Paolo found that commit 27ccdd52598290f introduced a regression in the
It can be easily reproduced in scenarios where you have a throttling
group with several drives but you only write to one of them. In that
case the round-robin algorithm can select the wrong drive all the time
and the actual requests are never completed.
QEMU 2.7 is affected, here's the patch to fix it, plus a test case.
Alberto Garcia (2):
throttle: Correct access to wrong BlockBackendPublic structures
qemu-iotests: Test I/O in a single drive from a throttling group
block/throttle-groups.c | 27 +++++++++++++++++++++++----
tests/qemu-iotests/093 | 33 ++++++++++++++++++++++++++++-----
tests/qemu-iotests/093.out | 4 ++--
3 files changed, 53 insertions(+), 11 deletions(-)