On 06/18/2013 05:29 PM, harald@xxxxxxxxxx wrote:
> From: Harald Hoyer <harald@xxxxxxxxxx>
>
> 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?
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