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libvirt-storage: Document volume upload/download stream format 

For libvirt, the volume is just a binary blob and it doesn't
interpret data on volume upload/download. But as it turns out,
this unspoken assumption is not clear to our users. Document it
explicitly.

Suggested in: https://bugzilla.redhat.com/show_bug.cgi?id=1851023#c17

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
This commit is contained in:
Michal Privoznik 2020-07-01 13:47:04 +02:00
parent 24793bdf28
commit 70b67c98d9
1 changed files with 8 additions and 2 deletions
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10
src/libvirt-storage.c
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@ -1590,7 +1590,10 @@ virStorageVolCreateXMLFrom(virStoragePoolPtr pool,
*
* Download the content of the volume as a stream. If @length
* is zero, then the remaining contents of the volume after
* @offset will be downloaded.
* @offset will be downloaded. Please note that the stream
* transports the volume itself as is, so the downloaded data may
* not correspond to guest OS visible state in cases when a
* complex storage format such as qcow2 or vmdk is used.
*
* If VIR_STORAGE_VOL_DOWNLOAD_SPARSE_STREAM is set in @flags
* effective transmission of holes is enabled. This assumes using
@ -1663,7 +1666,10 @@ virStorageVolDownload(virStorageVolPtr vol,
* will fail if @offset + @length exceeds the size of the
* volume. Otherwise, if @length is non-zero, an error
* will be raised if an attempt is made to upload greater
* than @length bytes of data.
* than @length bytes of data. Please note that the stream
* transports the volume itself as is, so the downloaded data may
* not correspond to guest OS visible state in cases when a
* complex storage format such as qcow2 or vmdk is used.
*
* If VIR_STORAGE_VOL_UPLOAD_SPARSE_STREAM is set in @flags
* effective transmission of holes is enabled. This assumes using