On 09/02/2014 12:04 PM, Prerna Saxena wrote:

When virsh vol-clone is attempted on a raw file where capacity > allocation, the resulting cloned volume has a size that matches the virtual-size of the parent; in place of matching its actual, disk size. For example : Given this image: [root@localhost]# qemu-img info /var/lib/libvirt/images/f20.raw image: /var/lib/libvirt/images/f20.raw file format: raw virtual size: 2.0G (2147483648 bytes) disk size: 617M

When this disk is copied using virsh vol-clone : [root@localhost~] vol-clone --vol f20.raw --newname f20-copy.raw --pool default Vol f20-copy.raw cloned from f20.raw [root@localhost~]

The characteristics of the cloned disk differ in "disk size". Its allocated disk size is more than the allocated size of parent file; which is an anomaly. It has picked up an allocated size matching the parent's virtual size.

[root@localhost~] qemu-img info /var/lib/libvirt/images/f20-copy.raw image: /var/lib/libvirt/images/f20-copy.raw file format: raw virtual size: 2.0G (2147483648 bytes) disk size: 2.0G

This patch fixes the cloned disk to have same _allocated_size_ as the parent file from which it was cloned.

A bug has been filed for this recently: https://bugzilla.redhat.com/show_bug.cgi?id=1130739 It would be nice to mention it in the commit message.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com> --- src/storage/storage_driver.c | 5 ----- 1 file changed, 5 deletions(-)

diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c index 433d7b7..930b45a 100644 --- a/src/storage/storage_driver.c +++ b/src/storage/storage_driver.c @@ -1821,11 +1821,6 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj, if (newvol->target.capacity < origvol->target.capacity) newvol->target.capacity = origvol->target.capacity;

- /* Make sure allocation is at least as large as the destination cap, - * to make absolutely sure we copy all possible contents */ - if (newvol->target.allocation < origvol->target.capacity) - newvol->target.allocation = origvol->target.capacity; -

This essentially reverts commit 5ea25b7 [1], which means requesting a clone with <allocation> less than <capacity> will result in only the first <allocation> bytes being copied, thus losing any data after that point. The virStorageBackendCopyToFD call in createRawFile also needs to be adjusted to copy the non-zero data after the 'allocation' position.

if (!backend->buildVolFrom) { virReportError(VIR_ERR_NO_SUPPORT, "%s", _("storage pool does not support volume creation from an existing volume"));

Jan [1] http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=5ea25b7