int bdrv_make_zero(BlockDriverState *bs, BdrvRequestFlags flags)
 {
     int64_t target_sectors, ret, nb_sectors, sector_num = 0;
+    BlockDriverState *file;
     int n;
 
     target_sectors = bdrv_nb_sectors(bs);
         if (nb_sectors <= 0) {
             return 0;
         }
-        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n);
+        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, &file);
         if (ret < 0) {
             error_report("error getting block status at sector %" PRId64 ": %s",
                          sector_num, strerror(-ret));
 typedef struct BdrvCoGetBlockStatusData {
     BlockDriverState *bs;
     BlockDriverState *base;
+    BlockDriverState **file;
     int64_t sector_num;
     int nb_sectors;
     int *pnum;
  *
  * 'nb_sectors' is the max value 'pnum' should be set to.  If nb_sectors goes
  * beyond the end of the disk image it will be clamped.
+ *
+ * If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set, 'file'
+ * points to the BDS which the sector range is allocated in.
  */
 static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
                                                      int64_t sector_num,
-                                                     int nb_sectors, int *pnum)
+                                                     int nb_sectors, int *pnum,
+                                                     BlockDriverState **file)
 {
     int64_t total_sectors;
     int64_t n;
         return ret;
     }
 
-    ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum);
+    *file = NULL;
+    ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum,
+                                            file);
     if (ret < 0) {
         *pnum = 0;
         return ret;
     if (ret & BDRV_BLOCK_RAW) {
         assert(ret & BDRV_BLOCK_OFFSET_VALID);
         return bdrv_get_block_status(bs->file->bs, ret >> BDRV_SECTOR_BITS,
-                                     *pnum, pnum);
+                                     *pnum, pnum, file);
     }
 
     if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
     if (bs->file &&
         (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
         (ret & BDRV_BLOCK_OFFSET_VALID)) {
+        BlockDriverState *file2;
         int file_pnum;
 
         ret2 = bdrv_co_get_block_status(bs->file->bs, ret >> BDRV_SECTOR_BITS,
-                                        *pnum, &file_pnum);
+                                        *pnum, &file_pnum, &file2);
         if (ret2 >= 0) {
             /* Ignore errors.  This is just providing extra information, it
              * is useful but not necessary.
         BlockDriverState *base,
         int64_t sector_num,
         int nb_sectors,
-        int *pnum)
+        int *pnum,
+        BlockDriverState **file)
 {
     BlockDriverState *p;
     int64_t ret = 0;
 
     assert(bs != base);
     for (p = bs; p != base; p = backing_bs(p)) {
-        ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum);
+        ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum, file);
         if (ret < 0 || ret & BDRV_BLOCK_ALLOCATED) {
             break;
         }
     data->ret = bdrv_co_get_block_status_above(data->bs, data->base,
                                                data->sector_num,
                                                data->nb_sectors,
-                                               data->pnum);
+                                               data->pnum,
+                                               data->file);
     data->done = true;
 }
 
 int64_t bdrv_get_block_status_above(BlockDriverState *bs,
                                     BlockDriverState *base,
                                     int64_t sector_num,
-                                    int nb_sectors, int *pnum)
+                                    int nb_sectors, int *pnum,
+                                    BlockDriverState **file)
 {
     Coroutine *co;
     BdrvCoGetBlockStatusData data = {
         .bs = bs,
         .base = base,
+        .file = file,
         .sector_num = sector_num,
         .nb_sectors = nb_sectors,
         .pnum = pnum,
 
 int64_t bdrv_get_block_status(BlockDriverState *bs,
                               int64_t sector_num,
-                              int nb_sectors, int *pnum)
+                              int nb_sectors, int *pnum,
+                              BlockDriverState **file)
 {
     return bdrv_get_block_status_above(bs, backing_bs(bs),
-                                       sector_num, nb_sectors, pnum);
+                                       sector_num, nb_sectors, pnum, file);
 }
 
 int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num,
                                    int nb_sectors, int *pnum)
 {
-    int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum);
+    BlockDriverState *file;
+    int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum,
+                                        &file);
     if (ret < 0) {
         return ret;
     }
 
 
 static int64_t coroutine_fn iscsi_co_get_block_status(BlockDriverState *bs,
                                                   int64_t sector_num,
-                                                  int nb_sectors, int *pnum)
+                                                  int nb_sectors, int *pnum,
+                                                  BlockDriverState **file)
 {
     IscsiLun *iscsilun = bs->opaque;
     struct scsi_get_lba_status *lbas = NULL;
         !iscsi_allocationmap_is_allocated(iscsilun, sector_num, nb_sectors)) {
         int64_t ret;
         int pnum;
-        ret = iscsi_co_get_block_status(bs, sector_num, INT_MAX, &pnum);
+        BlockDriverState *file;
+        ret = iscsi_co_get_block_status(bs, sector_num, INT_MAX, &pnum, &file);
         if (ret < 0) {
             return ret;
         }
 
     MirrorOp *op;
     int pnum;
     int64_t ret;
+    BlockDriverState *file;
 
     max_iov = MIN(source->bl.max_iov, s->target->bl.max_iov);
 
     trace_mirror_one_iteration(s, sector_num, nb_sectors);
 
     ret = bdrv_get_block_status_above(source, NULL, sector_num,
-                                      nb_sectors, &pnum);
+                                      nb_sectors, &pnum, &file);
     if (ret < 0 || pnum < nb_sectors ||
             (ret & BDRV_BLOCK_DATA && !(ret & BDRV_BLOCK_ZERO))) {
         bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
 
 
 
 static int64_t coroutine_fn parallels_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum)
+        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
 {
     BDRVParallelsState *s = bs->opaque;
     int64_t offset;
 
