From patchwork Thu Sep 5 21:15:14 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 11133947 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 37AFC14B4 for ; Thu, 5 Sep 2019 21:17:13 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0A198206CD for ; Thu, 5 Sep 2019 21:17:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0A198206CD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:49924 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i5z7v-0003Lf-IN for patchwork-qemu-devel@patchwork.kernel.org; Thu, 05 Sep 2019 17:17:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36342) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i5z6X-0001i2-Vf for qemu-devel@nongnu.org; Thu, 05 Sep 2019 17:15:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i5z6W-0002CO-IF for qemu-devel@nongnu.org; Thu, 05 Sep 2019 17:15:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36688) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i5z6T-0002A0-D6; Thu, 05 Sep 2019 17:15:41 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BADC73064FB0; Thu, 5 Sep 2019 21:15:40 +0000 (UTC) Received: from blue.redhat.com (ovpn-116-234.phx2.redhat.com [10.3.116.234]) by smtp.corp.redhat.com (Postfix) with ESMTP id CA9F36060D; Thu, 5 Sep 2019 21:15:36 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Date: Thu, 5 Sep 2019 16:15:14 -0500 Message-Id: <20190905211522.2824-2-eblake@redhat.com> In-Reply-To: <20190905211522.2824-1-eblake@redhat.com> References: <20190905211522.2824-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Thu, 05 Sep 2019 21:15:40 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL v2 1/9] nbd: Advertise multi-conn for shared read-only connections X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , John Snow , "open list:Block layer core" , Max Reitz Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" The NBD specification defines NBD_FLAG_CAN_MULTI_CONN, which can be advertised when the server promises cache consistency between simultaneous clients (basically, rules that determine what FUA and flush from one client are able to guarantee for reads from another client). When we don't permit simultaneous clients (such as qemu-nbd without -e), the bit makes no sense; and for writable images, we probably have a lot more work before we can declare that actions from one client are cache-consistent with actions from another. But for read-only images, where flush isn't changing any data, we might as well advertise multi-conn support. What's more, advertisement of the bit makes it easier for clients to determine if 'qemu-nbd -e' was in use, where a second connection will succeed rather than hang until the first client goes away. This patch affects qemu as server in advertising the bit. We may want to consider patches to qemu as client to attempt parallel connections for higher throughput by spreading the load over those connections when a server advertises multi-conn, but for now sticking to one connection per nbd:// BDS is okay. See also: https://bugzilla.redhat.com/1708300 Signed-off-by: Eric Blake Message-Id: <20190815185024.7010-1-eblake@redhat.com> [eblake: tweak blockdev-nbd.c to not request shared when writable, fix iotest 233] Reviewed-by: John Snow --- docs/interop/nbd.txt | 1 + include/block/nbd.h | 2 +- blockdev-nbd.c | 2 +- nbd/server.c | 4 +++- qemu-nbd.c | 2 +- tests/qemu-iotests/223.out | 2 +- 6 files changed, 8 insertions(+), 5 deletions(-) diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt index fc64473e02b2..6dfec7f47647 100644 --- a/docs/interop/nbd.txt +++ b/docs/interop/nbd.txt @@ -53,3 +53,4 @@ the operation of that feature. * 2.12: NBD_CMD_BLOCK_STATUS for "base:allocation" * 3.0: NBD_OPT_STARTTLS with TLS Pre-Shared Keys (PSK), NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE +* 4.2: NBD_FLAG_CAN_MULTI_CONN for sharable read-only exports diff --git a/include/block/nbd.h b/include/block/nbd.h index 7b36d672f046..991fd52a5134 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -326,7 +326,7 @@ typedef struct NBDClient NBDClient; NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, uint64_t size, const char *name, const char *desc, - const char *bitmap, uint16_t nbdflags, + const char *bitmap, uint16_t nbdflags, bool shared, void (*close)(NBDExport *), bool writethrough, BlockBackend *on_eject_blk, Error **errp); void nbd_export_close(NBDExport *exp); diff --git a/blockdev-nbd.c b/blockdev-nbd.c index c621686131fd..1fcfdb0997c6 100644 --- a/blockdev-nbd.c +++ b/blockdev-nbd.c @@ -188,7 +188,7 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name, } exp = nbd_export_new(bs, 0, len, name, NULL, bitmap, - writable ? 0 : NBD_FLAG_READ_ONLY, + writable ? 0 : NBD_FLAG_READ_ONLY, !writable, NULL, false, on_eject_blk, errp); if (!exp) { return; diff --git a/nbd/server.c b/nbd/server.c index f55ccf8edfde..0fb41c6c50ea 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -1461,7 +1461,7 @@ static void nbd_eject_notifier(Notifier *n, void *data) NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, uint64_t size, const char *name, const char *desc, - const char *bitmap, uint16_t nbdflags, + const char *bitmap, uint16_t nbdflags, bool shared, void (*close)(NBDExport *), bool writethrough, BlockBackend *on_eject_blk, Error **errp) { @@ -1487,6 +1487,8 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, perm = BLK_PERM_CONSISTENT_READ; if ((nbdflags & NBD_FLAG_READ_ONLY) == 0) { perm |= BLK_PERM_WRITE; + } else if (shared) { + nbdflags |= NBD_FLAG_CAN_MULTI_CONN; } blk = blk_new(bdrv_get_aio_context(bs), perm, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED | diff --git a/qemu-nbd.c b/qemu-nbd.c index 83b6c32d73aa..2403ef3d0f9f 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -1173,7 +1173,7 @@ int main(int argc, char **argv) } export = nbd_export_new(bs, dev_offset, fd_size, export_name, - export_description, bitmap, nbdflags, + export_description, bitmap, nbdflags, shared > 1, nbd_export_closed, writethrough, NULL, &error_fatal); diff --git a/tests/qemu-iotests/223.out b/tests/qemu-iotests/223.out index d5201b2356a3..2bca28ae72f9 100644 --- a/tests/qemu-iotests/223.out +++ b/tests/qemu-iotests/223.out @@ -40,7 +40,7 @@ exports available: 0 exports available: 2 export: 'n' size: 4194304 - flags: 0x4ef ( readonly flush fua trim zeroes df cache ) + flags: 0x5ef ( readonly flush fua trim zeroes df multi cache ) min block: 1 opt block: 4096 max block: 33554432