Merge tag 'pull-nbd-2024-04-25' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2024-04-25

- Avoid calling poll() within coroutine

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# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
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* tag 'pull-nbd-2024-04-25' of https://repo.or.cz/qemu/ericb:
  nbd/server: Mark negotiation functions as coroutine_fn
  nbd/server: do not poll within a coroutine context

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

4 files changed, 105 insertions, 72 deletions

diff --git a/nbd/client.c b/nbd/client.c
index 29ffc609a4..c89c750467 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -596,13 +596,31 @@ static int nbd_request_simple_option(QIOChannel *ioc, int opt, bool strict,
     return 1;
 }
 
+/* Callback to learn when QIO TLS upgrade is complete */
+struct NBDTLSClientHandshakeData {
+    bool complete;
+    Error *error;
+    GMainLoop *loop;
+};
+
+static void nbd_client_tls_handshake(QIOTask *task, void *opaque)
+{
+    struct NBDTLSClientHandshakeData *data = opaque;
+
+    qio_task_propagate_error(task, &data->error);
+    data->complete = true;
+    if (data->loop) {
+        g_main_loop_quit(data->loop);
+    }
+}
+
 static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
                                         QCryptoTLSCreds *tlscreds,
                                         const char *hostname, Error **errp)
 {
     int ret;
     QIOChannelTLS *tioc;
-    struct NBDTLSHandshakeData data = { 0 };
+    struct NBDTLSClientHandshakeData data = { 0 };
 
     ret = nbd_request_simple_option(ioc, NBD_OPT_STARTTLS, true, errp);
     if (ret <= 0) {
@@ -619,18 +637,20 @@ static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
         return NULL;
     }
     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls");
-    data.loop = g_main_loop_new(g_main_context_default(), FALSE);
     trace_nbd_receive_starttls_tls_handshake();
     qio_channel_tls_handshake(tioc,
-                              nbd_tls_handshake,
+                              nbd_client_tls_handshake,
                               &data,
                               NULL,
                               NULL);
 
     if (!data.complete) {
+        data.loop = g_main_loop_new(g_main_context_default(), FALSE);
         g_main_loop_run(data.loop);
+        assert(data.complete);
+        g_main_loop_unref(data.loop);
     }
-    g_main_loop_unref(data.loop);
+
     if (data.error) {
         error_propagate(errp, data.error);
         object_unref(OBJECT(tioc));
diff --git a/nbd/common.c b/nbd/common.c
index 3247c1d618..589a748cfe 100644
--- a/nbd/common.c
+++ b/nbd/common.c
@@ -47,17 +47,6 @@ int nbd_drop(QIOChannel *ioc, size_t size, Error **errp)
 }
 
 
-void nbd_tls_handshake(QIOTask *task,
-                       void *opaque)
-{
-    struct NBDTLSHandshakeData *data = opaque;
-
-    qio_task_propagate_error(task, &data->error);
-    data->complete = true;
-    g_main_loop_quit(data->loop);
-}
-
-
 const char *nbd_opt_lookup(uint32_t opt)
 {
     switch (opt) {
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
index dfa02f77ee..91895106a9 100644
--- a/nbd/nbd-internal.h
+++ b/nbd/nbd-internal.h
@@ -72,16 +72,6 @@ static inline int nbd_write(QIOChannel *ioc, const void *buffer, size_t size,
     return qio_channel_write_all(ioc, buffer, size, errp) < 0 ? -EIO : 0;
 }
 
-struct NBDTLSHandshakeData {
-    GMainLoop *loop;
-    bool complete;
-    Error *error;
-};
-
-
-void nbd_tls_handshake(QIOTask *task,
-                       void *opaque);
-
 int nbd_drop(QIOChannel *ioc, size_t size, Error **errp);
 
 #endif
diff --git a/nbd/server.c b/nbd/server.c
index c3484cc1eb..892797bb11 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -195,8 +195,9 @@ static inline void set_be_option_rep(NBDOptionReply *rep, uint32_t option,
 
 /* Send a reply header, including length, but no payload.
  * Return -errno on error, 0 on success. */
-static int nbd_negotiate_send_rep_len(NBDClient *client, uint32_t type,
-                                      uint32_t len, Error **errp)
+static coroutine_fn int
+nbd_negotiate_send_rep_len(NBDClient *client, uint32_t type,
+                           uint32_t len, Error **errp)
 {
     NBDOptionReply rep;
 
@@ -211,15 +212,15 @@ static int nbd_negotiate_send_rep_len(NBDClient *client, uint32_t type,
 
