storage: Fix regression cloning volume into a logical pool

https://bugzilla.redhat.com/show_bug.cgi?id=1318993

Commit id 'dd519a294' caused a regression cloning a volume into a
logical pool by removing just the 'allocation' adjustment during
storageVolCreateXMLFrom. Combined with the change to not require the
new volume input XML to have a capacity listed (commit id 'e3f1d2a8')
left the possibility that a zero allocation value (e.g., not provided)
would create a thin/sparse logical volume. When a thin lv becomes fully
populated, then LVM sets the partition 'inactive' and the subsequent
fdatasync() fails.

Add a new 'has_allocation' flag to be set at XML parse time to indicate
that allocation was provided. This is done so that if it's not provided
the create-from code uses the capacity value since we document that if
omitted, the volume will be fully allocated at time of creation.

For a logical backend, that creation time is 'createVol', while for a
file backend, creation doesn't set the size, but the 'createRaw' called
during buildVolFrom will decide whether the file is sparse or not based
on the provided capacity and allocation value.

For volume clones that provide different allocation and capacity values
to allow for sparse files, there is no change.

src/conf/storage_conf.c

@@ -1370,6 +1370,7 @@ virStorageVolDefParseXML(virStoragePoolDefPtr pool,
         unit = virXPathString("string(./allocation/@unit)", ctxt);
         if (virStorageSize(unit, allocation, &ret->target.allocation) < 0)
             goto error;
+        ret->target.has_allocation = true;
     } else {
         ret->target.allocation = ret->target.capacity;
     }

src/storage/storage_driver.c

@@ -2039,6 +2039,13 @@ storageVolCreateXMLFrom(virStoragePoolPtr obj,
     if (newvol->target.capacity < origvol->target.capacity)
         newvol->target.capacity = origvol->target.capacity;
 
+    /* If the allocation was not provided in the XML, then use capacity
+     * as it's specifically documented "If omitted when creating a volume,
+     * the  volume will be fully allocated at time of creation.". This
+     * is especially important for logical volume creation. */
+    if (!newvol->target.has_allocation)
+        newvol->target.allocation = newvol->target.capacity;
+
     if (!backend->buildVolFrom) {
         virReportError(VIR_ERR_NO_SUPPORT,
                        "%s", _("storage pool does not support"

src/util/virstoragefile.c

@@ -1835,6 +1835,7 @@ virStorageSourceCopy(const virStorageSource *src,
     ret->format = src->format;
     ret->capacity = src->capacity;
     ret->allocation = src->allocation;
+    ret->has_allocation = src->has_allocation;
     ret->physical = src->physical;
     ret->readonly = src->readonly;
     ret->shared = src->shared;

src/util/virstoragefile.h

@@ -260,6 +260,8 @@ struct _virStorageSource {
     unsigned long long capacity; /* in bytes, 0 if unknown */
     unsigned long long allocation; /* in bytes, 0 if unknown */
     unsigned long long physical; /* in bytes, 0 if unknown */
+    bool has_allocation; /* Set to true when provided in XML */
+
     size_t nseclabels;
     virSecurityDeviceLabelDefPtr *seclabels;