Re: [Libguestfs] [PATCH v4 09/24] nbd: Replace bool structured_reply with mode enum

The upcoming patches for 64-bit extensions requires various points in the protocol to make decisions based on what was negotiated. While we could easily add a 'bool extended_headers' alongside the existing 'bool structured_reply', this does not scale well if more modes are added in the future. Better is to expose the mode enum added in the previous patch out to a wider use in the code base. Where the code previously checked for structured_reply being set or clear, it now prefers checking for an inequality; this works because the nodes are in a continuum of increasing abilities, and allows us to touch fewer places if we ever insert other modes in the middle of the enum. There should be no semantic change in this patch. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- v4: new patch, expanding enum idea from v3 4/14 ---

diff --git a/nbd/server.c b/nbd/server.c index 8486b64b15d..bade4f7990c 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -143,7 +143,7 @@ struct NBDClient { uint32_t check_align; /* If non-zero, check for aligned client requests */ - bool structured_reply; + NBDMode mode; NBDExportMetaContexts export_meta; uint32_t opt; /* Current option being negotiated */ @@ -502,7 +502,7 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes, } myflags = client->exp->nbdflags; - if (client->structured_reply) { + if (client->mode >= NBD_MODE_STRUCTURED) { myflags |= NBD_FLAG_SEND_DF; } trace_nbd_negotiate_new_style_size_flags(client->exp->size, myflags); @@ -687,7 +687,7 @@ static int nbd_negotiate_handle_info(NBDClient *client, Error **errp) /* Send NBD_INFO_EXPORT always */ myflags = exp->nbdflags; - if (client->structured_reply) { + if (client->mode >= NBD_MODE_STRUCTURED) { myflags |= NBD_FLAG_SEND_DF; } trace_nbd_negotiate_new_style_size_flags(exp->size, myflags); @@ -985,7 +985,8 @@ static int nbd_negotiate_meta_queries(NBDClient *client, size_t i; size_t count = 0; - if (client->opt == NBD_OPT_SET_META_CONTEXT && !client->structured_reply) { + if (client->opt == NBD_OPT_SET_META_CONTEXT && + client->mode < NBD_MODE_STRUCTURED) { return nbd_opt_invalid(client, errp, "request option '%s' when structured reply " "is not negotiated", @@ -1261,13 +1262,13 @@ static int nbd_negotiate_options(NBDClient *client, Error **errp) case NBD_OPT_STRUCTURED_REPLY: if (length) { ret = nbd_reject_length(client, false, errp); - } else if (client->structured_reply) { + } else if (client->mode >= NBD_MODE_STRUCTURED) { ret = nbd_negotiate_send_rep_err( client, NBD_REP_ERR_INVALID, errp, "structured reply already negotiated"); } else { ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp); - client->structured_reply = true; + client->mode = NBD_MODE_STRUCTURED;

} break; @@ -1907,7 +1908,9 @@ static int coroutine_fn nbd_co_send_simple_reply(NBDClient *client, }; assert(!len || !nbd_err); - assert(!client->structured_reply || request->type != NBD_CMD_READ); + assert(client->mode < NBD_MODE_STRUCTURED || + (client->mode == NBD_MODE_STRUCTURED && + request->type != NBD_CMD_READ)); trace_nbd_co_send_simple_reply(request->cookie, nbd_err, nbd_err_lookup(nbd_err), len); set_be_simple_reply(&reply, nbd_err, request->cookie); @@ -2409,7 +2412,7 @@ static int coroutine_fn nbd_co_receive_request(NBDRequestData *req, NBDRequest * client->check_align); } valid_flags = NBD_CMD_FLAG_FUA;