Add qemu 2.4.0

Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>

1 files changed, 3042 insertions, 0 deletions

diff --git a/qemu/block/vvfat.c b/qemu/block/vvfat.c
new file mode 100644
index 000000000..206869712
--- /dev/null
+++ b/qemu/block/vvfat.c
@@ -0,0 +1,3042 @@
+/* vim:set shiftwidth=4 ts=4: */
+/*
+ * QEMU Block driver for virtual VFAT (shadows a local directory)
+ *
+ * Copyright (c) 2004,2005 Johannes E. Schindelin
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include <sys/stat.h>
+#include <dirent.h>
+#include "qemu-common.h"
+#include "block/block_int.h"
+#include "qemu/module.h"
+#include "migration/migration.h"
+#include "qapi/qmp/qint.h"
+#include "qapi/qmp/qbool.h"
+#include "qapi/qmp/qstring.h"
+
+#ifndef S_IWGRP
+#define S_IWGRP 0
+#endif
+#ifndef S_IWOTH
+#define S_IWOTH 0
+#endif
+
+/* TODO: add ":bootsector=blabla.img:" */
+/* LATER TODO: add automatic boot sector generation from
+    BOOTEASY.ASM and Ranish Partition Manager
+    Note that DOS assumes the system files to be the first files in the
+    file system (test if the boot sector still relies on that fact)! */
+/* MAYBE TODO: write block-visofs.c */
+/* TODO: call try_commit() only after a timeout */
+
+/* #define DEBUG */
+
+#ifdef DEBUG
+
+#define DLOG(a) a
+
+static void checkpoint(void);
+
+#ifdef __MINGW32__
+void nonono(const char* file, int line, const char* msg) {
+    fprintf(stderr, "Nonono! %s:%d %s\n", file, line, msg);
+    exit(-5);
+}
+#undef assert
+#define assert(a) do {if (!(a)) nonono(__FILE__, __LINE__, #a);}while(0)
+#endif
+
+#else
+
+#define DLOG(a)
+
+#endif
+
+/* dynamic array functions */
+typedef struct array_t {
+    char* pointer;
+    unsigned int size,next,item_size;
+} array_t;
+
+static inline void array_init(array_t* array,unsigned int item_size)
+{
+    array->pointer = NULL;
+    array->size=0;
+    array->next=0;
+    array->item_size=item_size;
+}
+
+static inline void array_free(array_t* array)
+{
+    g_free(array->pointer);
+    array->size=array->next=0;
+}
+
+/* does not automatically grow */
+static inline void* array_get(array_t* array,unsigned int index) {
+    assert(index < array->next);
+    return array->pointer + index * array->item_size;
+}
+
+static inline int array_ensure_allocated(array_t* array, int index)
+{
+    if((index + 1) * array->item_size > array->size) {
+	int new_size = (index + 32) * array->item_size;
+	array->pointer = g_realloc(array->pointer, new_size);
+	if (!array->pointer)
+	    return -1;
+	array->size = new_size;
+	array->next = index + 1;
+    }
+
+    return 0;
+}
+
+static inline void* array_get_next(array_t* array) {
+    unsigned int next = array->next;
+    void* result;
+
+    if (array_ensure_allocated(array, next) < 0)
+	return NULL;
+
+    array->next = next + 1;
+    result = array_get(array, next);
+
+    return result;
+}
+
+static inline void* array_insert(array_t* array,unsigned int index,unsigned int count) {
+    if((array->next+count)*array->item_size>array->size) {
+	int increment=count*array->item_size;
+	array->pointer=g_realloc(array->pointer,array->size+increment);
+	if(!array->pointer)
+            return NULL;
+	array->size+=increment;
+    }
+    memmove(array->pointer+(index+count)*array->item_size,
+		array->pointer+index*array->item_size,
+		(array->next-index)*array->item_size);
+    array->next+=count;
+    return array->pointer+index*array->item_size;
+}
+
+/* this performs a "roll", so that the element which was at index_from becomes
+ * index_to, but the order of all other elements is preserved. */
+static inline int array_roll(array_t* array,int index_to,int index_from,int count)
+{
+    char* buf;
+    char* from;
+    char* to;
+    int is;
+
+    if(!array ||
+	    index_to<0 || index_to>=array->next ||
+	    index_from<0 || index_from>=array->next)
+	return -1;
+
+    if(index_to==index_from)
+	return 0;
+
+    is=array->item_size;
+    from=array->pointer+index_from*is;
+    to=array->pointer+index_to*is;
+    buf=g_malloc(is*count);
+    memcpy(buf,from,is*count);
+
+    if(index_to<index_from)
+	memmove(to+is*count,to,from-to);
+    else
+	memmove(from,from+is*count,to-from);
+
+    memcpy(to,buf,is*count);
+
+    g_free(buf);
+
+    return 0;
+}
+
+static inline int array_remove_slice(array_t* array,int index, int count)
+{
+    assert(index >=0);
+    assert(count > 0);
+    assert(index + count <= array->next);
+    if(array_roll(array,array->next-1,index,count))
+	return -1;
+    array->next -= count;
+    return 0;
+}
+
+static int array_remove(array_t* array,int index)
+{
+    return array_remove_slice(array, index, 1);
+}
+
+/* return the index for a given member */
+static int array_index(array_t* array, void* pointer)
+{
+    size_t offset = (char*)pointer - array->pointer;
+    assert((offset % array->item_size) == 0);
+    assert(offset/array->item_size < array->next);
+    return offset/array->item_size;
+}
+
+/* These structures are used to fake a disk and the VFAT filesystem.
+ * For this reason we need to use QEMU_PACKED. */
+
+typedef struct bootsector_t {
+    uint8_t jump[3];
+    uint8_t name[8];
+    uint16_t sector_size;
+    uint8_t sectors_per_cluster;
+    uint16_t reserved_sectors;
+    uint8_t number_of_fats;
+    uint16_t root_entries;
+    uint16_t total_sectors16;
+    uint8_t media_type;
+    uint16_t sectors_per_fat;
+    uint16_t sectors_per_track;
+    uint16_t number_of_heads;
+    uint32_t hidden_sectors;
+    uint32_t total_sectors;
+    union {
+        struct {
+	    uint8_t drive_number;
+	    uint8_t current_head;
+	    uint8_t signature;
+	    uint32_t id;
+	    uint8_t volume_label[11];
+	} QEMU_PACKED fat16;
+	struct {
+	    uint32_t sectors_per_fat;
+	    uint16_t flags;
+	    uint8_t major,minor;
+	    uint32_t first_cluster_of_root_directory;
+	    uint16_t info_sector;
+	    uint16_t backup_boot_sector;
+	    uint16_t ignored;
+	} QEMU_PACKED fat32;
+    } u;
+    uint8_t fat_type[8];
+    uint8_t ignored[0x1c0];
+    uint8_t magic[2];
+} QEMU_PACKED bootsector_t;
+
+typedef struct {
+    uint8_t head;
+    uint8_t sector;
+    uint8_t cylinder;
+} mbr_chs_t;
+
+typedef struct partition_t {
+    uint8_t attributes; /* 0x80 = bootable */
+    mbr_chs_t start_CHS;
+    uint8_t   fs_type; /* 0x1 = FAT12, 0x6 = FAT16, 0xe = FAT16_LBA, 0xb = FAT32, 0xc = FAT32_LBA */
+    mbr_chs_t end_CHS;
+    uint32_t start_sector_long;
+    uint32_t length_sector_long;
+} QEMU_PACKED partition_t;
+
+typedef struct mbr_t {
+    uint8_t ignored[0x1b8];
+    uint32_t nt_id;
+    uint8_t ignored2[2];
+    partition_t partition[4];
+    uint8_t magic[2];
+} QEMU_PACKED mbr_t;
+
+typedef struct direntry_t {
+    uint8_t name[8 + 3];
+    uint8_t attributes;
+    uint8_t reserved[2];
+    uint16_t ctime;
+    uint16_t cdate;
+    uint16_t adate;
+    uint16_t begin_hi;
+    uint16_t mtime;
+    uint16_t mdate;
+    uint16_t begin;
+    uint32_t size;
+} QEMU_PACKED direntry_t;
+
+/* this structure are used to transparently access the files */
+
+typedef struct mapping_t {
+    /* begin is the first cluster, end is the last+1 */
+    uint32_t begin,end;
+    /* as s->directory is growable, no pointer may be used here */
+    unsigned int dir_index;
+    /* the clusters of a file may be in any order; this points to the first */
+    int first_mapping_index;
+    union {
+	/* offset is
+	 * - the offset in the file (in clusters) for a file, or
+	 * - the next cluster of the directory for a directory, and
+	 * - the address of the buffer for a faked entry
+	 */
+	struct {
+	    uint32_t offset;
+	} file;
+	struct {
+	    int parent_mapping_index;
+	    int first_dir_index;
+	} dir;
+    } info;
+    /* path contains the full path, i.e. it always starts with s->path */
+    char* path;
+
+    enum { MODE_UNDEFINED = 0, MODE_NORMAL = 1, MODE_MODIFIED = 2,
+	MODE_DIRECTORY = 4, MODE_FAKED = 8,
+	MODE_DELETED = 16, MODE_RENAMED = 32 } mode;
+    int read_only;
+} mapping_t;
+
+#ifdef DEBUG
+static void print_direntry(const struct direntry_t*);
+static void print_mapping(const struct mapping_t* mapping);
+#endif
+
+/* here begins the real VVFAT driver */
+
+typedef struct BDRVVVFATState {
+    CoMutex lock;
+    BlockDriverState* bs; /* pointer to parent */
+    unsigned int first_sectors_number; /* 1 for a single partition, 0x40 for a disk with partition table */
+    unsigned char first_sectors[0x40*0x200];
+
+    int fat_type; /* 16 or 32 */
+    array_t fat,directory,mapping;
+    char volume_label[11];
+
+    unsigned int cluster_size;
+    unsigned int sectors_per_cluster;
+    unsigned int sectors_per_fat;
+    unsigned int sectors_of_root_directory;
+    uint32_t last_cluster_of_root_directory;
+    unsigned int faked_sectors; /* how many sectors are faked before file data */
+    uint32_t sector_count; /* total number of sectors of the partition */
+    uint32_t cluster_count; /* total number of clusters of this partition */
+    uint32_t max_fat_value;
+
+    int current_fd;
+    mapping_t* current_mapping;
+    unsigned char* cluster; /* points to current cluster */
+    unsigned char* cluster_buffer; /* points to a buffer to hold temp data */
+    unsigned int current_cluster;
+
+    /* write support */
+    BlockDriverState* write_target;
+    char* qcow_filename;
+    BlockDriverState* qcow;
+    void* fat2;
+    char* used_clusters;
+    array_t commits;
+    const char* path;
+    int downcase_short_names;
+
+    Error *migration_blocker;
+} BDRVVVFATState;
+
+/* take the sector position spos and convert it to Cylinder/Head/Sector position
+ * if the position is outside the specified geometry, fill maximum value for CHS
+ * and return 1 to signal overflow.
+ */
+static int sector2CHS(mbr_chs_t *chs, int spos, int cyls, int heads, int secs)
+{
+    int head,sector;
+    sector   = spos % secs;  spos /= secs;
+    head     = spos % heads; spos /= heads;
+    if (spos >= cyls) {
+        /* Overflow,
+        it happens if 32bit sector positions are used, while CHS is only 24bit.