 /* Send a reply header with default 0 length.
  * Return -errno on error, 0 on success. */
-static int nbd_negotiate_send_rep(NBDClient *client, uint32_t type,
-                                  Error **errp)
+static coroutine_fn int
+nbd_negotiate_send_rep(NBDClient *client, uint32_t type, Error **errp)
 {
     return nbd_negotiate_send_rep_len(client, type, 0, errp);
 }
 
 /* Send an error reply.
  * Return -errno on error, 0 on success. */
-static int G_GNUC_PRINTF(4, 0)
+static coroutine_fn int G_GNUC_PRINTF(4, 0)
 nbd_negotiate_send_rep_verr(NBDClient *client, uint32_t type,
                             Error **errp, const char *fmt, va_list va)
 {
@@ -259,7 +260,7 @@ nbd_sanitize_name(const char *name)
 
 /* Send an error reply.
  * Return -errno on error, 0 on success. */
-static int G_GNUC_PRINTF(4, 5)
+static coroutine_fn int G_GNUC_PRINTF(4, 5)
 nbd_negotiate_send_rep_err(NBDClient *client, uint32_t type,
                            Error **errp, const char *fmt, ...)
 {
@@ -275,7 +276,7 @@ nbd_negotiate_send_rep_err(NBDClient *client, uint32_t type,
 /* Drop remainder of the current option, and send a reply with the
  * given error type and message. Return -errno on read or write
  * failure; or 0 if connection is still live. */
-static int G_GNUC_PRINTF(4, 0)
+static coroutine_fn int G_GNUC_PRINTF(4, 0)
 nbd_opt_vdrop(NBDClient *client, uint32_t type, Error **errp,
               const char *fmt, va_list va)
 {
@@ -288,7 +289,7 @@ nbd_opt_vdrop(NBDClient *client, uint32_t type, Error **errp,
     return ret;
 }
 
-static int G_GNUC_PRINTF(4, 5)
+static coroutine_fn int G_GNUC_PRINTF(4, 5)
 nbd_opt_drop(NBDClient *client, uint32_t type, Error **errp,
              const char *fmt, ...)
 {
@@ -302,7 +303,7 @@ nbd_opt_drop(NBDClient *client, uint32_t type, Error **errp,
     return ret;
 }
 
-static int G_GNUC_PRINTF(3, 4)
+static coroutine_fn int G_GNUC_PRINTF(3, 4)
 nbd_opt_invalid(NBDClient *client, Error **errp, const char *fmt, ...)
 {
     int ret;
@@ -319,8 +320,9 @@ nbd_opt_invalid(NBDClient *client, Error **errp, const char *fmt, ...)
  * If @check_nul, require that no NUL bytes appear in buffer.
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success. */
-static int nbd_opt_read(NBDClient *client, void *buffer, size_t size,
-                        bool check_nul, Error **errp)
+static coroutine_fn int
+nbd_opt_read(NBDClient *client, void *buffer, size_t size,
+             bool check_nul, Error **errp)
 {
     if (size > client->optlen) {
         return nbd_opt_invalid(client, errp,
@@ -343,7 +345,8 @@ static int nbd_opt_read(NBDClient *client, void *buffer, size_t size,
 /* Drop size bytes from the unparsed payload of the current option.
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success. */
-static int nbd_opt_skip(NBDClient *client, size_t size, Error **errp)
+static coroutine_fn int
+nbd_opt_skip(NBDClient *client, size_t size, Error **errp)
 {
     if (size > client->optlen) {
         return nbd_opt_invalid(client, errp,
@@ -366,8 +369,9 @@ static int nbd_opt_skip(NBDClient *client, size_t size, Error **errp)
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success.
  */
-static int nbd_opt_read_name(NBDClient *client, char **name, uint32_t *length,
-                             Error **errp)
+static coroutine_fn int
+nbd_opt_read_name(NBDClient *client, char **name, uint32_t *length,
+                  Error **errp)
 {
     int ret;
     uint32_t len;
@@ -402,8 +406,8 @@ static int nbd_opt_read_name(NBDClient *client, char **name, uint32_t *length,
 
 /* Send a single NBD_REP_SERVER reply to NBD_OPT_LIST, including payload.
  * Return -errno on error, 0 on success. */
-static int nbd_negotiate_send_rep_list(NBDClient *client, NBDExport *exp,
-                                       Error **errp)
+static coroutine_fn int
+nbd_negotiate_send_rep_list(NBDClient *client, NBDExport *exp, Error **errp)
 {
     ERRP_GUARD();
     size_t name_len, desc_len;
@@ -444,7 +448,8 @@ static int nbd_negotiate_send_rep_list(NBDClient *client, NBDExport *exp,
 
