Hi Everyone,
I'm looking at implementing some functionality in libvirt that would
allow it to call functions in an unpublished iSCSI library. Some of the
functionality I wish to implement is not currently part of the libvirt
storage API. I wanted to suggest the following additions to the storage
API: grow volumes, show whether thin provisioning is enabled, enable
thin provisioning, disable thin provisioning, create snapshots, and
delete snapshots. I've added a patch at the end of the mail showing how
I think these functions should be implemented. Note that I have not
included details about the virStorageSnapshotDefPtr yet, that's the next
step.
Perhaps this should be in a separate mail for better threading, but it
seems a bit strange to me that the storage interface isn't pluggable in
the traditional sense. In order to add a backend to libvirt, one has to
make modifications all over the place, for example: virt-inst, the
Makefile.am, the configure.ac, storage_backend.h, and several other
places. It would make sense to me to make this pluggable such that
someone could just load in a library that implements the required
functions and some identifying information (eg type of storage,
description, etc). A list of supported backends could be stored in
empty files in a directory somewhere, or some similar hack. This way
someone could write a plugin for tgtd for example, or in my case the
library I'm working with. I think this would also help others with
writing plugins for more storage backends. How difficult do you think
this would be? I'm willing to do a reasonable amount of work to get
this implemented, but I want to know what the experts think!
Best,
Patrick Dignan
--- libvirt-0.8.2.orig/src/storage/storage_backend.h 2010-06-16
17:27:22.000000000 -0500
+++ libvirt-0.8.2.work/src/storage/storage_backend.h 2010-07-27
16:36:08.321439851 -0500
@@ -43,6 +43,13 @@
typedef int (*virStorageBackendBuildVolFrom)(virConnectPtr conn,
virStoragePoolObjPtr pool,
virStorageVolDefPtr
origvol, virStorageVolDefPtr newvol,
unsigned int flags);
+typedef int (*virStorageBackendGrowVol)(virConnectPtr conn,
virStoragePoolObjPtr pool, virStorageVolDefPtr vol, unsigned long long
newsize);
+typedef bool (*virStorageBackendThinProvisionShow)(virConnectPtr conn,
virStoragePoolObjPtr pool, virStorageVolDefPtr vol);
+typedef int (*virStorageBackendThinProvisionEnable)(virConnectPtr conn,
virStoragePoolObjPtr pool, virStorageVolDefPtr vol);
+typedef int (*virStorageBackendThinProvisionDisable)(virConnectPtr
conn, virStoragePoolObjPtr pool, virStorageVolDefPtr vol);
+
+typedef int (virStorageBackendCreateSnapshot)(virConnectPtr conn,
virStoragePoolObjPtr pool, virStorageVolDefPtr vol,
virStorageSnapshotDefPtr snapshot);
+typedef int (virStorageBackendDeleteSnapshot)(virConnectPtr conn,
virStoragePoolObjPtr pool, virStorageVolDefPtr vol,
virStorageSnapshotDefPtr snapshot);
/* File creation/cloning functions used for cloning between backends */
int virStorageBackendCreateRaw(virConnectPtr conn,
@@ -76,6 +83,12 @@
virStorageBackendCreateVol createVol;
virStorageBackendRefreshVol refreshVol;
virStorageBackendDeleteVol deleteVol;
+ virStorageBackendGrowVol growVol;
+ virStorageBackendThinProvisionShow thinProvisionShow;
+ virStorageBackendThinProvisionEnable thinProvisionEnable;
+ virStorageBackendThinProvisionDisable thinProvisionDisable;
+ virStorageBackendCreateSnapshot createSnapshot;
+ virStorageBackendDeleteSnapshot deleteSnapshot;
};
virStorageBackendPtr virStorageBackendForType(int type);
--
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