diff --git a/block.c b/block.c
index 6c493ad457..183fec8aa5 100644
--- a/block.c
+++ b/block.c
@@ -1358,11 +1358,12 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state)
 
 void bdrv_close(BlockDriverState *bs)
 {
-    bdrv_flush(bs);
     if (bs->job) {
         block_job_cancel_sync(bs->job);
     }
-    bdrv_drain_all();
+    bdrv_drain_all(); /* complete I/O */
+    bdrv_flush(bs);
+    bdrv_drain_all(); /* in case flush left pending I/O */
     notifier_list_notify(&bs->close_notifiers, bs);
 
     if (bs->drv) {
diff --git a/block/curl.c b/block/curl.c
index 6af8cb7577..82d39ff53f 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -81,6 +81,7 @@ typedef struct BDRVCURLState {
     CURLState states[CURL_NUM_STATES];
     char *url;
     size_t readahead_size;
+    bool accept_range;
 } BDRVCURLState;
 
 static void curl_clean_state(CURLState *s);
@@ -110,14 +111,15 @@ static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
     return 0;
 }
 
-static size_t curl_size_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
+static size_t curl_header_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
 {
-    CURLState *s = ((CURLState*)opaque);
+    BDRVCURLState *s = opaque;
     size_t realsize = size * nmemb;
-    size_t fsize;
+    const char *accept_line = "Accept-Ranges: bytes";
 
-    if(sscanf(ptr, "Content-Length: %zd", &fsize) == 1) {
-        s->s->len = fsize;
+    if (realsize >= strlen(accept_line)
+        && strncmp((char *)ptr, accept_line, strlen(accept_line)) == 0) {
+        s->accept_range = true;
     }
 
     return realsize;
@@ -447,8 +449,11 @@ static int curl_open(BlockDriverState *bs, QDict *options, int flags)
 
     // Get file size
 
+    s->accept_range = false;
     curl_easy_setopt(state->curl, CURLOPT_NOBODY, 1);
-    curl_easy_setopt(state->curl, CURLOPT_WRITEFUNCTION, (void *)curl_size_cb);
+    curl_easy_setopt(state->curl, CURLOPT_HEADERFUNCTION,
+                     curl_header_cb);
+    curl_easy_setopt(state->curl, CURLOPT_HEADERDATA, s);
     if (curl_easy_perform(state->curl))
         goto out;
     curl_easy_getinfo(state->curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &d);
@@ -456,6 +461,13 @@ static int curl_open(BlockDriverState *bs, QDict *options, int flags)
         s->len = (size_t)d;
     else if(!s->len)
         goto out;
+    if ((!strncasecmp(s->url, "http://", strlen("http://"))
+        || !strncasecmp(s->url, "https://", strlen("https://")))
+        && !s->accept_range) {
+        pstrcpy(state->errmsg, CURL_ERROR_SIZE,
+                "Server does not support 'range' (byte ranges).");
+        goto out;
+    }
     DPRINTF("CURL: Size = %zd\n", s->len);
 
     curl_clean_state(state);
diff --git a/block/vmdk.c b/block/vmdk.c
index a28fb5e8e9..3756333c60 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1724,6 +1724,23 @@ static int64_t vmdk_get_allocated_file_size(BlockDriverState *bs)
     return ret;
 }
 
+static int vmdk_has_zero_init(BlockDriverState *bs)
+{
+    int i;
+    BDRVVmdkState *s = bs->opaque;
+
+    /* If has a flat extent and its underlying storage doesn't have zero init,
+     * return 0. */
+    for (i = 0; i < s->num_extents; i++) {
+        if (s->extents[i].flat) {
+            if (!bdrv_has_zero_init(s->extents[i].file)) {
+                return 0;
+            }
+        }
+    }
+    return 1;
+}
+
 static QEMUOptionParameter vmdk_create_options[] = {
     {
         .name = BLOCK_OPT_SIZE,
@@ -1762,21 +1779,22 @@ static QEMUOptionParameter vmdk_create_options[] = {
 };
 
 static BlockDriver bdrv_vmdk = {
-    .format_name    = "vmdk",
-    .instance_size  = sizeof(BDRVVmdkState),
-    .bdrv_probe     = vmdk_probe,
-    .bdrv_open      = vmdk_open,
-    .bdrv_reopen_prepare = vmdk_reopen_prepare,
-    .bdrv_read      = vmdk_co_read,
-    .bdrv_write     = vmdk_co_write,
-    .bdrv_co_write_zeroes = vmdk_co_write_zeroes,
-    .bdrv_close     = vmdk_close,
-    .bdrv_create    = vmdk_create,
-    .bdrv_co_flush_to_disk  = vmdk_co_flush,
-    .bdrv_co_is_allocated   = vmdk_co_is_allocated,
-    .bdrv_get_allocated_file_size  = vmdk_get_allocated_file_size,
+    .format_name                  = "vmdk",
+    .instance_size                = sizeof(BDRVVmdkState),
+    .bdrv_probe                   = vmdk_probe,
+    .bdrv_open                    = vmdk_open,
+    .bdrv_reopen_prepare          = vmdk_reopen_prepare,
+    .bdrv_read                    = vmdk_co_read,
+    .bdrv_write                   = vmdk_co_write,
+    .bdrv_co_write_zeroes         = vmdk_co_write_zeroes,
+    .bdrv_close                   = vmdk_close,
+    .bdrv_create                  = vmdk_create,
+    .bdrv_co_flush_to_disk        = vmdk_co_flush,
+    .bdrv_co_is_allocated         = vmdk_co_is_allocated,
+    .bdrv_get_allocated_file_size = vmdk_get_allocated_file_size,
+    .bdrv_has_zero_init           = vmdk_has_zero_init,
 
-    .create_options = vmdk_create_options,
+    .create_options               = vmdk_create_options,
 };
 
 static void bdrv_vmdk_init(void)