Instead of automatically transitioning from PENDING to CONCLUDED, gate
the .prepare() and .commit() phases behind an explicit acknowledgement
provided by the QMP monitor if manual completion mode has been requested.

This allows us to perform graph changes in prepare and/or commit so that
graph changes do not occur autonomously without knowledge of the
controlling management layer.

Transactions that have reached the "PENDING" state together can all be
moved to invoke their finalization methods by issuing block_job_finalize
to any one job in the transaction.

Jobs in a transaction with mixed job->manual settings will remain stuck
in the "WAITING" state until block_job_finalize is authored on the job(s)
that have reached the "PENDING" state.

These jobs are not allowed to progress because other jobs in the
transaction may still fail during their preparation phase during
finalization, so these jobs must remain in the WAITING phase until
success is guaranteed. These jobs will then automatically dismiss
themselves, but jobs that had the manual property set will remain
at CONCLUDED as normal.

Signed-off-by: John Snow <js...@redhat.com>
---
 block/trace-events       |  1 +
 blockdev.c               | 14 ++++++++++
 blockjob.c               | 69 +++++++++++++++++++++++++++++++++++++-----------
 include/block/blockjob.h | 17 ++++++++++++
 qapi/block-core.json     | 23 +++++++++++++++-
 5 files changed, 108 insertions(+), 16 deletions(-)

diff --git a/block/trace-events b/block/trace-events
index 5e531e0310..a81b66ff36 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -51,6 +51,7 @@ qmp_block_job_cancel(void *job) "job %p"
 qmp_block_job_pause(void *job) "job %p"
 qmp_block_job_resume(void *job) "job %p"
 qmp_block_job_complete(void *job) "job %p"
+qmp_block_job_finalize(void *job) "job %p"
 qmp_block_job_dismiss(void *job) "job %p"
 qmp_block_stream(void *bs, void *job) "bs %p job %p"
 
diff --git a/blockdev.c b/blockdev.c
index 3180130782..05fd421cdc 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3852,6 +3852,20 @@ void qmp_block_job_complete(const char *device, Error 
**errp)
     aio_context_release(aio_context);
 }
 
+void qmp_block_job_finalize(const char *id, Error **errp)
+{
+    AioContext *aio_context;
+    BlockJob *job = find_block_job(id, &aio_context, errp);
+
+    if (!job) {
+        return;
+    }
+
+    trace_qmp_block_job_finalize(job);
+    block_job_finalize(job, errp);
+    aio_context_release(aio_context);
+}
+
 void qmp_block_job_dismiss(const char *id, Error **errp)
 {
     AioContext *aio_context;
diff --git a/blockjob.c b/blockjob.c
index 23b4b99fd4..f9e8a64261 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -65,14 +65,15 @@ bool 
BlockJobVerbTable[BLOCK_JOB_VERB__MAX][BLOCK_JOB_STATUS__MAX] = {
     [BLOCK_JOB_VERB_RESUME]               = {0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0},
     [BLOCK_JOB_VERB_SET_SPEED]            = {0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0},
     [BLOCK_JOB_VERB_COMPLETE]             = {0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0},
+    [BLOCK_JOB_VERB_FINALIZE]             = {0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0},
     [BLOCK_JOB_VERB_DISMISS]              = {0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0},
 };
 
-static void block_job_state_transition(BlockJob *job, BlockJobStatus s1)
+static bool block_job_state_transition(BlockJob *job, BlockJobStatus s1)
 {
     BlockJobStatus s0 = job->status;
     if (s0 == s1) {
-        return;
+        return false;
     }
     assert(s1 >= 0 && s1 <= BLOCK_JOB_STATUS__MAX);
     trace_block_job_state_transition(job, job->ret, BlockJobSTT[s0][s1] ?
@@ -83,6 +84,7 @@ static void block_job_state_transition(BlockJob *job, 
BlockJobStatus s1)
                                                       s1));
     assert(BlockJobSTT[s0][s1]);
     job->status = s1;
+    return true;
 }
 
 static int block_job_apply_verb(BlockJob *job, BlockJobVerb bv, Error **errp)
@@ -432,7 +434,7 @@ static void block_job_clean(BlockJob *job)
     }
 }
 
-static int block_job_completed_single(BlockJob *job)
+static int block_job_finalize_single(BlockJob *job)
 {
     assert(job->completed);
 
@@ -581,18 +583,44 @@ static void block_job_completed_txn_abort(BlockJob *job)
             assert(other_job->cancelled);
             block_job_finish_sync(other_job, NULL, NULL);
         }
-        block_job_completed_single(other_job);
+        block_job_finalize_single(other_job);
         aio_context_release(ctx);
     }
 
     block_job_txn_unref(txn);
 }
 
+static int block_job_is_manual(BlockJob *job)
+{
+    return job->manual;
+}
+
+static void block_job_do_finalize(BlockJob *job)
+{
+    int rc;
+    assert(job && job->txn);
+
+    /* For jobs set !job->manual, transition to pending synchronously now */
+    block_job_txn_apply(job->txn, block_job_event_pending, false);
+
+    /* prepare the transaction to complete */
+    rc = block_job_txn_apply(job->txn, block_job_prepare, true);
+    if (rc) {
+        block_job_completed_txn_abort(job);
+    } else {
+        block_job_txn_apply(job->txn, block_job_finalize_single, true);
+    }
+}
+
+static int block_job_pending_conditional(BlockJob *job)
+{
+    return job->manual ? block_job_event_pending(job) : 0;
+}
+
 static void block_job_completed_txn_success(BlockJob *job)
 {
     BlockJobTxn *txn = job->txn;
     BlockJob *other_job;
-    int rc = 0;
 
     block_job_state_transition(job, BLOCK_JOB_STATUS_WAITING);
 
