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 <rjo...@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: -- 2.39.2