1 files changed, 16 insertions, 0 deletions

diff --git a/block/mirror.c b/block/mirror.c
index 010fdafd79..eb9a4cdf56 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -80,6 +80,7 @@ typedef struct MirrorBlockJob {
     bool initial_zeroing_ongoing;
     int in_active_write_counter;
     bool prepared;
+    bool in_drain;
 } MirrorBlockJob;
 
 typedef struct MirrorBDSOpaque {
@@ -683,6 +684,7 @@ static int mirror_exit_common(Job *job)
 
         /* The mirror job has no requests in flight any more, but we need to
          * drain potential other users of the BDS before changing the graph. */
+        assert(s->in_drain);
         bdrv_drained_begin(target_bs);
         bdrv_replace_node(to_replace, target_bs, &local_err);
         bdrv_drained_end(target_bs);
@@ -721,6 +723,7 @@ static int mirror_exit_common(Job *job)
     bs_opaque->job = NULL;
 
     bdrv_drained_end(src);
+    s->in_drain = false;
     bdrv_unref(mirror_top_bs);
     bdrv_unref(src);
 
@@ -1004,10 +1007,12 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
              */
             trace_mirror_before_drain(s, cnt);
 
+            s->in_drain = true;
             bdrv_drained_begin(bs);
             cnt = bdrv_get_dirty_count(s->dirty_bitmap);
             if (cnt > 0 || mirror_flush(s) < 0) {
                 bdrv_drained_end(bs);
+                s->in_drain = false;
                 continue;
             }
 
@@ -1055,6 +1060,7 @@ immediate_exit:
     bdrv_dirty_iter_free(s->dbi);
 
     if (need_drain) {
+        s->in_drain = true;
         bdrv_drained_begin(bs);
     }
 
@@ -1123,6 +1129,16 @@ static void coroutine_fn mirror_pause(Job *job)
 static bool mirror_drained_poll(BlockJob *job)
 {
     MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
+
+    /* If the job isn't paused nor cancelled, we can't be sure that it won't
+     * issue more requests. We make an exception if we've reached this point
+     * from one of our own drain sections, to avoid a deadlock waiting for
+     * ourselves.
+     */
+    if (!s->common.job.paused && !s->common.job.cancelled && !s->in_drain) {
+        return true;
+    }
+
     return !!s->in_flight;
 }