[libvirt] [RFC] Private data pointer for virStoragePool and virStorageVol structs

[Daniel P. Berrange]

On Sat, Oct 06, 2012 at 05:15:55PM +0200, Matthias Bolte wrote:
> Ata Bohra proposed a backend concept for the ESX storage driver to
> simplify the addition of iSCSI support to the ESX storage driver.
> 
> The problem here is that most of the storage driver functions need to
> determine the backend to be used from the pool name.
> 
> This overhead can be avoided by adding a private data pointer to the
> virStoragePool and virStorageVol structs that the ESX storage driver
> can use to store a pointer to the correct backend.
> 
> struct _virStoragePool {
>     virObject object;
>     virConnectPtr conn;
>     char *name;
>     unsigned char uuid[VIR_UUID_BUFLEN];
> 
>     void *privateData;
>     virFreeCallback privateDataFreeFunc;
> };
> 
> struct _virStorageVol {
>     virObject object;
>     virConnectPtr conn;
>     char *pool;
>     char *name;
>     char *key;
> 
>     void *privateData;
>     virFreeCallback privateDataFreeFunc;
> };
> 
> virGetStoragePool and virGetStorageVol would set privateData and
> privateDataFreeFunc as given by the caller. virStoragePoolDispose and
> virStorageVolDispose would call privateDataFreeFunc if set.
> 
> Comments?

The only other option I see would to have a hash table or similar
in the esxPrivate struct, and do a lookup in that from the pool
or volume name/uuid. I guess having privateData directly in the
virStorage{Vol,Pool} structs might make your life easier though.

Since this is ultimately an internal impl detail we can change
later, I don't have a strong opinion on it either way.

Daniel
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