Re: [PATCH 4/4] fix biosize option

[Christoph Hellwig <hch@lst.de>]

On Thu, Jul 24, 2008 at 05:15:19PM +1000, Dave Chinner wrote:
> On Sun, May 25, 2008 at 09:07:54PM +0200, Christoph Hellwig wrote:
> > iosizelog shouldn't be the same as iosize but the logarithm of it.  Then
> > again the current biosize option doesn't make much sense to me as it
> > doesn't set the preferred I/O size as mentioned in the comment next to
> 
> That's a hold-over from irix - biosize set the basic chunk size the
> cache used for mapping writes, so was effectively the size of write
> to use to avoid RMW cycles as well as the unit of delayed
> allocation. 
> 
> > it but rather the allocation size and thus is identical to the allocsize
> > option (except for the missing logarithm).  It's also not documented in
> > Documentation/filesystems/xfs.txt or the mount manpage.
> 
> So when it was first added (probably for compatibility) the
> allocation part was noticed and not the rest. Maybe we should
> hook it up to xfs_preferred_iosize() rather than allocation now
> that it exists...

Or just stop making the option have any effect and just print a message
that it's ignored..