zfs-ng: implement sr-create 1/4: SR.create

SR can then be disposed of using "xe sr-forget" and "zpool destroy".

Underlying zpool can be either separately created and given to
SR.create, or a set of devices can be specified to create a new zpool
on.

Notes:
- `SR.attach` will be necessary to complete `sr-create`: while from a
  calling user PoV things appear to have gone fine, SMlog reveals a
  call to `SR.attach`, which naturally failed as not yet implemented.
  Any attempt to `xe pbd-plug` naturally also fails.  See
  xapi-project/xen-api#5532.
- there is no plugin feature to shield from SR.* calls

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-ng/sr.py

@@ -12,13 +12,67 @@
 from xapi.storage.libs.libcow.volume import COWVolume
 import xapi.storage.api.v5.volume
 
+import zfsutils
+
 
 @util.decorate_all_routines(util.log_exceptions_in_function)
 class Implementation(xapi.storage.api.v5.volume.SR_skeleton):
     "SR driver to provide volumes from zvol's"
 
+    def create(self, dbg, sr_uuid, configuration, name, description):
+        log.debug('{}: SR.create: config={}, sr_uuid={}'.format(
+            dbg, configuration, sr_uuid))
+
+        # 2 ways to create a SR:
+        # - from an existing zpool (manually created for complex configs)
+        # - from a "devices" config string (comma-separated list of devices)
+
+        if 'zpool' in configuration:
+            if 'devices' in configuration:
+                log.error('"zpool" specified, "devices" should not be used')
+                raise Exception('"zpool" specified, "devices" should not be used')
+
+            # FIXME do we reject pools not under MOUNT_ROOT?
+
+            # FIXME validate existence of pool first?
+            pool_name = configuration['zpool']
+
+        elif 'devices' in configuration:
+            devs = configuration['devices'].split(',')
+
+            pool_name = "sr-{}".format(sr_uuid)
+            zfsutils.pool_create(dbg, pool_name, devs)
+
+            # "devices" is only used once to create the zpool, which
+            # then becomes the sole way to designate the SR
+            configuration["orig-devices"] = configuration['devices']
+            del configuration['devices']
+            configuration["zpool"] = pool_name
+
+        else:
+            log.error('devices config must have "zpool" or "devices"')
+            raise Exception('devices config must have "zpool" or "devices"')
+
+        # FIXME this assumes zpool is mounted/attached
+        mountpoint = zfsutils.pool_mountpoint(dbg, pool_name)
+        importlib.import_module('zfs-ng').Callbacks().create_database(mountpoint)
+
+        meta = {
+            'name': name,
+            'description': description,
+            'uuid': sr_uuid,
+        }
+        util.update_sr_metadata(dbg, 'file://' + mountpoint, meta)
+
+        log.debug('{}: SR.create: sr={}'.format(dbg, mountpoint))
+        return configuration
+
+
 if __name__ == '__main__':
     log.log_call_argv()
     cmd = xapi.storage.api.v5.volume.SR_commandline(Implementation())
     base = os.path.basename(sys.argv[0])
-    raise xapi.storage.api.v5.volume.Unimplemented(base)
+    if base == 'SR.create':
+        cmd.create()
+    else:
+        raise xapi.storage.api.v5.volume.Unimplemented(base)

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

@@ -0,0 +1,15 @@
+import os
+
+from xapi.storage.common import call
+
+MOUNT_ROOT = '/var/run/sr-mount'
+
+def pool_mountpoint(dbg, pool_name):
+    cmd = "zfs get mountpoint -H -o value".split() + [ pool_name ]
+    return call(dbg, cmd).strip()
+
+def pool_create(dbg, pool_name, devs):
+    cmd = ("zpool create".split() + [pool_name] # FIXME '-f' ?
+           + ['-R', MOUNT_ROOT]
+           + devs)
+    call(dbg, cmd)