From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 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> Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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); -- 1.8.2.1