Add multi-conn option to the NBD client. This commit just adds the
option, it is not functional.
Setting this to a value > 1 permits multiple connections to the NBD
server; a typical value might be 4. The default is 1, meaning only a
single connection is made. If the NBD server does not advertise that
it is safe for multi-conn then this setting is forced to 1.
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
block/nbd.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/block/nbd.c b/block/nbd.c
index bf2894ad5c..5ffae0b798 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -49,6 +49,7 @@
#define EN_OPTSTR ":exportname="
#define MAX_NBD_REQUESTS 16
+#define MAX_MULTI_CONN 16
#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ (uint64_t)(intptr_t)(bs))
#define INDEX_TO_HANDLE(bs, index) ((index) ^ (uint64_t)(intptr_t)(bs))
@@ -98,6 +99,7 @@ typedef struct BDRVNBDState {
/* Connection parameters */
uint32_t reconnect_delay;
uint32_t open_timeout;
+ uint32_t multi_conn;
SocketAddress *saddr;
char *export;
char *tlscredsid;
@@ -1803,6 +1805,15 @@ static QemuOptsList nbd_runtime_opts = {
"attempts until successful or until @open-timeout seconds "
"have elapsed. Default 0",
},
+ {
+ .name = "multi-conn",
+ .type = QEMU_OPT_NUMBER,
+ .help = "If > 1 permit up to this number of connections to the "
+ "server. The server must also advertise multi-conn "
+ "support. If <= 1, only a single connection is made "
+ "to the server even if the server advertises multi-conn. "
+ "Default 1",
+ },
{ /* end of list */ }
},
};
@@ -1858,6 +1869,10 @@ static int nbd_process_options(BlockDriverState *bs, QDict *options,
s->reconnect_delay = qemu_opt_get_number(opts, "reconnect-delay", 0);
s->open_timeout = qemu_opt_get_number(opts, "open-timeout", 0);
+ s->multi_conn = qemu_opt_get_number(opts, "multi-conn", 1);
+ if (s->multi_conn > MAX_MULTI_CONN) {
+ s->multi_conn = MAX_MULTI_CONN;
+ }
ret = 0;
@@ -1912,6 +1927,15 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
nbd_client_connection_enable_retry(s->conn);
+ /*
+ * We set s->multi_conn in nbd_process_options above, but now that
+ * we have connected if the server doesn't advertise that it is
+ * safe for multi-conn, force it to 1.
+ */
+ if (!(s->info.flags & NBD_FLAG_CAN_MULTI_CONN)) {
+ s->multi_conn = 1;
+ }
+
return 0;
fail:
--
2.39.2On Thu, Mar 09, 2023 at 11:39:43AM +0000, Richard W.M. Jones wrote:
> Add multi-conn option to the NBD client. This commit just adds the
> option, it is not functional.
Maybe add the phrase "until later in this patch series" ?
>
> Setting this to a value > 1 permits multiple connections to the NBD
> server; a typical value might be 4. The default is 1, meaning only a
> single connection is made. If the NBD server does not advertise that
> it is safe for multi-conn then this setting is forced to 1.
>
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> ---
> block/nbd.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/block/nbd.c b/block/nbd.c
> index bf2894ad5c..5ffae0b798 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -49,6 +49,7 @@
>
> #define EN_OPTSTR ":exportname="
> #define MAX_NBD_REQUESTS 16
> +#define MAX_MULTI_CONN 16
>
> #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ (uint64_t)(intptr_t)(bs))
> #define INDEX_TO_HANDLE(bs, index) ((index) ^ (uint64_t)(intptr_t)(bs))
> @@ -98,6 +99,7 @@ typedef struct BDRVNBDState {
> /* Connection parameters */
> uint32_t reconnect_delay;
> uint32_t open_timeout;
> + uint32_t multi_conn;
> SocketAddress *saddr;
> char *export;
> char *tlscredsid;
> @@ -1803,6 +1805,15 @@ static QemuOptsList nbd_runtime_opts = {
> "attempts until successful or until @open-timeout seconds "
> "have elapsed. Default 0",
> },
> + {
> + .name = "multi-conn",
> + .type = QEMU_OPT_NUMBER,
> + .help = "If > 1 permit up to this number of connections to the "
> + "server. The server must also advertise multi-conn "
> + "support. If <= 1, only a single connection is made "
> + "to the server even if the server advertises multi-conn. "
> + "Default 1",
> + },
> { /* end of list */ }
> },
> };
> @@ -1858,6 +1869,10 @@ static int nbd_process_options(BlockDriverState *bs, QDict *options,
>
> s->reconnect_delay = qemu_opt_get_number(opts, "reconnect-delay", 0);
> s->open_timeout = qemu_opt_get_number(opts, "open-timeout", 0);
> + s->multi_conn = qemu_opt_get_number(opts, "multi-conn", 1);
> + if (s->multi_conn > MAX_MULTI_CONN) {
> + s->multi_conn = MAX_MULTI_CONN;
> + }
This silently ignores out-of-range values (negative, greater than 16)
and treats 0 as a synonym for 1. The latter I'm okay with, the former
I wonder if we should instead raise an error that the user is
requesting something we can't honor, instead of silently bounding it.
>
> ret = 0;
>
> @@ -1912,6 +1927,15 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
>
> nbd_client_connection_enable_retry(s->conn);
>
> + /*
> + * We set s->multi_conn in nbd_process_options above, but now that
> + * we have connected if the server doesn't advertise that it is
s/connected/connected,/
> + * safe for multi-conn, force it to 1.
> + */
> + if (!(s->info.flags & NBD_FLAG_CAN_MULTI_CONN)) {
> + s->multi_conn = 1;
> + }
> +
> return 0;
Is there an intended QAPI counterpart for this command? We'll need
that if it is to be set during the command line of
qemu-storage-daemon.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
On Fri, Mar 10, 2023 at 04:17:17PM -0600, Eric Blake wrote:
> On Thu, Mar 09, 2023 at 11:39:43AM +0000, Richard W.M. Jones wrote:
> > + * safe for multi-conn, force it to 1.
> > + */
> > + if (!(s->info.flags & NBD_FLAG_CAN_MULTI_CONN)) {
> > + s->multi_conn = 1;
> > + }
> > +
> > return 0;
>
> Is there an intended QAPI counterpart for this command? We'll need
> that if it is to be set during the command line of
> qemu-storage-daemon.
Does it just need to be added to qapi/block-core.json?
It's a shame we can't add the API in one place and have everything
generated from there. Like some kind of 'generator' ...
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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