[PATCH v4 09/12] mirror: Check job_is_cancelled() earlier

[Hanna Reitz <hreitz@redhat.com>]

We must check whether the job is force-cancelled early in our main loop,
most importantly before any `continue` statement.  For example, we used
to have `continue`s before our current checking location that are
triggered by `mirror_flush()` failing.  So, if `mirror_flush()` kept
failing, force-cancelling the job would not terminate it.

Jobs can be cancelled while they yield, and once they are
(force-cancelled), they should not generate new I/O requests.
Therefore, we should put the check after the last yield before
mirror_iteration() is invoked.

Buglink: https://gitlab.com/qemu-project/qemu/-/issues/462
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/mirror.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 024fa2dcea..bf1d50ff1c 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1000,6 +1000,11 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
 
         job_pause_point(&s->common.job);
 
+        if (job_is_cancelled(&s->common.job)) {
+            ret = 0;
+            goto immediate_exit;
+        }
+
         cnt = bdrv_get_dirty_count(s->dirty_bitmap);
         /* cnt is the number of dirty bytes remaining and s->bytes_in_flight is
          * the number of bytes currently being processed; together those are
@@ -1078,8 +1083,6 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
             break;
         }
 
-        ret = 0;
-
         if (job_is_ready(&s->common.job) && !should_complete) {
             delay_ns = (s->in_flight == 0 &&
                         cnt == 0 ? BLOCK_JOB_SLICE_TIME : 0);
@@ -1087,9 +1090,6 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
         trace_mirror_before_sleep(s, cnt, job_is_ready(&s->common.job),
                                   delay_ns);
         job_sleep_ns(&s->common.job, delay_ns);
-        if (job_is_cancelled(&s->common.job)) {
-            break;
-        }
         s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     }
 
-- 
2.31.1