Re: [libvirt] A question for external snapshots with flag“VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE”

please don't include libvir-list-owner in your mails. Also, it would be nice if you could convince your mailer to wrap long lines.

On 02/28/2017 06:37 AM, lizhengui wrote: > Hello, I got a question here. When we create consistent active external snapshots with flag “VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE” , the qemuDomainSnapshotFSFreeze will be called firstly to freeze all filesystems in vm, and then create snapshots. For windows vm, freezing filesystems used by vss service. If IO pressure in vm is too big or internal error happened in vss , freezing filesytems will failed , and qemuDomainSnapshotFSFreeze returns 0 which meaning that no filesystems are frozen. That sounds like a bug in the qga implementation for freezing file systems on Windows - if the system is not frozen, qga should return failure, not 0. Since libvirt doesn't maintain qga, this should probably be reported to the qemu folks. > In the function qemuDomainSnapshotCreateActiveExternal, libvirt creates external snapshots all the same in such a situation that qemuDomainSnapshotFSFreeze returns 0, but the created snapshots are not consistent snapshots in such a situation . So shouldn't we abandon creating snapshots and goto cleanup in the situation that qemuDomainSnapshotFSFreeze returns 0? Yes, even if qga behavior is patched, libvirt should probably figure out if it is feasible to work around existing broken behavior.

-- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org

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