Re: [PATCH 3/3] rust: miscdevice: adjust the rust_misc_device sample to use RegistrationData.

[Greg Kroah-Hartman]

On Fri, Jan 24, 2025 at 08:29:38AM +0100, Alice Ryhl wrote:
> On Thu, Jan 23, 2025 at 6:57 PM Christian Schrefl
> <chrisi.schrefl@xxxxxxxxx> wrote:
> >
> > Hi Alice
> >
> > On 21.01.25 4:40 PM, Alice Ryhl wrote:
> > > On Sun, Jan 19, 2025 at 11:11 PM Christian Schrefl
> > > <chrisi.schrefl@xxxxxxxxx> wrote:
> > >>
> > >> Share the mutex stored in RustMiscDevice between all instances using an Arc
> > >> and the RegistrationData of MiscDeviceRegistration.
> > >>
> > >> This is mostly to Demonstrate the capability to share data in this way.
> > >>
> > >> Signed-off-by: Christian Schrefl <chrisi.schrefl@xxxxxxxxx>
> > >
> > > This change causes all open files to share the same value, instead of
> > > it being per-fd.
> >
> > I know, if that is unwanted I'm fine with dropping this patch,
> > it is mostly here to show how patch 2 can be used.
> 
> Perhaps instead of changing the per-fd value, we could add a new
> shared value? E.g., it could have a counter for the number of open
> files.

Counters don't work, sorry (think about dup() for file handles), please,
either make it per-file handle, or a "global" thing for the specific
object, don't attempt to count open/release calls, the vfs does this for
us already.

thanks,

greg k-h