mirror: return mirror-specific information upon query

To start out, only actively-synced is returned.

For example, this is useful for jobs that started out in background
mode and switched to active mode. Once actively-synced is true, it's
clear that the mode switch has been completed. Note that completion of
the switch might happen much earlier, e.g. if the switch happens
before the job is ready, once all background operations have finished.
It's assumed that whether the disks are actively-synced or not is more
interesting than whether the mode switch completed. That information
can still be added if required in the future.

In presence of an iothread, the actively_synced member is now shared
between the iothread and the main thread, so turn accesses to it
atomic.

Requires to adapt the output for iotest 109.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20231031135431.393137-10-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 23 insertions, 8 deletions

diff --git a/block/mirror.c b/block/mirror.c
index 4016d89253..c839542774 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -61,8 +61,12 @@ typedef struct MirrorBlockJob {
      */
     MirrorCopyMode copy_mode;
     BlockdevOnError on_source_error, on_target_error;
-    /* Set when the target is synced (dirty bitmap is clean, nothing
-     * in flight) and the job is running in active mode */
+    /*
+     * To be accessed with atomics.
+     *
+     * Set when the target is synced (dirty bitmap is clean, nothing in flight)
+     * and the job is running in active mode.
+     */
     bool actively_synced;
     bool should_complete;
     int64_t granularity;
@@ -126,7 +130,7 @@ typedef enum MirrorMethod {
 static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
                                             int error)
 {
-    s->actively_synced = false;
+    qatomic_set(&s->actively_synced, false);
     if (read) {
         return block_job_error_action(&s->common, s->on_source_error,
                                       true, error);
@@ -966,7 +970,7 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
     if (s->bdev_length == 0) {
         /* Transition to the READY state and wait for complete. */
         job_transition_to_ready(&s->common.job);
-        s->actively_synced = true;
+        qatomic_set(&s->actively_synced, true);
         while (!job_cancel_requested(&s->common.job) && !s->should_complete) {
             job_yield(&s->common.job);
         }
@@ -1080,7 +1084,7 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
                 job_transition_to_ready(&s->common.job);
             }
             if (qatomic_read(&s->copy_mode) != MIRROR_COPY_MODE_BACKGROUND) {
-                s->actively_synced = true;
+                qatomic_set(&s->actively_synced, true);
             }
 
             should_complete = s->should_complete ||
@@ -1283,6 +1287,15 @@ static void mirror_change(BlockJob *job, BlockJobChangeOptions *opts,
     }
 }
 
+static void mirror_query(BlockJob *job, BlockJobInfo *info)
+{
+    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
+
+    info->u.mirror = (BlockJobInfoMirror) {
+        .actively_synced = qatomic_read(&s->actively_synced),
+    };
+}
+
 static const BlockJobDriver mirror_job_driver = {
     .job_driver = {
         .instance_size          = sizeof(MirrorBlockJob),
@@ -1298,6 +1311,7 @@ static const BlockJobDriver mirror_job_driver = {
     },
     .drained_poll           = mirror_drained_poll,
     .change                 = mirror_change,
+    .query                  = mirror_query,
 };
 
 static const BlockJobDriver commit_active_job_driver = {
@@ -1416,7 +1430,7 @@ do_sync_target_write(MirrorBlockJob *job, MirrorMethod method,
         bitmap_end = QEMU_ALIGN_UP(offset + bytes, job->granularity);
         bdrv_set_dirty_bitmap(job->dirty_bitmap, bitmap_offset,
                               bitmap_end - bitmap_offset);
-        job->actively_synced = false;
+        qatomic_set(&job->actively_synced, false);
 
         action = mirror_error_action(job, false, -ret);
         if (action == BLOCK_ERROR_ACTION_REPORT) {
@@ -1475,7 +1489,8 @@ static void coroutine_fn GRAPH_RDLOCK active_write_settle(MirrorOp *op)
     uint64_t end_chunk = DIV_ROUND_UP(op->offset + op->bytes,
                                       op->s->granularity);
 
-    if (!--op->s->in_active_write_counter && op->s->actively_synced) {
+    if (!--op->s->in_active_write_counter &&
+        qatomic_read(&op->s->actively_synced)) {
         BdrvChild *source = op->s->mirror_top_bs->backing;
 
         if (QLIST_FIRST(&source->bs->parents) == source &&
@@ -1539,7 +1554,7 @@ bdrv_mirror_top_do_write(BlockDriverState *bs, MirrorMethod method,
     }
 
     if (!copy_to_target && s->job && s->job->dirty_bitmap) {
-        s->job->actively_synced = false;
+        qatomic_set(&s->job->actively_synced, false);
         bdrv_set_dirty_bitmap(s->job->dirty_bitmap, offset, bytes);
     }