Re: [PATCH 15/15][e2fsprogs] 64-bit mke2fs cleanup

Jose R. Santos
2008-07-16T18:03:46Z

On Wed, 16 Jul 2008 13:18:24 -0400
Theodore Tso <tytso@mit.edu> wrote:

> On Wed, Jul 16, 2008 at 11:02:42AM -0500, Jose R. Santos wrote:
> > > PS: Should functions that chop off upper bits like that make sure they
> > > are 0?
> >
> > I think this is something that need to be cheched at fsck since having
> > these be non-zero on a non-64-bit FS should be pointing to file system
> > corruption. Not sure if its something that need to be done every time
> > we set a value on the lower bit only though.
>
> Well, to quote Postel's law (also known as the robustness principle):
> "Be conservative in what you do; be liberal in what you accept from
> others."
>
> This is a generalization from what Jon Postel wrote in RFC 793: "TCP
> implementations will follow a general principle of robustness: be
> conservative in what you do, be liberal in what you accept from
> others," but it applies here as well. So yes, the library code should
> clear the upper bits even if 64-bit feature flag is not set. However,
> we should not depend on the upper bits being zero if the 64-bit
> feature flag is not set.
>
> Does that make sense?

Set it; don't check it. Got it.

I'll just check for large descriptors instead of the 64-bit feature
flag. That should set the upper bit regardless of whether we use a
64bit fs or not.

>
> - Ted
>

-JRS