Re: [Qemu-block] [PATCH 6/9] nbd: BLOCK_STATUS for standard get_block_status function: client part

[Vladimir Sementsov-Ogievskiy]

16.02.2018 23:40, Eric Blake wrote:
> On 02/15/2018 07:51 AM, Vladimir Sementsov-Ogievskiy wrote:
> > Minimal realization: only one extent in server answer is supported.
> > Flag NBD_CMD_FLAG_REQ_ONE is used to force this behavior.
> >
> > Tests 140, 147 and 205 are fixed due to now server failed on searching
> > export in context of NBD_OPT_SET_META_CONTEXT option negotiation.
> >
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> > ---

[...]

> > +++ b/nbd/client.c
> > @@ -594,6 +594,108 @@ static QIOChannel 
> > *nbd_receive_starttls(QIOChannel *ioc,
> >       return QIO_CHANNEL(tioc);
> >   }
> >   +/* nbd_negotiate_simple_meta_context:
> > + * Set one meta context. Simple means that reply must contain zero (not
> > + * negotiated) or one (negotiated) contexts. More contexts would be 
> > considered
> > + * as a protocol error.
> > + * return 1 for successful negotiation, context_id is set
> > + *        0 if operation is unsupported,
> > + *        -errno with errp set for any other error
> > + */
>
> Good enough for our first use.  Will obviously need improvements if we 
> support base:allocation AND dirty bitmap exposure at the same time, in 
> future patches ;)
>
> > +static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
> > +                                             const char *export,
> > +                                             const char *context,
> > +                                             uint32_t *context_id,
> > +                                             Error **errp)
> > +{
> > +    int ret;
> > +    NBDOptionReply reply;
> > +    uint32_t received_id;
> > +    bool received;
> > +    size_t export_len = strlen(export);
> > +    size_t context_len = strlen(context);
> > +    size_t data_len = 4 + export_len + 4 + 4 + context_len;

[...]

> +
> > +        if (nbd_read(ioc, &received_id, sizeof(received_id), errp) < 
> > 0) {
> > +            return -EIO;
> > +        }
> > +        be32_to_cpus(&received_id);
> > +
> > +        len = reply.length - sizeof(received_id);
> > +        name = g_malloc(len + 1);
> > +        if (nbd_read(ioc, name, len, errp) < 0) {
> > +            g_free(name);
> > +            return -EIO;
> > +        }
> > +        name[len] = '\0';
> > +        if (strcmp(context, name)) {
> > +            error_setg(errp, "Failed to negotiate meta context '%s', 
> > server "
> > +                       "answered with different context '%s'", context,
> > +                       name);
>
> This check may not be valid for other context namespaces, but is 
> correct for "base:allocation".

so, it is negotiation of "simple meta context". I'll improve somehow 
comment about the functions...




--
Best regards,
Vladimir