blockjobs: add block-job-finalize

Instead of automatically transitioning from PENDING to CONCLUDED, gate
the .prepare() and .commit() phases behind an explicit acknowledgement
provided by the QMP monitor if auto_finalize = false 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->auto_finalize settings will all
remain stuck in the "PENDING" state, as if the entire transaction was
specified with auto_finalize = false. Jobs that specified
auto_finalize = true, however, will still not emit the PENDING event.

Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 44 insertions, 16 deletions

diff --git a/blockjob.c b/blockjob.c
index 0a22b924fe..d6b8bea514 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -65,6 +65,7 @@ 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},
 };
 
@@ -449,7 +450,7 @@ 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);
 
@@ -590,18 +591,36 @@ 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_needs_finalize(BlockJob *job)
+{
+    return !job->auto_finalize;
+}
+
+static void block_job_do_finalize(BlockJob *job)
+{
+    int rc;
+    assert(job && job->txn);
+
+    /* 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 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);
 
@@ -616,16 +635,12 @@ static void block_job_completed_txn_success(BlockJob *job)
         assert(other_job->ret == 0);
     }
 
-    /* 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;
-    }
-
-    /* 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);
+
+    /* If no jobs need manual finalization, automatically do so */
+    if (block_job_txn_apply(txn, block_job_needs_finalize, false) == 0) {
+        block_job_do_finalize(job);
+    }
 }
 
 /* Assumes the block_job_mutex is held */
@@ -677,6 +692,15 @@ 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;
@@ -727,11 +751,15 @@ void block_job_cancel(BlockJob *job)
 {
     if (job->status == BLOCK_JOB_STATUS_CONCLUDED) {
         block_job_do_dismiss(job);
-    } else if (block_job_started(job)) {
-        block_job_cancel_async(job);
-        block_job_enter(job);
-    } else {
+        return;
+    }
+    block_job_cancel_async(job);
+    if (!block_job_started(job)) {
         block_job_completed(job, -ECANCELED);
+    } else if (job->deferred_to_main_loop) {
+        block_job_completed_txn_abort(job);
+    } else {
+        block_job_enter(job);
     }
 }