Re: [Ext2-devel] [RFC 0/13] extents and 48bit ext3

Joel Becker
2006-06-09T21:30:18Z

On Sat, Jun 10, 2006 at 01:20:31AM +0400, Alex Tomas wrote:
> two point here:
> a) warnings should be made visible at mount time,
> something like printk(KERN_CRIT ...)

Too late, they're already broken!

> b) I don't think you're going to fight all crazy people in the world,
> they'll definitely find a way to break something:
> data or something else.

Certainly not the crazy people. But the random person who's
just humming along? We should be nice to them.

> PS. in the end, "extents" option affects *new* files only. and one
> can boot extents-enabled kernel and convert fs back.

I just mentioned to Ted in another mail, since this is a
"permanent" change to the on-disk structure, why is this a mount option?
Shouldn't it rather be a tunefs(8)/mkfs(8) option?
In general, anything you pass to "mount -o" is optional. You
can mount with option X, then unmount and mount without option X. Most
people "expect" this to work (Principle of Least Surprise). So, when
you do:

# mount -o extents /fs1
# create_file /fs1/newfile
# umount /fs1
# mount /fs1

it breaks. Lease Surprise expects it to work.
However, tunefs(8) and mkfs(8) is generally understood to make
physical changes. Why not "tunefs -extents" to turn them on? It's
completely analogous to "tunefs -J", will fit everyone's expectation,
and won't surprise people. "mkfs -extents" does the same thing.

Joel

--

Life's Little Instruction Book #232

"Keep your promises."

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127