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

[Martin Kletzander]

On Sat, Feb 25, 2017 at 09:41:40AM +0800, WangJie (Captain) 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. 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?
>

Yeah, there should probably be a check that the number of frozen
filesystems is the same as requested and error out if it's lower.

Martin
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