Re: [libvirt] [PATCH 1/6] Add new API virDomainStreamDisk[Info] to header and drivers

After several long distractions, I am back to working on disk streaming. Before I hit the list with a new series of patches, I was hoping to reach some middle ground on the proposed streaming API. > Using flags to combine two separate tasks into one single API > is rather unpleasant. As raised in the previous patch, the API > should also be taking a offset+length in bytes, then there is > no need for a special case transfer of an individual sector. This is a fair point. I will work with Stefan to support an offset/length qemu API. Since there doesn't seem to be a great way to query device sizes, I think we do need a convenient way to request that the entire disk be streamed. We could either do this with a flag or by overriding (offset==0 && length==0) to mean stream the entire device. Do you have a preference?

> /* > * @path: fully qualified filename of the virtual disk > * @nregions: filled in the number of @region structs > * @regions: filled with a list of allocated regions > * > * Query the extents of allocated regions within the > * virtual disk file. The offsets in the list of regions > * are not guarenteed to be sorted in any explicit order. > */ > int virDomainBlockGetAllocationMap(virDomainPtr dom, > const char *path, > unsigned int *nregions, > virDomainBlockRegionPtr *regions); I am not convinced that we really need the block allocation map stuff.

It's a fun toy, but the layout of data within a device is far too low-level of a concept to be exposing to users.

typedef enum { /* If set, virDomainBlockAllocate() will return immediately * allowing polling for operation completion & status */ VIR_DOMAIN_DISK_STREAM_NONBLOCK, } virDomainBlockStreamFlags; /* * @device: alias of the target block device * @offset: logical position in bytes, within the virtual disk * @length: amount of data to copy, in bytes starting from @offset * @flags: One of virDomainBlockAllocateFlags, or zero * * Ensure the virtual disk @device is fully allocated * between @offset and @offset+@length. If a backing * store is present, data will be filled from the * backing store, otherwise data will be fileld with

* zeros. * * If @flags contains VIR_DOMAIN_DISK_STREAM_NONBLOCK, * this API will return immediately after initiating the * copy, otherwise it will block until copying is complete * */ int virDomainBlockStream(virDomainPtr dom, const char *device, unsigned long long offset, unsigned long long length, unsigned int flags); /* * @device: alias of the target block device * * Request that a disk streaming job be aborted at * the soonest opportunity. This API can only be used * when virDomainBlockStream() was invoked with the * VIR_DOMAIN_DISK_STREAM_NONBLOCK flag set. */ int virDomainBlockStreamAbort(virDomainPtr dom, const char *device); typedef enum { VIR_BLOCK_STREAM_STATE_COMPLETED = 0, VIR_BLOCK_STREAM_STATE_ACTIVE = 1, VIR_BLOCK_STREAM_STATE_FAILED = 2, } virBlockStreamStatus; typedef struct _virBlockStreamInfo virBlockStreamInfo; struct _virBlockStreamInfo { virBlockStreamStatus status; unsigned long long remaining; /* number of bytes remaining */ }; typedef virBlockStreamInfo *virBlockStreamInfoPtr;

/* * @device: alias of the target block device * @info: allocated struct to return progress info * * Query the progress of a disk streaming job. This * API must be used when virDomainBlockStream() was * invoked with the VIR_DOMAIN_DISK_STREAM_NONBLOCK * flag set. * */ int virDomainBlockStreamInfo(virDomainPtr dom, const char *device, virBlockStreamInfoPtr info);