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Re: [libvirt] [PATCH 04/20] snapshot: merge pre-snapshot checks



On 2012年10月23日 23:12, Peter Krempa wrote:
From: Eric Blake<eblake redhat com>

Both system checkpoint snapshots and disk snapshots were iterating
over all disks, doing a final sanity check before doing any work.
But since future patches will allow offline snapshots to be either
external or internal, it makes sense to share the pass over all
disks, and then relax restrictions in that pass as new modes are
implemented.  Future patches can then handle external disks when
the domain is offline, then handle offline --disk-snapshot, and
finally, combine with migration to file to gain a complete external
system checkpoint snapshot of an active domain without using 'savevm'.

* src/qemu/qemu_driver.c (qemuDomainSnapshotDiskPrepare)
(qemuDomainSnapshotIsAllowed): Merge...
(qemuDomainSnapshotPrepare): ...into one function.
(qemuDomainSnapshotCreateXML): Update caller.
---
  src/qemu/qemu_driver.c | 92 +++++++++++++++++++-------------------------------
  1 file changed, 34 insertions(+), 58 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index cbabd62..df02783 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -10516,34 +10516,6 @@ cleanup:
  }


-static bool
-qemuDomainSnapshotIsAllowed(virDomainObjPtr vm)
-{
-    int i;
-
-    /* FIXME: we need to figure out what else here might succeed; in
-     * particular, if it's a raw device but on LVM, we could probably make
-     * that succeed as well
-     */
-    for (i = 0; i<  vm->def->ndisks; i++) {
-        virDomainDiskDefPtr disk = vm->def->disks[i];
-        if (disk->type == VIR_DOMAIN_DISK_TYPE_NETWORK&&
-            (disk->protocol == VIR_DOMAIN_DISK_PROTOCOL_SHEEPDOG ||
-             disk->protocol == VIR_DOMAIN_DISK_PROTOCOL_RBD))
-            continue;
-
-        if ((disk->device == VIR_DOMAIN_DISK_DEVICE_LUN) ||
-            (disk->device == VIR_DOMAIN_DISK_DEVICE_DISK&&
-             disk->format>  0&&  disk->format != VIR_STORAGE_FILE_QCOW2)) {
-            virReportError(VIR_ERR_OPERATION_INVALID,
-                           _("Disk '%s' does not support snapshotting"),
-                           disk->src);
-            return false;
-        }
-    }
-
-    return true;
-}

  /* this function expects the driver lock to be held by the caller */
  static int
@@ -10697,8 +10669,8 @@ endjob:
  }

  static int
-qemuDomainSnapshotDiskPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,
-                              unsigned int *flags)
+qemuDomainSnapshotPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,
+                          unsigned int *flags)
  {
      int ret = -1;
      int i;
@@ -10710,7 +10682,8 @@ qemuDomainSnapshotDiskPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,
      int external = 0;
      qemuDomainObjPrivatePtr priv = vm->privateData;

-    if (reuse&&  !qemuCapsGet(priv->caps, QEMU_CAPS_TRANSACTION)) {
+    if (def->state == VIR_DOMAIN_DISK_SNAPSHOT&&
+        reuse&&  !qemuCapsGet(priv->caps, QEMU_CAPS_TRANSACTION)) {
          virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                         _("reuse is not supported with this QEMU binary"));
          goto cleanup;
@@ -10718,15 +10691,16 @@ qemuDomainSnapshotDiskPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,

      for (i = 0; i<  def->ndisks; i++) {
          virDomainSnapshotDiskDefPtr disk =&def->disks[i];
+        virDomainDiskDefPtr dom_disk = vm->def->disks[i];

          switch (disk->snapshot) {
          case VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL:
-            if (active) {
-                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                               _("active qemu domains require external disk "
-                                 "snapshots; disk %s requested internal"),
-                               disk->name);
-                goto cleanup;
+            if (def->state != VIR_DOMAIN_DISK_SNAPSHOT&&
+                dom_disk->type == VIR_DOMAIN_DISK_TYPE_NETWORK&&
+                (dom_disk->protocol == VIR_DOMAIN_DISK_PROTOCOL_SHEEPDOG ||
+                 dom_disk->protocol == VIR_DOMAIN_DISK_PROTOCOL_RBD)) {
+                found = true;
+                break;
              }
              if (vm->def->disks[i]->format>  0&&
                  vm->def->disks[i]->format != VIR_STORAGE_FILE_QCOW2) {
@@ -10738,10 +10712,25 @@ qemuDomainSnapshotDiskPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,
                                     vm->def->disks[i]->format));
                  goto cleanup;
              }
+            if (def->state == VIR_DOMAIN_DISK_SNAPSHOT&&  active) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("active qemu domains require external disk "
+                                 "snapshots; disk %s requested internal"),
+                               disk->name);
+                goto cleanup;
+            }
              found = true;
              break;

