if ( lcn >= vol->mft_zone_end )
    {
        if ( vol->full_zones & ZONE_DATA1 )
        {
            ntfs_cluster_update_zone_pos( vol, ZONE_DATA1, lcn );
            vol->full_zones &= ~ZONE_DATA1;
        }
    }
    else if ( lcn < vol->mft_zone_start )
    {
        if ( vol->full_zones & ZONE_DATA2 )
        {
            ntfs_cluster_update_zone_pos( vol, ZONE_DATA2, lcn );
            vol->full_zones &= ~ZONE_DATA2;
        }
    }
    else
    {
        if ( vol->full_zones & ZONE_MFT )
        {
            ntfs_cluster_update_zone_pos( vol, ZONE_MFT, lcn );
            vol->full_zones &= ~ZONE_MFT;
        }
    }
}

static s64 max_empty_bit_range( unsigned char *buf, int size )
{
    int i, j, run = 0;
    int max_range = 0;
    s64 start_pos = -1;

    ntfs_log_trace( "Entering\n" );

    i = 0;
    while ( i < size )
    {
        switch ( *buf )
        {
            case 0 :
                do
                {
                    buf++;
                    run += 8;
                    i++;
                }
                while ( ( i < size ) && !*buf );
                break;
            case 255 :
                if ( run > max_range )
                {
                    max_range = run;
                    start_pos = ( s64 )i * 8 - run;
                }
                run = 0;
                do
                {
                    buf++;
                    i++;
                }
                while ( ( i < size ) && ( *buf == 255 ) );
                break;
            default :
                for ( j = 0; j < 8; j++ )
                {

                    int bit = *buf & ( 1 << j );

                    if ( bit )
                    {
                        if ( run > max_range )
                        {
                            max_range = run;
                            start_pos = ( s64 )i * 8 + ( j - run );
                        }
                        run = 0;
                    }
                    else
                        run++;
                }
                i++;
                buf++;

        }
    }

    if ( run > max_range )
        start_pos = ( s64 )i * 8 - run;

    return start_pos;
}

static int bitmap_writeback( ntfs_volume *vol, s64 pos, s64 size, void *b,
                             u8 *writeback )
{
    s64 written;

    ntfs_log_trace( "Entering\n" );

    if ( !*writeback )
        return 0;

    *writeback = 0;

    written = ntfs_attr_pwrite( vol->lcnbmp_na, pos, size, b );
    if ( written != size )
    {
        if ( !written )
            errno = EIO;
        ntfs_log_perror( "Bitmap write error (%lld, %lld)",
                         ( long long )pos, ( long long )size );
        return -1;
    }

    return 0;
}

/**
 * ntfs_cluster_alloc - allocate clusters on an ntfs volume
 * @vol:    mounted ntfs volume on which to allocate the clusters
 * @start_vcn:  vcn to use for the first allocated cluster
 * @count:  number of clusters to allocate
 * @start_lcn:  starting lcn at which to allocate the clusters (or -1 if none)
 * @zone:   zone from which to allocate the clusters
 *
 * Allocate @count clusters preferably starting at cluster @start_lcn or at the
 * current allocator position if @start_lcn is -1, on the mounted ntfs volume
 * @vol. @zone is either DATA_ZONE for allocation of normal clusters and
 * MFT_ZONE for allocation of clusters for the master file table, i.e. the
 * $MFT/$DATA attribute.
 *
 * On success return a runlist describing the allocated cluster(s).
 *
 * On error return NULL with errno set to the error code.
 *
 * Notes on the allocation algorithm
 * =================================
 *
 * There are two data zones. First is the area between the end of the mft zone
 * and the end of the volume, and second is the area between the start of the
 * volume and the start of the mft zone. On unmodified/standard NTFS 1.x
 * volumes, the second data zone doesn't exist due to the mft zone being
 * expanded to cover the start of the volume in order to reserve space for the
 * mft bitmap attribute.
 *
 * The complexity stems from the need of implementing the mft vs data zoned
 * approach and from the fact that we have access to the lcn bitmap via up to
 * NTFS_LCNALLOC_BSIZE bytes at a time, so we need to cope with crossing over
 * boundaries of two buffers. Further, the fact that the allocator allows for
 * caller supplied hints as to the location of where allocation should begin
 * and the fact that the allocator keeps track of where in the data zones the
 * next natural allocation should occur, contribute to the complexity of the
 * function. But it should all be worthwhile, because this allocator:
 *   1) implements MFT zone reservation
 *   2) causes reduction in fragmentation.
 * The code is not optimized for speed.
 */
runlist *ntfs_cluster_alloc( ntfs_volume *vol, VCN start_vcn, s64 count,
                             LCN start_lcn, const NTFS_CLUSTER_ALLOCATION_ZONES zone )
{
    LCN zone_start, zone_end;  /* current search range */
    LCN last_read_pos, lcn;
    LCN bmp_pos;        /* current bit position inside the bitmap */
    LCN prev_lcn = 0, prev_run_len = 0;
    s64 clusters, br;
    runlist *rl = NULL, *trl;
    u8 *buf, *byte, bit, writeback;
    u8 pass = 1;    /* 1: inside zone;  2: start of zone */
    u8 search_zone; /* 4: data2 (start) 1: mft (middle) 2: data1 (end) */
    u8 done_zones = 0;
    u8 has_guess, used_zone_pos;
    int err = 0, rlpos, rlsize, buf_size;

    ntfs_log_enter( "Entering with count = 0x%llx, start_lcn = 0x%llx, "
                    "zone = %s_ZONE.\n", ( long long )count, ( long long )
                    start_lcn, zone == MFT_ZONE ? "MFT" : "DATA" );

    if ( !vol || count < 0 || start_lcn < -1 || !vol->lcnbmp_na ||
            ( s8 )zone < FIRST_ZONE || zone > LAST_ZONE )
    {
        errno = EINVAL;
        ntfs_log_perror( "%s: vcn: %lld, count: %lld, lcn: %lld",
                         __FUNCTION__, ( long long )start_vcn,
                         ( long long )count, ( long long )start_lcn );
        goto out;
    }

    /* Return empty runlist if @count == 0 */
    if ( !count )
    {
        rl = ntfs_malloc( 0x1000 );
        if ( rl )
        {
            rl[0].vcn = start_vcn;
            rl[0].lcn = LCN_RL_NOT_MAPPED;
            rl[0].length = 0;
        }
        goto out;
    }

    buf = ntfs_malloc( NTFS_LCNALLOC_BSIZE );
    if ( !buf )
        goto out;
    /*
     * If no @start_lcn was requested, use the current zone
     * position otherwise use the requested @start_lcn.
     */
    has_guess = 1;
    zone_start = start_lcn;

    if ( zone_start < 0 )
    {
        if ( zone == DATA_ZONE )
            zone_start = vol->data1_zone_pos;
        else
            zone_start = vol->mft_zone_pos;
        has_guess = 0;
    }

    used_zone_pos = has_guess ? 0 : 1;

    if ( !zone_start || zone_start == vol->mft_zone_start ||
            zone_start == vol->mft_zone_end )
        pass = 2;

    if ( zone_start < vol->mft_zone_start )
    {
        zone_end = vol->mft_zone_start;
        search_zone = ZONE_DATA2;
    }
    else if ( zone_start < vol->mft_zone_end )
    {
        zone_end = vol->mft_zone_end;
        search_zone = ZONE_MFT;
    }
    else
    {
        zone_end = vol->nr_clusters;
        search_zone = ZONE_DATA1;
    }

    bmp_pos = zone_start;

