On 29.05.19 19:56, Andrey Shinkevich wrote:
> This patch is used in the 'block/stream: introduce a bottom node'
> that is following. Instead of the base node, the caller may pass
> the node that has the base as its backing image to the function
> bdrv_is_allocated_above() with a new parameter include_base = true
> and get rid of the dependency on the base that may change during
> commit/stream parallel jobs. Now, if the specified base is not
> found in the backing image chain, the QEMU will abort.
> 
> Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
>  block/commit.c        |  2 +-
>  block/io.c            | 21 +++++++++++++++------
>  block/mirror.c        |  2 +-
>  block/replication.c   |  2 +-
>  block/stream.c        |  2 +-
>  include/block/block.h |  3 ++-
>  6 files changed, 21 insertions(+), 11 deletions(-)

This needs the following hunk squashed in so it still compiles:

(I can do that, if you agree.)

diff --git a/block/qcow2.c b/block/qcow2.c
index 9396d490d5..2a59eb27fe 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2148,7 +2148,8 @@ static bool is_unallocated(BlockDriverState *bs,
int64_t offset, int64_t bytes)
 {
     int64_t nr;
     return !bytes ||
-        (!bdrv_is_allocated_above(bs, NULL, offset, bytes, &nr) && nr
== bytes);
+        (!bdrv_is_allocated_above(bs, NULL, false, offset, bytes, &nr) &&
+         nr == bytes);
 }

 static bool is_zero_cow(BlockDriverState *bs, QCowL2Meta *m)
diff --git a/qemu-img.c b/qemu-img.c
index 158b3a505f..79983772de 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -3518,7 +3518,7 @@ static int img_rebase(int argc, char **argv)
                  * to take action
                  */
                 ret = bdrv_is_allocated_above(backing_bs(bs),
prefix_chain_bs,
-                                              offset, n, &n);
+                                              false, offset, n, &n);
                 if (ret < 0) {
                     error_report("error while reading image metadata: %s",
                                  strerror(-ret));