+        Windows/Dos is said to take 1023/255/63 as nonrepresentable CHS */
+        chs->head     = 0xFF;
+        chs->sector   = 0xFF;
+        chs->cylinder = 0xFF;
+        return 1;
+    }
+    chs->head     = (uint8_t)head;
+    chs->sector   = (uint8_t)( (sector+1) | ((spos>>8)<<6) );
+    chs->cylinder = (uint8_t)spos;
+    return 0;
+}
+
+static void init_mbr(BDRVVVFATState *s, int cyls, int heads, int secs)
+{
+    /* TODO: if the files mbr.img and bootsect.img exist, use them */
+    mbr_t* real_mbr=(mbr_t*)s->first_sectors;
+    partition_t* partition = &(real_mbr->partition[0]);
+    int lba;
+
+    memset(s->first_sectors,0,512);
+
+    /* Win NT Disk Signature */
+    real_mbr->nt_id= cpu_to_le32(0xbe1afdfa);
+
+    partition->attributes=0x80; /* bootable */
+
+    /* LBA is used when partition is outside the CHS geometry */
+    lba  = sector2CHS(&partition->start_CHS, s->first_sectors_number - 1,
+                     cyls, heads, secs);
+    lba |= sector2CHS(&partition->end_CHS,   s->bs->total_sectors - 1,
+                     cyls, heads, secs);
+
+    /*LBA partitions are identified only by start/length_sector_long not by CHS*/
+    partition->start_sector_long  = cpu_to_le32(s->first_sectors_number - 1);
+    partition->length_sector_long = cpu_to_le32(s->bs->total_sectors
+                                                - s->first_sectors_number + 1);
+
+    /* FAT12/FAT16/FAT32 */
+    /* DOS uses different types when partition is LBA,
+       probably to prevent older versions from using CHS on them */
+    partition->fs_type= s->fat_type==12 ? 0x1:
+                        s->fat_type==16 ? (lba?0xe:0x06):
+                         /*fat_tyoe==32*/ (lba?0xc:0x0b);
+
+    real_mbr->magic[0]=0x55; real_mbr->magic[1]=0xaa;
+}
+
+/* direntry functions */
+
+/* dest is assumed to hold 258 bytes, and pads with 0xffff up to next multiple of 26 */
+static inline int short2long_name(char* dest,const char* src)
+{
+    int i;
+    int len;
+    for(i=0;i<129 && src[i];i++) {
+        dest[2*i]=src[i];
+	dest[2*i+1]=0;
+    }
+    len=2*i;
+    dest[2*i]=dest[2*i+1]=0;
+    for(i=2*i+2;(i%26);i++)
+	dest[i]=0xff;
+    return len;
+}
+
+static inline direntry_t* create_long_filename(BDRVVVFATState* s,const char* filename)
+{
+    char buffer[258];
+    int length=short2long_name(buffer,filename),
+        number_of_entries=(length+25)/26,i;
+    direntry_t* entry;
+
+    for(i=0;i<number_of_entries;i++) {
+	entry=array_get_next(&(s->directory));
+	entry->attributes=0xf;
+	entry->reserved[0]=0;
+	entry->begin=0;
+	entry->name[0]=(number_of_entries-i)|(i==0?0x40:0);
+    }
+    for(i=0;i<26*number_of_entries;i++) {
+	int offset=(i%26);
+	if(offset<10) offset=1+offset;
+	else if(offset<22) offset=14+offset-10;
+	else offset=28+offset-22;
+	entry=array_get(&(s->directory),s->directory.next-1-(i/26));
+	entry->name[offset]=buffer[i];
+    }
+    return array_get(&(s->directory),s->directory.next-number_of_entries);
+}
+
+static char is_free(const direntry_t* direntry)
+{
+    return direntry->name[0]==0xe5 || direntry->name[0]==0x00;
+}
+
+static char is_volume_label(const direntry_t* direntry)
+{
+    return direntry->attributes == 0x28;
+}
+
+static char is_long_name(const direntry_t* direntry)
+{
+    return direntry->attributes == 0xf;
+}
+
+static char is_short_name(const direntry_t* direntry)
+{
+    return !is_volume_label(direntry) && !is_long_name(direntry)
+	&& !is_free(direntry);
+}
+
+static char is_directory(const direntry_t* direntry)
+{
+    return direntry->attributes & 0x10 && direntry->name[0] != 0xe5;
+}
+
+static inline char is_dot(const direntry_t* direntry)
+{
+    return is_short_name(direntry) && direntry->name[0] == '.';
+}
+
+static char is_file(const direntry_t* direntry)
+{
+    return is_short_name(direntry) && !is_directory(direntry);
+}
+
+static inline uint32_t begin_of_direntry(const direntry_t* direntry)
+{
+    return le16_to_cpu(direntry->begin)|(le16_to_cpu(direntry->begin_hi)<<16);
+}
+
+static inline uint32_t filesize_of_direntry(const direntry_t* direntry)
+{
+    return le32_to_cpu(direntry->size);
+}
+
+static void set_begin_of_direntry(direntry_t* direntry, uint32_t begin)
+{
+    direntry->begin = cpu_to_le16(begin & 0xffff);
+    direntry->begin_hi = cpu_to_le16((begin >> 16) & 0xffff);
+}
+
+/* fat functions */
+
+static inline uint8_t fat_chksum(const direntry_t* entry)
+{
+    uint8_t chksum=0;
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(entry->name); i++) {
+        chksum = (((chksum & 0xfe) >> 1) |
+                  ((chksum & 0x01) ? 0x80 : 0)) + entry->name[i];
+    }
+
+    return chksum;
+}
+
+/* if return_time==0, this returns the fat_date, else the fat_time */
+static uint16_t fat_datetime(time_t time,int return_time) {
+    struct tm* t;
+    struct tm t1;
+    t = &t1;
+    localtime_r(&time,t);
+    if(return_time)
+	return cpu_to_le16((t->tm_sec/2)|(t->tm_min<<5)|(t->tm_hour<<11));
+    return cpu_to_le16((t->tm_mday)|((t->tm_mon+1)<<5)|((t->tm_year-80)<<9));
+}
+
+static inline void fat_set(BDRVVVFATState* s,unsigned int cluster,uint32_t value)
+{
+    if(s->fat_type==32) {
+	uint32_t* entry=array_get(&(s->fat),cluster);
+	*entry=cpu_to_le32(value);
+    } else if(s->fat_type==16) {
+	uint16_t* entry=array_get(&(s->fat),cluster);
+	*entry=cpu_to_le16(value&0xffff);
+    } else {
+	int offset = (cluster*3/2);
+	unsigned char* p = array_get(&(s->fat), offset);
+        switch (cluster&1) {
+	case 0:
+		p[0] = value&0xff;
+		p[1] = (p[1]&0xf0) | ((value>>8)&0xf);
+		break;
+	case 1:
+		p[0] = (p[0]&0xf) | ((value&0xf)<<4);
+		p[1] = (value>>4);
+		break;
+	}
+    }
+}
+
+static inline uint32_t fat_get(BDRVVVFATState* s,unsigned int cluster)
+{
+    if(s->fat_type==32) {
+	uint32_t* entry=array_get(&(s->fat),cluster);
+	return le32_to_cpu(*entry);
+    } else if(s->fat_type==16) {
+	uint16_t* entry=array_get(&(s->fat),cluster);
+	return le16_to_cpu(*entry);
+    } else {
+	const uint8_t* x=(uint8_t*)(s->fat.pointer)+cluster*3/2;
+	return ((x[0]|(x[1]<<8))>>(cluster&1?4:0))&0x0fff;
+    }
+}
+
+static inline int fat_eof(BDRVVVFATState* s,uint32_t fat_entry)
+{
+    if(fat_entry>s->max_fat_value-8)
+	return -1;
+    return 0;
+}
+
+static inline void init_fat(BDRVVVFATState* s)
+{
+    if (s->fat_type == 12) {
+	array_init(&(s->fat),1);
+	array_ensure_allocated(&(s->fat),
+		s->sectors_per_fat * 0x200 * 3 / 2 - 1);
+    } else {
+	array_init(&(s->fat),(s->fat_type==32?4:2));
+	array_ensure_allocated(&(s->fat),
+		s->sectors_per_fat * 0x200 / s->fat.item_size - 1);
+    }
+    memset(s->fat.pointer,0,s->fat.size);
+
+    switch(s->fat_type) {
+	case 12: s->max_fat_value=0xfff; break;
+	case 16: s->max_fat_value=0xffff; break;
+	case 32: s->max_fat_value=0x0fffffff; break;
+	default: s->max_fat_value=0; /* error... */
+    }
+
+}
+
+/* TODO: in create_short_filename, 0xe5->0x05 is not yet handled! */
+/* TODO: in parse_short_filename, 0x05->0xe5 is not yet handled! */
+static inline direntry_t* create_short_and_long_name(BDRVVVFATState* s,
+	unsigned int directory_start, const char* filename, int is_dot)
+{
+    int i,j,long_index=s->directory.next;
+    direntry_t* entry = NULL;
+    direntry_t* entry_long = NULL;
+
+    if(is_dot) {
+	entry=array_get_next(&(s->directory));
+        memset(entry->name, 0x20, sizeof(entry->name));
+	memcpy(entry->name,filename,strlen(filename));
+	return entry;
+    }
+
+    entry_long=create_long_filename(s,filename);
+
+    i = strlen(filename);
+    for(j = i - 1; j>0  && filename[j]!='.';j--);
+    if (j > 0)
+	i = (j > 8 ? 8 : j);
+    else if (i > 8)
+	i = 8;
+
+    entry=array_get_next(&(s->directory));
+    memset(entry->name, 0x20, sizeof(entry->name));
+    memcpy(entry->name, filename, i);
+
+    if (j > 0) {
+        for (i = 0; i < 3 && filename[j + 1 + i]; i++) {
+            entry->name[8 + i] = filename[j + 1 + i];
+        }
+    }
+
+    /* upcase & remove unwanted characters */
+    for(i=10;i>=0;i--) {
+	if(i==10 || i==7) for(;i>0 && entry->name[i]==' ';i--);
+	if(entry->name[i]<=' ' || entry->name[i]>0x7f
+		|| strchr(".*?<>|\":/\\[];,+='",entry->name[i]))
+	    entry->name[i]='_';
+        else if(entry->name[i]>='a' && entry->name[i]<='z')
+            entry->name[i]+='A'-'a';
+    }
+
+    /* mangle duplicates */
+    while(1) {
+	direntry_t* entry1=array_get(&(s->directory),directory_start);
+	int j;
+
+	for(;entry1<entry;entry1++)
+	    if(!is_long_name(entry1) && !memcmp(entry1->name,entry->name,11))
+		break; /* found dupe */
+	if(entry1==entry) /* no dupe found */
+	    break;
+
+	/* use all 8 characters of name */
+	if(entry->name[7]==' ') {
+	    int j;
+	    for(j=6;j>0 && entry->name[j]==' ';j--)
+		entry->name[j]='~';
+	}
+
+	/* increment number */
+	for(j=7;j>0 && entry->name[j]=='9';j--)
+	    entry->name[j]='0';
+	if(j>0) {
+	    if(entry->name[j]<'0' || entry->name[j]>'9')
+	        entry->name[j]='0';
+	    else
+	        entry->name[j]++;
+	}
+    }
+
+    /* calculate checksum; propagate to long name */
+    if(entry_long) {
+        uint8_t chksum=fat_chksum(entry);
+
+	/* calculate anew, because realloc could have taken place */
+	entry_long=array_get(&(s->directory),long_index);
+	while(entry_long<entry && is_long_name(entry_long)) {
+	    entry_long->reserved[1]=chksum;
+	    entry_long++;
+	}
+    }
+
+    return entry;
+}
+
+/*
+ * Read a directory. (the index of the corresponding mapping must be passed).
+ */
+static int read_directory(BDRVVVFATState* s, int mapping_index)
+{
+    mapping_t* mapping = array_get(&(s->mapping), mapping_index);
+    direntry_t* direntry;
+    const char* dirname = mapping->path;
+    int first_cluster = mapping->begin;
+    int parent_index = mapping->info.dir.parent_mapping_index;
+    mapping_t* parent_mapping = (mapping_t*)
+        (parent_index >= 0 ? array_get(&(s->mapping), parent_index) : NULL);
+    int first_cluster_of_parent = parent_mapping ? parent_mapping->begin : -1;
+
+    DIR* dir=opendir(dirname);
+    struct dirent* entry;
+    int i;
+
+    assert(mapping->mode & MODE_DIRECTORY);
+
+    if(!dir) {
+	mapping->end = mapping->begin;
+	return -1;
+    }
+
+    i = mapping->info.dir.first_dir_index =
+	    first_cluster == 0 ? 0 : s->directory.next;
+
+    /* actually read the directory, and allocate the mappings */
+    while((entry=readdir(dir))) {
+	unsigned int length=strlen(dirname)+2+strlen(entry->d_name);
+        char* buffer;
+	direntry_t* direntry;
+        struct stat st;
+	int is_dot=!strcmp(entry->d_name,".");
+	int is_dotdot=!strcmp(entry->d_name,"..");
+
+	if(first_cluster == 0 && (is_dotdot || is_dot))
+	    continue;
+
+	buffer = g_malloc(length);
+	snprintf(buffer,length,"%s/%s",dirname,entry->d_name);
+
+	if(stat(buffer,&st)<0) {
+            g_free(buffer);
+            continue;
+	}
+
+	/* create directory entry for this file */
+	direntry=create_short_and_long_name(s, i, entry->d_name,
+		is_dot || is_dotdot);
+	direntry->attributes=(S_ISDIR(st.st_mode)?0x10:0x20);
+	direntry->reserved[0]=direntry->reserved[1]=0;
+	direntry->ctime=fat_datetime(st.st_ctime,1);
+	direntry->cdate=fat_datetime(st.st_ctime,0);
+	direntry->adate=fat_datetime(st.st_atime,0);
+	direntry->begin_hi=0;
+	direntry->mtime=fat_datetime(st.st_mtime,1);
+	direntry->mdate=fat_datetime(st.st_mtime,0);
+	if(is_dotdot)
+	    set_begin_of_direntry(direntry, first_cluster_of_parent);
+	else if(is_dot)
+	    set_begin_of_direntry(direntry, first_cluster);
+	else
+	    direntry->begin=0; /* do that later */
+        if (st.st_size > 0x7fffffff) {
+	    fprintf(stderr, "File %s is larger than 2GB\n", buffer);
+            g_free(buffer);
+            closedir(dir);
+	    return -2;
+        }
+	direntry->size=cpu_to_le32(S_ISDIR(st.st_mode)?0:st.st_size);
+
+	/* create mapping for this file */
+	if(!is_dot && !is_dotdot && (S_ISDIR(st.st_mode) || st.st_size)) {
+	    s->current_mapping = array_get_next(&(s->mapping));
+	    s->current_mapping->begin=0;
+	    s->current_mapping->end=st.st_size;
+	    /*
+	     * we get the direntry of the most recent direntry, which
+	     * contains the short name and all the relevant information.
