Re: JFS default behavior

[jw schultz]

On Mon, Feb 16, 2004 at 12:03:03AM +0100, Nicolas Mailhot wrote:
> | Linus Torvalds pointed the way of Tux :
> 
> | In short: the kernel talks bytestreams, and that implies that if you 
> | want to talk to the kernel, you HAVE TO USE UTF-8.
> 
> In that case :
> - should the kernel allow apps to write filenames that are invalid 
>   UTF-8 and will crash UTF-8 apps ?

Yes.  The kernel interface specifies it as a bytesteam with
0x00 and 0x2f having special meaning.  That is a constraint,
not a policy.  It is user space that determines the policy
of UTF-8.

>   UTF-8 and will crash UTF-8 apps ?

Fix the broken apps.  Crashing because of "invalid" UTF-8 is
no more excusable than crashing because of a string longer
than expected (buffer overrun).  Filenames as read from the
filesystem should be treated just like any other untrusted
input.

> - should this UTF-8 rule be noted somewhere (in a FAQ/man page/LSB spec/
> whatever) so apps authors know they are supposed to read and write UTF-8
> filenames and not apply locale rules to kernel objects ?

Since the LSB spec describes user space it might be a
suitable place.

> - what happens to already existing invalid UTF-8 filenames ? Should the
> kernel forcibly rewrite them (in 2.7.0...) to remove legacy mess ? What

If you have a filesystem with filenames that don't conform
to your policy write userspace tools to detect and/or fix
them.  If you have programs creating non-conforming
filenames, fix or rm those programs.

> kernel forcibly rewrite them (in 2.7.0...) to remove legacy mess ? What
> should happen if someone plug an unconverted FS in such a system
> afterwards ?

The kernel won't care.  Any user space code that treats the
filenames as something other than bytestreams should be able
to cope with any sequence of bytes.

> These are the questions people have been asking.

OK.  The questions have been asked and answered.
Asking again and again and again won't change the answer.



-- 
________________________________________________________________
	J.W. Schultz            Pegasystems Technologies
	email address:		jw@xxxxxxxxxx

		Remember Cernan and Schmitt
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