From patchwork Fri Jun 4 16:11:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kurz X-Patchwork-Id: 12300061 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 A36DEC07E94 for ; Fri, 4 Jun 2021 16:12:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9001E61405 for ; Fri, 4 Jun 2021 16:12:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231468AbhFDQON convert rfc822-to-8bit (ORCPT ); Fri, 4 Jun 2021 12:14:13 -0400 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:33335 "EHLO us-smtp-delivery-44.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229774AbhFDQOM (ORCPT ); Fri, 4 Jun 2021 12:14:12 -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-270-xGoyTos_OVKeYCaxchsOVA-1; Fri, 04 Jun 2021 12:12:22 -0400 X-MC-Unique: xGoyTos_OVKeYCaxchsOVA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1D8F6107ACC7; Fri, 4 Jun 2021 16:12:21 +0000 (UTC) Received: from bahia.lan (ovpn-112-232.ams2.redhat.com [10.36.112.232]) by smtp.corp.redhat.com (Postfix) with ESMTP id 969291B5B7; Fri, 4 Jun 2021 16:12:17 +0000 (UTC) From: Greg Kurz To: Miklos Szeredi Cc: linux-kernel@vger.kernel.org, Max Reitz , linux-fsdevel@vger.kernel.org, virtio-fs@redhat.com, Vivek Goyal , Greg Kurz Subject: [PATCH v2 5/7] fuse: Call vfs_get_tree() for submounts Date: Fri, 4 Jun 2021 18:11:54 +0200 Message-Id: <20210604161156.408496-6-groug@kaod.org> In-Reply-To: <20210604161156.408496-1-groug@kaod.org> References: <20210604161156.408496-1-groug@kaod.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kaod.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org We recently fixed an infinite loop by setting the SB_BORN flag on submounts along with the write barrier needed by super_cache_count(). This is the job of vfs_get_tree() and FUSE shouldn't have to care about the barrier at all. Split out some code from fuse_dentry_automount() to the dedicated fuse_get_tree_submount() handler for submounts and call vfs_get_tree(). Signed-off-by: Greg Kurz Reviewed-by: Max Reitz --- fs/fuse/dir.c | 53 +++++-------------------------------------------- fs/fuse/inode.c | 36 +++++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+), 48 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 3fa8604c21d5..b88e5785a3dd 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -309,12 +309,8 @@ static int fuse_dentry_delete(const struct dentry *dentry) static struct vfsmount *fuse_dentry_automount(struct path *path) { struct fs_context *fsc; - struct fuse_mount *parent_fm = get_fuse_mount_super(path->mnt->mnt_sb); - struct fuse_conn *fc = parent_fm->fc; - struct fuse_mount *fm; struct vfsmount *mnt; struct fuse_inode *mp_fi = get_fuse_inode(d_inode(path->dentry)); - struct super_block *sb; int err; fsc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry); @@ -323,48 +319,15 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) goto out; } - err = -ENOMEM; - fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL); - if (!fm) - goto out_put_fsc; + /* Pass the FUSE inode of the mount for fuse_get_tree_submount() */ + fsc->fs_private = mp_fi; - fsc->s_fs_info = fm; - sb = sget_fc(fsc, NULL, set_anon_super_fc); - if (IS_ERR(sb)) { - err = PTR_ERR(sb); - kfree(fm); + err = vfs_get_tree(fsc); + if (err) goto out_put_fsc; - } - fm->fc = fuse_conn_get(fc); - - /* Initialize superblock, making @mp_fi its root */ - err = fuse_fill_super_submount(sb, mp_fi); - if (err) { - fuse_conn_put(fc); - kfree(fm); - sb->s_fs_info = NULL; - goto out_put_sb; - } - - down_write(&fc->killsb); - list_add_tail(&fm->fc_entry, &fc->mounts); - up_write(&fc->killsb); - - sb->s_flags |= SB_ACTIVE; - fsc->root = dget(sb->s_root); - - /* - * FIXME: setting SB_BORN requires a write barrier for - * super_cache_count(). We should actually come - * up with a proper ->get_tree() implementation - * for submounts and call vfs_get_tree() to take - * care of the write barrier. - */ - smp_wmb(); - sb->s_flags |= SB_BORN; /* We are done configuring the superblock, so unlock it */ - up_write(&sb->s_umount); + up_write(&fsc->root->d_sb->s_umount); /* Create the submount */ mnt = vfs_create_mount(fsc); @@ -376,12 +339,6 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) put_fs_context(fsc); return mnt; -out_put_sb: - /* - * Only jump here when fsc->root is NULL and sb is still locked - * (otherwise put_fs_context() will put the superblock) - */ - deactivate_locked_super(sb); out_put_fsc: put_fs_context(fsc); out: diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index fa96a3762ea2..bec1676811d4 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1313,8 +1313,44 @@ int fuse_fill_super_submount(struct super_block *sb, return 0; } +/* Filesystem context private data holds the FUSE inode of the mount point */ static int fuse_get_tree_submount(struct fs_context *fsc) { + struct fuse_mount *fm; + struct fuse_inode *mp_fi = fsc->fs_private; + struct fuse_conn *fc = get_fuse_conn(&mp_fi->inode); + struct super_block *sb; + int err; + + fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL); + if (!fm) + return -ENOMEM; + + fsc->s_fs_info = fm; + sb = sget_fc(fsc, NULL, set_anon_super_fc); + if (IS_ERR(sb)) { + kfree(fm); + return PTR_ERR(sb); + } + fm->fc = fuse_conn_get(fc); + + /* Initialize superblock, making @mp_fi its root */ + err = fuse_fill_super_submount(sb, mp_fi); + if (err) { + fuse_conn_put(fc); + kfree(fm); + sb->s_fs_info = NULL; + deactivate_locked_super(sb); + return err; + } + + down_write(&fc->killsb); + list_add_tail(&fm->fc_entry, &fc->mounts); + up_write(&fc->killsb); + + sb->s_flags |= SB_ACTIVE; + fsc->root = dget(sb->s_root); + return 0; }