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nbd: convert to use qio_channel_yield

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In the client, read the reply headers from a coroutine, switching the
read side between the "read header" coroutine and the I/O coroutine that
reads the body of the reply.

In the server, if the server can read more requests it will create a new
"read request" coroutine as soon as a request has been read.  Otherwise,
the new coroutine is created in nbd_request_put.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20170213135235.12274-8-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-02-13 14:52:24 +01:00 committed by Stefan Hajnoczi
parent c4c497d27f
commit ff82911cd3
5 changed files with 85 additions and 143 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

121
block/nbd-client.c
View File

@ -33,8 +33,9 @@
#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs)) #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))
#define INDEX_TO_HANDLE(bs, index) ((index) ^ ((uint64_t)(intptr_t)bs)) #define INDEX_TO_HANDLE(bs, index) ((index) ^ ((uint64_t)(intptr_t)bs))
static void nbd_recv_coroutines_enter_all(NBDClientSession *s) static void nbd_recv_coroutines_enter_all(BlockDriverState *bs)
{ {
NBDClientSession *s = nbd_get_client_session(bs);
int i; int i;
for (i = 0; i < MAX_NBD_REQUESTS; i++) { for (i = 0; i < MAX_NBD_REQUESTS; i++) {
@ -42,6 +43,7 @@ static void nbd_recv_coroutines_enter_all(NBDClientSession *s)
qemu_coroutine_enter(s->recv_coroutine[i]); qemu_coroutine_enter(s->recv_coroutine[i]);
} }
} }
BDRV_POLL_WHILE(bs, s->read_reply_co);
} }
static void nbd_teardown_connection(BlockDriverState *bs) static void nbd_teardown_connection(BlockDriverState *bs)
@ -56,7 +58,7 @@ static void nbd_teardown_connection(BlockDriverState *bs)
qio_channel_shutdown(client->ioc, qio_channel_shutdown(client->ioc,
QIO_CHANNEL_SHUTDOWN_BOTH, QIO_CHANNEL_SHUTDOWN_BOTH,
NULL); NULL);
nbd_recv_coroutines_enter_all(client); nbd_recv_coroutines_enter_all(bs);
nbd_client_detach_aio_context(bs); nbd_client_detach_aio_context(bs);
object_unref(OBJECT(client->sioc)); object_unref(OBJECT(client->sioc));
@ -65,54 +67,43 @@ static void nbd_teardown_connection(BlockDriverState *bs)
client->ioc = NULL; client->ioc = NULL;
} }
static void nbd_reply_ready(void *opaque) static coroutine_fn void nbd_read_reply_entry(void *opaque)
{ {
BlockDriverState *bs = opaque; NBDClientSession *s = opaque;
NBDClientSession *s = nbd_get_client_session(bs);
uint64_t i; uint64_t i;
int ret; int ret;
if (!s->ioc) { /* Already closed */ for (;;) {
return; assert(s->reply.handle == 0);
}
if (s->reply.handle == 0) {
/* No reply already in flight. Fetch a header. It is possible
* that another thread has done the same thing in parallel, so
* the socket is not readable anymore.
*/
ret = nbd_receive_reply(s->ioc, &s->reply); ret = nbd_receive_reply(s->ioc, &s->reply);
if (ret == -EAGAIN) {
return;
}
if (ret < 0) { if (ret < 0) {
s->reply.handle = 0; break;
goto fail;
} }
/* There's no need for a mutex on the receive side, because the
* handler acts as a synchronization point and ensures that only
* one coroutine is called until the reply finishes.
*/
i = HANDLE_TO_INDEX(s, s->reply.handle);
if (i >= MAX_NBD_REQUESTS || !s->recv_coroutine[i]) {
break;
}
/* We're woken up by the recv_coroutine itself. Note that there
* is no race between yielding and reentering read_reply_co. This
* is because:
*
* - if recv_coroutine[i] runs on the same AioContext, it is only
* entered after we yield
*
* - if recv_coroutine[i] runs on a different AioContext, reentering
* read_reply_co happens through a bottom half, which can only
* run after we yield.
*/
aio_co_wake(s->recv_coroutine[i]);
qemu_coroutine_yield();
} }
s->read_reply_co = NULL;
/* There's no need for a mutex on the receive side, because the
* handler acts as a synchronization point and ensures that only
* one coroutine is called until the reply finishes. */
i = HANDLE_TO_INDEX(s, s->reply.handle);
if (i >= MAX_NBD_REQUESTS) {
goto fail;
}
if (s->recv_coroutine[i]) {
qemu_coroutine_enter(s->recv_coroutine[i]);
return;
}
fail:
nbd_teardown_connection(bs);
}
static void nbd_restart_write(void *opaque)
{
BlockDriverState *bs = opaque;
qemu_coroutine_enter(nbd_get_client_session(bs)->send_coroutine);
} }
static int nbd_co_send_request(BlockDriverState *bs, static int nbd_co_send_request(BlockDriverState *bs,
@ -120,7 +111,6 @@ static int nbd_co_send_request(BlockDriverState *bs,
QEMUIOVector *qiov) QEMUIOVector *qiov)
{ {
NBDClientSession *s = nbd_get_client_session(bs); NBDClientSession *s = nbd_get_client_session(bs);
AioContext *aio_context;
int rc, ret, i; int rc, ret, i;
qemu_co_mutex_lock(&s->send_mutex); qemu_co_mutex_lock(&s->send_mutex);
@ -141,11 +131,6 @@ static int nbd_co_send_request(BlockDriverState *bs,
return -EPIPE; return -EPIPE;
} }
s->send_coroutine = qemu_coroutine_self();
aio_context = bdrv_get_aio_context(bs);
aio_set_fd_handler(aio_context, s->sioc->fd, false,
