[Qemu-devel] [PATCH 30/47] mirror: implement completion

[Paolo Bonzini]

Switching to the target of the migration is done mostly asynchronously,
and reported to management via the BLOCK_JOB_COMPLETED event; the only
synchronous phase is opening the backing files.  Note that this can be
done always, even for migration of the full image, because the backing
file structure of the source and target are not in any relationship.
For full migration (aka sync: 'full') qmp_drive_mirror will create the
target disk with no backing file at all, and bdrv_ensure_backing_file
will be a no-op.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 block/mirror.c |   43 +++++++++++++++++++++++++++++++++++++------
 1 file changed, 37 insertions(+), 6 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 9c8ebd4..4454ef3 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -32,6 +32,8 @@ typedef struct MirrorBlockJob {
     RateLimit limit;
     BlockDriverState *target;
     MirrorSyncMode mode;
+    bool synced;
+    bool complete;
     int64_t sector_num;
     uint8_t *buf;
 } MirrorBlockJob;
@@ -70,7 +72,6 @@ static void coroutine_fn mirror_run(void *opaque)
     int64_t sector_num, end;
     int ret = 0;
     int n;
-    bool synced = false;
 
     if (block_job_is_cancelled(&s->common)) {
         goto immediate_exit;
@@ -135,10 +136,13 @@ static void coroutine_fn mirror_run(void *opaque)
              * I/O and report completion, so that drive-reopen can be
              * used to pivot to the mirroring target.
              */
-            synced = true;
             s->common.offset = end * BDRV_SECTOR_SIZE;
+            if (!s->synced) {
+                block_job_ready(&s->common);
+                s->synced = true;
+            }
 
-            should_complete = block_job_is_cancelled(&s->common);
+            should_complete = block_job_is_cancelled(&s->common) || 
s->complete;
             if (should_complete) {
                 /* The dirty bitmap is not updated while operations are 
pending.
                  * If we're about to exit, wait for pending operations before
@@ -155,8 +159,8 @@ static void coroutine_fn mirror_run(void *opaque)
         }
 
         ret = 0;
-        trace_mirror_before_sleep(s, cnt, synced);
-        if (!synced) {
+        trace_mirror_before_sleep(s, cnt, s->synced);
+        if (!s->synced) {
             /* Publish progress */
             s->common.offset = end * BDRV_SECTOR_SIZE - cnt * BLOCK_SIZE;
 
@@ -189,7 +193,11 @@ static void coroutine_fn mirror_run(void *opaque)
 immediate_exit:
     g_free(s->buf);
     bdrv_set_dirty_tracking(bs, false);
-    bdrv_close(s->target);
+    if (s->complete && ret == 0) {
+        bdrv_swap(s->target, s->common.bs);
+    } else {
+        bdrv_close(s->target);
+    }
     bdrv_delete(s->target);
     block_job_completed(&s->common, ret);
 }
@@ -215,11 +223,34 @@ static void mirror_query(BlockJob *job, BlockJobInfo 
*info)
     info->target->stats = bdrv_query_stats(s->target);
 }
 
+static void mirror_complete(BlockJob *job, Error **errp)
+{
+    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
+    int ret;
+
+    ret = bdrv_ensure_backing_file(s->target);
+    if (ret < 0) {
+        char backing_filename[PATH_MAX];
+        bdrv_get_full_backing_filename(s->target, backing_filename,
+                                       sizeof(backing_filename));
+        error_set(errp, QERR_OPEN_FILE_FAILED, backing_filename);
+        return;
+    }
+    if (!s->synced) {
+        error_set(errp, QERR_BLOCK_JOB_NOT_READY, job->bs->device_name);
+        return;
+    }
+
+    s->complete = true;
+    block_job_resume(job);
+}
+
 static BlockJobType mirror_job_type = {
     .instance_size = sizeof(MirrorBlockJob),
     .job_type      = "mirror",
     .set_speed     = mirror_set_speed,
     .query         = mirror_query,
+    .complete      = mirror_complete,
 };
 
 void mirror_start(BlockDriverState *bs, BlockDriverState *target,
-- 
1.7.10.4