Commit 75368aab authored by Eric Blake's avatar Eric Blake Committed by Paolo Bonzini
Browse files

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: default avatarEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-12-git-send-email-eblake@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 7d3123e1

nbd/client.c

+67 −72
Original line number Diff line number Diff line
@@ -254,19 +254,28 @@ static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply, 
    return result;

}



static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)

/* Process another portion of the NBD_OPT_LIST reply.  Set *@match if

 * the current reply matches @want or if the server does not support

 * NBD_OPT_LIST, otherwise leave @match alone.  Return 0 if iteration

 * is complete, positive if more replies are expected, or negative

 * with @errp set if an unrecoverable error occurred. */

static int nbd_receive_list(QIOChannel *ioc, const char *want, bool *match,

                            Error **errp)

{

    nbd_opt_reply reply;

    uint32_t len;

    uint32_t namelen;

    char name[NBD_MAX_NAME_SIZE + 1];

    int error;



    *name = NULL;

    if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {

        return -1;

    }

    error = nbd_handle_reply_err(ioc, &reply, errp);

    if (error <= 0) {

        /* The server did not support NBD_OPT_LIST, so set *match on

         * the assumption that any name will be accepted.  */

        *match = true;

        return error;

    }

    len = reply.length;
@@ -277,7 +286,14 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp) 
            nbd_send_opt_abort(ioc);

            return -1;

        }

    } else if (reply.type == NBD_REP_SERVER) {

        return 0;

    } else if (reply.type != NBD_REP_SERVER) {

        error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",

                   reply.type, NBD_REP_SERVER);

        nbd_send_opt_abort(ioc);

        return -1;

    }



    if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {

        error_setg(errp, "incorrect option length %" PRIu32, len);

        nbd_send_opt_abort(ioc);
@@ -295,88 +311,67 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp) 
        nbd_send_opt_abort(ioc);

        return -1;

    }

        if (namelen > NBD_MAX_NAME_SIZE) {

            error_setg(errp, "export name length too long %" PRIu32, namelen);

    if (namelen != strlen(want)) {

        if (drop_sync(ioc, len) != len) {

            error_setg(errp, "failed to skip export name with wrong length");

            nbd_send_opt_abort(ioc);

            return -1;

        }

        return 1;

    }



        *name = g_new0(char, namelen + 1);

        if (read_sync(ioc, *name, namelen) != namelen) {

    assert(namelen < sizeof(name));

    if (read_sync(ioc, name, namelen) != namelen) {

        error_setg(errp, "failed to read export name");

            g_free(*name);

            *name = NULL;

        nbd_send_opt_abort(ioc);

        return -1;

    }

        (*name)[namelen] = '\0';

    name[namelen] = '\0';

    len -= namelen;

    if (drop_sync(ioc, len) != len) {

        error_setg(errp, "failed to read export description");

            g_free(*name);

            *name = NULL;

        nbd_send_opt_abort(ioc);

        return -1;

    }

    } else {

        error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",

                   reply.type, NBD_REP_SERVER);

        nbd_send_opt_abort(ioc);

        return -1;

    if (!strcmp(name, want)) {

        *match = true;

    }

    return 1;

}





/* Return -1 on failure, 0 if wantname is an available export. */

static int nbd_receive_query_exports(QIOChannel *ioc,

                                     const char *wantname,

                                     Error **errp)

{

    bool foundExport = false;



    TRACE("Querying export list");

    TRACE("Querying export list for '%s'", wantname);

    if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {

        return -1;

    }



    TRACE("Reading available export names");

    while (1) {

        char *name = NULL;

        int ret = nbd_receive_list(ioc, &name, errp);

        int ret = nbd_receive_list(ioc, wantname, &foundExport, errp);



        if (ret < 0) {

            g_free(name);

            name = NULL;

            /* Server gave unexpected reply */

            return -1;

        }

        if (ret == 0) {

            /* Server doesn't support export listing, so

             * we will just assume an export with our

             * wanted name exists */

            foundExport = true;

            break;

        }

        if (name == NULL) {

            TRACE("End of export name list");

            break;

        }

        if (g_str_equal(name, wantname)) {

            foundExport = true;

            TRACE("Found desired export name '%s'", name);

        } else {

            TRACE("Ignored export name '%s'", name);

        }

        g_free(name);

    }



        } else if (ret == 0) {

            /* Done iterating. */

            if (!foundExport) {

        error_setg(errp, "No export with name '%s' available", wantname);

                error_setg(errp, "No export with name '%s' available",

                           wantname);

                nbd_send_opt_abort(ioc);

                return -1;

            }



            TRACE("Found desired export name '%s'", wantname);

            return 0;

        }

    }

}



static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,

                                        QCryptoTLSCreds *tlscreds,