Re: [Qemu-devel] [PATCH v3 10/19] nbd/client: Split out nbd_send_one_meta_context()

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

12.01.2019 20:58, Eric Blake wrote:
> Refactor nbd_negotiate_simple_meta_context() to pull out the
> code that can be reused to send a LIST request for 0 or 1 query.
> No semantic change.  The old comment about 'sizeof(uint32_t)'
> being equivalent to '/* number of queries */' is no longer
> needed, now that we are computing 'sizeof(queries)' instead.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Message-Id: <20181215135324.152629-14-eblake@redhat.com>
> Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
> 
> ---
> v3: Improve commit message [Rich], formatting tweak [checkpatch],
> rebase to dropped patch
> ---
>   nbd/client.c     | 67 +++++++++++++++++++++++++++++++++---------------
>   nbd/trace-events |  2 +-
>   2 files changed, 48 insertions(+), 21 deletions(-)
> 
> diff --git a/nbd/client.c b/nbd/client.c
> index 77993890f04..3c716be2719 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -629,6 +629,49 @@ static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
>       return QIO_CHANNEL(tioc);
>   }
> 
> +/*
> + * nbd_send_one_meta_context:
> + * Send 0 or 1 set/list meta context queries.
> + * Return 0 on success, -1 with errp set for any error
> + */
> +static int nbd_send_one_meta_context(QIOChannel *ioc,
> +                                     uint32_t opt,
> +                                     const char *export,
> +                                     const char *query,
> +                                     Error **errp)
> +{
> +    int ret;
> +    uint32_t export_len = strlen(export);
> +    uint32_t queries = !!query;

n_ or nb_ prefix may make it more clear

> +    uint32_t context_len = 0;
> +    uint32_t data_len;
> +    char *data;
> +    char *p;
> +
> +    data_len = sizeof(export_len) + export_len + sizeof(queries);
> +    if (query) {
> +        context_len = strlen(query);

looks like it then should be query_len

> +        data_len += sizeof(context_len) + context_len;
> +    } else {
> +        assert(opt == NBD_OPT_LIST_META_CONTEXT);
> +    }
> +    data = g_malloc(data_len);
> +    p = data;

may use p = data = g_malloc

> +
> +    trace_nbd_opt_meta_request(nbd_opt_lookup(opt), query ?: "(all)", export);
> +    stl_be_p(p, export_len);
> +    memcpy(p += sizeof(export_len), export, export_len);
> +    stl_be_p(p += export_len, queries);
> +    if (query) {
> +        stl_be_p(p += sizeof(uint32_t), context_len);

:), aha, please, s/uint32_t/queries, as you promised

Hmm, its my code. It's hard to read and not very comfortable to maintain..

In block/nbd-client.c we have
payload_advance* functions, to read such formatted data, I think, it should be
good to make something like this for server-part. Not about these series, of course.

Interesting, troubles around "don't use be64_to_cpuS, use only be64_to_cpu",
do they apply somehow to *_be_p functions family?

> +        memcpy(p += sizeof(context_len), query, context_len);
> +    }
> +
> +    ret = nbd_send_option_request(ioc, opt, data_len, data, errp);
> +    g_free(data);
> +    return ret;
> +}
> +
>   /* nbd_negotiate_simple_meta_context:
>    * Request the server to set the meta context for export @info->name
>    * using @info->x_dirty_bitmap with a fallback to "base:allocation",
> @@ -653,26 +696,10 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
>       NBDOptionReply reply;
>       const char *context = info->x_dirty_bitmap ?: "base:allocation";
>       bool received = false;
> -    uint32_t export_len = strlen(info->name);
> -    uint32_t context_len = strlen(context);
> -    uint32_t data_len = sizeof(export_len) + export_len +
> -                        sizeof(uint32_t) + /* number of queries */
> -                        sizeof(context_len) + context_len;
> -    char *data = g_malloc(data_len);
> -    char *p = data;
> 
> -    trace_nbd_opt_meta_request(context, info->name);
> -    stl_be_p(p, export_len);
> -    memcpy(p += sizeof(export_len), info->name, export_len);
> -    stl_be_p(p += export_len, 1);
> -    stl_be_p(p += sizeof(uint32_t), context_len);
> -    memcpy(p += sizeof(context_len), context, context_len);
> -
> -    ret = nbd_send_option_request(ioc, NBD_OPT_SET_META_CONTEXT, data_len, data,
> -                                  errp);
> -    g_free(data);
> -    if (ret < 0) {
> -        return ret;
> +    if (nbd_send_one_meta_context(ioc, NBD_OPT_SET_META_CONTEXT,
> +                                  info->name, context, errp) < 0) {
> +        return -1;
>       }
> 
>       if (nbd_receive_option_reply(ioc, NBD_OPT_SET_META_CONTEXT, &reply,
> @@ -689,7 +716,7 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
>       if (reply.type == NBD_REP_META_CONTEXT) {
>           char *name;
> 
> -        if (reply.length != sizeof(info->context_id) + context_len) {
> +        if (reply.length != sizeof(info->context_id) + strlen(context)) {
>               error_setg(errp, "Failed to negotiate meta context '%s', server "
>                          "answered with unexpected length %" PRIu32, context,
>                          reply.length);
> diff --git a/nbd/trace-events b/nbd/trace-events
> index c3966d2b653..59521e47a3d 100644
> --- a/nbd/trace-events
> +++ b/nbd/trace-events
> @@ -12,7 +12,7 @@ nbd_receive_query_exports_start(const char *wantname) "Querying export list for
>   nbd_receive_query_exports_success(const char *wantname) "Found desired export name '%s'"
>   nbd_receive_starttls_new_client(void) "Setting up TLS"
>   nbd_receive_starttls_tls_handshake(void) "Starting TLS handshake"
> -nbd_opt_meta_request(const char *context, const char *export) "Requesting to set meta context %s for export %s"
> +nbd_opt_meta_request(const char *optname, const char *context, const char *export) "Requesting %s %s for export %s"

Hmm, you forget nbd_opt_lookup()

With this and s/uint32_t/queries (other tiny things up to you):
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

>   nbd_opt_meta_reply(const char *context, uint32_t id) "Received mapping of context %s to id %" PRIu32
>   nbd_receive_negotiate(void *tlscreds, const char *hostname) "Receiving negotiation tlscreds=%p hostname=%s"
>   nbd_receive_negotiate_magic(uint64_t magic) "Magic is 0x%" PRIx64
> 


-- 
Best regards,
Vladimir