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=-13.8 required=3.0 tests=BAYES_00, 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 2EFE3C433B4 for ; Tue, 11 May 2021 10:09:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1AC461925 for ; Tue, 11 May 2021 10:09:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231255AbhEKKKt convert rfc822-to-8bit (ORCPT ); Tue, 11 May 2021 06:10:49 -0400 Received: from us-smtp-delivery-44.mimecast.com ([207.211.30.44]:26707 "EHLO us-smtp-delivery-44.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231177AbhEKKKt (ORCPT ); Tue, 11 May 2021 06:10:49 -0400 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-561-lrD21_EpNbGUvjV5ZkV2Xg-1; Tue, 11 May 2021 06:09:39 -0400 X-MC-Unique: lrD21_EpNbGUvjV5ZkV2Xg-1 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 272861883520; Tue, 11 May 2021 10:09:38 +0000 (UTC) Received: from bahia.lan (ovpn-112-143.ams2.redhat.com [10.36.112.143]) by smtp.corp.redhat.com (Postfix) with ESMTP id 031C25D9D5; Tue, 11 May 2021 10:09:25 +0000 (UTC) Date: Tue, 11 May 2021 12:09:24 +0200 From: Greg Kurz To: Vivek Goyal Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S. Tsirkin" , kvm@vger.kernel.org, "Dr. David Alan Gilbert" , Cornelia Huck , Paolo Bonzini , Stefan Hajnoczi , Miklos Szeredi Subject: Re: [for-6.1 v3 3/3] virtiofsd: Add support for FUSE_SYNCFS request Message-ID: <20210511120924.1cf2ee60@bahia.lan> In-Reply-To: <20210510191502.GA193692@horse> References: <20210510155539.998747-1-groug@kaod.org> <20210510155539.998747-4-groug@kaod.org> <20210510191502.GA193692@horse> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kaod.org Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, 10 May 2021 15:15:02 -0400 Vivek Goyal wrote: > On Mon, May 10, 2021 at 05:55:39PM +0200, Greg Kurz wrote: > > Honor the expected behavior of syncfs() to synchronously flush all data > > and metadata on linux systems. Simply loop on all known submounts and > > call syncfs() on them. > > > > Note that syncfs() might suffer from a time penalty if the submounts > > are being hammered by some unrelated workload on the host. The only > > solution to avoid that is to avoid shared submounts. > > > > Signed-off-by: Greg Kurz > > --- > > tools/virtiofsd/fuse_lowlevel.c | 11 ++++++++ > > tools/virtiofsd/fuse_lowlevel.h | 12 +++++++++ > > tools/virtiofsd/passthrough_ll.c | 38 +++++++++++++++++++++++++++ > > 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..3be95ec903c9 100644 > > --- a/tools/virtiofsd/fuse_lowlevel.c > > +++ b/tools/virtiofsd/fuse_lowlevel.c > > @@ -1870,6 +1870,16 @@ 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) > > +{ > > + if (req->se->op.syncfs) { > > + req->se->op.syncfs(req); > > + } 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 +2277,7 @@ 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..890c520b195a 100644 > > --- a/tools/virtiofsd/fuse_lowlevel.h > > +++ b/tools/virtiofsd/fuse_lowlevel.h > > @@ -1225,6 +1225,18 @@ 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 > > + */ > > + void (*syncfs)(fuse_req_t req); > > }; > > > > /** > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > > index dc940a1d048b..289900c6d274 100644 > > --- a/tools/virtiofsd/passthrough_ll.c > > +++ b/tools/virtiofsd/passthrough_ll.c > > @@ -3153,6 +3153,43 @@ 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) > > +{ > > + struct lo_data *lo = lo_data(req); > > + GHashTableIter iter; > > + gpointer key, value; > > + int err = 0; > > + > > + pthread_mutex_lock(&lo->mutex); > > + > > + g_hash_table_iter_init(&iter, lo->mnt_inodes); > > + while (g_hash_table_iter_next(&iter, &key, &value)) { > > + struct lo_inode *inode = value; > > + int fd; > > + > > + fuse_log(FUSE_LOG_DEBUG, "lo_syncfs(ino=%" PRIu64 ")\n", > > + inode->fuse_ino); > > + > > + fd = lo_inode_open(lo, inode, O_RDONLY); > > + if (fd < 0) { > > + err = -fd; > > + break; > > + } > > + > > + if (syncfs(fd) < 0) { > > I don't have a good feeling about calling syncfs() with lo->mutex held. > This seems to be that global mutex which is held at so many places > and will serialize everything else. I think we agreed that syncfs() > can take 10s of seconds if fs is busy. And that means we will stall > other filesystem operations too. > > So will be good if we can call syncfs() outside the lock. May be prepare > a list of inodes which are there, take a reference and drop the lock. > call syncfs and then drop the reference on inode. > You're right. I'll do that. > Vivek > > > + err = errno; > > + close(fd); > > + break; > > + } > > + > > + close(fd); > > + } > > + > > + pthread_mutex_unlock(&lo->mutex); > > + > > + fuse_reply_err(req, err); > > +} > > + > > static void lo_destroy(void *userdata) > > { > > struct lo_data *lo = (struct lo_data *)userdata; > > @@ -3214,6 +3251,7 @@ 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 > > >