From 3e0ff815da32944228b49c4ad33957c63dfd0f99 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Mon, 10 Sep 2018 18:18:03 +0200
Subject: [PATCH 25/25] blockdev: document transactional shortcomings

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20180910181803.11781-26-jsnow@redhat.com>
Patchwork-id: 82087
O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 25/25] blockdev: document transactional shortcomings
Bugzilla: 1626061
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

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>
(cherry picked from commit 97169e9959811e92e14c42afa0ec1fdeb09715ea)
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 blockdev.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 6325471..0eb6bba 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2333,7 +2333,13 @@ 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.
+     */
 };
 
 /**
-- 
1.8.3.1