Re: new architectures, time_t __kernel_long_t

From: H. Peter Anvin
Date: Fri Dec 21 2012 - 00:05:36 EST

On 12/20/2012 09:02 PM, Al Viro wrote:
On Thu, Dec 20, 2012 at 09:00:27PM -0800, H. Peter Anvin wrote:
On 12/20/2012 08:57 PM, Al Viro wrote:
On Wed, Nov 14, 2012 at 12:18:01PM +0000, Arnd Bergmann wrote:

The other types that are used as 64 bit on x32 are ino_t, nlink_t,
size_t, ssize_t, ptrdiff_t, and off_t.

*Kernel-side* we should not give a damn about the userland nlink_t, period.
Making it architecture-dependent had been a bad mistake that essentially
made nlink_t useless for the kernel. That mistake had been fixed; please,
do not bring it back. If some userland structure needs to include a field
encoding nlink_t values, please use an explicitly-sized type when refering
to it kernel-side.

We should never use userland types per se. We can use __kernel_*_t
typedefs to make the kernel headers neater if it makes sense, but that
is often not even necessary.

... as long as we do not have typedef __kernel_foo_t foo_t in linux/types.h.

In the case of things like nlink_t and dev_t I would suggest we explicitly call out the types as kernel and user. I would suggest knlink_t and unlink_t but the latter made me want to stab my eyes out due to its confusion potential, so I wonder if we should establish a new convention with _kt (kernel type) and _ut (user type) suffixes, so nlink_kt and nlink_ut, alternatively one could consider k_nlink_t and u_nlink_t.


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

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