 }
 
 static int64_t coroutine_fn qcow_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum)
+        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
 {
     BDRVQcowState *s = bs->opaque;
     int index_in_cluster, n;
 
 }
 
 static int64_t coroutine_fn qcow2_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum)
+        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
 {
     BDRVQcow2State *s = bs->opaque;
     uint64_t cluster_offset;
 
 
 static int64_t coroutine_fn bdrv_qed_co_get_block_status(BlockDriverState *bs,
                                                  int64_t sector_num,
-                                                 int nb_sectors, int *pnum)
+                                                 int nb_sectors, int *pnum,
+                                                 BlockDriverState **file)
 {
     BDRVQEDState *s = bs->opaque;
     size_t len = (size_t)nb_sectors * BDRV_SECTOR_SIZE;
 
  */
 static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
                                                     int64_t sector_num,
-                                                    int nb_sectors, int *pnum)
+                                                    int nb_sectors, int *pnum,
+                                                    BlockDriverState **file)
 {
     off_t start, data = 0, hole = 0;
     int64_t total_size;
 
 
 static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
                                             int64_t sector_num,
-                                            int nb_sectors, int *pnum)
+                                            int nb_sectors, int *pnum,
+                                            BlockDriverState **file)
 {
     *pnum = nb_sectors;
     return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA |
 
 
 static coroutine_fn int64_t
 sd_co_get_block_status(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
-                       int *pnum)
+                       int *pnum, BlockDriverState **file)
 {
     BDRVSheepdogState *s = bs->opaque;
     SheepdogInode *inode = &s->inode;
 
 }
 
 static int64_t coroutine_fn vdi_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum)
+        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
 {
     /* TODO: Check for too large sector_num (in bdrv_is_allocated or here). */
     BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
 
 }
 
 static int64_t coroutine_fn vmdk_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum)
+        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
 {
     BDRVVmdkState *s = bs->opaque;
     int64_t index_in_cluster, n, ret;
 
 }
 
 static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum)
+        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
 {
     BDRVVPCState *s = bs->opaque;
     VHDFooter *footer = (VHDFooter*) s->footer_buf;
 
 }
 
 static int64_t coroutine_fn vvfat_co_get_block_status(BlockDriverState *bs,
-       int64_t sector_num, int nb_sectors, int* n)
+       int64_t sector_num, int nb_sectors, int *n, BlockDriverState **file)
 {
     BDRVVVFATState* s = bs->opaque;
     *n = s->sector_count - sector_num;
 
 
 /*
  * Allocation status flags
- * BDRV_BLOCK_DATA: data is read from bs->file or another file
+ * BDRV_BLOCK_DATA: data is read from a file returned by bdrv_get_block_status.
  * BDRV_BLOCK_ZERO: sectors read as zero
- * BDRV_BLOCK_OFFSET_VALID: sector stored in bs->file as raw data
+ * BDRV_BLOCK_OFFSET_VALID: sector stored as raw data in a file returned by
+ *                          bdrv_get_block_status.
  * BDRV_BLOCK_ALLOCATED: the content of the block is determined by this
  *                       layer (as opposed to the backing file)
  * BDRV_BLOCK_RAW: used internally to indicate that the request
 bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs);
 bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs);
 int64_t bdrv_get_block_status(BlockDriverState *bs, int64_t sector_num,
-                              int nb_sectors, int *pnum);
+                              int nb_sectors, int *pnum,
+                              BlockDriverState **file);
 int64_t bdrv_get_block_status_above(BlockDriverState *bs,
                                     BlockDriverState *base,
                                     int64_t sector_num,
-                                    int nb_sectors, int *pnum);
+                                    int nb_sectors, int *pnum,
+                                    BlockDriverState **file);
 int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
                       int *pnum);
 int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
 
     int coroutine_fn (*bdrv_co_discard)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors);
     int64_t coroutine_fn (*bdrv_co_get_block_status)(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum);
+        int64_t sector_num, int nb_sectors, int *pnum,
+        BlockDriverState **file);
 
     /*
      * Invalidate any cached meta-data.
 
 
     for (;;) {
         int64_t status1, status2;
+        BlockDriverState *file;
+
         nb_sectors = sectors_to_process(total_sectors, sector_num);
         if (nb_sectors <= 0) {
             break;
         }
         status1 = bdrv_get_block_status_above(bs1, NULL, sector_num,
                                               total_sectors1 - sector_num,
-                                              &pnum1);
+                                              &pnum1, &file);
         if (status1 < 0) {
             ret = 3;
             error_report("Sector allocation test failed for %s", filename1);
 
         status2 = bdrv_get_block_status_above(bs2, NULL, sector_num,
                                               total_sectors2 - sector_num,
-                                              &pnum2);
+                                              &pnum2, &file);
         if (status2 < 0) {
             ret = 3;
             error_report("Sector allocation test failed for %s", filename2);
     n = MIN(s->total_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS);
 
     if (s->sector_next_status <= sector_num) {
+        BlockDriverState *file;
         ret = bdrv_get_block_status(blk_bs(s->src[s->src_cur]),
                                     sector_num - s->src_cur_offset,
-                                    n, &n);
+                                    n, &n, &file);
         if (ret < 0) {
             return ret;
         }
 {
     int64_t ret;
     int depth;
+    BlockDriverState *file;
 
     /* As an optimization, we could cache the current range of unallocated
      * clusters in each file of the chain, and avoid querying the same
 
     depth = 0;
     for (;;) {
-        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &nb_sectors);
+        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &nb_sectors,
+                                    &file);
         if (ret < 0) {
             return ret;
         }