diff --git a/block/backup.c b/block/backup.c
index d3c7d9f85d..965654d521 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -431,7 +431,7 @@ static void coroutine_fn backup_run(void *opaque)
 
     if (job->sync_bitmap) {
         BdrvDirtyBitmap *bm;
-        if (ret < 0) {
+        if (ret < 0 || block_job_is_cancelled(&job->common)) {
             /* Merge the successor back into the parent, delete nothing. */
             bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
             assert(bm);
diff --git a/block/curl.c b/block/curl.c
index 3a2b63e16e..032cc8ae22 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -22,6 +22,7 @@
  * THE SOFTWARE.
  */
 #include "qemu-common.h"
+#include "qemu/error-report.h"
 #include "block/block_int.h"
 #include "qapi/qmp/qbool.h"
 #include "qapi/qmp/qstring.h"
@@ -298,6 +299,18 @@ static void curl_multi_check_completion(BDRVCURLState *s)
             /* ACBs for successful messages get completed in curl_read_cb */
             if (msg->data.result != CURLE_OK) {
                 int i;
+                static int errcount = 100;
+
+                /* Don't lose the original error message from curl, since
+                 * it contains extra data.
+                 */
+                if (errcount > 0) {
+                    error_report("curl: %s", state->errmsg);
+                    if (--errcount == 0) {
+                        error_report("curl: further errors suppressed");
+                    }
+                }
+
                 for (i = 0; i < CURL_NUM_ACB; i++) {
                     CURLAIOCB *acb = state->acb[i];
 
@@ -305,7 +318,7 @@ static void curl_multi_check_completion(BDRVCURLState *s)
                         continue;
                     }
 
-                    acb->common.cb(acb->common.opaque, -EIO);
+                    acb->common.cb(acb->common.opaque, -EPROTO);
                     qemu_aio_unref(acb);
                     state->acb[i] = NULL;
                 }
diff --git a/block/mirror.c b/block/mirror.c
index d409337c4a..323f747c75 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -20,6 +20,7 @@
 
 #define SLICE_TIME    100000000ULL /* ns */
 #define MAX_IN_FLIGHT 16
+#define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
 
 /* The mirroring buffer is a list of granularity-sized chunks.
  * Free chunks are organized in a list.
@@ -444,11 +445,23 @@ static void coroutine_fn mirror_run(void *opaque)
     sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
     mirror_free_init(s);
 
+    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     if (!s->is_none_mode) {
         /* First part, loop on the sectors and initialize the dirty bitmap.  */
         BlockDriverState *base = s->base;
         for (sector_num = 0; sector_num < end; ) {
             int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;
+            int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+
+            if (now - last_pause_ns > SLICE_TIME) {
+                last_pause_ns = now;
+                block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
+            }
+
+            if (block_job_is_cancelled(&s->common)) {
+                goto immediate_exit;
+            }
+
             ret = bdrv_is_allocated_above(bs, base,
                                           sector_num, next - sector_num, &n);
 
@@ -467,7 +480,6 @@ static void coroutine_fn mirror_run(void *opaque)
     }
 
     bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
-    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     for (;;) {
         uint64_t delay_ns = 0;
         int64_t cnt;
@@ -690,6 +702,14 @@ static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
         return;
     }
 
+    if (buf_size < 0) {
+        error_setg(errp, "Invalid parameter 'buf-size'");
+        return;
+    }
+
+    if (buf_size == 0) {
+        buf_size = DEFAULT_MIRROR_BUF_SIZE;
+    }
 
     s = block_job_create(driver, bs, speed, cb, opaque, errp);
     if (!s) {
@@ -703,7 +723,7 @@ static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
     s->is_none_mode = is_none_mode;
     s->base = base;
     s->granularity = granularity;
-    s->buf_size = MAX(buf_size, granularity);
+    s->buf_size = ROUND_UP(buf_size, granularity);
     s->unmap = unmap;
 
     s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
diff --git a/blockdev.c b/blockdev.c
index 7fee519a1c..62a4586cd6 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2380,9 +2380,6 @@ void qmp_block_commit(const char *device,
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
 
-    /* drain all i/o before commits */
-    bdrv_drain_all();
-
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, errp)) {
         goto out;
     }
@@ -2642,8 +2639,6 @@ out:
     aio_context_release(aio_context);
 }
 
-#define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
-
 void qmp_drive_mirror(const char *device, const char *target,
                       bool has_format, const char *format,
                       bool has_node_name, const char *node_name,
@@ -2685,7 +2680,7 @@ void qmp_drive_mirror(const char *device, const char *target,
         granularity = 0;
     }
     if (!has_buf_size) {
-        buf_size = DEFAULT_MIRROR_BUF_SIZE;
+        buf_size = 0;
     }
     if (!has_unmap) {
         unmap = true;