[PULL v2 07/13] transactions: Invoke clean() after everything else

[Hanna Reitz]

Invoke the transaction drivers' .clean() methods only after all
.commit() or .abort() handlers are done.

This makes it easier to have nested transactions where the top-level
transactions pass objects to lower transactions that the latter can
still use throughout their commit/abort phases, while the top-level
transaction keeps a reference that is released in its .clean() method.

(Before this commit, that is also possible, but the top-level
transaction would need to take care to invoke tran_add() before the
lower-level transaction does.  This commit makes the ordering
irrelevant, which is just a bit nicer.)

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20211111120829.81329-8-hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-8-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
---
 include/qemu/transactions.h | 3 +++
 util/transactions.c         | 8 ++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/qemu/transactions.h b/include/qemu/transactions.h
index 92c5965235..2f2060acd9 100644
--- a/include/qemu/transactions.h
+++ b/include/qemu/transactions.h
@@ -31,6 +31,9 @@
  * tran_create(), call your "prepare" functions on it, and finally call
  * tran_abort() or tran_commit() to finalize the transaction by corresponding
  * finalization actions in reverse order.
+ *
+ * The clean() functions registered by the drivers in a transaction are called
+ * last, after all abort() or commit() functions have been called.
  */
 
 #ifndef QEMU_TRANSACTIONS_H
diff --git a/util/transactions.c b/util/transactions.c
index d0bc9a3e73..2dbdedce95 100644
--- a/util/transactions.c
+++ b/util/transactions.c
@@ -61,11 +61,13 @@ void tran_abort(Transaction *tran)
 {
     TransactionAction *act, *next;
 
-    QSLIST_FOREACH_SAFE(act, &tran->actions, entry, next) {
+    QSLIST_FOREACH(act, &tran->actions, entry) {
         if (act->drv->abort) {
             act->drv->abort(act->opaque);
         }
+    }
 
+    QSLIST_FOREACH_SAFE(act, &tran->actions, entry, next) {
         if (act->drv->clean) {
             act->drv->clean(act->opaque);
         }
@@ -80,11 +82,13 @@ void tran_commit(Transaction *tran)
 {
     TransactionAction *act, *next;
 
-    QSLIST_FOREACH_SAFE(act, &tran->actions, entry, next) {
+    QSLIST_FOREACH(act, &tran->actions, entry) {
         if (act->drv->commit) {
             act->drv->commit(act->opaque);
         }
+    }
 
+    QSLIST_FOREACH_SAFE(act, &tran->actions, entry, next) {
         if (act->drv->clean) {
             act->drv->clean(act->opaque);
         }
-- 
2.33.1