On 5/19/20 2:54 PM, Vladimir Sementsov-Ogievskiy wrote:
This leads to the following effect: ./qemu-img create -f qcow2 base.qcow2 2M ./qemu-io -c "write -P 0x1 0 2M" base.qcow2 ./qemu-img create -f qcow2 -b base.qcow2 mid.qcow2 1M ./qemu-img create -f qcow2 -b mid.qcow2 top.qcow2 2M Region 1M..2M is shadowed by short middle image, so guest sees zeroes: ./qemu-io -c "read -P 0 1M 1M" top.qcow2 read 1048576/1048576 bytes at offset 1048576 1 MiB, 1 ops; 00.00 sec (22.795 GiB/sec and 23341.5807 ops/sec) But after commit guest visible state is changed, which seems wrong for me: ./qemu-img commit top.qcow2 -b mid.qcow2 ./qemu-io -c "read -P 0 1M 1M" mid.qcow2 Pattern verification failed at offset 1048576, 1048576 bytes read 1048576/1048576 bytes at offset 1048576 1 MiB, 1 ops; 00.00 sec (4.981 GiB/sec and 5100.4794 ops/sec)
This no longer happens as of commit bf03dede47 and friends. As such, how much of this series is still needed for other reasons?
-- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
