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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable 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 B21C8C433ED for ; Thu, 6 May 2021 06:16:01 +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 05FF66112D for ; Thu, 6 May 2021 06:16:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05FF66112D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:47152 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1leXIm-0005vm-2W for qemu-devel@archiver.kernel.org; Thu, 06 May 2021 02:16:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44940) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1leXHZ-0005Oc-Oo for qemu-devel@nongnu.org; Thu, 06 May 2021 02:14:45 -0400 Received: from 8.mo52.mail-out.ovh.net ([46.105.37.156]:44837) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1leXHU-0003MX-Vx for qemu-devel@nongnu.org; Thu, 06 May 2021 02:14:45 -0400 Received: from mxplan5.mail.ovh.net (unknown [10.108.20.48]) by mo52.mail-out.ovh.net (Postfix) with ESMTPS id 176AC275CC1; Thu, 6 May 2021 08:14:30 +0200 (CEST) Received: from kaod.org (37.59.142.97) by DAG8EX1.mxp5.local (172.16.2.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2242.4; Thu, 6 May 2021 08:14:29 +0200 Authentication-Results: garm.ovh; auth=pass (GARM-97G002c35e9a4b-82c2-4398-9a74-d8a1be0523f7, A011F864E236C67B2AFE342ECDF08F9E86568858) smtp.auth=groug@kaod.org X-OVh-ClientIp: 78.197.208.248 Date: Thu, 6 May 2021 08:14:28 +0200 From: Greg Kurz To: Vivek Goyal Subject: Re: [for-6.1 v2 2/2] virtiofsd: Add support for FUSE_SYNCFS request Message-ID: <20210506081428.69d73bbc@bahia.lan> In-Reply-To: <20210505185242.GC244258@redhat.com> References: <20210426152135.842037-1-groug@kaod.org> <20210426152135.842037-3-groug@kaod.org> <20210505185242.GC244258@redhat.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [37.59.142.97] X-ClientProxiedBy: DAG3EX2.mxp5.local (172.16.2.22) To DAG8EX1.mxp5.local (172.16.2.71) X-Ovh-Tracer-GUID: c78b824e-59e7-468b-825f-a6735cd090d1 X-Ovh-Tracer-Id: 9891312157052475826 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgeduledrvdefledguddtvdcutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvuffkjghfofggtgfgihesthejredtredtvdenucfhrhhomhepifhrvghgucfmuhhriicuoehgrhhouhhgsehkrghougdrohhrgheqnecuggftrfgrthhtvghrnhepfedutdeijeejveehkeeileetgfelteekteehtedtieefffevhffflefftdefleejnecukfhppedtrddtrddtrddtpdefjedrheelrddugedvrdeljeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhhouggvpehsmhhtphdqohhuthdphhgvlhhopehmgihplhgrnhehrdhmrghilhdrohhvhhdrnhgvthdpihhnvghtpedtrddtrddtrddtpdhmrghilhhfrhhomhepghhrohhugheskhgrohgurdhorhhgpdhrtghpthhtohepphgsohhniihinhhisehrvgguhhgrthdrtghomh Received-SPF: pass client-ip=46.105.37.156; envelope-from=groug@kaod.org; helo=8.mo52.mail-out.ovh.net X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, 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: kvm@vger.kernel.org, Miklos Szeredi , Cornelia Huck , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , virtio-fs@redhat.com, "Michael S. Tsirkin" , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 5 May 2021 14:52:42 -0400 Vivek Goyal wrote: > On Mon, Apr 26, 2021 at 05:21:35PM +0200, Greg Kurz wrote: > > Honor the expected behavior of syncfs() to synchronously flush all > > data and metadata on linux systems. > > > > Flushing is done with syncfs(). This is suboptimal as it will also > > flush writes performed by any other process on the same file system, > > and thus add an unbounded time penalty to syncfs(). This may be > > optimized in the future, but enforce correctness first. > > > > Signed-off-by: Greg Kurz > > --- > > tools/virtiofsd/fuse_lowlevel.c | 19 ++++++++++++++++++ > > tools/virtiofsd/fuse_lowlevel.h | 13 ++++++++++++ > > tools/virtiofsd/passthrough_ll.c | 29 +++++++++++++++++++++++++++ > > tools/virtiofsd/passthrough_seccomp.c | 1 + > > 4 files changed, 62 insertions(+) > > > > diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c > > index 58e32fc96369..918ab11f54c2 100644 > > --- a/tools/virtiofsd/fuse_lowlevel.c > > +++ b/tools/virtiofsd/fuse_lowlevel.c > > @@ -1870,6 +1870,24 @@ static void