From 329a0c2d4967b6dac1530c010856119447385457 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Tue, 25 Sep 2018 22:34:31 +0100
Subject: [PATCH 28/28] blockdev: document transactional shortcomings

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20180925223431.24791-26-jsnow@redhat.com>
Patchwork-id: 82286
O-Subject: [RHEL8/rhel qemu-kvm PATCH 25/25] blockdev: document transactional shortcomings
Bugzilla: 1632939
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Max Reitz <mreitz@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 66da04ddd3dcb8c61ee664b6faced132da002006)
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 blockdev.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index bf026d2..b8e4b0d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2292,7 +2292,13 @@ 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