GPFS Raw file is copied by qemu-img even though copy-on-write option is specified

[Dinesh Subhraveti]

When an image is fetched from Glance and stored as a volume, the image bits are unnecessarily copied during format conversion by qemu-img when source and target formats are both raw.

Thanks to Avishay for pointing out the error.

[Avishay Traeger (avishay-il)]

Note that this will be fixed in the GPFS driver, not in the generic version, and therefore is not a duplicate bug.

[Avishay Traeger (avishay-il)]

So some more details to avoid confusion with similarly-named bugs:

In the GPFS driver implementation of copy-image-to-volume, the image is on the GPFS file system and the driver can test to see if it's raw ahead of time, and simply symlink the file if it's already raw, rather than calling 'qemu-img convert' which copies data. This saves space and copy time.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/38355

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/38355
Committed: http://github.com/openstack/cinder/commit/84ca4b3698ae8512f6ba4cd72a57f662e35b59a0
Submitter: Jenkins
Branch: master

commit 84ca4b3698ae8512f6ba4cd72a57f662e35b59a0
Author: Bill Owen <email address hidden>
Date: Sun Jul 21 17:35:50 2013 -0700

    GPFS convert glance image to raw only when needed

    Modify _gpfs_fetch_to_raw to check image format. If already in raw
    format, no need to call convert_image. In that case, simply rename
    to destination name.

    Change-Id: I197d99194f93c02ce3c501de25433d89b23e6a35
    Fixes: bug #1201676