commit f4de0f8c40b70c4c9308b4670e0a6ad9faed0262
author John Snow <jsnow@redhat.com> Fri Jan 11 11:59:16 2019 -0600
committer Eric Blake <eblake@redhat.com> Mon Jan 14 10:08:47 2019 -0600
tree 5cd6f77de676bcce66818feaaf95c11376ddaa3e
parent 7260438b7056469610ee166f7abe9ff8a26b8b16

blockdev: abort transactions in reverse order

Presently, we abort transactions in the same order they were processed in.
Bitmap commands, though, attempt to restore backup data structures on abort.

That's not valid, they need to be aborted in reverse chronological order.

Replace the QSIMPLEQ data structure with a QTAILQ one, so we can iterate
in reverse for the abort phase of the transaction.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20181221093529.23855-2-jsnow@redhat.com>
[eblake: rebase]
Signed-off-by: Eric Blake <eblake@redhat.com>

blockdev.c

diff --git a/blockdev.c b/blockdev.c
index 1cc893f..3d46f81 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1339,7 +1339,7 @@
     const BlkActionOps *ops;
     JobTxn *block_job_txn;
     TransactionProperties *txn_props;
-    QSIMPLEQ_ENTRY(BlkActionState) entry;
+    QTAILQ_ENTRY(BlkActionState) entry;
 };
 
 /* internal snapshot private data */
@@ -2266,8 +2266,8 @@
     BlkActionState *state, *next;
     Error *local_err = NULL;
 
-    QSIMPLEQ_HEAD(, BlkActionState) snap_bdrv_states;
-    QSIMPLEQ_INIT(&snap_bdrv_states);
+    QTAILQ_HEAD(, BlkActionState) snap_bdrv_states;
+    QTAILQ_INIT(&snap_bdrv_states);
 
     /* Does this transaction get canceled as a group on failure?
      * If not, we don't really need to make a JobTxn.
@@ -2298,7 +2298,7 @@
         state->action = dev_info;
         state->block_job_txn = block_job_txn;
         state->txn_props = props;
-        QSIMPLEQ_INSERT_TAIL(&snap_bdrv_states, state, entry);
+        QTAILQ_INSERT_TAIL(&snap_bdrv_states, state, entry);
 
         state->ops->prepare(state, &local_err);
         if (local_err) {
@@ -2307,7 +2307,7 @@
         }
     }
 
-    QSIMPLEQ_FOREACH(state, &snap_bdrv_states, entry) {
+    QTAILQ_FOREACH(state, &snap_bdrv_states, entry) {
         if (state->ops->commit) {
             state->ops->commit(state);
         }
@@ -2318,13 +2318,13 @@
 
 delete_and_fail:
     /* failure, and it is all-or-none; roll back all operations */
-    QSIMPLEQ_FOREACH(state, &snap_bdrv_states, entry) {
+    QTAILQ_FOREACH_REVERSE(state, &snap_bdrv_states, entry) {
         if (state->ops->abort) {
             state->ops->abort(state);
         }
     }
 exit:
-    QSIMPLEQ_FOREACH_SAFE(state, &snap_bdrv_states, entry, next) {
+    QTAILQ_FOREACH_SAFE(state, &snap_bdrv_states, entry, next) {
         if (state->ops->clean) {
             state->ops->clean(state);
         }