do_lseek(fuse_req_t req, fuse_ino_t nodeid, > > } > > } > > > > +static void do_syncfs(fuse_req_t req, fuse_ino_t nodeid, > > + struct fuse_mbuf_iter *iter) > > +{ > > + struct fuse_syncfs_in *arg; > > + > > + arg = fuse_mbuf_iter_advance(iter, sizeof(*arg)); > > + if (!arg) { > > + fuse_reply_err(req, EINVAL); > > + return; > > + } > > + > > + if (req->se->op.syncfs) { > > + req->se->op.syncfs(req, arg->flags); > > + } else { > > + fuse_reply_err(req, ENOSYS); > > + } > > +} > > + > > static void do_init(fuse_req_t req, fuse_ino_t nodeid, > > struct fuse_mbuf_iter *iter) > > { > > @@ -2267,6 +2285,7 @@ static struct { > > [FUSE_RENAME2] = { do_rename2, "RENAME2" }, > > [FUSE_COPY_FILE_RANGE] = { do_copy_file_range, "COPY_FILE_RANGE" }, > > [FUSE_LSEEK] = { do_lseek, "LSEEK" }, > > + [FUSE_SYNCFS] = { do_syncfs, "SYNCFS" }, > > }; > > > > #define FUSE_MAXOP (sizeof(fuse_ll_ops) / sizeof(fuse_ll_ops[0])) > > diff --git a/tools/virtiofsd/fuse_lowlevel.h b/tools/virtiofsd/fuse_lowlevel.h > > index 3bf786b03485..220bb3db4898 100644 > > --- a/tools/virtiofsd/fuse_lowlevel.h > > +++ b/tools/virtiofsd/fuse_lowlevel.h > > @@ -1225,6 +1225,19 @@ struct fuse_lowlevel_ops { > > */ > > void (*lseek)(fuse_req_t req, fuse_ino_t ino, off_t off, int whence, > > struct fuse_file_info *fi); > > + > > + /** > > + * Synchronize file system content > > + * > > + * If this request is answered with an error code of ENOSYS, > > + * this is treated as success and future calls to syncfs() will > > + * succeed automatically without being sent to the filesystem > > + * process. > > + * > > + * @param req request handle > > + * @param flags not used yet > > + */ > > + void (*syncfs)(fuse_req_t req, uint64_t flags); > > }; > > > > /** > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > > index 1553d2ef454f..6790a2f6fe10 100644 > > --- a/tools/virtiofsd/passthrough_ll.c > > +++ b/tools/virtiofsd/passthrough_ll.c > > @@ -3124,6 +3124,34 @@ static void lo_lseek(fuse_req_t req, fuse_ino_t ino, off_t off, int whence, > > } > > } > > > > +static void lo_syncfs(fuse_req_t req, uint64_t flags) > > +{ > > + struct lo_data *lo = lo_data(req); > > + int fd, ret; > > + > > + /* No flags supported yet */ > > + if (flags) { > > + fuse_reply_err(req, EINVAL); > > + return; > > + } > > + > > + fd = lo_inode_open(lo, &lo->root, O_RDONLY); > > + if (fd < 0) { > > + fuse_reply_err(req, errno); > > + return; > > + } > > + > > + /* > > + * FIXME: this is suboptimal because it will also flush unrelated > > + * writes not coming from the client. This can dramatically > > + * increase the time spent in syncfs() if some process is > > + * writing lots of data on the same filesystem as virtiofsd. > > + */ > > + ret = syncfs(fd); > > Hi Greg, > Hi Vivek, > As we discussed in the community call that this works only if there are > no other filesystems mounted as submounts under exported directory. > > We proably need to find a way to call syncfs() on all the filesystems > which are submounts of exported directory. Might not be easy at all. > I must confess I didn't investigate this case. I'll start looking. > Just mentioning it here so that we have a note about the limitation of > current patch. > Sure. I'll add a note for that. > Vivek > > > + fuse_reply_err(req, ret < 0 ? errno : 0); > > + close(fd); > > +} > > + > > static void lo_destroy(void *userdata) > > { > > struct lo_data *lo = (struct lo_data *)userdata; > > @@ -3184,6 +3212,7 @@ static struct fuse_lowlevel_ops lo_oper = { > > .copy_file_range = lo_copy_file_range, > > #endif > > .lseek = lo_lseek, > > + .syncfs = lo_syncfs, > > .destroy = lo_destroy, > > }; > > > > diff --git a/tools/virtiofsd/passthrough_seccomp.c b/tools/virtiofsd/passthrough_seccomp.c > > index 62441cfcdb95..343188447901 100644 > > --- a/tools/virtiofsd/passthrough_seccomp.c > > +++ b/tools/virtiofsd/passthrough_seccomp.c > > @@ -107,6 +107,7 @@ static const int syscall_allowlist[] = { > > SCMP_SYS(set_robust_list), > > SCMP_SYS(setxattr), > > SCMP_SYS(symlinkat), > > + SCMP_SYS(syncfs), > > SCMP_SYS(time), /* Rarely needed, except on static builds */ > > SCMP_SYS(tgkill), > > SCMP_SYS(unlinkat), > > -- > > 2.26.3 > > >