+	     */
+	    s->current_mapping->dir_index=s->directory.next-1;
+	    s->current_mapping->first_mapping_index = -1;
+	    if (S_ISDIR(st.st_mode)) {
+		s->current_mapping->mode = MODE_DIRECTORY;
+		s->current_mapping->info.dir.parent_mapping_index =
+		    mapping_index;
+	    } else {
+		s->current_mapping->mode = MODE_UNDEFINED;
+		s->current_mapping->info.file.offset = 0;
+	    }
+	    s->current_mapping->path=buffer;
+	    s->current_mapping->read_only =
+		(st.st_mode & (S_IWUSR | S_IWGRP | S_IWOTH)) == 0;
+        } else {
+            g_free(buffer);
+        }
+    }
+    closedir(dir);
+
+    /* fill with zeroes up to the end of the cluster */
+    while(s->directory.next%(0x10*s->sectors_per_cluster)) {
+	direntry_t* direntry=array_get_next(&(s->directory));
+	memset(direntry,0,sizeof(direntry_t));
+    }
+
+/* TODO: if there are more entries, bootsector has to be adjusted! */
+#define ROOT_ENTRIES (0x02 * 0x10 * s->sectors_per_cluster)
+    if (mapping_index == 0 && s->directory.next < ROOT_ENTRIES) {
+	/* root directory */
+	int cur = s->directory.next;
+	array_ensure_allocated(&(s->directory), ROOT_ENTRIES - 1);
+	s->directory.next = ROOT_ENTRIES;
+	memset(array_get(&(s->directory), cur), 0,
+		(ROOT_ENTRIES - cur) * sizeof(direntry_t));
+    }
+
+     /* reget the mapping, since s->mapping was possibly realloc()ed */
+    mapping = array_get(&(s->mapping), mapping_index);
+    first_cluster += (s->directory.next - mapping->info.dir.first_dir_index)
+	* 0x20 / s->cluster_size;
+    mapping->end = first_cluster;
+
+    direntry = array_get(&(s->directory), mapping->dir_index);
+    set_begin_of_direntry(direntry, mapping->begin);
+
+    return 0;
+}
+
+static inline uint32_t sector2cluster(BDRVVVFATState* s,off_t sector_num)
+{
+    return (sector_num-s->faked_sectors)/s->sectors_per_cluster;
+}
+
+static inline off_t cluster2sector(BDRVVVFATState* s, uint32_t cluster_num)
+{
+    return s->faked_sectors + s->sectors_per_cluster * cluster_num;
+}
+
+static int init_directories(BDRVVVFATState* s,
+                            const char *dirname, int heads, int secs,
+                            Error **errp)
+{
+    bootsector_t* bootsector;
+    mapping_t* mapping;
+    unsigned int i;
+    unsigned int cluster;
+
+    memset(&(s->first_sectors[0]),0,0x40*0x200);
+
+    s->cluster_size=s->sectors_per_cluster*0x200;
+    s->cluster_buffer=g_malloc(s->cluster_size);
+
+    /*
+     * The formula: sc = spf+1+spf*spc*(512*8/fat_type),
+     * where sc is sector_count,
+     * spf is sectors_per_fat,
+     * spc is sectors_per_clusters, and
+     * fat_type = 12, 16 or 32.
+     */
+    i = 1+s->sectors_per_cluster*0x200*8/s->fat_type;
+    s->sectors_per_fat=(s->sector_count+i)/i; /* round up */
+
+    array_init(&(s->mapping),sizeof(mapping_t));
+    array_init(&(s->directory),sizeof(direntry_t));
+
+    /* add volume label */
+    {
+	direntry_t* entry=array_get_next(&(s->directory));
+	entry->attributes=0x28; /* archive | volume label */
+        memcpy(entry->name, s->volume_label, sizeof(entry->name));
+    }
+
+    /* Now build FAT, and write back information into directory */
+    init_fat(s);
+
+    s->faked_sectors=s->first_sectors_number+s->sectors_per_fat*2;
+    s->cluster_count=sector2cluster(s, s->sector_count);
+
+    mapping = array_get_next(&(s->mapping));
+    mapping->begin = 0;
+    mapping->dir_index = 0;
+    mapping->info.dir.parent_mapping_index = -1;
+    mapping->first_mapping_index = -1;
+    mapping->path = g_strdup(dirname);
+    i = strlen(mapping->path);
+    if (i > 0 && mapping->path[i - 1] == '/')
+	mapping->path[i - 1] = '\0';
+    mapping->mode = MODE_DIRECTORY;
+    mapping->read_only = 0;
+    s->path = mapping->path;
+
+    for (i = 0, cluster = 0; i < s->mapping.next; i++) {
+	/* MS-DOS expects the FAT to be 0 for the root directory
+	 * (except for the media byte). */
+	/* LATER TODO: still true for FAT32? */
+	int fix_fat = (i != 0);
+	mapping = array_get(&(s->mapping), i);
+
+        if (mapping->mode & MODE_DIRECTORY) {
+	    mapping->begin = cluster;
+	    if(read_directory(s, i)) {
+                error_setg(errp, "Could not read directory %s",
+                           mapping->path);
+		return -1;
+	    }
+	    mapping = array_get(&(s->mapping), i);
+	} else {
+	    assert(mapping->mode == MODE_UNDEFINED);
+	    mapping->mode=MODE_NORMAL;
+	    mapping->begin = cluster;
+	    if (mapping->end > 0) {
+		direntry_t* direntry = array_get(&(s->directory),
+			mapping->dir_index);
+
+		mapping->end = cluster + 1 + (mapping->end-1)/s->cluster_size;
+		set_begin_of_direntry(direntry, mapping->begin);
+	    } else {
+		mapping->end = cluster + 1;
+		fix_fat = 0;
+	    }
+	}
+
+	assert(mapping->begin < mapping->end);
+
+	/* next free cluster */
+	cluster = mapping->end;
+
+	if(cluster > s->cluster_count) {
+            error_setg(errp,
+                       "Directory does not fit in FAT%d (capacity %.2f MB)",
+                       s->fat_type, s->sector_count / 2000.0);
+            return -1;
+	}
+
+	/* fix fat for entry */
+	if (fix_fat) {
+	    int j;
+	    for(j = mapping->begin; j < mapping->end - 1; j++)
+		fat_set(s, j, j+1);
+	    fat_set(s, mapping->end - 1, s->max_fat_value);
+	}
+    }
+
+    mapping = array_get(&(s->mapping), 0);
+    s->sectors_of_root_directory = mapping->end * s->sectors_per_cluster;
+    s->last_cluster_of_root_directory = mapping->end;
+
+    /* the FAT signature */
+    fat_set(s,0,s->max_fat_value);
+    fat_set(s,1,s->max_fat_value);
+
+    s->current_mapping = NULL;
+
+    bootsector=(bootsector_t*)(s->first_sectors+(s->first_sectors_number-1)*0x200);
+    bootsector->jump[0]=0xeb;
+    bootsector->jump[1]=0x3e;
+    bootsector->jump[2]=0x90;
+    memcpy(bootsector->name,"QEMU    ",8);
+    bootsector->sector_size=cpu_to_le16(0x200);
+    bootsector->sectors_per_cluster=s->sectors_per_cluster;
+    bootsector->reserved_sectors=cpu_to_le16(1);
+    bootsector->number_of_fats=0x2; /* number of FATs */
+    bootsector->root_entries=cpu_to_le16(s->sectors_of_root_directory*0x10);
+    bootsector->total_sectors16=s->sector_count>0xffff?0:cpu_to_le16(s->sector_count);
+    bootsector->media_type=(s->first_sectors_number>1?0xf8:0xf0); /* media descriptor (f8=hd, f0=3.5 fd)*/
+    s->fat.pointer[0] = bootsector->media_type;
+    bootsector->sectors_per_fat=cpu_to_le16(s->sectors_per_fat);
+    bootsector->sectors_per_track = cpu_to_le16(secs);
+    bootsector->number_of_heads = cpu_to_le16(heads);
+    bootsector->hidden_sectors=cpu_to_le32(s->first_sectors_number==1?0:0x3f);
+    bootsector->total_sectors=cpu_to_le32(s->sector_count>0xffff?s->sector_count:0);
+
+    /* LATER TODO: if FAT32, this is wrong */
+    bootsector->u.fat16.drive_number=s->first_sectors_number==1?0:0x80; /* fda=0, hda=0x80 */
+    bootsector->u.fat16.current_head=0;
+    bootsector->u.fat16.signature=0x29;
+    bootsector->u.fat16.id=cpu_to_le32(0xfabe1afd);
+
+    memcpy(bootsector->u.fat16.volume_label, s->volume_label,
+           sizeof(bootsector->u.fat16.volume_label));
+    memcpy(bootsector->fat_type,(s->fat_type==12?"FAT12   ":s->fat_type==16?"FAT16   ":"FAT32   "),8);
+    bootsector->magic[0]=0x55; bootsector->magic[1]=0xaa;
+
+    return 0;
+}
+
+#ifdef DEBUG
+static BDRVVVFATState *vvv = NULL;
+#endif
+
+static int enable_write_target(BDRVVVFATState *s, Error **errp);
+static int is_consistent(BDRVVVFATState *s);
+
+static void vvfat_rebind(BlockDriverState *bs)
+{
+    BDRVVVFATState *s = bs->opaque;
+    s->bs = bs;
+}
+
+static QemuOptsList runtime_opts = {
+    .name = "vvfat",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = "dir",
+            .type = QEMU_OPT_STRING,
+            .help = "Host directory to map to the vvfat device",
+        },
+        {
+            .name = "fat-type",
+            .type = QEMU_OPT_NUMBER,
+            .help = "FAT type (12, 16 or 32)",
+        },
+        {
+            .name = "floppy",
+            .type = QEMU_OPT_BOOL,
+            .help = "Create a floppy rather than a hard disk image",
+        },
+        {
+            .name = "label",
+            .type = QEMU_OPT_STRING,
+            .help = "Use a volume label other than QEMU VVFAT",
+        },
+        {
+            .name = "rw",
+            .type = QEMU_OPT_BOOL,
+            .help = "Make the image writable",
+        },
+        { /* end of list */ }
+    },
+};
+
+static void vvfat_parse_filename(const char *filename, QDict *options,
+                                 Error **errp)
+{
+    int fat_type = 0;
+    bool floppy = false;
+    bool rw = false;
+    int i;
+
+    if (!strstart(filename, "fat:", NULL)) {
+        error_setg(errp, "File name string must start with 'fat:'");
+        return;
+    }
+
+    /* Parse options */
+    if (strstr(filename, ":32:")) {
+        fat_type = 32;
+    } else if (strstr(filename, ":16:")) {
+        fat_type = 16;
+    } else if (strstr(filename, ":12:")) {
+        fat_type = 12;
+    }
+
+    if (strstr(filename, ":floppy:")) {
+        floppy = true;
+    }
+
+    if (strstr(filename, ":rw:")) {
+        rw = true;
+    }
+
+    /* Get the directory name without options */
+    i = strrchr(filename, ':') - filename;
+    assert(i >= 3);
+    if (filename[i - 2] == ':' && qemu_isalpha(filename[i - 1])) {
+        /* workaround for DOS drive names */
+        filename += i - 1;
+    } else {
+        filename += i + 1;
+    }
+
+    /* Fill in the options QDict */
+    qdict_put(options, "dir", qstring_from_str(filename));
+    qdict_put(options, "fat-type", qint_from_int(fat_type));
+    qdict_put(options, "floppy", qbool_from_bool(floppy));
+    qdict_put(options, "rw", qbool_from_bool(rw));
+}
+
+static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
+                      Error **errp)
+{
+    BDRVVVFATState *s = bs->opaque;
+    int cyls, heads, secs;
+    bool floppy;
+    const char *dirname, *label;
+    QemuOpts *opts;
+    Error *local_err = NULL;
+    int ret;
+
+#ifdef DEBUG
+    vvv = s;
+#endif
+
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    dirname = qemu_opt_get(opts, "dir");
+    if (!dirname) {
+        error_setg(errp, "vvfat block driver requires a 'dir' option");
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    s->fat_type = qemu_opt_get_number(opts, "fat-type", 0);
+    floppy = qemu_opt_get_bool(opts, "floppy", false);
+
+    memset(s->volume_label, ' ', sizeof(s->volume_label));
+    label = qemu_opt_get(opts, "label");
+    if (label) {
+        size_t label_length = strlen(label);
+        if (label_length > 11) {
+            error_setg(errp, "vvfat label cannot be longer than 11 bytes");
+            ret = -EINVAL;
+            goto fail;
+        }
+        memcpy(s->volume_label, label, label_length);
+    }
+
+    if (floppy) {
+        /* 1.44MB or 2.88MB floppy.  2.88MB can be FAT12 (default) or FAT16. */
+        if (!s->fat_type) {
+            s->fat_type = 12;
+            secs = 36;
+            s->sectors_per_cluster = 2;
+        } else {
+            secs = s->fat_type == 12 ? 18 : 36;
+            s->sectors_per_cluster = 1;
+        }
+        s->first_sectors_number = 1;
+        cyls = 80;
+        heads = 2;
+    } else {
+        /* 32MB or 504MB disk*/
+        if (!s->fat_type) {
+            s->fat_type = 16;
+        }
+        s->first_sectors_number = 0x40;
+        cyls = s->fat_type == 12 ? 64 : 1024;
+        heads = 16;
+        secs = 63;
+    }
+
+    switch (s->fat_type) {
+    case 32:
+	    fprintf(stderr, "Big fat greek warning: FAT32 has not been tested. "
+                "You are welcome to do so!\n");
+        break;
+    case 16:
+    case 12:
+        break;
+    default:
