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Fri, 05 Feb 2021 13:57:16 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-504-jvj9eX1xNumetmbsEntL3A-1; Fri, 05 Feb 2021 13:57:09 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6FAD5801962; Fri, 5 Feb 2021 18:57:08 +0000 (UTC) Received: from blue.redhat.com (ovpn-112-253.phx2.redhat.com [10.3.112.253]) by smtp.corp.redhat.com (Postfix) with ESMTP id 144C960BF1; Fri, 5 Feb 2021 18:57:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612551431; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=cC4lg8z4hEl4vnT21LmoiUYIEZbsMxVWyOmYhUg91d0=; b=PAGHkWU/irJd5Pqmf4h/z1ZNAZhJ791mdctaZGrbxW1hL+W43RvHlQGRRqw9QLpwKKiEaE Astg34W7h+xLcuJ3Ec880LmwzbDi13lJDUDJZGxnkBqGUIHtflwVVewpSrwHbBn0FU8KS2 czrTQle6w3mwqL1Hh7JaIDyEp22JRg0= X-MC-Unique: jvj9eX1xNumetmbsEntL3A-1 From: Eric Blake To: qemu-devel@nongnu.org Subject: [PATCH v2] qemu-nbd: Use SOMAXCONN for socket listen() backlog Date: Fri, 5 Feb 2021 12:57:05 -0600 Message-Id: <20210205185705.1502071-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=63.128.21.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.352, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: berrange@redhat.com, rjones@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" Our default of a backlog of 1 connection is rather puny, particularly for scenarios where we expect multiple listeners to connect (such as qemu-nbd -e X). This is especially important for Unix sockets, as a definite benefit to clients: at least on Linux, a client trying to connect to a Unix socket with a backlog gets an EAGAIN failure with no way to poll() for when the backlog is no longer present short of sleeping an arbitrary amount of time before retrying. See https://bugzilla.redhat.com/1925045 for a demonstration of where our low backlog prevents libnbd from connecting as many parallel clients as it wants. Reported-by: Richard W.M. Jones Signed-off-by: Eric Blake Tested-by: Richard W.M. Jones --- v2: target the correct API used by qemu-nbd, rather than an unrelated legacy wrapper [Dan] qemu-nbd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/qemu-nbd.c b/qemu-nbd.c index 608c63e82a25..cd20ee73be19 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -965,7 +965,8 @@ int main(int argc, char **argv) server =3D qio_net_listener_new(); if (socket_activation =3D=3D 0) { saddr =3D nbd_build_socket_address(sockpath, bindto, port); - if (qio_net_listener_open_sync(server, saddr, 1, &local_err) < 0) { + if (qio_net_listener_open_sync(server, saddr, SOMAXCONN, + &local_err) < 0) { object_unref(OBJECT(server)); error_report_err(local_err); exit(EXIT_FAILURE); --=20 2.30.0