qemu: command: Mark <shared/> disks as such in qemu

Qemu has now an internal mechanism for locking images to fix specific
cases of disk corruption. This requires libvirt to mark the image as
shared so that qemu lifts certain restrictions.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1378242

src/qemu/qemu_command.c

@@ -2159,6 +2159,10 @@ qemuBuildDriveDevStr(const virDomainDef *def,
         goto error;
     }
 
+    if (disk->src->shared &&
+        virQEMUCapsGet(qemuCaps, QEMU_CAPS_DISK_SHARE_RW))
+        virBufferAddLit(&opt, ",share-rw=on");
+
     if (!(drivealias = qemuAliasFromDisk(disk)))
         goto error;
     virBufferAsprintf(&opt, ",drive=%s,id=%s", drivealias, disk->info.alias);

tests/qemuxml2argvdata/qemuxml2argv-disk-drive-shared-locking.args

+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-i686 \
+-name QEMUGuest1 \
+-S \
+-M pc \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-QEMUGuest1/monitor.sock,\
+server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=readline \
+-no-acpi \
+-boot c \
+-device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x3 \
+-usb \
+-drive file=/dev/ide,format=raw,if=none,id=drive-ide0-0-0,cache=none \
+-device ide-drive,bus=ide.0,unit=0,share-rw=on,drive=drive-ide0-0-0,\
+id=ide0-0-0 \
+-drive file=/dev/scsi,format=raw,if=none,id=drive-scsi0-0-0-0,cache=none \
+-device scsi-disk,bus=scsi0.0,channel=0,scsi-id=0,lun=0,share-rw=on,\
+drive=drive-scsi0-0-0-0,id=scsi0-0-0-0 \
+-drive file=/dev/virtio,format=raw,if=none,id=drive-virtio-disk0,cache=none \
+-device virtio-blk-pci,bus=pci.0,addr=0x4,share-rw=on,drive=drive-virtio-disk0,\
+id=virtio-disk0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5

tests/qemuxml2argvdata/qemuxml2argv-disk-drive-shared-locking.xml

+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-i686</emulator>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/ide'/>
+      <target dev='hda' bus='ide'/>
+      <shareable/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/scsi'/>
+      <target dev='sda' bus='scsi'/>
+      <shareable/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/virtio'/>
+      <target dev='vda' bus='virtio'/>
+      <shareable/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='scsi' index='0' model='virtio-scsi'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -909,6 +909,8 @@ mymain(void)
     DO_TEST("disk-drive-shared",
             QEMU_CAPS_DRIVE_SERIAL);
     DO_TEST_PARSE_ERROR("disk-drive-shared-qcow", NONE);
+    DO_TEST("disk-drive-shared-locking",
+            QEMU_CAPS_VIRTIO_SCSI, QEMU_CAPS_DISK_SHARE_RW);
     DO_TEST("disk-drive-error-policy-stop",
             QEMU_CAPS_MONITOR_JSON);
     DO_TEST("disk-drive-error-policy-enospace",