Subject: Re: [PATCH] Re: Reduce XFS footprint (was Re: TAKE - remove a
	function xfs added to filemap.c
From: Eric Sandeen <sandeen@sgi.com>
To: Andi Kleen <ak@suse.de>
Cc: Nathan Scott <nathans@sgi.com>, linux-xfs@oss.sgi.com
In-Reply-To: <20020129202509.A31370@wotan.suse.de>
References: <200201291751.g0THp897004750@scare.vieo.com>
	<20020129194001.A16401@wotan.suse.de>  <20020129202509.A31370@wotan.suse.de>
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Date: 29 Jan 2002 13:56:41 -0600
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On Tue, 2002-01-29 at 13:25, Andi Kleen wrote:
> On Tue, Jan 29, 2002 at 07:40:01PM +0100, Andi Kleen wrote:
> > This patch does it. It's very simple and clean.
> > Saves another 18K on a xfs with BIG_FILESYSTEMS and BIG_FILES disabled. 
> 
> Oops. The patch had a silly mistake. The dep_mbools were missing the third
> parameter. It wasn't noticed by make oldconfig, but the more advanced
> configurators notice.
> 
> Here is an update. Should probably also write some help text. 

Yep, I just saw that.   And FWIW, the stated limit for the filesystem
size w/o XFS_BIG_FILESYSTEMS isn't quite right*.  I think these are
correct (these are internal XFS limitations):

File size:
o Without XFS_BIG_FILES, the max filesize is 1<<40, or 2TiB.
o With XFS_BIG_FILES, the max filesize is 1<<63-1.
  However, Linux can only handle 1<<(32+PAGE_SHIFT), or
  (2GiB * PAGE_SIZE), or 16TiB for machines w/ 4k pages.
  This limit has been added to the current Linux XFS code
  as well.

Filesystem size:
o Without XFS_BIG_FILESYSTEMS, the max filesystem size is the
  (filesystem block size * INT_MAX), or on x86 w/ 4k block sizes, 
  2^43, or about 8 TiB (which is bigger than Linux can handle).
o With XFS_BIG_FILESYSTEMS, it's 9 exabytes, I believe.
  (again, larger than Linux can handle).


-Eric

*Not that it matters, since Linux can't do > 2T anyway...

-- 
Eric Sandeen      XFS for Linux     http://oss.sgi.com/projects/xfs
sandeen@sgi.com   SGI, Inc.