          case VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL:
+            if (def->state != VIR_DOMAIN_DISK_SNAPSHOT) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("system checkpoint external snapshot for "
+                                 "disk %s not implemented yet"),
+                               disk->name);
+                goto cleanup;
+            }
+
              if (!disk->format) {
                  disk->format = VIR_STORAGE_FILE_QCOW2;
              } else if (disk->format != VIR_STORAGE_FILE_QCOW2&&
@@ -10789,11 +10778,11 @@ qemuDomainSnapshotDiskPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,

      if (!found) {
          virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                       _("disk snapshots require at least one disk to be "
+                       _("snapshots require at least one disk to be "
                           "selected for snapshot"));
          goto cleanup;
      }
-    if (active) {
+    if (def->state != VIR_DOMAIN_DISK_SNAPSHOT&&  active) {
          if (external == 1 ||
              qemuCapsGet(priv->caps, QEMU_CAPS_TRANSACTION)) {
              *flags |= VIR_DOMAIN_SNAPSHOT_CREATE_ATOMIC;
@@ -11004,7 +10993,7 @@ qemuDomainSnapshotCreateDiskActive(virConnectPtr conn,
      /* For multiple disks, libvirt must pause externally to get all
       * snapshots to be at the same point in time, unless qemu supports
       * transactions.  For a single disk, snapshot is atomic without
-     * requiring a pause.  Thanks to qemuDomainSnapshotDiskPrepare, if
+     * requiring a pause.  Thanks to qemuDomainSnapshotPrepare, if
       * we got to this point, the atomic flag now says whether we need
       * to pause, and a capability bit says whether to use transaction.
       */
@@ -11030,7 +11019,7 @@ qemuDomainSnapshotCreateDiskActive(virConnectPtr conn,

      /* No way to roll back if first disk succeeds but later disks
       * fail, unless we have transaction support.
-     * Based on earlier qemuDomainSnapshotDiskPrepare, all
+     * Based on earlier qemuDomainSnapshotPrepare, all
       * disks in this list are now either SNAPSHOT_NO, or
       * SNAPSHOT_EXTERNAL with a valid file name and qcow2 format.  */
      qemuDomainObjEnterMonitorWithDriver(driver, vm);
@@ -11334,31 +11323,18 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
              }
              align_location = VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL;
              align_match = false;
-            if (virDomainSnapshotAlignDisks(def, align_location,
-                                            align_match)<  0 ||
-                qemuDomainSnapshotDiskPrepare(vm, def,&flags)<  0)
-                goto cleanup;
              def->state = VIR_DOMAIN_DISK_SNAPSHOT;
              def->memory = VIR_DOMAIN_SNAPSHOT_LOCATION_NONE;
          } else {
-            /* In a perfect world, we would allow qemu to tell us this.
-             * The problem is that qemu only does this check
-             * device-by-device; so if you had a domain that booted from a
-             * large qcow2 device, but had a secondary raw device
-             * attached, you wouldn't find out that you can't snapshot
-             * your guest until *after* it had spent the time to snapshot
-             * the boot device.  This is probably a bug in qemu, but we'll
-             * work around it here for now.
-             */
-            if (!qemuDomainSnapshotIsAllowed(vm) ||
-                virDomainSnapshotAlignDisks(def, align_location,
-                                            align_match)<  0)
-                goto cleanup;
              def->state = virDomainObjGetState(vm, NULL);
              def->memory = (def->state == VIR_DOMAIN_SHUTOFF ?
                             VIR_DOMAIN_SNAPSHOT_LOCATION_NONE :
                             VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL);
          }
+        if (virDomainSnapshotAlignDisks(def, align_location,
+                                        align_match)<  0 ||
+            qemuDomainSnapshotPrepare(vm, def,&flags)<  0)
+            goto cleanup;
      }

      if (snap)

ACK


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