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SubjectRe: JFS default behavior
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

> - 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:
Remember Cernan and Schmitt
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