vm: Simplify extend_volume()

Previously we accepted the current and maximum size of the volume, and
computed the next volume size, including one chunk of free space, and
ensuring that the size is limited by the volume capacity and qcow2
overhead.

This works for auto extending thin volume and for pre extend during
replication, but it does not work correctly for internal live merge,
when we don't want to add one chunk of free space. It also ugly that in
active layer merge we have to lie and call with the maximum required
size as the "current" size.

Change extend_volume() to accept the new size, moving the responsibility
to the caller. The 3 callers were update to compute the size using
drive.getNextVolumeSize().

Signed-off-by: Nir Soffer <nsoffer@redhat.com>

lib/vdsm/virt/livemerge.py

@@ -473,8 +473,9 @@ def _start_extend(self, drive, job):
             job_id=job.id,
             attempt=job.extend["attempt"])
 
-        self._vm.extend_volume(
-            drive, job.base, max_alloc, capacity, callback=callback)
+        # New size includes one chunk of free space.
+        new_size = drive.getNextVolumeSize(max_alloc, capacity)
+        self._vm.extend_volume(drive, job.base, new_size, callback=callback)
 
     def _retry_extend(self, job):
         """

lib/vdsm/virt/thinp.py

@@ -387,11 +387,11 @@ def _handle_exceeded(self, drive, urgent=False):
             "Requesting an extension for volume %s on domain %s block_info %s",
             drive.volumeID, drive.domainID, drive.block_info)
 
-        self.extend_volume(
-            drive,
-            drive.volumeID,
-            drive.block_info.physical,
-            drive.block_info.capacity)
+        # New size includes one chunk of free space.
+        new_size = drive.getNextVolumeSize(
+            drive.block_info.physical, drive.block_info.capacity)
+
+        self.extend_volume(drive, drive.volumeID, new_size)
 
     def _can_extend_drive(self, drive):
         # NOTE: Physical may be larger than maximum volume size since it is
@@ -521,10 +521,10 @@ def _amend_block_info(self, drive, block_info):
 
     # Extending volumes.
 
-    def extend_volume(self, vmDrive, volumeID, curSize, capacity,
-                      callback=None):
+    def extend_volume(self, vmDrive, volumeID, newSize, callback=None):
         """
-        Extend drive volume and its replica volume during replication.
+        Extend drive volume and its replica volume during replication to
+        newSize.
 
         Must be called only when the drive or its replica are chunked.
 
@@ -535,8 +535,6 @@ def extend_volume(self, vmDrive, volumeID, curSize, capacity,
             def callback(error=None):
 
         """
-        newSize = vmDrive.getNextVolumeSize(curSize, capacity)
-
         # If drive is replicated to a block device, we extend first the
         # replica, and handle drive later in _extend_replica_completed.
 

lib/vdsm/virt/vm.py

@@ -1305,10 +1305,13 @@ def query_block_stats(self):
         _, raw_stats = res[0]
         return raw_stats
 
-    def extend_volume(self, vmDrive, volumeID, curSize, capacity,
-                      callback=None):
+    def extend_volume(self, vmDrive, volumeID, new_size, callback=None):
         """
-        Extend drive volume and its replica volume during replication.
+        Extend drive volume and its replica volume during replication to
+        new_size.
+
+        The new size of the volume may be bigger than the requested value
+        because the actual volume size is always aligned to lvm extent size.
 
         Must be called only when the drive or its replica are chunked.
 
@@ -1322,7 +1325,7 @@ def callback(error=None):
         called.
         """
         self.volume_monitor.extend_volume(
-            vmDrive, volumeID, curSize, capacity, callback=callback)
+            vmDrive, volumeID, new_size, callback=callback)
 
     def should_refresh_destination_volume(self):
         """
@@ -4373,11 +4376,9 @@ def diskReplicateStart(self, srcDisk, dstDisk, need_extend=True):
             try:
                 block_info = self.volume_monitor.query_block_info(
                     drive, drive.volumeID)
-                self.extend_volume(
-                    drive,
-                    drive.volumeID,
-                    block_info.physical,
-                    block_info.capacity)
+                new_size = drive.getNextVolumeSize(
+                    block_info.physical, block_info.capacity)
+                self.extend_volume(drive, drive.volumeID, new_size)
             except Exception:
                 self.log.exception("Initial extension request failed for %s",
                                    drive.name)