Consider the following scenario where the overlay is shorter than its
backing file:
base.qcow2: AAAAAAAA
overlay.qcow2: BBBB
When resizing (extending) overlay.qcow2, the new blocks should not stay
unallocated and make the additional As from base.qcow2 visible like
before this series, but zeros should be read.
A similar case happens with the various variants of a commit job when an
intermediate file is short (- for unallocated):
base.qcow2: A-A-AAAA
mid.qcow2: BB-B
top.qcow2: C--C--C-
After commit top.qcow2 to mid.qcow2, the following happens:
mid.qcow2: CB-C00C0 (correct result)
mid.qcow2: CB-C--C- (before this fix)
Without the fix, blocks that previously read as zeros on top.qcow2
suddenly turn into A.
Kevin Wolf (6):
block: bdrv_co_do_pwrite_zeroes: 64 bit 'bytes' parameter
block: truncate: Don't make backing file data visible
iotests: Add qemu_io_log()
iotests: Fix timeout in run_job()
iotests: Support job-complete in run_job()
iotests: Test committing to short backing file
block/io.c | 31 ++++++-
tests/qemu-iotests/274 | 131 +++++++++++++++++++++++++++++
tests/qemu-iotests/274.out | 150 ++++++++++++++++++++++++++++++++++
tests/qemu-iotests/group | 1 +
tests/qemu-iotests/iotests.py | 11 ++-
5 files changed, 319 insertions(+), 5 deletions(-)
create mode 100755 tests/qemu-iotests/274
create mode 100644 tests/qemu-iotests/274.out
--
2.20.1
