qemu: Add support for slices of type 'storage'

Implement support for the slice of type 'storage' which allows to set
the offset and size which modifies where qemu should look for the start
of the format container inside the image.

Since slicing is done using the 'raw' driver we need to add another
layer into the blockdev tree if there's any non-raw image format driver
used to access the data.

This patch adds the blockdev integration and setup of the image data so
that we can use the slices for any backing image.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_block.c

@@ -1423,11 +1423,16 @@ qemuBlockStorageSourceGetBlockdevProps(virStorageSourcePtr src,
                                        virStorageSourcePtr backingStore)
 {
     g_autoptr(virJSONValue) props = NULL;
+    const char *storagenode = src->nodestorage;
+
+    if (src->sliceStorage &&
+        src->format != VIR_STORAGE_FILE_RAW)
+        storagenode = src->sliceStorage->nodename;
 
     if (!(props = qemuBlockStorageSourceGetBlockdevFormatProps(src)))
         return NULL;
 
-    if (virJSONValueObjectAppendString(props, "file", src->nodestorage) < 0)
+    if (virJSONValueObjectAppendString(props, "file", storagenode) < 0)
         return NULL;
 
     if (backingStore) {
@@ -1456,6 +1461,32 @@ qemuBlockStorageSourceGetBlockdevProps(virStorageSourcePtr src,
 }
 
 
+static virJSONValuePtr
+qemuBlockStorageSourceGetBlockdevStorageSliceProps(virStorageSourcePtr src)
+{
+    g_autoptr(virJSONValue) props = NULL;
+
+    if (qemuBlockNodeNameValidate(src->sliceStorage->nodename) < 0)
+        return NULL;
+
+    if (virJSONValueObjectCreate(&props,
+                                 "s:driver", "raw",
+                                 "s:node-name", src->sliceStorage->nodename,
+                                 "U:offset", src->sliceStorage->offset,
+                                 "U:size", src->sliceStorage->size,
+                                 "s:file", src->nodestorage,
+                                 "b:auto-read-only", true,
+                                 "s:discard", "unmap",
+                                 NULL) < 0)
+        return NULL;
+
+    if (qemuBlockStorageSourceGetBlockdevGetCacheProps(src, props) < 0)
+        return NULL;
+
+    return g_steal_pointer(&props);
+}
+
+
 void
 qemuBlockStorageSourceAttachDataFree(qemuBlockStorageSourceAttachDataPtr data)
 {
@@ -1463,6 +1494,7 @@ qemuBlockStorageSourceAttachDataFree(qemuBlockStorageSourceAttachDataPtr data)
         return;
 
     virJSONValueFree(data->storageProps);
+    virJSONValueFree(data->storageSliceProps);
     virJSONValueFree(data->formatProps);
     virJSONValueFree(data->prmgrProps);
     virJSONValueFree(data->authsecretProps);
@@ -1513,6 +1545,13 @@ qemuBlockStorageSourceAttachPrepareBlockdev(virStorageSourcePtr src,
     data->storageNodeName = src->nodestorage;
     data->formatNodeName = src->nodeformat;
 
+    if (src->sliceStorage && src->format != VIR_STORAGE_FILE_RAW) {
+        if (!(data->storageSliceProps = qemuBlockStorageSourceGetBlockdevStorageSliceProps(src)))
+            return NULL;
+
+        data->storageSliceNodeName = src->sliceStorage->nodename;
+    }
+
     return g_steal_pointer(&data);
 }
 
@@ -1581,6 +1620,21 @@ qemuBlockStorageSourceAttachApplyFormat(qemuMonitorPtr mon,
 }
 
