zfs-vol: implement volume-create 2/2: Volume.create

We create sparse volumes, making the SR a thin-provisioning one.

Cache as vsize the actual size created by the zfs command (which in
zfs-2.1 unlike in zfs-0.8 does round up requested size to be acceptable).

Note that if Volume.set were not implemented yet (or indeed cannot
complete and returns an error), we face xapi-project/xen-api#5530: if
the Volume.set call fails (to add the vdi-type=user custom-key
record), then the VDI object is not created (though, as this happens
after Volume.create, the zvol and DB entries were indeed created and
there suppression was not requested by SMAPI after the error).  But
since all the VDI information that count are here, "xe sr-scan" will
bring those VDI to life (after implementation of SR.ls).

Originally-by: Matias Ezequiel Vara Larsen <matias.vara@vates.fr>
Signed-off-by: Yann Dirson <yann.dirson@vates.tech>

plugins/volume/org.xen.xapi.storage.zfs-vol/plugin.py

@@ -20,6 +20,7 @@ def query(self, dbg):
             "version": "3.0",
             "required_api_version": "5.0",
             "features": [
+                "VDI_CREATE",
             ],
             "configuration": {},
             "required_cluster_stack": []}

plugins/volume/org.xen.xapi.storage.zfs-vol/volume.py

@@ -15,18 +15,61 @@
 from xapi.storage.libs.libcow.volume_implementation import Implementation as \
     DefaultImplementation
 
+import zfsutils
+
 @util.decorate_all_routines(util.log_exceptions_in_function)
 class Implementation(DefaultImplementation):
     "Volume driver to provide raw volumes from zvol's"
 
+    def create(self, dbg, sr, name, description, size, sharable):
+        meta = util.get_sr_metadata(dbg, 'file://' + sr)
+        pool_name = meta["zpool"]
+
+        with VolumeContext(self.callbacks, sr, 'w') as opq:
+            image_type = ImageFormat.IMAGE_RAW
+            image_format = ImageFormat.get_format(image_type)
+            vdi_uuid = str(uuid.uuid4())
+
+            with PollLock(opq, 'gl', self.callbacks, 0.5):
+                with self.callbacks.db_context(opq) as db:
+                    volume = db.insert_new_volume(size, image_type)
+                    db.insert_vdi(
+                        name, description, vdi_uuid, volume.id, sharable)
+                    path = zfsutils.zvol_path(pool_name, volume.id)
+                    zfsutils.vol_create(dbg, path, size)
+
+                    vol_name = zfsutils.zvol_path(pool_name, volume.id)
+                    volume.vsize = zfsutils.vol_get_size(dbg, vol_name)
+                    if volume.vsize != size:
+                        log.debug("%s: VDI.create adjusted requested size %s to %s",
+                                  dbg, size, volume.vsize)
+                    db.update_volume_vsize(volume.id, volume.vsize)
+
+            vdi_uri = self.callbacks.getVolumeUriPrefix(opq) + vdi_uuid
+
+        return {
+            'key': vdi_uuid,    # FIXME check this
+            'uuid': vdi_uuid,
+            'name': name,
+            'description': description,
+            'read_write': True,
+            'virtual_size': volume.vsize,
+            'physical_utilisation': volume.vsize, # FIXME - incidently psize gets null in the db
+            'uri': [image_format.uri_prefix + vdi_uri],
+            'sharable': False,
+            'keys': {}
+        }
+
 def call_volume_command():
     """Parse the arguments and call the required command"""
     log.log_call_argv()
     fsp = importlib.import_module("zfs-vol")
     cmd = xapi.storage.api.v5.volume.Volume_commandline(
         Implementation(fsp.Callbacks()))
     base = os.path.basename(sys.argv[0])
-    if base == "Volume.set":
+    if base == "Volume.create":
+        cmd.create()
+    elif base == "Volume.set":
         cmd.set()
     elif base == "Volume.unset":
         cmd.unset()

plugins/volume/org.xen.xapi.storage.zfs-vol/zfs-vol.py

@@ -3,3 +3,6 @@
 
 class Callbacks(xapi.storage.libs.libcow.callbacks.Callbacks):
     "ZFS-vol callbacks"
+
+    def getVolumeUriPrefix(self, opq):
+        return "zfs-vol/" + opq + "|"

plugins/volume/org.xen.xapi.storage.zfs-vol/zfsutils.py

@@ -4,6 +4,11 @@
 
 MOUNT_ROOT = '/var/run/sr-mount'
 
+def zvol_path(pool_name, vol_id):
+    return "{}/{}".format(pool_name, vol_id)
+
+###
+
 def pool_mountpoint(dbg, pool_name):
     cmd = "zfs get mountpoint -H -o value".split() + [ pool_name ]
     return call(dbg, cmd).strip()
@@ -37,3 +42,9 @@ def pool_get_free_space(dbg, sr_path):
     # size is returned in bytes
     cmd = "zpool get -Hp -o value free".split() + [ sr_path ]
     return int(call(dbg, cmd))
+
+def vol_create(dbg, zvol_path, size_mib):
+    cmd = ("zfs create -s".split() + [zvol_path]
+           + ['-V', str(size_mib)]
+           )
+    call(dbg, cmd)