--- /dev/null
+From 2540abec85433596dd04640b14f75ceb13bbb342 Mon Sep 17 00:00:00 2001
+From: Fam Zheng <famz@redhat.com>
+Date: Wed, 13 May 2015 11:11:13 +0800
+Subject: [PATCH] block/mirror: Sleep periodically during bitmap scanning
+
+Before, we only yield after initializing dirty bitmap, where the QMP
+command would return. That may take very long, and guest IO will be
+blocked.
+
+Add sleep points like the later mirror iterations.
+
+Signed-off-by: Fam Zheng <famz@redhat.com>
+Reviewed-by: Wen Congyang <wency@cn.fujitsu.com>
+Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
+Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
+---
+ block/mirror.c | 13 ++++++++++++-
+ 1 file changed, 12 insertions(+), 1 deletion(-)
+
+diff --git a/block/mirror.c b/block/mirror.c
+index 4056164..0a05971 100644
+--- a/block/mirror.c
++++ b/block/mirror.c
+@@ -432,11 +432,23 @@ 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);
+
+@@ -455,7 +467,6 @@ static void coroutine_fn mirror_run(void *opaque)
+ }
+
+ bdrv_dirty_iter_init(bs, s->dirty_bitmap, &s->hbi);
+- last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+ for (;;) {
+ uint64_t delay_ns = 0;
+ int64_t cnt;
+--
+2.1.4
+
--- /dev/null
+From d1ca17e6bfcf8292b85474cc871e015088672df4 Mon Sep 17 00:00:00 2001
+From: Alexandre Derumier <aderumier@odiso.com>
+Date: Wed, 1 Jul 2015 05:07:06 +0200
+Subject: [PATCH] increase block_job_sleep_ns time to SLICE_TIME
+
+current value 0 is really too short to avoid qmp hangs
+
+Signed-off-by: Alexandre Derumier <aderumier@odiso.com>
+---
+ block/mirror.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/block/mirror.c b/block/mirror.c
+index 0a05971..2711249 100644
+--- a/block/mirror.c
++++ b/block/mirror.c
+@@ -442,7 +442,7 @@ static void coroutine_fn mirror_run(void *opaque)
+
+ if (now - last_pause_ns > SLICE_TIME) {
+ last_pause_ns = now;
+- block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
++ block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, SLICE_TIME);
+ }
+
+ if (block_job_is_cancelled(&s->common)) {
+--
+2.1.4
+