blockdev: document transactional shortcomings

Presently only the backup job really guarantees what one would consider
transactional semantics. To guard against someone helpfully adding them
in the future, document that there are shortcomings in the model that
would need to be audited at that time.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20180906130225.5118-17-jsnow@redhat.com
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/blockdev.c b/blockdev.c
index 0cf8feb..d4b4240 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2182,7 +2182,13 @@ static const BlkActionOps actions[] = {
         .instance_size = sizeof(BlockDirtyBitmapState),
         .prepare = block_dirty_bitmap_disable_prepare,
         .abort = block_dirty_bitmap_disable_abort,
-     }
+    },
+    /* Where are transactions for MIRROR, COMMIT and STREAM?
+     * Although these blockjobs use transaction callbacks like the backup job,
+     * these jobs do not necessarily adhere to transaction semantics.
+     * These jobs may not fully undo all of their actions on abort, nor do they
+     * necessarily work in transactions with more than one job in them.
+     */
 };
 
 /**