[libvirt] [PATCH RFC 28/39] qemu: hotplug: Prepare for blockdev-add/blockdev-del with backing chains

[Ján Tomko]

On Wed, Jul 25, 2018 at 05:57:59PM +0200, Peter Krempa wrote:
>Initialize data for the whole backing chain when plugging in or removing
>disks when a machine supports -blockdev.
>
>Similarly to startup we need to prepare the structures for the whole
>backing chain and take care of the copy-on-read feature.
>
>Signed-off-by: Peter Krempa <pkrempa at redhat.com>
>---
> src/qemu/qemu_hotplug.c | 75 ++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 61 insertions(+), 14 deletions(-)
>
>diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
>index 87efd3b411..3eddb0043e 100644
>--- a/src/qemu/qemu_hotplug.c
>+++ b/src/qemu/qemu_hotplug.c
>@@ -380,6 +380,10 @@ qemuHotplugRemoveManagedPR(virQEMUDriverPtr driver,
> struct _qemuHotplugDiskSourceData {
>     qemuBlockStorageSourceAttachDataPtr *backends;
>     size_t nbackends;
>+
>+    /* disk copy-on-read object */
>+    virJSONValuePtr corProps;
>+    char *corAlias;
> };
> typedef struct _qemuHotplugDiskSourceData qemuHotplugDiskSourceData;
> typedef qemuHotplugDiskSourceData *qemuHotplugDiskSourceDataPtr;
>@@ -393,6 +397,9 @@ qemuHotplugDiskSourceDataFree(qemuHotplugDiskSourceDataPtr data)
>     if (!data)
>         return;
>
>+    virJSONValueFree(data->corProps);
>+    VIR_FREE(data->corAlias);
>+
>     for (i = 0; i < data->nbackends; i++)
>         qemuBlockStorageSourceAttachDataFree(data->backends[i]);
>
>@@ -461,25 +468,40 @@ qemuHotplugRemoveStorageSourcePrepareData(virStorageSourcePtr src,
>
> static qemuHotplugDiskSourceDataPtr
> qemuHotplugDiskSourceRemovePrepare(virDomainDiskDefPtr disk,
>-                                   virQEMUCapsPtr qemuCaps ATTRIBUTE_UNUSED)
>+                                   virQEMUCapsPtr qemuCaps)
> {
>+    qemuDomainDiskPrivatePtr diskPriv = QEMU_DOMAIN_DISK_PRIVATE(disk);
>     qemuBlockStorageSourceAttachDataPtr backend = NULL;
>     qemuHotplugDiskSourceDataPtr data = NULL;
>     qemuHotplugDiskSourceDataPtr ret = NULL;
>     char *drivealias = NULL;
>+    virStorageSourcePtr n;
>
>     if (VIR_ALLOC(data) < 0)
>         return NULL;
>
>-    if (!(drivealias = qemuAliasDiskDriveFromDisk(disk)))
>-        goto cleanup;
>+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_BLOCKDEV)) {
>+        if (VIR_STRDUP(data->corAlias, diskPriv->nodeCopyOnRead) < 0)
>+            goto cleanup;
>
>-    if (!(backend = qemuHotplugRemoveStorageSourcePrepareData(disk->src,
>-                                                              drivealias)))
>-        goto cleanup;
>+        for (n = disk->src; virStorageSourceIsBacking(n); n = n->backingStore) {
>+            if (!(backend = qemuHotplugRemoveStorageSourcePrepareData(n, NULL)))
>+                goto cleanup;
>
>-    if (VIR_APPEND_ELEMENT(data->backends, data->nbackends, backend) < 0)
>-        goto cleanup;
>+            if (VIR_APPEND_ELEMENT(data->backends, data->nbackends, backend) < 0)
>+                goto cleanup;
>+        }
>+    } else {
>+        if (!(drivealias = qemuAliasDiskDriveFromDisk(disk)))
>+            goto cleanup;
>+
>+        if (!(backend = qemuHotplugRemoveStorageSourcePrepareData(disk->src,
>+                                                                  drivealias)))
>+            goto cleanup;
>+
>+        if (VIR_APPEND_ELEMENT(data->backends, data->nbackends, backend) < 0)
>+            goto cleanup;
>+    }
>
>     VIR_STEAL_PTR(ret, data);
>
>@@ -505,18 +527,36 @@ qemuHotplugDiskSourceAttachPrepare(virDomainDiskDefPtr disk,
>     qemuBlockStorageSourceAttachDataPtr backend;
>     qemuHotplugDiskSourceDataPtr data;
>     qemuHotplugDiskSourceDataPtr ret = NULL;
>+    virStorageSourcePtr n;
>
>     if (VIR_ALLOC(data) < 0)
>         return NULL;
>
>-    if (!(backend = qemuBuildStorageSourceAttachPrepareDrive(disk, qemuCaps, false)))
>-        goto cleanup;
>+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_BLOCKDEV)) {
>+        if (disk->copy_on_read == VIR_TRISTATE_SWITCH_ON &&
>+            !(data->corProps = qemuBlockStorageGetCopyOnReadProps(disk)))
>+            goto cleanup;

 CC       qemu/libvirt_driver_qemu_impl_la-qemu_hotplug.lo
qemu/qemu_hotplug.c:536:13: error: variable 'backend' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (disk->copy_on_read == VIR_TRISTATE_SWITCH_ON &&
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
qemu/qemu_hotplug.c:564:42: note: uninitialized use occurs here
    qemuBlockStorageSourceAttachDataFree(backend);
                                         ^~~~~~~
qemu/qemu_hotplug.c:536:9: note: remove the 'if' if its condition is always false
        if (disk->copy_on_read == VIR_TRISTATE_SWITCH_ON &&
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
qemu/qemu_hotplug.c:527:48: note: initialize the variable 'backend' to silence this warning
    qemuBlockStorageSourceAttachDataPtr backend;
                                               ^
                                                = NULL

>
>-    if (qemuBuildStorageSourceAttachPrepareCommon(disk->src, backend, qemuCaps) < 0)
>-        goto cleanup;
>+        for (n = disk->src; virStorageSourceIsBacking(n); n = n->backingStore) {
>+            if (!(backend = qemuBlockStorageSourceAttachPrepareBlockdev(n)))
>+                goto cleanup;
>
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