Hi,
Now block layer does not check whether backing_file chain can be a
circle, do you think it is necessary to do a check?
For example, 1.qcow2's backing_file is 2.qcow2 and 2.qcow2's
backing_file is 1.qcow2, then any IO operation will be a fault.
If necessary, I will post a patch to fix.
[$] qemu-img create -f qcow2 1.qcow2
qemu-img: Image creation needs a size parameter
[$] qemu-img create -f qcow2 1.qcow2 8M
Formatting '1.qcow2', fmt=qcow2 size=8388608 encryption=off
cluster_size=65536 lazy_refcounts=off
[$] qemu-img create -f qcow2 2.qcow2 -o backing_file=1.qcow2
Formatting '2.qcow2', fmt=qcow2 size=8388608 backing_file='1.qcow2'
encryption=off cluster_size=65536 lazy_refcounts=off
[$] qemu-img create -f qcow2 1.qcow2 -o backing_file=2.qcow2
Formatting '1.qcow2', fmt=qcow2 size=8388608 backing_file='2.qcow2'
encryption=off cluster_size=65536 lazy_refcounts=off
[$] qemu-io -c "read -v 0 512" 1.qcow2
^CSegmentation fault (core dumped)
Thanks.