 
+static int
+qemuBlockStorageSourceAttachApplyStorageSlice(qemuMonitorPtr mon,
+                                              qemuBlockStorageSourceAttachDataPtr data)
+{
+    if (data->storageSliceProps) {
+        if (qemuMonitorBlockdevAdd(mon, &data->storageSliceProps) < 0)
+            return -1;
+
+        data->storageSliceAttached = true;
+    }
+
+    return 0;
+}
+
+
 /**
  * qemuBlockStorageSourceAttachApply:
  * @mon: monitor object
@@ -1600,6 +1654,7 @@ qemuBlockStorageSourceAttachApply(qemuMonitorPtr mon,
 {
     if (qemuBlockStorageSourceAttachApplyStorageDeps(mon, data) < 0 ||
         qemuBlockStorageSourceAttachApplyStorage(mon, data) < 0 ||
+        qemuBlockStorageSourceAttachApplyStorageSlice(mon, data) < 0 ||
         qemuBlockStorageSourceAttachApplyFormatDeps(mon, data) < 0 ||
         qemuBlockStorageSourceAttachApplyFormat(mon, data) < 0)
         return -1;
@@ -1642,6 +1697,9 @@ qemuBlockStorageSourceAttachRollback(qemuMonitorPtr mon,
     if (data->formatAttached)
         ignore_value(qemuMonitorBlockdevDel(mon, data->formatNodeName));
 
+    if (data->storageSliceAttached)
+        ignore_value(qemuMonitorBlockdevDel(mon, data->storageSliceNodeName));
+
     if (data->storageAttached)
         ignore_value(qemuMonitorBlockdevDel(mon, data->storageNodeName));
 
@@ -1689,6 +1747,14 @@ qemuBlockStorageSourceDetachPrepare(virStorageSourcePtr src,
         data->formatAttached = true;
         data->storageNodeName = src->nodestorage;
         data->storageAttached = true;
+
+        /* 'raw' format doesn't need the extra 'raw' layer when slicing, thus
+         * the nodename is NULL */
+        if (src->sliceStorage &&
+            src->sliceStorage->nodename) {
+            data->storageSliceNodeName = src->sliceStorage->nodename;
+            data->storageSliceAttached = true;
+        }
     }
 
     if (src->pr &&

src/qemu/qemu_block.h

@@ -82,6 +82,10 @@ struct qemuBlockStorageSourceAttachData {
     const char *storageNodeName;
     bool storageAttached;
 
+    virJSONValuePtr storageSliceProps;
+    const char *storageSliceNodeName;
+    bool storageSliceAttached;
+
     virJSONValuePtr formatProps;
     const char *formatNodeName;
     bool formatAttached;

src/qemu/qemu_blockjob.c

@@ -1316,6 +1316,7 @@ qemuBlockJobProcessEventConcludedCreate(virQEMUDriverPtr driver,
     backend->formatAttached = false;
     if (job->data.create.storage) {
         backend->storageAttached = false;
+        backend->storageSliceAttached = false;
         VIR_FREE(backend->encryptsecretAlias);
     }
 

src/qemu/qemu_command.c

@@ -2411,6 +2411,14 @@ qemuBuildBlockStorageSourceAttachDataCommandline(virCommandPtr cmd,
         VIR_FREE(tmp);
     }
 
+    if (data->storageSliceProps) {
+        if (!(tmp = virJSONValueToString(data->storageSliceProps, false)))
+            return -1;
+
+        virCommandAddArgList(cmd, "-blockdev", tmp, NULL);
+        VIR_FREE(tmp);
+    }
+
     if (data->formatProps) {
         if (!(tmp = virJSONValueToString(data->formatProps, false)))
             return -1;

src/qemu/qemu_domain.c

@@ -16264,6 +16264,10 @@ qemuDomainPrepareStorageSourceBlockdev(virDomainDiskDefPtr disk,
     src->nodestorage = g_strdup_printf("libvirt-%u-storage", src->id);
     src->nodeformat = g_strdup_printf("libvirt-%u-format", src->id);
 
+    if (src->sliceStorage &&
+        src->format != VIR_STORAGE_FILE_RAW)
+        src->sliceStorage->nodename = g_strdup_printf("libvirt-%u-slice-sto", src->id);
+
     if (qemuDomainValidateStorageSource(src, priv->qemuCaps) < 0)
         return -1;