Re: [libvirt] [PATCH 2/5] Add public APIs for storage volume upload/download
On Tue, Mar 15, 2011 at 10:37:01AM -0600, Eric Blake wrote:
On 03/15/2011 06:30 AM, Daniel P. Berrange wrote:
> New APIs are added allowing streaming of content to/from
> storage volumes. A new API for creating volumes is also
> added allowing the content to be provided immediately at
> time of creation
>
> * include/libvirt/libvirt.h.in: Add virStorageVolUpload and
> virStorageVolDownload, virStorageVolCreateUpload APIs
I see virStorageVol{Up,Down}load, but not virStorageVolCreateUpload in
this patch.
As per previous posting, I removed VolCreateUpload since it isn't
needed and is complex to support.
> +++ b/src/libvirt.c
> @@ -9059,6 +9059,126 @@ error:
>
>
> /**
> + * virStorageVolDownload:
> + * @pool: pointer to volume to download
> + * @stream: stream to use as output
> + * @offset: position to start reading from
> + * @length: limit on amount of data to download
Does 0 (or UINT64_MAX) have a special meaning of read-to-end? If so,
document that.
I've added docs about '0'
> +
> + if (vol->conn->flags & VIR_CONNECT_RO ||
> + stream->conn->flags & VIR_CONNECT_RO) {
> + virLibConnError(VIR_ERR_OPERATION_DENIED, __FUNCTION__);
> + goto error;
> + }
Why is reading a volume prohibited on a RO connection?
The data inside a storage volume may be security sensitive. Thus
we don't want readonly users to be able to read guest disks.
> +/**
> + * virStorageVolUpload:
> + * @pool: pointer to volume to download
> + * @stream: stream to use as output
> + * @offset: position to start writing to
> + * @length: limit on amount of data to upload
Again, is there any special meaning of length 0, or a directive to
easily specify to end of input?
Added docs here.
> + * @flags: flags for creation (unused, pass 0)
Do we need a flag to allow for expansion of the volume if the input
stream (and length) are larger than the current size of the volume, for
volumes that can be expanded in size?
I prefer to keep this side-effect free. We should have a separate
API for enlarging storage, particularly since everything except
plain raw files cannot do grow-on-demand.
Daniel
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