On Thu, Jul 14, 2011 at 11:19 AM, Jiri Denemark <jdenemar@xxxxxxxxxx> wrote:
> On Thu, Jul 14, 2011 at 10:58:31 +0100, Stefan Hajnoczi wrote:
>> On Thu, Jul 14, 2011 at 10:21 AM, Jiri Denemark <jdenemar@xxxxxxxxxx> wrote:
>> > On Wed, Jul 13, 2011 at 15:46:30 -0500, Adam Litke wrote:
>> > ...
>> >> /*
>> >> * BlockPull API
>> >> */
>> >>
>> >> /* An iterator for initiating and monitoring block pull operations */
>> >> typedef unsigned long long virDomainBlockPullCursor;
>> >>
>> >> typedef struct _virDomainBlockPullInfo virDomainBlockPullInfo;
>> >> struct _virDomainBlockPullInfo {
>> >> /*
>> >> * The following fields provide an indication of block pull progress. @cur
>> >> * indicates the current position and will be between 0 and @end. @end is
>> >> * the final cursor position for this operation and represents completion.
>> >> * To approximate progress, divide @cur by @end.
>> >> */
>> >> virDomainBlockPullCursor cur;
>> >> virDomainBlockPullCursor end;
>> >> };
>> >> typedef virDomainBlockPullInfo *virDomainBlockPullInfoPtr;
>> > ...
>> >> /**
>> >> * virDomainBlockPullAbort:
>> >> * @dom: pointer to domain object
>> >> * @path: fully-qualified filename of disk
>> >> * @flags: currently unused, for future extension
>> >> *
>> >> * Cancel a pull operation previously started by virDomainBlockPullAll().
>> >> *
>> >> * Returns -1 in case of failure, 0 when successful.
>> >> */
>> >> int virDomainBlockPullAbort(virDomainPtr dom,
>> >> const char *path,
>> >> unsigned int flags);
>> >>
>> >> /**
>> >> * virDomainGetBlockPullInfo:
>> >> * @dom: pointer to domain object
>> >> * @path: fully-qualified filename of disk
>> >> * @info: pointer to a virDomainBlockPullInfo structure
>> >> * @flags: currently unused, for future extension
>> >> *
>> >> * Request progress information on a block pull operation that has been started
>> >> * with virDomainBlockPull(). If an operation is active for the given
>> >> * parameters, @info will be updated with the current progress.
>> >> *
>> >> * Returns -1 in case of failure, 0 when successful.
>> >> */
>> >> int virDomainGetBlockPullInfo(virDomainPtr dom,
>> >> const char *path,
>> >> virDomainBlockPullInfoPtr info,
>> >> unsigned int flags);
>> >>
>> >> /**
>> >> * virConnectDomainEventBlockPullStatus:
>> >> *
>> >> * The final status of a virDomainBlockPull() operation
>> >> */
>> >> typedef enum {
>> >> VIR_DOMAIN_BLOCK_PULL_COMPLETED = 0,
>> >> VIR_DOMAIN_BLOCK_PULL_FAILED = 1,
>> >> } virConnectDomainEventBlockPullStatus;
>> >>
>> >> /**
>> >> * virConnectDomainEventBlockPullCallback:
>> >> * @conn: connection object
>> >> * @dom: domain on which the event occurred
>> >> * @path: fully-qualified filename of the affected disk
>> >> * @status: final status of the operation (virConnectDomainEventBlockPullStatus
>> >> *
>> >> * The callback signature to use when registering for an event of type
>> >> * VIR_DOMAIN_EVENT_ID_BLOCK_PULL with virConnectDomainEventRegisterAny()
>> >> */
>> >> typedef void (*virConnectDomainEventBlockPullCallback)(virConnectPtr conn,
>> >> virDomainPtr dom,
>> >> const char *path,
>> >> int status,
>> >> void *opaque);
>> >
>> > Could these managing functions and event callback become general and usable by
>> > other block operations such as block copy?
>>
>> Hi Jiri,
>> Live block copy will certainly be possible using the streaming API.
>> Before you start streaming you need to use the snapshot_blkdev command
>> to create the destination file with the source file as its backing
>> image. You can then use the streaming API to copy data from the
>> source file into the destination file. On completion the source file
>> is no longer needed.
>
> Well, I'm not talking about using the same API for block copy or implementing
> block copy internally as block streaming. I'm talking about making GetInfo,
> Abort and event callback general to be usable not only for block streaming or
> block copy but also for other possible block operations in the future.
>
> The reason is that starting a block operation (streaming, copy, whatever) may
> need different parameters so they should be different APIs. But once the
> operation is started, we just need to know how far it got and we need the
> ability to abort the job. So this can share the same APIs for all operations.
> It doesn't make sense to require any block operation to provide their own set
> of managing APIs.
>
> It's analogous to virDomainSave, virDomainMigrate, virDomainCoreDump. They are
> all different jobs but all of them can be monitored and aborted using
> virDomainGetJobInfo and virDomainAbortJob.
I understand. I can't comment on libvirt API specifics but yes,
there's a similarity here and a chance we'll have other operations in
the future too.
I'm thinking things like compacting images, compressing images, etc.
Stefan
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