[PATCH v4 09/11] qemu: validate: Allow <transient/> disks

[Peter Krempa]

From: Masayoshi Mizuma <m.mizuma at jp.fujitsu.com>

Extract the validation of transient disk option. We support transient
disks in qemu under the following conditions:

 - -blockdev is used
 - the disk source is a local file
 - the disk type is 'disk'
 - the disk is not readonly

Signed-off-by: Masayoshi Mizuma <m.mizuma at jp.fujitsu.com>
Signed-off-by: Peter Krempa <pkrempa at redhat.com>
---
 docs/formatdomain.rst    |  5 ++--
 src/qemu/qemu_validate.c | 56 +++++++++++++++++++++++++++++++++++-----
 2 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index 888db5ea29..cc1467c0e6 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -2974,8 +2974,9 @@ paravirtualized driver is specified via the ``disk`` element.
 ``transient``
    If present, this indicates that changes to the device contents should be
    reverted automatically when the guest exits. With some hypervisors, marking a
-   disk transient prevents the domain from participating in migration or
-   snapshots. Only suppported in vmx hypervisor. :since:`Since 0.9.5`
+   disk transient prevents the domain from participating in migration,
+   snapshots, or blockjobs. Only suppported in vmx hypervisor
+   (:since:`Since 0.9.5`) and ``qemu`` hypervisor (:since:`Since 6.9.0`).
 ``serial``
    If present, this specify serial number of virtual hard drive. For example, it
    may look like ``<serial>WD-WMAP9A966149</serial>``. Not supported for
diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index 3ed4039cdf..3196814aca 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -2186,12 +2186,6 @@ qemuValidateDomainDeviceDefDiskFrontend(const virDomainDiskDef *disk,
         }
     }

-    if (disk->transient) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                       _("transient disks not supported yet"));
-        return -1;
-    }
-
     if (disk->iomode == VIR_DOMAIN_DISK_IO_NATIVE &&
         disk->cachemode != VIR_DOMAIN_DISK_CACHE_DIRECTSYNC &&
         disk->cachemode != VIR_DOMAIN_DISK_CACHE_DISABLE) {
@@ -2340,6 +2334,53 @@ qemuValidateDomainDeviceDefDiskBlkdeviotune(const virDomainDiskDef *disk,
 }


+static int
+qemuValidateDomainDeviceDefDiskTransient(const virDomainDiskDef *disk,
+                                         virQEMUCapsPtr qemuCaps)
+
+{
+    virStorageType actualType = virStorageSourceGetActualType(disk->src);
+
+    if (!disk->transient)
+        return 0;
+
+    if (virStorageSourceIsEmpty(disk->src)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("transient disk '%s' must not be empty"), disk->dst);
+        return -1;
+    }
+
+    if (disk->src->readonly) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("transient disk '%s' must not be read-only"), disk->dst);
+        return -1;
+    }
+
+    if (actualType != VIR_STORAGE_TYPE_FILE) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("transient disk supported only with 'file' type (%s)"),
+                       disk->dst);
+        return -1;
+    }
+
+    if (disk->device != VIR_DOMAIN_DISK_DEVICE_DISK) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("transient disk supported only with 'disk' device (%s)"),
+                       disk->dst);
+        return -1;
+    }
+
+    if (qemuCaps && !virQEMUCapsGet(qemuCaps, QEMU_CAPS_BLOCKDEV)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("transient disk not supported by this qemu binary (%s)"),
+                       disk->dst);
+        return -1;
+    }
+
+    return 0;
+}
+
+
 int
 qemuValidateDomainDeviceDefDisk(const virDomainDiskDef *disk,
                                 const virDomainDef *def,
@@ -2357,6 +2398,9 @@ qemuValidateDomainDeviceDefDisk(const virDomainDiskDef *disk,
     if (qemuValidateDomainDeviceDefDiskBlkdeviotune(disk, def, qemuCaps) < 0)
         return -1;

+    if (qemuValidateDomainDeviceDefDiskTransient(disk, qemuCaps) < 0)
+        return -1;
+
     if (disk->src->shared && !disk->src->readonly &&
         !qemuBlockStorageSourceSupportsConcurrentAccess(disk->src)) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-- 
2.26.2