    /* Loop until all clusters are allocated. */
    clusters = count;
    rlpos = rlsize = 0;
    while ( 1 )
    {
        /* check whether we have exhausted the current zone */
        if ( search_zone & vol->full_zones )
            goto zone_pass_done;
        last_read_pos = bmp_pos >> 3;
        br = ntfs_attr_pread( vol->lcnbmp_na, last_read_pos,
                              NTFS_LCNALLOC_BSIZE, buf );
        if ( br <= 0 )
        {
            if ( !br )
                goto zone_pass_done;
            err = errno;
            ntfs_log_perror( "Reading $BITMAP failed" );
            goto err_ret;
        }
        /*
         * We might have read less than NTFS_LCNALLOC_BSIZE bytes
         * if we are close to the end of the attribute.
         */
        buf_size = ( int )br << 3;
        lcn = bmp_pos & 7;
        bmp_pos &= ~7;
        writeback = 0;

        while ( lcn < buf_size )
        {
            byte = buf + ( lcn >> 3 );
            bit = 1 << ( lcn & 7 );
            if ( has_guess )
            {
                if ( *byte & bit )
                {
                    has_guess = 0;
                    break;
                }
            }
            else
            {
                lcn = max_empty_bit_range( buf, br );
                if ( lcn < 0 )
                    break;
                has_guess = 1;
                continue;
            }

            /* First free bit is at lcn + bmp_pos. */

            /* Reallocate memory if necessary. */
            if ( ( rlpos + 2 ) * ( int )sizeof( runlist ) >= rlsize )
            {
                rlsize += 4096;
                trl = realloc( rl, rlsize );
                if ( !trl )
                {
                    err = ENOMEM;
                    ntfs_log_perror( "realloc() failed" );
                    goto wb_err_ret;
                }
                rl = trl;
            }

            /* Allocate the bitmap bit. */
            *byte |= bit;
            writeback = 1;
            if ( vol->free_clusters <= 0 )
                ntfs_log_error( "Non-positive free clusters "
                                "(%lld)!\n",
                                ( long long )vol->free_clusters );
            else
                vol->free_clusters--;

            /*
             * Coalesce with previous run if adjacent LCNs.
             * Otherwise, append a new run.
             */
            if ( prev_lcn == lcn + bmp_pos - prev_run_len && rlpos )
            {
                ntfs_log_debug( "Cluster coalesce: prev_lcn: "
                                "%lld  lcn: %lld  bmp_pos: %lld  "
                                "prev_run_len: %lld\n",
                                ( long long )prev_lcn,
                                ( long long )lcn, ( long long )bmp_pos,
                                ( long long )prev_run_len );
                rl[rlpos - 1].length = ++prev_run_len;
            }
            else
            {
                if ( rlpos )
                    rl[rlpos].vcn = rl[rlpos - 1].vcn +
                                    prev_run_len;
                else
                {
                    rl[rlpos].vcn = start_vcn;
                    ntfs_log_debug( "Start_vcn: %lld\n",
                                    ( long long )start_vcn );
                }

                rl[rlpos].lcn = prev_lcn = lcn + bmp_pos;
                rl[rlpos].length = prev_run_len = 1;
                rlpos++;
            }

            ntfs_log_debug( "RUN:   %-16lld %-16lld %-16lld\n",
                            ( long long )rl[rlpos - 1].vcn,
                            ( long long )rl[rlpos - 1].lcn,
                            ( long long )rl[rlpos - 1].length );
            /* Done? */
            if ( !--clusters )
            {
                if ( used_zone_pos )
                    ntfs_cluster_update_zone_pos( vol,
                                                  search_zone, lcn + bmp_pos + 1 +
                                                  NTFS_LCNALLOC_SKIP );
                goto done_ret;
            }

            lcn++;
        }

        if ( bitmap_writeback( vol, last_read_pos, br, buf, &writeback ) )
        {
            err = errno;
            goto err_ret;
        }

        if ( !used_zone_pos )
        {

            used_zone_pos = 1;

            if ( search_zone == ZONE_MFT )
                zone_start = vol->mft_zone_pos;
            else if ( search_zone == ZONE_DATA1 )
                zone_start = vol->data1_zone_pos;
            else
                zone_start = vol->data2_zone_pos;

