nbd: Less allocation during NBD_OPT_LIST
Since we know that the maximum name we are willing to accept is small enough to stack-allocate, rework the iteration over NBD_OPT_LIST responses to reuse a stack buffer rather than allocating every time. Furthermore, we don't even have to allocate if we know the server's length doesn't match what we are searching for. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1476469998-28592-12-git-send-email-eblake@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
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7d3123e177
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75368aab9b
85
nbd/client.c
85
nbd/client.c
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@ -254,19 +254,28 @@ static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply,
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return result;
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return result;
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}
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}
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static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
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/* Process another portion of the NBD_OPT_LIST reply. Set *@match if
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* the current reply matches @want or if the server does not support
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* NBD_OPT_LIST, otherwise leave @match alone. Return 0 if iteration
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* is complete, positive if more replies are expected, or negative
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* with @errp set if an unrecoverable error occurred. */
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static int nbd_receive_list(QIOChannel *ioc, const char *want, bool *match,
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Error **errp)
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{
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{
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nbd_opt_reply reply;
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nbd_opt_reply reply;
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uint32_t len;
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uint32_t len;
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uint32_t namelen;
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uint32_t namelen;
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char name[NBD_MAX_NAME_SIZE + 1];
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int error;
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int error;
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*name = NULL;
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if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
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if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
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return -1;
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return -1;
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}
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}
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error = nbd_handle_reply_err(ioc, &reply, errp);
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error = nbd_handle_reply_err(ioc, &reply, errp);
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if (error <= 0) {
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if (error <= 0) {
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/* The server did not support NBD_OPT_LIST, so set *match on
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* the assumption that any name will be accepted. */
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*match = true;
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return error;
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return error;
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}
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}
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len = reply.length;
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len = reply.length;
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@ -277,7 +286,14 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
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nbd_send_opt_abort(ioc);
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nbd_send_opt_abort(ioc);
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return -1;
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return -1;
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}
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}
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} else if (reply.type == NBD_REP_SERVER) {
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return 0;
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} else if (reply.type != NBD_REP_SERVER) {
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error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
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reply.type, NBD_REP_SERVER);
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nbd_send_opt_abort(ioc);
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return -1;
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}
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if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
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if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
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error_setg(errp, "incorrect option length %" PRIu32, len);
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error_setg(errp, "incorrect option length %" PRIu32, len);
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nbd_send_opt_abort(ioc);
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nbd_send_opt_abort(ioc);
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@ -295,87 +311,66 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
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nbd_send_opt_abort(ioc);
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nbd_send_opt_abort(ioc);
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return -1;
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return -1;
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}
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}
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if (namelen > NBD_MAX_NAME_SIZE) {
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if (namelen != strlen(want)) {
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error_setg(errp, "export name length too long %" PRIu32, namelen);
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if (drop_sync(ioc, len) != len) {
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error_setg(errp, "failed to skip export name with wrong length");
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nbd_send_opt_abort(ioc);
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nbd_send_opt_abort(ioc);
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return -1;
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return -1;
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}
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}
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return 1;
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}
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*name = g_new0(char, namelen + 1);
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assert(namelen < sizeof(name));
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if (read_sync(ioc, *name, namelen) != namelen) {
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if (read_sync(ioc, name, namelen) != namelen) {
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error_setg(errp, "failed to read export name");
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error_setg(errp, "failed to read export name");
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g_free(*name);
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*name = NULL;
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nbd_send_opt_abort(ioc);
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nbd_send_opt_abort(ioc);
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return -1;
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return -1;
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}
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}
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(*name)[namelen] = '\0';
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name[namelen] = '\0';
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len -= namelen;
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len -= namelen;
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if (drop_sync(ioc, len) != len) {
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if (drop_sync(ioc, len) != len) {
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error_setg(errp, "failed to read export description");
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error_setg(errp, "failed to read export description");
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g_free(*name);
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*name = NULL;
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nbd_send_opt_abort(ioc);
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nbd_send_opt_abort(ioc);
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return -1;
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return -1;
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}
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}
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} else {
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if (!strcmp(name, want)) {
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error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
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*match = true;
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reply.type, NBD_REP_SERVER);
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nbd_send_opt_abort(ioc);
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return -1;
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}
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}
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return 1;
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return 1;
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}
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}
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/* Return -1 on failure, 0 if wantname is an available export. */
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static int nbd_receive_query_exports(QIOChannel *ioc,
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static int nbd_receive_query_exports(QIOChannel *ioc,
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const char *wantname,
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const char *wantname,
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Error **errp)
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Error **errp)
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{
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{
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bool foundExport = false;
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bool foundExport = false;
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TRACE("Querying export list");
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TRACE("Querying export list for '%s'", wantname);
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if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
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if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
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return -1;
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return -1;
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}
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}
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TRACE("Reading available export names");
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TRACE("Reading available export names");
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while (1) {
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while (1) {
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char *name = NULL;
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int ret = nbd_receive_list(ioc, wantname, &foundExport, errp);
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int ret = nbd_receive_list(ioc, &name, errp);
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if (ret < 0) {
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if (ret < 0) {
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g_free(name);
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/* Server gave unexpected reply */
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name = NULL;
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return -1;
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return -1;
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}
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} else if (ret == 0) {
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if (ret == 0) {
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/* Done iterating. */
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/* Server doesn't support export listing, so
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* we will just assume an export with our
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* wanted name exists */
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foundExport = true;
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break;
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}
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if (name == NULL) {
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TRACE("End of export name list");
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break;
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}
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if (g_str_equal(name, wantname)) {
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foundExport = true;
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TRACE("Found desired export name '%s'", name);
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} else {
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TRACE("Ignored export name '%s'", name);
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}
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g_free(name);
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}
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if (!foundExport) {
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if (!foundExport) {
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error_setg(errp, "No export with name '%s' available", wantname);
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error_setg(errp, "No export with name '%s' available",
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wantname);
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nbd_send_opt_abort(ioc);
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nbd_send_opt_abort(ioc);
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return -1;
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return -1;
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}
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}
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TRACE("Found desired export name '%s'", wantname);
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return 0;
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return 0;
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}
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}
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}
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}
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static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
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static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
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