Re: [PATCH 15/25] autofs: move ioctl32 to autofs{,4}/root.c

Ian Kent
2005-11-07T16:03:50Z

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On Mon, 7 Nov 2005, Arnd Bergmann wrote:

> On Sünndag 06 November 2005 07:22, Ian Kent wrote:
> > On Sat, 5 Nov 2005, Arnd Bergmann wrote:
> >
> > I'm not sure if I like conditional compilation in the code proper but I'll
> > leave it to you to make the final decision since your running with the
> > change. Is there a reason the definitions can't simply be left in place?
>
> I think the compat_ptr() macro is not defined on architectures that don't
> have 32 bit compat code, but we could change that.
>
> > Its been a while since I trawled through the compat ioctl code (please
> > point me to the right place) but with this change I think that the
> > AUTOFS_IOC_SETTIMEOUT32 is redundant. Consider a conditional define for
> > AUTOFS_IOC_SETTIMEOUT in include/linux/auto_fs.h instead. Both autofs and
> > autofs4 use that definition.
>
> The point here is that the two are different on 64 bit platforms, since
> sizeof (int) != sizeof (long). You also can't do
>
> switch (cmd) {
> case AUTOFS_IOC_SETTIMEOUT32:
> case AUTOFS_IOC_SETTIMEOUT:
> return do_stuff();
> }
>
> because then gcc would complain about duplicate case targets on 32 bit
> targets.

I was thinking that if the module was compiled for 64bit then the 64bit
definition would prevail and visa versa.

eg. In the include file.

#ifdef COMPAT_IOCTL
#define AUTOFS_IOC_SETTIMEOUT(..., unsigned int)
#else
#define AUTOFS_IOC_SETTIMEOUT(...,unsigned long)
#endif

I think I'm going to have to investigate further following the
implementation.

>
> > The lock_kernel()/unlock_kernel() in the autofs4 patch is ineffective as
> > the BKL is not used for syncronisation anywhere else in autofs4. If
> > removing it causes problems I need to know about'em so I can fix'em
> > (hopefully).
>
> I used the BKL here in order to maintain the current semantics, because
> ioctl is always called with BKL held, and compat_ioctl is called without
> it.

Of course a sensible approach.

>
> If you are sure you don't need the BKL, then you should also replace
> ".ioctl = ..." with ".unlocked_ioctl = ...".

Yep. I'll check and amend it later.
After all it will be part of the module then.

Thanks
Ian