[RFC][PATCH 04/36] btrfs: Add checkpoint file operations

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at cs.columbia.edu):
> 
> Serge E. Hallyn wrote:
> > Quoting Matt Helsley (matthltc at us.ibm.com):
> > 
> > ...
> > 
> >> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> >> index a7acfe6..f16be9d 100644
> >> --- a/fs/btrfs/super.c
> >> +++ b/fs/btrfs/super.c
> >> @@ -686,6 +686,7 @@ static const struct file_operations btrfs_ctl_fops = {
> >>  	.unlocked_ioctl	 = btrfs_control_ioctl,
> >>  	.compat_ioctl = btrfs_control_ioctl,
> >>  	.owner	 = THIS_MODULE,
> >> +	.checkpoint = generic_file_checkpoint,
> >>  };
> > 
> > Do we really want this one?
> 
> We need to checkpoint the open file regardless of whether the underlying
> filesystem has snapshot capabilities.

But maybe we need to refuse a checkpoint if a task is talking to the
underlying btrfs filesystem?

-serge