 /* Process the NBD_OPT_LIST command, with a potential series of replies.
  * Return -errno on error, 0 on success. */
-static int nbd_negotiate_handle_list(NBDClient *client, Error **errp)
+static coroutine_fn int
+nbd_negotiate_handle_list(NBDClient *client, Error **errp)
 {
     NBDExport *exp;
     assert(client->opt == NBD_OPT_LIST);
@@ -459,7 +464,8 @@ static int nbd_negotiate_handle_list(NBDClient *client, Error **errp)
     return nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
 }
 
-static void nbd_check_meta_export(NBDClient *client, NBDExport *exp)
+static coroutine_fn void
+nbd_check_meta_export(NBDClient *client, NBDExport *exp)
 {
     if (exp != client->contexts.exp) {
         client->contexts.count = 0;
@@ -468,8 +474,9 @@ static void nbd_check_meta_export(NBDClient *client, NBDExport *exp)
 
 /* Send a reply to NBD_OPT_EXPORT_NAME.
  * Return -errno on error, 0 on success. */
-static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes,
-                                            Error **errp)
+static coroutine_fn int
+nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes,
+                                 Error **errp)
 {
     ERRP_GUARD();
     g_autofree char *name = NULL;
@@ -536,9 +543,9 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes,
 /* Send a single NBD_REP_INFO, with a buffer @buf of @length bytes.
  * The buffer does NOT include the info type prefix.
  * Return -errno on error, 0 if ready to send more. */
-static int nbd_negotiate_send_info(NBDClient *client,
-                                   uint16_t info, uint32_t length, void *buf,
-                                   Error **errp)
+static coroutine_fn int
+nbd_negotiate_send_info(NBDClient *client, uint16_t info, uint32_t length,
+                        void *buf, Error **errp)
 {
     int rc;
 
@@ -565,7 +572,8 @@ static int nbd_negotiate_send_info(NBDClient *client,
  * -errno  transmission error occurred or @fatal was requested, errp is set
  * 0       error message successfully sent to client, errp is not set
  */
-static int nbd_reject_length(NBDClient *client, bool fatal, Error **errp)
+static coroutine_fn int
+nbd_reject_length(NBDClient *client, bool fatal, Error **errp)
 {
     int ret;
 
@@ -583,7 +591,8 @@ static int nbd_reject_length(NBDClient *client, bool fatal, Error **errp)
 /* Handle NBD_OPT_INFO and NBD_OPT_GO.
  * Return -errno on error, 0 if ready for next option, and 1 to move
  * into transmission phase.  */
-static int nbd_negotiate_handle_info(NBDClient *client, Error **errp)
+static coroutine_fn int
+nbd_negotiate_handle_info(NBDClient *client, Error **errp)
 {
     int rc;
     g_autofree char *name = NULL;
@@ -748,15 +757,33 @@ static int nbd_negotiate_handle_info(NBDClient *client, Error **errp)
     return rc;
 }
 
+/* Callback to learn when QIO TLS upgrade is complete */
+struct NBDTLSServerHandshakeData {
+    bool complete;
+    Error *error;
+    Coroutine *co;
+};
+
+static void
+nbd_server_tls_handshake(QIOTask *task, void *opaque)
+{
+    struct NBDTLSServerHandshakeData *data = opaque;
+
+    qio_task_propagate_error(task, &data->error);
+    data->complete = true;
+    if (!qemu_coroutine_entered(data->co)) {
+        aio_co_wake(data->co);
+    }
+}
 
 /* Handle NBD_OPT_STARTTLS. Return NULL to drop connection, or else the
  * new channel for all further (now-encrypted) communication. */
-static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
-                                                 Error **errp)
+static coroutine_fn QIOChannel *
+nbd_negotiate_handle_starttls(NBDClient *client, Error **errp)
 {
     QIOChannel *ioc;
     QIOChannelTLS *tioc;
-    struct NBDTLSHandshakeData data = { 0 };
+    struct NBDTLSServerHandshakeData data = { 0 };
 
     assert(client->opt == NBD_OPT_STARTTLS);
 
