On 22.12.20 19:00, Vladimir Sementsov-Ogievskiy wrote:
22.12.2020 19:07, Max Reitz wrote:
On 16.12.20 07:17, Vladimir Sementsov-Ogievskiy wrote:
The code already don't freeze base node and we try to make it prepared
for the situation when base node is changed during the operation. In
other words, block-stream doesn't own base node.
Let's introduce a new interface which should replace the current one,
which will in better relations with the code. Specifying bottom node
instead of base, and requiring it to be non-filter gives us the
following benefits:
- drop difference between above_base and base_overlay, which will be
renamed to just bottom, when old interface dropped
- clean way to work with parallel streams/commits on the same backing
chain, which otherwise become a problem when we introduce a filter
for stream job
- cleaner interface. Nobody will surprised the fact that base node may
disappear during block-stream, when there is no word about "base" in
the interface.
Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
---
qapi/block-core.json | 12 ++++---
include/block/block_int.h | 1 +
block/monitor/block-hmp-cmds.c | 3 +-
block/stream.c | 50 +++++++++++++++++++---------
blockdev.c | 59 ++++++++++++++++++++++++++++------
5 files changed, 94 insertions(+), 31 deletions(-)
diff --git a/qapi/block-core.json b/qapi/block-core.json
index b8094a5ec7..cb0066fd5c 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2517,10 +2517,14 @@
# @device: the device or node name of the top image
#
# @base: the common backing file name.
-# It cannot be set if @base-node is also set.
+# It cannot be set if @base-node or @bottom is also set.
#
# @base-node: the node name of the backing file.
-# It cannot be set if @base is also set. (Since 2.8)
+# It cannot be set if @base or @bottom is also set.
(Since 2.8)
+#
+# @bottom: the last node in the chain that should be streamed into
+# top. It cannot be set if @base or @base-node is also set.
+# It cannot be filter node. (Since 6.0)
As far as I can make out, one of the results of our discussion on v14
was that when using backing-file + bottom, we want to require the user
to specify backing-fmt as well. Now, backing-fmt isn’t present yet.
Doesn’t that mean we have to make bottom + backing-file an error until
we have backing-fmt (like it was in v14)?
See my answer on 09. I just have some doubts around backing-fmt and
decided to keep it as is.
I don't think that we really need backing-fmt. We shouldn't have
use-cases when backing-fmt is set to something another than final base
node. Therefore, using format_name of final base node is a correct thing
to do. So, I don't see the reason now for introducing new option.
Yup, yup, all good.
Reviewed-by: Max Reitz <[email protected]>
