From nobody Fri Oct 3 11:31:31 2025 Delivered-To: importer@patchew.org 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; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1579810357; cv=none; d=zohomail.com; s=zohoarc; b=JQuUgLva7Ew5yM/tHGlIAK/xJjQG7YtBN1MzbnJ4kZxNaGxZPJ+as3W9IVQ//SSDFcKfJM8sWdudj63aP52Ew7RuDxuCA8Roecx2bSW7lve57Ld2R84KVhu2RqEibc2bt3UVbsKQAhayNPFXWPM3eDhonkhb1iT5lwpk9hDiJKE= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1579810357; h=Content-Type:Content-Transfer-Encoding:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=aLZjkQwegSYpdgRATUG0pRrWmWYP1vk2vwHAPH7tVEg=; b=EYjfEgiTtykHosFWAZGUeXzN3iIMypQmM4rICgddHVlVgGOR+g6L7/lIE63UOnKOtfVvKpp/kiy5utMlBOV27YVQA+8N+KtluJL7Bzi3E+KP+WX3y70oKMWo7OJtchKob/cCArHIC8pC3qd9BUbw1sa0HzRSmpogsPyfuQ7059E= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1579810357299108.36099655165765; Thu, 23 Jan 2020 12:12:37 -0800 (PST) Received: from localhost ([::1]:33132 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iuiqC-0002ai-02 for importer@patchew.org; Thu, 23 Jan 2020 15:12:36 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:42588) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iufex-00068V-KG for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:48:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iufew-000086-4v for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:48:47 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:41798 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iufew-00007S-1c for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:48:46 -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-274-iPyKI7abPDqkggplkbi3bQ-1; Thu, 23 Jan 2020 11:48:43 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DC1E3100550E for ; Thu, 23 Jan 2020 16:48:42 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-116-110.ams2.redhat.com [10.36.116.110]) by smtp.corp.redhat.com (Postfix) with ESMTP id 371BF28990; Thu, 23 Jan 2020 16:48:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579798125; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aLZjkQwegSYpdgRATUG0pRrWmWYP1vk2vwHAPH7tVEg=; b=hBAyivFlisgVysK50KvZ+5n2CTJIjyyCx0lpzLAX6i342ea/qjv82o7iPFBa69D5m2BesB +u+i9g+rrp+2kXZyWDkaow0RxVgzNvk0Ewrprd2fJ4iXyJXf5K8SbrWDfZhiT5iglwgRus 2PI2Nybp34K4HsIplmbF9NhD6+iv3M4= From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com Subject: [PULL 097/108] virtiofsd: Fix data corruption with O_APPEND write in writeback mode Date: Thu, 23 Jan 2020 16:46:19 +0000 Message-Id: <20200123164630.91498-98-dgilbert@redhat.com> In-Reply-To: <20200123164630.91498-1-dgilbert@redhat.com> References: <20200123164630.91498-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: iPyKI7abPDqkggplkbi3bQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: Misono Tomohiro When writeback mode is enabled (-o writeback), O_APPEND handling is done in kernel. Therefore virtiofsd clears O_APPEND flag when open. Otherwise O_APPEND flag takes precedence over pwrite() and write data may corrupt. Currently clearing O_APPEND flag is done in lo_open(), but we also need the same operation in lo_create(). So, factor out the flag update operation in lo_open() to update_open_flags() and call it in both lo_open() and lo_create(). This fixes the failure of xfstest generic/069 in writeback mode (which tests O_APPEND write data integrity). Signed-off-by: Misono Tomohiro Reviewed-by: Daniel P. Berrang=C3=A9 Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_ll.c | 66 ++++++++++++++++---------------- 1 file changed, 33 insertions(+), 33 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough= _ll.c index 948cb19c77..4c61ac5065 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -1692,6 +1692,37 @@ static void lo_releasedir(fuse_req_t req, fuse_ino_t= ino, fuse_reply_err(req, 0); } =20 +static void update_open_flags(int writeback, struct fuse_file_info *fi) +{ + /* + * With writeback cache, kernel may send read requests even + * when userspace opened write-only + */ + if (writeback && (fi->flags & O_ACCMODE) =3D=3D O_WRONLY) { + fi->flags &=3D ~O_ACCMODE; + fi->flags |=3D O_RDWR; + } + + /* + * With writeback cache, O_APPEND is handled by the kernel. + * This breaks atomicity (since the file may change in the + * underlying filesystem, so that the kernel's idea of the + * end of the file isn't accurate anymore). In this example, + * we just accept that. A more rigorous filesystem may want + * to return an error here + */ + if (writeback && (fi->flags & O_APPEND)) { + fi->flags &=3D ~O_APPEND; + } + + /* + * O_DIRECT in guest should not necessarily mean bypassing page + * cache on host as well. If somebody needs that behavior, it + * probably should be a configuration knob in daemon. + */ + fi->flags &=3D ~O_DIRECT; +} + static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, mode_t mode, struct fuse_file_info *fi) { @@ -1721,12 +1752,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t par= ent, const char *name, goto out; } =20 - /* - * O_DIRECT in guest should not necessarily mean bypassing page - * cache on host as well. If somebody needs that behavior, it - * probably should be a configuration knob in daemon. - */ - fi->flags &=3D ~O_DIRECT; + update_open_flags(lo->writeback, fi); =20 fd =3D openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOL= LOW, mode); @@ -1936,33 +1962,7 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, = struct fuse_file_info *fi) fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=3D%" PRIu64 ", flags=3D%d)\n", i= no, fi->flags); =20 - /* - * With writeback cache, kernel may send read requests even - * when userspace opened write-only - */ - if (lo->writeback && (fi->flags & O_ACCMODE) =3D=3D O_WRONLY) { - fi->flags &=3D ~O_ACCMODE; - fi->flags |=3D O_RDWR; - } - - /* - * With writeback cache, O_APPEND is handled by the kernel. - * This breaks atomicity (since the file may change in the - * underlying filesystem, so that the kernel's idea of the - * end of the file isn't accurate anymore). In this example, - * we just accept that. A more rigorous filesystem may want - * to return an error here - */ - if (lo->writeback && (fi->flags & O_APPEND)) { - fi->flags &=3D ~O_APPEND; - } - - /* - * O_DIRECT in guest should not necessarily mean bypassing page - * cache on host as well. If somebody needs that behavior, it - * probably should be a configuration knob in daemon. - */ - fi->flags &=3D ~O_DIRECT; + update_open_flags(lo->writeback, fi); =20 sprintf(buf, "%i", lo_fd(req, ino)); fd =3D openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW); --=20 2.24.1