| Message ID | 20240405174523.844181-2-eblake@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] nbd/server: do not poll within a coroutine context | expand |
On 05.04.24 20:44, Eric Blake wrote: > From: Zhu Yangyang <zhuyangyang14@huawei.com> > > Coroutines are not supposed to block. Instead, they should yield. > > The client performs TLS upgrade outside of an AIOContext, during > synchronous handshake; this still requires g_main_loop. But the > server responds to TLS upgrade inside a coroutine, so a nested > g_main_loop is wrong. Since the two callbacks no longer share more > than the setting of data.complete and data.error, it's just as easy to > use static helpers instead of trying to share a common code path. > > Fixes: f95910f ("nbd: implement TLS support in the protocol negotiation") > Signed-off-by: Zhu Yangyang <zhuyangyang14@huawei.com> > [eblake: move callbacks to their use point] > Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> still, some notes below > --- > > v3: https://lists.gnu.org/archive/html/qemu-devel/2024-04/msg00375.html > > in v4, factor even the struct to the .c files, avoiding a union [Vladimir] > > nbd/nbd-internal.h | 10 ---------- > nbd/client.c | 27 +++++++++++++++++++++++---- > nbd/common.c | 11 ----------- > nbd/server.c | 29 +++++++++++++++++++++++------ > 4 files changed, 46 insertions(+), 31 deletions(-) > > diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h > index dfa02f77ee4..91895106a95 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/client.c b/nbd/client.c > index 29ffc609a4b..c7141d7a098 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 +637,19 @@ 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); > + g_main_loop_unref(data.loop); probably good to assert(data.complete); > } > - 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 3247c1d618a..589a748cfe6 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/server.c b/nbd/server.c > index c3484cc1ebc..ea13cf0e766 100644 > --- a/nbd/server.c > +++ b/nbd/server.c > @@ -748,6 +748,23 @@ 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. */ > @@ -756,7 +773,7 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client, > { > QIOChannel *ioc; > QIOChannelTLS *tioc; > - struct NBDTLSHandshakeData data = { 0 }; > + struct NBDTLSServerHandshakeData data = { 0 }; > > assert(client->opt == NBD_OPT_STARTTLS); > > @@ -777,17 +794,17 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client, preexisting: lack coroutine_fn, as well as caller nbd_negotiate_options() > > 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); > + while (!data.complete) { not "if", but "while".. Do we expect entering from somewhere except nbd_server_tls_handshake? if not, probably safer construction would be if (!data.complete) { qemu_coroutine_yield(); assert(data.complete); } - to avoid hiding unexpected coroutine switching bugs > + qemu_coroutine_yield(); > } > - g_main_loop_unref(data.loop); > + > if (data.error) { > object_unref(OBJECT(tioc)); > error_propagate(errp, data.error);
On Mon, Apr 08, 2024 at 11:46:39AM +0300, Vladimir Sementsov-Ogievskiy wrote: > On 05.04.24 20:44, Eric Blake wrote: > > From: Zhu Yangyang <zhuyangyang14@huawei.com> > > > > Coroutines are not supposed to block. Instead, they should yield. > > > > The client performs TLS upgrade outside of an AIOContext, during > > synchronous handshake; this still requires g_main_loop. But the > > server responds to TLS upgrade inside a coroutine, so a nested > > g_main_loop is wrong. Since the two callbacks no longer share more > > than the setting of data.complete and data.error, it's just as easy to > > use static helpers instead of trying to share a common code path. > > > > Fixes: f95910f ("nbd: implement TLS support in the protocol negotiation") > > Signed-off-by: Zhu Yangyang <zhuyangyang14@huawei.com> > > [eblake: move callbacks to their use point] > > Signed-off-by: Eric Blake <eblake@redhat.com> > > Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> I'm debating whether it is worth trying to shove this into 9.0; -rc3 is very late, and the problem is pre-existing, so I'm leaning towards no. At which point, it's better to get this right. > > still, some notes below > > > --- > > > > v3: https://lists.gnu.org/archive/html/qemu-devel/2024-04/msg00375.html > > > > in v4, factor even the struct to the .c files, avoiding a union [Vladimir] > > > > nbd/nbd-internal.h | 10 ---------- > > nbd/client.c | 27 +++++++++++++++++++++++---- > > nbd/common.c | 11 ----------- > > nbd/server.c | 29 +++++++++++++++++++++++------ > > 4 files changed, 46 insertions(+), 31 deletions(-) > > > > +++ 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 +637,19 @@ 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); > > + g_main_loop_unref(data.loop); > > probably good to assert(data.complete); Seems reasonable. > > +++ b/nbd/server.c > > @@ -748,6 +748,23 @@ 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. */ > > @@ -756,7 +773,7 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client, > > { > > QIOChannel *ioc; > > QIOChannelTLS *tioc; > > - struct NBDTLSHandshakeData data = { 0 }; > > + struct NBDTLSServerHandshakeData data = { 0 }; > > > > assert(client->opt == NBD_OPT_STARTTLS); > > > > @@ -777,17 +794,17 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client, > > preexisting: lack coroutine_fn, as well as caller nbd_negotiate_options() Indeed, so now would not hurt to add them now that a callback is no longer shared between callers in different context. But probably as a separate patch. > > > > > 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); > > + while (!data.complete) { > > not "if", but "while".. Do we expect entering from somewhere except nbd_server_tls_handshake? > > if not, probably safer construction would be > > if (!data.complete) { > qemu_coroutine_yield(); > assert(data.complete); > } > > - to avoid hiding unexpected coroutine switching bugs TLS handshake is early enough in the NBD connection that there should not be any parallel I/O yet (we can't switch to parallel outstanding transactions until after successful NBD_OPT_GO), so I like your idea of asserting that the coroutine is entered at most once. v5 coming up
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h index dfa02f77ee4..91895106a95 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/client.c b/nbd/client.c index 29ffc609a4b..c7141d7a098 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 +637,19 @@ 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); + 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 3247c1d618a..589a748cfe6 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/server.c b/nbd/server.c index c3484cc1ebc..ea13cf0e766 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -748,6 +748,23 @@ 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. */ @@ -756,7 +773,7 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client, { QIOChannel *ioc; QIOChannelTLS *tioc; - struct NBDTLSHandshakeData data = { 0 }; + struct NBDTLSServerHandshakeData data = { 0 }; assert(client->opt == NBD_OPT_STARTTLS); @@ -777,17 +794,17 @@ 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); + while (!data.complete) { + qemu_coroutine_yield(); } - g_main_loop_unref(data.loop); + if (data.error) { object_unref(OBJECT(tioc)); error_propagate(errp, data.error);