nbd_reply_ready, nbd_restart_write, NULL, bs);
if (qiov) { if (qiov) {
qio_channel_set_cork(s->ioc, true); qio_channel_set_cork(s->ioc, true);
rc = nbd_send_request(s->ioc, request); rc = nbd_send_request(s->ioc, request);
@ -160,9 +145,6 @@ static int nbd_co_send_request(BlockDriverState *bs,
} else { } else {
rc = nbd_send_request(s->ioc, request); rc = nbd_send_request(s->ioc, request);
} }
aio_set_fd_handler(aio_context, s->sioc->fd, false,
nbd_reply_ready, NULL, NULL, bs);
s->send_coroutine = NULL;
qemu_co_mutex_unlock(&s->send_mutex); qemu_co_mutex_unlock(&s->send_mutex);
return rc; return rc;
} }
@ -174,8 +156,7 @@ static void nbd_co_receive_reply(NBDClientSession *s,
{ {
int ret; int ret;
/* Wait until we're woken up by the read handler. TODO: perhaps /* Wait until we're woken up by nbd_read_reply_entry. */
* peek at the next reply and avoid yielding if it's ours? */
qemu_coroutine_yield(); qemu_coroutine_yield();
*reply = s->reply; *reply = s->reply;
if (reply->handle != request->handle || if (reply->handle != request->handle ||
@ -209,13 +190,19 @@ static void nbd_coroutine_start(NBDClientSession *s,
/* s->recv_coroutine[i] is set as soon as we get the send_lock. */ /* s->recv_coroutine[i] is set as soon as we get the send_lock. */
} }
static void nbd_coroutine_end(NBDClientSession *s, static void nbd_coroutine_end(BlockDriverState *bs,
NBDRequest *request) NBDRequest *request)
{ {
NBDClientSession *s = nbd_get_client_session(bs);
int i = HANDLE_TO_INDEX(s, request->handle); int i = HANDLE_TO_INDEX(s, request->handle);
s->recv_coroutine[i] = NULL; s->recv_coroutine[i] = NULL;
if (s->in_flight-- == MAX_NBD_REQUESTS) { s->in_flight--;
qemu_co_queue_next(&s->free_sema); qemu_co_queue_next(&s->free_sema);
/* Kick the read_reply_co to get the next reply. */
if (s->read_reply_co) {
aio_co_wake(s->read_reply_co);
} }
} }
@ -241,7 +228,7 @@ int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset,
} else { } else {
nbd_co_receive_reply(client, &request, &reply, qiov); nbd_co_receive_reply(client, &request, &reply, qiov);
} }
nbd_coroutine_end(client, &request); nbd_coroutine_end(bs, &request);
return -reply.error; return -reply.error;
} }
@ -271,7 +258,7 @@ int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t offset,
} else { } else {
nbd_co_receive_reply(client, &request, &reply, NULL); nbd_co_receive_reply(client, &request, &reply, NULL);
} }
nbd_coroutine_end(client, &request); nbd_coroutine_end(bs, &request);
return -reply.error; return -reply.error;
} }
@ -306,7 +293,7 @@ int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
} else { } else {
nbd_co_receive_reply(client, &request, &reply, NULL); nbd_co_receive_reply(client, &request, &reply, NULL);
} }
nbd_coroutine_end(client, &request); nbd_coroutine_end(bs, &request);
return -reply.error; return -reply.error;
} }
@ -331,7 +318,7 @@ int nbd_client_co_flush(BlockDriverState *bs)
} else { } else {
nbd_co_receive_reply(client, &request, &reply, NULL); nbd_co_receive_reply(client, &request, &reply, NULL);
} }
nbd_coroutine_end(client, &request); nbd_coroutine_end(bs, &request);
return -reply.error; return -reply.error;
} }
@ -357,23 +344,23 @@ int nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int count)
} else { } else {
nbd_co_receive_reply(client, &request, &reply, NULL); nbd_co_receive_reply(client, &request, &reply, NULL);
} }
nbd_coroutine_end(client, &request); nbd_coroutine_end(bs, &request);
return -reply.error; return -reply.error;
} }
void nbd_client_detach_aio_context(BlockDriverState *bs) void nbd_client_detach_aio_context(BlockDriverState *bs)
{ {
aio_set_fd_handler(bdrv_get_aio_context(bs), NBDClientSession *client = nbd_get_client_session(bs);
nbd_get_client_session(bs)->sioc->fd, qio_channel_detach_aio_context(QIO_CHANNEL(client->sioc));
false, NULL, NULL, NULL, NULL);
} }
void nbd_client_attach_aio_context(BlockDriverState *bs, void nbd_client_attach_aio_context(BlockDriverState *bs,
AioContext *new_context) AioContext *new_context)
{ {
aio_set_fd_handler(new_context, nbd_get_client_session(bs)->sioc->fd, NBDClientSession *client = nbd_get_client_session(bs);
false, nbd_reply_ready, NULL, NULL, bs); qio_channel_attach_aio_context(QIO_CHANNEL(client->sioc), new_context);
aio_co_schedule(new_context, client->read_reply_co);
} }
void nbd_client_close(BlockDriverState *bs) void nbd_client_close(BlockDriverState *bs)
@ -434,7 +421,7 @@ int nbd_client_init(BlockDriverState *bs,
/* Now that we're connected, set the socket to be non-blocking and /* Now that we're connected, set the socket to be non-blocking and
* kick the reply mechanism. */ * kick the reply mechanism. */
qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL); qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
client->read_reply_co = qemu_coroutine_create(nbd_read_reply_entry, client);
nbd_client_attach_aio_context(bs, bdrv_get_aio_context(bs)); nbd_client_attach_aio_context(bs, bdrv_get_aio_context(bs));
logout("Established connection with NBD server\n"); logout("Established connection with NBD server\n");

2
block/nbd-client.h
View File

@ -25,7 +25,7 @@ typedef struct NBDClientSession {
CoMutex send_mutex; CoMutex send_mutex;
CoQueue free_sema; CoQueue free_sema;
Coroutine *send_coroutine; Coroutine *read_reply_co;
int in_flight; int in_flight;
Coroutine *recv_coroutine[MAX_NBD_REQUESTS]; Coroutine *recv_coroutine[MAX_NBD_REQUESTS];

2
nbd/client.c
View File

@ -778,7 +778,7 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply)
ssize_t ret; ssize_t ret;
ret = read_sync(ioc, buf, sizeof(buf)); ret = read_sync(ioc, buf, sizeof(buf));
if (ret < 0) { if (ret <= 0) {
return ret; return ret;
} }

9
nbd/common.c
View File

@ -43,14 +43,7 @@ ssize_t nbd_wr_syncv(QIOChannel *ioc,
} }
if (len == QIO_CHANNEL_ERR_BLOCK) { if (len == QIO_CHANNEL_ERR_BLOCK) {
if (qemu_in_coroutine()) { if (qemu_in_coroutine()) {
/* XXX figure out if we can create a variant on qio_channel_yield(ioc, do_read ? G_IO_IN : G_IO_OUT);
* qio_channel_yield() that works with AIO contexts
* and consider using that in this branch */
qemu_coroutine_yield();
} else if (done) {
/* XXX this is needed by nbd_reply_ready. */
qio_channel_wait(ioc,
do_read ? G_IO_IN : G_IO_OUT);
} else { } else {
return -EAGAIN; return -EAGAIN;
} }

94
nbd/server.c
View File

@ -95,8 +95,6 @@ struct NBDClient {
CoMutex send_lock; CoMutex send_lock;
Coroutine *send_coroutine; Coroutine *send_coroutine;
bool can_read;
QTAILQ_ENTRY(NBDClient) next; QTAILQ_ENTRY(NBDClient) next;
int nb_requests; int nb_requests;
bool closing; bool closing;
@ -104,9 +102,7 @@ struct NBDClient {
/* That's all folks */ /* That's all folks */
static void nbd_set_handlers(NBDClient *client); static void nbd_client_receive_next_request(NBDClient *client);
static void nbd_unset_handlers(NBDClient *client);
static void nbd_update_can_read(NBDClient *client);
static gboolean nbd_negotiate_continue(QIOChannel *ioc, static gboolean nbd_negotiate_continue(QIOChannel *ioc,
GIOCondition condition, GIOCondition condition,
@ -785,7 +781,7 @@ void nbd_client_put(NBDClient *client)
*/ */
assert(client->closing); assert(client->closing);
nbd_unset_handlers(client); qio_channel_detach_aio_context(client->ioc);
object_unref(OBJECT(client->sioc)); object_unref(OBJECT(client->sioc));
object_unref(OBJECT(client->ioc)); object_unref(OBJECT(client->ioc));
if (client->tlscreds) { if (client->tlscreds) {
@ -826,7 +822,6 @@ static NBDRequestData *nbd_request_get(NBDClient *client)
assert(client->nb_requests <= MAX_NBD_REQUESTS - 1); assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
client->nb_requests++; client->nb_requests++;
nbd_update_can_read(client);
req = g_new0(NBDRequestData, 1); req = g_new0(NBDRequestData, 1);
nbd_client_get(client); nbd_client_get(client);
@ -844,7 +839,8 @@ static void nbd_request_put(NBDRequestData *req)
g_free(req); g_free(req);
client->nb_requests--; client->nb_requests--;
nbd_update_can_read(client); nbd_client_receive_next_request(client);
nbd_client_put(client); nbd_client_put(client);
} }
@ -858,7 +854,13 @@ static void blk_aio_attached(AioContext *ctx, void *opaque)
exp->ctx = ctx; exp->ctx = ctx;
QTAILQ_FOREACH(client, &exp->clients, next) { QTAILQ_FOREACH(client, &exp->clients, next) {
nbd_set_handlers(client); qio_channel_attach_aio_context(client->ioc, ctx);
if (client->recv_coroutine) {
aio_co_schedule(ctx, client->recv_coroutine);
}
if (client->send_coroutine) {
aio_co_schedule(ctx, client->send_coroutine);
}
} }
} }
@ -870,7 +872,7 @@ static void blk_aio_detach(void *opaque)
TRACE("Export %s: Detaching clients from AIO context %p\n", exp->name, exp->ctx); TRACE("Export %s: Detaching clients from AIO context %p\n", exp->name, exp->ctx);
QTAILQ_FOREACH(client, &exp->clients, next) { QTAILQ_FOREACH(client, &exp->clients, next) {
nbd_unset_handlers(client); qio_channel_detach_aio_context(client->ioc);
} }
exp->ctx = NULL; exp->ctx = NULL;
@ -1045,7 +1047,6 @@ static ssize_t nbd_co_send_reply(NBDRequestData *req, NBDReply *reply,
g_assert(qemu_in_coroutine()); g_assert(qemu_in_coroutine());
qemu_co_mutex_lock(&client->send_lock); qemu_co_mutex_lock(&client->send_lock);
client->send_coroutine = qemu_coroutine_self(); client->send_coroutine = qemu_coroutine_self();
nbd_set_handlers(client);
if (!len) { if (!len) {
rc = nbd_send_reply(client->ioc, reply); rc = nbd_send_reply(client->ioc, reply);
@ -1062,7 +1063,6 @@ static ssize_t nbd_co_send_reply(NBDRequestData *req, NBDReply *reply,
} }
client->send_coroutine = NULL; client->send_coroutine = NULL;
nbd_set_handlers(client);
qemu_co_mutex_unlock(&client->send_lock); qemu_co_mutex_unlock(&client->send_lock);
return rc; return rc;
} }
@ -1079,9 +1079,7 @@ static ssize_t nbd_co_receive_request(NBDRequestData *req,
ssize_t rc; ssize_t rc;
g_assert(qemu_in_coroutine()); g_assert(qemu_in_coroutine());
client->recv_coroutine = qemu_coroutine_self(); assert(client->recv_coroutine == qemu_coroutine_self());