@@ -606,16 +634,15 @@ static void block_job_completed_txn_success(BlockJob *job)
         }
     }
 
-    /* Jobs may require some prep-work to complete without failure */
-    rc = block_job_txn_apply(txn, block_job_prepare, true);
-    if (rc) {
-        block_job_completed_txn_abort(job);
-        return;
-    }
+    /* For jobs with (job->manual), transition to the PENDING state.
+     * jobs with !job->manual are left WAITING (on their pending comrades). */
+    block_job_txn_apply(txn, block_job_pending_conditional, false);
 
-    /* We are the last completed job, commit the transaction. */
-    block_job_txn_apply(txn, block_job_event_pending, false);
-    block_job_txn_apply(txn, block_job_completed_single, true);
+    /* Transactions with any manual jobs must await finalization.
+     * do_finalize will handle lingering WAITING->PENDING transitions. */
+    if (!block_job_txn_apply(txn, block_job_is_manual, false)) {
+        block_job_do_finalize(job);
+    }
 }
 
 /* Assumes the block_job_mutex is held */
@@ -667,6 +694,15 @@ void block_job_complete(BlockJob *job, Error **errp)
     job->driver->complete(job, errp);
 }
 
+void block_job_finalize(BlockJob *job, Error **errp)
+{
+    assert(job && job->id && job->txn);
+    if (block_job_apply_verb(job, BLOCK_JOB_VERB_FINALIZE, errp)) {
+        return;
+    }
+    block_job_do_finalize(job);
+}
+
 void block_job_dismiss(BlockJob **jobptr, Error **errp)
 {
     BlockJob *job = *jobptr;
@@ -826,7 +862,10 @@ static void block_job_event_completed(BlockJob *job, const 
char *msg)
 
 static int block_job_event_pending(BlockJob *job)
 {
-    block_job_state_transition(job, BLOCK_JOB_STATUS_PENDING);
+    /* If we're already pending, don't re-announce */
+    if (!block_job_state_transition(job, BLOCK_JOB_STATUS_PENDING)) {
+        return 0;
+    }
     if (job->manual && !block_job_is_internal(job)) {
         qapi_event_send_block_job_pending(job->driver->job_type,
                                           job->id,
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 9bb0be1b13..e09064c342 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -245,6 +245,23 @@ void block_job_cancel(BlockJob *job);
  */
 void block_job_complete(BlockJob *job, Error **errp);
 
+
+/**
+ * block_job_finalize:
+ * @job: The job to fully commit and finish.
+ * @errp: Error object.
+ *
+ * For jobs that have finished their work and are pending
+ * awaiting explicit acknowledgement to commit their work,
+ * This will commit that work.
+ *
+ * FIXME: Make the below statement universally true:
+ * For jobs that support the manual workflow mode, all graph
+ * changes that occur as a result will occur after this command
+ * and before a successful reply.
+ */
+void block_job_finalize(BlockJob *job, Error **errp);
+
 /**
  * block_job_dismiss:
  * @job: The job to be dismissed.
diff --git a/qapi/block-core.json b/qapi/block-core.json
index acf9e56876..549c6c02d8 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -972,10 +972,13 @@
 #
 # @dismiss: see @block-job-dismiss
 #
+# @finalize: see @block-job-finalize
+#
 # Since: 2.12
 ##
 { 'enum': 'BlockJobVerb',
-  'data': ['cancel', 'pause', 'resume', 'set-speed', 'complete', 'dismiss' ] }
+  'data': ['cancel', 'pause', 'resume', 'set-speed', 'complete', 'dismiss',
+           'finalize' ] }
 
 ##
 # @BlockJobStatus:
@@ -2274,6 +2277,24 @@
 ##
 { 'command': 'block-job-dismiss', 'data': { 'id': 'str' } }
 
+##
+# @block-job-finalize:
+#
+# Once a job that has manual=true reaches the pending state, it can be
+# instructed to finalize any graph changes and do any necessary cleanup
+# via this command.
+# For jobs in a transaction, instructing one job to finalize will force
+# ALL jobs in the transaction to finalize, so it is only necessary to instruct
+# a single member job to finalize.
+#
+# @id: The job identifier.
+#
+# Returns: Nothing on success
+#
+# Since: 2.12
+##
+{ 'command': 'block-job-finalize', 'data': { 'id': 'str' } }
+
 ##
 # @BlockdevDiscardOptions:
 #
-- 
2.14.3


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