From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:47446 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752516Ab3INL0Z (ORCPT ); Sat, 14 Sep 2013 07:26:25 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r8EBQOHt008806 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Sat, 14 Sep 2013 07:26:25 -0400 Received: from [10.36.4.106] (vpn1-4-106.ams2.redhat.com [10.36.4.106]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r8EBQMoA012685 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO) for ; Sat, 14 Sep 2013 07:26:24 -0400 Message-ID: <523447DE.1080507@redhat.com> Date: Sat, 14 Sep 2013 13:26:22 +0200 From: Harald Hoyer MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options References: <1371569344-2978-1-git-send-email-harald@redhat.com> <52246E91.2050500@redhat.com> In-Reply-To: <52246E91.2050500@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 09/02/2013 12:55 PM, Harald Hoyer wrote: > On 06/18/2013 05:29 PM, harald@redhat.com wrote: >> 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); >> >> > > Any comments? > Not even a "no, we don't want that" ?