@@ -777,17 +804,18 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
 
     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-server-tls");
     trace_nbd_negotiate_handle_starttls_handshake();
-    data.loop = g_main_loop_new(g_main_context_default(), FALSE);
+    data.co = qemu_coroutine_self();
     qio_channel_tls_handshake(tioc,
-                              nbd_tls_handshake,
+                              nbd_server_tls_handshake,
                               &data,
                               NULL,
                               NULL);
 
     if (!data.complete) {
-        g_main_loop_run(data.loop);
+        qemu_coroutine_yield();
+        assert(data.complete);
     }
-    g_main_loop_unref(data.loop);
+
     if (data.error) {
         object_unref(OBJECT(tioc));
         error_propagate(errp, data.error);
@@ -803,10 +831,9 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
  *
  * For NBD_OPT_LIST_META_CONTEXT @context_id is ignored, 0 is used instead.
  */
-static int nbd_negotiate_send_meta_context(NBDClient *client,
-                                           const char *context,
-                                           uint32_t context_id,
-                                           Error **errp)
+static coroutine_fn int
+nbd_negotiate_send_meta_context(NBDClient *client, const char *context,
+                                uint32_t context_id, Error **errp)
 {
     NBDOptionReplyMetaContext opt;
     struct iovec iov[] = {
@@ -831,8 +858,9 @@ static int nbd_negotiate_send_meta_context(NBDClient *client,
  * Return true if @query matches @pattern, or if @query is empty when
  * the @client is performing _LIST_.
  */
-static bool nbd_meta_empty_or_pattern(NBDClient *client, const char *pattern,
-                                      const char *query)
+static coroutine_fn bool
+nbd_meta_empty_or_pattern(NBDClient *client, const char *pattern,
+                          const char *query)
 {
     if (!*query) {
         trace_nbd_negotiate_meta_query_parse("empty");
@@ -849,7 +877,8 @@ static bool nbd_meta_empty_or_pattern(NBDClient *client, const char *pattern,
 /*
  * Return true and adjust @str in place if it begins with @prefix.
  */
-static bool nbd_strshift(const char **str, const char *prefix)
+static coroutine_fn bool
+nbd_strshift(const char **str, const char *prefix)
 {
     size_t len = strlen(prefix);
 
@@ -865,8 +894,9 @@ static bool nbd_strshift(const char **str, const char *prefix)
  * Handle queries to 'base' namespace. For now, only the base:allocation
  * context is available.  Return true if @query has been handled.
  */
-static bool nbd_meta_base_query(NBDClient *client, NBDMetaContexts *meta,
-                                const char *query)
+static coroutine_fn bool
+nbd_meta_base_query(NBDClient *client, NBDMetaContexts *meta,
+                    const char *query)
 {
     if (!nbd_strshift(&query, "base:")) {
         return false;
@@ -885,8 +915,9 @@ static bool nbd_meta_base_query(NBDClient *client, NBDMetaContexts *meta,
  * and qemu:allocation-depth contexts are available.  Return true if @query
  * has been handled.
  */
-static bool nbd_meta_qemu_query(NBDClient *client, NBDMetaContexts *meta,
-                                const char *query)
+static coroutine_fn bool
+nbd_meta_qemu_query(NBDClient *client, NBDMetaContexts *meta,
+                    const char *query)
 {
     size_t i;
 
@@ -950,8 +981,9 @@ static bool nbd_meta_qemu_query(NBDClient *client, NBDMetaContexts *meta,
  *
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success. */
-static int nbd_negotiate_meta_query(NBDClient *client,
-                                    NBDMetaContexts *meta, Error **errp)
+static coroutine_fn int
+nbd_negotiate_meta_query(NBDClient *client,
+                         NBDMetaContexts *meta, Error **errp)
 {
     int ret;
     g_autofree char *query = NULL;
@@ -990,7 +1022,8 @@ static int nbd_negotiate_meta_query(NBDClient *client,
  * Handle NBD_OPT_LIST_META_CONTEXT and NBD_OPT_SET_META_CONTEXT
  *
  * Return -errno on I/O error, or 0 if option was completely handled. */
-static int nbd_negotiate_meta_queries(NBDClient *client, Error **errp)
+static coroutine_fn int
+nbd_negotiate_meta_queries(NBDClient *client, Error **errp)
 {
     int ret;
     g_autofree char *export_name = NULL;
@@ -1118,7 +1151,8 @@ static int nbd_negotiate_meta_queries(NBDClient *client, Error **errp)
  * 1       if client sent NBD_OPT_ABORT, i.e. on valid disconnect,
  *         errp is not set
  */
-static int nbd_negotiate_options(NBDClient *client, Error **errp)
+static coroutine_fn int
+nbd_negotiate_options(NBDClient *client, Error **errp)
 {
     uint32_t flags;
     bool fixedNewstyle = false;