Re: [Qemu-devel] [PATCH v8 01/26] block/mirror: Small absolute-paths simplification

[Kevin Wolf]

Am 05.02.2018 um 16:18 hat Max Reitz geschrieben:
> When invoking drive-mirror in absolute-paths mode, the target's backing
> BDS is assigned to it in mirror_exit(). The current logic only does so
> if the target does not have that backing BDS already; but it actually
> cannot have a backing BDS at all (the BDS is opened with O_NO_BACKING in
> qmp_drive_mirror()), so just assert that and assign the new backing BDS
> unconditionally.
> 
> Signed-off-by: Max Reitz <address@hidden>
> Reviewed-by: Alberto Garcia <address@hidden>

Introducing new assumptions that the graph stays unmodified between the
start of a block job and its completion feels a bit adventurous when all
of the blockdev work is moving towards making things more flexible.

If we really do want to enforce this, I guess you finally found a use
case for BLK_PERM_GRAPH_MOD.

Kevin