On Tue, May 01, 2012 at 07:09:21PM +0200, Hubert Kario wrote:
> Let me rephrase it:
>
> People don't want to be able to do:
>
> mount /dev/lvm/btrfs /mnt/a -t btrfs -o subvol=volA
> mount /dev/lvm/btrfs /mnt/b -t btrfs -o subvol=volB
> cp --reflink=always /mnt/a/file /mnt/b
>
> Just like you can't do hardlinks over `mount --bind` mountpoints, you
> shouldn't be able to cp reflink over mountpoints. That's expected as this
> *does* break VFS semantics.
Proposed fix (incremental on top of the cross-subvol):
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2321,6 +2321,10 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
goto out_drop_write;
}
+ ret = -EXDEV;
+ if (src_file->f_path.mnt != file->f_path.mnt)
+ goto out_fput;
+
src = src_file->f_dentry->d_inode;
ret = -EINVAL;
david
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