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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 4B8D2C433ED for ; Wed, 5 May 2021 18:53:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1563261168 for ; Wed, 5 May 2021 18:53:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234880AbhEESx7 (ORCPT ); Wed, 5 May 2021 14:53:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:55006 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229810AbhEESx6 (ORCPT ); Wed, 5 May 2021 14:53:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620240781; 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: in-reply-to:in-reply-to:references:references; bh=ezT8mOSwWO06goNK+CmRyw7YAeqCfnbCUWH9/kMObNE=; b=NLM6WRKFRtllahrz+UUKevgViQAnmLJw1QMHEsmVoIGOY0Io8B+m8XjNILO0HRf4Kxq7GY 9JB60Qq/Hy4f/1ncaOx+QiC/XH4lPYhOl8+fFbzSK5iS/8tivNp2jKVVfLSwAkuL+rDZwy OFT5wBgrmkyOULpawQbdOFEg10in7vw= 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-194-DEo3dZPQNr-JdpazMfhRug-1; Wed, 05 May 2021 14:52:59 -0400 X-MC-Unique: DEo3dZPQNr-JdpazMfhRug-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5E18D18B62AD; Wed, 5 May 2021 18:52:58 +0000 (UTC) Received: from horse.redhat.com (ovpn-114-239.rdu2.redhat.com [10.10.114.239]) by smtp.corp.redhat.com (Postfix) with ESMTP id 029D019C9B; Wed, 5 May 2021 18:52:43 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 83A5222054F; Wed, 5 May 2021 14:52:42 -0400 (EDT) Date: Wed, 5 May 2021 14:52:42 -0400 From: Vivek Goyal To: Greg Kurz Cc: qemu-devel@nongnu.org, Cornelia Huck , "Dr. David Alan Gilbert" , Stefan Hajnoczi , kvm@vger.kernel.org, virtio-fs@redhat.com, Miklos Szeredi , "Michael S. Tsirkin" , Paolo Bonzini Subject: Re: [for-6.1 v2 2/2] virtiofsd: Add support for FUSE_SYNCFS request Message-ID: <20210505185242.GC244258@redhat.com> References: <20210426152135.842037-1-groug@kaod.org> <20210426152135.842037-3-groug@kaod.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210426152135.842037-3-groug@kaod.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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, 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. Just mentioning it here so that we have a note about the limitation of current patch. 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 >