[libvirt] [PATCH 2/9] qemu: domain: Reject copy_on_read for read-only disks
The sectors read from the backing image need to be written to the top
level image. If a disk is marked read-only the image can't be written.
QEMU handled that by disabling copy_on_read and reporting a warning:
-drive file=/var/lib/libvirt/images/c,format=qcow2,if=none,
id=drive-scsi0-0-1,readonly=on,copy-on-read=on:
warning: disabling copy-on-read on read-only drive
Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
---
src/qemu/qemu_domain.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index e29d01c828..0821ce769b 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -4650,6 +4650,13 @@ qemuDomainDeviceDefValidateDisk(const virDomainDiskDef *disk,
return -1;
}
+ if (disk->src->readonly && disk->copy_on_read ==
VIR_TRISTATE_SWITCH_ON) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+ _("copy_on_read is not compatible with read-only disk
'%s'"),
+ disk->dst);
+ return -1;
+ }
+
if (disk->geometry.cylinders > 0 &&
disk->geometry.heads > 0 &&
disk->geometry.sectors > 0) {
--
2.16.2