Re: Removing Mandatory Locks

[Eric Biggers]

On Thu, Aug 19, 2021 at 12:15:08PM -0700, Linus Torvalds wrote:
> On Thu, Aug 19, 2021 at 11:39 AM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> >
> > I'm all for ripping it out too. It's an insane interface anyway.
> >
> > I've not heard a single complaint about this being turned off in
> > fedora/rhel or any other distro that has this disabled.
> 
> I'd love to remove it, we could absolutely test it. The fact that
> several major distros have it disabled makes me think it's fine.
> 
> But as always, it would be good to check Android.
> 
> The desktop distros tend to have the same tools and programs, so if
> Fedora and RHEL haven't needed it for years, then it's likely stale in
> Debian too (despite being enabled).
> 
> But Android tends to be very different. Does anybody know?
> 

As far as I know, Android never uses mandatory file locking.  While
CONFIG_MANDATORY_LOCKING=y is typically set (as it's "default y" upstream),
I can't find anywhere in the Android source tree that uses the "mand" mount
option, let alone anything actually using mandatory locks.  (I'm assuming that
Documentation/filesystems/mandatory-locking.rst is up-to-date regarding what
userspace actually has to do to use it.)

- Eric