Re: Union mount and lockdep design issues

[Miklos Szeredi]

David Howells <dhowells@xxxxxxxxxx> writes:

> Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
>> Overlayfs never locks both upper and lower at the same time, which means
>> there's no AB-BA locking dependency.  The lock orderings are:
>
> What you're talking about is not analogous to the situation I'm seeing with
> unionmount.
>
> You actually have three filesystems in overlayfs.  The interaction between
> overlayfs-and-upperfs and overlayfs-and-lowerfs is the equivalent in
> unionmount terms to upperfs-and-lowerfs.  This is where the lockdep issue
> lies.

Normally overlayfs would be immune to this, since lower/upper are
different filesystem types.  But overlayfs-over-overlayfs would see the
same lockdep warnings, right?

Thanks,
Miklos
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