nbd_update_can_read(client);
rc = nbd_receive_request(client->ioc, request); rc = nbd_receive_request(client->ioc, request);
if (rc < 0) { if (rc < 0) {
if (rc != -EAGAIN) { if (rc != -EAGAIN) {
@ -1163,23 +1161,25 @@ static ssize_t nbd_co_receive_request(NBDRequestData *req,
out: out:
client->recv_coroutine = NULL; client->recv_coroutine = NULL;
nbd_update_can_read(client); nbd_client_receive_next_request(client);
return rc; return rc;
} }
static void nbd_trip(void *opaque) /* Owns a reference to the NBDClient passed as opaque. */
static coroutine_fn void nbd_trip(void *opaque)
{ {
NBDClient *client = opaque; NBDClient *client = opaque;
NBDExport *exp = client->exp; NBDExport *exp = client->exp;
NBDRequestData *req; NBDRequestData *req;
NBDRequest request; NBDRequest request = { 0 }; /* GCC thinks it can be used uninitialized */
NBDReply reply; NBDReply reply;
ssize_t ret; ssize_t ret;
int flags; int flags;
TRACE("Reading request."); TRACE("Reading request.");
if (client->closing) { if (client->closing) {
nbd_client_put(client);
return; return;
} }
@ -1338,60 +1338,21 @@ static void nbd_trip(void *opaque)
done: done:
nbd_request_put(req); nbd_request_put(req);
nbd_client_put(client);
return; return;
out: out:
nbd_request_put(req); nbd_request_put(req);
client_close(client); client_close(client);
nbd_client_put(client);
} }
static void nbd_read(void *opaque) static void nbd_client_receive_next_request(NBDClient *client)
{ {
NBDClient *client = opaque; if (!client->recv_coroutine && client->nb_requests < MAX_NBD_REQUESTS) {
nbd_client_get(client);
if (client->recv_coroutine) { client->recv_coroutine = qemu_coroutine_create(nbd_trip, client);
qemu_coroutine_enter(client->recv_coroutine); aio_co_schedule(client->exp->ctx, client->recv_coroutine);
} else {
qemu_coroutine_enter(qemu_coroutine_create(nbd_trip, client));
}
}
static void nbd_restart_write(void *opaque)
{
NBDClient *client = opaque;
qemu_coroutine_enter(client->send_coroutine);
}
static void nbd_set_handlers(NBDClient *client)
{
if (client->exp && client->exp->ctx) {
aio_set_fd_handler(client->exp->ctx, client->sioc->fd, true,
client->can_read ? nbd_read : NULL,
client->send_coroutine ? nbd_restart_write : NULL,
NULL, client);
}
}
static void nbd_unset_handlers(NBDClient *client)
{
if (client->exp && client->exp->ctx) {
aio_set_fd_handler(client->exp->ctx, client->sioc->fd, true, NULL,
NULL, NULL, NULL);
}
}
static void nbd_update_can_read(NBDClient *client)
{
bool can_read = client->recv_coroutine ||
client->nb_requests < MAX_NBD_REQUESTS;
if (can_read != client->can_read) {
client->can_read = can_read;
nbd_set_handlers(client);
/* There is no need to invoke aio_notify(), since aio_set_fd_handler()
* in nbd_set_handlers() will have taken care of that */
} }
} }
@ -1409,11 +1370,13 @@ static coroutine_fn void nbd_co_client_start(void *opaque)
goto out; goto out;
} }
qemu_co_mutex_init(&client->send_lock); qemu_co_mutex_init(&client->send_lock);
nbd_set_handlers(client);
if (exp) { if (exp) {
QTAILQ_INSERT_TAIL(&exp->clients, client, next); QTAILQ_INSERT_TAIL(&exp->clients, client, next);
} }
nbd_client_receive_next_request(client);
out: out:
g_free(data); g_free(data);
} }
@ -1439,7 +1402,6 @@ void nbd_client_new(NBDExport *exp,
object_ref(OBJECT(client->sioc)); object_ref(OBJECT(client->sioc));
client->ioc = QIO_CHANNEL(sioc); client->ioc = QIO_CHANNEL(sioc);
object_ref(OBJECT(client->ioc)); object_ref(OBJECT(client->ioc));
client->can_read = true;
client->close = close_fn; client->close = close_fn;
data->client = client; data->client = client;