From patchwork Mon Sep 14 10:31:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= X-Patchwork-Id: 1363502 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=fdVUyTYk; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 4BqjP14N52z9sTK for ; Mon, 14 Sep 2020 20:32:53 +1000 (AEST) Received: from localhost ([::1]:46934 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kHln1-0001vB-Jh for incoming@patchwork.ozlabs.org; Mon, 14 Sep 2020 06:32:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36362) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kHlll-0001ES-Bd for qemu-devel@nongnu.org; Mon, 14 Sep 2020 06:31:33 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:40630) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kHlli-0001XY-Bp for qemu-devel@nongnu.org; Mon, 14 Sep 2020 06:31:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600079484; 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=Fle0bSrXP9esjMoswH7JR0vVF4fePVd2FffhvZ0/LD0=; b=fdVUyTYkJib7qk/NygLOvufatdh/FAuhRuEnz51ageTsA0GY+HCNa8RmG30uFOLCjkBJ5N VHAJ0fEWRuXryp7tw5ft9hwicY/ESoH6VZKeYqIOBHclXSNeQ9SpbStBxvT7IQ6w7sL+wP 7KQSPOB3a+IUQxhADyZf3qVGX3tnV7Y= 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-190-CKjzUam8NZOqznT-nRBBIg-1; Mon, 14 Sep 2020 06:31:20 -0400 X-MC-Unique: CKjzUam8NZOqznT-nRBBIg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EC7061008567 for ; Mon, 14 Sep 2020 10:31:19 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-114-99.ams2.redhat.com [10.36.114.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 38001100EBC0; Mon, 14 Sep 2020 10:31:10 +0000 (UTC) From: =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= To: qemu-devel@nongnu.org Subject: [PATCH] char: fix logging when chardev write fails Date: Mon, 14 Sep 2020 11:31:09 +0100 Message-Id: <20200914103109.1327875-1-berrange@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=63.128.21.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/14 02:55:39 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -38 X-Spam_score: -3.9 X-Spam_bar: --- X-Spam_report: (-3.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.792, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=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: Paolo Bonzini , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , =?utf-8?q?Marc?= =?utf-8?q?-Andr=C3=A9_Lureau?= Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The qemu_chr_write_buffer() method sends data to the chardev backend for writing, and then also writes to the log file. In case the chardev backend only writes part of the data buffer, we need to make sure we only log the same subset. qemu_chr_write_buffer() will be invoked again later to write the rest of the buffer. In the case the chardev backend returns an error though, no further attempts to likely to be made to write the data. We must therefore write the entire buffer to the log immediately. An example where this is important is with the socket backend. This will return -1 for all writes if no client is currently connected. We still wish to write data to the log file when no client is present though. This used to work because the chardev would return "len" to pretend it had written all data when no client is connected, but this changed to return an error in commit 271094474b65de1ad7aaf729938de3d9b9d0d36f Author: Dima Stepanov Date: Thu May 28 12:11:18 2020 +0300 char-socket: return -1 in case of disconnect during tcp_chr_write and this broke the logging, resulting in all data being discarded when no client is present. Fixes: https://bugs.launchpad.net/qemu/+bug/1893691 Signed-off-by: Daniel P. Berrangé Reviewed-by: Marc-André Lureau --- chardev/char.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/chardev/char.c b/chardev/char.c index 77e7ec814f..e30cd025f5 100644 --- a/chardev/char.c +++ b/chardev/char.c @@ -138,7 +138,20 @@ static int qemu_chr_write_buffer(Chardev *s, } } if (*offset > 0) { + /* + * If some data was written by backend, we should + * only log what was actually written. This method + * may be invoked again to write the remaining + * method, thus we'll log the remainder at that time. + */ qemu_chr_write_log(s, buf, *offset); + } else if (res < 0) { + /* + * If a fatal error was reported by the backend, + * assume this method won't be invoked again with + * this buffer, so log it all right away. + */ + qemu_chr_write_log(s, buf, len); } qemu_mutex_unlock(&s->chr_write_lock);