[libvirt] [PATCH 3/3] qemuMigrationPrecreateDisk: Preserve sparse files

[Michal Privoznik]

https://bugzilla.redhat.com/show_bug.cgi?id=817700

When pre-creating a disk on the destination, a volume XML is
constructed. The XML is then passed to virStorageVolCreateXML() which
does the work. But, since there's no <allocation/> in the XML, the
disk are fully allocated. This possibly breaks sparse allocation user
has on the migration source.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_migration.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 3adb949..a2f68ed 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -144,6 +144,7 @@ typedef qemuMigrationCookieNBDDisk *qemuMigrationCookieNBDDiskPtr;
 struct _qemuMigrationCookieNBDDisk {
     char *target;                   /* Disk target */
     unsigned long long capacity;    /* And its capacity */
+    unsigned long long allocation;  /* And its allocation */
 };
 
 typedef struct _qemuMigrationCookieNBD qemuMigrationCookieNBD;
@@ -591,6 +592,7 @@ qemuMigrationCookieAddNBD(qemuMigrationCookiePtr mig,
                        disk->dst) < 0)
             goto cleanup;
         mig->nbd->disks[mig->nbd->ndisks].capacity = entry->capacity;
+        mig->nbd->disks[mig->nbd->ndisks].allocation = entry->wr_highest_offset;
         mig->nbd->ndisks++;
     }
 
@@ -831,8 +833,9 @@ qemuMigrationCookieXMLFormat(virQEMUDriverPtr driver,
             for (i = 0; i < mig->nbd->ndisks; i++) {
                 virBufferEscapeString(buf, "<disk target='%s'",
                                       mig->nbd->disks[i].target);
-                virBufferAsprintf(buf, " capacity='%llu'/>\n",
-                                  mig->nbd->disks[i].capacity);
+                virBufferAsprintf(buf, " capacity='%llu' allocation='%llu'/>\n",
+                                  mig->nbd->disks[i].capacity,
+                                  mig->nbd->disks[i].allocation);
             }
             virBufferAdjustIndent(buf, -2);
             virBufferAddLit(buf, "</nbd>\n");
@@ -970,7 +973,7 @@ static qemuMigrationCookieNBDPtr
 qemuMigrationCookieNBDXMLParse(xmlXPathContextPtr ctxt)
 {
     qemuMigrationCookieNBDPtr ret = NULL;
-    char *port = NULL, *capacity = NULL;
+    char *port = NULL, *capacity = NULL, *allocation = NULL;
     size_t i;
     int n;
     xmlNodePtr *disks = NULL;
@@ -998,6 +1001,7 @@ qemuMigrationCookieNBDXMLParse(xmlXPathContextPtr ctxt)
         for (i = 0; i < n; i++) {
             ctxt->node = disks[i];
             VIR_FREE(capacity);
+            VIR_FREE(allocation);
 
             if (!(ret->disks[i].target = virXPathString("string(./@target)", ctxt))) {
                 virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
@@ -1014,12 +1018,26 @@ qemuMigrationCookieNBDXMLParse(xmlXPathContextPtr ctxt)
                                NULLSTR(capacity));
                 goto error;
             }
+
+            allocation = virXPathString("string(./@allocation)", ctxt);
+            if (allocation) {
+                if (virStrToLong_ull(allocation, NULL, 10,
+                                     &ret->disks[i].allocation) < 0) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("Malformed disk allocation: '%s'"),
+                                   allocation);
+                    goto error;
+                }
+            } else {
+                ret->disks[i].allocation = -1;
+            }
         }
     }
 
  cleanup:
     VIR_FREE(port);
     VIR_FREE(capacity);
+    VIR_FREE(allocation);
     VIR_FREE(disks);
     ctxt->node = save_ctxt;
     return ret;
@@ -1539,6 +1557,8 @@ qemuMigrationPrecreateDisk(virConnectPtr conn,
     virBufferAdjustIndent(&buf, 2);
     virBufferEscapeString(&buf, "<name>%s</name>\n", volName);
     virBufferAsprintf(&buf, "<capacity>%llu</capacity>\n", nbd->capacity);
+    if (nbd->allocation != -1)
+        virBufferAsprintf(&buf, "<allocation>%llu</allocation>\n", nbd->allocation);
     virBufferAddLit(&buf, "<target>\n");
     virBufferAdjustIndent(&buf, 2);
     virBufferAsprintf(&buf, "<format type='%s'/>\n", format);
@@ -1583,8 +1603,9 @@ qemuMigrationPrecreateStorage(virConnectPtr conn,
         int indx;
         const char *diskSrcPath;
 
-        VIR_DEBUG("Looking up disk target '%s' (capacity=%llu)",
-                  nbd->disks[i].target, nbd->disks[i].capacity);
+        VIR_DEBUG("Looking up disk target '%s' (capacity=%llu allocation=%llu)",
+                  nbd->disks[i].target, nbd->disks[i].capacity,
+                  nbd->disks[i].allocation);
 
         if ((indx = virDomainDiskIndexByName(vm->def,
                                              nbd->disks[i].target, false)) < 0) {
-- 
2.0.5