From patchwork Tue Jun 18 15:29:04 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Harald Hoyer X-Patchwork-Id: 2743001 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id DAA079F39E for ; Tue, 18 Jun 2013 15:29:29 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 358EC204B2 for ; Tue, 18 Jun 2013 15:29:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EBAF7204C3 for ; Tue, 18 Jun 2013 15:29:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932575Ab3FRP3R (ORCPT ); Tue, 18 Jun 2013 11:29:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41322 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932302Ab3FRP3Q (ORCPT ); Tue, 18 Jun 2013 11:29:16 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r5IFTGfK025496 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 18 Jun 2013 11:29:16 -0400 Received: from lenovo.fritz.box (vpn1-6-15.ams2.redhat.com [10.36.6.15]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r5IFTEWW031679; Tue, 18 Jun 2013 11:29:15 -0400 From: harald@redhat.com To: linux-btrfs@vger.kernel.org Cc: Harald Hoyer Subject: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options Date: Tue, 18 Jun 2013 17:29:04 +0200 Message-Id: <1371569344-2978-1-git-send-email-harald@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Harald Hoyer Given the following /etc/fstab entries: /dev/sda3 /mnt/foo btrfs subvol=foo,ro 0 /dev/sda3 /mnt/bar btrfs subvol=bar,rw 0 you can't issue: $ mount /mnt/foo $ mount /mnt/bar You would have to do: $ mount /mnt/foo $ mount -o remount,rw /mnt/foo $ mount --bind -o remount,ro /mnt/foo $ mount /bar or $ mount /mnt/bar $ mount --rw /mnt/foo $ mount --bind -o remount,ro /mnt/foo With this patch you can do $ mount /mnt/foo $ mount /mnt/bar $ cat /proc/self/mountinfo 49 33 0:41 /foo /mnt/foo ro,relatime shared:36 - btrfs /dev/sda3 rw,ssd,space_cache 87 33 0:41 /bar /mnt/bar rw,relatime shared:74 - btrfs /dev/sda3 rw,ssd,space_cache --- fs/btrfs/super.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index f0857e0..80ed3e2 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -64,6 +64,8 @@ static const struct super_operations btrfs_super_ops; static struct file_system_type btrfs_fs_type; +static int btrfs_remount(struct super_block *sb, int *flags, char *data); + static const char *btrfs_decode_error(int errno) { char *errstr = "unknown"; @@ -1036,6 +1038,26 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name, newargs); kfree(newargs); + + if (PTR_RET(mnt) == -EBUSY) { + if (flags & MS_RDONLY) { + mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY, device_name, + newargs); + } else { + int r; + mnt = vfs_kern_mount(&btrfs_fs_type, flags | MS_RDONLY, device_name, + newargs); + if (IS_ERR(mnt)) + return ERR_CAST(mnt); + + r = btrfs_remount(mnt->mnt_sb, &flags, NULL); + if (r < 0) { + /* FIXME: release vfsmount mnt ??*/ + return ERR_PTR(r); + } + } + } + if (IS_ERR(mnt)) return ERR_CAST(mnt);