On 04/26/2013 08:34 AM, Stefan Hajnoczi wrote: > On Fri, Apr 26, 2013 at 05:31:12PM +0800, Wenchao Xia wrote: >> To make it clear about id and name in searching, the API is changed >> a bit to distinguish them, and caller can choose to search by id or name. >> If not found, *errp will be set to tip why. >> >> Note that the caller logic is changed a bit: >> 1) In del_existing_snapshots() called by do_savevm(), it travers twice > > s/travers/traverse/ > > Also in comments in the code. > >> to find the snapshot, instead once, so matching sequence may change >> if there are unwisely chosen, mixed id and names. >> 2) In do_savevm(), same with del_existing_snapshot(), when it tries to >> find the snapshot to overwrite, matching sequence may change for same >> reason. >> 3) In load_vmstate(), first when it tries to find the snapshot to be loaded, >> sequence may change for the same reason of above. Later in validation, the >> logic is changed to be more strict to require both id and name matching. >> 4) In do_info_snapshot(), in validation, the logic is changed to be more >> strict to require both id and name matching. > > It's easy to avoid changing semantics: keep the old name or id behavior > around. Use the new name-and-id behavior for #3 and #4. > > Please include a justification for breaking the search order.
A good start for such a justification would be to edit parts of my email [1] into your commit message, showing how the old semantics make it IMPOSSIBLE to delete or load 'id 2 tag 1' without first getting 'id 1 tag 2' out of the way, assuming that a qcow2 file with poor naming conventions exists (even if such a bad file can only be created externally). The goal of a commit message is to convince the readers that a change in semantics is appropriate because the alternative of leaving things broken is worse. [1]https://lists.gnu.org/archive/html/qemu-devel/2013-04/msg03501.html -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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