On 04.12.20 23:07, Vladimir Sementsov-Ogievskiy wrote:
From: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com>
This patch completes the series with the COR-filter applied to
block-stream operations.
Adding the filter makes it possible in future implement discarding
copied regions in backing files during the block-stream job, to reduce
the disk overuse (we need control on permissions).
Also, the filter now is smart enough to do copy-on-read with specified
base, so we have benefit on guest reads even when doing block-stream of
the part of the backing chain.
Several iotests are slightly modified due to filter insertion.
Signed-off-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
block/stream.c | 78 ++++++++++++++++++++++++++------------
tests/qemu-iotests/030 | 8 ++--
tests/qemu-iotests/141.out | 2 +-
tests/qemu-iotests/245 | 20 ++++++----
4 files changed, 72 insertions(+), 36 deletions(-)
diff --git a/block/stream.c b/block/stream.c
index a7fd8945ad..b92f7de55b 100644
--- a/block/stream.c
+++ b/block/stream.c
[...]
@@ -295,17 +287,49 @@ void stream_start(const char *job_id, BlockDriverState
*bs,
[...]
+ opts = qdict_new();
+
+ qdict_put_str(opts, "driver", "copy-on-read");
+ qdict_put_str(opts, "file", bdrv_get_node_name(bs));
+ /* Pass the base_overlay node name as 'bottom' to COR driver */
+ qdict_put_str(opts, "bottom", base_overlay->node_name);
Hm. Should we set this option even if no base was specified?
On one hand, omitting this option would cor_co_preadv_part() a bit quicker.
On the other, what happens when you add a backing file below the bottom
node during streaming (yes, a largely theoretical case)... Now, all
data from it is ignored. That seemed a bit strange to me at first, but
on second thought, it makes more sense. Doing anything else would
produce a garbage result basically, because stream_run() doesn’t take
such a change into account.
So... After all I think I agree with setting @bottom unconditionally.
And that’s the only comment I had. :)
Reviewed-by: Max Reitz <mre...@redhat.com>
