nbd/client: Change signature of nbd_negotiate_simple_meta_context()

Pass 'info' instead of three separate parameters related to info,
when requesting the server to set the meta context.  Update the
NBDExportInfo struct to rename the received id field to match the
fact that we are currently overloading the field to match whatever
context the user supplied through the x-dirty-bitmap hack, as well
as adding a TODO comment to remind future patches about a desire
to request two contexts at once.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190117193658.16413-11-eblake@redhat.com>

1 files changed, 25 insertions, 28 deletions

diff --git a/nbd/client.c b/nbd/client.c
index 8227e69478..77993890f0 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -630,26 +630,30 @@ static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
 }
 
 /* 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. It's also implied that meta-data query equals queried
- * context name, so, if server replies with something different than @context,
- * it is considered an error too.
- * return 1 for successful negotiation, context_id is set
+ * Request the server to set the meta context for export @info->name
+ * using @info->x_dirty_bitmap with a fallback to "base:allocation",
+ * setting @info->context_id to the resulting id. Fail if the server
+ * responds with more than one context or with a context different
+ * than the query.
+ * return 1 for successful negotiation,
  *        0 if operation is unsupported,
  *        -1 with errp set for any other error
  */
 static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
-                                             const char *export,
-                                             const char *context,
-                                             uint32_t *context_id,
+                                             NBDExportInfo *info,
                                              Error **errp)
 {
+    /*
+     * TODO: Removing the x_dirty_bitmap hack will mean refactoring
+     * this function to request and store ids for multiple contexts
+     * (both base:allocation and a dirty bitmap), at which point this
+     * function should lose the term _simple.
+     */
     int ret;
     NBDOptionReply reply;
-    uint32_t received_id = 0;
+    const char *context = info->x_dirty_bitmap ?: "base:allocation";
     bool received = false;
-    uint32_t export_len = strlen(export);
+    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 */
@@ -657,9 +661,9 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
     char *data = g_malloc(data_len);
     char *p = data;
 
-    trace_nbd_opt_meta_request(context, export);
+    trace_nbd_opt_meta_request(context, info->name);
     stl_be_p(p, export_len);
-    memcpy(p += sizeof(export_len), export, 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);
@@ -685,7 +689,7 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
     if (reply.type == NBD_REP_META_CONTEXT) {
         char *name;
 
-        if (reply.length != sizeof(received_id) + context_len) {
+        if (reply.length != sizeof(info->context_id) + context_len) {
             error_setg(errp, "Failed to negotiate meta context '%s', server "
                        "answered with unexpected length %" PRIu32, context,
                        reply.length);
@@ -693,12 +697,13 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
             return -1;
         }
 
-        if (nbd_read(ioc, &received_id, sizeof(received_id), errp) < 0) {
+        if (nbd_read(ioc, &info->context_id, sizeof(info->context_id),
+                     errp) < 0) {
             return -1;
         }
-        received_id = be32_to_cpu(received_id);
+        info->context_id = be32_to_cpu(info->context_id);
 
-        reply.length -= sizeof(received_id);
+        reply.length -= sizeof(info->context_id);
         name = g_malloc(reply.length + 1);
         if (nbd_read(ioc, name, reply.length, errp) < 0) {
             g_free(name);
@@ -715,7 +720,7 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
         }
         g_free(name);
 
-        trace_nbd_opt_meta_reply(context, received_id);
+        trace_nbd_opt_meta_reply(context, info->context_id);
         received = true;
 
         /* receive NBD_REP_ACK */
@@ -744,12 +749,7 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
         return -1;
     }
 
-    if (received) {
-        *context_id = received_id;
-        return 1;
-    }
-
-    return 0;
+    return received;
 }
 
 int nbd_receive_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
@@ -848,10 +848,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
             }
 
             if (info->structured_reply && base_allocation) {
-                result = nbd_negotiate_simple_meta_context(
-                        ioc, info->name,
-                        info->x_dirty_bitmap ?: "base:allocation",
-                        &info->meta_base_allocation_id, errp);
+                result = nbd_negotiate_simple_meta_context(ioc, info, errp);
                 if (result < 0) {
                     goto fail;
                 }