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=-11.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 711F4C4363D for ; Thu, 24 Sep 2020 11:10:35 +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 A17C420717 for ; Thu, 24 Sep 2020 11:10:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ipjCrXdP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A17C420717 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]:45800 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kLP8z-0000y6-Dy for qemu-devel@archiver.kernel.org; Thu, 24 Sep 2020 07:10:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35286) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLP89-0000Vl-9g for qemu-devel@nongnu.org; Thu, 24 Sep 2020 07:09:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:22556) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kLP87-0002fO-Ab for qemu-devel@nongnu.org; Thu, 24 Sep 2020 07:09:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600945778; 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=FPRp3Q96TmPVU7JbVrAuQ8TD+AA0NNz4NrCcBTnnIpU=; b=ipjCrXdPGaWCkbTvPY8J55DRUpzbZGLsNVIfm977OFxemSvDqbqLVtcc5Dxn14irOO8AGN kFlHURbj2gAn+aRjHM1saIQNQnzGCY4c5B33h8UBFkFmtWWQzo3Ki/mqoaXKh90kW18prr 8z6rcBDaySMgw2SUnvE9w+eU26FA1hc= 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-22-XHToIbktNBC0gbmnErMf-g-1; Thu, 24 Sep 2020 07:09:36 -0400 X-MC-Unique: XHToIbktNBC0gbmnErMf-g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 92AAA802B4A; Thu, 24 Sep 2020 11:09:35 +0000 (UTC) Received: from work-vm (ovpn-114-250.ams2.redhat.com [10.36.114.250]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A52175C1C7; Thu, 24 Sep 2020 11:09:31 +0000 (UTC) Date: Thu, 24 Sep 2020 12:09:28 +0100 From: "Dr. David Alan Gilbert" To: Jiachen Zhang Subject: Re: [PATCH v2] virtiofsd: Add -o allow_direct_io|no_allow_direct_io options Message-ID: <20200924110928.GD2792@work-vm> References: <20200824105957.61265-1-zhangjiachen.jaycee@bytedance.com> MIME-Version: 1.0 In-Reply-To: <20200824105957.61265-1-zhangjiachen.jaycee@bytedance.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/24 01:10:00 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: Yongji Xie , qemu-devel@nongnu.org, Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Jiachen Zhang (zhangjiachen.jaycee@bytedance.com) wrote: > Due to the commit 65da4539803373ec4eec97ffc49ee90083e56efd, the O_DIRECT > open flag of guest applications will be discarded by virtiofsd. While > this behavior makes it consistent with the virtio-9p scheme when guest > applications use direct I/O, we no longer have any chance to bypass the > host page cache. > > Therefore, we add a flag 'allow_direct_io' to lo_data. If '-o > no_allow_direct_io' option is added, or none of '-o allow_direct_io' or > '-o no_allow_direct_io' is added, the 'allow_direct_io' will be set to > 0, and virtiofsd discards O_DIRECT as before. If '-o allow_direct_io' > is added to the starting command-line, 'allow_direct_io' will be set to > 1, so that the O_DIRECT flags will be retained and host page cache can > be bypassed. > > Signed-off-by: Jiachen Zhang > Reviewed-by: Stefan Hajnoczi Queued > --- > tools/virtiofsd/helper.c | 4 ++++ > tools/virtiofsd/passthrough_ll.c | 20 ++++++++++++++------ > 2 files changed, 18 insertions(+), 6 deletions(-) > > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > index 3105b6c23a..45b310ff3c 100644 > --- a/tools/virtiofsd/helper.c > +++ b/tools/virtiofsd/helper.c > @@ -180,6 +180,10 @@ void fuse_cmdline_help(void) > " (0 leaves rlimit unchanged)\n" > " default: min(1000000, fs.file-max - 16384)\n" > " if the current rlimit is lower\n" > + " -o allow_direct_io|no_allow_direct_io\n" > + " retain/discard O_DIRECT flags passed down\n" > + " to virtiofsd from guest applications.\n" > + " default: no_allow_direct_io\n" > ); > } > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 94e0de2d2b..c1ae897b77 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -151,6 +151,7 @@ struct lo_data { > int timeout_set; > int readdirplus_set; > int readdirplus_clear; > + int allow_direct_io; > struct lo_inode root; > GHashTable *inodes; /* protected by lo->mutex */ > struct lo_map ino_map; /* protected by lo->mutex */ > @@ -179,6 +180,8 @@ static const struct fuse_opt lo_opts[] = { > { "cache=always", offsetof(struct lo_data, cache), CACHE_ALWAYS }, > { "readdirplus", offsetof(struct lo_data, readdirplus_set), 1 }, > { "no_readdirplus", offsetof(struct lo_data, readdirplus_clear), 1 }, > + { "allow_direct_io", offsetof(struct lo_data, allow_direct_io), 1 }, > + { "no_allow_direct_io", offsetof(struct lo_data, allow_direct_io), 0 }, > FUSE_OPT_END > }; > static bool use_syslog = false; > @@ -1516,7 +1519,8 @@ static void lo_releasedir(fuse_req_t req, fuse_ino_t ino, > fuse_reply_err(req, 0); > } > > -static void update_open_flags(int writeback, struct fuse_file_info *fi) > +static void update_open_flags(int writeback, int allow_direct_io, > + struct fuse_file_info *fi) > { > /* > * With writeback cache, kernel may send read requests even > @@ -1541,10 +1545,13 @@ static void update_open_flags(int writeback, struct fuse_file_info *fi) > > /* > * 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. > + * cache on host as well. Therefore, we discard it by default > + * ('-o no_allow_direct_io'). If somebody needs that behavior, > + * the '-o allow_direct_io' option should be set. > */ > - fi->flags &= ~O_DIRECT; > + if (!allow_direct_io) { > + fi->flags &= ~O_DIRECT; > + } > } > > static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, > @@ -1576,7 +1583,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, > goto out; > } > > - update_open_flags(lo->writeback, fi); > + update_open_flags(lo->writeback, lo->allow_direct_io, fi); > > fd = openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOLLOW, > mode); > @@ -1786,7 +1793,7 @@ 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=%" PRIu64 ", flags=%d)\n", ino, > fi->flags); > > - update_open_flags(lo->writeback, fi); > + update_open_flags(lo->writeback, lo->allow_direct_io, fi); > > sprintf(buf, "%i", lo_fd(req, ino)); > fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW); > @@ -2824,6 +2831,7 @@ int main(int argc, char *argv[]) > .debug = 0, > .writeback = 0, > .posix_lock = 1, > + .allow_direct_io = 0, > .proc_self_fd = -1, > }; > struct lo_map_elem *root_elem; > -- > 2.11.0 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK