Re: grub-probe detects ext4 wronly as ext2

[Pavel Roskin]

On Tue, 2008-07-01 at 20:42 +0200, Javier Martín wrote:

> Well, what can I say about this: INCOMPAT_* flags are so for a reason,
> and they are telling us "don't even try to read this filesystem if you
> don't implement this". It's true that _maybe_ the files we need don't
> have extents, or compression, or other incompatible things, but then
> we'd have to strengthen _every other_ routine in the driver, like those
> that read inodes, guarding them against format changes that we have
> probably ignored bypassing the incompatible features check. From the POV
> of correctness I'd prefer to have a single point of "failure" in the
> mount routine.
> 
> Also, as a GRUB user I would find it quite strange that a filesystem
> that is listed as recognized and whose files can be lsed would not let
> me access a particular file because (insert unrecognized inode format
> error here). I _would_ understand such errors if the system showed the
> partition as "unrecognized" and then I had to specifically request it to
> be mounted as ext2 with a possible --ignore-incompatible flag, because
> then I would be knowingly doing something "risky", but the system should
> not take such kind of decisions on its own unless the GRUB developers
> _know_ about a particular flag and, after weighing the pros and cons,
> specifically decide to ignore it (like the proposed patch does with
> needs_recovery). However, doing that with possibly unknown future flags
> is a no-go.

OK, I wasn't arguing against your patch.  I just tried to explain why we
can relax some criteria compared to what a filesystem driver in a kernel
would do.  I actually agree with most of your arguments.

-- 
Regards,
Pavel Roskin