diff --git a/block/qcow.c b/block/qcow.c
index 326ef87..b16955d 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -368,14 +368,16 @@
     return cluster_offset;
 }
 
-static int qcow_is_allocated(BlockDriverState *bs, int64_t sector_num,
-                             int nb_sectors, int *pnum)
+static int coroutine_fn qcow_co_is_allocated(BlockDriverState *bs,
+        int64_t sector_num, int nb_sectors, int *pnum)
 {
     BDRVQcowState *s = bs->opaque;
     int index_in_cluster, n;
     uint64_t cluster_offset;
 
+    qemu_co_mutex_lock(&s->lock);
     cluster_offset = get_cluster_offset(bs, sector_num << 9, 0, 0, 0, 0);
+    qemu_co_mutex_unlock(&s->lock);
     index_in_cluster = sector_num & (s->cluster_sectors - 1);
     n = s->cluster_sectors - index_in_cluster;
     if (n > nb_sectors)
@@ -844,7 +846,7 @@
     .bdrv_co_readv          = qcow_co_readv,
     .bdrv_co_writev         = qcow_co_writev,
     .bdrv_co_flush_to_disk  = qcow_co_flush,
-    .bdrv_is_allocated      = qcow_is_allocated,
+    .bdrv_co_is_allocated   = qcow_co_is_allocated,
 
     .bdrv_set_key           = qcow_set_key,
     .bdrv_make_empty        = qcow_make_empty,
diff --git a/block/qcow2.c b/block/qcow2.c
index 3f8a128..5ac9fb4 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -344,16 +344,19 @@
     return 0;
 }
 
-static int qcow2_is_allocated(BlockDriverState *bs, int64_t sector_num,
-                              int nb_sectors, int *pnum)
+static int coroutine_fn qcow2_co_is_allocated(BlockDriverState *bs,
+        int64_t sector_num, int nb_sectors, int *pnum)
 {
+    BDRVQcowState *s = bs->opaque;
     uint64_t cluster_offset;
     int ret;
 
     *pnum = nb_sectors;
-    /* FIXME We can get errors here, but the bdrv_is_allocated interface can't
-     * pass them on today */
+    /* FIXME We can get errors here, but the bdrv_co_is_allocated interface
+     * can't pass them on today */
+    qemu_co_mutex_lock(&s->lock);
     ret = qcow2_get_cluster_offset(bs, sector_num << 9, pnum, &cluster_offset);
+    qemu_co_mutex_unlock(&s->lock);
     if (ret < 0) {
         *pnum = 0;
     }
@@ -1277,7 +1280,7 @@
     .bdrv_open          = qcow2_open,
     .bdrv_close         = qcow2_close,
     .bdrv_create        = qcow2_create,
-    .bdrv_is_allocated  = qcow2_is_allocated,
+    .bdrv_co_is_allocated = qcow2_co_is_allocated,
     .bdrv_set_key       = qcow2_set_key,
     .bdrv_make_empty    = qcow2_make_empty,
 
diff --git a/block/vmdk.c b/block/vmdk.c
index f544159..5623ac1 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -861,8 +861,8 @@
     return NULL;
 }
 
-static int vmdk_is_allocated(BlockDriverState *bs, int64_t sector_num,
-                             int nb_sectors, int *pnum)
+static int coroutine_fn vmdk_co_is_allocated(BlockDriverState *bs,
+        int64_t sector_num, int nb_sectors, int *pnum)
 {
     BDRVVmdkState *s = bs->opaque;
     int64_t index_in_cluster, n, ret;
@@ -873,8 +873,10 @@
     if (!extent) {
         return 0;
     }
+    qemu_co_mutex_lock(&s->lock);
     ret = get_cluster_offset(bs, extent, NULL,
                             sector_num * 512, 0, &offset);
+    qemu_co_mutex_unlock(&s->lock);
     /* get_cluster_offset returning 0 means success */
     ret = !ret;
 
@@ -1596,7 +1598,7 @@
     .bdrv_close     = vmdk_close,
     .bdrv_create    = vmdk_create,
     .bdrv_co_flush_to_disk  = vmdk_co_flush,
-    .bdrv_is_allocated      = vmdk_is_allocated,
+    .bdrv_co_is_allocated   = vmdk_co_is_allocated,
     .bdrv_get_allocated_file_size  = vmdk_get_allocated_file_size,
 
     .create_options = vmdk_create_options,