Re: possible deadlock in ovl_write_iter

[Amir Goldstein <amir73il@gmail.com>]

> > This looks like a false positive because lockdep is not aware of
> > s_stack_depth of the file (fs) associated with the pipe.
>
> There must be some annotation to tell lockdep about this.
>

It's a long story that can be summed up as "not simple":
https://lkml.org/lkml/2017/9/21/63

Overlayfs annotates inode mutex in lockdep friendly manner.
This is why you see:
 (&ovl_i_mutex_key[depth]){+.+.}, at: inode_lock

But this does not extend to other locks that may be associated
with filesystem or blockdev objects (e.g. pipe_lock()) and does
not cover the case of stacked blockdev (e.g. loop).

Thanks,
Amir.