            if ( !zone_start || zone_start == vol->mft_zone_start ||
                    zone_start == vol->mft_zone_end )
                pass = 2;
            bmp_pos = zone_start;
        }
        else
            bmp_pos += buf_size;

        if ( bmp_pos < zone_end )
            continue;

zone_pass_done:
        ntfs_log_trace( "Finished current zone pass(%i).\n", pass );
        if ( pass == 1 )
        {
            pass = 2;
            zone_end = zone_start;

            if ( search_zone == ZONE_MFT )
                zone_start = vol->mft_zone_start;
            else if ( search_zone == ZONE_DATA1 )
                zone_start = vol->mft_zone_end;
            else
                zone_start = 0;

            /* Sanity check. */
            if ( zone_end < zone_start )
                zone_end = zone_start;

            bmp_pos = zone_start;

            continue;
        }
        /* pass == 2 */
done_zones_check:
        done_zones |= search_zone;
        vol->full_zones |= search_zone;
        if ( done_zones < ( ZONE_MFT + ZONE_DATA1 + ZONE_DATA2 ) )
        {
            ntfs_log_trace( "Switching zone.\n" );
            pass = 1;
            if ( rlpos )
            {
                LCN tc = rl[rlpos - 1].lcn +
                         rl[rlpos - 1].length + NTFS_LCNALLOC_SKIP;

                if ( used_zone_pos )
                    ntfs_cluster_update_zone_pos( vol,
                                                  search_zone, tc );
            }

            switch ( search_zone )
            {
                case ZONE_MFT:
                    ntfs_log_trace( "Zone switch: mft -> data1\n" );
switch_to_data1_zone:       search_zone = ZONE_DATA1;
                    zone_start = vol->data1_zone_pos;
                    zone_end = vol->nr_clusters;
                    if ( zone_start == vol->mft_zone_end )
                        pass = 2;
                    break;
                case ZONE_DATA1:
                    ntfs_log_trace( "Zone switch: data1 -> data2\n" );
                    search_zone = ZONE_DATA2;
                    zone_start = vol->data2_zone_pos;
                    zone_end = vol->mft_zone_start;
                    if ( !zone_start )
                        pass = 2;
                    break;
                case ZONE_DATA2:
                    if ( !( done_zones & ZONE_DATA1 ) )
                    {
                        ntfs_log_trace( "data2 -> data1\n" );
                        goto switch_to_data1_zone;
                    }
                    ntfs_log_trace( "Zone switch: data2 -> mft\n" );
                    search_zone = ZONE_MFT;
                    zone_start = vol->mft_zone_pos;
                    zone_end = vol->mft_zone_end;
                    if ( zone_start == vol->mft_zone_start )
                        pass = 2;
                    break;
            }

            bmp_pos = zone_start;

            if ( zone_start == zone_end )
            {
                ntfs_log_trace( "Empty zone, skipped.\n" );
                goto done_zones_check;
            }

            continue;
        }

        ntfs_log_trace( "All zones are finished, no space on device.\n" );
        err = ENOSPC;
        goto err_ret;
    }
done_ret:
    ntfs_log_debug( "At done_ret.\n" );
    /* Add runlist terminator element. */
    rl[rlpos].vcn = rl[rlpos - 1].vcn + rl[rlpos - 1].length;
    rl[rlpos].lcn = LCN_RL_NOT_MAPPED;
    rl[rlpos].length = 0;
    if ( bitmap_writeback( vol, last_read_pos, br, buf, &writeback ) )
    {
        err = errno;
        goto err_ret;
    }
done_err_ret:
    free( buf );
    if ( err )
    {
        errno = err;
        ntfs_log_perror( "Failed to allocate clusters" );
        rl = NULL;
    }
out:
    ntfs_log_leave( "\n" );
    return rl;

