On Thu, Jan 23, 2014 at 07:55:50AM -0500, Theodore Ts'o wrote:
> On Thu, Jan 23, 2014 at 07:35:58PM +1100, Dave Chinner wrote:
> > >
> > > I expect it would be relatively simple to get large blocksizes working
> > > on powerpc with 64k PAGE_SIZE. So before diving in and doing huge
> > > amounts of work, perhaps someone can do a proof-of-concept on powerpc
> > > (or ia64) with 64k blocksize.
> >
> > Reality check: 64k block sizes on 64k page Linux machines has been
> > used in production on XFS for at least 10 years. It's exactly the
> > same case as 4k block size on 4k page size - one page, one buffer
> > head, one filesystem block.
>
> This is true for ext4 as well. Block size == page size support is
> pretty easy; the hard part is when block size > page size, due to
> assumptions in the VM layer that requires that FS system needs to do a
> lot of extra work to fudge around. So the real problem comes with
> trying to support 64k block sizes on a 4k page architecture, and can
> we do it in a way where every single file system doesn't have to do
> their own specific hacks to work around assumptions made in the VM
> layer.
Yup, ditto for ocfs2.
Joel
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