+        error_setg(errp, "Valid FAT types are only 12, 16 and 32");
+        ret = -EINVAL;
+        goto fail;
+    }
+
+
+    s->bs = bs;
+
+    /* LATER TODO: if FAT32, adjust */
+    s->sectors_per_cluster=0x10;
+
+    s->current_cluster=0xffffffff;
+
+    /* read only is the default for safety */
+    bs->read_only = 1;
+    s->qcow = s->write_target = NULL;
+    s->qcow_filename = NULL;
+    s->fat2 = NULL;
+    s->downcase_short_names = 1;
+
+    fprintf(stderr, "vvfat %s chs %d,%d,%d\n",
+            dirname, cyls, heads, secs);
+
+    s->sector_count = cyls * heads * secs - (s->first_sectors_number - 1);
+
+    if (qemu_opt_get_bool(opts, "rw", false)) {
+        ret = enable_write_target(s, errp);
+        if (ret < 0) {
+            goto fail;
+        }
+        bs->read_only = 0;
+    }
+
+    bs->total_sectors = cyls * heads * secs;
+
+    if (init_directories(s, dirname, heads, secs, errp)) {
+        ret = -EIO;
+        goto fail;
+    }
+
+    s->sector_count = s->faked_sectors + s->sectors_per_cluster*s->cluster_count;
+
+    if (s->first_sectors_number == 0x40) {
+        init_mbr(s, cyls, heads, secs);
+    }
+
+    //    assert(is_consistent(s));
+    qemu_co_mutex_init(&s->lock);
+
+    /* Disable migration when vvfat is used rw */
+    if (s->qcow) {
+        error_setg(&s->migration_blocker,
+                   "The vvfat (rw) format used by node '%s' "
+                   "does not support live migration",
+                   bdrv_get_device_or_node_name(bs));
+        migrate_add_blocker(s->migration_blocker);
+    }
+
+    ret = 0;
+fail:
+    qemu_opts_del(opts);
+    return ret;
+}
+
+static inline void vvfat_close_current_file(BDRVVVFATState *s)
+{
+    if(s->current_mapping) {
+	s->current_mapping = NULL;
+	if (s->current_fd) {
+		qemu_close(s->current_fd);
+		s->current_fd = 0;
+	}
+    }
+    s->current_cluster = -1;
+}
+
+/* mappings between index1 and index2-1 are supposed to be ordered
+ * return value is the index of the last mapping for which end>cluster_num
+ */
+static inline int find_mapping_for_cluster_aux(BDRVVVFATState* s,int cluster_num,int index1,int index2)
+{
+    while(1) {
+        int index3;
+	mapping_t* mapping;
+	index3=(index1+index2)/2;
+	mapping=array_get(&(s->mapping),index3);
+	assert(mapping->begin < mapping->end);
+	if(mapping->begin>=cluster_num) {
+	    assert(index2!=index3 || index2==0);
+	    if(index2==index3)
+		return index1;
+	    index2=index3;
+	} else {
+	    if(index1==index3)
+		return mapping->end<=cluster_num ? index2 : index1;
+	    index1=index3;
+	}
+	assert(index1<=index2);
+	DLOG(mapping=array_get(&(s->mapping),index1);
+	assert(mapping->begin<=cluster_num);
+	assert(index2 >= s->mapping.next ||
+		((mapping = array_get(&(s->mapping),index2)) &&
+		mapping->end>cluster_num)));
+    }
+}
+
+static inline mapping_t* find_mapping_for_cluster(BDRVVVFATState* s,int cluster_num)
+{
+    int index=find_mapping_for_cluster_aux(s,cluster_num,0,s->mapping.next);
+    mapping_t* mapping;
+    if(index>=s->mapping.next)
+        return NULL;
+    mapping=array_get(&(s->mapping),index);
+    if(mapping->begin>cluster_num)
+        return NULL;
+    assert(mapping->begin<=cluster_num && mapping->end>cluster_num);
+    return mapping;
+}
+
+static int open_file(BDRVVVFATState* s,mapping_t* mapping)
+{
+    if(!mapping)
+	return -1;
+    if(!s->current_mapping ||
+	    strcmp(s->current_mapping->path,mapping->path)) {
+	/* open file */
+	int fd = qemu_open(mapping->path, O_RDONLY | O_BINARY | O_LARGEFILE);
+	if(fd<0)
+	    return -1;
+	vvfat_close_current_file(s);
+	s->current_fd = fd;
+	s->current_mapping = mapping;
+    }
+    return 0;
+}
+
+static inline int read_cluster(BDRVVVFATState *s,int cluster_num)
+{
+    if(s->current_cluster != cluster_num) {
+	int result=0;
+	off_t offset;
+	assert(!s->current_mapping || s->current_fd || (s->current_mapping->mode & MODE_DIRECTORY));
+	if(!s->current_mapping
+		|| s->current_mapping->begin>cluster_num
+		|| s->current_mapping->end<=cluster_num) {
+	    /* binary search of mappings for file */
+	    mapping_t* mapping=find_mapping_for_cluster(s,cluster_num);
+
+	    assert(!mapping || (cluster_num>=mapping->begin && cluster_num<mapping->end));
+
+	    if (mapping && mapping->mode & MODE_DIRECTORY) {
+		vvfat_close_current_file(s);
+		s->current_mapping = mapping;
+read_cluster_directory:
+		offset = s->cluster_size*(cluster_num-s->current_mapping->begin);
+		s->cluster = (unsigned char*)s->directory.pointer+offset
+			+ 0x20*s->current_mapping->info.dir.first_dir_index;
+		assert(((s->cluster-(unsigned char*)s->directory.pointer)%s->cluster_size)==0);
+		assert((char*)s->cluster+s->cluster_size <= s->directory.pointer+s->directory.next*s->directory.item_size);
+		s->current_cluster = cluster_num;
+		return 0;
+	    }
+
+	    if(open_file(s,mapping))
+		return -2;
+	} else if (s->current_mapping->mode & MODE_DIRECTORY)
+	    goto read_cluster_directory;
+
+	assert(s->current_fd);
+
+	offset=s->cluster_size*(cluster_num-s->current_mapping->begin)+s->current_mapping->info.file.offset;
+	if(lseek(s->current_fd, offset, SEEK_SET)!=offset)
+	    return -3;
+	s->cluster=s->cluster_buffer;
+	result=read(s->current_fd,s->cluster,s->cluster_size);
+	if(result<0) {
+	    s->current_cluster = -1;
+	    return -1;
+	}
+	s->current_cluster = cluster_num;
+    }
+    return 0;
+}
+
+#ifdef DEBUG
+static void print_direntry(const direntry_t* direntry)
+{
+    int j = 0;
+    char buffer[1024];
+
+    fprintf(stderr, "direntry %p: ", direntry);
+    if(!direntry)
+	return;
+    if(is_long_name(direntry)) {
+	unsigned char* c=(unsigned char*)direntry;
+	int i;
+	for(i=1;i<11 && c[i] && c[i]!=0xff;i+=2)
+#define ADD_CHAR(c) {buffer[j] = (c); if (buffer[j] < ' ') buffer[j] = 0xb0; j++;}
+	    ADD_CHAR(c[i]);
+	for(i=14;i<26 && c[i] && c[i]!=0xff;i+=2)
+	    ADD_CHAR(c[i]);
+	for(i=28;i<32 && c[i] && c[i]!=0xff;i+=2)
+	    ADD_CHAR(c[i]);
+	buffer[j] = 0;
+	fprintf(stderr, "%s\n", buffer);
+    } else {
+	int i;
+	for(i=0;i<11;i++)
+	    ADD_CHAR(direntry->name[i]);
+	buffer[j] = 0;
+	fprintf(stderr,"%s attributes=0x%02x begin=%d size=%d\n",
+		buffer,
+		direntry->attributes,
+		begin_of_direntry(direntry),le32_to_cpu(direntry->size));
+    }
+}
+
+static void print_mapping(const mapping_t* mapping)
+{
+    fprintf(stderr, "mapping (%p): begin, end = %d, %d, dir_index = %d, "
+        "first_mapping_index = %d, name = %s, mode = 0x%x, " ,
+        mapping, mapping->begin, mapping->end, mapping->dir_index,
+        mapping->first_mapping_index, mapping->path, mapping->mode);
+
+    if (mapping->mode & MODE_DIRECTORY)
+	fprintf(stderr, "parent_mapping_index = %d, first_dir_index = %d\n", mapping->info.dir.parent_mapping_index, mapping->info.dir.first_dir_index);
+    else
+	fprintf(stderr, "offset = %d\n", mapping->info.file.offset);
+}
+#endif
+
+static int vvfat_read(BlockDriverState *bs, int64_t sector_num,
+                    uint8_t *buf, int nb_sectors)
+{
+    BDRVVVFATState *s = bs->opaque;
+    int i;
+
+    for(i=0;i<nb_sectors;i++,sector_num++) {
+	if (sector_num >= bs->total_sectors)
+	   return -1;
+	if (s->qcow) {
+	    int n;
+            if (bdrv_is_allocated(s->qcow, sector_num, nb_sectors-i, &n)) {
+DLOG(fprintf(stderr, "sectors %d+%d allocated\n", (int)sector_num, n));
+                if (bdrv_read(s->qcow, sector_num, buf + i*0x200, n)) {
+                    return -1;
+                }
+                i += n - 1;
+                sector_num += n - 1;
+                continue;
+            }
+DLOG(fprintf(stderr, "sector %d not allocated\n", (int)sector_num));
+	}
+	if(sector_num<s->faked_sectors) {
+	    if(sector_num<s->first_sectors_number)
+		memcpy(buf+i*0x200,&(s->first_sectors[sector_num*0x200]),0x200);
+	    else if(sector_num-s->first_sectors_number<s->sectors_per_fat)
+		memcpy(buf+i*0x200,&(s->fat.pointer[(sector_num-s->first_sectors_number)*0x200]),0x200);
+	    else if(sector_num-s->first_sectors_number-s->sectors_per_fat<s->sectors_per_fat)
+		memcpy(buf+i*0x200,&(s->fat.pointer[(sector_num-s->first_sectors_number-s->sectors_per_fat)*0x200]),0x200);
+	} else {
+	    uint32_t sector=sector_num-s->faked_sectors,
+	    sector_offset_in_cluster=(sector%s->sectors_per_cluster),
+	    cluster_num=sector/s->sectors_per_cluster;
+	    if(cluster_num > s->cluster_count || read_cluster(s, cluster_num) != 0) {
+		/* LATER TODO: strict: return -1; */
+		memset(buf+i*0x200,0,0x200);
+		continue;
+	    }
+	    memcpy(buf+i*0x200,s->cluster+sector_offset_in_cluster*0x200,0x200);
+	}
+    }
+    return 0;
+}
+
+static coroutine_fn int vvfat_co_read(BlockDriverState *bs, int64_t sector_num,
+                                      uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVVVFATState *s = bs->opaque;
+    qemu_co_mutex_lock(&s->lock);
+    ret = vvfat_read(bs, sector_num, buf, nb_sectors);
+    qemu_co_mutex_unlock(&s->lock);
+    return ret;
+}
+
+/* LATER TODO: statify all functions */
+
+/*
+ * Idea of the write support (use snapshot):
+ *
+ * 1. check if all data is consistent, recording renames, modifications,
+ *    new files and directories (in s->commits).
+ *
+ * 2. if the data is not consistent, stop committing
+ *
+ * 3. handle renames, and create new files and directories (do not yet
+ *    write their contents)
+ *
+ * 4. walk the directories, fixing the mapping and direntries, and marking
+ *    the handled mappings as not deleted
+ *
+ * 5. commit the contents of the files
+ *
+ * 6. handle deleted files and directories
+ *
+ */
+
+typedef struct commit_t {
+    char* path;
+    union {
+	struct { uint32_t cluster; } rename;
+	struct { int dir_index; uint32_t modified_offset; } writeout;
+	struct { uint32_t first_cluster; } new_file;
+	struct { uint32_t cluster; } mkdir;
+    } param;
+    /* DELETEs and RMDIRs are handled differently: see handle_deletes() */
+    enum {
+	ACTION_RENAME, ACTION_WRITEOUT, ACTION_NEW_FILE, ACTION_MKDIR
+    } action;
+} commit_t;
+
+static void clear_commits(BDRVVVFATState* s)
+{
+    int i;
+DLOG(fprintf(stderr, "clear_commits (%d commits)\n", s->commits.next));
+    for (i = 0; i < s->commits.next; i++) {
+	commit_t* commit = array_get(&(s->commits), i);
+	assert(commit->path || commit->action == ACTION_WRITEOUT);
+	if (commit->action != ACTION_WRITEOUT) {
+	    assert(commit->path);
+            g_free(commit->path);
+	} else
+	    assert(commit->path == NULL);
+    }
+    s->commits.next = 0;
+}
+
+static void schedule_rename(BDRVVVFATState* s,
+	uint32_t cluster, char* new_path)
+{
+    commit_t* commit = array_get_next(&(s->commits));
+    commit->path = new_path;
+    commit->param.rename.cluster = cluster;
+    commit->action = ACTION_RENAME;
+}
+
+static void schedule_writeout(BDRVVVFATState* s,
+	int dir_index, uint32_t modified_offset)
+{
+    commit_t* commit = array_get_next(&(s->commits));
+    commit->path = NULL;
+    commit->param.writeout.dir_index = dir_index;
+    commit->param.writeout.modified_offset = modified_offset;
+    commit->action = ACTION_WRITEOUT;
+}
+
+static void schedule_new_file(BDRVVVFATState* s,
+	char* path, uint32_t first_cluster)
+{
+    commit_t* commit = array_get_next(&(s->commits));
+    commit->path = path;
+    commit->param.new_file.first_cluster = first_cluster;
+    commit->action = ACTION_NEW_FILE;
+}
+
+static void schedule_mkdir(BDRVVVFATState* s, uint32_t cluster, char* path)
+{
+    commit_t* commit = array_get_next(&(s->commits));
+    commit->path = path;
+    commit->param.mkdir.cluster = cluster;
+    commit->action = ACTION_MKDIR;
+}
+
+typedef struct {
+    /*
+     * Since the sequence number is at most 0x3f, and the filename
+     * length is at most 13 times the sequence number, the maximal
+     * filename length is 0x3f * 13 bytes.
