Re: [REVIEW] Don't make lazy counters default for mkfs

[Eric Sandeen <sandeen@sandeen.net>]

Josef 'Jeff' Sipek wrote:
> On Mon, Mar 03, 2008 at 11:30:14AM +1100, Mark Goodwin wrote:
> ...
>> Maybe I'm missing something, but if we export all the feature bits,
>> both new and old, then (a) an old mkfs will continue to ignore them,
>> and (b) future versions of mkfs will have all the information needed,
>> but will need t be smart about how that information is used.
> 
> IMHO:
> 
> 1) mkfs should make a filesystem, the defaults should be conservative (say
>    using features that have been around >1 year)

I suppose I have to agree, unfortunately that means most competetive
benchmarks will be using sub-optimal mkfs's, but...

> 2) xfs should export supported features to userspace
> 
> 3) if you want to make sure that the fs you create will be mountable with
>    your current kernel, write a small shell script or something along those
>    lines that reads the features from some kernel interface, and based on
>    those passes the right options to mkfs

> 4) if you just use mkfs and it creates a fs that's incompatible with your
>    current kernel, the mount will fail - as it does today, but perhaps a
>    less cryptic error message would be in order

Ya know, good point.  We already have "running kernel compatibility
checks" built in; it's called "see what happens when you mount it"

It's not like we're running mkfs.ext3 here... ;)  mkfs; mount will tell
you quickly if there's a problem, won't it.  Adding complexity to mkfs
might not make a lot of sense.

And I still am not a huge fan of checking the currently-running kernel;
that's just a point in time, and not necessarily what you're gonna mount
it with.  (heck maybe you're mkfs'ing a san filesystem?)

it's unix, after all.  hand out the hangin' rope... just make the kernel
 explain exactly how & why you've just hung yourself at mount time, in
that case....

-Eric