From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B81BCA9EB9 for ; Wed, 23 Oct 2019 20:14:14 +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 012D020659 for ; Wed, 23 Oct 2019 20:14:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KKw6MPyW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 012D020659 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+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46792 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iNN1I-0001Wl-MS for qemu-devel@archiver.kernel.org; Wed, 23 Oct 2019 16:14:12 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35312) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iNMvU-0006R1-0n for qemu-devel@nongnu.org; Wed, 23 Oct 2019 16:08:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iNMvR-0000X8-Ea for qemu-devel@nongnu.org; Wed, 23 Oct 2019 16:08:11 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:20965 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iNMvN-0000Te-T9 for qemu-devel@nongnu.org; Wed, 23 Oct 2019 16:08:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571861278; 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: in-reply-to:in-reply-to:references:references; bh=DV57IeAGE7muFbgsSXEAzr7szdNnSscAymHx15rpSdo=; b=KKw6MPyWFclqIWBcAS8PAxCF0YuZSJ6om1tT7CjWK3Nd6ONeL18WYjooDmnE7/UYrCkNrS v72q1IfnEdh2ol3EdmbK5Z0IrTg300olD6PtHVNT5JScAJVA/9akQQ0mz+3q2+KQjI/C4Y V6de736IGssng4bdBjI2Z3FcDH7Wd8s= 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-351-weEFzt3MOt6ISbq2U7NGZg-1; Wed, 23 Oct 2019 16:07:56 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2C6595E6; Wed, 23 Oct 2019 20:07:56 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.35]) by smtp.corp.redhat.com (Postfix) with ESMTP id 737545DE5B; Wed, 23 Oct 2019 20:07:53 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 068A52202E5; Wed, 23 Oct 2019 16:07:53 -0400 (EDT) Date: Wed, 23 Oct 2019 16:07:52 -0400 From: Vivek Goyal To: Misono Tomohiro Subject: Re: [Virtio-fs] [PATCH] virtiofsd: Fix data corruption with O_APPEND wirte in writeback mode Message-ID: <20191023200752.GB6942@redhat.com> References: <20191023122523.1816-1-misono.tomohiro@jp.fujitsu.com> MIME-Version: 1.0 In-Reply-To: <20191023122523.1816-1-misono.tomohiro@jp.fujitsu.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: weEFzt3MOt6ISbq2U7NGZg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: virtio-fs@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Oct 23, 2019 at 09:25:23PM +0900, Misono Tomohiro wrote: > 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. >=20 > 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(). >=20 > This fixes the failure of xfstest generic/069 in writeback mode > (which tests O_APPEND write data integrity). >=20 Hi, Consolidating updation of flags both for lo_create() and lo_open() makes sense to me. I will test it tomorrow. Thanks Vivek > Signed-off-by: Misono Tomohiro > --- > contrib/virtiofsd/passthrough_ll.c | 56 +++++++++++++++--------------- > 1 file changed, 28 insertions(+), 28 deletions(-) >=20 > diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passt= hrough_ll.c > index e8892c3c32..79fb78ecce 100644 > --- a/contrib/virtiofsd/passthrough_ll.c > +++ b/contrib/virtiofsd/passthrough_ll.c > @@ -1733,6 +1733,32 @@ static void lo_releasedir(fuse_req_t req, fuse_ino= _t ino, struct fuse_file_info > =09fuse_reply_err(req, 0); > } > =20 > +static void update_open_flags(int writeback, struct fuse_file_info *fi) > +{ > +=09/* With writeback cache, kernel may send read requests even > +=09 when userspace opened write-only */ > +=09if (writeback && (fi->flags & O_ACCMODE) =3D=3D O_WRONLY) { > +=09=09fi->flags &=3D ~O_ACCMODE; > +=09=09fi->flags |=3D O_RDWR; > +=09} > + > +=09/* With writeback cache, O_APPEND is handled by the kernel. > +=09 This breaks atomicity (since the file may change in the > +=09 underlying filesystem, so that the kernel's idea of the > +=09 end of the file isn't accurate anymore). In this example, > +=09 we just accept that. A more rigorous filesystem may want > +=09 to return an error here */ > +=09if (writeback && (fi->flags & O_APPEND)) > +=09=09fi->flags &=3D ~O_APPEND; > + > +=09/* > +=09 * O_DIRECT in guest should not necessarily mean bypassing page > +=09 * cache on host as well. If somebody needs that behavior, it > +=09 * probably should be a configuration knob in daemon. > +=09 */ > +=09fi->flags &=3D ~O_DIRECT; > +} > + > static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *nam= e, > =09=09 mode_t mode, struct fuse_file_info *fi) > { > @@ -1760,12 +1786,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t p= arent, const char *name, > =09if (err) > =09=09goto out; > =20 > -=09/* > -=09 * O_DIRECT in guest should not necessarily mean bypassing page > -=09 * cache on host as well. If somebody needs that behavior, it > -=09 * probably should be a configuration knob in daemon. > -=09 */ > -=09fi->flags &=3D ~O_DIRECT; > +=09update_open_flags(lo->writeback, fi); > =20 > =09fd =3D openat(parent_inode->fd, name, > =09=09 (fi->flags | O_CREAT) & ~O_NOFOLLOW, mode); > @@ -1966,28 +1987,7 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino= , struct fuse_file_info *fi) > =20 > =09fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=3D%" PRIu64 ", flags=3D%d)\n", = ino, fi->flags); > =20 > -=09/* With writeback cache, kernel may send read requests even > -=09 when userspace opened write-only */ > -=09if (lo->writeback && (fi->flags & O_ACCMODE) =3D=3D O_WRONLY) { > -=09=09fi->flags &=3D ~O_ACCMODE; > -=09=09fi->flags |=3D O_RDWR; > -=09} > - > -=09/* With writeback cache, O_APPEND is handled by the kernel. > -=09 This breaks atomicity (since the file may change in the > -=09 underlying filesystem, so that the kernel's idea of the > -=09 end of the file isn't accurate anymore). In this example, > -=09 we just accept that. A more rigorous filesystem may want > -=09 to return an error here */ > -=09if (lo->writeback && (fi->flags & O_APPEND)) > -=09=09fi->flags &=3D ~O_APPEND; > - > -=09/* > -=09 * O_DIRECT in guest should not necessarily mean bypassing page > -=09 * cache on host as well. If somebody needs that behavior, it > -=09 * probably should be a configuration knob in daemon. > -=09 */ > -=09fi->flags &=3D ~O_DIRECT; > +=09update_open_flags(lo->writeback, fi); > =20 > =09sprintf(buf, "%i", lo_fd(req, ino)); > =09fd =3D openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW); > --=20 > 2.21.0 >=20 > _______________________________________________ > Virtio-fs mailing list > Virtio-fs@redhat.com > https://www.redhat.com/mailman/listinfo/virtio-fs