[libvirt] [PATCH] Allow shrinking of file based volumes

While the main storage driver code allows the flag VIR_STORAGE_VOL_RESIZE_SHRINK to be set, none of the backend drivers are supporting it. At the very least this can work for plain file based volumes since we just ftruncate() them to the new size. It does not work with qcow2 volumes, but we can arguably delegate to qemu-img for error reporting for that instead of second guessing this for ourselves: $ virsh vol-resize --shrink /home/berrange/VirtualMachines/demo.qcow2 2G error: Failed to change size of volume 'demo.qcow2' to 2G error: internal error: Child process (/usr/bin/qemu-img resize /home/berrange/VirtualMachines/demo.qcow2 2147483648) unexpected exit status 1: qemu-img: qcow2 doesn't support shrinking images yet qemu-img: This image does not support resize See also https://bugzilla.redhat.com/show_bug.cgi?id=1021802 --- src/storage/storage_backend_fs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/storage/storage_backend_fs.c b/src/storage/storage_backend_fs.c index 34f2153..79543a6 100644 --- a/src/storage/storage_backend_fs.c +++ b/src/storage/storage_backend_fs.c @@ -1262,7 +1262,8 @@ virStorageBackendFileSystemVolResize(virConnectPtr conn ATTRIBUTE_UNUSED, unsigned long long capacity, unsigned int flags) { - virCheckFlags(VIR_STORAGE_VOL_RESIZE_ALLOCATE, -1); + virCheckFlags(VIR_STORAGE_VOL_RESIZE_ALLOCATE | + VIR_STORAGE_VOL_RESIZE_SHRINK, -1); bool pre_allocate = flags & VIR_STORAGE_VOL_RESIZE_ALLOCATE; -- 2.1.0