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Date: Thu, 19 Apr 2001 22:23:39 -0400 (EDT)
From: Alexander Viro <viro@math.psu.edu>
To: tytso@valinux.com
cc: linux-kernel@vger.kernel.org, Andreas Dilger <adilger@turbolinux.com>,
        "Theodore Y. Ts'o" <tytso@mit.edu>,
        Ext2 development mailing list 
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Subject: Re: [Ext2-devel] ext2 inode size (on-disk)
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On Thu, 19 Apr 2001 tytso@valinux.com wrote:

> This was a project that was never completed.  I thought at one point
> of allowing the inode size to be not a power of 2, but if you do that,
> you really want to avoid letting an inode cross a block boundary ---
> for reliability and performance reasons if nothing else.   

Agreed.

> In the long run, it probably makes sense to adjust the algorithms to
> allow for non-power-of-two inode sizes, but require an incompatible
> filesystem feature flag (so that older kernels and filesystem
> utilities won't choke when mounting filesystems with non-standard
> sized inodes.

I don't think that it's needed - old kernels (up to -CURRENT ;-) will
simply refuse to mount if ->s_inode_size != 128. Old utilites may be
trickier, though...

I'm somewhat concerned about the following: last block of inode table
fragment may have less inodes than the rest. Reason: number of inodes
per group should be a multiple of 8 and with inodes bigger than 128
bytes it may give such effect. Comments?

I would really, really like to end up with accurate description of
inode table layout somewhere in Documentation/filesystems. Heck, I
volunteer to write it down and submit into the tree ;-)
							Al

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