linux-kernel - Re: [Lsf-pc] [LSF/MM TOPIC] really large storage sectors

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Date:	Thu, 23 Jan 2014 13:21:26 -0800
From:	Joel Becker <jlbec@...lplan.org>
To:	Theodore Ts'o <tytso@....edu>, Dave Chinner <david@...morbit.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Chris Mason <clm@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"mgorman@...e.de" <mgorman@...e.de>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"lsf-pc@...ts.linux-foundation.org" 
	<lsf-pc@...ts.linux-foundation.org>,
	Ric Wheeler <rwheeler@...hat.com>
Subject: Re: [Lsf-pc] [LSF/MM TOPIC] really large storage sectors - going
 beyond 4096 bytes

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

-- 

"One of the symptoms of an approaching nervous breakdown is the
 belief that one's work is terribly important."
         - Bertrand Russell 

			http://www.jlbec.org/
			jlbec@...lplan.org
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