+     */
+    unsigned char name[0x3f * 13 + 1];
+    int checksum, len;
+    int sequence_number;
+} long_file_name;
+
+static void lfn_init(long_file_name* lfn)
+{
+   lfn->sequence_number = lfn->len = 0;
+   lfn->checksum = 0x100;
+}
+
+/* return 0 if parsed successfully, > 0 if no long name, < 0 if error */
+static int parse_long_name(long_file_name* lfn,
+	const direntry_t* direntry)
+{
+    int i, j, offset;
+    const unsigned char* pointer = (const unsigned char*)direntry;
+
+    if (!is_long_name(direntry))
+	return 1;
+
+    if (pointer[0] & 0x40) {
+	lfn->sequence_number = pointer[0] & 0x3f;
+	lfn->checksum = pointer[13];
+	lfn->name[0] = 0;
+	lfn->name[lfn->sequence_number * 13] = 0;
+    } else if ((pointer[0] & 0x3f) != --lfn->sequence_number)
+	return -1;
+    else if (pointer[13] != lfn->checksum)
+	return -2;
+    else if (pointer[12] || pointer[26] || pointer[27])
+	return -3;
+
+    offset = 13 * (lfn->sequence_number - 1);
+    for (i = 0, j = 1; i < 13; i++, j+=2) {
+	if (j == 11)
+	    j = 14;
+	else if (j == 26)
+	    j = 28;
+
+	if (pointer[j+1] == 0)
+	    lfn->name[offset + i] = pointer[j];
+	else if (pointer[j+1] != 0xff || (pointer[0] & 0x40) == 0)
+	    return -4;
+	else
+	    lfn->name[offset + i] = 0;
+    }
+
+    if (pointer[0] & 0x40)
+	lfn->len = offset + strlen((char*)lfn->name + offset);
+
+    return 0;
+}
+
+/* returns 0 if successful, >0 if no short_name, and <0 on error */
+static int parse_short_name(BDRVVVFATState* s,
+	long_file_name* lfn, direntry_t* direntry)
+{
+    int i, j;
+
+    if (!is_short_name(direntry))
+	return 1;
+
+    for (j = 7; j >= 0 && direntry->name[j] == ' '; j--);
+    for (i = 0; i <= j; i++) {
+	if (direntry->name[i] <= ' ' || direntry->name[i] > 0x7f)
+	    return -1;
+	else if (s->downcase_short_names)
+	    lfn->name[i] = qemu_tolower(direntry->name[i]);
+	else
+	    lfn->name[i] = direntry->name[i];
+    }
+
+    for (j = 2; j >= 0 && direntry->name[8 + j] == ' '; j--) {
+    }
+    if (j >= 0) {
+	lfn->name[i++] = '.';
+	lfn->name[i + j + 1] = '\0';
+	for (;j >= 0; j--) {
+            uint8_t c = direntry->name[8 + j];
+            if (c <= ' ' || c > 0x7f) {
+                return -2;
+            } else if (s->downcase_short_names) {
+                lfn->name[i + j] = qemu_tolower(c);
+            } else {
+                lfn->name[i + j] = c;
+            }
+	}
+    } else
+	lfn->name[i + j + 1] = '\0';
+
+    lfn->len = strlen((char*)lfn->name);
+
+    return 0;
+}
+
+static inline uint32_t modified_fat_get(BDRVVVFATState* s,
+	unsigned int cluster)
+{
+    if (cluster < s->last_cluster_of_root_directory) {
+	if (cluster + 1 == s->last_cluster_of_root_directory)
+	    return s->max_fat_value;
+	else
+	    return cluster + 1;
+    }
+
+    if (s->fat_type==32) {
+        uint32_t* entry=((uint32_t*)s->fat2)+cluster;
+        return le32_to_cpu(*entry);
+    } else if (s->fat_type==16) {
+        uint16_t* entry=((uint16_t*)s->fat2)+cluster;
+        return le16_to_cpu(*entry);
+    } else {
+        const uint8_t* x=s->fat2+cluster*3/2;
+        return ((x[0]|(x[1]<<8))>>(cluster&1?4:0))&0x0fff;
+    }
+}
+
+static inline int cluster_was_modified(BDRVVVFATState* s, uint32_t cluster_num)
+{
+    int was_modified = 0;
+    int i, dummy;
+
+    if (s->qcow == NULL)
+	return 0;
+
+    for (i = 0; !was_modified && i < s->sectors_per_cluster; i++)
+	was_modified = bdrv_is_allocated(s->qcow,
+		cluster2sector(s, cluster_num) + i, 1, &dummy);
+
+    return was_modified;
+}
+
+static const char* get_basename(const char* path)
+{
+    char* basename = strrchr(path, '/');
+    if (basename == NULL)
+	return path;
+    else
+	return basename + 1; /* strip '/' */
+}
+
+/*
+ * The array s->used_clusters holds the states of the clusters. If it is
+ * part of a file, it has bit 2 set, in case of a directory, bit 1. If it
+ * was modified, bit 3 is set.
+ * If any cluster is allocated, but not part of a file or directory, this
+ * driver refuses to commit.
+ */
+typedef enum {
+     USED_DIRECTORY = 1, USED_FILE = 2, USED_ANY = 3, USED_ALLOCATED = 4
+} used_t;
+
+/*
+ * get_cluster_count_for_direntry() not only determines how many clusters
+ * are occupied by direntry, but also if it was renamed or modified.
+ *
+ * A file is thought to be renamed *only* if there already was a file with
+ * exactly the same first cluster, but a different name.
+ *
+ * Further, the files/directories handled by this function are
+ * assumed to be *not* deleted (and *only* those).
+ */
+static uint32_t get_cluster_count_for_direntry(BDRVVVFATState* s,
+	direntry_t* direntry, const char* path)
+{
+    /*
+     * This is a little bit tricky:
+     * IF the guest OS just inserts a cluster into the file chain,
+     * and leaves the rest alone, (i.e. the original file had clusters
+     * 15 -> 16, but now has 15 -> 32 -> 16), then the following happens:
+     *
+     * - do_commit will write the cluster into the file at the given
+     *   offset, but
+     *
+     * - the cluster which is overwritten should be moved to a later
+     *   position in the file.
+     *
+     * I am not aware that any OS does something as braindead, but this
+     * situation could happen anyway when not committing for a long time.
+     * Just to be sure that this does not bite us, detect it, and copy the
+     * contents of the clusters to-be-overwritten into the qcow.
+     */
+    int copy_it = 0;
+    int was_modified = 0;
+    int32_t ret = 0;
+
+    uint32_t cluster_num = begin_of_direntry(direntry);
+    uint32_t offset = 0;
+    int first_mapping_index = -1;
+    mapping_t* mapping = NULL;
+    const char* basename2 = NULL;
+
+    vvfat_close_current_file(s);
+
+    /* the root directory */
+    if (cluster_num == 0)
+	return 0;
+
+    /* write support */
+    if (s->qcow) {
+	basename2 = get_basename(path);
+
+	mapping = find_mapping_for_cluster(s, cluster_num);
+
+	if (mapping) {
+	    const char* basename;
+
+	    assert(mapping->mode & MODE_DELETED);
+	    mapping->mode &= ~MODE_DELETED;
+
+	    basename = get_basename(mapping->path);
+
+	    assert(mapping->mode & MODE_NORMAL);
+
+	    /* rename */
+	    if (strcmp(basename, basename2))
+		schedule_rename(s, cluster_num, g_strdup(path));
+	} else if (is_file(direntry))
+	    /* new file */
+	    schedule_new_file(s, g_strdup(path), cluster_num);
+	else {
+            abort();
+	    return 0;
+	}
+    }
+
+    while(1) {
+	if (s->qcow) {
+	    if (!copy_it && cluster_was_modified(s, cluster_num)) {
+		if (mapping == NULL ||
+			mapping->begin > cluster_num ||
+			mapping->end <= cluster_num)
+		mapping = find_mapping_for_cluster(s, cluster_num);
+
+
+		if (mapping &&
+			(mapping->mode & MODE_DIRECTORY) == 0) {
+
+		    /* was modified in qcow */
+		    if (offset != mapping->info.file.offset + s->cluster_size
+			    * (cluster_num - mapping->begin)) {
+			/* offset of this cluster in file chain has changed */
+                        abort();
+			copy_it = 1;
+		    } else if (offset == 0) {
+			const char* basename = get_basename(mapping->path);
+
+			if (strcmp(basename, basename2))
+			    copy_it = 1;
+			first_mapping_index = array_index(&(s->mapping), mapping);
+		    }
+
+		    if (mapping->first_mapping_index != first_mapping_index
+			    && mapping->info.file.offset > 0) {
+                        abort();
+			copy_it = 1;
+		    }
+
+		    /* need to write out? */
+		    if (!was_modified && is_file(direntry)) {
+			was_modified = 1;
+			schedule_writeout(s, mapping->dir_index, offset);
+		    }
+		}
+	    }
+
+	    if (copy_it) {
+		int i, dummy;
+		/*
+		 * This is horribly inefficient, but that is okay, since
+		 * it is rarely executed, if at all.
+		 */
+		int64_t offset = cluster2sector(s, cluster_num);
+
+		vvfat_close_current_file(s);
+                for (i = 0; i < s->sectors_per_cluster; i++) {
+                    if (!bdrv_is_allocated(s->qcow, offset + i, 1, &dummy)) {
+                        if (vvfat_read(s->bs, offset, s->cluster_buffer, 1)) {
+                            return -1;
+                        }
+                        if (bdrv_write(s->qcow, offset, s->cluster_buffer, 1)) {
+                            return -2;
+                        }
+                    }
+                }
+	    }
+	}
+
+	ret++;
+	if (s->used_clusters[cluster_num] & USED_ANY)
+	    return 0;
+	s->used_clusters[cluster_num] = USED_FILE;
+
+	cluster_num = modified_fat_get(s, cluster_num);
+
+	if (fat_eof(s, cluster_num))
+	    return ret;
+	else if (cluster_num < 2 || cluster_num > s->max_fat_value - 16)
+	    return -1;
+
+	offset += s->cluster_size;
+    }
+}
+
+/*
+ * This function looks at the modified data (qcow).
+ * It returns 0 upon inconsistency or error, and the number of clusters
+ * used by the directory, its subdirectories and their files.
+ */
+static int check_directory_consistency(BDRVVVFATState *s,
+	int cluster_num, const char* path)
+{
+    int ret = 0;
+    unsigned char* cluster = g_malloc(s->cluster_size);
+    direntry_t* direntries = (direntry_t*)cluster;
+    mapping_t* mapping = find_mapping_for_cluster(s, cluster_num);
+
+    long_file_name lfn;
+    int path_len = strlen(path);
+    char path2[PATH_MAX + 1];
+
+    assert(path_len < PATH_MAX); /* len was tested before! */
+    pstrcpy(path2, sizeof(path2), path);
+    path2[path_len] = '/';
+    path2[path_len + 1] = '\0';
+
+    if (mapping) {
+	const char* basename = get_basename(mapping->path);
+	const char* basename2 = get_basename(path);
+
+	assert(mapping->mode & MODE_DIRECTORY);
+
+	assert(mapping->mode & MODE_DELETED);
+	mapping->mode &= ~MODE_DELETED;
+
+	if (strcmp(basename, basename2))
+	    schedule_rename(s, cluster_num, g_strdup(path));
+    } else
+	/* new directory */
+	schedule_mkdir(s, cluster_num, g_strdup(path));
+
+    lfn_init(&lfn);
+    do {
+	int i;
+	int subret = 0;
+
+	ret++;
+
+	if (s->used_clusters[cluster_num] & USED_ANY) {
+	    fprintf(stderr, "cluster %d used more than once\n", (int)cluster_num);
+            goto fail;
+	}
+	s->used_clusters[cluster_num] = USED_DIRECTORY;
+
+DLOG(fprintf(stderr, "read cluster %d (sector %d)\n", (int)cluster_num, (int)cluster2sector(s, cluster_num)));
+	subret = vvfat_read(s->bs, cluster2sector(s, cluster_num), cluster,
+		s->sectors_per_cluster);
+	if (subret) {
+	    fprintf(stderr, "Error fetching direntries\n");
+	fail:
+            g_free(cluster);
+	    return 0;
+	}
+
+	for (i = 0; i < 0x10 * s->sectors_per_cluster; i++) {
+	    int cluster_count = 0;
+
+DLOG(fprintf(stderr, "check direntry %d:\n", i); print_direntry(direntries + i));
+	    if (is_volume_label(direntries + i) || is_dot(direntries + i) ||
+		    is_free(direntries + i))
+		continue;
+
+	    subret = parse_long_name(&lfn, direntries + i);
+	    if (subret < 0) {
+		fprintf(stderr, "Error in long name\n");
+		goto fail;
+	    }
+	    if (subret == 0 || is_free(direntries + i))
+		continue;
+
+	    if (fat_chksum(direntries+i) != lfn.checksum) {
+		subret = parse_short_name(s, &lfn, direntries + i);
+		if (subret < 0) {
+		    fprintf(stderr, "Error in short name (%d)\n", subret);
+		    goto fail;
+		}
+		if (subret > 0 || !strcmp((char*)lfn.name, ".")
