On 2018-04-23 15:19, Alberto Garcia wrote: > On Sat 21 Apr 2018 12:09:10 AM CEST, Max Reitz wrote: >> Currently we do not take permissions on a file while it is being >> created. That is a bit sad. The simplest way to test this is the >> following: >> >> $ qemu-img create -f qcow2 foo.qcow2 64M >> Formatting 'foo.qcow2', fmt=qcow2 size=67108864 cluster_size=65536 >> lazy_refcounts=off refcount_bits=16 >> $ qemu-img convert -f qcow2 -O qcow2 foo.qcow2 foo.qcow2 >> qemu-img: foo.qcow2: error while converting qcow2: Failed to get "write" >> lock >> Is another process using the image? >> $ qemu-img info foo.qcow2 >> image: foo.qcow2 >> file format: raw >> virtual size: 0 (0 bytes) >> disk size: 0 > > Not quite the same problem, but here's another example of QEMU creating > an image before checking if it can be created: > > $ qemu-img create -o cluster_size=2M -f qcow2 img.qcow2 7E > Formatting 'img.qcow2', fmt=qcow2 size=8070450532247928832 encryption=off > cluster_size=2097152 lazy_refcounts=off refcount_bits=16 > qemu-img: img.qcow2: The image size is too large for file format 'qcow2' (try > using a larger cluster size) > > $ qemu-img info img.qcow2 > image: img.qcow2 > file format: qcow2 > virtual size: 0 (0 bytes) > disk size: 6.0M > cluster_size: 2097152 > Format specific information: > compat: 1.1 > lazy refcounts: false > refcount bits: 16 > corrupt: false > > Berto
Actually a very different problem, and I think we are not going to change this behavior -- especially considering the direction blockdev-create is taking (that is, separating protocol file creation and formatting). The main reason why it's a different problem, though, is because it doesn't mean any data loss. You just get a stale file lying around. (You could argue that in any case the file should at least be a raw file of size 0, because the qcow2 driver should not start formatting until it has checked all options, but, well... I don't know how that would help anyone.) Max
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