On 05/24/2011 07:19 AM, Daniel P. Berrange wrote:
> On Mon, May 23, 2011 at 11:56:03AM -0500, Adam Litke wrote:
>> Here is version 4 of the BlockStream API (now called BlockPull). Hopefully this
>> version addresses all remaining concerns and I can begin to work on the code.
>> Does everyone approve of the new name 'virDomainBlockPull'?
>>
>>
>> Changes since V3:
>> - Renamed the API to 'Block Pull' to emphasize the effect of the API over its
>> method of operation.
>> - Changed virDomainGetBlockPullInfo() to accept a path argument and to return
>> information about that path alone.
>> - Added a new virDomainEvent to report final status when using CONTINUOUS mode.
>>
>> /*
>> * Block Pull API
>> */
>> typedef enum {
>> /*
>> * If set, virDomainBlockPull() will operate on the entire device in the
>> * background. The status can be checked and the operation aborted by
>> * using the functions virDomainBlockPullInfo() and
>> * virDomainBlockPullAbort().
>> */
>> VIR_DOMAIN_BLOCK_PULL_CONTINUOUS = 1,
>> } virDomainBlockPullFlags;
>>
>> /* 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;
>>
>> /**
>> * virDomainBlockPull:
>> * @dom: pointer to domain object
>> * @path: Fully-qualified filename of disk
>> * @cursor: pointer to a virDomainBlockPullCursor, or NULL
>> * @flags: One of virDomainBlockPullFlags, or zero
>> *
>> * Populate a disk image with data from its backing image. Once all data from
>> * its backing image has been pulled, the disk no longer depends on a backing
>> * image.
>> *
>> * If VIR_DOMAIN_BLOCK_PULL_CONTINUOUS is specified, the entire device will be
>> * streamed in the background. Otherwise, the value stored in @cursor will be
>> * used to stream an increment.
>> *
>> * Returns -1 in case of failure, 0 when successful. On success and when @flags
>> * does not contain VIR_DOMAIN_BLOCK_PULL_CONTINUOUS, the iterator @cursor will
>> * be updated to the proper value for use in a subsequent call.
>> */
>> int virDomainBlockPull(virDomainPtr dom,
>> const char *path,
>> virDomainBlockPullCursor *cursor,
>> unsigned int flags);
>>
>> /**
>> * virDomainBlockPullAbort:
>> * @dom: pointer to domain object
>> * @path: fully-qualified filename of disk
>> * @flags: currently unused, for future extension
>> *
>> * Cancel a pull operation that has been previously started by a call to
>> * virDomainBlockPull() with the VIR_DOMAIN_BLOCK_PULL_CONTINUOUS flag.
>> *
>> * 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 the VIR_DOMAIN_BLOCK_PULL_CONTINUOUS flag set. 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,
>> virDomainBlockStreamInfoPtr info,
>> unsigned int flags);
>>
>>
>> The following new asynchronous event will be made available for subscription:
>>
>> VIR_DOMAIN_EVENT_ID_BLOCK_PULL = 7,
>>
>> typedef enum {
>> VIR_DOMAIN_BLOCK_PULL_COMPLETED,
>> VIR_DOMAIN_BLOCK_PULL_FAILED,
>> } virConnectDomainEventBlockPullStatus;
>>
>> typedef void (*virConnectDomainEventBlockPullCallback(virConnectPtr conn,
>> virDomainPtr dom,
>> const char *path,
>> int status);
>>
>> Upon receipt of this event and when the status field indicates success, libvirt
>> will revoke access to the backing file which is no longer needed by the domain.
>>
>> NOTE: Qemu will emit an asynchronous event (VIR_DOMAIN_BLOCK_PULL_COMPLETED)
>> after any operation that eliminates the dependency on the backing file. This
>> could be a virDomainBlockPull() without VIR_DOMAIN_BLOCK_PULL_CONTINUOUS and
>> will allow libvirt to manage backing file security regardless of the pull mode
>> used.
>
> I assume it will also emit VIR_DOMAIN_BLOCK_PULL_FAILED when a continuous
> streaming operation aborts, because in that case you obviously still have
> the backing file present so PULL_COMPLETED wouldn't be issued ?
I don't think abort is the same as failed in this case. An abort is
triggered by the API user whereas a failure is not. If a user issues an
abort, they should know to stop waiting around for PULL_COMPLETED. A
failure is unexpected and thus absolutely needs an event to be raised.
--
Adam Litke
IBM Linux Technology Center
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list