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description: using vol-resize with a negative value and "--delta --shrink" will cause size increasing instead of decreasing. versions: kernel-3.10.0-242.el7.x86_64 qemu-kvm-rhev-2.3.0-1.el7.x86_64 libvirt-1.2.14-1.el7.x86_64 repro steps: 1. has a volume in default pool. # virsh vol-list default Name Path ------------------------------------------------------------------------------ ........ rs.raw /var/lib/libvirt/images/rs.raw ....... 2. check the volume's info # qemu-img info /var/lib/libvirt/images/rs.raw image: /var/lib/libvirt/images/rs.raw file format: raw virtual size: 2.0G (2098200576 bytes) 3. use vol-resize on this volume with --shrink --delta and a positive value (200M) # virsh vol-resize /var/lib/libvirt/images/rs.raw 200M --shrink --delta Size of volume 'rs.raw' successfully changed by 200M # qemu-img info /var/lib/libvirt/images/rs.raw image: /var/lib/libvirt/images/rs.raw file format: raw virtual size: 2.2G (2357198848 bytes) <==== 200M added as expected disk size: 0 4. use vol-resize on this volume with --shrink --delta and a negative value (-200M) # virsh vol-resize /var/lib/libvirt/images/rs.raw -200M --shrink --delta Size of volume 'rs.raw' successfully changed by 200M # qemu-img info /var/lib/libvirt/images/rs.raw image: /var/lib/libvirt/images/rs.raw file format: raw virtual size: 2.4G (2566914048 bytes) <==== still 200M added disk size: 0 Actual result: When use "vol-resize -200M --delta --shrink", the volume size was increased by 200M Expected result: when use a negative capacity value with "--delta --shrink", volume size should be decreased.
I think even a positive value (if combined with --delta) should shrink the volume with the --shrink flag. Upstream patches: https://www.redhat.com/archives/libvir-list/2015-May/msg01041.html
Jan, Currently a positive value (which is larger than current capacity) combined with --shrink will extend the volume. Is it the expected result ? # virsh vol-info yy default Name: yy Type: file Capacity: 1.00 GiB Allocation: 1.00 GiB # virsh vol-resize --pool default yy 2G --shrink Size of volume 'yy' successfully changed to 2G # virsh vol-info yy default Name: yy Type: file Capacity: 2.00 GiB Allocation: 1.00 GiB Regards Yang
Yes, unfortunately. --shrink copies the behavior of VIR_STORAGE_VOL_RESIZE_SHRINK This flag is documented as 'allow shrinking the volume' not 'shrink the volume': http://libvirt.org/html/libvirt-libvirt-storage.html#virStorageVolResizeFlags Only with the DELTA flag is it documented to mean 'shrink the volume': http://libvirt.org/html/libvirt-libvirt-storage.html#virStorageVolResize but it was not implemented until my patch: https://www.redhat.com/archives/libvir-list/2015-May/msg01043.html
Shrinking volumes with the --delta flag is merged upstream now: (both "-200M' and "200M" will shrink the volume by 200M) commit 8b316fe5da8e459349b1a3ee0037bc7988d6f8aa Author: Ján Tomko <jtomko@redhat.com> CommitDate: 2015-05-28 14:10:32 +0200 Fix shrinking volumes with the delta flag This never worked. In 0.9.10 when this API was introduced, it was intended that the SHRINK flag combined with DELTA would shrink the volume by the specified capacity (to avoid passing negative numbers). See commit 055bbf4. When the SHRINK flag was finally implemented for the first backend in 1.2.13 (commit aa9aa6a), it was only implemented for the absolute values and with the delta flag the volume is always extended, regardless of the SHRINK flag. Treat the SHRINK flag as a minus sign when used together with DELTA, to allow shrinking volumes as was documented in the API since 0.9.10. https://bugzilla.redhat.com/show_bug.cgi?id=1220213 git describe: v1.2.16-rc1-9-g8b316fe
Using a negative value implies --delta since: commit 0a33bba1aeec04ccf6963b6942bac4586f04dda7 CommitDate: 2015-06-01 13:56:49 +0200 virsh: make negative values with vol-resize more convenient When shrinking a volume by a certain size, instead of typing vol-resize volume 1G --delta --shrink we allow the convience of specifying a negative value: vol-resize volume -1G --delta --shrink getting the same results with one more character. A negative value only makes sense as a delta. Imply the --delta parameter if the value is negative. Still require --shrink, because the operation is potentially destructive. git describe: v1.2.16-6-g0a33bba
verified on libvirt-1.2.17-1.el7.x86_64 1. prepare a pool with a volume with 5GiB capacity # virsh vol-info disk1.img pool Name: disk1.img Type: file Capacity: 5.00 GiB Allocation: 196.00 KiB 2. resize with negative value and --shrink # virsh vol-resize /home/test/disk1.img -1G --shrink Size of volume 'disk1.img' successfully changed by 1G # virsh vol-info disk1.img pool Name: disk1.img Type: file Capacity: 4.00 GiB <===== expected. Allocation: 0.00 B 3. resize with positive value with --delta --shrink # virsh vol-resize /home/test/disk1.img 1G --delta --shrink Size of volume 'disk1.img' successfully changed by 1G # virsh vol-info disk1.img pool Name: disk1.img Type: file Capacity: 3.00 GiB <=== expected Allocation: 0.00 B 4. resize with negative value with --delta --shrink # virsh vol-resize /home/test/disk1.img -1G --delta --shrink Size of volume 'disk1.img' successfully changed by 1G # virsh vol-info disk1.img pool Name: disk1.img Type: file Capacity: 2.00 GiB <===== expected Allocation: 0.00 B 5. resize with lager-than-current value with shrink # virsh vol-resize /home/test/disk1.img 5G --shrink Size of volume 'disk1.img' successfully changed to 5G # virsh vol-info disk1.img pool Name: disk1.img Type: file Capacity: 5.00 GiB <==== expected as comment 4 pointed out Allocation: 0.00 B
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHBA-2015-2202.html