+			|| !strcmp((char*)lfn.name, ".."))
+		    continue;
+	    }
+	    lfn.checksum = 0x100; /* cannot use long name twice */
+
+	    if (path_len + 1 + lfn.len >= PATH_MAX) {
+		fprintf(stderr, "Name too long: %s/%s\n", path, lfn.name);
+		goto fail;
+	    }
+            pstrcpy(path2 + path_len + 1, sizeof(path2) - path_len - 1,
+                    (char*)lfn.name);
+
+	    if (is_directory(direntries + i)) {
+		if (begin_of_direntry(direntries + i) == 0) {
+		    DLOG(fprintf(stderr, "invalid begin for directory: %s\n", path2); print_direntry(direntries + i));
+		    goto fail;
+		}
+		cluster_count = check_directory_consistency(s,
+			begin_of_direntry(direntries + i), path2);
+		if (cluster_count == 0) {
+		    DLOG(fprintf(stderr, "problem in directory %s:\n", path2); print_direntry(direntries + i));
+		    goto fail;
+		}
+	    } else if (is_file(direntries + i)) {
+		/* check file size with FAT */
+		cluster_count = get_cluster_count_for_direntry(s, direntries + i, path2);
+		if (cluster_count !=
+			(le32_to_cpu(direntries[i].size) + s->cluster_size
+			 - 1) / s->cluster_size) {
+		    DLOG(fprintf(stderr, "Cluster count mismatch\n"));
+		    goto fail;
+		}
+	    } else
+                abort(); /* cluster_count = 0; */
+
+	    ret += cluster_count;
+	}
+
+	cluster_num = modified_fat_get(s, cluster_num);
+    } while(!fat_eof(s, cluster_num));
+
+    g_free(cluster);
+    return ret;
+}
+
+/* returns 1 on success */
+static int is_consistent(BDRVVVFATState* s)
+{
+    int i, check;
+    int used_clusters_count = 0;
+
+DLOG(checkpoint());
+    /*
+     * - get modified FAT
+     * - compare the two FATs (TODO)
+     * - get buffer for marking used clusters
+     * - recurse direntries from root (using bs->bdrv_read to make
+     *    sure to get the new data)
+     *   - check that the FAT agrees with the size
+     *   - count the number of clusters occupied by this directory and
+     *     its files
+     * - check that the cumulative used cluster count agrees with the
+     *   FAT
+     * - if all is fine, return number of used clusters
+     */
+    if (s->fat2 == NULL) {
+	int size = 0x200 * s->sectors_per_fat;
+	s->fat2 = g_malloc(size);
+	memcpy(s->fat2, s->fat.pointer, size);
+    }
+    check = vvfat_read(s->bs,
+	    s->first_sectors_number, s->fat2, s->sectors_per_fat);
+    if (check) {
+	fprintf(stderr, "Could not copy fat\n");
+	return 0;
+    }
+    assert (s->used_clusters);
+    for (i = 0; i < sector2cluster(s, s->sector_count); i++)
+	s->used_clusters[i] &= ~USED_ANY;
+
+    clear_commits(s);
+
+    /* mark every mapped file/directory as deleted.
+     * (check_directory_consistency() will unmark those still present). */
+    if (s->qcow)
+	for (i = 0; i < s->mapping.next; i++) {
+	    mapping_t* mapping = array_get(&(s->mapping), i);
+	    if (mapping->first_mapping_index < 0)
+		mapping->mode |= MODE_DELETED;
+	}
+
+    used_clusters_count = check_directory_consistency(s, 0, s->path);
+    if (used_clusters_count <= 0) {
+	DLOG(fprintf(stderr, "problem in directory\n"));
+	return 0;
+    }
+
+    check = s->last_cluster_of_root_directory;
+    for (i = check; i < sector2cluster(s, s->sector_count); i++) {
+	if (modified_fat_get(s, i)) {
+	    if(!s->used_clusters[i]) {
+		DLOG(fprintf(stderr, "FAT was modified (%d), but cluster is not used?\n", i));
+		return 0;
+	    }
+	    check++;
+	}
+
+	if (s->used_clusters[i] == USED_ALLOCATED) {
+	    /* allocated, but not used... */
+	    DLOG(fprintf(stderr, "unused, modified cluster: %d\n", i));
+	    return 0;
+	}
+    }
+
+    if (check != used_clusters_count)
+	return 0;
+
+    return used_clusters_count;
+}
+
+static inline void adjust_mapping_indices(BDRVVVFATState* s,
+	int offset, int adjust)
+{
+    int i;
+
+    for (i = 0; i < s->mapping.next; i++) {
+	mapping_t* mapping = array_get(&(s->mapping), i);
+
+#define ADJUST_MAPPING_INDEX(name) \
+	if (mapping->name >= offset) \
+	    mapping->name += adjust
+
+	ADJUST_MAPPING_INDEX(first_mapping_index);
+	if (mapping->mode & MODE_DIRECTORY)
+	    ADJUST_MAPPING_INDEX(info.dir.parent_mapping_index);
+    }
+}
+
+/* insert or update mapping */
+static mapping_t* insert_mapping(BDRVVVFATState* s,
+	uint32_t begin, uint32_t end)
+{
+    /*
+     * - find mapping where mapping->begin >= begin,
+     * - if mapping->begin > begin: insert
+     *   - adjust all references to mappings!
+     * - else: adjust
+     * - replace name
+     */
+    int index = find_mapping_for_cluster_aux(s, begin, 0, s->mapping.next);
+    mapping_t* mapping = NULL;
+    mapping_t* first_mapping = array_get(&(s->mapping), 0);
+
+    if (index < s->mapping.next && (mapping = array_get(&(s->mapping), index))
+	    && mapping->begin < begin) {
+	mapping->end = begin;
+	index++;
+	mapping = array_get(&(s->mapping), index);
+    }
+    if (index >= s->mapping.next || mapping->begin > begin) {
+	mapping = array_insert(&(s->mapping), index, 1);
+	mapping->path = NULL;
+	adjust_mapping_indices(s, index, +1);
+    }
+
+    mapping->begin = begin;
+    mapping->end = end;
+
+DLOG(mapping_t* next_mapping;
+assert(index + 1 >= s->mapping.next ||
+((next_mapping = array_get(&(s->mapping), index + 1)) &&
+ next_mapping->begin >= end)));
+
+    if (s->current_mapping && first_mapping != (mapping_t*)s->mapping.pointer)
+	s->current_mapping = array_get(&(s->mapping),
+		s->current_mapping - first_mapping);
+
+    return mapping;
+}
+
+static int remove_mapping(BDRVVVFATState* s, int mapping_index)
+{
+    mapping_t* mapping = array_get(&(s->mapping), mapping_index);
+    mapping_t* first_mapping = array_get(&(s->mapping), 0);
+
+    /* free mapping */
+    if (mapping->first_mapping_index < 0) {
+        g_free(mapping->path);
+    }
+
+    /* remove from s->mapping */
+    array_remove(&(s->mapping), mapping_index);
+
+    /* adjust all references to mappings */
+    adjust_mapping_indices(s, mapping_index, -1);
+
+    if (s->current_mapping && first_mapping != (mapping_t*)s->mapping.pointer)
+	s->current_mapping = array_get(&(s->mapping),
+		s->current_mapping - first_mapping);
+
+    return 0;
+}
+
+static void adjust_dirindices(BDRVVVFATState* s, int offset, int adjust)
+{
+    int i;
+    for (i = 0; i < s->mapping.next; i++) {
+	mapping_t* mapping = array_get(&(s->mapping), i);
+	if (mapping->dir_index >= offset)
+	    mapping->dir_index += adjust;
+	if ((mapping->mode & MODE_DIRECTORY) &&
+		mapping->info.dir.first_dir_index >= offset)
+	    mapping->info.dir.first_dir_index += adjust;
+    }
+}
+
+static direntry_t* insert_direntries(BDRVVVFATState* s,
+	int dir_index, int count)
+{
+    /*
+     * make room in s->directory,
+     * adjust_dirindices
+     */
+    direntry_t* result = array_insert(&(s->directory), dir_index, count);
+    if (result == NULL)
+	return NULL;
+    adjust_dirindices(s, dir_index, count);
+    return result;
+}
+
+static int remove_direntries(BDRVVVFATState* s, int dir_index, int count)
+{
+    int ret = array_remove_slice(&(s->directory), dir_index, count);
+    if (ret)
+	return ret;
+    adjust_dirindices(s, dir_index, -count);
+    return 0;
+}
+
+/*
+ * Adapt the mappings of the cluster chain starting at first cluster
+ * (i.e. if a file starts at first_cluster, the chain is followed according
+ * to the modified fat, and the corresponding entries in s->mapping are
+ * adjusted)
+ */
+static int commit_mappings(BDRVVVFATState* s,
+	uint32_t first_cluster, int dir_index)
+{
+    mapping_t* mapping = find_mapping_for_cluster(s, first_cluster);
+    direntry_t* direntry = array_get(&(s->directory), dir_index);
+    uint32_t cluster = first_cluster;
+
+    vvfat_close_current_file(s);
+
+    assert(mapping);
+    assert(mapping->begin == first_cluster);
+    mapping->first_mapping_index = -1;
+    mapping->dir_index = dir_index;
+    mapping->mode = (dir_index <= 0 || is_directory(direntry)) ?
+	MODE_DIRECTORY : MODE_NORMAL;
+
+    while (!fat_eof(s, cluster)) {
+	uint32_t c, c1;
+
+	for (c = cluster, c1 = modified_fat_get(s, c); c + 1 == c1;
+		c = c1, c1 = modified_fat_get(s, c1));
+
+	c++;
+	if (c > mapping->end) {
+	    int index = array_index(&(s->mapping), mapping);
+	    int i, max_i = s->mapping.next - index;
+	    for (i = 1; i < max_i && mapping[i].begin < c; i++);
+	    while (--i > 0)
+		remove_mapping(s, index + 1);
+	}
+	assert(mapping == array_get(&(s->mapping), s->mapping.next - 1)
+		|| mapping[1].begin >= c);
+	mapping->end = c;
+
+	if (!fat_eof(s, c1)) {
+	    int i = find_mapping_for_cluster_aux(s, c1, 0, s->mapping.next);
+	    mapping_t* next_mapping = i >= s->mapping.next ? NULL :
+		array_get(&(s->mapping), i);
+
+	    if (next_mapping == NULL || next_mapping->begin > c1) {
+		int i1 = array_index(&(s->mapping), mapping);
+
+		next_mapping = insert_mapping(s, c1, c1+1);
+
+		if (c1 < c)
+		    i1++;
+		mapping = array_get(&(s->mapping), i1);
+	    }
+
+	    next_mapping->dir_index = mapping->dir_index;
+	    next_mapping->first_mapping_index =
+		mapping->first_mapping_index < 0 ?