wb_err_ret:
    ntfs_log_trace( "At wb_err_ret.\n" );
    if ( bitmap_writeback( vol, last_read_pos, br, buf, &writeback ) )
        err = errno;
err_ret:
    ntfs_log_trace( "At err_ret.\n" );
    if ( rl )
    {
        /* Add runlist terminator element. */
        rl[rlpos].vcn = rl[rlpos - 1].vcn + rl[rlpos - 1].length;
        rl[rlpos].lcn = LCN_RL_NOT_MAPPED;
        rl[rlpos].length = 0;
        ntfs_debug_runlist_dump( rl );
        ntfs_cluster_free_from_rl( vol, rl );
        free( rl );
        rl = NULL;
    }
    goto done_err_ret;
}

/**
 * ntfs_cluster_free_from_rl - free clusters from runlist
 * @vol:    mounted ntfs volume on which to free the clusters
 * @rl:     runlist from which deallocate clusters
 *
 * On success return 0 and on error return -1 with errno set to the error code.
 */
int ntfs_cluster_free_from_rl( ntfs_volume *vol, runlist *rl )
{
    s64 nr_freed = 0;
    int ret = -1;

    ntfs_log_trace( "Entering.\n" );

    for ( ; rl->length; rl++ )
    {

        ntfs_log_trace( "Dealloc lcn 0x%llx, len 0x%llx.\n",
                        ( long long )rl->lcn, ( long long )rl->length );

        if ( rl->lcn >= 0 )
        {
            update_full_status( vol, rl->lcn );
            if ( ntfs_bitmap_clear_run( vol->lcnbmp_na, rl->lcn,
                                        rl->length ) )
            {
                ntfs_log_perror( "Cluster deallocation failed "
                                 "(%lld, %lld)",
                                 ( long long )rl->lcn,
                                 ( long long )rl->length );
                goto out;
            }
            nr_freed += rl->length ;
        }
    }

    ret = 0;
out:
    vol->free_clusters += nr_freed;
    if ( vol->free_clusters > vol->nr_clusters )
        ntfs_log_error( "Too many free clusters (%lld > %lld)!",
                        ( long long )vol->free_clusters,
                        ( long long )vol->nr_clusters );
    return ret;
}

/*
 *      Basic cluster run free
 *  Returns 0 if successful
 */

int ntfs_cluster_free_basic( ntfs_volume *vol, s64 lcn, s64 count )
{
    s64 nr_freed = 0;
    int ret = -1;

    ntfs_log_trace( "Entering.\n" );
    ntfs_log_trace( "Dealloc lcn 0x%llx, len 0x%llx.\n",
                    ( long long )lcn, ( long long )count );

    if ( lcn >= 0 )
    {
        update_full_status( vol, lcn );
        if ( ntfs_bitmap_clear_run( vol->lcnbmp_na, lcn,
                                    count ) )
        {
            ntfs_log_perror( "Cluster deallocation failed "
                             "(%lld, %lld)",
                             ( long long )lcn,
                             ( long long )count );
            goto out;
        }
        nr_freed += count;
    }
    ret = 0;
out:
    vol->free_clusters += nr_freed;
    if ( vol->free_clusters > vol->nr_clusters )
        ntfs_log_error( "Too many free clusters (%lld > %lld)!",
                        ( long long )vol->free_clusters,
                        ( long long )vol->nr_clusters );
    return ret;
}

/**
 * ntfs_cluster_free - free clusters on an ntfs volume
 * @vol:    mounted ntfs volume on which to free the clusters
 * @na:     attribute whose runlist describes the clusters to free
 * @start_vcn:  vcn in @rl at which to start freeing clusters
 * @count:  number of clusters to free or -1 for all clusters
 *
 * Free @count clusters starting at the cluster @start_vcn in the runlist
 * described by the attribute @na from the mounted ntfs volume @vol.
 *
 * If @count is -1, all clusters from @start_vcn to the end of the runlist
 * are deallocated.
 *
 * On success return the number of deallocated clusters (not counting sparse
 * clusters) and on error return -1 with errno set to the error code.
 */
int ntfs_cluster_free( ntfs_volume *vol, ntfs_attr *na, VCN start_vcn, s64 count )
{
    runlist *rl;
    s64 delta, to_free, nr_freed = 0;
    int ret = -1;

