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Fri, 25 Sep 2020 12:08:41 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-114-177.ams2.redhat.com [10.36.114.177]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8CD3A73695; Fri, 25 Sep 2020 12:08:36 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, zhengchuan@huawei.com, dovmurik@linux.vnet.ibm.com, hgcoin@gmail.com, zhangjiachen.jaycee@bytedance.com, lvivier@redhat.com, peterx@redhat.com, stefanha@redhat.com, vgoyal@redhat.com, jinyan12@huawei.com, ann.zhuangyanying@huawei.com Subject: [PULL 26/26] virtiofsd: Add -o allow_direct_io|no_allow_direct_io options Date: Fri, 25 Sep 2020 13:06:55 +0100 Message-Id: <20200925120655.295142-27-dgilbert@redhat.com> In-Reply-To: <20200925120655.295142-1-dgilbert@redhat.com> References: <20200925120655.295142-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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 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 = 2020/09/25 01:07:33 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: quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Jiachen Zhang 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 Message-Id: <20200824105957.61265-1-zhangjiachen.jaycee@bytedance.com> Signed-off-by: Dr. David Alan Gilbert --- 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 7bc5d7dc5a..85770d63f1 100644 --- a/tools/virtiofsd/helper.c +++ b/tools/virtiofsd/helper.c @@ -178,6 +178,10 @@ 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 784330e0e4..0b229ebd57 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); @@ -2823,6 +2830,7 @@ int main(int argc, char *argv[]) .debug = 0, .writeback = 0, .posix_lock = 0, + .allow_direct_io = 0, .proc_self_fd = -1, }; struct lo_map_elem *root_elem;