+		array_index(&(s->mapping), mapping) :
+		mapping->first_mapping_index;
+	    next_mapping->path = mapping->path;
+	    next_mapping->mode = mapping->mode;
+	    next_mapping->read_only = mapping->read_only;
+	    if (mapping->mode & MODE_DIRECTORY) {
+		next_mapping->info.dir.parent_mapping_index =
+			mapping->info.dir.parent_mapping_index;
+		next_mapping->info.dir.first_dir_index =
+			mapping->info.dir.first_dir_index +
+			0x10 * s->sectors_per_cluster *
+			(mapping->end - mapping->begin);
+	    } else
+		next_mapping->info.file.offset = mapping->info.file.offset +
+			mapping->end - mapping->begin;
+
+	    mapping = next_mapping;
+	}
+
+	cluster = c1;
+    }
+
+    return 0;
+}
+
+static int commit_direntries(BDRVVVFATState* s,
+	int dir_index, int parent_mapping_index)
+{
+    direntry_t* direntry = array_get(&(s->directory), dir_index);
+    uint32_t first_cluster = dir_index == 0 ? 0 : begin_of_direntry(direntry);
+    mapping_t* mapping = find_mapping_for_cluster(s, first_cluster);
+
+    int factor = 0x10 * s->sectors_per_cluster;
+    int old_cluster_count, new_cluster_count;
+    int current_dir_index = mapping->info.dir.first_dir_index;
+    int first_dir_index = current_dir_index;
+    int ret, i;
+    uint32_t c;
+
+DLOG(fprintf(stderr, "commit_direntries for %s, parent_mapping_index %d\n", mapping->path, parent_mapping_index));
+
+    assert(direntry);
+    assert(mapping);
+    assert(mapping->begin == first_cluster);
+    assert(mapping->info.dir.first_dir_index < s->directory.next);
+    assert(mapping->mode & MODE_DIRECTORY);
+    assert(dir_index == 0 || is_directory(direntry));
+
+    mapping->info.dir.parent_mapping_index = parent_mapping_index;
+
+    if (first_cluster == 0) {
+	old_cluster_count = new_cluster_count =
+	    s->last_cluster_of_root_directory;
+    } else {
+	for (old_cluster_count = 0, c = first_cluster; !fat_eof(s, c);
+		c = fat_get(s, c))
+	    old_cluster_count++;
+
+	for (new_cluster_count = 0, c = first_cluster; !fat_eof(s, c);
+		c = modified_fat_get(s, c))
+	    new_cluster_count++;
+    }
+
+    if (new_cluster_count > old_cluster_count) {
+	if (insert_direntries(s,
+		current_dir_index + factor * old_cluster_count,
+		factor * (new_cluster_count - old_cluster_count)) == NULL)
+	    return -1;
+    } else if (new_cluster_count < old_cluster_count)
+	remove_direntries(s,
+		current_dir_index + factor * new_cluster_count,
+		factor * (old_cluster_count - new_cluster_count));
+
+    for (c = first_cluster; !fat_eof(s, c); c = modified_fat_get(s, c)) {
+	void* direntry = array_get(&(s->directory), current_dir_index);
+	int ret = vvfat_read(s->bs, cluster2sector(s, c), direntry,
+		s->sectors_per_cluster);
+	if (ret)
+	    return ret;
+	assert(!strncmp(s->directory.pointer, "QEMU", 4));
+	current_dir_index += factor;
+    }
+
+    ret = commit_mappings(s, first_cluster, dir_index);
+    if (ret)
+	return ret;
+
+    /* recurse */
+    for (i = 0; i < factor * new_cluster_count; i++) {
+	direntry = array_get(&(s->directory), first_dir_index + i);
+	if (is_directory(direntry) && !is_dot(direntry)) {
+	    mapping = find_mapping_for_cluster(s, first_cluster);
+	    assert(mapping->mode & MODE_DIRECTORY);
+	    ret = commit_direntries(s, first_dir_index + i,
+		array_index(&(s->mapping), mapping));
+	    if (ret)
+		return ret;
+	}
+    }
+
+    return 0;
+}
+
+/* commit one file (adjust contents, adjust mapping),
+   return first_mapping_index */
+static int commit_one_file(BDRVVVFATState* s,
+	int dir_index, uint32_t offset)
+{
+    direntry_t* direntry = array_get(&(s->directory), dir_index);
+    uint32_t c = begin_of_direntry(direntry);
+    uint32_t first_cluster = c;
+    mapping_t* mapping = find_mapping_for_cluster(s, c);
+    uint32_t size = filesize_of_direntry(direntry);
+    char* cluster = g_malloc(s->cluster_size);
+    uint32_t i;
+    int fd = 0;
+
+    assert(offset < size);
+    assert((offset % s->cluster_size) == 0);
+
+    for (i = s->cluster_size; i < offset; i += s->cluster_size)
+	c = modified_fat_get(s, c);
+
+    fd = qemu_open(mapping->path, O_RDWR | O_CREAT | O_BINARY, 0666);
+    if (fd < 0) {
+	fprintf(stderr, "Could not open %s... (%s, %d)\n", mapping->path,
+		strerror(errno), errno);
+        g_free(cluster);
+	return fd;
+    }
+    if (offset > 0) {
+        if (lseek(fd, offset, SEEK_SET) != offset) {
+            qemu_close(fd);
+            g_free(cluster);
+            return -3;
+        }
+    }
+
+    while (offset < size) {
+	uint32_t c1;
+	int rest_size = (size - offset > s->cluster_size ?
+		s->cluster_size : size - offset);
+	int ret;
+
+	c1 = modified_fat_get(s, c);
+
+	assert((size - offset == 0 && fat_eof(s, c)) ||
+		(size > offset && c >=2 && !fat_eof(s, c)));
+
+	ret = vvfat_read(s->bs, cluster2sector(s, c),
+	    (uint8_t*)cluster, (rest_size + 0x1ff) / 0x200);
+
+        if (ret < 0) {
+            qemu_close(fd);
+            g_free(cluster);
+            return ret;
+        }
+
+        if (write(fd, cluster, rest_size) < 0) {
+            qemu_close(fd);
+            g_free(cluster);
+            return -2;
+        }
+
+	offset += rest_size;
+	c = c1;
+    }
+
+    if (ftruncate(fd, size)) {
+        perror("ftruncate()");
+        qemu_close(fd);
+        g_free(cluster);
+        return -4;
+    }
+    qemu_close(fd);
+    g_free(cluster);
+
+    return commit_mappings(s, first_cluster, dir_index);
+}
+
+#ifdef DEBUG
+/* test, if all mappings point to valid direntries */
+static void check1(BDRVVVFATState* s)
+{
+    int i;
+    for (i = 0; i < s->mapping.next; i++) {
+	mapping_t* mapping = array_get(&(s->mapping), i);
+	if (mapping->mode & MODE_DELETED) {
+	    fprintf(stderr, "deleted\n");
+	    continue;
+	}
+	assert(mapping->dir_index < s->directory.next);
+	direntry_t* direntry = array_get(&(s->directory), mapping->dir_index);
+	assert(mapping->begin == begin_of_direntry(direntry) || mapping->first_mapping_index >= 0);
+	if (mapping->mode & MODE_DIRECTORY) {
+	    assert(mapping->info.dir.first_dir_index + 0x10 * s->sectors_per_cluster * (mapping->end - mapping->begin) <= s->directory.next);
+	    assert((mapping->info.dir.first_dir_index % (0x10 * s->sectors_per_cluster)) == 0);
+	}
+    }
+}
+
+/* test, if all direntries have mappings */
+static void check2(BDRVVVFATState* s)
+{
+    int i;
+    int first_mapping = -1;
+
+    for (i = 0; i < s->directory.next; i++) {
+	direntry_t* direntry = array_get(&(s->directory), i);
+
+	if (is_short_name(direntry) && begin_of_direntry(direntry)) {
+	    mapping_t* mapping = find_mapping_for_cluster(s, begin_of_direntry(direntry));
+	    assert(mapping);
+	    assert(mapping->dir_index == i || is_dot(direntry));
+	    assert(mapping->begin == begin_of_direntry(direntry) || is_dot(direntry));
+	}
+
+	if ((i % (0x10 * s->sectors_per_cluster)) == 0) {
+	    /* cluster start */
+	    int j, count = 0;
+
+	    for (j = 0; j < s->mapping.next; j++) {
+		mapping_t* mapping = array_get(&(s->mapping), j);
+		if (mapping->mode & MODE_DELETED)
+		    continue;
+		if (mapping->mode & MODE_DIRECTORY) {
+		    if (mapping->info.dir.first_dir_index <= i && mapping->info.dir.first_dir_index + 0x10 * s->sectors_per_cluster > i) {
+			assert(++count == 1);
+			if (mapping->first_mapping_index == -1)
+			    first_mapping = array_index(&(s->mapping), mapping);
+			else
+			    assert(first_mapping == mapping->first_mapping_index);
+			if (mapping->info.dir.parent_mapping_index < 0)
+			    assert(j == 0);
+			else {
+			    mapping_t* parent = array_get(&(s->mapping), mapping->info.dir.parent_mapping_index);
+			    assert(parent->mode & MODE_DIRECTORY);
+			    assert(parent->info.dir.first_dir_index < mapping->info.dir.first_dir_index);
+			}
+		    }
+		}
+	    }
+	    if (count == 0)
+		first_mapping = -1;
+	}
+    }
+}
+#endif
+
+static int handle_renames_and_mkdirs(BDRVVVFATState* s)
+{
+    int i;
+
+#ifdef DEBUG
+    fprintf(stderr, "handle_renames\n");
+    for (i = 0; i < s->commits.next; i++) {
+	commit_t* commit = array_get(&(s->commits), i);
+	fprintf(stderr, "%d, %s (%d, %d)\n", i, commit->path ? commit->path : "(null)", commit->param.rename.cluster, commit->action);
+    }
+#endif
+
+    for (i = 0; i < s->commits.next;) {
+	commit_t* commit = array_get(&(s->commits), i);
+	if (commit->action == ACTION_RENAME) {
+	    mapping_t* mapping = find_mapping_for_cluster(s,
+		    commit->param.rename.cluster);
+	    char* old_path = mapping->path;
+
+	    assert(commit->path);
+	    mapping->path = commit->path;
+	    if (rename(old_path, mapping->path))
+		return -2;
+
+	    if (mapping->mode & MODE_DIRECTORY) {
+		int l1 = strlen(mapping->path);
+		int l2 = strlen(old_path);
+		int diff = l1 - l2;
+		direntry_t* direntry = array_get(&(s->directory),
+			mapping->info.dir.first_dir_index);
+		uint32_t c = mapping->begin;
+		int i = 0;
+
+		/* recurse */
+		while (!fat_eof(s, c)) {
+		    do {
+			direntry_t* d = direntry + i;
+
+			if (is_file(d) || (is_directory(d) && !is_dot(d))) {
+			    mapping_t* m = find_mapping_for_cluster(s,
+				    begin_of_direntry(d));
+			    int l = strlen(m->path);
+			    char* new_path = g_malloc(l + diff + 1);
+
+			    assert(!strncmp(m->path, mapping->path, l2));
+
+                            pstrcpy(new_path, l + diff + 1, mapping->path);
+                            pstrcpy(new_path + l1, l + diff + 1 - l1,
+                                    m->path + l2);
+
+			    schedule_rename(s, m->begin, new_path);
+			}
+			i++;
+		    } while((i % (0x10 * s->sectors_per_cluster)) != 0);
+		    c = fat_get(s, c);
+		}
+	    }
+
+            g_free(old_path);
+	    array_remove(&(s->commits), i);
+	    continue;
+	} else if (commit->action == ACTION_MKDIR) {
+	    mapping_t* mapping;
+	    int j, parent_path_len;
+
+#ifdef __MINGW32__
+            if (mkdir(commit->path))
+                return -5;
+#else
+            if (mkdir(commit->path, 0755))
+                return -5;
+#endif
+
+	    mapping = insert_mapping(s, commit->param.mkdir.cluster,
+		    commit->param.mkdir.cluster + 1);
+	    if (mapping == NULL)
+		return -6;
+
+	    mapping->mode = MODE_DIRECTORY;
+	    mapping->read_only = 0;
+	    mapping->path = commit->path;
+	    j = s->directory.next;
+	    assert(j);
+	    insert_direntries(s, s->directory.next,
+		    0x10 * s->sectors_per_cluster);
+	    mapping->info.dir.first_dir_index = j;
+
+	    parent_path_len = strlen(commit->path)
+		- strlen(get_basename(commit->path)) - 1;
+	    for (j = 0; j < s->mapping.next; j++) {
+		mapping_t* m = array_get(&(s->mapping), j);
+		if (m->first_mapping_index < 0 && m != mapping &&
+			!strncmp(m->path, mapping->path, parent_path_len) &&
+			strlen(m->path) == parent_path_len)
+		    break;
+	    }
+	    assert(j < s->mapping.next);
+	    mapping->info.dir.parent_mapping_index = j;
+
+	    array_remove(&(s->commits), i);
+	    continue;
+	}
+
+	i++;
+    }
+    return 0;
+}
+
+/*
+ * TODO: make sure that the short name is not matching *another* file
+ */
+static int handle_commits(BDRVVVFATState* s)
+{
+    int i, fail = 0;
+
+    vvfat_close_current_file(s);
+
+    for (i = 0; !fail && i < s->commits.next; i++) {
+	commit_t* commit = array_get(&(s->commits), i);
+	switch(commit->action) {
+	case ACTION_RENAME: case ACTION_MKDIR:
+            abort();
+	    fail = -2;
+	    break;
+	case ACTION_WRITEOUT: {
+#ifndef NDEBUG
+            /* these variables are only used by assert() below */
+	    direntry_t* entry = array_get(&(s->directory),
+		    commit->param.writeout.dir_index);
+	    uint32_t begin = begin_of_direntry(entry);
+	    mapping_t* mapping = find_mapping_for_cluster(s, begin);
+#endif
+
+	    assert(mapping);
+	    assert(mapping->begin == begin);
+	    assert(commit->path == NULL);
+
+	    if (commit_one_file(s, commit->param.writeout.dir_index,
+			commit->param.writeout.modified_offset))
+		fail = -3;
+
+	    break;
+	}
+	case ACTION_NEW_FILE: {
+	    int begin = commit->param.new_file.first_cluster;
+	    mapping_t* mapping = find_mapping_for_cluster(s, begin);
+	    direntry_t* entry;
+	    int i;
+
+	    /* find direntry */
+	    for (i = 0; i < s->directory.next; i++) {
+		entry = array_get(&(s->directory), i);
+		if (is_file(entry) && begin_of_direntry(entry) == begin)
+		    break;
+	    }
+
+	    if (i >= s->directory.next) {
+		fail = -6;
+		continue;
+	    }
+
+	    /* make sure there exists an initial mapping */
+	    if (mapping && mapping->begin != begin) {
+		mapping->end = begin;
+		mapping = NULL;
+	    }
+	    if (mapping == NULL) {
+		mapping = insert_mapping(s, begin, begin+1);
+	    }
+	    /* most members will be fixed in commit_mappings() */
+	    assert(commit->path);
+	    mapping->path = commit->path;
+	    mapping->read_only = 0;
+	    mapping->mode = MODE_NORMAL;
+	    mapping->info.file.offset = 0;
+
+	    if (commit_one_file(s, i, 0))
+		fail = -7;
+
+	    break;
+	}
+	default:
+            abort();
+	}
+    }
+    if (i > 0 && array_remove_slice(&(s->commits), 0, i))
+	return -1;
+    return fail;
+}
+
+static int handle_deletes(BDRVVVFATState* s)
+{
+    int i, deferred = 1, deleted = 1;
+
+    /* delete files corresponding to mappings marked as deleted */
+    /* handle DELETEs and unused mappings (modified_fat_get(s, mapping->begin) == 0) */
+    while (deferred && deleted) {
+	deferred = 0;
+	deleted = 0;
+
+	for (i = 1; i < s->mapping.next; i++) {
+	    mapping_t* mapping = array_get(&(s->mapping), i);
+	    if (mapping->mode & MODE_DELETED) {
+		direntry_t* entry = array_get(&(s->directory),
+			mapping->dir_index);
+
+		if (is_free(entry)) {
+		    /* remove file/directory */
+		    if (mapping->mode & MODE_DIRECTORY) {
+			int j, next_dir_index = s->directory.next,
+			first_dir_index = mapping->info.dir.first_dir_index;
+
+			if (rmdir(mapping->path) < 0) {
+			    if (errno == ENOTEMPTY) {
+				deferred++;
+				continue;
+			    } else
+				return -5;
+			}
+
+			for (j = 1; j < s->mapping.next; j++) {
+			    mapping_t* m = array_get(&(s->mapping), j);
+			    if (m->mode & MODE_DIRECTORY &&
+				    m->info.dir.first_dir_index >
+				    first_dir_index &&
+				    m->info.dir.first_dir_index <
+				    next_dir_index)
+				next_dir_index =
+				    m->info.dir.first_dir_index;
+			}
+			remove_direntries(s, first_dir_index,
+				next_dir_index - first_dir_index);
+
+			deleted++;
+		    }
+		} else {
+		    if (unlink(mapping->path))
+			return -4;
+		    deleted++;
+		}
+		DLOG(fprintf(stderr, "DELETE (%d)\n", i); print_mapping(mapping); print_direntry(entry));
+		remove_mapping(s, i);
+	    }
+	}
+    }
+
+    return 0;
+}
+
+/*
+ * synchronize mapping with new state:
+ *
+ * - copy FAT (with bdrv_read)
+ * - mark all filenames corresponding to mappings as deleted
+ * - recurse direntries from root (using bs->bdrv_read)
+ * - delete files corresponding to mappings marked as deleted
+ */
+static int do_commit(BDRVVVFATState* s)
+{
+    int ret = 0;
+
+    /* the real meat are the commits. Nothing to do? Move along! */
+    if (s->commits.next == 0)
+	return 0;
+
+    vvfat_close_current_file(s);
+
+    ret = handle_renames_and_mkdirs(s);
+    if (ret) {
+	fprintf(stderr, "Error handling renames (%d)\n", ret);
+        abort();
+	return ret;
+    }
+
+    /* copy FAT (with bdrv_read) */
+    memcpy(s->fat.pointer, s->fat2, 0x200 * s->sectors_per_fat);
+
+    /* recurse direntries from root (using bs->bdrv_read) */
+    ret = commit_direntries(s, 0, -1);
+    if (ret) {
+	fprintf(stderr, "Fatal: error while committing (%d)\n", ret);
+        abort();
+	return ret;
+    }
+
+    ret = handle_commits(s);
+    if (ret) {
+	fprintf(stderr, "Error handling commits (%d)\n", ret);
+        abort();
+	return ret;
+    }
+
+    ret = handle_deletes(s);
+    if (ret) {
+	fprintf(stderr, "Error deleting\n");
+        abort();
+	return ret;
+    }
+
+    if (s->qcow->drv->bdrv_make_empty) {
+        s->qcow->drv->bdrv_make_empty(s->qcow);
+    }
+
+    memset(s->used_clusters, 0, sector2cluster(s, s->sector_count));
+
+DLOG(checkpoint());
+    return 0;
+}
+
+static int try_commit(BDRVVVFATState* s)
+{
+    vvfat_close_current_file(s);
+DLOG(checkpoint());
+    if(!is_consistent(s))
+	return -1;
+    return do_commit(s);
+}
+
+static int vvfat_write(BlockDriverState *bs, int64_t sector_num,
+                    const uint8_t *buf, int nb_sectors)
+{
+    BDRVVVFATState *s = bs->opaque;
+    int i, ret;
+
+DLOG(checkpoint());
+
+    /* Check if we're operating in read-only mode */
+    if (s->qcow == NULL) {
+        return -EACCES;
+    }
+
+    vvfat_close_current_file(s);
+
+    /*
+     * Some sanity checks:
+     * - do not allow writing to the boot sector
+     * - do not allow to write non-ASCII filenames
+     */
+
+    if (sector_num < s->first_sectors_number)
+	return -1;
+
+    for (i = sector2cluster(s, sector_num);
+	    i <= sector2cluster(s, sector_num + nb_sectors - 1);) {
+	mapping_t* mapping = find_mapping_for_cluster(s, i);
+	if (mapping) {
+	    if (mapping->read_only) {
+		fprintf(stderr, "Tried to write to write-protected file %s\n",
+			mapping->path);
+		return -1;
+	    }
+
+	    if (mapping->mode & MODE_DIRECTORY) {
+		int begin = cluster2sector(s, i);
+		int end = begin + s->sectors_per_cluster, k;
+		int dir_index;
+		const direntry_t* direntries;
+		long_file_name lfn;
+
+		lfn_init(&lfn);
+
+		if (begin < sector_num)
+		    begin = sector_num;
+		if (end > sector_num + nb_sectors)
+		    end = sector_num + nb_sectors;
+		dir_index  = mapping->dir_index +
+		    0x10 * (begin - mapping->begin * s->sectors_per_cluster);
+		direntries = (direntry_t*)(buf + 0x200 * (begin - sector_num));
+
+		for (k = 0; k < (end - begin) * 0x10; k++) {
+		    /* do not allow non-ASCII filenames */
+		    if (parse_long_name(&lfn, direntries + k) < 0) {
+			fprintf(stderr, "Warning: non-ASCII filename\n");
+			return -1;
+		    }
+		    /* no access to the direntry of a read-only file */
+		    else if (is_short_name(direntries+k) &&
+			    (direntries[k].attributes & 1)) {
+			if (memcmp(direntries + k,
+				    array_get(&(s->directory), dir_index + k),
+				    sizeof(direntry_t))) {
+			    fprintf(stderr, "Warning: tried to write to write-protected file\n");
+			    return -1;
+			}
+		    }
+		}
+	    }
+	    i = mapping->end;
+	} else
+	    i++;
+    }
+
+    /*
+     * Use qcow backend. Commit later.
+     */
+DLOG(fprintf(stderr, "Write to qcow backend: %d + %d\n", (int)sector_num, nb_sectors));
+    ret = bdrv_write(s->qcow, sector_num, buf, nb_sectors);
+    if (ret < 0) {
+	fprintf(stderr, "Error writing to qcow backend\n");
+	return ret;
+    }
+
+    for (i = sector2cluster(s, sector_num);
+	    i <= sector2cluster(s, sector_num + nb_sectors - 1); i++)
+	if (i >= 0)
+	    s->used_clusters[i] |= USED_ALLOCATED;
+
+DLOG(checkpoint());
+    /* TODO: add timeout */
+    try_commit(s);
+
+DLOG(checkpoint());
+    return 0;
+}
+
+static coroutine_fn int vvfat_co_write(BlockDriverState *bs, int64_t sector_num,
+                                       const uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVVVFATState *s = bs->opaque;
+    qemu_co_mutex_lock(&s->lock);
+    ret = vvfat_write(bs, sector_num, buf, nb_sectors);
+    qemu_co_mutex_unlock(&s->lock);
+    return ret;
+}
+
+static int64_t coroutine_fn vvfat_co_get_block_status(BlockDriverState *bs,
+	int64_t sector_num, int nb_sectors, int* n)
+{
+    BDRVVVFATState* s = bs->opaque;
+    *n = s->sector_count - sector_num;
+    if (*n > nb_sectors) {
+        *n = nb_sectors;
+    } else if (*n < 0) {
+        return 0;
+    }
+    return BDRV_BLOCK_DATA;
+}
+
+static int write_target_commit(BlockDriverState *bs, int64_t sector_num,
+	const uint8_t* buffer, int nb_sectors) {
+    BDRVVVFATState* s = *((BDRVVVFATState**) bs->opaque);
+    return try_commit(s);
+}
+
+static void write_target_close(BlockDriverState *bs) {
+    BDRVVVFATState* s = *((BDRVVVFATState**) bs->opaque);
+    bdrv_unref(s->qcow);
+    g_free(s->qcow_filename);
+}
+
+static BlockDriver vvfat_write_target = {
+    .format_name        = "vvfat_write_target",
+    .bdrv_write         = write_target_commit,
+    .bdrv_close         = write_target_close,
+};
+
+static int enable_write_target(BDRVVVFATState *s, Error **errp)
+{
+    BlockDriver *bdrv_qcow = NULL;
+    QemuOpts *opts = NULL;
+    int ret;
+    int size = sector2cluster(s, s->sector_count);
+    s->used_clusters = calloc(size, 1);
+
+    array_init(&(s->commits), sizeof(commit_t));
+
+    s->qcow_filename = g_malloc(PATH_MAX);
+    ret = get_tmp_filename(s->qcow_filename, PATH_MAX);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "can't create temporary file");
+        goto err;
+    }
+
+    bdrv_qcow = bdrv_find_format("qcow");
+    if (!bdrv_qcow) {
+        error_setg(errp, "Failed to locate qcow driver");
+        ret = -ENOENT;
+        goto err;
+    }
+
+    opts = qemu_opts_create(bdrv_qcow->create_opts, NULL, 0, &error_abort);
+    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, s->sector_count * 512,
+                        &error_abort);
+    qemu_opt_set(opts, BLOCK_OPT_BACKING_FILE, "fat:", &error_abort);
+
+    ret = bdrv_create(bdrv_qcow, s->qcow_filename, opts, errp);
+    qemu_opts_del(opts);
+    if (ret < 0) {
+        goto err;
+    }
+
+    s->qcow = NULL;
+    ret = bdrv_open(&s->qcow, s->qcow_filename, NULL, NULL,
+                    BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH,
+                    bdrv_qcow, errp);
+    if (ret < 0) {
+        goto err;
+    }
+
+#ifndef _WIN32
+    unlink(s->qcow_filename);
+#endif
+
+    bdrv_set_backing_hd(s->bs, bdrv_new());
+    s->bs->backing_hd->drv = &vvfat_write_target;
+    s->bs->backing_hd->opaque = g_new(void *, 1);
+    *(void**)s->bs->backing_hd->opaque = s;
+
+    return 0;
+
+err:
+    g_free(s->qcow_filename);
+    s->qcow_filename = NULL;
+    return ret;
+}
+
+static void vvfat_close(BlockDriverState *bs)
+{
+    BDRVVVFATState *s = bs->opaque;
+
+    vvfat_close_current_file(s);
+    array_free(&(s->fat));
+    array_free(&(s->directory));
+    array_free(&(s->mapping));
+    g_free(s->cluster_buffer);
+
+    if (s->qcow) {
+        migrate_del_blocker(s->migration_blocker);
+        error_free(s->migration_blocker);
+    }
+}
+
+static BlockDriver bdrv_vvfat = {
+    .format_name            = "vvfat",
+    .protocol_name          = "fat",
+    .instance_size          = sizeof(BDRVVVFATState),
+
+    .bdrv_parse_filename    = vvfat_parse_filename,
+    .bdrv_file_open         = vvfat_open,
+    .bdrv_close             = vvfat_close,
+    .bdrv_rebind            = vvfat_rebind,
+
+    .bdrv_read              = vvfat_co_read,
+    .bdrv_write             = vvfat_co_write,
+    .bdrv_co_get_block_status = vvfat_co_get_block_status,
+};
+
+static void bdrv_vvfat_init(void)
+{
+    bdrv_register(&bdrv_vvfat);
+}
+
+block_init(bdrv_vvfat_init);
+
+#ifdef DEBUG
+static void checkpoint(void) {
+    assert(((mapping_t*)array_get(&(vvv->mapping), 0))->end == 2);
+    check1(vvv);
+    check2(vvv);
+    assert(!vvv->current_mapping || vvv->current_fd || (vvv->current_mapping->mode & MODE_DIRECTORY));
+#if 0
+    if (((direntry_t*)vvv->directory.pointer)[1].attributes != 0xf)
+	fprintf(stderr, "Nonono!\n");
+    mapping_t* mapping;
+    direntry_t* direntry;
+    assert(vvv->mapping.size >= vvv->mapping.item_size * vvv->mapping.next);
+    assert(vvv->directory.size >= vvv->directory.item_size * vvv->directory.next);
+    if (vvv->mapping.next<47)
+	return;
+    assert((mapping = array_get(&(vvv->mapping), 47)));
+    assert(mapping->dir_index < vvv->directory.next);
+    direntry = array_get(&(vvv->directory), mapping->dir_index);
+    assert(!memcmp(direntry->name, "USB     H  ", 11) || direntry->name[0]==0);
+#endif
+}
+#endif