    if ( !vol || !vol->lcnbmp_na || !na || start_vcn < 0 ||
            ( count < 0 && count != -1 ) )
    {
        ntfs_log_trace( "Invalid arguments!\n" );
        errno = EINVAL;
        return -1;
    }

    ntfs_log_enter( "Entering for inode 0x%llx, attr 0x%x, count 0x%llx, "
                    "vcn 0x%llx.\n", ( unsigned long long )na->ni->mft_no,
                    na->type, ( long long )count, ( long long )start_vcn );

    rl = ntfs_attr_find_vcn( na, start_vcn );
    if ( !rl )
    {
        if ( errno == ENOENT )
            ret = 0;
        goto leave;
    }

    if ( rl->lcn < 0 && rl->lcn != LCN_HOLE )
    {
        errno = EIO;
        ntfs_log_perror( "%s: Unexpected lcn (%lld)", __FUNCTION__,
                         ( long long )rl->lcn );
        goto leave;
    }

    /* Find the starting cluster inside the run that needs freeing. */
    delta = start_vcn - rl->vcn;

    /* The number of clusters in this run that need freeing. */
    to_free = rl->length - delta;
    if ( count >= 0 && to_free > count )
        to_free = count;

    if ( rl->lcn != LCN_HOLE )
    {
        /* Do the actual freeing of the clusters in this run. */
        update_full_status( vol, rl->lcn + delta );
        if ( ntfs_bitmap_clear_run( vol->lcnbmp_na, rl->lcn + delta,
                                    to_free ) )
            goto leave;
        nr_freed = to_free;
    }

    /* Go to the next run and adjust the number of clusters left to free. */
    ++rl;
    if ( count >= 0 )
        count -= to_free;

    /*
     * Loop over the remaining runs, using @count as a capping value, and
     * free them.
     */
    for ( ; rl->length && count != 0; ++rl )
    {
        // FIXME: Need to try ntfs_attr_map_runlist() for attribute
        //    list support! (AIA)
        if ( rl->lcn < 0 && rl->lcn != LCN_HOLE )
        {
            // FIXME: Eeek! We need rollback! (AIA)
            errno = EIO;
            ntfs_log_perror( "%s: Invalid lcn (%lli)",
                             __FUNCTION__, ( long long )rl->lcn );
            goto out;
        }

        /* The number of clusters in this run that need freeing. */
        to_free = rl->length;
        if ( count >= 0 && to_free > count )
            to_free = count;

        if ( rl->lcn != LCN_HOLE )
        {
            update_full_status( vol, rl->lcn );
            if ( ntfs_bitmap_clear_run( vol->lcnbmp_na, rl->lcn,
                                        to_free ) )
            {
                // FIXME: Eeek! We need rollback! (AIA)
                ntfs_log_perror( "%s: Clearing bitmap run failed",
                                 __FUNCTION__ );
                goto out;
            }
            nr_freed += to_free;
        }

        if ( count >= 0 )
            count -= to_free;
    }

    if ( count != -1 && count != 0 )
    {
        // FIXME: Eeek! BUG()
        errno = EIO;
        ntfs_log_perror( "%s: count still not zero (%lld)", __FUNCTION__,
                         ( long long )count );
        goto out;
    }

    ret = nr_freed;
out:
    vol->free_clusters += nr_freed ;
    if ( vol->free_clusters > vol->nr_clusters )
        ntfs_log_error( "Too many free clusters (%lld > %lld)!",
                        ( long long )vol->free_clusters,
                        ( long long )vol->nr_clusters );
leave:
    ntfs_log_leave( "\n" );
    return ret;
}