[PATCH 06/15] mkfs: validate logarithmic parameters sanely

[Christoph Hellwig]

On Fri, Nov 29, 2013 at 12:43:41PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> Testing logarithmic paramters like "-n log=<num>" shows that we do a
> terrible job of validating such input. e.g.:
> 
> # mkfs.xfs -f -n log=456858480 /dev/vda
> .....
> naming   =version 2              bsize=65536  ascii-ci=0 ftype=0
> ....
> 
> Yeah, I just asked for a block size of 2^456858480, and it didn't
> get rejected. Great, isn't it?
> 
> So, factor out the parsing of logarithmic parameters, and pass in
> the maximum valid value that they can take. These maximum values
> might not be completely accurate (e.g. block/sector sizes will
> affect the eventual valid maximum) but we can get rid of all the
> overflows and stupidities before we get to fine-grained validity
> checking later in mkfs once things like block and sector sizes have
> been finalised.

Btw, is there any good reason not to deprecate the logarithmic
parameters?  I can't see why anyone would want to use them, but I see
lots of potential for confusion (happened to myself in the past).

The patch itself looks good:


Reviewed-by: Christoph Hellwig <hch at lst.de>