[libvirt] [PATCH] storage pool discovery

Hi - The attached patch implements virConnectDiscoverStoragePools mostly as specified by Daniel Berrange in: http://www.redhat.com/archives/libvir-list/2008-February/msg00107.html Daniel wasn't happy with the interface for this function because it wasn't sufficiently general, so it currently doesn't exist. I've attempted to generalize his proposed interface by changing the "hostname" argument to a "srcSpec" argument, which is intended to be a XML storage pool <source> element. Note that srcSpec is not necessary for some (local) pool types. For example, to discover existing LVM volume groups, there's no need to specify a source: virsh # pool-discover logical While discovering nfs shares requires a <source> document to specify the host to query: virsh # pool-discover netfs "<source><host name='share' /></source>" Currently (i.e., in this patch) I've implemented discovery support only for the "logical" and "netfs" pools. I plan on covering the other types once we've agreed upon the API. While this patch is rather large, the vast majority of it is "generic" (not specific to any particular type of storage pool) code, which I mostly took from Daniel's submission. I could easily break the storage-pool-type-specific pieces into separate patches, but those changes are already segregated into the appropriate storage_backend_ files. * Known Issues * I made the virsh interface take a XML string rather than a filename. I found it convenient, but AFAIK the rest of the commands that take XML take it from a file, so perhaps that should be changed (just let me know what you'd prefer). I realize the description of srcSpec is kind of fuzzy. For instance, for netfs discovery, the <source> must have a <host> element (to specify the host to query), but shouldn't have a <dir> element since the exported dirs are exactly what we're trying to discover in this case. So this really needs to be documented accurately for each storage pool type. (Where?) Finally, there's an underspecification issue. The XML pool descriptions returned are supposed to be usable as valid input to virStoragePoolDefineXML. But these descriptions include some data (pool name, target path) that isn't specified by the discover input or the discovered resources. For now, I'm making up a somewhat arbitrary pool name (logical: VolGroup name, netfs: last component of export path). And I don't even specify <target><path> in the "netfs" discovery output (which means it's not valid input to virStoragePoolDefineXML until a target path is added). Dave